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robin_astro

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About robin_astro

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  1. Nice resolution! Did you need to refocus for the different wavelengths ? Cheers Robin
  2. Taken last night using the ALPY 600 Spectrograph guider image Processed spectrum here https://britastro.org/comment/7756#comment-7756 Cheers Robin
  3. The long term trends for V,H and J do indicate though that The H,J IR bands have similarly been unaffected by previous dimmings suggesting we may well just be seeing a similar pulsation driven dimming though deeper than normal.
  4. That is what the AAVSO data is suggesting. One caveat though is that the last two points were taken by the same observer who's name does not appear in earlier data so I would be interested in any corroborating evidence. There is some suggestion from I band spectrophotometry done using a Star Analyser that the drop in brightness reduces into the IR https://www.cloudynights.com/topic/645652-betelgeuse-is-faint-for-it/?p=9904083 (part of a long thread with lots of other discussions and speculation on the subject) H,J band brightnesses are not easy measurements to make and amateurs with the capability of measuring in the IR are rare (they use photelectric photometry, essentially a single pixel camera with an IR sensitive photodiode) https://www.aavso.org/infrared-photoelectric-photometry-program AFAIK there was only one commercial instrument for work in the IR and that appears to have been discontinued https://www.optecinc.com/astronomy/catalog/ssp/ssp4.htm
  5. Note also that is possible that Betelgeuse may not actually be dimming at all when all wavelengths are considered as most of the radiation is in the IR and a recent measurements in H,J bands in the AAVSO database appear to show no significant change.
  6. Betelgeuse is one of the MILES standard stars which was recorded in 2000/2001 when the brightness was more typical so you could compare with that (the non deredened version eg in ISIS, filtered to match the Star Analyser resolution.) My spectrum with the ALPY 600 on 30th December 2019 shows only very subtle changes in the visible spectrum compared to then http://www.spectro-aras.com/forum/viewtopic.php?f=38&t=2433#p13514 and there has been no further change up to 9th January. (The later spectrum is with the modified ALPY at R~130 so the typical Star Analyser resolution) http://www.spectro-aras.com/forum/viewtopic.php?f=38&t=2433&start=20#p13584 The spectra are in the BAA database Cheers Robin
  7. You can also tell the type of supernova from the spectrum (Core collapse of a massive star or explosion of a white dwarf which exceeds critical mass)
  8. Here is another spectrum of a type II about 1 month after it exploded (A very early spectrum of mine using a simple diffraction grating mounted directly in front of the camera. ) You can measure the velocity of the explosion from the blue shift in the material coming in our direction (about 8000km/s at this point) http://www.threehillsobservatory.co.uk/astro/spectra_6.htm
  9. Supernova spectroscopy is a particular interest of mine. Most supernovae are very faint even at maximum so I am one of only a couple of amateurs who confirm and classify supernovae spectroscopically using a spectorgraph I specially modified for the job. http://www.threehillsobservatory.co.uk/astro/spectroscopy_20.htm The spectrum changes quite rapidly in the first few days/months, mainly due to the hot material cooling (shifting from blue to red over all) and becoming more diffuse (giving a spectrum with strong emission lines like a nebula) . You also see different lines appearing as the new elements produced decay. Most SN are too faint to be followed very long spectroscopically by amateurs but it is possible with the brightest ones. Here is one (a type II like Betelgeuse will become) which I followed for a year from mag 13 to mag 18 (from from a BAA presentation I gave) Cheers Robin
  10. There would still be much of interest from a spectroscopic point of view though and something that bright would give professionals a big headache. Even with my equipment I am not sure how I would cope. I would probably have to resort to defocusing and sampling the defocused image using the spectrograph slit as I did for Vega with this simple setup here for example http://www.threehillsobservatory.co.uk/astro/spectroscopy_18.htm (Off topic in this sub forum though)
  11. Not likely to be a problem for the secondary as the light (and heat) is unfocussed at that point and being a mirror, most of the light and heat is reflected. But once focused then a source as bright as the moon concentrated from a telescope of signifcant aperture onto a few pixels (or on the retina) would be something to avoid
  12. Supernovae put out a lot of light though (Around a billion or so times more luminous than the sun at visible wavelengths) so yes, around the brightness of the full moon by the time it gets here. Something with the apparent size of a star in the sky producing as much light as the full moon will be painfully bright.
  13. SN 1987A (another type II but a very different progenitor) was ~0.1-0.2 arcsec apparent diameter after 3.5 years according to this Hubble image https://hubblesite.org/image/20 which given the ~300x difference in distance would suggest the Betelgeuse remnant would be perhaps Jupiter size in the same timescale?. SN 1987A was made more interesting because is also lit up a ring of previously shed circumstellar material but I am not sure if there is much of that from Betelgeuse. (SN 1987A was a blue supergiant)
  14. That will be mainly high energy (gamma to UV) though initially. We have to wait for it to cool a bit and for the energy from the decay of newly formed unstable elements to be generated to see the maximum in the visible light.
  15. The first evidence of it having gone supernova will be from a burst of neutrinos from the initial core collapse, some hours before the shock wave breaks though the outer surface of the star and we see the first light from the explosion
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