Starship Asterisk*

The Fornax Cluster of Galaxies

Explanation: How do clusters of galaxies form and evolve? To help find out, astronomers continue to study the second closest cluster of galaxies to Earth: the Fornax cluster, named for the southern constellation toward which most of its galaxies can be found. Although almost 20 times more distant than our neighboring Andromeda galaxy, Fornax is only about 10 percent further that the better known and more populated Virgo cluster of galaxies. Fornax has a well-defined central region that contains many galaxies, but is still evolving. It has other galaxy groupings that appear distinct and have yet to merge. Seen here, almost every yellowish splotch on the image is an elliptical galaxy in the Fornax cluster. The picturesque barred spiral galaxy NGC 1365 visible on the lower right is also a prominent Fornax cluster member.

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...almost every yellowish sploch... I like scientific descriptions like that. They're simple, and don't contain BIG non-understandable scientific words and phrases

Star clusters = often lots of blue stars (and sometimes pink nebulosity)!

Galaxy clusters = very few blue stars, but lots of yellow splotches!

But thanks for NGC 1365, Marco, and it's a nice APOD!

Ann

Not to nitpick, but is this Fornax cluster then the 'second closest cluster', or the 3rd, being just '10% further' than the next closest after the nearest? A minor and irrelevant point, no problem, but I was just trying to wrap my brain around that fact...

Anyway, my main question would be: if we on planet Earth, in the Milky Way, were part of this same cluster, how would we see the night sky with the naked eye? Would we be able to see these numerous galaxies with the unaided eye on a clear night sky, or still need binoculars or small telescope to view the beauty?? Thanks for reply...

APOD Robot wrote: The Fornax Cluster of Galaxies

Seen here, almost every yellowish splotch on the image is an elliptical galaxy in the Fornax cluster.

• Lewis Carroll's _Sylvie and Bruno_
  Chapter 7 : THE BARONS EMBASSY.

By the time my Lady had returned, from explaining things to the
music-master, the map had been hung up, and the Baron was already much
bewildered by the Vice-Warden's habit of pointing to one place while he
shouted out the name of another.

My Lady joining in, pointing out other places, and shouting
other names, only made matters worse; and at last the Baron,
in despair, took to pointing out places for himself, and feebly asked

"Is that great yellow splotch Fairyland?"

"Yes, that's Fairyland," said the Vice-warden

SouthEastAsia wrote:Not to nitpick, but is this Fornax cluster then the 'second closest cluster', or the 3rd, being just '10% further' than the next closest after the nearest? A minor and irrelevant point, no problem, but I was just trying to wrap my brain around that fact...

The Fornax Cluster is 10% further away than the nearest cluster. That makes it the second nearest. But perhaps they changed the wording after your post.

SouthEastAsia wrote:Anyway, my main question would be: if we on planet Earth, in the Milky Way, were part of this same cluster, how would we see the night sky with the naked eye? Would we be able to see these numerous galaxies with the unaided eye on a clear night sky, or still need binoculars or small telescope to view the beauty??

We on planet Earth, in the Milky Way galaxy, are part of a Local Group (a small cluster, I suppose you could say), so I don't think the sky would look all that different if we were part of a different cluster. We might be able to see a few more galaxies like Andromeda, or the SMC and LMC, but that would depend on just where we were in the cluster.

Rob

It's pictures like these that help me put the size of the universe into perspective. We are so small...

But, I'm okay with that.

ddorn777 wrote:
It's pictures like these that help me put the size of the universe into perspective.

We are so small... But, I'm okay with that.

Constantin Stanislavski famously remarked that "there are no small parts, only small actors".

http://en.wikipedia.org/wiki/Constantin_Stanislavski wrote:

Click to play embedded YouTube video.

<<Konstantin Sergeyevich Stanislavski (Константи́н Серге́евич Станисла́вский]; 17 January 1863 – 7 August 1938) was a Russian Empire actor and theatre director. Stanislavski grew up in one of the richest families in Russia, the Alekseyevs. "Stanislavski" was a stage name that he adopted in 1884 in order to keep his performance activities secret from his parents. The prospect of becoming a professional actor was taboo for someone of his social class; actors had an even lower social status in Russia than in the rest of Europe, having only recently been serfs and the property of the nobility. The Alexeyevs were a prosperous, bourgeois family, whose factories manufactured gold and silver braiding for military decorations and uniforms.

As a child, Stanislavski was exposed to the rich cultural life of his family. His interests included the circus, the ballet, and puppetry. In 1877, his father, Sergei Vladimirovich Alekseyev, was elected head of the merchant class in Moscow (one of the most important and influential positions in the city); that year, he had a fully equipped theatre built on his estate at Liubimovka, providing a forum for Stanislavski's adolescent theatrical impulses. The family's second theatre was added in 1881 to their mansion at Red Gates, on Sadovaya Street in Moscow (where Stanislavski lived from 1863 to 1903).

Increasingly interested in "living the part," Stanislavski experimented with the ability to maintain a characterization in real life, disguising himself as a tramp or drunk and visiting the railway station, or disguising himself as a fortune-telling gypsy; he extended the experiment to the rest of the cast of a short comedy in which he performed in 1883, and as late as 1900 he amused holiday-makers in Yalta by taking a walk each morning "in character".>>

SouthEastAsia wrote:
Not to nitpick, but is this Fornax cluster then the 'second closest cluster', or the 3rd, being just '10% further' than the next closest after the nearest? A minor and irrelevant point, no problem, but I was just trying to wrap my brain around that fact...

I think SouthEastAsia's point is that the Local Group and the Virgo Cluster are both closer than the Fornax cluster, so the Fornax Cluster is the 3rd closest, and I think SouthEastAsia is right.

RonDavis wrote:

SouthEastAsia wrote:

Not to nitpick, but is this Fornax cluster then the 'second closest cluster', or the 3rd, being just '10% further' than the next closest after the nearest? A minor and irrelevant point, no problem, but I was just trying to wrap my brain around that fact...

I think SouthEastAsia's point is that the Local Group and the Virgo Cluster are both closer than the Fornax cluster, so the Fornax Cluster is the 3rd closest, and I think SouthEastAsia is right.

SouthEastAsia wrote:Anyway, my main question would be: if we on planet Earth, in the Milky Way, were part of this same cluster, how would we see the night sky with the naked eye? Would we be able to see these numerous galaxies with the unaided eye on a clear night sky, or still need binoculars or small telescope to view the beauty?? Thanks for reply...

Ann already mentioned that we have a local group... but only 2 other big galaxies are in our group.

Andromeda is rather large (bigger than the Milky Way and is only 2M light years away). Apparently it covers a fairly large patch of the sky. The problem is, its surface brightness is so dim that it's hard for our eyes to see it.... it's ghostly, essentially transparent.

I once got a chance to look at it through a 20" refractor telescope and even then I could only barely recognize a blurry glowy smudge in the center of the telescope. My eyes weren't really dark adjusted and we were looking at it in the Bay Area which is a light poluted area, so that helps explain some of the difficulty. Really though, galaxies outside our own are dimmer than the strip of the Milky Way and so they don't really present the spectacular sky-scapes that some people imagine that they should.

Blah.

The sky is too dim
Beauty and wonder hidden
Grow some bigger eyes

-s

Undim the sky

As Rob and Spif pointed out, we live in a moderately large galaxy, and our even larger (or at least more star-rich) neighbor, the Andromeda galaxy, is only about two million light-years away and is seen in a relatively unobscured part of the sky. And yet, neither the brighter parts of our own galaxy or the Andromeda galaxy look really spectacular. I googled to try to find out when the Andromeda galaxy was first discovered by humans, or at least when humans first described it. This site (and I don't know how reliable it is) wrote:

The earliest recorded observation of the Andromeda Galaxy was in 964 CE by the Persian astronomer, Abd al-Rahman al-Sufi (Azophi) who described it as a "small cloud" in his Book of Fixed Stars.

Remember that our ancestors lived under very dark skies. And yet, Andromeda doesn't seem to have made a very great impression on them.

If we lived inside a galaxy cluster, there would be more large and bright galaxies to be seen in the night sky than there are in our present location. I still don't think these galaxies would be very impressive, however. And if we ourselves lived inside an elliptical galaxy, there would be no Orion, no Sirius, no Vega, no Big Dipper and no Pleiades in our night sky. These stars are all quite young, and there would be extremely few young stars around in an elliptical galaxy. There would indeed be some bright red giants like Arcturus or Aldebaran (but no supergiants like Betelgeuse), but these bright red giants would not form clusters. They would be randomly scattered across the sky. There might be large numbers of globulars, however, and some of them might look quite bright.

Personally I would guess that the core of an elliptical galaxy might be visible over vast distances inside that galaxy. It would probably be fairly unobscured by dust, and it might indeed be very bright.

Ann

RonDavis wrote:

SouthEastAsia wrote:
Not to nitpick, but is this Fornax cluster then the 'second closest cluster', or the 3rd, being just '10% further' than the next closest after the nearest? A minor and irrelevant point, no problem, but I was just trying to wrap my brain around that fact...

I think SouthEastAsia's point is that the Local Group and the Virgo Cluster are both closer than the Fornax cluster, so the Fornax Cluster is the 3rd closest, and I think SouthEastAsia is right.

Hmmmmm. Try this... Imagine you are inside a house which is the end one of three houses on a block. Would you say the house at the other end of the block was the second closest to you or the third closest to you? Our Local Group is our "house."

Rob

Spif wrote:Andromeda is rather large (bigger than the Milky Way and is only 2M light years away). Apparently it covers a fairly large patch of the sky. The problem is, its surface brightness is so dim that it's hard for our eyes to see it.... it's ghostly, essentially transparent.

Its surface brightness is essentially the same as that of our own galaxy, which is why to the naked eye, Andromeda looks very similar to the brighter parts of the Milky Way. You only think it is dimmer than the Milky Way because it is smaller and your brain lies to you about its true brightness.

I once got a chance to look at it through a 20" refractor telescope and even then I could only barely recognize a blurry glowy smudge in the center of the telescope.

Aperture doesn't really matter, except to the extent it allows greater magnification before we start seeing a reduction in brightness. No telescope can increase the brightness of an extended object beyond what we see with our eyes alone. Because of the way our eyes work, making an object bigger can make it easier to see, and give the impression of increased brightness, but that's an illusion.

rstevenson wrote:

RonDavis wrote:

SouthEastAsia wrote:

Not to nitpick, but is this Fornax cluster then the 'second closest cluster', or the 3rd, being just '10% further' than the next closest after the nearest? A minor and irrelevant point, no problem, but I was just trying to wrap my brain around that fact...

I think SouthEastAsia's point is that the Local Group and the Virgo Cluster are both closer than the Fornax cluster, so the Fornax Cluster is the 3rd closest, and I think SouthEastAsia is right.

Hmmmmm. Try this... Imagine you are inside a house which is the end one of three houses on a block. Would you say the house at the other end of the block was the second closest to you or the third closest to you? Our Local Group is our "house."

Our Local Group is our "pup-tent" surrounded by
7 other "pup-tents" and one local house: the VIRGO CLUSTER.

We are all part of the VIRGO SUPER CLUSTER neighborhood.

Chris Peterson wrote:

Spif wrote:Andromeda is rather large (bigger than the Milky Way and is only 2M light years away). Apparently it covers a fairly large patch of the sky. The problem is, its surface brightness is so dim that it's hard for our eyes to see it.... it's ghostly, essentially transparent.

Its surface brightness is essentially the same as that of our own galaxy, which is why to the naked eye, Andromeda looks very similar to the brighter parts of the Milky Way. You only think it is dimmer than the Milky Way because it is smaller and your brain lies to you about its true brightness.

I once got a chance to look at it through a 20" refractor telescope and even then I could only barely recognize a blurry glowy smudge in the center of the telescope.

Aperture doesn't really matter, except to the extent it allows greater magnification before we start seeing a reduction in brightness. No telescope can increase the brightness of an extended object beyond what we see with our eyes alone. Because of the way our eyes work, making an object bigger can make it easier to see, and give the impression of increased brightness, but that's an illusion.

Spif -- If you were looking through Rachel, the 20-inch f/17 refractor at Chabot Space and Science Center, that is not a good instrument for viewing an extended object such as the Andromeda galaxy. Even at its lowest magnification Rachel's field of view is only about 0.4 degrees in diameter -- too small to show the full Moon, which is about 0.5 degrees in diameter. Andromeda is about 3 degrees in diameter. So through Rachel you see the brighter central core of Andromeda against the background glow of Andromeda's spiral arms.

Try looking at Andromeda through a 12-inch f/5 reflector sometime. At low magnification through a wide-field eyepiece you will be able to see the entire galaxy against the background of intergalactic space. If the sky is clear and relatively dark, she's a breathtakingly beautiful sight! In the same field of view you should also be able to see Andromeda's satellite galaxies M32 and M110.

Chris -- I think I understand what you're saying about surface brightness, and that aperture creates an illusion of increased brightness. But does the increase in perceived brightness happen in the brain so much as the retina? Gathering more photons and projecting them onto more receptor cells makes the object appear brighter. If that's an illusion, it's good enough for me!

And I'm always thrilled when I see the Andromeda galaxy with my unaided eyes in a dark moonless sky. Just thinking about those photons travelling through space for two and a half million years ... .

Anthony Barreiro wrote:Chris -- I think I understand what you're saying about surface brightness, and that aperture creates an illusion of increased brightness. But does the increase in perceived brightness happen in the brain so much as the retina? Gathering more photons and projecting them onto more receptor cells makes the object appear brighter.

The retina is actually part of the brain, so separating what happens where is tricky. I do think a major reason that magnified images are easier to see is because more retinal cells are involved... regardless of where all the processing and perceptual steps occur.

"The picturesque barred spiral galaxy NGC 1365 visible on the lower right is also a prominent Fornax cluster member. "

http://apod.nasa.gov/apod/ap070328.html APOD 2007-mar-28

Chris Peterson wrote:The retina is actually part of the brain, so separating what happens where is tricky. I do think a major reason that magnified images are easier to see is because more retinal cells are involved... regardless of where all the processing and perceptual steps occur.

Huh. I assumed that the retina and optic nerve are part of the peripheral nervous system, like other sensory receptors and cranial nerves. But developmentally and anatomically they're actually part of the brain. I learned something new today. Thanks. This makes me want to be a bit more careful about what I stare at.

Spif wrote: The sky is too dim
Beauty and wonder hidden
Grow some bigger eyes
-s

I imagine a special kind of glasses which are opposite of sunglasses. I call them "astronomy glasses". It brightens the night sky without distorting or magnifying it.

By the way, is there a binocular which has a large objective diameter but a magnification of x1? For example a binocular of 50x1 would be great! Just brightens the sky, no magnification.

Ps. How night owls do see the sky, I wonder. I think they can see the Andromeda and other nebulae as bright objects with their naked eye.

Does anyone see any Galactic Lensing, or is it too close for that?

Nice blue Spiral in lower right, nice picture.

It is not enough to have just larger aperture, or magnification. It takes LONG EXPOSURE PHOTOGRAPHY to capture enough light for a good image. I don't even see the Andromeda Galaxy with my GOOD GLASSES. A bit of haze with my 10-30 power zoom binocs. I see only a bright core with my 10inch Meade. Even with a 30 exposure with my Deep Sky Imager 2 color camera. But M51 and the same exposure, I see disk shape, structure, dust lanes, etc... But without photography, I see a hazy patch, even at high magnification. Even with Nebula, M27, The Dumbbell Nebula, is a cloud like, (black and white-ish), patch. With photography, I get the colors, and shapes, some details. I got a bigger scope so I could at least tell what I was looking at. When I was looking at a galaxy, I could at least say, "oh, yeah, I can tell it is a galaxy". But they were only patches. That is what spurred me into Astrophotography. I wanted to see more details.
Some of the APODs, are taken with JUST A CAMERA, really GOOD, expensive, LARGE LENS camera, long exposure, no scope. Some are taken with a small, wider field refractor scope. Some AWESOME pictures, but it is not really the aperture, (which I admit IS a plus!!!), but the exposure time, AND THE QUALITY OF THE CAMERA and Sensor CHIP. Multiple pictures are taken, then stacked together, and then post processed to bring out the details. This is what I learned from Tony Hallas, expert.
Here are two pictures I took with my 10inch Meade. The "Dingy" photo is what I originally took, the clear one is post-processed. I took about 38, 30 second photos originally. Then made an AVI movie of them, put them in RegiStax. It aligns the pictures, and you get a nice, smooth looking image. Then I Photoshopped it with auto level, auto color, auto contrast, and then there is a Color Balancer or "smoother" from AKVIS software. In my processed photo, I can see details that are even in the HUBBLE pictures. Not as clearly, but they are there. Those pinkish, splotchy areas, are nice and clear in the Hubble images. But I can at least see them.

Aperture and magnification are not everything, you can get good detailed photos with the right and good equipment, even with small but high quality lenses and scopes. If I had known, I might have gone with a 4-5 inch refractor and a better camera, BUT I WAS THINKING BIGGER APERTURE AND MAGNIFICATION!!!!! I also wanted an automatic and computer controlled scope. And overall, I am happy with what I can do. Especially after learning how to bring out a better picture.

It even helps with moon photos.

You want to capture photons? Photography is the way to go! Otherwise you would not be enjoying these fine APODS!!!

:---[===] *

Sinan İpek wrote:I imagine a special kind of glasses which is the opposite of sunglasses. I call it "astronomy glasses". It brightens the night sky without distorting or magnifying it.

They are called night vision goggles, and work by increasing the quantum efficiency of our vision. That is, they effectively allow us to see nearly 100% of the photons that reach us. The combination of aperture and electronic gain allows for a significant apparent sensitivity to the night sky, but is at its theoretical limit. Further sensitivity is only possible by increasing exposure time... essentially, eliminating a real-time view.

By the way, is there a binoculars which has a large objective diameter but a magnification of x1? For example a binocular of 50x1 would be great! Just brightens the sky, and not magnifies.

That's not optically possible. No matter how large the aperture, a unit gain telescope (that is, the objective focal length equals the ocular focal length) will only pass photons into your eye that pass through a virtual aperture on the objective that is the same size as the pupil of your eye. So you'd see exactly the same thing as if you used no telescope at all.

Ps. How night owls do see the sky, I wonder. I think they can see the Andromeda and other nebulae by their naked eyes.

People can easily see Andromeda, and a number of other nebulas. Animals with exceptional night vision achieve it through a combination of mechanisms, including a reflective membrane behind the retina to double the number of photon captures, different sensory neuron densities, different sensory neuron chemistry, and different processing in the retina and brain. I don't think any animals achieve better than a five or six-fold sensitivity improvement over humans. Impressive, but not as good as what humans get with a high quality image intensifier, and nothing like we get with cameras that integrate for even a second or two.

Further sensitivity is only possible by increasing exposure time... essentially, eliminating a real-time view.

I thought the objective diameter matters. The bigger the objective diameter, the more photons it captures. We could get a brighter image either by doubling the objective diameter or by doubling exposure time. That is same with telescopes. If you increase mirror diameter, then you catch more photons, I think.

People can easily see Andromeda, and a number of other nebulas.

But we see only its core. It would be nice to see its spiral arms, too.

They are called night vision goggles, and work by increasing the quantum efficiency of our vision.

No electronic device could substitue our own sight, I think. The electronic noise is disgusting. By the way, does human sight have noise also?
I think, a kind of glass material can be produced such that it multiplies the number of photons.

Sinan İpek wrote:I thought the objective diameter matters. The bigger the objective diameter, the more photons it captures. We could get a brighter image either by doubling the objective diameter or by doubling exposure time. That is the same think as telescopes. If you increase the mirror diameter, then you catch more photons, I think.

No, with a telescope (that is, an afocal optical system) the size of the aperture does not have any impact on brightness. Nothing observed through a telescope can be any brighter than the same thing observed without a telescope. It is possible to get more photons into the eye, but they also cover a larger area (that's what magnification does). That can enhance how something appears, but not actually make it brighter. Aperture size is very important with focal optical systems (objectives with a camera at the focus), however, since such systems do capture every photon that passes through the aperture.

People can easily see Andromeda, and a number of other nebulas.

But we see only its core. It would be nice to see its spiral arms, too.

With good vision it is possible to just start making out some structure in Andromeda with the naked eye. By magnifying it, we involve more of the retina and that also allows us to see a little structure. But ultimately, the object just has too little contrast (even if it is relatively bright) to let us see much structure visually.