A presentation about a celestial body, pulsar.

2. The Light House of the Universe
PULSARS

3. WHAT ARE PULSARS?
• “Lighthouses of the Universe”
• Special kind of neutron star
• Emits beam of gamma rays, x rays,
or radio waves which sweeps
through Earth’s line of sight;
pulsating effect
• Spins up to several 100 times a
second
• Have highly intense magnetic and
electric field (several trillion Gauss
and Volts)

4. DISCOVERY
• First one discovered by Cambridge
University Researchers Jocelyn Bell
and Antony Hewish in 1967
• Detected pulses separated by 1.33
seconds from same position in the
sky
• Second pulsar was discovered in the
Crab Nebula with a period of 33
milliseconds; confirmed it was a
rotating a neutron star
• Around 1600 pulsars found

5. FORMATION
• Stars having 8 to 25 times
mass of sun initially
• At end of life undergoes
supernova explosion (outer
layers burst out)
• Electrons and protons are
crushed together to form neutron core
• collapses into neutron star
without collapsing into black hole
• 1.4 to 3.2 times mass of sun
• About 20 kilometres in diameter and extremely high density

6. STRUCTURE AND MECHANISM
• When star collapses into a neutron
star radius is dramatically
decreased to fraction of original
star; very high speed
• As mass moves closer to centre of
mass rotational speed increases
• Produces strong magnetic field
• Magnetic axis and rotational axis
not aligned

7. • Combination of strong magnetic field
and rapid rotation produces powerful
electric field
• Electric field accelerates electrons
• High energy electrons produce
radiations
 By acting as plasma to produce radiation
 By interacting with photons or magnetic
field
• Point of emission of radiation is
somewhere around magnetic poles
• When beam around magnetic poles is
in earth’s line of sight, radiation is
detected
• Lighthouse effect

8. STRUCTURE AND MECHANISM
• rotation slows down over
time as electromagnetic
power is emitted
• When a pulsar's spin
period slows down
sufficiently, the radio
pulsar mechanism turns
off

9. HOW WE DETECT PULSARS
• When rotating pulse is pointed towards earth, signal is detected
(mainly as x ray, gamma or radiowaves by spectroscopic methods)
• When pointed away signal fades
• Appear as pulses at very regular intervals

10. ACCRETION POWERED PULSARS
• Binary System of pulsar and
companion star
• Gas from companion gets pulled in
or “accreted” to magnetic polar
caps (gravity)
• Mass transfer increases speed of
rotation tremendously
• Converts them into millisecond
pulsars

11. • CRAB PULSAR
Situated in Crab Nebula
Second Pulsar discovered
Has period 33 milliseconds
Forms major portion of
emissions from the Crab
Nebula
IMPORTANT PULSARS
A slow-motion movie of the Crab Pulsar
taken at 800 nm wavelength (near-
infrared) using a Lucky Imaging camera
from Cambridge University, showing the
bright pulse and fainter interpulse

12. • VELA PULSAR
Spins 11.195 times per second
Emits radio, optical and gamma
rays
Brightest known object in gamma
ray sky
Cycle of pulsed gamma rays
from Vela Pulsar

13. • PSR J0108-1431
Oldest Pulsar known (200 million years old)
Only 770 LY from earth

14. • PSR J1823−3021A
Youngest millisecond pulsar yet observed (25 million years
old)
Fastest pulsar yet observed 183.8 times per second
Detected in NGC 6624 (spherical cluster of ancient stars)

15. APPLICATIONS
• Maps and Navigation – pulsar position to create a spacecraft navigation
system; eg. Sun’s position relative to 14 pulsars mapped out; identified by
unique periods
• Precise Clocks – very regular period, more accurate than atomic clocks
• To Test theories of Gravity – strong gravitational force

16. THANK YOU