The Largest Rock Known
2.01.2000

There, that faint dot in the center - that's the largest rock known. It is larger than every known asteroid, moon, and comet nucleus. It is larger than any other rocky planet. (Nobody knows...

Deimos: A Small Martian Moon
15.11.1998

Mars has two tiny moons, Phobos and Deimos. Pictured above is Deimos, the smaller moon of Mars. In fact, Deimos is one of the smallest known moons in the Solar System measuring only 9 miles across.

Planets Around Sun-Like Stars
31.01.1996

Do many Sun-like stars have planets? Speculation on this point has been ongoing since humanity's realization that other stars existed. Only in the past year, however, have answers and discoveries been realized. The above plot summarizes the four known cases of normal stars having planets.

Comet Hyakutake's Orbit
14.03.1996

Where did Comet Hyakutake come from? The orbits of the Earth and this brightening comet are shown in the above diagram. The blue disk is bounded by the circular orbit of the Earth about the central Sun. The comet's path outlines the green shape.

Venus: Just Passing By
29.09.2002

Venus, the second closest planet to the Sun, is a popular way-point for spacecraft headed for the gas giant planets in the outer reaches of the solar system. Why visit Venus first? Using...

Valles Marineris: The Grand Canyon of Mars
30.07.2006

The largest canyon in the Solar System cuts a wide swath across the face of Mars. Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep.

Morning, Moon, and Mercury
26.04.2012

Last week Mercury wandered far to the west of the Sun. As the solar system's innermost planet neared its greatest elongation or greatest angle from the Sun (for this apparition about 27 degrees) it was joined by an old crescent Moon.

Swimming on Jupiter
14.12.2018

On October 29, the Juno spacecraft once again dove near the turbulent Jovian cloud tops. Its 16th orbital closest approach or perijove passage, brought Juno within 3,500 kilometers of the Solar System's largest planetary atmosphere.

Jupiter Engulfed and the Milky Way
7.08.2019

This is a good month to see Jupiter. To find our Solar System's largest planet in your sky, look toward the southeast just after sunset -- Jupiter should be the brightest object in that part of the sky.

Mercury Transits the Sun
13.05.2003

How big is the Sun? The Sun is not only larger than any planet, it is larger than all of the planets put together. The Sun accounts for about 99.9 percent of all the mass in its Solar System.