The North Pole of Uranus


This snapshot of Uranus taken by the Hubble Space Telescope reveals a vast bright cloud cap across the north pole which is believed to be caused by the planet’s odd orientation. Unlike the other planet in the Solar System, Uranus is tipped over almost onto its side. During the planet’s summer the Sun shines almost directly onto the north pole as a result of the extreme tilt and never sets. It’s almost mid summer on Uranus, and the polar storm may have formed because of seasonal changes in atmospheric flow.

Uranus is an ice giant planet. It has no solid surface but rather mantles of hydrogen and helium surrounding a water-rich interior which is probably wrapped around a rocky core. Methane in the atmosphere absorbs red light and scattered blue-green light back into space, giving each planet its cyan hue.

Image Credit: NASA

Uranus and Ariel


Uranus_ArielUranus’ moon Ariel (white dot) and its shadow (black dot) were caught crossing the face of Uranus in this Hubble Space Telescope image. Note that the cloud bands which are aligned with the planet’s rotation are nearly vertical in the picture. Uranus is the giant planet whose equator is nearly at right angles to its orbit. A collision with an Earth-sized object several billion years ago is the likely cause of Uranus’ tilt. Nearly a twin to Neptune, Uranus has more methane in its mainly hydrogen and helium atmosphere than Jupiter or Saturn. Methane gives Uranus its blue tint.

Image Credit: NASA

To Be or Not To Be Among the Fairies


What is Hamlet doing hanging out with Oberon from A Midsummer Night’s Dream?

Since 1919, the International Astronomical Union has been charged with the task of establishing “conventional” nomenclature for planets, satellites, and surface features. Namesakes from Shakespearean works have been chosen for moons and objects around Uranus. Thus, Oberon, king of the fairies, is also Uranus’ most distant and second largest moon, and Hamlet is a tragically large and princely crater on its surface, the large dark crater to the right of center. This picture shows the known surface features of Oberon. It was constructed by the U.S. Geological Survey based on data from NASA’s Voyager 2.

Image Credit: NASA/USGS

Uranus and Four of Its Satellites


This infrared image of the planet Uranus was captured by the European Southern Observatory’s Very Large Telescope during the planet’s 2008 equinox. Every 42 years, the ring (and satellites) plane of Uranus line up with the Sun causing them to appear on edge from Earth’s point of view. A one minute exposure time was used, the maximum allowable to prevent the moving satellites from appearing as streaks. The IR filter used matches the absorption bands of the methane in the atmosphere of Uranus, making the relatively bright planet (almost) completely disappear. That permits the otherwise invisible rings and small satellites of Uranus to be detected instead of being lost in the glare of the planet. The bright spots on each side of Uranus are Miranda (~470 km diameter) and Ariel (~1100 km diameter). Two much smaller satellites can be seen just above the ring plane,to the left of the planet. Puck (~150 km diameter) is closer to the Planet than Portia (~100 km diameter).

Image Credit: ESO

The Rings of Uranus


Saturn’s rings are so prominent that they easily visible from Earth with a small telescope. All the other gas giant planets have ring as well, but they weren’t discovered until we were able to look at those planets from above the Earth’s atmosphere. Here are some pictures of the ring system around Uranus taken by the Hubble Space Telescope as our point of view shifted over several years. The next time the rings will be edge-on will be in 2049.

Image Credit: NASA / ESA / STScI

Titania


titania3_voyg2Titania’s tortured terrain is a mix of valleys and craters. Voyager 2 passed this moon of Uranus in 1986 and took this photograph. The long valleys indicate that Titania underwent some unknown tumultuous resurfacing event in its distant past. Titania is essentially a large dirty iceball composed of a roughly 50/50 mix of water ice and rock. It was discovered by William Hershel in 1787.

Image Credit: NASA