Ask Astro | Astronomy.com

The Sun

Before Einstein, what did astronomers think powered the Sun?

Illustration of the main belt of asteroids

Was there ever a planet between Mars and Jupiter?

Sirius A and B

Will Sirius B explode as a type Ia supernova?

Eyepiece showing field stop

Telescopes and Equipment

What is the difference between a 2″ eyepiece and a 1¼” eyepiece?

DSCOVR image of Earth and Moon

Science, Solar System

How much less would you weigh on the Moon than on Earth?

Lagrangian points of the Earth-Sun system

What are Lagrangian points?

Saturn ring shadows

Do Saturn’s rings cast shadows?

Artist's concept of what Andromeda will look like in the sky in the future

Milky Way, Solar System

What will happen to the solar system when the Milky Way and Andromeda Galaxy merge?

Solar system planets

Why do the solar system’s planets have different compositions?

Artist's concept of the interior of a white dwarf

Solar System, Stars

After our Sun becomes a white dwarf and cools completely, what will be left?

Comet 67P/Churyumov-Gerasimenko

Does a comet’s period change because it loses mass every time it nears the Sun?

The Carina Nebula, imaged with and without adaptive optics

How does adaptive optics work?