The Creature from the Red Lagoon - 2014-11-25

What creature lurks near the red Lagoon nebula? Mars. This gorgeous color deep-sky photograph has captured the red planet passing below two notable nebulae -- cataloged by the 18th century cosmic registrar Charles Messier as M8 and M20. M20 (upper right of center), the Trifid Nebula, presents a striking contrast in red/blue colors and dark dust lanes. Just below and to the left is the expansive, alluring red glow of M8, the Lagoon Nebula. Both nebulae are a few thousand light-years distant. By comparison, temporarily situated below them both, is the dominant "local" celestial beacon Mars. Taken late last month posing near its southernmost point in Earth's sky, the red planet was 14 light-minutes away. Now Available: APOD 2015 Wall Calendars  

Infrared Helix - 1997-09-01

Five hundred light years from Earth, in the constellation Aquarius, a sun-like star is dying. Its last few thousand years have produced the Helix, a well studied and nearby example of a Planetary Nebula - typical of this final phase of stellar evolution. The emission in this Infrared Space Observatory image of the Helix nebula comes mostly from the expanding shells of molecular hydrogen gas. Dust, normally expected in such nebulae, should also radiate strongly at infrared wavelengths but mysteriously seems to be absent here. The culprit may may well be the Helix's central star, a contracting white dwarf. This small but extremely hot star radiates most of its energy at short Ultraviolet wavelengths and is invisible in this infrared mage. Astronomers suspect that over time, this intense Ultraviolet radiation may have destroyed the dust. The Sun is expected to go through its own Planetary Nebula phase ... in another 5 billion years.  

Dusting Spiral Galaxies - 1998-01-16

How much dust is in spiral galaxies? Does it block out much of the starlight? Because astronomers rely on an accurate knowledge of galaxy properties to investigate a wide range of problems, like galaxy and quasar evolution and the nature of dark matter, answers to simple questions like this are key. This striking, detailed Hubble Space Telescope image of dust in the outer reaches of a foreground spiral galaxy (left) back lit by an elliptical galaxy offers an elegant approach to providing the answers. As expected, dust lanes in the foreground galaxy seem to be associated with spiral arms. But surprisingly, many dust regions are not completely opaque and the dust is more smoothly distributed than anticipated. This "overlapping" pair of galaxies is cataloged as AM1316-241 and is about 400 million light-years away in the constellation Hydra.  

Io's Shadow Credit: - 1996-10-07

Caught in the act earlier this summer by the Hubble Space Telescope, the volcanic moon Io (above and right of center) and its shadow (black dot) are seen here against Jupiter's clouds. Io's shadow is 2,262 miles in diameter (about the size of Io) as it races across the swirling cloud tops at about 38,000 miles per hour. From our perspective in the inner Solar System, dramatic scenes like this one are possible when Jupiter, Io, and the Sun line up. What would this scene look like when viewed from Jupiter's cloud tops? As the shadow passed over Jupiter, for observers along the shadow's track, Io's disk would appear to eclipse the sun. The situation is familiar to those Earth Dwellers who have seen a Solar Eclipse - visible from along the track of the Moon's shadow passing across the surface of the Earth.  

Lunokhod: Reflections on a Moon Robot - 2010-06-06

It may look like some sort of cute alien robot, but it was created here on Earth, launched to the Moon in 1970, and now reflects laser light in a scientifically useful way. On November 17, 1970 the Soviet Luna 17 spacecraft landed the first roving remote-controlled robot on the Moon. Known as Lunokhod 1, it weighed just under 2,000 pounds and was designed to operate for 90 days while guided in real-time by a five person team near Moscow, USSR. Lunokhod 1 toured the lunar Sea of Rains (Mare Imbrium) for 11 months in one of the greatest successes of the Soviet lunar exploration program. This Lunokhod's operations officially ceased in 1971. Earlier this year, however, the position of the rover was recovered by NASA's moon-orbiting Lunar Reconnaissance Orbiter. Given that position, laser pulses from Earth were successfully bounced off the old robot's reflector. Bouncing laser pulses off of this and other lunar reflectors could yield range data to the moon accurate enough to track millimeter-sized deviations in the Moon's orbit, effectively probing lunar composition and testing gravitational theories.