A dying galaxy very close to the Milky Way is apparently sowing the seeds of its own rebirth, a phenomena researchers believe may hold the secret to the reincarnation of several other similar galaxies. About 20 small galaxies are known to exist around our galaxy.
Most fall into two main categories: dwarf spheroidals, which are dead because they lack the gas needed for making new stars, and dwarf irregulars, which have plenty of gas and show signs of ongoing star formation. Some astronomers have suggested that dwarf galaxies can switch back and forth between the two types by dying and being reborn repeatedly.
Now new observations of a gas cloud expelled from one such galaxy and moving enough that it will eventually fall back into the galaxy it and trigger a new star formation have bolstered the theory about galaxies taking a rebirth.
Lisa Young, a New Mexico Institute of Mining and Technology researcher led a team of astronomers that observed the gas cloud using the Very Large Array of radio telescopes near Socorro.
The cloud is in the vicinity of a small satellite galaxy of the Milky Way called the Phoenix galaxy and lies about 1.4 million light years from Earth. It has the mass of 33 million Suns. According to Young, though the Phoenix is a dwarf spheroidal with no sign of current star formation, Hubble Space Telescope observations of the colours — and thus ages — of 22,000 of its stars suggest it underwent a burst of star formation just 50 million years ago.
“If that stellar baby boom was responsible for expelling the gas cloud, its current position means it is moving too slowly to escape the galaxy forever, according to the team’s calculations.
The galaxy’s gravity will pull most of the gas back in a few hundred million years from now, providing enough raw material to form about 100,000 Suns,” said Young.
As she said, this made the galaxy’s name all the more fitting. The finding is important as earlier there was not enough evidence to suggest that a galaxy had been reborn, even though astronomers had identified signs of such cycles of rebirth.