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Lasers Measure Earth’s Rotation and Wobble
The Earth spins around once every 24 hours on its axis, creating the continuous cycle of day and night. But this rotation isn’t as straightforward as it sounds: Forces large and small cause the Earth to wobble as it spins. This wobbling can pose a problem for navigation systems like GPS.
Scientists working with lasers and mirrors are refining a new system to track the Earth’s rotation and its kinks.
The pull of gravity from the sun and the moon contribute to the planet’s wobble. So do variations in atmospheric pressure, ocean loading and the wind, which change the position of the Earth’s axis relative to the surface. Together their effect is called the Chandler wobble, and it has a period of 435 days.
Another force causes the rotational axis to move over a period of a year. This “annual wobble” is due to the Earth’s elliptical orbit around the sun.
Published April 9, 2010
Like part of a cosmic Russian doll, our universe may be nested inside a black hole that is itself part of a larger universe.
In turn, all the black holes found so far in our universe—from the microscopic to the supermassive—may be doorways into alternate realities.
According to a mind-bending new theory, a black hole is actually a tunnel between universes—a type of wormhole. The matter the black hole attracts doesn’t collapse into a single point, as has been predicted, but rather gushes out a “white hole” at the other end of the black one, the theory goes.
(Related: “New Proof Unknown ‘Structures’ Tug at Our Universe.”)
In a recent paper published in the journal Physics Letters B, Indiana University physicist Nikodem Poplawski presents new mathematical models of the spiraling motion of matter falling into a black hole. His equations suggest such wormholes are viable alternatives to the “space-time singularities” that Albert Einstein predicted to be at the centers of black holes.
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Now Entering The Exoplanet Catalog: Kepler-20e & Kepler-20f
Two Earth-Size Alien Planets, the Smallest Exoplanets Yet
Imaged Above: An artist’s rendering of the newfound alien planet Kepler-20e, which scientists say is smaller than Earth, at about 0.87 times the width of our planet. Credit: NASA/JPL-Caltech/T. Pyle
Two planets orbiting a star 950 light-years from Earth are the smallest, most Earth-size alien worlds known, astronomers announced today (Dec. 20). One of the planets is actually smaller than Earth, scientists say.
These planets, while roughly the size of our planet Earth, are circling very close to their star, giving them fiery temperatures that are most likely too hot to support life, researchers said. The discovery, however, brings scientists one step closer to finding a true twin of Earth that may be habitable.
“We’ve crossed a threshold: For the first time, we’ve been able to detect planets smaller than the Earth around another star,” said lead researcher François Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “We proved that Earth-size planets exist around other stars like the sun, and most importantly, we proved that humanity is able to detect them. It’s the beginning of an era.”
To discover the new planets, Fressin and his colleagues used NASA’s Kepler space telescope, which noticed the tiny dips in the parent star’s brightness when the planets passed in front of it, blocking some of its light (this is called the transit method). The researchers then used ground-based observatories to confirm that the planets actually exist by measuring minute wobbles in the star’s position caused by gravitational tugs from its planets.
New “Deep Fried” Planets Found—Survivors of Star Death
Imaged Above: An artist’s impression of planets orbiting close to a hot sub dwarf star. Illustration courtesy S. Charpinet
Two newfound Earth-size planets are probably the charred survivors of a near-death encounter with their fading parent star, scientists say.
The planetary pair, discovered using NASA’s Kepler space telescope, are about 0.76 and 0.87 times Earth’s radius, making the alien worlds the smallest planets detected so far around an active star, other than our sun.
But the planets didn’t start small—astronomers think the worlds were once gas giants, akin to Jupiter or Saturn, that were stripped down after being swallowed by their swollen, aging parent.
News of the “deep fried” duo comes hot on the heels of the announcement of the first Earth-size planets found by the Kepler team.
Just yesterday scientists announced the discovery of Kepler-20e and Kepler-20f, two planets that are 0.87 and 1.03 times Earth’s radius, respectively.
There are some similarities between the Earth-size planets discovered so far, said Valérie Van Grootel, an astronomer at the University of Liège in Belgium and a co-author on the latest study.
Kepler-20e and -20f “orbit very close to their star, so they are very hot planets, and that is the case with our planets, too,” Van Grootel told National Geographic News.
“But there are major differences, too. In our case, we have a post red-giant star, whereas the other team’s planets orbit a star like our own sun. We think that our Earth-size planets are the rocky cores of former gas planets.”
Meanwhile, interactions with gases in a red giant star’s expanded atmosphere will force some planets a bit farther from the star to migrate inward—which actually gives those worlds a shot at survival.
Scientists think the newly discovered Earth-size planets were once gas giants that got sucked in toward the star during its red giant phase.
As the planets plowed through their star’s hot atmosphere, their gaseous and liquid layers were stripped off, leaving behind only the rocky cores.
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Water Ice on Mercury? NASA Probe Close to Proof, Teams Say
New studies add to evidence of ice in polar craters.
Move over, Mars: Evidence is mounting that water exists even on the hot, barren planet closest to the sun, Mercury.
Based on new data from a NASA probe, astronomers say they’re close to proving that mysterious “bright” spots at Mercury’s poles are patches of water ice.
Ice on Mercury might seem strange. After all, the planet’s surface can get hot enough to melt lead on the side facing the sun.
But Mercury doesn’t tilt very far on its axis, raising the prospect that the bottoms of some polar craters might be in permanent shadow.
Since Mercury lacks an atmosphere to trap heat, being in constant shade could turn these craters into “cold traps”—zones in which debris or vapor drifting in from interplanetary space could be permanently captured as ever deepening rimes of frost.
Similar cold traps exist near the moon’s south pole, where scientists recently found substantial quantities of water ice.
“Exciting Times” on Mercury
Currently scientists are working to calibrate MESSENGER’s neutron spectrometer to obtain a good map of neutron flux.
“We promise results within three or four months,” Solomon said, although even finding hydrogen wouldn’t be definitive proof of water.
Scientists ultimately confirmed water on the moon by crashing a spent rocket cylinder into one of the permanently shadowed craters and watching the resulting plume—an experiment not currently possible on Mercury.
“With the discovery of water and other volatiles on the moon, the search by MESSENGER for hidden polar ices [on Mercury] surely reflects exciting times.”
Optical image courtesy NASA/JHUAPL/CIW; radar image courtesy NAIC/Arecibo](http://24.media.tumblr.com/tumblr_lwgldjS0wW1qe649zo1_500.jpg)
Water Ice on Mercury? NASA Probe Close to Proof, Teams Say
New studies add to evidence of ice in polar craters.
Move over, Mars: Evidence is mounting that water exists even on the hot, barren planet closest to the sun, Mercury.
Based on new data from a NASA probe, astronomers say they’re close to proving that mysterious “bright” spots at Mercury’s poles are patches of water ice.
Ice on Mercury might seem strange. After all, the planet’s surface can get hot enough to melt lead on the side facing the sun.
But Mercury doesn’t tilt very far on its axis, raising the prospect that the bottoms of some polar craters might be in permanent shadow.
Since Mercury lacks an atmosphere to trap heat, being in constant shade could turn these craters into “cold traps”—zones in which debris or vapor drifting in from interplanetary space could be permanently captured as ever deepening rimes of frost.
Similar cold traps exist near the moon’s south pole, where scientists recently found substantial quantities of water ice.
“Exciting Times” on Mercury
Currently scientists are working to calibrate MESSENGER’s neutron spectrometer to obtain a good map of neutron flux.
“We promise results within three or four months,” Solomon said, although even finding hydrogen wouldn’t be definitive proof of water.
Scientists ultimately confirmed water on the moon by crashing a spent rocket cylinder into one of the permanently shadowed craters and watching the resulting plume—an experiment not currently possible on Mercury.
“With the discovery of water and other volatiles on the moon, the search by MESSENGER for hidden polar ices [on Mercury] surely reflects exciting times.”
Optical image courtesy NASA/JHUAPL/CIW; radar image courtesy NAIC/Arecibo
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Spiral Galaxy
Resembling festive lights on a holiday wreath, this NASA/ESA Hubble Space Telescope image of the nearby spiral galaxy M74 is an iconic reminder of the impending season. Bright knots of glowing gas light up the spiral arms, indicating a rich environment of star formation.
Messier 74, also called NGC 628, is a stunning example of a grand-design spiral galaxy that is viewed by Earth observers nearly face-on. Its perfectly symmetrical spiral arms emanate from the central nucleus and are dotted with clusters of young blue stars and glowing pink regions of ionized hydrogen (hydrogen atoms that have lost their electrons). These regions of star formation show an excess of light at ultraviolet wavelengths.
Tracing along the spiral arms are winding dust lanes that also begin very near the galaxy’s nucleus and follow along the length of the spiral arms. M74 is located roughly 32 million light-years away in the direction of the constellation Pisces, the Fish. It is the dominant member of a small group of about half a dozen galaxies, the M74 galaxy group. In its entirety, it is estimated that M74 is home to about 100 billion stars, making it slightly smaller than our Milky Way.
Image Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration
A Star is Born: Skywatcher Photo Captures Dark-Hued Nebula
This photo shows the cosmic region known as Sh2-239 and LDN 155, where star formation activity has caused the mix of dust and colors in the nebulas visible here. The deep colors and dark clouds in this image resemble paintings by some of history’s greatest artists.
Astrophotographer Adam Block of the Mt. Lemmon SkyCenter at the University of Arizona was one of the first to capture the nebula in such detail. He took multiple exposures to collect enough light for an image that would otherwise not be evident to the eye.
“Sh2-239 is my favorite object, because although it is a well-studied nebula, not even professional astronomers have seen it in such detail and in the visible light.” Block wrote in an email.
The region lies near the southern end of the constellation Taurus, near the border of the constellation Perseus, more than 400 light-years away. A light-year is the distance light travels in one year, or about 6 trillion miles (10 trillion kilometers).
The region is often photographed by skywatchers and consists of bright red emission nebulas, star clusters, complex dark nebulas and blue reflected light. The spot is known as a birthplace for stars.A star develops from a giant, slowly rotating cloud that is made up almost entirely of hydrogen and helium. The process creates new stars and releases cosmic dust and gas.
CREDIT: Adam Block/Mount Lemmon SkyCenter/University of Arizona
String Theorists Simulate the Big Bang
Japanese physicists have created a string theory model that simulates the birth of the universe. In their model, the Big Bang was a “symmetry-breaking event” — a fluctuation that caused three spatial dimensions to break free from the other six dimensions of string theory, then rapidly unfurl to produce our universe’s observed 3D structure.
String theory — a proposed “theory of everything” that unites quantum mechanics and general relativitytogether in one complete picture — models elementary particles as oscillating lines (“strings”) rather than dimensionless points. In order for the math to work, string theory requires that there be 10 dimensions: nine of space and one of time. Our universe only appears to have three spatial dimensions, string theorists say, because the other six are curled up in undetectably tiny bundles called Calabi-Yau manifolds, which are a minuscule 10^-33 centimeters across.
Like many other underlying aspects of string theory, there’s no feasible experiment that could verify that these manifolds exist, and thus that the universe really does have a 9-dimensional spatial structure. And if it does, physicists wonder why three of those dimensions would be enormous and the other six extremely small. Nonetheless, the string theory framework is compelling because it gracefully explains most aspects of the universe that we do observe, from electromagnetism to gravity to thethermodynamics of black holes.
The new research — by Sang-Woo Kim of Osaka University, Jun Nishimura of the High Energy Accelerator Research Organization (KEK) and Asato Tsuchiya of Shizuoka University — shows that string theory plausibly accounts for the universe’s origin and its apparent 3D structure. “We have been able to see how three directions start to expand at some point in time,” Nishimura told Life’s Little Mysteries.
