Kepler 22B compared to the solar terrestrial planets

It's 600 light years from Earth, orbits a star very similar to our Sun in a period of about 290 days, and has a diameter about two and a half times that of Earth. What is it? It's the NASA Kepler mission's most recent exciting confirmed discovery, the extrasolar-planet (exoplanet) Kepler 22B.

Another real, Earth-sized planet to imagine? Cool! I'm on it….

It's fun to play around with the planetary possibilities, as science fiction writers have done for decades, but having a real find out there to pin our thoughts on is something more. On that blank ball-shaped canvass we can paint whatever atmosphere, hydrosphere, lithosphere–and who knows, biosphere?–we care to imagine, at least until scientific observation starts to fill in those details.

But, Kepler 22B offers something more to our fancy than a mere Earthoid dress-up doll. Being somewhat larger than our world, though still smaller than a Neptune or a Uranus, places it in the category of "super-Earth," a type of planet that we have very little experience with.

What do we know of Kepler 22B beyond the barebone figures revealed by the Kepler spacecraft? In a word, not much. Kepler—a really big camera orbiting the Sun and staring at a patch of 150,000 or so stars in the constellation Cygnus—was designed to detect the presence of Earth-like exoplanets. Using the "transit" method of exoplanet detection, Kepler watches unblinkingly for the slight dimming of a star's light as one of its planets "transits," or moves across, its face.

That dimming can tell us exactly three things: the approximate diameter of the planet by how much of the star's light is blocked, the orbital period of the planet by how often it transits, and the distance between the planet and its star (because once you know the orbital period, you can calculate that distance–or visa versa–as long as you know the mass of the star the planet orbits…which we do).

Being relatively close to the size of the Earth makes Kepler 22B an important find, but maybe more important is the fact of the planet's distance from its star. Kepler's mission isn't merely to find Earth-sized planets, but ones that are within their stars' habitable zones: the right distance so that, given a sufficient atmosphere, liquid water could exist on their surfaces.

Kepler 22B is at that correct distance. Though it is closer to its star than Earth is from the Sun, that star is slightly cooler than the Sun, so its habitable zone is closer in. (Earth is obviously in the Sun's habitable zone; if you're not sure, go get yourself a glass of water.)

But back to what we know, and don't know, about Kepler 22B. Not having a super-Earth in our own Solar System, we don't have an up-close example to study. Is it like Earth, a rocky sphere from the core right up to the visible surface, with an apple-peel thin layer of gas and liquid on top? Or is it more like Uranus, with a solid core deep down with massive layers of fluid and gas upholstered around it? Or something between?

We don't know. Future observations may reveal more about this planet, and others. One day we might know more about Kepler 22B's atmosphere (if it has one) through spectroscopic measurements. If we can make a measurement of the planet's mass, we could calculate its average density and better place it on the spectrum between super-Earth and infra-Uranus.

Were we to travel there, could we land, step outside and breathe the air (as well as strain under a super-Earth's gravity)? Would we sink into the fluid envelope around the hidden core, falling to ever greater depths and atmospheric pressure? Would we find ourselves surrounded by human-sized chimpanzees?

That adventure is yet far in the future…but a lot of fun to imagine in the meantime….

The Allen Telescope Array near Redding, California

It takes a certain type of person to devote an entire career to chasing something she'’ll probably never find. One such person is Jill Tarter.

Tarter is the director for SETI Research at the SETI institute in Mountain View, California. She’s also the inspiration for the Jodi Foster character in the 1997 movie Contact, based on the book by Carl Sagan.

In real life, Jill Tarter’s career at SETI has been a lot less momentous. In her 60s now, with her gray hair in a short, no-nonsense cut, Tarter says she knows she may not hear a signal from intelligent extra-terrestrials in her lifetime. “I don’t know whether anyone will ever find a signal,” she says.

Listen to the QUEST radio story Is it Time for SETI to Stop Looking?

Back when Tarter joined SETI, the project was funded by NASA. But that support ended in 1993. Since then, she and others have spent almost as much time searching for money as they have searching for ET. Three years ago, SETI celebrated what felt like a turning point: the opening of the Allen Telescope Array, near Redding, California.

SETI's powerful new tool

Before the Allen Array, Tarter and other SETI scientists took their equipment around the world, borrowing time from telescopes owned by other institutions. But with Allen, which was constructed with money from Microsoft co-founder Paul Allen and is jointly managed with the University of California, Berkeley, SETI scientists could scan the skies full-time, hoping a clear, tell-tale radio signal would distinguish itself from the universe’s background hiss.

“We look,” says Tarter, “for signals that are compressed in frequency. Because nature doesn’t do that, technology does.”

Tarter is the first to admit that this may never work. She says SETI is searching the cosmic haystack for a needle that might not even exist.

Ben Zuckerman, a professor of astronomy at UCLA, is skeptical humans will ever find intelligent extra-terrestrials.

“Frankly I don’t think technological ETs exist in our Milky Way galaxy,” says Zuckerman. “Or if they do, they’re very, very scarce.”

Zuckerman didn’t always feel this way. In grad school, he studied with Carl Sagan. He even worked on some of the early radio searches back in the 1970s. But then he started to have doubts.

“If there are so many technological civilizations out there, and they’re so far in advance of our own technological civilization, then why haven’t they found us?”

Then there’s the problem of timing. If intelligent ETs are out there, what are the odds that their signals would reach Earth at the precise moment in cosmic history that we happen to be listening?

NASA's Kepler Mission delivers new targets

Recently, something happened that gave critics new hope: NASA’s Kepler Mission, a program designed to survey the Milky Way galaxy in search of Earth-size and smaller planets, delivered its results.

Kepler found what it was looking for: More than a thousand planets orbiting distant stars like our sun. Dozens of them are thought to be roughly Earth-sized. Of those, some may turn out to have climates that could be hospitable to life.

Dimitar Sasselov directs Harvard’s Origins of Life Initiative and is also a member of the Kepler team. He says Kepler has given SETI something it never had before: targets.

“This is where we should be looking for the signals coming from other civilizations,” says Sasselov, referring to the so-called Kepler planets. “SETI is already in possession of this list.”

As of April, that list has been filed away for future use. SETI’s Allen Telescope Array is officially in “hibernation.” Tight budgets at the state and federal level have left UC Berkeley without enough money to operate the telescopes. Sasselov says it’s a shame.

“This is our only shot to listen for such signals,” he says. “When the array is down, we are blind and we are deaf.”

The "longest long shot"

Jill Tarter says it would cost $5 million and two years to systematically go through the Kepler planets, listening for radio signals produced by an intelligent civilization. She’s looking for private money to make it happen.

Even Ben Zuckerman, the UCLA skeptic, believes that’s a small price to pay. “Given that the costs are not very high,” he says, “why not continue the search?”

Zuckerman says it’s a long shot. Maybe the longest long shot in the history of science. But the payoff?

“The payoff, one could argue, is the most important science discovery of all time.”

There are hundreds of billions of stars in our Milky Way galaxy alone, and hundreds of billions of galaxies. Tarter says someday, it may make sense to stop looking, to come to what she calls the “extraordinary conclusion” that we really are alone.

“It isn’t an impossible conclusion,” says Tarter. “That may be the answer. But it certainly isn’t time to draw that conclusion. Let’s search a little more. A lot more, actually.”

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Kepler's patch of sky (one four hundredth of the total sky) filled
with possible planets. Credit: NASA/Kepler

When I heard that NASA was holding a press conference to make a major announcement from findings by the Kepler mission—a “historic” announcement, as was alluded to by a trusted expert source—the first thing I thought was, “Kepler has found its Holy Grail: an Earth-sized planet orbiting a Sun-like star within the Habitable Zone!” I mean, what else could it be?

When the first panelist started by saying that finding and confirming an Earth-sized planet in a habitable zone is of course what we want to do…, I thought I was going to be disappointed (because that, of course, is what I wanted to hear, and it didn’t sound like the talk was going that way). Had Kepler merely detected a Grail-shaped beacon—a potential, but not confirmed, exo-Earth? A “candidate”?

Only two minutes later the threatened disappointment washed away, and I was reassured that the news was in fact big and I was in fact witnessing history….

The frame of the announcement were the results from Kepler’s first 4 months of observations, from May to September in 2009. At the time of launch, a couple hundred extra-solar planets had been detected, over the previous two decades, by ground-based observatories.

Early in 2010, NASA released some of the results from the initial observations: about 400 candidate worlds, mostly the big “hot Jupiter” planets (big balls of gas close to their stars, “easy” to detect) of the ilk that were being discovered monthly through ground based observations. Along with this announcement it was stated that a batch of Kepler data was being “embargoed” (or sequestered) to give Kepler scientists time to analyze it in more detail and make additional observations.

In December 2010 NASA announced the discovery of Kepler 10b, the first bonafide Earth-size rocky planet detection—albeit a red-hot lump of rock that orbits its star in less than a day.

Curtain lifts; drumroll please…. In Kepler’s first 4 months of staring at its target patch of sky in the constellation Cygnus, fully 1235 (with a capital T) candidate planets wink at us from the transit data—and after dusting away the “chaff” of hot-Jupiters and super-Jupiters, what’s left may be the very jewels Kepler set out to find.

Of the 1235 candidate planets (candidates because they still need to be confirmed—though Kepler scientists have said they believe 80-90% of them will turn out to be real planets, and not spurious blips in the data), 68 of them are approximately Earth-sized (some larger, some smaller, some spot on), and of those, 5 orbit their stars within the Habitable Zone: the right distance for sunlight to enable liquid water to exist.

Five worlds with the right proportions of material and heat to make the porridge “just right”! Awesome!

And this is not counting the “Avatar effect”: 49 other candidates found within habitable zones range in size from “super-Earths” all the way up to “super-Jupiters”—any of which could theoretically possess one or more moons of near-Earth stature, which would place those moons within habitable zones as well.

My head’s still reeling. What’s next? Will Kepler produce pictures of worlds with oceans, continents, and shorelines—or maybe 12-foot tall blue aliens? Is it time to start drafting a charter for a United Federation of Planets? Not yet….

Kepler was designed to do one thing: find Earth-sized worlds at water-friendly distances from their stars—and pending confirming follow-up observations, it may already have wildly outperformed NASA’s expectations on that front. Another two or so years of observations will be required for confirmations, but that’s only another Superbowl or two.

One thing is clear to me: From now on when I go out at night and look up at the sky, I won’t see stars; I’ll see planets. Lots of them….

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Size comparison between Earth and Kepler 10b.

Delta Vega, Alderaan, Malacandra, Altair IV, Kepler 10-b. Which one of these worlds is not like the other? Answer: Kepler 10-b. Why? Because among the thousands of small, rocky, Earth-sized planets that we have come to know over the past century, Kepler 10-b is not a piece of fiction, but real.

After over a century of science fiction storytelling involving distant aliens worlds—many of which are depicted as being not so unlike Earth, right down to oddly similar vegetation, human-like inhabitants, and one particular rock formation that is the spitting image of one I’ve seen in the Mojave desert—NASA’s Kepler mission has made good on its “promise” to find an Earth-sized exoplanet. “Sci-Fa” has finally caught up with Sci-Fi….

Kepler 10-b: 1.4 times Earth’s diameter, 4.6 times Earth’s mass, and 8.8 grams per cubic centimeter average density. In all the physical categories, a heavy-weight compared to Earth’s newly (dare I say) demoted middle-weight status. Were you to stand on Kepler 10b’s surface, you would weigh about 2.3 times what you weigh on Earth. (Interestingly, that’s just a small bit less than you’d weigh if you could stand on the surface of Jupiter—if Jupiter had a solid surface, that is; imagine instead that you’re standing on a floating gas mining facility, like that one in the second Star Wars movie….)

But how Earthlike is Kepler 10b? Well—not knowing anything about its atmosphere (if it has one), the fact that this rocky planet is about twenty times closer to its star than Mercury, and its surface is estimated to be 2,400 degrees Fahrenheit, means that it’s hot enough down there to melt most minerals, as well as about half of the list of metals you might jot down mentally. Since I keep alluding to worlds out of science fiction, I guess I’d say this makes Kepler 10b more like the planet from Star Trek (the original series) inhabited by the hot rock beings who recreated Abraham Lincoln, among other figures…okay, I’ll try to stop….

Though the first finding of an Earth-stature planet is a really big deal (it shows us evidence that other planets Earth’s size do exist beyond our solar system), this hit is actually only halfway to the bullseye of the Kepler agenda (Kepler the spacecraft, that is). Kepler’s ultimate goal is to find an Earth-sized planet orbiting its star within its “habitable zone”: at the right distance for its star’s light to allow liquid water to exist on the surface. (In other words, where most of the invented worlds of science fiction serendipitously revolve….)

How about a closer look? Well—it took the Kepler spacecraft and the enormous ground-based Keck Observatory telescopes just to detect Kepler 10b’s presence, by observing the tiny amount of light the planet blocks as it crosses in front of (or “transits”) its star (Kepler’s method), and by the gravitational tug it has on its star (Keck’s confirming observation). Why can’t all this telescope power give us a nice picture of what the planet actually looks like?

Well, consider that the Hubble Space Telescope, which has given us the best image of Pluto so far, has only revealed Pluto as a globe of blurry, slightly different-shaded regions—about as clear an image as a near-sighted person would have of the Moon without their contact lenses, and no telescope. And at a distance of 560 light years, Kepler 10b is over 900,000 times farther away than Pluto!

We’re still a long way from Delta Vega, or Altair IV, with their vivid vistas of distant outposts and extinct alien civilizations—but we’re now a great deal closer to a real other-Earth….

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Artist concept of an Earthlike Exoplanet. Credit: ESO

It's been 15 years since the first extrasolar planet (exoplanet: planet orbiting a star other than our Sun) was confirmed to exist. Since that time and until the launch of Kepler, subsequent detections have racked up the number by about one a month to well over 400. Planets, see? Worlds! What would we name them if we knew them more intimately, as we do Jupiter and Neptune?

What are they like, and how are we seeing them? Well—we don't exactly see them; we detect their presence by their affect on their parent stars: small wiggles and wobbles that their gravity and motion cause in their star, or tiny dips in star brightness when they pass in front of it ("transit").

As for what they're like, so far we've detected mostly very large planets—gas giants, like Jupiter, Saturn, Uranus, and Neptune—that are relatively close to their stars. "Hot Jupiters" they've been called, for obvious reasons. The bigger the planet, the greater its gravitational or eclipsing effects; the closer the planet to its star, the shorter its orbital period and so the more frequently we can detect their influences.

NASA's Kepler mission has a slightly different goal than finding Hot Jupiters. Using the "transit method" of looking for small drops in star brightness, Kepler is looking for Earth-sized planets orbiting their stars at Earth-like distances—in a nutshell, we're looking for environments similar to those of Earth, since Earth's environment is the one that we know supports life.

Since the drop in light caused by the transit of a small planet is much more difficult to detect, Kepler is located in space, outside of Earth's distorting atmosphere. And since Kepler is looking for transits that should occur only one time in many months, and which may last only hours, it must observe constantly over a long time, without "blinking".

So what has Kepler come up with so far? NASA recently released data from Kepler taken in the first 43 days of its science mission. How many candidates for exoplanethood, you ask? The report announced a total of 706 possible detections in that 43 days—although NASA has only released the data on 306 of the lower priority detections, holding back a balance of about 400 "more interesting" candidates for more detailed study. What has piqued their interest on these, I really want to know….

And the Kepler candidates are not a mix of Hot Jupiters; as the mission was designed for, these potential planets are smaller and with longer orbital periods. In the mix there are a number of Neptune-like possibilities, and a larger number further down the size scale closer to true Earth-like character.

So, in 15 years of observations made from Earth telescopes, a bit over 400 exoplanets. In Kepler's first 43 days of observation: 706.

Okay, the numbers look cool, but I must point out that the 400 (actually closer to 460 as of June 2010) convenctional exoplanet detections are all confirmed to exist, while the 706 from Kepler have yet to be—but that's mostly a matter of time and followup. They may not all end up being confirmed; a number of them will likely turn out to be "false positives". But, I expect many of them will end up being confirmed–and Kepler has another couple of years of left before its mission ends.

How many planets—and how many Earth-sized worlds—will end up being discovered between now and then? Maybe someone should start a Kepler exoplanet poll….

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Yuri Alexyevich Gagarin, "Columbus of the Cosmos"

Yuri Alexyevich Gagarin was a Soviet cosmonaut.  He was the first human in space and is often referred to as "the Columbus of the Cosmos".   His spacecraft Vostok-1 orbited the Earth on April 12, 1961 for the duration of 108 minutes.   Yuri's Night, usually celebrated on April 12^th celebrates this historic first flight.

Yuri's Night also celebrates another April 12^th anniversary notable in the annals of space travel.  Twenty years after Yuri Gagarin's historic flight, the first NASA space shuttle flight, STS-1 was launched into space.  STS is short for Space Transportation System.  NASA names each flight STS with the chronological number after it.  STS-1 was launched on April 12, 1981; the shuttle orbited the earth 37 times during a 54.5 hour mission.

Since 1961, our interest in space and the exploration of its depths has magnified.  Recently NASA launched the Kepler mission.  On March 7^th, 2009, the Kepler Mission successfully launched from Cape Canaveral, Florida.  Kepler, which is a specialized telescope, was designed to find the first Earth-size planets orbiting stars within a "habitable zone". A habitable zone is an orbit around a star that would enable a planet to formulate and upkeep an atmosphere and the ability for water to form in pools on the planet's surface.  Liquid water is believed to be essential for the formation of life.  Thus from the nascent flight of orbiting our own Earth, space travels has evolved to look amongst other start.  This progress is certainly something worthy of celebration!

An exhibit on the Kepler Mission along with other NASA initiatives like SOFIA, LCROSS and NLSI fascinated guests last Thursday night.  For one guest, meeting Buzz Aldrin in person was the highlight of his night.   My favorite aspect of the evening was a 3-D rendered tour of the moon and neighboring space.  I am anxious to see what will be the new annal of space exploration when April 12^th and Yuri's Night comes around again in 2010.

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The main method for detecting exoplanets is by spectroscopically observing a tiny "wobble" in a star caused by the gravitational tug of a massive planet in orbit. Only Jupiter-sized planets have enough pull to produce a wobble in their star that we can detect—and the closer they are to their star, the shorter their orbital period and the more wobbles we can measure in a given period of time. The gravity of an Earth-sized planet is too feeble for this and planets at Earth-like distance orbit only once in many months.

But NASA is about to launch a new spacecraft, Kepler, whose mission is to detect Earth-sized planets at Earth-like distances from their stars. Kepler will launch on March 5th, and will eventually move into an orbit around the Sun. In essence, Kepler is a giant space camera designed to "stare" at a chosen patch of the sky continuously for years to come.

So what exactly is Kepler looking for in its unblinking stare contest with the stars in its vision? Kepler won’t be looking for microwobbles in those stars. Kepler will detect planets through the transit method. A transit is when a planet crosses in front of its star, blocking off a tiny amount of the star's light for a time.

A number of the hot Jupiters have been detected by their transits across their stars: a large planet can block a measurable amount of their star's light. But the drop in a star's brightness caused by an Earth-sized planet is far smaller—and if that planet only orbits its star every year or so, with its infrequent transit lasting only a few hours, an observer would have to stare long and hard to notice it.

Kepler will be based in space, and will be able to observe its target patch of sky continuously, uninterrupted by the cycles of day and night on Earth. Also by virtue of being in space, Kepler won't be hampered by Earth's turbulent and obscuring atmosphere—so there will be far less "noise" in the starlight, noise that can hide a minute drop in brightness. Finally, Kepler's sensitive digital camera system is an array of 42 CCD chips positioned at the focus of a 0.95 meter telescope, which will image an area of the sky about 12 degrees in diameter—equivalent to the area of sky you can cover with your open hand at arm's length.

Kepler will stare at a patch of sky near the constellation Cygnus, constantly monitoring about 150,000 stars for the next few years, looking for minute drops in brightness that may be the passage of Earth-sized planets.

Kepler won't reveal the composition or atmospheres of Earth-sized planets, or any telltale signs of life. Perhaps more importantly at this stage of our exploration of space, Kepler should give us an idea of how numerous Earth-sized planets are out there—whether or not they are as commonplace as depicted on Star Trek…

Good luck, Kepler, and stare on!

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Artistic rendition of exoplanet Gilese 436 b, created in Celestia

Once astronomers have found an extrasolar planet, also called an exoplanet, they look to see if it is in the Goldilocks zone. This is an area of space in which a planet is just the right distance from its' parent star so that the surface is neither too hot nor too cold. A habitable temperature means that the planet could possibly host liquid water, an ingredient for life.

A number of exoplanet findings have come from astronomy teams in Switzerland and near San Jose at Lick Observatory. Astronomers at Lick made news in the fall of 2007 when they discovered 55 Cancri. The discovery of the five-planet system came after nearly 20 years of observations. Also in 2007, astronomers with the Geneva Extrasolar Planet Search Program discovered the most earth-like planet ever found. Gilese 581 c lies in the Goldilocks Zone, it's surface temperature ranges from an estimated 32 degrees Fahrenheit to 102 degrees Fahrenheit. The research team that discovered the new planet believes it may have a developed atmosphere and be covered with oceans.

Curious to see how astronomers hunt for extrasolar planets, I took the trip up the long, windy road to the top of Mt. Hamilton. It is a beautiful drive up to the observatory and it's wise to take your time so that you can enjoy the ideal California landscape of rolling hills dotted with oak trees and wildflowers. The 365 sharp curves along the 19 mile road will also slow you down.

At the top of Mt. Hamilton are several white domes dotting the 4,200-foot crestline. From Lick Observatory you can see forever– not just across the vast northern California landscape but out into our own galaxy and beyond. By coincidence, the night I was there astronomer Debra Fischer confirmed five new planets outside our solar system. The discovery was the culmination of five years of watching these specific planets from Lick's 3-meter Shane Telescope. Fischer and her colleague Geoff Marcy will publish their findings soon. These two astronomers are obsessed with looking for exoplanets, they just returned from the Andes mountains in Chile, where they spent day and night for several weeks hunting for planets. But Fischer and Marcy are not the only ones who have caught the exoplanet bug.

Scientists at NASA are nearly ready to launch a bus-sized telescope into space. NASA's Kepler Telescope which will orbit our sun, will be trained on a hundred thousand stars at a time. It may be our best chance yet for finding new life in outer space. The telescope is scheduled to launch in February. Kepler will find planets by looking for tiny dips in the brightness of a star caused by planetary transits.

Make sure to check out our photo set on Flickr which includes: photos of Lick Observatory; the Kepler testbed at NASA Ames in Mountain View; the Kepler spacecraft assembly in Boulder, Colorado; and artists' renditions of exoplanets discussed in this report.You can also hear our radio story on the search for exoplanets, watch the Planet Hunters TV story online and find additional links and resources.

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