DEPARTMENT OF PHYSICS AND ASTRONOMY
3671: Multi-wavelength Astronomy
Dr. Matthew Burleigh
www.star.le.ac.uk/~mbu
The Electro-magnetic Spectrum
100MeV 100keV 0.1keV
1000A 5000A 1micron
Gamma Ray Xray EUV UV Optical IR
1cm
Micro-wave Radio
http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
Dr. Matt Burleigh
100m
Multi-wavelength Astronomy
Waveband
Wavelength
/Energy
Temperature
What can be
studied
Gamma rays
100keV-100MeV
>108K
accretion disks, gammaray bursts
X-rays
<1-100keV
106-108K
Hot gas in clusters of
galaxies, stellar coronae,
accretion disks,
Ultra-violet
900-3000A
104-106K
Hot stars, white dwarfs,
instellar gas
Optical
3000-10,000A
103-104K
Sun-like stars.
Infra-red
1-100 micron
10-103K
Dust, planets, brown
dwarfs
Microwave
1cm
<10K
Background radiation of
the Universe (remnant of
Big Bang)
Radio
>1m
<10K
Radiation from electrons
moving in a magnetic
field: pulsars
Dr. Matt Burleigh
Wavelength scales
• Rather annoyingly, astronomers use a variety of
wavelength scales depending on the waveband
involved (see diagram on last slide)
– Radio astronomers use m and cm
– Infra-red astronomers use microns
– Optical and UV astronomers use Angstroms or nanometers
– X-ray and gamma ray observers switch to an energy
scale, i.e. in electron-Volts
Dr. Matt Burleigh
Conversion factors
• E = hn = hc/l in Joules
• 1eV = 1.6x10-19J
• Wavelength l in Angstroms -> Energy in keV
– keV = 12.4/l
• 1Angstrom = 10-10m
• 1 nm = 10-9m
• 1mm (micron) = 10-6m = 10,000A
– Point at which optical becomes infra-red!
Dr. Matt Burleigh
What is multi-wavelength astronomy?
• Astronomers used to think of themselves as
either ‘optical’, ‘radio’, ‘IR’ or ‘Xray’
• But modern astrophysics requires studying an
object across the whole EM spectrum
• Different physical processes can be studied
at different wavelengths
• Xray, gamma ray and radio astronomers need
to identify their sources with optical
counterparts
http://imagine.gsfc.nasa.gov/docs/science/know_l1/multiwavelength.html
Dr. Matt Burleigh
The Milky Way: Optical
Stars,
Dust
lanes
Dr. Matt Burleigh
The Milky Way: IR
See
through
dust
Dr. Matt Burleigh
The Milky Way: Xray
Hot gas
Dr. Matt Burleigh
Andromeda (M31): Optical
Dr. Matt Burleigh
Andromeda (M31): IR
Star forming
regions in
spiral arms
Dr. Matt Burleigh
Andromeda (M31): UV
Young,
hot stars
in spiral
arms
Dr. Matt Burleigh
Andromeda (M31): Xray
Xray binaries,
supernova
remnants, hot gas
Dr. Matt Burleigh
Orion in the optical and xrays
Optical
Dr. Matt Burleigh
Xrays
Multi-wavelength study of Xray sources
Dr. Matt Burleigh
Binary stars: Sirius A & B
Chandra: Xrays
Optical
photograph
Dr. Matt Burleigh
Binary white dwarfs revealed in the
ultra-violet
HST
Optical
Dr. Matt Burleigh
UV: white dwarf
companion (star Ab)
Brown dwarfs & extra-solar planets in
the infra-red
HST IR image
Gl 229:
Red dwarf + brown
dwarf companion
Dr. Matt Burleigh
Brown dwarfs & extra-solar planets in
the infra-red
J band (IR) image from Gemini North of a nearby white dwarf
Estimate a 10Mjup planet would have a magnitude of J~20.5
Dr. Matt Burleigh
Effect of atmosphere
Band
Gamma rays
Xrays
UV
Optical
Dr. Matt Burleigh
Stopped by
Observe
from
Ionisation,
compton
scattering
Ionisation O2,
N2
O2, N2, O3
disassociation
Balloon,
space
Clear!
Ground
Space
Space
Example
Effect of atmosphere
Band
Infra-red
<10microns
Stopped by Observe
from
CO2, H2O
but clear
bands
mountain
Infra-red >20 Molecular
microns
absorption
Space,
aircraft
Sub mm
Molecular
absorption
Mountain
Radio
Clear!
Ground
Dr. Matt Burleigh
Example
Types of observation
• Photometry – the brightness of an object
in a certain waveband
• Time-resolved photometry -
Dr. Matt Burleigh
Types of observation
• Spectroscopy -
http://imagine.gsfc.nasa.gov/docs/science/how_l1/analysis.html
Dr. Matt Burleigh
Course Outline
• Overview: Today
– The electro-magnetic spectrum
– What is multi-wavelength astronomy?
– Observing at different wavelengths
Dr. Matt Burleigh
Course Outline
• Basic physical processes: Tomorrow
– Attenuation of radiation by matter
• (important to IR, UV and X-ray)
– BB radiation
• (how to decide which waveband to observe in)
• Emission processes
Dr. Matt Burleigh
Optical astronomy
• Telescopes
– Modern telescope design
– Diffraction limit, resolution
– Seeing
– Adaptive optics
• Detectors
– CCDs
Dr. Matt Burleigh
Optical astronomy
• Techniques
– Spectroscopy: grating equation, resolution
– Imaging: magnitude system, filters, colour
Dr. Matt Burleigh
Infra-red Astronomy
• Infra-red
– Absorption by and emission from dust
– Interstellar reddening
– Detectors, telescopes and satellite
missions
Dr. Matt Burleigh
Ultraviolet Astronomy
• Ultraviolet
– Satellite Missions
– Interstellar absorption
– Curve of growth
Dr. Matt Burleigh
Radio Astronomy
• Radio astronomy
– Differences between optical and radio
– The radio telescope
– Interferometers
– Examples: Pulsars, radio galaxies, neutral H
Dr. Matt Burleigh
The High-Energy Universe
• X-ray astronomy
– History
– X-ray detectors
– Absorption processes
– X-ray emitting objects
– Accretion onto compact objects
– Black holes and the Eddington luminosity
Dr. Matt Burleigh
Complimentary courses
•
•
•
•
•
•
4326 Interaction radiation/matter – Wynn
3611.2 Galaxies – O’Brien
3611.1 Active Galaxies – Stewart
3631.2 Interstellar Medium - Jameson
3631.1 Binary stars – Wynn
3677 Life in the Universe –
Raine/Sims/Burleigh
• 4424 High Energy Astrophysics –
Ward/Watson
Dr. Matt Burleigh
Lecture timetable
• Thursdays 10.30am LRB
• Fridays 1.30pm LRB
3rd Yr Support course TBD
Dr. Matt Burleigh
Books
• Modern Astrophysics – Carroll & Ostlie
• High Energy Astrophysics – Longair
(Cambridge University Press) ISBN 0-52138873-6
• Active Galactic Nuclei – Robson
(Wiley) ISBN 0-471-96050-0
• Active Galactic Nuclei – Peterson
(Cambridge University Press) ISBN 0-52147911-8
• Observational Astronomy - Kitchin
Dr. Matt Burleigh