The Andromeda Galaxy in Ultraviolet
18.07.2021

What does the Andromeda galaxy look like in ultraviolet light? Young blue stars circling the galactic center dominate. A mere 2.5 million light-years away, the Andromeda Galaxy, also known as M31, really is just next door as large galaxies go.

Melting Snow and the Gullies of Mars
21.02.2003

Tantalizing images of gullies on Mars have offered striking evidence for recent flows of liquid water. But Mars is too cold and its atmosphere too thin for liquid water to exist on the surface.

Solar Shock Wave
30.04.1999

On September 24, 1997 a shock wave blasted across the surface of the sun at speeds of 250 to 600 kilometers per second. On planet Earth, observer Barry Reynolds photographed the expanding shock front (left) in the light emitted by hydrogen atoms at the solar surface.

A Mars Panorama from the Phoenix Lander
12.08.2008

If you could stand on Mars, what would you see? The robotic Phoenix spacecraft that just landed on Mars in May recorded the above spectacular panorama. The above image is actually a digital combination of over 100 camera pointings and surveys fully 360 degrees around the busy robotic laboratory.

Moons, Rings, and Unexpected Colors on Saturn
20.10.2008

Why would Saturn show such strange colors? The robotic Cassini spacecraft currently orbiting Saturn has beamed back images showing that the northern hemisphere our Solar System's most spectacularly ringed planet has changed noticeably since Cassini arrived in 2004, now sporting unusual and unexpected colors. No one is sure why.

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...

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.

The Colorful Clouds of Rho Ophiuchi
12.03.1996

The many spectacular colors of the Rho Ophiuchi (oh'-fee-yu-kee) clouds highlight the many processes that occur there. The blue regions shine primarily by reflected light. Blue light from the star rho Ophiuchi and nearby stars reflects more efficiently off this portion of the nebula than red light.

Cassini Spacecraft Crosses Saturns Ring Plane
23.02.2014

If this is Saturn, where are the rings? When Saturn's "appendages" disappeared in 1612, Galileo did not understand why. Later that century, it became understood that Saturn's unusual protrusions were rings and that when the Earth crosses the ring plane, the edge-on rings will appear to disappear.

APOD: 2023 January 24 Б LHS 475 b: Earth Sized Exoplanet
24.01.2023

If you could stand on exoplanet LHS 475 b, what might you see? No one knows for sure but pictured here is an interesting guess made by an Earth-based artificial intelligence (AI) engine.