|View of Earth and it's Moon from 2010 SO16. Depiction by SW/LITS|
Newly discovered asteroid is Earth's companion
By Dr Emily Baldwin
AstronomyNow.com- A 200-400 metre wide asteroid first discovered by the Wide-field Infrared Survey Explorer (WISE) has been found by astronomers at Armagh Observatory to have been following Earth in its orbit for at least a quarter of a million years, and could represent a theorized but not-yet-seen population of asteroid.
2010 SO16's average distance from the Sun is identical to that of the Earth, unlike typical near Earth asteroids (NEAs) that loop through the Solar System on highly elliptical orbits. It is also the largest of Earth’s so-called "horseshoe" asteroids, which mimic closely the orbital motion of our planet around the Sun, but as seen from Earth, appear to slowly trace out a horseshoe shape in space.
"The asteroid takes 175 years to move from one end of the horseshoe to the next," Apostolos “Tolis” Christou tells Astronomy Now. "For example, SO16 was near the leading edge of the horseshoe in the 1830s and before that in the 1660s. Also, its elongation from the Sun (and thus its visibility) is maximum near the ends of the horseshoe."
Even though its orbit is remarkably similar to Earth’s, “this asteroid is terraphobic”, says Christou. “It keeps well away from the Earth. So well, in fact, that it has likely been in this orbit for several hundred thousand years, never coming closer to our planet than 50 times the distance to the Moon”. This is where it is now, near the end of the horseshoe trailing the Earth.
Christou and colleague David Asher wanted to find out how stable its orbit is and how long it has been locked in this configuration. To eliminate uncertainty in an asteroid's orbit usually requires months or years' worth of observations, but the team sidestepped this by using computer simulations to investigate every possible orbit that it could conceivably occupy, by following the evolution of the orbits for two million years into the past and future. The majority of the asteroids remained in the observed horseshoe state for between 200,000 and 500,000 years.
But, says Christou, if it's in a stable orbit, it is difficult to put it there by a random process. "It could be a piece of the Moon that wandered into the horseshoe a million years ago or so," he speculates. "The problem with that hypothesis is that most lunar impact ejecta are usually smaller than the size of the object. It could also have been a run-of-the-mill NEO that drifted in there through the vaunted Yarkovsky effect [which is caused by heat emitted from a small rotating body, carrying momentum with it] but that would mean it was at some point close to the Earth's orbit but not protected from close encounters with the Earth by the horseshoe mechanism. Hence its orbit would have quickly become un-Earth-like."
Instead, Christou and Asher propose that SO16 is "leakage" from a population of Earth Trojans, a breed of asteroid located at triangular equilibrium points 60 degrees ahead of and behind the Earth in its orbit that have only ever been theorized and never yet observed due to their proximity to the Sun in the sky. Similar populations of asteroids are known at Jupiter and Neptune (see our news story Tojan asteroid found in Neptune's gravity 'void' here).
"This is the simplest process-wise, although one has to show that there is such a reservoir of objects," says Christou. "That's the way it usually works; one question answered, a million spawned!"
The Faulkes Telescope project is already being used to refine the asteroid's orbit, and further investigation to uncover the asteroid's physical properties will enable the astronomers to reach their conclusion regarding its origin.
Asteroid Follows Earth's Orbit
A long-lived horseshoe companion to the Earth
The coolest star in the sky! Newly discovered 'Brown Dwarf' has same temperature as a cup of tea
By Julian Gavaghan
Dailymail- Scientists were this week amazed after the discovery of space's dimmest and coldest star - with a temperature the same as a cup of tea.
The two brown dwarf stars stunned astronomers when they were spotted through a set of three high-powered telescopes.
Both of them are about the same size as Jupiter but the smaller, more distant, star has a surface temperature of around 100 degrees.
The incredibly cool temperature - the same as a freshly boiled cup of tea - makes it the coldest one in the night sky.
A warmer and brighter companion had originally obscured the brown dwarf which has been named CFBDSIR J1458+1013B.
But with new, more powerful telescopes, astronomers were able to see the star, which is almost five times dimmer and 130 degrees cooler than the previous record.
The brown dwarf may represent a new class of cosmic objects straddling the division between stars and planets.
'We were very excited to see that this object had such a low temperature, but we couldn't have guessed that it would turn out to be a double system and have an even more interesting, even colder component,' said star-gazer Philippe Delorme of the Institut de planétologie et d'astrophysique de Grenoble which studied the brown dwarf.
Brown dwarfs are balls of warm gas that lack the mass necessary to fuse hydrogen at their core.
Stars, such as their cousins, white dwarfs, can do this and consequently can burn for more than 4.5billion years at a temperature of 5,500C.
What separates brown dwarfs from huge planets is not yet defined. However, planets are generally not big enough to generate their own heat by fusing deuterium.
The brown dwarf may be the first evidence of a new type of star, called a ‘Y spectral’ object, that more closely resembles a planet.
CFBDSIR J1458+1013B is bluer than is typical of brown dwarf, which are usually have a varied red or brownish hue.
It was first identified by astronomers at the Keck II and Canada-France-Hawaii telescopes, located near the summit of Hawaii’s Mauna Kea mountain.
Researchers at the European Southern Observatory’s Very Large Telescope measured its ultra-low temperature.
However, CFBDSIR J1458+1013B’s record-holding days may already be numbered as fellow satellite, the Spitzer Space Telescope, recently spotted two similar stars await precise temperature measurements.
‘At such temperatures we expect the brown dwarf to have properties that are different from previously known brown dwarfs and much closer to those of giant exoplanets,’ astronomer Michael Liu of the University of Hawaii told Wired.com
‘It could even have water clouds in its atmosphere.’
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Final tuning on next Mars rover mission
By Miriam Hernandez
PASADENA, Calif. (KABC) -- Technicians are applying the finishing touches to an elaborate Mars rover at the California Institute of Technology's Jet Propulsion Laboratory in Pasadena. It's unlike any Mars mission that has gone before.
NASA scientists are envisioning its most ambitious mission yet, a journey that will haul its largest payload of scientific instruments.
Then, as a laboratory on wheels, the rover Curiosity will explore the Red Planet for signs of past life, secrets buried in the Martian terrain.
"From that we will be able to determine whether or not the ancient environment that once existed on Mars was suitable for microorganisms that might have been living on the surface," said John Grotzinger, a scientist on the project.
Among many challenges: a wheel system that will enable the rover to rove. Earlier explorers were the size of golf carts. Curiosity is closer to a small SUV. It is atomic-powered to work for 23 months.
Its weight makes for a trickier voyage and landing.
"It takes about nine months to make it to Mars, and we approach Mars at a little over 12,000 miles an hour," said Adam Steltzner, chief engineer of entry, descent and landing.
And it must slow down to 1 mile per hour. To slam on the brakes, parachutes will open and rockets must activate. Moments from impact, the rover is released.
"It is going to hang below the jetpack and the pair of them are going to touch down on the surface of Mars a little bit over 1 mile an hour," said Steltzner.
Scientists will aim for a zone that appears shaped by ancient flooding. There, the rover will bore in to determine mineral content. Or with a laser beam, zap a rock farther away. The vapor will reflect different kinds of light according to what that material it is.
At JPL, engineers work in a sterile lab, fine-tuning for a November launch.
The project's cost is $2.5 billion. Scientists break that down to what the average American will pay.
"What this is worth to you as an individual is about the cost of a latte," said Grotzinger.
And scientists hope it will yield more knowledge about how life begins and ends.
Please read more at KABC.