Thread by @HUBBLE_space

1/ 🥳 Happy 32, dear Hubble! To celebrate this anniversary, here is an unusual Hubble snapshot: a close-knit collection of five galaxies: the Hickson Compact Group 40. #Hubble32

Full story: 🔗 esahubble.org/news/heic2205/

Details 👇

2/ This menagerie includes three spiral-shaped galaxies, an elliptical galaxy and a lenticular (lens-like) galaxy. Somehow, these different galaxies have crossed paths to create an exceptionally crowded and eclectic galaxy sampler.

3/ Caught in a leisurely gravitational dance, the whole group is so crowded that it could fit within a region of space that is less than twice the diameter of our Milky Way’s stellar disc.

4/ Though such galaxy groupings can be found in the heart of huge galaxy clusters, these galaxies are notably isolated in their own small patch of the Universe, in the direction of the constellation Hydra. But why?

5 / One possibility is that there’s a lot of dark matter associated with these galaxies. If they come close together the dark matter can form a big cloud within which the galaxies orbit.

6/ This snapshot catches the galaxies at a very special moment in their lifetimes. In about 1 billion years they will eventually collide and merge to form a single giant elliptical galaxy. Here is an annotated image of the group

7/ Almost every one of the galaxies has a compact radio source at its core, which could be evidence for the presence of a supermassive black hole. X-ray observations show that the galaxies have been gravitationally interacting.

8/ Hickson Compact Group 40 is one of the most densely packed galaxy groups. Observations suggest that such tight groups may have been more abundant in the early Universe and provided fuel for powering black holes. Widefield view 📷

9. Credit: @NASA / @esa & @stsci (Tweets 1 & 6); ESA / @HUBBLE_space , Digitized Sky Survey 2. Acknowledgement: D. De Martin (Tweet 8)