Hubble maps temperature, water vapour on wild exoplanet

An artist's conception of exoplanet WASP-43b orbiting an orange dwarf star roughly 260 light-years from Earth. 

About twice as massive as Jupiter, WASP-43b heats up to about 3,000 degrees Fahrenheit during its closest passes by its star, a temperature hot enough to melt steel. 

Credit: NASA, ESA

A team of scientists including a University of Colorado Boulder professor used NASA's Hubble Space Telescope to make the most detailed global map yet of the glow from a giant, oddball planet orbiting another star, an object twice as massive as Jupiter and hot enough to melt steel.

The Hubble observations show that the planet, called WASP-43b, is no place to call home.

It's a world of extremes, where winds howl at the speed of sound from a 3,000-degree-Fahrenheit dayside to a pitch-black nightside when temperatures plunge to a relatively cool 1,000 degrees Fahrenheit, still hot enough to melt silver.

The map provides information about temperatures at different layers of the planet's atmosphere and traces the amount and distribution of water present.

The findings have ramifications for understanding the atmospheric dynamics and the formation of giant planets like Jupiter, said team leader Jacob Bean of the University of Chicago.

"These measurements have opened the door for a new kind of comparative planetology."

A paper on the subject was published online Oct. 9 in Science Express.

As a ball of predominately hot hydrogen gas, there are no surface features on WASP-43b like oceans or continents that can be used to track its rotation, said CU-Boulder Assistant Professor Jean-Michel Désert, second author on the new study.

Only the drastic temperature difference between the dayside and nightside can be used by remote observers to mark the passage of a day on the strange, gaseous planet, he said.

"WASP-43b is extreme in many ways," said Désert. "It's the size of Jupiter with twice its mass. Its orbit around its host star, called an orange dwarf, takes only about 19 hours – the blink of an eye compared to the 365 days it takes Earth to orbit the sun."

Désert said the study is compelling to those trying to understand planetary formation. "Basically it is like taking a planet like Jupiter into a giant laboratory, then warming it at such a high temperature that all of the atoms and molecules comprising its atmosphere are in a gas phase."

Another bizarre thing about WASP-43b is its orbit. It orbits so close to its host star it always "shows" the same hemisphere, a phenomena similar to the orbit of the moon around Earth that is known as known as "tidal locking."

Discovered in 2011, WASP-43b is 260 light-years away, too distant to be photographed, but because its orbit is observed "edge-on" to Earth, astronomers detected it by observing regular dips in the light of its parent star as the planet passed in front of it, said Désert of CU-Boulder's Department of Astrophysical and Planetary Sciences.

More information: "Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy," by K.B. Stevenson et al. Science, 2014. www.sciencemag.org/lookup/doi/… 1126/science.1256758

NASA TESS: Exoplanet Mission to Hunt Down Earth-sized Worlds

Set to launch in 2017, NASA's Transiting Exoplanet Survey Satellite (TESS) will monitor more than half a million stars over its two-year mission, with a focus on the smallest, brightest stellar objects.

During its observations, TESS is expected to find more than 3,000 new planets outside of our solar system, most of which will be possible for ground-based telescopes to observe.

"Bright host stars are the best ones for follow-up studies of their exoplanets to pin down planet masses, and to characterize planet atmospheres," said TESS principal investigator George Ricker, of the Massachusetts Institute of Technology's Kavli Institute for Astrophysics.

"TESS should be able to find over 200 Earths and super-Earths, defined as being twice the size of Earth," said Peter Sullivan, a physics doctoral student at MIT.

"Ten to 20 of those are habitable-zone planets.”

Sullivan, who works with Ricker on TESS, led an analysis of the number of planets TESS would likely find based on the number and types of planets found by NASA's Kepler mission.

Kepler focused on a single region of the sky and studied all transiting planets within it.

TESS, on the other hand, will examine almost the entire sky over its two-year mission, but capture only the brightest stars, many of which are expected to host terrestrial planets.

NASA's Transiting Exoplanet Survey Satellite (TESS) mission is scheduled to launch in 2017 to hunt for Earth-size alien worlds.

Credit: MIT KAVLI Institute for Astrophysics and Space Research

TESS will travel around Earth in a highly elliptical orbit that will range as distant as the moon.

Along the way, it will use four cameras to observe a swatch of sky running from the celestial equator to the poles.

TESS will observe each swatch for approximately a month before switching to the next region.



Courtney Dressing, a doctoral student at the Harvard-Smithsonian Center for Astrophysics, compares the satellite's observations to peeling an apple in vertical cuts that overlap near the stem.

Because of the overlap, stars near the pole will be observed for more than 100 days, while stars near the equator will be observed for only 27 days.

Dressing worked on a second model, based on Sullivan's work, that predicts the number of planets near Earth that pass between the sun and their host star.

"We predicted there should be about 100 transiting planets within 20 parsecs [about 65 light-years], and that roughly three of them should lie within the habitable zone of their host stars," Dressing said.

Not all of these planets will be detectable to the TESS mission. According to Dressing, the new telescope will be most sensitive to small planets orbiting stars 20 to 50 percent the size of our sun.

NASA Chandra: Exoplanet WASP-18b makes star act deceptively old

A new study from NASA’s Chandra X-ray Observatory shows that a giant exoplanet, WASP-18b, is making the star that it orbits very closely act much older than it actually is. 

This artist’s illustration depicts WASP-18b and its star, which are about 330 light years away 

Credit: NASA/CXC/M. Weiss

A planet may be causing the star it orbits to act much older than it actually is, according to new data from NASA's Chandra X-ray Observatory. This discovery shows how a massive planet can affect the behavior of its parent star.

The star, WASP-18, and its planet, WASP-18b, are located about 330 light-years from Earth. WASP-18b has a mass about 10 times that of Jupiter and completes one orbit around its star in less than 23 hours, placing WASP-18b in the "hot Jupiter" category of exoplanets, or planets outside our solar system.

WASP-18b is the first known example of an orbiting planet that has apparently caused its star, which is roughly the mass of our sun, to display traits of an older star.

"WASP-18b is an extreme exoplanet," said Ignazio Pillitteri of the Istituto Nazionale di Astrofisica (INAF)-Osservatorio Astronomico di Palermo in Italy, who led the study.

"It is one of the most massive hot Jupiters known and one of the closest to its host star, and these characteristics lead to unexpected behaviour. This planet is causing its host star to act old before its time."

Pillitteri's team determined WASP-18 is between 500 million and 2 billion years old, based on theoretical models and other data.

While this may sound old, it is considered young by astronomical standards. By comparison, our sun is about 5 billion years old and thought to be about halfway through its lifetime.

Younger stars tend to be more active, exhibiting stronger magnetic fields, larger flares, and more intense X-ray emission than their older counterparts.

Magnetic activity, flaring, and X-ray emission are linked to the star's rotation, which generally declines with age.

However, when astronomers took a long look with Chandra at WASP-18 they didn't detect any X-rays.

Using established relations between the magnetic activity and X-ray emission of stars, as well as its actual age, researchers determined WASP-18 is about 100 times less active than it should be.

"We think the planet is aging the star by wreaking havoc on its innards," said co-author Scott Wolk of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

The researchers argue that tidal forces created by the gravitational pull of the massive planet, similar to those the moon has on Earth's tides, but on a much larger scale, may have disrupted the magnetic field of the star.

The strength of the magnetic field depends on the amount of convection in the star, or how intensely hot gas stirs the interior of the star.

"The planet's gravity may cause motions of gas in the interior of the star that weaken the convection," said co-author Salvatore Sciortino also of INAF-Osservatorio Astronomico di Palermo in Italy.

"This has a domino effect that results in the magnetic field becoming weaker and the star to age prematurely."

WASP-18 is particularly susceptible to this effect because its convection zone is narrower than most stars.

This makes it more vulnerable to the impact of tidal forces that tug at it.

The effect of tidal forces from the planet may also explain an unusually high amount of Lithium found in earlier optical studies of WASP-18.

Lithium is usually abundant in younger stars, but over time convection carries lithium to the hot inner regions of a star, where it is destroyed by nuclear reactions.

If there is less convection, the lithium does not circulate into the interior of the star as much, allowing more lithium to survive.

These results were published in the July issue of Astronomy and Astrophysics and are available online.

More information: For a preprint of the study results in The Astrophysical Journal, visit: arxiv.org/abs/1406.2620

Half of all exoplanet host stars are binaries

The Kepler field of view, located between two bright stars in the summer triangle, rising over the WIYN 3.5m telescope in southern Arizona.

Imagine living on an exoplanet with two suns. One, you orbit and the other is a very bright, nearby neighbour looming large in your sky.

With this "second sun" in the sky, nightfall might be a rare event, perhaps only coming seasonally to your planet. A new study suggests that this could be far more common than we realized.

The NASA Kepler Space Telescope has confirmed about 1000 exoplanets, as well as thousands more stars considered "Kepler objects of interest", dubbed KOIs, stars that could possibly host planets.

Until now, there has been an unanswered question about exoplanet host stars; how many host stars are binaries?

Binary stars have long been known to be commonplace, about half the stars in the sky are believed to consist of two stars orbiting each other.

So, are stars with planets equally likely to have a companion star, or do companion stars affect the formation of planets?

A team of astronomers, led by Dr. Elliott Horch, Southern Connecticut State University, have shown that stars with exoplanets are just as likely to have a binary companion: that is, 40% to 50% of the host stars are actually binary stars.

As Dr. Horch said, "It's interesting and exciting that exoplanet systems with stellar companions turn out to be much more common than was believed even just a few years ago."

Their study makes use of very high spatial resolution observations that were carried out on the WIYN 3.5m telescope located on Kitt Peak in southern Arizona and the Gemini North telescope located on Mauna Kea in Hawaii.

The technique used by the team is called speckle imaging and consists of obtaining digital images of a small portion of the sky surrounding a star of interest, 15 to 25 times a second.

The images are then combined in software using a complex set of algorithms, yielding a final picture of the star with a resolution better that that of the Hubble space telescope.

By using this technique, the team can detect companion stars that are up to 125 times fainter than the target, but only 0.05 arcseconds away.

For the majority of the Kepler stars, this means companion stars with a true separation of a few to about 100 times the Sun-Earth distance (termed the astronomical distance, or AU).

By noting the occurrence rate of these true binary companion stars, the discoveries can be extended to show that half of the stars that host exoplanets are probably binaries.

Artist’s concept of exoplanets in a two-stars system. Credit: NASA/JPL-Caltech/T. Pyle

Co-author of the study, Dr. Steve B. Howell (NASA Ames Research Center), commented, "An interesting consequence of this finding is that in the half of the exoplanet host stars that are binary we can not, in general, say which star in the system the planet actually orbits."

Steve B. Howell

Kepler has discovered a number of circumbinary planets, that is, a planet that orbits both stars in very close binary systems.

There also exist exoplanets that are known to orbit one of the stars in very wide binary systems.

If the two stars are very close to each other and the planet far away, a circumbinary planet will be reminiscent of Tatooine in Star Wars.

If instead the exoplanet orbits one of the stars in a very wide pair, the companion star might appear simply as a bright star among others in the night sky.

"Somewhere there will be a transition between these two scenarios," Howell said," but we are far from knowing where."

In a study like this, it is critical to rule out faint companions that are only in the line of sight with the KOI star.

To allow for these possibilities, the team performed a model simulation that relied on known statistical properties of binary star systems and line of sight companions.

The results suggest that the large majority of the stellar companions to KOIs are true bound companions, not line of sight stars unconnected with the system.

More Information: "LIMITS ON STELLAR COMPANIONS TO EXOPLANET HOST STARS WITH ECCENTRIC PLANETS" has been accepted for publication in the Astrophysical Journal: Authors - Stephen R. Kane et al. 2014 ApJ 785 93 doi:10.1088/0004-637X/785/2/93.

Exoplanet measured with remarkable precision

Barely 30 years ago, the only planets astronomers had found were located right here in our own solar system.

The Milky Way is chock-full of stars, millions of them similar to our own sun. Yet the tally of known worlds in other star systems was exactly zero.

What a difference a few decades can make.

As 2014 unfolds, astronomers have not only found more than a thousand "exoplanets" circling distant suns, but also they're beginning to make precise measurements of them.

The old void of ignorance about exoplanets is now being filled with data precise to the second decimal place.

A team led by Sarah Ballard, a NASA Carl Sagan Fellow at the University of Washington in Seattle, recently measured the diameter of a "super Earth" to within an accuracy of 148 miles total or about 1 percent, remarkable accuracy for an exoplanet located about 300 light years from Earth.

"It does indeed seem amazing," says Ballard. "The landscape of exoplanet research has changed to an almost unrecognizable degree since I started graduate school in 2007."

To size up the planet, named "Kepler 93 b," Ballard used data from NASA's Kepler and Spitzer Space Telescopes.

First, Kepler discovered the planet. As seen from Earth, Kepler 93 b passes directly in front of its parent star, causing the starlight to dim during the transit.

That dimming, which occurs once per orbit, is what allowed Kepler mission scientists to find the planet in the first place.

Kepler Space Telescope

Next, both Spitzer and Kepler Space Telescope recorded multiple transits at visible and infrared wavelengths.

Data from the observatories agreed: Kepler 93 b was really a planet and not some artefact of stellar variability.

Ballard then knew that by looking carefully at the light curve she could calculate the size of the planet relative to the star.

At that point, the only missing piece was the diameter of the star itself.

"The precision with which we measured the size of the planet is linked directly to our measurement of the star," says Ballard. "And we measured the star using a technique called astero-seismology."

Most people have heard of "seismology," the study of seismic waves moving through the Earth. "We can learn a lot about the structure of our planet by studying seismic waves," she says.

Asteroseismology is the same thing, except for stars: The outer layers of stars boil like water on top of a hot stove. Those convective motions create seismic waves that bounce around inside the core, causing the star to ring like an enormous bell. Kepler can detect that "ringing," which reveals itself as fluctuations in a star's brightness.

Ballard's colleague, University of Birmingham professor Bill Chaplin led the asteroseismic analysis for Kepler-93 b.

"By analyzing the seismic modes of the star, he was able to deduce its radius and mass to an accuracy of a percent," she says.

The new measurements confirm that Kepler-93 b is a "super-Earth" sized exoplanet, with a diameter about one-and-a-half times the size of our planet.

Previous measurements by the Keck Observatory in Hawaii had put Kepler-93 b's mass at about 3.8 times that of Earth.

The density of Kepler-93 b, derived from its mass and newly obtained radius, suggests the planet is very likely made of iron and rock, like Earth itself.

Although super-Earths are common in the galaxy, none exist in our solar system. That makes them tricky to study.

Ballard's team has shown, however, that it is possible to learn a lot about an exoplanet even when it is very far away.

Robo-AO laser: Laser-wielding robot probes exoplanet systems

The ultraviolet Robo-AO laser originating from the Palomar 1.5-meter Telescope dome. 

Although the laser is invisible to the human eye, it shows up in digital SLR cameras once their internal UV blocking filters are removed. 

The apparent colour of the laser beam is a result of the UV light leaking through the camera's red, green and blue pixel filters by slightly different amounts.

An international team, including Dr. Christoph Baranec of the University of Hawaii at Manoa's Institute for Astronomy, is using the world's first robotic laser adaptive optics system, Robo-AO, to explore thousands of exoplanet systems (planets around other stars) at resolutions approaching those of the Hubble Space Telescope.

The results, which shed light on the formation of exotic exoplanet systems and confirm hundreds of exoplanets, have just been published in the Astrophysical Journal.

The design and operation of the unprecedented instrument has just been published in the Astrophysical Journal Letters.

Laser adaptive optics systems are used by terrestrial telescopes to remove the image-blurring effects of Earth's turbulent atmosphere, thereby capturing much sharper images than are otherwise possible from the ground.

Baranec, Robo-AO's principal investigator and lead author of the Astrophysical Journal Letter, led the development of the innovative Robo-AO system on the Palomar 1.5-meter Telescope.

It is the world's first instrument that fully automates the complex and often inefficient operation of laser adaptive optics.

"We're using Robo-AO's extreme efficiency to survey in exquisite detail all of the candidate exoplanet host stars that have been discovered by NASA's Kepler mission," said Baranec.

"While Kepler has an unrivaled ability to discover exoplanets that pass between us and their host star, it comes at the price of reduced image quality, and that's where Robo-AO excels."


In fact, analysis of the first part of the Robo-AO/Kepler exoplanet host survey is already yielding surprising results.

Nicholas Law

"We're finding that "hot Jupiters," rare giant exoplanets in tight orbits, are almost three times more likely to be found in wide binary star systems than other exoplanets, shedding light on how these exotic objects formed," said Prof. Nicholas Law (University of North Carolina at Chapel Hill's College of Arts and Sciences), Robo-AO's project scientist and lead author on the Astrophysical Journal paper.

"Going further, Robo-AO's unique capabilities have allowed us to discover even rarer objects: binary star systems where each star has a Kepler-detected planetary system of its own.

These systems will be uniquely interesting for studies of how the planets formed, and for science fiction about what life would be like with another planetary system right next door," continued Law.

Indeed, the first Robo-AO survey, covering 715 Kepler candidate exoplanet hosts, is the single largest scientific adaptive optics survey ever.

That record won't stand for very long, as the Robo-AO team is extending the survey to image each and every of the 4,000 Kepler candidate exoplanet hosts, and is ready to observe exoplanet hosts from Kepler's new K2 mission as they are discovered.

The Robo-AO laser being used to probe exoplanet host stars in the Kepler field. Images of the stars on the Robo-AO science camera (inset) are the same size as a single Kepler pixel. Credit: Robo-AO Collaboration.

The key to Robo-AO's success is its efficiency, allowing it to observe hundreds more targets per night than conventional adaptive optics systems.

So far, the Robo-AO system has already been used to make over 13,000 observations. "The automation of laser adaptive optics has allowed us to tackle scientific questions that were unimaginable just a few years ago.

We can now observe tens of thousands of objects at Hubble-Space-Telescope-like resolution in short periods of time," Baranec said.

"Now that the technology has been proven, we're looking to bring it to the pristine skies of Maunakea, Hawaii, where it will be even more powerful."

More information: Christoph Baranec et al. "HIGH-EFFICIENCY AUTONOMOUS LASER ADAPTIVE OPTICS." The Astrophysical Journal Letters Volume 790 Number 1, 2014 ApJ 790 L8 DOI: 10.1088/2041-8205/790/1/L8

Nicholas M. Law et al. "ROBOTIC LASER ADAPTIVE OPTICS IMAGING OF 715 KEPLER EXOPLANET CANDIDATES USING ROBO-AO" The Astrophysical Journal Volume 791 Number 1. 2014 ApJ 791 35 DOI: 10.1088/0004-637X/791/1/35

Kepler-186f: First potentially habitable Earth-sized planet confirmed - water

The artist's concept depicts Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone, a range of distances from a star where liquid water might pool on the surface of an orbiting planet.

The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zone of other stars and signals a significant step closer to finding a world similar to Earth.

The artistic concept of Kepler-186f is the result of scientists and artists collaborating to help imagine the appearance of these distant worlds. 

Credit: Danielle Futselaar.

The first Earth-sized exoplanet orbiting within the habitable zone of another star has been confirmed by observations with both the W. M. Keck Observatory and the Gemini Observatory.

The initial discovery, made by NASA's Kepler Space Telescope, is one of a handful of smaller planets found by Kepler and verified using large ground-based telescopes.

It also confirms that Earth-sized planets do exist in the habitable zone of other stars.

"What makes this finding particularly compelling is that this Earth-sized planet, one of five orbiting this star, which is cooler than the Sun, resides in a temperate region where water could exist in liquid form," says Elisa Quintana of the SETI Institute and NASA Ames Research Center who led the paper published in the current issue of the journal Science.

The region in which this planet orbits its star is called the habitable zone, as it is thought that life would most likely form on planets with liquid water.

Steve Howell, Kepler's Project Scientist and a co-author on the paper, adds that neither Kepler (nor any telescope) is currently able to directly spot an exoplanet of this size and proximity to its host star.

"However, what we can do is eliminate essentially all other possibilities so that the validity of these planets is really the only viable option."

With such a small host star, the team employed a technique that eliminated the possibility that either a background star or a stellar companion could be mimicking what Kepler detected.

To do this, the team obtained extremely high spatial resolution observations from the eight-meter Gemini North telescope on Mauna Kea in Hawai`i using a technique called speckle imaging, as well as adaptive optics (AO) observations from the ten-meter Keck II telescope, Gemini's neighbour on Mauna Kea.

Together, these data allowed the team to rule out sources close enough to the star's line-of-sight to confound the Kepler evidence, and conclude that Kepler's detected signal has to be from a small planet transiting its host star.

The diagram compares the planets of the inner solar system to Kepler-186, a five-planet system about 500 light-years from Earth in the constellation Cygnus. 

The five planets of Kepler-186 orbit a star classified as a M1 dwarf, measuring half the size and mass of the sun. 

The Kepler-186 system is home to Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone—a range of distances from a star where liquid water might pool on the surface of an orbiting planet. 

The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zone of other stars and signals a significant step closer to finding a world similar to Earth. 

Kepler-186f is less than ten percent larger than Earth in size, but its mass and composition are not known. 

Kepler-186f orbits its star once every 130-days and receives one-third the heat energy that Earth does from the sun, placing it near the outer edge of the habitable zone. 

The inner four companion planets all measure less than fifty percent the size of Earth. Kepler-186b, Kepler-186c, Kepler-186d, and Kepler-186e, orbit every three, seven, 13, and 22 days, respectively, making them very hot and inhospitable for life as we know it. 

The Kepler space telescope, which simultaneously and continuously measured the brightness of more than 150,000 stars, is NASA's first mission capable of detecting Earth-size planets around stars like our sun. 

Kepler does not directly image the planets it detects. The space telescope infers their existence by the amount of starlight blocked when the orbiting planet passes in front of a distant star from the vantage point of the observer. 

The artistic concept of Kepler-186f is the result of scientists and artists collaborating to help imagine the appearance of these distant Credit: Credit: NASA Ames/SETI Institute/JPL-CalTech.

More information: "An Earth-Sized Planet in the Habitable Zone of a Cool Star," by E.V. Quintana et al. Science, 2014.

Exoplanet Astronomers: 'Tilt-a-worlds' could harbour life

Tilted orbits such as those shown might make some planets wobble like a top that’s almost done spinning, an effect that could maintain liquid water on the surface, thus giving life a chance. 

Credit: NASA

A fluctuating tilt in a planet's orbit does not preclude the possibility of life, according to new research by astronomers at the University of Washington, Utah's Weber State University and NASA. In fact, sometimes it helps.

That's because such "tilt-a-worlds," as astronomers sometimes call them, turned from their orbital plane by the influence of companion planets, are less likely than fixed-spin planets to freeze over, as heat from their host star is more evenly distributed.

This happens only at the outer edge of a star's habitable zone, the swath of space around it where rocky worlds could maintain liquid water at their surface, a necessary condition for life.

Further out, a "snowball state" of global ice becomes inevitable, and life impossible.

The findings, which are published online and will appear in the April issue of Astrobiology, have the effect of expanding that perceived habitable zone by 10 to 20 percent.

And that in turn dramatically increases the number of worlds considered potentially right for life.

Such a tilt-a-world becomes potentially habitable because its spin would cause poles to occasionally point toward the host star, causing ice caps to quickly melt.

Rory Barnes

"Without this sort of 'home base' for ice, global glaciation is more difficult," said UW astronomer Rory Barnes.

"So the rapid tilting of an exoplanet actually increases the likelihood that there might be liquid water on a planet's surface."

John Armstrong

Barnes is second author on the paper. First author is John Armstrong of Weber State, who earned his doctorate at the UW.

Earth and its neighbour planets occupy roughly the same plane in space. But there is evidence, Barnes said, of systems whose planets ride along at angles to each other.

As such, "they can tug on each other from above or below, changing their poles' direction compared to the host star."

The team used computer simulations to reproduce such off-kilter planetary alignments, wondering, he said, "what an Earthlike planet might do if it had similar neighbours."

Their findings also argue against the long-held view among astronomers and astrobiologists that a planet needs the stabilizing influence of a large moon, as Earth has, to have a chance at hosting life.

"We're finding that planets don't have to have a stable tilt to be habitable," Barnes said. Minus the moon, he said, Earth's tilt, now at a fairly stable 23.5 degrees, might increase by 10 degrees or so. Climates might fluctuate, but life would still be possible.

"This study suggests the presence of a large moon might inhibit life, at least at the edge of the habitable zone."

The work was done through the UW's Virtual Planetary Laboratory, an interdisciplinary research group that studies how to determine if exoplanets—those outside the solar system—might have the potential for life.

"The research involved orbital dynamics, planetary dynamics and climate studies. It's bigger than any of those disciplines on their own," Barnes said.

Armstrong said that expanding the habitable zone might almost double the number of potentially habitable planets in the galaxy.

Applying the research and its expanded habitable zone to our own celestial neighborhood for context, he said, "It would give the ability to put Earth, say, past the orbit of Mars and still be habitable at least some of the time, and that's a lot of real estate."

More information: Paper: online.liebertpub.com/doi/abs/10.1089/ast.2013.1129

NASA Kepler finds a very wobbly planet - Kepler-413b Binary System

This illustration shows the unusual orbit of planet Kepler-413b around a close pair of orange and red dwarf stars. 

The planet's 66-day orbit is tilted 2.5 degrees with respect to the plane of the binary star's orbit. 

The orbit of the planet wobbles around the central stars over 11 years, an effect called precession. 

This planet is also very unusual in that it can potentially precess wildly on its spin axis, much like a child's top. 

Credit: NASA, ESA, and A. Feild (STScI)

Imagine living on a planet with seasons so erratic you would hardly know whether to wear Bermuda shorts or a heavy overcoat.

That is the situation on a weird, wobbly world found by NASA's planet-hunting Kepler space telescope.

The planet, designated Kepler-413b, precesses, or wobbles, wildly on its spin axis, much like a child's top.

NASA's planet-hunting Kepler space telescope

The tilt of the planet's spin axis can vary by as much as 30 degrees over 11 years, leading to rapid and erratic changes in seasons.

In contrast, Earth's rotational precession is 23.5 degrees over 26,000 years.

Researchers are amazed that this far-off planet is precessing on a human timescale.

Precession : the axis of rotation of a precessing body itself rotates around another axis.

Kepler 413-b is located 2,300 light-years away in the constellation Cygnus. It circles a close pair of orange and red dwarf stars every 66 days.

Constellation Cygnus

The planet's orbit around the binary stars appears to wobble, too, because the plane of its orbit is tilted 2.5 degrees with respect to the plane of the star pair's orbit.

As seen from Earth, the wobbling orbit moves up and down continuously.

Kepler finds planets by noticing the dimming of a star or stars when a planet transits, or travels in front of them.

Normally, planets transit like clockwork. Astronomers using Kepler discovered the wobbling when they found an unusual pattern of transiting for Kepler-413b.

Veselin Kostov

"Looking at the Kepler data over the course of 1,500 days, we saw three transits in the first 180 days—one transit every 66 days—then we had 800 days with no transits at all. After that, we saw five more transits in a row," said Veselin Kostov, the principal investigator on the observation.

Kostov is affiliated with the Space Telescope Science Institute (STSCI) and Johns Hopkins University in Baltimore, Md.

The next transit visible from Earth's point of view is not predicted to occur until 2020.

This is because the orbit moves up and down, a result of the wobbling, in such a great degree that it sometimes does not transit the stars as viewed from Earth.

Astronomers are still trying to explain why this planet is out of alignment with its stars. There could be other planetary bodies in the system that tilted the orbit.

Or, it could be that a third star nearby that is a visual companion may actually be gravitationally bound to the system and exerting an influence.

Peter McCullough

"Presumably there are planets out there like this one that we're not seeing because we're in the unfavourable period," said Peter McCullough, a team member with the Space Telescope Science Institute (STSCI) and Johns Hopkins University.

"And that's one of the things that Veselin is researching: Is there a silent majority of things that we're not seeing?"

Even with its changing seasons, Kepler-413b is too warm for life as we know it.

Because it orbits so close to the stars, its temperatures are too high for liquid water to exist, making it inhabitable.

It also is a super Neptune—a giant gas planet with a mass about 65 times that of Earth—so there is no surface on which to stand.

First Exoplanet found around solar twin in star cluster

This artist's impression shows one of the three newly discovered planets in the star cluster Messier 67. 

In this cluster the stars are all about the same age and composition as the Sun. 

This makes it a perfect laboratory to study how many planets form in such a crowded environment. 

Very few planets in clusters are known and this one has the additional distinction of orbiting a solar twin -- a star that is almost identical to the Sun in all respects. Credit: ESO/L. Calçada

ESO HARPS detector cryostat

Astronomers have used ESO's HARPS planet hunter in Chile, along with other telescopes around the world, to discover three planets orbiting stars in the cluster Messier 67.

Although more than one thousand planets outside the Solar System are now confirmed, only a handful have been found in star clusters.

Remarkably one of these new exoplanets is orbiting a star that is a rare solar twin—a star that is almost identical to the Sun in all respects.

Planets orbiting stars outside the Solar System are now known to be very common.

These exoplanets have been found orbiting stars of widely varied ages and chemical compositions and are scattered across the sky but, up to now, very few planets have been found inside star clusters.

This is particularly odd as it is known that most stars are born in such clusters. Astronomers have wondered if there might be something different about planet formation in star clusters to explain this strange paucity.

Anna Brucalassi

Anna Brucalassi (Max Planck Institute for Extraterrestrial Physics, Garching, Germany), lead author of the new study, and her team wanted to find out more.

"In the Messier 67 star cluster the stars are all about the same age and composition as the Sun. This makes it a perfect laboratory to study how many planets form in such a crowded environment, and whether they form mostly around more massive or less massive stars."

The team used the HARPS planet-finding instrument on ESO's 3.6-metre telescope at the La Silla Observatory.

These results were supplemented with observations from several other observatories around the world.

They carefully monitored 88 selected stars in Messier 67 over a period of six years to look for the tiny telltale motions of the stars towards and away from Earth that reveal the presence of orbiting planets.

The small faint constellation Cancer is rich in open clusters and double stars. 

Credit: Starry Night Software, Space.com

This cluster lies about 2500 light-years away in the constellation of Cancer (The Crab) and contains about 500 stars.

Many of the cluster stars are fainter than those normally targeted for exoplanet searches and trying to detect the weak signal from possible planets pushed HARPS to the limit.

Three planets were discovered, two orbiting stars similar to the Sun and one orbiting a more massive and evolved red giant star.

The first two planets both have about one third the mass of Jupiter and orbit their host stars in seven and five days respectively. The third planet takes 122 days to orbit its host and is more massive than Jupiter.

The first of these planets proved to be orbiting a remarkable star—it is one of the most similar solar twins identified so far and is almost identical to the Sun.

It is the first solar twin in a cluster that has been found to have a planet.

Two of the three planets are "hot Jupiters"—planets comparable to Jupiter in size, but much closer to their parent stars and hence much hotter.

All three are closer to their host stars than the habitable zone where liquid water could exist.

Luca Pasquini

"These new results show that planets in open star clusters are about as common as they are around isolated stars—but they are not easy to detect," adds Luca Pasquini (ESO, Garching, Germany), co-author of the new paper.

"The new results are in contrast to earlier work that failed to find cluster planets, but agrees with some other more recent observations. We are continuing to observe this cluster to find how stars with and without planets differ in mass and chemical makeup."

More information: This research was presented in a paper entitled "Three planetary companions around M67 stars", by A. Brucalassi et al., to appear in the journal Astronomy & Astrophysics. (PDF)

Gemini Planet Imager: Powerful exoplanet camera turns skyward

Gemini Planet Imager's first light image of Beta Pictoris b, a planet orbiting the star Beta Pictoris. 

The star, Beta Pictoris, is blocked in this image by a mask so its light doesn't interfere with the light of the planet. 

In addition to the image, GPI obtains a spectrum from every pixel element in the field of view to allow scientists to study the planet in great detail. 

Beta Pictoris b is a giant planet – several times larger than Jupiter -- and is approximately ten million years old. 

These near-infrared images (1.5-1.8 microns) show the planet glowing in infrared light from the heat released in its formation. 

The bright star Beta Pictoris is hidden behind a mask in the center of the image. 

Credit: Processing by Christian Marois, NRC Canada.

After nearly a decade of development, construction, and testing, the world's most advanced instrument for directly imaging and analyzing planets around other stars is pointing skyward and collecting light from distant worlds.

The instrument, called the Gemini Planet Imager (GPI), was designed, built, and optimized for imaging faint planets next to bright stars and probing their atmospheres.

It will also be a powerful tool for studying dusty, planet-forming disks around young stars. It is the most advanced such instrument to be deployed on one of the world's biggest telescopes – the 8-meter Gemini South telescope in Chile.

Bruce Macintosh

"Even these early first-light images are almost a factor of 10 better than the previous generation of instruments. In one minute, we are seeing planets that used to take us an hour to detect," says Bruce Macintosh of the Lawrence Livermore National Laboratory who led the team that built the instrument.

GPI detects infrared (heat) radiation from young Jupiter-like planets in wide orbits around other stars, those equivalent to the giant planets in our own Solar System not long after their formation. Every planet GPI sees can be studied in detail.

"Most planets that we know about to date are only known because of indirect methods that tell us a planet is there, a bit about its orbit and mass, but not much else," says Macintosh.

"With GPI we directly image planets around stars – it's a bit like being able to dissect the system and really dive into the planet's atmospheric makeup and characteristics."

Stephen Goodsell

GPI carried out its first observations last November – during an extremely trouble-free debut for an extraordinarily complex astronomical instrument the size of a small car.

"This was one of the smoothest first-light runs Gemini has ever seen" says Stephen Goodsell, who manages the project for the observatory.

This is Gemini Planet Imager's first light image of the light scattered by a disk of dust orbiting the young star HR4796A. 

This narrow ring is thought to be dust from asteroids or comets left behind by planet formation; some scientists have theorized that the sharp edge of the ring is defined by an unseen planet.

The left image (1.9-2.1 microns) shows normal light, including both the dust ring and the residual light from the central star scattered by turbulence in the Earth's atmosphere. 

The right image shows only polarized light. Leftover starlight is unpolarized and hence removed from this image. 

The light from the back edge of the disk is strongly polarized as it scatters towards us.

Credit: Processing by Marshall Perrin, Space Telescope Science Institute.

For GPI's first observations, the team targeted previously known planetary systems, including the well-known Beta Pictoris system; in it GPI obtained the first-ever spectrum of the very young planet Beta Pictoris b.

The first-light team also used the instrument's polarization mode – which can detect starlight scattered by tiny particles – to study a faint ring of dust orbiting the very young star HR4796A.

With previous instruments, only the edges of this dust ring, (which may be the debris remaining from planet formation), could be seen, but with GPI astronomers can follow the entire circumference of the ring.

First detection of a predicted unseen exoplanet

Artist impression of the Kepler-88 system. 

Credit: Alexandre Santerne (CAUP)/ESO/Serge Brunier

A team of European astronomers, including EXOEarths member Alexandre Santerne (CAUP), used the SOPHIE spectrograph at the Observatoire de Haute-Provence (France), to confirm the presence of Kepler-88 c, an unseen planet that was previously predicted thanks to the gravitational perturbation it caused on its transiting brother planet, Kepler-88 b.

Searching for periodic transits in hundreds of thousands of stars was the primary goal of the Kepler space telescope. More than 3,500 of such periodic transits were found during the 4 years of the mission.

However, not all the planets located in the Kepler field-of-view are transiting their host star. Indeed, if their orbital plane is slightly misaligned (only a few degrees is enough) with the line of sight from the Earth, the planet is not transiting and, thus, is "unseen" from the Kepler spacecraft.

Planets that share the same host star gravitationally interact with each other. This interaction between planets can cause perturbations in the predicted times of transit of planets in multi-planetary systems.

"This is called transit timing variations (TTV)" explains the leading author of the paper, Susana Barros, a researcher at the Laboratoire d'Astrophysique de Marseille (LAM).

The TTV technique is sensitive to planets in multiple systems down to the mass of the Earth, and can therefore be used to unveil the existence of non-transiting planets, that cause perturbations in the orbital motion of transiting planets.

This is the case of the Kepler-88 system, which hosts a transiting planet (Kepler-88 b), discovered by the Kepler space telescope (NASA) , that is strongly perturbed by a non-transiting planet (Kepler-88 c).

"This system presents such strong interactions that it has earned the nickname of the king of transit variations" adds Rodrigo Diaz, a researcher working at the Geneva Observatory (OAUG).

Picture of the dome of the 1.93-m telescope of Haute-Provence Observatory (France) which hosts the SOPHIE spectrograph, with the Kepler field-of-view. 

Credit: Alexandre Santerne (CAUP)

A careful analysis of the dynamical interaction between planets, previously performed by a team led by David Nesvorny (Southwest Research Institute), predicted that this system had two planets near a two-to-one resonance (the orbital period of the unseen outer planet is exactly two times longer than the transiting inner planet).

This configuration is similar to the Earth and Mars in the solar system, with Mars orbiting the Sun in nearly 2 years.

Using the SOPHIE velocimeter, the team independently measured the mass of Kepler-88 c.

"SOPHIE is a French instrument capable of measuring the velocity of stars with a precision equivalent to the speed of a bicycle.

It has been used to characterize nearly 20 Kepler planets so far" adds Alexandre Santerne a researcher at Centro de Astrofísica da Universidade do Porto (CAUP) and responsible of the observations of Kepler targets with SOPHIE.

The article "SOPHIE Velocimetry of Kepler Transit Candidates X KOI-142c: First Radial Velocity Confirmation of a Non-Transiting Exoplanet Discovered by Transit Timing," is published 17 December 2013 in Astronomy & Astrophysics: dx.doi.org/10.1051/0004-6361/201323067