Astronomy questions and answers


How many nested stable (1 Mio years) orbits are theoretically possible?

If we look at our solar system we have the sun which has planet orbits and planets have moon orbits. If we look at the possible size difference from hypergiants to small asteroids why shouldn't it be possible to nest orbits to an astounding degree: supergiant orbit a hypergiant, star ....

Austin Austin: 3 hours ago


Nature and mechanism of the short-term variability in radio strength of Sgr A*?

The article Cosmic filament probes our galaxy's giant black hole ( links to A Nonthermal Radio Filament Connected to the Galactic Black Hole? ( which discusses (among other things) the importance of achieving high dynamic range to study these filaments in the proximity of the strong emission associated with ....

Emilia Emilia: 8 hours ago


Why black holes have positive energy?

How could Hawking get the conclusion " and black holes have positive energy. That’s why empty space is stable. Bodies such as stars or black holes cannot just appear out of nothing. But a whole universe can."? It would make sense to me, if a black hole has negative energy. ....

Everleigh Everleigh: 9 hours ago


Do other planets affect the Earth?

Let say Mercury, Venus, the Moon were all in alignment between the Earth and Sun. They are all closest to each other in respective elliptical orbit. On the other side of the Sun you have the rest of the planets. Would their gravity combine to have any gravitational effects on ....

Isabella Isabella: 12 hours ago


Align multiple fits images without WCS for future aperture photometry analysis

Recently I have got a bunch of raw fits images (2048x2048 pixels) of the same sky region without WCS to process in iraf. However, those images are not well-aligned. There would be around 4~5 pixels' deviation for a specific star, thus giving me choppy batch photometry analysis result. Are there ....

Daniel Daniel: 18 hours ago


How could time only have started with the Big Bang?

I understand that before the Big Bang time (as well as dimensions) didn't exist. But how could this be? If there was no time then nothing could change, and so time itself couldn't come into existence. ....

Thomas Thomas: 18 hours ago


Is the mass of Kuiper belt dominated by large objects?

There is a problem in my example sheet trying to teach me distributions. My result is that Kuiper belt objects are dominated by large mass objects. Is this supported by observational evidence? ....

Jeremiah Jeremiah: 23 hours ago


Boltzmann brains - probability

A question about the Boltzmann brains assuming heat death of the Universe. It is said that if so, than it's more likely were are such constructs instead of having reality as we perceive it, however it seems to me that it makes certain (very strict) assumptions about the time, which ....

Charlie Charlie: yesterday


How can many stars be formed from the remains of one supernova?

A supernova is the explosion of a single star; so how is it that thousands of stars can "be born of" that one explosion (presumably only using the unspent fuel / lighter elements of the original)? Does that also mean the stars coming from a supernova cannot possibly become supernovae ....

Claire Claire: yesterday


Are black holes really black?

I don’t think that black holes are really black as they are the only ones who have the capacity to bend light. At the centre of the black hole the laws of physics are totally defied, black holes appear black as space is black in colour. ....

Isaac Isaac: yesterday