1. Exploring the Extreme Universe with the Fermi Gamma-ray Space Telescope
Prof. Lynn Cominsky
Sonoma State University
Director, Education and Public Outreach

2. What turned Bruce Banner into the Hulk?
Gamma rays!
Why?
Because gamma rays are powerful!

3. How powerful?
100 MeV

4. How to study gamma rays? Absorbed by the Earth’s atmosphere
Use rockets, balloons or satellites
Can’t image or focus gamma rays
Special detectors: scintillating crystals, silicon-strips
Balloon 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 fields
Milky 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 mysterious 
Gamma-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 communities
International partners from France, Germany, Italy, Japan & Sweden
Launched June 11, 2008
Expected duration 5-10 years

9. Before launch
Large Area Telescope
Gamma-ray
Burst Monitor

10. Gamma-ray Burst Monitor (GBM)
PI Charles Meegan (NASA/MSFC)
US-German secondary instrument
12 sodium iodide scintillators
10 keV to 1 MeV
Burst triggers and locations
2 bismuth germanate detectors
150 keV to 30 MeV
Overlap with LAT

11. 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

12. What is “pair-conversion”?
E = mc2
Positrons are anti-electrons
When they meet, they annihilate each other!

13. What is a Pair Conversion Telescope?

14. How does the LAT work?
Anticoincidence Detectors – screen out charged particles
Tungsten converts gamma rays into e+ e- pairs
Calorimeter measures total energy

15. 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

16. 9 month skymap Bright blazar Gamma-ray pulsar High-mass binary
Radio galaxy
High-mass binary
Gamma-ray pulsar
Bright blazar
Globular cluster
Unidentified

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 week
Follow bursts on

19. Typical strong GRB seen by GBM
190+ GBM bursts seen to date
Eight 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 seen
Studying the high-energy gamma rays tells us that the charged particles which made those gamma rays were moving at % of light speed
Observing the GRB using visible light tells us that it happened12.2 billion years ago
First 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 rays
Galaxies 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 telescopes
GRBs and flaring blazars
Coordinated with Fermi and other satellite data
GORT at Pepperwood

24. Active Galaxies in the Classroom
Elementary-Middle School: Active Galaxy Pop-up Book – write us for a classroom demonstration
High 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 = ms
age ~1.4 x 104 yr
CTA 1 supernova remnant
RX J
Fermi 95% error box
3EG J % error box +
Pulsar is not at center of SNR
It’s moving at 450 km/sec – kicked by the supernova explosion that created it 27

28. How do gamma ray pulsars work?
Pulsars are not simply lighthouses anymore
Radio beams are emitted from polar caps
Gamma rays come from outer magnetosphere

29. The Pulsing Sky (Romani)
Pulses at
1/10th true rate

30. Supernovae in the Classroom
Supernova Educator’s Guide:
Fishing for Supernovae
Crawl of the Crab
Magnetic Poles and Pulsars

31. NASA at Sonoma State Swift NuSTAR Who are we?
Education and Public Outreach at Sonoma State University in Rohnert Park, California
A group of students, faculty and staff working collaboratively to educate the public about current and future NASA high energy astrophysics missions.
Fermi Gamma-ray
Space Telescope
XMM-Newton
Swift
NuSTAR
8/15/09

32. Photo Credit: Linnea Mullins
For more information:
Also see my group’s site:
Photo Credit: Linnea Mullins

33. Backups Follow

34. LAT Hardware
Grid Structure
Trackers
16 Towers
Calorimeters

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 View
Angular Resolution
Sensitivity
Source Location
Lifetime
20 MeV - 30 GeV
10%
1500 cm 2
0.5 sr
100 MeV
~ 10-7 cm-2 s-1
arcmin
20 MeV GeV
<10%
> 8000 cm 2
> 2 sr
< 100 MeV
< 0.15o > 10 GeV
<6 x 10-9 cm-2 s-1
< 0.5 arcmin
2008 – 2013+

37. EGRET’s Legacy
Established blazars as largest class of extra-galactic g-ray emitters
Observed many blazar flares, some <1 day
> 60% of ~270 sources are unidentified
Measured extra-galactic g-ray background
Discovered gamma-rays from 4 pulsars
Showed E<1015 eV cosmic rays are galactic
Detected solar flares and some g-ray bursts at E>1 GeV

38. EGRET All-Sky Map

39. 3rd EGRET Catalog
LAT should detect thousands of sources

40. GRB Observations with Fermi
GBM:
160 GRBs so far (18% are short)
Detection rate: ~ GRB/yr
A fair fraction are in LAT FoV
Automated repoint enabled
LAT detections: (5 in 1st 8 months)
GRB080825C: >10 events above 100 MeV
GRB080916C:
>10 events above 1 GeV and >140 events above 100 MeV
GRB081024B: first short GRB with >1 GeV emission
5 + 2 more possible detections

41. Unidentified Sources
170 of the 270 sources in the 3rd EGRET catalog have no counterparts at longer wavelengths
Variable sources appear at both low and high galactic latitudes
High-latitude sources appear to be both extra-galactic and galactic
Steady 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 searches
Previously unknown blazars: flaring objects will have good positions, helping IDs
Binary systems: shocked winds between companions will show time variability
Microquasars: time variability, X/g correlation
Clusters of galaxies: steady, high-latitude sources should show shock spectra

43. EGRET pulsars

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 cutoff
Probe history of star formation to z ~4 by determining spectral cutoff in AGN due to EBL

46. LAT vs. Ground-based HE Arrays

47. LAT Single GR Event Displays
green = charged particles
blue = reconstructed track
yellow = gamma-ray estimated direction
red = energy depositions in the calorimeter

48. Mission Data Relay Gamma-ray Detectors: LAT & GBM Spacecraft GPS m•
TDRSS Relay
DELTA • • -
Spacecraft - - •
LAT
Operations Center
SLAC
Schedules
GLAST Mission
Operations Center
GSFC
GLAST Science
Support Center
GSFC
Archive
HEASARC
GSFC
Schedules
GBM
Operations Center
MSFC
Alerts

49. Mission timeline
We are here!

50. First Light Results
We renamed the mission after Enrico Fermi, an Italian-American scientist on 8/26/08 when we announced our first results
Enrico Fermi
Nobel in 1938

51. GRB080825C: the 1st LAT GRB
The 1st LAT events coincide with the 2nd GBM peak
The high-energy emission lasts longer: highest energy photon arrives when the GBM emission is very weak

52. First Light LAT Skymap
3C454.3 located about 7 billion light-years has now faded, and PKS , located about 10 billion light-years
Is now bright
95 hours of LAT data = about 1 year of EGRET sensitivity

53. Orthographic projection

54. 3 month skymap

55. Searching for dark matter
Dark matter makes up 80% of the matter in the Universe
The leading particle candidate for dark matter is theorized to self-annihilate, creating gamma-ray lines in the energy range 30 GeV - 10 TeV
Fermi could see these lines up to 300 GeV (if they exist)
More lines are expected near the center of our Galaxy
R- parity conservation means that supersymmetric particles cannot turn into standard particles
R=+1 for standard particles, and R=-1 for supersymmetric particles
Z 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 site
Join the Global Telescope Network

58. Conclusions
Fermi has already gone far beyond the sensitivity of EGRET and is discovering new classes of high-energy gamma ray sources
Fermi is opening wide a new window on the Universe – which may show us connections between the infinite and the infinitesimal
Stay tuned – the best is yet to come!
For more info:

59. Monitoring Flares from “Blazars”
Fermi scans the entire sky every 3 hours
So blazar flares can be seen on relatively short time scales
Coordinated 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)