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The Formation of Massive Stars
Stars are born in clouds
of gas and dust, and they are most probably born in the centres of
particularly cool and dense regions, sometimes referred to as
cores. These cores are quasi-stable. They may
survive for many times their free-fall collapse timescales, but at some
time they begin to fall under the force of their self gravity and collapse
to create new star. The more massive such a core is, the faster
the collapse and the evolution of the resulting young (proto-)star.
And the more massive the core, the more massive the new star will be.
Because these massive stars (M > 8Msun) form so quickly,
they are embedded inside the dense clouds for a considerable fraction
of their lifetime and are thus hard to observe by astronomers during
their childhood. And because these stars are also very hot, they
are doing rather violent things to the dense cloud around them: The
dust gets molten and/or blown away, the gas becomes ionized. Sometimes
they even start destroying accretion disks around neighbouring
(lower-mass) stars. By these means, such young massive stars
create the objects that I am most interested in:
Ultracompact HII Regions.
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