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Stellar luminosity versus star brightness
Some extremely large and hot stars blaze away with the stellar luminosity of a million suns! But other stars look bright only because they're near Earth.
January 18, 2025
What is a variable star?
What is a variable star? It's a star that brightens and dim in a cycle that might last hours, or weeks, or months, or longer. Astronomers know millions!
January 15, 2025
Lunar occultation of Mars on January 13, 2025. Images here!
The full Wolf Moon passed in front of red Mars for some observers last night. Here are some great images of the lunar occultation of Mars.
January 14, 2025
What is the Big Bang?
In the view of modern cosmologists, the Big Bang is the event that marked the birth of our universe. What was it - when was it - and what are modern theories?
January 1, 2025
Comets are icy balls of gas, dust and rock
Comets are diffuse balls of ice and dust orbiting the sun. They're sometimes visible in our skies. A comet's tail can stretch millions of miles across space.
November 28, 2024
Gegenschein is the glow of interplanetary dust
The gegenschein is a play of light on interplanetary dust of the solar system. It's a diffuse path of light that lies exactly opposite the sun.
November 27, 2024
Is there a North Star for Mars?
Is there a North Star for Mars ... a guide star for future explorers? Not in any satisfying way. But Martian stargazers wouldn't lack for things to see!
November 17, 2024
Mirach is your guide star to finding 3 galaxies
Mirach in the constellation Andromeda helps stargazers locate the Andromeda Galaxy, the Triangulum Galaxy, and "Mirach's Ghost" (NGC 404).
November 10, 2024
Open star clusters are loose groups of stars
Open star clusters are young, loosely bound gatherings of stars that may still be surrounded by the nebula - or space cloud - in which they were born.
November 5, 2024
Alpheratz belongs to Andromeda, but is part of the Great Square
Alpheratz appears to our eyes as a single star but it is actually a close binary star system. Many stargazers use it to locate the Andromeda galaxy.
October 9, 2024
