According to reports in The Astronomer’s Telegram, a star in the region of the constellation Cassiopeia has just turned nova and its glow is still visible in the night sky. If you live in the Northern Hemisphere and even have a base telescope, you may want to go out and point it in that direction.
The first detection was made on March 18, 2021 by amateur astronomer Yuji Nakamura from Mie prefecture in Japan. In four frames captured with a 135 millimeter lens and an exposure time of 15 seconds, a bright glow of magnitude 9.6 was visible, where none had been four days earlier.
The find was quickly reported to the National Astronomical Observatory of Japan, and scientists set out to find out what was going on.
Using the Kyoto University’s Seimei telescope, astronomers from NAOJ and Kyoto University performed spectroscopic observations and used Kyoto University’s 0.4-meter telescope for multi-color photometric observations.
They confirmed that the event is indeed what we classify as a classic nova, the most common of the stellar explosions, and named it V1405 Cas.
A classic nova is not the massive kaboom of a massive star, but an explosion on the surface of a white dwarf with a binary companion of the main sequence in a short orbit – generally less than 12 hours. As the two stars swirl around each other, the small, dense white dwarf sucks hydrogen off its larger, fluffier companion.
This hydrogen ends up in the atmosphere of the smaller star and is heated there. When the hydrogen gets hot and dense enough, nuclear fusion is activated on the surface of the white dwarf, releasing a tremendous amount of energy that explosively blasts the unburned hydrogen into space.
Unlike a Type Ia supernova, in which the white dwarf explodes, both stars survive and continue their strange relationship to explode again another day. The nova itself can continue to glow for several days or months.
It is not immediately clear which star V1405 produced Cas, but there is a strong candidate: the eclipse variable (double) star CzeV3217, which is about 5,500 light-years away from the Solar System.
Further observations will help astronomers better understand the nova and confirm that the source is indeed CzeV3217.
(Yuji Nakamura / NAOJ)
Because such explosive events are so unpredictable, they are not always easy to catch quickly, so the discovery of the V1405 Cas is quite exciting.
If you want to go out and try it for yourself, the right ascension coordinates are 23 24 47.73, declination +61 11 14.8 – not far from the Cassiopeia star Caph, and an even shorter distance from the B- type star HIP 115566.
While you’re out there, keep your eyes peeled for something out of the ordinary …