APOD: 2025 April 13 Б An Unusual Hole in Mars
13.04.2025

What created this unusual hole in Mars? Actually, there are numerous holes pictured in this Swiss cheese-like landscape, with all-but-one of them showing a dusty, dark, Martian terrain beneath evaporating, light, carbon dioxide ice.

Comet Halley's Nucleus
10.12.1996

Here is what a comet nucleus really looks like. For all active comets except Halley, it was only possible to see the surrounding opaque gas cloud called the coma. During Comet Halley's most...

Young Suns of NGC 7129
11.08.2005

Young suns still lie within dusty NGC 7129, some 3,000 light-years away toward the royal constellation Cepheus. While these stars are at a relatively tender age, only about a million years old, it is likely that our own Sun formed in a similar stellar nursery some five billion years ago.

The Starry Night of Alamut
25.06.2010

A meteor's streak and the arc of the Milky Way hang over the imposing mountain fortress of Alamut in this starry scene. Found in the central Alborz Mountains of Iran, Alamut Castle was built into the rock in the 9th century. The name means Eagle's Nest.

Rosetta s Target Comet
23.05.2014

The Rosetta spacecraft captured this remarkable series of 9 frames between March 27 and May 4, as it closed from 5 million to 2 million kilometers of its target comet. Cruising along...

Noctilucent Clouds over London
10.07.2014

This scene from the early morning hours of July 3 looks out across the River Thames from the Westminster Bridge. Part of a luminous timelapse video (vimeo), the frame captures a sight familiar in London, the nighttime glow of the London Eye.

Chilean Skyscape
29.11.2008

Night skies over Chilean mountain top observatories can be dark and clear, with glorious cosmic vistas. In this recent example, the plane of our Milky Way galaxy stretches parallel to the horizon, the galactic center's star clusters, dark dust clouds, and glowing nebulae hovering in the west.

Starlink Satellite Trails over Brazil
10.12.2019

What are those streaks over the horizon? New Starlink satellites reflecting sunlight. SpaceX launched 60 Starlink communication satellites in May and 60 more in November. These satellites and thousands more are planned by communications companies in the next few years that may make streaks like these relatively common.

Highlights of the Summer Sky
5.06.2017

What's up in the sky this summer? The featured graphic gives a few highlights for Earth's northern hemisphere. Viewed as a clock face centered at the bottom, early summer sky events fan out toward the left, while late summer events are projected toward the right.

A Sonic Boom
21.02.2001

Many people have heard a sonic boom, but few have seen one. When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane.