NASA Astronomers Catch Dwarf Galaxy Ramming into Large Spiral in Massive Collision

NASA astronomers have caught a dwarf galaxy in the act of ramming into a large spiral galaxy. The resulting collision is spawning a massive cloud of multimillion-degree gas, revealing for the first time how galaxies interact by crashing into one another.

The larger spiral galaxy is known as NGC 1232. Located about 60 million light-years from Earth, the galaxy is dominated by millions of bright stars and dark dust, its spiral arms rotating about the center. Yet it seems like its latest encounter may change the galaxy a bit. The collision, which was witnessed with the help of NASA's Chandra X-ray Observatory, was measured after scientists combined X-rays and optical light to show the scene of the crime.

Using the data, the scientists saw that the impact between the two galaxies caused a shock wave, similar to a sonic boom on Earth. This massive blast generated hot gas with a temperature of about 6 million degrees. The Chandra X-ray data revealed that this gas has a comet-like appearance, most likely caused by the motion of the dwarf galaxy.

Near the head of the comet-shaped gas is a region containing several optically bright stars and enhanced X-ray emissions. It's very possible that this area is the site of star formation, triggered by the shock wave. This means that the X-rays may be the result of massive stellar winds and the remains of supernova explosions as massive stars evolve.

Currently, astronomers aren't sure exactly how large the gas cloud is; they can't determine its mass from the two-dimensional image that they've recorded since it could either be concentrated into a thin pancake or distributed over a large, spherical region. If the gas is a pancake, though, its mass is equivalent to forty thousand suns. If spread uniformly, it could be even larger.

It's likely that this extremely hot gas will continue to glow for tens to hundreds of millions of years, depending on the geometry of the collision. This massive crash should also last for quite some time--about 50 million years. By studying this mass of gas, astronomers may be able to estimate the frequency of collisions with dwarf galaxies and understand how important such events are for galaxy growth.

The findings are published in The Astrophysical Journal.