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- Terrae
- Latin for “lands”, terra is singular. The lighter regions on the Moon that you can see, also called the highlands, are the terrae.
- Terraforming
- a process of altering a planet or moon to make it habitable for humans. Terra is a Greek prefix meaning Earth, so terraforming a planet means to make it more like Earth.
- Terrestrial
- rocky planets that are made of rock and minerals, have solid surfaces, and typically have radii smaller than 10,000 km (6,213.7 miles) with a mass less than 1 x 1024 kg. They typically have only one or two moons, if any.
- Tidal Force
- the net force that results when the gravitational pull on one side of an object is greater than that on the other side.
- Tides
- the changes in sea level due to gravitational forces exerted primarily by the Moon, but also in part by the Sun.
- Time Dilation
- the name given to the phenomenon by which a clock closer to a massive object, like a black hole, will run slower than an identical clock that is farther away. This type of time dilation is predicted by Einstein’s General Theory of Relativity and has been tested successfully by flying a chronometer on an airplane and testing the effect against an identical clock that was left stationary on the ground. Another type of time dilation occurs when a clock is moving with respect to an observer. In this case the observer will see the moving clock tick slower than the clock that is stationary with respect to the observer. This type of time dilation is predicted by Einstein’s Special Theory of Relativity and has also been tested with great accuracy.
- Torus
- A doughnut-shaped object. Gas and dust outside the accretion disk in an active galaxy orbit the central black hole in a torus-shaped region.
- Twin Quasar
- also known as QSO 0957+561 A/B, was the first gravitationally lensed object to be discovered (1979) and consists of a double imaged quasar formed by a foreground galaxy’s gravity which is nearly directly inline with QSO 0957+561 B and Earth.
- Type 1A Supernova
- a huge thermonuclear explosion resulting when certain white dwarf stars exceed the Chandrasekhar mass limit.
- T90
- A characteristic time associated with a celestial object’s light curve describing the amount of time needed to collect 90% of the photons associated with a given event.
