Starship Asterisk*

by **Chris Peterson** » Sat Jan 31, 2009 4:45 pm

apodman wrote:
Chris Peterson wrote:... the parsec units aren't even used in the calculation. Any units would suffice, as they cancel out immediately.
But they are needed in your second method, right? I left that detail and others for the reader to sort out.

Sort of. But only to the extent that we need the distance to Betelgeuse in parsecs, in order to have the same units used for absolute magnitude. At that point, we're only considering a ratio, so the units drop out.

by **apodman** » Sat Jan 31, 2009 4:26 pm

Chris Peterson wrote:... the parsec units aren't even used in the calculation. Any units would suffice, as they cancel out immediately.

But they are needed in your second method, right? I left that detail and others for the reader to sort out.

by **Chris Peterson** » Sat Jan 31, 2009 2:50 pm

apodman wrote:That alone is sufficient reason to think in parsecs, but my brain will hear of nothing but light years as a first language.

I, also, prefer light years. Parsecs make sense for parallax calculations, but otherwise I think the light year is a more "natural" unit. In this case, however, the parsec units aren't even used in the calculation. Any units would suffice, as they cancel out immediately.

by **apodman** » Sat Jan 31, 2009 6:03 am

Chris Peterson wrote:... easy ... The absolute magnitude of a star is its magnitude normalized for a distance of 10 parsecs.

That alone is sufficient reason to think in parsecs, but my brain will hear of nothing but light years as a first language.

Chris Peterson wrote:Betelgeuse ... is variable

Some non-variable single stars of well known distances demonstrate the method with more exact results.

by **Chris Peterson** » Sat Jan 31, 2009 4:34 am

apodman wrote:Sol is magnitude 11+ at about 600 ly, making it impossible for the naked eye but an easy object with a medium telescope in the clear dark skies of Xqsrpsb.

Here's a real easy way to do the problem. The absolute magnitude of a star is its magnitude normalized for a distance of 10 parsecs. For Betelgeuse that value is -5.14, for the Sun it is 4.83. The difference is 9.97 magnitudes. Add that to the apparent magnitude of Betelgeuse, 0.58 (or so- the star is variable), to get the apparent magnitude of the Sun from there: 10.6.

A little more work, Betelgeuse is 200 parsecs away, which is 20 times 10 parsecs. So from there, the Sun would be 20^2, or 400 times dimmer than its absolute magnitude. A factor of 400 is 6.5 magnitudes, plus the apparent magnitude of 4.83, is 11.3.

by **apodman** » Sat Jan 31, 2009 3:13 am

apodman wrote:What is our sun's apparent magnitude as seen from the distance of Betelgeuse?

Sol is magnitude 11+ at about 600 ly, making it impossible for the naked eye but an easy object with a medium telescope in the clear dark skies of Xqsrpsb. Sol is magnitude 0 at about 3.5 ly. Sol is magnitude 6 at about 56 ly.

Add 1 to the magnitude every time you increase the distance by a factor of about 1.585 (the 10th root of 100).
Doubling the distance makes one quarter the brightness.
Similarly, 100^0.1 (~= 1.585) times the distance makes 1/100^0.2 (~= 1/2.512) the brightness (= +1 magnitude).

by **astrolabe** » Fri Jan 30, 2009 10:20 pm

Hello aristarchusinexile,

aristarchusinexile wrote:some form of the pinhole effect

Could you be a little more specific, maybe in the A-Cafe?

by **Chris Peterson** » Fri Jan 30, 2009 5:40 pm

aristarchusinexile wrote:What? No comments on this one? "I wonder if some form of the pinhole effect accounts for different parts of the universe looking like mirror images of each other?"

How does one respond to an arbitrary string of words strung into a meaningless sentence?

by **aristarchusinexile** » Fri Jan 30, 2009 4:45 pm

What? No comments on this one? "I wonder if some form of the pinhole effect accounts for different parts of the universe looking like mirror images of each other?"

by **Chris Peterson** » Fri Jan 30, 2009 3:13 pm

jimmysnyder wrote:If such a photo were taken at a location where the sun was visible as a complete ring around the moon, then would the reflections on the t-shirt also be complete rings?

Yes, assuming the "pinholes" created by the leaves were small enough, and the lighting conditions were suitable for good contrast.

by **neufer** » Fri Jan 30, 2009 2:15 pm

jimmysnyder wrote:
neufer wrote: I went 1 light year beyond Betelgeuse and looked back at Betelgeuse (blocking an invisible earth but in earth's location).
Betelgeuse is so far away that most of the stars that we are familiar with are too faint to see from Betelgeuse.
Three bright Gemini stars are visible however.
That is way cool software. Sorry about the constellation flub, but you know the old Xqzrpsbian saying "All Xqzrpsbians are liars".

So that's where Blagojevich comes from!

Actually, from the closer vantage point of Sirius A
I can envision the sun (Sol) as part of a Neuman (or Blagojevich) constellation:

: Our Sun from Sirius A; sirius.jpg (65.26 KiB) Viewed 1838 times

Downloaded free Celestia program boldly go where no one has gone before:
http://en.wikipedia.org/wiki/Celestia
http://www.shatters.net/celestia/

by **jimmysnyder** » Fri Jan 30, 2009 12:14 pm

neufer wrote: I went 1 light year beyond Betelgeuse and looked back at Betelgeuse (blocking an invisible earth but in earth's location).
Betelgeuse is so far away that most of the stars that we are familiar with are too faint to see from Betelgeuse.
Three bright Gemini stars are visible however.

That is way cool software. Sorry about the constellation flub, but you know the old Xqzrpsbian saying "All Xqzrpsbians are liars".

by **neufer** » Thu Jan 29, 2009 11:49 pm

apodman wrote:
jimmysnyder wrote:My contacts on ... a planet orbiting Betelgeuse tell me that our sun ... is ... in the constellation Alfred E. Newman.
Okay, I know some of us (alas, I don't) have the software to plot the sky from the neighborhood of Betelgeuse. I want to see what this constellation looks like, and our sun's position and prominence (no pun intended, much) in it. Failing that, some of us (again, not I) have the data and formula handy to answer this one: What is our sun's apparent magnitude as seen from the distance of Betelgeuse?

If I were orbiting Betelgeuse, I would look for our sun near Nu Ophiuchi and not too far from globular cluster M14.

I just downloaded the necessary free program and am enjoying playing with it.
http://en.wikipedia.org/wiki/Celestia
http://www.shatters.net/celestia/

I went 1 light year beyond Betelgeuse and looked back at Betelgeuse (blocking an invisible earth but in earth's location).

: 1 light year beyond Betelgeuse and looking back at Betelgeuse; betel1.jpg (43.02 KiB) Viewed 1969 times

Betelgeuse is so far away that most of the stars that we are familiar with are too faint to see from Betelgeuse.
Three bright Gemini stars are visible however.

by **apodman** » Thu Jan 29, 2009 9:48 pm

jimmysnyder wrote:My contacts on ... a planet orbiting Betelgeuse tell me that our sun ... is ... in the constellation Alfred E. Newman.

Okay, I know some of us (alas, I don't) have the software to plot the sky from the neighborhood of Betelgeuse. I want to see what this constellation looks like, and our sun's position and prominence (no pun intended, much) in it. Failing that, some of us (again, not I) have the data and formula handy to answer this one: What is our sun's apparent magnitude as seen from the distance of Betelgeuse?

If I were orbiting Betelgeuse, I would look for our sun near Nu Ophiuchi and not too far from globular cluster M14.

by **aristarchusinexile** » Thu Jan 29, 2009 6:44 pm

jimmysnyder wrote:If such a photo were taken at a location where the sun was visible as a complete ring around the moon, then would the reflections on the t-shirt also be complete rings?

The star on the upper right is Betelgeuse in the constellation Orion. Next to it is not a star at all, but the image of a DC-9 constellation that happened to be there when the artist drew the picture. The picture was posed on the USS Constellation which appears in the lower half of the image. My contacts on Xqzrpsb, a planet orbiting Betelgeuse tell me that our sun, which appears in many places on the t-shirt, is known there as the star Pluto in the constellation Alfred E. Newman.

Oh yeah! Well MY contacts on Xqzrpsb declare Pluto to be real dog and not a cartoon character!

(Why do I get caught up in these kinds of debates!)

by **neufer** » Thu Jan 29, 2009 6:34 pm

jimmysnyder wrote:The star on the upper right is Betelgeuse in the constellation Orion. Next to it is not a star at all, but the image of a DC-9 constellation that happened to be there when the artist drew the picture. The picture was posed on the USS Constellation which appears in the lower half of the image. My contacts on Xqzrpsb, a planet orbiting Betelgeuse tell me that our sun, which appears in many places on the t-shirt, is known there as the star Pluto in the constellation Alfred E. Newman.

NEWMAN!!

I stand corrected (yet again).

by **jimmysnyder** » Thu Jan 29, 2009 6:05 pm

If such a photo were taken at a location where the sun was visible as a complete ring around the moon, then would the reflections on the t-shirt also be complete rings?

The star on the upper right is Betelgeuse in the constellation Orion. Next to it is not a star at all, but the image of a DC-9 constellation that happened to be there when the artist drew the picture. The picture was posed on the USS Constellation which appears in the lower half of the image. My contacts on Xqzrpsb, a planet orbiting Betelgeuse tell me that our sun, which appears in many places on the t-shirt, is known there as the star Pluto in the constellation Alfred E. Newman.

by **aristarchusinexile** » Thu Jan 29, 2009 4:15 pm

I wonder if some form of the pinhole effect accounts for different parts of the universe looking like mirror images of each other?

by **neufer** » Thu Jan 29, 2009 3:16 pm

http://apod.nasa.gov/apod/ap090129.html

I defy anyone to pick out a constellation in the IYA Eclipse Shirt 2009

[b] http://www.websters-online-dictionary.org/translation/IYA [/b] wrote:
IYA : very strong yes (Indonesian, Sranan Tongo)
IYA : exclamation of astonishment (Yao)
IYA : expressing impatience (Ndebele)
IYA : here (Meru, Kimochi Unn, Siha)
IYA : his, its (Bisayan, Hiligaynon )
IYA : he, she (Ivatan, Itbayaten)
IYA : cry, wail (Meru, Machame)
IYA : blow on, blow up (Kikuyu)
IYA : mother (Ntuzu, Tuveta)
IYA : new (Machambe, Unn)
IYA : become burnt (Siha)
IYA : here (Kimochi, Unn)
IYA : steal (Yao,Taabwa)
IYA : which (Jita, Kilegi)
IYA : rock (Merutig)
IYA : eat (Gweno)

Starship Asterisk*

IYA Eclipse Shirt 2009 (APOD 2009 January 29)

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