M20 - The Trifid Nebula (Peter Hannah)

Celestial hemisphere: Southern · Constellation: Sagittarius (Sgr) · Contains: M 20 · NGC 6514 · Trifid Nebula

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M20 - The Trifid Nebula

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M20 - The Trifid Nebula

The Trifid nebula is really four nebulae in one: an emission nebula, a reflection nebula, a dark nebula and a star cluster. The reflection nebula is not visible in this image.

The Trifid is about 40 light years across, though there is some uncertainty about its size because its distance is not precisely known, with estimates ranging from 3000 to 9000 light years.

This is a narrowband image with an unusual SOH palette mapping: the red channel displays the S-II signal, the green the OIII and the blue, the H-α. As the H-α emission is by far the strongest, this gives the image its unusual blue colour. As there is no ‘natural’ way to view narrowband images, the way they are presented for human vision is at the discretion of the image processor.

Embedded in the nebula is a star cluster, and it is the powerful radiation from these stars that causes the gas to glow. Meanwhile the dark lanes that give the nebula its name (trifid meaning three-lobe – no connection to The Day of the Triffids) have their own designation as a dark nebula (Barnard 85).

The fourth component of the Trifid is a blue reflection nebula made visible by reflected (broadband) starlight. If it were visible in this image it would be situated to the left of the main nebula (north is in the 10-o’clock direction). However it really requires a broadband image to be shown.

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Distribution of astrophotographers

This table shows the number of distinct astrophotographers who have been assigned and IOTD/TP award compared to the total number of images awarded.
	Distinct awarded users	Total awarded images
Image of the day
Top picks
Top pick nominations

Distribution of subject types

This table shows the distribution of awards per subject type, compared to the popularity of images of that subject type.
	Image of the day	Top pick	Top pick nominations	Total submitted
Deep sky
Solar system
Extremely wide field
Star trails
Northern lights
Noctilucent clouds
Landscape

Distribution of data sources

This table shows the distribution of awards per data source, compared to the popularity of images acquired from that data source.
	Image of the day	Top pick	Top pick nominations	Total submitted
Backyard
Traveller
Own remote observatory
Amateur hosting facility
Public amaeteur data
Professional, scientific grade data
Mix of multiple sources
Other
Unknown

The “AstroBin Image of the Day and Top Picks”, or IOTD/TP, is a long-running system to promote beautiful, interesting, peculiar, or otherwise amazing astrophotographs, with a focus on technical excellence. Learn more.

Submitted The date and time when you submitted this image for IOTD/TP consideration.	...
Views by Submitters (available since September 19th, 2023) Every image is assigned to 50% of available Submitters. In the event that at least 80% of them don't view the image before its time in the IOTD/TP process expires, it's assigned to the other 50% of Submitters and the process begins anew.
Promotions by Submitters When 3 distinct Submitters promote the image, it moves on to the next stage of the process: evaluation for Top Pick status. This requirement, in addition to anonymization of images and distribution to only a subset of them, prevents biases and ensures that the best images are selected.
Promotions by Reviewers When 3 distinct Reviewers promote the image, it moves on to the next stage of the process: evaluation for IOTD status.
Early dismissal Staff members have a lot of images to inspect on a daily basis, and they can dismiss images if they believe they don't meet the requirements for IOTD/TP selection. If an image is dismissed 5 times, it's removed from the process. This streamlines the process and ensures that any bias present in promotions could be overruled by other staff members.

Status	Basic success
Started	...
Astrometry.net job	8047691
PixInsight job	n/a
PixInsight queue size	n/a
PixInsight stage	n/a

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M20 - The Trifid Nebula

M20 - The Trifid Nebula

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M20 - The Trifid Nebula

M20 - The Trifid Nebula

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