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Indian telescope AstroSat measures X-ray polarisation of Crab pulsar star in Taurus constellation

The Crab pulsar is the rotating neutron star which is the main energy source of the nebula. A pulsar is a rotating neutron star or white dwarf that emits electromagnetic radiation. Neutron stars and black holes are also described as pulsars.

Nov 7, 2017 14:37 IST
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India’s multi-wavelength space telescope AstroSat has been successful in measuring the X-ray polarisation of the Crab pulsar star in the Taurus constellation. The findings were published in the journal Nature Astronomy on 6 November 2017.

The Astrosat team documented the results of their 18-month study of the Crab pulsar in the Taurus constellation and measured the variations of polarisation as a highly-magnetised and exotic object that spins about 30 times every second.

Taurus is the second astrological sign in the present zodiac. It spans the 30-60th degree of the zodiac.

Key Findings

• The Crab pulsar is the rotating neutron star which is the main energy source of the nebula. A pulsar is a rotating neutron star or white dwarf that emits electromagnetic radiation. Neutron stars and black holes are also described as pulsars.
• The X-ray polarisation measurement is so complex that so far the only measurement obtained worldwide is for the Crab Nebula pulsar. Crab Nebula pulsar, the remains of a massive stellar explosion known as Supernova, was observed in 1054 AD.
• Pulsars possess strong gravitational and magnetic fields trillion times than that on the Earth. They are sources of intense X-ray radiation, electromagnetic waves similar to light but have ten to hundred thousand times higher energy.
• Astronomers studied properties of this radiation to make a picture of compact objects and their surroundings.
• Another feature of the measurements is the study of polarisation properties at different rotation phases of the pulsar, which has not been done so far.
• The team had to observe the Crab pulsar many times and combine data of months due to its small rotation period.

Instruments used by scientists to measure X-ray polarisation
• Indian scientists used the data from the CZT Imager (CZTI) which is made of a semiconductor called “Cadmium Zinc Telluride” and consists of 16384 tiny essentially independent detectors to measure X-rays coming from the celestial objects.
• In order to get the micro-second accuracy for combining the data, the AstroSat team utilised one of the world’s best radio telescopes – the Indian Giant Meter-wave Radio Telescope (GMRT) at Khodad near Pune.

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About AstroSat
• AstroSat was launched by Indian Space Research Organisaion (ISRO) on a Polar Satellite Launch Vehicle (rocket) as its first dedicated space observatory on 28 September 2015.
• The 1513 kg space observatory built at a cost of Rs 180 crore has five scientific instruments to study celestial objects in the universe for the first time at optical, ultraviolet and x-ray wavebands simultaneously.
• The instruments are a soft x-ray telescope, an ultraviolet imaging telescope, an imager and a scanning sky monitor.

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