Gamma Cassiopeiae shines high in northern autumn evening skies. It’s the brightest spiky star in this telescopic field of view toward the constellation Cassiopeia. Gamma Cas shares the ethereal-looking scene […]

History’s second known periodic comet is Comet Encke (2P/Encke). As it swings through the inner Solar System, Encke’s orbit takes it from an aphelion, its greatest distance from the Sun, […]

History’s first known periodic comet, Comet Halley (1P/Halley), returns to the inner Solar System every 76 years or so. The famous comet made its last appearance to the naked-eye in […]

In 60 seconds, this setting Sun will turn green. Actually, the top of the Sun already appears not only green, but wavey — along with all of its edges. The […]

This dance is to the death. As these two large galaxies duel, a cosmic bridge of stars, gas, and dust currently stretches over 75,000 light-years and joins them. The bridge […]

There goes another one! Volcanoes on Jupiter’s moon Io keep erupting. To investigate, NASA’s robotic Juno spacecraft has begun a series of visits to this very strange moon. Io is […]

What does this aurora look like to you? While braving the cold to watch the skies above northern Canada early one morning in 2013, a most unusual aurora appeared. The […]

Half way between New Moon and Full Moon is the Moon’s first quarter phase. That’s a quarter of the way around its moonthly orbit. At the first quarter phase, half […]

Galaxies abound in this sharp telescopic image recorded on October 12 in dark skies over June Lake, California. The celestial scene spans nearly 2 degrees within the boundaries of the […]

Most galaxies don’t have any rings of stars and gas — why does M94 have two? First, spiral galaxy M94 has an inner ring of newly formed stars surrounding its […]