APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 09)

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APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 09)

Post by APOD Robot » Sun Sep 09, 2012 4:05 am

Image Wisps Surrounding the Horsehead Nebula

Explanation: The famous Horsehead Nebula in Orion is not alone. A deep exposure shows that the dark familiar shaped indentation, visible just below center, is part of a vast complex of absorbing dust and glowing gas. To bring out details of the Horsehead's pasture, amateur astronomers at the Star Shadow Remote Observatory in New Mexico, USA fixed a small telescope on the region for over seven hours filtering out all but a very specific color of red light emitted by hydrogen. They then added the image to a full color frame taken over three hours. The resulting spectacular picture details an intricate tapestry of gaseous wisps and dust-laden filaments that were created and sculpted over eons by stellar winds and ancient supernovas. The Horsehead Nebula lies 1,500 light years distant towards the constellation of Orion. Two stars from the Orion's Belt can be found in the above image.

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Ann
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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Ann » Sun Sep 09, 2012 5:40 am

This is a beautiful and spectacular image that deservedly makes a comeback on this Sunday. Sundays are, after all, the "repeat day" of APOD.

I have a question about one of the many interesting links. The "light years" link takes us to a Chandra page that says that the Hubble constant, the rate at which the (local) universe is expanding, is around 60 km/s/Mpc. I thought that the currently accepted value was more like 70 km/s/Mpc.

By the way, the same Chandra link suggests that the expansion of the universe is constant:
According to Hubble's law, the universe is expanding in such a way that distant galaxies are receding from one another with a speed which is proportional to their distance.
One of the most fascinating problems of modern cosmology is that the universe doesn't appear to be expanding at a constant rate, but instead it is accelerating.

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Case » Sun Sep 09, 2012 7:21 am

Ann wrote:a Chandra page that says that the Hubble constant, is around 60 km/s/Mpc. I thought that the currently accepted value was more like 70 km/s/Mpc.
Funny that this “60” number comes up on a Chandra page. In 2006, a new number for the Hubble constant had been independently determined using Chandra data (and radio observations): 77 ± 6 (km/s)/Mpc.
Using the HST data, researchers found a number of 72 ± 8 (2001).
Using WMAP data, researchers found a number of 71 ± 2.5 (2010) for the simplest version of the ΛCDM model. More general models find around 67 ± 4.

“71” seems to fit all these margins, but “60” seems exceptionally low.

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Boomer12k » Sun Sep 09, 2012 2:20 pm

Wondrous.... :D

And it rises now up in the morning now...too bad it is getting chilli here for the moment, and is going to be overcast. M42 is always a favorite...

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Chris Peterson » Sun Sep 09, 2012 3:10 pm

Ann wrote:I have a question about one of the many interesting links. The "light years" link takes us to a Chandra page that says that the Hubble constant, the rate at which the (local) universe is expanding, is around 60 km/s/Mpc. I thought that the currently accepted value was more like 70 km/s/Mpc.
The number is a bit odd. While there are still proponents of values as low as ~50 km/s/Mpc, and higher than 80 km/s/Mpc, multiple independent measurements in the last few years have all homed in on values around 70 km/s/Mpc. The Chandra page shows a recent revision date, but it seems like this old value may have slipped through the cracks.
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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Psnarf » Sun Sep 09, 2012 3:11 pm

Four words: Speck Tack You Lar
Spectacular image! Well worth the work and patience it took to produce the image. Adding a short burst of hydrogen over a long exposure with hydrogen filtered out was a brilliant idea. Kudos.

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Chris Peterson » Sun Sep 09, 2012 3:28 pm

Psnarf wrote:Adding a short burst of hydrogen over a long exposure with hydrogen filtered out was a brilliant idea. Kudos.
That's not how the image was constructed. It's a relatively short RGB exposure combined with a very long Ha exposure. That's a common imaging technique: the deep Ha is treated as a luminance channel, which shows the dominant hydrogen structure with excellent S/N, and the RGB data serves to colorize the image. Nothing is filtered out (except by virtue of being outside any filter's bandpass); the Ha light is present in both the Ha luminance channel as well as the R channel.
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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by emc » Sun Sep 09, 2012 4:01 pm

I feel obligated to make a comment here… about the Horsehead’s glowing gas… but I refuse to embarrass myself… again!
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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by biddie67 » Sun Sep 09, 2012 5:02 pm

A wonderous photograph!! I usually see the Horse Head as a closeup ~~ this picture gives a fantastic sense of proportion to the whole area.

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Chris Peterson » Sun Sep 09, 2012 10:48 pm

emc wrote:I feel obligated to make a comment here… about the Horsehead’s glowing gas… but I refuse to embarrass myself… again!
hh-ass.jpg
Better the glowing head gas than the glowing...
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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Beyond » Sun Sep 09, 2012 11:20 pm

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Moonlady » Mon Sep 10, 2012 12:16 am

Chris Peterson wrote:
emc wrote:I feel obligated to make a comment here… about the Horsehead’s glowing gas… but I refuse to embarrass myself… again!
hh-ass.jpg
Better the glowing head gas than the glowing...
Best horsehead picture ever, now I see that there is the body, more it's rear there too! :D :thumb_up:

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Ann » Mon Sep 10, 2012 12:31 am

Straight from the horse's rear!

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by emc » Tue Sep 11, 2012 12:12 pm

One never knows what will end up in these threads!
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drerchem

another nebula?

Post by drerchem » Tue Sep 11, 2012 3:10 pm

All the other posts here are actually useful. I just submit this to suggest that if the Horsehead in the center of this image, then there is Rabbit to the left of it.

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Ricardo_2095 » Wed Jan 01, 2014 7:33 pm

The text of the image says:

Two stars from the Orion's Belt can be found in the above image.

But note that we can observe three star of the Orion's Belt: Alnilam, Alnitak and other to the right of Alnitak.

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Re: APOD: Wisps Surrounding the Horsehead Nebula (2012 Sep 0

Post by Ann » Wed Jan 01, 2014 7:48 pm

Ricardo_2095 wrote:The text of the image says:

Two stars from the Orion's Belt can be found in the above image.

But note that we can observe three star of the Orion's Belt: Alnilam, Alnitak and other to the right of Alnitak.
The three stars of Orion's Belt are Alnitak, Alnilam and Mintaka, but Mintaka can't be seen in this image. Near the image center, though, is Sigma Orionis, an important multiple O-type star that plays an important part in sculpting the Horsehead Nebula. To the lower right of Alnitak, to the lower left of the Horsehead Nebula, is reflection nebula NGC 2023. There is a star inside that nebula, but it is hidden behind so much dust that it looks quite faint to our eyes.

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