ASTROSAT captures Crab Nebula image, its first space snap since its launch by ISRO on September 28, 2015. (ISRO)

ASTROSAT Clicks Crab Nebula in Space, ISRO Upbeat; What Next?

Indian Space Research Organisation’s recent space observatory mission ASTROSAT has taken its first snap of Crab Nebula, the brightest X-ray source, sending cheers among the space scientists of ISRO.

Nearing almost one month since its launch on Sept. 29, ASTROSAT began to beam its images to ground control near Bangalore and the first one on Oct. 6 was about Crab Nebula that is known for its X-rays of above 35 Kev.

The Charged Particle Monitor (CPM) was the first payload to go operational followed by the Cadmium Zinc Telluride Imager (CZTI), the hard X-ray detector on board Astrosat, said ISRO. The CZTI went fully operational on October 5, and the next day Astrosat was oriented towards Crab Nebula, remnant of the Supernova detected by Chinese astronomers in the year 1054. The Crab Nebula, which also includes the Crab Pulsar, is the brightest hard X-ray source in the sky, and is very often used to calibrate hard X-ray detectors.

Giving the latest update, ISRO said the first Astroronomer’s telegram (Atel no. 8185) on SSM observations of GRS 1915+105 was released on 18 October 2015. “The Scanning sky Monitor (SSM) was pointed to GRS 1915+105 and caught it exhibiting the ‘beta’ class of variability on 14 October 2015. This is one of the many types of variability this source exhibits some of which are associated with its spectral states also.”

Earlier, the Soft X-ray Telescope (SXT) door of ASTROSAT was opened successfully on October 15, 2015 to observe the sky. This will entail the camera function from October 25 onwards to snap images in deep space.

The High voltage of Near UV, Visible channel and Far UV channel of the UV Imaging telescope (UVIT) was switched ON and detectors tested with low gain and found satisfactory and put back in OFF condition on 16th and 17th October.

Otherwise, the ASTROSAT is an earth orbiting scientific satellite with payloads capable of simultaneously observing the universe in the visible, ultraviolet and X-ray regions of the electromagnetic spectrum, said ISRO.

The satellite has the capability to observe multiple wavelengths including ultraviolet and X-rays which will help scientists in studying distant star, white dwarfs and pulsars. In addition, it will also study the super massive black hole situated at the centre of our galaxy Milky Way. According to ISRO, equipments of satellite are designed to train itself while observing the black hole.

Developed in collaboration with Tata Institute of Fundamental Research, Indian Institute of Astrophysics, Inter-University Centre for Astronomy and Astrophysics and Raman Research Institute, ASTROSAT is India’s first space obervatory mission and ISRO has become the fourth to join the club of the US, Russia and Japan with their own observatories — NASA’s GALEX (Galaxy Evolution Explorer) and Japan’s X-ray astronomy observatory — to cite.

What Next?

In the next few weeks, other X-ray instruments of Astrosat would be made operational and in November, all X-ray instruments (CZTI, LAXPC and SXT) will be ready to stare at different and interesting stars. Astrosat would be looking at some of the black hole sources / candidates like GRS 1915+105, Cygnus X-1, Cygnus X-3 next month once its Soft X-ray Telescope (SXT) opens up on October 25.

ISRO also plans simultaneous observations soon using an Infra-red telescope at Mt Abu, radio observations at GMRT, Khodad (near Pune) and using the Himalayan Chandra Telescope, located at Hanle, Ladakh, for science analysis of CZTI.

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