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The Solar System travels alone through the Milky Way in a circular orbit approximately 30,000 light years from the Galactic Center. Its speed is about 220 km/s. The period required for the Solar System to complete one revolution around the Galactic Center, the galactic year, is in the range of 220–250 million years. Since its formation, the ...
The most widely accepted model of planetary formation is known as the nebular hypothesis. This model posits that, 4.6 billion years ago, the Solar System was formed by the gravitational collapse of a giant molecular cloud spanning several light-years. Many stars, including the Sun, were formed within this collapsing cloud.
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 ...
This timeline of artificial satellites and space probes includes uncrewed spacecraft including technology demonstrators, observatories, lunar probes, and interplanetary probes. First satellites from each country are included. Not included are most Earth science satellites, commercial satellites or crewed missions .
Historical models of the Solar System. Approximate sizes of the planets relative to each other. Outward from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Jupiter's diameter is about 11 times that of the Earth's and the Sun's diameter is about 10 times Jupiter's.
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, and Neptune, their satellites, as well as smaller bodies including comets ...
Three of the probes, Voyager 1, Voyager 2, and New Horizons are still functioning and are regularly contacted by radio communication, while Pioneer 10 and Pioneer 11 are now defunct. In addition to these spacecraft, some upper stages and de-spin weights are leaving the Solar System, assuming they continue on their trajectories.
Explorer 1 was designed and built by California Institute of Technology 's JPL under the direction of Dr. William Hayward Pickering. It was the second satellite to carry a mission payload (Sputnik 2 was the first). The total mass of the satellite was 13.97 kg (30.8 lb), of which 8.3 kg (18 lb) were instrumentation.