APOD: The Big Dipper (2011 Jun 24)

[APOD Robot]

The Big Dipper

Explanation: The best known asterism in northern skies, The Big Dipper is easy to recognize, though some might see The Plough. Either way, the star names and the familiar outlines will appear in this thoughtfully composed 24 frame mosaic when you slide your cursor over the image. Dubhe, alpha star of the dipper's parent constellation Ursa Major is at the upper right. Together with beta star Merak below, the two form a line pointing the way to Polaris and the North Celestial Pole off the top edge of the field. Notable too in skygazing lore Mizar, second star from the left in the dipper's handle, forms a vision-testing visual double star with apparently close Alcor. Also identified in the famous star field are Messier catalog objects. Download the higher resolution image to hunt for exquisite views of some of Messier's distant spiral galaxies and a more local owl.

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[Beyond]

The Big Dipper may be Big, but it doesn't look like it could hold any water. But it is nice to get a look at owlice's homeland.

[neufer]

M40: The “Unknown” Messier Object
Glenn Chaple

<<What is the most most-observed deep-sky object in the Messier Catalog? Some might suggest the Orion Nebula (M42) or Andromeda Galaxy (M31), both cosmic showpieces. More likely, it’s the Pleiades (M45), a striking and easily observed naked eye cluster.

What about the other end of the spectrum – those Messier objects that receive scant attention? The least-observed might well be Messier 40. Arguably the oddest member of the Catalog, M40 isn’t a cluster, nebula, or galaxy. It’s a double star! We might well label M40 “Messier’s Mistake.”

Messier stumbled upon this stellar duo while searching for a nebulous object reported to be in the area. For some reason, perhaps because it might appear nebulous at low power or in an inferior instrument, he added it to his Catalog. A century later, another comet hunter, Friedrich Auguste Theodor Winnecke, rediscovered the object. He correctly catalogued it as a double star, and it bears the alternate identity Winnecke 4. As double stars go, M40 isn’t a very inspirational sight. Its magnitude 9.7 and 10.1 component stars are separated by over 52 arc-seconds. Quite likely, it’s an optical pair. It may not be one of the night sky’s spectacles, but the path to observing all of the Messier objects goes through M40.>>

[owlice]

What a fabulous image!

[kaigun]

They mentioned the pointers to the polestar, but what about "follow the arc to Arcturus?"

[Ann]

Fantastic imge! I got stuck identifying all those galaxies. Among the more famous ones, apart from the Messier galaxies here, are NGC 3718 and companion 3729, http://www.universetoday.com/wp-content ... -small.jpg, and NGC 3631, http://www.biblioteca-tercer-milenio.co ... GC3631.gif. I'd also like to point out NGC 3642, http://www.aanda.org/index.php?option=c ... img264.gif, and Arp 299, http://www.rochesterastronomy.org/snima ... arp299.jpg, http://www.nrao.edu/pr/2003/arp299/arp2 ... t.crop.jpg. Personally I like NGC 4605, too: http://cosmo.nyu.edu/hogg/rc3/NGC_4605_ ... g_hard.jpg. I'm kind of fascinated by NGC 3549, too, one of those bulgeless fast-rotating rather yellow galaxies that are classified as Sc galaxies even though they are rather poor in star formation: http://cosmo.nyu.edu/hogg/rc3/NGC_3549_ ... g_hard.jpg. And I want to mention NGC 3953, a handsome galaxy that can be seen below M109 in today's APOD: http://www.noao.edu/outreach/aop/observ ... ayness.jpg

I also have to mention NGC 3733, which appears to be "sticking out of a red star"! Here is a lovely image of this galaxy-star pair by R Jay GaBany:

Click to view full size image

As for the rest of the galaxies I found, I'll spare you...

Fantastic image, Rogelio!

Ann

[Alessandro]

What about the object at X=6274, Y=2254 (from top left)?
an easter egg or a photographic artifact?
C°°)

[Ann]

What about the object at X=6274, Y=2254 (from top left)?
an easter egg or a photographic artifact?
C°°)

I'm afraid I don't understand your coordinates, Alessandro. Can you explain a bit better? Slide your cursor over the image and you'll get several names and designations. Is your "Easter egg" close to any of the labelled objects in the picture?

By the way, thanks for the explanation about M40, Neufer! I couldn't make head or tail of it, and I absolutely couldn't remember ever reading about it, either. What's worse, when I told my software to take me to M40, I got - zilch! No, I got two faint stars, HD 238107 and HD 238108, two circa G0-type stars. They are very probably an optical pair, like you said. Sheesh! Oh, but Charles Messier did well anyway... I mean, he didn't have access to splendid images like today's APOD when he was scanning the sky.

Ann

[Alessandro]

Ops, sorry.. It is a small bluish circle below and left of M108, near Merak
C°°)

[Alessandro]

Gulp. Squared sorry, it's M97, I suppose.. (thanks to Ann for her kindness: i promise to hold back further superficial posts C°°(

[mexhunter]

It is an extraordinary mosaic, anyone who sees the size of the "dipper" knows the immense work involved in this picture.
Congratulations Rogelio.
Greetings
César

[matsutoya]

This higher resolution of todays picture of the Big Dipper has what appears to be an unusual string of 28 stars or so trailing away from the star Merak. I have never seen something like this before, nor have I seen any attempt at explaining this sort of phenonema. I was wondering if M 108 and/or M 97 may have played a part in causing of this, since we see on the Owl Nebula photo what appears to be a small remnant of the same color trailing that beatiful nebula.

[Jake81499]

Im not much of a star gazer so please excuse me for not knowing the names of the stars. On the far right hand side of this photo under the bottom star of the dipper there is a streak. Does anyone know what that might be?

[neufer]

On the far right hand side of this photo under the bottom star of the dipper there is a streak. Does anyone know what that might be?

http://apod.nasa.gov/apod/ap101216.html

[orin stepanek]

Very nice APOD.

[Chris Peterson]

They mentioned the pointers to the polestar, but what about "follow the arc to Arcturus?"

And from there, "on to Antares".

[kshiarella]

What a great image! My favorite APOD addiction is scanning the backgrounds of high resolution mosaic shots for background galaxies. I find that fascinating. But happening upon the Owl was the true treat here.

[luigi]

This is a beautiful constellation portraits. Maybe I'm crazy but I believe constellations are nicer than people for portraits
Thank you to APOD and Rogelio!

[bystander]

They mentioned the pointers to the polestar, but what about "follow the arc to Arcturus?"

Big Dipper Navigation

[islader2]

Neufer: great post! But I wonder if nontypical Messier objects {such as M40} might not have something to do with Messier's obsession about having 100 items to list? Some of us psychometricians often dwell on stuff like that. Thanx.

[graydawn]

Hello,
Near top left corner of Big Dipper mosaic is M101. Enlarge the picture. At about 8 o'clock from M101, 2 inches away from M101, is what appears to be a transparent sphere, looking carefully, another object can barely be seen at about 1 o'clock within the spere.
What is this object?

thank you,

[peter2]

In poland we call it "The big wheel-cart", as opposed to the small(er) one

[neufer]

Neufer: great post! But I wonder if nontypical Messier objects {such as M40} might not have something to do with Messier's obsession about having 100 items to list? Some of us psychometricians often dwell on stuff like that. Thanx.

I don't think that Messier every had exactly 100 items in his catalogue.

However, his first catalogue containing 45 objects came out in Messier's 45th year. (Candles on the cake?)

<<Charles Messier (26 June 1730 – 12 April 1817) was a French astronomer most notable for publishing an astronomical catalogue consisting of deep sky objects such as nebulae and star clusters that came to be known as the 110 "Messier objects". The purpose of the catalogue was to help astronomical observers, in particular comet hunters such as himself, distinguish between permanent and transient objects in the sky.

The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. The final version of the catalogue was published in 1781, in Connoissance des Temps for 1784. The final list of Messier objects had grown to 103.

On several different occasions between 1921 and 1966, astronomers and historians discovered evidence of another seven deep-sky objects that were observed either by Messier or his friend and assistant, Pierre Méchain, shortly after the final version was published. These seven objects, M104 through M110, are accepted by astronomers as "official" Messier objects.

The catalogue is not organized scientifically by object type or by location, as the later New General Catalogue would be. Nonetheless, the Messier catalogue comprises nearly all the most spectacular examples of the five types of deep sky object -- diffuse nebulae, planetary nebulae, open clusters, globular clusters and galaxies -- visible from European latitudes. Because these objects could be observed with the relatively small-aperture refracting telescope (approximately four inches) used by Messier to study the sky, they are among the brightest and most attractive deep sky objects observable from earth. Furthermore, almost all of the Messier objects are among the closest to our planet in their respective classes, which makes them heavily studied with professional class instruments that today can resolve very small and visually spectacular details in them.>>

[Wolf Kotenberrg]

I grew up where the Southern Cross pointed south. Maybe someday they will put a telescope on the Moon, or even some asteroid. With some really good batteries and a fantastic ZOOM lens.

[Ann]

Hello,
Near top left corner of Big Dipper mosaic is M101. Enlarge the picture. At about 8 o'clock from M101, 2 inches away from M101, is what appears to be a transparent sphere, looking carefully, another object can barely be seen at about 1 o'clock within the spere.
What is this object?

thank you,

That is NGC 5474, one of M101's satellite galaxies.

Click to view full size image

NGC 5474 by Adam Block. The object that seems to be inside this galaxy is actually the galaxy's bulge. The disk has been displaced to one side, probably due to interaction with M101.

Ann