The Umbra of Earth
15.12.2011

The dark, inner shadow of planet Earth is called the umbra. Shaped like a cone extending into space, it has a circular cross section most easily seen during a lunar eclipse. For example, last Saturday the Full Moon slid across the southern half of Earth's umbral shadow, entertaining moonwatchers around much of the planet.

Galaxy and Planets Beyond Bristlecone Pines
19.06.2016

What's older than these ancient trees? Nobody you know -- but almost everything in the background of this picture. The trees are impressively old -- each part of the Ancient Bristlecone Pine Forest located in eastern California, USA.

NGC 247 and Friends
16.01.2020

About 70,000 light-years across, NGC 247 is a spiral galaxy smaller than our Milky Way. Measured to be only 11 million light-years distant it is nearby though. Tilted nearly edge-on as seen from our perspective, it dominates this telescopic field of view toward the southern constellation Cetus.

NGC 247 and Friends
5.09.2024

About 70,000 light-years across, NGC 247 is a spiral galaxy smaller than our Milky Way. Measured to be only 11 million light-years distant it is nearby though. Tilted nearly edge-on as seen from our perspective, it dominates this telescopic field of view toward the southern constellation Cetus.

COBE Dipole: Speeding Through the Universe
5.02.1996

Our Earth is not at rest. The Earth moves around the Sun. The Sun orbits the center of the Milky Way Galaxy. The Milky Way Galaxy orbits in the Local Group. The Local Group falls toward the Virgo Cluster of Galaxies.

Perseid Trail
14.08.2008

This bright and colorful meteor flashed through Tuesday's early morning skies, part of the annual Perseid Meteor Shower. The lovely image is one of over 350 frames captured on August 12 from...

An Anomalous SETI Signal
6.02.2011

No one knows for sure what caused this signal. There is a slight possibility that it just might originate from an extraterrestrial intelligence. The bright colors on the blue background indicate that an anomalous signal was received here on Earth by a radio telescope involved in a Search for Extraterrestrial Intelligence (SETI).

The Flare and the Galaxy
2.09.2015

Is this person throwing a lightning bolt? No. Despite appearances, this person is actually pointing in the direction of a bright Iridium flare, a momentary reflection of sunlight off of a communications satellite in orbit around the Earth.

Stars over an Erupting Volcano
3.03.2021

Mt. Etna has been erupting for hundreds of thousands of years. Located in Sicily, Italy, the volcano produces lava fountains over one kilometer high. Mt. Etna is not only one of the most active...

APOD: 2025 March 23 Б Ancient Ogunquit Beach on Mars
23.03.2025

This was once a beach -- on ancient Mars. The featured 360-degree panorama, horizontally compressed, was taken in 2017 by the robotic Curiosity rover that explored the red planet. Named Ogunquit Beach after its terrestrial...