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

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

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