Small Worlds Ceres and Vesta
22.06.2007

Ceres and Vesta are, respectively, only around 950 kilometers and 530 kilometers in diameter - about the size of Texas and Arizona. But they are two of the largest of over 100,000 minor bodies orbiting in the main asteroid belt between Mars and Jupiter.

A Halo for NGC 6164
27.10.2012

Beautiful emission nebula NGC 6164 was created by a rare, hot, luminous O-type star, some 40 times as massive as the Sun. Seen at the center of the cosmic cloud, the star is a mere 3 to 4 million years old.

The Sun in X rays from NuSTAR
28.12.2014

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.

Composite Messier 20 and 21
28.06.2017

The beautiful Trifid Nebula, also known as Messier 20, lies about 5,000 light-years away, a colorful study in cosmic contrasts. It shares this nearly 1 degree wide field with open star cluster Messier 21 (top left).

A Phoenix Aurora over Iceland
3.01.2021

All of the other aurora watchers had gone home. By 3:30 am in Iceland, on a quiet September night, much of that night's auroras had died down. Suddenly, unexpectedly, a new burst of particles streamed down from space, lighting up the Earth's atmosphere once again.

APOD: 2024 October 2 Б The Large Magellanic Cloud Galaxy
2.10.2024

It is the largest satellite galaxy of our home Milky Way Galaxy. If you live in the south, the Large Magellanic Cloud (LMC) is quite noticeable, spanning about 10 degrees across the night sky, which is 20 times larger than the full moon towards the southern constellation of the dolphinfish (Dorado).

APOD: 2025 October 19 Б Comet Churyumov Gerasimenko Creates Its Tails
19.10.2025

Where do comet tails come from? There are usually no obvious places on the nuclei of comets from which the jets that create comet tails emanate. One of the best images of emerging jets...

ROSAT Explores The X-Ray Sky
19.08.2000

Launched in 1990, the orbiting ROSAT observatory explored the Universe by viewing the entire sky in x-rays -- photons with about 1,000 times more energy than visible light. This ROSAT survey produced the sharpest, most sensitive image of the x-ray sky to date.

Celebrating Hubble With NGC 6751
16.04.2005

Planetary nebulae can look simple, round, and planet-like in small telescopes. But images from the orbiting Hubble Space Telescope have become well known for showing these fluorescent gas shrouds of dying Sun-like stars to possess a staggering variety of detailed symmetries and shapes.

NGC 1097: Spiral Galaxy with a Central Eye
27.07.2009

What's happening at the center of spiral galaxy NGC 1097? No one is sure, but it likely involves a supermassive black hole. Matter falling in from a bar of stars and gas across the center is likely being heated by an extremely energetic region surrounding the central black hole.