It's a nice image, to be sure! But a pistachio nebula?
To resemble a pistachio, maybe the OIII emission from this nebula, which is this color:
███, should have been mapped as green, like this,
███, rather than as blue,
███, the way it is mapped in the APOD?
Anyway, an unknown nebula.
APOD Robot wrote:
The pictured Pistachio Nebula is shown in oxygen emission (blue) and hydrogen emission (red). The nature of the hot central star is currently unknown, and the nebula might be labeled a planetary nebula if it turns out to be a white dwarf star.
Right. The Pistachio Nebula might be labeled a planetary nebula if the central star turns out to be a white dwarf star. Well, that reminds me of nebula Ou4, where the jury is still out on the nature of this thing:
Like the Pistachio Nebula, Ou4 or the Squid Nebula also glows in OIII.
Is the central star inside Ou4 a white dwarf? Yes, says Astrodrudis:
Astrodrudis wrote:
Outters 4 (Ou4) is a very faint planetary nebula located in the constellation Cepheus.
No, says NASA:
Though apparently completely surrounded by the reddish hydrogen emission region Sh2-129, the true distance and nature of the Squid Nebula have been difficult to determine. Still, a more recent investigation suggests Ou4 really does lie within Sh2-129 some 2,300 light-years away. Consistent with that scenario, Ou4 would represent a spectacular outflow driven by HR8119, a triple system of hot, massive stars seen near the center of the nebula. The truly giant Squid Nebula would physically be nearly 50 light-years across.
So according to NASA, HR 8119 is probably a massive fusion-driven star rather than a white-hot cinder of a dead star surrounded by its own death shroud, a planetary nebula.
What says Gaia, our best tool for measuring distances to stars? Unfortunately, Gaia says nothing!
![🤫](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/1f92b.svg)
It apparently hasn't measured the distance to HR 8119! How incredibly disappointing and frustrating!
I would so much love to know the nature of Ou4! But I would certainly like to know the nature of the Pistachio Nebula, too.
Ann