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The observable universe contains as many as an estimated 2 trillion galaxies [41] [42] [43] and, overall, as many as an estimated 10 24 stars [44] [45] – more stars (and, potentially, Earth-like planets) than all the grains of beach sand on planet Earth.
720,000 km/h (450,000 mi/h) [ 10] Orbital period. ~230 million years [ 10] The Solar System[ d] is the gravitationally bound system of the Sun and the objects that orbit it. [ 11] It was formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc.
There are eight planets within the Solar System; planets outside of the solar system are also known as exoplanets . Artist's concept of the potentially habitable exoplanet Kepler-186f. As of 25 July 2024, there are 5,741 confirmed exoplanets in 4,285 planetary systems, with 960 systems having more than one planet. [1]
Perhaps unsurprisingly, our universe has just the right mass–energy density, equivalent to about 5 protons per cubic metre, which has allowed it to expand for the last 13.8 billion years, giving time to form the universe as observed today. [65] [66] There are dynamical forces acting on the particles in the universe which affect the expansion ...
List of planet types. From top to bottom: Mercury, Venus without its atmosphere, Earth and the Moon, Mars, Jupiter, Saturn, Uranus, and Neptune in false colour (not to scale) The following is a list of planet types by their mass, orbit, physical and chemical composition, or by another classification. The IAU defines that a planet in the Solar ...
KOI-1686.01 was also considered a potentially habitable exoplanet after its detection in 2011, until proven a false positive by NASA in 2015. [ 72] Several other KOIs, like Kepler-577b and Kepler-1649b, were considered potentially habitable prior to confirmation, but with new data are no longer considered habitable.
At that time, Uranus, Neptune, nor the asteroid belts have been discovered yet. Discovery and exploration of the Solar System is observation, visitation, and increase in knowledge and understanding of Earth 's "cosmic neighborhood". [1] This includes the Sun, Earth and the Moon, the major planets Mercury, Venus, Mars, Jupiter, Saturn, Uranus ...
List of former planets. This is a list of astronomical objects formerly widely considered planets under any of the various definitions of this word in the history of astronomy. As the definition of planet has evolved, the de facto and de jure definitions of planet have changed over the millennia. As of 2024, there are eight official planets in ...