Starship Asterisk*

starsurfer wrote:
Isn't it 2.5 million light years away?

Unless its distance has been more refined with newer observations, lots of ongoing studies of this fascinating galaxy!

• 2.54 ± 0.1 Mly

http://outreach.atnf.csiro.au/education/senior/astrophysics/variable_cepheids.html wrote:

<<In 1924 Edwin Hubble detected Cepheids in the Andromeda nebula, M31 and the Triangulum nebula M33. Using these he determined that their distances were 900,000 and 850,000 light years respectively. He thus established conclusively that these "spiral nebulae" were in fact other galaxies and not part of our Milky Way.

In the mid 20th century, significant problems with the astronomical distance scale were resolved by dividing the Cepheids into different classes with very different properties. In the 1940s, Walter Baade recognized two separate populations of Cepheids (classical and Type II). Classical Cepheids are younger and more massive population I stars, whereas Type II Cepheids are older fainter population II stars. Classical Cepheids and Type II Cepheids follow different period-luminosity relationships. The luminosity of Type II Cepheids is, on average, less than classical Cepheids by about 1.5 magnitudes (but still brighter than RR Lyrae stars). Initial studies of Cepheid variable distances were complicated by the inadvertent admixture of classical Cepheids and Type II Cepheids. Walter Baade's seminal discovery led to a [doubling] in the distance to M31, and the extragalactic distance scale. RR Lyrae stars were recognized fairly early (by the 1930s) as being a separate class of variable, due in part to their short periods.>>

http://en.wikipedia.org/wiki/Ernst_%C3%96pik wrote:

<<In 1922, Ernst Öpik published a paper where he estimated the distance of the Andromeda Galaxy. He determined the distance using a novel astrophysical method based on the observed rotational velocities of the galaxy, which depends on the total mass around which stars are rotating, and on the assumption that the luminosity per unit mass was the same as that of our galaxy. He concluded that the distance was 450 kpc. His result was closer to recent estimates (778 kpc) than Hubble's result (275 kpc). That same year Öpik also correctly predicted the frequency of craters on Mars.

Earlier, in 1916 Öpik published article in Astrophysical Journal, where he estimates the densities of visual binary stars. It is interesting to note that in his sample was ο2 Eridani, a white dwarf star. Öpik determined its density as 25,000 times the density of the Sun but concluded that the result is impossible.

In 1932 Öpik postulated a theory concerning the origins of comets in our solar system. He believed that they originated in a cloud orbiting far beyond the orbit of Pluto. This cloud is now known as the Oort cloud or alternatively the Öpik-Oort Cloud in his honour.

In 1951 Öpik published a paper concerning the triple-alpha process, describing the burning of helium-4 into carbon-12 in the cores of red giant stars.>>

starsurfer wrote:
Isn't it 2.5 million light years away?

Unless its distance has been more refined with newer observations, lots of ongoing studies of this fascinating galaxy!

• 2.9 Mly

http://www.universetoday.com/33475/messier-31/ wrote:
Messier 31
by Tammy Plotner< Universe Today, June 25, 2009

Object Name: Messier 31
Alternative Designations: M31, NGC 224, Andromeda Galaxy
Object Type: Type Sb Galaxy
Distance: 2900 (kly)
Visual Brightness: 3.4 (mag)

[b][color=#00AF00][size=135]M31 has a double nucleus separated by 5 light-years. The true center of M31 is the dimmer component.[/size] Green-light image taken with HST’s Wide Field & Planetary Camera.[/color][/b]

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<<“We present the first detailed spectroscopic and photometric analysis of an eclipsing binary in the Andromeda Galaxy (M31). This is a 19.3 mag semidetached system with late O and early B spectral type components.” says Ignasi Ribas (et al), “From the light and radial velocity curves we have carried out an accurate determination of the masses and radii of the components. Their effective temperatures have been estimated by modeling the absorption-line spectra. The analysis yields an essentially complete picture of the properties of the system, and hence an accurate distance determination to M31.”

Approaching us at roughly 300 kilometers per second, our massive galactic neighbor has been the object of studies of spiral structure, globular and open clusters, interstellar matter, planetary nebulae, supernova remnants, galactic nucleus, companion galaxies, and more for as long as we’ve been peering its way with a telescope. It’s part of our Local Group of galaxies and its two easily visible companions are only part of the eleven others that swarm around it. One day we’ll join forces, much as it M31 is now consuming its neighbor – M32 – but not for many millions of years yet!

How many times has the Great Andromeda Galaxy consumed another? More than once. In 1993 the Hubble Space Telescope revealed that M31 has a double nucleus – a ‘leftover’ from another meal! “Each of the two light-peaks contains a few million densely packed stars. The brighter object is the “classic” nucleus as studied from the ground. However, HST reveals that the true center of the galaxy is really the dimmer component. One possible explanation is that the brighter cluster is the leftover remnant of a galaxy cannibalized by M31. Another idea is that the true center of the galaxy has been divided in two by deep dust absorption across the middle, creating the illusion of two peaks.

[b][color=#0000FF]The true blue center of M31 in X-ray[/color][/b]

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Perhaps one of the most fascinating discovery recent years in Messier 31 was made by the orbiting Chandra X-Ray Observatory. This X-ray image, made with the Chandra X-Ray Astronomy Center’s Advanced CCD Imaging Spectrometer (ACIS), shows the central portion of the Andromeda Galaxy. The blue dot in the center of the image is a “cool” million degree X-ray source where Andromeda’s massive central object, with the mass of 30 million suns, is located, which many astronomers consider to be a supermassive black hole. Most of these are probably due to X-ray binary systems, in which a neutron star (or perhaps a stellar black hole) is in a close orbit around a normal star.”

In 2005, we discovered more. From the Astrophysical Journal: “Scott Chapman of the California Institute of Technology, Rodrigo Ibata of the Observatoire de Strasbourg, and their colleagues report that their detailed studies of the motions and metals of nearly 10,000 stars in Andromeda show that the galaxy’s stellar halo is “metal-poor.” In astronomical parlance, this means that the stars lying in the outer bounds of the galaxy are pretty much lacking in all the elements heavier than hydrogen. This is surprising, says Chapman, because one of the key differences thought to exist between Andromeda and the Milky Way was that the former’s stellar halo was metal-rich and the latter’s was metal-poor. If both galaxies are metal-poor, then they must have had very similar evolutions.” Probably, both galaxies got started within a half billion years of the Big Bang, and over the next three to four billion years, both were building up in the same way by protogalactic fragments containing smaller groups of stars falling into the two dark-matter haloes,” Chapman explains. Galaxies like Andromeda and the Milky Way have each probably gobbled up about 200 smaller galaxies and protogalactic fragments over the last 12 billion years. The stars that dominate closer to the center of the galaxy, by contrast, are those that formed and merged later, and contain heavier elements due to stellar evolution processes. In addition to being metal-poor, the stars of the halo follow random orbits and are not in rotation. By contrast, the stars of Andromeda’s visible disk are rotating at speeds upwards of 200 kilometers per second.According to Ibata, the study could lead to new insights on the nature of dark matter. “This is the first time we’ve been able to obtain a panoramic view of the motions of stars in the halo of a galaxy,” says Ibata. “These stars allow us to weigh the dark matter, and determine how it decreases with distance.”
........................................................................................
History: Known as the “Little Cloud” to to the Persian astronomer Abd-al-Rahman Al-Sufi, who described and depicted it in 964 AD in his Book of Fixed Stars, this wonderful galaxy was also cataloged by Giovanni Batista Hodierna in 1654, Edmund Halley in 1716, by Bullialdus 1664, and again by Charles Messier who wrote in his notes: “The sky has been very good in the night of August 3 to 4, 1764; and the constellation Andromeda was near the Meridian, I have examined with attention the beautiful nebula in the girdle of Andromeda, which was discovered in 1612 by Simon Marius, and which has been observed since with great care by different astronomers, and at last by M. le Gentil who has given a very ample and detailed description in the volume of the Memoirs of the Academy for 1759, page 453, with a drawing of its appearance. I will not report here what I have written in my Journal: I have employed different instruments for examining that nebula, and above all an excellent Gregorian telescope of 30 pouces [French inch ~ 27mm] focal length, the large mirror having 6 pouces in diameter, and magnifying 104 times these objects: the middle of that nebula appeared rather bright with this instrument, without any appearance of stars; the light went diminishing up to extinguishing; it resembles two cones or pyramids of light, opposed at their bases, of which the axis was in the direction form North-West to South-East; the two points of light or the two summits are about 40 minutes of arc apart; I say about, because of the difficulty to recognize these two extremities. The common base of the two pyramids is 15 minutes: these measures have been made with a Newtonian telescope of 4 feet and a half focal length, equipped with a micrometer of silk wires. With the same instrument I have compared the middle of the summits of the two cones of light with the star Gamma Andromedae of fourth magnitude which is very near to it, and little distant from its parallel. From these observations, I have concluded the right ascension of the middle of this nebula as 7d 26′ 32″, and its declination as 39d 9′ 32″ north. Since fifteen years during which I viewed and observed this nebula, I have not noticed any change in its appearances; having always perceived it in the same shape.”

Sir William Herschel knew way ahead of everyone else, that there was something very, very different about Messier’s Object 31! Although he never publicly published his observing notes on another astronomer’s discoveries, it’s a shame he did not for this is what he had to say: “.. But when an object is of such a construction, or at such a distance from us, that the highest power of penetration, which hitherto has been applied to it, leaves it undetermined whether it belongs to the class of nebulae or of stars, it may be called ambiguous. As there is, however, a considerable difference in the ambiguity of such objects, I have arranged 71 of them into the following four collections. The first contains seven objects that may be supposed to consist of stars, but where the observations hitherto made, of either their appearance or form, leave it undecided into which class they should be placed. Connoiss. 31 [M31] is: A large nucleus with very extensive nebulous branches, but the nucleus is very gradually joined to them. The stars which are scattered over it appear to be behind it, and seem to lose part of their lustre in the passage of their light through the nebulosity; there are not more of them scattered over the immediate neighborhood. I examined it in the meridian with a mirror of 24 inches in diameter, and saw it in high perfection; but its nature remains mysterious. Its light, instead of appearing resolvable with this aperture, seemed to be more milky. The objects in this collection must at present remain ambiguous.”>>

tkc wrote:Just out of curiosity, what are the two background galaxies?

bystander wrote:

tkc wrote:Just out of curiosity, what are the two background galaxies?

The larger one is M32, the smaller M110.

Lorenzo Comolli wrote:Thanks for comments and for selection! :-)

@Boomer12k: the up-down flipped image is the small one, while the linked one is ok. I suppose the editors preferred to put in "foreground" the dust bands just for aestetical purposes.

Lorenzo

Chris Peterson wrote:

bystander wrote:

tkc wrote:
Just out of curiosity, what are the two background galaxies?

The larger one is M32, the smaller M110.

I think it's the other way around.

geckzilla wrote:
The depth of the Universe is lost when we view it because it essentially becomes a two dimensional plane to us.

It's rather difficult to judge both size and distance without some interesting measurement techniques.

neufer wrote:Semantics?
M32 is twice as bright as M110 and contains a supermassive black hole estimated at 1.5 to 5 million solar masses.

Chris Peterson wrote:

neufer wrote:
Semantics? M32 is twice as bright as M110 and contains a supermassive black hole estimated at 1.5 to 5 million solar masses.

Not quite the word I'd choose, but certainly, discussions about size can be ambiguous. However, since the question was with respect to the image itself, asking for the identity of a couple of fuzzies, I'd interpret size in this case to refer to apparent size.

APOD Robot wrote: The Porpoise Galaxy from Hubble

Chris Peterson wrote:

bystander wrote:

tkc wrote:Just out of curiosity, what are the two background galaxies?

The larger one is M32, the smaller M110.

I think it's the other way around.

neufer wrote:

Chris Peterson wrote:

neufer wrote:
Semantics? M32 is twice as bright as M110 and contains a supermassive black hole estimated at 1.5 to 5 million solar masses.

Not quite the word I'd choose, but certainly, discussions about size can be ambiguous. However, since the question was with respect to the image itself, asking for the identity of a couple of fuzzies, I'd interpret size in this case to refer to apparent size.

There was a spirited debate recently on whether NGC 2936 resembled a porpoise/penguin or a hummingbird.

It sort of depended upon the rather arbitrary fuzzy brightness level that one wished to concentrate upon.

APOD Robot wrote: The Porpoise Galaxy from Hubble

owlice wrote:
Someone made a good case for a kiwi in email.
(To be clear, that'd be the kiwi bird.)

• KiwiLeaks

freidaV wrote:Hello.

I'm new to the science of astronomy, so my questions may seem naïve. Please be tolerant in your answers?

First, aren't the Milky Way and Andromeda already gravitationally interacting? Two million light years is not so far away, universally speaking....

Second, if the galactic arm where we're located is adjacent to Andromeda, could that interaction be a culprit in global warming?

Thank you!

freidaV wrote:First, aren't the Milky Way and Andromeda already gravitationally interacting? Two million light years is not so far away, universally speaking...

Second, if the galactic arm where we're located is adjacent to Andromeda, could that interaction be a culprit in global warming?

bystander wrote:

Chris Peterson wrote:

bystander wrote:<<< Just out of curiosity, what are the two background galaxies?>>>
The larger one is M32, the smaller M110.

I think it's the other way around.

You are correct, I did get them backwards. M32 has the smaller apparent size and M110 the larger.

neufer wrote:

geckzilla wrote:
The depth of the Universe is lost when we view it because it essentially becomes a two dimensional plane to us.

It's rather difficult to judge both size and distance without some interesting measurement techniques.

Anthony Barreiro wrote:Here's another interesting complication: while on Lorenzo's beautiful long-exposure photograph M110 appears bigger and brighter than M32, when you look at Andromeda and her satellite galaxies through a telescope, M32 is much more obvious than M110. Objects that have larger apparent sizes tend to have lower surface brightnesses, and thus appear dimmer.