North Star: Polaris and Surrounding Dust
28.04.2021

Why is Polaris called the North Star? First, Polaris is the nearest bright star toward the north spin axis of the Earth. Therefore, as the Earth turns, stars appear to revolve around Polaris, but Polaris itself always stays in the same northerly direction -- making it the North Star.

A Vortex Aurora over Iceland
4.04.2022

No, the car was not in danger of being vacuumed into space by the big sky vortex. For one reason, the vortex was really an aurora, and since auroras are created by particles striking the Earth from space, they do not create a vacuum.

Phobos: Doomed Moon of Mars
18.08.2001

Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These Martian moons may well...

NGC 7023: The Iris Nebula
4.11.2004

Like delicate cosmic petals, these clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula and dutifully cataloged as NGC 7023, this is not the only nebula in the sky to evoke the imagery of flowers.

Leonid Glowworm
28.04.2000

Recent Leonid meteor showers have been rich in bright fireball meteors which leave lingering trails stretching across the night sky. These trails, or persistent trains, are mysteriously self-luminescent and do not shine by reflected light.

A Proton Arc Over Lake Superior
3.08.2015

The setting had been picked out -- all that was needed was an aurora. And late last August, forecasts predicted that an otherwise beautiful night sky would be lit up with auroral green. Jumping into...

Young Stars and Dusty Nebulae in Taurus
30.03.2017

This complex of dusty nebulae lingers along the edge of the Taurus molecular cloud, a mere 450 light-years distant. Stars are forming on the cosmic scene. Composed from almost 40 hours of image data...

The Leo Trio
18.04.2019

This group is popular in the northern spring. Famous as the Leo Triplet, the three magnificent galaxies gather in one field of view. Crowd pleasers when imaged with even modest telescopes, they can be introduced individually as NGC 3628 (left), M66 (bottom right), and M65 (top).

Moon Pi and Mountain Shadow
14.03.2024

What phase of the Moon is 3.14 radians from the Sun? The Full Moon, of course. Even though the Moon might look full for several days, the Moon is truly at its full phase when it is Pi radians (aka 180 degrees) from the Sun in ecliptic longitude.

APOD: 2025 April 28 Б Gum 37 and the Southern Tadpoles
28.04.2025

This cosmic skyscape features glowing gas and dark dust clouds alongside the young stars of NGC 3572. A beautiful emission nebula and star cluster, it sails far southern skies within the nautical constellation Carina.