Hydrogen, Helium, and the Stars of M10
12.03.1999

Stars like the Sun use hydrogen for fuel, "burning" hydrogen into helium at their cores through nuclear fusion. But what happens when that hydrogen runs out? For a while, hydrogen burns in a shell surrounding the stellar core and the star expands to become a red giant.

Symbiotic R Aquarii
29.06.2017

A long recognized naked-eye variable star, R Aquarii is actually an interacting binary star system, two stars that seem to have a close, symbiotic relationship. About 710 light years away, it consists of a cool red giant star and hot, dense white dwarf star in mutual orbit around their common center of mass.

The Near Infrared Sky
18.05.2000

Was this picture taken from outside our Galaxy? No, it is a composite taken from Earth orbit, well inside our Milky Way Galaxy. In light just a little too red for human eyes...

M57: The Ring Nebula
17.04.2018

Except for the rings of Saturn, the Ring Nebula (M57) is probably the most famous celestial band. Its classic appearance is understood to be due to our own perspective, though. The recent mapping...

Eclipse on a Polar Day
10.12.2021

During polar day, in Arctic and Antarctic summer, the Sun stays above the horizon for periods of 24 hours or more. Recorded on December 4, this fisheye timelapse image tracks the Sun in multiple frames as it completes a circle in the summer sky above Union Glacier, Antarctica.

NGC 7789: Caroline s Rose
6.07.2024

Found among the rich starfields of the Milky Way, star cluster NGC 7789 lies about 8,000 light-years away toward the constellation Cassiopeia. A late 18th century deep sky discovery of astronomer Caroline Lucretia Herschel, the cluster is also known as Caroline's Rose.

The Reddening of M71
9.12.2014

Now known to be a globular star cluster at the tender age of 10 billion years, M71 is a mere 13,000 light-years away within the narrow boundaries of the faint constellation Sagitta. Close...

Cassini Approaches Saturn
10.12.2003

Cassini, a robot spacecraft launched in 1997 by NASA, is close enough now to resolve many rings and moons of its destination planet: Saturn. The spacecraft has now closed to within a single Earth-Sun separation from the ringed giant. Early last month, Cassini snapped the contrast-enhanced color composite pictured above.

NGC 7789: Caroline s Rose
26.10.2013

Found among the rich starfields of the Milky Way toward the constellation Cassiopeia, star cluster NGC 7789 lies about 8,000 light-years away. A late 18th century deep sky discovery of astronomer Caroline Lucretia Herschel, the cluster is also known as Caroline's Rose.

Microwave Hotspots: The Oldest Structures Known
29.10.2000

These spots are the oldest, most distant structures known. They are seen on the above two images of the microwave sky, north and south of our galaxy's equator, based on four-year's worth of data from NASA's COsmic Background Explorer (COBE) satellite (1989-1993). The spots represent temperature variations in the early universe.