Under The Dipper’s Handle, Part 3

May 22, 2009

Since you’ve been looking under the Dipper’s handle these last two issues, let’s try one more short tour of the area for the sake of efficiency.  Today, two “challenge objects”, both galaxies, that will test your optics, your sky, and… perhaps your patience.

(Note… these last three issues were for northerners only.  We haven’t forgotten about you in the southern hemisphere… we’ll tour a patch of southern sky in the near future.)

—– Highly Recommended —–

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Messier 101

• Pierre Mechain discovered this galaxy in 1781 and suggested Charles Messier include it in his famed catalog.  While it was discovered with a modest telescope by today’s standards,  M101 is hard for most modern stargazers to find.  It shines at magnitude 7.7, which is quite bright, but its light is spread over an area as large as the full moon.  So its surface brightness is quite low.  If you live in the city, you may not see M101 at all, no matter how big your telescope, because the background sky is brighter than the galaxy itself.

• In long-exposure images, M101 is a dazzler.  It’s one of three galaxies, along with M99 and M33, that’s referred to as the “Pinwheel” galaxy, since we view this spiral galaxy face on.   It’s some 17 million light years away.

• The position of M101 is easy enough to locate: it makes an equilateral triangle with Mizar and Alkaid, the last two stars in the Dipper’s handle.  See the map here. And yes, M101 is OVER the Dipper’s handle, but it’s a fine object and a good test of your observing skills.

Messier 106

• Unlike the nearly-symmetrical M101, M106 is a wracked mess of a galaxy, torn and misshapen by violent upheaval like the nearby M82.  It’s dimmer than M101.  But it’s a little easier to see since it has a smaller apparent surface area.  You’ll find it under the handle, about halfway between the star Chara in Canes Venatici and Phad in the Dipper’s bowl.  It’s coordinates are RA12h19m, Dec+47d18m.

• M106 is a Seyfert galaxy, which means it has unusual emission of intense X-rays and light at other wavelengths.  M106 hosts a black hole that emits high-intensity radio waves as it gobbles up stars near its core.

• M106 also contains a naturally occurring “water maser”, which is essentially a laser that emits microwaves instead of visible light.  This is one strange galaxy.

Good To Know

If you can see M101, I have good news… you’ve also seen M102.  A duplicate observation of M101 led to an incorrect entry in Messier’s catalog.  They are really the same galaxy.

Personal View

From my near-urban backyard, I can’t see M101 no matter how hard I try.  The sky is just too bright.  But it’s easy enough with a 4-inch scope from nearby rural sky.

Posted in Celestial Objects



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