When the Andromeda galaxy collides with our own, beloved Milky Way, there will be a period of, shall we say, readjustment. “It is likely the sun will be flung into a new region of our galaxy,” NASA scientists working with Baltimore’s Space Telescope Science Institute predicted this week. “The Milky Way has had a lot of small mergers, but this indeed will be unprecedented,” Johns Hopkins astronomer Rosemary Wyse explains. And this isn’t a what-if situation; the NASA crew is throwing around phrases like “predict with certainty,” which they don’t do lightly.
That’s the bad news. The good news is, earth won’t necessarily be destroyed! Stars inside both galaxies are widely spaced enough that the odds of a head-on smash up is unlikely. But all the usual orbits we know and love will be shaken up; our own solar system will probably be flung much farther out from the galactic core than it is today. With its stars jostled out of their mostly-circular orbits, the Milky Way will no longer resemble a flattened pancake; instead, the post-collision galaxies will merge into a huge elliptical galaxy, whose bright core will dominate the night sky.
(In case all this talk of galaxy-smashing makes you nervous, we should point out that by the time this happens — in billions of years — the sun will have probably become a red giant and engulfed the Earth already, anyways.)
So if you’re feeling upset about something petty today, just meditate on these two sentences: “The universe is expanding and accelerating, and collisions between galaxies in close proximity to each other still happen because they are bound by the gravity of the dark matter surrounding them. The Hubble Space Telescope’s deep views of the universe show such encounters between galaxies were more common in the past when the universe was smaller.” Kinda puts everything into perspective, huh?
Some beautiful NASA pictures of galaxy collisions below:
Per NASA, this is what it might look like:
- First Row, Left: Present day.
- First Row, Right: In 2 billion years the disk of the approaching Andromeda galaxy is noticeably larger.
- Second Row, Left: In 3.75 billion years Andromeda fills the field of view.
- Second Row, Right: In 3.85 billion years the sky is ablaze with new star formation.
- Third Row, Left: In 3.9 billion years, star formation continues.
- Third Row, Right: In 4 billion years Andromeda is tidally stretched and the Milky Way becomes warped.
- Fourth Row, Left: In 5.1 billion years the cores of the Milky Way and Andromeda appear as a pair of bright lobes.
- Fourth Row, Right: In 7 billion years the merged galaxies form a huge elliptical galaxy, its bright core dominating the nighttime sky.
Do you mean in 4 billion years?
Light years connotes a distance, not a unit of time.