Free Astronomy Magazine May-June 2018

54 MAY-JUNE 2018 SPACE CHRONICLES T his image shows the sky around the ultra diffuse galaxy NGC 1052-DF2. It was created from images forming part of the Digitized Sky Survey 2. NGC 1052-DF2 is basically in- visible in this image. It is located to the southwest of the bright elliptical galaxy NGC 1052, which is dominating the field of view, and east of the bright red star HD 16873. [ESA/Hubble, NASA, Digitized Sky Survey 2] nated by the giant elliptical galaxy NGC 1052. Galaxy formation is tur- bulent and violent, and van Dokkum sug- gests that the growth of the fledgling mas- sive galaxy billions of years ago perhaps played a role in NGC 1052-DF2’s dark-mat- ter deficiency. Another idea is that gas moving toward the giant elliptical NGC 1052 may have fragmented and formed NGC 1052- DF2. The formation of NGC 1052-DF2 may have been helped by powerful winds ema- nating from the young black hole that was growing in the don’t explain all of the characteris- tics of the observed galaxy, the re- searchers said. The team is already hunting for more dark-matter deficient galaxies. They are an- alyzing Hubble images of 23 other diffuse galaxies. Three of them appear similar to NGC 1052-DF2. “Every galaxy we knew about before has dark matter, and they all fall in familiar categories like spiral or elliptical galaxies,” van Dokkum said. “But what would you get if there were no dark matter at all? Maybe this is what you would get .” T his video zooms in from a view of the night sky, through the constellation of Cetus (the Whale), to end on the NASA/ESA Hub- ble Space Telescope observations of the ultra diffuse galaxy NGC 1052-DF2. This is the first galaxy to be found to not have dark mat- ter. [ESA/Hubble, Digitized Sky Survey, Nick Risinger (skysurvey.org )] center of NGC 1052. These possibil- ities are speculative, however, and !