Strange 'Lava World' Is Most Earthlike Alien Planet Yet

[Buster's Uncle]

Strange 'Lava World' Is Most Earthlike Alien Planet Yet
SPACE.com
By Mike Wall, Senior Writer  2 hours ago



An artist's illustration of the strange Earth-like rocky planet Kepler-78b, which orbits a sun-like star



A puzzling alien planet is the closest thing to an Earth twin in size and composition known beyond our solar system, though it's far too hot to support life, scientists say.

The exoplanet Kepler-78b, whose supertight orbit baffles astronomers, is just 20 percent wider and about 80 percent more massive than Earth, with a density nearly identical to that of our planet, two research teams report in separate papers published online today (Oct. 30) in the journal Nature.

"This is the planet that, in many respects, is the most like Earth that's been discovered outside our solar system," said Andrew Howard, of the University of Hawaii at Manoa's Institute for Astronomy and lead author of one of the studies. "It has approximately the same size. It has the same density, which means it's made out of the same stuff as Earth, in all likelihood."


Studying a lava world

Kepler-78b, whose discovery was announced last month, orbits a sunlike star in the constellation Cygnus, about 400 light-years from Earth.

The alien world circles 900,000 miles (1.5 million kilometers) or so from its parent star — just 1 percent of the distance between Earth and the sun— and completes one lap every 8.5 hours. Surface temperatures on Kepler-78b likely top 3,680 degrees Fahrenheit (2,000 degrees Celsius), Howard said.

The planet was found by NASA's prolific Kepler space telescope, which has spotted nearly 3,600 potential exoplanets since its March 2009 launch. (Kepler was hobbled in May of this year when the second of its orientation-maintaining reaction wheels failed, but scientists are still sifting through the instrument's huge databases.)

Kepler flagged alien worlds by noting the telltale brightness dips they caused when passing in front of, or transiting, their parent stars from the spacecraft's perspective. Kepler's measurements allow researchers to estimate an exoplanet's size but not its mass, meaning that other strategies are required to get a handle on a world's density and composition.

One such method is the radial velocity technique, which measures the wobble in a host star's light induced by the gravitational pull of an orbiting planet. Both new studies employed this method to investigate the Kepler-78 system, with Howard's group using the HIRES spectrograph at Hawaii's Keck Observatory and another team, led by Francesco Pepe of the University of Geneva, relying on the new HARPS-N instrument on the Telescopio Nazionale Galileo in the Canary Islands.

The two teams came to very similar conclusions. Howard's group determined Kepler-78b's mass to be 1.69 times greater than that of Earth, while Pepe's team calculated it to be 1.86 times higher than Earth's. The results of the Pepe-led study suggest a density of 5.57 grams per cubic centimeter for Kepler-78b, while those of Howard's team imply a density of 5.3 grams per cubic cm.

These numbers agree to within the error range independently estimated by both teams, suggesting that they are quite accurate, Howard said.

"The fact that we agree to within our errors — in science, that's basically as good as you can do," Howard told SPACE.com.

Earth's density is about 5.5 grams per cubic cm, so Kepler-78b probably has an Earth-like composition, complete with a rocky interior and an iron core, both studies suggest.


A mysterious origin

The extremely tight orbit of Kepler-78b puzzles astronomers. According to prevailing theory, the alien world shouldn't exist where it does, because its host star was significantly larger when the planet was taking shape.

"It couldn't have formed in place because you can't form a planet inside a star," Dimitar Sasselov, of the Harvard-Smithsonian Center for Astrophysics and a member of the Pepe-led team, said in a statement. "It couldn't have formed further out and migrated inward, because it would have migrated all the way into the star. This planet is an enigma."

What is clear, however, is that Kepler-78b's days are numbered. The planet will continue circling lower and lower until the immense gravity of its host star tears it apart, likely within 3 billion years or so.

"Kepler-78b is going to end up in the star very soon, astronomically speaking," Sasselov said.


The search for another Earth

The hellishly hot Kepler-78b is not a good place to hunt for alien life. But the determination of its density marks a milestone in the ongoing search for a true "Earth twin" — a planet very much like Earth in size, composition and surface temperature.

"The existence of Kepler-78b shows that, at the very least, extrasolar planets of Earth-like composition are not rare," astronomer Drake Deming, of the University of Maryland, writes in an accompanying commentary article today in the same issue of Nature.

Deming points to NASA's upcoming Transiting Exoplanet Survey Satellite mission, or TESS, which is slated to launch in 2017 to hunt for transiting planets around nearby stars (as contrasted with Kepler, whose gaze was more distant).

"By focusing particularly on small stars cooler than the sun, TESS should find exo-Earths whose mass can be measured by trading the close-in orbit of Kepler-78b for more distant orbits around low-mass stars, approaching orbital zones where life is possi­ble," Deming writes. "That trade-off probably cannot be pushed to the point of measuring an Earth twin orbiting once per year around a sun twin, but it will allow future scientific teams to probe habitable planets orbiting small stars."


http://news.yahoo.com/strange-lava-world-most-earthlike-alien-planet-yet-180625300.html

[Buster's Uncle]

Scientists discover Earth’s fiery doppelganger
Kepler-78b is the first known planet that's similar in size and composition to Earth
By Alexander Thompson on October 30, 2013 02:05 pm






The sci-fi worlds of Star Wars and Star Trek have trained us to think there are rocky, solid planets orbiting far away stars that are so similar to Earth we could walk upright and breathe their atmosphere. In reality, scientists have yet to identify a single planet outside of our solar system that's comparable to the size and composition of Earth.

Until now, that is.
 
Two independent research groups, reporting in Nature, have found that a far-off planet, Kepler-78b, has a similar mass and composition to Earth. While previous observations of Kepler-78b had estimated the size of the planet to be 1.2 times wider than Earth, these latest measurements focused on observing the gravitational interactions between the planet and its star. The result? Researchers can combine the previously known size of the planet with the newly measured mass to determine its makeup.

The gravitational interactions between the planet and its star

Of course a star has a strong gravitational pull on a planet — that's why planets orbit stars. But planets also exert a gravitational force on their host star, causing a small wobble in the star's position. This wobble can be seen as a change in the wavelength of the light coming from the star, which is analogous to the change in sound of a train passing you — the pitch drops (the wavelength changes) because of the motion of the train. Researchers used this wobble to conclude that Kepler-78b has a mass 1.69 times larger than that of Earth. The combination of the size and mass of the planet yields the planet's density, allowing researchers to determine what combination of materials comprise the planet. The density of Kepler-78b, they found, corresponds to an Earth-like makeup of rock and iron.

An Earthlike makeup of rock and iron

"Having a planet made largely of rock and iron, like our Earth, means that we have a good surface for life to evolve on," says Andrew Howard, one of the researchers behind the new findings. Unfortunately, the composition of Kepler-78b doesn't necessarily make it hospitable to life. "From an Earth-centric perspective, we'd like to have liquid water on the surface [and] this planet is obviously way too hot."

Indeed, Kepler-78b is about 100 times closer to its star than we are to the sun, and it orbits the star in a blazingly fast 8.5 hours. As a consequence, the planet's surface temperature is somewhere between 3700 and 5100ºF. That heat, combined with huge amounts of UV radiation, means the planet could not support an Earthlike atmosphere, nor any liquid surface water. "It's probably a lava planet, so the surface is just red lava flowing. It's completely different [from Earth]," said Francesco Pepe, lead author of the second study. "The sun would occupy half of the sky."

The surface is just red lava flowing.

Kepler-78b might not be habitable, but scientists aren't done studying the mysterious planet. "We have now more questions we have to answer," Pepe says, noting that the particular geometry of this planet–star pair remains puzzling. "Theories cannot really explain why this planet did not fall into the star at some point."

The planet might also help find answers for broader questions in the search for exoplanets. Scientists continue to wonder, for instance, whether an iron and rock composition is the rule or an exception for Earth-sized planets. To help address these questions, NASA has a planned mission in 2017 that will provide better tools for finding more exoplanets and will help put planets like Kepler-78b and Earth in context.


http://www.theverge.com/2013/10/30/5044096/exoplanet-kepler-78b-discovery

[Buster's Uncle]

Earth-size planet found with rocky core like ours
Associated Press
By MARCIA DUNN 43 minutes ago



This artist's rendering provided by the Harvard-Smithsonian Center for Astrophysics on Wednesday, Oct. 30, 2013 shows the planet Kepler-78b, foreground, orbiting less than one million miles from its sun. Astrophysicists reported Wednesday in the journal Nature that the exoplanet appears to be made of rock and iron just like Earth. (AP Photo/Harvard-Smithsonian Center for Astrophysics, David A. Aguilar)



CAPE CANAVERAL, Fla. (AP) — Scientists have found a planet way out in the cosmos that's close in size and content to Earth — an astronomical first.

But hold off on the travel plans. This rocky world is so close to its sun that it's at least 2,000 degrees hotter than here, almost certainly too hot for life.

Astrophysicists reported Wednesday in the journal Nature that the exoplanet Kepler-78b appears to be made of rock and iron just like Earth. They measured the planet's mass to determine its density and content. It's actually a little bigger than Earth and nearly double its mass, or weight.

Kepler-78b is located in the Cygnus constellation hundreds of light-years away. Incredibly, it orbits its sun every 8½ hours, a mystery to astronomers who doubt it could have formed or moved that close to a star. They agree the planet will be sucked up by the sun in a few billion years, so its time remaining, astronomically speaking, is short.

More than 1,000 exoplanets — worlds outside our solar system — have been confirmed so far.





NASA's Kepler Space Telescope, used to discover Kepler-78b, has identified 3,500 more potential candidates. The telescope lost its precise pointing ability earlier this year, and NASA has given up trying to fix it.

Scientific teams in the United States and Switzerland used ground observatories to measure Kepler-78b.

___

Online:

Kepler: http://kepler.nasa.gov/


http://news.yahoo.com/earth-size-planet-found-rocky-core-ours-180241792.html

[Buster's Uncle]

Planet hunters find Earth-like twin beyond the solar system
Reuters
By Irene Klotz 1 hour ago



CAPE CANAVERAL, Florida (Reuters) - For the first time, scientists have found a planet beyond the solar system that not only is the same size as Earth, but has the same proportions of iron and rock, a key step in an ongoing quest to find potentially habitable sister worlds.

The planet, known as Kepler-78b, circles a star that is slightly smaller than the sun located in the constellation Cygnus, about 400 light years away.

One light year, is the distance light, moving at 186,282 miles per second (299,792 kilometers per second) travels in a year, or about 6 trillion miles (10 trillion kilometers).

Kepler-78b was discovered last year with NASA's now-idled Kepler space telescope, which detected potential planets as they circled in front of their parent stars, blocking a bit of light.

That measurement not only revealed that Kepler-78b was relatively small, with a diameter just 20 percent larger than Earth's, but that it was practically orbiting on the surface of its host star.

While the planet's presumably molten surface and searing temperatures make it ill-suited for life, two independent teams of astronomers jumped at the opportunity to follow up the discovery with ground-based measurements to try to determine the density of Kepler-78b.

Using different telescopes, the teams zeroed in on how strongly the little planet's gravity tugs at its parent star, information that could be used to figure out Kepler-78b's weight and composition.

In two papers in this week's journal Nature, the teams report that not only were they successful, but that they came to the same conclusion: Kepler-78b has roughly the same density as Earth, suggesting that it also is made primarily of rock and iron.

Earth's density is 343 pounds per cubic foot (5.5 grams per cubic centimeter). Kepler-78b is 331 pounds per cubic foot (5.3 grams per cubic centimeter).

Scientists would like to be able to make the same measurements of Earth-sized planets in more life-friendly orbits, but that is beyond today's technology.

"The only reason they've been able to do this is because it's an Earth-mass planet in really close to the star," said University of Maryland astronomer Drake Deming.

"To me this means that planets like the Earth are probably not all that uncommon," he added.

Kepler-78b is among a dozen or so recently discovered small planets that orbit very close to their parent stars. Kepler-78b, for example, completes an orbit in just 8.5 hours.

Scientists do not know how the planets ended up so close to their host stars. One theory is that the bodies are the rocky remains of larger gas planets that migrated inward and had their atmospheres stripped away


http://news.yahoo.com/planet-hunters-earth-twin-beyond-solar-system-223358737.html