Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

Old galaxies stick together

New evidence suggests old galaxies stay together and grow into large galaxies.
Provided by JAC/UKIRT in Honolulu, Hawaii
old galaxies
The white arrows point to a few of the old, massive galaxies at a distance of 10 billion light years, discovered in the UKIDSS Ultra-Deep survey. This cut-out image represents just 1/150th of the full survey.
UKIDSS UDS Survey Team
April 2, 2008
Using the most sensitive images ever obtained with the United Kingdom Infra-Red Telescope (UKIRT), astronomers have found convincing evidence that galaxies, which look old early in the history of the universe, reside in enormous clouds of invisible dark matter and will eventually evolve into the most massive galaxies that exist in the present day.

The distant galaxies identified in the UKIRT images are considered elderly because they are rich in old, red stars. However, because the light from these systems has taken up to 10 billion years to reach Earth, they are seen as they appeared in the very early universe, just 4 billion years after the Big Bang. The presence of such fully evolved galaxies so early in the life of the cosmos is hard to explain and has been a major puzzle to astronomers studying how galaxies form and evolve.
United Kingdom Infrared Telescope
The United Kingdom Infrared Telescope sits on Mauna Kea, Hawaii
JAC/UKIRT
University of Nottingham PhD student Will Hartley, who led the study, and collaborators used the deep UKIRT images to estimate the mass of the dark matter surrounding the old galaxies by measuring how strongly the galaxies cluster together. All galaxies are thought to form within massive halos of dark matter which collapse under their own gravity from a smooth distribution of matter after the Big Bang.

These halos are invisible to normal telescopes but their mass can be estimated through analysis of galaxy clustering.

Hartley explains, "Luckily, even if we don't know what dark matter is, we can understand how gravity will affect it and make it clump together. We can see that the old, red galaxies clump together far more strongly than the young, blue galaxies, so we know that their invisible dark matter halos must be more massive."
United Kingdom Infrared Telescope
The Wide Field Camera (long black tube) on the United Kingdom Infrared Telescope on Mauna Kea, Hawaii.
JAC/UKIRT
The halos surrounding the old galaxies in the early universe are found to be extremely massive, containing material up to one hundred thousand billion times the mass of our Sun. In the nearby universe, halos of this size are known to contain giant elliptical galaxies, the largest galaxies known.

"This provides a direct link to the present day universe," says Hartley, "and tell us that these distant old galaxies must evolve into the most massive but more familiar elliptical-shaped galaxies we see around us today. Understanding how these enormous elliptical galaxies formed is one of the biggest open questions in modern astronomy and this is an important step in comprehending their history."

Hartley spoke at the RAS National Astronomy Meeting in Belfast on Tuesday April 1.
0

JOIN THE DISCUSSION

Read and share your comments on this article
Comment on this article
Want to leave a comment?
Only registered members of Astronomy.com are allowed to comment on this article. Registration is FREE and only takes a couple minutes.

Login or Register now.
0 comments
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

ADVERTISEMENT
ADVERTISEMENT
BoxProductcovernov

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook

Loading...