Avi Blizovsky
Direct link to this page:
https://www.hayadan.org.il/hubble240404.html
The Hubble Space Telescope recently observed a bright circle of bright blue stars in a rare example of a "ring galaxy" the result of a collision between galaxies. The galaxy is larger than our Milky Way and is far away in the direction of the southern Dorado system. The image was released for publication on the occasion of the 14th birthday of Hubble's operations in space.
Earlier this year, NASA said that the manned service flight to Hubble was canceled, a decision that will limit the lifespan of the telescope. The galaxy, whose catalog number is AM 0644-741 is a prime example of a ring galaxy. Ring galaxies are formed as a result of a galaxy collision that dramatically changes the structure of the galaxies involved in the collision and also spurs the formation of new stars.
Such galaxies are formed as a result of a particularly specific type of collision, in which one galaxy plunges directly through the disk of the other galaxy. In the case of AM 0644-741, the galaxy that passed through the ring galaxy is out of the picture but is visible in the wider field images.
The shock of the collision drastically changed the orbits of the stars and gas in the galaxy's disk, causing them to rush outward. As the ring spreads out the gas clouds collide and compress. Then they collapse under their own gravity and form new bright stars. The vigorous star formation explains why the ring is blue, and that is because of the blue hot stars.
Another sign of massive star formation can also be seen in the pink areas along the ring. These are clouds of glowing hydrogen gas, illuminated by the strong ultraviolet radiation from the newly formed massive stars. Theoretical studies show that the blue ring will not continue to expand forever. After about 300 million years, it will reach the maximum radius and then just start to break up.
For news at the BBC
Yadan Astrophysics 2 - stars and galaxies
https://www.hayadan.org.il/BuildaGate4/general2/data_card.php?Cat=~~~824685298~~~97&SiteName=hayadan
