APOD: 2025 March 4 Б A Quadruple Alignment over Italy
3.03.2025

Why does this Moon look so unusual? A key reason is its vivid red color. The color is caused by the deflection of blue light by Earth's atmosphere -- the same reason that the daytime sky appears blue. The Moon also appears unusually distorted.

A Telescope Laser Creates an Artificial Star
6.02.2005

What do you get when you combine one of the world's most powerful telescopes with a powerful laser? An artificial star. Monitoring fluctuations in brightness of a genuine bright star can indicate how the Earth's atmosphere is changing, but many times no bright star exists in the direction where atmospheric information is needed.

An Aurora Before the Storm
19.05.2000

Early April brought some of the most intense auroral storms this decade. An aurora on April 6 was reported to be the largest visible on Earth since 1989, and was seen throughout Europe and much of northern North America.

Moon Pi and Mountain Shadow
13.03.2025

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.

A Twisted Meteor Train
1.02.2005

Did this meteor leave a twisting path? Evidently. Meteor trains that twist noticeably are rare - and even more rarely photographed - but have been noted before. The underlying reason for unusual meteors trains is that many meteors are markedly non-spherical in shape and non-uniform in composition.

APOD: 2025 April 23 Б An Almost Everything Sky
22.04.2025

This surprising sky has almost everything. First, slanting down from the upper left and far in the distance is the central band of our Milky Way Galaxy. More modestly, slanting down from the upper right and high in Earth's atmosphere is a bright meteor.

A Perseid Meteor
11.08.2002

The ongoing Perseid Meteor Shower should be at its strongest on August 12 and 13. The best time to watch will be between 2:00 AM and dawn on Monday morning (so plan on setting your alarm tonight!) and then again on Tuesday.

APOD: 2025 January 7 Б A New Years Aurora and SAR Arc
6.01.2025

It was a new year, and the sky was doubly red. The new year meant that the Earth had returned to its usual place in its orbit on January 1, a place a few days before its closest approach to the Sun.

APOD: 2023 July 24 Б Chemicals Glow as a Meteor Disintegrates
23.07.2023

Meteors can be colorful. While the human eye usually cannot discern many colors, cameras often can. Pictured here is a fireball, a disintegrating meteor that was not only one of the brightest the photographer has ever seen, but colorful.

Blue Ghost s Diamond Ring
18.03.2025

On March 14 the Full Moon slid through Earth's dark umbral shadow and denizens of planet Earth were treated to a total lunar eclipse. Of course, from the Moon's near side that same astronomical syzygy was seen as a solar eclipse.