Trees, Stars, Aurora
9.02.2012

Have you ever seen an aurora? Auroras are occurring again with increasing frequency. With the Sun being unusually dormant over the past four years, the amount of Sun-induced auroras has been unusually low. More recently, however, our Sun has become increasingly active and exhibiting a greater abundance of sunspots, flares, and coronal mass ejections.

APOD: 2020 July 27 Б Comet and Lightning Beyond Bighorn Mountains
27.07.2020

Normally, Steamboat Point looks cool -- but not this cool. Every day, the iconic peak of the Bighorn Mountains is an interesting sight, in particular from US Highway 14 in Wyoming. On some rare days, the rocky vertical ridges look even more incredible when seen in front of a distant lightning storm.

The Sun in X rays from NuSTAR
23.11.2021

Why are the regions above sunspots so hot? Sunspots themselves are a bit cooler than the surrounding solar surface because the magnetic fields that create them reduce convective heating. It is therefore unusual that regions overhead -- even much higher up in the Sun's corona -- can be hundreds of times hotter.

Doomed Star Eta Carinae
13.08.2000

Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown su

Doomed Star Eta Carinae
28.04.2002

Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova.

Possible Mud Volcanoes on Mars
30.03.2009

Is this a mud volcano on Mars? If so, could it be dredging up martian microbes? This strange possibility has been suggested recently and seems to fit several recent observations of Mars. First of all, hills like this seem to better resemble mud volcanoes on Earth than lava volcanoes and impact craters on Mars.

Draconid Meteors Over Spain
19.10.2011

What are those streaks in the sky? They're meteors from the Draconids meteor shower that peaked earlier this month. The above composite image captured numerous meteor streaks over 90 minutes above the Celtic ruins of Capote in Badajoz province, Spain.

Three Tails of Comet NEOWISE
8.03.2021

What created the unusual red tail in Comet NEOWISE? Sodium. A spectacular sight back in the summer of 2020, Comet NEOWISE, at times, displayed something more than just a surprisingly striated white dust tail and a pleasingly patchy blue ion tail.

A Radar View of Titan
24.11.2004

Where are Titan's craters? Throughout our Solar System's five billion-year history, dangerous rocks and chunks of ice have continually slammed into planets and moons - usually creating numerous long lasting impact craters. When the robot spacecraft Cassini swooped past Saturn's moon Titan last month, however, radar images showed few craters.

Flyby Image of Saturns Sponge Moon Hyperion
3.06.2015

Why does this moon look like a sponge? To better investigate, NASA and ESA sent the Saturn-orbiting robotic spacecraft Cassini zooming past Saturn's moon Hyperion, once again, earlier this week. One of the images beamed back to Earth is featured above, raw and unprocessed.