by Ann » Sat Nov 27, 2010 7:29 am
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
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! :D
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