Hubble Space Telescope Finds Source of Magellanic Stream
Astronomers using NASA's Hubble Space Telescope have solved a 40-year mystery
on the origin of the Magellanic Stream, a long ribbon of gas stretching nearly
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. Since the stream's discovery by
radio telescopes in the early 1970s, astronomers have wondered whether the gas
comes from one or both of the satellite galaxies. 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.
A team of astronomers, led by Andrew J. Fox of the Space Telescope Science
Institute in Baltimore, Md., 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 sulfur, at six locations along the Magellanic Stream. 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 sulfur 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 sulfur in a region of the stream that is
closer to the Magellanic Clouds.
Image Credit: NASA
Guillermo Gonzalo Sánchez Achutegui
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