Vy 1-2 is a planetary nebula discovered by Russian-American astronomer Alexander N. Vyssotsky in 1942.
General information Vy 1-2 contains a faint outer shell and two much fainter knots at a (position angle) PA of 305°. The S knot is located 14.5 arcsec from the central star while the N knot is located 11.5 arcsec form the central star. The knots deprojected radial expansion velocity is 90–100 km s−1, and their kinematic age is found to be 5200 ± 750 yr for a distance = 9.7 kpc. Vy 1-2 also has a bright-elliptical ring like structure with a minor axis of 2.4 arcsec and a major axis of 3.2 arcsec. The distance of Vy 2-1 remains uncertain, with estimates ranging from 7.0 to 14.5 kpc, calculated using a mean radius of ~1.4 arcsec. The systemic heliocentric radial velocity of the nebula is Vsys = -85 ± 4 km s-1. Vy 1-2 has been a candidate for a halo PN because of its high systemic velocity (~500 pc) from the galactic plane. The Zanstra temperature of the He I line is 75.4 ± 10.2kK while the He II line is 99.8 ±4.3kK. The logarithmic Hβ flux is estimated to be -11.52 ± 0.01. The [N II] emission line shows a high expansion velocity of 90–100 km s−1 only along the PA = 310° whereas the He II expansion velocity is ~23-25 ± 4 km s-1. The electron temperatures of the [N II] and [O I] emission line is Te = 10,850 ±2100 K and 10,400 ± 5400 K respectively, while the electron densities of the following emission lines are: the [S II] with a Ne = 4500 ± 650 cm-3, the [Cl III] with a Ne = 4330 ± 1600 cm-3, and the [Ar IV] with a Ne = 4550 ± 1300 cm-3.
Central star The central star is relatively unknown, it is possibly a WR or a strong and fast WEL nucleus, with the detection of [C II], [C IV], and [O III] stellar lines supports the scenario. Anonther scenario used to prove a anomaly in BD +30° 3639" suggests the central star is a binary system.
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