![]() ![]() There are an unknown number of smaller dwarf planets and innumerable small bodies orbiting the Sun. All giant planets and a few smaller bodies are encircled by planetary rings, composed of ice, dust and sometimes moonlets. Six planets, the six largest possible dwarf planets and many other bodies have natural satellites or moons orbiting around them. In the present day, 99.86% of the Solar System's mass is in the Sun and most of the remaining mass is contained in the planet Jupiter. That is the reason why all eight planets have an orbit that lies near the same plane. Over time, the cloud formed the Sun and a protoplanetary disk that gradually coalesced to form planets and other objects. The Solar System was formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. In some texts, these terrestrial and giant planets are called the inner Solar System and outer Solar System planets respectively. The gas giants are mostly made of hydrogen and helium, while the ice giants are mostly made of volatile substances such as water, ammonia, and methane. The terrestrial planets have a definite surface and are mostly made of rock and metal. The largest of such objects are the eight planets, in order from the Sun: four terrestrial planets, named Mercury, Venus, Earth and Mars and four giant planets, including two gas giants, Jupiter and Saturn, and two ice giants, named Uranus and Neptune. The Solar System is the gravitationally bound system of the Sun and the objects that orbit it. ![]() NASA History Program Office, 2018.Invariable-to- galactic plane inclination Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. 7, 1981, to preclude any possible radio interference with other spacecraft in the future. Ground controllers shut down the spacecraft Jan. Helios 2’s downlink transmitter, however, failed March 3, 1980, and no further usable data was received from the spacecraft. The spacecraft provided important information on solar plasma, the solar wind, cosmic rays, and cosmic dust, and also performed magnetic field and electrical field experiments.īesides investigations of the Sun and the solar environment, both Helios 1 and Helios 2 observed the dust and ion tails of at least three comets: C/1975V1 West, C/1978H1 Meier, and C/1979Y1 Bradfield. In contrast to Helios 1, Helios 2, flew about 1.9 million miles (3 million kilometers) closer to the Sun, achieving perihelion April 17, 1976, at a distance of 0.29 AU (about 27 million miles or 43.432 million kilometers), a distance that made Helios 2 the record holder at that time for the closest flyby of the Sun.Īs a result, the spacecraft was exposed to 10 percent more heat (68 degrees Fahrenheit or 20 degrees Celsius more) than its predecessor. Like its twin, the spacecraft was put into heliocentric orbit all communications with the spacecraft were directed from the German Space Operation Center near Munich. ![]() Helios 2 was the second spacecraft launched to investigate solar processes as part of a cooperative project between the Federal Republic of Germany and the United States in which the former provided the spacecraft and the latter the launch vehicle.Īlthough similar to Helios 1, the second spacecraft had improved systems designed to help it survive longer. ![]()
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