The Formation of Stars Where do they come

The Formation of Stars Where do they come from? How do they form?

Star Formation • Last week…stellar evolution. What happens after the main sequence. (Will return to shortly) • Now, how to stars form? What do they form from? Space seems to be empty. Where does the material come from?

Space isn’t really empty • Stars move in a dilute “atmosphere” called the interstellar medium. • Typical density of 10100 atoms/cc • Compare with density of 4 E+19 atoms/cc in the Earth’s atmosphere • Compare with 1024 atoms/cc mean density for Sun.

Putting together the pieces in the puzzle • To see how stars form, look at places where there are young stars. • When we see massive main sequence stars (spectral class O), we know they are young. • With fairly simple observations, we can find groups of O and B stars (OB associations)

Young star clusters (the Rosette Nebula and Chi & h Persei)

The primary example: The Orion Nebula

Fact that stars form in star clusters means the Sun has siblings out there

Stars form in the presence of dark clouds

Dark clouds due to particulate matter • Small particle absorb and scatter light • Demo • Particles primarily formed of carbon, silicates • Most of matter which forms stars must be elsewhere

Where the gas is: molecular and very cold • Emission Discovery was a from contribution of molecules radio Like CO, astronomy water, • ammonia Utilized Made with radio of observations telescopes rotational transitions of molecules

The sky in the glow of the carbon monoxide molecule

How do stars form from these molecular clouds?

A Star is born….

A Star is born (Part 2) …

What a new star (protostar) looks like. We can study nearby examples in Taurus

Molecular Clouds as Chemistry Sets in the Sky • Number of molecules discovered in molecular clouds = 152 • 8 species with 10 or more atoms • Deuterated species overrepresented

The future of molecular cloud studies…ALMA • 64 antenna interferometer • 2010 August, “first science” • 2012 December, “full science operations”

ALMA