Wednesday 12 September 2012

The Farthest Spiral Galaxy Ever Seen

At the edge of the observable universe, where most galaxies appear as blobs, lies BX442. It is found within the constellation Pegasus and has a redshift of 2.18; meaning it is 10.7 billion light-years from Earth and therefore existed just 3 billion years after the big bang.

Astronomer David Law and his team at the University of Toronto, St. George, in Canada used the Hubble Space Telescope to examine 306 distant galaxies. They spied a galaxy with three spiral arms, and confirmed the distance of the galaxy with subsequent observations using the Keck II telescope in Hawaii. The Doppler shifts from different parts of the galaxy’s disk show that it spins as fast as the Milky Way does. The galaxy is 50,000 light years across and though half the size of the Milky Way, it harbours more gas and spawns more stars. 

In the distant past, spiral galaxies were rare, as stars and gas clouds moved fast relative to each other which suppressed spiral structure and also caused more galactic collisions. Other galaxies from such early epochs appear clumpy and irregular. Almost two thirds of today’s bright galaxies are spirals. BX442’s spiral nature may be due to the small companion it has, stirring up the spiral structure, though it could be down to the large amount of gas in the galaxy.

In the time it has taken for the light of this galaxy to travel to Earth, it may already have collided with another galaxy, tearing apart the spirals and leaving the galaxy as an ellipsoidal shape.

The image shows an artist’s conception of the galaxy to the right; the image at left is of a companion galaxy whose gravity may have caused the spiral structure.

Photo: THE FARTHEST SPIRAL GALAXY EVER SEEN

At the edge of the observable universe, where most galaxies appear as blobs, lies BX442. It is found within the constellation Pegasus and has a redshift of 2.18; meaning it is 10.7 billion light-years from Earth and therefore existed just 3 billion years after the big bang.

Astronomer David Law and his team at the University of Toronto, St. George, in Canada used the Hubble Space Telescope to examine 306 distant galaxies. They spied a galaxy with three spiral arms, and confirmed the distance of the galaxy with subsequent observations using the Keck II telescope in Hawaii. The Doppler shifts from different parts of the galaxy’s disk show that it spins as fast as the Milky Way does. The galaxy is 50,000 light years across and though half the size of the Milky Way, it harbours more gas and spawns more stars. 

In the distant past, spiral galaxies were rare, as stars and gas clouds moved fast relative to each other which suppressed spiral structure and also caused more galactic collisions. Other galaxies from such early epochs appear clumpy and irregular. Almost two thirds of today’s bright galaxies are spirals. BX442’s spiral nature may be due to the small companion it has, stirring up the spiral structure, though it could be down to the large amount of gas in the galaxy.

In the time it has taken for the light of this galaxy to travel to Earth, it may already have collided with another galaxy, tearing apart the spirals and leaving the galaxy as an ellipsoidal shape.

The image shows an artist’s conception of the galaxy to the right; the image at left is of a companion galaxy whose gravity may have caused the spiral structure.

-TEL

http://news.sciencemag.org/sciencenow/2012/07/hubble-spots-the-farthest-spiral.html; http://www.nature.com/nature/journal/v487/n7407/full/nature11256.html

Image Credit: (left) David Law; (right) Joe Bergeron, Dunlap Institute for Astronomy and Astrophysics http://news.sciencemag.org/sciencenow/assets_c/2012/07/sn-spiral-thumb-800xauto-13979.jpg

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