Hubble zooms in on beautiful spring spiral galaxy
EUROPEAN SPACE AGENCY NEWS RELEASE
Posted: February 28, 2001
Astronomers have long suspected that the bar systems that dominate the appearance of some spiral galaxies provide an efficient mechanism for fuelling star births at their centers. New results from the NASA/ESA Hubble Space Telescope provide evidence that this is indeed the case.
NGC 2903's swirling whirlpool of stars spans 80,000 light-years -- slightly less than our own Milky Way -- and is located at a distance of some 25 million light-years. NGC 2903 is one of the more conspicuous northern objects that Charles Messier missed when compiling his catalogue of nebulous objects, so leaving its discovery to William Herschel.
This colorful image, obtained by the Wide Field and Planetary Camera 2 (WFPC2) onboard Hubble, lays bare the fine detail in the central part of the galaxy's bar. The image is dominated by the bar running diagonally just above the center of the image. It is the structure with a slightly reddish glow lying within the bluish spiral arms. The reddish colour arises from large amounts of dust in the bar.
Bars in spiral galaxies seem to be ubiquitous in our local Universe. Up to two-thirds of all spirals contain bars. Astronomers have long suspected that the bars provide an efficient mechanism for fuelling star births in the centers of barred galaxies.
Circumnuclear rings are also seen in other galaxies and are often interpreted as being due to interstellar gas falling in towards their centers. "We believe that the ring of newly-born stars around the core of NGC 2903 is created because the bar acts as a transport mechanism, funnelling gas inwards," says Almudena Alonso-Herrero. "Bars seem to be extremely efficient in triggering the formation of stars and they act as funnels for the flow of material from the outer parts of galaxy disks towards their centers."
Hubble's close-up view also shows other interesting details in the galaxy's center: huge dust lanes and lots of young stars are gathered in hot blue clusters sprinkled all over the spiral arms. NGC 2903 bears a close resemblance to the Milky Way, which is also believed to be a barred spiral galaxy. Barred spirals are excellent laboratories in which to study the processes that trigger star formation, and bars may be responsible for providing the gaseous fuel being gobbled up by massive central black holes in so-called active galaxies.