The document provides an overview of the electromagnetic spectrum and its application in astronomy, detailing different regions such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma-rays. It explains how each type of radiation helps in understanding the universe, including the formation of celestial objects and the properties of stars and galaxies. The conclusion emphasizes the importance of further exploration and research opportunities in this area for future students.

1. Electromagnetic Spectrum in
Astronomy
Department of Physics
2022
By: Mariam Maher

2. Chapter 1
Theoretical
Concepts
Contents
Conclusion and
Recommendation
Introduction Chapter 2
Electromagnet
ic Spectrum
through
Astronomy
Chapter 3
Application in
Astronomy

3. Chapter1
Theoretical Concepts

4. 1. Electromagnetic Radiation
Vibrating
electric
charge
Electric and Magnetic fields perpendicular
to each others

5. 2. Electromagnetic
Spectrum
Low Energy
Low frequency
High Energy
High Frequency

6. 3. Thermal and non-thermal
Radiation
• Electromagnetic radiation may be thermal or non-thermal,
• Non-thermal radiation, emitted when charged particles accelerated to a very high speed,
close to the speed of light, and when deflected by the magnetic field.
• The amount of energy emitted at each wavelength not only depends on the temperature but
also on the velocities and properties of the particles responsible for the emission
• Thermal radiation or blackbody radiation emitted from the transitions of electrons
between the orbits, the energy of emitted radiation depend on the temperature.

7. Chapter2
Electromagnetic Spectrum through
Astronomy

8. Electromagnetic Spectrum
1. Radio waves 2. Microwaves 3. Infrared 4. Visible light 5. Ultraviolet
6. High-Energy
Astrophysics
X-Rays
Gamma-rays

9. 1. Radio Waves
Non-ionizing radiation
Has the longest wavelength
Lowest photon energy
Most of it can penetrate the Earth’s atmosphere
Using the “Arraying ” method
 Use parabolic antennas

10. Thermal emission
Non-thermal
emission
Observation of Radio waves coming from celestial objects help us to know the molecular information of
clouds in our galaxy and the distant galaxies, it also helped to get knowledge about the star and planet
formation.

11. 1. The Very Large Array (VLA) 2. The Very Long Baseline Array (VLBA)
• Consists of 28 radio antennas
• Have Y-shape
• Consists of 10 antennas located
across the USA

12. 2. Microwaves
It considered as a subset of Radio-frequency radiation (RFR), the highest energy part of
the RFR.
The birth of microwave astronomy started when scientists discovered the cosmic
microwave background (CMB).
 The water vapor molecules absorb most of the microwaves, so that the atmosphere is
partially transparent to most of it.
So that, scientists must put the ground-based telescopes at high altitude or construct space-based
telescopes

13. Space-based missions
1.TheCosmicBackground Explorersatellite(COBE)
• The payload is to take accurate measurements of
the radiation between 100 µm to a 1 cm over the
entirecelestialsphere.
2.TheWilkinsonMicrowaveAnisotropy Probe(WMAP)
• It measured the temperature and intensity of the CMB with much finer detail
andgreatersensitivity than the COBE
3.TheEuropeanSpaceAgency’sprobe,Planck
• Accurately determine the age of
theuniverse

14. • It has longer wavelength than the visible light but less energy
3. Infrared Radiation
• Is subdivided into three regions.
Near-infrared (NIR),
Mid-infrared (MIR),
Far-infrared (FIR).
• Ground- based telescopes that used to detect the IR radiation must be
placed at very high altitude, as mountains

15. Ground-basedtelescope
 TheUnitedKingdomInfraredTelescope(UKIRT)that locatedatMauna Kea
 TheInfraredAstronomicalSatellite(IRAS)wasthefirst
telescopesentinto space
Space-based Telescope
 Itdiscovered“interstellarcirri”,that is anenormousclouds
ofdusthangingoutbetweenthestars
 Italsoshowedthat manygalaxies arestrongradiatorsin the
IRregionofthespectrum.

16.  As the object grow hotter, they radiate energy dominated by
shorter wavelength.
4. Visible light
 Is the part of electromagnetic spectrum that is visible to the
human eyes
 The color of the stars tells us about the temperature of
that star.
Surface temperature is 5,500 ̊C Cooler
Hotter

17. HubbleSpaceTelescope  One of Hubble’s most fascinating images is the Eagle
nebula(M16), “ThePillarsofCreation”.
Columns of cold gas

18. JohannRitterexperiment
5. Ultraviolet Radiation
UV divided into three regions:
Near Ultraviolet
Far Ultraviolet
Extreme Ultraviolet

19.  The most active and the hottest objects in the
universe as sun, galaxies and stars give off large
amounts of ultraviolet energy.
The UV spectrum is also used to determine the
densities, chemical compositions, and temperatures of
thestars, galaxies andthe interstellar medium.
 The most recent UV observatory was the Galaxy
Evolution Explorer (GALEX) satellite, its aim was to
observe the history of star formation in the universe
intheUVwaveband.

20. 6. High-Energy Astrophysics (HEA)
Itfocussesonthehighestenergycosmicelectromagneticradiations,X-rays,andgamma-rays.
 Itstudytheextraterrestrialphenomenaintheirmostenergeticandextremeforms,suchasstarexplosionsand
operationonthesupermassiveblackholes.
The Supermassive blackhole in the center of M87
galaxy, captured by Event Horizon telescope
It’s done by observing the high energy electromagnetic
radiations by spaceborne telescopes.

21.  Gamma-raysandX-rays donotreachtheground
 X-ray and gamma-ray photons tend to interact with the telescope material, so it is difficult to
focus thesignal withthe conventional mirrors/lenses.
 Use the principal of “grazing incidence”, it is achieved by making the X-ray photons fall on the
mirrorsurfaces atsmall incidentangles knownasgrazingangles.

22. a. X-Rays
• Havea thousandtimes theenergy ofopticalphotons butshorter wavelength thanthatofthe
visible portion.
Celestial bodies produceX-rays in3ways:
Bremsstrahlung radiation Synchrotron radiation
Thermal or Blackbody
radiation
Non-thermal emission

23.  ChandraObservatory
• The most powerful x-ray observatory
• It Observed one of the most fascinating objects in the
sky that is the Crab Nebula which is the remnant of a
supernova explosion.
• Another great observation is the center of Centaurus A
(Cen A, NGC 5128) galaxy.
Crab nebula

24. b.Gamma-rays
• It have the lowest wavelength of all other radiation, and the highest energy.
• The most powerful space telescope for the detection of the cosmic gamma rays and the
study of the universe in this region is the Fermi Space Observatory.
The Gamma-ray sky The Fermi Bubbles, it is formed as result of an explosion from the
monster black hole at thecenter of our galaxy

25. Chapter3
Application in Astronomy

26. TheSun
Very high Temperature of
1 million degree
The atmosphere
is very dense
The Radio Sun
Active regions
Infrared Sun

27. Gamma Ray Sun
• This Image is combined from three telescopes, it
shows an impressive coronal mass ejection leaving
thefarsideofthesun.
• This massive cloud raced away and likely
accelerated particles that later produced gamma
rays.

28. Conclusion and Recommendation

29.  After getting through the explanation of the different regions of the
electromagnetic spectrum (EM), its importance, and uses in astronomy to
discovery and study the temperature, structure and composition of stars and
galaxies in the universe, and the explanation of the most fascinating phenomena in
the universe.
 My Research was as an overview on the Electromagnetic spectrum in
Astronomy, but each one of the regions is a research field. So, I would like to
recommend that the students in the next years may have the opportunity to work
in points of research related to this topic.

30. Thank you