Energy High Astrophysics
Observatories & Instrumentation
Giampaolo Pisano
Jodrell Bank Centre for Astrophysics - University of Manchester
[e-mail]
March 2009
The great observatories
- Brief summary of some of the current observatories and related techniques in the wavebands:
- Radio - Millimetre and Sub-millimetre - Infrared - Optical - X-ray - Gamma-ray
Future observatories at the end of the course
Observatories across the e.m. spectrum
Radio
mm/sub-mm
FIR
MIR
NIR V
NUV
UV
Soft X-ray
Hard X-ray
-ray
10 3
10 2
101
10
10 1 10 2 10 3 10 4 10 5 10 6 10 7
10 8 10 9 10 10 10 11 10 12
[m ]
The atmospheric windows
Atmosphere Trasparency
Radio mm/sub-mm
FIR MIR NIR V
NUV
UV
Soft X-ray
Hard X-ray
-ray
10 3
10 5
10 2
10 6
101
10 7
10
10 8
10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12
10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18 10 19 10 20
[m ]
[ Hz ]
Altitude [km]
Minimum altitude for transparent atmosphere
Sea Level
Angular resolution of a telescope
- In general, the angular resolution of an optical system is:
: Wavelength D : Telescope diameter
1.22
D
- Optical system angular resolution
Example - Jodrell Bank dish operating at:
= 408MHz D = 76m
3 108 0.735m = = 8 4.08 10 c
0.735 1.22 = 0.0116 76
0.66 deg 40 arcmin
A bit bigger than the Moon angular size
Radio wavelengths
Radio mm/sub-mm
FIR MIR NIR V
NUV
UV
Soft X-ray
Hard X-ray
-ray
10 3
10 5
10 2
10 6
101
10 7
10
10 8
10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12
10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18 10 19 10 20
[m ]
[ Hz ]
Radio waveband - Technology:
3MHz 30GHz 100m 1cm
0.01eV E 100eV
T ~ (10 4 1) K
- Single radio antennas: need to be extremely large - Radio interferometry: antenna arrays (aperture synthesis) - Observations: - 30 GHz -10 MHz : Atmosphere Radio window 1 - 10 MHz : very difficult reflection from ionosphere reflection interplanetary/interstellar plasmas
< 1 MHz : even more difficult
Radio Astronomy 1/5
Jodrell Bank: 76 m Effelsberg: 100 m Green Bank: 100 m
- Frequencies: ~ 300 MHz - 86 GHz - Resolution: 10 arcsec - 30 arcmins - Observation: galactic plane, SNR, neutral H, molecular lines, radio galaxies, quasars, pulsars, etc.
Radio Astronomy 2/5
- Arecibo
(Arecibo, Puerto Rico)
- Frequencies: ~ 300 MHz - 30 GHz - Diameter: 305 m World largest filled-aperture telescope - Technique: Steerable beam by means of moving receiver
Radio Astronomy 3/5
Radio Interferometry
- Technique: Observation of the same object made simultaneously by many telescopes connected together (need phase information) - Resolution: Vast increase on angular resolution emulation of a telescope of the size of the array - Telescopes: Need many telescopes and baselines to have good quality images
Radio Astronomy 4/5
Very Large Array (VLA)
(NRAO New Mexico)
- Frequencies: 73 MHz - 50 GHz - Telescopes: 27 independent antennas, each with 25 m diameter (sensitivity equivalent to a 130 m diameter dish) - Resolution: 0.05 - 700 arcsec (equivalent to a 36 km antenna) - Technique: Aperture synthesis interferometry - Observations: AGN, jets, pulsars and GRBs
Radio Astronomy 5/5
- VLBI Arrays in the world
Galaxy M87
- Technique: - Resolution:
Very Long Baseline Interferometry Extremely high micro-arcsec
Higher than any other astronomical instrument - Data from each antenna recorded using atomic clocks and analysed later
Millimetre and Sub-millimetre wavelengths
Radio mm/sub-mm
FIR MIR NIR V
NUV
UV
Soft X-ray
Hard X-ray
-ray
10 3
10 5
10 2
10 6
101
10 7
10
10 8
10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12
10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18 10 19 10 20
[m ]
[ Hz ]
Millimetre and sub-mm - Technology:
30GHz 3THz 10mm 0.1mm 0.1meV E 10meV T ~ (1 100) K
- Solid state mixers for heterodyne receivers - Bolometers for continuum receivers - Observations: - <1mm : strong absorption bands atmosphere (water vapour, CO2, ...) - Windows available at 0.8, 0.65, 0.45 and 0.35 mm - High dry sites, aircrafts, balloons or satellites
Millimetre and sub-mm Astronomy 1/3
- Cosmic Background Explorer (COBE)
- Observation: Black-body spectrum & 7 degrees scale full sky anisotropies Nobel Price in 2006
Millimetre and sub-mm Astronomy 2/3
- Wilkinson Microwave Anisotropy Probe (WMAP)
- Frequencies: 23 - 94 GHz - Observation: Full sky CMB anisotropies at small angular scales and Temperature anisotropy - Polarisation correlation
Millimetre and sub-mm Astronomy 3/3
- Planck Mission (2009)
- Frequencies: LFI: 30 70 GHz ; HFI: 100 - 857 GHz - Observation: Full sky CMB anisotropies and E-Modes polarisation
Infrared Wavelengths
Radio mm/sub-mm
FIR MIR NIR V
NUV
UV
Soft X-ray
Hard X-ray
-ray
10 3
10 5
10 2
10 6
101
10 7
10
10 8
10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12
10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18 10 19 10 20
[m ]
[ Hz ]
Infrared waveband - Technology: - Silicon detectors - Observations:
3THz 300THz
100m 1m
0.01eV E 1eV T ~ (102 10 4 ) K
- Atmosphere windows at 1.2, 1.65, 2.2, 3.5, 5, 10, 20 and 30 m. - Atmosphere as strong thermal emitter (a 300K Black-Body peaks at 10m) - High dry sites, balloons, aircrafts or satellites
Infrared Astronomy 1/3
- Spitzer Space Telescope (2003)
- Wavelength: 3-180 micron - Observation: interstellar dust, star formation, extra-solar planets, young stellar objects, etc. - Characteristics: - Largest IR telescope ever in space - Unprecedented resolution & sensitivity
Infrared Astronomy 2/3
- Spitzer Space Telescope
- Revealed inner dust ring in galaxy M31 evidence of a violent head-on collision with companion dwarf galaxy M32 happened 210 My ago.
Infrared Astronomy 3/3
- Spitzer Space Telescope
- Object: Supernova Remnants images superposition at different wavelengths - Infrared emission: warm dust emission from dust heated by the primary blast wave
Optical wavelengths
Radio mm/sub-mm
FIR MIR NIR V
NUV
UV
Soft X-ray
Hard X-ray
-ray
10 3
10 5
10 2
10 6
101
10 7
10
10 8
10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12
10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18 10 19 10 20
[m ]
[ Hz ]
Optical waveband - Technology:
3 1014 Hz 1015 Hz 1m 300nm 1eV E 4eV T ~ 3 10 4 K
- Photographic emulsions (few % efficiency) - Charge Coupled Devices (CCDs) (70% efficiency) (small field of view) - Observations: - Optical window wider than our eyes sensitivity (from ~ 400nm to 700 nm ) - < 320 nm : absorption ozone begins
Optical Astronomy 1/3
- Hubble Space Telescope (HST)
- Largest telescope in orbit - It revolutionised Optical Astronomy but greatly contributed to HEA discoveries
Optical Astronomy 2/3
Mauna Kea - Keck telescope (4145 m)
- Telescope: Two twin telescopes 10 m each in diameter World largest optical and infrared telescopes - Resolution: 0.04 - 0.4 arcsec Interferometer mode: 5 - 24 milliarcsec (infrared) - Techniques: - Adaptive optics mirrors composed of 36 hexagonal segments - Interferometer the two telescope can operate together
Optical Astronomy 3/3
- Very Large Telescope (VLT) - Chile (2635 m)
- Telescope: Four 8.2 m diameter telescope array, plus additional telescopes - Wavelengths: From Infrared to UV - Resolution: will be 0.002 arcsec at 2um - Techniques: Adaptive optics & different interferometric modes (VLTI)
Ultraviolet wavelengths
Radio mm/sub-mm
FIR MIR NIR V
NUV
UV
Soft X-ray
Hard X-ray
-ray
10 3
10 5
10 2
10 6
101
10 7
10
10 8
10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12
10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18 10 19 10 20
[m ]
[ Hz ]
Ultraviolet waveband - Technology:
1015 Hz 3 1016 Hz
300nm 10nm
4eV E 100eV T ~ (105 106 ) K
- NUV: 300nm > >100nm : similar to optical waveband - UV: 100nm > >10nm : reflection at grazing incidence necessary - Observations: - Atmosphere opaque because of ozone absorption - Rockets and satellites - < 91.2 nm : Hydrogen Lyman limit interstellar gas opaque (neutral H clumps)
The great observatories
- Brief summary of some of the current observatories and related techniques in the wavebands:
- Radio - Millimetre and Sub-mm - Infrared - Optical X-ray - - Gamma-ray
X-ray wavelengths
Radio mm/sub-mm
FIR MIR NIR V
NUV
UV
Soft X-ray
Hard X-ray
-ray
10 3
10 5
10 2
10 6
101
10 7
10
10 8
10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12
10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18 10 19 10 20
[m ]
[ Hz ]
X-ray waveband
- Technology:
3 1016 Hz 3 1019 Hz 10nm 0.01nm 0.1KeV E 100KeV T ~ (106 109 ) K
- Detectors similar to particle physics detectors - Proportional counters, scintillation detectors, CCDs - Telescopes as collimators
- Observations:
- Wholly above atmosphere because of photoelectric absorption of X-rays by atoms and molecules of Earth atmosphere.
X-ray Astronomy 1/21
Wilhelm Conrad Roentgen discovered Roentgen or X-ray emission in November 1895
X-ray Astronomy 2/21
1948: First evidence of solar corona X-ray emission
X-ray Astronomy 3/21: Detectors
Proportional Counter
( & Mechanical Collimator ) X-Ray Photon Energy < 20keV
- X-ray photons ionise atoms gas - Electrons drift to the central wire-anode (2000 V) - Further ionisation - Pulse of electrons avalanche of electrons close to the anode electronics count Spectrum
Number electrons proportional to X-ray photon energy
X-ray Astronomy 4/21: Detectors
Scintillation Counter
Hard X-Ray
Scintillators
Balloon-based mission 50 Km altitude Photon Energies: 20 - 200 keV
- Gas proportional counter not massive enough to stop high energy photons - Solid state detector Crystal of sodium iodide or caesium iodide scintillation detected by a photomultiplier - Photon absorbed by an atom of the crystal and part of this energy immediately reappears as a pulse of light Amount of scintillation light proportional to X-ray photon energy
X-ray Astronomy 5/21
- Discovery and identification of Tau X-1
(Boyer 1964)
- 1963: Discovery of Tau X-1 - 1964: Identification with Crab Nebula using Moon coverage Source emission is diffused Pulsar account only for 5% X-ray emission
X-ray Astronomy 6/21: Detectors
Rotation Modulator Collimator
Incident X-rays Wires of first grid
Strips of Sky seen by collimator
Direction of Maximum transmisison
Wires second grid
Wire
Thin window Proportional Counter
- Wire-grids defining a set of bands in the sky - Rotating the spacecraft - Accuracy at arcmin level modulated count rate for a point source
X-ray Astronomy 7/21
- Sco X-1 localisation
Rotation Modulation Collimator data
- It was very difficult to identify the object associated with Sco X-1 - The Modulation Collimator technique allowed to find the counterpart
X-ray Astronomy 8/21
es
transients) mission
X-ray Astronomy 9/21
- Most important satellite missions
X-ray Astronomy 10/21
- ROSAT
- Optics: Wolter type mirrors for grazing incidence reflection - Detector using photoelectrical absorption in gas - Anti-coincidence circuits to check for charged particles - Detector window produced artefacts
X-ray Astronomy 11/21
- ROSAT results
- Resolution: 1 arcmin - First deep all sky survey in soft X-ray followed by point source phase
X-ray Astronomy 12/21
Chandra (NASA)
Dedicated to the Astrophysicist S. Chandrasekhar
- Optics: Wolter type mirrors and CCDs detectors - Best angular (0.5arcsec) and spectral resolution ever; Energies: 0.1-10 KeV - Capable to measure emission variations as short as 16 s (bursts) - Discoveries: stellar black-holes, shock accelerations in SNRs, X-rays from AGN jets
X-ray Astronomy 13/21
- Chandras elliptical orbit
- Cosmic rays
extremely energetic particles
can pass through the detectors
- High energy protons and electrons are trapped in the van Allen radiation belts It is better to operate outside the radiation belt
X-ray Astronomy 14/21
- Wolter type X-ray Mirrors
- A mirror used at normal incidence would scatter the x-ray photons - Wolter type I X-ray mirrors are used in Chandra and XMM-Newton
X-ray Astronomy 15/21
Chandra: X-ray Mirrors
- Four nested Zerodur glass mirrors, polished, coated with iridium on a binding layer of chromium
X-ray Astronomy 16/21
XMM-Newton (ESA)
X-Ray Multi-Mirror Mission
- CCDs as detectors - Optics: three independent X-ray telescopes pointing same direction - Largest collecting area ever Highest sensitivity (5 x Chandra) - Additional Optical-UV telescope - Angular resolution: 6 arcsec - Results: detection heavy elements in GBRs, mapping elements SNRs
X-ray Astronomy 17/21
XMM-Newton: Optics
- Grazing incidence reflection gratings spectrometers
X-ray Astronomy 18/21
X-MM Newton: X-ray Mirrors
- Each mirror system has 58 Wolter gold plated mirrors less than 2 mm thick ! - Separation between mirrors 1-2mm - Surface accuracy better than 0.1 nm !
X-ray Astronomy 19/21
X-ray Mirrors
- Grazing geometry implies large focal length
Big satellites
X-ray Astronomy 20/21
XMM-Newton: CCD detectors
- CCD (Charge Coupled Device) developed in UK and Germany - Semiconductor device giving both spectral and imaging information - Simpler versions used in digital cameras
X-ray Astronomy 21/21
- Instrum...