From ‘Bumper Cars’ to a Celestial ‘Race Track’ UA Astronomers Continue Groundbreaking Finds

  • June 9th, 2001
This image captured by the Hubble Space Telescope, during observation time awarded to Dr. William Keel, shows two galaxies colliding.
This image captured by the Hubble Space Telescope, during observation time awarded to Dr. William Keel, shows two galaxies colliding.

With the help of the famed Hubble Space Telescope, University of Alabama astronomers have continued to uncover some impressive findings, with groundbreaking discoveries being presented separately this year to the prestigious American Astronomical Association. From the discovery of two galaxies that collided millions of years ago, to a star-forming ring that resembles a race track in form and function, the continued work of UA’s researchers is creating new levels of understanding about the cosmos for scientists and lay people alike.

Dr. William Keel, professor of astronomy, captured an image of two galaxies that actually collided more than 100 million years ago. Keel’s dramatic finding shows a lane of gas and star dust winding its way from one galaxy and being caught up by the gravity of another galaxy after the two bumped into one another.

Astronomers refer to the two neighboring galaxies as NGC 1410 and NGC 1409, respectively. Each is about half the size of our galaxy, the Milky Way, and is more than 300 million lightyears away from Earth. Scientists are interested in the transfer of mass between the two galaxies, partly because of what it can tell them about star formation. Keel’s image is one of the clearest depictions of such a transfer, and he says the galaxies are expected to continue bumping and moving apart until they finally merge — in about 200 million years.

Keel, who has been awarded observation time with the space-based telescope 11 times, presented his findings to the American Astronomical Association in January.

Drs. Ron Buta and Gene Byrd, both professors of astronomy at UA, collaborated on a spectacular finding — a star-forming ring in the disk of a distant galaxy. The images, which were officially presented at the American Astronomical Association’s 198th meeting in Pasadena, are of special interest because the distribution of new stars in the ring directly shows the shape of a real galactic orbit, something only rarely seen. Usually, single orbits are not well traced out in galaxies, and one cannot tell orbit shapes by looking at the appearance of a galaxy.

“These images help us understand how stars form and then grow older in galaxies,” said Buta. “Giant clouds of interstellar gas and dust are moving along an elliptical orbit centered on the nucleus of the galaxy. Just like cars on a flat oval racetrack, when these clouds reach the more sharply curved ends of the ellipse, they may bump into each other. This leads to formation of young star clusters that are observed to be concentrated around the ends of the ellipse. As these star clusters age, they move away from the ends around the orbit, leading to a beautiful ring-shaped elliptical pattern,” Buta continued.

“We have calculated gas cloud orbital positions at different times in NGC 3081 based on the bar’s gravitational field,” said Byrd. “The ring is caused by the way orbiting clouds of hydrogen gas in the plane of the galaxy are affected by the presence of the bar. This material is forced to move in an elliptical orbit around the ends of the bar, and we can see how the star clusters age as they move away from their birth places at the ends of the elongated ring.”

According to Buta, the team members involved in the findings were particularly surprised with the clarity of their views while using the space-based telescope. “We saw a surprising confirmation of our expectation that the gas and dust disk was not too thick in our first views of the Hubble Space Telescope images,” said Buta.

“Besides remarkably clear views of the star clusters of different ages around the ring, the Hubble Telescope images also show a group of more distant galaxies which are actually being viewed through the disk of NGC 3081.

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