Out in the deep dark recesses of interstellar space lie vast sprawling clouds of molecular gas and dust. You can actually think of them a little bit like rainclouds. As they get denser, they scatter more light. Eventually light becomes unable to penetrate them and they look dark. Just like dark nimbus clouds, these “dark nebulae” then start to condense stars as if they were raindrops. Over millions of years, a patch of this interstellar material condenses enough that it forms a newborn star. A star rather like T Tauri here…
The first star recognised to have only just formed, T Tauri lies around 400 light years away on the edge of just such a dense molecular cloud. Only about a million years since it first ignited, T Tauri isn’t fully condensed yet. Being the first of its kind recognised (the “prototypical example”), it gives its name to an entire class of young Sun-like stars: the T Tauri stars.
Being young stellar objects (at most, only a few million years old), T Tauri stars aren’t yet at hydrostatic equillibrium, so they’re much puffier than adult stars. Being so puffy, they’re highly convective, giving them potent magnetic fields which can unleash violent x-ray flares. They also don’t yet fuse hydrogen in their cores. That won’t happen until they’re fully condensed. Young stars like T Tauri also have a powerful stellar wind. This stellar wind blows away any excess gas, preventing the star from growing further in size and fixing its initial mass.
T Tauri itself is actually part of a system containing at least 3 stars, though it’s hard to tell because of all the dust still surrounding the system. Being so young, these stars haven’t had time to settle into a stable orbit yet. Their orbits are still quite erratic. As a result, there’s actually a chance that T Tauri itself is in the process of being ejected from the system after a recent brush with one of its siblings. Perhaps a similar thing once happened to the Sun, explaining why our star is a loner in a Universe full of multiple star systems.