M55: Globular Star Cluster
18.09.2004

The fifty-fifth entry in Charles Messier's catalog, M55 is a large and lovely globular cluster of around 100,000 stars. Only 20,000 light-years away in the constellation Sagittarius, M55 appears to earth-bound observers to be nearly 2/3 the size of the full moon.

Analemma of the Moon
13.07.2005

An analemma is that figure-8 curve you get when you mark the position of the Sun at the same time each day for one year. But the trick to imaging an analemma...

The Galaxy Within Centaurus A
4.03.2006

Peering deep inside Centaurus A, the closest active galaxy to Earth, the Spitzer Space Telescope's penetrating infrared cameras recorded this startling vista in February 2004. About 1,000 light-years across, the twisted cosmic...

The Sombrero Galaxy from Hubble
26.07.2015

Why does the Sombrero Galaxy look like a hat? Reasons include the Sombrero's unusually large and extended central bulge of stars, and dark prominent dust lanes that appear in a disk that we see nearly edge-on. Billions of old stars cause the diffuse glow of the extended central bulge.

Virtual Flyby of the Whirlpool Galaxy
6.05.2019

What would it look like to fly over a spiral galaxy? To help visualize this, astronomers and animators at the Space Telescope Science Institute computed a virtual flyby of the Whirlpool Galaxy (M51) using data and images from the Hubble Space Telescope.

Orion and the Running Man
13.11.2025

Few cosmic vistas can excite the imagination like The Great Nebula in Orion. Visible as a faint, bland celestial smudge to the naked-eye, the nearest large star-forming region sprawls across this sharp colorful telescopic image. Designated M42 in the Messier Catalog, the Orion Nebula's glowing gas and dust surrounds hot, young stars.

Stellar Spectral Types: OBAFGKM
30.05.2001

Astronomers divide stars into different spectral types. First started in the 1800s, the spectral type was originally meant to classify the strength of hydrogen absorption lines. A few types that best describe the temperature of the star remain in use today.

Solar Sail
26.05.2000

Nearly 400 years ago astronomer Johannes Kepler observed comet tails blown by a solar breeze and suggested that vessels might likewise navigate through space using appropriately fashioned sails. It is now widely recognized that...

The Deep Field
9.02.1997

Galaxies like colorful pieces of candy fill the Hubble Deep Field - humanity's most distant yet optical view of the Universe. The dimmest, some as faint as 30th magnitude (about four billion times fainter...

The Swarm
28.01.2005

What do you call a group of black holes ... a flock, a brace, a swarm? Monitoring a region around the center of our Galaxy, astronomers have indeed found evidence for a surprisingly large number...