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Posts by Christopher Crockett

Color spectrum via Shutterstock
Blogs | FAQs | May 19, 2014

What is the electromagnetic spectrum?

The electromagnetic spectrum describes all the wavelengths of light. From dark nebulae to exploding stars, it reveals an otherwise invisible universe.

Image via Brews OHare on Wikimedia Commons.
FAQs | Feb 20, 2013

What is a light-year?

Hint: A light-year is a unit of distance, not time.

Stellar parallax
Blogs | Jan 02, 2013

What is a parsec?

Astronomers typically speak of distance in the universe in parsecs, not light-years. One parsec is about 30 trillion kilometers, or just over three light-years.

Aug 2012 CME
Blogs | FAQs | Dec 13, 2012

What is a coronal mass ejection or CME?

Coronal mass ejections are powerful eruptions on the sun’s surface.  Caused by instabilities in the sun’s magnetic field, they can launch a billion tons of superheated gas into space at over one million miles per hour. 

Eta Carinae
Blogs | Dec 11, 2012

Wolf-Rayets are the most massive and brightest stars known

Wolf-Rayet stars make our sun look tiny. They can be hundreds of times more massive, millions of times brighter, and tens of thousands of degrees hotter.

Elliptical galaxy ESO 325 G004
Blogs | Dec 05, 2012

What are elliptical galaxies?

Elliptical galaxies are among the largest single star systems in the universe and are built by the collisions of many smaller galaxies.

Ionized gas in the Milky Way
Blogs | Nov 28, 2012

What lives between the stars?

The interstellar medium is the stuff between the stars. Made up mostly of hydrogen and helium gas, it contains all the material needed to make stars and planets. It is shaped by stellar winds, dying stars, galactic magnetic fields, and supernova explosions.

mars_retro_single_crop
Blogs | Nov 25, 2012

What is retrograde motion?

Sometimes the planets appear to change direction in the sky. This retrograde motion is entirely an illusion caused by the Earth passing the slower moving outer planets.

The path of the sun through the zodiac.
Blogs | Nov 23, 2012

What is the ecliptic?

The ecliptic marks the path of the sun.  It’s the projection of Earth’s orbit onto the sky. And it’s an essential part of any stargazer’s vocabulary.

Sunset via EarthSky Facebook friend Lucy Bee in Dallas.
Blogs | Nov 13, 2012

Why does the sun shine?

The sun generates about 400 billion billion megawatts of power and it has done so for five billion years. Nuclear fusion – combining lighter atoms to make heavier one – is what makes it possible.