From the smallest microbe to the most powerful oak, death is as true for the above as for the below, even for the most powerful galaxies.
However, the process is not fast. A haunting new Hubble image of the galaxy NGC 1947 demonstrates this well: Even from a distance of about 45.4 million light-years away (in the southern constellation of Dorado) we can see that the galaxy is slowly in decline.
The clue lies in dust and gas. A galaxy at the best age of its life will be filled with things and use it to create new stars. Eventually the star material runs up, and that’s what astronomers think we see with NGC 1947.
It is a rare type of galaxy known as a lens-shaped galaxy ̵
Galaxies that have not created new stars for billions of years are considered dead – but the universe is not old enough that we have seen what happens when all these stars also die.
What about our own galaxy? In fact, the Milky Way may have died at least once about 7 billion years ago; it revived after a period of 2 billion years in which a whole bunch of stars died, the supernova went and pushed their outer envelopes into space, filling the galaxy with material to create new stars.
The Milky Way currently has a relatively slow star formation rate, about 1 to 2 solar masses per year, but that does not hurt new material either. Our galaxy is a cannibal with a history of absorbing other galaxies and all their wonderful star-forming material through its 13.5 billion-year lifespan, and it is far from done.
Eventually, Magellanic clouds will be slurped down the Milky Way, and we are heading for a merger with the Andromeda Galaxy in a few billion years. This could trigger a period of elevated star formation, as tidal interactions shock and compress material in both galaxies.
Based on observations of space around NGC 1947, it is unlikely, at least soon, to inject fresh material from a fusion with another galaxy. It will continue to fade until the only thing left is a series of dead stars.
You can download versions of this image in background size on the ESA website.