Transcript IR Astronomy - Viraj Jayaweera

P.V.V. Jayaweera
Institute of Fundamental Studies
Hantana Road, Kandy.
Discovery of Infrared
Sir Frederick William
Herschel (1738-1822)
musician and an
astronomer
famous for his discovery
of the planet Uranus in
1781
Discover “calorific rays”
in 1800 later renamed as
“Infrared rays”
What is Infrared (IR) ?
(the prefix infra means `below‘)
The electromagnetic spectrum includes gamma rays, X-rays,
ultraviolet, visible, infrared, microwaves, and radio waves. The
only difference between these different types of radiation is
their wavelength or frequency.
Infrared is usually divided into
3 spectral regions
Visible near-IR
= 0.75 m
0.8–5 m
mid-IR
5-40 m
Micro
Far-IR wave
40-250 m
Cannot see (human eye)
Some animals can "see" in the infrared. For example, snakes in
the pit viper family (e.g. rattlesnakes) have sensory "pits,"
which are used to detect infrared light. This allows the snake
to find warm-blooded animals.
The primary source of infrared radiation is heat or thermal
radiation.
This is the radiation produced by the motion of atoms and
molecules in an object.
Any object which has a temperature above absolute zero (0 K)
radiates in the infrared.
person
holding burning match
Infrared image of
Orion
Landing space shuttle
Cat
Human & vehicle at total darkness
thermal image in white=hot mode
Human Suspect climbing
over fence at 2:49 AM in
total darkness
same image in Black=hot mode
Suspect attempting to burglarize vehicle
at 1:47 AM in total darkness.
IR Astronomy
Infrared Astronomy is the detection and study of the
infrared radiation (heat energy) emitted from objects in
the Universe.
•Viewing the Invisible
•Exploring the Hidden Universe
•Detecting Cool Objects
•Exploring the Early Universe
•Adding To Our Knowledge of Visible Objects
Infrared Windows
Object in the Universe sends us light at all wavelengths of the
electromagnetic spectrum. However, most of this light does not reach
us at ground level.
Viewing the Invisible
The Universe sends us a tremendous amount of information in the form of
electromagnetic radiation (or light). Much of this information is in the infrared,
which we cannot see with our eyes or with visible light telescopes. Only a
small amount of this infrared information reaches the Earth's surface, yet by
studying this small range of infrared wavelengths, astronomers have
uncovered a wealth of new information
Exploring the Hidden Universe
In space, there are many regions
which are hidden from optical
telescopes because they are
embedded in dense regions of gas
and dust. However, infrared
radiation can pass through dusty
regions of space without being
scattered.
This means that we can study
objects hidden by gas and dust
such as the center of our galaxy.
Central region of Milky
Way Galaxy
Detecting Cool Objects
Many objects in the
universe which are much
too cool and faint to be
detected in visible light,
can be detected in the
infrared. These include
cool
stars,
infrared
galaxies,
clouds
of
particles around stars,
nebulae,
interstellar
molecules, brown dwarfs
and
planets.
For
example, the visible
light from a planet is
hidden
by
the
brightness of the star
that it orbits.
Exploring the Early Universe
As a result of the Big Bang, the universe is expanding
and most of the galaxies within it are moving away
from each other. Astronomers have discovered that
all distant galaxies are moving away from us and that
the farther away they are, the faster they are
moving.
This recession of galaxies away from us has an
interesting effect on the light emitted from these
galaxies. When an object is moving away from us, the
light that it emits is "redshifted". This means that
the wavelengths get longer and thereby shifted
towards the red part of the spectrum.
Adding to Our Knowledge of Visible
Objects
Objects which can be seen in visible light can also be
studied in the infrared.
Infrared astronomy can not only allow us to discover new
objects and view previously unseen areas of the universe,
but it can add to what we already know about visible
objects. To get a complete picture of any object in the
Universe we need to study all of the radiation that it
emits.
Infrared Astronomy has, and will continue to, add a great
deal to our knowledge about the Universe and the origins
of our Solar System.
Infrared array detectors
Manufacturer/type size (pixel) technology pixel pitch
Hawaii
1k x 1k HgCdTe 18.5 u m
Aladdin
Hawaii
1k x 1k
2k x 2k
HgCdTe (Mercury-Cadmium-Telluride)
InSb
HgCdTe
27 u m
18.0
InSb (Indium Antimonide)