kOur universe keeps getting more crowded. Very smart people using very cool data have peered through the heart of our Milky Way’s galactic heart to spy a very big galaxy just next door.
Astronomers using data from ESA’s Gaia satellite have discovered a new dwarf satellite galaxy of the Milky Way. The dwarf galaxy, named Antlia 2, is located roughly 130,000 light-years from Earth in the constellation Antlia. It has avoided detection until now thanks to its extremely low density as well as a perfectly-chosen hiding place — behind the Milky Way’s bright central disk.
Antlia 2 is a whopping 1/3rd the diameter of our Milky Way. Despite having a similar footprint to the dense star-factory that is the Large Magellanic Cloud, it has 10,000th the brightness. It is a deep rural expanse of ancient low-metal stars meandering in unison with long dead nebulae, white dwarves, neutron stars, black holes and a lot of gas around a disorganized axis.
“The simplest explanation of why Antlia 2 appears to have so little mass today is that it is being taken apart by the Galactic tides of the Milky Way,” said co-author Dr. Sergey Koposov, a scientist at Carnegie Mellon University.
“What remains unexplained, however, is the object’s giant size. Normally, as galaxies lose mass to the Milky Way’s tides, they shrink, not grow.”
Dr Koposov undermines his own theory that Antlia has been the victim or Milky Way vampirism with his second sentence. We may wonder if this isn’t a galaxy whose black hole has somehow depleted Antlia’s gravitational core from overfeeding or underfeeding. This is all new as of right now so my guess is probably as good as the next. We may never know but it’s cool to think about this space ghost next door.