Interstellar Matter

Emily Linden & Fiona Ward

INTERSTELLAR MATTER

Specify the radio techniques used to probe the nature

of interstellar matter.

QUESTION

• Optical Spectral Analysis Requires-Background source of radiation-Stars viewed through clouds to be relatively close to

earth (w/in a few thousand pcs)• Low-energy Radio Emissions produced by the gas of the

nebula itself is more versatile• Astronomers examine hydrogen spin-rates to determine

radio spectral lines• Hydrogen 21-Centimeter Radiation

BOOK EXAMPLE

• Hydrogen ground state spin patterns: parallel or antiparallel• Antiparallel has slightly less energy than parallel• All matter tends to achieve lowest possible energy state.• When hydrogen atom drops down to antiparallel spin, a

photon is emitted.• High energy low energy: Emitted photon is equal to energy

lost• Energy difference is very low, so energy of photon is very low• Wavelength= 21.1 cm (radio portion)• 21-centimeter radiation: the spectral line that results from

this hydrogen-spin-flip process

BOOK EXAMPLE

• Requires no visible light• Can be used on any interstellar region that

contains enough hydrogen gas to produce a detectable signal

• This includes low-density regions between dark clouds

• Wavelength much larger than typical interstellar dust particles

• Radio radiation reaches Earth unscattered by interstellar debris

• Can reach well beyond a few thousand parsecs• Can reach in directions lacking background

stars

BOOK EXAMPLE

• Hubble's Wide Field Planetary Camera 2 in 1994, 1995, and 2001

• Color filters were used to isolate light emitted by hydrogen, oxygen, nitrogen, and sulfur atoms

• This nebula is an emission

• NGC 604 (Nicolas-Claude Fabri de Peiresc.)

• First noted by the English astronomer William Herschel

ULTRAVIOLET, VISIBLE, AND

INFRARED

http://hubblesite.org/newscenter/archive/releases/2003/30/image/a/

• Radio signals will be sent out

• Usually up to five satellites in space

• Higher the frequency the father the distance

GRAVITATIONAL LENS

http://spectrevision.net/2013/05/31/interstellar-radio/

• Gives off a blue color• The star Rigel supplying

the light • Retains light from other

source

REFLECTION NEBULA

http://www.nasa.gov/multimedia/imagegallery/image_feature_701.html

• Book Example: Astronomers use Hydrogen 21-Centimeter Radiation to probe the nature of interstellar matter.

• Web Example: Astronomers use cameras from telescopes such as Hubble equipped with color filters and radio emissions to probe the nature of interstellar matter.

ANSWER