quinta-feira, 24 de fevereiro de 2011
Os planetas anões.
No site da União Astronômica Internacional (www.iau.org)há algumas explicações sobre os planetas anões.
Q: Based on this new definition, how many planets are there in our Solar System?
A: There are eight planets in our Solar System; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Mnemonic: My Very Educated Mother Just Served Us Nachos.
Q: Is that all, only eight planets?
A: No. In addition to the eight planets, there are also five known dwarf planets. Many more dwarf planets are likely to be discovered soon.
Q: What is a dwarf planet?
A: A dwarf planet is an object in orbit around the Sun that is large enough (massive enough) to have its own gravity pull itself into a round (or nearly round) shape. Generally, a dwarf planet is smaller than Mercury. A dwarf planet may also orbit in a zone that has many other objects in it. For example, an orbit within the asteroid belt is in a zone with lots of other objects.
Q: How many dwarf planets are there?
A: Currently there are five objects accepted as dwarf planets. Ceres, Pluto, Eris, Makemake and Haumea.
Q: What is Ceres?
A: Ceres is (or now we can say it was) the largest asteroid, about 1000 km across, orbiting in the asteroid belt between Mars and Jupiter. Ceres now qualifies as a dwarf planet because it is now known to be large enough (massive enough) to have self-gravity pulling itself into a nearly round shape. (Thomas, 2005) Ceres orbits within the asteroid belt and is an example of the case of an object that does not orbit in a clear path. There are many other asteroids that can come close to the orbital path of Ceres.
Q: Are there additional dwarf planet candidates currently being considered?
A: Yes. Some of the largest asteroids may be candidates for dwarf planet status and some additional dwarf planet candidates beyond Neptune will soon be considered.
Q: When will additional new dwarf planets likely be announced?
A: Probably within the next few years.
Q: How many more new dwarf planets are there likely to be?
A: There may be dozens or perhaps even more than a hundred waiting to be discovered.
Ou seja galera, logo teremos mais planetas anões. Por enquanto (2011) são apenas 5. Plutão, Ceres, Éris, Makemake e Haumea.