Seeing the Invisible Prof. Lynn Cominsky Sonoma State University Director, Education and Public Outreach
Sources of light Which of these things are sources of light? If things are not emitting light, how do you see them?
Seeing the light Do you know of any type of light that is not visible to your eyes? Are people sources of light?
Have you ever seen the invisible?
How do you detect light? What are common light detectors for –Visible light? –Infrared light? –X-ray light?
Radio transmission towers TV transmission towers Cold objects Planets Collapsed stars Radio galaxies Intergalactic matter Radio
microwave generator in ovens warm molecular clouds Planets Galaxies The Universe! Microwave
warm objects People Ovens Planets “Normal” stars Protostars Galaxies Infrared
hot objects (thousands of degrees) Sun Lightbulbs Planets “Normal” stars, sun-like and hotter Galaxies Visible
hotter objects (10,000 to about 100,000 Kelvin) UV lights (“black lights”) Nebulae Aurorae Hot stars Galaxies Ultraviolet
very hot objects (millions of degrees) X-ray generators Solar corona Pulsars Black holes Galaxy clusters X-rays
Electronic light detectors Solid state devices that detect individual light particles (“photons”) Digital dental x-ray Do you know of any others?
What you can see from the Earth VLA WMAP Spitzer FUSE Chandra Fermi
Why study the extreme Universe? Universe as seen by eye is peaceful
The Fermi mission… First space-based collaboration between astrophysics and particle physics communities International partners from France, Germany, Italy, Japan & Sweden Launched June 11, 2008 Expected duration 5-10 years
Before launch Large Area Telescope Gamma-ray Burst Monitor
Large Area Telescope (LAT) PI Peter Michelson (Stanford) International Collaboration: USA NASA and DoE, France, Italy, Japan, Sweden LAT is a 4 x 4 array of towers Each tower is a pair conversion telescope with calorimeter
Pair-conversion Anti-matter partners of e- are positrons (e+) When they meet, they annihilate each other! E = mc 2 m = mass of the electron or positron E = energy of gamma ray
Now in reverse…. This process is called “pair conversion” as the incoming gamma-ray converts into an electron/positron pair tungsten
How does the LAT work? Anticoincidence Detectors – screen out charged particles Tungsten converts gamma rays into e+ e- pairs Calorimeter measures total energy
Launched! June 11, 2008 Delta II Heavy (9 solid rocket boosters) Mass is 4300 kg 555 km circular orbit 1500 W total power 40 Mb/sec downlink
What the sky looks like in gamma rays
What types of things emit gamma rays? Really big lightning storms Our Sun when it flares Our Milky Way galaxy – charged particles hitting gas between the stars Huge explosions of stars that are dying (some make collapsed stars) Collapsed stars sending out jets of charged particles Black holes sending out jets of charged particles
Gamma-ray bursts on the sky About 4-5 bursts per week
Typical strong GRB seen by GBM Each burst has as much energy as our Sun puts out in its entire lifetime
Gamma-ray Jets from Black Holes Jets flare dramatically in gamma rays Galaxies that point their jets at us are called “blazars” How do the black holes send out jets? Art by Aurore Simonnet
Gamma rays from pulsars Collapsed stars – size of San Francisco, mass of our Sun Sending out beams of particles like lighthouses
What is the Universe made of? Matter – what we experience in our everyday lives Dark matter – you can’t see it but you can feel it Dark Energy – a mysterious force that is tearing the Universe apart
Searching for dark matter Dark matter makes up 80% of the matter in the Universe The leading particle candidate for dark matter is a “WIMP” =weakly interacting massive particle Fermi could see gamma rays from WIMPS annihilating with each other More gamma rays are expected near the center of our Galaxy
Many places to look! All-sky map of simulated gamma ray signal from DM annihilation (Baltz 2006) Satellite Galaxies Galactic Center Milky Way Halo Spectral Lines Extra-galactic 31 No detections so far, but the search continues…