This ominous, dark shape sprawling across the face of the Sun is a coronal hole - a low density region extending above the surface where the solar magnetic field opens freely into interplanetary space. Studied extensively from space since the 1960s in ultraviolet and x-ray light, coronal holes are known to be the source of the high-speed solar wind, atoms and electrons which flow outward along the open magnetic field lines. During periods of low activity, coronal holes typically cover regions just above the Sun's poles.
At least five planets circle the star HD 10180 in regular orbits, some 127 light years away. This new star system could set the extrasolar record for most known planets.
Neptune has come almost full circle since it was first discovered in 1846, and on Aug. 20, it will be in a straight line with the sun and the Earth.
Trojan asteroid 2008 LC18 is orbiting in a fixed spot in Neptune's orbit where the gravitational pull of Neptune and the sun balance out. Its discovery may help shed light on questions about planetary formation.
NASA's Swift satellite views Comet Lulin as it made its closest approach to Earth in February 2009. Lulin, like all comets, is a clump of frozen gases mixed with dust. These 'dirty snowballs' cast off gas and dust whenever they venture near the sun. Comet Lulin, which is formally known as C/2007 N3, was discovered in 2008 by astronomers at Taiwan's Lulin Observatory. Lulin passed closest to Earth -- 38 million miles, or about 160 times farther than the moon -- late on the evening of Feb. 23, 2009, for North America.
A prominence eruption from the sun is seen in this image taken by NASA's Solar Dynamics Observatory on March 30. With a telescope and the right kinds of filters, an amateur astronomer can view prominences on the sun, too.
The Cat's Eye Nebula, NGC 6543, located in the constellation of Draco, is seen in this undated image.
Scientists have succeeded in clocking the winds in the atmosphere of a planet orbiting a star in the constellation Pegasus. Windiest planet in our solar system is Neptune, at 1,200 m.p.h.
Ceres and Pluto will come into opposition with the sun, offering a rare view of these two dwarf planets.