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Celestial hemisphere:  Northern  ·  Constellation: Pisces (Psc)
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PHL 932 and its nebula, José Manuel López Arlandis
PHL 932 and its nebula
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PHL 932 and its nebula

Getting plate-solving status, please wait...
PHL 932 and its nebula, José Manuel López Arlandis
PHL 932 and its nebula
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PHL 932 and its nebula

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PHL 932 (HIP 4666, TYC1189-1457-1) is the name of a 12th magnitude star located in Pisces, about 298 pc away (972 light-years). It was designated No. 932 in the Haro-Luyten Palomar (PHL) catalogue (1962) [1].  It is surrounded by a faint nebula discovered in 1967 by Arp and Scargle [2], who thought it was a planetary nebula. Hence its names: PNG 125.9−47.0 and PK125-47.1. It remained classified as planetary until 2010, when Frew et al  [3] confirmed that it was an HII region, a zone of hydrogen ionized by the star. In theoretical physics the model of this ionization is called an “Strömgren sphere”. The Rosette Nebula is the most striking of these spheres. PHL 932 is a B-type hot subdwarf (sdB). These are stars of mass similar to our Sun that somehow detach from their hydrogen envelopes before initiating the fusion of the helium core. In this way, instead of evolving into red giants, they directly follow the cooling curve of a white dwarf. These types of stars are not the ones that typically cause a planetary nebula. The spectrum of PK 125-47.1 in OIII is negligible, with the emission in HII being dominant. PHL 932 is located in a wide region in which there are three large molecular clouds, and it is likely that the star ionizes a small condensation region of the interstellar medium (ISM) in its path. The speeds of the star and the nebula are different, which implies that they are not related.

As a photographic object, the PHL 932 nebula is neither small nor large (9.5 x 6 arcmin), but it is very faint and very inconspicuous except for its signal in HII. Perhaps that is why it is rarely photographed. For my photography, in view of the already known color spectrums, I gave up on getting an RGB signal from the nebula. Broadband images were used only for the stars and to neutralize the background color. The R channel was exclusively the HII master image, and the luminance is also that of the HII master. I planned to obtain at least 12 hours in HII, but in mid-February the object was already hidden very early and I had to stop with 103 images of 300s (8h 35m). I got more detail than expected, minimizing the use of deconvolution (BXT) in order not to create false structures. I turned the brightest regions of the center to a slightly more orange tone, since the pure red tone allowed fewer contrasts to be appreciated.  

The shape of the nebula is reminiscent of a comet. In the article by Arp and Scargle , two H-alpha rings were already described around the star, the outer one having a cometary appearance due to a possible interaction with the environment (remember that in this article it was argued that the object was an ancient planetary) . However, Frew et al conclude that  "the nebula is not moving through the ISM and we interpret the observed wake as a recombining fossil 'contrail' ".  Dark bands are observed above the nebula, probably due to the interposition of dust clouds. To the south of PHL 932, at 2.75 arc min (at 6 o'clock in the photograph), a small lenticular-shaped spot of about 20-30 seconds in greatest diameter is obsrved. Its appearance is galactic. I have identified it with Aladin as a source detected by the WISE project (Wide-field Infrared Survey Explorer), and named as WISEA J005954.86+154131.2 (coordinates 0h 59m 54.86s, +15d 41m 31.2s / Equ J2000). In the NED database (NASA/IPAC Extragalactic Database) the entry “NED preferred object type”  marks  it as “G” (galaxy) [see annotated image].

[1]  Haro G, Luyten WJ.  Faint blue stars in the región  near the South galactic pole. BOLETÍN DE LOS OBSERVATORIOS DE TONANTZINTLA Y TACUBAYA, VOL. 3, N°22, 1962. https://www.astroscu.unam.mx/bott/BOTT..3-22/PDF/BOTT..3-22_gharo.pdf

[2]  Arp H, Scargle JD.A HIGH-LATITUDE PLANETARY NEBULA. The Astrophysical Journal, Vol. 150, November 1967.https://articles.adsabs.harvard.edu/pdf/1967ApJ...150..707A

[3]  Frew DJ, Madsen GJ, O’Toole SJ,  Parker QA. PHL 932: When Is a Planetary Nebula Not a Planetary Nebula? Publications of the Astronomical Society of Australia, 2010, 27, 203–209. https://arxiv.org/pdf/0910.2078.pdf


PHL 932-Anotated.jpg

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PHL 932 and its nebula, José Manuel López Arlandis
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