Observing the Universe
From the Lens to Multi-wavelength Astronomy
Outline
History
Modern Observatories
The Electromagnetic Spectrum
Multi-wavelength Astronomy Radio Astronomy Sub-mm, IR Astronomy X-ray Astronomy Gamma-ray Astronomy
In the beginning...
~500 bc
Planetary Motion http://www.syz.com/DU/mac/animations/planetarymotion.html
Post-Renaissance
Developments
Dutch Lens Maker
Invented the Telescope in 1608
Hans Lippershey (1570-1619)
Galileo Galilei (1564-1642)
Italian Mathematician who laid the foundations of modern science and established the Copernican Model of Solar System
Sir Isaac Newton (1642-1727)
British Mathematician who (amongst many great achievements) invented the reflecting telescope and discovered the spectral nature of light
The Spectral Nature of Light
The Development of Astrophysicsand Modern Astronomy
(or build a bigger telescope)
Sir William Herschel (1738-1822)
18” Reflector
Catalogued the sky by eye
Earl of Rosse (1800-1867) and the his 72” Leviathan
Sir William Huggins (1842-1910)
The first astrophysicist
Observed the spectra of Herschel's nebulae
Photographic Developments
Modern Astronomy
In the 20th Century all new observatories were built on mountain tops to evade light pollution and
improve the seeing.
z
z0
nn+dn
n0
z+dz
Atmospheric Refractionand Adaptive Optics
Hubble Space Telescope
2m reflector
The Electromagnetic Spectrum
Blackbody Radiation
As the temperature of an object increases its brightness will increase as T4 and its peak wavelength will decrease as T-1.
Therefore, hot things emit shorter wavelength radiation, e.g. X-rays. Whereas cooler things emit longer wavelength radiation e.g. IR.
Karl Guthe Jansky (1905-1950)Grote Reber (1911-2002)
Radio Astronomy
∝ / D
Radio Interferometry
Radio Astronomy Observations
Radio galaxies, and Quasars
Radar Astronomy
or Active Radio Astronomy
transmit radio waves to nearby planets and asteroids to determine distances and shapes
just like aircraft radar
X-ray Astronomy
XMM Satellite
X-ray Astronomy – Observations
Gamma-ray Astronomy – INTEGRAL Satellite
x
I
Coded Mask
Point-sources
Detector
1 2
Shadowgramof ps 1
Shadowgramof ps 2
Gamma-ray Astronomy – Coded Mask Imaging
Cannot focus gamma-rays by reflection, so use coded masks. A pattern of opaque and transparent elements produces a shadowgram. Decode image by moving pattern over shadowgram with image processing software.
Required to observed the highest energy gamma-rays
Gamma-ray Astronomy – Cerenkov Detectors