Scientists at the Harvard-Smithsonian Center for Astrophysics believe they’ve discovered the first extragalactic planet ever observed by humans.
Up front: I’ve got “extragalactic planetary, planetary extragalactic” to the tune of the Beastie Boys’ “Intergalactic” stuck in my head. And, now, you probably do too.
Now that we’ve gotten that out of the way: An extragalactic planet is one that’s not only outside of our own solar system, such as the thousands we’ve found floating around the Milky Way, but also outside of our own galaxy.
In this case, the team thinks they’ve found a Saturn-sized planet in the far off galaxy called Messier 51 (M51).
How far away? About 28 million light years. That’s a big deal because the universe has a speed limit. According to the laws of physics, we can’t go faster than the speed of light.
So that tells us it’d only take us 28 million years get reach the lonely little planet we’ve discovered in M51 — if we were travelling at the speed of light and didn’t have to account for acceleration and deceleration.
It’s a safe bet we won’t be borrowing a cup of milk from anyone in that galaxy any time soon.
Background: The search for alien life isn’t a simple matter of just pointing a telescope in a given direction and looking for biological indicators. From 28 million light years away, there’s not much definition. That means the scientists had to measure x-rays.
They found the planet by observing either a black hole or neutron star (it’s too far away to tell which it is) orbiting a companion star. As the planet revolves around the binary bodies, it casts a brief shadow where it blocks the x-ray signal.
Per the team’s research paper:
The data are well fit by a planet transit model in which the eclipser is most likely to be the size of Saturn. We also find that the locations of possible orbits are consistent with the survival of a planet bound to a mass-transfer binary.
A bit deeper: We recently discussed the idea that the vast majority of the universe is forever off-limits to humans because it would take us longer than infinity to reach anywhere that’s currently more than 14.5 billion light-years away. This is due to universe’s rate of expansion.
Luckily M51 is, technically, within our reach. At only 25 million light-years away, we could potentially send a robot probe there. But it would take a planet-sized fuel tank and somewhere around a trillion years or so to reach it with our current technology.
Quick take: We never say “never” in science, but it’s a pretty safe bet that we’re several generations away from even being able to approach the problem of getting a spacecraft out as far as the planet we’ve detected at M51.
And that’s probably for the better. Based on the fact it’s stuck between a random star and some sort of neutron-heavy body, it’s probably not a fun place to visit.
But these new techniques could lead to the discovery of innumerable planets. We’re detecting objects at greater distances than we can feasibly travel so, perhaps, the future of space isn’t about going places or visiting alien worlds.
Perhaps it’s more of a metaverse/information paradigm. Can we exchange signals with a planet too far away to visit? Conventional wisdom says no.
If the speed of light is the universal speed limit, we might be left on read for 50 million years after sending our first text message to M51.
We’ve been pondering the mystery of life for as long as we’ve existed. But the closer we get to finding aliens – that is, the better we get at looking for them – the sooner we may have to reckon with the terrifying possibility that any alien life we locate could be too far away to ever communicate with.
H/t: SciTech Daily