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The Light House of the Universe
PULSARS
WHAT ARE PULSARS?
• “Lighthouses of the Universe”
• Special kind of neutron star
• Emits beam of gamma rays, x rays,
or ra...
DISCOVERY
• First one discovered by Cambridge
University Researchers Jocelyn Bell
and Antony Hewish in 1967
• Detected pul...
FORMATION
• Stars having 8 to 25 times
mass of sun initially
• At end of life undergoes
supernova explosion (outer
layers ...
STRUCTURE AND MECHANISM
• When star collapses into a neutron
star radius is dramatically
decreased to fraction of original...
• Combination of strong magnetic field
and rapid rotation produces powerful
electric field
• Electric field accelerates el...
STRUCTURE AND MECHANISM
• rotation slows down over
time as electromagnetic
power is emitted
• When a pulsar's spin
period ...
HOW WE DETECT PULSARS
• When rotating pulse is pointed towards earth, signal is detected
(mainly as x ray, gamma or radiow...
ACCRETION POWERED PULSARS
• Binary System of pulsar and
companion star
• Gas from companion gets pulled in
or “accreted” t...
• CRAB PULSAR
Situated in Crab Nebula
Second Pulsar discovered
Has period 33 milliseconds
Forms major portion of
emissions...
• VELA PULSAR
Spins 11.195 times per second
Emits radio, optical and gamma
rays
Brightest known object in gamma
ray sky
Cy...
• PSR J0108-1431
Oldest Pulsar known (200 million years old)
Only 770 LY from earth
• PSR J1823−3021A
Youngest millisecond pulsar yet observed (25 million years
old)
Fastest pulsar yet observed 183.8 times ...
APPLICATIONS
• Maps and Navigation – pulsar position to create a spacecraft navigation
system; eg. Sun’s position relative...
THANK YOU
Pulsars
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Pulsars

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A presentation about a celestial body, pulsar.

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Pulsars

  1. 1. The Light House of the Universe PULSARS
  2. 2. 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)
  3. 3. 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
  4. 4. 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
  5. 5. 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
  6. 6. • 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
  7. 7. 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
  8. 8. 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
  9. 9. 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
  10. 10. • 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
  11. 11. • 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
  12. 12. • PSR J0108-1431 Oldest Pulsar known (200 million years old) Only 770 LY from earth
  13. 13. • 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)
  14. 14. 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
  15. 15. THANK YOU

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