This appears to be a mostly Hα (red) and OIII (blue) APOD:
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Supernova Remnants Big and Small
Image Credit & Copyright: Stéphane Vetter (Nuits sacrées)
APOD Robot wrote:
The blue soccer ball-looking nebula toward the upper left is SNR G179.0+02.6, which appears to be the smaller one. This supernova, about 11,000 light years distant, detonated about 50,000 years ago. Although composed mostly of hydrogen gas, the blue light is emitted by a trace amount of oxygen.
Well, either the caption is trying to tell us that SNR G179.0+02.6 is a core-collapse supernova, the remnant of a massive star, which always contains hydrogen. Or else the caption is suggesting that, for some reason, only oxygen is ionized in this supernova remnant, while the abundant hydrogen is not. (Why not?) Either way, I find it problematic to suggest that this supernova remnant is made mostly of hydrogen even though it glows almost exclusively in oxygen.
Here is another image of the Spaghetti Nebula and SNR G179.0+02.6, this one by Rolf Dietrich:
As you can see (and you could see it in the APOD, too) the Spaghetti Nebula contains a lot of hydrogen and shows a lot of red color, more red than blue.
Rolf Dietrich wrote:
The beautiful Spaghetti Nebula has a real rarity in its vicinity, the SNR 179.0+2.6.
It is a very old SNR that mainly emits OIII.
Yes, SNR 179.0+2.6 mainly emits OIII. Why would it, if it is mainly composed of hydrogen?
Here is another picture of SNR 179.0+2.6, this time by Swedish photographer Göran Nilsson:
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Credit: Göran Nilsson
Göran Nilsson described some technical details of how he acquired his image:
Caught last night with my dual-RASA8 rig with ASI2600MC and IDAS NBZ dual band filter (
Ha+Oiii). 72 x 5 min, so 6 hours. Processed in PI and PS, of course using the new XTerminator tools.
So again, Göran Nilsson used an Hα filter for this image but hardly recorded any Hα from the supernova remnant. But you can see a star cluster at right, at 3 o'clock, and that is the bright and well-known M37. You can also see some red nebulosity emanating from this cluster, although M37 is way too old to be surrounded by its birth cloud or contain any hot OB stars. That red nebulosity is a planetary nebula! Some planetaries mostly lack oxygen and appear to be "all red" from hydrogen, and the M37 planetary, IPHASX J055226.2+323724, is an example of that.
Here is a closeup of the planetary:
Marcel Drechsler wrote about planetary nebula IPHASX J055226.2+323724 in M37:
The planetary nebula, known as IPHASX J055226.2+323724, is only the 3rd example of an association between a planetary nebula and open cluster out of the ~4,000 planetary nebulae known in our Galaxy.
It also appears to be the oldest planetary nebula ever found. The small team led by Professor Quentin Parker, Director of the HKU LSR, have determined some interesting properties for their discovery:
the authors found the PN has a “kinematic age” of 70,000 years. This estimate is based on how fast the nebula is expanding, as determined from the PN emission lines, and assuming this speed has remained effectively the same since the beginning, and is the time elapsed since the nebular shell was first ejected by the host, a dying star. This compares to typical PN ages of 5,000-25,000 years. It is truly a grand old dame in planetary nebula terms but of course a mere “blink of the eye” in terms of the life of the original star itself that runs to hundreds of millions of years.
Marcel Drechsler posted an Hα and an OIII image of M37 on his website, and you can see from these images that IPHASX J055226.2+323724 is mostly an Hα nebula, but it does contain some very small amounts of OIII, too. See
here (Hα) and
here (OIII).
According to what I found on the net, the distance to M37 is believed to be
4,500 light-years. According to the caption, the distance to SNR G179.0+02.6 is
11,000 light-years. You math nerds may want to calculate how much bigger in size SNR G179.0+02.6 is compared to IPHASX J055226.2+323724! Have fun!
Let's return to what Rolf Dietrich said about SNR G179.0+02.6:
The SNR 179.0+2.6 is extremely faint.
In my Bortle 4-5 Homeplace it could hardly be seen even after a long exposure time with the 4nm OIII filter.
So I had to drive with batteries to a rural area and take images in the open countryside.
Could the faintness and age of this supernova remnant contribute to its apparent lack of hydrogen emission? Why else would the supernova remnant emit hardly any Hα light at all?
Ann
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Supernova Remnants Big and Small
