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A team of astronomers from Israel, the United States and Russia has identified a disturbed galaxy resembling a giant tadpole, with an elliptical head and a long straight tail, located about 300 million light years away. of the earth. The galaxy extends over 1 million light-years long, 10 times longer than the Milky Way.
"We have found an exceptional and exceptional relic of a disturbed galaxy," says Dr. Noah Brosch, of The Florence and George Wise Observatory of the School of Physics and Astronomy of the United States. Tel Aviv University, who led the research.
When galaxies are disturbed and disappear, their stars are either incorporated into more massive galaxies or ejected into an intergalactic space. "What makes this object extraordinary is that its tail alone is nearly 500,000 light-years away," says Professor R. Michael Rich of UCLA. "If it was at the distance from the Andromeda galaxy, which lies about 2.5 million light-years away from Earth, it would reach one-fifth of the way to our own lane. milk. "
Drs. Brosch and Rich collaborated on the study with Dr. Alexandr Mosenkov from the University of St. Petersburg and Dr. Shuki Koriski from the Florence and George Wise Observatory of the TAU and the School of Physics and Astronomy . The results were published in the Monthly Notices from the Royal Astronomical Society.
According to the study, the giant "tadpole" was created by the disruption of a small, previously invisible, dwarf galaxy, containing mostly stars. When the gravitational force of two visible galaxies attracted stars into this vulnerable galaxy, the closest stars of the pair formed the "head" of the tadpole. The stars trailing in the victim galaxy formed the "tail".
"The extragalactic tadpole contains a system of two very close" normal "galaxy discs, each about 40,000 light-years in diameter," says Dr. Brosch. "Together with other nearby galaxies, galaxies form a compact group." The galaxy is part of a small group of galaxies called HCG098, which will merge into a single galaxy over the next billion years.
These groups of compact galaxies were identified in 1982 by astronomer Paul Hickson, who published a catalog of 100 of these groups. The Hickson compact groups are looking at environments with high galaxy densities that are not at the core of a "group" of galaxies (the clusters contain thousands of galaxies themselves). The "tadpole galaxy" is listed in the Hickson Group catalog under number 98.
"In the compact working groups, we think we can study" clean "examples of interactions between galaxies, learn how material is transferred between members, and how newly accumulated material can modify and influence the growth and development of galaxies, "says Dr. Brosch.
For research, scientists have collected dozens of target images, each exposed through a wide filter that selects red light while virtually eliminating any light pollution. "We used a relatively small 70 cm telescope at the Wise Observatory and an identical UCLA telescope, both equipped with state-of-the-art CCD cameras," says Dr. Brosch. The two telescopes are collaborating on a project called Survey of Halos and Near-galaxy Environments.
The new study is part of a long-term project led by Florence's TAU observatory and George Wise, which explores the low-light sky to detect the smallest details of the galaxies studied.
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