Indian astro satellite captures X-ray image of debris from 446-year-old supernova explosion
For the first time, country’s dedicated multi-wavelength astronomy satellite, Astrosat, has captured an X-ray image of the debris of a supernova. Called SN 1572, the supernova is located 10,000 light years away.
The debris is around 3.7 times smaller than the full moon and the emission gets brighter near the edge as it expands.
Danish astronomer Tycho Brahe was among many astronomers across Europe and China to see the supernova explosion as a new star in November 1572.
He studied the explosion till it faded away in 1574 following which he wrote ‘Concerning the Star, new and never before seen in the life or memory of anyone’. The writing included a position chart of the explosion in the sky.
Since then, the debris from the Tycho supernova — named after Brahe — has been captured by NASA’s Chandra X-ray Observatory and Spitzer Space Telescope and Spain-based Calar Alto observatory, among others.
But this is the first observation of SN 1572 captured by the indigenously built soft x-ray telescope (SXT) on board Astrosat in constellation Cassiopeia — considered as the most recognisable W shaped constellation in the northern sky. Astrosat, with five instruments on board, was launched in September 2015.
“This exercise was to prove that our telescope and camera CCD can provide useful information. Our telescope can clearly see lines of emissions from various ions such as iron, magnesium and silicon,” said KP Singh, project manager, Astrosat, and visiting faculty at IISER Mohali.
He added, “The spectra from SXT are better and comparable with other similar satellites from the past. We can now show that we have the capability to study strong spectral lines in the x-ray band that are emitted by atoms in the highly ionised plasma. This plasma is being heated by the shock wave that blasted out when the star originally exploded.”
Based on historic data, SN 1572 is Type 1a supernova explosion that occurs when a white dwarf star (very compact object in its end stage) pulls material from a normal companion star. The material, which makes the white dwarf star heavier, then explodes in a thermonuclear reaction resulting in a Type 1a supernova explosion.
Astronomers said what they saw is what is left of this explosion. But when the explosion occurred in 1572, the theory to explain the natural world till then was based on the Aristotle’s ideas of an unchanging universe believed as the last word for many centuries.
“So when a new star suddenly appeared from nowhere and faded away, it was philosophically a challenge to Aristotle’s idea of an unchanging universe. One of the many reason that astronomers thought the new star should be looked at and Aristotle could be wrong because stars till then were considered to be distant objects and very far away. This discovery also made astronomers realise the importance of making accurate maps of the stars for future reference,” said Niruj Mohan Ramanujam, astronomer and member of the Public Outreach and Education Committee of the Astronomy Society of India.