Nearby Galaxy Surprisingly Young 63
Pi_0's don't shower writes "The hubblesite is reporting that a galaxy discovered 70 years ago, I Zwicky 18, has been confirmed to be one of the youngest galaxies in the universe, at only 500 million years old. By contrast, our Milky Way, Andromeda, and most other nearby galaxies are 12 billion years old. This galaxy is the closest newly-formed galaxy, at only 45 million light years away, which has rather interesting implications for galaxy formation."
Interactions (Score:4, Funny)
Re:Interactions (Score:1)
Galactic ignition (Score:4, Interesting)
Experts only, not Trekkie wannabees!
Re:Galactic ignition (Score:5, Informative)
now the rate at which collapse occurs is difficult to calculate. it is non-linear, too many parameters and depends heavily on initial condition that you start. It may be possible, that these galaxy could produce internal lumps only recently which were dense enough to form stars.
in the beginning the stars are massive, since thermonuclear reaction is hard to start in "pristine" gas composed of only primordial hydrogen and helium. However, these large stars are also short lived, since they produce heat very fast and consume internal fuel and then they explode and generate heavy elements as by-products, which helps other smaller start formation like our sun.
Re:Galactic ignition (Score:1)
I. Gravity does not increase as density increases, you probably were thinking mass.
II. Heat plays no role in Hydrostatic Equillibrium, which is the balance of the inward gravitational force of the star and the outward pressure of it's mass.
Wrong! (Score:1)
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Re:Galactic ignition (Score:2)
Re:Galactic ignition (Score:1)
http://www.space.com/scienceastronomy/blackhole_h
I trust this is what you were looking for?
Melodrama (Score:2)
Meanwhile, in #stellarformations.. (Score:5, Funny)
Re:Meanwhile, in #stellarformations.. (Score:4, Funny)
Zwicky: But if you want some inside info, I heard NGC-4725 really has the hots for you. Her center hole has been getting larger with each passing millennia.
Re:Meanwhile, in #stellarformations.. (Score:3, Funny)
How accurate is this? (Score:2)
Given that there is still considerable dispute about the range of accuracy of various dating methods here on earth that use laboratory equipment to examine objects extremel
Re:How accurate is this? (Score:1)
Hubble's exquisite sensitivity allowed astronomers to do a reliable census of the total stellar population in the galaxy. This allowed them to reliably identify the oldest stars inhabiting the galaxy, thereby setting an upper limit on the galaxy's age
Re:How accurate is this? (Score:2)
Re:How accurate is this? (Score:5, Informative)
So, here on earth, we can do all sorts of laboratory tests. We can figure out under what conditions Hydrogen fuses. We can test the strength of gravity. We can test the way various elements react at various tempuratures and pressures. So, while there isn't a 100% guarantee that we have a good handle on how stellar evolution works in another galaxy, we can be pretty confident that we have a very good handle on it. Accurate to many decimal places.
Based on what we know about how the elements, we can make some calculations about stellar evolution in general. We can figure out how far away nearby stars are by using parallax while the earth goes around the sun. The nearby stars are the ones we can use to best test our theories, because we can be very very sure how far away they are. Because we know how far away they are, and how bright they appear, we can figure out how bright they actually are (as if they were all the same distance). We can also use spectrography to figure out what elements are giving off the starlight (which we can double check by heating up the elements in a lab and using the same spectroscope). Thankfully, our mathematical models of how bright a star should be with a certain element mixture line up perfectly with what we actually see, so we can safely apply our models to stars so far away that we can't use parallax to measure the brightness.
So, if you are still with me... We can look at a star, analyse the spectra emitted, and plug it into our mathematical models of stellar evolution. It seems like crazy guessing, and there is certainly some guessing involved, but the theories we use on distant stars have been tested in laboratories, and on nearby stars, with everything being double checked for crazy shit as the tests get farther out.
Given that this galaxy is so unusual, it is possible that somewhere along the line, we may need to update our models. It's possible our models are just giving us a wrong answer. It's wildly unlikely. But, science is the unending quest for a less-wrong answer. That's the difference between dogma and science. Science will freely admit it is wrong, but it usually turns out to be only slightly so. Dogma just finds ways to explain away new information in terms of the existing dogma, or dismisses it entirely.
Re:How accurate is this? (Score:2)
I can prove you wrong. Humans have created very small stars (fusion of hydrogen and
Re:How accurate is this? (Score:1)
Your statement about proving me wrong is flawed.
As regards the hydrogen bomb, this is exactly what I was talking about. It uses the pressure and heat from the reaction of a critical mass of uranium or plutonium to fuse lithium duride into helium! This is exactly what I said befor
Re:How accurate is this? (Score:2)
There are plenty of reasons why planets might rotate in the opposite direction (and Neptune is on its "side", don't forget). The early solar system was a busy place, with lots of collisions going on.
Gravity is an interesting force. Most forces (such as magnetism) have an opposite force (like charges repel, opposite charge
Re:How accurate is this? (Score:3, Informative)
Re:How accurate is this? (Score:2)
If you don't have any objections, I'm making that my new
Re:How accurate is this? (Score:2)
Re:How accurate is this? (Score:1)
Up front, I will state that I am a young earth creationist, and believe that the universe is only around 6000-7000 years old.
I am very interested in any suggestions as to HOW you would determine the age of a galaxy which is far off in space, when you can't take into a lab and anylise it.
Speaking of galaxies, doesn't the existence of spiral galixies prove that the universe is relatively "young"?
I mean, if the universe was older wouldn't the galixies have had enough time to spin
Re:How accurate is this? (Score:2)
As for your question, google found this [stsci.edu].
Re:How accurate is this? (Score:2)
Seriously, here's an educated guess: The Bible spends quit a bit of time on family geneologies. Because of that you know how many generations of people were born between Adam and the end of the end of the biblical period (a date we know). Making an estimate for the time span per generation would yeild something in the 5000-8000 year neighborhood.
Re:How accurate is this? (Score:1)
The Bible is an incredible God inspired book, which contains, among other things, a genialogy trail which when added up, gives a fairly exact date for the creation of the universe.
There are also many tests that you can do to demonstrate that the universe can't be as old as some people claim.
But anyway, this coonversaation is beginning to stray off topic.
Re:How accurate is this? (Score:2)
I'd be interested to hear about them. The method I discribed above isn't terribly convincing.
Re:How accurate is this? (Score:2)
Finally, Egyptians have been proved to have been writing about the world before your calculations
Re:How accurate is this? (Score:5, Informative)
Hertzsprung-Russell diagram, named after the two astronomers who came up with this method of classification.
There are two primary aspects that allow you to plot an individual star on this diagram: Its spectral color (litterally, what color you see the star as) This can be assigned a number as a specific peak color frequency. This also can be interpreted as the temperature of the "surface" of the star. The other axis is the absolute brightness of the star. This is the number of photons you can count in a given period of time relative to how far away it is. For measuring stars in a galaxy, distance measurements can pretty much assume that all of the stars are roughly the same distance away, thus simplifying this task. Close stars will obviously be brighter, but stars like Alpha Centari, an ordinary yellow star, are apparently as bright as Betelguese, a star almost 100 times further away.
Keep in mind that only until the Hubble telescope was able to resolve the individual stars in this galaxy, this study wasn't able to happen for this particular galaxy... which is why this is now news. Really a neat project on the whole.
The point here is that young stars fall onto what is called "The Main Sequence". These are stars like our sun that are still mostly converting Hydrogen to Helium as the primary source of nuclear energy. This relationship is quite well defined, and has been observed in not only the Milky Way Galaxy, but in other galaxies where individual stars have been able to be identified.
Stars that run out of Hydrogen fall into a very different pattern. Like I mentioned with Betelguese (in the constellation Orion), it is much further away but yet just as bright. Also, its color is more Red (in a clear rural sky you can even see this reddish color), which puts it outside of the Main Sequence. That is because (according to current theory) it has run out of Hydrogen and is now in the process of turning Helium into Carbon. This group of stars, known as "Red Giants" play a huge role in determining the age of a galaxy or other group of stars.
When stars finally run out of Helium, the rest of the elemental transmutation takes place rather quickly, or the fusion simply stops. Without going through the subsequent steps, the star eventually turns into a Super Nova (if there is enough stuff in the star to produce it) and leaves behind a white dwarf or neutron star (for really big stars... black holes are yet more stuff). A white dwarf is quite dim even for its distance, but yet its surface temperature is quite hot. These give yet another very distinctive plot on the HR Diagram.
So the whole point here is that you can measure the age of a group of stars based on the relative brightness of the stars in that group. Very large stars tend to live very short lifespans because they do a very efficient job of doing the fusion. Small stars (like Wolf 359) will be still doing the hydrogen fusion 20 billion years from now. Over time (and based on considerable observation examples... not just this galaxy in the article but also concrete parallax measurements of close stars to our own as well) you will see fewer and fewer stars on the very blue end of the HR diagram and more and more Red Dwarfs, with white dwarves showing up in increasing numbers as well.
One other critical tool for measurement is also trying to determine what elements are in the spectra of the stars. Different elements show up in stars and can be measured based on if they are absorbing or emitting light from the surface of the star. Mind you, this doesn't indicate much in terms of what is happening in the center of the star, but rather what is on the surface of the star. The current assumption is that the Universe started out with mainly Hydrogen and Helium, and only very small amounts of other elements. If you find large quantities of other elements in a star (like significant quantities of Iron on the sur
Re:How accurate is this? (Score:2)
Re:How accurate is this? (Score:5, Informative)
In 1987 a supernova was extensively sutidied in one of the Magenellic clouds (galaxies very close to our own that are so close that their apparent size takes up a significant portion of the southern hemesphere's sky). Previous sky survey's demonstrated that it was in the Red Dwarf stage of its life, and after the explosion a pulsar was found in the same physical position. That was pretty convincing evidence that at least that portion of stellar evolution is quite accurate, and can still be verified with current measurements.
Another major scientific measurement took place with the "Eagle Nebula" [wikipedia.org], which is the one that has the really cool columns of gases and has been done as poster you can buy in Wal-Mart and put on T-Shirts. In this case over the course of just a few years you can see stars litterally form right out of the gasses of the nebula. These new stars demonstrate that they are right on the "Main Sequence" after their formation. This certainly was a major plus to confirming these theories.
There are some suspected stars that are in transition from Main Sequence to Red Giant, but that takes considerably longer to happen.
With some very recent sky surveys, there have also been some significant confirmation of these theories, if simply from the huge amount of data that simply confirms this information. Keep in mind that many of these theories started out simply as a way to try and come up with a classification system of any kind, and have evloved from there.
The spectral classification originally started out when a bunch of researchers at Harvard University put star names and coordinates on a bunch of 3" x 5" cards and based on the spectrum lines and measured brightness, they litterally dropped these cards into boxes labeled "A", "B", "C", ect. After some more research the boxes were rearranged by temperature to become "O","B","A","F","G","K","M","R","N","S" ("Oh, Be A Fine Girl, Kiss Me") As can be seen, the original classification was very arbitrary, but based on formal measurements. Our sun is of type "G", and blue stars as type "O".
We know about spectral lines because we can do that in laboratories here on the Earth. Really quite cool to do as well, and each element puts out its own specrum. I'm sure you've seen a Neon sign with its pink glow, which is exactly what is done with other elements to identify their spectra as well. BTW, this spectra is also critical to understanding the atomic structure of each element, but that is another story to itself.
The distance measurements are calculated from steallar parallax as the base measurement. We know from several other measurements how far the Earth is away from the Sun, and when the Earth travels around the Sun, stars appear to move relative to each other. This is like taking two photographs a few feet apart and seeing stuff in the background at different angles. Doing this you can directly measure how far away something is from where you are at. This measurement is accurate to about 1000 light years with the Hubble Telescope. Other techniques try to approximate distances based on similar looking stars to ones that are close to us and assuming that stars next to those are probably about the same distance. Obviously that means even further distances are less accurate as you go further away from us. These distance measurements are IMHO very accurate, and their accuracy can be expressed precisely to a certain range of accuracy as well.
Stellar color is pretty easy, as you just have to have filters at different wavelengths when you take pictures of the stars. That is what gives the color to the photo in this article, and you can
Re:How accurate is this? (Score:3, Insightful)
Then, you can try to look for connections between these groups -- you don't have to live out an entire 100 years and watch them change in order to develop a theory about their characteristics and how they relate to each other. By studying some of the subtle changes over a year's time, you
Re:How accurate is this? (Score:3, Insightful)
What I was trying to point out (unfortunately not too clearly) was that in addition to this sort of classification, we have seen some glimpses of stellar transitions to help confirm the theories. And when new scientific tools come around and used in astronomy, the results tend to confirm rather than debunk the stellar evolution theories. You know that you have a solid scientific theory when it gets confirmation from addition kinds of observations, and better
Re:How accurate is this? (Score:1)
The part I would disagree with is about star formation. For you see, it would take tremendous pressure to compress gas into a star. I have read calculations before which stated it would take around twenty stars exploding near each other to create enough pressure for a new star to form. I agree, these calculations may not be accurate, but still, I am sure it would take more that one star, and at that rate someday all the stars will be gone! (Not good for
Re:How accurate is this? (Score:3, Informative)
Straightforward calculations, starting from equations of gas pressure and gravtational attraction, show that any overdense region in a gas cloud, larger than a certain critical mass (called the Jeans mass), will collapse in on itself. It is true that the simplest calculation of the Jeans mass gives 10^5 solar masses, much larger than any star; but if you take into account that a cloud will fragment as it collapses, the Jeans mass becomes much smaller. For typical conditions, the critical m
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Re:How accurate is this? (Score:1)
More reason to keep Hubble ... (Score:2)
As little as I understand all of the particulars of the parent post, the fact that we keep getting new science out of Hubble like this tells me that we definitely need to keep Hubble going and not just abandon it.
We're still learning too much from it to just throw it away.
Yet more proof (Score:4, Funny)
Re:Yet more proof (Score:1)
I think that's an important point. The probability of the cosmos presenting us with some optical illusion or other cannot be underestimated. Even the voyager spacecraft leaving the solar system provided us with unexpected data concerning the composition of interstellar space. We really don't know that much beyond that, simply because we are unable to travel these distances and have a look for ourselves. We're left with circumstantial evidence and deduction.
Nevertheless, the
Re:How fast? (Score:1)
If that was the case you would see some spectral shifting inconsistant with the general expansion of the universe. As far as I know this is not the case. More likely is that the gas cloud comp
Re:Yet more proof (Score:2)
The cosmological principle is sheer speculation -- useful, but speculative.
If English was good enough for Jesus... (Score:1)
Re:If English was good enough for Jesus... (Score:2, Informative)
Re:If English was good enough for Jesus... (Score:1)
Re:If English was good enough for Jesus... (Score:2)
Re:If English was good enough for Jesus... (Score:1)
Through careful reading, you will notice that the first account deals with the creation of the world.
The second account deals with creation in the garden of eden, when God created one of each creature for Adam to name.
So really, when you say creation, it should be OBVIOUS that you mean the creation of the entire world. The only way you could come to any other conclusion is by anylising someone's post intentionally looking for ways to confuse them.
Re:If English was good enough for Jesus... (Score:2)
Re:If English was good enough for Jesus... (Score:2)
Re:If English was good enough for Jesus... (Score:1)