Starship Asterisk*

Star Streams of NGC 4216

Explanation: Some 40 million light-years distant, edge-on spiral galaxy NGC 4216 is nearly 100,000 light-years across, about the size of our own Milky Way. Found in the dense Virgo Galaxy Cluster, NGC 4216 is centered in this deep telescopic portrait flanked by fellow Virgo cluster members NGC 4206 (right) and NGC 4222. Like other large spirals, including the Milky Way, NGC 4216 has grown by cannibalizing smaller satellite galaxies. In fact, this view has caught it in the act, with still distinct satellite galaxies showing faint star streams extending for thousands of light-years into the halo of NGC 4216. Taken as part of a survey hunting for star streams in nearby spirals, the image was recorded with a small telescope and camera able to convincingly detect faint, extended features. Having trouble spotting the star streams? Slide your cursor over the image to see a composite negative view. The streams should more easily stand out as dark swaths against a white background.

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I love this image simply for the manner in which the three galaxies are positioned, aligned in near symmetrical fashion, as if placed by some artist in a painting, incoming flying saucers in a row on approach to invasion.

That's a great image! Thanks!

Good old James D Wray of "The Color Atlas of Galaxies" taught me to recognize NGC 4216 because it has "a yellow brightening" between the dusty disk and the bright bulge. You can see the yellow brightening to the left of the bright, almost white bulge in this picture.

Wray's image of NGC 4216 showed no star formation regions at all, but today's APOD really does show emission nebulae in the thick dust lane. But it is also obvious that the galaxy has a very substantial "thick disk" without any dust at all (look at the region "below" the dust lane). Or maybe that's the halo? No, the halo would be more spherical, so this must be the thick disk, I think. In any case, the galaxy is a yellow specimen with few hot blue stars. The color index of NGC 4216 is B-V = 0.99 and U-B = 0.55, which is really red for a galaxy. But the color is clearly affected by the presence of dust, and as I said, this image does indeed reveal the presence of star formation. Thanks, Ken Crawford!

To the upper left of NGC 4216 in this picture is a small face-on galaxy, PGC 39247. PGC 39247 has a slightly larger recession velocity than NGC 4216, but the difference isn't great, and I suspect that PGC 39247 is a satellite of NGC 4216 - or at least, it could be a member of the 4216 group in the same way as smallish M33 is a member of our own Local Group. Edge-on galaxy NGC 4222 on the left also appears to be a member of the group, whereas larger edge-on galaxy NGC 4206 on the right, with the noticably blue disk, appears to be more distant.

Well, the star streams stretching around NGC 4216 and flowing into it are marvellously shaped! The most obvious star stream appears to emanate from PGC 39247, flow in a long semicircle passing close to NGC 4222, and then suddenly making such a sharp turn "upwards" toward NGC 4216 which is so sudden that you could almost cut your finger if you touched the star stream at the bend! In that long sharp stream "upwards" in the direction of NGC 4216 two small faintly bluish disintegrating dwarf galaxies are visible. Fantastic!

Also note the strange "comma-shaped" small but brightish yellow stream of stars emanating from PGC 39247. Also note the small white galaxy immediately above the disk of NGC 4206 (use the highest magification of the picture to see it). This small white galaxy seems to be completely surrounded by a thin white "loop" of stars, almost as if the galaxy was skipping rope!

This is truly a great image!

Ann

hey, you have a wrong link posted: Nov 27'th "previous day" links to Nov 16th rather than 26th.

Shabbat Shalom

APOD Robot wrote: Star Streams of NGC 4216

http://asterisk.apod.com/vie ... 31&t=22112

It was fun finding NGC 4216 in this link! http://www.atlasoftheuniverse.com/galgrps/vir.html

looks like there is a ring galaxy just above NCG 4206

Ann wrote:That's a great image! Thanks!

Good old James D Wray of "The Color Atlas of Galaxies" taught me to recognize NGC 4216 because it has "a yellow brightening" between the dusty disk and the bright bulge. You can see the yellow brightening to the left of the bright, almost white bulge in this picture.

Wray's image of NGC 4216 showed no star formation regions at all, but today's APOD really does show emission nebulae in the thick dust lane. But it is also obvious that the galaxy has a very substantial "thick disk" without any dust at all (look at the region "below" the dust lane). Or maybe that's the halo? No, the halo would be more spherical, so this must be the thick disk, I think. In any case, the galaxy is a yellow specimen with few hot blue stars. The color index of NGC 4216 is B-V = 0.99 and U-B = 0.55, which is really red for a galaxy. But the color is clearly affected by the presence of dust, and as I said, this image does indeed reveal the presence of star formation. Thanks, Ken Crawford!

This is truly a great image!

Ann

Ann, Thank You for this post! I learned a ton from your information here that I did not know about this galaxy (and the entire image). I am so happy that there are some who really study the results as there is allot of work that went into this image. I am very happy you noticed the small HII regions as I was careful not to damage them in the processing. I know this galaxy is very strong in the red channel and I had to go very deep on the exposures to bring out all of the RGB signal.

Again, thanks so much for the kind words and the education . .

Kindest Regards,

Ken Crawford
http://www.imagingdeepsky.com

Your link to the previous day's (Nov 26) photo (Flame Nebula) is erroneously to Nov 16 (Atoms-for-Peace Galaxy).
Kindly rectify.

My heartfelt thanks to APOD for the lovely images which daily show up on our screens!

The link has been fixed.