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