Starship Asterisk*

Image Credit: ESO/Ragusa, Spavone et al.

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Space can be a lonely place. But not so for this quartet of galaxies making up HCG 86 and observed here with ESO’s VLT Survey Telescope (VST). The four galaxies located approximately 270 million light years from Earth in the Sagittarius constellation, are seen from Earth as arranged in triangular shape, with three of them on a straight line and one underneath; the bright objects to the right of the elongated galaxy are not part of the quartet.

HCG stands for Hickson Compact Group, and is used to describe groups of four to ten galaxies where members are physically very close to each other. Because of their compactness, such groups are ideal environments to study galactic interactions, which can sometimes lead to galaxies merging with each other.

This image of HCG 86 was taken by a team of astronomers led by Rossella Ragusa of the Istituto Nazionale di Astrofisica in Italy as part of the VST Early-type Galaxy Survey (VEGAS) programme. “With VST we are able to investigate very faint structures in the galaxies' outskirts, which are the relics of past gravitational interactions and merging events,” says Ragusa. In particular, by mapping the light distribution in and around the group’s galaxies in this study, the team concluded that these faint structures are the leftovers of satellite galaxies gobbled by the group approximately seven billion years ago. ...

Image Credit: ESA/Hubble & NASA, J. Dalcanton

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A dramatic triplet of galaxies takes centre stage in this latest Picture of the Week from the NASA/ESA Hubble Space Telescope, which captures a three-way gravitational tug-of-war between interacting galaxies. This system —known as Arp 195— is featured in the Atlas of Peculiar Galaxies, a list which showcases some of the weirder and more wonderful galaxies in the universe.

Observing time with the Hubble Space Telescope is extremely valuable, so astronomers don't want to waste a second. The schedule for Hubble observations is calculated using a computer algorithm which allows the spacecraft to occasionally gather bonus snapshots of data between longer observations. This image of the clashing triplet of galaxies in Arp 195 is one such snapshot. Extra observations such as these do more than provide spectacular images — they also help to identify promising targets to follow up with telescopes such as the upcoming NASA/ESA/CSA James Webb Space Telescope.