4 How to study gamma rays? Absorbed by the Earth’s atmosphere Use rockets, balloons or satellitesCan’t image or focus gamma raysSpecial detectors: scintillating crystals, silicon-stripsBalloon experiment
5 Why study the extreme Universe? Universe as seen by eye is peaceful
6 But what if you had gamma-ray vision? Imagine the night sky. Now imagine the gamma-ray sky. It is very different.But what if you had gamma-ray vision?
7 The Gamma-ray Sky in False Color – from EGRET/Compton Gamma Ray Observatory Pulsars – rapidly spinning neutron stars with enormous magnetic and electric fieldsMilky Way – Gamma rays from powerful cosmic ray particles smashing into the tenuous gas between the stars.Blazars – supermassive black holes with huge jets of particles and radiation pointed right at Earth.The Unknown – over half the sources seen by EGRET remain mysteriousGamma-ray bursts – extreme exploding stars or merging black holes or neutron stars.
8 So we need a new mission… First space-based collaboration between astrophysics and particle physics communitiesInternational partners from France, Germany, Italy, Japan & SwedenLaunched June 11, 2008Expected duration 5-10 years
9 Before launchLarge Area TelescopeGamma-rayBurst Monitor
10 Gamma-ray Burst Monitor (GBM) PI Charles Meegan (NASA/MSFC)US-German secondary instrument12 sodium iodide scintillators10 keV to 1 MeVBurst triggers and locations2 bismuth germanate detectors150 keV to 30 MeVOverlap with LAT
11 Large Area Telescope (LAT) PI Peter Michelson (Stanford)International Collaboration: USA NASA and DoE, France, Italy, Japan, SwedenLAT is a 4 x 4 array of towersEach tower is a pair conversion telescope with calorimeter
12 What is “pair-conversion”? E = mc2Positrons are anti-electronsWhen they meet, they annihilate each other!
17 Gamma-ray Bursts from “Hypernovae” A billion trillion times the power from the Sun
18 GBM Bursts in first 10 months About 4-5 bursts per weekFollow bursts on
19 Typical strong GRB seen by GBM 190+ GBM bursts seen to dateEight LAT-GBM bursts seen in first 10 months
20 GRB080916C: most extreme GRB yet Greatest total energy, the fastest motions and the highest-energy initial emissions ever seenStudying the high-energy gamma rays tells us that the charged particles which made those gamma rays were moving at % of light speedObserving the GRB using visible light tells us that it happened12.2 billion years agoFirst 3 lightcurves are background subtracted
21 Gamma-ray Bursts in the Classroom GRB Educator Guide with an accompanying poster that uses GRBs as a way to get your students excited about Math and Science (FREE! From SSU E/PO)‘Invisible Universe from Radio Waves to Gamma-rays” (available for purchase from GEMS)
22 Gamma-ray Jets from Active Galaxies Jets flare dramatically in gamma raysGalaxies that point their jets at us are called “blazars”How do the black holes send out jets?Art by Aurore Simonnet
23 Global Telescope Network Students do ground-based visible-light observations using remote telescopesGRBs and flaring blazarsCoordinated with Fermi and other satellite dataGORT at Pepperwood
24 Active Galaxies in the Classroom Elementary-Middle School: Active Galaxy Pop-up Book – write us for a classroom demonstrationHigh school: Active Galaxies Educator Guide
25 This figure is from a packet of materials on supernova that was developed for the Night Sky Network. It shows the star-gas cycle. On the left is a schematic of the life cycle for low mass stars (below a few times the mass of the Sun). They evolve through their hydrogen burning phase to become red giants (when they burn helium to carbon). When these stars run out of helium, they are done. They become planetary nebula and leave behind a white dwarf compact remnant. Stellar material blown off during the red giant and planetary nebula phases can be incorporated back into gas clouds, which can then form new stars. For low- mass stars the entire process from birth to white dwarf will require more than one billion years (the sun will require more than ten billion years).
26 Supernova!This video depicts the inner structure of a red giant star. The outer parts are composed of hydrogen. Within the core, there will be an outer layer of hydrogen burning to helium, within that a layer of helium burning to carbon. Within that, a layer of carbon burning to oxygen, etc. As the center of the star is approached, heavier and heavier elements are fused as the temperature rises. In the most massive stars, beyond 8 to 10 solar masses, central core temperatures will be high enough to burn silicon into iron, and beyond, resulting in a supernova explosion.
27 … discovers the 1st gamma-ray only pulsar in CTA1 P = msage ~1.4 x 104 yrCTA 1 supernova remnantRX JFermi 95% error box3EG J % error box+Pulsar is not at center of SNRIt’s moving at 450 km/sec – kicked by the supernova explosion that created it27
28 How do gamma ray pulsars work? Pulsars are not simply lighthouses anymoreRadio beams are emitted from polar capsGamma rays come from outer magnetosphere
29 The Pulsing Sky (Romani) Pulses at1/10th true rate
30 Supernovae in the Classroom Supernova Educator’s Guide:Fishing for SupernovaeCrawl of the CrabMagnetic Poles and Pulsars
31 NASA at Sonoma State Swift NuSTAR Who are we? Education and Public Outreach at Sonoma State University in Rohnert Park, CaliforniaA group of students, faculty and staff working collaboratively to educate the public about current and future NASA high energy astrophysics missions.Fermi Gamma-raySpace TelescopeXMM-NewtonSwiftNuSTAR8/15/09
32 Photo Credit: Linnea Mullins For more information:Also see my group’s site:Photo Credit: Linnea Mullins
34 LAT HardwareGrid StructureTrackers16 TowersCalorimeters
35 LAT Hardware 16 Towers Global Electronics Anticoincidence Detectors Integrated LAT with radiators
36 EGRET vs. Fermi LAT Energy Range Energy Resolution Effective Area Field of ViewAngular ResolutionSensitivitySource LocationLifetime20 MeV - 30 GeV10%1500 cm 20.5 sr100 MeV~ 10-7 cm-2 s-1arcmin20 MeV GeV<10%> 8000 cm 2> 2 sr< 100 MeV< 0.15o > 10 GeV<6 x 10-9 cm-2 s-1< 0.5 arcmin2008 – 2013+
37 EGRET’s LegacyEstablished blazars as largest class of extra-galactic g-ray emittersObserved many blazar flares, some <1 day> 60% of ~270 sources are unidentifiedMeasured extra-galactic g-ray backgroundDiscovered gamma-rays from 4 pulsarsShowed E<1015 eV cosmic rays are galacticDetected solar flares and some g-ray bursts at E>1 GeV
39 3rd EGRET CatalogLAT should detect thousands of sources
40 GRB Observations with Fermi GBM:160 GRBs so far (18% are short)Detection rate: ~ GRB/yrA fair fraction are in LAT FoVAutomated repoint enabledLAT detections: (5 in 1st 8 months)GRB080825C: >10 events above 100 MeVGRB080916C:>10 events above 1 GeV and >140 events above 100 MeVGRB081024B: first short GRB with >1 GeV emission5 + 2 more possible detections
41 Unidentified Sources170 of the 270 sources in the 3rd EGRET catalog have no counterparts at longer wavelengthsVariable sources appear at both low and high galactic latitudesHigh-latitude sources appear to be both extra-galactic and galacticSteady medium latitude sources may be associated with Gould’s belt (star forming region)
42 Possible Unidentified Sources Radio-quiet pulsars: Geminga-like objects can be found with direct pulsation searchesPreviously unknown blazars: flaring objects will have good positions, helping IDsBinary systems: shocked winds between companions will show time variabilityMicroquasars: time variability, X/g correlationClusters of galaxies: steady, high-latitude sources should show shock spectra
44 Outer gap vs. polar cap models Where are particles accelerated?How is particle beam energy converted into photons?What is shape of pulsar beam?How many pulsars are there? Birth rate?Where is most of the energy?
45 LAT studies EBL cutoffProbe history of star formation to z ~4 by determining spectral cutoff in AGN due to EBL
55 Searching for dark matter Dark matter makes up 80% of the matter in the UniverseThe leading particle candidate for dark matter is theorized to self-annihilate, creating gamma-ray lines in the energy range 30 GeV - 10 TeVFermi could see these lines up to 300 GeV (if they exist)More lines are expected near the center of our GalaxyR- parity conservation means that supersymmetric particles cannot turn into standard particlesR=+1 for standard particles, and R=-1 for supersymmetric particlesZ is Z boson
56 Dark Matter line detectability 2 years of simulated data – detectable galactic center halo from Kuhlen, Diamand and Madau 2007
57 Fly the Gamma-ray Skies Follow GRBs on the GRB Skymap siteJoin the Global Telescope Network
58 ConclusionsFermi has already gone far beyond the sensitivity of EGRET and is discovering new classes of high-energy gamma ray sourcesFermi is opening wide a new window on the Universe – which may show us connections between the infinite and the infinitesimalStay tuned – the best is yet to come!For more info:
59 Monitoring Flares from “Blazars” Fermi scans the entire sky every 3 hoursSo blazar flares can be seen on relatively short time scalesCoordinated campaigns with many ground-based telescopes are providing information about how the flares are occurring
60 Fermi sees the EGRET pulsars…. Vela (P=89.3 ms)Geminga (P=237.1 ms)Fermi sees the EGRET pulsars….PSR B (P=102.4 ms)PSR B (P=197 ms)Crab pulsar (P=33.4 ms)