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Astronomers discover huge disturbed galaxy relic | Astronomy



The disturbed galaxy "tadpole" has an elliptical head and a long straight tail, and is about a million light-years long – about 10 times larger than our own Milky Way galaxy, according to astronomer Noah Brosch -authors.

This image shows the HCG 98 group. The heart of HCG 98 consists of both

This image shows the HCG 98 group. The heart of HCG 98 consists of the two "spots" in the center of the image. Each is a galaxy very similar to our own galaxy of the Milky Way. The tadpole structure covers the pair of central galaxies and formed when the pair demolished a much smaller galaxy. Image credit: Brosch et al, doi: 10.1093 / mnras / sty2717.

The new galaxy is part of Hickson Compact Group 98 (HCG 98), a small group of galaxies located about 300 million light-years away from Earth.

"In compact group environments, we believe we can study" clean "examples of galaxy interactions, learn how matter is transferred between members, and how newly accumulated matter can alter and influence the growth and development of galaxies." said Dr. Brosch.

Dr. Brosch and his colleagues observed the HCG 98 group with a 28-inch (71 cm) telescope at the Wise Observatory and confirmed it with additional observations with a similar 28-inch screen at the same time. 39, Polaris observatory.

They also used the Sloan Digital Sky Survey archive images of the IAC Stripe 82 Legacy project.

"The extragalactic tadpole contains a system of two very close" normal "galaxy discs, each about 40,000 light years away," said Dr. Brosch.

"Together with other nearby galaxies, galaxies form a compact group."

"What makes this object extraordinary is that the tail alone is almost 500,000 light-years long," added Professor Michael Rich, a member of the team, astronomer at the University of Toronto. University of California at Los Angeles.

"If it was at the distance from the Andromeda galaxy, which is about 2.5 million light-years away from Earth, it would reach one-fifth of the way to our own lane. milk. "

The giant "tadpole" was created by the disruption of a small dwarf galaxy, previously invisible, containing mainly stars, discovered astronomers.

"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," they said.

"The stars trailing in the victim galaxy formed the" tail "."

The discovery is reported in the Monthly Notices from the Royal Astronomical Society.

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Noah Brosch et al. 2019. Hickson Compact Group 98: A complex merging group with a giant tide and a gigantic envelope. MNRAS 482 (2): 2284-2293; doi: 10.1093 / mnras / sty2717


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