Tuesday, September 30, 2014

Cassini Watches Mysterious Feature Evolve in Titan Sea

These three images, created from Cassini Synthetic Aperture Radar (SAR) data, show the appearance and evolution of a mysterious feature in Ligeia Mare, one of the largest hydrocarbon seas on Saturn's moon Titan. Image credit: NASA/JPL-Caltech/ASI/Cornell. Full image and caption(Images of the feature taken during the Cassini flybys)

NASA's Cassini spacecraft is monitoring the evolution of a mysterious feature in a large hydrocarbon sea on Saturn's moon Titan. The feature covers an area of about 100 square miles (260 square kilometers) in Ligeia Mare, one of the largest seas on Titan. It has now been observed twice by Cassini's radar experiment, but its appearance changed between the two apparitions.

The mysterious feature, which appears bright in radar images against the dark background of the liquid sea, was first spotted during Cassini's July 2013 Titan flyby. Previous observations showed no sign of bright features in that part of Ligeia Mare. Scientists were perplexed to find the feature had vanished when they looked again, over several months, with low-resolution radar and Cassini's infrared imager. This led some team members to suggest it might have been a transient feature. But during Cassini's flyby on August 21, 2014, the feature was again visible, and its appearance had changed during the 11 months since it was last seen.

Scientists on the radar team are confident that the feature is not an artifact, or flaw, in their data, which would have been one of the simplest explanations. They also do not see evidence that its appearance results from evaporation in the sea, as the overall shoreline of Ligeia Mare has not changed noticeably.

The team has suggested the feature could be surface waves, rising bubbles, floating solids, solids suspended just below the surface, or perhaps something more exotic. 

The researchers suspect that the appearance of this feature could be related to changing seasons on Titan, as summer draws near in the moon's northern hemisphere. Monitoring such changes is a major goal for Cassini's current extended mission.

"Science loves a mystery, and with this enigmatic feature, we have a thrilling example of ongoing change on Titan," said Stephen Wall, the deputy team lead of Cassini's radar team, based at NASA's Jet Propulsion Laboratory in Pasadena, California. "We're hopeful that we'll be able to continue watching the changes unfold and gain insights about what's going on in that alien sea."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.

For more information about Cassini and its mission, visit:  http://www.nasa.gov/cassini - http://saturn.jpl.nasa.gov


Preston Dyches
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-7013

preston.dyches@jpl.nasa.gov

  Source: JPL - Caltech


Signs of the formation of a planetary system around the star HD 169142

Image at 7 mm wavelength of the dusty disk around the star HD 169142 obtained with the Very Large Array (VLA) at 7 mm wavelength. The positions of the protoplanet candidates are marked with plus signs (+) (Osorio et al. 2014, ApJ, 791, L36). The insert in the upper right corner shows, at the same scale, the bright infrared source in the inner disk cavity, as observed with the Very Large Telescope (VLT) at 3.8 micron wavelength (Reggiani et al. 2014, ApJ, 792, L23). 

Young star HD169142 displays a disk of gas and dust with two annular gaps possibly due to the formation of planets

Planets are formed from disks of gas and dust that orbit around young stars. Once the “seed” of the planet —composed of a small aggregate of dust— is formed, it will continue to gather material and it will carve out a cavity or gap in the disk along its orbital path.

This transitional stage between the original disk and the planetary system, difficult to study and as yet little known, is precisely what has been observed in the star HD169142 and is discussed in two articles published in The Astrophysical Journal Letters.

"Although in recent years more than seventeen hundred extrasolar planets have been discovered, few of them have been directly imaged, and so far we have never been able to capture an unequivocal image of an still-forming planet”, says Mayra Osorio, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) heading one of the articles. “In HD 169142 we may be seeing indeed those seeds of gas and dust which will later become planets."

HD169142 is a young star with twice the mass of the Sun and whose disk extends up to two hundred and fifty astronomical units (an astronomical unit, or AU, is a unit equivalent to the distance between the Sun and the Earth: one hundred and fifty million kilometers). The system is in an optimal orientation for the study of planet formation because the disk is seen face-on.

The first article explores the disk of HD169142 with the Very Large Array radio telescope, which can detect centimeter-sized dust grains. The results, combined with infrared data which trace the presence of microscopic dust, reveal two gaps in the disk, one in the inner region (between 0.7 and 20 AU) and another, farther out and less developed, between 30 and 70 AU. 

"This structure already suggested that the disk was being modified by two planets or sub-stellar objects, but, additionally, the radio data reveal the existence of a clump of material within the external gap, located approximately at the distance of Neptune’s orbit, which points to the existence of a forming planet”, says Mayra Osorio (IAA-CSIC).

ONE (OR TWO) COMPANIONS AROUND HD169142

The second study focused on searching for infrared sources in the gaps of the disk, using the Very Large Telescope. They found a bright signal in the inner gap, which could correspond to a still-forming planet or to a young brown dwarf (a sort of failed star that never reached the threshold mass to trigger the nuclear reactions characteristic of stars).

Infrared data did not, however, corroborate the presence of an object in the outer gap as radio observations suggested. This non detection could be due to technical limitations: the researchers have calculated that an object with a mass between one tenth and 18 times the Jupiter’s mass surrounded by a cold envelope may well remain undetected at the observed wavelength.   

"In future observations we will be able to verify whether the disk harbors one or two objects. In any case, HD 169142 remains as a promising object since it is one of the few known transitional disks and it is revealing to us the environment where planets are formed", says Mayra Osorio (IAA-CSIC).

An artist's impression of a protoplanetary disk
Credit: ESO/L. Calçada

Reference:

M. Osorio et al. "Imaging the Inner and Outer Gaps of the Pre-Transitional Disk of HD 169142 at 7 mm". The Astrophysical Journal ApJ 791 L36. DOI: 10.1088/2041-8205/791/2/L36

M. Reggiani et al. "Discovery of a companion candidate in the HD169142 transition disk and the possibility of multiple planet formation". The Astrophysical Journal. 792, L23, DOI: 10.1088/2041-8205/792/1/L23

Contact:
Instituto de Astrofísica de Andalucía (IAA-CSIC)
Unidad de Divulgación y Comunicación
Silbia López de Lacalle
- Email:  sll@iaa.es - 958230532

Instituto de Astrofísica de Andalucía - (IAA- CSIC)
http://www-divulgacion.iaa.es


Monday, September 29, 2014

Interstellar molecules are branching out

Dust and molecules in the central region of our Galaxy: The background image shows the dust emission in a combination of ... [more] © MPIfR/A. Weiß (background image), University of Cologne/M. Koerber (molecular models), MPIfR/A. Belloche (montage).

The central region of the Milky Way above the antennas of the ALMA observatory. The direction to the Galactic center is ... [more] © Y. Beletsky (LCO)/ESO


Detection of iso-propyl cyanide with ALMA, the Atacama Large Millimeter/submillimeter Array

Scientists from the Max Planck Institute for Radio Astronomy (Bonn, Germany), Cornell University (USA), and the University of Cologne (Germany) have for the first time detected a carbon-bearing molecule with a "branched" structure in interstellar space. The molecule, iso-propyl cyanide (i-C3H7CN), was discovered in a giant gas cloud called Sagittarius B2, a region of ongoing star formation close to the center of our galaxy that is a hot-spot for molecule-hunting astronomers. The branched structure of the carbon atoms within the iso-propyl cyanide molecule is unlike the straight-chain carbon backbone of other molecules that have been detected so far, including its sister molecule normal-propyl cyanide. The discovery of iso-propyl cyanide opens a new frontier in the complexity of molecules found in regions of star formation, and bodes well for the presence of amino acids, for which this branched structure is a key characteristic.
The results are published in this week’s issue of “Science”.

While various types of molecules have been detected in space, the kind of hydrogen-rich, carbon-bearing (organic) molecules that are most closely related to the ones necessary for life on Earth appear to be most plentiful in the gas clouds from which new stars are being formed. "Understanding the production of organic material at the early stages of star formation is critical to piecing together the gradual progression from simple molecules to potentially life-bearing chemistry," says Arnaud Belloche from the Max Planck Institute for Radio Astronomy, the lead author of the paper.

The search for molecules in interstellar space began in the 1960's, and around 180 different molecular species have been discovered so far. Each type of molecule emits light at particular wavelengths, in its own characteristic pattern, or spectrum, acting like a fingerprint that allows it to be detected in space using radio telescopes.

Until now, the organic molecules discovered in star-forming regions have shared one major structural characteristic: they each consist of a "backbone" of carbon atoms that are arranged in a single and more or less straight chain. The new molecule discovered by the team, iso-propyl cyanide, is unique in that its underlying carbon structure branches off in a separate strand. "This is the first ever interstellar detection of a molecule with a branched carbon backbone," says Holger Müller, a spectroscopist at the University of Cologne and co-author on the paper, who measured the spectral fingerprint of the molecule in the laboratory, allowing it to be detected in space.

But it is not just the structure of the molecule that surprised the team - it is also plentiful, at almost half the abundance of its straight-chain sister  molecule, normal-propyl cyanide (n-C3H7CN), which the team had already  detected using the single-dish radio telescope of the Institut de Radioastronomie Millimétrique (IRAM) a few years ago. "The enormous abundance of iso-propyl cyanide suggests that branched molecules may in fact be the rule, rather than the exception, in the interstellar medium," says Robin Garrod, an astrochemist at Cornell University and a co-author of the paper.

The team used the Atacama Large Millimeter/submillimeter Array (ALMA), in Chile, to probe the molecular content of the star-forming region Sagittarius B2 (Sgr B2). This region is located close to the Galactic Center, at a distance of about 27,000 light years from the Sun, and is uniquely rich in emission from complex interstellar organic molecules. "Thanks to the new capabilities offered by ALMA, we were able to perform a full spectral survey toward Sgr B2 at wavelengths between 2.7 and 3.6 mm, with sensitivity and spatial resolution ten times greater than our previous survey," explains Belloche. "But this took only a tenth of the time." The team used this spectral survey to search systematically for the fingerprints of new interstellar molecules. "By employing predictions from the Cologne Database for Molecular Spectroscopy, we could identify emission features from both varieties of propyl cyanide," says Müller. As many as 50 individual features for i-propyl cyanide and even 120 for n-propyl cyanide were unambiguously identified in the ALMA spectrum of Sgr B2. The two molecules, each consisting of 12 atoms, are also the joint-largest molecules yet detected in any star-forming region.

The team constructed computational models that simulate the chemistry of formation of the molecules detected in Sgr B2. In common with many other complex organics, both forms of propyl cyanide were found to be efficiently formed on the surfaces of interstellar dust grains. "But," says Garrod, "the models indicate that for molecules large enough to produce branched side-chain structure, these may be the prevalent forms. The detection of the next member of the alkyl cyanide series, n-butyl cyanide (n-C4H9CN), and its three branched isomers would allow us to test this idea".

"Amino acids identified in meteorites have a composition that suggests they originate in the interstellar medium," adds Belloche. “Although no interstellar amino acids have yet been found, interstellar chemistry may be responsible for the production of a wide range of important complex molecules that eventually find their way to planetary surfaces."

"The detection of iso-propyl cyanide tells us that amino acids could indeed be present in the interstellar medium because the side-chain structure is a key characteristic of these molecules", says Karl Menten, director at MPIfR and head of its Millimeter and Submillimeter Astronomy research department. "Amino acids have already been identified in meteorites and we hope to detect them in the interstellar medium in the future", he concludes.

Original Paper

 



Contact

Dr. Arnaud Belloche
Phone:+49 228 525-376
Max-Planck-Institut für Radioastronomie, Bonn
Email: belloche@mpifr-bonn.mpg.de

Dr. Robin T. Garrod
Phone:+1 607-255-8967
Center for Radiophysics and Space Research, Cornell University, U.S.A.
Email: rgarrod@astro.cornell.edu

Dr. Holger Müller
Phone:+49 221 470-4528
I. Physikalisches Institut, Universität zu Köln
Email: hspm@ph1.uni-koeln.de

Dr. Norbert Junkes
Presse- und Öffentlichkeitsarbeit
Phone:+49 228 525-399
Max-Planck-Institut für Radioastronomie, Bonn
Email: njunkes@mpifr-bonn.mpg.de




Saturday, September 27, 2014

The Architecture of Planetary Systems

Astronomers have analyzed the orbits of 365 observed systems of suspected, multiple exoplanets. This figure shows the relative placements and sizes of the planets in systems with three or more planets. The horizontal axis shows the orbital period in days for these systems, in all of which the planets are very to their stars and so complete their annual orbit in under about 100 days (a few suspected planets orbit in under one day!). The planetary radii are colored with the largest in each system being red; most of the planets in this study are between about one and four Earth-radii. NASA/Kepler; Fabrycky

There are 1822 confirmed exoplanets reported so far, and NASA's Kepler satellite has found evidence for more than two thousand others. Many exoplanets are expected to be in systems with multiple planets; indeed, one Kepler system is thought to contain seven or perhaps even more planets. As astronomers amass data on the characteristics of planets of all kinds, the large number of expected planetary systems allows them to study as well the nature of these systems and the stability of the orbits over time.

CfA astronomers Darin Ragozzine, John Geary, and Matt Holman, together with their colleagues, have analyzed 899 transiting planet candidates in 365 systems in an effort to understand the statistical properties of planetary systems and the extent to which our solar system might be unusual. The most complex system in their set has six planets. The sample is dominated by planets between about one and four Earth-radii in size and which orbit their stars in about ten days, making the planets hot and not Earth-like.

The astronomers found one striking feature of these exoplanetary systems: the planets seemed to lie in the same plane, to within an estimated 2.5 degrees (the team also estimates how this value might vary in time). For comparison, the solar system's planets are coplanar to about 3 degrees, with Mercury being an outlier with its angle of seven degrees; Pluto (not a planet) has an orbital angle of seventeen degrees. The team argues that this exoplanet result suggests that the individual planetary orbits are each nearly circular, a significant conclusion because it means the orbits are not likely to overlap, and hence implies (at least for systems of close-in planets) that they have long-term stability. The new paper marks continuing significant progress in unraveling the picture of planets and planetary systems in the universe.

Reference(s): 

"Architecture of Kepler's Multi-Transiting Systems. II. New Investigations with Twice as Many Candidates," Daniel C. Fabrycky, Jack J. Lissauer, Darin Ragozzine, Jason F. Rowe, Jason H. Steffen, Eric Agol, Thomas Barclay, Natalie Batalha, William Borucki, David R. Ciardi, Eric B. Ford, Thomas N. Gautier, John C. Geary, Matthew J. Holman, Jon M. Jenkins, Jie Li, Robert C. Morehead, Robert L. Morris, Avi Shporer, Jeffrey C. Smith, Martin Still, and Jeffrey Van Cleve, ApJ 790, 146, 2014


Earth’s Water is Older than the Sun

An illustration of water in our Solar System through time from before the Sun’s birth through the creation of the planets. The image is credited to Bill Saxton, NSF/AUI/NRAO. A larger version is available here. Another image is available here.

Washington, D.C.—Water was crucial to the rise of life on Earth and is also important to evaluating the possibility of life on other planets. Identifying the original source of Earth’s water is key to understanding how life-fostering environments come into being and how likely they are to be found elsewhere. New work from a team including Carnegie’s Conel Alexander found that much of our Solar System’s water likely originated as ices that formed in interstellar space. Their work is published in Science.

Water is found throughout our Solar System. Not just on Earth, but on icy comets and moons, and in the shadowed basins of Mercury. Water has been found included in mineral samples from meteorites, the Moon, and Mars.

Comets and asteroids in particular, being primitive objects, provide a natural “time capsule” of the conditions during the early days of our Solar System. Their ices can tell scientists about the ice that encircled the Sun after its birth, the origin of which was an unanswered question until now.

In its youth, the Sun was surrounded by a protoplanetary disk, the so-called solar nebula, from which the planets were born. But it was unclear to researchers whether the ice in this disk originated from the Sun’s own parental interstellar molecular cloud, from which it was created, or whether this interstellar water had been destroyed and was re-formed by the chemical reactions taking place in the solar nebula.

“Why this is important? If water in the early Solar System was primarily inherited as ice from interstellar space, then it is likely that similar ices, along with the prebiotic organic matter that they contain, are abundant in most or all protoplanetary disks around forming stars,” Alexander explained. “But if the early Solar System’s water was largely the result of local chemical processing during the Sun’s birth, then it is possible that the abundance of water varies considerably in forming planetary systems, which would obviously have implications for the potential for the emergence of life elsewhere.”

In studying the history of our Solar System’s ices, the team—led by L. Ilsedore Cleeves from the University of Michigan—focused on hydrogen and its heavier isotope deuterium. Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. The difference in masses between isotopes results in subtle differences in their behavior during chemical reactions. As a result, the ratio of hydrogen to deuterium in water molecules can tell scientists about the conditions under which the molecules formed.

For example, interstellar water-ice has a high ratio of deuterium to hydrogen because of the very low temperatures at which it forms. Until now, it was unknown how much of this deuterium enrichment was removed by chemical processing during the Sun’s birth, or how much deuterium-rich water-ice the newborn Solar System was capable of producing on its own.

So the team created models that simulated a protoplanetary disk in which all the deuterium from space ice has already been eliminated by chemical processing, and the system has to start over “from scratch” at producing ice with deuterium in it during a million-year period. They did this in order to see if the system can reach the ratios of deuterium to hydrogen that are found in meteorite samples, Earth’s ocean water, and “time capsule” comets. They found that it could not do so, which told them that at least some of the water in our own Solar System has an origin in interstellar space and pre-dates the birth of the Sun.

“Our findings show that a significant fraction of our Solar System’s water, the most-fundamental ingredient to fostering life, is older than the Sun, which indicates that abundant, organic-rich interstellar ices should probably be found in all young planetary systems,” Alexander said.

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This research was supported by the NSF, the Rackham Predoctoral Fellowship, NASA Astrobiology, NASA Cosmochemistry and NASA.



Friday, September 26, 2014

How NASA Watches CMEs

Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME Week from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with.


Space weather models combined with real time observations help scientists track CMEs. These images were produced from a model known as ENLIL named after the Sumerian storm god. It shows the journey of a CME on March 5, 2013, as it moved toward Mars.  Image Credit: NASA/Goddard/SWRC/CCMC. Download video

A March 5, 2013, CME as seen by the Solar and Heliospheric Observatory. Combining the information gleaned from such imagery with state-of-the-art models helps scientists better understand how CMEs move toward, and affect, Earth. Image Credit: ESA/NASA/SOHO/Jhelioviewer 

Those who study Earth's weather have a luxury of data points to study. From thousands of weather stations measuring temperature and rainfall to satellites tracking storm fronts up in space, meteorologists can watch detailed maps of the weather as it sweeps across land or sea.

Compared to this, the study of space weather – including CMEs – is a much younger science, with far fewer observatories available. However, our resources have grown dramatically in the last decade: NASA currently flies 18 missions to study the sun's effects at Earth and on the entire solar system, a field known as heliophysics, and additionally launches numerous short-flight rockets for observations of solar impacts in and above Earth's atmosphere. Coupled with improved computer modeling, keeping an eye on – and getting a better understanding of – CMEs has taken a giant leap forward in the 21st century.

"Over the past ten years, we have had a major breakthrough in understanding space weather," said Antti Pulkkinen a space weather scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We can now track the basic properties of CMEs. When our solar observatories see a CME, we can tell what direction it's going in and how fast it's traveling."

Improved observations combined with improved models has led to hybrid descriptions of a CME, relying partially on computer simulations and partially on actual observations. NASA houses a collection of space weather models available for public access at the Community Coordinated Modeling Center at Goddard. Together with observations they can provide a holistic picture of any given CME.

For example, NASA's Solar and Terrestrial Relations Observatory, or STEREO, might see a CME erupt on the sun. When that imagery is combined with observations from the European Space Agency and NASA's Solar and Heliospheric Observatory, or SOHO, scientists can create a 3-dimensional picture of the giant cloud. Scientists then input this data into a model and then track how the CME unfolded and spread through space until it passed by NASA observatories closer to Earth. These observatories can directly measure the magnetic fields and speed of the CME as it passes by, as well as see how it affected Earth's own magnetic fields – the magnetosphere.

By gathering data from numerous observatories, scientists can create models and explore what-if scenarios about what would happen near Earth due to a given CME. Watch the video to learn more about what scientists can see in these models. Image Credit: NASA/Bridgman/Duberstein. Download video

Such information on the CME's entire path opens the door to understanding why any given characteristic of the CME near the sun might lead to a given effect near Earth. Each additional piece of the puzzle helps us better understand just what causes these giant eruptions -- and whether or not any particular CME could pose a hazard to astronauts as well as technology in space and on the ground.

Related Links


Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, Md.

Jets and explosions in NGC 7793

Credit: ESA/Hubble & NASA
Acknowledgement: D. Calzetti (University of Massachusetts) and the LEGUS Team

This new image from the NASA/ESA Hubble Space Telescope shows NGC 7793, a spiral galaxy in the constellation of Sculptor some 13 million light-years away from Earth. NGC 7793 is one of the brightest galaxies in the Sculptor Group, and one of the closest groups of galaxies to the Local Group — the group of galaxies containing our galaxy, the Milky Way and the Magellanic Clouds.

The image shows NGC 7793’s spiral arms and small central bulge. Unlike some other spirals, NGC 7793 doesn’t have a very pronounced spiral structure, and its shape is further muddled by the mottled pattern of dark dust that stretches across the frame. The occasional burst of bright pink can be seen in the galaxy, highlighting stellar nurseries containing newly-forming baby stars.

Although it may look serene and beautiful from our perspective, this galaxy is actually a very dramatic and violent place. Astronomers have discovered a powerful microquasar within NGC 7793 — a system containing a black hole actively feeding on material from a companion star. While many full-sized quasars are known at the cores of other galaxies, it is unusual to find a quasar in a galaxy’s disc rather than at its centre.

Micro-quasars are almost like scale models — they allow astronomers to study quasars in detail. As material falls inwards towards this black hole, it creates a swirling disc around it. Some of the infalling gas is propelled violently outwards at extremely high speeds, creating jets streaking out into space in opposite directions. In the case of NGC 7793, these jets are incredibly powerful, and are in the process of creating an expanding bubble of hot gas some 1000 light-years across.

Source: ESA/Hubble - Space Telescope


Thursday, September 25, 2014

A galaxy of deception Hubble snaps what looks like a young galaxy in the local Universe

Dwarf galaxy DDO 68

The area around dwarf galaxy DDO 68 (ground-based image) 

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 Videos

Zooming in on dwarf galaxy DDO 68
Zooming in on dwarf galaxy DDO 68

Panning across DDO 68
Panning across DDO 68


Hubble snaps what looks like a young galaxy in the local Universe

Astronomers usually have to peer very far into the distance to see back in time, and view the Universe as it was when it was young. This new NASA/ESA Hubble Space Telescope image of galaxy DDO 68, otherwise known as UGC 5340, was thought to offer an exception. This ragged collection of stars and gas clouds looks at first glance like a recently-formed galaxy in our own cosmic neighbourhood. But, is it really as young as it looks?


Astronomers have studied galactic evolution for decades, gradually improving our knowledge of how galaxies have changed over cosmic history. The NASA/ESA Hubble Space Telescope has played a big part in this, allowing astronomers to see further into the distance, and hence further back in time, than any telescope before it — capturing light that has taken billions of years to reach us.

Looking further into the very distant past to observe younger and younger galaxies is very valuable, but it is not without its problems for astronomers. All newly-born galaxies lie very far away from us and appear very small and faint in the images. On the contrary, all the galaxies near to us appear to be old ones.

DDO 68, captured here by the NASA/ESA Hubble Space Telescope, was one of the best candidates so far discovered for a newly-formed galaxy in our cosmic neighbourhood. The galaxy lies around 39 million light-years away from us; although this distance may seem huge, it is in fact roughly 50 times closer than the usual distances to such galaxies, which are on the order of several billions of light years.

By studying galaxies of various ages, astronomers have found that those early in their lives are fundamentally different from those that are older. DDO 68 looks to be relatively youthful based on its structure, appearance, and composition. However, without more detailed modelling astronomers cannot be sure and they think it may be older than it lets on.

Elderly galaxies tend to be larger thanks to collisions and mergers with other galaxies that have bulked them out, and are populated with a variety of different types of stars — including old, young, large, and small ones. Their chemical makeup is different too. Newly-formed galaxies have a similar composition to the primordial matter created in the Big Bang (hydrogen, helium and a little lithium), while older galaxies are enriched with heavier elements forged in stellar furnaces over multiple generations of stars.

DDO 68 is the best representation yet of a primordial galaxy in the local Universe as it appears at first glance to be very low in heavier elements — whose presence would be a sign of the existence of previous generations of stars.

Hubble observations were carried out in order to study the properties of the galaxy’s light, and to confirm whether or not there are any older stars in DDO 68. If there are, which there seem to be, this would disprove the hypothesis that it is entirely made up of young stars. If not, it would confirm the unique nature of this galaxy. More complex modelling is needed before we can know for sure but Hubble's picture certainly gives us a beautiful view of this unusual object.

The image is made up of exposures in visible and infrared light taken with Hubble's Advanced Camera for Surveys.

Notes

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

More information


Image credit: NASA & ESA
Acknowledgement: A. Aloisi (Space Telescope Science Institute)

Links


Contacts


Georgia Bladon
Hubble/ESA
Garching, Germany
Tel: +49-89-3200-6855
Email:
gbladon@partner.eso.org

Mapping the Journey of a Giant Coronal Mass Ejection

Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and X-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME Week from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from our closest star.


Three NASA observatories work together to help scientists track the journey of a massive coronal mass ejection, or CME, in July 2012. Image Credit: NASA/SDO/STEREO/ESA/SOHO/Wiessinger. Download video

On July 23, 2012, a massive cloud of solar material erupted off the sun's right side, zooming out into space. It soon passed one of NASA's Solar Terrestrial Relations Observatory, or STEREO, spacecraft, which clocked the CME as traveling between 1,800 and 2,200 miles per second as it left the sun. This was the fastest CME ever observed by STEREO.

Two other observatories – NASA's Solar Dynamics Observatory and the joint European Space Agency/NASA Solar and Heliospheric Observatory -- witnessed the eruption as well. The July 2012 CME didn't move toward Earth, but watching an unusually strong CME like this gives scientists an opportunity to observe how these events originate and travel through space.

STEREO's unique viewpoint from the sides of the sun combined with the other two observatories watching from closer to Earth.Together they helped scientists create models of the entire July 2012 event. They learned that an earlier, smaller CME helped clear the path for the larger event, thus contributing to its unusual speed.

Such data helps advance our understanding of what causes CMEs and improves modeling of similar CMEs that could be Earth-directed.

Watch the movie to see how NASA's solar-observing missions worked together to track this CME.

Related Links

Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, Md.

Wednesday, September 24, 2014

NASA Telescopes Find Clear Skies and Water Vapor on Exo-Neptune

Artist's Illustration of Clear Skies on Exoplanet HAT-P-11b
Scientists were excited to discover clear skies on a relatively small planet, about the size of Neptune, using the combined power of NASA's Hubble, Spitzer, and Kepler space telescopes. The view from this planet — were it possible to fly a spaceship into its gaseous layers — is illustrated at right. Before now, all of the planets observed in this size range had been found to have high cloud layers that blocked the ability to detect molecules in the planet's atmosphere (illustrated at left).


The clear planet, called HAT-P-11b, is gaseous with a rocky core, much like our own Neptune. Its atmosphere may have clouds deeper down, but the new observations show that the upper region is cloud-free. This good visibility enabled scientists to detect water vapor molecules in the planet's atmosphere. Illustration Credit: NASA, ESA, and R. Hurt (JPL-Caltech)

Artist's Illustration of Exoplanet HAT-P-11b
A Neptune-size planet with a clear atmosphere is shown crossing in front of its star in this artist's depiction. Such crossings, or transits, are observed by telescopes like NASA's Hubble and Spitzer to glean information about planets' atmospheres. As starlight passes through a planet's atmosphere, atoms and molecules absorb light at certain wavelengths, blocking it from the telescope's view. The more light a planet blocks, the larger the planet appears. By analyzing the amount of light blocked by the planet at different wavelengths, researchers can determine which molecules make up the atmosphere.


The problem with this technique is that sometimes planets have thick clouds that block any light from coming through, hiding the signature of the molecules in the atmosphere. This is particularly true of the handful of Neptune-sized and super-Earth planets examined to date, all of which appear to be cloudy.


As a result, astronomers were elated to find clear skies on a Neptune-sized planet called HAT-P-11b, as illustrated here. Without clouds to block their view, they were able to identify water vapor molecules in the planet's atmosphere. The blue rim of the planet in this image is due to scattered light, while the orange rim on the part of the planet in front of the star indicates the region where water vapor was detected.  Illustration Credit: NASA, ESA, and R. Hurt (JPL-Caltech)


Artist's Illustration of HAT-P-11b Transmission Spectrum Plot
A plot of the transmission spectrum for exoplanet HAT-P-11b, with Kepler, Hubble WFC3, and Spitzer transits combined. The results show a robust detection of water absorption in the WFC3 data. Transmission spectra of selected atmospheric models are plotted for comparison.  Credit: NASA, ESA, and A. Feild (STScI)
 
Astronomers using data from three of NASA's space telescopes — Hubble, Spitzer, and Kepler — have discovered clear skies and steamy water vapor on a gaseous planet outside our solar system. The planet is about the size of Neptune, making it the smallest for which molecules of any kind have been detected.

"This discovery is a significant milepost on the road to eventually analyzing the atmospheric composition of smaller, rocky planets more like Earth," said John Grunsfeld, assistant administrator of NASA's Science Mission Directorate in Washington. "Such achievements are only possible today with the combined capabilities of these unique and powerful observatories."

Clouds in the atmospheres of planets can block the view to underlying molecules that reveal information about the planets' compositions and histories. Finding clear skies on a Neptune-size planet is a good sign that smaller planets might have similarly good visibility.

"When astronomers go observing at night with telescopes, they say 'clear skies' to mean good luck," said Jonathan Fraine of the University of Maryland, College Park, lead author of a new study appearing in Nature. "In this case, we found clear skies on a distant planet. That's lucky for us because it means clouds didn't block our view of water molecules."

The planet, HAT-P-11b, is a so-called exo-Neptune — a Neptune-size planet that orbits another star. It is located 120 light-years away in the constellation Cygnus. Unlike our Neptune, this planet orbits closer to its star, making one lap roughly every five days. It is a warm world thought to have a rocky core and gaseous atmosphere. Not much else was known about the composition of the planet, or other exo-Neptunes like it, until now.

Part of the challenge in analyzing the atmospheres of planets like this is their size. Larger, Jupiter-like planets are easier to see because of their impressive girth and relatively puffy atmospheres. In fact, researchers have already been able to detect water vapor in those planets. Smaller planets are more difficult to probe, and what's more, the ones observed to date all appeared to be cloudy.

In the new study, astronomers set out to look at the atmosphere of HAT-P-11b, not knowing if its weather would call for clouds or not. They used Hubble's Wide Field Camera 3, and a technique called transmission spectroscopy, in which a planet is observed as it crosses in front of its parent star. Starlight filters through the rim of the planet's atmosphere and into a telescope's lens. If molecules like water vapor are present, they absorb some of the starlight, leaving distinct signatures in the light that reaches our telescopes.

Using this strategy, Hubble was able to detect water vapor in HAT-P-11b. This technique  indicates the planet did not have clouds blocking the view, a hopeful sign that more cloudless planets can be located and analyzed in the future.

But before the team could celebrate clear skies on the exo-Neptune, they had to show that starspots — cooler "freckles" on the face of stars — were not the real sources of water vapor. Cool starspots on the parent star can contain water vapor that might appear erroneously to be from the planet. That's when the team turned to Kepler and Spitzer. Kepler had been observing one patch of sky for years, and HAT-P-11b happens to lie in the field. Those visible-light data were combined with targeted Spitzer observations taken at infrared wavelengths. By comparing these observations, the astronomers figured out that the starspots were too hot to have any steam.

It was at that point the team could celebrate detecting water vapor on a world unlike any in our solar system. "We think that exo-Neptunes may have diverse compositions, which reflect their formation histories," said Heather Knutson of the California Institute of Technology, Pasadena, co-author of the study. "Now with data like these, we can begin to piece together a narrative for the origin of these distant worlds."

The results from all three telescopes demonstrate that HAT-P-11b is blanketed in water vapor, hydrogen gas, and likely other yet-to-be-identified molecules. Theorists will be drawing up new models to explain the planet's makeup and origins.

"We are working our way down the line, from hot Jupiters to exo-Neptunes," said Drake Deming, a co-author of the study also from University of Maryland, College Park. "We want to expand our knowledge to a diverse range of exoplanets."

The astronomers plan to examine more exo-Neptunes in the future, and hope to apply the same method to smaller super-Earths — the massive, rocky cousins to our home world with up to 10 times the mass. Our solar system doesn't have a super-Earth, but NASA's Kepler mission is finding them around other stars in droves. NASA's James Webb Space Telescope, scheduled to launch in 2018, will search super-Earths for signs of water vapor and other molecules; however, finding signs of oceans and potentially habitable worlds is likely a ways off.

"The work we are doing now is important for future studies of super-Earths and even smaller planets, because we want to be able to pick out in advance the planets with clear atmospheres that will let us detect molecules," said Knutson.
Once again, astronomers will be crossing their fingers for clear skies.

Release Images:  http://hubblesite.org/newscenter/archive/releases/2014/42/image/

CONTACT

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514

villard@stsci.edu

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, California
818-354-4673

whitney.clavin@jpl.nasa.gov

Source: HubbleSite 


Most stars are born in clusters, some leave “home” Molecular cloud core model

  Molecular cloud core model
These images show the distribution of density in the central plane of a three-dimensional model of a molecular cloud core from which stars are born. The model computes the cloud’s evolution over the free-fall timescale, which is how long it would take an object to collapse under its own gravity without any opposing forces interfering. The free-fall time is a common metric for measuring the timescale of astrophysical processes. In a) the free-fall time is 0.0, meaning this is the initial configuration of the cloud, and moving on the model shows the cloud core in various stages of collapse: b) a free-fall time of 1.40 or 66,080 years; c) a free-fall time of 1.51 or 71,272 years; and d) a free-fall time of 1.68 or 79,296 years. Collapse takes somewhat longer than a free-fall time in this model because of the presence of magnetic fields, which slow the collapse process, but are not strong enough to prevent the cloud from fragmenting into a multiple protostar system (d). For context, the region shown in a) and b) is about 0.21 light years (or 2.0 x 1017 centimeters) across, while the region shown in c) and d) is about 0.02 light years (or 2.0 x 1016 cm) across. Image is provided courtesy of Alan Boss.  

Washington, D.C.—New modeling studies from Carnegie’s Alan Boss demonstrate that most of the stars we see were formed when unstable clusters of newly formed protostars broke up. These protostars are born out of rotating clouds of dust and gas, which act as nurseries for star formation. Rare clusters of multiple protostars remain stable and mature into multi-star systems. The unstable ones will eject stars until they achieve stability and end up as single or binary stars. The work is published in The Astrophysical Journal.

About two-thirds of all stars within 81 light years (25 parsecs) of Earth are binary or part of multi-star systems. Younger star and protostar populations have a higher frequency of multi-star systems than older ones, an observation that ties in with Boss’ findings that many single-star systems start out as binary or multi-star systems from which stars are ejected to achieve stability.

Protostar clusters are formed when the core of a molecular cloud collapses due to its own gravity and breaks up into pieces, a process called fragmentation. The physical forces involved in the collapse are subjects of great interest to scientists, because they can teach us about the life cycles of stars and how our own Sun may have been born. One force that affects collapse is the magnetic field that threads the clouds, potentially stifling the fragmentation process.

Boss’ work shows that when a cloud collapses, the fragmentation process depends on the initial strength of the magnetic field, which acts against the gravity that causes the collapse. Above a certain magnetic field strength, single protostars are formed, while below it, the cloud fragments into multiple protostars. This second scenario is evidently commonplace, given the large number of binary and multi-star systems, although single stars can form by this mechanism as well through ejection from a cluster.

“When we look up at the night sky,” Boss said, “the human eye is unable to see that binary stars are the rule, rather than the exception. These new calculations help to explain why binaries are so abundant.”

*   *   *

This work was partially supported by the NSF. The calculations were performed on the Carnegie Xenia Cluster, the purchase of which was also partially supported by the NSF.


 

Tuesday, September 23, 2014

NOAO/NRAO: Infant Solar System Shows Signs of Windy Weather

Artist’s rendition of AS 205 N, a T Tauri star that is part of a multiple star system.
Image Credit: P. Marenfeld & NOAO/AURA/NSF

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have observed what may be the first-ever signs of windy weather around a T Tauri star, an infant analog of our own Sun. This may help explain why some T Tauri stars have disks that glow weirdly in infrared light while others shine in a more expected fashion.

T Tauri stars are the infant versions of stars like our Sun. They are relatively normal, medium-size stars that are surrounded by the raw materials to build both rocky and gaseous planets. Though nearly invisible in optical light, these disks shine in both infrared and millimeter-wavelength light.

“The material in the disk of a T Tauri star usually, but not always, emits infrared radiation with a predictable energy distribution,” said Colette Salyk, an astronomer with the National Optical Astronomical Observatory (NOAO) in Tucson, Ariz., and lead author on a paper published in the Astrophysical Journal. “Some T Tauri stars, however, like to act up by emitting infrared radiation in unexpected ways.”

To account for the different infrared signature around such similar stars, astronomers propose that winds may be emanating from within some T Tauri stars’ protoplanetary disks. These winds could have important implications for planet formation, potentially robbing the disk of some of the gas required for the formation of giant Jupiter-like planets, or stirring up the disk and causing the building blocks of planets to change location entirely. These winds have been predicted by astronomers, but have never been clearly detected.

Using ALMA, Salyk and her colleagues looked for evidence of a possible wind in AS 205 N – a T Tauri star located 407 light-years away at the edge of a star-forming region in the constellation Ophiuchus, the Snake Bearer. This star seems to exhibit the strange infrared signature that has intrigued astronomers.

With ALMA’s exceptional resolution and sensitivity, the researchers were able to study the distribution of carbon monoxide around the star. Carbon monoxide is an excellent tracer for the molecular gas that makes up stars and their planet-forming disks. These studies confirmed that there was indeed gas leaving the disk’s surface, as would be expected if a wind were present. The properties of the wind, however, did not exactly match expectations.

This difference between observations and expectations could be due to the fact that AS 205 N is actually part of a multiple star system – with a companion, dubbed AS 205 S, that is itself a binary star.

This multiple star arrangement may suggest that the gas is leaving the disk’s surface because it’s being pulled away by the binary companion star rather than ejected by a wind.

“We are hoping these new ALMA observations help us better understand winds, but they have also left us with a new mystery,” said Salyk. “Are we seeing winds, or interactions with the companion star?”

The study’s authors are not pessimistic, however. They plan to continue their research with more ALMA observations, targeting other unusual T Tauri stars, with and without companions, to see whether they show these same features.

T Tauri stars are named after their prototype star, discovered in 1852 – the third star in the constellation Taurus whose brightness was found to vary erratically. At one point, some 4.5 billion years ago, our Sun was a T Tauri star.

Other authors include Klaus Pontoppidan, Space Telescope Science Institute; Stuartt Corder, Joint ALMA Observatory; Diego Muñoz, Center for Space Research, Department of Astronomy, Cornell University; and Ke Zhang and Geoffrey Blake, Division of Geological & Planetary Sciences, California Institute of Technology,

The National Optical Astronomy Observatory is operated by Association of Universities for Research in Astronomy Inc. under a cooperative agreement with the National Science Foundation.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. NRAO, together with its international partners, operates ALMA – the world’s most powerful observatory operating at millimeter and submillimeter wavelengths. 

ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Media Contact:

Dr. Katy Garmany
Deputy Press Officer
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
+1 520-318-8526
E-mail:
kgarmany@noao.edu

 
Science Contact

Dr. Colette Salyk
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
e-mail:
csalyk@noao.edu

 
NRAO Media Contact

Charles Blue
Public Information Officer
National Radio Astronomy Observatory
520 Edgemont Road
Charlottesville, VA 22904
+1 434-296-0314
E-mail:
cblue@nrao.edu

 

Monday, September 22, 2014

A cosmic hurricane

Cosmic Hurricane
Copyright: NASA/JPL-Caltech/SSI/Hampton University

The giant planet Saturn is mostly a gigantic ball of rotating gas, completely unlike our solid home planet. But Earth and Saturn do have something in common: weather, although the gas giant is home to some of the most bizarre weather in our Solar System, such as the swirling storm shown in this Cassini view.

Known as “the hexagon”, this weather feature is an intense, six-sided jet stream at Saturn’s north pole. Spanning some 30 000 km across, it hosts howling 320 km/h winds that spiral around a massive storm rotating anticlockwise at the heart of the region.

Numerous small vortices rotate in the opposite direction to the central storm and are dragged around with the jet stream, creating a terrifically turbulent region. While a hurricane on Earth may last a week or more, the hexagon has been raging for decades, and shows no signs of letting up.

This false-colour image of the hexagon was made using ultraviolet, visible and infrared filters to highlight different regions.

The dark centre of the image shows the large central storm and its eye, which is up to 50 times bigger than a terrestrial hurricane eye. The small vortices show up as pink-red clumps. Towards the lower right of the frame is a white-tinted oval storm that is bigger than any of the others — this is the largest of the vortices at some 3500 km across, twice the size of the largest hurricane ever recorded on Earth.

The darker blue region within the hexagon is filled with small haze particles, whereas the paler blue region is dominated by larger particles. This divide is caused by the hexagonal jet stream acting as a shepherding barrier — large particles cannot enter the hexagon from the outside.

These large particles are created when sunlight shines onto Saturn’s atmosphere, something that only started relatively recently in the northern hemisphere with the beginning of northern spring in August 2009.

Cassini will continue to track changes in the hexagon, monitoring its contents, shape and behaviour as summer reaches Saturn’s northern hemisphere in 2017.

The Cassini–Huygens mission is a cooperative project of NASA, ESA and Italy's ASI space agency.
An animated version is available here.

 Source: ESA


Monster galaxies gain weight by eating smaller neighbours


Some of the many thousands of merging galaxies identified within the GAMA survey.
Credit: Professor Simon Driver and Dr Aaron Robotham, ICRAR.
Hi-res image

In about five billion years time, nearby massive galaxy Andromeda will merge with our own galaxy, the Milky Way, in an act of gallactic cannibalism (technically Andromeda will be eating us, as it's the bigger of the two galaxies.). There haven't been any large mergers with our galaxy recently, but we can see the remnants of galaxies that have previously been snacked on by the Milky Way. We're also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds sometime in the future. This simulation shows what will happen when the Milky Way and Andromeda get closer together and then collide, and then finally come together once more to merge into an even bigger galaxy. Simulation Credit: Prof Chris power (ICRAR-UWA), Dr Alex Hobbs (ETH Zurich), Prof Justin Reid (University of Surrey), Dr Dave Cole (University of Central Lancashire) and the Theoretical Astrophysics Group at the University of Leicester.Video Production Credit: Pete Wheeler, ICRAR.

Dr Aaron Robotham
Credit: Joe Liske

Massive galaxies in the Universe have stopped making their own stars and are instead snacking on nearby galaxies, according to research by Australian scientists.

Astronomers looked at more than 22,000 galaxies and found that while smaller galaxies were very efficient at creating stars from gas, the most massive galaxies were much less efficient at star formation, producing hardly any new stars themselves, and instead grew by eating other galaxies.

The study was released today in the journal Monthly Notices of the Royal Astronomical Society, published by Oxford University Press.

Dr Aaron Robotham based at The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), said smaller ‘dwarf’ galaxies were being eaten by their larger counterparts.

“All galaxies start off small and grow by collecting gas and quite efficiently turning it into stars,” he said.
“Then every now and then they get completely cannibalised by some much larger galaxy.”

Dr Robotham, who led the research, said our own Milky Way was at a tipping point and expected to now grow mainly by eating smaller galaxies, rather than by collecting gas.

“The Milky Way hasn’t merged with another large galaxy for a long time but you can still see remnants of all the old galaxies we’ve cannibalised,” he said.

“We’re also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds, in about four billion years.”But Dr Robotham said the Milky Way would eventually get its comeuppance when it merged with the nearby Andromeda Galaxy in about five billion years.

“Technically, Andromeda will eat us because it’s the more massive one,” he said.

Almost all of the data for the research was collected with the Anglo-Australian Telescope in New South Wales as part of the Galaxy And Mass Assembly (GAMA) survey, led by Professor Simon Driver at ICRAR.

The GAMA survey involves more than 90 scientists and took seven years to complete.

This study is one of more than 60 publications to have come from the work, with another 180 in progress.
Dr Robotham said as galaxies grew they had more gravity and could therefore more easily pull in their neighbours.

He said the reason star formation slowed down in really massive galaxies was thought to be because of extreme feedback events in a very bright region at the centre of a galaxy known as an active galactic nucleus.
“The topic is much debated, but a popular mechanism is where the active galactic nucleus basically cooks the gas and prevents it from cooling down to form stars,” Dr Robotham said.

Ultimately, gravity is expected to cause all the galaxies in bound groups and clusters to merge into a few super-giant galaxies, although we will have to wait many billions of years before that happens.

“If you waited a really, really, really long time that would eventually happen but by really long I mean many times the age of the Universe so far,” Dr Robotham said.

Further Information

ICRAR is a joint venture between Curtin University and The University of Western Australia with support and funding from the State Government of Western Australia.

Original publication details

Galaxy and Mass Assembly (GAMA): Galaxy close-pairs, mergers and the future fate of stellar mass’ in the Monthly Notices of the Royal Astronomical Society. Published online 19/9/2014 at: http://mnras.oxfordjournals.org/lookup/doi/10.1093/mnras/stu1604

Preprint version accessible at: http://arxiv.org/abs/1408.1476

Contacts
 

Dr Aaron Robotham
ICRAR – UWA (Currently travelling in South Africa, GMT +2:00)
E
: aaron.robotham@icrar.org

Professor Simon Driver
Principal Investigator of the GAMA project. ICRAR – UWA (Perth, GMT +8:00)
Ph: +61 8 6488 7747    M: +61 400 713 514     

E: simon.driver@icrar.org

Kirsten Gottschalk
Media Contact, ICRAR (Perth, GMT +8:00)
Ph: +61 8 6488 7771     M: +61 438 361 876     

E: kirsten.gottschalk@icrar.org

UWA Media Office
Ph: +61 8 6488 7977

Friday, September 19, 2014

An interacting colossus

Credit: Image credit: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt (geckzilla.com)

This picture, taken by the NASA/ESA Hubble Space Telescope’s Wide Field Planetary Camera 2 (WFPC2), shows a galaxy known as NGC 6872 in the constellation of Pavo (The Peacock). Its unusual shape is caused by its interactions with the smaller galaxy that can be seen just above NGC 6872, called IC 4970. They both lie roughly 300 million light-years away from Earth.

From tip to tip, NGC 6872 measures over 500 000 light-years across, making it the second largest spiral galaxy discovered to date. In terms of size it is beaten only by NGC 262, a galaxy that measures a mind-boggling 1.3 million light-years in diameter! To put that into perspective, our own galaxy, the Milky Way, measures between 100 000 and 120 000 light-years across, making NGC 6872 about five times its size.

The upper left spiral arm of NGC 6872 is visibly distorted and is populated by star-forming regions, which appear blue on this image. This may have been be caused by IC 4970 recently passing through this arm — although here, recent means 130 million years ago! Astronomers have noted that NGC 6872 seems to be relatively sparse in terms of free hydrogen, which is the basis material for new stars, meaning that if it weren’t for its interactions with IC 4970, NGC 6872 might not have been able to produce new bursts of star formation.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

Source: ESA/Hubble - Space Telescope