Isn’t an event horizon just a question of being dense enough to bend light past the point of no escape?
A hollow planet supporting a detached core with enough density to have an event horizon seems kinda ridiculous… If even light can’t escape it, I don’t see some rocky ‘shell’ withstanding that much gravity. Any hollow section would have collapsed well before reaching the point of the planet’s densest point forming an event horizon.
What matters is the total mass of the black hole, not its density. If you replaced Earth’s core with a black hole of the same mass, the gravity you’d feel at the surface (or beneath the surface) would be the same. You’d only notice a difference if you were in the hollow region formed by removing the core.
The way I see it, the real problem with a planet like Earth is that because the inside is so hot, the inner parts are too soft to support their own weight, and the crust is probably too fragile to support its own weight. That’s not a problem, though, in an asteroid or a planet that’s solid all the way through.
Depending on the mass of the black hole, the “shell” doesn’t need to be a shell it could be effectively completely solid with an atom sized black hole at the centre.
PBH’s as discussed in this article have pretty wild mass ranges, so anything is possible. It’s entirely possible to have black holes so small they can’t easily absorb new matter as they’re smaller than protons. Tiny black holes only have large surface gravity, nothing noteworthy at a distance.
So, there’s nothing in universe that is longer than “soon”. This prediction of going nova this year, only means it already happened but you can’t see it yet. And since it’s going super nova, that means entire even will be boring anyway. You’ll see a white dot that will increase in intensity during this year and then fade away equally slowly.
For people wondering about dates, there are none. Just like Beetlejuice is expected to explode soon™, that actually means 3000-10000+ years of waiting. So don’t get your hopes up. Out lives are but a blink in universe. All you can do is be diligent and watch it constantly. Doesn’t mean you’ll see much either since at peak magnitude of 2.5 it will be dim enough that you’ll need telescope to see it.
Nova, not supernova. Novas happen multiple times. Supernova do not but it doesn’t say supernova. Soon, as in within the next 6 months since its following a cycle that happened about 80 and 160 years ago.
Visible with unaided eyes for several days (but still dimmer than about 120 stars in the sky), and with binoculars for about a week, according to NASA.
On 20 April 2016, the Sky and Telescope website reported a sustained brightening since February 2015 from magnitude 10.5 to about 9.2. A similar event was reported in 1938, followed by another outburst in 1946.[20] By June 2018, the star had dimmed slightly but still remained at an unusually high level of activity. In March or April 2023, it dimmed to magnitude 12.3.[21] A similar dimming occurred in the year before the 1945 outburst, indicating that it will likely erupt between March and September 2024.
And if I’m interpreting some of the other content correctly, it’ll come and go in one night? Maybe someone who knows more about these can confirm or correct me.. See update below.
Also …
Even when at peak magnitude of 2.5, this recurrent nova is dimmer than about 120 stars in the night sky.
Once its brightness peaks, it should be visible to the unaided eye for several days and just over a week with binoculars before it dims again, possibly for another 80 years.
Reminds me of when Betelgeuse, the orange upper star of Orion, went dim in 2020. Lots of amateur reports on its brightness, 3x per night, for a few months waiting for it to go nova. It settled down a bit before disappearing behind the sun for the season and came back just fine. It was kinda fun to monitor, but soooo many false alarms from people trying to call it first
The team’s measurements even suggest that the supernovae that virtually cleared the bubble of space in which the Milky Way resides was born in a cluster of stars within the Radcliffe Wave.
Wait, the Milky Way is inside of a bubble generated by novae which were inside a cluster which is inside the Radcliffe Wave which is… itself… inside the Milky Way?
The Radcliffe Wave formation is a bunch of gas that is apparently, wiggling, in incredibly huge time and distance scales, like a sinusoidal wave.
So, imagine very, very long ago, before the Milky Way formed, you have a particular dense gaseous region/formation.
Dense gaseous regions tend to give birth to new stars. This region did so, and then one of them supernova’d.
Next, the Milky Way ended up forming in the void created by this supernova.
Then, this dense gaseous region was basically incorporated into the Milky Way (seems like one of its spiral arms) over another absurdly long period of time.
But, for some reason, it is wiggling, in a manner that dense gaseous regions have not been observed to behave in.
Thats the best I can do here, I am not an astrophysicist, though I did take two quarters of intro level astronomy in college lol.
Probably worthwhile to note that the article says that their data ‘suggests’ not ‘shows’ or ‘proves’ the bit about the supernova clearing the Milky Way void.
To actually prove that would encompass, among many other things, running the clock backward on star orbits/trajectories over billions of years using extremely complicated models and mountains of data I am absolutely not qualified to comment on.
Im just trying to very broadly explain the chain of events here if this supernova really did cause the void the Milky Way formed in.
Anyway, other fun fact: Our Milky Way Galaxy is not actually a pure spiral Galaxy as it has so often been depicted for quite a long time.
It is actually a barred spiral galaxy. Basically, instead of just swirly arms, there are actually short, more or less straight parts to the arms as they emanate out from the center, which then begin to curve into spirally arms.
sciencealert.com
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