The Edge of Space
24.07.2021

Where does space begin? For purposes of spaceflight some would say at the Karman line, currently defined as an altitude of 100 kilometers (60 miles). Others might place a line 80 kilometers (50 miles) above Earth's mean sea level.

Perseids and MAGIC
11.08.2022

On August 11, 2021 a multi-mirror, 17 meter-diameter MAGIC telescope reflected this starry night sky from the Roque de los Muchachos European Northern Observatory on the Canary Island of La Palma. MAGIC stands for Major Atmospheric Gamma Imaging Cherenkov.

APOD: 2024 October 13 Б Aurora Timelapse Over Italian Alps
13.10.2024

Did you see last night's aurora? This question was relevant around much of the world a few days ago because a powerful auroral storm became visible unusually far from the Earth's poles.

APOD: 2025 September 9 Б Up from the Earth: Gigantic Jet Lightning
9.09.2025

What's that rising up from the Earth? When circling the Earth on the International Space Station early in July, astronaut Nicole Ayers saw an unusual type of lightning rising up from the Earth: a gigantic jet. The powerful jet appears near the center of the featured image in red, white, and blue.

Jagged Hills on Jupiters Callisto
28.08.2001

Why does Jupiter's moon Callisto have unusual jagged hills? This mystery came to light after the robot spacecraft Galileo, in orbit around Jupiter since 1995, swooped past the dark moon in May. The resulting pictures were the highest resolution yet obtained for a Jovian moon: objects as small as 3 meters across are discernable.

The Clouds of Jupiter
20.09.1997

What makes the colors in Jupiter's clouds? With a mean temperature of 120 degrees Kelvin (-153 degrees Celsius) and a composition dominated by hydrogen (about 90%), and helium (about 10%) with a smattering...

Mars Opposition
27.07.2018

Look opposite the Sun in the sky tonight and you'll see Mars at its brightest. Also within days of its closest approach Mars rises at sunset, near its brightest and best for telescopic observers too, except for the dust storm still blanketing the Red Planet.

BATSE's Biggest Gamma Ray Burst (Yet)
1.10.1996

Something big exploded but astronomers have no idea what. On September 24^th, the Burst and Transient Source Experiment (BATSE) onboard the orbiting Compton Gamma Ray Observatory recorded the most intense gamma ray burst in its five year history.

IC 4603: Reflection Nebula in Ophiuchius
21.07.2003

Why does this starfield photograph resemble an impressionistic painting? The effect is created not by digital trickery but by large amounts of interstellar dust. Dust, minute globs rich in carbon and similar in size to cigarette smoke, frequently starts in the outer atmospheres of large, cool, young stars.

Reflections on NGC 6188
25.08.1999

NGC 6188 is an interstellar carnival of young blue stars, hot red gas, and cool dark dust. Located 4000 light years away in the disk of our Galaxy, NGC 6188 is home to the Ara OB1 association, a group of bright young stars whose nucleus forms the open cluster NGC 6193.