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Glossary term: Escape Velocity

Description: Escape velocity is the minimum speed that an object must have to permanently escape from the gravitational field of a celestial body. The escape velocity at a distance r from the center of a massive body of mass m, is given by √(2Gm/r), where G is the gravitational constant. This means that the escape velocity depends on the radius of the celestial body and its mass. In the case of the Sun, it is 617.5 kilometers per second (km/s), and Earth is 11.2 km/s. It is 2.4 km/s for the Moon, which means that an object that wants to leave the Moon needs a lower speed than an object that wants to leave Earth, and therefore can enter lunar orbit at slower speeds.

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Term and definition status: This term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".