Download Visit to Monroe County High Schools

A Visit to
Ghost Ranch
Jim Linnemann
Michigan State University &
Los Alamos National Laboratory
June 18, 2003
The Milagro All-Sky TeV Gamma-Ray
Telescope
 Look for high energy photons
 “particles” of light
 Photons point back
see where they came from
 Recent Results
Crab nebula
All-sky survey
Galactic Plane
GRB searches
What are Cosmic Rays?
• Fast moving particles from—
the cosmos: of no earthly
origin
`
But then, the same is true of starlight
– Most are electrically charged
• How do you see them? (Experimental Physics)
– Finding a way to detect things
– “extrasensory” perception
• Real phenomena, right under our noses
• The lure of secret knowledge still attracts…
Milagro Detector
Moon Shadow: Energy Scale Calibration
Proton Response
E = 640±70 GeV (MC 690 GeV)
sq = 0.9o
The moon’s shadow is
sharp:
blurred only by
earth’s magnetic
field and detector’s
resolution
The Sun Produces some Cosmic Rays:
A Solar Prominence
Material Ejected from the Sun by Magnetic Fields
The sun’s magnetic
field deflects
cosmic rays and
blurs its image
Can use to
study the sun
A satellite
The Milky Way—seen in light 100 million times
more energetic than light from the sun
A Source of Gamma Rays: The Crab Nebula
Supernova seen in 1054 AD
Still shining: light particles with 1 trillion
times more energy than sunlight photons
A spinning neutron star
with a strong magnetic
field (pulsar)
Accelerates electrons,
which transfer much of
their energy to photons
The Crab Nebula
Raw Data
On: 16,987,703
Off: 16,981,520
Significance: 1.4 s
Cut Data
On: 1,952,917
Off: 1,945,109
Excess: 7,808 (~10/day)
Significance: 5.4 s
An Active Galactic Nucleus
Gravity, Magnetic Fields,
and Relativity combine to
send energetic light particles
across the universe…
Colliding neutron stars making
black holes: one model for distant
gamma ray bursts
Sources change with
energy:
Leave traces in
spectrum