Long
tendrils stretching across 400,000 light-years connect a disturbed spiral
galaxy to an elliptical galaxy, as seen by the Mayall telescope at Kitt Peak
National Observatory in Arizona.
A
suspected high-speed collision took place between the elliptical M86 (right)
and spiral NGC 4438 (left), as evidenced by the long red filaments of ionized
hydrogen gas in this image. The green filament barely visible at the lower
right edge of the image shows higher-velocity gas that may not be related to
M86.
Astronomers
suspect that galactic run-ins such as this are responsible for the mystery of
why the biggest galaxies in the universe stop forming stars. Previous research
had tentatively fingered massive black holes as the culprit, but high-speed collisions
appear to heat up gas so much that they cannot cool enough to form stars. By
contrast, low-speed collisions often boost star formation by concentrating gas
without the overheating.
— ESA/NASA/SOHO and SPACE.com Staff
Credit: NASA/Johns
Hopkins University Applied Physics Laboratory/Carnegie Institution of
Washington
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