Starship Asterisk*

Does anyone know the origin of the A, B, C, M, X classification system for solar flares? I'm curious as to why it jumps from C to M and then to X (instead of A, B, C, D, E, for example). I figured there might be a historical explanation, like with the OBAFGKM stellar classification system, but searc...

Wonderful galaxy, one of my favorites. The picture of the galaxy was the front page of the "Galaxies" book from Timothey Ferris from 1983 ... long time ago. 8-) Thanks for reminding me of that great book. We ran a planetarium show based on that book at one time, with Ferris providing narr...

I understand the logic behind using a hydrogen-alpha filter, but could someone explain to me the logic behind using oxygen and sulfur filters, as opposed to using some other elemental filters? And are those filters centered on specific wavelengths, ala hydrogen-alpha (e.g. sulfur-alpha, or something)?

A shadow from one of Jupiter's moons is visible in the red belt up to the left of the Red Spot.

Is it really scheduled to go into Jupiter this summer? I thought it was intended to go until late 2019 now since it never made it into its shorter 2-week orbit.

Chris Peterson wrote: Well, why should it be on the equatorial plane? Satellite orbits are stable at any inclination.

I don't know, other than that nearly all of the other major moons in the Solar System orbit very near to their planet's equatorial plane.

Chris Peterson wrote:It's also a problem that the Moon isn't in a circular orbit, and doesn't lie on our equatorial plane.

I've long wondered why the Moon's orbit lies so much closer to the ecliptic than to the celestial equator, but I've had a difficult time finding explanations online. Does anybody here have any?

Does anybody know what's happened to Hubble Heritage? They used to put out a new image every month, but it's been awhile.

Dawn reached it's lowest orbit in mid-December and since then there have been hardly any images released at the website. They've been releasing a new image pretty much every day, just as before, on their website: http://dawn.jpl.nasa.gov/multimedia/images/ceres.html Just scroll down below the "...

All the peaks in that enlargement are about the same size and shape, which is a symmetrical triangle in section. Some are conic, some longer in one direction. Such symmetry would suggest they are made of a single, homogeneous material. I think water ice has been suggested? But no mountain or mounta...

Quick question about Ceres' density - anyone know how it was measured before Dawn's arrival? Can't imagine how without any moons. Thanks for any insight...

Interesting that the position of the sunset barely moves, but sunrise moves markedly east throughout the period. Must be an effect of perihelion, but I don't understand orbital mechanics well enough to see the reason straight away. Is there a short explanation? The migration of sunrise and sunset s...

Chris Peterson wrote:But our eyes? No. It doesn't matter how big a telescope you use, what you see will never be brighter than your naked eye sees the same thing. Only larger.

But when I look through a telescope at the Moon, it seems both larger and brighter...?

Indeed, this is true for all nebulas. None can appear to our eyes as anything other than a vague grayish fog with bit of subtle structure visible (think of the Milky Way). Doesn't matter where we observe from, or what kind of purely optical instruments we use. These things are all extremely dim. Bu...

Can someone answer a question for me? I know that nearly all of the gas out there is hydrogen, but in this picture the hydrogen is colored green and the sulfur is colored red, and the picture appears to have a lot more reds than greens (or yellows). So anyway, why does the glowing sulfur seem so muc...