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Eris has been measured at 2,326 ± 12 kilometres (1,445 ± 7 mi) in diameter; [12] its mass is 0.28% that of the Earth and 27% greater than that of Pluto, [23] [24] although Pluto is slightly larger by volume. [25] Both Eris and Pluto have a surface area that is comparable to that of Russia or South America. Eris has one large known moon, Dysnomia.
For the giant planets, the "radius" is defined as the distance from the center at which the atmosphere reaches 1 bar of atmospheric pressure. [ 11 ] Because Sedna and 2002 MS 4 have no known moons, directly determining their mass is impossible without sending a probe (estimated to be from 1.7x10 21 to 6.1×10 21 kg for Sedna [ 12 ] ).
According to the IAU's explicit count, there are eight planets in the Solar System; four terrestrial planets (Mercury, Venus, Earth, and Mars) and four giant planets, which can be divided further into two gas giants (Jupiter and Saturn) and two ice giants (Uranus and Neptune). When excluding the Sun, the four giant planets account for more than ...
Mars comes closer to Earth more than any other planet save Venus at its nearest—56 million km is the closest distance between Mars and Earth, whereas the closest Venus comes to Earth is 40 million km. Mars comes closest to Earth every other year, around the time of its opposition, when Earth is sweeping between the Sun and Mars. Extra-close ...
The Mars time of noon is 12:00 which is in Earth time 12 hours and 20 minutes after midnight. For the Mars Pathfinder, Mars Exploration Rover (MER), Phoenix, and Mars Science Laboratory missions, the operations teams have worked on "Mars time", with a work schedule synchronized to the local time at the landing site on Mars, rather than the ...
Dwarf planet Eris, similar in size to its better-known cosmic cousin Pluto, has remained an enigma since being discovered in 2005 lurking in the solar system's far reaches. While Pluto was ...
Mass in M E, the unit of mass equal to that of Earth ( 5.97 × 10 24 kg). Λ is the capacity to clear the neighbourhood (greater than 1 for planets) by Stern & Levison (2002): [ 28 ] Λ = k m 2 a − + 3 / 2 , where k = 0.0043 for m in units of yottagrams (10 18 metric tons ) and a in astronomical units ( AU ), where a is the body's semi ...
For planet Earth, which can be approximated as an oblate spheroid with radii 6 378.1 km and 6 356.8 km, the mean radius is = (( ) ) / = . The equatorial and polar radii of a planet are often denoted r e {\displaystyle r_{e}} and r p {\displaystyle r_{p}} , respectively.