Protostar
An early-stage star formed by collapsing gas that heats up before nuclear fusion begins, often emitting bright infrared light and driving outflows. Seen in images from NASA's James Webb Space Telescope, protostars like FS Tau B are luminous cores within dusty regions, marking the start of stellar birth.
A protostar is an early-stage stellar object that forms when a dense region within a molecular cloud collapses under gravity, heating up long before nuclear fusion begins. It is characterized by bright infrared emissions and often drives energetic outflows, serving as the precursor to a true star. In observations by NASA's James Webb Space Telescope, protostars like FS Tau B appear as luminous cores embedded in dusty regions, revealing the dynamic processes of stellar birth.
What this means in real life
Imagine a snowball rolling downhill, gathering more snow as it goes and getting denser and hotter—but it hasn't yet reached the point where it spontaneously ignites. A protostar is similar: it's pulling in surrounding material and heating up, but hasn't yet 'turned on' its nuclear engine.
What it isn’t
A protostar is not a failed star or a dead star; it's an unfinished one. It's also not the same as a brown dwarf, which never gets hot enough to fuse hydrogen at all, even after formation stops.
Commonly misused online
Social media often conflates protostars with 'baby stars' as if they're already fusing hydrogen, when in fact they're pre-fusion objects still in the gravitational collapse phase.