Recent content by Ken G

Interesting point about the difficulty in identifying a neutron star from its radio spectrum alone. It might still be possible in the time domain, however. I think what you'd look for is a nearly continuous but still periodically varying source, as if the beam was nearly, but not exactly...

It does seem odd that no neutron stars have been detected with continuous radio emission that looks like a normal pulsar beam except that it is aligned with the rotation axis, given that it seems the probability the beam crosses Earth is about 1/10. It is important to realize we should not...

I'm not sure where this number that 2/3 rotate the opposite way comes from, in the article it says: "Of these galaxies, 105 rotate counterclockwise, while 158 rotate clockwise." So that looks like 3/5 not 2/3. They claim that the probability of flipping 263 coins and getting 158 heads is...

And there lies the problem. The pressure on astronomers to achieve "cool" results can lead to them overstate their claims, as happened here. Maybe this isn't bad for astronomy, since people like the headlines and aren't bothered by (or never even hear) the retractions later. It's a sticky...

It's part of a fair summary. But it only touches on whether the signal is a biomarker, there are also the other two issues mentioned above: is the planet really an ocean world, or just a mini Neptune? (It's more likely just a mini Neptune, so the assumption of what the world is like could be...

It might also help the beginner trying to understand the spirit of general relativity to remember Wheeler's famous way of describing that spirit: "Matter tells spacetime how to curve, and spacetime tells matter how to move." The point is, there is a connection between matter and spacetime that...

Your questions really require someone who is an expert on binary mass transfer, not to mention someone who understands the particular assumptions being made in the simulation you are citing the graph from (binary mass transfer cannot be simulated from first principles, it requires uncertain ad...

In radiative equilibrium, the temperature is set by the flux entering and leaving. As in any equilibrium, you drop all time dependent terms. It does not mean the temperature cannot change though, things change in equilibrium all the time. It's not a statement that the time derivative is zero...

Radiative equilibrium means that if you look at a parcel of gas, the same radiant energy enters it as leaves it. It doesn't put any requirements on movement of the gas, or lack thereof. I don't understand the question, it seems to me the "upward propagation velocity" of a gas parcel is the...

Yes, that's the convectively stable but very optically thick region that might be considered the "deep photosphere," if one uses the photosphere word to apply to the region of radiative equilibrium. If instead one uses the word to just mean some kind of surface of last interaction with the...

No, not if you use these words to describe physically real regions of the Sun. The photosphere is connected to the convective regions below, so is put into motion by them, and carries waves and magnetic stresses, it is a real gas that has real dynamics, but its energy balance is simply to pass...

If one goes with the energy transport way of defining the photosphere, in which the photosphere is in "radiative equilibrium" (meaning it just passes along whatever radiation is welling up from below with no additional local heating going on), then granulation doesn't affect what you are calling...

Different sources define them differently, but the one I like bases it on the different energy transport. The photosphere carries the luminosity radiatively (so not convectively like the region below), the chromosphere has net heating so it emits more light than it absorbs (while most of the...

And to add to that, not only does Kepler's third law about the total motion (its period and semimajor axis) apply, so does Kepler's first and second laws! The laws all apply to the motion of the displacement vector between the two bodies (so now we have left high school but you said you wanted...

Incredible photo, looks like a composite.