Caldwell 90, in Carina
| Image exposure: 27 minutes (54x30s) | Image field of view: 4.9 x 3.3 arcmin | Image date: 2022-03-12 |
NGC 2867 is a planetary nebula in the southern constellation of Carina.
The outer ring appears almost heart-shaped, with a bright condensation at the top.
It’s a bright nebula but very concentrated, with an exceedingly small apparent diameter of about 0.5 arc minutes – so as well as heavily cropping the image, I had to digitally enlarge it. The real diameter is of the order of half a light year.
Here is a shot I took two years ago, with the tiny planetary nebula over-exposed and looking a bit like a planet (which it is not):
The central star which ejected the nebula is a very energetic Wolf-Rayet type, which is not very common for stars that have created a planetary nebula. Its surface temperature is probably a whopping 165,000°K.
The star is listed as a very dim magnitude +16.6. For comparison, the nearby star HD 8119 (just below the nebula in the feature image) is magnitude +9.1, making it about 1,000 times brighter than the central star and it is disappointing but unsurprising that my image, consisting of stacked 30s images, fails to pick it out.
The nebula is believed to be very young about 2,750 years old and the star is expected to eventually evolve into a white dwarf.
Its distance is listed as 7,270 light years in Wikipedia but only 5,500 light years in Sky Safari Pro, so there is still some uncertainty about how far away it is.
(Astrometry,net)
The exciting astronomy news of the week is the continuing progress of the commissioning of the Webb space telescope as it orbits Lagrange Point 2. Webb is now in the latter stages of telescope commissioning and produced this wonderful test image this week:
The bright central star is of course an object in the Milky Way galaxy. Many of the background objects are remote galaxies. I can’t wait for what is to come when the science begins!
| Telescope: | Meade LX-90 200mm Schmidt-Cassegrain (deforked); 2000 mm f/l @ f/10. |
| Optics: | Astronomik light pollution filter. |
| Mount & Guiding: | SkyWatcher EQ6-R Pro mount. |
| Imaging camera: | ZWO ASI 071 MC cooled. |
Cosmic Focus Observatory
34° South
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Good job capturing that nebula. It is small and faint.
The science team is excited about that image with the many galaxies behind the star. You and your readers might find this post interesting about the next phase of JWST deployment.
https://blogs.nasa.gov/webb/2022/03/17/webb-begins-multi-instrument-alignment/
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The more I read about Webb, the more impressed I get. Multiple cameras operating at the same time through the same telescope!
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You captured far more detail of NGC 2867 this time than you did two years ago. How do you account for the improvement? Better technique and/or equipment? Maybe better conditions?
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Thanks for the question. In short, I used two different telescopes.
The earlier attempt was taken with my 120mm refractor which has a wider field of view, so not really suitable for small planetaries. The object was also considerably over-exposed. I didn’t think I would achieve any improvement from cropping and enlarging, so I opted for the wider field view.
In recent months I have reverted to the much narrower field of view of my old 200mm Schmidt-Cassegraine telescope to help me pick out tiny planetary nebulae. With a higher resolution, combined with a reduced exposure time, it provided the ability to enlarge and crop to pick out some of the detail in planetary nebulae.
🙃
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Thank you Roger for the insight.
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