Skip to comments.Hubble telescope makes new discovery
Posted on 11/16/2006 9:07:52 PM PST by NormsRevenge
NEW YORK - The Hubble Space Telescope has shown that a mysterious form of energy first conceived by Albert Einstein, then rejected by the famous physicist as his "greatest blunder," appears to have been fueling the expansion of the universe for most of its history.
This so-called "dark energy" has been pushing the universe outward for at least 9 billion years, astronomers said Thursday.
"This is the first time we have significant, discrete data from back then," said Adam Riess, a professor of astronomy at Johns Hopkins University and researcher at NASA's Space Telescope Science Institute.
He and several colleagues used the Hubble to observe 23 supernovae exploding white dwarf stars so distant that their light took more than half the history of the universe to reach the orbiting telescope. That means the supernovae existed when the universe was less than half its current age of approximately 13.7 billion years.
Because the physics of supernova explosions is extremely well-known, it is possible for the astronomers to gauge not just their distance, but how fast the universe was expanding at the time they went off.
"This finding continues to validate the use of these supernovae as cosmic probes," Riess said.
He and his colleagues describe their research in a paper that is scheduled for publication in the Feb. 10 issue of Astrophysical Journal.
The idea of dark energy was first proposed by Einstein as a means of explaining how the universe could resist collapsing under the pull of gravity. But then Edwin Hubble the astronomer for whom the NASA telescope is named demonstrated in 1929 that the universe is expanding, not a constant size. That led to the big-bang theory, and Einstein tossed his notion on science's scrap heap.
There it languished until 1998, when astronomers who were using supernova explosions to gauge the expansion of the universe made a shocking observation. It appeared that older supernovae, whose light had traveled a greater distance across space to reach the Hubble telescope, were receding from Earth more slowly than simple big-bang theory would predict. Nearby supernovae were receding more quickly than expected. That could only be true if some mysterious force were causing the expansion of the universe to accelerate over time.
Cosmologists dubbed the force "dark energy," and ever since they've been trying to figure out what it is.
"Dark energy makes us nervous," said Sean Carroll, a theoretical physicist at the California Institute of Technology who was not involved in the supernova study. "It fits the data, but it's not what we really expected."
Answers may come once NASA upgrades the Hubble Space Telescope in a space shuttle mission scheduled for 2008. NASA and the Department of Energy are also planning to launch an orbiting observatory specifically designed to address the mystery in 2011.
Dark energy could be some property of space itself, which is what Einstein was thinking of when he proposed it. Or it could be something akin to an electromagnetic field pushing on the universe. And then there's the possibility that the whole thing is caused by some hitherto undiscovered wrinkle in the laws of gravity.
These snapshots, taken by NASA's Hubble Space Telescope, reveal five supernovae, or exploding stars, and their host galaxies in these images released November 16, 2006. The top row of images point to the supernovae. The bottom row shows the host galaxies before or after the stars exploded. The supernovae exploded between 3.5 and 10 billion years ago. FOR EDITORIAL USE ONLY (NASA, ESA, and A. Riess - STScI/Handout/Reuters)
The Orion Nebula is seen in an image taken from the Hubble and Spitzer space telescopes. FOR EDITORIAL USE ONLY (NASA/Handout/Reuters)
My BS meter is full on this one.
U.S. Senator Barbara Mikulski (D-MD), ranking Democrat on the commerce, justice and science subcommittee of the Senate Appropriations Committee, answers questions at a news conference at the Goddard Space Flight Center in Maryland, October 31, 2006. NASA announced earlier in the day that there will be a shuttle mission, planned for May 2008, to service the Hubble Telescope and keep it operational through 2013. (Jonathan Ernst/Reuters)
That picture explains why the repulsive force causing the universe to expand.
The cosmological constant was a fudge factor introduced by Einstein in an attempt to create a static Universe. Does this prove that the Universe is static?
No - as I understand it, it means accelleration, with more rapid acccelleration over time, as objects get further apart. Truely anti gravity.
It was an artificial mathematical quantity. Invented by Einstein to stabilize his world view. It made the equations work.
News Release Number: STScI-2006-52
Hubble Finds Evidence for Dark Energy in the Young Universe
Whatever it is it is "dark" only to us, because we don't have the means to "see" it (to detect it) because we don't know exactly what it is. I think "dark" is an unfortunate label for it.
Background information useful for exploring this news release:
What Are HST's New Results on Dark Energy Telling Us?
1. Astronomers have greatly improved the accuracy in the measurements of the acceleration in the cosmic expansion. In 1998, astronomers discovered that the expansion of our universe is speeding up, propelled by the repulsive force of "dark energy." The nature of this dark energy remains a mystery.
2. Astronomers have strengthened the evidence that the early universe was decelerating, but that it gave way to acceleration by around 4 to 5 billion years ago.
3. Astronomers have obtained the first meaningful measurement of the strength of dark energy in the distant past. It appears to have roughly the same strength that it does today, with a value consistent with Einstein's cosmological constant but does not prove Einstein was right. Astronomers are trying in particular to determine how much pressure this dark energy exerts for a given energy density, and if the relation between pressure and density remains constant or changes with time.
4. The "pressure" exerted by dark energy far back in time was negative, as it remains today, resulting in a repulsive gravitational force.
5. The new results rule out any rapid changes of in the "strength" of the dark energy's pressure, and in so doing, they rule out certain models for the dark energy. By observing a larger sample of supernovae, the researches have been able to place tighter constraints both on this "strength" of the dark energy and on its constancy. One possibility is that the dark energy represents the energy of empty space (the physical vacuum). The physical vacuum has a peculiar property that its pressure is negative, resulting in a repulsive force of gravity. Other models for the nature of dark energy involve fields (a bit like the electromagnetic field) that decay with time.
6. There is strong evidence that the Supernovae Type Ia, the "standard candles" used to measure the rate of cosmic expansion, have not changed over the past 10 billions years, i.e., supernova evolution is not fooling astronomers into drawing false conclusions about dark energy. The new results yield the tightest constraints to date on both the "strength" of the dark energy pressure and on its constancy. The results are consistent with Einstein's cosmological constant. This means that at least some models that involve varying fields can be ruled out.
Hmmm.... the "Cosmological 'Constant'" is not so 'constant' after all. 'Fudging' with equations to satisfy the data on the false premise of a static universe yields an expanding universe in observational fact, as we now understand. If the universe were to be slightly less homogenous than presently perceived, could the "Big Bang" itself be a more local universe phenomenon in a greater whole?
Further, because Einstein was trying to account for a static universe, his "dark energy" equation could not possibly be the explanation for this phenomenon.
This article is really saying that this data no longer supports the Big Bang theory.
Oh, I see. The article wasn't very clear. Here's how it works.
Einstein's equations without the cosmological constant provide for essentially three solutions: a universe that collapses back upon itself, or a universe that expands forever, slowing down somewhat as it goes, or a universe that expands forever, but whose expansion eventually slows to a crawl. You can think of these as being akin to ballistic trajectories: the parabolic arc of an artillery shell, the escape trajectory of a deep space probe, or the orbital launch of a space shuttle.
Einstein assumed that the universe would neither expand nor contract, so he added in the cosmological constant. This parameter, depending on its value, can fine-tune the fate of the universe: the universe can collapse like the spiking of a volleyball, or it can accelerate outwards ever faster, like a rocket, or it can just hover in place, which is what Einstein wanted it to do.
Some time later, Edwin Hubble discovered that the universe was indeed expanding. It wasn't what Einstein expected, but it did seem to fit with the expanding cosmologies predicted if the constant were zero. So everyone assumed the constant was simply zero.
In recent years, however, it was discovered that the universal expansion isn't slowing down as required. In fact, it's speeding up! This most recent measurement confirms it by using Type 1a supernovae, which all have the same brightness. This allows us to measure how far away they are by how dim they appear. Also, we can measure how fast they are moving away from us by their redshift, and by how slowly they appear to cool off. That gives us all we need to see how the expansion has changed over time, if we can find enough Type 1a supernovae at a wide variety of distances.
If the expansion of the universe is speeding up, that means it can't be following one of the "ballistic" trajectories described by a zero cosmological constant. The constant must have a nonzero value very different from what Einstein originally wanted--opposite sign, in fact--but it must be nonzero nevertheless.
Wrong! It all depends on the value of the parameter. Read reply #17.
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