Looking at What You Can't See


Kye Ewing - June 2, 1999


We live in some truly unique times for astronomy! Improvements in technology have given us much better information to draw on in recent years. Unfortunately technology has also brought us the worst sky pollution ever, making it much harder to view objects of interest. Old familiars like M106 in Canes Venatici (mentioned in last month's article) can now be seen in a new light in our mind's eye, if not visually seen as well as in the past. I find it really helps in the enjoyment of looking them over carefully when you know a few things about your target, even if it's something you can't actually see.

Early in 1995 American and Japanese astronomers announced surprising new findings on M106. Using the Very Long Baseline Array they obtained a spectroscopic map of the galaxy. It provided a picture with a resolution of 0.2 light-years and line-of-sight velocity readings that are accurate to better than one kilometer per second. This map revealed several surprises. Compelling evidence for a massive black hole in the heart of this commonly observed galaxy was seen. Orbiting the nucleus of the spiral are signs of a water maser -- emitting radio waves at finely tuned wavelengths. It is theorized that a water maser is formed when water molecules in a galaxy's gas clouds are excited by x-rays coming from the area around a black hole. This sends out intense microwaves, similar to laser beams. This narrow wavelength allows researchers to "see" deep inside galaxies, past the obscuring dust and nebulae, at the very high-energy activities near the center. M106's maser data suggests that a warped disk of high energy particles exists, spinning around a central attractor (probably a black hole) with 36 million solar masses confined to a region less than one lightyear across. This exceeds the estimated densities of any other black hole candidate within a galaxy nucleus.

At 12h19m +47° 19' this spiral galaxy is listed in the NGC2000 Catalogue as being 8.3 magnitude and 18.2' across. That's big and bright enough to see in almost any telescope! When you are finished looking M106 over with high magnification switch back to low power; a one degree field would be good. Slew ½º to the west-southwest to the edge-on spiral galaxy NGC4217. At 12th magnitude this galaxy will need an 8" or larger scope and fairly dark skies to pick it up. If you can see it center M106 in the wide field again and swing east to a 5th magnitude (bright!) star, ½º away. Center the star in your field and look southeast, less than ½º from it for another small, 12th magnitude galaxy. This is the elliptical NGC4346. Bringing M106 back to the center, go ¾º north-northwest to a fainter star. Look just south of the star for another small elliptical, NGC4220.

These 12th magnitude galaxies may only look like barely perceptible smudges, but if you are lucky enough to be under dark skies take some time to look them over carefully. The atmosphere often goes steady for a moment and if you are looking carefully you can pick up more details. Using as much magnification as circumstances will permit can help, but it narrows the steadying "windows of opportunity", too. If nothing else, just being able to find them can be as rewarding as actually being able to see them in fine detail! Being close to a bright object like M106 and nearby stars makes this a much easier endeavor.

M106:

* Right Ascension: 12h 19m
    * Declination: +47°:18'
    * Distance: 25 million lightyears
    * Visual Brightness: 8.4 magnitude


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