by Ann » Sun Sep 05, 2021 4:31 am
alter-ego wrote: ↑Sun Sep 05, 2021 12:01 am
Ann wrote: ↑Sat Sep 04, 2021 4:43 pm
neufer wrote: ↑Sat Sep 04, 2021 3:57 pm
Pretty sure:
Anne's Astronomy wrote:
The Iris Nebula (LBN 487, VDB 139 and Caldwell 4) is a bright reflection nebula some 6 light-years across and about 1,300 light-years away in the constellation Cepheus.
The nebula is often mistakenly labelled for its associated open star cluster NGC 7023, which is present in the triangular “top hat” just above center in the image.
Wikipedia wrote:
The Iris Nebula (also known as NGC 7023 and Caldwell 4) is a bright reflection nebula in the constellation Cepheus. The designation NGC 7023 refers to the open cluster within the larger reflection nebula designated LBN 487.
And when I asked my software Guide to take me to NGC 7023, it clearly took me to the "top hat cavity" of the nebulosity, not to the star HD 200775.
Ann
I can't find any substantive data to support the open cluster as NGC 7023. Most hits support the nebula. The ones that ID the cluster aren't trustworthy they don't have good supporting data, or are self-inconsistent. Although "Anne" says confidently says the nebula is mistakenly ID'd, the heavy-weight reputable databases don't support that. Even the Wiki reference is not self consistent.
Searching for NGC 7023 using the best databases and search engines (
NED,
SIMBAD,
AAS Worldwide Telescope,
NGC/IC Project ,
VizieR,
Aladin, and my
3-Volume Millenium Star Atlas), I find the ID NGC 7023 = Iris Nebula in all cases, not the open cluster. In the Wiki article, the SEDS and VizieR links list the star cluster, but I don't trust these. First, Wiki VizieR link references 4 catalogs, but only the oldest catalog (
VII/1B, 1973) lists the cluster, and getting to this result is funky - If you input NGC 7023 ID, you also have to introduce a search radius large enough to overlap the cluster location. Then the result shows the new location for NGC 7023 (LIke I said, funky). The other 3 newer catalogs take you to the nebula without forcing a coordinate change via an unknown search radius. Second, I don't trust the Wiki SEDS link because several supporting links don't go anywhere, and the associated link to the Digitize Sky Survey image does not agree with survey image result made today. The present survey image shows NGC 7023 as the nebula.
Sorry Ann, I think Anne's Astronomy is lacking up-to-date data, or the rest of the databases need correcting.
Thank you, alter-ego. I placed the NGC 7023 star cluster in the triangular cavity because of Anne's Astronomy and because my own software Guide so clearly placed NGC 7023 in that cavity. However, when I googled "NGC 7023 star cluster", I only got references to the nebula, apart from the link to Anne's Astronomy.
My main concern about placing a cluster in the triangular opening is that it doesn't
look as if there is a cluster there. The stars inside look just like they are part of the background stars. Also, of course, if there is a cluster at the same distance as the Iris Nebula whose stars are so few, faint and scattered, the cluster would have to be way, way older - hundreds of millions of years older - than the illuminating star of the nebula, which seems decidedly odd.
So my claim that cluster NGC 7023 can be found in that triangular opening should be regarded as unsubstantiated and in all likelihood incorrect.
Ann
[quote=alter-ego post_id=316385 time=1630800065 user_id=125299]
[quote=Ann post_id=316384 time=1630773782 user_id=129702]
[quote=neufer post_id=316383 time=1630771051 user_id=124483]
[list]Are you sure :?: https://apod.nasa.gov/apod/ap180801.html[/list]
[/quote]
Pretty sure:
[quote][url=http://annesastronomynews.com/photo-gallery-ii/nebulae-clouds/the-iris-nebula-lbn-487-is-a-reflection-nebula-6-light-years-across-and-1300-light-years-away-in-cepheus-ngc-7023-is-the-star-cluster-within-the-nebula/]Anne's Astronomy[/url] wrote:
The Iris Nebula (LBN 487, VDB 139 and Caldwell 4) is a bright reflection nebula some 6 light-years across and about 1,300 light-years away in the constellation Cepheus. [b][color=#0040FF]The nebula is often mistakenly labelled for its associated open star cluster NGC 7023, which is present in the triangular “top hat” just above center in the image.[/color][/b][/quote]
[quote][url=https://en.wikipedia.org/wiki/Iris_Nebula]Wikipedia[/url] wrote:
The Iris Nebula (also known as NGC 7023 and Caldwell 4) is a bright reflection nebula in the constellation Cepheus. The designation NGC 7023 refers to the open cluster within the larger reflection nebula designated LBN 487.[/quote]
And when I asked my software Guide to take me to NGC 7023, it clearly took me to the "top hat cavity" of the nebulosity, not to the star HD 200775.
Ann
[/quote]
I can't find any substantive data to support the open cluster as NGC 7023. Most hits support the nebula. The ones that ID the cluster aren't trustworthy they don't have good supporting data, or are self-inconsistent. Although "Anne" says confidently says the nebula is mistakenly ID'd, the heavy-weight reputable databases don't support that. Even the Wiki reference is not self consistent.
Searching for NGC 7023 using the best databases and search engines ([url=http://ned.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=NGC%207023]NED[/url], [url=http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+7023&submit=SIMBAD+search]SIMBAD[/url], [url=http://worldwidetelescope.org/webclient/?wtml=http%3A%2F%2Fwwtcoreapp-data-app.azurewebsites.net%3A80%2Fwwtweb%2Fgoto.aspx%3Fobject%3DNGC%25207023%26ra%3D21.026913%26dec%3D68.1633%26zoom%3D1.40625%26wtml%3Dtrue]AAS Worldwide Telescope[/url],[url=https://vizier.u-strasbg.fr/viz-bin/VizieR-4l]NGC/IC Project [/url], [url=https://vizier.u-strasbg.fr/viz-bin/VizieR-2]VizieR[/url], [url=https://aladin.u-strasbg.fr/aladin.gml]Aladin[/url], and my [url=https://www.cosmos.esa.int/web/hipparcos/millennium-star-atlas]3-Volume Millenium Star Atlas[/url]), I find the ID NGC 7023 = Iris Nebula in all cases, not the open cluster. In the Wiki article, the SEDS and VizieR links list the star cluster, but I don't trust these. First, Wiki VizieR link references 4 catalogs, but only the oldest catalog ([b]VII/1B[/b], 1973) lists the cluster, and getting to this result is funky - If you input NGC 7023 ID, you also have to introduce a search radius large enough to overlap the cluster location. Then the result shows the new location for NGC 7023 (LIke I said, funky). The other 3 newer catalogs take you to the nebula without forcing a coordinate change via an unknown search radius. Second, I don't trust the Wiki SEDS link because several supporting links don't go anywhere, and the associated link to the Digitize Sky Survey image does not agree with survey image result made today. The present survey image shows NGC 7023 as the nebula.
Sorry Ann, I think Anne's Astronomy is lacking up-to-date data, or the rest of the databases need correcting.
[/quote]
Thank you, alter-ego. I placed the NGC 7023 star cluster in the triangular cavity because of Anne's Astronomy and because my own software Guide so clearly placed NGC 7023 in that cavity. However, when I googled "NGC 7023 star cluster", I only got references to the nebula, apart from the link to Anne's Astronomy.
My main concern about placing a cluster in the triangular opening is that it doesn't [b][i]look[/i][/b] as if there is a cluster there. The stars inside look just like they are part of the background stars. Also, of course, if there is a cluster at the same distance as the Iris Nebula whose stars are so few, faint and scattered, the cluster would have to be way, way older - hundreds of millions of years older - than the illuminating star of the nebula, which seems decidedly odd.
So my claim that cluster NGC 7023 can be found in that triangular opening should be regarded as unsubstantiated and in all likelihood incorrect.
Ann