Starship Asterisk*

[quote="Ricardo_2095"]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.[/quote]

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 [url=http://www.rc-astro.com/php/phpthumb/cache/phpThumb_cache_rc-astro.com_srcd7f178376a8ff9feab9963acc2df5486_par0ddf367c5f01d9ba090bf356b6761f52_dat1265599437.jpeg]reflection nebula NGC 2023[/url]. There is a star inside that nebula, but it is hidden behind so much dust that it looks quite faint to our eyes.

Ann

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.

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.

[url=http://t1.gstatic.com/images?q=tbn:ANd9GcSAgeU7EtYkozVu1SngiPLvh6aqVwQSdgiwJ-kPosJWryq_Rey9Yg]One[/url] never knows what will [url=http://asterisk.apod.com/download/file.php?id=7718]end[/url] up in these threads!

Straight from the [url=http://www.equest4truth.com/images/DSC_0079.jpg]horse's rear[/url]!

Ann

[quote="Chris Peterson"][quote="emc"]I feel obligated to make a comment here… about the Horsehead’s glowing gas… but I refuse to embarrass myself… again![/quote]
[float=left][attachment=0]hh-ass.jpg[/attachment][/float]Better the glowing head gas than the glowing...[/quote]

Best horsehead picture ever, now I see that there is the body, more it's rear there too! :D :thumb_up:

[attachment=0]emo30.gif[/attachment]

[quote="emc"]I feel obligated to make a comment here… about the Horsehead’s glowing gas… but I refuse to embarrass myself… again![/quote]
[float=left][attachment=0]hh-ass.jpg[/attachment][/float]Better the glowing head gas than the glowing...

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

I feel obligated to make a comment here… about the Horsehead’s glowing gas… but I refuse to embarrass myself… again!

[quote="Psnarf"]Adding a short burst of hydrogen over a long exposure with hydrogen filtered out was a brilliant idea. Kudos.[/quote]
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.

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.

[quote="Ann"]I have a question about one of the many interesting links. The [url=http://chandra.harvard.edu/photo/cosmic_distance.html]"light years" link[/url] 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.[/quote]
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.

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...

:---[===] *

[quote="Ann"]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.[/quote]
Funny that this “60” number comes up on a Chandra page. In 2006, a new number for the [url=http://en.wikipedia.org/wiki/Hubble%27s_law#Determining_the_Hubble_constant]Hubble constant[/url] had been [url=http://spaceflightnow.com/news/n0608/08hubbleconstant/]independently determined using Chandra data[/url] (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.

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 [url=http://chandra.harvard.edu/photo/cosmic_distance.html]"light years" link[/url] 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:

[quote]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.[/quote]

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.

Ann

[url=http://apod.nasa.gov/apod/ap120909.html][img]http://apod.nasa.gov/apod/calendar/S_120909.jpg[/img] [size=150]Wisps Surrounding the Horsehead Nebula[/size][/url]

[b] Explanation: [/b] The famous Horsehead Nebula in Orion is not alone. A deep exposure shows that the [url=http://apod.nasa.gov/apod/ap030713.html]dark familiar shaped[/url] indentation, visible just below center, is part of a [url=http://apod.nasa.gov/apod/ap040115.html]vast complex[/url] of absorbing [url=http://en.wikipedia.org/wiki/Interstellar_dust]dust[/url] and [url=http://seds.org/messier/nebula.html]glowing gas[/url]. To bring out details of the [url=http://en.wikipedia.org/wiki/Horse]Horse[/url]head's pasture, amateur astronomers at the [url=http://starshadows.com/aboutus/]Star Shadow Remote Observatory[/url] in [url=http://en.wikipedia.org/wiki/New_Mexico]New Mexico[/url], [url=https://www.cia.gov/library/publications/the-world-factbook/geos/us.html]USA[/url] fixed a [url=http://www.starshadows.com/equipment/]small telescope[/url] on the [url=http://www.youtube.com/watch?v=NWNWaWUxS5g]region[/url] for over seven hours filtering out all but a [url=http://en.wikipedia.org/wiki/H_alpha]very specific color[/url] of red light emitted by [url=http://periodic.lanl.gov/1.shtml]hydrogen[/url]. They then added the image to a full color frame taken over three hours. The [url=http://www.starshadows.com/galley/display.cfm?imgID=30]resulting spectacular picture[/url] details an intricate tapestry of gaseous wisps and dust-laden [url=https://plus.google.com/u/1/103211579003359376826/posts]filaments[/url] that were created and [url=http://www.youtube.com/watch?v=-aX45GCZzVY]sculpted[/url] over eons by [url=http://www-spof.gsfc.nasa.gov/Education/wsolwind.html]stellar winds[/url] and ancient [url=http://heasarc.gsfc.nasa.gov/docs/snr.html]supernovas[/url]. The [url=http://www.google.com/search?hl=en&biw=1293&bih=977&q=horsehead+site:apod.nasa.gov&um=1&ie=UTF-8&tbm=isch]Horsehead Nebula[/url] lies 1,500 [url=http://chandra.harvard.edu/photo/cosmic_distance.html]light years[/url] distant towards the [url=http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html]constellation[/url] of [url=http://apod.nasa.gov/apod/ap040304.html]Orion[/url]. Two stars from the [url=http://apod.nasa.gov/apod/ap051013.html]Orion's Belt[/url] can be found in the [url=http://starshadows.com/galley/display.cfm?imgID=30]above image[/url].

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