What causes a blue band to cross the Moon during a lunar eclipse? The blue band is real but usually quite hard to see. The featured HDR image of last […]

What’s that moving across the sky? A planet just a bit too faint to see with the unaided eye: Uranus. The gas giant out past Saturn was tracked earlier this […]

What created the strange spiral structure on the upper left? No one is sure, although it is likely related to a star in a binary star system entering the planetary […]

This high cliff occurs not on a planet, not on a moon, but on a comet. It was discovered to be part of the dark nucleus of Comet Churyumov-Gerasimenko (CG) […]

Big, beautiful spiral galaxy M101 is one of the last entries in Charles Messier’s famous catalog, but definitely not one of the least. About 170,000 light-years across, this galaxy is […]

Rain clouds passed and the dome of the Lick Observatory’s 36 inch Great Refractor opened on November 19. The historic telescope was pointed toward a partially eclipsed Moon. Illuminated by […]

Shaped like a cone tapering into space, the Earth’s dark central shadow or umbra has a circular cross-section. It’s wider than the Moon at the distance of the Moon’s orbit […]

Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as large and clear as this. Perhaps the most famous star cluster […]

Why are the regions above sunspots so hot? Sunspots themselves are a bit cooler than the surrounding solar surface because the magnetic fields that create them reduce convective heating. It […]

Why is the Moon on top of this building? Planning. It took the astrophotographer careful planning — including figuring out exactly where to place the camera and exactly when to […]