APOD: 2025 January 20 Б Comet ATLAS Rounds the Sun
19.01.2025

Why does Comet ATLAS have such colorful tails? Last week Comet C/2024 G3 (ATLAS) passed its closest to the Sun -- well inside the orbit of Mercury -- and brightened dramatically. Unfortunately, the comet was then so angularly near the Sun that it was very hard for humans to see. But NASA's SOHO spacecraft saw it.

APOD: 2025 February 24 Б Light Pillar over Erupting Etna
23.02.2025

Can a lava flow extend into the sky? No, but light from the lava flow can. One effect is something quite unusual -- a volcanic light pillar. More typically, light pillars are caused by sunlight and so appear as a bright column that extends upward above a rising or setting Sun.

NGC 7023: The Iris Nebula
15.01.2026

These cosmic clouds have blossomed 1,300 light-years away in the fertile starfields of the constellation Cepheus. Called the Iris Nebula, NGC 7023 is not the only nebula to evoke the imagery of flowers.

APOD: 2026 May 14 Б The Messier Catalog at Uniform Scale
13.05.2026

What are some of the most interesting astronomical objects you can see in the night sky? Armed with a good pair of binoculars or a small telescope, if you live in the Northern Hemisphere, you can look for the very popular objects in the Messier Catalog.

X Ray Moon and X Ray Star
9.09.2000

An x-ray star winks out behind the Moon in these before (left) and after views of a lunar occultation of the galactic x-ray source designated GX5-1. The false color images were made using data from the ROSAT (ROentgen SATellite), orbiting observatory.

Europa Rotating
15.01.2001

Evidence has been mounting that beneath the vast planes of ice that cover Europa lies water -- liquid oceans that might be home to alien life. The smallest of Jupiter's Galilean Moons (which include Io, Ganymede, and Callisto), Europa's deep interior is composed of mostly of silicate rock.

X-ray Moon and X-ray Star
26.02.1996

An X-ray star winks out behind the Moon in these before and after views of a lunar occultation of the galactic X-ray source designated GX5-1. The false color images were made using data...

Helios Helium
20.05.1996

Above is an image of the relatively quiet Sun made on May 18 in light emitted by ionized Helium atoms in the Solar chromosphere. Helium was first discovered in the Sun in 1868, its name fittingly derived from from the Greek word Helios, meaning Sun. Credit for the discovery goes to astronomer Joseph Lockyer.

The Radio Sky: Tuned to 408MHz
25.11.1996

Tune your radio telescope to 408MHz (408 million cycles per second) and check out the Radio Sky! You should find that frequency on your dial somewhere between US broadcast television channels 13 and 14.

Sojourner's View: The Sagan Memorial Station
10.07.1997

The robot rover Sojourner sees Mars from the perspective of a house cat. During the 7 month cruise to Mars aboard the Pathfinder spacecraft, Sojourner measured only seven inches tall in a stowed position but prowling the martian landscape it has stretched to its full height of 1 foot (30 centimeters).