Monday, July 30, 2012

SN 1957D in M83: X-Rays Discovered from Young Supernova Remnant

SN 1957D in M83
Credit: X-ray: NASA/CXC/STScI/K.Long et al.,
Optical: NASA/STScI

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Over fifty years ago, a supernova was discovered in M83, a spiral galaxy about 15 million light years from Earth. Astronomers have used NASA's Chandra X-ray Observatory to make the first detection of X-rays emitted by the debris from this explosion.

Named SN 1957D because it was the fourth supernova to be discovered in the year of 1957, it is one of only a few located outside of the Milky Way galaxy that is detectable, in both radio and optical wavelengths, decades after its explosion was observed. In 1981, astronomers saw the remnant of the exploded star in radio waves, and then in 1987 they detected the remnant at optical wavelengths, years after the light from the explosion itself became undetectable.

A relatively short observation -- about 14 hours long -- from NASA's Chandra X-ray Observatory in 2000 and 2001 did not detect any X-rays from the remnant of SN 1957D. However, a much longer observation obtained in 2010 and 2011, totaling nearly 8 and 1/2 days of Chandra time, did reveal the presence of X-ray emission. The X-ray brightness in 2000 and 2001 was about the same as or lower than in this deep image.

This new Chandra image of M83 is one of the deepest X-ray observations ever made of a spiral galaxy beyond our own. This full-field view of the spiral galaxy shows the low, medium, and high-energy X-rays observed by Chandra in red, green, and blue respectively. The location of SN 1957D, which is found on the inner edge of the spiral arm just above the galaxy's center, is outlined in the box (or can be seen by mousing over the image.)

The new X-ray data from the remnant of SN 1957D provide important information about the nature of this explosion that astronomers think happened when a massive star ran out of fuel and collapsed. The distribution of X-rays with energy suggests that SN 1957D contains a neutron star, a rapidly spinning, dense star formed when the core of pre-supernova star collapsed. This neutron star, or pulsar, may be producing a cocoon of charged particles moving at close to the speed of light known as a pulsar wind nebula.

If this interpretation is confirmed, the pulsar in SN 1957D is observed at an age of 55 years, one of the youngest pulsars ever seen. The remnant of SN 1979C in the galaxy M100 contains another candidate for the youngest pulsar, but astronomers are still unsure whether there is a black hole or a pulsar at the center of SN 1979C.

An image from the Hubble Space Telescope (in the box labeled "Optical Close-Up") shows that the debris of the explosion that created SN 1957D is located at the edge of a star cluster less than 10 million years old. Many of these stars are estimated to have masses about 17 times that of the Sun. This is just the right mass for a star's evolution to result in a core-collapse supernova as is thought to be the case in SN 1957D.

Multipanel with Optical, H-alpha & X-ray
Credit: Optical: NASA/STScI)

These results will appear in an upcoming issue of The Astrophysical Journal. The researchers involved with this study were Knox Long (Space Telescope Science Institute), William Blair (Johns Hopkins University), Leith Godfrey (Curtain University, Australia), Kip Kuntz (Johns Hopkins), Paul Plucinsky (Harvard-Smithsonian Center for Astrophysics), Roberto Soria (Curtain University), Christopher Stockdale (University of Oklahoma and the Australian Astronomical Observatory), Bradley Whitmore (Space Telescope Science Institute), and Frank Winkler (Middlebury College).

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Fast Facts for SN 1957D in M83:

Credit: X-ray: NASA/CXC/STScI/K.Long et al., Optical: NASA/STScI
Release Date: July 30, 2012
Scale: 9.5 arcmin on a side (~41,000 light years); Inset image: 1.6 x 1.3 arcsec (~120 x ~100 light years)
Category: Normal Galaxies & Starburst Galaxies
Coordinates: (J2000) RA 13h 37m 00.80s | Dec -29 51 58.60
Observation Date: 12 pointings between April 29, 2000 and Dec 28, 2011
Observation Time: 219 hours 49 min.
Obs. ID: 793, 2064, 12420, 12992-12996, 13202, 13241, 13248, 14332, 14342
Also Known As: NGC 5236
References: Long, K. et al, 2012, (in press)
Color Code: X-ray: (Red, Green, Blue); Optical inset (Red, Green, Blue)

Friday, July 27, 2012

Petite AGNs Reveal New Secrets

Figure 1. Michelle and T-ReCS mid-infrared images of some of the low-luminosity AGN in this study. Some of the galaxies, such as NGC 1052, have strong, compact nuclei reminiscent of higher-luminosity Seyfert galaxies or quasars. Others, like NGC 3169, show extended emission that could be due to stars forming around the active nucleus. To the right of each of the mid-infrared images is a Hubble Space Telescope optical image of the same region.

Figure 2. The strength of the silicate dust emission feature in many of the low-luminosity AGN (denoted S10, the black circles), is unusually large compared to the amount of gas in their nucleus (measured by log NH). One possible explanation is that these galaxies harbour just a small amount of optically-thin dust, which is expected according to some models that predict the disappearance of the dusty torus in low-luminosity AGN.

High-resolution, mid-infrared observations at Gemini North and South have revealed a wide range of morphologies for low-luminosity active galactic nuclei (AGN). While the data present a broad characterization of these objects' properties in this spectral region, they also present an interesting puzzle to ponder.

Active galactic nuclei (AGN), the supermassive black holes that feed on gas, dust, and stars at the centers of galaxies, spend most of their existence in a near dormant state. Until recently, astronomers had observed only a handful of low-luminosity AGN in the infrared at high resolution. Therefore, we didn't have a good, general overview of their properties in this potentially revealing spectral region. Our observations of 22 low-luminosity AGN, taken with both of Gemini's mid-infrared instruments (Michelle and T-ReCS), have changed this situation.

The images reveal a wide range of morphologies, from galaxies dominated by a central, compact source (much like images of higher-luminosity Seyferts and quasars) to those with weak nuclei embedded in large amounts of extended, mid-infrared emitting material that could signal star formation around the nucleus (Figure 1). To complement these observations, we combed the literature for other high-resolution measurements that reveal the emission of the nucleus from radio to X-ray frequencies. We also took advantage of low-resolution but exquisitely sensitive spectroscopy from the Spitzer Space Telescope archive.

A rather complex picture emerged from the data. In some of the most weakly-accreting AGN, even Gemini's resolution doesn’t separate the infrared emission of the nucleus from that of the surrounding galaxy. However, we do find some cases where the infrared emission comes not from dust or the outer regions of the accretion disk, but from synchrotron radiation –– fast-moving electrons spiraling round magnetic field lines in the galaxy’s core. In a couple of those galaxies, the evidence suggests that the dusty torus is indeed absent (see sidebar). This is predicted by some models describing the nature and origin of the torus.

The more strongly-accreting AGN (but still weaker than most of those studied to date), look in many ways a lot like "conventional" Seyfert galaxies in the infrared. It's possible, then, that these low-luminosity AGN aren't as different as we had thought. However, the data do present some tantalizing hints that in these AGN, too, the dusty torus no longer exists. When we compare the dust emission features in their Spitzer spectra with the amount of gas around the nucleus (determined from published X-ray observations), it appears that there is an unusually small amount of dust compared to gas (Figure 2). This, again, is expected from some models that attempt to explain the origin of the torus.

If the torus doesn't exist in these objects, then we will need to find another way of explaining their Seyfert-like infrared emission. To better understand the observations, we have started to compare detailed models of the accretion disk, dust and synchrotron emission to the data. But right now we are simply happy to have high-quality observations to puzzle over in the months to come.

The article about this research has been published by the Astronomical Journal.

AGN: A Closer Look

When astronomers think about active galactic nuclei (AGN), the first thing that springs to mind is often one of the more dramatic examples: a luminous quasar or bright Seyfert galaxy, for instance. In reality, though, an active galaxy will spend only a tiny fraction of its existence in such a spectacular state. Most of the time the central engine will be more like the near-dormant black hole in the center of our own Galaxy, starved of the gas that feeds it and shining only weakly. These "low-luminosity AGN" differ from their luminous cousins in other ways, too.

Theory predicts that the accretion disk of material circling the black hole is extremely hot, puffed-up, and unable to radiate its energy efficiently. Also, whereas quasars and luminous Seyfert galaxies are surrounded by dusty clouds that can hide the accretion disk (collectively known as the "torus"), several models suggest that low-luminosity AGN should have bare, almost dust-free centers. Given how common, and yet how odd, these low-luminosity AGN appear to be, we need to test our hypotheses about them if we want to really understand how active galaxies ingest material and evolve over the course of their lives.

Dust near an AGN heats up and emits copious amounts of infrared radiation. The outer regions of the accretion disk in a low-luminosity AGN might well do the same. Therefore, the natural place to look for signatures of the torus and accreting material is the infrared region of the spectrum. Although ground-based telescopes aren’t as sensitive to infrared light as space-borne observatories like Spitzer –– the Earth's atmosphere itself shines brightly at infrared wavelengths –– telescopes like Gemini have a big advantage: spatial resolution.

Low-luminosity AGN are, by definition, faint compared to the stars that surround the galaxy’s black hole. This means that astronomers need the high resolution of a big ground-based telescope (about a factor of 10 better than Spitzer at a wavelength of 10 microns), due to its ability to separate the central engine from the host galaxy. Only then will astronomers get an uncontaminated view of the nuclei of these commonplace yet poorly-understood objects.

Gemini's mission is to advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky.

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai'i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in seven partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country's contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the UK Science and Technology Facilities Council (STFC), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq). The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

Thursday, July 26, 2012

The Brightest Stars Don't Live Alone

PR Image eso1230a
Artist’s impression of a vampire star and its victim

PR Image eso1230b
Hot and brilliant O stars in star-forming regions


Artist's impression of the evolution of a hot high-mass binary star

Artist's impression of the evolution of a hot high-mass binary star
(annotated version)

VLT finds most stellar heavyweights come in interacting pairs

A new study using ESO’s Very Large Telescope (VLT) has shown that most very bright high-mass stars, which drive the evolution of galaxies, do not live alone. Almost three quarters of these stars are found to have a close companion star, far more than previously thought. Surprisingly most of these pairs are also experiencing disruptive interactions, such as mass transfer from one star to the other, and about one third are even expected to ultimately merge to form a single star. The results are published in the 27 July 2012 issue of the journal Science.

The Universe is a diverse place, and many stars are quite unlike the Sun. An international team has used the VLT to study what are known as O-type stars, which have very high temperature, mass and brightness [1]. These stars have short and violent lives and play a key role in the evolution of galaxies. They are also linked to extreme phenomena such as “vampire stars”, where a smaller companion star sucks matter off the surface of its larger neighbour, and gamma-ray bursts.

“These stars are absolute behemoths,” says Hugues Sana (University of Amsterdam, Netherlands), the lead author of the study. “They have 15 or more times the mass of our Sun and can be up to a million times brighter. These stars are so hot that they shine with a brilliant blue-white light and have surface temperatures over 30 000 degrees Celsius.”

The astronomers studied a sample of 71 O-type single stars and stars in pairs (binaries) in six nearby young star clusters in the Milky Way. Most of the observations in their study were obtained using ESO telescopes, including the VLT.

By analysing the light coming from these targets [2] in greater detail than before, the team discovered that 75% of all O-type stars exist inside binary systems, a higher proportion than previously thought, and the first precise determination of this number. More importantly, though, they found that the proportion of these pairs that are close enough to interact (through stellar mergers or transfer of mass by so-called vampire stars) is far higher than anyone had thought, which has profound implications for our understanding of galaxy evolution.

O-type stars make up just a fraction of a percent of the stars in the Universe, but the violent phenomena associated with them mean they have a disproportionate effect on their surroundings. The winds and shocks coming from these stars can both trigger and stop star formation, their radiation powers the glow of bright nebulae, their supernovae enrich galaxies with the heavy elements crucial for life, and they are associated with gamma-ray bursts, which are among the most energetic phenomena in the Universe. O-type stars are therefore implicated in many of the mechanisms that drive the evolution of galaxies.

“The life of a star is greatly affected if it exists alongside another star,” says Selma de Mink (Space Telescope Science Institute, USA), a co-author of the study. “If two stars orbit very close to each other they may eventually merge. But even if they don’t, one star will often pull matter off the surface of its neighbour.”

Mergers between stars, which the team estimates will be the ultimate fate of around 20–30% of O-type stars, are violent events. But even the comparatively gentle scenario of vampire stars, which accounts for a further 40–50% of cases, has profound effects on how these stars evolve.

Until now, astronomers mostly considered that closely-orbiting massive binary stars were the exception, something that was only needed to explain exotic phenomena such as X-ray binaries, double pulsars and black hole binaries. The new study shows that to properly interpret the Universe, this simplification cannot be made: these heavyweight double stars are not just common, their lives are fundamentally different from those of single stars.

For instance, in the case of vampire stars, the smaller, lower-mass star is rejuvenated as it sucks the fresh hydrogen from its companion. Its mass will increase substantially and it will outlive its companion, surviving much longer than a single star of the same mass would. The victim star, meanwhile, is stripped of its envelope before it has a chance to become a luminous red super giant. Instead, its hot, blue core is exposed. As a result, the stellar population of a distant galaxy may appear to be much younger than it really is: both the rejuvenated vampire stars, and the diminished victim stars become hotter, and bluer in colour, mimicking the appearance of younger stars. Knowing the true proportion of interacting high-mass binary stars is therefore crucial to correctly characterise these faraway galaxies. [3]

“The only information astronomers have on distant galaxies is from the light that reaches our telescopes. Without making assumptions about what is responsible for this light we cannot draw conclusions about the galaxy, such as how massive or how young it is. This study shows that the frequent assumption that most stars are single can lead to the wrong conclusions,” concludes Hugues Sana.

Understanding how big these effects are, and how much this new perspective will change our view of galactic evolution, will need further work. Modeling binary stars is complicated, so it will take time before all these considerations are included in models of galaxy formation.


[1] Most stars are classified according to their spectral type, or colour. This in turn is related to the stars’ mass and surface temperature. From bluest (and hence hottest and highest mass) to reddest (and hence coolest and lowest mass), the most common classification sequence is O, B, A, F, G, K and M. O-type stars have surface temperatures of around 30 000 degrees Celsius or more, and appear a brilliant pale blue. They have a mass of 15 or more times the mass of the Sun.

[2] The component stars in binary star systems are usually located too close to each other to be seen directly as separate points of light. However, the team were able to detect their binary nature using the VLT’s Ultraviolet and Visible Echelle Spectrograph (UVES). Spectrographs spread out a stars’s light much like a prism breaks up sunlight into a rainbow. Imprinted in the starlight are subtle barcode-like patterns caused by elements in the stars atmospheres which darken specific colours of light. When astronomers observe single stars, these so-called absorption lines are fixed, but in binaries, the lines from the two stars are slightly shifted relative to each other by the stars’ motion. The extent to which these lines are offset from each other and the way they move over time allow astronomers to determine the stars’ motion, and hence their orbital characteristics, including whether they are close enough to each other to exchange mass or even merge.

[3] The existence of this large number of vampire stars fits well with a previously unexplained phenomenon. Around a third of stars that explode as supernovae are observed to have surprisingly little hydrogen in them. However, the proportion of hydrogen-poor supernovae closely matches the proportion of vampire stars found by this study. Vampire stars are expected to cause hydrogen-poor supernovae in their victims, as the hydrogen-rich outer layers are torn off by the vampire star’s gravity before the victim has a chance to explode as a supernova.
More information

This research was presented in a paper “Binary interaction dominates the evolution of massive stars”, H. Sana et al., to appear in the journal Science on 27 July 2012.

The team is composed of H. Sana (Amsterdam University, The Netherlands), S.E. de Mink (Space Telescope Science Institute, Baltimore, USA; Johns Hopkins University, Baltimore, USA), A. de Koter (Amsterdam University; Utrecht University, The Netherlands), N. Langer (University of Bonn, Germany), C.J. Evans (UK Astronomy Technology Centre, Edinburgh, UK), M. Gieles (University of Cambridge UK), E. Gosset (Liege University, Belgium), R.G. Izzard (University of Bonn), J.-B. Le Bouquin (Université Joseph Fourier, Grenoble, France) and F.R.N. Schneider (University of Bonn).

The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

  • Research paper from Science magazine:

Photos of the VLT


Hugues Sana
Astronomical Institute “Anton Pannekoek”, Amsterdam University
Amsterdam, The Netherlands
Tel: +31 20 525 8496
Cell: +31 6 83 200 917

Selma de Mink
Space Telescope Science Institute
Baltimore, USA
Tel: +1 410 338 4304
Cell: +1 443 255 3793

Richard Hook
ESO, La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591

Tuesday, July 24, 2012

A Galaxy Festooned with Stellar Nurseries

NGC 4700
ESA/Hubble & NASA

The galaxy NGC 4700 bears the signs of the vigorous birth of many new stars in this image captured by the NASA/ESA Hubble Space Telescope.

The many bright, pinkish clouds in NGC 4700 are known as H II regions, where intense ultraviolet light from hot young stars is causing nearby hydrogen gas to glow. H II regions often come part-and-parcel with the vast molecular clouds that spawn fresh stars, thus giving rise to the locally ionised gas.

In 1610, French astronomer Nicolas-Claude Fabri de Peiresc peered through a telescope and found what turned out to be the first H II region on record: the Orion Nebula, located relatively close to our Solar System here in the Milky Way. Astronomers study these regions throughout the Milky Way and those easily seen in other galaxies to gauge the chemical makeup of cosmic environments and their influence on the formation of stars.

NGC 4700 was discovered back in March 1786 by the British astronomer William Herschel who noted it as a “very faint nebula”. NGC 4700, along with many other relatively close galaxies, is found in the constellation of Virgo (The Virgin) and is classified as a barred spiral galaxy, similar in structure to the Milky Way. It lies about 50 million light-years from us and is moving away from us at about 1400 km/second due to the expansion of the Universe.

 Source: ESA/Hubble - Space Telescope


Monday, July 23, 2012

Heliophysics Nugget: Colorful Science Sheds Light on Solar Heating

Heliophysics nuggets are a collection of early science results, new research techniques, and instrument updates that further our attempt to understand the sun and the dynamic space weather system that surrounds Earth.

Left: This image was captured by NASA's Solar Dynamics Observatory (SDO) on June 19, 2010, the image shows the area in the wavelength of 171 Angstroms, which has here been colorized in yellow. Credit: NASA/SDO.
Right: This visualization, based on the image on the left, uses specific colors to describe which areas on the sun cooled or heated over a 12-hour period. The use of reds and yellows imply that higher temperatures dominated earlier in the time period, while lower temperatures dominated later, meaning that the area showed steady cooling over time, but any heating happened too quickly and impulsively to be measured. The image compares wavelength 211 (which shows material in the 2 million K range) to wavelength 171 (which shows material about ten times cooler). Credit: NASA/Viall.

A crucial, and often underappreciated, facet of science lies in deciding how to turn the raw numbers of data into useful, understandable information – often through graphs and images. Such visualization techniques are needed for everything from making a map of planetary orbits based on nightly measurements of where they are in the sky to colorizing normally invisible light such as X-rays to produce "images" of the sun.

More information, of course, requires more complex visualizations and occasionally such images are not just informative, but beautiful too.

Such is the case with a new technique created by Nicholeen Viall, a solar scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. She creates images of the sun reminiscent of Van Gogh, with broad strokes of bright color splashed across a yellow background. But it's science, not art. The color of each pixel contains a wealth of information about the 12-hour history of cooling and heating at that particular spot on the sun. That heat history holds clues to the mechanisms that drive the temperature and movements of the sun's atmosphere, or corona.

"We don't understand why the corona is so hot," says Viall who wrote about this technique and her conclusions about the corona in a paper that appeared in The Astrophysical Journal on TK date. "The corona is 1,000 times hotter than the sun's surface, when we would expect it to get cooler as the atmosphere gets further away from the hot sun, the same way the air gets cooler further away from a fire."

Scientists generally agree that energy in the roiling magnetic fields of the sun must transfer energy and heat up into the atmosphere, but the exact details of that process are still debated. Viall created her technique to see if she could distinguish between theories that describe coronal heating as uniform over time, versus those that say it comes from numerous nanoflares on the sun's surface.

To look at the corona from a fresh perspective, Viall created a new kind of picture, making use of the high resolution provided by NASA's Solar Dynamics Observatory (SDO). SDO's Atmospheric Imaging Assembly (AIA) provides images of the sun in 10 different wavelengths, each approximately corresponding to a single temperature of material. Therefore, when one looks at the wavelength of 171 Angstroms, for example, one sees all the material in the sun's atmosphere that is a million degrees Kelvin. By looking at an area of the sun in different wavelengths, one can get a sense of how different swaths of material change temperature. If an area seems bright in a wavelength that shows a hotter temperature an hour before it becomes bright in a wavelength that shows a cooler temperature, one can gather information about how that region has changed over time.

Nicholeen Viall, a solar scientist at NASA's Goddard Space Flight Center creates images of the sun reminiscent of Van Gogh, but it's science, not art. The color of each pixel contains a wealth of information about the 12-hour history of cooling and heating at that spot on the sun. That history holds clues to what drives the temperature and movements of the sun's atmosphere, or corona. Credit: NASA/Goddard Science Visualization Studio. Download video

To study such temperature changes, many scientists focus on analyzing a specific subset of solar material, such as giant arcs of charged particles that leap up off the sun's surface called coronal loops. Scientists gather information about the loops by comparing nearly simultaneous images of the sun in different wavelengths. Analysis of the loops in each image requires time-consuming, manual analysis to subtract the background observations away from the loops themselves, a process which is also inherently subject to human judgment and bias. In addition, each individual image represents light from only a narrow range of wavelengths, representing material at a narrow range of temperatures.

Viall wanted to look at as much of the solar material in a given area of the corona as she could, incorporating information about a variety of temperatures simultaneously. She also wanted to avoid the subjective process of subtracting out the background. Instead, she decided to look at all light coming from a given spot on the sun at the same time. That meant coming up with a visualization technique to convey all that information at once -- and thus her Van Gogh-like images were born.

For an interesting spot on the sun, Viall examines six channels over an entire 12-hour stretch. She compares each channel to the other channels in turn, assigning it a red, orange, or yellow color if the area has cooled, and assigning it a blue or green color if the area has heated up. She assigns the exact shade of the color based on how much time it took for the temperature change to occur.

"In essence, I'm measuring the time lag of how long it takes a given area to heat up or cool down," says Viall. "But it's totally automated, with no need for humans to make a decision about what to incorporate or ignore. And all of the solar material is represented statistically, not just one wavelength of light."

Viall's images show a wealth of reds, oranges, and yellow, meaning that over a 12-hour period the material appear to be cooling. Obviously there must have been heating in the process as well, since the corona isn't on a one-way temperature slide down to zero degrees. Any kind of steady heating throughout the corona would have shown up in Viall's images, so she concludes that the heating must be quick and impulsive – so fast that it doesn't show up in her images. This lends credence to those theories that say numerous nanobursts of energy help heat the corona.

Karen C. Fox

NASA Goddard Space Flight Center, Greenbelt, MD

Saturday, July 21, 2012

Solar Corona Revealed in Super-High-Definition

These photos of the solar corona, or million-degree outer atmosphere, show the improvement in resolution offered by NASA's High Resolution Coronal Imager, or Hi-C (bottom), versus the Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory (top). Both images show a portion of the sun's surface roughly 85,000 by 50,000 miles in size. Hi-C launched on a sounding rocket on July 11, 2012 in a flight that lasted about 10 minutes. The representative-color images were made from observations of ultraviolet light at a wavelength of 19.3 nanometers (25 times shorter than the wavelength of visible light). Credit: NASA. High Resolution Image (jpg)

This time-lapse movie shows activity in the sun's corona on July 11, 2012, with 10 minutes compressed into 10 seconds. It begins with images from the Atmospheric Imaging Assembly (AIA) on board NASA's Solar Dynamics Observatory. About three seconds in, the view switches to super-high-resolution photos of the same region from NASA's High Resolution Coronal Imager (Hi-C). Hi-C flew on a sounding rocket and only took data for about five minutes, so the view switches back to AIA data at the end. The representative-color images were made from observations of ultraviolet light at a wavelength of 19.3 nanometers (25 times shorter than the wavelength of visible light). Credit: NASA. Animation (mov) (8,85 mb)

Same time-lapse movie as above, with ultraviolet light color-coded red
Credit: NASA. Animation (mov) (8,33 mb)

Cambridge, MA - Today, astronomers are releasing the highest-resolution images ever taken of the Sun's corona, or million-degree outer atmosphere, in an extreme-ultraviolet wavelength of light. The 16-megapixel images were captured by NASA's High Resolution Coronal Imager, or Hi-C, which was launched on a sounding rocket on July 11th. The Hi-C telescope provides five times more detail than the next-best observations by NASA's Solar Dynamics Observatory.

"Even though this mission was only a few minutes long, it marks a big breakthrough in coronal studies," said Smithsonian astronomer Leon Golub (Harvard-Smithsonian Center for Astrophysics), one of the lead investigators on the mission.

Understanding the Sun's activity and its effects on Earth's environment was the critical scientific objective of Hi-C, which provided unprecedented views of the dynamic activity and structure in the solar atmosphere.

The corona surrounds the visible surface of the Sun. It's filled with million-degree ionized gas, or plasma, so hot that the light it emits is mainly at X-ray and extreme-ultraviolet wavelengths. For decades, solar scientists have been trying to understand why the corona is so hot, and why it erupts in violent solar flares and related blasts known as "coronal mass ejections," which can produce harmful effects when they hit Earth. The Hi-C telescope was designed and built to see the extremely fine structures thought to be responsible for the Sun's dynamic behavior.

"The phrase 'think globally, act locally' applies to the Sun too. Things happening at a small, local scale can impact the entire Sun and result in an eruption," explained Golub.

Hi-C focused on an active region on the Sun near sunspot NOAA 1520. The target, which was finalized on launch day, was selected specifically for its large size and active nature. The resulting high-resolution snapshots, at a wavelength of 19.3 nanometers (25 times shorter than the wavelength of visible light), reveal tangled magnetic fields channeling the solar plasma into a range of complex structures.

"We have an exceptional instrument and launched at the right time," said Jonathan Cirtain, senior heliophysicist at NASA's Marshall Space Flight Center. "Because of the intense solar activity we're seeing right now, we were able to clearly focus on a sizeable, active sunspot and achieve our imaging goals."

Since Hi-C rode on a suborbital rocket, its flight lasted for just 10 minutes. Of that time, only about 330 seconds were spent taking data. Yet those images contain a wealth of information that astronomers will analyze for months to come.

"The Hi-C flight might be the most productive five minutes I've ever spent," Golub smiled.

The high-resolution images were made possible because of a set of innovations on Hi-C's telescope, which directs light to the camera detector. The telescope includes some of the finest mirrors ever made for a space mission. Initially developed at NASA's Marshall Space Flight Center in Huntsville, Ala., the mirrors were completed with inputs from partners at the Smithsonian Astrophysical Observatory (SAO) in Cambridge, Mass., and a new manufacturing technique developed in coordination with L-3Com/Tinsley Laboratories of Richmond, Calif. The mirrors were made to reflect extreme-ultraviolet light from the Sun by Reflective X-ray Optics LLC of New York, NY, and the telescope was assembled at the SAO labs in Cambridge, Mass.

For more information about Hi-C, visit


Key partners in the development of Hi-C include the University of Alabama in Huntsville; the Smithsonian Astrophysical Observatory; Lockheed Martin's Solar Astrophysical Laboratory in Palo Alto, Calif.; the University of Central Lancashire in Lancashire, England; and the Lebedev Physical Institute of the Russian Academy of Sciences in Moscow.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics

Friday, July 20, 2012

Five Potential Habitable Exoplanets Now

New data suggest the confirmation of the exoplanet Gliese 581g and the best candidate so far of a potential habitable exoplanet. The nearby star Gliese 581 is well known for having four planets with the outermost planet, Gliese 581d, already suspected habitable. This will be the first time evidence for any two potential habitable exoplanets orbiting the same star. Gliese 581g will be included, together with Gliese 667Cc, Kepler-22b, HD85512, and Gliese 581d, in the Habitable Exoplanets Catalog of the PHL @ UPR Arecibo as the best five objects of interest for Earth-like exoplanets.

Doubts about the existence of Gliese 581g appeared only two weeks after its announcement on September 29, 2010 by astronomers of the Lick-Carnegie Exoplanet Survey. Scientists from the HARPS Team from the Geneva Observatory, which discovered all the previously known four planets around Gliese 581, were not able to detect Gliese 581g out of their own data, which included additional observations. Further analysis by others scientists also questioned the existence of Gliese 581g in the last two years.

Now the original discoverers of Gliese 581g, led by Steven S. Vogt of UC Santa Cruz, present a new analysis with an extended dataset from the HARPS instrument that shows more promising evidence for its existence. The new analysis strength their original assumption that all the planets around Gliese 581 are in circular and not elliptical orbits as currently believed. It is under this likely assumption that the Gliese 581g signal appears in the new data.

“This signal has a False Alarm Probability of < 4% and is consistent with a planet of minimum mass 2.2M [Earth masses], orbiting squarely in the star’s Habitable Zone at 0.13 AU, where liquid water on planetary surfaces is a distinct possibility” said Vogt. Based on the new data Gliese 581g probably has a radius not larger than 1.5 times Earth radii. It receives about the same light flux as Earth does from the Sun due to its closer orbital position around a dim red dwarf star. These factors combine to make Gliese 581g the most Earth-like planet known with an Earth Similarity Index, a measure of Earth-likeness from zero to one, of 0.92 and higher than the previously top candidate Gliese 667Cc, discovered last year. “The controversy around Gliese 581g will continue and we decided to include it to our main catalog based on the new significant evidence presented, and until more is known about the architecture of this interesting stellar system” said Abel Méndez, Director of the PHL @ UPR Arecibo. Authors on the original paper are Steven S. Vogt, UCO/Lick Observatory, UCSC; Paul Butler, Department of Terrestrial Magnetism, Carnegie Institution; and Nader Haghighipour of the Institute for Astronomy and NASA Astrobiology Institute. Their research is published online on July 20, 2012 in the journal Astronomical Notes, 333, No. 7, 561-575.

Caption: Artistic representation of all the five known potential habitable worlds including now Gliese 581g, the best candidate for an Earth-like exoplanet so far. All of these planets are superterrans (aka Super-Earths) with masses estimated between two and ten Earth masses. Numbers below the planet names correspond to their similarity with Earth as measured in a scale from zero to one with the Earth Similarity Index, one being identical to Earth.

Caption: Comparison of the estimated relative size and orbits of the five exoplanets around Gliese 581. The green shade represent the size of the habitable zone, or the orbital region where an Earth-size planet could have surface liquid water. Planets e, b, and c are too hot for liquid water and life but g and d are in the habitable zone. Planet g is specially in the right spot for Earth-like conditions while d is marginally within these limits, and colder. This is the first case of a stellar system with two potential habitable exoplanets orbiting the same star.

Additional Resources

by Abel Mendez Torres

An Audience of Stellar Flashbulbs

Messier 107
Credit: ESA/Hubble & NASA

The NASA/ESA Hubble Space Telescope has captured a crowd of stars that looks rather like a stadium darkened before a show, lit only by the flashbulbs of the audience’s cameras. Yet the many stars of this object, known as Messier 107, are not a fleeting phenomenon, at least by human reckoning of time — these ancient stars have gleamed for many billions of years.

Messier 107 is one of more than 150 globular star clusters found around the disc of the Milky Way galaxy. These spherical collections each contain hundreds of thousands of extremely old stars and are among the oldest objects in the Milky Way. The origin of globular clusters and their impact on galactic evolution remains somewhat unclear, so astronomers continue to study them through pictures such as this one obtained by Hubble.

As globular clusters go, Messier 107 is not particularly dense. Visually comparing its appearance to other globular clusters, such as Messier 53 or Messier 54 reveals that the stars within Messier 107 are not packed as tightly, thereby making its members more distinct like individual fans in a stadium's stands.

Messier 107 can be found in the constellation of Ophiuchus (The Serpent Bearer) and is located about 20 000 light-years from the Solar System.

French astronomer Pierre Méchain first noted the object in 1782, and British astronomer William Herschel documented it independently a year later. A Canadian astronomer, Helen Sawyer Hogg, added Messier 107 to Charles Messier's famous astronomical catalogue in 1947.

This picture was obtained with the Wide Field Camera of Hubble’s Advanced Camera for Surveys. The field of view is approximately 3.4 by 3.4 arcminutes.

Source: ESA/Hubble - Space Telescope

How to Build a Middleweight Black Hole

This simulated image shows the interaction between a massive gas giant planet (comparable in mass to Jupiter) and a surrounding protoplanetary disk of gas and dust. New research predicts that intermediate-mass black holes can create gaps in gas disks around supermassive black holes, analogous to the gaps produced by giant planets in disks around stars. The gap provides a signature that might give scientists the first glimpse of this elusive type of black hole. Credit: Phil Armitage, University of Colorado.

"We know about small black holes, which tend to be close to us and have masses a few to 10 times that of our Sun, and we know about supermassive black holes, which are found in the centres of galaxies and have a mass that's millions to billions of times the mass of the sun," said co-author Saavik Ford, who is a research associate in the Museum's Department of Astrophysics as well as a professor at the Borough of Manhattan Community College, City University of New York (CUNY) and a faculty member at CUNY's Graduate Center. "But we have no evidence for the middle stage. Intermediate-mass black holes are much harder to find."

The birth of an intermediate black hole starts with the death of a star that forms a stellar or low-mass black hole. In order for this "seed" to grow, it must collide with and consume other dead and living stars. But even though there are many billions of stars in large galaxies, there's an even greater proportion of empty space, making collisions a very rare occurrence.

The researchers' new model suggests that previous searches for middleweight black holes might have been focused on the wrong birthing ground.

"The recent focus had been on star clusters, but objects there move very quickly and there's no gas, which makes the chances of a collision very slim,"
said Barry McKernan, a research associate in the Museum's Department of Astrophysics who is a professor at CUNY's Borough of Manhattan Community College and a faculty member at CUNY's Graduate Center.

The new mechanism turns attention instead to active galactic nuclei, the piping hot and ultra-bright cores of galaxies that feed supermassive black holes. The gas in this system is the key, causing the stars to slow down and conform to a circularised orbit.

"You can think of the stars as cars travelling on a 10-lane highway," McKernan said. "If there were no gas, the cars would be going at very different speeds and mostly staying in their lanes, making the odds of collision low. When you add gas, it slows the cars to matching speeds but also moves them into other lanes, making the odds of collision and consumption much higher."

The resulting collisions allow a stellar black hole to swallow stars and grow. The black hole's size and gravitational pull increase as its mass expands, escalating its chance of further collisions. This phenomenon, called "runaway growth," can lead to the creation of an intermediate-mass black hole.

As they increase in size, the black holes start altering the gas disk that controls them. The researchers' model shows that black holes of a certain mass can create a gap in the gas disk, a signature that might give scientists the first glimpse of intermediate black holes.

The model describing this growth is a scaled-up version of the mechanism for the formation of gas giant planets like Jupiter and Saturn. Like intermediate black holes, these planets are thought to have grown in gas disks. The planets, though, developed in disks surrounding newly forming stars. Mordecai-Mark Mac Low, chair of the Department of Astrophysics at the Museum, has modelled that case.

"In some regions, we showed that rocky planets could be moved by the gas into common orbits, where they collide to form objects more than ten times the mass of the Earth, massive enough to attract gas and form gas giant planets,"
Mac Low said. "The creative work described here applies the same principles to the far more massive disks found at the centres of galaxies, to form black holes rather than giant planets."

Other authors on the paper include Museum research associate Wladimir Lyra from the Jet Propulsion Laboratory at the California Institute of Technology and Hagai Perets from the Harvard-Smithsonian Center for Astrophysics.

This work was supported in part by NASA and CUNY.

Media contact

Kendra Snyder
Department of Communications
American Museum of Natural History
New York City, United States
Tel: +1 212 496 3419

Image and caption

An image can be downloaded from

Caption: This simulated image shows the interaction between a massive gas giant planet (comparable in mass to Jupiter) and a surrounding protoplanetary disk of gas and dust. New research predicts that intermediate-mass black holes can create gaps in gas disks around supermassive black holes, analogous to the gaps produced by giant planets in disks around stars. The gap provides a signature that might give scientists the first glimpse of this elusive type of black hole. Credit: Phil Armitage, University of Colorado

Further information

Research paper: B. McKernan, K.E.S. Ford, W. Lyra, H.B. Perets, "Intermediate mass black holes in AGN disks - I. Production & Growth," Mon. Not. R. Astron. Soc. (2012).

doi: 10.1111/j.1365-2966.2012.21486.x

A preprint of the paper can be downloaded from

Notes for editors

The American Museum of Natural History (, founded in 1869, is one of the world's preeminent scientific, educational, and cultural institutions. The Museum encompasses 45 permanent exhibition halls, including the Rose Center for Earth and Space and the Hayden Planetarium, as well as galleries for temporary exhibitions. Five active research divisions and three cross-disciplinary centres support 200 scientists, whose work draws on a world-class permanent collection of more than 32 million specimens and artefacts, including specialized collections for frozen tissue and genomic and astrophysical data, as well as one of the largest natural history libraries in the Western Hemisphere. Through its Richard Gilder Graduate School, it is the first American museum authorized to grant the Ph.D. degree. In 2012, the Museum will begin offering a pilot Master of Arts in Teaching with a specialisation in earth science. Approximately 5 million visitors from around the world came to the Museum last year, and its exhibitions and Space Shows can be seen in venues on five continents. The Museum's website and collection of apps for mobile devices extend its collections, exhibitions, and educational programs to millions more beyond its walls. Visit for more information.

Become a fan of the Museum on Facebook via, or visit to follow us on Twitter.

The Royal Astronomical Society (RAS,, founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

Follow the RAS on Twitter via @royalastrosoc

Thursday, July 19, 2012

Sun Sends Out Mid-Level Solar Flare

The sun emitted an M7.7 class solar flare on July 19, 2012. This video, taken by the Solar Dynamics Observatory (SDO), shows the flare in 304 and 335 wavelengths. Credit: NASA/SDO.

A coronal mass ejection (CME) was also associated with the July 19, 2012 flare. A CME is another solar phenomenon that can send solar particles into space and can reach Earth one to three days later, affecting electronic systems in satellites and on the ground. Initial NASA research models show that this CME is not headed toward Earth, but could impact STEREO-A.

NOAA's Space Weather Prediction Center ( is the United States Government official source for space weather forecasts and alerts. Space Weather Prediction Center reports "Region 1520, now past the west limb, continues to erupt. It produced an R2 (moderate) Radio Blackout and a CME earlier today. Although not clearly Earth-directed, forecasters are analyzing it for tangential effects on the geomagnetic field. An S1 (minor) Solar Radiation Storm soon followed the eruption."

More information on different types of space weather including Solar Radiation Storms and Radio Blackouts:

Link to high-resolution media

This image was captured by NASA's Solar Dynamics Observatory (SDO) on July 19, 2012 of an M7.7 class solar flare. The image represents light in the 131 Angstrom wavelength, which is particularly good for seeing flares, and which is typically colorized in teal. Credit: NASA/SDO. View larger

The sun emitted a mid-level solar flare on July 19, 2012, beginning at 1:13 AM EDT and peaking at 1:58 AM. Solar flares are gigantic bursts of radiation that cannot pass through Earth's atmosphere to harm humans on the ground, however, when strong enough, they can disrupt the atmosphere and degrade GPS and communications signals.

The flare is classified as an M7.7 flare. This means it is weaker than the largest flares, which are classified as X-class. M-class flares can cause brief radio communications blackouts at the poles.

Increased numbers of flares are currently quite common, since the sun's standard 11-year activity cycle is ramping up toward solar maximum, which is expected in 2013. It is quite normal for there to be many flares a day during the sun’s peak activity.

Updates will be provided as they are available on the flare and whether there was an associated Earth-directed coronal mass ejection (CME), another solar phenomenon that can send solar particles into space and affect electronic systems in satellites and on Earth.

What is a solar flare? What is a coronal mass ejection?

For answers to these and other space weather questions, please visit the Spaceweather Frequently Asked Questions page.

Related Link
View Past Solar Eruptions

Karen C. Fox
NASA Goddard Space Flight Center, Greenbelt, MD

Cassini Spots Daytime Lightning on Saturn

These false color mosaics from NASA's Cassini spacecraft capture lightning striking within the huge storm that encircled Saturn's northern hemisphere for much of 2011. Full image and caption

PASADENA, Calif. - Saturn was playing the lightning storm blues. NASA's Cassini spacecraft has captured images of last year's storm on Saturn, the largest storm seen up-close at the planet, with bluish spots in the middle of swirling clouds. Those bluish spots indicate flashes of lightning and mark the first time scientists have detected lightning in visible wavelengths on the side of Saturn illuminated by the sun.

"We didn't think we'd see lightning on Saturn's day side - only its night side," said Ulyana Dyudina, a Cassini imaging team associate based at the California Institute of Technology in Pasadena. "The fact that Cassini was able to detect the lightning means that it was very intense."

Images can be found at, and

The storm occurred last year. The lightning flashes appear brightest in the blue filter of Cassini's imaging camera on March 6, 2011. Scientists aggressively heightened the blue tint of the image to determine its size and location. Scientists are still analyzing why the blue filter catches the lightning. It might be that the lightning really is blue, or it might be that the short exposure of the camera in the blue filter makes the short-lived lightning easier to see.

What scientists do know is that the intensity of the flash is comparable to the strongest flashes on Earth. The visible energy alone is estimated to be about 3 billion watts lasting for one second. The flash is approximately 100 miles (200 kilometers) in diameter when it exits the tops of the clouds. From this, scientists deduce that the lightning bolts originate in the clouds deeper down in Saturn's atmosphere where water droplets freeze. This is analogous to where lightning is created in Earth's atmosphere.

In composite images that show the band of the storm wrapping all the way around Saturn, scientists have seen multiple flashes. In one composite image, they recorded five flashes, and in another, three flashes.

"As summer storm season descends upon Earth's northern latitudes, Cassini provides us a great opportunity to see how weather plays out at different places in our solar system," said Linda Spilker, Cassini project scientist, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Saturn's atmosphere has been changing over the eight years Cassini has been at Saturn, and we can't wait to see what happens next."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute in Boulder, Colo.

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.

Earliest Spiral Galaxy Surprises Astronomers

Credit: David Law; Dunlap Insitute for Astronomy & Astrophysics

Credit: Dunlap Institute for Astronomy & Astrophysics; Joe Bergeron

Kinematic velocity and velocity dispersion maps of BX442
Credit: David Law; Dunlap Institute for Astronomy & Astrophysics

Kamuela, HI – In the beginning, galaxies were hot and clumpy – too hot to settle down and form grand spirals like the Milky Way and other galaxies seen in the nearby universe today. But astronomers have now been surprised by the discovery of a solitary grand design spiral galaxy in the early universe which could hold clues to how spirals start to take shape. The find was announced in a report in the July 19 edition of the journal Nature.

The ancient spiral, called BX442, was found by astronomers who first surveyed 300 distant galaxies using the Hubble Space Telescope, then followed up and confirmed using detailed observations and analyses from the W. M. Keck Observatory in Hawaii.

“As you go back in time to the early universe — about three billion years after the Big Bang; the light from this galaxy has been travelling to us for about 10.7 billion years —galaxies look really strange, clumpy and irregular, not symmetric” said astronomer Alice Shapley of UCLA. “The vast majority of old galaxies look like train wrecks. Our first thought was, why is this one so different, and so beautiful?”

Not only was the spiral shape clearly visible, but by using Keck’s OSIRIS instrument (OH-Suppressing Infrared Imaging Spectrograph), astronomers were able to study different parts of BX442 and determine that it is, in fact, rotating and not just two unrelated disk galaxies along the same line of sight that give the appearance of being a single spiral galaxy.

“We first thought this could just be an illusion and that perhaps we were being led astray by the picture,”
said Shapley, a coauthor on the Nature paper. “What we found when we took spectra of this galaxy is that the spiral arms do belong to this galaxy; it wasn’t an illusion. Not only does it look like a rotating spiral disk galaxy; it really is. We were blown away.”

Using laser adaptive optics (AO) to cancel out much of the Earth’s atmospheric distortions, the Keck II Telescope is able to get equal or better resolution than the Hubble Space Telescope. This was critical in this case, said astronomer David Law of the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto and the lead author on the paper.

“Galaxies at this distance appear super, super faint and super, super tiny,” said Law. “We needed every inch of Keck’s light collecting area, exquisite image quality from the AO system, and a sensitive instrument to not only detect the galaxy but chop up its light into 3,600 pieces to analyze. OSIRIS is really one of the only instruments in the world that could do what we needed, and everything came together beautifully.”

In the end, it took thirteen hours over three nights with the Keck II Telescope to gather the spectra from BX422 needed to confirm the nature of the distant and early spiral.

“We got a beautiful map that told us this thing is a rotating disk,” said Shapley.

What also sets BX442 apart from other galaxies of its epoch is that it appears to be in the process of merging with another galaxy. That, in fact, could be the reason it is beginning to form a spiral.

“Indeed, many of the most well-known grand design spiral galaxies in the nearby universe (e.g., M51, M81, M101) are observed to have nearby companions, and small satellites such as the Sagittarius dwarf galaxy may even be partly responsible for producing spiral patterns in our own Milky Way galaxy,” the researchers wrote in their paper.

They tested the idea with a simulation and found that the spiral pattern could be formed by such a merger. The simulations indicate that its glory may be fleeting though; the spiral may dissipate again in just 100 million years.

“BX442 represents a link between early galaxies that are much more turbulent and the rotating spiral galaxies that we see around us,” Shapley said. “Indeed, this galaxy may highlight the importance of merger interactions at any cosmic epoch in creating grand design spiral structure.”


Co-authors are Charles Steidel, the Lee A. DuBridge Professor of Astronomy at the California Institute of Technology; Naveen Reddy, assistant professor of physics and astronomy at UC Riverside; Charlotte Christensen, postdoctoral scholar at the University of Arizona, and Dawn Erb, assistant professor of physics at the University of Wisconsin, Milwaukee.

Shapley’s research is funded by the David and Lucile Packard Foundation.

The W. M. Keck Observatory operates two 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Big Island of Hawaii. The twin telescopes feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectroscopy and a world-leading laser guide star adaptive optics system which cancels out much of the interference caused by Earth’s turbulent atmosphere. The Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

(Partially adapted from a press release by UCLA)

Wednesday, July 18, 2012

Spitzer Finds Possible Exoplanet Smaller Than Earth

Astronomers using NASA's Spitzer Space Telescope have detected what they believe is an alien world just two-thirds the size of Earth - one of the smallest on record. The exoplanet candidate, known as UCF-1.01, orbits a star called GJ 436, which is located a mere 33 light-years away. UCF-1.01 might be the nearest world to our solar system that is smaller than our home planet. Credit: NASA/JPL-Caltech.

PASADENA, Calif. -- Astronomers using NASA's Spitzer Space Telescope have detected what they believe is a planet two-thirds the size of Earth. The exoplanet candidate, called UCF-1.01, is located a mere 33 light-years away, making it possibly the nearest world to our solar system that is smaller than our home planet.

Exoplanets circle stars beyond our sun. Only a handful smaller than Earth have been found so far. Spitzer has performed transit studies on known exoplanets, but UCF-1.01 is the first ever identified with the space telescope, pointing to a possible role for Spitzer in helping discover potentially habitable, terrestrial-sized worlds.

"We have found strong evidence for a very small, very hot and very near planet with the help of the Spitzer Space Telescope," said Kevin Stevenson from the University of Central Florida in Orlando. Stevenson is lead author of the paper, which has been accepted for publication in The Astrophysical Journal. "Identifying nearby small planets such as UCF-1.01 may one day lead to their characterization using future instruments."

The hot, new-planet candidate was found unexpectedly in Spitzer observations. Stevenson and his colleagues were studying the Neptune-sized exoplanet GJ 436b, already known to exist around the red-dwarf star GJ 436. In the Spitzer data, the astronomers noticed slight dips in the amount of infrared light streaming from the star, separate from the dips caused by GJ 436b. A review of Spitzer archival data showed the dips were periodic, suggesting a second planet might be orbiting the star and blocking out a small fraction of the star's light.

This technique, used by a number of observatories including NASA's Kepler space telescope, relies on transits to detect exoplanets. The duration of a transit and the small decrease in the amount of light registered reveals basic properties of an exoplanet, such as its size and distance from its star. In UCF-1.01's case, its diameter would be approximately 5,200 miles (8,400 kilometers), or two-thirds that of Earth. UCF-1.01 would revolve quite tightly around GJ 436, at about seven times the distance of Earth from the moon, with its "year" lasting only 1.4 Earth days. Given this proximity to its star, far closer than the planet Mercury is to our sun, the exoplanet's surface temperature would be more than 1,000 degrees Fahrenheit (almost 600 degrees Celsius).

If the roasted, diminutive planet candidate ever had an atmosphere, it almost surely has evaporated. UCF-1.01 might therefore resemble a cratered, mostly geologically dead world like Mercury. Paper co-author Joseph Harrington, also of the University of Central Florida and principal investigator of the research, suggested another possibility; that the extreme heat of orbiting so close to GJ 436 has melted the exoplanet's surface.

"The planet could even be covered in magma," Harrington said.

In addition to UCF-1.01, Stevenson and his colleagues noticed hints of a third planet, dubbed UCF-1.02, orbiting GJ 436. Spitzer has observed evidence of the two new planets several times each. However, even the most sensitive instruments are unable to measure exoplanet masses as small as UCF-1.01 and UCF-1.02, which are perhaps only one-third the mass of Earth. Knowing the mass is required for confirming a discovery, so the paper authors are cautiously calling both bodies exoplanet candidates for now.

Of the approximately 1,800 stars identified by NASA' Kepler space telescope as candidates for having planetary systems, just three are verified to contain sub-Earth-sized exoplanets. Of these, only one exoplanet is thought to be smaller than the Spitzer candidates, with a radius similar to Mars, or 57 percent that of Earth.

"I hope future observations will confirm these exciting results, which show Spitzer may be able to discover exoplanets as small as Mars," said Michael Werner, Spitzer project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Even after almost nine years in space, Spitzer's observations continue to take us in new and important scientific directions."

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit and .

More information about exoplanets and NASA's planet-finding program is at .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

J.D. Harrington 202-358-5241
Headquarters, Washington

APEX takes part in sharpest observation ever

Artist’s impression of the quasar 3C 279

PR Image eso1229b
Positions of the telescopes used in the 1.3 mm
VLBI observations of the quasar 3C 279

PR Image eso1229c
The Atacama Pathfinder Experiment (APEX)

PR Image eso1229d
The Submillimeter Telescope (SMT)
at the Arizona Radio Observatory

PR Image eso1229e
The Submillimeter Array (SMA) on Mauna Kea, Hawaii

PR Image eso1229f
Position of the quasar 3C 279 in the constellation of Virgo


PR Video eso1229a
Artist’s impression of the quasar 3C 279

PR Video eso1229b
Positions of the telescopes used in the 1.3 mm
VLBI observations of the quasar 3C 279

PR Video eso1229c
Artist’s impression of the quasar 3C 279
(alternative version)

Telescopes in Chile, Hawaii, and Arizona reach sharpness two million times finer than human vision

An international team of astronomers has observed the heart of a distant quasar with unprecedented sharpness, two million times finer than human vision. The observations, made by connecting the Atacama Pathfinder Experiment (APEX) telescope [1] to two others on different continents for the first time, is a crucial step towards the dramatic scientific goal of the “Event Horizon Telescope” project [2]: imaging the supermassive black holes at the centre of our own galaxy and others.

Astronomers connected APEX, in Chile, to the Submillimeter Array (SMA) [3] in Hawaii, USA, and the Submillimeter Telescope (SMT) [4] in Arizona, USA. They were able to make the sharpest direct observation ever [5], of the centre of a distant galaxy, the bright quasar 3C 279, which contains a supermassive black hole with a mass about one billion times that of the Sun, and is so far from Earth that its light has taken more than 5 billion years to reach us. APEX is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. APEX is operated by ESO.

The telescopes were linked using a technique known as Very Long Baseline Interferometry (VLBI). Larger telescopes can make sharper observations, and interferometry allows multiple telescopes to act like a single telescope as large as the separation — or “baseline” — between them. Using VLBI, the sharpest observations can be achieved by making the separation between telescopes as large as possible. For their quasar observations, the team used the three telescopes to create an interferometer with transcontinental baseline lengths of 9447 km from Chile to Hawaii, 7174 km from Chile to Arizona and 4627 km from Arizona to Hawaii. Connecting APEX in Chile to the network was crucial, as it contributed the longest baselines.

The observations were made in radio waves with a wavelength of 1.3 millimetres. This is the first time observations at a wavelength as short as this have been made using such long baselines. The observations achieved a sharpness, or angular resolution, of just 28 microarcseconds — about 8 billionths of a degree. This represents the ability to distinguish details an amazing two million times sharper than human vision. Observations this sharp can probe scales of less than a light-year across the quasar — a remarkable achievement for a target that is billions of light-years away.

The observations represent a new milestone towards imaging supermassive black holes and the regions around them. In future it is planned to connect even more telescopes in this way to create the so-called Event Horizon Telescope. The Event Horizon Telescope will be able to image the shadow of the supermassive black hole in the centre of our Milky Way galaxy, as well as others in nearby galaxies. The shadow — a dark region seen against a brighter background — is caused by the bending of light by the black hole, and would be the first direct observational evidence for the existence of a black hole’s event horizon, the boundary from within which not even light can escape.

The experiment marks the first time that APEX has taken part in VLBI observations, and is the culmination of three years hard work at APEX’s high altitude site on the 5000-metre plateau of Chajnantor in the Chilean Andes, where the atmospheric pressure is only about half that at sea level. To make APEX ready for VLBI, scientists from Germany and Sweden installed new digital data acquisition systems, a very precise atomic clock, and pressurised data recorders capable of recording 4 gigabits per second for many hours under challenging environmental conditions [6]. The data — 4 terabytes from each telescope — were shipped to Germany on hard drives and processed at the Max Planck Institute for Radio Astronomy in Bonn.

The successful addition of APEX is also important for another reason. It shares its location and many aspects of its technology with the new Atacama Large Millimeter/submillimeter Array (ALMA) telescope [7]. ALMA is currently under construction and will finally consist of 54 dishes with the same 12-metre diameter as APEX, plus 12 smaller dishes with a diameter of 7 metres. The possibility of connecting ALMA to the network is currently being studied. With the vastly increased collecting area of ALMA’s dishes, the observations could achieve 10 times better sensitivity than these initial tests. This would put the shadow of the Milky Way's supermassive black hole within reach for future observations.


[1] APEX is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. Operation of APEX at Chajnantor is entrusted to ESO. APEX is a pathfinder for the next-generation submillimetre telescope, the Atacama Large Millimeter/submillimeter Array (ALMA), which is being built and operated on the same plateau.

[2] The Event Horizon Telescope project is an international collaboration, coordinated by the MIT Haystack Observatory (USA).

[3] The Submillimeter Array (SMA) on Mauna Kea, Hawaii, consisting of 8 dishes of 6 m diameter each, is operated by the Smithsonian Astrophysical Observatory (USA) and the Academia Sinica Institute of Astronomy and Astrophysics (Taiwan).

[4] The Submillimeter Telescope (SMT) of 10 m diameter on top of Mount Graham, Arizona, is operated by the Arizona Radio Observatory (ARO) in Tucson, Arizona (USA).

[5] Some indirect techniques have been used to probe finer scales, for example using microlensing (see heic1116) or interstellar scintillation, but this is a record for direct observations.

[6] These systems were developed in parallel in the USA (MIT-Haystack observatory) and in Europe (MPIfR, INAF — Istituto di Radioastronomia Noto VLBI Station, and HAT-Lab). A hydrogen maser time standard (T4Science) was installed as the very precise atomic clock. The SMT and SMA had already been equipped similarly for VLBI.

[7] The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ESO is the European partner in ALMA.
More information

The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.



Alan Roy
APEX VLBI Project Lead, Max-Planck-Institut für Radioastronomie
Bonn, Germany
Tel: +49 228 525 191

Thomas Krichbaum
APEX VLBI Project Scientist, Max-Planck-Institut für Radioastronomie
Bonn, Germany
Tel: +49 228 525 295

Shep Doeleman
MIT Haystack Observatory
Westford, USA
Tel: +1 781 981 5400 x5904

Michael Lindqvist
Onsala Space Observatory
Onsala, Sweden
Tel: +46 31 772 5508

Lucy Ziurys
Director, Arizona Radio Observatory
Tucson, USA
Tel: +1 520 621-6525

Jonathan Weintroub
Harvard-Smithsonian Center for Astrophysics
Cambridge, USA
Tel: +1 617 495 7319

Douglas Pierce-Price
APEX Public Information Officer, ESO
Garching bei München, Germany
Tel: +49 89 3200 6759