Free-floating objects in young star clusters with masses below the limiting mass for thermonuclear fusion of deuterium are not "planets", but are "sub-brown dwarfs" (or whatever name is most appropriate). [75] One of the most detailed images of Earth. The montage was created from photographs taken by the Visible/Infrared Imager Radiometer Suite (VIIRS) instrument onboard the Suomi NPP satellite. (Image credit: NASA) When four satellites of Jupiter (the Galilean moons) and five of Saturn were discovered in the 17th century, they were thought of as "satellite planets" or "secondary planets" orbiting the primary planets, though in the following decades they would come to be called simply "satellites" for short. Scientists generally considered planetary satellites to also be planets until about the 1920s, although this usage was not common among non-scientists. [7] There have been five human-made objects so far, Voyager 1, Voyager 2, New Horizons, Pioneer 10 and Pioneer 11, that have crossed the threshold into interstellar space.

Schneider, Jean; Dedieu, Cyril; Le Sidaner, Pierre; Savalle, Renaud; Zolotukhin, Ivan (2011). "Defining and cataloging exoplanets: The exoplanet.eu database". Astronomy & Astrophysics. 532 (79): A79. arXiv: 1106.0586. Bibcode: 2011A&A...532A..79S. doi: 10.1051/0004-6361/201116713. S2CID 55994657. The sun is by far the largest object in our solar system, containing 99.8% of the solar system's mass. It sheds most of the heat and light that makes life possible on Earth and possibly elsewhere. Planets orbit the sun in oval-shaped paths called ellipses, with the sun slightly off-center of each ellipse. Jupiter has a strong magnetic field, and with 75 moons, including the largest moon in the solar system, Ganymede. Prialnik, Dina K., Antonella Barucci, and Leslie Young, eds. The Trans-Neptunian Solar System. Elsevier, 2019.Astronomers, however, are still hunting for another possible planet in our solar system, a true ninth planet, after mathematical evidence of its existence was revealed on Jan. 20, 2016. The alleged "Planet Nine," also called "Planet X," is believed to be about 10 times the mass of Earth and 5,000 times the mass of Pluto.

Uranus holds the record for the coldest temperature ever measured in the solar system — minus 371.56 degrees F (minus 224.2 degrees C). The average temperature of Uranus is minus 320 degrees Fahrenheit (-195 degrees Celsius). A newly processed (2020) image of Venus that was captured by NASA's Mariner 10 spacecraft. (Image credit: NASA/JPL-Caltech) Mayor, Michel; Queloz, Didier (1995). "A Jupiter-mass companion to a solar-type star". Nature. 378 (6356): 355–359. Bibcode: 1995Natur.378..355M. doi: 10.1038/378355a0. S2CID 4339201. Recent Videos & Visualizations Above the Earth, Below the Surface: Landsat's Role in Monitoring Water Quality Related: 15 stunning places on Earth that look like they're from another planet Types of planets in the solar systemWhen polymath Galileo Galilei first studied Saturn in the early 1600s, he thought it was an object with three parts: a planet and two large moons on either side. Not knowing he was seeing a planet with rings, the stumped astronomer entered a small drawing — a symbol with one large circle and two smaller ones — in his notebook, as a noun in a sentence describing his discovery. More than 40 years later, Christiaan Huygens proposed that they were rings.