APOD: GALEX: The Andromeda Galaxy (2012 May 18)

[APOD Robot]

GALEX: The Andromeda Galaxy

Explanation: A mere 2.5 million light-years away, the Andromeda Galaxy really is just next door as large galaxies go. So close, and spanning some 260,000 light-years, it took 11 different image fields from the Galaxy Evolution Explorer (GALEX) satellite's telescope to produce this gorgeous portrait of the spiral galaxy in ultraviolet light. While its spiral arms stand out in visible light images of Andromeda (also known as M31), the arms look more like rings in the GALEX ultraviolet view, dominated by hot, young, massive stars. As sites of intense star formation, the rings have been interpreted as evidence Andromeda collided with its smaller neighboring elliptical galaxy M32 more than 200 million years ago. The large Andromeda galaxy and our own Milky Way are the dominant members of the local galaxy group.

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[bystander]

GALEX to resume operations

http://asterisk.apod.com/viewtopic.php?t=27169#p175713

[IleneK]

is it not "galaxies" instead of "galaxy's"? and does not a sentence near the end really need editing?

PS love APOD

[Flase]

I thought the diameter was a lot smaller than that

[Ann]

I really like today's APOD! It is so beautiful!

As for the ring-like structures that are seen in ultraviolet by GALEX in today's APOD, they have been seen infrared light, too. This WISE image shows how the cool, starforming dust in Andromeda forms ring-like structures.

A few details are very interesting in the GALEX image. Note that one of Andromeda's satellite galaxies, M32, is barely visible here. Note, too, that although Andomeda's other bright satellite, NGC 205, is easy to spot, it is yellower in color than any part of M31. In visual light, NGC 205 is actually somewhat bluer than the Andromeda galaxy, but apparently ultraviolet light is produced by very many sources all over the disk of M31, whereas NGC 205 is "quiet". (There are actually a few young stars near the center of NGC 205, and you can just barely spot their bluish color in this picture.)

Finally, I find myself scratching my head over the color of the foreground stars. At three o'clock and five o'clock, there are two blue stars that might possibly be two ninth magnitude A-type stars. At ten o'clock, there is a blue source which actually corresponds to a cool M-type star, EG Andromedae! Yes, but the M-type primary apparently has a white dwarf companion, whose ultraviolet light is detected by GALEX.

And then at seven o'clock there is a bright blue star. The only match I have tentatively found for it is an A-type star, seventh magnitude HD 3431. How strange to see this visually unimpressive star shine so brightly in an ultraviolet image.

Ann

[gwrede]

is it not "galaxies" instead of "galaxy's"? and does not a sentence near the end really need editing?

I find this an alarming trend. These articles used to be so well written.

[tr@tjroberts2]

APOD is wonderful - a pity to see spelling/grammar mistakes creeping in - [i]galaxy's[/i] should be [i]galaxies[/i]. Please note, and keep up the good work!

[owlice]

Thanks for the notice on the error; I've sent an email to the editors.

[JuanAustin]

i spotted a mistake at the end of the paragraph, "the local galaxy group" should read as the Oyervides Group. I claimed it over these web site pages not long ago since it has gone without a name all these years!

[HellCat]

Love APoD - number one site on the web.

There's one more grammatical error:

... as large galaxy's go. [ galaxies ]
... been interpreted has evidence [ as ]

[smitty]

A quick note of thanks to Ann for her helpful comments about some of the artifacts in today's apod. Was surprised not to find comments about some of these artifacts in the main apod comment section, especially about the prominent blue and orange features at 7 and 4 o'clock, respectively. We're accustomed to seeing foreground stars as spiky features in images produced by optical instruments. Anyway, thanks again, Ann; your comments are exactly what I see this forum as having been designed for (unlike some of the childish clowning around too often found here these days).

[bactame]

The opening sentence of this apod is interesting.: "The most distant object easily visible to the eye is M31, the great Andromeda Galaxy some two and a half million light-years away. But without a telescope, even this immense spiral galaxy - spanning over 200,000 light years - appears as a faint, nebulous cloud in the constellation Andromeda."

Here in one remarkable sentence is a contradiction of meanings, M31 is easily seen without any special apparatus yet by the end of the sentence you will need the time and a special telescope to look at it at all.

These professional astronomers sound like clergy and only in going to church can you learn to ignore them. Today the moon cannot be readily seen since it is new and rose nearly with the sun. But yes the moon is easily found. M31 is a red glob at best for a couple weeks of the year depending on where you live.

[geckzilla]

I find nothing contradictory at all in that sentence, bactame. It doesn't state that you need a telescope to look at it. You need a telescope to see any details. And it's completely true. I don't even know what to say in regards to your comparison to church clergy. I think you are confused.

[Chris Peterson]

The opening sentence of this apod is interesting.: "The most distant object easily visible to the eye is M31, the great Andromeda Galaxy some two and a half million light-years away. But without a telescope, even this immense spiral galaxy - spanning over 200,000 light years - appears as a faint, nebulous cloud in the constellation Andromeda."

Here in one remarkable sentence is a contradiction of meanings, M31 is easily seen without any special apparatus yet by the end of the sentence you will need the time and a special telescope to look at it at all.

I don't see any contradiction. There is a small error, however. Even with a telescope, M31 appears as a faint, nebulous cloud. That's what it is, and no telescope can make it brighter than it appears to the naked eye. To see more requires a camera that can collect and store photons.

[orin stepanek]

I think this is the best picture yet of Andromeda! Keep up the good work APOD!

[moonstruck]

It's a beautiful APOD. What's with all these grammar police anyway? This is astronomy not an English class.

[neufer]

Explanation: A mere 2.5 million light-years away, the Andromeda Galaxy really is just next door as large galaxies go. So close, and spanning some 260,000 light-years,

I thought the diameter was a lot smaller than that

Perhaps they meant that the original GALEX photo-mosaic spanned 260,000 light-years.

<<Distance measurements give a combined distance estimate of 2.54 ± 0.06 Mly (780 ± 18 kpc). Based upon the above distance, the diameter of M31 at the widest point is estimated to be 141 ± 3 kly (43,000 ± 920 pc). Applying trigonometry (arctangent), that figures to extending at an apparent 3.18° angle in the sky.>>

[Theodorusm]

At the lower right there is a bright star . Just above it at about 11 o'clock are two overlapping circles. What is that.?

[Moonlady]

Wow, what a picture, never seen Andromeda in such a detail, when was this picture taken?
I wish I could see Andromeda and our Galaxy joining together, what a beautiful sight it will be!

Take a ride to the center of Andromeda Galaxy: Ann you might like the A type hot blue stars there!

http://video.google.com/videoplay?docid ... 573305331#

[Ann]

A quick note of thanks to Ann for her helpful comments about some of the artifacts in today's apod. Was surprised not to find comments about some of these artifacts in the main apod comment section, especially about the prominent blue and orange features at 7 and 4 o'clock, respectively. We're accustomed to seeing foreground stars as spiky features in images produced by optical instruments. Anyway, thanks again, Ann; your comments are exactly what I see this forum as having been designed for (...)

Thank you so much, smitty!

Theodorusm wrote:
At the lower right there is a bright star . Just above it at about 11 o'clock are two overlapping circles. What is that.?

That is clearly a photographic effect. The circles are not real, rather some sort of reflection inside the camera. However, I will leave the details of what causes this kind of reflections to the expert photographers here.

Ann

[Ann]

Moonlady wrote:

Take a ride to the center of Andromeda Galaxy: Ann you might like the A type hot blue stars there!

Yes, you are indeed right that there are hot blue A-type stars near the nucleus of the Andromeda Galaxy, and I'm sure I would like them! Unfortunately, I fear that the environment close to the nucleus of the Andromeda Galaxy might be sufficiently hazardous to my health that I might not be able to enjoy the blue stars there for long!

Ann

[C0ppert0p]

I would love to know about the cause of the circular artifacts. Anyone have an detailed explanation?

[neufer]

Click to play embedded YouTube video.

Ann; your comments are exactly what I see this forum as having been designed for (unlike some of the childish clowning around too often found here these days).

[c]Hey, man - what are you hassling me for?

This is just a gig, it's not my life.[/c]

[saturno2]

Andromeda Galaxy is very beautiful, indeed.
It´s has some of special.
I don´t know what is

[Boomer12k]

I would like to see a scale normal telescope view that would overlay this when you hover the mouse over the picture...
Very Nice picture.

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