Julius Caesar and Leap Days

2024-02-29

In 46 BC Julius Caesar reformed the calendar system. Based on advice by astronomer Sosigenes of Alexandria, the Julian calendar included one leap day every four years to account for the fact that an Earth year is slightly more than 365 days long. ...

Shades of Night

2024-02-28 Dario Giannobile

How does the sky turn dark at night? In stages, and with different characteristic colors rising from the horizon. The featured image shows, left to right, increasingly late twilight times after sunset in 20 different vertical bands. The picture ...

Supernova Remnant Simeis 147

2024-02-27 Stéphane Vetter (Nuits sacrées)

It's easy to get lost following the intricate, looping, and twisting filaments of supernova remnant Simeis 147. Also cataloged as Sharpless 2-240, the filamentary nebula goes by the popular nickname the Spaghetti Nebula. Seen toward the ...

Martian Moon Eclipses Martian Moon

2024-02-26

What if there were two moons in the sky -- and they eclipsed each other? This happens on Mars. The featured video shows a version of this unusual eclipse from space. Pictured are the two moons of Mars: the larger Phobos, which orbits closer to ...

A Phoenix Aurora over Iceland

2024-02-25 Hallgrimur P. Helgason; Rollover Annotation: Judy Schmidt

All of the other aurora watchers had gone home. By 3:30 am in Iceland, on a quiet September night, much of that night's auroras had died down. Suddenly, unexpectedly, a new burst of particles streamed down from space, lighting up the ...

To the Moon

2024-02-24

Intuitive Machines' robotic lander Odysseus has accomplished the first U.S. landing on the Moon since the Apollo 17 mission in 1972. Launched on a SpaceX rocket on February 15, the phone booth sized lander reached lunar orbit on the 21st and ...

The Pencil Nebula Supernova Shock Wave

2024-02-23 Helge Buesing

This supernova shock wave plows through interstellar space at over 500,000 kilometers per hour. Centered and moving upward in the sharply detailed color composite its thin, bright, braided filaments are actually long ripples in a cosmic sheet of ...

A View Toward M106

2024-02-22 Kyunghoon Lim

Big, bright, beautiful spiral, Messier 106 dominates this cosmic vista. The nearly two degree wide telescopic field of view looks toward the well-trained constellation Canes Venatici, near the handle of the Big Dipper. Also known as NGC 4258, ...

Seagull Nebula over Pinnacles' Peak

2024-02-21 Dheera Venkatraman

The bird is bigger than the peak. Nicknamed for its avian shape, the Seagull Nebula is an emission nebula on the night sky that is vast, spanning an angle over five times the diameter of the full moon and over 200 light years. The head of the ...

AM1054: Stars Form as Galaxies Collide

2024-02-20

When galaxies collide, how many stars are born? For AM1054-325, featured here in a recently released image by the Hubble Space Telescope, the answer is millions. Instead of stars being destroyed as galaxy AM1054-325 and a nearby galaxy circle ...