Hubble 5 (Hb 5) is a large bipolar planetary nebula with a complex shape. The nebula was discovered by American astronomer Edwin Hubble in 1921. Hb 5 has an estimated size of 52" x 18" in Hα. The distance of Hb 5 remains uncertain, with estimates ranging between 0.7 kpc and 2 kpc. The electron temperature of the nebula is 13,000K-16,000K based on the Ne III temperature being lower than the Ne V temperature. The Hβ flux is ~3.0 x 10-12 erg cm-2 s-1 or 1.19 x 10-10 erg cm-2 s-1. The nebula is a bipolar, point-symmetric PN.
Central star Central star is very faint and the presence of the Ne VI line proves that the star is quite hot. The star has a Zanstra temperature ranging from ~100,000 K for hydrogen to ~130,000 K for helium II. The star has a radius of about ~0.17 R☉ and a luminosity of 2 x 10⁴ Lʘ.
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