Stars from the early universe, formed shortly after the big bang, have been discovered in a "nearby" dwarf galaxy.
A related recent post:
http://jmahony.posterous.com/light-shed-on-mysterious-supernova-and-the-st
Showing posts with label cosmology. Show all posts
Showing posts with label cosmology. Show all posts
Thursday, March 4, 2010
Tuesday, February 16, 2010
Light Shed on Mysterious Supernova and the Star Behind It
A supernova that lasted an unprecedented 555 days, SN2007bi, appears to have been caused by a star that technically should not exist....today. The monster that led to this supernova ought to have been more than 300 solar masses, but this seems to contradict current theories, backed by observational data. A protostellar cloud would gravitationally collapse to form a star at 150 solar masses or less, and would never get even close to 300 solar masses. Stars this large just can't form.
However, that's in todays universe.
Back in the early days, when the universe was less than a few hundred million years old, the universe consisted only of hydrogen, helium and a little lithium which were forged in the first three furious minutes following the Big Bang. Heavier elements had not yet been formed as the universe cooled too quickly after the Big Bang to continue building elements, and the stars that would eventually synthesise them didn't yet exist. Huge amounts of these light elements had to come together before reaching the critical mass necessary for gravitational collapse that leads to stellar ignition, hence the truly enormous mass of these early stars. These first stars burned quickly (quickly for stars, ie a few million years) and brightly before exhausting their reserves of hydrogen and exploding in supernovae, creating heavier elements and sending them out into the universe, in the process reducing and eventually killing off any possibility of these types of stars from forming in the future. But why did it it burn so long? A hypothetical "pair-instability"-type supernova occurrs in stars this big. Hypothetical because it wasn't believed that stars this big could exist.
So how could stars this big exist today?
This supernova was seen in a dwarf galaxy 1.6 billion light years away, too nearby to be from the early universe. From observations, these dwarf galaxies seem to have significantly less of the heavier-than-lithium elements than they should have for their size. The implication here is that these dwarf galaxies may in fact be leftover "islands" of the early universe! The low mass could explain why they never accumulated to form fully sized galaxies.
This is why I love cosmology. The timescales, the distances and the concepts are so awesome, the processes so ferociously elegant....it's humbling to think that a complex glob of carbon compounds on a rock orbiting a yellow star in an insignificant galaxy can even exist to contemplate such things.
For lots more on this amazing story: http://www.newscientist.com/article/mg20527470.900-primordial-giant-the-star-that-time-forgot.html?full=true
Thursday, January 14, 2010
Dark matter's effect on planetary orbits
Interesting story on how dark matter being swept up by the sun appears to be affecting the orbits of the planets in our solar system. Yes, Earth too.
Thursday, January 7, 2010
WISE is calibrating and already releasing images!
WISE is being calibrated and has released this preliminary image:
http://tinyurl.com/yh5afucHere's the BA's take:
http://tinyurl.com/yefpbxo Here's the press release:
http://tinyurl.com/yar36gr
http://tinyurl.com/yh5afucHere's the BA's take:
http://tinyurl.com/yefpbxo Here's the press release:
http://tinyurl.com/yar36gr
Wednesday, January 6, 2010
Our Galaxy, a squished beach ball and dark matter
Using inferences from all sky observations of out nearest galactic neighbours, researchers at UCLA have hypothesised a shape for our galaxy that's not at all expected.....more here: http://www.universetoday.com/2010/01/06/milky-way-has-a-squashed-beachball-shaped-dark-matter-halo/
Tuesday, January 5, 2010
The hubble hits just keep on coming!
Check out this latest image from Hubble: http://tinyurl.com/ykt547o Just think, each little speck is a galaxy, with hundreds of billions of stars...mindblowing! You can actually see the oldest ones in the bigger picture. They're the red blobs, displaying that famous red-shifting, and - get this - we're seeing them as they were up to 13 billion years ago! The image was created by combining several different images, taken in ultraviolet, visible light and near-infrared. (bigger image here: http://tinyurl.com/ya3h3vp) We are so small.......
Monday, January 4, 2010
Dark Energy and the Casimir Effect
It's a weird, weird universe, at the quantum level, with implications for the eventual fate of the universe....probably a Big Fizzle. Check out the APOD:http://antwrp.gsfc.nasa.gov/apod/ap100103.html
Wednesday, December 30, 2009
Friday, December 18, 2009
Dark Matter: Encouraging results, but no smoking gun
Some possible events that might be dark matter interactions, but not statistically significant enough to warrant a definite yes. See the link below for a pdf summary from CDMS. http://cdms.berkeley.edu/results_summary.pdf
Tuesday, December 15, 2009
Dark matter news, maybe......
Something is happening, it seems, but no-one can tell for sure.....new techniques, or a major announcement? as Ted Bunn says, all eyes will be on ArXiv when the article is supposed to appear!
Ted Bunn's blog entry on the subject:
http://blog.richmond.edu/physicsbunn/2009/12/15/dark-matter-update/
Monday, December 14, 2009
Hubble does it again
Orion nebula protoplanetary disks, future solar systems forming around new stars! As usual, Hubble delivers amazingly beautiful images.
More info here:http://www.spacetelescope.org/news/html/heic0917.htmlThursday, December 10, 2009
Twinkle, twinkle little star........
....... how I wonder what you are.
That little line of verse summarises most of humanity's history in looking at the night sky. Just what are those little lights up there, anyway? Many theories were put forward, from holes in a cosmic animal skin covering the night sky allowing pinholes of daylight to peek through, to campfires of other peoples far, far away. Little wandering "stars" that appeared to change position regularly (planets, from the ancient Greek word for "moving") added to the confusion, as did stars that suddenly flared up and blazed brightly for a few days or weeks, and then fade out again. With mysteries of this kind, is it any wonder our ancestors tried to associate such appearances and behaviours with events on earth? Careful observation shows that the same patterns occur again and again every year at around about the same time. Why not see what happens each time, for example, the planet Mars is passing through the constellation Gemini? And thus was born the pseudoscience of astrology. It was comforting to know that we were linked with the sky, that we could have a semblance of control in an otherwise chaotic world.
But today, we know what the stars are. We know that constellations are temporary and that the planets and stars have no bearing on our lives, aside from inspiring us with awe at their beauty every time we look up.
So, what are the stars? Let me answer with another question. What is the closest star to Earth? (Hint: If you don't know, it's closer than you might think.) That's right. The sun. Our sun is a star. That implies that all stars are suns, however, not necessarily like ours.
All stars are suns.
Think about that for a moment. Every little star twinkling up there on a clear moonless night is a sun. Some are bigger, smaller, brighter and dimmer, than our sun, but are essentially similar. And now imagine that what we see is only the tiniest fraction of what's out there. It's estimated that there are up to 400 billion stars in our galaxy alone, and there are billions of galaxies. Isn't that amazing? How enormous is even just our galaxy?
Ok, so all stars are suns, but what are they exactly?
Essentially, they're big balls of plasma, no more, no less. And they have a life cycle, just like people do, but over a much vaster timescale. A star is born when enough hydrogen gas accumulates to ignite, a process called nuclear fusion. This is caused when the mass of hydrogen accumulation reaches a point where its gravity causes the internal pressure to fuse hydrogen atoms together to form helium nuclei, releasing huge amounts of energy in the process. This is what causes our sun, and all other stars, to shine. So the balancing act that is a star's life is between gravity, which makes it want to contract, and heat and outward pressure which make it want to expand. A successful star is one where these two forces are more or less equalised. And so it goes for millions of years in what we call the star's main sequence.
Eventually, though, the supply of hydrogen begins to run out and what happens then depends on the star's mass. It may begin to convert helium to carbon, or if it isn't massive enough, fusion reactions stop and the expansion pressure is enough to overcome the gravitational force and the star expands into a bloated red giant. Eventually it sheds it's outer region to leave a planetary nebula and a white dwarf star if it's between 0.08 and 5 times the suns mass, but over 5 it will explode in to one of the most violent events in the universe: a supernova.
When the helium is used up, the carbon gets fused into oxygen, magnesium, silicon and on until we hit iron. But wait, what's happening here? We know these substances from the periodic table of the elements. The star is building them, it's an element factory! That's right. Everything around you is built of star debris. But how did the iron on earth get here from the star's insides? Due to one of the most violent events in the universe, one that happens when the star starts to try "burning" iron. Iron removes most of the energy from the star, and gravity finally gets the upper hand. The iron core collapses in on itself, and the effect of this is like pulling the rug out from under the upper layers: they fall on the iron core and bounce back out, causing the star to explode in a supernova. Some are so bright, they can be seen in broad daylight for days, weeks or months before fading away again. All that remains is a neutron star formed by the supernova blast.
But, if the star is even bigger, more than 20 times the mass of our sun, it may end up as one of the most mysterious objects in the universe: a black hole.
But that's another story.
Twinkle twinkle little star, now I know just what you are..........
That little line of verse summarises most of humanity's history in looking at the night sky. Just what are those little lights up there, anyway? Many theories were put forward, from holes in a cosmic animal skin covering the night sky allowing pinholes of daylight to peek through, to campfires of other peoples far, far away. Little wandering "stars" that appeared to change position regularly (planets, from the ancient Greek word for "moving") added to the confusion, as did stars that suddenly flared up and blazed brightly for a few days or weeks, and then fade out again. With mysteries of this kind, is it any wonder our ancestors tried to associate such appearances and behaviours with events on earth? Careful observation shows that the same patterns occur again and again every year at around about the same time. Why not see what happens each time, for example, the planet Mars is passing through the constellation Gemini? And thus was born the pseudoscience of astrology. It was comforting to know that we were linked with the sky, that we could have a semblance of control in an otherwise chaotic world.
But today, we know what the stars are. We know that constellations are temporary and that the planets and stars have no bearing on our lives, aside from inspiring us with awe at their beauty every time we look up.
So, what are the stars? Let me answer with another question. What is the closest star to Earth? (Hint: If you don't know, it's closer than you might think.) That's right. The sun. Our sun is a star. That implies that all stars are suns, however, not necessarily like ours.
All stars are suns.
Think about that for a moment. Every little star twinkling up there on a clear moonless night is a sun. Some are bigger, smaller, brighter and dimmer, than our sun, but are essentially similar. And now imagine that what we see is only the tiniest fraction of what's out there. It's estimated that there are up to 400 billion stars in our galaxy alone, and there are billions of galaxies. Isn't that amazing? How enormous is even just our galaxy?
Ok, so all stars are suns, but what are they exactly?
Essentially, they're big balls of plasma, no more, no less. And they have a life cycle, just like people do, but over a much vaster timescale. A star is born when enough hydrogen gas accumulates to ignite, a process called nuclear fusion. This is caused when the mass of hydrogen accumulation reaches a point where its gravity causes the internal pressure to fuse hydrogen atoms together to form helium nuclei, releasing huge amounts of energy in the process. This is what causes our sun, and all other stars, to shine. So the balancing act that is a star's life is between gravity, which makes it want to contract, and heat and outward pressure which make it want to expand. A successful star is one where these two forces are more or less equalised. And so it goes for millions of years in what we call the star's main sequence.
Eventually, though, the supply of hydrogen begins to run out and what happens then depends on the star's mass. It may begin to convert helium to carbon, or if it isn't massive enough, fusion reactions stop and the expansion pressure is enough to overcome the gravitational force and the star expands into a bloated red giant. Eventually it sheds it's outer region to leave a planetary nebula and a white dwarf star if it's between 0.08 and 5 times the suns mass, but over 5 it will explode in to one of the most violent events in the universe: a supernova.
When the helium is used up, the carbon gets fused into oxygen, magnesium, silicon and on until we hit iron. But wait, what's happening here? We know these substances from the periodic table of the elements. The star is building them, it's an element factory! That's right. Everything around you is built of star debris. But how did the iron on earth get here from the star's insides? Due to one of the most violent events in the universe, one that happens when the star starts to try "burning" iron. Iron removes most of the energy from the star, and gravity finally gets the upper hand. The iron core collapses in on itself, and the effect of this is like pulling the rug out from under the upper layers: they fall on the iron core and bounce back out, causing the star to explode in a supernova. Some are so bright, they can be seen in broad daylight for days, weeks or months before fading away again. All that remains is a neutron star formed by the supernova blast.
But, if the star is even bigger, more than 20 times the mass of our sun, it may end up as one of the most mysterious objects in the universe: a black hole.
But that's another story.
Twinkle twinkle little star, now I know just what you are..........
Wednesday, December 9, 2009
Forget the last post
Looks like it's going nowhere, for now. The blogosphere's rumourmill gota lot of people jumping the gun.....apparently no dark matter just yet.
http://blog.richmond.edu/physicsbunn/2009/12/09/mea-culpa/
http://blog.richmond.edu/physicsbunn/2009/12/09/mea-culpa/
Tuesday, December 8, 2009
Rumours that first dark matter particle found
Whoah. Let's see where this goes.
Rumours that first dark matter particle found - Short Sharp Science - New Scientist
Rumours that first dark matter particle found - Short Sharp Science - New Scientist
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