On Dec. 30, 2023, Juno came within about 930 miles (1,500 kilometers) of the surface of the solar system's most volcanic world. It made a second ultra-close flyby of Io just this week.
spacecraft Juno out there buzzing Io at high speed
These are the massive black holes that lurk at the core of most galaxies. Like the one at the center of our own milkyway galaxy. The question remains do they form at the center of baby galaxies or are they the seed which triggers a galaxy to develop and they just grow even larger over time. If early galaxies had massive black holes for their galaxy size, that suggests the last option. Primordial black holes that is ones that were formed in the big bang have been a possibility for a long time. They have been talked about by astronomers since the 1970s. It great that so much is being discovered now. Lots of surprises still coming I suspect. More info on primeval black holes here. https://physicsworld.com/a/concerning-primordial-black-holes/
“Ok boys, we need ideas. We’re fucking the planet up irreparably in a way that will cost many, many millions of lives… but I feel like we could be doing it a lot faster. Get off your ass and invent a way for rich assholes to screw us even more than they already are”
given the age of the Universe and the relatively short time it would take for an advanced civilization to spread across the Milky Way Galaxy (650,000 years, by Hart’s estimate), Earth should have been visited by an extraterrestrial civilization (ETC) by now.
It took humans 30,000 years to cross the Atlantic. Using modem propolsion systems, it takes us two years to get to Mars and 40 to reach the edge of the solar system. This seems like an extremely generous estimate considering the Milky Way has a 50,000 light year radius.
I’m as bullish about extraterrestrial life as anyone, and I think a fuller survey of even just the current Solar System has potential. But I have no idea how you get a full galactic survey in so short a time, given what we know about the soft limits on speed of travel and communication.
By Tipler’s refined estimate, an ETC would be able to explore the entire galaxy in “less than 300 million years.”
That definitely feels like it’s more in the ballpark. But, again, it presumes a certain amount of steady cartography by the hypothetical fleet of Von Neuman probes.
There’s a Sci-fi series called The Bobverse that explores the idea of a sentiment fleet of Von Neumans exploring the galaxy, and the various trial and tribulations involved. One point it discusses is that even with a saturation of probes, you don’t get real time communication. So even in a hypothetical universe where alien life did exist and survey earth, what are they odds they’d be watching us at the moment of our development. What would an alien AI be looking for and what would it do when it was discovered?
We could still be too primitive to bare noticing. Or we could be living in between blinks of an alien camera that only reports back every 1000 years.
As we look out at the cosmos, we could be looking at things we don’t understand. After all, what does a star surrounded by a Dyson Sphere look like to a telescope that is searching for glimmers of light, heat, and gravity? SETI is operating purely on conjecture. That’s assuming alien civilizations are even capable of creating these hypothetical superstructures. Or that the structures would function as we intuit.
At some level, I have to question if we know what we’re looking for. Because so much of this feels like we’re searching for humans deep in space. Perhaps the reason we can’t find aliens is that they are simply… too alien.
In case anyone wasn't aware, nearly all space photos that you've ever seen have had their colours tweaked. It's standard practice in space photography. Nebulae and galaxies and planets aren't as colourful as they appear in photos. They do it either to make the features more obvious for study, or just to make them pop more to drum up interest in space exploration. Nothing wrong with it, just be aware that what you see isn't reality but an interpretation.
Much more likely is that the galaxies will zoom relatively close to each other – say, a little under 500,000 light years away.
In To Sleep In A Sea Of Stars by C. Paolini, there is a group that aims to prevent or circumvent the heat death of the universe, although the post-human civilisation has barely touched a few star systems (<30 ly). In a similar fashion, I recommend to take the necessary steps to build up a galaxy defense force soon.
With Newtons law of gravity, there is a big, but seemingly solved problem that’s been known for a long time: things must not touch. Potential energy is calculated by dividing a term by the distance of two objects. You can’t devide by zero, so if the distance goes to zero, energy goes to infinity, which doesn’t make sense. The solution is to prevent the centers of mass of things from touching. This isn’t a problem, because in real life, masses aren’t points, but solid objects and the centers of mass are in the middle, so they can’t touch, because the outer parts collide first. And in simulations you can just make a rule that says no touching.
This kind of gap in a formula, where it stops being defined, is called a singularity in math. And to deal with them, you just have to know, when to expect them. For hundreds of years, people thought, collisions were the only singularities in Newtonian gravity. Easy to avoid, so not a problem. Now in this paper, they prove, that there are other, non-collission singularities and give an explicit example.
The arrangement in the picture has the middle mass going back and forth between the two binaries faster and faster and it reaches infinite speed in finite time. It basically leaves the universe, like a glitch in a video game. Also the reverse is allowed too: you just need the four masses from the two binary systems and there is nothing in Newtonian gravity that says a fifth mass can’t randomly appear from out of nowhere with infinite speed, slow down and settle between the too binaries.
Since only five masses were necessary to create this problematic constellation, it’s likely that there are many more possible.
Luckily, we have Einsteins theory of gravity now, so don’t have to worry about Newton too much. However, this does have its own, completely different kind of singularity, where the curvature of spacetime goes to infinity. People initially thought, that would be a problematic, unphysical behavior, like Newtons singularities, but it turns out that’s just a real thing that happens: black holes. Here the annoying singularities are mercifully shrouded in an event horizon, so at least we don’t have to look at them. Unless… But there is a solution for that too.
I think that !space is the most general community, and communities like “!astronomy” and “!spaceflight” are subsets.
Interesting data from a telescope? Astronomy and space, but not spaceflight.
A new GPS satellite is launched? Spaceflight and space, but not astronomy.
The Perseverance rover drills into a neat rock on Mars? Space, but not really astronomy or spaceflight.
A new space telescope is launched? Definitely all three.
These are just my thoughts though, and I’d love to hear what others think.
@Bee, @otter, @Bitswap Thoughts on changing the display name of !space from “Space & Astronomy” to just “Space”? Not that astronomy posts wouldn’t be welcome, but it could help reduce confusion with this community.
It looks like the icon and banner are broken, even on mander.xyz. @Bitswap, were you in the process of updating those? It could be a cross instance moderation issue. Otherwise how are these:
Neat to see a 6-7 solar mass black hole spotted. First one without a companion star to give it away! As we get better at finding black holes of this size, will be interesting to see if they end up explaining part of the “dark matter” problem.
astronomy
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