Jim's Corner Blog

Messier Objects in Ursa Major: A Mini-Messier Marathon

M40

Ursa Major

RA 12h 20.0m

Dec +58°22′

Mag 9.0 and 9.3

M81

Alternate: NGC 3031, Bode’s Galaxy

Ursa Major

RA 9h 55.6 m

Dec +69º 04′

Magnitude 6.9

M82

Alternate: NGC 3034

Ursa Major

RA 9h 55.8 m

Dec +69º 04′

Magnitude 8.4

M97

Alternate: Owl Nebula

Ursa Major

RA 11h 12.0m

Dec +55º18′

Mag 9.6

M101

Alternate: M102

Ursa Major

RA 14h 3m 2s

Dec +54º35′

Mag 9.6

M108

Ursa Major

RA 11h 08m 7s

Dec +55º57′

Mag 10.0

M109

Ursa Major

RA 11h 55.0m

Dec +53º39′

Mag 11.0

With March fast approaching, now is a good time to practice Messier object location finding and observational skills. Ursa Major is a perfect constellation to familiarize with deep sky observing, with seven Messier objects within this favorite constellation.

As an somewhat odd start, M40 is NOT a deep sky object, but a double star! Historians have long felt that Charles Messier mistook this double star for a nebula. But it must still be accounted for in a mini- or full Messier Marathon. M40 is easily observed with a four-inch telescope.

M81 and M82 are a cosmic duet pair of galaxies is one of the deep sky showpieces that captures the imagination of every backyard astronomer. Easily seen through a 4-inch refractor on a dark moonless night and a favorite target for 8-inch SCT owners, M81 and M82 are separated by only 38′. M81 and M82 can even be seen through 50-mm or greater binoculars from a dark country site.

Pierre Mechain independently recovered both galaxies in August 1779 and reported their positions to his friend Charles Messier. Messier added both galaxies to his catalog after his position measurements on February 9, 1781.

The pronounced grand-design spiral galaxies M81 and M82 are part of a nearby group called M81. M81 is characterized in the Hubble classification system as a classic Sa-type galaxy, while M82 is an irregular or IO classification. Astronomers believe tens of million years ago, a close encounter occurred between the galaxies M81 and M82. During this near-miss, the larger and more massive M81 has dramatically deformed M82 by gravitational interaction. The encounter has also left traces in the spiral pattern of the brighter and larger galaxy M81, first making it overall more pronounced, and second in the form of the dark linear feature in the nuclear region. The galaxies are still close together, their centers separated by a linear distance of only about 150,000 light years.

This pair of galaxies can be seen with 12×60 or 20×80 binoculars, and occasionally with 7×50 binoculars by sharp-eyed observers in very dark sites. My f/7.8 4-inch refractor with a wide-field 24-mm eyepiece with an AFOV of 68ºyields a magnification of 36x and a true field of 2.24º. This combination easily captures M81 as a bright oval haze and M82 as a slim cigar shape. The 8-inch SCT with the same eyepiece at 83x and a true FOV of 0.98º begins to show a hazy halo of nebulosity around M81, with M82 displaying a nucleus. Higher magnifications will help bring out the detail, and a larger telescope will bring out additional detail.

The Owl Nebula, M97, is a planetary nebula that is noted for features that faintly resembles an owl’s head. The Owl Nebula monicker was attached to M97 following Lord Rosse’s observations of the planetary nebula through his famous 72-inch Leviathan of Parsonstown.

This is an object that benefits form the use of a large aperture telescope or the use of an UHC nebula filter or OIII nebula filter. The “owl eyes” are clearly obvious with a telescope of apertures larger than 8”, especially with a nebula filter. Dark skies and nebula filter is needed with smaller apertures.

The Owl Nebula is an interesting object to test the effectiveness of light pollution filters and nebula filters. Under suburban skies, even an eleven inch SCT had difficulty seeing M97 without a filter aid. The addition of an LPR filter enabled sighting the Owl with averted vision. However the use of an OIII or UHC filter enabled the direct observation of the Owl Nebula even under light polluted suburban skies.

M101 was initially discovered by Pierre Mechain in 1781. He later that year made a duplicate observation of this galaxy, which was cataloged by Messier as M102. Mechain retracted is

his M102 sighting in 1783, realizing his duplication mistake. Thus, in counting Messier objects captured during a mini- or full Marathon, this galaxy counts as two objects.

M101 in astrophotos is a beautiful face-on Sc spiral galaxy with clearly separated arms filled with blue stars. The arms can be observed in telescopes of double digit apertures, but the spiral shape will not be seen in a four inch refractor. Instead only the central concentration of stars can be seen.

M108 is a Sc spiral galaxy seen from a nearly edge-on perspective. Another Pierre Mechain discovery from his 1781-1782 observations. This rather large object can be seen in dark skies through binoculars, and is easily captured by a four-inch refractors and 120x or higher. It is only 1ºfrom M97. It is visually a series of mottled patches of light. Larger apertures brings a broken patched structure into view.

M109 is an unspectacular barred galaxy that can be seen through binoculars just 1ºfrom the Ursa Major star Phecda at the bottom of the Big Dipper bowl. Seen through a 4-inch refractor the bright central region can be seen. M109 is another Pierre Mechain discovery during his productive 1781-1782 period.

Locating and observing Ursa Major Messier objects is good practice for the March Messier Marathon, or half-marathon if you want to go to sleep at midnight!

Jim's Corner Blog

M81, M82

This cosmic duet pair of galaxies is one of the deep sky showpieces that captures the imagination of every backyard astronomer. Easily seen through a 4-inch refractor on a dark moonless night and a favorite target for 8-inch SCT owners, M81 and M82 are separated by only 38′. M81 and M82 can even be seen through 50-mm or greater binoculars from a dark country site.

M81 and M82 with NGC 3077 (Illustration courtesy of Jon Talbot)

M81
Alternate: NGC 3031, Bode’s Galaxy
Ursa Major
RA 9h 55.6 m
Dec +69º 04′
Magnitude 6.9

M82
Alternate: NGC 3034
Ursa Major
RA 9h 55.8 m
Dec +69º 04′
Magnitude 8.4

Historically, both galaxies were first discovered by Johann Elert Bode on December 31, 1774. Bode described M81, now nicknamed Bode’s Galaxy, as a “nebulous patch,” about 0.75 degrees away from M82, which “appears mostly round and has a dense nucleus in the middle.” According to Bode’s historical notes:

I found through the seven-foot telescope, closely above the head of UMa, east near the star d at its ear, two small nebulous patches separated by about 0.75 degrees, the positions of which relative to the neighbored small stars are shown in the tenth figure. The patch Alpha (M81) appears mostly round and has a dense nucleus in the middle. The other, Beta (M82), on the other hand, is very pale and of elongated shape. I could determine the separation of Alpha to d as 2deg 7′, to Rho as 5deg 2′ and to 2 Sigma as 4deg 32′ with some accuracy; Beta was too faint and disappeared from my eyes as soon as I shifted apart the halves of the objective glass.

Pierre Mechain independently recovered both galaxies in August 1779 and reported their positions to his friend Charles Messier. Messier added both galaxies to his catalog after his position measurements on February 9, 1781, and wrote of the cosmic duet:

Nebula (M82) without star, near the preceding [M81]; both are appearing in the same field of the telescope, this one is less distinct than the preceding; its light faint and [it is] elongated: at its extremity is a telescopic star. Seen at Berlin, by M. Bode, on December 31, 1774, and by M. Mechain in the month August 1779.

The pronounced grand-design spiral galaxies M81 and M82 are part of a nearby group called M81. M81 is characterized in the Hubble classification system as a classic Sa-type galaxy, while M82 is an irregular or IO classification. Astronomers believe tens of million years ago, a close encounter occurred between the galaxies M81 and M82. During this near-miss, the larger and more massive M81 has dramatically deformed M82 by gravitational interaction. The encounter has also left traces in the spiral pattern of the brighter and larger galaxy M81, first making it overall more pronounced, and second in the form of the dark linear feature in the nuclear region. The galaxies are still close together, their centers separated by a linear distance of only about 150,000 light years.

M81 is home to over 250 million stars.  M81 is the namesake of the M81 cluster of galaxies, and exhibits a Doppler blue shift, meaning it is approaching the Milky Way instead of receding.

At the center of M81 is a nucleus containing a supermassive black hole that is 15 times the size of the supermassive black hole at the center of the Milky Way.

M81 has two spiral arms containing large quantities of interstellar dust and a number of starburst regions.  Spitzer Space Telescope data have revealed young hot blue stars forming in these regions that are heating the interstellar dust, thus increasing the infrared emissions of  the galaxy.

M82, the Cigar Galaxy, is one of the most interesting galaxies in the Messier catalog, and has undergone extensive study by astronomers.  It is the closest starburst galaxy to Earth and is the prototypical galaxy of this type.  M82 also represents one of the smallest galaxies in the Messier catalog.  Unlike M81, M82 is redshifted and is receding at a rate of 203 km/sec. 

M82 has been long classified as an irregular galaxy.  However, near-infrared observations of M82 within the past two decades have revealed two symmetric spiral arms in the galaxy.  The near-miss encounter with M81 stimulated star-forming activity within M82 that is ten times that of the Milky Way galaxy.

This pair of galaxies can be seen with 12×60 or 20×80 binoculars, and occasionally with 7×50 binoculars by sharp-eyed observers in very dark sites. My f/7.8 4-inch refractor with a wide-field 24-mm eyepiece with an AFOV of 68º yields a magnification of 36x and a true field of 2.24º. This combination easily captures M81 as a bright oval haze and M82 as a slim cigar shape. The 8-inch SCT with the same eyepiece at 83x and a true FOV of 0.98º begins to show a hazy halo of nebulosity around M81, with M82 displaying a nucleus. Higher magnifications will help bring out the detail, and a larger telescope will bring out additional detail.