Missing Link" Revealing Fast-Spinning Pulsar Mysteries

Astronomers have discovered a unique double-star system that representsa "missing link" stage in what they believe is the birth process of the most rapidly-spinning stars in the Universe -- millisecond pulsars.

"We've thought for some time that we knew how these pulsars get 'spun up' to rotate so swiftly, and this system looks like it's showing us the process in action," said Anne Archibald, of McGill University in Montreal, Canada.

Neutron star with accretion disk (left)
drawing material from companion star (right).
CREDIT:Bill Saxton, NRAO/AUI/NSF
Animations of this system and its evolution.

Pulsars are superdense neutron stars, the remnants left after massive stars have exploded as supernovae. Their powerful magnetic fields generate lighthouse-like beams of light and radio waves that sweep around as the star rotates. Most rotate a few to tens of times a second, slowing down over thousands of years.

However, some, dubbed millisecond pulsars, rotate hundreds of times a second. Astronomers believe the fast rotation is caused by a companion star dumping material onto the neutron star and spinning it up. The material from the companion would form a flat, spinning disk around the neutron star, and during this period, the radio waves characteristic of a pulsar would not be seen coming from the system. As the amount of matter falling onto the neutron star decreased and stopped, the radio waves could emerge, and the object would be recognized as a pulsar.

This sequence of events is apparently what happened with a binary-star system some 4000 light-years from Earth. The millisecond pulsar in this system, called J1023, was discovered by the National Science Foundation's (NSF) Robert C. Byrd Green Bank Telescope (GBT) in West Virginia in 2007 in a survey led by astronomers at West Virginia University and the National Radio Astronomy Observatory (NRAO).

The astronomers then found that the object had been detected by NSF's Very Large Array (VLA) radio telescope during a large sky survey in 1998, and had been observed in visible light by the Sloan Digital Sky Survey in 1999, revealing a Sun-like star.

When observed again in 2000, the object had changed dramatically, showing evidence for a rotating disk of material, called an accretion disk, surrounding the neutron star. By May of 2002, the evidence for this disk had disappeared.

"This strange behavior puzzled astronomers, and there were several different theories for what the object could be," said Ingrid Stairs of the University of British Columbia, who has been visiting the Australia Telescope National Facility and Swinburne University this year.

The 2007 GBT observations showed that the object is a millisecond pulsar, spinning 592 times per second.

"No other millisecond pulsar has ever shown evidence for an accretion disk," Archibald said. "We know that another type of binary-star system, called a low-mass X-ray binary (LMXB), also contains a fast-spinning neutron star and an accretion disk, but these don't emit radio waves. We've thought that LMXBs probably are in the process of getting spun up, and will later emit radio waves as a pulsar. This object appears to be the 'missing link' connecting the two types of systems," she explained.

"It appears this thing has flipped from looking like an LMXB to looking like a pulsar, as it experienced an episode during which material pulled from the companion star formed an accretion disk around the neutron star. Later, that mass transfer stopped, the disk disappeared, and the pulsar emerged," said Scott Ransom of the NRAO.

The scientists have studied J1023 in detail with the GBT, with the Westerbork radio telescope in the Netherlands, with the Arecibo radio telescope in Puerto Rico, and with the Parkes radio telescope in Australia. Their results indicate that the neutron star's companion has less than half the Sun's mass, and orbits the neutron star once every four hours and 45 minutes.

"This system gives us an unparalled 'cosmic laboratory' for studying how millisecond pulsars evolve," Stairs said. Maura McLaughlin, of West Virginia University, agrees: "Future observations of this system at radio and other wavelengths are sure to hold many surprises."

Archibald, Ransom, Stairs and McLaughlin are members of an international scientific team with representatives from McGill University, the University of British Columbia, the NRAO, West Virginia University, and others. The scientists announced their discovery in the May 21 online issue of the journal Science.

Contact:
Dave Finley, Public Information Officer
Socorro, NM
(575) 835-7302
dfinley@nrao.edu

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Giant Galaxy Messier 87 finally sized up

Using ESO's Very Large Telescope, astronomers have succeeded in measuring the size of giant galaxy Messier 87 and were surprised to find that its outer parts have been stripped away by still unknown effects. The galaxy also appears to be on a collision course with another giant galaxy in this very dynamic cluster.

ESO PR Photo 19a/09
The Intercluster Light

About this image: This deep image of the Virgo Cluster obtained by Chris Mihos and his colleagues using the Burrell Schmidt telescope shows the diffuse light between the galaxies belonging to the cluster. North is up, east to the left. The dark spots indicate where bright foreground stars were removed from the image.

ESO PR Photo 19b/09
Intergalactic Planetary Nebulae

About this image: Location of the planetary nebulae in the outskirts of the giant galaxy Messier 87 and in the intergalactic space around the centre of the Virgo Cluster of galaxies. By measuring the motions of these objects very precisely, using the highly efficient FLAMES spectrograph on the ESO Very Large Telescope at the Paranal Observatory (Chile), astronomers have probed the edge of Messier 87 for the first time, and found it to be about three times as large as our own Milky Way.

ESO PR Photo 19c/09
The Virgo Cluster

About this image: Image of the Virgo cluster of galaxies taken with the Palomar Observatory 48-inch Schmidt telescope as part of the Digitized Sky Survey 2. The giant elliptical galaxy Messier 87 is seen in the centre, while Messier 84 and 86 are the two bright galaxies forming part of the small group on the centre right of the image. New observations obtained with ESO’s Very Large Telescope have shown that the halo of stars around Messier 87 has been truncated, possibly because of some interaction with Messier 84. The observations also reveal that Messier 87 and 86 are moving towards each other.

The new observations reveal that Messier 87’s halo of stars has been cut short, with a diameter of about a million light-years, significantly smaller than expected, despite being about three times the extent of the halo surrounding our Milky Way [1]. Beyond this zone only few intergalactic stars are seen.

“This is an unexpected result,” says co-author Ortwin Gerhard. “Numerical models predict that the halo around Messier 87 should be several times larger than our observations have revealed. Clearly, something must have cut the halo off early on.”

The team used FLAMES, the super-efficient spectrograph at ESO’s Very Large Telescope at the Paranal Observatory in Chile, to make ultra-precise measurements of a host of planetary nebulae in the outskirts of Messier 87 and in the intergalactic space within the Virgo Cluster of galaxies, to which Messier 87 belongs. FLAMES can simultaneously take spectra many sources, spread over an area of the sky about the size of the Moon.

The new result is quite an achievement. The observed light from a planetary nebula in the Virgo Cluster is as faint as that from a 30-Watt light bulb at a distance of about 6 million kilometres (about 15 times the Earth–Moon distance). Furthermore, planetary nebulae are thinly spread through the cluster, so even FLAMES’s wide field of view could only capture a few tens of nebulae at a time.

“It is a little bit like looking for a needle in a haystack, but in the dark”, says team member Magda Arnaboldi. “The FLAMES spectrograph on the VLT was the best instrument for the job”.

At a distance of approximately 50 million light-years, the Virgo Cluster is the nearest galaxy cluster. It is located in the constellation of Virgo (the Virgin) and is a relatively young and sparse cluster. The cluster contains many hundreds of galaxies, including giant and massive elliptical galaxies, as well as more homely spirals like our own Milky Way.

The astronomers have proposed several explanations for the discovered “cut-off” of Messier 87’s, such as collapse of dark matter nearby in the galaxy cluster. It might also be that another galaxy in the cluster, Messier 84, came much closer to Messier 87 in the past and dramatically perturbed it about a billion years ago. “At this stage, we can’t confirm any of these scenarios,” says Arnaboldi. “We will need observations of many more planetary nebulae around Messier 87”.

One thing the astronomers are sure about, however, is that Messier 87 and its neighbour Messier 86 are falling towards each other. “We may be observing them in the phase just before the first close pass”, says Gerhard. “The Virgo Cluster is still a very dynamic place and many things will continue to shape its galaxies over the next billion years.”

More Information
Planetary nebulae (PNe) are the spectacular final phase in the life of Sun-like stars, when the star ejects its outer layers into the surrounding space. Their name is a relic of an earlier era: early observers, using only small telescopes, thought that some of these nearby objects, such as the “Helix Nebula” resembled the discs of the giant planets in the Solar System. Planetary nebulae have strong emission lines, which make them relatively easy to detect at great distances, and also allow their radial velocities to be measured precisely. So planetary nebulae can be used to investigate the motions of stars in the faint outer regions of distant galaxies where velocity measurements are otherwise not possible. Moreover, planetary nebulae are representative of the stellar population in general. As they are relatively short-lived (a few tens of thousands of years — a mere blip on astronomical timescales), astronomers can estimate that one star in about 8000 million of Sun-like stars is visible as a planetary nebula at any given moment. Thus planetary nebulae can provide a unique handle on the number, types of stars and their motions in faint outer galaxy regions that may harbour a substantial amount of mass. These motions contain the fossil record of the history of galaxy interaction and the formation of the galaxy cluster.

This research is presented in a paper to appear in Astronomy and Astrophysics: “The Edge of the M87 Halo and the Kinematics of the Diffuse Light in the Virgo Cluster Core,” by Michelle Doherty et al.

The team is composed of Michelle Doherty and Magda Arnaboldi (ESO), Payel Das and Ortwin Gerhard (Max-Planck-Institute for Extraterrestrial Physics, Garching, Germany), J. Alfonso L. Aguerri (IAC, Tenerife, Spain), Robin Ciardullo (Pennsylvania State University, USA), John J. Feldmeier (Youngstown State University, USA), Kenneth C. Freeman (Mount Stromlo Observatory, Australia), George H. Jacoby (WIYN Observatory, Tucson, AZ, USA), and Giuseppe Murante (INAF, Osservatorio Astronomico di Pino Torinese, Italy).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe. It is supported by 14 countries: Austria, Belgium, 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 the Atacama Desert region of Chile: La Silla, Paranal and Chajnantor.

Notes
[1] Although the standard value for the diameter of the Milky Way is about 100 000 light-years, its stellar halo is thought to extend out almost twice as far.

Links
Science paper: arxiv:0905.1958 (download the PDF file - 1.15 MB)

Contacts
Magda Arnaboldi
ESO, Garching, Germany
Phone: +49-89-3200-6599
E-mail: marnabol@eso.org

Ortwin Gerhard
MPE, Garching, Germany
Phone: +49-89-30000-3539
E-mail: gerhard@mpe.mpg.de


ESO La Silla - Paranal - ELT Press Officer: Dr. Henri Boffin - +49 89 3200 6222 - hboffin@eso.org
ESO Press Officer in Chile: Valeria Foncea - +56 2 463 3123 - vfoncea@eso.org

National contacts for the media: http://www.eso.org/public/outreach/eson/

MMTO Confirms Ultra-faint Object in Milky Way Halo is Dwarf Galaxy

UA and MMT astronomers are searching for the smallest galaxies in the universe.

How small can a galaxy be?

The MMTO, Mount Hopkins, Ariz.

(Photo: Howard Lester, MMTO)

Astronomers are now finding small-fry galaxies that contain fewer than a million, possibly as few as a thousand, stars.

Until recently, these very faint, dwarf galaxies in the halo of the Milky Way have eluded discovery.

Now astronomers are using advanced techniques and instruments at The University of Arizona/Smithsonian 6.5-meter MMT Observatory at Mount Hopkins, Ariz., to find them.

They reported their latest discovery of such a galaxy, in the constellation Aires, in an online preprint last March. Their research article will be published in Monthly Notices, a publication of the Royal Astronomical Society, this summer.

Ed Olszewski

"These are galaxies that might contain as few as a thousand stars, and those stars are being pulled out into the halo of our Milky Way," said UA astronomer Ed Olszewski. UA astronomy professor Jill Bechtold and MMTO astronomer Tim Pickering are also on the project.

This model shows the halo of the Milky Way created solely from destroyed dwarf galaxies. It mimics the large-scale structure of the Milky Way halo and is qualitatively consistent with modern models of the evolution of structure in the Universe. The Milky Way galactic center is at the very center of the illustration. (Illustration credit: Paul Harding, Case University)

"We're trying to understand whether these unbelievably faint objects are intact or have been mostly pulled apart by the Milky Way," Olszewski said. "We're trying to understand what the halo of the Milky Way really looks like, how many of these objects are in the halo, and whether our census of the population in the halo agrees or conflicts with the cosmological models.

"Knowing how many of these incredibly puny satellite galaxies populate our galactic neighborhood is important if we are to know whether cosmological models used to describe the evolution of the structure of galaxies are correct or way off base," he added.

"The sorts of objects we're finding have so few stars that one might think they're not galaxies at all, except that their internal motions imply that, unlike star clusters, they contain dark matter just like big galaxies do," Olszewski said.

A more accurate census of very faint, local dwarf galaxies is important because it will help scientists determine how much dark matter they might contain, he said. Scientists believe that "dark matter," or matter that is observed only by the effects of gravity but cannot be seen otherwise because it emits no radiation, makes up about 25 percent of the universe. "Normal" matter is thought to make up between 2 percent and 4 percent of the universe, with the remaining bulk being dark energy.

A decade ago, theoretical simulations showed that there must be 10 to 100 times as many objects in the Milky Way halo than observers had seen, Olszewski said. "Now we're coming closer to solving the ‘missing satellites' problem and, simultaneously, understanding how the Milky Way was put together."

Olszewski is a member of the observing team who has been using a wide-field imager called Megacam and a wide-field multi-fiber spectrograph called Hectochelle at the MMTO to confirm the existence of what British collaborators analyzing Sloan Digital Sky Survey data have identified as possible dwarf satellite galaxies.

"Until recently, astronomers could find small satellite galaxies just by looking at a photograph," Olszewski said. "We can image small galaxies that typically have one one-millionth as many stars as the Milky Way has. But the ones we're searching for now are 100 times fainter and won't show up in photographs. They are ridiculously hard to find, because they're so faint and because they're hidden in the foreground stars of the Milky Way itself."

The UA/MMT team collaborates with astronomers at the Institute for Astronomy in Cambridge, England. The British astronomers use a mathematical model of stars with the color and brightness of stars in galaxies they're searching for, moving their model as a kind of template against fields of stars recorded in Sloan Digital Sky Survey maps until they find a pattern match.

The Cambridge astronomers have found about 10 satellite galaxies by this "data mining" technique, Olszewski said, but now they're searching for fainter galaxies, which are harder to find. The Cambridge group works with the UA/MMT to confirm the fainter galaxies are real.

"It's a hard observational follow-up project that couldn't be done without the wonderful instruments built for the MMTO by people at the (Harvard-Smithsonian) Center for Astrophysics," Olszewski said.

Megacam has 36 CCDs that give it power to take deep sky images. Hectochelle has 300 fibers for gathering the spectra, or colors, of stars, which shows how far away stars are.

Observers use star velocity and star chemistry to determine if they have actually found an object in the Milky Way halo rather than in the Milky Way itself.

"Given what we know of the Milky Way halo in the context of all the discoveries so far, the model we made of the Milky Way 10 years ago is still a good one," Olszewski said.

The model can be visualized as a big meatball in a bowl of spaghetti. The meatball is the Milky Way, and spaghetti strands winding away in all different directions represent ripped apart small galaxies.

"We are finding not only little galaxies, we are finding some that are embedded in, or near the bigger, million-star sized galaxies," Olszewski said.

"It's getting to look more and more that that's what the halo of the Milky Way is like, and how the halo is assembled. The halo of a big galaxy largely arises from destruction of littler ones. Over time, the Milky Way will eat not only the little satellite galaxies falling in, but also the Magellanic clouds, " he added. "We're far from done forming the Milky Way."

By Lori Stiles, University Communications
Source: UA News - University of Arizona

NASA's Spitzer Begins Warm Mission

After more than five-and-a-half years of probing the cool cosmos, NASA's Spitzer Space Telescope has run out of the coolant that kept its infrared instruments chilled. The telescope will warm up slightly, yet two of its infrared detector arrays will still operate successfully. The new, warm mission will continue to unveil the far, cold and dusty universe.

Spitzer entered an inactive state called standby mode at 3:11 p.m. Pacific Time (6:11 p.m. Eastern Time or 22:11 Universal Time), May 15, as result of running out of its liquid helium coolant. Scientists and engineers will spend the next few weeks recalibrating the instrument at the warmer temperature, and preparing it to begin science operations.

Additional information, including the following items, is at: http://www.nasa.gov/mission_pages/spitzer/news/spitzer-warm.html.

* A full news release about Spitzer's warm mission and past accomplishments
* A mock interview titled "If Spitzer Could Talk: An Interview with NASA's Coolest Space Mission"
* A video about the Spitzer mission
* An article about the late astronomer Lyman Spitzer, the mission's namesake

Who's Who of the Spitzer mission: NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA's Science Mission Directorate in Washington, D.C. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Lockheed Martin Space Systems in Denver, and Ball Aerospace & Technologies Corp., in Boulder, Colo., support mission and science operations. NASA's Goddard Space Flight Center in Greenbelt, Md., built Spitzer's infrared array camera; the instrument's principal investigator was Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Ball Aerospace & Technologies Corp. built Spitzer's infrared spectrograph; its principal investigator was Jim Houck of Cornell University in Ithaca, N.Y. Ball Aerospace & Technologies Corp. and the University of Arizona in Tucson, built the multiband imaging photometer for Spitzer; its principal investigator was George Rieke of the University of Arizona.

Whitney Clavin 818-354-4673 Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

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3C305 - An Intriguing Glowing Galaxy

Credit: X-ray (NASA/CXC/CfA/F.Massaro, et al.);
Optical (NASA/STScI/C.P.O'Dea);
Radio (NSF/VLA/CfA/F.Massaro, et al.)

Blog: An Intriguing Glowing
GalaxyHandout: html | pdf
Zoom-In (flash)
More Images

Activity from a supermassive black hole is responsible for the intriguing appearance of this galaxy, 3C305, located about 600 million light years away from Earth. The structures in red and light blue are X-ray and optical images from the Chandra X-ray Observatory and Hubble Space Telescope respectively. The optical data is from oxygen emission only, and therefore the full extent of the galaxy is not seen. Radio data are shown in darker blue and are from the National Science Foundation's Very Large Array in New Mexico, as well as the Multi-Element Radio-Linked Interferometer Network in the United Kingdom.

An unexpected feature of this multiwavelength image of 3C305 is that the radio emission -- produced by a jet from the central black hole -- does not closely overlap with the X-ray data. The X-ray emission does, however, seem to be associated with the optical emission.

Using this information, astronomers believe that the X-ray emission could be caused by either one of two different effects. One option is jets from the supermassive black hole (not visible in this image) are interacting with interstellar gas in the galaxy and heating it enough for it to emit X-rays. In this scenario, gas heated by shocks would lie ahead of the jets. The other possibility is that bright radiation from regions close to the black hole infuses enough energy into the interstellar gas to cause it to glow. Deeper X-ray data will be needed to decide between these alternatives.

Fast Facts for 3C305:

Scale: Image is 6 arcsec across
Category: Quasars & Active Galaxies
Coordinates: (J2000) RA 14h 49m 21.37s | Dec +63° 16’ 14.00''
Constellation: Draco
Observation Date: April 7, 2008
Observation Time: 2 hours 10 minutes
Obs. ID: 9330
Color Code: X-ray (Red); Optical (Cyan); Radio (Blue)
Instrument: ACIS
Distance Estimate: About 592 million light years

Let the Planet Hunt Begin

Artist concept of Kepler
Image credit: NASA

Kepler Mission Status Report

NASA's Kepler spacecraft has begun its search for other Earth-like worlds. The mission, which launched from Cape Canaveral, Fla., on March 6, will spend the next three-and-a-half years staring at more than 100,000 stars for telltale signs of planets. Kepler has the unique ability to find planets as small as Earth that orbit sun-like stars at distances where temperatures are right for possible lakes and oceans.

"Now the fun begins," said William Borucki, Kepler science principal investigator at NASA's Ames Research Center, Moffett Field, Calif. "We are all really excited to start sorting through the data and discovering the planets."

Scientists and engineers have spent the last two months checking out and calibrating the Kepler spacecraft. Data have been collected to characterize the imaging performance as well as the noise level in the measurement electronics. The scientists have constructed the list of targets for the start of the planet search, and this information has been loaded onto the spacecraft.

"If Kepler got into a staring contest, it would win," said James Fanson, Kepler project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The spacecraft is ready to stare intently at the same stars for several years so that it can precisely measure the slightest changes in their brightness caused by planets." Kepler will hunt for planets by looking for periodic dips in the brightness of stars -- events that occur when orbiting planets cross in front of their stars and partially block the light.

The mission's first finds are expected to be large, gas planets situated close to their stars. Such discoveries could be announced as early as next year.

Kepler is a NASA Discovery mission. NASA Ames Research Center, Moffett Field, Calif., is the home organization of the science principal investigator, and is responsible for the ground system development, mission operations and science data analysis. JPL manages the Kepler mission development. Ball Aerospace & Technologies Corp. of Boulder, Colo., is responsible for developing the Kepler flight system and supporting mission operations.

For more information about the Kepler mission, visit:
http://www.nasa.gov/kepler and http://www.kepler.nasa.gov .

Media contacts: Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

Michael Mewhinney 650-604-3937
NASA's Ames Research Center, Moffett Field, Calif.
michael.s.mewhinney@nasa.gov

Spitzer Catches Star Cooking Up Comet Crystals

Seeing Crystals Form Around a Young Star

Credit: NASA/JPL-Caltech/P. Ábrahám (Konkoly Obs., Hungarian Academy of Sciences)

Silicate Crystal Formation in the Disk of an Erupting Star
Credit: NASA/JPL-Caltech

Silicate Crystal Formation in the Disk of an Erupting Star
Credit: NASA/JPL-Caltech

Scientists have long wondered how tiny silicate crystals, which need sizzling high temperatures to form, have found their way into frozen comets, born in the deep freeze of the solar system's outer edges. The crystals would have begun as non-crystallized silicate particles, part of the mix of gas and dust from which the solar system developed.

A team of astronomers believes they have found a new explanation for both where and how these crystals may have been created, by using NASA's Spitzer Space Telescope to observe the growing pains of a young, sun-like star. Their study results, which appear in the May 14 issue of Nature, provide new insight into the formation of planets and comets.

The researchers from Germany, Hungary and the Netherlands found that silicate appears to have been transformed into crystalline form by an outburst from a star. They detected the infrared signature of silicate crystals on the disk of dust and gas surrounding the star EX Lupi during one of its frequent flare-ups, or outbursts, seen by Spitzer in April 2008. These crystals were not present in Spitzer's previous observations of the star's disk during one of its quiet periods.

"We believe that we have observed, for the first time, ongoing crystal formation," said one of the paper's authors, Attila Juhasz of the Max-Planck Institute for Astronomy in Heidelberg, Germany. "We think that the crystals were formed by thermal annealing of small particles on the surface layer of the star's inner disk by heat from the outburst. This is a completely new scenario about how this material could be created."

Annealing is a process in which a material is heated to a certain temperature at which some of its bonds break and then re-form, changing the material's physical properties. It is one way that silicate dust can be transformed into crystalline form.

Scientists previously had considered two different possible scenarios in which annealing could create the silicate crystals found in comets and young stars' disks. In one scenario, long exposure to heat from an infant star might anneal some of the silicate dust inside the disk's center. In the other, shock waves induced by a large body within the disk might heat dust grains suddenly to the right temperature to crystallize them, after which the crystals would cool nearly as quickly.

What Juhasz and his colleagues found at EX Lupi didn't fit either of the earlier theories. "We concluded that this is a third way in which silicate crystals may be formed with annealing, one not considered before," said the paper's lead author, Peter Abraham of the Hungarian Academy of Sciences' Konkoly Observatory, Budapest, Hungary.

EX Lupi is a young star, possibly similar to our sun four or five billion years ago. Every few years, it experiences outbursts, or eruptions, that astronomers think are the result of the star gathering up mass that has accumulated in its surrounding disk. These flare-ups vary in intensity, with really big eruptions occurring every 50 years or so.

The researchers observed EX Lupi with Spitzer's infrared spectrograph in April 2008. Although the star was beginning to fade from the peak of a major outburst detected in January, it was still 30 times brighter than when it was quiet. When they compared this new view of the erupting star with Spitzer measurements made in 2005 before the eruption began, they found significant changes.

In 2005, the silicate on the surface of the star's disk appeared to be in the form of amorphous grains of dust. In 2008, the spectrum showed the presence of crystalline silicate on top of amorphous dust. The crystals appear to be forsterite, a material often found in comets and in protoplanetary disks. The crystals also appear hot, evidence that they were created in a high-temperature process, but not by shock heating. If that were the case, they would already be cool.

"At outburst, EX Lupi became about 100 times more luminous," said Juhasz. "Crystals formed in the surface layer of the disk but just at the distance from the star where the temperature was high enough to anneal the silicate--about 1,000 Kelvin (1,340 degrees Fahrenheit)--but still lower than 1,500 Kelvin (2,240 degrees Fahrenheit). Above that, the dust grains will evaporate." The radius of this crystal formation zone, the researchers note, is comparable to that of the terrestrial-planet region in the solar system.

"These observations show, for the first time, the actual production of crystalline silicates like those found in comets and meteorites in our own solar system," said Spitzer Project Scientist Michael Werner of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "So what we see in comets today may have been produced by repeated bursts of energy when the sun was young."

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory
whitney.clavin@jpl.nasa.gov

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Surfing on the light of planet forming dust clouds

Combination of radiation pressure from the star and the disk creates a net force that enables dust grains to surf along the disk surface from inner to outer regions of the disk.

High resolution image: TIFF, JPG

VIDEO: A short animation showing how the newly proposed mechanism of dust movement works.

wmv format - HighRes (9.8Mb)
wmv format - LowRes (4.8Mb)

Rocky planets such as Earth are all believed to have begun as dust circling newly born stars. Ample evidence of this is found in today's meteorites and comets of the solar system, as well as observations of circumstellar disks around young stars. However, details of the evolution of dust and how it eventually comes to form larger objects such as comets and planets are still largely unexplained.
One of the key ingredients in planet and comet formation studies is to understand and account for all mechanisms that influence dust movements through the "protoplanetary disk" - the thick disk of dust and gas where planets and comets are forming. In a paper published in this week's Nature, Dejan Vinković, associate professor of astrophysics at the University of Split, Croatia, describes a new mechanism that moves particles in a previously unexpected way and has the ability to transport them over large distances.

The force produced by the light shining on an object is a well known phenomenon called radiation pressure. We do not feel it in daily lives because we are too massive for this effect to be noticeable. For very small particles, on the other hand, this force can be larger even than the gravity that keeps particles in the orbit around the star. Investigations have been focused so far only to the radiation pressure due to the starlight. The results showed that individual grains would not travel far and would be pushed deeper into the disk.

However, Vinković points out that it is not only the star, but also the disk that shines. When studying effects on protoplanetary dust grains larger than one micrometer, which is comparable to the particle size of cigarette smoke, Vinković has discovered that the intense infrared light from the hottest regions of the protoplanetary disk is capable of pushing such dust out of the disk. Infrared radiation is what we can feel as "heat" on our skin. Combination of radiation pressure from the star and the disk creates a net force that enables dust grains to surf along the disk surface from inner to outer regions of the disk.

The temperatures in this hot region reach around 1500 degrees Kelvin (2200 degrees Fahrenheit), enough to vaporize solid dust particles or to alter their physical and chemical structure. The mechanism that Vinković describes in his paper would transfer such altered dust particles to colder disk regions away form the star. This can explain why comets contain a puzzling combination of ices and particles altered at high temperatures. Astronomers have been perplexed by this mixture, since comets form in cold disk regions out of frozen substances like water, carbon dioxide or methane. Rocky dust particles that end up mixed with ices are therefore expected to never experience high temperatures.

This mechanism is also important for our understanding of the structure of the inner hot part of protoplantary disk, as well as in the interpretation of images and spectra of inner disks that astronomers detect around young stars. Theories aiming at reconstructing the planet formation process need a realistic description of the initial conditions and the disk structure. Vinković points out that his mechanism has to be taken into account because it helps with local mixing of dust grains in the inner disk.

Source: Dejan Vinkovic'
Contact: vinkovic@pmfst.hr

New Horizons Team Remembers Venetia Phair, the ‘Girl Who Named Pluto’

Venetia Burney at age 11, when she suggested the name "Pluto" for the newly discovered ninth planet in 1930. Credit: Venetia Burney Phair (via the BBC)

New Horizons Principal Investigator Alan Stern presents a plaque(1) to Venetia Burney Phair in December 2006, commemorating the name “Venetia” for the New Horizons Student Dust Counter. Read Stern’s account of their meeting at the end of this “PI Perspective” entry.

The team guiding the first mission to Pluto is fondly remembering Venetia Burney Phair, the “little girl” who named the ninth planet when it was discovered nearly 80 years ago. Mrs. Phair died April 30 at her home in Epsom, England, at age 90.

“Venetia's interest and success in naming Pluto as a schoolgirl caught the attention of the world and earned her a place in the history of planetary astronomy that lives on,” says New Horizons Principal Investigator Alan Stern.

In June 2006, the New Horizons team renamed the spacecraft’s Student Dust Counter instrument in her honor, calling it the “Venetia Burney Student Dust Counter” (VBSDC, or just “Venetia” for short). Six months later, in a small ceremony in Mrs. Phair’s home, Stern and SDC Principal Investigator Mihaly Horanyi presented her with a plaque, certificate and spacecraft model to commemorate the renaming. “She was a thoroughly intelligent, likable and endearing woman,” Stern says. “The entire New Horizons team is saddened by her passing.”

The New Horizons dust counter is the first the first science instrument on a NASA planetary mission to be designed, built and operated by students, and by late next year it will be operating farther out in the solar system than any dust measurement instrument in history. Stern and the SDC team members thought it fitting to name instrument built by students after Mrs. Phair, who was just an 11-year-old student herself when she made her historic suggestion of a name for Pluto in 1930.

“Her death deeply saddens the former and current crew of the VBSDC instrument,” says Horanyi, who, like the dust counter student team, is from the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder. “Her contribution will be lasting, not only by naming Pluto, but also by giving an example to young people of the value of intellectual curiosity and the rewards of a lifelong interest in science and discovery.”

(1) Plaque Commemorating the Venetia Burney SDC:
"New Horizons, the first mission to Pluto and the Kuiper Belt, is proud to announce that the student instrument aboard our spacecraft is hereby named “The Venetia Burney Student Dust Counter” in honor of Mrs. Venetia Burney Phair, who at age of eleven nominated the name Pluto for our solar system's ninth planet. May “Venetia” inspire a new generation of students to explore our solar system, to make discoveries which challenge the imagination, and to pursue learning all through their lives."

Links:

Read about the instrument renaming and see photos of the Venetia Burney Student Dust Counter

The Guardian: Venetia Phair, who named Pluto, dies at 90

The Telegraph: Venetia Phair

Forty Thousand Meteor Origins Across the Sky

Forty Thousand Meteor Origins Across the Sky
Credit & Copyright: SonotaCo Network, Japan
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Explanation: Where do meteors come from? Visible meteors are typically sand-sized grains of ice and rock that once fragmented from comets.

Many a meteor shower has been associated with a known comet, although some intriguing orphan showers do remain. Recently, a group of meteor enthusiasts created a network of over 100 video cameras placed at 25 well-separated locations across Japan.

This unprecedented network recorded not only 240,000 optically bright meteors over two years, but almost 40,000 meteors seen by more than one station.

These multiple-station events were particularly interesting because they enabled the observers to extrapolate meteor trajectories back into the Solar System.

The resulting radiant map is shown above, with many well known meteor showers labelled by the first three letters of the home constellation.

Besides known meteor showers, eleven new showers were identified by new radiants on the sky from which meteors appear to flow.

The meteor sky is ever changing, and it may be possible that new shower radiants will appear in the future.

Research like this could also potentially identify previously unknown comets or asteroids that might one day pass close to the Earth.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
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A service of: ASD at NASA / GSFC
& Michigan Tech. U.

Hubble Photographs a Planetary Nebula to Commemorate Decommissioning of Super Camera

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Compass and Scale File for K 4-55

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

The Hubble community bids farewell to the soon-to-be decommissioned Wide Field Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope. In tribute to Hubble's longest-running optical camera, a planetary nebula has been imaged as WFPC2's final "pretty picture."

This planetary nebula is known as Kohoutek 4-55 (or K 4-55). It is one of a series of planetary nebulae that were named after their discoverer, Czech astronomer Lubos Kohoutek. A planetary nebula contains the outer layers of a red giant star that were expelled into interstellar space when the star was in the late stages of its life. Ultraviolet radiation emitted from the remaining hot core of the star ionizes the ejected gas shells, causing them to glow.

In the specific case of K 4-55, a bright inner ring is surrounded by a bipolar structure. The entire system is then surrounded by a faint red halo, seen in the emission by nitrogen gas. This multi-shell structure is fairly uncommon in planetary nebulae.

This Hubble image was taken by WFPC2 on May 4, 2009. The colors represent the makeup of the various emission clouds in the nebula: red represents nitrogen, green represents hydrogen, and blue represents oxygen. K 4-55 is nearly 4,600 light-years away in the constellation Cygnus.

The WFPC2 instrument, which was installed in 1993 to replace the original Wide Field/Planetary Camera, will be removed to make room for Wide Field Camera 3 during the upcoming Hubble Servicing Mission.

During the camera's amazing, nearly 16-year run, WFPC2 provided outstanding science and spectacular images of the cosmos. Some of its best-remembered images are of the Eagle Nebula pillars, Comet P/Shoemaker-Levy 9's impacts on Jupiter's atmosphere, and the 1995 Hubble Deep Field — the longest and deepest Hubble optical image of its time.

The scientific and inspirational legacy of WFPC2 will be felt by astronomers and the public alike, for as long as the story of the Hubble Space Telescope is told.

WFPC2 was developed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Acknowledgment: R. Sahai and J. Trauger (Jet Propulsion Laboratory)

Refined Hubble Constant Narrows Possible Explanations for Dark Energy

Image Type: Astronomical/Illustration
Credit: NASA, ESA, and A. Riess (STScI/JHU)

About this image: This is a Hubble Space Telescope photo of the spiral galaxy NGC 3021. This was one of several hosts of recent Type Ia supernovae observed by astronomers to refine the measure of the universe's expansion rate, called the Hubble constant. Hubble made precise measurements of Cepheid variable stars in the galaxy, highlighted by green circles in the four inset boxes. These stars pulsate at a rate that is matched closely to their intrinsic brightness. This makes them ideal for measuring intergalactic distances. The Cepheids are used to calibrate an even brighter milepost marker that can be used over greater distances, a Type Ia supernova. The supernova was observed in the galaxy in 1995. The images in the boxes were taken with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).

Image Type: Illustration

Credit: NASA, ESA, and A. Feild (STScI)

About this image: Hubble measurements have simplified the cosmic "distance ladder," which is needed to calculate a more precise value for the universe's expansion rate, called the Hubble constant. At select host galaxies, Cepheid variable stars — known as reliable milepost markers — are cross-calibrated to Type Ia supernovae in the same host galaxy. The new technique reduced the distance ladder to three "rungs": (1) The distance to galaxy NGC 4258 is measured using straightforward geometry and Kepler's laws; (2) Cepheids in six more distant galaxies are used to calibrate the luminosity of Type Ia supernovae; (3) The Hubble constant is measured by observing a brighter milepost marker, Type Ia supernovae, in more distant galaxies hundreds of millions of light-years away, embedded in the expanding universe.

INTRODUCTION

Less than 100 years ago scientists didn't know if the universe was coming or going, literally. It even fooled the great mind of Albert Einstein. He assumed the universe must be static. But to keep the universe from collapsing under gravity like a house of cards, Einstein hypothesized there was a repulsive force at work, called the cosmological constant, that counterbalanced gravity's tug. Along came Edwin Hubble in 1923 who found that galaxies were receding from us at a proportional rate, called the Hubble constant, which meant the universe was uniformly expanding, so there was no need to shore it up with any mysterious force from deep space. In measuring how this expansion was expected to slow down over time, 11 years ago, two studies, one led by Adam Riess of the Space Telescope Science Institute and the Johns Hopkins University and Brian Schmidt of Mount Stromlo Observatory, and the other by Saul Perlmutter of Lawrence Berkeley National Laboratory, independently discovered dark energy, which seems to behave like Einstein's cosmological constant.

To better characterize dark energy, Riess used Hubble Space Telescope's crisp view (combined with 2003 data from NASA's Wilkinson Microwave Anisotropy Probe, WMAP) to refine the value of the universe's expansion rate to a precision of three percent. That's a big step from 20 years ago when astronomers' estimates for the Hubble constant disagreed by a factor of two. This new value implies that dark energy really is a steady push on the universe as Einstein imagined, rather than something more effervescent (like the early inflationary universe) that changes markedly over time.

Whatever dark energy is, explanations for it have less wiggle room following a Hubble Space Telescope observation that has refined the measurement of the universe's present expansion rate to a precision where the error is smaller than five percent. The new value for the expansion rate, known as the Hubble constant, or H0 (after Edwin Hubble who first measured the expansion of the universe nearly a century ago), is 74.2 kilometers per second per megaparsec (error margin of ± 3.6). The results agree closely with an earlier measurement gleaned from Hubble of 72 ± 8 km/sec/megaparsec, but are now more than twice as precise.

The Hubble measurement, conducted by the SHOES (Supernova H0 for the Equation of State) Team and led by Adam Riess, of the Space Telescope Science Institute and the Johns Hopkins University, uses a number of refinements to streamline and strengthen the construction of a cosmic "distance ladder," a billion light-years in length, that astronomers use to determine the universe's expansion rate.

Hubble observations of pulsating stars called Cepheid variables in a nearby cosmic mile marker, the galaxy NGC 4258, and in the host galaxies of recent supernovae, directly link these distance indicators. The use of Hubble to bridge these rungs in the ladder eliminated the systematic errors that are almost unavoidably introduced by comparing measurements from different telescopes.

Riess explains the new technique: "It's like measuring a building with a long tape measure instead of moving a yard stick end over end. You avoid compounding the little errors you make every time you move the yardstick. The higher the building, the greater the error."

Lucas Macri, professor of physics and astronomy at Texas A&M, and a significant contributor to the results, said, "Cepheids are the backbone of the distance ladder because their pulsation periods, which are easily observed, correlate directly with their luminosities. Another refinement of our ladder is the fact that we have observed the Cepheids in the near-infrared parts of the electromagnetic spectrum where these variable stars are better distance indicators than at optical wavelengths."

This new, more precise value of the Hubble constant was used to test and constrain the properties of dark energy, the form of energy that produces a repulsive force in space, which is causing the expansion rate of the universe to accelerate.

By bracketing the expansion history of the universe between today and when the universe was only approximately 380,000 years old, the astronomers were able to place limits on the nature of the dark energy that is causing the expansion to speed up. (The measurement for the far, early universe is derived from fluctuations in the cosmic microwave background, as resolved by NASA's Wilkinson Microwave Anisotropy Probe, WMAP, in 2003.)

Their result is consistent with the simplest interpretation of dark energy: that it is mathematically equivalent to Albert Einstein's hypothesized cosmological constant, introduced a century ago to push on the fabric of space and prevent the universe from collapsing under the pull of gravity. (Einstein, however, removed the constant once the expansion of the universe was discovered by Edwin Hubble.)

"If you put in a box all the ways that dark energy might differ from the cosmological constant, that box would now be three times smaller," says Riess. "That's progress, but we still have a long way to go to pin down the nature of dark energy."

Though the cosmological constant was conceived of long ago, observational evidence for dark energy didn't come along until 11 years ago, when two studies, one led by Riess and Brian Schmidt of Mount Stromlo Observatory, and the other by Saul Perlmutter of Lawrence Berkeley National Laboratory, discovered dark energy independently, in part with Hubble observations. Since then astronomers have been pursuing observations to better characterize dark energy.

Riess's approach to narrowing alternative explanations for dark energy—whether it is a static cosmological constant or a dynamical field (like the repulsive force that drove inflation after the big bang)—is to further refine measurements of the universe's expansion history.

Before Hubble was launched in 1990, the estimates of the Hubble constant varied by a factor of two. In the late 1990s the Hubble Space Telescope Key Project on the Extragalactic Distance Scale refined the value of the Hubble constant to an error of only about ten percent. This was accomplished by observing Cepheid variables at optical wavelengths out to greater distances than obtained previously and comparing those to similar measurements from ground-based telescopes.

The SHOES team used Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Advanced Camera for Surveys (ACS) to observe 240 Cepheid variable stars across seven galaxies. One of these galaxies was NGC 4258, whose distance was very accurately determined through observations with radio telescopes. The other six galaxies recently hosted Type Ia supernovae that are reliable distance indicators for even farther measurements in the universe. Type Ia supernovae all explode with nearly the same amount of energy and therefore have almost the same intrinsic brightness.

By observing Cepheids with very similar properties at near-infrared wavelengths in all seven galaxies, and using the same telescope and instrument, the team was able to more precisely calibrate the luminosity of supernovae. With Hubble's powerful capabilities, the team was able to sidestep some of the shakiest rungs along the previous distance ladder involving uncertainties in the behavior of Cepheids.

Riess would eventually like to see the Hubble constant refined to a value with an error of no more than one percent, to put even tighter constraints on solutions to dark energy.

CONTACT

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

Adam Riess
Space Telescope Science Institute/Johns Hopkins University, Baltimore, Md.
410-516-4474
ariess@stsci.edu

ESA to launch two large observatories to look deep into space and time

Herschel and Planck

Credits: ESA

Two of the most sophisticated astronomical spacecraft ever built – Herschel and Planck – will be launched by ESA this month towards deep space orbits around a special observation point beyond the Moon’s orbit.

From there, both spacecraft will begin a revolutionary observation campaign that will further our understanding of the history of the Universe.
Herschel is a large far-infrared space telescope designed to study some of the coldest objects in space, in a part of the electromagnetic spectrum still mostly unexplored. Planck is a telescope that will map the fossil light of the Universe - light from the Big Bang – with unprecedented sensitivity and accuracy. The two missions are among the most ambitious ever carried out by Europe and mark the crossing of new frontiers in the field of space-based astronomy.

The pair will be lofted in tandem by an Ariane 5 ECA launcher. Lift-off is now scheduled for 15:12 CEST (13:12 GMT) on Thursday 14 May, from Europe’s Spaceport in French Guiana. Herschel and Planck will separate shortly after launch and head independently towards the L2 Lagrangian point of the Sun-Earth system, a gravitational stability point suspended in space some 1.5 million kilometres from Earth in the opposite direction to the Sun. While orbiting around that point, they will be able to conduct continuous observations in a thermally-stable environment, far from radiation disturbance caused by the Sun, Earth and Moon.

The 7.5-m-tall, 4-m-wide Herschel is the largest infrared telescope ever launched. The extremely smooth surface of its 3.5-m-diameter primary mirror – made of lightweight silicon carbide – is almost one and a half times bigger than that of Hubble’s, and six times bigger than that of its predecessor ISO launched by ESA in 1995.

With its huge light-collection capability and set of sophisticated detectors cooled to the vicinity of absolute zero by over 2000 litres of superfluid helium, Herschel will look at the faintest and farthest infrared sources and peer into the as-yet uncharted far infrared and submillimetric parts of the spectrum.

Herschel will be able to see through the opacity of cosmic dust and gas and observe structures and events far away that date back to the early Universe – such as the birth and evolution of early stars and galaxies – ten thousand million years ago, in an effort to determine exactly how it all started. Closer by, within our galaxy, Herschel will also observe extremely cold objects, such as the clouds of dust and interstellar gases from which stars and planets are formed, and even the atmosphere around comets, planets and their moons in our own solar system.

Featuring a 1.5 m telescope and instruments sensitive to microwave radiation, Planck will measure temperature variations in the very early Universe. It will monitor the so- called Cosmic Microwave Background, the relic of the very first light ever emitted in space about 380 thousand years after the Big Bang, when the density and temperature of the young Universe had decreased enough to finally allow light to separate from matter and travel freely in space.

With its ‘heart’ operating at unprecedented low temperatures, Planck will deliver unrivalled sensitivity and resolution. By measuring the tiny fluctuations in the temperature of the microwave background radiation, scientists will extract at least 15 times more information about the Universe’s origin, evolution and future than with its most recent predecessor.

Herschel’s detectors will be cooled down to 0.3 degrees above absolute zero. Planck’s detectors will reach even colder temperatures, just 0.1 degrees above 0 K. Indeed, throughout the mission, the coldest points of the Universe may well be inside its payload. The satellite is planned to take some 500 thousand million of raw samples to produce a set of multi-million-pixel sky maps that will also help scientists to understand the Universe’s structure and account as never before for all of its constituents. Planck will be able to determine the total amount of atoms in the Universe, infer the total density of dark matter – an elusive component still inaccessible to direct observations but ‘visible’ through its effects on the surroundings – and even shed new light on the nature of the mysterious dark energy.

Herschel and Planck, two impressive missions designed to revolutionise our understanding of the cosmos, also represent a tremendous technological challenge that has been overcome by ESA thanks to the mobilising of over 100 industrial partners and institutes in Europe, the United States and elsewhere.

Attending the launch

The main launch event for Herschel/Planck will be held at ESOC, the Agency’s establishment in Darmstadt, Germany. There, ESA senior management and programme specialists will be on hand to give explanations and interviews

The Press Centre at ESOC will be open from 10:00 to 18:00 hours, hosting a media workshop from 11:00 to 12:15 hours and the launch event from 14:00 to 16:15 hours.

A live TV transmission of the launch will supply images from Kourou and from mission control at ESOC/Darmstadt to broadcasters (further details will soon be available at http://television.esa.int).

The general public can also follow the launch video transmission via web-streaming at: http://www.esa.int

Media representatives wishing to follow the event at ESOC or watch the launch live from another ESA establishment are requested to fill in the attached accreditation form (linked from the right menu on this page) and fax it back to the venue of their choice.

Note for editors

Herschel and Planck under ESA’s Science Programme

Herschel and Planck are the last missions to be launched under ESA’s Horizon 2000 long-term plan for space science initiated in 1985, which has already brought the worldwide scientific community a series of trail-blazing successes including: the Integral gamma-ray and XMM-Newton X-ray observatories; the Huygens probe that landed on Saturn’s largest moon, Titan; the Ulysses, Soho and Cluster missions monitoring the Sun, its sphere of influence and Sun-Earth interaction; the Smart-1, Mars Express and Venus Express lunar and planetary explorers; and the Rosetta comet chaser currently mid-way to its final target, the nucleus of comet Churyumov-Gerasimenko. Over the past 25 years, the Horizon 2000 plan and its successors Horizon 2000+ and Cosmic Vision, have set the standard for successful space science in Europe and laid the foundations for the future scientific exploration of space, giving Europe international stature when it comes to cooperation.

Herschel and Planck – the result of a huge international effort
Herschel and Planck have been built under a common engineering programme carried out on ESA’s behalf by Thales Alenia Space (Cannes, France) as prime contractor, also responsible for the Planck payload module, heading a consortium of industrial partners with Astrium (Friedrichshafen, Germany) responsible for the Herschel payload module and Thales Alenia Space (Turin, Italy) responsible for the service modules. Astrium (Toulouse, France) provided the Herschel telescope. The Planck telescope was provided through collaboration between ESA and the Danish National Space Centre.

Academic and industrial consortia from across the world have designed and manufactured the Herschel and Planck onboard instruments.

Herschel features three instruments: the HIFI high-resolution spectrometer, consortium led by the SRON Netherlands Institute for Space Research (The Netherlands); the PACS camera and imaging spectrometer, consortium led by the Max Planck Institute for Extraterrestrial Physics (Germany); and the SPIRE camera and imaging spectrometer, consortium led by Cardiff University (Wales, United Kingdom). Important contributions were also made by the United States (NASA), Canada and Poland.

Planck features two instruments: the HFI high-frequency instrument, consortium led by the Institut d’Astrophysique Spatiale (France); and the LFI low-frequency instrument, consortium led by the Istituto di Astrofisica Spaziale e Fisica Cosmica (Italy), with the United States (NASA) making an important contribution.

NASA's Spitzer Telescope Warms up to New Career

The primary mission of NASA's Spitzer Space Telescope is about to end after more than five and a half years of probing the cosmos with its keen infrared eye. Within about a week of May 12, the telescope is expected to run out of the liquid helium needed to chill some of its instruments to operating temperatures.

The end of the coolant will begin a new era for Spitzer. The telescope will start its "warm" mission with two channels of one instrument still working at full capacity. Some of the science explored by a warm Spitzer will be the same, and some will be entirely new.

"We like to think of Spitzer as being reborn," said Robert Wilson, Spitzer project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Spitzer led an amazing life, performing above and beyond its call of duty. Its primary mission might be over, but it will tackle new scientific pursuits, and more breakthroughs are sure to come."

Spitzer is the last of NASA's Great Observatories, a suite of telescopes designed to see the visible and invisible colors of the universe. The suite also includes NASA's Hubble and Chandra space telescopes. Spitzer has explored, with unprecedented sensitivity, the infrared side of the cosmos, where dark, dusty and distant objects hide.

For a telescope to detect infrared light — essentially heat — from cool cosmic objects, it must have very little heat of its own. During the past five years, liquid helium has run through Spitzer's "veins," keeping its three instruments chilled to -456 degrees Fahrenheit (-271 Celsius), or less than 3 degrees above absolute zero, the coldest temperature theoretically attainable. The cryogen was projected to last as little as two and a half years, but Spitzer's efficient design and careful operations enabled it to last more than five and a half years.

Spitzer's new "warm" temperature is still quite chilly at -404 degrees Fahrenheit (-242 Celsius) — much colder than a winter day in Antarctica when temperatures sometimes reach -75 degrees Fahrenheit (-59 Celsius). This temperature rise means two of Spitzer's instruments — its longer wavelength multiband imaging photometer and its infrared spectrograph — will no longer be cold enough to detect cool objects in space.

However, the telescope's two shortest-wavelength detectors in its infrared array camera will continue to function perfectly. They will still pick up the glow from a range of objects: asteroids in our solar system, dusty stars, planet-forming disks, gas-giant planets and distant galaxies. In addition, Spitzer still will be able to see through the dust that permeates our galaxy and blocks visible-light views.

"We will do exciting and important science with these two infrared channels," said Spitzer Project Scientist Michael Werner of JPL. Werner has been working on Spitzer for more than 30 years. "Our new science program takes advantage of what these channels do best. We're focusing on aspects of the cosmos that we still have much to learn about."

Since its launch from Cape Canaveral, Fla., on Aug. 25, 2003, Spitzer has made countless breakthroughs in astronomy. Observations of comets both near and far have established that the stuff of comets and planets is similar throughout the galaxy. Breathtaking photos of dusty stellar nests have led to new insights into how stars are born. And Spitzer's eye on the very distant universe, billions of light-years away, has revealed hundreds of massive black holes lurking in the dark.

Perhaps the most revolutionary and surprising Spitzer finds involve planets around other stars, called exoplanets. Exoplanets are, in almost all cases, too close to their parent stars to be seen from our Earthly point of view. Nevertheless, planet hunters continue to uncover them by looking for changes in the parent stars. Before Spitzer, everything we knew about exoplanets came from indirect observations such as these.

In 2005, Spitzer detected the first light, or photons, from an exoplanet. In a clever technique, now referred to as the secondary-eclipse method, Spitzer was able to collect the light of a hot, gaseous exoplanet and learn about its temperature. Further detailed spectroscopic studies later revealed more about the atmospheres, or "weather," on similar planets. More recently, Spitzer witnessed changes in the weather on a wildly eccentric gas exoplanet — a storm of colossal proportions brewing up in a matter of hours before quickly settling down.

"Nobody had any idea Spitzer would be able to directly study exoplanets when we designed it," Werner said. "When astronomers planned the first observations, we had no idea if they would work. To our amazement and delight, they did."

These are a few of Spitzer's achievements during the past five and a half years. Data from the telescope are cited in more than 1,500 scientific papers. And scientists and engineers expect the rewards to keep on coming during Spitzer's golden years.

Some of Spitzer's new pursuits include refining estimates of Hubble's constant, or the rate at which our universe is stretching apart; searching for galaxies at the edge of the universe; assessing how often potentially hazardous asteroids might impact Earth by measuring the sizes of asteroids; and characterizing the atmospheres of gas-giant planets expected to be discovered soon by NASA's Kepler mission. As was true during the cold Spitzer mission, these and the other programs are selected through a competition in which scientists from around the world are invited to participate.

Whitney Clavin 818-354-4673 Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

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