Universe

Collision between galaxies. Active Universe

Collision between galaxies. Active Universe

Two colliding spiral galaxies, photographed by the Hubble Space Telescope. The largest galaxy is cataloged as NGC 2207, the smallest is CI 2163. The gravitational tidal forces of NGC 2207 have distorted the shape of CI 2163, while expelling stars and pouring gases into long streamers that protrude a hundred thousand light-years through The right edge of the image.

When galaxies collide, direct crashes between stars are very rare, but collisions between the huge gas clouds of the galaxies cause a stellar birth rate growth. Massive newborn stars evolve rapidly in a few million years and explode like supernovae. The heavy elements manufactured in these stars are expelled by the explosions and enrich the gas that surrounds them over thousands of light years.

The quantity of supernovae in Las Antenas is almost 30 times that of the Milky Way. Supernova explosions heat gas in these galaxies to millions of degrees Celsius. They become so hot that they emit X-rays. These clouds are virtually invisible to optical telescopes, but they are easy targets for the Chandra X-ray Observatory. Chandra data reveals regions with a high and varied proportion of metals. In a cloud, for example, magnesium and silicon are 16 and 24 times more abundant than in the Sun.

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