APOD: Moon Over Andromeda (2013 Aug 01)

Comments and questions about the APOD on the main view screen.
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APOD: Moon Over Andromeda (2013 Aug 01)

Post by APOD Robot » Thu Aug 01, 2013 4:08 am

Image Moon Over Andromeda

Explanation: The Great Spiral Galaxy in Andromeda (aka M31), a mere 2.5 million light-years distant, is the closest large spiral to our own Milky Way. Andromeda is visible to the unaided eye as a small, faint, fuzzy patch, but because its surface brightness is so low, casual skygazers can't appreciate the galaxy's impressive extent in planet Earth's sky. This entertaining composite image compares the angular size of the nearby galaxy to a brighter, more familiar celestial sight. In it, a deep exposure of Andromeda, tracing beautiful blue star clusters in spiral arms far beyond the bright yellow core, is combined with a typical view of a nearly full Moon. Shown at the same angular scale, the Moon covers about 1/2 degree on the sky, while the galaxy is clearly several times that size. The deep Andromeda exposure also includes two bright satellite galaxies, M32 and M110 (bottom).

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Boomer12k » Thu Aug 01, 2013 4:10 am

Oh.....neat perspective....no wonder I only get the central portion of M31....my scope and camera are good for CLOSE-UPS....now I understand why I don't get a good full picture...I wonder if an Afocal setup with a wide angle lens would do anything....will have to check that out....hmmmmm.....project for the next nice night!!!! :D :D :D

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Ann » Thu Aug 01, 2013 5:15 am

This is a nice and interesting composite image.

M31 is quite large in our skies, and since it is approaching us, it is growing bigger every day!!! :shock: :shock:

The Moon appears relatively big in our skies, but it is actually receding, so it will look smaller and smaller.

But the surface brightness of the Moon will remain much, much higher than the surface brightness of the bulge of M31 - from our point of view, that is - for as long as the Moon is in orbit around the Earth.

A few notes on the Andromeda system: Adam Block's picture shows us the bright blue stars of the outer parts of M31 very clearly, and the blue stars are certainly there. But the relative proportion of blue stars in M31 is low, and Andromeda is actually a really red galaxy.

Note the "star streams" emanating from satellite galaxy NGC 205 to the lower left of M31! Those tidal forces are not to be trifled with.

Ann
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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by madtom1999 » Thu Aug 01, 2013 6:38 am

It just doesnt look right.

Uwe

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Uwe » Thu Aug 01, 2013 8:43 am

Nice composite to comprehend the relative sizes, thank you!
"Typical view of a nearly full moon", well, a little nit-picking, in this image it is correct for maybe Australia, with Mare Crisium at the lower left. :wink:
On the other hand, they don't get much of a glimpse of M31 down under. So, indeed, nice composite. ^^

Mr.Terry

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Mr.Terry » Thu Aug 01, 2013 11:14 am

Todays post looks very familiar, just like December 28,2006??? It's part of one of my sreen savers.

Barry

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Barry » Thu Aug 01, 2013 11:43 am

I have several astro targets that I've superimposed the full moon on here:

http://barryetter.zenfolio.com/p1045793279

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Moggie » Thu Aug 01, 2013 12:19 pm

I had little idea the real size of many astronomical objects that I've seen here on APOD. It would be great if a circle representing the size of the moon could be added as a mouse over. What a glorious sky we have, if only we could see it when looking up in the night.

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Wadsworth » Thu Aug 01, 2013 12:48 pm

Barry wrote:I have several astro targets that I've superimposed the full moon on here:

http://barryetter.zenfolio.com/p1045793279
Cool!

Guest

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Guest » Thu Aug 01, 2013 1:10 pm

I feel compelled to write to say that I am astonished by the APOD photo published today - Moon Over Andromeda.

I have followed APOD for years and never realised these structures were actually so large (albeit feint) in the sky. I wish to thank you for the education on this and suspect not many members of the public realise the fact you have made clear.

Thank you
Alan Smith

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by NGC3314 » Thu Aug 01, 2013 1:12 pm

Uwe wrote:"Typical view of a nearly full moon", well, a little nit-picking, in this image it is correct for maybe Australia, with Mare Crisium at the lower left. :wink:
Hemisphere chauvinist! Actually the whole image is shown with south at the top. SInce we see the far side of the disk of M31 to our celestial south, inverting it makes the perspective work better for many people (looking "down" instead of "up" across its spiral arms).

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Psnarf » Thu Aug 01, 2013 2:16 pm

Go find your helmet.
Put your helmet on.
Run for your lives!
It's the Andromeda Strain!

Siriusly, nice superposition!

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by neufer » Thu Aug 01, 2013 4:17 pm

Guest wrote:
I have followed APOD for years and never realised these structures were actually so large (albeit feint) in the sky.
http://en.wikipedia.org/wiki/Feint wrote:
<<Feint is a French term that entered English via the discipline of swordsmanship and fencing. Feints are maneuvers designed to distract or mislead, done by giving the impression that a certain maneuver will take place, while in fact another, or even none, will. In military tactics and many types of combat, there are two types of feints: feint attacks and feint retreats.

A feint attack is designed to draw defensive action towards the point under assault. It is usually used as a diversion to force the enemy to concentrate more manpower in a given area, to weaken the opposing force in another area. Unlike a related diversionary maneuver, the demonstration, a feint involves actual contact with the enemy.

A feint retreat is performed by briefly engaging the enemy, then retreating. It is intended to draw the enemy pursuit into a prepared ambush, or to cause disarray. For example, the Battle of Hastings was lost when Saxons pursued the Norman cavalry. This forfeited the advantage of height and the line was broken, providing the opportunity to fight in single handed combat on a neutral vantage point, a battle for which the Saxons were not ready. The Parthian shot is another example of a feint retreat, where mounted Parthian archers would retreat from a battle and then, while still riding, turn their bodies back to shoot at the pursuing enemy.>>
Art Neuendorffer

DvR

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by DvR » Thu Aug 01, 2013 4:35 pm

Ann wrote:M31 is quite large in our skies, and since it is approaching us, it is growing bigger every day

Ann

How fast is it approaching? I want to be prepared :cry:

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Anthony Barreiro » Thu Aug 01, 2013 5:30 pm

My initial reaction was, "there is so much wrong with this picture!" But I'm happy to read that this helps people understand how big the Andromeda galaxy appears in the sky. If you remember that the Moon is one-half degree (30 arcminutes) across, you can do this comparison mentally for any object in the sky.

The best instrument for seeing the full extent of the Andromeda galaxy is a steadily mounted pair of large (70 mm or bigger) binoculars. You'll need a dark, moonless sky to see the faint outer arms.
May all beings be happy, peaceful, and free.

retrogalax

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by retrogalax » Thu Aug 01, 2013 7:02 pm

Thank you, i was tired to look at the Moon only...:x

chuckster

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by chuckster » Thu Aug 01, 2013 8:18 pm

There are a lot of celestial objects like this aren't there ? Too dim or too far out of our visual range of light for us to
see up there. What a great project for some observatory, to design and build a view screen, like, say, a Federation
starship bridge would have, that can display objects in our sky in all frequencies, and at relative scales. To think that
Andromeda is THAT BIG, and we can't see it . . .I feel gypped !!!!

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Chris Peterson » Thu Aug 01, 2013 8:22 pm

chuckster wrote:There are a lot of celestial objects like this aren't there ? Too dim or too far out of our visual range of light for us to
see up there. What a great project for some observatory, to design and build a view screen, like, say, a Federation
starship bridge would have, that can display objects in our sky in all frequencies, and at relative scales. To think that
Andromeda is THAT BIG, and we can't see it . . .I feel gypped !!!!
Andromeda is quite easy to see under relatively dark skies. Even to the naked eye, it is larger than the Moon. The problem is, the Moon is small- we are fooled by its brightness into thinking it is much larger than it actually is. Even things we easily see, like the Pleiades, are larger than the Moon... but it's hard to convince somebody of that when you're out under the stars.
Chris

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Diana

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Diana » Thu Aug 01, 2013 10:43 pm

Chris Peterson wrote:
chuckster wrote:There are a lot of celestial objects like this aren't there ? Too dim or too far out of our visual range of light for us to
see up there. What a great project for some observatory, to design and build a view screen, like, say, a Federation
starship bridge would have, that can display objects in our sky in all frequencies, and at relative scales. To think that
Andromeda is THAT BIG, and we can't see it . . .I feel gypped !!!!
Andromeda is quite easy to see under relatively dark skies. Even to the naked eye, it is larger than the Moon. The problem is, the Moon is small- we are fooled by its brightness into thinking it is much larger than it actually is. Even things we easily see, like the Pleiades, are larger than the Moon... but it's hard to convince somebody of that when you're out under the stars.

Diana

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Diana » Thu Aug 01, 2013 10:48 pm

I ment to quote part of what Chris just posted. About it being difficult to convice someone that the moon is much smaller than it appears.

I just tell folks to extend their hand and cover the moon with their index finger. For other than small children, the moon will be about the size of your fingernail, or smaller. So the Andromeda Galaxy will be just over two fingers wide.

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by stephen63 » Thu Aug 01, 2013 11:00 pm

Link to some images of well known astronomical objects with the moon to scale.
http://astroanarchy.zenfolio.com/p162076373

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by Anthony Barreiro » Thu Aug 01, 2013 11:37 pm

Chris Peterson wrote:Andromeda is quite easy to see under relatively dark skies. Even to the naked eye, it is larger than the Moon.
And even in a city or the suburbs, if you get out of the immediate glare of streetlights etc., a small pair of binoculars will show the bright central bulge of the Andromeda galaxy.
May all beings be happy, peaceful, and free.

DvR

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by DvR » Fri Aug 02, 2013 12:17 am

DvR wrote:
Ann wrote:M31 is quite large in our skies, and since it is approaching us, it is growing bigger every day

Ann

How fast is it approaching? I want to be prepared :cry:

NM...WIKI

The Andromeda Galaxy is approaching the Milky Way at about 300 kilometres per second (190 mi/s),[1] making it one of the few blueshifted galaxies. The Andromeda Galaxy and the Milky Way are thus expected to collide in about 4.5 billion years

That's a relieve... I have time to live out retirement.

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Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by APODFORIST » Fri Aug 02, 2013 8:37 am

Those size comparisons are impressive.
When I first detected andromada nebula with my eyes I thougt I see the whole galaxy ... must have been a small part of the bright center only.
Barry wrote:I have several astro targets that I've superimposed the full moon on here:
http://barryetter.zenfolio.com/p1045793279
WOW, thats great!

chuckster

Re: APOD: Moon Over Andromeda (2013 Aug 01)

Post by chuckster » Sun Sep 15, 2013 7:54 pm

Chris Peterson wrote:
chuckster wrote:There are a lot of celestial objects like this aren't there ? Too dim or too far out of our visual range of light for us to
see up there. What a great project for some observatory, to design and build a view screen, like, say, a Federation
starship bridge would have, that can display objects in our sky in all frequencies, and at relative scales. To think that
Andromeda is THAT BIG, and we can't see it . . .I feel gypped !!!!
Andromeda is quite easy to see under relatively dark skies. Even to the naked eye, it is larger than the Moon. The problem is, the Moon is small- we are fooled by its brightness into thinking it is much larger than it actually is. Even things we easily see, like the Pleiades, are larger than the Moon... but it's hard to convince somebody of that when you're out under the stars.
I'd often wondered what it would be like to live on a planet where at least a couple big, bright galaxies were not only naked-eye visible in the sky at night, but easily and spectacularly so. And now I learn we have one, but it has "low surface brightness". How can an immense galaxy have low surface brightness ? What is a galactic "surface", the dust clouds surrounding it ? A dark matter/energy cocoon messing with the light? Maybe I need to get out in Death Valley on a cool Fall night and take another gander, but my wish has always been to be clobbered over the head by a nearby galaxy sparkling hugely and brightly in our sky, though I suppose that means we would already be dangerously interacting, gravitationally .
Maybe I should be careful what I wish for.