`Spirals galaxies of modern universe were ugly 6-bn-yr-ago`

Last Updated: Thursday, February 4, 2010 - 23:52

Washington: The beautiful spirals galaxies
of modern Universe were ugly ducklings six billion years ago,
European astronomers have claimed.

Using data from the NASA/ESA Hubble Space Telescope, the
team led by Francois Hammer of the Observatories de Paris has
created a census of galaxy types and shapes from a time before
the earth and the sun existed, up to the present day.

After sampling 116 local galaxies and 148 distant
galaxies, they found that contrary to contemporary thought,
more than half of the present-day spiral galaxies had peculiar
shapes as recently as 6 billion years ago.

"This means that in the last six billion years, these
peculiar galaxies must have become normal spirals, giving us a
more dramatic picture of the recent Universe than we had
before," Hammer said.

The team, for the first time, completed a 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, European Space Agency reported.

The astronomers show that the Hubble sequence six
billion years ago was very different from the one that
astronomers see today.

"Six billion years ago, there were many more peculiar
galaxies than now a very surprising result," said Rodney
Delgado-Serrano, lead author of the related paper recently
published in Astronomy and Astrophysics.

"This means that in the last six billion years, these
peculiar galaxies must have become normal spirals, giving us a
more dramatic picture of the recent Universe than we had
before," Delgado-Serrano said.

The study of the shapes and formation of galaxies, known
as morphology, is a critical and much-debated topic in
astronomy.

An important tool for this is the `Hubble sequence` or
the `Hubble tuning-fork diagram`, a classification scheme
invented in 1926 by the same Edwin Hubble in whose honour the
space telescope is named.

Hubble`s scheme divides regular galaxies into three broad
classes elliptical, lenticulars and spirals based on
their visual appearance. A fourth class contains galaxies with
an irregular appearance.

"Our aim was to find a scenario that would connect the
current picture of the Universe with the morphologies of
distant, older galaxiesto find the right fit for this
puzzling view of galaxy evolution," says Hammer.

Also contrary to the widely held opinion that galaxy
mergers result in the formation of elliptical galaxies, Hammer
and his team support a scenario in which these cosmic clashes
result in spiral galaxies.

PTI



First Published: Thursday, February 4, 2010 - 23:52

More from zeenews

 
comments powered by Disqus