Astronomy Picture of the Day

photo RS Puppis

RS Puppis

Pulsating RS Puppis, the brightest star in the image center, is some ten times more massive than our Sun and on average 15,000 times more luminous. In fact, RS Pup is a Cepheid variable star, a class of stars whose brightness is used to estimate ...

See full description

photo Dark Skies: Turn on the Night

Dark Skies: Turn on the Night

Have you ever experienced a really dark night sky? One common and amazing feature is the glowing band of our Milky Way galaxy stretching from horizon to horizon. If you live in or near a big city, though, you might not know this because city ...

See full description

photo Anemic Spiral NGC 4921 from Hubble

Anemic Spiral NGC 4921 from Hubble

How far away is spiral galaxy NGC 4921? It's surpringly important to know. Although presently estimated to be about 300 million light years distant, a more precise determination could be coupled with its known recession speed to help humanity ...

See full description


photo Young Star Cluster Trumpler 14 from Hubble

Young Star Cluster Trumpler 14 from Hubble

Why does star cluster Trumpler 14 have so many bright stars? Because it is so young. Many cluster stars have formed only in the past 5 million years and are so hot they emit detectable X-rays. In older star clusters, most stars this young have ...

See full description

photo Rho Ophiuchi Wide Field

Rho Ophiuchi Wide Field

The colorful clouds surrounding the star system Rho Ophiuchi compose one of the closest star forming regions. Rho Ophiuchi itself is a binary star system visible in the blue reflection nebula just to the left of the image center. The star ...

See full description

photo Ash and Lightning above an Icelandic Volcano

Ash and Lightning above an Icelandic Volcano

Why did a picturesque volcanic eruption in Iceland create so much ash? Although the large ash plume was not unparalleled in its abundance, its location was particularly noticeable because it drifted across such well-populated areas. The ...

See full description

photo Milky Way, Launch, and Landing

Milky Way, Launch, and Landing

The Milky Way doesn't look quite this colorful and bright to the eye, but a rocket launch does. So a separate deep exposure with a sensitive digital camera was used in this composite skyscape to bring out our galaxy's central crowded starfields ...

See full description

photo Halley Dust and Milky Way

Halley Dust and Milky Way

Grains of cosmic dust streaked through the mostly moonless night skies of May 7. Swept up as planet Earth plowed through the debris streams left behind by periodic Comet Halley, the annual meteor shower is known as the Eta Aquarids. Though it was ...

See full description

photo Messier 5

Messier 5

"Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] ..." begins the description of the 5th entry in 18th century astronomer Charles Messier's famous catalog of nebulae and star clusters. Though it appeared to Messier ...

See full description

photo Jupiter Marble from Juno

Jupiter Marble from Juno

What does Jupiter look like up close? Most images of Jupiter are taken from far away, either from Earth or from a great enough distance that nearly half the planet is visible. This shot, though, was composed from images taken relatively close in, ...

See full description