Latecomers to the universe
A frequent sign of the maturity of a spiral galaxy is the formation of a ribbon of stars and gas that slices across the nucleus, like the slash across a ‘no smoking’ sign.
In a landmark study of more than 2,000 spiral galaxies from the largest galaxy census conducted by NASA’s Hubble Space Telescope, astronomers found that so-called barred spiral galaxies were far less plentiful 7 billion years ago than they are t
oday, in the local universe.
The study’s results confirm the idea that bars are a sign of galaxies reaching full maturity as the ‘formative years’ end.
The observations are part of the Cosmic Evolution Survey (COSMOS).
This new detailed look at the history of bar formation, made with Hubble’s Advanced Camera for Surveys, provides clues to understanding when and how spiral galaxies formed and evolved over time.
A team found that only 20 percent of the spiral galaxies in the distant past possessed bars, compared with nearly 70 per cent of their modern counterparts. — Our Bureau
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