WASHINGTON, June 28 (UPI) -- Tadpole galaxies are rare in the universe, and even more rare in the local universe -- there are just 20 in the "local" areas closest to Earth -- and new Hubble telescope images of one relatively close by is shedding new light on their formation.
New images of LEDA 36252, also known as Kiso 5639, were captured by Hubble, suggesting many of the stars in the galaxy are still forming as it drifts through a relatively gasless "desert" in the universe, which is why it has formed so slowly, astronomers suggest in a study published in The Astrophysical Journal.
About 10 percent of galaxies in the universe are referred to as tadpoles, because of how they are shaped, while most take on the usual circular, spinning shapes. Few have been found in parts of the universe closest to the Milky Way, with LEDA 36252 just 82 million light-years away.
Even with the continued formation of stars within LEDA 36252, it is still a remnant of the early universe, leading astronomers to study it to learn about the accretion of cosmic gas, starburst activity and the formation of globular star clusters, according to a press release.
Astronomers were surprised to find the head of the tadpole contains a high number of young stars with a total mass equal to about 10,000 suns. The stars mainly consist of hydrogen and helium with few other detectable elements, leading astronomers to think the new stars began to form when the galaxy accreted gas only slightly enriched by other elements from its surroundings.
"There is much more star formation going on in the head than what you would expect in such a tiny galaxy," Dr. Bruce Elmegreen, an astronomer at IBM's Thomas J. Watson Research Center, said in a press release. "And we think the star formation is triggered by the ongoing accretion of metal-poor gas onto a part of an otherwise quiescent dwarf galaxy."
The head of the LEDA 36252 measures about 2,700 light-years across and contains dozens of clusters of stars with an average age of less than 1 million years old, but mass three to six times larger than the rest of the stars in the galaxy -- although stars are forming throughout the galaxy at different speeds. Some star clusters farther away from the head are several million to billions of years old, the astronomers said.
Based on the images and computer simulations, the astronomers think the leading edge of the galaxy hit a filament of gas, dropping "a large clump" of matter onto it and instigating the birth of stars -- which they think could possibly happen again.
"Galaxies rotate, and as LEDA 36252 continues to spin, another part of the galaxy may receive an infusion of new gas from this filament, instigating another round of star birth," said Dr. Debra Elmegreen, an astronomer at Vassar College who led the study.