From ETEN IAS (www.etenias.com)
Hubble discovers source of Magellanic Stream : Aug 09, 2013
Astronomers have solved a 40-year mystery on the origin of Magellanic Stream — a ribbon of gas stretching almost halfway around our Milky Way galaxy. The Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way, are at the head of the gaseous stream. New Hubble observations reveal most of the gas was stripped from the Small Magellanic Cloud about 2 billion years ago, and a second region of the stream originated more recently from the Large Magellanic Cloud.
Background
Who were the Observers?
Astronomers, led by Andrew J Fox of the Space Telescope Science Institute in Baltimore, determined the source of the gas filament by using Hubble’s Cosmic Origins Spectrograph to measure the amount of heavy elements, such as oxygen and sulphur, at six locations along the Magellanic Stream.
What did they observe?
They observed faraway quasars, the brilliant cores of active galaxies, that emit light that passes through the stream. They detected the heavy elements from the way the elements absorb ultraviolet light. Fox’s team found a low amount of oxygen and sulphur along most of the stream, matching the levels in the Small Magellanic Cloud about 2 billion years ago, when the gaseous ribbon is thought to have formed. In a surprising twist, the team discovered a much higher level of sulphur in a region of the stream that is closer to the Magellanic Clouds.
Why the discovery is important?
The Magellanic Stream is a stream of high-velocity clouds of gas extending from the Large and Small Magellanic Clouds over 100° through the Galactic south pole. It formed due to tidal interactions between the Magellanic Clouds and the Milky Way. Owing to the closeness of the Magellanic Clouds and the ability to resolve individual stars and their parallaxes, researchers made various observations, giving the full 6 dimensional phase space information of both clouds (with very large relative errors for the transverse velocities). This enabled the calculation of the likely past orbit of the Large and the Small Magellanic Cloud in relation to the Milky Way. The calculation necessitated large assumptions, for example, on the shapes and masses of the 3 galaxies, and the nature of dynamical friction between the moving objects. Observations of individual stars revealed details of star formation history.
This discovery was a wrinkle Fox’s team didn’t expect, because computer models of the stream predicted that the gas came entirely out of the Small Magellanic Cloud, which has less gravity than its more massive cousin. Astronomers have debated whether the two Magellanic Clouds are on their first pass near our Milky Way or are bound to it. The discovery confirmed that despite all the other nearby satellite galaxies of the Milky Way losing their gas, Magellanic Clouds retained their gas and still form stars due to higher mass.
What is a quasar?
The word quasar stands for quasi-stellar radio source. They are the brightest and most distant objects in the universe as we know it. The term quasar has fallen out of common use by astronomers and they are now known as quasi-stellar objects (QSOs) because we now know that they are not true stars. Quasars have a very high redshift. They are the most luminous, powerful, and energetic objects known of at this time. They seem to inhabit the centers of active young galaxies and can emit up to a thousand times the energy output of our entire galaxy. According to Hubble’s law, the redshift shows that quasars are very distant and due to their distance, much older than our universe. The most luminous quasars radiate in excess of the output of one trillion Suns. This radiation is emitted across the spectrum from X-rays to the far-infrared, but peaks in the ultraviolet-optical bands. Some quasars are strong sources of radio emission and gamma-rays. In early optical images, quasars looked like single points of light. Infrared telescopes and the Hubble Space Telescope have identified the galaxies surrounding the quasars. These galaxies are normally too dim to be seen against the glare of the quasar otherwise.
Questions
• What is the importance of research on Megallanic stream? How is it related to stars of a galaxy?
• How could the discovery about the source of Megallenic stream favour the improvement of our understanding of our galaxy?
• Space research isn’t confined to explorations on existence of Life. Comment on the basis of the recent discovery made using the Hubble Telescope.
References
• http://www.universetoday.com/73222/what-is-a-quasar/#ixzz2be9Pybkb
• http://en.wikipedia.org/wiki/Magellanic_Stream
• http://www.thehindu.com/sci-tech/science/hubble-discovers-source-of-magellanic-stream/article5006538.ece
Hubble discovers source of Magellanic Stream : Aug 09, 2013
Astronomers have solved a 40-year mystery on the origin of Magellanic Stream — a ribbon of gas stretching almost halfway around our Milky Way galaxy. The Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way, are at the head of the gaseous stream. New Hubble observations reveal most of the gas was stripped from the Small Magellanic Cloud about 2 billion years ago, and a second region of the stream originated more recently from the Large Magellanic Cloud.
Background
Who were the Observers?
Astronomers, led by Andrew J Fox of the Space Telescope Science Institute in Baltimore, determined the source of the gas filament by using Hubble’s Cosmic Origins Spectrograph to measure the amount of heavy elements, such as oxygen and sulphur, at six locations along the Magellanic Stream.
What did they observe?
They observed faraway quasars, the brilliant cores of active galaxies, that emit light that passes through the stream. They detected the heavy elements from the way the elements absorb ultraviolet light. Fox’s team found a low amount of oxygen and sulphur along most of the stream, matching the levels in the Small Magellanic Cloud about 2 billion years ago, when the gaseous ribbon is thought to have formed. In a surprising twist, the team discovered a much higher level of sulphur in a region of the stream that is closer to the Magellanic Clouds.
Why the discovery is important?
The Magellanic Stream is a stream of high-velocity clouds of gas extending from the Large and Small Magellanic Clouds over 100° through the Galactic south pole. It formed due to tidal interactions between the Magellanic Clouds and the Milky Way. Owing to the closeness of the Magellanic Clouds and the ability to resolve individual stars and their parallaxes, researchers made various observations, giving the full 6 dimensional phase space information of both clouds (with very large relative errors for the transverse velocities). This enabled the calculation of the likely past orbit of the Large and the Small Magellanic Cloud in relation to the Milky Way. The calculation necessitated large assumptions, for example, on the shapes and masses of the 3 galaxies, and the nature of dynamical friction between the moving objects. Observations of individual stars revealed details of star formation history.
This discovery was a wrinkle Fox’s team didn’t expect, because computer models of the stream predicted that the gas came entirely out of the Small Magellanic Cloud, which has less gravity than its more massive cousin. Astronomers have debated whether the two Magellanic Clouds are on their first pass near our Milky Way or are bound to it. The discovery confirmed that despite all the other nearby satellite galaxies of the Milky Way losing their gas, Magellanic Clouds retained their gas and still form stars due to higher mass.
What is a quasar?
The word quasar stands for quasi-stellar radio source. They are the brightest and most distant objects in the universe as we know it. The term quasar has fallen out of common use by astronomers and they are now known as quasi-stellar objects (QSOs) because we now know that they are not true stars. Quasars have a very high redshift. They are the most luminous, powerful, and energetic objects known of at this time. They seem to inhabit the centers of active young galaxies and can emit up to a thousand times the energy output of our entire galaxy. According to Hubble’s law, the redshift shows that quasars are very distant and due to their distance, much older than our universe. The most luminous quasars radiate in excess of the output of one trillion Suns. This radiation is emitted across the spectrum from X-rays to the far-infrared, but peaks in the ultraviolet-optical bands. Some quasars are strong sources of radio emission and gamma-rays. In early optical images, quasars looked like single points of light. Infrared telescopes and the Hubble Space Telescope have identified the galaxies surrounding the quasars. These galaxies are normally too dim to be seen against the glare of the quasar otherwise.
Questions
• What is the importance of research on Megallanic stream? How is it related to stars of a galaxy?
• How could the discovery about the source of Megallenic stream favour the improvement of our understanding of our galaxy?
• Space research isn’t confined to explorations on existence of Life. Comment on the basis of the recent discovery made using the Hubble Telescope.
References
• http://www.universetoday.com/73222/what-is-a-quasar/#ixzz2be9Pybkb
• http://en.wikipedia.org/wiki/Magellanic_Stream
• http://www.thehindu.com/sci-tech/science/hubble-discovers-source-of-magellanic-stream/article5006538.ece
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