Introduction and Overview 1.X-ray/Gamma-ray Astronomy. 2.The Great Observatories. 3.Chandra. 4.High Energy Astrophysics 5.Sample Sources Professor George F. Smoot Extreme Universe Lab, SINP Moscow State University

Great Observatories

Opacity of Atmosphere

Versus characteristic temperature

characteristic temperature

Chandra

X-ray Producing Collision

Synchrotron Radiation

Inverse Compton Scattering

Atomic Emission

Birth of an X-ray

Martin Elvis, Chandra X-ray Center Chandra: Revolution through Resolution

The Chandra X-ray Observatory Launched 23 July 1999 revolutionized X-ray astronomy, and all of astronomy. What is X-ray Astronomy? What is Chandra? Why has Chandra done its job so well? And what exactly has Chandra done?

When we look up at the night sky we see it filled with stars Outside the narrow range of colors our eyes are sensitive to, something quite different dominates the night sky… What is X-ray Astronomy?

Powerful sources of X-rays A power source entirely different from the nuclear fusion that drives the Sun and stars …and much more efficient X-ray Astronomy tries to find out what could cause such extraordinary power Rosat All Sky Survey (MPE) X-ray map of the whole sky: 100,000 `sources ’

Compton gamma-ray Observatory Chandra Hubble MMT Sub-millimeter array VLA range of wavelength in astronomy million billion between shortest & longest Whipple 10 meter X-rays Visible X-ray Astronomy studies short wavelength light from the Universe 1/1000

Compare Visible light and X-rays: “ 1000 times ” X-rays have:  Wavelengths: 1/1000 visible light  nm (1-60A) vs. 500 nm (5000A)  Energies: 1000 x visible light  “ keV ” instead of “ eV ” (electron volts)  About 0.02 Joules/photon  Temperatures: 1000 times hotter  10 million degrees vs. 10 thousand degrees for stars  E=kT (k= Boltzman ’ s constant, 1.398x10 -9 J/K) SNR G (Hughes et al.)

What gets so hot? Surely not much can get so hot as a million degrees? Oh yes it can… Sounds obscure but … gravity power is the most common source of X-rays in the sky Explosions : Supernovae and their remnants Particles moving near the speed of light in magnetic fields Matter falling into deep gravitational wells Supernova 1987aCrab NebulaAbell 2029 Cluster of galaxies Andromeda nearest galaxy ¼ sun –  centauri sun  centauri sun

40 Years of X-ray Astronomy: 1 billion times more sensitive Good for 1 (one) Nobel Prize good enough for my thesis 1999 Sco X-1: the brightest source of X- rays in the sky NGC3783: a quasar appearing 10,000 times fainter than Sco X Chandra Distant galaxy 100,000 times fainter than NGC3783 Moon to scale Resolution is the key

X-ray astronomy took just 40 years to match 400 years of optical astronomy ” 1”1” 10 ” 100 ” Galileo Hubble Space Telescope Dawn of History Optical Astronomy X-ray Astronomy Chandra Year Sharpest Detail detectable Chandra takes X-ray Astronomy from its ‘ Galileo ’ era to its ‘ Hubble ’ era in a single leap

What is Chandra? Chandra is the greatest X-ray Observatory ever built Orbits the Earth to be above the atmosphere (which absorbs X-rays, luckily!) Goes 1/3 of the way to the Moon every 64 hours (2 2 / 3 days) Chandra takes superbly sharp images: ‘ high resolution imaging ’

X-ray Telescopes are different Chandra ’ s mirrors are almost cylinders X-rays don ’ t reflect off a normal mirror – they get absorbed. Only by striking a mirror at a glancing angle, about 1 o, do X-rays reflect. Then they act like visible light and can be focused This makes for looooooooong telescopes

Chandra is as big as a moving truck 10 meters (32 ft) from mirror to detector, 1.2 meters (4ft) across mirror …but focuses X-rays onto a spot only 0.025mm (1/1000 inch) across That ’ s why Chandra is powerful

Chandra detects individual photons Uses Wave-Particle Duality of Light …but can disperse the incoming X-ray light: Light as Waves CCD detectors count each X-ray individually Delicate gold gratings diffract the light each X-ray knocks free enough electrons to detect as a pulse of electricity Light as particles Chandra provides a great example of how Quantum wave/particle duality works in a real machine

Chandra ’ s sharp focus revolutionizes our understanding Best X-ray image of whole sky (ROSAT) Best X-ray images before Chandra (ROSAT) Chandra images Earth observing satellite equivalents of … SPACE IMAGING Any sign of life?What’s this odd thing?I get it!

Like looking up the answers at the back of the book Chandra has solved 20 year old mysteries in just one shot: Yes – the background X-ray light is made up of contributions from millions of quasars No – gas is not pouring down onto the galaxy at the center of a cluster of galaxies. Something stops it, but what? Yes -- Our Milky Way sits in a bath of hot gas stretching to the Andromeda galaxy and beyond Yes – quasars have hot winds blowing from their cores, at 2 million miles per hour

…but also being given a whole new SAT test, without taking the class Antennae – colliding galaxies Nest of super-bright black holes in binaries – bigger than any star? Centaurus A – nearest quasar X-ray ‘ smoke ring ’ from explosion in core? 2 examples: What are we looking at?

Chandra ’ s Revolution through Resolution continues… Antennae: Deep Exposure Chandra set to run for 5 more years & may last much longer Deeper looks show more and more detail, more and more surprises

High energy astrophysics typically deals with x-rays and higher energy radiation. It also deals with high energy neutrinos and other particles such as protons, electrons, positrons etc. High energy radiation is produced by objects at high temperatures and/or relativistic particles. 1 ev = 10,000 K, 1 kev = 10 7 K This usually requires compact objects such as white dwarfs, neutron stars or blackholes with deep gravitational potential. V esc =(2GM/R) 1/2 approaching c Or R not much greater than the Schwarzschild radius: 2 GM/c 2 (2.95 km for a solar mass object). High Energy Astrophysics

Roentgen historic X-ray

E=h = k T ==> x-rays probe K and gamma-rays > 10 9 K Eddington Luminosity: 1.3x10 38 erg/s for 1 M o. (derive the Eddington limit) Optically thick blackbody radiation in x-ray requires a compact object! T as a function of object mass, radius (in units of Schwarzschild radius) and Luminosity (in units of Eddington luminosity), is given by: T ~ 7 kev (L/L_Edd)^{1/4} (R/R_s)^{-1/2} (M/M_sun)^{-1/4} Thus if the radiation is black-body and luminosity is close to Eddington, Then x-ray temperature is reached provided that R\sim R_s and M is not much greater than M_sun. This result is violated, as it often is, when the radiation is non-thermal. X-ray astronomy: 0.1 to 100 kev Gamma-ray astronomy: >100 kev.

White dwarfs: R~10,000 km, V esc ~0.02 c, density~ 10 6 g/cc (Nuclear reaction is more efficient source of energy than the PE release of in-falling gas on WDs) : Adams-- Sirius B has M~ 1M o, T~ 8000 K, R~10,000km : Adams confirmed M & R by measuring gravitational redshift -- z ~ GM/(R c 2 )= : F-D statistics discovered. Fowler applied it to model WDs : Chandrasekhar: WD model including relativity; mass limit : Nobel prize to Chandrasekhar. Brief Property and History of Compact Objects

: Nobel prize to Ryle (aperture synthesis) Hewish (pulsars). Neutron Stars : Chadwick --discovers neutrons :Baade & Zwicky suggested neutron-stars, and postulated their formation in supernovae : Hewish, Bell et al. Discover radio pulsars : Gold proposed rotating NS model : Hulse & Taylor discover binary pulsar PSR : Nobel prize to Hulse & Taylor. Neutron stars: R~15 km, V esc ~0.32 c, density~ g/cc (Nuclear reaction is much less efficient source of energy than the PE release of in-falling gas on NSs - gravitation).

1795: Laplace noted the possibility of light not being able to escape. 1915: Einstein ’ s theory of general relativity. 1916: Schwarzschild -- metric for a spherical object 1963: Kerr --metric for a spinning BH. 1972: Discovery of Cyg X : Miyoshi et al. -- NGC : Eckart & Genzel -- (Sgr A*) Galactic center. 2002: Nobel prize in physics to Giacconi (x-ray astronomy). Schwarzschild radius = 2.95 km M/M o Efficiency of energy production 6% to 42%. Black Holes

1. Derivation of the Eddington limit. 2. We found that bright sources of high energy photons are typically compact objects such as WD, NS or BH. High speed, strong, shocks are another way of generating high energy photons; however high speed shocks are usually produced when compact objects form eg. SNe, GRB etc. (an exception is x-rays from clusters.) Summary

(1 A o = 12.5 kev) Atmospheric Transmission

Eary All Skly Catalog

EUV picture of the Sun at 171 A = 74 ev (SOHO) Corona & several Active regions are visible Coronal luminosity: ~ erg/s EUV picture of the Sun at 171 A = 74 ev (SOHO)

Corona, active regions and a flare are visible EUV picture of the Sun at 195 A = 65 ev from SOHO

at 195 A = 65 ev Sun approaching Solar Max

Accretion to create X-ray binary

An artist’s view

Crab nebula Blue: x-ray Red: optica Green:radio Luminosity ~ erg/s (mostly x-ray & gamma) Synchrotron radiation: (linear polarization of 9% averaged over nebula). Electrons with energy > ev are needed for emission at 10 kev; lifetime for these e ’ s < 1 year. So electrons must be injected continuously & not come from SNe. (Plerion) Crab Pulsar

Plerion: is derived from the Greek word “ pleres ” which means “ full ”. Crab nebula is the remnant of Sne explosion (perhaps type II) observed by the Chinese Astronomers in 1054 (July 4th). The pulsar at the center has a period of 33milli-sec. Crab redux Crab shows pulsed emission from radio to optical to >50 Mev! Moreover, The pulse shape is nearly the same over this entire EM spectrum, suggesting A common origin for the radition which is believed to be synchrotron (curvature radiation). The radio is produced not too far away from the Neutron star (within 5-10 radii) and high energy pulsed radiation is Likely produced near the light cylinder. The bolometric luminosity is pulsed radiation is about a factor 100 smaller Than nebular radiation; pulsed radio is smaller than total pulsed radiation By a factor of 10^4.

Age 300 yr (1670 AD) SNe II remnant Mass of x-ray gas solar mass. X-ray luminosity: 3.8x10 36 erg/s SN remnant: Cas A (3-70 kev; Chandra) Plerion

Pulsar wind nebula G292(Chandra 3-80 kev) (Plerion)

X-ray luminosity: ~ erg/s. The radiation is produced by shock heated gas at ~ 10 9 K via bremsstrahlung. Note the bright (blue) Pulsar nebula at the Center. Produced in SN of 386 AD SN remnant G in x-ray (Chandra)

Gamma-ray burst: note the relativistic jet, and supernova explosion

Chandra x-ray obs. (x-ray produced by IC of CMB-photons with jet e - s) Obs. jet size~30 kpc AGN jet from the quasar GB ( distance 4Gpc)

HST & 6 cm VLA VLA: 6 cm (distance ~ 2.5 Mpc) Radio lobe size ~ 200 kpc! The radio lobes are fed by relativistic jets; we see only one sided jet due to relativistic beaming. Centaurus A

NGC 4261

Blue: Chandra x-ray SDSS optical Yellow: Compact group of interacting galaxies. Gas is stipped and shock heated to 6 million K produces x-rays. F is a foreground galaxy. So the cluster (A, B, D & E) is in fact a quartet. Stephan ’ s Quintet

Chandra x-ray; ~ 2 kev HST - optical image (note lensing of background gals) Abel Gpc MS (1 Gpc) Cluster X-ray & Optical

SN remnant G

M87 jet