The outer planets

Rock and metal are still present in the outer solar system, but both are outnumbered and outweighed by the hydrogen compounds. You can read about this and other Astronaut sightings at this web site.

Thus, the planetesimals that formed in the outer solar system are composed primarily of hydrogen compounds with traces of rock and metal. Uranus is the third-largest planet and the least massive of the four outer planets. The International Astronomical Union IAUthe official scientific body for astronomical nomenclature, defines a "dwarf planet" as a celestial body that, within the Solar System, is in orbit around the Sun; has sufficient mass for its self-gravity so that it assumes a near-spherical shape; has not cleared the neighbourhood around its orbit; and is not a satellite The term "dwarf planet" was adopted in as part of a three-way classification of bodies orbiting the Sun.

Numerous bright stars are evident in the background. Second is that gas from the big bang created stars and planets all over the universe, and they migrated through gravity into galaxies.

They orbit Jupiter as Jupiter orbits the sun. If you are searching for more information, NASA has many articles, including one on the planets and Science Daily is also a rich resource for information on the outer planets.

The four terrestrial or inner planets have dense, rocky compositions, few or no moonsand no ring systems.

How the rings got there is one subject under investigation. The last communication with Pioneer 11 was made in It has approximately 20 years of daytime and 20 years of nighttime because one pole faces the sun for a couple of decades and then the other for a couple.

Forced to rely on a low gain antenna for communications, the resulting data transmission rate much lower then planned. Voyager 2 flew by Jupiter on 9 Julyand Saturn on 25 August The closer they are to the Sun, the faster they travel inner planets on the left, all planets except Neptune on the right.

From top to bottom: Hundreds of protoplanets may have existed in the early Solar System, but they either merged or were destroyed, leaving the planets, dwarf planets, and leftover minor bodies. The planet has no moons, but has a tenuous atmosphere exosphere containing oxygen, sodium, hydrogen, helium and potassium.

Among other accomplishments, Galileo was the discoverer of Io, Europa, Ganymede, and Callisto, the four largest moons of Jupiter. Mars is a planet under intense study because it shows signs of liquid water flowing on its surface in the ancient past.

Learn about the wonders of the solar system and the secrets of the universe! A brief introduction to the 8 planets in our Solar System. A new set of postage stamps to be issued this month will mark the half century since the world first came together to discuss the peaceful uses of outer space.

Outer Planets. The next four planets out from the sun are Jupiter, Saturn, Uranus, and Neptune. They are collectively referred to as the Jovian planets (means Jupiter like).

They are significantly different from the terrestrial planets. Astronomers have divided the eight planets of our solar system into the inner planets and the outer planets.

The 4 inner planets are the closest to the Sun, and the outer planets are the other four – Jupiter, Saturn, Uranus, and Neptune. The outer planets are also called the Jovian planets or gas giants. Gas giants are large planets that contain more than 10 times the mass of Earth, they are also known as the Jovian or Outer Planets.

Their compositions are mostly gases, such as hydrogen, and small amounts of rocky material (mostly at their cores). The four gas giants in .

The outer planets