Newborn stars shine like celestial sparklers in a new portrait of the nearby Triangulum Galaxy â the most detailed ultraviolet image of a galaxy ever taken. Astronomers will use the image, taken by NASAâs Swift telescope, to create an âage mapâ of the galaxyâs components to understand how galaxies evolve over time.
The Triangulum galaxy, also known as M33, lies about 2.9 million light years from Earth and is a member of the âLocal Groupâ of galaxies that includes the Milky Way.
It is about 10 times less massive than our galaxy and about half as wide. â[But] despite M33âs small size, it has a much higher star-formation rate than either the Milky Way or Andromeda,â says image creator Stefan Immler of NASAâs Goddard Space Flight Center in Greenbelt, Maryland, US. âAll of this star birth lights up the galaxy in the ultraviolet.â
Advertisement
The high fertility rate is likely due to the fact that M33 is at a younger evolutionary stage than its larger neighbours, which have used up most of their star-forming gas, Immler says. âThis period of star formation has basically come to an end [in the Milky Way] because the supply of gas has been exhausted already,â he told New ĐÓ°ÉÔ´´.
The history of all that star formation can be decoded by studying hundreds of stellar groups called globular clusters, says Immler. Thatâs because stars are nuclear furnaces that create heavy elements such as carbon, so each generation of stars tends to be richer in such elements than its predecessor.
âFierce windsâ
By studying the chemical composition of the various globular clusters, scientists can âcreate an age map of the galaxyâ, says Immler. âWe can see what are the young parts of the galaxy, what are the old parts and see how galaxies evolve over time.â
The image should also shed light on the processes that shape a galaxy over time, Immler says. âThese young stars have strong and fierce stellar winds, and blow out heavier, chemically enriched gas that affects the entire chemical evolution of the galaxy,â he says.
The new picture, which was stitched together from a series of snapshots taken by Swiftâs Ultraviolet/Optical Telescope (UVOT) in December 2007 and January 2008, is the most detailed UV image ever made of a galaxy.
The Hubble Space Telescope can take sharper UV images, but its field of view is much smaller than Swiftâs. Hubble would need 100 different âpointingsâ or views to encompass all of M33 â which would take a prohibitively long time to make, whereas Swift needed only 13.
Another space telescope, called , has a wider field of view than Swift, requiring just one or two pointings to image M33, but its resolution is two to three times less sharp than Swiftâs.
