Pluto gets new name, as does "Xena"

Pluto is now just a number, officially speaking.

The former planet has been dubbed asteroid number 134340 to reflect its new status as a "dwarf planet."

Pluto was ousted from the official pantheon of planets late last month when the International Astronomical Union, the governing authority over celestial bodies, finalized the first official definition of "planet" at a meeting in Prague in the Czech Republic.

According to the IAU, a planet is an object that orbits the sun, forms itself into a sphere, and has enough gravitational pull to clear its path of space debris.

The move downgraded Pluto and finalized a long-running debate about Pluto's planetary status. Unlike the eight planets once considered its peers, Pluto does not sweep its neighborhood clear and has an orbit that is much more eccentric, informs National Geographic.

Many planets detected around other stars have been "hot Jupiters", gas giants like Jupiter or larger, in very close orbits. The new planet falls into that category, circling at a distance one 20th that between Earth and the sun.

Gas giants are primarily hydrogen and helium, but have rocky cores and crushing pressures that squeeze the hydrogen and helium to higher densities.

Jupiter's average density is 133 per cent greater than that of water. The density of HAT-P-1 is one-quarter that of water, informs Sydney Morning Herald.