APOD: The Big Dipper Enhanced (2015 Mar 17)

APOD Robot · Post by **APOD Robot** » Tue Mar 17, 2015 4:11 am

The Big Dipper Enhanced

Explanation: Do you see it? This common question frequently precedes the rediscovery of one of the most commonly recognized configurations of stars on the northern sky: the Big Dipper. This grouping of stars is one of the few things that has likely been seen, and will be seen, by every human generation. In this featured image, however, the stars of the Big Dipper have been digitally enhanced -- they do not really appear this much brighter than nearby stars. The image was taken earlier this month from France. The Big Dipper is not by itself a constellation. Although part of the constellation of the Great Bear (Ursa Major), the Big Dipper is an asterism that has been known by different names to different societies. Five of the Big Dipper stars are actually near each other in space and were likely formed at nearly the same time. Relative stellar motions will cause the Big Dipper to slowly change its apparent configuration over the next 100,000 years.

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Ann · Post by **Ann** » Tue Mar 17, 2015 5:37 am

I saw this picture recently in the Recent Submissions folder and I really, really like it! Blue-white Alkaid, end star of the handle of the Big Dipper, is truly made to sparkle here!

Thanks, VegaStar, for this lovely enhanced cosmic Dipper!

Ann

starsurfer · Post by **starsurfer** » Tue Mar 17, 2015 7:23 am

It is indeed a marvellous image of a marvellous asterism! I think some of its stars are part of the Ursa Major moving group?

chuckster · Post by **chuckster** » Tue Mar 17, 2015 7:43 am

Constellations will all change over time, but I wonder if anyone has figured out what they'd all look like from somewhere
else besides Earth, such as the Kuiper belt, or Alpha Centauri. I wonder how many of the distances to the stars comprising the 88 constellations are known.

hoohaw · Post by **hoohaw** » Tue Mar 17, 2015 9:08 am

chuckster wrote:Constellations will all change over time, but I wonder if anyone has figured out what they'd all look like from somewhere
else besides Earth, such as the Kuiper belt, or Alpha Centauri. I wonder how many of the distances to the stars comprising the 88 constellations are known.

Get the Voyager software! You can view the sky from off the Earth!

RJN · Post by **RJN** » Tue Mar 17, 2015 1:47 pm

Why is this image so popular? I would appreciate insight into this. This image did very well on Facebook Sky. So well, in fact, that I APODed it with the hope that it would also be a popular APOD. (No, potential popularity is not the only selection criterion for APOD.) Sure enough, it is also "Liking" quite well on Facebook APOD, and seems destined to be one of the few APODs to garner over 2,000 Facebook Likes in a single day.

But why? I would not have guessed that this image would be this popular. The image does not have an interesting foreground, for example, nor an interesting tapestry of colors or textures. The image is not related to a topical news event, nor mimics an obvious anthropological icon. It is clearly enhanced to bring it out of the range of what people would actually see. Yet it is undeniably very popular. One might guess that after nearly 20 years I would be somewhat adept at guessing which image submissions would anchor popular APODs, but once again I am surprised. Your thoughts would be appreciated!

- RJN

Peter Bradford · Post by **Peter Bradford** » Tue Mar 17, 2015 1:57 pm

In my opinion, this image undeniably very popular because it is of the one "constellation" that we all learned about as a child; perhaps because of the way it can be used to locate Polaris, the North Star.

Does anybody still call it by the name it was given when I was a child growing up in the UK--"The Plough"? I guess we don't use the word "dipper" much in Britain.

Chris Peterson · Post by **Chris Peterson** » Tue Mar 17, 2015 2:24 pm

chuckster wrote:Constellations will all change over time, but I wonder if anyone has figured out what they'd all look like from somewhere else besides Earth, such as the Kuiper belt, or Alpha Centauri.

Yes, if by "constellations" you are referring to the primary asterisms we associate with them. From the Kuiper belt we could not see any difference in shape. From Alpha Centauri, I doubt any difference would be obvious, although a few stars might shift just a little. These distances are simply too small compared with the distance to the stars in the asterisms.

I wonder how many of the distances to the stars comprising the 88 constellations are known.

Every star in the sky is in one of those constellations. For most, we don't have very accurate distances. But for the bright stars making up the primary asterisms, we generally do have reasonably accurate distances, because these stars are mostly quite close to the Earth, making parallax measurements possible.

Tszabeau · Post by **Tszabeau** » Tue Mar 17, 2015 2:37 pm

Peter Bradford wrote:In my opinion, this image undeniably very popular because it is of the one "constellation" that we all learned about as a child; perhaps because of the way it can be used to locate Polaris, the North Star.

Does anybody still call it by the name it was given when I was a child growing up in the UK--"The Plough"? I guess we don't use the word "dipper" much in Britain.

Ron-Astro Pharmacist · Post by **Ron-Astro Pharmacist** » Tue Mar 17, 2015 3:12 pm

chuckster wrote:Constellations will all change over time, but I wonder if anyone has figured out what they'd all look like from somewhere
else besides Earth, such as the Kuiper belt, or Alpha Centauri. I wonder how many of the distances to the stars comprising the 88 constellations are known.

I don't know about the other 87 but this shows today's relatively well.

: Big Dipper Distance.jpg (8.22 KiB) Viewed 3811 times

And if someone needs a project this could be fun - age appropriate.

http://www.google.com/url?sa=t&rct=j&q= ... G62oKAa0Tw

Ron-Astro Pharmacist · Post by **Ron-Astro Pharmacist** » Tue Mar 17, 2015 3:26 pm

Unfortunately I have trouble telling heads from tails?

: Big Dipper 2.jpg (4.14 KiB) Viewed 3805 times

: Big Dipper One.jpg (3.43 KiB) Viewed 3805 times

rstevenson · Post by **rstevenson** » Tue Mar 17, 2015 3:32 pm

Ron-Astro Pharmacist wrote:
chuckster wrote:Constellations will all change over time, but I wonder if anyone has figured out what they'd all look like from somewhere else besides Earth, such as the Kuiper belt, or Alpha Centauri. I wonder how many of the distances to the stars comprising the 88 constellations are known.
I don't know about the other 87 but this shows today's relatively well.

Big Dipper Distance.jpg
And if someone needs a project this could be fun - age appropriate.

http://www.google.com/url?sa=t&rct=j&q= ... G62oKAa0Tw

Thereby illustrating the difficulties of measuring star distances. Your diagram Big Dipper Distance.jpg shows Alkaid at 210 ly from Earth, and Dubhe at 105 ly. The exercise you link to sets both of them at 123 ly, thereby yielding a quite different 3D view. Wikipedia, ever helpful, puts Dubhe at 124 ly and Alkaid at 101 ly.

Rob

rstevenson · Post by **rstevenson** » Tue Mar 17, 2015 3:41 pm

RJN wrote:Why is this image so popular? ...

Some years ago my wife and I ran our own greeting card publishing business, featuring fine art images. We coined the term "cardable art" to define the images we could publish as greeting cards, and to distinguish them from the many other fine art images which, however interesting, meaningful, or powerful they may have been, simply would not work as greeting cards. That sounds as if we were being cynical, but that's not how we meant it. It was simply a practical way to sift out the saleable images (we hoped) from those that would not do well in the broad marketplace. Occasionally, because we loved the art so much, we would publish a more difficult image. We knew what would happen, and it did -- they sold poorly. But we felt better for making the attempt.

This image of the Big Dipper seems to me to be an excellent example of "cardable art". It's simple, clear, and enjoyable, and it doesn't make demands on the viewer. It's approachable by all.

Rob

Cousin Ricky · Post by **Cousin Ricky** » Tue Mar 17, 2015 3:50 pm

Ron-Astro Pharmacist wrote:
Big Dipper Distance.jpg

If VegaStar portrayed the stars as if they were all the same distance from us, this would explain why Alkaid is so much brighter than the other stars. But there is no information posted on how the image was maide.

MarkBour · Post by **MarkBour** » Tue Mar 17, 2015 3:54 pm

Of course Merak and Dubhe do not point to Polaris in true 3-D. It would be just too much of a coincidence to hope for. On the other hand, since the distances do increase as one goes from Merak to Dubhe to Polaris (Wikipedia is saying 80 LY, 123 LY, and 433 LY). Then I suppose it is not as far from lining up as it could have been.

I wonder if the popularity of the APOD has anything to do with St. Patrick? After a lot of drinking, people do tend to see stars, one way or another. And the big dipper has been associated with drinking in the past http://en.wikipedia.org/wiki/Follow_the ... n%27_Gourd.

Ron-Astro Pharmacist · Post by **Ron-Astro Pharmacist** » Tue Mar 17, 2015 4:09 pm

Cousin Ricky wrote:
Ron-Astro Pharmacist wrote:
Big Dipper Distance.jpg
If VegaStar portrayed the stars as if they were all the same distance from us, this would explain why Alkaid is so much brighter than the other stars. But there is no information posted on how the image was maide.

I found the image on Google images. Its sourse was as listed below.

http://www.britannica.com/EBchecked/med ... -to-belong

geckzilla · Post by **geckzilla** » Tue Mar 17, 2015 4:21 pm

RJN wrote:Why is this image so popular?

1. It is easily readable from a thumbnail, even a very small thumbnail. This is a big plus. When something is nondescript in a thumbnail, there isn't enough information presented to interest someone into clicking into the bigger version, much less clicking a "like" button.
2. People love shiny stuff. It has bling. The stars have been edited to appear to shine very brightly, especially the tip of the dipper's handle. Note however that even though they have been "Photoshopped" the image does not clearly exude a "Photoshopped" look to it. You may have noticed that even if something is totally real, if it looks faked people get angry or disappointed because they feel like someone is trying to fool them.
3. And yes, the Big Dipper itself is a well-known and well-loved asterism as others have noted. Moreover, it's a single, recognizable image. Contrast against Rogelio's Orion mosaic of yesterday. Visually interesting but no focal point. The eye wanders endlessly over the image without recognizing anything familiar until some effort is exerted.

Edit: I should note I would also not have guessed this image would be so popular. I think when you pretty much look at images for a living you become somewhat blind to seeing images in the same way as someone who never views them critically or as a job.

Ann · Post by **Ann** » Tue Mar 17, 2015 4:51 pm

RJN wrote:Why is this image so popular? I would appreciate insight into this. This image did very well on Facebook Sky. So well, in fact, that I APODed it with the hope that it would also be a popular APOD. (No, potential popularity is not the only selection criterion for APOD.) Sure enough, it is also "Liking" quite well on Facebook APOD, and seems destined to be one of the few APODs to garner over 2,000 Facebook Likes in a single day.

But why? I would not have guessed that this image would be this popular. The image does not have an interesting foreground, for example, nor an interesting tapestry of colors or textures. The image is not related to a topical news event, nor mimics an obvious anthropological icon. It is clearly enhanced to bring it out of the range of what people would actually see. Yet it is undeniably very popular. One might guess that after nearly 20 years I would be somewhat adept at guessing which image submissions would anchor popular APODs, but once again I am surprised. Your thoughts would be appreciated!

- RJN

Here are my guesses:

1) Recognition. If there is one "constellation" that people in general recognize, I would guess it is Orion's Belt. If there is another "constellation" that is recognized by almost anyone in the northern hemisphere that has bothered to learn any patterns in the night sky at all, I'd say it's the Big Dipper.

2) It stands alone. Unlike Orion's Belt, the Big Dipper doesn't have a lot of competition when it comes to bright stars in its general Earth sky vicinity. This relative emptiness in the sky around the Big Dipper makes it stand out more.

3) Elegant shape. The shape of the Big Dipper is elegant and satisfying. Rather few constellations or asterisms are.

4) Similar brightness and spacing. The Big Dipper is interesting in that its stars are quite regularly spaced, widely but not too widely spaced, and they are of relatively similar brightness. (Megrez, admittedly, is an underachiever.)

5) Signpost in the sky. Many of those who recognize the Big Dipper also know that two stars in this asterism point in the direction of Polaris, the North Star. Since Polaris is a very popular star in itself, the Big Dipper's role in helping us find this northern gem in the sky also helps making the Dipper popular.

6) Dependable. For many (all?) of us in the northern hemisphere, the Big Dipper never sets, and so it is visible in a dark sky all year round. That makes it a dependable and trustworthy companion.

7) Compass. The fact that the Big Dipper is always visible every clear night in the northern hemisphere, plus the fact that it points the way to the North Star, means that you can use it to navigate. If you are out in the wilderness and lose your way, you can use the Big Dipper to find your way back again (at least you can make sure that you don't walk in circles).

8) "Idealized reality". Vegastar Carpentier's enhanced portrait of the Big Dipper has accentuated several of the characteristics that make this asterism so popular. The Dipper shape really stands out, and no one will have any trouble finding it! Also, the stars except Alkaid look more alike in this picture than they do in reality - all of them are the same color in this picture, whereas in reality Dubhe looks yellowish. The fact that they are so bright and blue-white here makes them look like "idealized" stars.

9) Cosmic gem. The special treatment that VegaStar Carpentier has given to Alkaid adds an almost magical quality to the picture. Alkaid resembles a marvelously brilliant precious stone that hangs from a stellar pendant. So beautiful! Alkaid also resembles a brilliant supernova, which adds real drama to the picture. Finally, this enhancement of Alkaid might just make many people think of Polaris, because many of us know that the Big Dipper points at Polaris.

A memory older than ourselves. All in all, I'd say that this portrait of the Big Dipper is so beautiful and perfect that it speaks directly to our emotions without stumbling on too many of our intellectual objections. It seems to speak to a memory or a recognition that is older than ourselves. This may be particularly true for those who like the stars, but don't know too much about them.

And hey, the picture speaks directly to me, even though I pride myself on being somewhat knowledgeable about Alpha, Beta, Gamma, Delta, Epsilon, Zeta and Eta Ursa Majoris!

Ann

BMAONE23 · Post by **BMAONE23** » Tue Mar 17, 2015 4:55 pm

Adding to that, it is probably the FIRST asterism that everyone learns as a child from their parents and passes along to their children so it is foremost recognizable and often carries a special place in memory (at least for those in the Northern Hemisphere). Similar to Orion

Cousin Ricky · Post by **Cousin Ricky** » Tue Mar 17, 2015 8:08 pm

Ann wrote:6) Dependable. For many (all?) of us in the northern hemisphere, the Big Dipper never sets, and so it is visible in a dark sky all year round. That makes it a dependable and trustworthy companion.

Definitely not all of us. Alkaid's declination is +49°19', so it sets for anyone south of about 40¼°N. It barely skims the horizon from Madrid or New York City, and just sets from Beijing. Dubhe's declination is +61°45', so the entire Big Dipper sets for anyone south of about 27¾°N. Dubhe barely skims the horizon from Tampa, and sets completely from Riyadh or Jaipur. This all assumes a clear horizon, which, at my location, never happens.

I once found a set of tasks for the astronomy merit badge for the Boy Scouts of America. One of the tasks was to name all of the circumpolar constellations. That would be very easy from the Virgin Islands, because there are none from here. (Gamma UMi, the southernmost star of the Little Dipper, just barely makes it, but the Little Dipper isn't the whole constellation.)

BillBixby · Post by **BillBixby** » Tue Mar 17, 2015 10:29 pm

RJN wrote:Why is this image so popular? I would appreciate insight into this. This image did very well on Facebook Sky. So well, in fact, that I APODed it with the hope that it would also be a popular APOD. (No, potential popularity is not the only selection criterion for APOD.) Sure enough, it is also "Liking" quite well on Facebook APOD, and seems destined to be one of the few APODs to garner over 2,000 Facebook Likes in a single day.

But why? I would not have guessed that this image would be this popular.
- RJN

For some of us who are sky challenged it just seems like an image we should be able to find in the sky and pretend to be able to navigate using it as a pointer. We wish we could find and recognize these stars and use them to guide ourselves.

Sky challenged means being able to find the sky and then trying to recognize ANYTHING up there. Orion is the only thing my brain is able to home on. Even the big dipper eludes me. Yes, I have poor sense of direction on the Earth's ground as well. But, seeing the picture gives me hope; and the history and legends of the dipper make it a familiar object like a favorite story one might read over and over, even though one has never been there to experience it.

Plus the beauty of the sky is never ending. The part of the sky marked by the dipper is special, even if it hides from my mind.

Guest · Post by **Guest** » Wed Mar 18, 2015 1:03 am

The "slowly change" link which points to:
http://en.wikipedia.org/wiki/Big_Dipper ... g_anim.gif

Is absolutely amazing.

Nitpicker · Post by **Nitpicker** » Wed Mar 18, 2015 4:10 am

I feel a similar affection for Crux (the Southern Cross) which also evokes childhood memories for me. I may still get lost in a shopping mall, or forget where I parked my car, but I always know where South is on a clear night. (I tend to use Sirius and Canopus, when Crux is too low.)

chuckster · Post by **chuckster** » Wed Mar 18, 2015 4:18 am

Chris Peterson wrote:
chuckster wrote:Constellations will all change over time, but I wonder if anyone has figured out what they'd all look like from somewhere else besides Earth, such as the Kuiper belt, or Alpha Centauri.
Yes, if by "constellations" you are referring to the primary asterisms we associate with them. From the Kuiper belt we could not see any difference in shape. From Alpha Centauri, I doubt any difference would be obvious, although a few stars might shift just a little. These distances are simply too small compared with the distance to the stars in the asterisms.

I wonder how many of the distances to the stars comprising the 88 constellations are known.
Every star in the sky is in one of those constellations. For most, we don't have very accurate distances. But for the bright stars making up the primary asterisms, we generally do have reasonably accurate distances, because these stars are mostly quite close to the Earth, making parallax measurements possible.

Thanks for the reply !
I had no idea about all stars (visible by both us and the ancients, I suppose) being part of a constellation. I should read more.
It took years before I found out Astrology is based on the constellations that intersect our solar system's ecliptic.
The orbital mechanics of Iridium satellites, total solar eclipse paths across the Earth's surface, the family of planets,etc are all so well known that things like Iridium flashes, regions of eclipse totality, and asteroid proximitys to Earth can all be calculated, and sometimes even animated. I was imagining a view of our solar system, from, say, the orbit of Sedna, along with all the background stars, being generated in 3D, then you pick a direction to start travelling away from the Sun, and start watching for (or having the computer watch for) changes in the shapes of any of the constellations, then note the distance from Sol it took to do that. I guess we have nowhere near the data to set that up. If an FTL technique ever got developed, it might be good to have such software in the nav system. I wonder what direction and distance would produce the closest viewpoint that displays total disruption of the appearance of all 88 constellations.

starsurfer · Post by **starsurfer** » Wed Mar 18, 2015 10:20 am

Nitpicker wrote:I feel a similar affection for Crux (the Southern Cross) which also evokes childhood memories for me. I may still get lost in a shopping mall, or forget where I parked my car, but I always know where South is on a clear night. (I tend to use Sirius and Canopus, when Crux is too low.)

I feel the same way about Cassiopeia, it's W in the sky feels familiar.

Click to play embedded YouTube video.

Starship Asterisk*

APOD: The Big Dipper Enhanced (2015 Mar 17)

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