Astronomy Picture of the Day

1999-07-16

The sun's corona is a tenuous outer atmosphere composed of streams of energetic charged particles, but it is only easily seen from Earth during a total solar eclipse. For example, this 1991 image of totality from atop Mauna Kea, Hawaii forms a ...

1999-07-15

Known for his sense of humor and infectious grin, Charles P. "Pete" Conrad, as commander of the Apollo 12 mission, was the third person to walk on the moon. Not a tall man, Conrad stepped down onto the lunar surface in November of 1969 and ...

1999-07-13

What lights up the Flame Nebula? Fifteen hundred light years away towards the constellation of Orion lies a nebula which, from its glow and dark dust lanes, appears like a billowing fire. But fire, the rapid acquisition of oxygen, is not what ...

1999-07-11

What happens when a meteor hits the ground? Usually nothing much, as most meteors are small, and indentations they make are soon eroded away. 49,000 years ago, however, a large meteor created Barringer Meteor Crater in Arizona, pictured above. ...

1999-07-10

Neptune, the Solar System's outermost gas giant planet, is 30 times farther from the Sun than Earth. Twelve years after a 1977 launch, Voyager 2 flew by Neptune and found surprising activity on a planet that receives only 3 percent as much ...

1999-07-09

At 1.6 billion years old, this cluster of stars is beginning to show its age. NGC 7789 is an open or galactic star cluster about 8,000 light-years distant toward the constellation Cassiopeia and lies near the plane of our Milky Way galaxy. All ...

1999-07-08

Activity on our parent star continues to increase as the sun approaches a maximum in its 11-year solar cycle, expected in the year 2000. On June 14 - only a week before the solstice - the space-based SOHO observatory recorded this stunning view ...

1999-07-07

If our Sun were part of M80, the night sky would glow like a jewel box of bright stars. M80, also known as NGC 6093, is one of about 250 globular clusters that survive in our Galaxy. Most of the stars in M80 are older and redder than our Sun, ...

1999-07-06

Have you ever seen a sun pillar? When the air is cold and the Sun is rising or setting, falling ice crystals can reflect sunlight and create an unusual column of light. Ice sometimes forms flat, stop-sign shaped crystals as it falls from ...

1999-07-05

As Mars rotates, most of its surface becomes visible. During Earth's recent pass between Mars and the Sun, the Hubble Space Telescope was able to capture the most detailed time-lapse pictures ever from the Earth. Dark and light sand and gravel ...