Tuesday, June 25, 2013

MRK 1034

Looking towards the constellation of Triangulum (The Triangle), in the northern sky, lies the galaxy pair MRK 1034. The two very similar galaxies, named PGC 9074 and PGC 9071, are close enough to one another to be bound together by gravity, although no gravitational disturbance can yet be seen in the image. These objects are probably only just beginning to interact gravitationally.

Both are spiral galaxies, and are presented to our eyes face-on, so we are able to appreciate their distinctive shapes. On the left of the image, spiral galaxy PGC 9074 shows a bright bulge and two spiral arms tightly wound around the nucleus, features which have led scientists to classify it as a type Sa galaxy. Close by, PGC 9071 — a type Sb galaxy — although very similar and almost the same size as its neighbor, has a fainter bulge and a slightly different structure to its arms: their coils are further apart.

The spiral arms of both objects clearly show dark patches of dust obscuring the light of the stars lying behind, mixed with bright blue clusters of hot, recently-formed stars. Older, cooler stars can be found in the glowing, compact yellowish bulge towards the center of the galaxy. The whole structure of each galaxy is surrounded by a much fainter round halo of old stars, some residing in globular clusters.

Gradually, these two neighbors will attract each other, the process of star formation will be increased and tidal forces will throw out long tails of stars and gas. Eventually, after maybe hundreds of millions of years, the structures of the interacting galaxies will merge together into a new, larger galaxy.

The images combined to create this picture were captured by Hubble's Advanced Camera for Surveys (ACS).

Photo credit: ESA/Hubble & NASA; Acknowledgement: Judy Schmidt


kopernik2 said...

How can we know if the two are approaching each other or putting more distance between? K2

JDsg said...

Basically, by measuring the redshift of the galaxies using a spectrometer. The redshift, which is the Doppler effect applied to astronomical objects, measures how far away from Earth an object is using a number called "z". Each of these two galaxies has their own z score, and it turns out that the z score for the bottom galaxy is slightly smaller than that of the upper galaxy; thus, the lower galaxy is slightly closer to Earth. But redshift can also measure the velocity objects move away or toward Earth, which can give a direction as to which the galaxies are moving. The fact of the matter is that these two galaxies are close enough to each other that a merger between the two will be inevitable, just as the Milky Way and Andromeda galaxy (2.5 million light years away from us) will also merge in time.

JDsg said... to which way the galaxies are moving.