Download The Birth of Stars

The Birthplace of Stars
The space between the stars is not completely empty. Thin clouds of hydrogen
and helium, seeded with the “dust” from dying stars, form in interstellar space.
Dark Clouds
gather
Molecular Clouds
Sometimes (especially in spiral arms), the gas is compressed
enough that the dust is thick and gravity can collapse knots in these
“molecular” clouds to make new stars.
The Initial
Collapse
The center of the cloud
is densest, so it
collapses first.
Pressure is removed in
an wave moving out at
the speed of sound.
Material free-falls
inside this wave and
crashes into a growing
(and glowing) central
object. We see only the
infrared light emerging
from the large dust
core.
Galactic shear and turbulence
give every core a little spin
(once round in 10 million
years). But they get a lot
smaller, and the spin goes up –
to orbital!
It is for this reason that we
believe there are many planetary
systems – it is part and parcel of
the star formation process to
make a disk. Typical Galactic
spin makes disks about the size
of our Solar System…
A little bit of
spin goes a
long way…
The Sword of Orion
The nearest great stellar nursery to us is the great Orion molecular cloud
which is about 1000 light years away, and manufacturing thousands of
stars. This is probably how the typical
star is made.
The glowing tip of a molecular “cigar”
The Orion nebula is powered by 4 high mass luminous stars, which
have cleared out their birthplace and are eating at a long cloud
pointed at us.
The Trapezium
Nearby, lower mass stars are forming
Hubble Space Telescope
They look like little windsocks
The blast from the luminous stars is eating away at the little guys
The heart of them contains a potential new solar system
“Proplyds” are new star-disk systems
With powerful bipolar jets
The Star-Disk System Forms
while infall continues
Jets remove
excess angular
momentum
In the center - T Tauri Stars
The new young star is exposed,
while the accretion disk is still
in place. The spectrum of all is
seen together (so we don’t
have to image disks in order to
know they are there).
Half the time, two (or more) stars form
Most stars form in clusters
The typical cluster doesn’t
stay bound once the stars
form. The remaining 80-90%
of the gas dissipates and the
stars drift apart.
Star Formation is Beautiful, but ephemeral
Within about 10 million
years, the birth-cloud is
shredded, and the disks
are dissipated.
The process of starbirth
has ended.
The stage is set
for planet
formation