From the tiniest microbe to the mightiest oak, death is above and below even the most powerful of galaxies.
However, the process is not fast. A terrifying new Hubble photo of the galaxy NGC 1947 shows this well: Even from a distance of about 45.4 million light years (in the southern constellation of Dorado), we can see that the galaxy is slowly deteriorating.
The clue lies in the dust and gas. A galaxy in its prime will be filled with the stuff and use it to create new stars. Eventually, the star stuff will run out, and that’s what astronomers think we’re seeing with NGC 1947.
It is a rare type of galaxy known as a lenticular galaxy – disk-shaped, like the Milky Way or Andromeda, but without the spiral arms. NGC 1947 used to have spiral arms, but has used up almost all the gas and dust that gave them structure; all that remains are a few wisps illuminated by starlight.
(ESA / Hubble & NASA, D. Rosario; L. Shatz)
Galaxies that have not created new stars in billions of years are considered dead – but the Universe is not old enough to see what happens if all those stars die too.
What about our own galaxy? In fact, the Milky Way died at least once about 7 billion years ago; it revived after a period of 2 billion years during which a whole series of stars died, went supernova and threw their outer envelopes into space, filling the galaxy with material to make new stars.
The Milky Way currently has a relatively slow star formation rate, about 1 to 2 solar masses per year, but it doesn’t hurt for new material either. Our galaxy is a cannibal, with a history of absorbing other galaxies and all of their beautiful star-forming material over its 13.5 billion-year-old lifespan, and it is far from finished.
Eventually, the Magellanic Clouds will be slurped into the Milky Way, and in a few billion years, we will be on the road to fusing with the Andromeda Galaxy. This could trigger a period of increased star formation as the tidal interactions shock and compress the material in both galaxies.
Based on observations of space around NGC 1947, an injection of fresh material from a fusion with another galaxy is unlikely, at least not soon. It will keep fading until all that’s left is a raft of dead stars.
You can download wallpaper versions of this image from the ESA website.