APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

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APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby APOD Robot » Thu Nov 23, 2017 5:08 am

Image Alnitak, Alnilam, Mintaka

Explanation: Alnitak, Alnilam, and Mintaka, are the bright bluish stars from east to west (lower right to upper left) along the diagonal in this cosmic vista. Otherwise known as the Belt of Orion, these three blue supergiant stars are hotter and much more massive than the Sun. They lie from 800 to 1,500 light-years away, born of Orion's well-studied interstellar clouds. In fact, clouds of gas and dust adrift in this region have some surprisingly familiar shapes, including the dark Horsehead Nebula and Flame Nebula near Alnitak at the lower right. The famous Orion Nebula itself is off the right edge of this colorful starfield. This well-framed, 2-panel telescopic mosaic spans about 4 degrees on the sky.

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby Boomer12k » Thu Nov 23, 2017 9:06 am

Awesome View....

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby DL MARTIN » Thu Nov 23, 2017 9:51 am

HAPPY THANKSGIVING TO OUR AMERICAN FRIENDS.

heehaw

Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby heehaw » Thu Nov 23, 2017 10:39 am

Ah, Orion! As a young "astronomer" long ago who had never looked at the sky, I vividly remember casually looking out my window one winter evening and being startled to see in the sky something I'd only seen in my astronomy books: glorious Orion! That set me going on learning the (northern!) constellations.

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Shadrach, Meshach, Abednego

Postby neufer » Thu Nov 23, 2017 1:09 pm

Click to play embedded YouTube video.
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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby Case » Thu Nov 23, 2017 1:41 pm

APOD Robot wrote:Alnitak, Alnilam, and Mintaka … They lie from 800 to 1,500 light-years away

The first three links mention 800, 1340, and 915 light-years, but these Hipparcos geometric distances are further than parallax can be used for with accuracy (up to ~200 pc/652 ly).
In contrast, Wikipedia shows distances for these stars based on newer measurements using photometric methods and other assumptions. This turns out as 1260, 2000, and 1200 ly, thus about 45% further away.
We’ll see if Gaia will provide yet other distances with its higher precision, although its instruments are optimized for much fainter objects (<20 mag).

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby NCTom » Thu Nov 23, 2017 4:34 pm

Beautiful picture. Thankful for APOD, you folks that make my daily visit to APOD so educational, and I have eyes to see these stars in the NC, USA winter skies.

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby De58te » Thu Nov 23, 2017 6:04 pm

"They lie from 800 to 1,500 light-years away,"
Some other site "Universe guide dot com/star/Mintaka" says new 2007 Hipparcos data has a new measurement of Mintaka being 692.49 light years away. Yet Wikipedia has Mintaka at 1,200 lys away. Wonder what the true distance really is?

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby Chris Peterson » Thu Nov 23, 2017 6:31 pm

De58te wrote:"They lie from 800 to 1,500 light-years away,"
Some other site "Universe guide dot com/star/Mintaka" says new 2007 Hipparcos data has a new measurement of Mintaka being 692.49 light years away. Yet Wikipedia has Mintaka at 1,200 lys away. Wonder what the true distance really is?

A recent paper, in section 4.1, discusses the discrepancy between the Hipparcos data and more recent, non-parallax estimates. There is a suggestion that Hipparcos produces poor numbers with bright stars (a problem that Gaia also has).
Chris

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby Ann » Thu Nov 23, 2017 6:35 pm

Wow! This is a truly great image!

Just look at those faint, delicate dust details, and the way they so subtly change from brown (possibly faintly reflecting the overall color of the Milky Way) to blue (reflecting blue starlight) to pink (becoming "very slightly ionized" by nearby hot stars).

Note how bright Alnilam (the middle star of the Belt) seems to have blown a cavity of emptiness around itself, by pushing gas and dust away with its tremendous stellar winds. Alnilam is believed to be by far the most massive and brilliant of the Belt stars, but it looks no brighter than the other two because it is farther away.

Note the little blue clouds of reflection nebulosity near Alnilam, and also note all the rather small blue stars forming a sort of arc or a ring around Alnilam. I'm too lazy to look it up now, but I do believe that these stars are physically associated with Alnilam. The other two Belt stars, strange as it might seem, may be unrelated to Alnilam, because they are perhaps only half as far away as the supergiant star in the middle of the Belt.

The name Alnilam means "a string of pearls", a beautiful name for a beautiful star.

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby ta152h0 » Thu Nov 23, 2017 7:43 pm

the three pyramids. I think I need some medical Mary Jane after watching the black hole explanation on " how the Universe Works " by prof Kaku and prof Krauss.
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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby Petrus » Wed Nov 29, 2017 12:56 pm

Would it be possible to take a picture like this without a telescope, I mean with a standard reflex camera equipped with a telephoto zoom and a tripod? If so, what would be the suitable ISO sensitivity and exposure time?

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby Chris Peterson » Wed Nov 29, 2017 2:48 pm

Petrus wrote:Would it be possible to take a picture like this without a telescope, I mean with a standard reflex camera equipped with a telephoto zoom and a tripod? If so, what would be the suitable ISO sensitivity and exposure time?

You could certainly take a similar image with a good telephoto and a modern camera. In fact, that's not much different than what the imager did with this picture. ISO is a misunderstood concept... it doesn't really do anything when you're considering long exposures. If you were using an ordinary camera, you'd find the ISO setting that gave the lowest noise, which is usually in the range of 100-400, and then shoot as long as necessary to get the desired signal-to-noise. For an image like that, you need many minutes, and that's the real problem: the sky is moving during your exposure. So where your approach is going to fail is with the tripod. You can only make an image like this using a mount that tracks the sky. (There are inexpensive tracking camera mounts, however, which in theory could do the job. The problem is that everything needs to be very steady and the tracking very accurate, and that's what really shows the quality of equipment and skill of the imager.)
Chris

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby geckzilla » Wed Nov 29, 2017 8:05 pm

[snark]
Chris Peterson wrote:[...] the sky Earth is moving during your exposure. [...]

Fixed!
[/snark]
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: Alnitak, Alnilam, Mintaka (2017 Nov 23)

Postby Chris Peterson » Wed Nov 29, 2017 8:48 pm

geckzilla wrote:[snark]
Chris Peterson wrote:[...] the sky Earth is moving during your exposure. [...]

Fixed!
[/snark]

You heretical Copernican!
Chris

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