A “dwarf” star is just what astronomers call a main sequence star. So, a blue dwarf star is a main sequence stars of spectral class O or B. There are also blue giant stars, which occur in stars more massive than the Sun after they reach their red giant phase (there are also orange and yellow giants, for those stars that aren’t quite massive enough to reach blue hot in this phase).
What you’re thinking of are black dwarfs. Black dwarfs are what remain after a white dwarf cools off. Red dwarfs are thought to become white dwarfs, just like the sun will, at the end of their lives.
Yeah, that was just a regular O-class star, just so we have both ends of the spectrum.
There are supposedly stars that are colder than red dwarfs, which would be more red than the orange shown in the picture, but those are arguably not even stars, per se.
Carbon stars – red giant stars with enough carbon for soot to form in their atmosphere – are supposed to be excessively red. They’re rare, but we see enough of 'em.
Ok, clearly there’s some confusion here. There are “blue dwarf stars”, which are blue stars of luminosity class V (dwarfs), and there are “blue-dwarf stars”, which a hypothetical evolutionary counterparts to blue giant (where “giants” are of the luminosity class III) stars. Blue evolved red dwarf stars are neither established via observation (obviously), nor are they a generally accepted concept in the stellar evolution community. Modern stellar evolutionary simulations don’t show red dwarf stars becoming blue near the ends of their lives. They do have an exaggerated increase in temperature and luminosity as they leave the main sequence, as compared to more massive stars, but they get nowhere near the blue end of the spectrum.
Haha. Are we talking ISS astronauts, or those who have actually walked on the moon? Because those who have walked on the moon characterize its colour as being basically the same as pavement.
I’ve seen moon rocks in person (taken from the Apollo 15 landing site, I believe, though it may have been Apollo 14 – it’s been a few years now), and, as far as their colour goes, they were almost spot on for old, worn asphalt. They were darker than cement or plaster of paris, but not quite as dark as… I’m having trouble coming up with a dark grey.
Take your standard grey t-shirt, and that’s the colour of your average moon rock.
Maybe that’s more brown than we expect it to be (I think we usually picture the moon as slightly blueish in colour, so lack of blue can be interpreted as excess of red).
I don’t remember but I’m thinking an Apollo.
and " Around noon, sunlight takes a short, direct path through the atmosphere and appears pale yellow. When near the horizon around sunset and sunrise, it passes through the lower, ”dirtier” part of our atmosphere the entire distance. All that extra dust, smoke, etc. effectively scatter much of the sun’s light, leaving only oranges and reds. "
From http://astrobob.areavoices.com/2012/08/26/what-color-is-the-sun/
At a guess, I would say once the Sun’s light hits the atmosphere, some of the shorter wavelengths begin to be filtered out (i.e. scattered). So the bluer/greener light would be the first to go, but redder light can travel further through stuff.
It’s the same reason UV light can’t give you sunburn through a glass window, but radio signals can still be picked up through building walls.
But it’s been a while since I studied physics, so reality may have changed since then.
[quote=“Japa, post:68, topic:524, full:true”]
I guess you missed the forum tradition to turn every thread into a sciencediscussion.
[/quote] I know about the tradition, it’s just that I think that people should just branch off a new thread if they want to discuss science.
