Kepler 37-b: tiniest planet spotted

The University of Sydney

The detection of exoplanet Kepler-37b demonstrates that sun-like stars in our galaxy are able of hosting much smaller planets than anything seen before in our solar system. Image: NASA/Ames /JPL-Caltech/ The detection of a tiny planet has shown for the first time that stars in our galaxy are able to host much smaller planets than anything seen in our own solar system. The existence of the planet, Kepler-37b, the innermost of three planets that orbit the sun-like host star, Kepler-37, is announced in the journal Nature. The University of Sydney's Professor Tim Bedding, Head of the School of Physics, and Dr Dennis Stello, an Australian Research Fellow in the School, contributed to the discovery effort of an international team. "That we have found one of these small and hard-to-detect planets suggests that they are abundant around other stars and lends weight to the belief that as planet size decreases their occurrence increases exponentially," said Dr Stello. Kepler-37b is an exoplanet, or planet located outside the solar system, and is estimated to be a similar size to Earth's moon, which is only 3475 kilometres in diameter. Owing to this extremely small size and its highly irradiated surface, Kepler-37b is believed to be a rocky planet with no atmosphere or water, similar to Mercury. The Kepler spacecraft made the Kepler-37b finding possible. The spacecraft was launched in 2009 with the goal of determining how often rocky planets occur in the habitable zone around sun-like host stars in our galaxy. Over 150,000 stars are continuously monitored for transits of planetary bodies. Over the course of 978 days of observations by the Kepler spacecraft, transit signals of three planets of the star Kepler-37, a slightly cooler and older star than our sun, were identified. "While theoretically such small planets are expected, detection of tiny planet Kepler-37b is remarkable given its transit signal is detectable on less than 0.5 percent of stars observed by Kepler," Professor Bedding said. "Since the discovery of the first exoplanet we have known that other planetary systems can look quite unlike our own, but it is only now, thanks to the precision of the Kepler space telescope that we have been able to find planets smaller than the ones we see in our own solar system." Professor Bedding and Dr Stello contributed to the analysis of Kepler-37, the star Kepler-37b orbits. "We analysed the frequencies of standing sound waves inside the star to tell its size in the same way that you could tell the difference in size of a violin and cello by the difference in the pitch of the sound they produce," said Dr Stello. This asteroseismic analysis showed that the radius of Kepler-37 is about 20 percent smaller than the sun. "Knowing this stellar radius is very important because the accuracy with which we can measure the radius of the planet Kepler-37b is limited by how accurately we can calculate the radius of Kepler-37," said Dr Stello. "Our work from here is to keep working with the planet team at NASA to make seismic analyses of planet-hosting stars, and there are some exciting results in the pipeline," said Dr Stello. Editor's Note: Original news release can be found here.

NASA predicts total blackout on 23-25 Dec 2012 during alignment of Universe.

NASA predicts total blackout on 23-25 Dec 2012 during alignment of Universe. US scientists predict Universe change, total blackout  of planet for 3 days from Dec 23 2012. It is not the end of the world, it is an alignment of the Universe, where the Sun and the earth will align for the first time. The earth will shift from the current third dimension to zero dimension, then shift to the forth dimension. During this transition, the entire Universe will face a big change, and we will see a entire brand new world.  The 3 days blackout is predicted to happen on Dec 23, 24, 25....during this time, staying calm is most important, hug each other, pray, pray, pray, sleep for 3 nights...and those who survive will face a brand new world....for those not prepared, many will die because of fear. Be happy, enjoy every moment now.  Don't worry, pray to God everday. There is a lot of talk about what will happen in 2012, but many people don't believe it, and don't want to talk about it for fear of creating fear and panic.  We don't know what will happen, but it is worth listening to  USA 's NASA talk about preparation. http://www.youtube.com/watch?v=6aj1lyEHbZE&feature=related Whether it's true or not, better be prepared. No panic, stay calm, just pray. Remember to smile more, love more, forgive more...everyday. Better avoid traveling during December.         

 

Research Links Extreme Summer Heat Events to Global Warming

  (Science Daily)

Earth's Northern Hemisphere over the past 30 years has seen more "hot" (orange), "very hot" (red) and "extremely hot" (brown) summers, compared to a base period defined in this study from 1951 to 1980. This visualization shows how the area experiencing "extremely hot" summers grows from nearly nonexistent during the base period to cover 12 percent of land in the Northern Hemisphere by 2011. Watch for the 2010 heat waves in Texas, Oklahoma and Mexico, or the 2011 heat waves the Middle East, Western Asia and Eastern Europe. (Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio)—                                                                          A new statistical analysis by NASA scientists has found that Earth's land areas have become much more likely to experience an extreme summer heat wave than they were in the middle of the 20th century.

The research was published today in the journal Proceedings of the National Academy of Sciences.

The statistics show that the recent bouts of extremely warm summers, including the intense heat wave afflicting the U.S. Midwest this year, very likely are the consequence of global warming, according to lead author James Hansen of NASA's Goddard Institute for Space Studies (GISS) in New York.

"This summer people are seeing extreme heat and agricultural impacts," Hansen says. "We're asserting that this is causally connected to global warming, and in this paper we present the scientific evidence for that."

Hansen and colleagues analyzed mean summer temperatures since 1951 and showed that the odds have increased in recent decades for what they define as "hot," "very hot" and "extremely hot" summers.

The researchers detailed how "extremely hot" summers are becoming far more routine. "Extremely hot" is defined as a mean summer temperature experienced by less than one percent of Earth's land area between 1951 and 1980, the base period for this study. But since 2006, about 10 percent of land area across the Northern Hemisphere has experienced these temperatures each summer.

In 1988, Hansen first asserted that global warming would reach a point in the coming decades when the connection to extreme events would become more apparent. While some warming should coincide with a noticeable boost in extreme events, the natural variability in climate and weather can be so large as to disguise the trend.

To distinguish the trend from natural variability, Hansen and colleagues turned to statistics. In this study, the GISS team including Makiko Sato and Reto Ruedy did not focus on the causes of temperature change. Instead the researchers analyzed surface temperature data to establish the growing frequency of extreme heat events in the past 30 years, a period in which the temperature data show an overall warming trend.

NASA climatologists have long collected data on global temperature anomalies, which describe how much warming or cooling regions of the world have experienced when compared with the 1951 to 1980 base period. In this study, the researchers employ a bell curve to illustrate how those anomalies are changing.

A bell curve is a tool frequently used by statisticians and society. School teachers who grade "on the curve" use a bell curve to designate the mean score as a C, the top of the bell. The curve falls off equally to both sides, showing that fewer students receive B and D grades and even fewer receive A and F grades.

Hansen and colleagues found that a bell curve was a good fit to summertime temperature anomalies for the base period of relatively stable climate from 1951 to 1980. Mean temperature is centered at the top of the bell curve. Decreasing in frequency to the left of center are "cold," "very cold" and "extremely cold" events. Decreasing in frequency to the right of center are "hot," "very hot" and "extremely hot" events.

Plotting bell curves for the 1980s, 1990s, and 2000s, the team noticed the entire curve shifted to the right, meaning that more hot events are the new normal. The curve also flattened and widened, indicating a wider range of variability. Specifically, an average of 75 percent of land area across Earth experienced summers in the "hot" category during the past decade, compared to only 33 percent during the 1951 to 1980 base period. Widening of the curve also led to the designation of the new category of outlier events labeled "extremely hot," which were almost nonexistent in the base period.

Hansen says this summer is shaping up to fall into the new extreme category. "Such anomalies were infrequent in the climate prior to the warming of the past 30 years, so statistics let us say with a high degree of confidence that we would not have had such an extreme anomaly this summer in the absence of global warming," he says.

Other regions around the world also have felt the heat of global warming, according to the study. Global maps of temperature anomalies show that heat waves in Texas, Oklahoma and Mexico in 2011, and in the Middle East, Western Asia and Eastern Europe in 2010 fall into the new "extremely hot" category.

NASA | Evolution of the Moon

From year to year, the moon never seems to change. Craters and other formations appear to be permanent now, but the moon didn't always look like this. Thanks to NASA's Lunar Reconnaissance Orbiter, we now have a better look at some of the moon's history. Learn more in this video!

Study Finds Surprising Arctic Methane Emission Source

A new airborne study with NASA contributions measured surprising levels of the potent greenhouse gas methane coming from cracks in Arctic sea ice and areas of partial sea ice cover. This image was taken over the Arctic Ocean at a latitude of approximately 71 degrees North on April 15, 2010. (Credit: NASA/JPL)                                                            Science Daily  — The fragile and rapidly changing Arctic region is home to large reservoirs of methane, a potent greenhouse gas. As Earth's climate warms, the methane, frozen in reservoirs stored in Arctic tundra soils or marine sediments, is vulnerable to being released into the atmosphere, where it can add to global warming. Now a multi-institutional study by Eric Kort of NASA's Jet Propulsion Laboratory, Pasadena, Calif., has uncovered a surprising and potentially important new source of Arctic methane: the ocean itself.

Kort, a JPL postdoctoral scholar affiliated with the Keck Institute of Space Studies at the California Institute of Technology in Pasadena, led the analysis while he was a student at Harvard University, Cambridge, Mass. The study was conducted as part of the HIAPER Pole-to-Pole Observations (HIPPO) airborne campaign, which flew a specially instrumented National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V aircraft over the Pacific Ocean from nearly pole to pole, collecting atmospheric measurements from Earth's surface to an altitude of 8.7 miles (14 kilometers). The campaign, primarily funded by NSF with additional funding from NCAR, NASA and the National Oceanic and Atmospheric Administration, was designed to improve our understanding of where greenhouse gases are originating and being stored in the Earth system.

During five HIPPO flights over the Arctic from 2009 to 2010, Kort's team observed increased methane levels while flying at low altitudes over the remote Arctic Ocean, north of the Chukchi and Beaufort Seas. The methane level was about one-half percent larger than normal background levels.

But where was the methane coming from? The team detected no carbon monoxide in the atmosphere that would point to possible contributions from human combustion activities. In addition, based on the time of year, location and nature of the emissions, it was extremely unlikely the methane was coming from high-latitude wetlands or geologic reservoirs.

By comparing locations of the enhanced methane levels with airborne measurements of carbon monoxide, water vapor and ozone, they pinpointed a source: the ocean surface, through cracks in Arctic sea ice and areas of partial sea ice cover. The cracks expose open Arctic seawater, allowing the ocean to interact with the air, and methane in the surface waters to escape into the atmosphere. The team detected no enhanced methane levels when flying over areas of solid ice.

Kort said previous studies by others had measured high concentrations of methane in Arctic surface waters, but before now no one had predicted that these enhanced levels of ocean methane would find their way to the overlying atmosphere.

So how is the methane being produced? The scientists aren't yet sure, but Kort hinted biological production from living things in Arctic surface waters may be a likely culprit. "It's possible that as large areas of sea ice melt and expose more ocean water, methane production may increase, leading to larger methane emissions," he said. He said future studies will be needed to understand the enhanced methane levels and associated emission processes and to measure their total contribution to overall Arctic methane levels.

"While the methane levels we detected weren't particularly large, the potential source region, the Arctic Ocean, is vast, so our finding could represent a noticeable new global source of methane," he added. "As Arctic sea ice cover continues to decline in a warming climate, this source of methane may well increase. It's important that we recognize the potential contribution from this source of methane to avoid falsely interpreting any changes observed in Arctic methane levels in the future."

The study, published April 22 in Nature Geoscience, included participation from JPL and Caltech; NSF, Arlington, Va.; NOAA's Earth System Research Laboratory, Boulder, Colo.; the University of Colorado's Cooperative Institute for Research in Environmental Sciences, Boulder; Harvard University, Cambridge, Mass.; Princeton University, Princeton, New Jersey; Universidad Nacional de Colombia, Bogota, Colombia; and Science and Technology Corporation, Boulder, Colo. JPL is a division of Caltech.

NASA Wants to Launch Floating Algae Farms

A $10 million project aims to grow algae for biofuels inside plastic bags.

• BY KEVIN BULLIS

Audio »

Bio bags: A prototype algae plant for making biofuels.
NASA

Next week, NASA will show off some of its latest technology: a system for growing algae in floating plastic bags. The system is the result of a $10 million, two-year project that investigated whether the algae could be used to make biofuels, including jet fuel.

The system is designed to reduce the cost of making fuel from algae by making it possible to put algae farms near wastewater facilities, which offer a large source of nutrients.

But it may prove difficult to implement. For one thing, it will require a lot of plastic. In one possible setup, five square kilometers of plastic bags would be used to produce 2.4 million gallons of algae oil per year—a drop in the bucket compared to the 800 million gallons of oil the U.S. consumes every day. And the bags will likely need to be replaced every year.

The setup has been tested in four nine-meter-long plastic bags at a wastewater plant near San Francisco. The researchers demonstrated that they can grow enough algae to produce nearly 2,000 gallons of fuel per acre per year—if the weather cooperates. So if a commercial system gets built, it may need to be in someplace warmer and sunnier.

e lead researcher, Jonathan Trent, normally works on life-support systems for space travel. Those systems involve recycling human waste, and so does the algae fuel technology.

Trent plans to pump wastewater left over from treating sewage into bags made from common polyethylene. The wastewater is a good fertilizer, providing nutrients such as ammonia and phosphates. He also plans to pump carbon dioxide from power plants into the system to help algae grow. San Francisco produces enough wastewater to feed a floating algae farm that covers 1,200 acres, he says.

The setup is meant to solve some of the difficulties with making inexpensive fuels from algae. Algae need fertilizer to grow quickly, and wastewater is an excellent source of that. But large sources of wastewater—big cities—don't have the space needed for the artificial ponds that algae are typically grown in. Pumping the water to areas where land is cheap and plentiful is expensive and energy-intensive. Clear containers called photobioreactors might take up less space, but those, too, are expensive.

A few years ago, Trent wondered if floating plastic bags could serve as relatively cheap bioreactors. They don't need as much support as land-based ones—at least if they're floating on protected bays. And they solve another major problem with conventional bioreactors, which get too hot from sitting in the sun, and require expensive cooling systems as a result. In Trent's plastic bag system, the surrounding water helps keep the bags cool.

But while it may solve some problems—and it's far from clear that the bags will prove superior to ponds or other photobioreactors—the system creates others. Trent acknowledges, for example, that there will be an "enormous amount of plastic" to dispose of. The plastic could be recycled, although cleaning out the algae may be difficult. A better option may be reusing it, he suggests. For example, it could be used to replace the black plastic that many farmers in California cover their fields with to reduce weeds and evaporation.

The approach will face several other challenges. Working in corrosive saltwater environments is very difficult. And it's not clear how well the bags would survive storms.

If the bags break, the wastewater—which is normally released directly into the bay from treatment plants—wouldn't present a problem. And the algae they would use would die in the saltwater, so there's little threat to the bay ecosystem, Trent says. But it's hard to predict how expensive it would be to replace bags damaged by storms or infected with competing microbes.

The researchers also don't know how much the system will cost at a large scale. This month, they started a detailed economic analysis based on their results so far. The project also received $800,000 from the California Energy Commission.

Hubble Reveals a New Class of Extrasolar Planet

GJ1214b, shown in this artist’s view, is a super-Earth orbiting a red dwarf star 40 light-years from Earth. New observations from the NASA/ESA Hubble Space Telescope show that it is a waterworld enshrouded by a thick, steamy atmosphere. GJ 1214b represents a new type of planet, like nothing seen in the Solar System or any other planetary system currently known. (Credit: NASA, ESA, and D. Aguilar (Harvard-Smithsonian Center for Astrophysics))                                          Science Daily  — Observations by the NASA/ESA Hubble Space Telescope have come up with a new class of planet, a waterworld enshrouded by a thick, steamy atmosphere. It's smaller than Uranus but larger than Earth.

An international team of astronomers led by Zachory Berta of the Harvard-Smithsonian Center for Astrophysics (CfA) made the observations of the planet GJ 1214b.

"GJ 1214b is like no planet we know of," Berta said. "A huge fraction of its mass is made up of water."

The ground-based MEarth Project, led by CfA's David Charbonneau, discovered GJ 1214b in 2009. This super-Earth is about 2.7 times Earth's diameter and weighs almost seven times as much. It orbits a red-dwarf star every 38 hours at a distance of 2 million kilometres, giving it an estimated temperature of 230 degrees Celsius.

In 2010, CfA scientist Jacob Bean and colleagues reported that they had measured the atmosphere of GJ 1214b, finding it likely that it was composed mainly of water. However, their observations could also be explained by the presence of a planet-enshrouding haze in GJ 1214b's atmosphere.

Berta and his co-authors, who include Derek Homeier of ENS Lyon, France, used Hubble's Wide Field Camera 3 (WFC3) to study GJ 1214b when it crossed in front of its host star. During such a transit, the star's light is filtered through the planet's atmosphere, giving clues to the mix of gases.

"We're using Hubble to measure the infrared colour of sunset on this world," Berta explained.

Hazes are more transparent to infrared light than to visible light, so the Hubble observations help to tell the difference between a steamy and a hazy atmosphere.

They found the spectrum of GJ 1214b to be featureless over a wide range of wavelengths, or colours. The atmospheric model most consistent with the Hubble data is a dense atmosphere of water vapour.

"The Hubble measurements really tip the balance in favour of a steamy atmosphere," Berta said.

Since the planet's mass and size are known, astronomers can calculate the density, of only about 2 grams per cubic centimetre. Water has a density of 1 gram per cubic centimetre, while Earth's average density is 5.5 grams per cubic centimetre. This suggests that GJ 1214b has much more water than Earth does, and much less rock.

As a result, the internal structure of GJ 1214b would be extraordinarily different from that of our world.

"The high temperatures and high pressures would form exotic materials like 'hot ice' or 'superfluid water', substances that are completely alien to our everyday experience," Berta said.

Theorists expect that GJ 1214b formed further out from its star, where water ice was plentiful, and migrated inward early in the system's history. In the process, it would have passed through the star's habitable zone, where surface temperatures would be similar to Earth's. How long it lingered there is unknown.

GJ 1214b is located in the constellation of Ophiuchus (The Serpent Bearer), and just 40 light-years from Earth. Therefore, it's a prime candidate for study by the NASA/ESA/CSA James Webb Space Telescope, planned for launch later this decade.

Making the Blackest of Black Materials

"We made carbon nanotubes that are blacker than anything else."

By NASA Goddard Staff, as told to Flora Lichtman

Little Light Traps

Our material absorbs more than 99 percent of visible and ultraviolet light and 98 percent of infrared light. It’s at least 10 times as good at capturing light as black paint, so we can use it in telescopes, where stray light can contaminate measurements. The nanotubes are sparse enough that light passes between them, like sunlight through trees in a forest. When photons hit the sides of the carbon tubes, they transfer their energy to the carbon’s electrons, which start to move. The light is converted to motion—heat— which dissipates in the tube. —John Hagopian,optical physicist at NASA’s Goddard Space Flight Center

To grow carbon nanotubes, we use a substrate, an adhesion layer and a catalyst: iron. The catalyst condenses on the substrate, a lot like if you boiled water and leaned over the pot with your glasses on. Then we put the whole thing in a quartz tube furnace at 1,382°F. We introduce ethylene gas, which is where the carbon comes from. The catalyst reacts with the gas, and the carbon molecules dissociate and form a tubular hexagonal lattice—a nanotube—on the surface of the iron. The nanotubes can grow in less than a minute. —Stephanie Getty, technologist, NASA Goddard

We put the nanotubes in an integrating sphere—a globe with a highly reflective coating inside. We shine light at the sample and, using a detector, measure the amount of light that bounces off the material. We put a shader near the detector to make sure it’s not getting direct radiation and skewing the results. One thing that’s kind of amazing is that the nanotubes, which are just 100 microns tall, can absorb infrared rays, which have wavelengths the same size as the nanotubes.—Manuel Quijada, engineer, NASA Goddard

What Can Be Done to Slow Climate Change?

Upgrade Brick Kilns: Traditional brick kilns, which emit large amounts of black carbon, are still common in some parts of the world, particularly Asia. Shindell's team found that replacing them with cleaner and more fuel efficient technologies, such as vertical shaft or Hoffman kilns, could reduce global black carbon emissions by approximately four percent. (Credit: The University of York/Kevin Hicks)                                        Science Daily  — A new study led by a NASA scientist highlights 14 key air pollution control measures that, if implemented, could slow the pace of global warming, improve health and boost agricultural production.

"We've shown that implementing specific practical emissions reductions chosen to maximize climate benefits would also have important 'win-win' benefits for human health and agriculture," said Shindell.The research, led by Drew Shindell of NASA's Goddard Institute for Space Studies (GISS) in New York City, finds that focusing on these measures could slow mean global warming 0.9 ºF (0.5ºC) by 2050, increase global crop yields by up to 135 million metric tons per season and prevent hundreds of thousands of premature deaths each year. While all regions of the world would benefit, countries in Asia and the Middle East would see the biggest health and agricultural gains from emissions reductions.

The study was recently published in the journal Science.

Shindell and an international team considered about 400 control measures based on technologies evaluated by the International Institute for Applied Systems Analysis in Laxenburg, Austria. The new study focused on 14 measures with the greatest climate benefit. All 14 would curb the release of either black carbon or methane, pollutants that exacerbate climate change and damage human or plant health either directly or by leading to ozone formation.

Black carbon, a product of burning fossil fuels or biomass such as wood or dung, can worsen a number of respiratory and cardiovascular diseases. The small particles also absorb radiation from the sun causing the atmosphere to warm and rainfall patterns to shift. In addition, they darken ice and snow, reducing their reflectivity and hastening global warming.

Methane, a colorless and flammable substance that is a major constituent of natural gas, is both a potent greenhouse gas and an important precursor to ground-level ozone. Ozone, a key component of smog and also a greenhouse gas, damages crops and human health.

While carbon dioxide is the primary driver of global warming over the long term, limiting black carbon and methane are complementary actions that would have a more immediate impact because these two pollutants circulate out of the atmosphere more quickly.

Shindell and his team concluded that these control measures would provide the greatest protection against global warming to Russia, Tajikistan and Kyrgyzstan, countries with large areas of snow or ice cover. Iran, Pakistan and Jordan would experience the most improvement in agricultural production. Southern Asia and the Sahel region of Africa would see the most beneficial changes to precipitation patterns.

The south Asian countries of India, Bangladesh and Nepal would see the biggest reductions in premature deaths. The study estimates that globally between 700,000 and 4.7 million premature deaths could be prevented each year.

Black carbon and methane have many sources. Reducing emissions would require that societies make multiple infrastructure upgrades. For methane, the key strategies the scientists considered were capturing gas escaping from coal mines and oil and natural gas facilities, as well as reducing leakage from long-distance pipelines, preventing emissions from city landfills, updating wastewater treatment plants, aerating rice paddies more, and limiting emissions from manure on farms.

For black carbon, the strategies analyzed include installing filters in diesel vehicles, keeping high-emitting vehicles off the road, upgrading cooking stoves and boilers to cleaner burning types, installing more efficient kilns for brick production, upgrading coke ovens and banning agricultural burning.

The scientists used computer models developed at GISS and the Max Planck Institute for Meteorology in Hamburg, Germany, to model the impact of emissions reductions. The models showed widespread benefits from the methane reduction because it is evenly distributed throughout the atmosphere. Black carbon falls out of the atmosphere after a few days so the benefits are stronger in certain regions, especially ones with large amounts of snow and ice.

"Protecting public health and food supplies may take precedence over avoiding climate change in most countries, but knowing that these measures also mitigate climate change may help motivate policies to put them into practice," Shindell said. The new study builds on a United Nations Environment Program/World Meteorological Organization report, also led by Shindell, published last year.

"The scientific case for fast action on these so-called 'short-lived climate forcers' has been steadily built over more than a decade, and this study provides further focused and compelling analysis of the likely benefits at the national and regional level," said United Nations Environment Program Executive Director Achim Steiner.

Comet Lovejoy, as Seen from the International Space Station

By Clay Dillow

Comet Lovejoy, As Seen from the ISS NASA/Dan Burbank via Bad Astronomy

Today in pretty space pics: Comet Lovejoy, still alive and heading back out toward the far reaches of the solar system, as seen from the International Space Station. This photograph was snapped yesterday as the ISS passed over Australia by Dan Burbank, one of the station’s current crew members. And needless to say, it’s one of those once-in-a-lifetime shots.

What you’re seeing in the top of the shot is actually the dark side or our dear planet, with the lit up arc traversing the image being Earth’s atmosphere, backlit by the sun (the thin green line is the upper atmosphere, where energized particles are tickling the edge of space). And of course, there’s Comet Lovejoy, which narrowly escaped a flyby of the Sun last week and came out not so worse for wear on the other side. Burbank managed to capture it from the ISS just as it was darting behind the home planet on its way back out into interplanetary space.

Click through to Bad Astronomy for a quick primer on comets, Lovejoy, and the two tails--yes, there’s actually two--that you’re seeing here. And, as always, the Bad Astronomer has links up to the larger version of this pic, should you feel the need to take a closer look. And you should.

[Bad Astronomy]

Discovered: The First Earth-Sized Worlds Outside Our Solar System

The smallest exoplanets yet

By Rebecca Boyle

Kepler-20e Kepler-20e orbits its star every 6.1 days. At just 4.7 million miles from its star, its surface temperature reaches a searing 1,400 degrees F. NASA/JPL-Caltech/T. Pyle

Two small, scorched Earth-sized worlds orbiting a reddish sun-like star in the Cygnus constellation mark yet another milestone for the storied Kepler Space Telescope mission. They're the smallest exoplanets found to date — one of them is just 1.03 times the size of Earth, a veritable body double. The planets aren't in their star's habitable zone, but they are the right size — and as such, they fill in even more of the interstellar planetary puzzle.

The planets exist in a strange configuration that sandwiches them among three gas giants, and they're all well within the orbit of Mercury. They were buried in nearly two years of data, and astronomers had to use some ultra-refined computational techniques to be sure they're really planets.

One of the planets, Kepler-20f, could potentially harbor a water-vapor atmosphere, although astronomers don't know for sure. What they do know is that it's just barely bigger than our own planet (and only slightly more massive).

"It is the closest object to the Earth that we have seen in the universe," said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics, lead author of a paper on the new worlds.

Kepler-20f: This world is 1.03 times the size of Earth, the closest to our own planet's size of any exoplanet yet discovered. It has somewhere less than three times Earth's mass. It's just 10.3 million miles from its star (we're 93 million from ours) and as such makes an orbit in just 19.6 days. Its surface temperature is about 800 degrees F, but astronomers believe it may have held on to a water-vapor atmosphere.  NASA/JPL-Caltech/T. Pyle

Both planets orbit around a star called Kepler-20, a G-type star slightly cooler than the Sun, located 950 light-years away. (It would take the space shuttle 36 million years to travel to Kepler-20, as the CfA helpfully points out.)

Based on their size and location around their star, the planets might have a very Earth-like composition, Fressin said in an interview. Their proximity to Kepler-20 exposes them to prodigious doses of radiation, and they’re too small to have held on to lighter elements like hydrogen and helium in the face of those stellar winds — so the evidence would suggest that they’re rocky. It’s just a matter of the ingredients, whether they have significant amounts of iron or silicate.

The planets could not have formed where they’re currently located, and must have migrated inward, he said. It’s possible that earlier in its life, Kepler-20f had an atmosphere with significant water vapor, which would make it habitable, at least according to most planetary habitability indices.

“If it indeed migrated from the outer solar system, it could have been habitable in its earlier history,” Fressin said.

Kepler-20 Planetary Comparison:  NASA/JPL-Caltech/T. Pyle

The discovery comes on the heels of a major data dump by the Kepler team earlier this month, which also included the news of the first Earth-like world orbiting in an Earth-like place around its star. That planet, Kepler-22b, is much bigger than Earth, but exists in a temperate zone just right for liquid water to exist. It may not have a rocky surface, however. These new planets are too hot for water, but they’re much more Earth-like in rocky form and smaller size.

“I think of Kepler-22b on one side, and Kepler-20e and 20f on the other, as two pieces of the puzzle,” Fressin said. “We need to combine the finding of an Earth-sized planet in a habitable zone.”

Kepler was designed to look for blips in brightness across the faces of 144,000 stars in the constellations Cygnus and Lyra, aiming to find sun-like systems harboring Earth-like planets. In its two years of operation, the cosmic census has mushroomed to more than 2,000 worlds, including super-Jupiters, super-Earths, inky black light- and heat-absorbing worlds, and many more. But the hunt for an Earth twin has proven difficult. Part of the problem is criteria — an Earth analogue would need a similar size, location, composition, rotation and many other factors to be truly Earth-like, Fressin said. Take Kepler-22b: It’s the right temperature, but it’s 2.4 times the radius of Earth, so it has much more volume.

“I don’t foresee us finding a true, clear Earth twin very soon — there are so many different levels,” Fressin said. “Maybe we don’t only need a planet in a habitable zone and at the right size, but the star similarity. If we don’t know what is in the atmosphere, or we don’t have any constraints on the atmosphere, how can we say it has the right signature to be an Earth twin?”

These small planets are actually the newest known members of an already-discovered solar system at Kepler-20. The three largest planets are designated Kepler-20b, 20c, and 20d, and have diameters of 15,000, 24,600, and 22,000 miles, orbiting every 3.7, 10.9, and 77.6 days, respectively. Kepler-20b has 8.7 times the mass of Earth and Kepler-20c has 16.1 times Earth’s mass, the CfA notes. Kepler-20d weighs less than 20 times Earth.

These planets are arrayed in a very strange system, alternating between rocky and gassy, which is unlike anything astronomers have ever seen, said co-author David Charbonneau of the CfA. He challenged his fellow astronomers to help him explain it.

"The freshmen in my class are going to be quick to point out that the model of our solar system formation is deeply challenged by the discovery that is being presented today," he said.

Their small companions were difficult to see because of their size, and previous attempts to spot them were unsuccessful, Fressin explained. Astronomers had seen some blips they thought might be transiting planets moving across the face of Kepler-20, but an analysis a year ago couldn’t rule out other possible sources. Additional data from the space telescope and additional calculations by Fressin and colleagues led to the final eureka moment.

When a planet moves across the face of its star, the star dims a tad, and this is what Kepler is designed to notice. Scientists have to rule out other possible causes like a background star, a brown dwarf, an eclipsing binary, and so on. To confirm planets’ existence, astronomers check for a tiny wobble caused by the planets’ gravitational pull. This can be verified from the ground, using the huge Keck telescopes in Hawaii. But in this case, the new planets were too small for these ground-based verifications.

Fressin used software called Blender, which he developed with CfA astronomer Willie Torres (and which has also been used to verify other planet findings, including Kepler-22b). Fressin and nearly 30 collaborators used Blender to run millions of simulations, and were able to rule out any other source of dimming other than the putative planets.

This is neat, because as astronomers enter this new mass range of planets — little worlds the size of Earth or smaller — they’ll need sophisticated analysis to verify what they’re seeing. This paper combines a new computational technique with the old, pre-Kepler technique of checking for stellar wobble.

The study appears online today in the advance online edition of the journal Nature.

Kepler-20 System: The planets of the Kepler-20 star system are arranged in a bizarre pattern, with small, Earth-sized and probably rocky worlds sandwiched between gas mini-giants. This system of flip-flopping planets is very different from other solar systems discovered thus far. The planets could not have formed in their current locations, but must have migrated inward, probably through gravitational interactions with the dusty gas disk from which they were born. They orbit their star very tightly, closer than Mercury is to our sun.  Harvard-Smithsonian Center for Astrophysics