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Comment by Tepix | Hacker News Reader

Fascinating. I wonder if any planets survived this "flinging manoeuvre".

This star is also covered in the latest episode #159 of the Interplanetary Podcast: https://www.interplanetary.org.uk/post/159-andrew-rader-beyo...

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Imagine being an astronomer in a society living on a planet orbiting an intergalactic star like that: no proper stars in the sky, just smudges of distant galaxies. It might be difficult to discover the "Copernican principle" in such circumstances.

There'll be plenty of quasars to act as stars, the big problem is they will be very hard pressed to measure any exosolar distances at all.

This particular star is not that big too, so over its lifetime of 1Gyr it'll make it pretty far in the local group. For fictional purposes you could therefore imagine a solar system being sent from one galaxy into another one, that'll make for some interesting astronomical history!

> If we were in the center of the void, we would see no stars in the sky with the naked eye. According to astronomer Greg Aldering, the scale of the void is such that "If the Milky Way had been in the center of the Boötes void, we wouldn't have known there were other galaxies until the 1960s."

Via https://en.wikipedia.org/wiki/Bo%C3%B6tes_void. Pretty eerie to think about.

Also _Against a Dark Background_ by Iain M. Banks. It describes a very, very old civilization with no stars close enough to even think about interstellar travel.

Check out The World at the End of Time by Frederik Pohl. This is exactly what this is about!

I assume you mean planet's orbiting the star?

It's a fascinating problem. I've been thinking about it for about ten minutes now and I honestly don't know what would happen in this situation.

Ask Ethan had a great answer to this question "Can Stars Escape From The Galaxy, With Planets Intact?":

https://www.forbes.com/sites/startswithabang/2016/09/10/ask-...

So? What's the answer? The closest thing I can find is:

"Mira has a white dwarf companion, meaning that large gravitational "kicks" often aren't enough to unbind a solar system!"

Which still doesn't tell me whether a star could be ejected from the galaxy like this with its planets intact and orbiting it roughly the same way as before.

There's this sentence later in the article:

> While an interaction that happens too close to a planet could eject that as well, simulations indicate that's a rarity, and that most planets should remain intact.

But the way it's phrased, it could be read either way, with the most plausible reading for me being that the planets remain intact, but turn into rogue planets, no longer orbiting the star that's speeding away from them.

The author of the paper was active on reddit and he said the only way to explain this is that there were initially two stars orbiting in very close proximity and there could not have been any planets to begin with.

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