How Galaxy CGCG254-021 Got its Tail

A tale of two galactic cities 

Space news (galaxy formation: galaxy tails; the largest ever) – 680 million light-years from Earth toward the constellation Hercules – 

The ghostly blue, diffuse ribbon of hot gas seen trailing behind galaxy CGCG254-021 in the upper right of this composite image is the longest, largest galaxy tail observed during the human journey to the beginning of space and time. This stunning view was made using X-ray data (blue) collected by NASA’s Chandra Observatory and data (yellow) from the Isaac Newton Group of Telescopes.

NASA’s Galaxy Evolution Explorer found a tail behind a galaxy called IC 3418. The star-studded tail can be seen on the left, as detected by the space telescope in ultraviolet light. The tail has escaped detection in visible light, as shown by the image on the right, taken by a visible-light telescope on the ground. This tail was created as the galaxy plunged into gas in a family of galaxies known as the Virgo cluster.
The image on the left is a composite of data from the Galaxy Evolution Explorer (far-ultraviolet light is dark blue and near-ultraviolet light is light blue); and the Sloan Digital Sky Survey (visible light is colored green and red). The image on the right is from the Sloan Digital Sky Survey.
Other galaxies and stars can be seen scattered throughout the image. Another galaxy called IC 3413, which is part of the Virgo cluster, can be seen to the right of IC 3418 as an oval-shaped blob. The bright large dot at upper right is a star in our Milky Way galaxy.
Image Credit:
NASA/JPL-Caltech

Galaxy tails are wispy ribbons of hot gas stripped from a galaxy as it travels through an immense cloud of hot intergalactic gas. In the case of galaxy CGCG254-021, a tail of hot gas estimated at over 250,000 light-years in length, and around 10 million degrees Centigrade, which is half the estimated temperature of the intergalactic gas cloud. 

Astronomers think CGCG254-021’s tail was stripped from the galaxy as it moved through hot gas in galaxy cluster Zwicky 8338. The pressure exerted by this rapid motion stripped gas away from the galaxy, creating the ghostly blue ribbon of hot gas observed. A ribbon astronomers think could be completely free of the galaxy, considering the distance between the two as seen in this image. 

Astronomers have been studying interactions between the ribbon and galaxy CGCG254-021 by examining the characteristics and properties of the galaxy and its ghostly tail. They noted it has a brighter spot they call its head with a tail of diffuse x-ray emission trailing behind. This could indicate the gas in the head in cooler and richer in elements heavier than helium compared to the rest of the ribbon. There’s also a hint of a bow shock at the head of the tail with the galaxy at the front.  

Additional observations by researchers at infrared wavelengths also show galaxy CGCG254-021 has more mass than any other galaxy in galaxy cluster Zwicky 8338. Using the data obtained and models of the evolution of galaxies astrophysicists predicted it recently had the highest rate of new star formation in the cluster. However, they can find no evidence of new stars recently forming within the galaxy. They think this lack of new stars is due to the stripping of gas as it traveled through galaxy cluster Zwicky 8338.  

The foreground galaxy is NGC 4569 of the Virgo cluster. The red filaments at the right of the galaxy show the hydrogen gas that has been removed. The tail represents about 95 per cent of the gas reservoir the galaxy needs to feed the formation of new stars. Credit: CFHT/Coelum

What’s next?

Astrophysicists plan on additional observations of galaxy CGCG254-021 and Zwicky 8383 in the future using Chandra, the Newton Group of telescopes, and other assets. They hope to fill in the blanks on how it obtained the largest galaxy tail recorded during the human journey to the beginning of space and time. To learn the story of how this galaxy got its ghostly blue tail. 

Read the PDF on the study of the tail of galaxy CGCG254-021 in galaxy cluster Zwicky 8383.

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Read a study on the galaxy tail of galaxy NGC 4569 in the Virgo Cluster.

You can learn more about galaxy CGCG254-021 here. 

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Isaac Newton Group of Telescopes (yellow) in the Canary Island. 

Discover galaxy cluster Zwicky 8338 here. 

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