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Lacy Galaxies

StarDate: 
March 31, 2016

Big telescopes are usually better than small ones, but the little guys can still make some big discoveries. Astronomers recently proved that point by detecting dozens of ghostly galaxies with an array of telephoto lenses, each of which is just 16 inches across. Named Dragonfly and located in New Mexico, the array of small telescopes captures a large swath of sky with just one exposure.

Astronomers aimed it at the Coma cluster, a huge gathering of galaxies about 340 million light-years from Earth. It’s in the constellation Coma Berenices.

The images revealed 47 large but ghostly galaxies. Many are as big as the Milky Way, but they emit roughly a thousandth as much light, because they have few stars, and the stars are spread out from one another.

These ultra-diffuse galaxies must have lots of dark matter, which exerts a gravitational force but emits no detectable energy. Without dark matter to hold them together, these galaxies would get torn apart by the other galaxies in the Coma cluster.

No one knows how these odd galaxies formed. Perhaps they were on their way to becoming brilliant galaxies like the Milky Way when some of their stars exploded and blew gas out into intergalactic space. Gas is the raw material for stars, so the loss of gas would have shut down the process of starbirth.

Whatever the case, their discovery demonstrates that even in the twenty-first century, small telescopes can still play a big role in astronomy.


Script by Ken Croswell, Copyright 2015

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