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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 ...
Parts-per-million chart of the relative mass distribution of the Solar System, each cubelet denoting 2 × 10 24 kg. This article includes a list of the most massive known objects of the Solar System and partial lists of smaller objects by observed mean radius.
1980 – Gravity Probe A verifies gravitational redshift to approximately 0.007% using a space-born hydrogen maser. [208] 1980 – James Bardeen explains structure in the Universe using cosmological perturbation theory. [209] 1981 – Alan Guth proposes cosmic inflation in order to solve the flatness and horizon problems. [210]
The timeline of discovery of Solar System planets and their natural satellites charts the progress of the discovery of new bodies over history. Each object is listed in chronological order of its discovery (multiple dates occur when the moments of imaging, observation, and publication differ), identified through its various designations (including temporary and permanent schemes), and the ...
Average surface gravity; Lowest Highest Lowest Highest Lowest Highest Star: 1.4 g/cm 3. Sun [7] [8] 5778 K. Sun [9] [10] 274 m/s 2. Sun [11] Major planet: 0.7 g/cm 3 Saturn [12] [13] 5.51 g/cm 3 Earth [14] [15] 73 K Neptune [16] [17] [18] 733 K Venus [19] 3.70 m/s 2 Mercury [18] 23.1 m/s 2 Jupiter [18] Dwarf planet: 1.4 ±0.2 g/cm 3 Orcus [20 ...
The Sun and planets of the Solar System (distances not to scale). The Solar System is the gravitationally bound system of the Sun and the objects that orbit it. It formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc.
Consequently, Venus transits above Earth only occur when an inferior conjunction takes place during some days of June or December, the time where the orbits of Venus and Earth cross a straight line with the Sun. [185] This results in Venus transiting above Earth in a sequence of currently 8 years, 105.5 years, 8 years and 121.5 years, forming ...
The principal change was to space leap years differently so as to make the average calendar year 365.2425 days long, more closely approximating the 365.2422-day 'tropical' or 'solar' year that is determined by the Earth's revolution around the Sun. The reform advanced the date by 10 days: Thursday 4 October 1582 was followed by Friday 15 ...