Is the Sun yellow or white?

I’ve heard multiple sources say the sun is white, that it just looks yellow because the Earth’s atmosphere is scattering the blue light. I’ve heard in other places that the sun is yellow because of its position in the Hertzsprung-Russell (H-R) Diagram. Which is it? It can’t be both yellow and white at the same … Read more Is the Sun yellow or white?

How long does it take for stars to explode?

I understand stars are millions of light years away and it takes a long, long time for the light of say a star exploding to reach us. We have pictures of stars exploding 50 years ago. Why are those stars still exploding? Do they explode in slow motion?? Also, why don’t we see galaxies turning? … Read more How long does it take for stars to explode?

How much of the Sun has been used up?

That’s a very interesting question, and one that can often be very difficult to answer when getting deep into the details, but I’ll try and do a quick “back-of-the-envelope” calculation for you and mention when these tricky little details might become important and change my answer. Here is the basic problem to solve. The Sun … Read more How much of the Sun has been used up?

Is Betelgeuse shrinking?

I read that Betelgeuse is shrinking. Is it true, and will there be any consequences? Betelgeuse is a star very often studied by astronomers. Before answering why Betelgeuse is shrinking, let’s explain how to keep a star in a stable state. To do that, two forces must be in equilibrium: gravity, which pulls inward and tries … Read more Is Betelgeuse shrinking?

Do single stars tend to rotate in the same direction as the Sun and/or the Galaxy?

Do single stars tend to rotate in the same direction as the Sun and/or the Galaxy? This is a more technical question, so I am going to give a more technical answer, but first the simple answer. No, the rotation of a single star is not aligned with the galactic rotation because there are more … Read more Do single stars tend to rotate in the same direction as the Sun and/or the Galaxy?

What is the difference between “twin suns” and “binary suns”?

Thanks for the great question! Many people get confused about these two terms as you do. Hopefully I can help clarifying the difference. The dictionary definition of “Twin” is a person or thing that is exactly like each other, or something containing or consisting of two matching or corresponding parts. Therefore, when an article says … Read more What is the difference between “twin suns” and “binary suns”?

How do astronomers zero in on the spectrum of a single star?

How can astronomers zero in on one single star for spectral analysis yet be sure they are not receiving light pollution from other stars in the field of view? Before the spectrum is taken, we are usually able to image the star field and we can also image the position of the slit, which lets … Read more How do astronomers zero in on the spectrum of a single star?

Is it possible to see the Andromeda galaxy with the unaided eye when in dark sky country within Texas?

I live in Dallas, where we feel lucky to see Jupiter and Saturn. Is it possible to see the Andromeda galaxy with the unaided eye when in dark sky country? It is, as you obviously know, a function of relative brightness. The darker the night sky, the dimmer the objects that can be seen. In, … Read more Is it possible to see the Andromeda galaxy with the unaided eye when in dark sky country within Texas?

When I look up and see the Milky Way galaxy, am I looking towards the center of the galaxy or towards outer space?

When I look up and see the Milky Way galaxy, am I looking towards the center of the galaxy or towards outer space? Tell me a good astronomy joke while you’re at it. That is a great question! In fact, you are generally looking into the DISC of the Milky Way galaxy. I’m sure you’ve … Read more When I look up and see the Milky Way galaxy, am I looking towards the center of the galaxy or towards outer space?

In an expanding universe, why are Andromeda and the Milky Way destined to collide?

If the Universe is expanding and all galaxies are moving apart from one another, why is it that the Milky Way and Andromeda will one day collide? Thanks for the great question! To get to the answer, we will need to look at which forces operate on small and large astronomical scales (distances). The two … Read more In an expanding universe, why are Andromeda and the Milky Way destined to collide?