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Jennifer Hatchell


Star birth

In the submillimetre-wavelength maps below, young stars (orange/black) are seen at the earliest stages of formation, still embedded in their parent molecular cloud (dark green contours). This cloud, in the constellation of Perseus, is one of the nearest star formation regions to Earth at a distance of around 1000 light years.

There are many unanswered questions in star formation:
  • Where do stars form? We know that stars form in dense clouds of dust and gas, but exactly what are the physical conditions required for star formation?
  • Masses: The IMF (Initial Mass Function) is a measure of how many stars form at each mass. We know that this roughly follows a power law at masses around one solar mass but at low masses and high masses it is less certain. At what stage in star formation is the IMF determined?
  • Star formation efficiency: How much of a molecular cloud ultimately ends up in stars?
  • Timescales: How long does it take an individual star to form? How long does a molecular cloud go on forming starsbefore it is dispersed and destroyed?
  • Feedback mechanisms: Molecular outflows and stellar winds feed energy and momentum back into the interstellar medium. Material is chemically processed by freezeout, evaporation and shocks. How does this affect the subsequent star formation process?

Unlike visible or infrared, submillimetre and millimetre wavelength radiation penetrates deep inside these molecular cloud to detect the youngest (proto)stars. Because these wavelengths are blocked by water vapour in the Earth's atmosphere, submm telescopes are found on high, dry sites such as Mauna Kea in Hawaii and the Atacama Desert in Chile.

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