Post by glactus on Feb 6, 2010 3:02:53 GMT
Galaxy classification
Using data from the NASA/ESA Hubble Space Telescope, astronomers have, for the first time, created a demographic census of galaxy types and shapes from a time before the Earth and the Sun existed, to the present day.
Distant galaxies
The results show that, contrary to contemporary thought, more than half of the present-day spiral galaxies had so-called peculiar shapes only 6000 million years ago, which, if confirmed, highlights the importance of collisions and mergers in the recent past of many galaxies. It also provides clues for the unique status of our own galaxy, the Milky Way.
Galaxy morphology, or the study of the shapes and formation of galaxies, is a critical and much-debated topic in astronomy. An important tool for this is the Hubble sequence or Hubble tuning-fork diagram, a classification scheme invented in 1926 by the same Edwin Hubble in whose honour the space telescope is named.
A team of European astronomers led by François Hammer of the Observatoire de Paris has, for the first time, completed a demographic census of galaxy types at two different points in the Universe's history - in effect, creating two Hubble sequences - that help explain how galaxies form. In this survey, researchers sampled 116 local galaxies and 148 distant galaxies.
Contrary to previous thought, the astronomers showed that the Hubble sequence six thousand million years ago was very different from the one that astronomers see today.
"Six thousand million years ago, there were many more peculiar galaxies than now - a very surprising result," says Rodney Delgado-Serrano, lead author of the related paper recently published in and highlighted on the cover of Astronomy and Astrophysics.
Although our own Milky Way galaxy is a spiral galaxy, it seems to have been spared much of the teenage drama; its formation history has been rather quiet and it has avoided violent collisions in astronomically recent times. However, the large Andromeda galaxy from our neighbourhood has not been so lucky and fits well into the "spiral rebuilding" scenario. Researchers continue to seek out explanations for this.
Credits: image: www.kof.zcu.cz/st/dis/schwarzmeier/dissSchwarzmeier2_files/image409.jpg
This is part text only. See full text and all scientists involved at Spacedailt .com
www.spacedaily.com/reports/Do_Spirals_Make_Us_So_999.html