Earth’s magnetosphere behaves like a sieve

ESA - Cluster II Mission patch.

24 October 2012

ESA’s quartet of satellites studying Earth’s magnetosphere, Cluster, has discovered that our protective magnetic bubble lets the solar wind in under a wider range of conditions than previously believed.

Earth’s magnetic field is our planet’s first line of defence against the bombardment of the solar wind. This stream of plasma is launched by the Sun and travels across the Solar System, carrying its own magnetic field with it.

Depending on how the solar wind’s interplanetary magnetic field – IMF – is aligned with Earth’s magnetic field, different phenomena can arise in Earth’s immediate environment.

Solar wind entry at low latitudes

One well-known process is magnetic reconnection, where magnetic field lines pointing in opposite directions spontaneously break and reconnect with other nearby field lines. This redirects their plasma load into the magnetosphere, opening the door to the solar wind and allowing it to reach Earth.

Under certain circumstances this can drive ‘space weather’, generating spectacular aurorae, interrupting GPS signals and affecting terrestrial power systems.

In 2006, Cluster made the surprising discovery that huge, 40 000 km swirls of plasma along the boundary of the magnetosphere – the magnetopause – could allow the solar wind to enter, even when Earth’s magnetic field and the IMF are aligned.

These swirls were found at low, equatorial latitudes, where the magnetic fields were most closely aligned.

These giant vortices are driven by a process known as the Kelvin–Helmholtz (KH) effect, which can occur anywhere in nature when two adjacent flows slip past each other at different speeds.

Examples include waves whipped up by wind sliding across the surface of the ocean, or in atmospheric clouds.

Solar wind entry at high latitudes

Analysis of Cluster data has now found that KH waves can also occur at a wider range of magnetopause locations and when the IMF is arranged in a number of other configurations, providing a mechanism for the continuous transport of the solar wind into Earth’s magnetosphere.

“We found that when the interplanetary magnetic field is westward or eastward, magnetopause boundary layers at higher latitude become most subject to KH instabilities, regions quite distant from previous observations of these waves,” says Kyoung-Joo Hwang of NASA’s Goddard Space Flight Center and lead author of the paper published in the Journal of Geophysical Research.

“In fact, it’s very hard to imagine a situation where solar wind plasma could not leak into the magnetosphere, since it is not a perfect magnetic bubble.”

The findings confirm theoretical predictions and are reproduced by simulations presented by the authors of the new study.

“The solar wind can enter the magnetosphere at different locations and under different magnetic field conditions that we hadn’t known about before,” says co-author Melvyn Goldstein, also from Goddard Space Flight Center.

ESA's four Cluster's in orbit (Artist view)

“That suggests there is a ‘sieve-like’ property of the magnetopause in allowing the solar wind to continuously flow into the magnetosphere.”

The KH effect is also seen in the magnetospheres of Mercury and Saturn, and the new results suggest that it may provide a possible continuous entry mechanism of solar wind into those planetary magnetospheres, too.

“Cluster’s observations of these boundary waves have provided a great advance on our understanding of solar wind – magnetosphere interactions, which are at the heart of space weather research,” says Matt Taylor, ESA’s Cluster project scientist.

“In this case, the relatively small separation of the four Cluster satellites as they passed through the high-latitude dayside magnetopause provided a microscopic look at the processes ripping open the magnetopause and allowing particles from the Sun direct entry into the atmosphere.”

Related links:

Exploring the Sun-Earth connection: http://www.esa.int/SPECIALS/Cluster/

Cluster overview: http://www.esa.int/esaSC/120383_index_0_m.html

Cluster in depth: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=8

Space weather: http://www.esa.int/esaSC/SEMLC2T1VED_index_0.html

Images, Text, Credits: ESA / AOES Medialab.

Cheers, Orbiter.ch

84 Million Stars and Counting

ESO - European Southern Observatory logo.

24 October 2012

VISTA creates largest ever catalogue of centre of our galaxy

(Click on the images for enlarge)

VISTA gigapixel mosaic of the central parts of the Milky Way

Using a whopping nine-gigapixel image from the VISTA infrared survey telescope at ESO’s Paranal Observatory, an international team of astronomers has created a catalogue of more than 84 million stars in the central parts of the Milky Way. This gigantic dataset contains more than ten times more stars than previous studies and is a major step forward for the understanding of our home galaxy. The image gives viewers an incredible, zoomable view of the central part of our galaxy. It is so large that, if printed with the resolution of a typical book, it would be 9 metres long and 7 metres tall.

Wide-field view of the Milky Way, showing the extent of a new VISTA gigapixel image

“By observing in detail the myriads of stars surrounding the centre of the Milky Way we can learn a lot more about the formation and evolution of not only our galaxy, but also spiral galaxies in general,” explains Roberto Saito (Pontificia Universidad Católica de Chile, Universidad de Valparaíso and The Milky Way Millennium Nucleus, Chile), lead author of the study.

Optical/infrared comparison of the central parts of the Milky Way

Most spiral galaxies, including our home galaxy the Milky Way, have a large concentration of ancient stars surrounding the centre that astronomers call the bulge. Understanding the formation and evolution of the Milky Way’s bulge is vital for understanding the galaxy as a whole. However, obtaining detailed observations of this region is not an easy task.

“Observations of the bulge of the Milky Way are very hard because it is obscured by dust,” says Dante Minniti (Pontificia Universidad Catolica de Chile, Chile), co-author of the study. “To peer into the heart of the galaxy, we need to observe in infrared light, which is less affected by the dust.”

Colour–magnitude diagram of the Galactic bulge

The large mirror, wide field of view and very sensitive infrared detectors of ESO’s 4.1-metre Visible and Infrared Survey Telescope for Astronomy (VISTA) make it by far the best tool for this job. The team of astronomers is using data from the VISTA Variables in the Via Lactea programme (VVV) [1], one of six public surveys carried out with VISTA. The data have been used to create a monumental 108 200 by 81 500 pixel colour image containing nearly nine billion pixels. This is one of the biggest astronomical images ever produced. The team has now used these data to compile the largest catalogue of the central concentration of stars in the Milky Way ever created [2].

Annotated map of VISTA’s view of the centre of the Milky Way

To help analyse this huge catalogue the brightness of each star is plotted against its colour for about 84 million stars to create a colour–magnitude diagram. This plot contains more than ten times more stars than any previous study and it is the first time that this has been done for the entire bulge. Colour–magnitude diagrams are very valuable tools that are often used by astronomers to study the different physical properties of stars such as their temperatures, masses and ages [3].

“Each star occupies a particular spot in this diagram at any moment during its lifetime. Where it falls depends on how bright it is and how hot it is. Since the new data gives us a snapshot of all the stars in one go, we can now make a census of all the stars in this part of the Milky Way,” explains Dante Minniti.

Video above: Infrared/visible light comparison of VISTA’s gigapixel view of the centre of the Milky Way.

The new colour–magnitude diagram of the bulge contains a treasure trove of information about the structure and content of the Milky Way. One interesting result revealed in the new data is the large number of faint red dwarf stars. These are prime candidates around which to search for small exoplanets using the transit method [4].

“One of the other great things about the VVV survey is that it’s one of the ESO VISTA public surveys. This means that we’re making all the data publicly available through the ESO data archive, so we expect many other exciting results to come out of this great resource," concludes Roberto Saito.

Notes:

[1] The VISTA Variables in the Via Lactea (VVV) survey is an ESO public survey dedicated to scanning the southern plane and bulge of the Milky Way through five near-infrared filters. It started in 2010 and was granted a total of 1929 hours of observing time over a five-year period. Via Lactea is the Latin name for the Milky Way.

[2] The image used in this work covers about 315 square degrees of the sky (a bit less than 1% of the entire sky) and observations were carried out using three different infrared filters. The catalogue lists the positions of the stars along with their measured brightnesses through the different filters. It contains about 173 million objects, of which about 84 million have been confirmed as stars. The other objects were either too faint or blended with their neighbours or affected by other artefacts, so that accurate measurements were not possible. Others were extended objects such as distant galaxies.

The image used here required a huge amount of data processing, which was performed by Ignacio Toledo at the ALMA OSF. It corresponds to a pixel scale of 0.6 arcseconds per pixel, down-sampled from the original pixel scale of 0.34 arcseconds per pixel.

[3] A colour–magnitude diagram is a graph that plots the apparent brightnesses of a set of objects against their colours. The colour is measured by comparing how bright objects look through different filters. It is similar to a Hertzsprung-Russell (HR) diagram but the latter plots luminosity (or absolute magnitude) rather than just apparent brightness and a knowledge of the distances of the stars plotted is also needed.

[4] The transit method for finding planets searches for the small drop in brightness of a star that occurs when a planet passes in front of it and blocks some of its light. The small size of the red dwarf stars, typically with spectral types K and M, gives a greater relative drop in brightness when low-mass planets pass in front of them, making it easier to search for planets around them.

More information:

This research was presented in a paper “Milky Way Demographics with the VVV Survey I. The 84 Million Star Colour–Magnitude Diagram of the Galactic Bulge“ by R. K. Saito et al., which was published in the journal Astronomy & Astrophysics (A&A, 544, A147).

The team is composed of R. K. Saito (Pontificia Universidad Católica de Chile, Santiago, Chile; Universidad de Valparaíso, Chile; The Milky Way Millennium Nucleus, Chile), D. Minniti (Pontificia Universidad Católica de Chile; Vatican Observatory), B. Dias (Universidade de São Paulo, Brazil), M. Hempel (Pontificia Universidad Católica de Chile), M. Rejkuba (ESO, Garching, Germany), J. Alonso-García (Pontificia Universidad Católica de Chile), B. Barbuy (Universidade de São Paulo), M. Catelan (Pontificia Universidad Católica de Chile), J. P. Emerson (Queen Mary University of London, United Kingdom), O. A. Gonzalez (ESO, Garching, Germany), P. W. Lucas (University of Hertfordshire, Hatfield, United Kingdom) and M. Zoccali (Pontificia Universidad Católica de Chile).

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

Links:

    Research paper (A&A, 544, A147): http://www.aanda.org/10.1051/0004-6361/201219448

    Photos of the VISTA telescope: http://www.eso.org/public/images/archive/search/?adv=&subject_name=Visible%20and%20Infrared%20Survey%20Telescope%20for%20Astronomy

    Images taken with the VISTA telescope: http://www.eso.org/public/images/archive/search/?adv=&facility=30

Image, Text, Credits: ESO/VVV Consortium/Acknowledgement: Ignacio Toledo, Martin Kornmesser/Nick Risinger (skysurvey.org)/Videos: ESO/VVV Consortium/Nick Risinger (skysurvey.org)/Music: Delmo -- Acoustic (disasterpeace.com)/Acknowledgement: Ignacio Toledo, Martin Kornmesser.

Greetings, Orbiter.ch

NASA's NuSTAR Spots Flare From Milky Way's Black Hole

NASA - NuSTAR Mission patch.

Oct.23, 2012

Image above: NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has captured these first, focused views of the supermassive black hole at the heart of our galaxy in high-energy X-ray light. Image credit: NASA/JPL-Caltech .

NASA's newest set of X-ray eyes in the sky, the Nuclear Spectroscopic Telescope Array (NuSTAR), has caught its first look at the giant black hole parked at the center of our galaxy. The observations show the typically mild-mannered black hole during the middle of a flare-up.

"We got lucky to have captured an outburst from the black hole during our observing campaign," said Fiona Harrison, the mission's principal investigator at the California Institute of Technology (Caltech) in Pasadena. "These data will help us better understand the gentle giant at the heart of our galaxy and why it sometimes flares up for a few hours and then returns to slumber."

The new images can be seen by visiting: http://www.nasa.gov/nustar .

NuSTAR Black Hole X-ray Satellite. Image credit: NASA/JPL-Caltech

NuSTAR, launched June 13, is the only telescope capable of producing focused images of the highest-energy X-rays. For two days in July, the telescope teamed up with other observatories to observe Sagittarius A* (pronounced Sagittarius A-star and abbreviated Sgr A*), the name astronomers give to a compact radio source at the center of the Milky Way. Observations show a massive black hole lies at this location. Participating telescopes included NASA's Chandra X-ray Observatory, which sees lower-energy X-ray light; and the W.M. Keck Observatory atop Mauna Kea in Hawaii, which took infrared images.

Compared to giant black holes at the centers of other galaxies, Sgr A* is relatively quiet. Active black holes tend to gobble up stars and other fuel around them. Sgr A* is thought only to nibble or not eat at all, a process that is not fully understood. When black holes consume fuel -- whether a star, a gas cloud or, as recent Chandra observations have suggested, even an asteroid -- they erupt with extra energy.

In the case of NuSTAR, its state-of-the-art telescope is picking up X-rays emitted by consumed matter being heated up to about 180 million degrees Fahrenheit (100 million degrees Celsius) and originating from regions where particles are boosted very close to the speed of light. Astronomers say these NuSTAR data, when combined with the simultaneous observations taken at other wavelengths, will help them better understand the physics of how black holes snack and grow in size.

Image above: These are the first, focused high-energy X-ray views of the area surrounding the supermassive black hole, called Sagittarius A*, at the center of our galaxy. Image credit: NASA/JPL-Caltech.

"Astronomers have long speculated that the black hole's snacking should produce copious hard X-rays, but NuSTAR is the first telescope with sufficient sensitivity to actually detect them," said NuSTAR team member Chuck Hailey of Columbia University in New York City.

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory in Pasadena for NASA's Science Mission Directorate in Washington. Orbital Sciences Corporation of Dulles, Va., built the spacecraft. Its instrument was built by a consortium including Caltech; JPL; the University of California (UC) Berkeley; Columbia University; NASA's Goddard Space Flight Center in Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory in Livermore, Calif.; and ATK Aerospace Systems of Goleta, Calif.

NuSTAR's mission operations center is at UC Berkeley, with the Italian Space Agency providing an equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University in Rohnert Park, Calif. Goddard manages NASA's Explorer Program. Caltech manages JPL for NASA.

For information about NASA and agency programs, visit: http://www.nasa.gov .

Images (mentioned), Text, Credits: NASA / J.D. Harrington / JPL / Alan Buis.

Best regards, Orbiter.ch

New Crew Headed to the International Space Station

ROSCOSMOS - Soyuz TMA-06M patch.

Oct. 23, 2012

Crew posing front the Soyuz TMA-06M space capsule

NASA astronaut Kevin Ford and Russian cosmonauts Evgeny Tarelkin and Oleg Novitskiy launched aboard a Russian Soyuz rocket on their mission to the International Space Station at 5:51 a.m. CDT Tuesday (4:51 p.m. Kazakhstan time). The trio lifted off from Site 31 at the Baikonur Cosmodrome in Kazakhstan. This is the first time in 28 years the pad has been used for human spaceflight.

New Trio Launches to Join Expedition 33

Ford, Tarelkin and Novitskiy will spend the next two days inside their Soyuz TMA-06M spacecraft as they close in on the space station. Novitskiy is serving as the commander of the Soyuz and will be at the controls as the spacecraft docks with the Poisk module of the station Thursday. The three will join Expedition 33 Commander Sunita Williams of NASA and Flight Engineers Aki Hoshide of the Japan Aerospace Exploration Agency and Yuri Malenchenko of the Russian Federal Space Agency, who have been living aboard the orbiting laboratory since July.

Expedition 33 liftoff

NASA TV will provide live coverage of the Soyuz docking beginning at 7 a.m. CDT (8 a.m. EDT) Thursday. Coverage of the hatch opening and welcome ceremony aboard the space station will begin at 9:45 a.m. Hatch opening is scheduled for approximately 10:15 a.m.

Ford, Novitskiy and Tarelkin will remain aboard the station until March 2013. Williams, Malenchenko and Hoshide will return to Earth Nov. 19. When Williams, Malenchenko and Hoshide undock from the station, it will signal the end of Expedition 33 and the beginning of Expedition 34 with Ford as commander.

For NASA TV downlink information, up-to-date schedules and links to streaming video, visit: http://www.nasa.gov/ntv

For information on the International Space Station and the Expedition 33 crew, visit: http://www.nasa.gov/station

Images, Video, Text, Credits: ROSCOSMOS / NASA / NASA TV.

Greetings, Orbiter.ch

Big Bang interfaces and knowledge: towards a common language?

CERN - European Organization for Nuclear Research logo.

Oct. 22, 2012

CERN the LHC - To discover the secrets of the Universe. (Image: CERN)

This week, scientists from CERN participated in a meeting organized by Wilton Park organization, held near Geneva, from 15 to 18 October. Eminent personalities were invited to consider different worldviews from science, philosophy and theology, and to reflect that these visions were shared. Is it possible to develop a common language for meaningful dialogue?

Wilton Park is an organization designed to provide a framework for discussion and reflection on the major political issues worldwide, bringing together experts from around the world to discuss current topics. More than 50 events are organized each year by this structure, which is a neutral environment in which divergent views can be expressed and confront calmly.

The meeting, organized in partnership with CERN, has enabled scientists from different disciplines to engage in dialogue with philosophers and theologians of different faiths on the nature of the Big Bang theory. A report and an electronic book will be published later.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 20 Member States.

For more information:

   - On Wilton Park: http://www.wiltonpark.org.uk/en/about-wilton-park/

   - The meeting: http://www.wiltonpark.org.uk/en/conferences/policy-programmes/human-rights-democracy-and-governance/?view=Conference&id=762366482

For more information about the European Organization for Nuclear Research (CERN), visit: http://public.web.cern.ch/public/Welcome.html

Image, Text, Credits: CERN / Translation: Orbiter.ch.

Best regards, Orbiter.ch

The Solar System’s grandest canyon

ESA - Mars Express Mission patch.

22 October 2012

 Valles Marineris

Earth’s Grand Canyon inspires awe for anyone who casts eyes upon the vast river-cut valley, but it would seem nothing more than a scratch next to the cavernous scar of Valles Marineris that marks the face of Mars.

Stretching over 4000 km long and 200 km wide, and with a dizzying depth of 10 km, it is some ten times longer and five times deeper than Earth’s Grand Canyon, a size that earns it the status of the largest canyon in the Solar System.

Seen here in new light and online for the first time, this bird’s-eye view of Valles Marineris was created from data captured during 20 individual orbits of ESA’s Mars Express. It is presented in near-true colour and with four times vertical exaggeration.

A wide variety of geological features can be seen, reflecting the complex geological history of the region.

The canyon’s formation is likely intimately linked with the formation of the neighbouring Tharsis bulge, which is out of shot and to the left of this image and home to the largest volcano in the Solar System, Olympus Mons.

The volcanic activity is revealed by the nature of the rocks in the walls of the canyon and the surrounding plains, which were built by successive lava flows.

ESA's Mars Express

As the Tharsis bulge swelled with magma during the planet’s first billion years, the surrounding crust was stretched, ripping apart and eventually collapsing into the gigantic troughs of Valles Marineris.

Intricate fault patterns have also developed due to the imposing extensional forces; the most recent are particularly evident in the middle portion of the image and along the lower boundary of the frame.

Landslides have also played a role in shaping the scene, especially in the northern-most troughs, where material has recently slumped down the steep walls. Mass wasting has also created delicate erosion of the highest part of the walls.

Strong water flows may have reshaped Valles Marineris after it was formed, deepening the canyon. Mineralogical information collected by orbiting spacecraft, including Mars Express, shows that the terrain here was altered by water hundreds of millions of years ago. 

Related links:

High Resolution Stereo Camera: http://berlinadmin.dlr.de/Missions/express/indexeng.shtml

Behind the lens: http://www.esa.int/SPECIALS/Mars_Express/SEMSXE1PGQD_0.html

Mars Express in depth: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=9

Frequently asked questions: http://www.esa.int/SPECIALS/Mars_Express/SEM76D9OY2F_0.html

Images, Text, Credits: ESA/DLR/FU Berlin (G. Neukum).

Greetings, Orbiter.ch

Astronomers Uncover A Surprising Trend in Galaxy Evolution

NASA - Hubble Space Telescope patch. / W. M. Keck Observatory logo.

Oct. 19, 2012

Video above: A study of 544 star-forming galaxies observed by the Keck and Hubble telescopes shows that disk galaxies like our own Milky Way unexpectedly reached their current state long after much of the universe's star formation had ceased. Over the past 8 billion years, the galaxies lose chaotic motions and spin faster as they develop into settled disk galaxies. Credit: NASA's Goddard Space Flight Center.

A comprehensive study of hundreds of galaxies observed by the Keck telescopes in Hawaii and NASA's Hubble Space Telescope has revealed an unexpected pattern of change that extends back 8 billion years, or more than half the age of the universe.

"Astronomers thought disk galaxies in the nearby universe had settled into their present form by about 8 billion years ago, with little additional development since," said Susan Kassin, an astronomer at NASA's Goddard Space Flight Center in Greenbelt, Md., and the study's lead researcher. "The trend we've observed instead shows the opposite, that galaxies were steadily changing over this time period."

Today, star-forming galaxies take the form of orderly disk-shaped systems, such as the Andromeda Galaxy or the Milky Way, where rotation dominates over other internal motions. The most distant blue galaxies in the study tend to be very different, exhibiting disorganized motions in multiple directions. There is a steady shift toward greater organization to the present time as the disorganized motions dissipate and rotation speeds increase. These galaxies are gradually settling into well-behaved disks.

Graphic above: This plot shows the fractions of settled disk galaxies in four time spans, each about 3 billion years long. There is a steady shift toward higher percentages of settled galaxies closer to the present time. At any given time, the most massive galaxies are the most settled. More distant and less massive galaxies on average exhibit more disorganized internal motions, with gas moving in multiple directions, and slower rotation speeds. Credit: NASA's Goddard Space Flight Center.

Blue galaxies -- their color indicates stars are forming within them -- show less disorganized motions and ever-faster rotation speeds the closer they are observed to the present. This trend holds true for galaxies of all masses, but the most massive systems always show the highest level of organization.

Researchers say the distant blue galaxies they studied are gradually transforming into rotating disk galaxies like our own Milky Way.

"Previous studies removed galaxies that did not look like the well-ordered rotating disks now common in the universe today," said co-author Benjamin Weiner, an astronomer at the University of Arizona in Tucson. "By neglecting them, these studies examined only those rare galaxies in the distant universe that are well-behaved and concluded that galaxies didn't change."

Rather than limit their sample to certain galaxy types, the researchers instead looked at all galaxies with emission lines bright enough to be used for determining internal motions. Emission lines are the discrete wavelengths of radiation characteristically emitted by the gas within a galaxy. They are revealed when a galaxy's light is separated into its component colors. These emission lines also carry information about the galaxy's internal motions and distance.

Simulations such as this will help astronomers better understand the new findings in galaxy evolution. It tracks the development of a single disk galaxy from shortly after the Big Bang to the present day. Colors reveal old stars (red), young stars (white and bright blue) and the distribution of gas density (pale blue); the view is 300,000 light-years across. Credit: F. Governato and T. Quinn (Univ. of Washington), A. Brooks (Univ. of Wisconsin, Madison), and J. Wadsley (McMaster Univ.).

The team studied a sample of 544 blue galaxies from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) Redshift Survey, a project that employs Hubble and the twin 10-meter telescopes at the W. M. Keck Observatory in Hawaii. Located between 2 billion and 8 billion light-years away, the galaxies have stellar masses ranging from about 0.3 percent to 100 percent of the mass of our home galaxy.

A paper describing these findings will be published Oct. 20 in The Astrophysical Journal.

The Milky Way galaxy must have gone through the same rough-and-tumble evolution as the galaxies in the DEEP2 sample, and gradually settled into its present state as the sun and solar system were being formed.

In the past 8 billion years, the number of mergers between galaxies large and small has decreased sharply. So has the overall rate of star formation and disruptions of supernova explosions associated with star formation. Scientists speculate these factors may play a role in creating the evolutionary trend they observe.

Now that astronomers see this pattern, they can adjust computer simulations of galaxy evolution until these models are able to replicate the observed trend. This will guide scientists to the physical processes most responsible for it.

The DEEP2 survey is led by Lick Observatory at the University of California at Santa Cruz in collaboration with the University of California at Berkeley, the University of Hawaii at Manoa, Johns Hopkins University in Baltimore, Md., the University of Chicago and the California Institute of Technology in Pasadena.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc. in Washington.

Related Links:

› NASA's Hubble website: http://www.nasa.gov/hubble

› Narrated video on the NASA Explorer YouTube channel: http://youtu.be/voq3Wfr5cho

› Cosmology simulation video on the NASA Explorer YouTube channel: https://www.youtube.com/watch?v=_Ssc1GsqHds

› Download videos and other visuals in broadcast quality: http://svs.gsfc.nasa.gov/goto?11087

› Paper: The Epoch of Disk Settling: z ~ 1 to Now. doi:10.1088/0004-637X/758/2/106: http://iopscience.iop.org/0004-637X/758/2/106

› Talk by Susan Kassin at the University of California High-Performance Astrocomputing Center: http://hipacc.ucsc.edu/Talk_single.php?Tid=242&SerId=20&Aid=20

› The Deep Extragalactic Evolutionary Probe project: http://deep.ucolick.org/

› University of California High-Performance AstroComputing Center press release: http://hipacc.ucsc.edu/GalaxyDiskSettling.html

Image (mentioned), Videos (mentioned), Text, Credit: NASA's Goddard Space Flight Center / Francis Reddy.

Greetings, Orbiter.ch