If you could stand on the surface of Kepler-16b, you'd have two shadows. At sunset, you would see an orange star about the size of the sun and next to it a much fainter red star. As the stars slipped toward the horizon, they would change places in the sky, like partners in a square dance.
You would not need to be Luke Skywalker visiting his home planet of Tatooine in the movie "Star Wars" to watch the twin sunset. The only science fiction in this story is how to make the 200 light-year journey to Kepler-16, a binary star system jointly sharing the Saturn-sized planet, Kepler-16b.
The finding, reported by scientists on NASA's Kepler planet-hunting space telescope team, adds a new page into Mother Nature's recipe book for extrasolar planets.
"It's the first one that circles two stars, so it's a fundamentally different kind of planet," lead researcher Laurance Doyle, with the SETI Institute in Mountain View, Calif., told Discovery News.
From a distance about as far as Venus orbits the sun, Kepler-16b circles both its parent stars in 221 days. The stars, which on average have about 21 million miles between them, fly around each other about every 41 days.
The whole system is perfectly aligned to Kepler's viewing spot, with the bodies crossing paths so that tiny amounts of their radiating starlight regularly, repeatedly and predictably vanish and reappear as the stars and the planet fly past one another.
Astronomers on Monday announced the discovery of 50 new planets circling stars beyond the sun, including one “super-Earth” that is the right distance from its star to possibly have water.
“If we are really, really lucky, this planet could be a habitat” like Earth, said Lisa Kaltenegger of the Max Planck Institute for Astronomy in Heidelberg, Germany.
The planet, dubbed HD85512b, circles an orange star somewhat smaller and cooler than our sun about 36 light-years away. The star, HD85512, is visible in the southern sky in the constellation Vela.
The newly found planet circles this star every 59 days, putting it at the edge of the “habitable zone” where water could exist if atmospheric conditions were right.
In a teleconference, Kaltenegger said that the planet is at the warm edge of its star’s habitable zone, as if “standing next to a bonfire.” That means the planet would require a lot of cloud cover — which reflects starlight — to keep the surface cool enough to prevent any water from boiling, she said.
Astronomers have not determined whether the new super-Earth is rocky like the Earth or gassy like Jupiter, let alone whether it has an atmosphere. The new super-Earth is 3.5 times the mass of Earth.
On its way to the biggest planet in the solar system -- Jupiter, NASA's Juno spacecraft took time to capture its home planet and its natural satellite -- the moon.
"This is a remarkable sight people get to see all too rarely," said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. "This view of our planet shows how Earth looks from the outside, illustrating a special perspective of our role and place in the universe. We see a humbling yet beautiful view of ourselves."
The image was taken by the spacecraft's camera, JunoCam, on Aug. 26 when the spacecraft was about 6 million miles (9.66 million kilometers) away. The image was taken as part of the mission team's checkout of the Juno spacecraft. The team is conducting its initial detailed checks on the spacecraft's instruments and subsystems after its launch on Aug. 5.
Juno covered the distance from Earth to the moon (about 250,000 miles or 402,000 kilometers) in less than one day's time. It will take the spacecraft another five years and 1,740 million miles (2,800 million kilometers) to complete the journey to Jupiter. The spacecraft will orbit the planet's poles 33 times and use its eight science instruments to probe beneath the gas giant's obscuring cloud cover to learn more about its origins, structure, atmosphere and magnetosphere, and look for a potential solid planetary core.
Read more: Jupiter-Bound Space Probe Captures Earth And Moon
On Aug. 9, the golf cart-sized rover relayed its arrival at a location named Spirit Point on the crater's rim. Opportunity drove approximately 13 miles (21 kilometers) since climbing out of the Victoria crater.
"NASA is continuing to write remarkable chapters in our nation's story of exploration with discoveries on Mars and trips to an array of challenging new destinations," NASA Administrator Charles Bolden said. "Opportunity's findings and data from the upcoming Mars Science Laboratory will play a key role in making possible future human missions to Mars and other places where humans have not yet been."
Endeavour crater, which is more than 25 times wider than Victoria crater, is 14 miles (22 kilometers) in diameter. At Endeavour, scientists expect to see much older rocks and terrains than those examined by Opportunity during its first seven years on Mars. Endeavour became a tantalizing destination after NASA's Mars Reconnaissance Orbiter detected clay minerals that may have formed in an early warmer and wetter period.
"We're soon going to get the opportunity to sample a rock type the rovers haven't seen yet," said Matthew Golombek, Mars Exploration Rover science team member, at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "Clay minerals form in wet conditions so we may learn about a potentially habitable environment that appears to have been very different from those responsible for the rocks comprising the plains."
Striking new images from the mountains of Mars may be the best evidence yet of flowing, liquid water, an essential ingredient for life.
The findings, reported today in the journal Science, come from a joint US-Swiss study.
A sequence of images from the Mars Reconnaissance Orbiter show many long, dark "tendrils" a few metres wide.
They emerge between rocky outcrops and flow hundreds of metres down steep slopes towards the plains below.
They appear on hillsides warmed by the summer sun, flow around obstacles and sometimes split or merge, but when winter returns, the tendrils fade away.
This suggests that they are made of thawing mud, say the researchers.
"It's hard to imagine they are formed by anything other than fluid seeping down slopes," said Mars Reconnaissance Orbiter Project Scientist Richard Zurek of Nasa's Jet Propulsion Laboratory, but they appear when it's still too cold for fresh water.
Salty water
"The best explanation we have for these observations so far is flow of briny water, although this study does not prove that," said planetary geologist and lead author Professor Alfred McEwen of the Lunar and Planetary Laboratory, University of Arizona.
Saltiness lowers the temperature at which water freezes, and water about as salty as Earth's oceans could exist at these sites in summer.
"This could be the first flowing water," said Professor McEwen. This has profound implications in the search for extraterrestrial life.
"Liquid water is absolutely essential for life, and we've found life on Earth in pretty much every moist niche," said Dr Lewis Dartnell, astrobiologist at University College London, who was not involved in the study.
"So perhaps there could be hardy microbes surviving in these short periods of summer meltwater on the desert surface of Mars."
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