Star Formation

Protostars, Disks & Bipolar Jets

Class I Protostar

Material falls in along the disk plane while bipolar jets shoot perpendicular along the rotation axis. Background nebulosity is the parent molecular cloud the protostar is still embedded in. Real bipolar jets reach 0.5 light-years long.

From Cloud to Star

Stars form in cold, dense molecular clouds — vast regions of H₂ and dust at temperatures around 10 K. When a cloud fragment exceeds the Jeans mass, gravity wins over thermal and magnetic pressure and the fragment collapses.

Conservation of angular momentum spins the collapsing cloud into a flattened disk. Material spirals in, releasing gravitational energy as heat. The centre forms a hot, dense protostar — not yet fusing, but glowing brightly from compression.

When the core reaches ~15 MK, hydrogen fusion ignites and the star joins the main sequence — typically after a few Myr for solar-mass stars.

Why Bipolar Jets?

Magnetic launch — Disk's magnetic field flings ionised gas along rotation axis

Mass loss — Up to 10% of accreted material is ejected back out as jet

Speeds — 200–1000 km/s — visible as Herbig-Haro objects when shock-heated

Lifetime — Active during embedded protostar phases (~100 kyr)

Cleared cavity — Sweeps away the natal envelope, revealing the young star

ED: Nebula Sites

Elite Dangerous places named nebulae across the galaxy — many are the visible afterglow of recent star-formation episodes. The Pleiades, Witch Head, and California Nebula all host(ed) active formation regions.

The disk that forms a star also forms its planetary system. Material that doesn't accrete onto the protostar eventually settles into the planets, asteroids, and rings you see today. Every system in ED started this way.

T Tauri stars appear in ED as a distinct stellar variety — pre-main-sequence stars still in their disk-bearing phase.

Stages of Star Formation

Stage	Duration	Key Feature	Note
Molecular cloud	~10 Myr	Cold (~10 K) dense H₂ + dust	Triggered by SN shocks or galactic density waves
Cloud collapse	~100 kyr	Gravitational free-fall of fragment	Jeans-mass criterion determines minimum cloudlet
Class 0 protostar	~10 kyr	Deeply embedded, infalling envelope	Visible only in IR / sub-mm — optically invisible
Class I protostar	~100 kyr	Disk + jets visible, envelope thinning	Strong bipolar outflows clear cavity
T Tauri (Class II)	~1–10 Myr	Pre-main-sequence, thick disk	Optical visibility; H-alpha emission lines
Class III / WTTS	~10 Myr	Disk dispersing, no accretion	Weak T Tauri — late pre-main-sequence
Main sequence	Myr–Tyr	Hydrostatic H fusion ignites	Star joins the OBAFGKM main sequence