Prototype for a class of very young stars, still in the process of gravitational contraction. They constitute a type of variable star, often shedding mass, still forming and contracting; and yet to evolve to reach the main sequence.
On a Hertzsprung-Russell Diagram, they plot above the main sequence. T Tauri stars are mostly between 10,000 and 10 million years in age; of low mass (0.5 to 3.0 M sol); surrounded by hot, dense envelopes; and losing mass via stellar winds with typical velocity of around 100 km/s. Many T Tauri stars are in binary systems. Higher-mass stars of a comparable age are known as Herbig Ae/Be stars, and are usually considerably brighter.
Text by Chris Clowes
Initially published on 31 December 2007.