According to reports in The Astronomer’s Telegram, a star in the region of the constellation Cassiopeia has just become nova, and the brightness is still visible in the night sky. If you live in the northern hemisphere and even have a basic telescope, we recommend that you go out and point it in that direction.
The first detection was made on March 18, 2021 by amateur astronomer Yuji Nakamura of Mie Prefecture in Japan. In four frames captured using a 135 millimeter lens and a 15-second exposure, a brightness of magnitude 9.6 was visible where none had been just four days earlier.
The discovery was quickly reported to the National Astronomical Observatory in Japan, and scientists approached to find out what was happening.
Using Kyoto University’s Seima telescope, astronomers at NAOJ and Kyoto University made spectroscopic observations and used the 0.4-meter telescope at Kyoto University for multicolored photometric observations.
They confirmed that the event is indeed what we classify as a new classic, the most common of the stellar explosions, and gave it the name V1405 Cas.
A new nova is not the huge kaboom of a massive star, but an explosion on the surface of a white dwarf with a main sequence binary companion in a tight orbit – generally less than 12 hours. As the two stars rotate around each other, the small, dense white dwarf siphons hydrogen from its larger, fluffier companion.
This hydrogen reaches the atmosphere of the smaller star, where it is heated. When hydrogen heats up and is dense enough, nuclear fusion is triggered on the surface of the white dwarf, releasing an extraordinary amount of energy that explosively discharges the hydrogen burned 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. Nova itself may continue to shine for days or months.
It is not clear immediately which star produced the V1405 Cas, but there is a strong candidate: the eclipsing (binary) variable star CzeV3217, which is about 5,500 light-years from the solar system.
Additional observations will help astronomers better understand the nova and confirm that the source is indeed CzeV3217.
(Yuji Nakamura / NAOJ)
Because such stellar explosion events are so unpredictable, they are not always easy to catch quickly, so the discovery of the V1405 Cas is quite interesting.
If you want to get out there and try to see it for yourself, its coordinates are at the right ascent 23 24 47.73, declination +61 11 14.8 – not far from the star Cassiopeia Caph and an even smaller distance from the type B star HIP 115566.
While you’re there, keep your eyes peeled for anything out of the ordinary …