Nova Herculis 2021 ( N Her 2021 ), 17 Jun 2021
Several months after Nova Cassiopeiae 2021, another prominent galactic nova appeared in the constellation of Hercules. It was discovered on June 12, 2021 at apparent magnitude 8.4 by Seidji Ueda from Japan at coordinates 18 57 31 +16 53 40. On June 13, only one day after discovery, the nova reached peak magnitude of 5.5, and should have been visible to the unaided eye under good sky conditions.Approximately 60 novas flare in the Milky Way galaxy annually, of which only about 10 are detected because the majority are hidden behind dense clouds of galactic gas and dust. Novas form in binary systems where a white dwarf star pulls matter from a red giant companion, reigniting nuclear fusion on the dwarf's surface. The resulting explosion blows away the surface layers composed mostly of hydrogen, without destroying either star. The hot shell of gas, expanding at several thousand km/s, fluoresces with the typical hydrogen emission spectrum, imparting reddish color to the new star. If the process of matter accretion continues after the initial explosion, additional explosions may result in the rare phenomenon called a "recurrent nova". This is precisely what happened to N Cas 2021, which flared three times over 90 days. Nova events usually reach maximum brightness over a period of days, then gradually fade over several weeks. N Her 2021 is somewhat unusual in that it manifested a very rapid rise and very rapid fading. By June 14, one day after the maximum, it dropped to magnitude 8.5, and approximately to magnitude 10 (compared to star HD 230191) by June 17, when the attached image was taken.
The still image was taken with a remote Takahashi TOA 150 x 1105 mm telescope, 3 x 300 sec OSC subexposures.
The GIF image compares the still image against the DSS2 sky survey taken about 60 years ago. In addition to the nova, the GIF image shows a small amount of proper motion in several stars.
Click on the GIF image if it does not blink.
Wider angle GIF image:
https://www.cloudyni...21-17-jun-2021/
Annotated image:
https://www.cloudyni...05mm-3x300-osc/
Edited by rekokich, 19 June 2021 - 09:01 PM.
