by
Claudia Knez
Outline
• What is star formation?
• Why study the star formation using infrared radiation and not visible light?
• Why SOFIA is important for our
observations?
Star Formation• Large clouds of cold, dense gas
(molecular clouds) collapse to form stars.
• Cold gas means temperature T~10–50 K
0 oC = 273 K• Stars of different masses form in
these regions.• Massive stars do not form in
isolation. • As the clouds collapse and stars
begin to form, the temperature of the gas and dust rises.
From Stars to Planets
• Chemical studies in star forming regions reveal the composition of the gas.
• Planets form from gas around stars.• Comets have similar composition as
the interstellar medium.
•Are organic molecules common in star forming regions?
Dust
• At low temperatures, the gas freezes onto dust grains.
• Chemical reactions occurs on the surface of grains.
• As gas is heated by protostars, the ice is evaporated from the dust grains.
Gas
• Newly evaporated molecules such as acetylene, C2H2, and methane, CH4, are observed.
• These and other complex organic molecules are seen towards protostars.
• The molecules necessary for life seem to be COMMON!
Why Study Protostars in the Infrared?
• Gas around forming stars is dense and it traps light from protostars.
• The gas and dust heat up and re-emit the light at longer wavelength (infrared and radio).
• Molecules along the line of sight absorb the light and create an absorption spectrum.
• Visible light does not get through the cloud!
Absorption SpectrumAbsorption spectrum
Continuum spectrum Emission spectrum
Challenge of Infrared Astronomy
EARTH’S
ATMOSPHERE ! !
Infrared Water Vapor Image
Hurricane in Infrared
Earth’s atmosphere at 16.7 microns
Earth’s Atmosphere at 11.9 microns
Absorbers in Atmosphere
• Main absorbers in the atmosphere are:– Water– Carbon dioxide– Ozone
• Other absorbers include:– Methane
Ground telescope
SOFIA
Space Observatory
SOFIA
• SOFIA will fly above most of the troposphere
• Absorption by most atmospheric molecules will be decreased.
• The study of molecules such as water and methane will be possible!
Telescope
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