Showing posts with label Large Magellanic Cloud. Show all posts
Showing posts with label Large Magellanic Cloud. Show all posts

Herschel and Spitzer See Nearby Galaxies' Stardust

Posted by carsimulator on Tuesday, January 10, 2012

This new image shows the Large Magellanic Cloud galaxy in infrared light as seen by the Herschel Space Observatory, a European Space Agency-led mission with important NASA contributions, and NASA's Spitzer Space Telescope. Image credit: ESA/NASA/JPL-Caltech/STScI. Full image and caption

This new image shows the Small Magellanic Cloud galaxy in infrared light from the Herschel Space Observatory a European Space Agency-led mission with important NASA contributions, and NASA's Spitzer Space Telescope. Image credit: ESA/NASA/JPL-Caltech/STScI. Full image and caption - enlarge image

PASADENA, Calif. - The cold dust that builds blazing stars is revealed in new images that combine observations from the Herschel Space Observatory, a European Space Agency-led mission with important NASA contributions; and NASA's Spitzer Space Telescope. The new images map the dust in the galaxies known as the Large and Small Magellanic Clouds, two of the closest neighbors to our own Milky Way galaxy.

The new images are available at the following links: http://www.nasa.gov/mission_pages/herschel/multimedia/pia15254.html and http://www.nasa.gov/mission_pages/herschel/multimedia/pia15255.html

The Large Magellanic Cloud looks like a fiery, circular explosion in the combined Herschel-Spitzer infrared data. Ribbons of dust ripple through the galaxy, with significant fields of star formation noticeable in the center, center-left and top right (the brightest center-left region is called 30 Doradus, or the Tarantula Nebula, for its appearance in visible light). The Small Magellanic Cloud has a much more irregular shape. A stream of dust extends to the left in this image, known as the galaxy's "wing," and a bar of star formation appears on the right.

The colors in these images indicate temperatures in the dust that permeate the Magellanic Clouds. Colder regions show where star formation is at its earliest stages or is shut off, while warm expanses point to new stars heating dust surrounding them. The coolest areas and objects appear in red, corresponding to infrared light taken up by Herschel's Spectral and Photometric Imaging Receiver at 250 microns, or millionths of a meter. Herschel's Photodetector Array Camera and Spectrometer fills out the mid-temperature bands, shown in green, at 100 and 160 microns. The warmest spots appear in blue, courtesy of 24- and 70-micron data from Spitzer.

"Studying these galaxies offers us the best opportunity to study star formation outside of the Milky Way," said Margaret Meixner, an astronomer at the Space Telescope Science Institute, Baltimore, Md., and principal investigator for the mapping project. "Star formation affects the evolution of galaxies, so we hope understanding the story of these stars will answer questions about galactic life cycles."

The Large and Small Magellanic Clouds are the two biggest satellite galaxies of our home galaxy, the Milky Way, though they are still considered dwarf galaxies compared to the big spiral of the Milky Way. Dwarf galaxies also contain fewer metals, or elements heavier than hydrogen and helium. Such an environment is thought to slow the growth of stars. Star formation in the universe peaked around 10 billion years ago, even though galaxies contained lesser abundances of metallic dust. Previously, astronomers only had a general sense of the rate of star formation in the Magellanic Clouds, but the new images enable them to study the process in more detail.

The results were presented today at the 219th meeting of the American Astronomical Society in Austin, Texas.

Herschel is a European Space Agency cornerstone mission, with science instruments provided by consortia of European institutes and with important participation by NASA. NASA's Herschel Project Office is based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, supports the United States' astronomical community.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA.


For more information about Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer .

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

Trent J. Perrotto 202-358-0321
NASA Headquarters, Washington
trent.j.perrotto@nasa.gov


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Probing a super-giant shell of gas and stars

Posted by carsimulator on Monday, November 21, 2011

Large Magellanic Cloud
Credit: ESA/Hubble, NASA and D. A. Gouliermis

In one of the largest known star formation regions in the Large Magellanic Cloud (LMC), a small satellite galaxy of the Milky Way, lie young and bright stellar groupings known as OB associations. One of these associations, called LH 72, was captured in this dramatic NASA/ESA Hubble Space Telescope image. It consists of a few high-mass, young stars embedded in a beautiful and dense nebula of hydrogen gas.

Much of the star formation in the LMC occurs in super-giant shells. These regions of interstellar gas are thought to have formed due to strong stellar winds and supernova explosions that cleared away much of the material around the stars creating wind-blown shells. The swept-up gas eventually cools down and fragments into smaller clouds that dot the edges of these regions and eventually collapse to form new stars.

The biggest of these shells, home to LH 72, is designated LMC4. With a diameter of about 6000 light-years, it is the largest in the Local Group of galaxies that is home to both the Milky Way and LMC. Studying gas-embedded young associations of stars like LH 72 is a way of probing the super-giant shells to understand how they formed and evolved.

This image was taken with Hubble’s Wide Field Planetary Camera 2 using five different filters in ultraviolet, visible and infrared light. The field of view is approximately 1.8 by 1.8 arcminutes.

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Neighbor Galaxy Caught Stealing Stars

Posted by carsimulator on Tuesday, July 19, 2011

The Milky Way’s near neighbor, the Large Magellanic Cloud (LMC), has accreted a smattering of stars from its smaller neighbor, the Small Magellanic Cloud (SMC). In this image, the LMC is shown as it appears in observations by the Spitzer Space Telescope at 3.6, 8.0, and 24 microns. Overlaid in red and blue, with colors representing the light of sight velocities (red = away, blue = towards) are the locations of stars whose origin has been traced to the SMC. These stars were discovered by a team led by NOAO astronomer Knut Olsen, through analysis of spectra obtained at the CTIO 4-m Blanco telescope. Spitzer image credit: Karl Gordon and Margaret Meixner (Space Telescope Science Institute/AURA/NASA). Compilation by K. Olsen (NOAO/AURA/NSF). Download: Web resolution - Print resolution

Astronomers from the National Optical Astronomy Observatory (NOAO) and their collaborators have found that hundreds of the stars found in the Large Magellanic Cloud (LMC) were stolen from another nearby galaxy – the Small Magellanic Cloud (SMC). The Large and Small Magellanic Clouds are both neighbor galaxies to our Milky Way Galaxy and easily visible to the unaided eye from the southern hemisphere.

By analyzing the spectra of 5900 giant and supergiant stars in the Large Magellanic Cloud galaxy, NOAO astronomers Knut Olsen and Bob Blum, and their collaborators Dennis Zaritsky (University of Arizona), and Martha Boyer and Karl Gordon (Space Telescope Science Institute) found that over 5% of the stars they observed in the LMC are rotating counter to the direction of the majority of LMC stars, or perhaps in a plane that is greatly inclined to the rotation of the LMC. An ambiguity remains in the result, because the astronomers were only able to measure the projection of the stellar velocities into the line of sight, and not their full velocity vectors. In either case, these peculiar orbits indicate that these stars probably did not form from the rotating and collapsing cloud of gas that formed the LMC, a galaxy located about 160,000 light years away.

Further examination of these counter-rotating stars revealed another anomaly. The chemical composition of these stars is different. They have fewer heavy elements such as iron and calcium than typical stars in the Large Magellanic Cloud. However, their composition closely matches that of stars in another nearby galaxy, the Small Magellanic Cloud, whose stars are also depleted in these “metals”.

These two lines of evidence – motion and composition – indicated to the research team that these stars were stolen from the smaller galaxy by the gravitational pull of the larger galaxy. The astronomers used a multi-object spectrometer on the Cerro Tololo Inter-American Observatory 4-meter Blanco Telescope in Chile to observe 4600 stars. The spectrometer allowed the spectral characteristics of a large number of stars to be observed simultaneously. These observations were then combined with data on 1300 other stars to look for patterns. According to Olsen “It is not always easy to tell whether the stars in a galaxy formed in the galaxy or formed somewhere else and then were captured. Since the LMC is so close to us, we were able to observe a large number of individual stars. And to our surprise, the LMC contained a significant number of stars that must have formed elsewhere.”

The same team is also using infrared observations made with the Spitzer Space Telescope to study how stars form and evolve in the Large Magellanic Cloud. NOAO Deputy Director Bob Blum indicated the importance of this approach: “Using observations with the Spitzer Space Telescope, we were able to get a complete census of the stellar populations in the LMC. With the ground-based observations we could determine the properties and motions of a large sample of stars throughout that galaxy. By combining both, we were able to tell that some of the stars must have come from the neighboring SMC. This led us to a deeper understanding of how galaxies can and do interact, and change over time.”

This result might also help explain the unusually large amount of star formation in the LMC nebula called 30 Doradus, also known as the Tarantula Nebula due to its appearance in a small telescope. This area is on the southwestern rim of the Large Magellanic Cloud and is a current hotbed of star formation.

If the 30 Doradus region was in our galaxy and as close to us as the Orion Nebula (the nearest stellar nursery to us), it would have the area of 60 full moons in our sky and its glow would cast shadows on the ground. The 30 Doradus region is located at the position where gas from the Small Magellanic Cloud that is being pulled into the Large Magellanic Cloud along with the captured stars collides with the LMC’s own gas at high velocity. The resultant shock wave from this collision of gas pressurizes and concentrates the gas, making star formation much more likely and leading to the formation of large, unstable stars which can explode, like the famous supernova that appeared in 1987. Remnants from an older supernova have also been found in this region by x-ray telescopes.

***

This research appears in a paper “A Population Of Accreted Small Magellanic Cloud Stars In The Large Magellanic Cloud” accepted for publication by The Astrophysical Journal. The paper authors are: Knut A.G. Olsen, National Optical Astronomy Observatory, Tucson, Arizona Dennis Zaritsky, Steward Observatory, University of Arizona Robert D. Blum, National Optical Astronomy Observatory, Tucson, Arizona Martha L. Boyer, Space Telescope Science Institute, Baltimore, Maryland Karl D. Gordon, Space Telescope Science Institute, Baltimore, Maryland

NOAO is operated by Association of Universities for Research in Astronomy Inc. (AURA) under a cooperative agreement with the National Science Foundation.

Science Contacts

Dr. Knut Olsen
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
+1 520-318-8555
Email: kolsen@noao.edu

Dr. Robert Blum
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
+1 520-318-8233
Email: rblum@noao.edu

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