APOD: The Color of IC 1795 (2011 Oct 13)

APOD Robot · Post by **APOD Robot** » Thu Oct 13, 2011 4:06 am

The Color of IC 1795

Explanation: This sharp cosmic portrait features glowing gas and obscuring dust clouds in IC 1795, a star forming region in the northern constellation Cassiopeia. Also cataloged as NGC 896, the nebula's remarkable details, shown in its dominant red color, were captured using a sensitive camera, and long exposures that include image data from a narrowband filter. The narrow filter transmits only H-alpha light, the red light of hydrogen atoms. Ionized by ultraviolet light from energetic young stars, a hydrogen atom emits the characteristic H-alpha light as its single electron is recaptured and transitions to lower energy states. Not far on the sky from the famous Double Star Cluster in Perseus, IC 1795 is itself located next to IC 1805, the Heart Nebula, as part of a complex of star forming regions that lie at the edge of a large molecular cloud. Located just over 6,000 light-years away, the larger star forming complex sprawls along the Perseus spiral arm of our Milky Way Galaxy. At that distance, this picture would span about 70 light-years across IC 1795.

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Ann · Post by **Ann** » Thu Oct 13, 2011 4:42 am

I think that IC 1795 may be very slightly similar to the Omega Nebula, M17. As is the case of M17, IC 1795 is a bright emission nebula where the massive stars energizing it and making it glow red have not yet emerged from their natal cocoon. In other words, we can't see the massive stars lighting up this nebula. This suggests that the stars inside are very young, and also probably quite massive, since the nebula is so prominent and bright. NGC 1795 is, as far as I have understood, the part of the Heart Nebula complex where star formation is most actively still going on.

Today's APOD is very beautiful, and I'm very glad to see Bob and Janice Fera here. They have been making great astrophotos for many years, and they sure deserve this honor!

Ann

zerro1 · Post by **zerro1** » Thu Oct 13, 2011 5:38 am

Sweet! wonder what scope they used?

bystander · Post by **bystander** » Thu Oct 13, 2011 5:46 am

zerro1 wrote:Sweet! wonder what scope they used?

APOD Robot wrote: This sharp cosmic portrait

Boomer12k · Post by **Boomer12k** » Thu Oct 13, 2011 6:19 am

Looks like an EEL head coming out of a den...

:-------========= ### <--Smiley looking at a Nebula...

cketter · Post by **cketter** » Thu Oct 13, 2011 8:49 am

This is such a wonderful exposure that you can easily identify some interesting features in the foreground stars: In the bottom left of the image, the two bright stars appear to be binary systems, having white dwarf companions at 1 O'clock and 8 O'clock; In the center of the nebula is possibly another binary or just a chance pairing; In the top left of the nebula there is possibly a trinary system of roughly equivalent mass stars.
Once again, wonderful exposure, I'm very pleased!

-- this smiley face is wearing H-alpha shades.

Chris

Dick Henry · Post by **Dick Henry** » Thu Oct 13, 2011 10:25 am

Another boring nebula - I want more product labels! (Hey, just joking!)

neufer · Post by **neufer** » Thu Oct 13, 2011 11:03 am

APOD Robot wrote: The Colors of IC 1795

Explanation: This colorful cosmic portrait features glowing gas and obscuring dust clouds in IC 1795, a star forming region in the northern constellation Cassiopeia. The nebula's colors were created by adopting the Hubble false-color palette for mapping narrow emission from oxygen, hydrogen, and sulfur atoms to blue, green and red colors, and further blending the data with images of the region recorded through broadband filters. Not far on the sky from the famous Double Star Cluster in Perseus, IC 1795 is itself located next to IC 1805, the Heart Nebula, as part of a complex of star forming regions that lie at the edge of a large molecular cloud. Located just over 6,000 light-years away, the larger star forming complex sprawls along the Perseus spiral arm of our Milky Way Galaxy. At that distance, this picture would span about 70 light-years across IC 1795.

APOD Robot :roll: wrote: The Color of IC 1795

Explanation: This sharp cosmic portrait features glowing gas and obscuring dust clouds in IC 1795, a star forming region in the northern constellation Cassiopeia. Also cataloged as NGC 896, the nebula's remarkable details, shown in its dominant red color, were captured using a sensitive camera, and long exposures that include image data from a narrowband filter. The narrow filter transmits only H-alpha light, the red light of hydrogen atoms. Ionized by ultraviolet light from energetic young stars, a hydrogen atom emits the characteristic H-alpha light as its single electron is recaptured and transitions to lower energy states. Not far on the sky from the famous Double Star Cluster in Perseus, IC 1795 is itself located next to IC 1805, the Heart Nebula, as part of a complex of star forming regions that lie at the edge of a large molecular cloud. Located just over 6,000 light-years away, the larger star forming complex sprawls along the Perseus spiral arm of our Milky Way Galaxy. At that distance, this picture would span about 70 light-years across IC 1795.

http://www.allthesky.com/clusters/hchi.html wrote:
Open Clusters h + chi Persei (NGC 869 & NGC 884) and

Emission Nebulae IC 1795, IC 1805 and IC 1848

orin stepanek · Post by **orin stepanek** » Thu Oct 13, 2011 12:04 pm

Kudos to Bob and Janice for this lovely picture.

NoelC · Post by **NoelC** » Thu Oct 13, 2011 3:24 pm

It's a beautiful image!

Normally we only see this as part of a wide field of the Heart Nebula, but so much more detail is visible at this scale! I've always wondered whether that dark "ridge" is a ring of dust circling the gas cloud, and at this resolution it looks all the more like it is.

I personally most appreciate astroimages presented in visual color like this. If we were "out there" and could achieve a ridiculous level of dark adaption (or just had bigger eyes with much the same spectral response), this is what we'd see.

I wonder how many stars could be made from all that hydrogen.

Well done!

-Noel

Chris Peterson · Post by **Chris Peterson** » Thu Oct 13, 2011 3:59 pm

NoelC wrote:I personally most appreciate astroimages presented in visual color like this. If we were "out there" and could achieve a ridiculous level of dark adaption (or just had bigger eyes with much the same spectral response), this is what we'd see.

Well... not really. Our sensitivity to Ha is fairly low, and this image has had the Ha signal dramatically boosted. In effect, much of the continuum light here has been blocked with respect to the narrow Ha. This makes the image look very red, but to our eyes, we'd see something much less saturated (because of all the "white" light that would be present). So the visual effect would be more like a soft pink or pink-magenta. In addition, the surrounding stars would be relatively much brighter.

A simple RGB image, properly processed, comes closest to representing how an object would appear if we had super eyes. Mix in narrow band data, and while you enhance all sorts of important detail, you push the result away from "true" color (not that there's anything wrong with that, of course).

gingerdd · Post by **gingerdd** » Thu Oct 13, 2011 7:32 pm

"How many stars from all that Hydrogen"?

At one atom per cubic centimeter and assuming seventy cubic light years I make that One Hundred and Seventy Nine Thousand Six Hundred and Sixty Six (and a half) solar masses!!

I have a lot of time on my hands

NoelC · Post by **NoelC** » Thu Oct 13, 2011 7:42 pm

Chris Peterson wrote:Well... not really.

I suppose you're right... I got kind of carried away. It would look more like this (RGB image)...

: RGB Nebula Image

179,666 solar masses in that nebula, eh? Thanks for that number, gingerdd!

-Noel

Starship Asterisk*

APOD: The Color of IC 1795 (2011 Oct 13)

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