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Post Info TOPIC: NGC 7023
Blobrana


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Posts: 131433
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Caldwell 4
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Blobrana


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RE: NGC 7023
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NGC 7023 (also LBN487 and Caldwell 4) is a magnitude +6.8 bright reflection nebula located 1,300 light-years away in the constellation Cepheus.

The nebula was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Datchet, Berkshire, on the 18th October 1784.

Position (J2000): R.A. 21h 01m 35.60s  |  Dec. +68° 10' 10.0"



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Blobrana


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The Iris Nebula, also NGC 7023 and Caldwell 4, is a bright reflection nebula and Caldwell object in the constellation Cepheus. NGC 7023 is actually the cluster within the nebula, LBN 487, and the nebula is lit by a magnitude +7 star, SAO 19158. It shines at magnitude +6.8. It is located near the Mira-type variable star T Cephei, and near the bright magnitude +3.23 variable star Beta Cephei (Alphirk).
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Blobrana


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Posts: 131433
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B175
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Title: A Search for Herbig-Haro Objects in NGC 7023 and Barnard 175
Authors: Travis A. Rector, Heidi Schweiker

Wide-field optical imaging was obtained of the cluster and reflection nebula NGC 7023 and the Bok globule B175. We report the discovery of four new Herbig-Haro (HH) objects in NGC 7023, the first HH objects to be found in this region. They were first detected by their H-alpha and [S II] emission but are also visible at 3.6 and 4.5micron in archival Spitzer observations of this field. These HH objects are part of at least two distinct outflows. Both outflows are aligned with embedded "Class I" YSOs in a tight group on the western edge of the nebula. One of the outflows may have a projected distance of 0.75pc, which is a notable length for an embedded source.
No new HH objects were discovered in B175. However, we reclassify the knot HH450X, in B175, as a background galaxy. The discovery that HH 450X is not a shock front weakens the argument that HH 450 and SNR G110.3+11.3 are co-located and interacting.

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Blobrana


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Posts: 131433
Date:
RE: NGC 7023
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Blushing dusty nebula

On Earth, we tend to find dust nothing more than a nuisance that blankets our furniture and causes us to sneeze. Cosmic dust can also be a hindrance to astronomers because cameras using visible light cannot see through it. However, studying cosmic dust in detail helps astronomers to pin down the ingredients of the raw mixture that eventually gives birth to stars.This close-up of an area in the northwest region of the large Iris Nebula seems to be clogged with cosmic dust. With bright light from the nearby star HD 200775 illuminating it from above, the dust resembles thick mounds of billowing cotton. It is actually made up of tiny particles of solid matter, with sizes from ten to a hundred times smaller than those of the dust grains we find at home. Both background and foreground stars are dotted throughout the image.
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Blobrana


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The Iris Nebula is 1,300 light-years away in the constellation Cepheus. It is catalogued as NGC 7023. This digital image shows off the Iris Nebula's range of colours and symmetries in impressive detail.


Credit Jean-Charles Cuillandre (CFHT)

Within the dusty nebula is a massive, hot, young star in its formative years. Central filaments of cosmic dust glow with a reddish photoluminescence as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Yet the dominant colour of the nebula is blue, characteristic of dust grains reflecting starlight. Dark, obscuring clouds of dust and cold molecular gas are also present and can lead the eye to see other convoluted and fantastic shapes. Infrared observations indicate that this nebula may contain complex carbon molecules known as PAHs.
The Iris Nebula is about 6 light-years across.

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