Hubble Telescope discovers a “dead” galaxy in our cosmic neighbourhood

Credits: NASA, ESA, M. Beasley (Instituto de Astrofísica de Canarias) and P. Kehusmaa

A recent study published in Nature reports the discovery of a “relic galaxy” -NGC 1277 -around 240 million light years from the Milky Way. 

This galaxy is unique, considered to be an example of what galaxies would have looked like in the primitive universe. The galaxy is made up exclusively of ageing stars that were born 10 billion years ago. Four times smaller than the Milky Way, it however has twice as many stars. But contrary to other galaxies in the local universe, this one hasn’t formed any new stars since then. Astronomers nickname such galaxies “red and dead”, because the stars are ageing and there are no successive generations of younger stars.

The key sign of this “machine shut down” resides in the ancient globular clusters that surround it. The reddish clusters are proof that the galaxy has not been forming new stars for a very long time. Otherwise, there would be many blue globular clusters of stars, which are in this case mainly absent. On the other hand, over 10 billion years ago, this galaxy was very active, producing stars 1,000 times faster than our own Milky Way nowadays.

This galaxy is found near to the centre of the Perseus cluster -a cluster of galaxies situated in the Perseus constellation around 240 million light years away. This is part of the Perseus-Pisces Supercluster, and contains around 190 galaxies of the 1,000 others that are out there. It is the brightest known galaxy cluster to date. NGC 1277 moves so rapidly around this group -at over 3 million km/h -that it can’t fuse with other galaxies to collect stars or draw gas to support the formation of new stars. Additionally, near to its centre, the intergalactic gas is so hot that it can’t cool down enough to condense and form new stars.

Although the Hubble Telescope has already observed such galaxies, none has ever been detected in such proximity. NGC 1277 thus offers a unique opportunity to learn more about the conditions of the primitive universe.