ANDROMEDA GALAXY, M31

Far, far away, so far that the light we see today started its journey 2.2 million years ago, is an ordinary galaxy about the size our Milky Way galaxy.  At it's center is a black hole, like in the Milky Way galaxy.  It's central region looks like this:

Although in this image the galaxy, called M31, looks like the "foreground" stars in our Milky Way galaxy, it really covers a larger area of the sky.  To see more of it we must use a longer exposure.

If you look closely you can see a faint spiral arm structure.  You can't see it?  Ok, let's increase the exposure.

Narrow dark lanes separate wide spiral arms to the upper-left of the bright central region.  To the upper-right is a dark lane with detailed structure, and farther out from it is another spiral arm.  Let's increase the exposure once more.
 

Figure 1.  The image of the central region of the Andromeda Galaxy was made with a Meade Pictor 416XTE CCD imager, a Meade LX200 10-inch Schmidt-Cassegrain telscope, and an f/3 Focal Reducer/Field Flattener, yielding an effective focal length of 27 inches and an effective f-ratio of f/3.00.  This is the average of six 20-second exposures, with another set of six 20-second "reference" images taken for subtraction of the CCD's thermal noise.  Since the Pictor CCD imager has a "pixel depth" of 16 bits (65,536 gray levels), it is possible to produce many versions of the same image for display on a monitor, where each rendition emphasizes a particular small range of light levels.  All previous images were made in this manner, and are derived from the image shown here. The image width is 34 'arc, which is slightly larger than the diameter of the average full moon (31'arc).


Figure 2.  Color version of the central region using a different telescope and camera and employing a contrast-changing procedure (digital development) that reduces saturation of the bright center while retaining contrast of the faint spiral arm structure.  [Meade RCX400 14-inch SCT, Canon 10D digital camera, exposure times of 20-sec, 61 images, 2004.09.24Z; residence at 4650 feet in Hereford, AZ].

Figure 3.  Three 20-second images of a region to the lower-right of the previous image.  The darkest lane in the previous image is now accompanied by an outer dark lane, defining three spiral arms.

Figure 4.  This is an average of 15 20-second images (equivalent to a well-guided 5-minute exposure) of a region below the previous image, taken on a different date, 2000.10.27/28.  In the upper-middle is a bright region within a spiral arm (perhaps a region of new star formation).  Note the delicate dark lanes that obscure starlight from behind them.

Figure 5.  Color picture of the same region.  [SBIG ST-8XE CCD, bin 3, RGB color combination, each color consists of median combine of 3 10-minute exposures, auto-guided; LX200 10-inch SCT; Sierra Vista, AZ, 2002.11.22 UT]

Let's "zoom in" to the bright cluster of stars in a spiral arm just upper-right of the center of the image, above. We'll do this using my Meade LX200GPS 14-inch telescope.


Figure 6.  Zoom factor of two showing the star formation region in greater detail. FWHM = 3.1 "arc. The sky area in this image is ~5% of the galaxy. [SBIG ST-8XE CCD, combine of 5 2-minute exposures, auto-guided; LX200 14-inch SCT; Hereford, AZ, 2007.12.03 UT]


Figure 7. This image shows 1) the immense size of the galaxy by inserting a full moon image having the same scale as the galaxy, and 2) the FOV of the previous image's two images. The previous image's FOV is shown by the small square and the color image's FOV is shown by the larger square.  [Nikon 400 mm EFL telephoto lens, SBIG ST-8XE CCD, mounted to Meade LX-200 SCT for guiding, 15 minute exposure, 2002.11.24/25, Hereford, AZ] 

Figure 8.  Two images (Fig.'s 3 and 4) were joined to show this larger area of the southern spiral arm region.

Figure 9.  This is the opposite end of the galaxy, the upper-left third.  Two imaged areas were joined together to produce a coverage of 34 x 57 'arc.

__________________  Images in next section are a zoom sequence, starting from a wide angle view  ______________________

Figure 10.  This wide angle picture shows M31 as part of the constellation Andromeda (two sets of lines emanating from a bright star in constellation Pegasus, in lower-right).  This image is 38 degrees wide.  [Nikon F3, 50 mm FL lens, f/2.8, mounted to Meade ETX125 telescope for guiding, 2.4-minute exposure, Fujicolor 800, 2001.09.18, Pine Mountain, 6000 ft, Ventura County, north of Ojai, CA.)

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Figure 11.  Zoom factor of 3.7.  [Nikor 105 mm FL telephoto lens, f/8,attached to a SBIG ST-8XE CCD, both mounted to Meade LX200 10-inch SCT for guiding; 16 2-minute exposures for red, green and blue filters, digital development x1.5, double size, erosion x2; 4650-foot altitude residence near Sierra Vista, AZ; 2002.12.09 UT]

Figure 12.  Same image as above (without erosion), but at full resolution (1.6 zoom factor) and cropped.


Interesting Note:

The Andromeda Galaxy, M31, is approaching our Milky Way galaxy with a speed of 300,000 miles per hour.  It is estimated that our two galaxies may collide in 3 billion years (Science, January 7, 2000, pg 64). This could cause some stars to be "flung" away from their galaxy, condemned to roam empty intergalactic space forever.  Presumably, if this happened to our sun, the solar system would go with it.

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This site opened:  October 24, 2000.  Last Update:  December 08, 2007