Hubble Sees a Star About to Ignite

We know how stars form. Clouds of interstellar gas and dust gravitationally collapse to form a burst of star formation we call a stellar nursery. Eventually, the cores of these protostars become dense enough to ignite their nuclear furnace and shine as true stars. But catching stars in that birth-moment act is difficult. Young stars are often hidden deep within their dense progenitor cloud, so we don’t see their light until they’ve already started shining. But new observations from the Hubble Space Telescope have given us our earliest glimpse of a shiny new star.

You can see this image above, which captures the dusty region of the FS Tau system. The bright star just to the right of center is FS Tau A, which is a young star just 2.8 million years old. An infant compared to our Sun’s 4.6 billion years. But the exciting discovery is a bit higher and further right, known as FS Tau B. That line of dust obscuring the protostar is its protoplanetary disk seen edge-on. The light coming from the obscured star isn’t produced by nuclear fusion, but rather the late stages of gravitational collapse.

You can also see that the protostar has begun to produce radiant jets, which are reflected against the dusty nebula as regions of blue light. Because of this reflected light, FS Tau B is classified as a Herbig-Haro (HH) object. HH objects are great for helping astronomers understand the early dynamics of these stars.

FS Tau B is likely in the early stages of becoming a T Tauri star. These are sun-like stars just on the edge of becoming true stars. They can be quite active, with starspots and large flares, but can take 100 million years for one to ignite their cores and settle into a true main-sequence star. As that happens, protoplanets will form within the dusty disk, ready to become full planets in time.

You can find more information about the FS Tau system, as well as high-resolution images and videos, on the ESA Hubble website.