The universe is growing. It is a well-established fact that even after millions of years and billions of lights years away from the Big Bang, there are new star formations in various parts of the universe. However, a new study suggests that in certain galaxies, star formation has stopped and they house just extremely ancient stars now. The dying galaxies might have something to do with tidal tails.
There are two types of galaxies- spiral, like our own home the Milky Way. Spirals have uneven edges on account of the extending spiral arms. Second, Elliptical, which are smooth-edged as they are basically a stretched-out circle.
The study published in the journal Nature tries to shed some light on how and why these “dead” galaxies come into being.
Star formation is a complex process. Dense, molecular clouds within a galaxy collapse and clump together in a dance of energy and gravity eventually leading to a star-birth. So that makes gas essential for star formation. The researchers then found a galaxy ID2299 which was observed to be ejecting nearly half of its star-forming gas. The actual amount of disused gas can be equivalent of 10,000 Suns per year.
On the other hand, the star formation rate of this particular galaxy was found to be much faster than the Milky Way. With 46% of their total gas clouds emitted, and the remaining gas is being consumed at a rapid rate will lead to depletions. The researchers posit that with this situation, the galaxy will effectually “shut-down” in about tens of million years. A star formation takes billion years at the least which means no new stars will be formed in this particular galaxy.
The researchers have explained this unlikely ejection to a phenomenon called tidal tail. These are formed when two galaxies collide, ultimately merging with one another. The effect of tidal tail, which is basically a stream of gas and stars at the galaxy’s end and extending out into the interstellar space, is caused by interaction. Think of the moon’s tidal pull effect on Earth.
The study is pathbreaking. The fact the galaxies can potentially die due to gas expulsion has never been observed before. Formerly, ejections have been associated with galactic winds (commonly generated by supermassive black holes or star formation). However, this particular ejection doesn’t seem to be affected by galactic winds.
It is the merger itself that holds the key to a galaxy’s survival. A collision can induce a galaxy to expel gas to a limit it can no longer sustain any new star formation.
Though this cannot be confirmed until another galaxy is observed with a similar fate. As one might guess, observing galaxies millions and billions of light years away isn’t always the easiest thing to do.