Nova Cassiopeiae 2021, also known V1405 Cassiopeiae, was a nova in the constellation Cassiopeia. It reached a peak brightness of magnitude 5.449 on May 9, 2021, making it visible to the naked eye.[4] It was discovered by Japanese amateur astronomer Yuji Nakamura of Kameyama, Japan, at 10:10 UT on March 18, 2021. The nova was first seen by Nakamura in four 15 second CCD exposures with a 135mm F/4 lens, when it was at magnitude 9.3. Nothing was seen brighter than magnitude 13.0 with the same equipment in exposures taken at 10:12 UT on March 14, 2021.[4][5][6] For the first seven months after discovery, the nova's brightness stayed at a rough plateau, fading and rebrightening at least eight times; it is considered a very slow nova.[7] After the seven month long series of peaks, Nova Cassiopeiae began a linear decline in brightness.[4] This nova has been detected throughout the electromagnetic spectrum, from radio to gamma rays.[8][9]
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Cassiopeia |
Right ascension | 23h 24m 47.73165s[2] |
Declination | +61° 11′ 14.7951″[2] |
Apparent magnitude (V) | 5.2 - 15.6[3] |
Astrometry | |
Proper motion (μ) | RA: −0.912±0.026[2] mas/yr Dec.: −1.319±0.026[2] mas/yr |
Parallax (π) | 0.5776 ± 0.0254 mas[2] |
Distance | 5,600 ± 200 ly (1,730 ± 80 pc) |
Characteristics | |
Variable type | Nova |
Other designations | |
Database references | |
SIMBAD | data |
All novae are binary stars, consisting of a white dwarf orbiting a "donor star" from which the white dwarf accretes material. Spectra taken of Nova Cassiopeiae around maximum brightness showed that the nova was an FE II type novae.[10] The ejecta from FE II novae is believed to come from a large circumbinary envelope of gas (which was lost from the donor star), rather than the white dwarf.[11] TESS observations revealed an orbital period of 4.52138±0.00012 hours for the binary system.[12]