Jurassic Space: Ancient Galaxies Come Together After Billions of Years

February 18, 2010, University of Western Ontario
These four dwarf galaxies waited billions of years to come together, setting off a fireworks show as thousands of new star clusters come to life. The distorted galaxies are quickly producing massive, hot, young stars that are pumping out ultraviolet radiation, heating up surrounding gas clouds, and causing them to glow. Credit: NASA, ESA, S. Gallagher (The University of Western Ontario), and J. English (University of Manitoba)

(PhysOrg.com) -- Imagine finding a living dinosaur in your backyard. Astronomers have found the astronomical equivalent of prehistoric life in our intergalactic backyard: a group of small, ancient galaxies that has waited 10 billion years to come together. These "late bloomers" are on their way to building a large elliptical galaxy.

Such encounters between dwarf galaxies are normally seen billions of light-years away and therefore occurred billions of years ago. But these galaxies, members of Hickson Compact Group 31, are relatively nearby, only 166 million light-years away.

New images of this foursome by NASA's offer a window into the universe's formative years when the buildup of large galaxies from smaller building blocks was common.

Astronomers have known for decades that these dwarf galaxies are gravitationally tugging on each other. Their classical spiral shapes have been stretched like taffy, pulling out long streamers of gas and dust. The brightest object in the Hubble image is actually two . The entire system is aglow with a firestorm of star birth, triggered when is compressed by the close encounters between the galaxies, and collapses to form stars.

The Hubble observations have added important clues to the story of this interacting group, allowing astronomers to determine when the encounter began and to predict a future merger.

"We found the oldest stars in a few ancient globular star clusters that date back to about 10 billion years ago. Therefore, we know the system has been around for a while," says astronomer Sarah Gallagher of The University of Western Ontario in London, Ontario, leader of the Hubble study. "Most other like these interacted billions of years ago, but these galaxies are just coming together for the first time. This encounter has been going on for at most a few hundred million years, the blink of an eye in cosmic history. It is an extremely rare local example of what we think was a quite common event in the distant universe."

Everywhere the astronomers looked in this group they found batches of infant star clusters and regions brimming with . The entire system is rich in hydrogen gas, the stuff of which stars are made. Gallagher and her team used Hubble's Advanced Camera for Surveys to resolve the youngest and brightest of those clusters, which allowed them to calculate the clusters' ages, trace the star-formation history, and determine that the galaxies are undergoing the final stages of galaxy assembly.

The analysis was bolstered by infrared data from NASA's Spitzer Space Telescope and ultraviolet observations from the Galaxy Evolution Explorer (GALEX) and NASA's Swift satellite. Those data helped the astronomers measure the total amount of star formation in the system. "Hubble has the sharpness to resolve individual star clusters, which allowed us to age-date the clusters," Gallagher adds.

Hubble reveals that the brightest clusters, hefty groups each holding at least 100,000 stars, are less than 10 million years old. The stars are feeding off of plenty of gas. A measurement of the gas content shows that very little has been used up — further proof that the "galactic fireworks" seen in the images are a recent event. The group has about five times as much hydrogen gas as our Milky Way Galaxy.

"This is a clear example of a group of galaxies on their way toward a merger because there is so much gas that is going to mix everything up," Gallagher says. "The galaxies are relatively small, comparable in size to the Large Magellanic Cloud, a satellite galaxy of our Milky Way. Their velocities, measured from previous studies, show that they are moving very slowly relative to each other, just 134,000 miles an hour (60 kilometers a second). So it's hard to imagine how this system wouldn't wind up as a single in another billion years."

Adds team member Pat Durrell of Youngstown State University: "The four small galaxies are extremely close together, within 75,000 light-years of each other — we could fit them all within our Milky Way."

Why did the galaxies wait so long to interact? Perhaps, says Gallagher, because the system resides in a lower-density region of the universe, the equivalent of a rural village. Getting together took billions of years longer than it did for galaxies in denser areas.
Hickson Compact Group 31 is one of 100 compact galaxy groups catalogued by Canadian astronomer Paul Hickson.

Gallagher's results appear in the February issue of the Astronomical Journal.

Explore further: Colliding galaxies make love, not war

Related Stories

Colliding galaxies make love, not war

October 17, 2006

A new Hubble image of the Antennae galaxies is the sharpest yet of this merging pair of galaxies. As the two galaxies smash together, billions of stars are born, mostly in groups and clusters of stars. The brightest and most ...

Antennae Galaxies

May 19, 2008

This image of the Antennae galaxies is the sharpest yet of this merging pair of galaxies. During the course of the collision, billions of stars will be formed. The brightest and most compact of these star birth regions are ...

Hubble Eyes Star Birth in the Extreme

June 13, 2006

Staring into the crowded, dusty core of two merging galaxies, NASA's Hubble Space Telescope has uncovered a region where star formation has gone wild.

Stars forced to relocate near the Southern Fish

March 3, 2009

About 100 million light-years away, in the constellation of Piscis Austrinus (the Southern Fish), three galaxies are playing a game of gravitational give-and-take that might ultimately lead to their merger into one enormous ...

Survey Reveals Building Block Process For Biggest Galaxies

April 12, 2006

A new study of the universe's most massive galaxy clusters shows how mergers play a critical role in their evolution. Astronomers used the twin Gemini Observatory instruments in Hawaii and Chile, and the Hubble Space Telescope ...

Hubble Sees Star Cluster 'Infant Mortality'

January 10, 2007

Astronomers have long known that young or "open" star clusters must eventually disrupt and dissolve into the host galaxy. They simply don't have enough gravity to hold them together, unlike their much more massive cousins, ...

Recommended for you

Black hole spin cranks-up radio volume

January 12, 2018

Statistical analysis of supermassive black holes suggests that the spin of the black hole may play a role in the generation of powerful high-speed jets blasting radio waves and other radiation across the universe.

NASA team first to demonstrate X-ray navigation in space

January 11, 2018

In a technology first, a team of NASA engineers has demonstrated fully autonomous X-ray navigation in space—a capability that could revolutionize NASA's ability in the future to pilot robotic spacecraft to the far reaches ...


Adjust slider to filter visible comments by rank

Display comments: newest first

4 / 5 (1) Feb 19, 2010
GASP! these pictures of todays telescopes and sensors show so much more rich detail and info than 20 years ago, its absolutely awesome. Maybe the money that is freed up by halting a return to the moon could be used for bringing even better telescopes in space, so that we perhaps even could see individual continents (life?) and such on exoplanets, wouldn't that be much more exciting than replant a flag on the moon?
3 / 5 (2) Feb 19, 2010
How about an international effort/funding to assemble modules into a humongous spacetelescope attached to the international space station, where already is good infrastructure in place (robotic arm, people, solar arrays, datacenters) to service such a contraption?
not rated yet Feb 19, 2010
I like the idea, but it might not work well. The more asymmetric(both in shape and mass distribution) the ISS becomes, the more tricky it will be to dock with, and the more complicated it will be to maneuver.

L4 or L5 would be a good place to put such a telescope, (L3 would be cool too, but getting it there, and getting data back would be no simple endeavor)
5 / 5 (3) Feb 19, 2010
wouldn't that be much more exciting than replant a flag on the moon?
The moon has virtually no atmosphere and is almost tidally locked to the Earth. Put a telescope there, save on the fuel required to keep it in orbit, and invalidate the potential of collision or space junk creation.

When you head back up there to replace it, take the old one back with you and recycle it.

Does that not make more sense than continually littering Earth Orbit?

5 / 5 (1) Feb 19, 2010
Sure, plus there was some materials-science research done on the composition of moon dust a while back. Turns out we could make a kind of cement out of it. Now we'd just need the mirrors(and detectors and computers, all that stuff), and suddenly we have a giant and (most likely) fairly cheap telescope that has no atmospheric interference.
2.5 / 5 (2) Feb 19, 2010
The moon would be a great place to colonize simply for the scientific aspects.

Think of the experiments you can perform when you know the population impact is ZERO. Studies considered too harmful to study outside of hyper expensive labs can use more lax procedures on the moon.

Bacterial outbreak? blow it out the airlock.
Fusion experiment got too hot? Vent it into space.
Particle accelerator magneto-quench becomming a problem? Expose the materials to the void and use the "vaccuum" as an energy sink.

I know we couldn't do it today without massive expense, but if you evaluate the risk as an expense, then the moon becomes a far more attractive option.
4 / 5 (2) Feb 20, 2010
It would take far more energy to land the materials for a telescope on the moon than to keep that mass in orbit around the earth.
2.5 / 5 (2) Feb 20, 2010
It would take far more energy to land the materials for a telescope on the moon than to keep that mass in orbit around the earth.

Not when you can build the majority of the installation with materials already on the moon.
not rated yet Feb 21, 2010
Just try to measure the scientific returns from a very simple series of HST multiwavelength observations with that obtained by visual/photometric observations or lower resolution multiwavelenghth observations made by earthbound astronomers, including terrestrial weather complications and equipment malfunctions.
1 / 5 (5) Feb 21, 2010
Just consider the absurdity of this article; "Galaxies come together after billions of years". "New star clusters come to life". What fairy tails. Folks, this is not science. Were these people there to see them form? I would expect that light travels at a known speed. These galazies are far away, how do we know that space dust or something was just blocking the view until now? Cut the crappy, so-called "science". Science should be provable, repeatable, and certain. What energy is responsible for the so-called star birth?
not rated yet Feb 21, 2010
A fairly thorough 2004 analysis of HCG 31 is available here: http://www.iop.or...b1733e56
not rated yet Feb 21, 2010
Additional HST imagery and analysis (of NGC 1741=HCG 31) is also available in this 1999 paper: http://www.iop.or...587ce9e2
not rated yet Feb 21, 2010
Put a telescope there, save on the fuel required to keep it in orbit, and invalidate the potential of collision or space junk creation.

Doing it on the moon is a good idea. But it doesn't help to alleviate collision damage (the moon is pockmarked with craters for a reason). If anything the chance of impacts would be increased since the moon does have gravity but no atmosphere to burn up potentially damaging micrometeorites.

An advantage of orbital telescopes is that they can be kept pointed at an object for a long time (which telescopes on rotating objects like the earth and the moon cannot). This is essential for imaging faint objects.

Particle accelerator magneto-quench becomming a problem? Expose the materials to the void and use the "vaccuum" as an energy sink.

Surprisingly this doesn't work very well (vaccuum means: no convection, just radiation losses. Most space objects - like the ISS - have a massive problem in getting rid of their excess heat.)

not rated yet Feb 22, 2010
I was referring to atmospheric collision with other orbiting bodies, not collision on the whole, there's no way to stop all potential collision in space.
5 / 5 (3) Feb 22, 2010

i think you miss the point. It doesnt matter that we just discovered it, what matters is that a galaxy merger that typically would have occurred multiple billions of years ago is ongoing as of at least ~160 million years ago.
A dust cloud covering the galaxy cluster would have nothing whatsoever to do with the merger being a late bloomer...or anything to do with the article come to think of it....
not rated yet Feb 22, 2010
Indeed, the paper linked to this image: http://hubblesite.../pdf.pdf goes to great pains to point out that material is indeed present and IS forming new stellar systems in this this assemblage.
1 / 5 (2) Mar 07, 2010
There has not been enough time to observe any of the evolutionary changes they propose in the writing. The assumptions they use to support their theory is difficult to prove. In fact, testing such claims would fall outside the realm of current, empirical science.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.