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Tag: dark matter
Watch This: Soar Through A 3D Map of the Universe
Note: You may want to click the full-screen button down there and watch this in its full hi-def glory.
Ever wished you could float through space, drifting past stars and cosmic dust clouds? The largest-ever 3D map of the universe, shown in the video above, gives you a sense of what that might be like, though the bright dots surrounding you are not stars, but whole galaxies, and you’re not quite drifting, but ripping along at a quadrillion times the speed of light.
To get a sense of the speed, just look at those galaxies and remind yourself that each is home to hundreds of billions of stars like our own. And you can even see, as the video progresses, the distinctive soap-bubble arrangement of the universe’s galaxies, arrayed in closely packed groups around vast tracts of empty space.
The Sloan Digital Sky Survey produced the 3D map from newly released data collected during two years of a six-year project. Knowing the locations of over a million galaxies will help astronomers find out how dark matter and dark energy are affecting the visible universe.
In the meantime, we’ll just watch this video again. And again. And again.
New Way to Hunt Dark Matter: With Dangling, Fuzzy Strands of DNA
The universe is more massive than it looks. Although it’s invisible to the eye, this extra mass, called dark matter, seems to interact with visible matter through gravity and the weak nuclear force. Some researchers hypothesize that dark matter consists of WIMPs, or weakly interacting massive particles, which form an invisible “sea” through which the Earth passes as our planet travels through space. While these WIMPs would ordinarily fly right through ordinary matter, we might be able to observe the rare occasions when one directly strikes a nucleus.
One big challenge to WIMP detection is proving that a collision was due to a WIMP, and not to another type of fly-by particle. Some projects are dealing with this problem by burying their detectors deep underground where no interfering radiation can reach; some are using the fact that the number of WIMP collisions is expected to change throughout each day and each year, as Earth’s position in the sea of WIMPS changes. (This approach is similar to the Michaelson-Morley experiment, which disproved the existence of luminiferous aether, another invisible “sea” we supposedly orbited through.) Now an interdisciplinary group of physicists and biologists has an idea to take the comparison of daily and annual measurements to the next level.
From White Dwarfs to Dark Matter Clouds, the Universe May Have Many Homes for Habitable Planets
What’s the News: While the Kepler spacecraft is busy finding solar system-loads of new planets, other astronomers are expanding our idea where planets could potentially be found. One astronomer wants to look for habitable planets around white dwarfs, arguing that any water-bearing exoplanets orbiting these tiny, dim stars would be much easier to find than those around main-sequence stars like our Sun. Another team dispenses with stars altogether and speculates that dark matter explosions inside a planet could hypothetically make it warm enough to be habitable, even without a star. “This is a fascinating, and highly original idea,” MIT exoplanet expert Sara Seager told Wired, referring to the dark matter hypothesis. “Original ideas are becoming more and more rare in exoplanet theory.”
How the Heck:
- Because white dwarfs are much smaller than our Sun, an Earth-sized planet that crossed in front of it would block more of its light, which should make these planets easier to spot. So astronomer Eric Agol suggests survey the 20,000 white dwarfs closest to Earth with relatively meager 1-meter ground telescopes.
- And because white dwarfs are so cool, a planet in a white dwarfs habitable zone would be very close, meaning its transit would happen very fast. Agol says we’d only need to watch a star for 32 hours to pick up on any transiting, habitable planets.
- One leading theory about dark matter is that it’s made of theoretical particles called WIMPS (weakly interacting massive particles). It’s thought that when WIMPs collide (if, of course, they exist), they would explode. Astronomers think that these WIMP explosions could possibly heat a planet enough to make it habitable.
- There are no immediate plans to test the dark matter hypothesis, which is quite theoretical, and any plan to find dark matter-fueled planets would need to look far from here: our part of the universe doesn’t have nearly enough dark matter to bring a planet to habitability.
What’s the Context:
- In other white dwarf news, astronomers have discovered a red dwarf in an extremely tight orbit with a white dwarf.
- And others are still wrangling over what dark matter really is.
- As for exoplanets, astronomers have actually seen one—as in, with visible light—orbiting its star.
Not So Fast:
- It’s not at all clear if white dwarfs have any planets, and if so, whether any of them could possibly support water or life as we know it. For one thing, planets in the habitable zone would be tidally locked with the star—permanent scalding daylight on one side; permanent frozen nighttime on the other.
- Taking 32 hours to find a planet orbiting a white dwarf may seem like a short time, but when you’re looking at tens of thousands of stars, it adds up. Agol told UW Today, “This could take a huge amount of time, even with [a network of telescopes].”
- And just like star-orbiting planets have their Goldilocks zones (not to hot or too cold), dark matter-containing planets would need the right amount of dark matter to be habitable. “It’s not something that’s likely to produce a lot of habitable planets,” Fermilab researcher Dan Hooper told Wired. “But in very special places and in very special models, it could do the trick.”
References: Eric Agol. “TRANSIT SURVEYS FOR EARTHS IN THE HABITABLE ZONES OF WHITE DWARFS.” doi: 10.1088/2041-8205/731/2/L31
Dan Hooper and Jason H. Steffen. “Dark Matter And The Habitability of Planets.” arXiv:1103.5086v1
Image: NASA/European Space Agency
The Estimated Number of Stars in the Universe Just Tripled
A study by Yale astronomer Pieter van Dokkum just took the estimated number of stars in the universe—100,000,000,000,000,000,000,000, or 100 sextillion—and tripled it. And you thought nothing good ever happens on Wednesdays.
Van Dokkum’s study in the journal Nature focuses on red dwarfs, a class of small, cool stars. They’re so small and cool, in fact, that up to now astronomers haven’t been able to spot them in galaxies outside our own. That’s a serious holdup when you’re trying to account for all the stars there are.
As a consequence, when estimating how much of a galaxy’s mass stars account for – important to understanding a galaxy’s life history – astronomers basically had to assume that the relative abundance of red-dwarf stars found in the Milky Way held true throughout the universe for every galaxy type and at every epoch of the universe’s evolution, Dr. van Dokkum says. “We always knew that was sort of a stretch, but it was the only thing we had. Until you see evidence to the contrary you kind of go with that assumption,” he says. [Christian Science Monitor]
Dark Energy Theory Gets a Boost From New Galactic Measurements
A new study of binary galaxies in deep space is inching us closer to understanding the nature of dark energy, the mysterious force pulling our universe apart at an ever-increasing rate.
“We have an amazingly simple picture of the universe,” says Princeton University astrophysicist Michael Strauss. “Of course, we don’t understand that picture—we don’t know what dark energy is, and we don’t know what dark matter is.” [Scientific American]
To get a better handle on these “dark” forces, which we can’t detect with our puny human equipment, researchers Christian Marinoni and graduate student Adeline Buzzi from the University of Provence used an approach that’s actually been around longer than the idea of dark energy–a 1979 theory from Charles Alcock.
A Particle Physics First: Researchers Watch Neutrinos Change Flavors
For the first time, physicists say they have witnessed a subatomic particle change its “flavor.” Physicists at OPERA, run by Italy’s national nuclear physics institute, announced yesterday that they have observed one neutrino change its type, or flavor, spontaneously. The experiment solves a 50-year-old physics mystery, and may uncover some of the universe’s hidden mass.
The Mystery
Neutrinos, which come in three different flavors, can have fairly violent births: they can come into the world via nuclear reactions in the sun, particle decay, or collisions in particle accelerators. But, once formed, they seem to ignore almost everything around them, including magnetic fields, electric fields, and matter. In fact, there are trillions of them zipping through each of us every second; they go right through our bodies and keep on moving through the planet itself.
The mystery of “neutrino oscillations” began with the number of neutrinos that should be coming from the sun. Theory predicted a certain number of various flavors to arrive, but observation showed much less:
The neutrino puzzle began with a pioneering and ultimately Nobel Prize winning experiment conducted by US scientist Ray Davis beginning in the 1960s. He observed far fewer neutrinos arriving at the Earth from the Sun than solar models predicted: either solar models were wrong, or something was happening to the neutrinos on their way. [CERN]
In 1969, Bruno Pontecorvo and Vladimir Gribov theorized that the neutrinos weren’t disappearing, they were changing their flavors mid-journey. Though physicists were looking for one type, they weren’t finding what they ordered.
Einstein Proven Right (Again!) by the Movements of Galaxies
The theory of general relativity: It works. OK, it’s not exactly Earth-shattering news that Albert Einstein’s century-old idea works in real life. That’s been shown over and over. But what had been difficult for researchers to do until now was verify the theory on truly massive scales beyond the solar system, that of whole galaxies and clusters of galaxies. This week in Nature, Reinabelle Reyes and colleagues report that they did it, and that Einstein was proven correct once more.
While the find is a nice coup for Reyes’ team, its importance goes beyond just reaffirming the great scientists of yesteryear with yet another “Einstein was right” story. The existence of dark matter and dark energy is based on the assumption that Einstein’s gravity is affecting galaxies billions of light-years from Earth in the same way that it affects objects in our solar system [National Geographic]. However, if the study had shown that general relativity needed a slight adjustment at vast distances (like the nudge Einstein himself provided to Newton’s physics), that could have altered prevailing ideas about dark matter and energy. This research indicates those pesky ideas may be here to stay [Space.com].
Scientists Predict: The 2010s Will Be Freakin' Awesome—With Lasers
There’s nothing like the round number at the start of a new decade to get everyone prognosticating (yes, we know some of you are in the crowd that says the new decade doesn’t begin until 2011; OK, fine). To predict what the scientific scene will be like in 2020, the journal Nature brought in experts from 18 fields. Though the collection doesn’t encapsulate the “world of tomorrow” feel of, say, the old Omni magazine, it’s still packed with sunny (and scary) forecasts. Some show lingering uncertainty, some unbridled optimism, and some give warnings to the world to make a much-needed course correction. Here are five we thought were particularly telling.
1. In 2020, Google defines your reality (even more than it does already).
Peter Norvig, Google’s director of research, tackles the question of where search will be a decade hence. Advanced, he says, but also troublesome: Most searches will be spoken rather than typed, and designers will be experimenting with search systems that read your brain waves. “Users will decide how much of their lives they want to share with search engines, and in what ways”—such is Norvig’s polite description of a world with even less digital privacy than today’s.
What search engines give you back will change, too. Particularly, he says, they will come up with a way to judge relevance and quality that doesn’t rely on popularity: “Thus, a site that claims that the Moon landings were a hoax and seems to have a coherent argument structure will be judged to be lower quality than a legitimate astronomy site, because the premises of the hoax argument are at odds with reality.”
Physicists Find Hints of Dark Matter But No Clear Discovery
If you were following Cosmic Variance yesterday, you saw its live blogging of one of the most anticipated recent announcements in physics: the team from Cryogenic Dark Matter Search (CDMS) telling the world whether a Minnesota detector spotted evidence of dark matter. The answer? Maybe (pdf).
CDMS scientists use super-cooled detectors made of germanium and silicon to search for weakly interacting massive particles (WIMPs), one of the leading suspects for what could make up dark matter. The detector is deep underground in the Soudan mine in Minnesota, which scientists also use to hunt for neutrinos. WIMPs streaming in from space would very rarely jostle the germanium nuclei, some 800 meters underground in the Soudan mine, generating a tiny amount of heat and slightly altering the charge on the detectors in a characteristic pattern [Science News].
We Knew Black Holes Were Massive. Now Double That.
Researchers have recalculated the mass of a gigantic black hole at the core of the M87 galaxy, and found that it’s about two times as massive as previously estimated: The new study says that M87′s black hole weighs the same as 6.4 billion suns. Researchers say the findings may indicate that many black holes have been underestimated, and also say that the results from this “local” galaxy only 50 million light-years away may solve a mystery regarding the extremely distant black holes known as quasars.
Astronomers had previously estimated M87′s total mass, calculating how much of that mass came from both the galaxy’s stars and its central black hole. But previous models didn’t have the supercomputing power to estimate the mass contributed by the galaxy’s “dark halo.” The dark halo is a spherical region surrounding the galaxy that extends beyond its main visible structure. It contains “dark matter”, an as yet unidentified material that cannot be directly detected by telescopes but which astronomers know is there from its gravitational interaction with everything else that can be seen [BBC News].
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