Today is the 21st anniversary of the Hubble Space Telescope’s deployment into space. To celebrate the occasion, astronomers at the Space Telescope Science Institute in Baltimore pointed the telescope’s eye to a particularly beautiful object: Arp 273.

Hubble was launched April 24, 1990, aboard Discovery’s STS-31 mission. It has made numerous discoveries, some of them leading to revolutions in all areas of astronomical research, from planetary science to cosmology. For 21 years, it has also allowed everyone to get a glimpse of what these tiny dots in our night sky really look like, revealing the beauty of our cosmos through breathtaking images. It has inspired, and will keep inspiring generations of astronomers.


© NASA, ESA and the Hubble Heritage Team (STScI/AURA)

This new image (click to enlarge) shows a pair of interacting galaxies called Arp 273. The larger of the spiral galaxies, called UGC 1810, shows a rose-like shape: its disk is distorted by the gravitational tidal pull of its smaller companion galaxy, UGC 1813. The shiny blue dots at the top of this “galactic rose” are clusters of extremely bright young and massive blue stars, glowing in ultraviolet light.

The smaller companion harbors a star forming region at its nucleus: many baby stars are being born in this area, perhaps because of the encounter with the other galaxy.

Arp 273 is located about 300 million light-years away from our home planet, in the constellation Andromeda. The two galaxies are tens of thousands of light-years away from each other, with a tidal bridge of material between them, visible in the image.

The outer arm of the larger galaxy appears partially as a ring, suggesting the smaller galaxy actually passed through the larger one, off-center. Many uncommon spiral patterns visible in UGC 1810 are also a strong sign of interaction. One of the inner arms of the galaxy goes behind the bulge and comes back out the other side; the inner set of spiral arms is highly warped out of the plane. The connection between these two spiral patterns is not precisely known.

The larger galaxy in this rose-like pair is about five times heavier than its companion. In such galaxy pairs, the rapid passage of a companion galaxy produces the asymmetric structure in the main spiral. In that kind of encounters, the starburst activity usually begins in the minor galaxies, probably because they have consumed less of the gas present in their nuclei, from which new stars are born.

In case some of you would like a higher resolution of the picture, the original file is available here (do this at your own risk! – the file is about 120 MB).

Finally, let’s wish hubble a happy birthday one more time, waiting for more astonishing images of the Universe we live in.