Mars in the Loop
30.05.2025

This composite of images spaced a weather-permitting 5 to 9 days apart, from 2024 September 19 (top right) through 2025 May 18 (bottom left), faithfully traces ruddy-colored Mars as it makes a clockwise loop through the constellations Gemini and Cancer in planet Earth's night sky.

X Ray Rainbows
11.05.2001

A drop of water or prism of glass can spread out visible sunlight into a rainbow of colors. In order of increasing energy, the well known spectrum of colors in a rainbow runs red, orange, yellow, green, blue, indigo, violet.

Sunspots and Solar Active Regions
1.08.2002

July was a good month for sunspots ... really big sunspots. In fact, the full disk and inset pictures above show three large groups of spots, photographed only a few days ago on July 28. Together the sunspots span a region about thirty times the diameter of planet Earth.

X Ray Rainbows
28.09.2002

A drop of water or prism of glass can spread out visible sunlight into a rainbow of colors. In order of increasing energy, the well known spectrum of colors in a rainbow runs red, orange, yellow, green, blue, indigo, violet.

Small Star
5.06.1997

A dim double star system cataloged as Gliese 623 lies 25 light-years from Earth, in the constellation of Hercules. The individual stars of this binary system were distinguished for the first time when the Hubble Space Telescope's Faint Object Camera recorded this image in June 1994.

M27: Not a Comet
26.08.2010

While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list.

The El Gordo Massive Galaxy Cluster
22.04.2014

It is bigger than a bread box. In fact, it is much bigger than all bread boxes put together. Galaxy cluster ACT-CL J0102-4915 is one of the largest and most massive objects known. Dubbed...

Stereo Eros
13.02.2021

Get out your red/blue glasses and float next to asteroid 433 Eros. Orbiting the Sun once every 1.8 years, the near-Earth asteroid is named for the Greek god of love. Still, its shape more closely resembles a lumpy potato than a heart.

APOD: 2026 May 21 Б A Collision of Galaxy Clusters
21.05.2026

This big beautiful spiral shines in X-ray light. It is about 20 times larger than our Galaxy. It belongs to Abell 2029, a galaxy cluster one billion light-years away. (To see only the galaxies...

Supernova Remnant N132D in Optical and X Rays
25.10.2005

Thousands of years after a star exploded, its expanding remnant still glows brightly across the spectrum. Such is the case with N132D, a supernova remnant located in the neighboring Large Magellanic Cloud (LMC) galaxy. The expanding shell from this explosion now spans 80 light-years and has swept up about 600 Suns worth of mass.