Hubble finds source of Magellanic Stream

Hubble finds source of Magellanic Stream

Astronomers explore origin of gas ribbon wrapped around our galaxy

The Magellanic Clouds, two dwarf galaxies orbiting our galaxy, are at the head of a huge gaseous filament known as the Magellanic Stream. Since the Stream’s discovery in the early 1970s, astronomers have wondered whether this gas comes from one or both of the satellite galaxies. Now, new Hubble observations show that most of the gas was stripped from the Small Magellanic Cloud about two billion years ago — but surprisingly, a second region of the stream was formed more recently from the Large Magellanic Cloud.

Astronomers using the NASA/ESA Hubble Space Telescope have solved the 40-year-old mystery of the origin of the Magellanic Stream, a long ribbon of gas stretching nearly halfway around the Milky Way. New Hubble observations reveal that most of this stream was stripped from the Small Magellanic Cloud some two billion years ago, with a smaller portion originating more recently from its larger neighbour.

Astronomers using the NASA/ESA Hubble Space Telescope have solved the 40-year-old mystery of the origin of the Magellanic Stream, a long ribbon of gas stretching nearly halfway around the Milky Way. New Hubble observations reveal that most of this stream was stripped from the Small Magellanic Cloud some two billion years ago, with a smaller portion originating more recently from its larger neighbour.

A team of astronomers determined the source of the gas filament by using Hubble’s Cosmic Origins Spectrograph (COS), along with observations from ESO’s Very Large Telescope, to measure the abundances [1] of heavy elements, such as oxygen and sulphur, at six locations along the Magellanic Stream. COS detected these elements from the way they absorb the ultraviolet light released by faraway quasars as it passes through the foreground Stream. Quasars are the brilliant cores of active galaxies.

The team found low abundances of oxygen and sulphur along most of the stream, matching the levels in the Small Magellanic Cloud about two billion years ago, when the gaseous ribbon was thought to have been formed.

In a surprising twist, the team discovered a much higher level of sulphur in a region closer to the Magellanic Clouds. “We’re finding a consistent amount of heavy elements in the stream until we get very close to the Magellanic Clouds, and then the heavy element levels go up,” says Andrew Fox, a staff member supported by ESA at the Space Telescope Science Institute, USA, and lead author of one of two new papers reporting these results. “This inner region is very similar in composition to the Large Magellanic Cloud, suggesting it was ripped out of that galaxy more recently.”
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This discovery was unexpected; computer models of the Stream predicted that the gas came entirely out of the Small Magellanic Cloud, which has a weaker gravitational pull than its more massive cousin.

As Earth’s atmosphere absorbs ultraviolet light, it’s hard to measure the amounts of these elements accurately, as you need to look in the ultraviolet part of the spectrum to see them,” says Philipp Richter of the University of Potsdam, Germany, and lead author on the second of the two papers. “So you have to go to space. Only Hubble is capable of taking measurements like these.

All of the Milky Way’s nearby satellite galaxies have lost most of their gas content — except the Magellanic Clouds. As they are more massive than these other satellites they can cling on to this gas, using it to form new stars. However, these Clouds are approaching the Milky Way and its halo of hot gas. As they drift closer to us, the pressure of this hot halo pushes their gas out into space. This process, together with the gravitational tug-of-war between the two Magellanic Clouds, is thought to have formed the Magellanic Stream [2].

Exploring the origin of such a large stream of gas so close to the Milky Way is important,” adds Fox. “We now know which of our famous neighbours, the Magellanic Clouds, created this gas ribbon, which may eventually fall onto our own galaxy and spark new star formation. It’s an important step forward in figuring out how galaxies obtain gas and form new stars.

Notes

[1] The “abundance” of an element is a measure of how common it is in its environment relative to other elements.

[2] The Magellanic Clouds can be used as a good testing ground for theories on how galaxies strip gas from one another and form new stars. This process seems episodic rather than smooth, without a continuous, slow stream of gas being stripped away from a small galaxy by a larger one. As both of the Magellanic Clouds are approaching our own galaxy, the Milky Way, they can be used to explore the dynamics of this process.

Notes for editors

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

These results are presented in a set of two papers, both published in the 1 August issue of The Astrophysical Journal.

The first of these papers is entitled “The COS/UVES absorption survey of the Magellanic Stream: I. One-tenth solar abundances along the body of the stream”.

The international team of astronomers in this study consists of A. J. Fox (STScI, USA; ESA), P. Richter (University of Potsdam; Leibniz Institute for Astrophysics, Potsdam, Germany), B. P. Wakker (University of Wisconsin-Madison, USA), N. Lehner (University of Notre Dame, USA), J. C. Howk (University of Notre Dame, USA), N. B. Bekhti (University of Bonn, Germany), J. Bland-Hawthorn (University of Sydney, Australia), S. Lucas (University College London, UK).

The second of these papers is entitled “The COS/UVES absorption survey of the Magellanic Stream: II. Evidence for a complex enrichment history of the stream from the Fairall 9 sightline”.

The international team of astronomers in this study consists of P. Richter (University of Potsdam; Leibniz Institute for Astrophysics, Potsdam, Germany), A. J. Fox (STScI, USA; ESA), B. P. Wakker (University of Wisconsin-Madison, USA), N. Lehner (University of Notre Dame, USA), J. C. Howk (University of Notre Dame, USA), J. Bland-Hawthorn (University of Sydney, Australia), N. B. Bekhti (University of Bonn, Germany), C. Fechner (University of Potsdam, Germany).

More information

Image credit: David L. Nidever, et al., NRAO/AUI/NSF and Mellinger, LAB Survey, Parkes Observatory, Westerbork Observatory, and Arecibo Observatory.

Links

Editors note: Original article can be found here.

Credit: Spacetelescope

Is this the most distant galaxy?

Is this the most distant galaxy?

In the big image at left, the many galaxies of a massive cluster called MACS J1149+2223 dominate the scene. Gravitational lensing by the giant cluster brightened the light from the newfound galaxy, known as MACS 1149-JD, some 15 times. At upper right, a partial zoom-in shows MACS 1149-JD in more detail, and a deeper zoom appears to the lower right.Image credit: NASA/ESA/STScI/JHU

In the big image at left, the many galaxies of a massive cluster called MACS J1149+2223 dominate the scene. Gravitational lensing by the giant cluster brightened the light from the newfound galaxy, known as MACS 1149-JD, some 15 times. At upper right, a partial zoom-in shows MACS 1149-JD in more detail, and a deeper zoom appears to the lower right.
Image credit: NASA/ESA/STScI/JHU

The pixelated image on the lower right may not look like much to any of you, but it in fact, may very well be the most distant galaxy ever photographed by Spitzer and Hubble. So distant, the light from this galaxy first shone when the universe was a mere 500 MILLION years old. It may provide some valuable answers to astronomers about the transitional period between a dark, colorless universe to the cosmic expanse filled with the light of trillions of stars, with brilliant nebulae looming through stellar nurseries and an untold number of planets that may circle alien suns.

A common method of determining cosmic distances relies on measuring the red-shift of objects in the universe. Objects that are traveling away from our line of sight (due to the accelerated expansion of the universe) will shift towards a longer wavelength, which happens to be red. Objects that are traveling towards us (like the Andromeda galaxy) will shift towards a shorter wavelength, thus appearing blue. This galaxy has a red-shift of 9.6. Actually seeing the thing to begin with is slaying a whole other beast entirely since even the most sensitive of our space telescopes have their limits. So instead, we rely on a method called gravitational lensing. In this scenario, the light from background objects is amplified due to to the warping of spacetime from objects that have mass. Since there are massive galaxy clusters lying on the outskirts of our galaxy and the one we’re recently observed, the warping of spacetime magnifies the light, bringing the galaxy into focus some 15 times more so than it would appear had the cluster of galaxies not provided gravitational lensing as a tool for detection.

The so-called “cosmic dark ages” has been a bugaboo to understand for astronomers that are trying to put the pieces together of how the universe has evolved from the inception of spacetime initiated after the big bang, to the exotic particles and baffling observations made since Hubble took to the skies back in April of 1990. The light from this particular primordial galaxy has traveled 13.2 billion light-years before it was ultimately captured by Hubble’s infrared filters. To put that into perspective, the universe was only 3.6 percent of its current age when the light set forth on its path to the Milky Way.

Astronomers have estimated that we’re looking at the galaxy as it appeared when it was a mere 200 million year old. Since its total mass is only 1% that of the Milky Way, this gives creedence to the theories put forth that suggests the first galaxies in a young universe started out very tiny before they progressively merged together, forming the large galaxies we see surrounding us today. It’s also thought that the transition between tiny galaxies to the ones we see now played a role in the “epoch of reionization,” which began around 400,000 years after the big bang. During this time, neutral hydrogen gas was formed cooling particles as entropy increased as the universe began to cool. It was at that point when the first stars arose in the tiny galaxies formed in that period. The energy released from them is believed to be the catalyst for the neutral hydrogen to lose an electron through a process called ionization — a state the gas has remained in even billions of years later.

When Hubble’s successor, the James Webb telescope is launched in 2018 – this galaxy is sure to be looked at much closer. As Leonidas Moustakas, a research scientist at NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif said: “In essence, during the epoch of re-ionization, the lights came on in the universe.”

By Jaime Trosper

For more Information:

“NASA Telescopes Spy Ultra-Distant Galaxy:”
http://www.jpl.nasa.gov/news/news.php?release=2012-294

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The Galaxy Puzzle in the Constellation of Centaurus

The Galaxy Puzzle in the Constellation of Centaurus

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The Universe loves to fool our eyes, giving the impression that celestial objects are located at the same distance from Earth. A good example can be seen in this spectacular image produced by the NASA/ESA Hubble Space Telescope. The galaxies NGC 5011B and NGC 5011C are imaged against a starry background.

Located in the constellation of Centaurus, the nature of these galaxies has puzzled astronomers. NGC 5011B (on the right) is a spiral galaxy belonging to the Centaurus Cluster of galaxies lying 156 million light-years away from the Earth. Long considered part of the faraway cluster of galaxies as well, NGC 5011C (the bluish galaxy at the center of the image) is a peculiar object, with the faintness typical of a nearby dwarf galaxy, and the size of an early-type spiral.

Astronomers were curious about the appearance of NGC 5011C. If the two galaxies were at roughly the same distance from Earth, they would expect the pair to show signs of interactions between them. However, there was no visual sign of interaction between the two. How could this be possible?

To solve this problem, astronomers studied the velocity at which these galaxies are receding from the Milky Way and found that NGC 5011C is moving away far more slowly than its apparent neighbor, and its motion is more consistent with that of the nearby Centaurus A group at a distance of 13 million light-years. Thus, NGC 5011C, with only about ten million times the mass of the sun in its stars, must indeed be a nearby dwarf galaxy rather than a member of the distant Centaurus Cluster as was believed for many years.

Problem solved.

This image was taken with Hubble’s Advanced Camera for Surveys using visual and infrared filters.

ESA/Hubble & NASA

Credit: www.nasa.gov
Original linK: http://www.nasa.gov/mission_pages/hubble/science/ngc5011b-c.html

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Hubble Images a Swarm of Ancient Stars

Hubble Images a Swarm of Ancient Stars

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This stellar swarm is M80 (NGC 6093), one of the densest of the 147 known globular star clusters in the Milky Way galaxy. Located about 28,000 light-years from Earth, M80 contains hundreds of thousands of stars, all held together by their mutual gravitational attraction. Globular clusters are particularly useful for studying stellar evolution, since all of the stars in the cluster have the same age (about 15 billion years), but cover a range of stellar masses. Every star visible in this image is either more highly evolved than, or in a few rare cases more massive than, our own Sun. Especially obvious are the bright red giants, which are stars similar to the Sun in mass that are nearing the ends of their lives. By analyzing the Wide Field and Planetary Camera 2 (WFPC2) images, including images taken through an ultraviolet filter, astronomers have found a large population of “blue stragglers” in the core of the cluster.

These stars appear to be unusually young and more massive than the other stars in a globular cluster. However, stellar collisions can occur in dense stellar regions like the core of M80 and, in some cases, the collisions can result in the merger of two stars. This produces an unusually massive single star, which mimics a normal, young star. M80 was previously unknown to contain blue stragglers, but is now known to contain more than twice as many as any other globular cluster surveyed with NASA’s Hubble Space Telescope (HST). Based on the number of blue stragglers, the stellar collision rate in the core of M80 appears to be exceptionally high. M80 is also unusual because it was the site of a nova explosion in the year 1860. Nova outbursts occur when a close companion star transfers fresh hydrogen fuel to a burned-out white dwarf. Eventually the hydrogen ignites a thermonuclear explosion on the surface of the white dwarf, giving rise to the nova outburst. The ultraviolet Hubble observations have revealed the hot, faint remnant of this exploding star, which was named T Scorpii in the 19th century. Curiously, however, the WFPC2 observations have revealed only two other nova-like close binary stars in M80, far fewer than expected theoretically based on the stellar collision rate. So the blue stragglers in M80 seem to indicate that there are lots of collisions, yet the nova-like stars suggest only a few. Sometimes life for astronomers isn’t so simple, but it is from exploring discrepancies like this that our understanding eventually deepens.

This high-resolution image was created from 2 separate pointings of HST. One WFPC2 data set was obtained by Francesco R. Ferraro (ESO, Bologna Obs.), Barbara Paltrinieri (U. La Sapienza), Robert T. Rood (U. Virginia), and Ben Dorman (Raytheon/STX), who study blue stragglers. The other data set was acquired by Michael Shara (STScI, AMNH), David Zurek (STScI), and Laurent Drissen (U. Laval) to search for dwarf novae. Technical facts about this news release: About this Object Object Name: NGC 6093 (M80) Object Description: Globular Cluster in the Milky Way Galaxy Position (J2000): R.A. 16h 17m 03s Dec. -22° 58′ 30″ Constellation: Scorpius Distance: 8.7 kiloparsecs (28,000 light-years) Dimensions: The image is 3 arcminutes on the vertical side. About the Data Instrument: WFPC2 Exposure Dates: October 1994, August-October, 1997; January/April, 1996 Filters: F336W(U), F439(B), F555W(V), F675W(R) Principal Astronomers: 1994/1997 Image: M. Shara (STScI, AMNH), D. Zurek (STScI), L. Drissen (Laval University). 1996 Image: F. Ferraro (ESO), B. Paltrinieri (Universita La Sapienza), R. Rood (University of Virginia), B. Dorman (Raytheon STX & Laboratory for Astronomy & Solar Physics).About this Image Image Credit: NASA and The Hubble Heritage Team (STScI/AURA) Release Date: July 1, 1999 12:00 noon (EDT) Orientation: North is toward the upper right of the image. What is Hubble Heritage? A monthly showcase of new and archival Hubble images. Go to the Heritage site. This stellar swarm is M80 (NGC 6093), one of the densest of the 147 known globular star clusters in the Milky Way Galaxy. Located about 28,000 light-years from Earth, M80 contains hundreds of thousands of stars, all held together by their mutual gravitational attraction. Globular clusters are particularly useful for studying stellar evolution, since all of the stars in the cluster have the same age (about 15 billion years), but cover a range of stellar masses. Every star visible in this image is either more highly evolved than, or in a few rare cases more massive than, our own Sun. Especially obvious are the bright red giants, which are stars similar to the Sun in mass that are nearing the ends of their lives. *News Release Number:*: STScI-1999-26a

NASA Identifier: SPD-HUBBLE-STScI-1999-26a

Read more: http://www.dvidshub.net/image/692947/hubble-images-swarm-ancient-stars#.UOqzOm-6eSo#ixzz2HIe3LAJX

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Credit: http://www.dvidshub.net

Eyes and Nebulas, profoundly amazing! A must see!

Eyes and Nebulas, profoundly amazing! A must see!

Credit: The hubble site: www.hubblesite.org