Now’s the time to catch Nova Herculis 2021, before it fades from view.
…And then, there were two. Fresh off of the eruption of Nova Cassiopeiae 2021 early this year, another galactic nova made itself known earlier this past weekend, as a ‘new star’ or nova flirted with naked eye visibility in the constellation Hercules the Hero on its border with Aquila the Eagle.
The Discovery: The nova was discovered at +8th magnitude ‘with a bullet’ on the night of June 12th by astronomer Seiji Ueda from Hokkaido, Japan. The nova initially gained the telephone number-like monikers TCP J18573095+1653396 (denoting its position in the sky), and ZTF (Zwicky Transient Facility) 19aasfsjq (another alphabet soup designation), before getting the much more straightforward designation of Nova Herculis 2021, or simply N Her 2021. Just a few days ago, the American Association of Variable Star Observers (AAVSO) released the formal Alert Notice 745, notifying observers that a new bright northern hemisphere nova was indeed afoot.
The story thus far: This one came up fast, as Nova Her 2021 topped out at magnitude +5.5 on Sunday, June 13th, just a day after discovery. As of writing this, the nova has faded a bit but is still sitting at a respectable magnitude +9, worth hunting for with binoculars or a small telescope. Keep in mind, if history sets any precedent, Nova Her 2021 could well brighten again… and soon. Just look at how it flared and faded in this amazing sequence:
As imagens mostram a “nova” recém-descoberta e agora já oficialmente batizada como V1674 Herculis (V1674 Her). As imagens feitas em torno de 0H BRT nos dias 13, 14 e 15 mostram a nítida variação do brilho. Vem saber mais:#ObservatorioNacional #Nova #Constelação #estrelas@mcti pic.twitter.com/IsUD7tTTaD
— Observatório Nacional (@Obs_Nacional) June 15, 2021
Nova Her 2021’s position in the sky: First, the good part: the region hosting Nova Her 2021 is currently rising to the east for northern hemisphere observers at sunset in mid-June. With the Moon waxing towards Full on June 24th, the time to catch Nova Her 2021 is tonight.
The nova’s position in the sky is:
Right Ascension 18 hours 57’ 31”
Declination +16 degrees north, 53’ 40”
The general field of view for Nova Her 2021 (centered on the Telrad finder). Credit: Stellarium/Dave Dickinson.
…and here’s a narrow, two degree wide finder chart:
N Her 2021 finder. Note that FF Aquilae is the brightest star in the field, just north of center. Credit: AAVSO.
The nova is very near (less than one degree away from) the +5.3 magnitude variable star FF Aquilae. Note that the famous ‘Coat-Hanger’ asterism is in the same general field of view:
Nova Herculis (marked) in the center of the field of view. Credit: Filipp Romanov
The nova’s position in the galaxy: Like extra-galactic supernovae seen in other galaxies, galactic novae tend to flare in a predicable fashion, making them good standard candles to roughly gauge distance. Based on this, Nova Her 2021 seems to be about 18 to 20 kilo light-years (kly) distant, in the Sagittarius Arm of the galaxy, offset from the direction from the core of the Milky Way and about five degrees north of the galactic plane.
Possible location (based on direction and brightness) for Nova Herculis 2021 in the Milky Way Galaxy. Credit: NASA
What exactly is Nova Herculis 2021? Galactic novae occur when a white dwarf star accretes material from a large nearby main sequence star. This material builds up, compresses, and ultimately gives way to a violent runaway fusion process, igniting in a brilliant flash over a period of several weeks. U Scorpii and T Pyxidis are members of a rare sub-category of variable stars known as recurrent novae.
An eVscope capture of Nova Herculis 2021. Credit: Mario Billiani
How common are novae seen in our galaxy? On average, a dozen or so novae are cataloged in our galaxy every year; once every decade or so, we get a good naked eye nova, which may top out as bright as magnitude +1, rivaling all but the very brightest stars, briefly changing the outline of the host constellation. The last such example was Nova Delphini 2013 in the tiny constellation of Delphinus the Dolphin.
Be sure to check out Nova Herculis 2021 while you can!