Astronomers confirm the existence of a lone black hole

Lone stars are actually the exception, so not radically more as you might think. But there are also binary black holes.

Fun to realize there's barely any way for us to detect if there's one heading for us right this very moment.

A type-1a supernova peer would produce this effect, leaving only the black hole (or the oversize star that would become it). I don't know any other types where the star is completely destroyed.

Thanks, the original article is unreadable on mobile due to the ads.

It can't really "gobble" anything any more than a star "gobbles" things that fly into its photosphere or a planet "gobbles" things that crash into it.

Unless you cross its event horizon, its gravity works just like any other celestial object. Maybe at worst it slingshots you off in a different direction.

Space between stars is amazingly empty. It's almost unlikely that we would bump into another star (or black hole). For instance, if the whole Milky way were the size of the US (east to west), our sun would be smaller than 1/20th the size of human hair and the closest star to us would be at least a football field away. (Credits for this analogy: Kurzgesagt app https://play.google.com/store/apps/details?id=org.kurzgesagt... https://apps.apple.com/us/app/universe-in-a-nutshell/id15263...)

> gobble planets and stars

Direct interaction isn't needed for havoc. A supermassive object sweeping by the Solar System could destabilize Jovian orbits. In the Nice model, Neptune flung Kuiper belt asteroids sunward, gifting the inner planets with a late heavy bombardment.

Rogue gas giants, brown dwarfs accelerated to relativistic speeds, giant asteroids approaching from the Sun's direction, Carrington Events, an ill-directed gamma ray, etc. So many ways life on Earth can see its 250 million remaining years cut short, and those are only a few of the cosmic threats we can imagine.

A black hole with a Schwarzschild radius of 20 km would weigh about 6.8 Solar masses. It wouldn't even need to get super close to affect the Solar System.

No more unsettling than space in general is. It’s pretty hostile to life. We’re not just making turns around the orbital racetrack setup around the Sun, we’re also flying through space following the gravitational trail of the Sun as it races forward without a destination.

I was playing with Universe Sandbox over the weekend trying to figure out how to terraform Venus. Changing its axial rotation period to a day to match the Earth while I screwed around with its chemistry was enough to cause Europa and some of the other famous moons of Jupiter and Saturn as well as Charon to yeet themselves outside of the solar system within about 10 or 20 years of simulated time.

It would be nice to get a rigorous estimate on how big and nearby a black hole could be before we'd notice it with routine sky surveys or orbital deviations. A 6-solar-mass black hole only has a radius of around 18km or 11 miles. How often will one pass in front of a star precisely enough for OGLE and MOA to detect it, as they did with this one?

Apparently the Roman Space Telescope will be great at detecting these, if it doesn't get cancelled.

There are many theoretical astronomical risks. For example, if we happened to come into the path of a relatively nearby gamma-ray burst, it could eliminate all life. Given that life has existed on the earth for quite some time, the 'Lindy effect' suggests that the sum of these presumably-constant risks is small. We are much more likely to become extinct due to an anthropogenic cause.

No, not me anyway. we are all floating (falling) in the (nigh) void of space (equally) alone ... which is great protection from all the monsters everywhere!

Deliberately hitting things in space is hard, accidentally, more-so.

Consider the chance of our sun getting whacked when the entire Andromeda galaxy gets here ... billions or more likely trillions to one. The chance of a single mass in our own galaxy getting us should be less than that.

edit: as far as I know the only difference between getting gobbled by a black hole v.s. anything else is our atoms won't get to continue their evolution into larger atoms in this universe. (or maybe see it as our atoms get to complete their evolution in this universe)

It can't gobble planets and stars any more than any stars of the same mass.

In practical terms, not so very far away from the NEAs that we have no idea of, and which we notice after they've just skimmed by the Earth.

There's something existentially creepy about a massive, invisible object just wandering the galaxy, indifferent to everything

I don't. If the sun were replaced by a black hole of equal mass next Tuesday at noon, the only thing we would notice is that it suddenly got very dark and very cold. We would continue orbiting the thing while freezing to death over the next few days.

The size of the black hole described in the paper is ~ 20 km, so it is tiny. Even we have millions of such objects (and most likely we do), the chance of hitting something, given the enormous size of the galaxy is negligible.

It's really, really hard to fire something into the Sun. We can't do it. The same goes for black holes. Things don't just get sucked in. They usually end up in orbit instead.

Are you worried? :-) I bit like bringing sunscreen to the apocalypse no? :-)

Relax, it’s probably traveling in a straight path at constant velocity.

The crazy thing is the answer is quite possibly TRILLIONS.

Excellent question.

Gravity pulls things in by causing space-time to accelerate in a particular direction. In other words we accelerate towards the Earth at 9.8 meters per second per second because that is what space-time itself does. The space-time that is in our frame of reference accelerates down, carrying us with it. The floor pushes up on us, causing us to accelerate up. Balancing things out so that we remain where we are.

A dense mass will cause flat space-time to start falling in. Enough mass, densely enough, will cause it to fall in so fast that not even light can escape. This is a black hole.

However the Big Bang wasn't a flat space-time. The space-time that was the structure of the universe was moving apart extremely quickly. There was more than enough mass around to create a black hole today. But what it did is cause the expansion rate to slow. Not to stop, reverse, and fall back in on itself into a giant black hole.

While not a direct answer in itself, I think it's noteworthy that the big bang already requires esoteric physics, like inflation [1], that have no known explanation, source, or parallel anywhere else in existence -- and in fact contradict everything we know about known physics. It's an entirely ad-hoc hypothesis that was largely developed to solve numerous other problems with a big bang, in particular our universe not fitting what would be expected following a "normal" big bang, such as the Horizon Problem. [2]

And so looking for logical explanations for the big bang is already a nonstarter. At this point it remains highly dependent upon ad hoc constructions.

[1] - https://en.wikipedia.org/wiki/Cosmic_inflation

[2] - https://en.wikipedia.org/wiki/Horizon_problem

One of the theories is that the properties of the Higgs Field changed and so the laws of physics changed. And that if they ever change again that we'll likely be dead before we know to be afraid, since the change would propagate through the universe at the speed of light. We wouldn't even see the stars blink out before the molecules in our bodies stopped being the molecules in our bodies.

Well, imagine that the big bang is really something more akin to a white hole, which is a black hole running backwards: all the stuff has outward momentum, and lots of it, so it can't get pulled back. In standard cosmology the big bang happens not at a point (so it's not really like a white hole) but everywhere, but there's also really strong repellent forces that cause "inflation", which defeats the mass-energy's gravitational pull's attempt to collapse the whole thing. But still, perhaps the thought of a white hole might help you bridge the gap.

Mind you, this is a pop science, handwavy explanation.

The layman's answer is that since everywhere was very dense there wasn't a gravitational pull to one direction or another since it all cancelled out.

Because space expanded faster than the speed of light.

> rouge black holes

They makeup much of the stylish universe in the cosmos ;-)

Just kidding, I know you meant rogue.

I would assume we'd see a lot of more tricks of light bending if they did. Light lensing was used to confirm relativity by looking for multiple super novae signatures from the same event, which passed by large black holes on their way here!

These would be 'primordial' black holes: https://en.m.wikipedia.org/wiki/Primordial_black_hole

This would certainly be some of it but the awkward fact is that we've positively identified so very little of the matter that makes the universe the shape that it appears to us to be that we could double the known matter in the universe with black holes and we'd still only be a 10th of the way there.

However if we could eliminate the false signals from invisible (singularity) matter I am hopeful that will give us a clearer idea of whatever the rest is.

I can't remember who I heard talk about this, but scientists have considered this. I think there was a good reason for why it doesn't seem to match observations.

That was my first thought too. A cursory search indicates we would see a lot more gravitational lensing in our observations if that was the case.

Found a couple of videos on it too

https://youtu.be/qy8MdewY_TY

https://youtu.be/d0wV5frSb6s

Probably not the main component of dark matter, but definitely a spooky and fascinating piece of the cosmic jigsaw

There are some theories that primordial black holes could be dark matter. It's not a mainstream view though.

You're not the only one. This is a fairly old idea.

Black hole loneliness epidemic

More like it eats the dust that brushes pass the front door, but neighbours are safe.