Dark matter has been something that astrophysicists have postulated about for some time – matter we cannot see but must exist for things to make sense in the universe. A new technique has been demonstrated in a paper published in the Monthly Notices of the Royal Astronomical Society that indicates that entirely starless galaxies conclusively exist, even if we don’t know the exact shape and size of them.
These galaxies are composed of cosmic dust and dark matter in proportions that don’t quite meet the requirements for star formation.
The technique involves examining the illumination of hydrogen in these “dark galaxies”. The hydrogen glows in the intense light released from a nearby quasar – a black-hole powered object. The glow released is a specific UV frequency that, once stretched out from the voyage to Earth, becomes visible to us at blue-violet light.
As the team filtered down their readings to the specific frequency required, they eventually narrowed the findings to the 12 brightest galaxies – the “dark dozen” – around a particularly luminous quasar, HE0109-3518, nicknamed “the phone number”. While 12 might not seem like a huge number in astronomical terms, it is the very first evidence of confirmed dark galaxies, which is pretty special.
“The first study was really just discovery research, to demonstrate that the technique works,” says Sebastiano Cantalupo, from the University of California, Santa Cruz, who was lead author of the paper.
The observations were performed at the Very Large Telescope (VLT) (a highly creative name dontchya think?) in Chile, as the quasar is in a southern hemisphere constellation. Further observations are scheduled for the fall to fully examine the dark dozen, and the team is hoping to conduct a search from the Keck telescope in Hawaii for northern hemisphere dark galaxies.