The Zodiac is defined by 13 constellations that lie along the annual path of the sun across the sky.
Posts by Christopher Crockett
The electromagnetic spectrum describes all the wavelengths of light. From dark nebulae to exploding stars, it reveals an otherwise invisible universe.
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.
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.
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 galaxies are among the largest single star systems in the universe and are built by the collisions of many smaller galaxies.
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.
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 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.