Gas Giants
Four of the outer planets in our solar system are known as gas giants. They are Jupiter, Saturn, Uranus, and Neptune. Gas giants are composed mainly of hydrogen and helium and are quite large in size. Jupiter, for example, is 1000 times larger than the Earth. Gas giants also have low densities and tend have a very fast period of rotation. All four of the gas giants in our solar system have ring systems and a large number of moons. This may be due to the intense gravity of these planets. They may have more of a tendency to capture wandering asteroids and planetoids then the terrestrial planets. It is believed that the ring systems may have formed from old moons that were pulverized by the tidal forces of the planets’ gravity.
Images Credit: solarsystem.nasa.gov
Earthshine and Venus Over Sierra de Guadarrama
Image Credit: Daniel Fernández (DANIKXT)
Explanation: What just above that ridge? The Moon. Specifically, the Earth’s Moon was caught just above the horizon in a young crescent phase. The familiar Moon might look a bit odd as the exposure shows significant Earthshine — the illumination of the part of the Moon hidden from direct sunlight by the sun-reflecting Earth. Also captured in the image is the bright planet Venus on the right. Venus and Jupiter passed only three degrees from each other last week during a photogenic planetary conjunction. The above image was taken two days ago near Madrid, Spain. The foreground horizon silhouette includes some of the Seven Peaks of the Sierra de Guadarrama mountain range. Just a few minutes after this picture was taken, the Moon set.
Bright Planets at McMath-Pierce Solar Telescope
Image Credit: Mike Line (Caltech), Ed Mierkiewicz (Univ. Wisconsin-Madison), Ron Oliversen (NASA-GSFC)
Explanation: Bright planets Venus and Jupiter are framed by the National Solar Observatory’s McMath-Pierce Solar Telescope in this very astronomical scene. The photo was taken at Kitt Peak National Observatory on March 9. A heliostat sits atop the 100 foot high solar telescope tower to focus the Sun’s rays down a long diagonal shaft that reaches underground to the telescope’s primary mirror. Of course, after sunset shadows were cast and the structure illuminated by light from the nearly full rising Moon. Opened to begin the night’s work, the dome housing Kitt Peak’s 2.1 meter reflector is included in the frame, while the Pleiades star cluster shines above the heliostat tower. The angular McMath-Pierce was commissioned 50 years ago to study the Sun, but has also made many observations of these two bright planets. On this night it was conducting observations of sodium atoms in the tenuous lunar atmosphere.
Conjunction Over Reunion Island
Image Credit & Copyright: Luc Perrot
Explanation: You don’t have to be on Reunion Island to see this week’s planetary conjunction. Only if you want to see this picturesque seascape as well. To see the conjunction from just about anywhere in the world, look to the west after sunset. The first planet you may notice is Venus, the brightest object in the western sky. Above Venus, the second brightest object is Jupiter. The hardest planet to spot is Mercury, which is visible only briefly after sunset as a faint dot just above the horizon. Picturesque rocks leading out from Reunion Island to the Indian Ocean populate the foreground of the above picture. Taken last week, the distant planets Venus and Jupiter were joined by a bright crescent Moon, which has now moved away.
Ganymede Transit of Jupiter
One of Jupiter’s many moons (Ganymede) caught transiting across Jupiter’s orbital belt with almost purpose and beauty.
Copyright: Mark Shelley
Image Credit & Copyright: Juan Carlos Casado (TWAN)
Explanation: Venus and Jupiter will appear unusually close in the sky over the next month. The planetary conjunction will be easily visible to the unaided eye because Venus will appear brighter than any background star, and Jupiter will be nearly as bright. To see the near-alignment, simply look to the west after sunset. At their closest, on March 15, the two planets will appear only about three degrees apart. The planets will not be significantly closer in space - Venus will just be passing nearly in front of Jupiter as seen from the Earth. In the above image composite taken late last week from Catalonia, Spain, a bright crescent moon appears to the right of Venus, while Jupiter appears near the top of the image. The distant sun-illuminated spheres were photographed behind a sculpture depicting the legendary battle between a warrior and a dragon. The next Jupiter-Venus conjunction will occur in May 2013.
