1. MERLIN map of 22GHz water maser emission
What is a MASER?
Microwave
Amplification by the
Stimulation
Emission of
Radiation
MERLIN map of 22GHz water maser emission
from IK Tan (Gonzalez 1996).
MASERs are naturally occurring stimulated microwave emission from molecular clouds.
MASERs 1

2. MASERs and LASERs are the same, except
that they involve different wavelengths of light.
The first MASER was created in a lab in 1954
while the LASER was developed in 1960.
The first natural MASER was discovered in the
Orion Nebula in 1965.
MASERs 2 2

3. Spontaneous Emission Atoms don't stay in exited states.
They move to a lower energy, spontaneously emitting a photon.
Spontaneous because no outside influence triggers the emission.
MASERs

4. Amplified Stimulated Emission
A photon with a wavelength equal to the energy of an
exited atom is fired at the atom.
The photon stimulates the electron to emit a photon, so
two photons of the same wavelength are now emitted.
MASERs 4 4

5. Coherent Radiation
Both of the emitted photons have the same wavelength and move in the same direction
MASERs

6. An illustration of the two-photon stimulated emission process
The two photons can now stimulate two more molecules to radiate, causing a chain reaction.
As a result, a MASER is intense, narrowly
directed, and at a single frequency.
An illustration of the two-photon stimulated emission process
MASERs

7. MASERs occur in several places:
Image from Anna Bartkiewicz
MASERs occur in several places:
Around young stars.
Around stars at the end of their life.
Near a black hole at an active galactic center.
Stars near MASERs provide the necessary
energy for MASER emission.
MASERs

8. MASERs can also be inorganic. SiO MASERS8

9. composition of nebulae. MASERs emit light at the same frequency and
MASERs tell us about
the molecular
composition of nebulae.
MASERs emit light at
the same frequency and
are high precision
atomic clocks.
MASERs

10. MASERs can be detected billions of light years away.
Through MASERs many different molecules
necessary for life have been found.
MASERs