University of Cambridge | 2018 Nov 13
The Gaia satellite has spotted an enormous ‘ghost’ galaxy lurking on the outskirts of the Milky Way.
An international team of astronomers, including from the University of Cambridge, discovered the massive object when trawling through data from the European Space Agency’s Gaia satellite. The object, named Antlia 2 (or Ant 2), has avoided detection until now thanks to its extremely low density as well as a perfectly-chosen hiding place, behind the shroud of the Milky Way’s disc. The researchers have published their results online today.
Ant 2 is known as a dwarf galaxy. As structures emerged in the early Universe, dwarfs were the first galaxies to form, and so most of their stars are old, low-mass and metal-poor. But compared to the other known dwarf satellites of our Galaxy, Ant 2 is immense: it is as big as the Large Magellanic Cloud (LMC), and a third the size of the Milky Way itself.
What makes Ant 2 even more unusual is how little light it gives out. Compared to the LMC, another satellite of the Milky Way, Ant 2 is 10,000 times fainter. In other words, it is either far too large for its luminosity or far too dim for its size. ...
The Most Diffuse Galaxy in the Universe Found
Academia Sinica Institute of Astronomy and Astrophysics | 2018 Nov 14
The Hidden Giant: Discovery of an Enormous Galactic Dwarf Satellite in Gaia DR2 ~ G. Torrealba et al
- arXiv.org > astro-ph > arXiv:1811.04082 > 09 Nov 2018