Comet with tail upward in a sunset sky.

What’s the difference between asteroids and comets?

Asteroids and comets are generally composed of different stuff. They both orbit our sun, but, for the most part, reside in different parts of our solar system. Yet some rare objects display characteristics of both asteroids and comets.

What’s the youngest moon you can see with your eye alone?

It has long been a sport for skywatchers to spot the youngest possible crescent moon after sunset, with the eye alone. What does it take to see a very young moon? Details here.

Is it possible to hear meteors?

Can you hear a meteor as it streaks overhead? Some people have reported hearing meteors with a sizzling sound like bacon frying. Scientists now say you can, and explain how it happens.

Born in June? Here’s your birthstone

Happy birthday June babies! Your month has 3 birthstones – pearl, moonstone, and alexandrite.

January’s birthstone is the garnet

Happy birthday, January babies!  Your birthstone is the garnet.

Rainbow-like halo around the shadow of a man, in a mountainous setting.

What is the Brocken Spectre?

The Brocken Spectre is your own shadow, cast on mists below you, when you are mountain climbing. The shadow may appear enormous and has a ring around it.

Born in March? Here’s your birthstone

Happy birthday to all you March babies. Your month has 2 birthstones – the aquamarine and the bloodstone.

A nearly face-on disk of gas and dust, with interesting gaps.

Do all planets orbit in a flat plane around their suns?

The major planets in our solar system orbit, more or less, in a single plane. That’s why you can look for them along the same sky path traveled by the sun and moon. Is the same true for exoplanets in distant solar systems?

What makes a halo around the sun or moon?

A large ring or circle of light around the sun or moon is called a 22-degree halo by scientists.

How much moon do we see?

One side of the moon always faces Earth. Even so, over time, it’s possible to see as much as 59% of the moon’s surface, due to lunar libration.

Star brightness versus star luminosity

Some extremely large and hot stars blaze away with the luminosity of a million suns! But other stars look bright only because they’re near Earth.

Circumpolar stars never rise or set

From Earth’s North and South Poles, all the stars appear as circumpolar. Meanwhile, at the equator, no star is circumpolar. And what about in between?

How big are the biggest monster stars?

How big can stars get? And how do these monster stars get so big?

What are the seasons like on Uranus?

Uranus lies nearly sideways with respect to the plane of its orbit around the sun. That sideways tilt makes a huge difference between winter-summer on Uranus, and autumn-spring.

Lucky New Year’s foods

Lucky New Year’s foods in the U.S. South and around the world. Happy 2017!

How long to orbit Milky Way’s center?

One journey of our sun and planets around the center of our Milky Way galaxy is sometimes called a cosmic year. That’s approximately 225-250 million Earth-years.

Are solar eclipses more common than lunar eclipses?

It’s sometimes said that, on a worldwide scale, solar eclipses outnumber lunar eclipses by about a three to two margin. True?

What is time?

… And why does it move forward?

See 5 bright planets at once

First time we can see 5 planets at once since 2005. All 5 are up before dawn, still, and all 5 will remain visible until Mercury disappears in the dawn just after mid-February.

Why does the new year begin on January 1?

New Year’s Day is a civil event. Its date isn’t precisely fixed by any natural seasonal marker.