Browse NASA Astronomy Picture of the Day archive by date and media: Archive Discoveries
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Kepler Discovers How Planets Move
Johannes Kepler used simple mathematics to describe how planets move. Kepler was an assistant to the most accurate astronomical observer of the time, Tycho Brahe . Kepler was able…
A Sky Full Of Hydrogen
Interstellar space is filled with extremely tenuous clouds of gas which are mostly Hydrogen. The neutral Hydrogen atom (HI in astronomer's shorthand) consists of 1 proton and 1…
NGC 1410/1409: Intergalactic Pipeline
These two galaxies are interacting in a surprising way, connected by a “pipeline” of obscuring material that runs between them over 20,000 light-years of intergalactic space.…
X-rays From The Cat's Eye
Haunting patterns within planetary nebula NGC 6543 readily suggest its popular moniker -- the Cat's Eye nebula. In 1995, a stunning false-color optical image from the Hubble Space…
Watch the Sky Rotate
If you could watch the sky for an entire night, what would you see? The above time-lapse sequence from the CONtinuous CAMera (CONCAM) project shows the answer for the skies above…
A Cosmic Call to Nearby Stars
If you could send a message to an alien civilization , what would you say? The people from the Cosmic Call project sent the above image as the first page of a longer message. The…
Help NASA Classify Martian Craters
The large Martian crater above just left of center: is this a fresh crater, a degraded crater, or a ghost crater? Complex image recognition tasks like these are currently done…
Tycho Brahe Measures the Sky
Tycho Brahe was the most meticulous astronomical observer of his time. Brahe , who lived between 1546 and 1601, set out to solve the day's most pressing astronomical problem: to…
Apollo 17's Moonship
Awkward and angular looking, Apollo 17's lunar module Challenger was designed for flight in the vacuum of space. This sharp picture from the command module America , shows…
Second Millennium, Last Eclipse
Christmas Day 2000 featured the final eclipse of the Second Millennium -- a partial solar eclipse visible from much of North America . Astrophotographer Phil Rau recorded the…
Third Millennium, First Eclipse
The first eclipse of the third millennium is coming up! A total lunar eclipse mainly visible from Europe, Asia, and Africa, will occur on January 9th as the full Moon glides…
M8: In the Center of the Lagoon Nebula
In the center of the Lagoon Nebula one finds glowing gas , star clusters, and dense knots of gas and dust just now forming stars. The young open cluster of stars, designated NGC…
Jupiter, Europa, and Callisto
As the robot Cassini spacecraft rounds Jupiter on its way toward Saturn , it has taken a sequence of images of the gas giant with its four largest moons . Previously released…
The Millennium that Defines Universe
Welcome to millennium three . During millennium two , humanity continually redefined its concept of “Universe”: first as spheres centered on the Earth , in mid-millennium as the…
The Millennium that Defined Earth
When the second millennium began, people generally knew that the Earth was round, but few saw much of it beyond their local village. As the millennium progressed, humans mapped…
A Year of Resolving Backgrounds
No matter which direction you look, no matter what type of light you see, the sky glows - but why? The sources of many of these background radiations have remained long-standing…
The Dark Horsehead Nebula
While drifting through the cosmos this magnificent interstellar dust cloud, sculpted by stellar winds and radiation, has chanced to assume a recognizable shape. Fittingly named…
Moon Mare and Montes
This arresting image of the third quarter moon in the excellent skies above the Pine Crest Farm Observatory, Dell Prairie, Wisconsin, was recorded with a 24 inch telescope and…
The Dust and Ion Tales of Comet Hale-Bopp
In 1997, Comet Hale-Bopp 's intrinsic brightness exceeded any comet since 1811 . Since it peaked on the other side of the Earth's orbit, however, the comet appeared only brighter…
Jupiter, Io, and Shadow
Just as planets orbit our Sun, Jupiter's Moons orbit Jupiter. Pictured above is the closest of Jupiter's Galilean Satellites , Io , superposed in front of the giant planet it…
The Eclipse Tree
If you look closely at the shadow of this tree, you will see something quite unusual: it is composed of hundreds of images of a partially eclipsed Sun . Early today , trees across…
NGC 1850: Gas Clouds and Star Clusters
There's nothing like it in our own Galaxy . Globular clusters as young as NGC 1850 don't exist here. Globular clusters only 40 millions of years old can still be found in the…
Summer at the South Pole
The December solstice brings the beginning of Winter to Earth's Northern Hemisphere and Summer time to the South! This view of Earth's Southern Hemisphere near the beginning of…
Simulated Supergiant Star
Looking for that perfect holiday gift for an astronomer? Consider this “star in a box”. Of course, the box is actually a computational box consisting of a three dimensional grid…
Viewing discoveries from 14 January 2001 through 22 December 2000.