Starship Asterisk*

But the western US also had massive wildfires. If wildfires are illuminating western Australia and north-central Siberia, then why not the western US? Had they died down before October?

I came here because I wondered about Western Australia as well. Glad to see everyone pondering that.

How about north-central Siberia? Pretty lit-up -- more than I'd expect. Perhaps mining?

Supergiant stars are very tenuous. Planets could be orbiting inside of them. (They are still very dense at their cores, but have huge, tenuous outer layers.) Thanks, Chris. That's amazing. It makes me think that a supergiant must not really have a surface -- at least not the way that we think of ou...

If the diameter of Antares is 850 times that of the sun, then its volume would be a factor of 850^3 greater, right? Yet it is only 15 times more massive than the sun?

That would make its average density something like 15/850^3 that of our sun.

So Hanny's Voorwerp is illuminated by quasar that has shut off. Does that mean that we are seeing reflected light from a source that is closer to us, but has shut off? And does that mean that the Voorwerp will lose it's glow in the (galactically) near future?

To me, this is the most interesting thing about today's post: "Since the sideways velocity of the Andromeda Galaxy (M31) is presently unknown,..." Can anyone explain that to me in more detail? I assume that our relative motion on the axis between the Milky Way and Andromeda is known. But w...