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 Spectrum
Continuum spectrum
Absorption spectrum
Emission spectrum
Challenge of Infrared
Astronomy
EARTH’S
ATMOSPHERE ! !
Infrared Water Vapor Image
Hurricane in Infrared
Fish at Depth
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
Space
Observatory
SOFIA
Ground telescope
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