APOD: The Large Cloud of Magellan (2010 Oct 16)

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Expand view Topic review: APOD: The Large Cloud of Magellan (2010 Oct 16)

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by KoolKatHebert » Wed Oct 20, 2010 1:42 pm

Is anyone aware of an image created (and provide a link) to show what the Milky Way galaxy might look like from the vantage point of the Magellenic Clouds? Thanks!

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by Chris Peterson » Tue Oct 19, 2010 5:43 am

BMAONE23 wrote:That makes sense. One of the properties of light in space is diffusion such that the farther you are from the light source, the fainter the source appears to become. For example by the time that the light from the sun reaches Pluto, it is only between 200 and 250 times brighter than the full moon or about 1/1600th as bright as on earth.
It is reasonable to presume that the Milky Way, although its angular size would be dramatically larger than Andromeda, would appear slightly less bright than it does in our own sky, about as bright as the magellanic clouds appear to our unaided eye
Surface brightness doesn't change with distance for extended objects (or with magnification). Imagine some little area of the Milky Way, which appears to have a certain brightness. If you get twice as far from it, the amount of light is reduced by a factor of four, but the area of the patch is also reduced by a factor of four. So the intensity per unit area is unchanged.

Under skies dark enough to see the Milky Way, you can also see the Andromeda galaxy. They both look about the same brightness- not surprising, as they are similar objects.

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by BMAONE23 » Tue Oct 19, 2010 5:36 am

That makes sense. One of the properties of light in space is diffusion such that the farther you are from the light source, the fainter the source appears to become. For example by the time that the light from the sun reaches Pluto, it is only between 200 and 250 times brighter than the full moon or about 1/1600th as bright as on earth.
It is reasonable to presume that the Milky Way, although its angular size would be dramatically larger than Andromeda, would appear slightly less bright than it does in our own sky, about as bright as the magellanic clouds appear to our unaided eye

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by Chris Peterson » Tue Oct 19, 2010 5:14 am

neufer wrote:The pertinent question is: Did it dominate the night sky or not :?:
If it dominated the night sky then it was, by definition, spectacular.
I don't think I'd say it dominated the sky. In a sense it did, but only because it was so unusual. In absolute terms, it was less impressive than the Milky Way, and less obvious. It was spectacular for what it was; if it was a fixed feature of the sky, there every night, I don't think I'd be calling it spectacular at all.

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by neufer » Tue Oct 19, 2010 4:40 am

Chris Peterson wrote:
neufer wrote:It would be comparable to a near earth great comet of magnitude -2
(i.e., 6 times the brightness of Hyakutake at maximum brightness).
No, it wouldn't. That's a measure of integrated brightness. The Milky Way has the same surface brightness as most any similar spiral galaxy, 20-22 magnitudes per square arcsecond. You would not see anything like a concentrated magnitude -2 area when viewing the Milky Way from the LMC.

The estimate for Hyakutake is also based on its extended size. I saw it under extremely dark skies, and it was impressive for its size (the tail crossed the sky), but not for its brightness. It could barely be seen at all except from dark sites; magnitude 0 stars, however, can be seen from the brightest cities.
The pertinent question is: Did it dominate the night sky or not :?:

If it dominated the night sky then it was, by definition, spectacular.

(You don't think they have extremely dark skies in the LMC?)

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by Chris Peterson » Tue Oct 19, 2010 4:28 am

neufer wrote:It would be comparable to a near earth great comet of magnitude -2
(i.e., 6 times the brightness of Hyakutake at maximum brightness).
No, it wouldn't. That's a measure of integrated brightness. The Milky Way has the same surface brightness as most any similar spiral galaxy, 20-22 magnitudes per square arcsecond. You would not see anything like a concentrated magnitude -2 area when viewing the Milky Way from the LMC.

The estimate for Hyakutake is also based on its extended size. I saw it under extremely dark skies, and it was impressive for its size (the tail crossed the sky), but not for its brightness. It could barely be seen at all except from dark sites; magnitude 0 stars, however, can be seen from the brightest cities.

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by neufer » Tue Oct 19, 2010 4:04 am

Chris Peterson wrote:
I don't think that our galaxy from the LMC would look all that different than it does from here, in terms of brightness.

The main difference would be the shape of the galaxy, and the sort of structure that would be apparent.
I think it would be noticeably brighter near the center
though I do agree that the main difference would be it's awesome structure.

It would be comparable to a near earth great comet of magnitude -2
(i.e., 6 times the brightness of Hyakutake at maximum brightness).

It would dominate the sky in a spectacular fashion.
http://en.wikipedia.org/wiki/Comet_Hyakutake wrote: <<Hyakutake became visible to the naked eye in early March 1996. By March 24, the comet was one of the brightest objects in the night sky, and its tail stretched 35 degrees. The comet had a notably bluish-green colour. The closest approach occurred on 25 March. Hyakutake was moving so rapidly across the night sky that its movement could be detected against the stars in just a few minutes. Observers estimated its magnitude as around 0, and tail lengths of up to 80 degrees were reported. Its coma, now close to the zenith for observers at mid-northern latitudes, appeared approximately 1.5 to 2 degrees across.>>

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by Chris Peterson » Tue Oct 19, 2010 3:11 am

neufer wrote:But it wouldn't really! We can only see the Milky Way from within a dusty band...
That's not really true. In the Milky Way we see very rich stellar regions, largely unoccluded, and we see sections of this blocked by dust. The unoccluded areas we see, especially around Sagittarius, have a similar surface brightness to the central part of M31.

I don't think that our galaxy from the LMC would look all that different than it does from here, in terms of brightness. The main difference would be the shape of the galaxy, and the sort of structure that would be apparent.

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by neufer » Tue Oct 19, 2010 3:02 am

Chris Peterson wrote:
neufer wrote:It would be like seeing the Andromeda Nebula through 120x12 binoculars (without having to use the binoculars).
Well, sort of. There's an exit pupil problem here. At 12X, the largest aperture you can use (if you're young) is about 80mm.
Indeed!

So the Milky Way would be EVEN MORE SPECTACULAR than seeing
the Andromeda Nebula through 80x12 binoculars (without having to use the binoculars).
Chris Peterson wrote:In any case, a highly magnified view of M31 looks about like... the Milky Way.
But it wouldn't really! We can only see the Milky Way from within a dusty band:

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by rstevenson » Tue Oct 19, 2010 2:04 am

Something like this perhaps? Or did I hop out too far? (Toroids are hard to control at superluminal speeds.)
Milky Fake.jpg
Rob

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by ElGordo » Mon Oct 18, 2010 11:23 pm

I posted this on the next day's APOD about the small Magellanic Cloud:

"Could APOD staff consider giving us fabricated photo or artist's rendition of how the Milky Way galaxy would appear in the night sky to residents of a planet on the near side of the Large Magellanic cloud? Maybe also the from Sagittarius and Canis Major dwarf galaxies given their closer proximity? Just curious as to how beautiful their naked eye stargazing would be on a dark (assume moonless) alien night there when the Milky Way is high above their horizons? Thanks!"

So I see someone here had a similar question and I read the responses. Thank you.

But how about a Photoshop or artist's rendition version.... assuming the proper oblique angles and such?'

Thanks

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by Chris Peterson » Mon Oct 18, 2010 7:08 pm

neufer wrote:It would be like seeing the Andromeda Nebula through 120x12 binoculars (without having to use the binoculars).
Well, sort of. There's an exit pupil problem here. At 12X, the largest aperture you can use (if you're young) is about 80mm.

In any case, a highly magnified view of M31 looks about like... the Milky Way.

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by neufer » Mon Oct 18, 2010 5:52 pm

Chris Peterson wrote:
neufer wrote:
http://en.wikipedia.org/wiki/Large_Magellanic_Cloud wrote:
<<From a viewpoint in the LMC, the Milky Way would be a spectacular sight. The galaxy's total apparent magnitude would be -2.0—over 14 times brighter than the LMC appears to us on Earth—and it would span about 36° across the sky. Furthermore, because of the LMC's high galactic latitude, an observer there would get an oblique view of the entire galaxy, free from the interference of interstellar dust which makes studying in the Milky Way's plane difficult from Earth>>
However, the surface brightness would be about the same as we see from here. In other words, the sky would appear to have a broader band of light, but it would be otherwise similar to our own sky- some sections of dark sky, with sections of faint, diffuse gray where galactic structure is present. While pretty, I'm not sure "spectacular" is necessarily descriptive.
It would be like seeing the Andromeda Nebula through 120x12 binoculars (without having to use the binoculars).

(My guess is that Chris would 'give his eye teeth' to experience it. :wink: )
  • Spectacular, a. [F., fr. L. spectaculum, fr. spectare to look at, to behold.]
    • 1. Of or pertaining to a shows; of the nature of a show.

      2. Adapted to excite wonder and admiration by a display of pomp or of scenic effects.

      3. Pertaining to spectacles, or glasses for the eyes.

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by Chris Peterson » Mon Oct 18, 2010 5:19 pm

BMAONE23 wrote:But deep images from that perspective would be awe inspiring
They would look no different than deep images we make of M31, or any other large, fairly close galaxy.

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by BMAONE23 » Mon Oct 18, 2010 4:40 pm

Chris Peterson wrote:
neufer wrote:
LBM wrote:<<From a viewpoint in the LMC, the Milky Way would be a spectacular sight. The galaxy's total apparent magnitude would be -2.0—over 14 times brighter than the LMC appears to us on Earth—and it would span about 36° across the sky. Furthermore, because of the LMC's high galactic latitude, an observer there would get an oblique view of the entire galaxy, free from the interference of interstellar dust which makes studying in the Milky Way's plane difficult from Earth>>
However, the surface brightness would be about the same as we see from here. In other words, the sky would appear to have a broader band of light, but it would be otherwise similar to our own sky- some sections of dark sky, with sections of faint, diffuse gray where galactic structure is present. While pretty, I'm not sure "spectacular" is necessarily descriptive.
But deep images from that perspective would be awe inspiring

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by rstevenson » Mon Oct 18, 2010 2:34 pm

Unless they have larger eyes than we have...
attachment2.jpg
attachment2.jpg (35.58 KiB) Viewed 3202 times
Rob

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by Chris Peterson » Mon Oct 18, 2010 2:23 pm

neufer wrote:
LBM wrote:<<From a viewpoint in the LMC, the Milky Way would be a spectacular sight. The galaxy's total apparent magnitude would be -2.0—over 14 times brighter than the LMC appears to us on Earth—and it would span about 36° across the sky. Furthermore, because of the LMC's high galactic latitude, an observer there would get an oblique view of the entire galaxy, free from the interference of interstellar dust which makes studying in the Milky Way's plane difficult from Earth>>
However, the surface brightness would be about the same as we see from here. In other words, the sky would appear to have a broader band of light, but it would be otherwise similar to our own sky- some sections of dark sky, with sections of faint, diffuse gray where galactic structure is present. While pretty, I'm not sure "spectacular" is necessarily descriptive.

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by neufer » Mon Oct 18, 2010 12:05 pm

LBM wrote:
How should be the sky we would see if the Earth were in the Magellan cloud and we looked to the Milk Way?
http://en.wikipedia.org/wiki/Large_Magellanic_Cloud wrote:
<<From a viewpoint in the LMC, the Milky Way would be a spectacular sight. The galaxy's total apparent magnitude would be -2.0—over 14 times brighter than the LMC appears to us on Earth—and it would span about 36° across the sky. Furthermore, because of the LMC's high galactic latitude, an observer there would get an oblique view of the entire galaxy, free from the interference of interstellar dust which makes studying in the Milky Way's plane difficult from Earth>>

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by LBM » Mon Oct 18, 2010 10:55 am

How should be the sky we wold see if the Earth were in the Magellan cloud and we looked to the Milk Way?

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by Ann » Sun Oct 17, 2010 3:48 am

Personally I think that the Bar of LMC looks a bit like the blue star cloud in Sagittarius, M24.
Messier 24, the blue star cloud of Sagittarius. It is not nearly as well-populated as the Bar of the Large Cloud of Magellan, I'll bet!

Image

Magellan's Bar, fairly well-populated.

Ann

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by neufer » Sat Oct 16, 2010 9:55 pm

orin stepanek wrote:
Did you know how many stars in the LMC?

I don't know how accurate this answer is though.
Two's company, five billion's a cloud.
http://en.wikipedia.org/wiki/Large_Magellanic_Cloud wrote:
<<Like many irregular galaxies, the LMC is rich in gas and dust, and it is currently undergoing vigorous star formation activity. It is home to the Tarantula Nebula, the most active star-forming region in the Local Group. The LMC is full of a wide range of galactic objects and phenomena that make it aptly known as an "astronomical treasure-house, a great celestial laboratory for the study of the growth and evolution of the stars," as described by Robert Burnham, Jr. Surveys of the galaxy have found roughly 60 globular clusters, 400 planetary nebulae, and 700 open clusters, along with hundreds of thousands of giant and supergiant stars.

From a viewpoint in the LMC, the Milky Way would be a spectacular sight. The galaxy's total apparent magnitude would be -2.0—over 14 times brighter than the LMC appears to us on Earth—and it would span about 36° across the sky. Furthermore, because of the LMC's high galactic latitude, an observer there would get an oblique view of the entire galaxy, free from the interference of interstellar dust which makes studying in the Milky Way's plane difficult from Earth>>

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by orin stepanek » Sat Oct 16, 2010 9:33 pm

WOW! We're today's APOD is the LMC and most of the replies are about 747! :? Did you know how many stars in the LMC? http://answers.yahoo.com/question/index ... 558AABC4pd I don't know how accurate this answer is though.

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by rstevenson » Sat Oct 16, 2010 7:55 pm

Ann wrote:No, but check out the NGC numbers again - that's NGC 474, not NGC 747! But both came up at the same googling. Hey, NGC 474, I think Google considers you the most interesting galaxy of the seven-four-seven four-seven-fours!
Innerestin'! I found my image in SDSS data release two, found here. I also just now found the Deep Sky Browser page for NGC 747 which appears to be very similar to the one I posted -- they circle the larger galaxy in the center of the pic and identify it as NGC 747. So I think I got it covered. But not to worry, you're well past ol' 747 anyway.

Rob

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by neufer » Sat Oct 16, 2010 7:32 pm

Ann wrote:
And guess what? NGC 474, the inverted airplane, has even been the Astronomy picture of the day on October 8, 2007!
http://en.wikipedia.org/wiki/Inverted_Jenny wrote: The Inverted Jenny (also known as an Upside Down Jenny or Jenny Invert) is a United States postage stamp first issued on May 10, 1918 in which the image of the Curtiss JN-4 airplane in the center of the design was accidentally printed upside-down; it is probably the most famous error in American philately. Only one pane of 100 of the invert stamps was ever found, making this error one of the most prized in all philately. A block of four inverted Jennys was sold at auction in October 2005 for US $2.7 million and a single inverted Jenny was sold in November 2007 for US $977,500.

During the 1910s, the United States Post Office had made a number of experimental trials of carrying mail by air, and decided to inaugurate regular service on May 15, 1918, flying between Washington, D.C., Philadelphia, and New York City. The Post Office set a controversial rate of 24 cents for the service, much higher than the 3 cents for first-class mail of the time, and decided to issue a new stamp just for this rate, patriotically printed in red and blue, and depicting a Curtiss Jenny, the biplane chosen to shuttle the mail.

The job of designing and printing the new stamp was carried out in a great rush; engraving only began on May 4, and stamp printing on May 10 (a Friday), in sheets of 100 (contrary to the usual practice of printing 400 at a time and cutting into 100-stamp panes). Since the stamp was printed in two colors, each sheet had to be fed through the printing press twice, an error-prone process that had resulted in invert errors in stamps of 1869 and 1901, and at least three misprinted sheets were found during the production process and were destroyed. It is believed that only one misprinted sheet of 100 stamps got through unnoticed, and stamp collectors have spent the ensuing years trying to find them all.

Initial deliveries went to post offices on Monday, May 13. Aware of the potential for inverts, a number of collectors went to their local post offices to buy the new stamps and keep an eye out for errors. Collector W. T. Robey was one of those; he had written to a friend on May 10 mentioning that "it would pay to be on the lookout for inverts". On May 14, Robey went to the post office to buy the new stamps, and as he wrote later, when the clerk brought out a sheet of inverts, "my heart stood still". He paid for the sheet, and asked to see more, but the remainder of the sheets were normal. After a week that included visits from postal inspectors and the hiding of the sheet, Robey sold the sheet to noted Philadelphia dealer Eugene Klein for $15,000.

In The Simpsons fifth season's first episode, "Homer's Barbershop Quartet", Homer Simpson, along with finding an original copy of the U.S. Declaration of Independence, an Action Comics 1 and a Stradivarius violin, all of which he throws away not knowing their value, then comes across a full sheet of Inverted Jennys in the 5 cent box at a local swap meet. He also throws it away saying "Airplane's upside down!".>>

Re: APOD: The Large Cloud of Magellan (2010 Oct 16)

by bystander » Sat Oct 16, 2010 6:07 pm

Go ask owlice, I think she'll know

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