[AZ-Observing] Re: NGC 2024 - The Flame Nebula
- From: Brian Skiff <bas@xxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Sun, 03 Feb 2019 13:10:45 -0700
On Sun, 2019-02-03 at 12:16 -0700, Bernard Miller wrote:
Brian,
The star causing the ionization is actually Alnitak, which is the eastern
most star in Orion's belt.
Turns out we are both wrong! The idea that zeta Ori is
the source of the ionizing photons is due to Hubble in 1922,
and is wrong for several reasons, but consistent with what Hubble
could have known about. The less-old lore regards the star I
mentioned as "it", but although that star turns out to be hot
enough, it is not luminous enough.
A quick trawl through the literature in SIMBAD indicates
that the culprit lies in the embedded star cluster --- completely
obscured in the visible behind the dark cloud of the nebula.
Specifically, the most luminous star there, called NGC 2024 IRS 2b,
is doing most of the work. It is obscured by something like 24
magnitudes at visible wavelengths, so is not detectable by
visual observers or visible-light imaging. See the paper and
nice images linked from:
http://simbad.u-strasbg.fr/simbad/sim-ref?bibcode=2003A%26A...404..249B
\Brian
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