Observed magnitudes of Qianfan spacecraft range from 4 when they are near zenith to 8 when low in the sky.
Since this is the first run of the Qianfan satellite constellation, the most appropriate comparison would be to Starlink’s original satellites. As you can see below, the notion that China’s satellites are “significantly brighter than those of Western systems” is a inaccurate.
The Original spacecrafts have a relatively flat phase function, so they are comparatively bright over a wide range of phase angle. […] the characteristic magnitudes are: 4.7 (Original) […]
The mean apparent magnitude of Starlink Mini Direct-To-Cell (DTC) satellites is 4.62 while the mean of magnitudes adjusted to a uniform distance of 1000 km is 5.50.
Clearly, even the newest Starlink satellites are well above the magnitude 7 limit astronomers recommend for satellite brightness.
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.
Super cool photo, but does this technically count as astronomy? Isn’t astronomy “a camera on (usually) on earth, pointed up into space”, not the other way around?
The science which treats of the celestial bodies, of their magnitudes, motions, distances, periods of revolution, eclipses, constitution, physical condition, and of the causes of their various phenomena.
A treatise on, or text-book of, the science.
From the GNU version of the Collaborative International Dictionary of English.
oh boy, get ready people. it starts with a movie, then it’s a debut single, then you’re buying the fanzines, the hats, the shirts. this ends in commemorative plates.
I find it fascinating that so much of astronomy is having data and trying to make educated guesses about what that data could maybe indicate. It shows just how much more there is to find out, realy.
They have quite big plans, but almost 14. Million € on hand. I hope they manage to achieve their goal.
We produce for the first time high-resolution multi-colour movies with the EHT combined with new telescopes probing the variable extremes of the electromagnetic spectrum (e.g. CTA, MeerKAT/SKA1). The data are analysed and interpreted with innovative models finally combining micro- and macrophysics. The PIs bring together complementary expertise over the entire black hole mass scale in radio imaging and multi-wavelength monitoring, astroparticle physics, and theoretical modelling to bear on the problem. This is accompanied by four major investments: construction of a new mm-wave telescope in Africa enabling full dynamical imaging of black holes with the EHT, new model development, supercomputing hardware, and a vibrant team of young scientists to help develop a new, truly universal black hole paradigm.
Somewhen in there are creatures we’d really get along with were it not for the 58.71M light years between our galaxies, and the unlikelihood we both exist as simultaneous civilizations.
astronomy
Najstarsze
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