Exoplanets: Worlds Beyond Our Solar System Exoplanets: Worlds Beyond Our Solar System By Elizabeth Howell, Space.com Contributor | August 24, 2016 01:00pm ET MORE The youngest exoplanet yet discovered is less than 1 million years old and orbits Coku Tau 4, a star 420 light-years away. Astronomers inferred the planet’s presence from an enormous hole in the dusty disk that girdles the star. The hole is 10 times the size of Earth’s orbit around the Sun and probably caused by the planet clearing a space in the dust as it orbits the star. Credit: NASA Exoplanets are planets beyond our own solar system. Thousands have been discovered in the past two decades, mostly with NASA's Kepler space telescope. These worlds come in a huge variety of sizes and orbits. Some are gigantic planets hugging close to their parent stars; others are icy, some rocky. NASA and other agencies are looking for a special kind of planet: one that’s the same size as Earth, orbiting a sun-like star in the habitable zone.

The habitable zone is the range of distances from a star where a planet’s temperature allows liquid water oceans, critical for life on Earth. The earliest definition of the zone was based on simple thermal equilibrium, but current calculations of the habitable zone include many other factors, including the greenhouse effect of a planet’s atmosphere. This makes the boundaries of a habitable zone "fuzzy." Astronomers announced in August 2016 that they may have found such a planet orbiting Proxima Centauri . The newfound world, known as Proxima b, is about 1.3 times more massive than Earth, which suggests that the exoplanet is a rocky world, researchers said. The planet is also in the star's habitable zone , just 4.7 million miles (7.5 million kilometers) from its host star. It completes one orbit every 11.2 Earth-days. As a result, it's likely that the exoplanet is tidally locked, meaning it always shows the same face to its host star, just as the moon shows only one face (the near side) to Earth.

Early discoveries While exoplanets were not confirmed until the 1990s, for years beforehand astronomers were convinced they were out there. That wasn’t just wishful thinking, but because of how slowly our own sun and other stars like it spin, University of British Columbia astrophysicist Jaymie Matthews told Space.com. Matthews, the mission scientist of occasional exoplanet telescope observer MOST (Microvariability and Oscillations of STars), was involved in some of the early exoplanet discoveries. Astronomers had an origin story for our solar system. Simply put, a spinning cloud of gas and dust (called the protosolar nebula) collapsed under its own gravity and formed the sun and planets. As the cloud collapsed, conservation of angular momentum meant the soon-to-be-sun should have spun faster and faster. But, while the sun contains 99.8 percent of the solar system's mass, the planets have 96 percent of the angular momentum. Astronomers asked themselves why the sun rotates so slowly. The young sun would have had a very strong magnetic field, whose lines of force reached out into the disk of swirling gas from which the planets would form.

These field lines connected with the charged particles in the gas, and acted like anchors, slowing down the spin of the forming sun and spinning up the gas that would eventually turn into the planets. Most stars like the sun rotate slowly, so astronomers inferred that the same “magnetic braking” occurred for them, meaning that planet formation must have occurred for them. The implication: Planets must be common around sun-like stars. For this reason and others, astronomers at first restricted their search for exoplanets to stars similar to the sun, but the first two discoveries were around a pulsar (rapidly spinning corpse of a star that died as a supernova) called PSR 1257+12, in 1992. The first confirmed discovery of a world orbiting a sun-like star, in 1995, was 51 Pegasi b — a Jupiter-mass planet 20 times closer to its sun than we are to ours. That was a surprise. But another oddity popped up seven years earlier that hinted at the wealth of exoplanets to come.

A Canadian team discovered a Jupiter-size planet around Gamma Cephei in 1988, but because its orbit was much smaller than Jupiter’s, the scientists did not claim a definitive planet detection. “We weren’t expecting planets like that. It was different enough from a planet in our own solar system that they were cautious," Matthews said. Alien Worlds Infographic 20"x60" Poster. Buy Here Credit: Space.com Store Explosion of data Most of the first exoplanet discoveries were huge Jupiter-size (or larger) gas giants orbiting close to their parent stars. That's because astronomers were relying on the radial velocity technique, which measures how much a star “wobbles” when a planet or planets orbit it. These large planets close in produce a correspondingly big effect on their parent star, causing an easier-to-detect wobble. Before the era of exoplanet discoveries, instruments could only measure stellar motions down to a kilometer per second, too imprecise to detect a wobble due to a planet. Now, some instruments can measure velocities as low as a centimeter per second, according to Matthews.

“Partly due to better instrumentation, but also because astronomers are now more experienced in teasing subtle signals out of the data.” Today, there are more than 1,000 confirmed exoplanets discovered by a single telescope: the Kepler space telescope, which reached orbit in 2009 and hunted for habitable planets for four years. Kepler uses a technique called the “transit” method, measuring how much a star's light dims when a planet passes in front of it. Kepler has revealed a cornucopia of different types of planets. Besides gas giants and terrestrial planets , it has helped define a whole new class known as “ super-Earths ”: planets that are between the size of Earth and Neptune. Some of these are in the habitable zones of their stars, but astrobiologists are going back to the drawing board to consider how life might develop on such worlds. In 2014, Kepler astronomers (including Matthews’ former student Jason Rowe) unveiled a “verification by multiplicity” method that should increase the rate at which astronomers promote candidate planets to confirmed planets.

The technique is based on orbital stability — many transits of a star occurring with short periods can only be due to planets in small orbits, since multiply eclipsing stars that might mimic would gravitationally eject each other from the system in just a few million years. While the Kepler (and French CoRoT) planet-hunting satellites have ended their original missions, scientists are still mining the data for discoveries, and there are more to come. MOST is still operating, and the NASA TESS (Transiting Exoplanet Survey Satellite), Swiss CHEOPS (Characterizing ExOPlanets Satellite) and ESA’s PLATO missions will soon pick up the transit search from space. From the ground, the HARPS spectrograph on the European Southern Observatory's La Silla 3.6-meter telescope in Chile is leading the Doppler wobble search, but there are many other telescopes in the hunt. One too-neglected example, Matthews said, is NASA’s Spitzer Space Telescope. Because it is sensitive in the infrared, it can sense the temperature profile of an exoplanet and give insights into its atmosphere. A diagram showing the relative sizes of the new alien planets discovered by Kepler, compared to Earth and Jupiter.

Credit: NASA/Tim Pyle Notable exoplanets With almost 2,000 to choose from, it’s hard to narrow down a few. Small solid planets in the habitable zone are automatically standouts, but Matthews singled out five other exoplanets that have expanded our perspective on how planets form and evolve: 51 Pegasi b: As mentioned earlier, this was the first planet to be confirmed around a sun-like star. Half the mass of Jupiter, it orbits around its sun at roughly the distance of Mercury from our Sun. 51 Pegasi b is so close to its parent star that it is likely tidally locked, meaning one side always faces the star. HD 209458 b: This was the first planet found (in 1999) to transit its star (although it was discovered by the Doppler wobble technique) and in subsequent years more discoveries piled up. It was the first planet outside the solar system for which we could determine aspects of its atmosphere, including temperature profile and the lack of clouds.

(Matthews participated in some of the observations using MOST.) 55 Cancri e: This super-Earth orbits a star that is bright enough to see by eye, meaning astronomers can study the system in more detail than almost any other. Its "year" is only 17 hours and 41 minutes long (recognized when MOST gazed at the system for two weeks in 2011). Theorists speculate that the planet may be carbon-rich, with a diamond core. HD 80606 b: At the time of its discovery in 2001, it held the record as the most eccentric exoplanet ever discovered. It is possible that its odd orbit (which is similar to Halley's Comet around the sun) may be due to the influence of another star. Its extreme orbit would make the planet’s environment extremely variable. WASP-33b: This planet was discovered in 2011 and has a sort of "sunscreen" layer — a stratosphere — that absorbs some of the visible and ultraviolet light from its parent star. Not only does this planet orbit its star "backward," but it also triggers vibrations in the star, seen by the MOST satellite.

Author Bio Elizabeth Howell, Space.com Contributor Elizabeth Howell is a contributing writer for Space.com who is one of the few Canadian journalists to report regularly on space exploration. She is pursuing a Ph.D. part-time in aerospace sciences (University of North Dakota) after completing an M.Sc. (space studies) at the same institution. She also holds a bachelor of journalism degree from Carleton University. Besides writing, Elizabeth teaches communications at the university and community college level. To see her latest projects, follow Elizabeth on Twitter at @HowellSpace . Elizabeth Howell, Space.com Contributor on Latest on Exoplanets: Worlds Beyond Our Solar System Planets Outside Our Solar System - Exoplanets Exoplanets An artist's impression of an Earth like planet outside our solar system. Exoplanet Facts Exoplanets also known as extrasolar planets, are planets which exist outside our solar system. As of May 2016, there have been 3,264 confirmed discoveries of exoplanets. In 1992 two planets orbiting a distant pulsar became the first exoplanets to be detected. In 1995 51 Pegasi B was the first exoplanet to be discovered orbiting a sun like star.

Since 2009 NASA's Kepler Misson has detected over 3,000 possible planets using its space based telescope. The habitable zone is an area around a star which is at just the right temperature to allow liquid water to exist on a planet's surface. Several possible Earth like planets, known as Super-Earths, have already been detected orbiting in the habitable zone of stars. Small Earth like planets could exist around our nearest stellar neighbor Alpha Centauri. Only two exoplanets have ever been directly observed using Earth based telescopes. Exoplanets - The Search for Life Could there possibly be another Earth like planet in our galaxy? Are we alone in the Universe? This is a question mankind has pondered for centuries, but only now do we have the technology to begin to answer that age old question. The search is truly on to find another Earth like world but as yet we're still the only known planet in the Universe where life exists. New evidence being compiled suggests that its highly unlikely that Earth is unique, it is estimated there are habitable planets around 10 to 20% of the stars in our galaxy.

When you consider that there are 200 billion stars in the Milky Way then it could possibly contain billions of worlds similar to our own. The problem with Earth like planets is that they're very small, making them extremely difficult to detect, even so scientists are predicting that its only a matter of time before one is discovered somewhere in our galaxy. Types of Exoplanets Gas Giants Gas giants are planets similar to Jupiter and Saturn. Their mass is mostly composed of hydrogen and helium with possibly a dense rocky or metallic core. Exoplanets with a mass of more than 10 times the Earth are classified as gas giants. Around a quarter of the planets that have been discovered outside our solar system are gas giants. Hot Jupiters Hot Jupiters are gas giant planets similar in mass to Jupiter but which orbit very close to their parent star. As a result of the close proximity to their star their surface temperatures exceed 700C (1300F). It seems that Hot Jupiters are very common in our galaxy, making up more than half of exoplanet discoveries, which is not what astronomers expected at all.

Super Earths Super Earths are ‘potentially’ rocky planets with up to 10 times the mass of Earth. The term ‘Super Earth’ simply refers to the mass of the planet and not to any planetary conditions, so some of these may actually be gas dwarfs. The first two exoplanets to be detected were Super Earths orbiting around the pulsar PSR B1257+12. Free Floating Planets Free floating planets or orphan planets do not orbit around any star. It is believed that these isolated worlds were somehow ejected from developing systems and now free-float around the galaxy. Although very few have been detected they are believed to very common in our galaxy. Pulsar Planets Pulsar planets orbit around Pulsars or Neutron Stars. These super dense, rapidly spinning stars are the core remains of a large star after a supernova explosion. It is highly unlikely that any orbiting planet could survive the blast from a supernova so Pulsar Planets probably formed after the event and now orbit around the dead star. Water Worlds Water Worlds are planets whose surfaces are entirely covered in water. Evidence suggests that these planets originally formed as objects made of ice and rock far from their parent star.

As they drifted towards the star they heated up melting the ice and so became covered in oceans. Under the surface the water is so dense its consistency is more like ice. Chthonian Planets Chthonian Planets were once gas giants but have migrated far too close to their parent star. As a result their atmospheres have been roasted away, leaving only a rocky or metallic core. It is possible their surface may be covered in molten lava. Due to their similarity to terrestrial planets some Super Earths may actually be Chthonian Planets. Exo Earths These are planets that have a similar mass, radius and atmosphere to Earth and orbit in the habitable zone of its star. This is an area where the temperature would allow water to flow on the planet’s surface and possibly allow life to flourish. To date there have been no discoveries of any Exo Earths. Exoplanet Hunting Techniques Radial Velocity Radial Velocity also known as Doppler Spectroscopy is the most successful method of finding exoplanets. This technique measures how much a star wobbles due to the gravitational effects of orbiting planets. It is not strictly true to say that planets orbit around stars, they actually both orbit around their common center of mass.

As stars are much more massive than planets the common center of mass is very close to the star and very far from the planet, as a result the star has a very slight, circular or elliptical orbit. You can see this demonstrated in the video to the right. This wobble can be detected by measuring the light from the star as it moves back and forth from Earth. As the star moves towards Earth its light moves very slightly towards the blue part of the spectrum, known as blue-shifting, and as the star moves away its light moves very slightly towards the red part of the spectrum, known as red-shifting. This is called the Doppler Effect. You can see this demonstrated in the video above, if you imagine Earth is below the video then as the star moves away it turns red and as it gets nearer it turns blue. Of course this is an exaggerated version of what actually happens, the shifts in the spectrum are so small only highly sensitive instruments can pick them up. By observing these shifts over a period of time a regular pattern may emerge signalling that a planet or other object is orbiting the star.

Transit Method The planet Venus transiting the sun When a planet transits it is simply passing between Earth and its star, the image on the left is of a Venus transit of the Sun. This event causes the light from the star to dim very slightly which can be detected by sensitive instrumentation. If the dimming occurs regularly and for fixed periods of time then it is probable the star is being orbited by a planet. The advantage of this method is that it gives more information about the planet than Radial Velocity. As the size of the star is known any dimming in its luminosity can provide a fairly accurate assessment of the planet’s size. Also the composition of the planet’s atmosphere can be deduced by analyzing the light that gets absorbed by elements as it passes through its atmosphere. By combining the results of the Transit Method and Radial Velocity an estimate of the planets size, mass and composition can be gained. The main issue with this method is that a transit must occur in order for a detection to be made. The observer has to be in the exact alignment and at the right time to detect the transit, this means that this method of detection can only be applied to a very small minority of stars.

NASA’s space based Kepler Mission overcomes this issue by scanning more than 100,000 stars simultaneously over a number of years, so far the mission has provided thousands of exoplanet candidates. Notable Exoplanets 'Planet 9' Said to Be First Exoplanet in Our Solar System | NDTV Gadgets360.com 'Planet 9' Said to Be First Exoplanet in Our Solar System Share on Facebook Tweet Share Share Email Reddit Through a computer-simulated study, astronomers showed that it was highly likely that the so-called Planet 9 is an exoplanet - a first exoplanet to be discovered inside our solar system. The theory is that our Sun, in its youth some 4.5 billion years ago, stole Planet 9 from its original star. An exoplanet is by definition a planet located outside our solar system. Now it appears that this definition is no longer viable. According to astronomers from Lund University in Sweden, there is a lot to indicate that Planet 9 was captured by the young sun and has been a part of our solar system completely undetected ever since.

"It is almost ironic that while astronomers often find exoplanets hundreds of light years away in other solar systems, there's probably one hiding in our own backyard", said Alexander Mustill, astronomer at Lund University. Stars are born in clusters and often pass by one another. It is during these encounters that a star can "steal" one or more planets in orbit around another star. This is probably what happened when our own sun captured Planet 9. In a computer-simulated model, Mustill together with astronomers in Lund and Bordeaux showed that Planet 9 was probably captured by the Sun when coming in close contact while orbiting another star. Planet 9 may very well have been "shoved" by other planets and when it ended up in an orbit that was too wide around its own star, our Sun may have taken the opportunity to steal and capture Planet 9 from its original star. "When the sun later departed from the stellar cluster in which it was born, Planet 9 was stuck in an orbit around the Sun," Mustill explained. There is still no image of Planet 9, not even a point of light. It is now known if it is made up of rock, ice, or gas.

"All we know is that its mass is probably around 10 times the mass of earth," Mustill added. If the theory is correct, Mustill believes that the study of space and the understanding of the sun and the Earth will take a giant leap forward. "This is the only exoplanet that we, realistically, would be able to reach using a space probe," he noted in the journal Monthly Notices of the Royal Astronomical Society Letters. Will We Ever Get to See an Exoplanet Outside Our Own Solar System? Will We Ever Get to See an Exoplanet Outside Our Own Solar System? published during a waning gibbous moon. 04/29/2016 51 Eridani as captured by the Gemini Planet Imager . The dot labeled “b” is a young, hot Jupiter-like planet. Credit: J. Rameau, University of Montreal / C. Marois, Herzberg Institute of Astrophysics . Why is it so hard to see an exoplanet? Sure, we have found a whole lot of exoplanets. At the time of this article, we have confirmed 1642 planets and another 3000 await confirmation.

The Kepler Space Telescope discovered all but 40 of those. These Kepler planets, however, were not imaged; instead, they were identified indirectly by measuring the subtle dimming of the stars in the telescope’s field of view as planet-sized objects passed in front of them. We have actually seen only a few of them. Take a look at this photo, captured by a telescope called the Gemini Planet Imager (GPI), of a star named 51 Eri (short for Eridani). That little blob labeled “b” is one of the most remarkable directly imaged photos of an exoplanet we have to date. 51 Eri b, a planet twice the size of Jupiter, may not look like much compared to the gorgeous scientific artwork that typically accompanies the discovery of a new exoplanet, but consider the challenges involved in getting an image like this in the first place. “You’re looking at something that’s a million times fainter than the star at a separation of less than an arcsecond,” said Eric Nielsen, an astronomer at the SETI Institute who studies exoplanets using GPI.

That’s equivalent, Nielsen said, to viewing an unlit object next to an unimaginably bright light that is as close, to the viewer’s eyes, as the width of a dime placed two miles away. The planets are almost insurmountably close to the overpowering light of the star they orbit to get a clear picture. But once your instruments find a way to remove that starlight, you are left with very little light to work with. That means this little bit of light that can make it to the telescope’s camera has a higher chance of being distorted by things like turbulence in Earth’s atmosphere (for ground telescopes), temperature changes, and minute imperfections in its optics. “The horrible thing is, most defects in your optics will show up as something that looks exactly like a planet,” he said. The best we can do right now In terms of direct imaging, the Gemini Planet Imager is one of the best tools we have at the moment. It gets rid of the star’s light by using something called a coronagraph. There are some ways to make one. At their simplest, they are literally just a solid disk that blocks light. For GPI, it’s a mirror with a hole in it.

The light from the star goes through the hole; all the other light reflects off the mirror into the camera. That light, uncorrected, is kind of a scattered mess. For GPI, which is on the ground, the light has to make it through the atmosphere, which can bend the light and sent it to different places on the telescope’s detector. Slight imperfections in the optics or changes to it caused by temperature and other factors can produce nearly insurmountable distortions. Even a 99.9% perfect lens would cast light one thousand times brighter than a planet that’s a million times fainter than the star, obscuring the planet you are trying to image, he said. The only way to address the challenges of light distorted either by atmospheric diffraction or minuscule imperfections in the lens is with a constant supply of corrections based on super complex algorithms—a process known as extreme adaptive optics. The result, if you get it right, is something like that hazy image of 51 Eri b.

Even though a pixel-sized image of a hot Jupiter-sized planet is easier to image than many other smaller or older exoplanets, it is probably the best we will ever be able to do with a ground-based setup like GPI, Nielsen said. The Gemini Planetary Imager. Credit: GPIES What we can expect to see in the near future If we want to image smaller planets that are closer to their star we are going to have to move the whole setup to space. That gets rid of the all the work you need to do to correct for the influence of the atmosphere. Building this telescope is something NASA is currently working on. “There’s only so [much] that even extreme adaptive optics systems are ever going to be able to correct on the ground,” said Jeremy Kasdin, a professor of mechanical and aerospace engineering at Princeton University. He’s the project scientist for the coronagraph on a space telescope mission called WFIRST . This telescope, tentatively scheduled for a launch in the mid-2020s, will employ the same basic principles as GPI—a chronograph with the framework to correct for optical errors caused by imperfections and temperature changes in space. “That’s what makes this unique,” said Kasdin.

These optical systems are fairly common on ground-based telescopes but generally non-existent on space-based ones like Hubble or the future James Webb Space Telescope . For something as precise as exoplanet imaging you need to be able to correct for even the slightest shift in the lense caused by temperature fluctuations driven by our sun. The upper limit of this kind of telescope is probably going to be around the size of a mini-Neptune or a super-Earth style planet. It’s certainly more challenging than a hot Jupiter, but we are also still talking about only pixel. What about the far future? Building our way down to an Earth-sized planet, which Nielsen said would be about 10,000 times dimmer than 51 Eri b, is going to be challenging enough. Resolving the surface of a planet using a coronagraph telescope would be another thing altogether. You’d need something like a two-kilometer telescope just to split a Jupiter-sized planet into two pixels, he said. This according to the cold, hard laws of fundamental optics. For smaller planets, another complication comes from the is the coronagraph itself. Like a stick in a flowing stream, it creates its own turbulence for the beams of light flowing near its edges.

The further away the coronagraph from the camera, the less turbulence is sent to the camera, making the resolution higher, said Kasdin. One way to improve upon the coronagraph and reduce the size of the telescope, both Kasdin and Nielsen said, would be to build a “star shade.” A star shade is essentially a second spacecraft that can be positioned in such a way so as to block the star’s light from a huge distance away. “You very carefully maneuver the two so that the star is behind the star shade [and] the planet just peeks out,” he said. This method still needs to be tested, and it’s pretty complex from a technical standpoint, but it would certainly improve the resolution, Neilson said. An even more technically complex idea would be to build a fleet of space telescopes that fly in formation. This technique would employ something called interferometry. Basically, all would be trained on a star, and then the light from each telescope would be mixed together. The telescopes would then be able, in concert, to block out the starlight and analyze the light that remains — hopefully from a planet. The technical challenges for this set up are probably too daunting for it to be taken seriously anytime soon, Kasdin said.

So will we see the surface of an exoplanet? Probably no time soon. Is it ~technically~ possible with some herculean engineering? Probably. But let’s not get too greedy— until 1989 we couldn’t even prove planets outside our solar system even existed. One possible design for a star shade. Credit: NASA/JPL Giant ExoPlanet in our Solar System?! Or how The Sun stole Planet 9. - YouTube Giant ExoPlanet in our Solar System?! Or how The Sun stole Planet 9. Want to watch this again later? Sign in to add this video to a playlist. Need to report the video? Sign in to report inappropriate content. The interactive transcript could not be loaded. Loading... Rating is available when the video has been rented. This feature is not available right now. Please try again later. Published on Jun 17, 2016 Scientists and Astronomers from Lund University have deduced that The Sun and Jupiter stole Planet 9 from another solar system. You can get excited because they made a cool educational animation. But you might be disappointed because they do not tell us which solar system Planet 9 came from. Really?

Through a computer-simulated study, astronomers at Lund University in Sweden show that it is highly likely that the so-called Planet 9 is an exoplanet. This would make it the first exoplanet to be discovered inside our own solar system. The theory is that our sun, in its youth some 4.5 billion years ago, stole Planet 9 from its original star. An extrasolar planet, or exoplanet, is by definition a planet located outside our solar system. Now it appears that this definition is no longer viable. According to astronomers in Lund, there is a lot to indicate that Planet 9 was captured by the young sun and has been a part of our solar system completely undetected ever since. "It is almost ironic that while astronomers often find exoplanets hundreds of light years away in other solar systems, there's probably one hiding in our own backyard", says Alexander Mustill, astronomer at Lund University. Stars are born in clusters and often pass by one another. It is during these encounters that a star can "steal" one or more planets in orbit around another star. This is probably what happened when our own sun captured Planet 9.

In a computer-simulated model, Alexander together with astronomers in Lund and Bordeaux has shown that Planet 9 was probably captured by the sun when coming in close contact while orbiting another star. "Planet 9 may very well have been 'shoved' by other planets, and when it ended up in an orbit that was too wide around its own star, our sun may have taken the opportunity to steal and capture Planet 9 from its original star. When the sun later departed from the stellar cluster in which it was born, Planet 9 was stuck in an orbit around the sun", says Alexander Mustill. "There is still no image of Planet 9, not even a point of light. We don't know if it is made up of rock, ice, or gas. All we know is that its mass is probably around ten times the mass of earth." It requires a lot more research before it can be ascertained that Planet 9 is the first exoplanet in our solar system. If the theory is correct, Alexander Mustill believes that the study of space and the understanding of the sun and the Earth will take a giant leap forward.

"This is the only exoplanet that we, realistically, would be able to reach using a space probe", he says. Read more at: IANS Through a computer-simulated study, astronomers showed that it was highly likely that the so-called Planet 9 is an exoplanet - a first exoplanet to be discovered inside our solar system.(Photo: Twitter) Through a computer-simulated study, astronomers showed that it was highly likely that the so-called Planet 9 is an exoplanet - a first exoplanet to be discovered inside our solar system. The theory is that our Sun, in its youth some 4.5 billion years ago, stole Planet 9 from its original star. An exoplanet is by definition a planet located outside our solar system. Now it appears that this definition is no longer viable. According to astronomers from Lund University in Sweden, there is a lot to indicate that Planet 9 was captured by the young sun and has been a part of our solar system completely undetected ever since. “It is almost ironic that while astronomers often find exoplanets hundreds of light years away in other solar systems, there’s probably one hiding in our own backyard”, said Alexander Mustill, astronomer at Lund University.

Stars are born in clusters and often pass by one another. It is during these encounters that a star can “steal” one or more planets in orbit around another star. This is probably what happened when our own sun captured Planet 9. In a computer-simulated model, Mustill together with astronomers in Lund and Bordeaux showed that Planet 9 was probably captured by the Sun when coming in close contact while orbiting another star. Planet 9 may very well have been “shoved” by other planets and when it ended up in an orbit that was too wide around its own star, our Sun may have taken the opportunity to steal and capture Planet 9 from its original star. “When the sun later departed from the stellar cluster in which it was born, Planet 9 was stuck in an orbit around the Sun,” Mustill explained. There is still no image of Planet 9, not even a point of light. It is now known if it is made up of rock, ice, or gas. “All we know is that its mass is probably around 10 times the mass of earth,” Mustill added.

If the theory is correct, Mustill believes that the study of space and the understanding of the sun and the Earth will take a giant leap forward. “This is the only exoplanet that we, realistically, would be able to reach using a space probe,” he noted in the journal Monthly Notices of the Royal Astronomical Society Letters. tags Jupiter-like planet discovered outside our solar system | UCLA Jupiter-like planet discovered outside our solar system 6 UCLA astronomers playing important roles in the international research Stuart Wolpert | August 13, 2015 Danielle Futselaar and Franck Marchis/SETI Institute An artist’s conception of the Jupiter-like exoplanet 51 Eridani b, seen in the near-infrared light that shows the hot layers deep in its atmosphere glowing through clouds. A planet 100 light-years away that resembles a young Jupiter has been discovered by an international team of astronomers that includes six UCLA scientists. The discovery is reported Aug. 13 in the online edition of the journal Science. The planet, called 51 Eridani b, is only 20 million years old — a mere infant by astronomy standards.

(Jupiter, the sun and Earth are all about 4.5 billion years old.) It is the first planet detected by the Gemini Planet Imager , or GPI, which was designed to discover and analyze faint, young planets orbiting bright, nearby stars. The vast majority of solar systems that have been discovered are very different from our own, with massive planets close to their stars, said co-author James Larkin, a UCLA professor of physics and astronomy. “Previous search methods couldn’t find systems like our own, with small, rocky worlds close to their star and large, gas giants at large distances like Jupiter and Saturn,” Larkin said. “The search for large planets at large separations from their star is exactly the goal of GPI. These solar systems are likely much more similar to our own. GPI will reveal to us how common our solar system architecture truly is.” Larkin and colleagues at UCLA’s Infrared Laboratory for Astrophysics developed and built GPI’s highly advanced spectrometer, which enabled the instrument to detect the presence of methane on 51 Eridani b.

It revealed that the planet has the strongest concentration of methane ever detected on a planet outside the Milky Way — as well as the presence of water — which indicates that it’s similar to planets in our solar system and should yield additional clues about how the planet formed. The spectrograph produces 18 images at different wavelengths of light, which enables GPI to reject light from nearby stars, which can be up to 10 million times brighter than the planets being studied. The light from 51 Eridani b is very faint; its nearest star is 3 million times brighter. Michael Fitzgerald, UCLA associate professor of physics and astronomy, is a co-author of the Science paper and a lead co-investigator of GPI’s survey team. Other UCLA co-authors are Benjamin Zuckerman, a professor of physics and astronomy; and graduate students Thomas Esposito, Li-Wei Hung and Pauline Arriaga. The project’s lead investigator is Bruce Macintosh, who received his doctorate from UCLA in 1995, working in the infrared laboratory, and who is now a professor of physics at Stanford University’s Kavli Institute.

“Many of the exoplanets astronomers have imaged before have atmospheres that look like very cool stars,” Macintosh said. “This one looks like a planet.” (An exoplanet is a planet outside our solar system.) GPI was installed on the 8-meter Gemini South Telescope in Chile in 2013, and its science operation began in 2014. The GPI team has studied almost 100 stars already. The newly discovered planet orbits a little farther from its parent star than Saturn does from the sun. It is roughly twice the mass of Jupiter. Until now, the gas giant planets that have been directly detected have been much larger — five to 13 times Jupiter’s mass, Fitzgerald said. The scientists reported that 51 Eridani b has a temperature of 800 degrees Fahrenheit, hot enough to melt lead, but still rather cold compared with other gas giants, which reach temperatures above 1,000 degrees. Previous Jupiter-like exoplanets have shown only faint traces of methane, far different from the heavy methane atmospheres of the gas giants in our solar system.

“This is exactly the kind of planet we envisioned discovering when we designed GPI,” said James Graham, a UC Berkeley professor and GPI’s project scientist. GPI will provide new insights about how solar systems form. Astronomers believe that the gas giants in our solar system formed by building up a large core over a few million years and then pulling in a huge amount of hydrogen and other gasses to form an atmosphere. But the Jupiter-like exoplanets that have been discovered so far are much hotter than models have predicted, hinting that they could have formed much faster as material collapses quickly to make a very hot planet. The core-buildup process can also form rocky planets like the Earth, while the process of fast-collapsing materials might make only giant gas planets, the researchers said. 51 Eridani b is young enough to reveal clues about how it was created. “This planet really could have formed the same way Jupiter did; the whole solar system could be a lot like ours,” Macintosh said. There are hundreds of planets a little bigger than Earth, but so far no way to know if they are “super-Earths,” or micro-sized gas and ice planets like Neptune, or something different altogether, he said.

Tags: Exoplanet Exploration: Planets Beyond our Solar System: Exoplanets 101 Inventing the Future Exoplanets 101 An artist's illustration of a young, sun-like star encircled by its disk of gas and dust. The gas and dust will in time form exoplanets. Credit: NASA/JPL-Caltech/T. Pyle Exoplanet– a planet that orbits another star The blocky space telescope was still getting its bearings, just a few months after launch, when the floodgates burst open. As NASA’s Kepler Space Telescope science team was wrapping up a 10-day trial run, they saw something that bordered on the unbelievable: the telescope's first detection of a rocky, Earth-sized world outside our solar system. The sun and our solar system in relation to the Milky Way galaxy. The white circle indicates the area where the majority of exoplanets have been found with current telescopes. Credit: NASA/JPL-Caltech/T.

Pyle The planet, a hot, heavy world dubbed Kepler 10b, would be among the early nuggets in a coming gold rush of exoplanet discovery—taking us from a handful of planets confirmed to be in orbit around other stars to more than 3,300 today, all in the space of two decades. Thousands more candidate planets found by Kepler await confirmation. “In that trial run we saw, already, the signal of what could be a small planet orbiting a star about 540 light years away,” Natalie Batalha, an astrophysicist and member of the Kepler team, told a public radio host about the discovery, announced in 2011. “This was our first indication—‘Oh my god! We’re going to find lots of these things. We’re going to find lots of Earth-size planets.’” Since the first confirmation of an exoplanet orbiting a sun-like star in 1995, and with only a few, narrow slices of our Milky Way galaxy so far surveyed, we’ve already struck many rich veins. A recent statistical estimate places, on average, at least one planet around every star in the galaxy.

That means there's something on the order of a trillion planets in our galaxy alone, many of them in Earth’s size range. “Right now we know, for the first time, that small planets are very common,” said Sara Seager, a professor at the Massachusetts Institute of Technology and an exoplanet research pioneer. “It’s phenomenal. We had no way to know that before Kepler. We’ll just say, colloquially: They’re everywhere.” Billions of stars light up a panorama of our Milky Way galaxy, including the entire southern and northern celestial sphere. Astronomers now believe that every single star in the galaxy has at least one planet. Credit: ESO/S. Brunier Hot Jupiters and wobbling suns The planet discovered in 1995 was a hot, star-hugging gas giant believed to be about half the size of Jupiter. It tugged so hard on its parent star as it raced around in a four-day orbit that the star’s wobbling was obvious to earthly telescopes—once astronomers knew what to look for. 51 Pegasi b, also called "Dimidium," was the first exoplanet discovered orbiting a star like our sun.

This groundbreaking find in 1995 confirmed planets like Earth could exist elsewhere in the universe. Finding this fast-moving giant, known as 51 Pegasi b, kicked off what might be called the “classical” period of planet hunting. The early technique of tracking wobbling stars revealed one planet after another, many of them large “hot Jupiters” with tight, blistering orbits. The wobble method measures changes in a star’s “radial velocity.” The wavelengths of starlight are alternately squeezed and stretched as a star moves slightly closer, then slightly farther away from us. Those gyrations are caused by gravitational tugs, this way and that, from orbiting planets. The European team of Michel Mayor and Didier Queloz announced their discovery of 51 Peg using this method in 1995, and the race was on to find others. The others came—first by the dozens, then by the hundreds. Swiss astronomers Didier Queloz and Michel Mayor in front of La Silla Observatory in Chile. The pair discovered 51 Pegasi b in 1995, the first planet found orbiting a star like our sun. Credit: L.

Weinstein/Ciel et Espace Photos After confirming the existence of 51 Peg, a science team led by Paul Butler and Geoff Marcy, then of San Francisco State University, took a second look at data from their own radial velocity observations. They and the rest of the astronomical community hadn’t anticipated large planets orbiting so closely and rapidly around their parent stars. Sure enough, big, star-hugging planets began popping out of their data. They announced two somewhat more plausible exoplanets, 70 Virginis and 47 Ursae Majoris, in 1996. The first had a 116-day orbit, the second an orbit of 2.5 years, helping overcome skepticism among their fellow astronomers; these distant solar systems looked a lot more like ours. The Butler and Marcy team went on to discover at least 70 of the first 100 exoplanets in the decade that followed, attaining celebrity status. Scores of other ground-based research projects also joined the hunt, sending the tally of known exoplanets into the low hundreds. Then a new space telescope, and a new planet-hunting method, stole the show.

Staring into space Enter NASA’s Kepler Space Telescope, launched in 2009 to inaugurate what we could call the “modern” era of planet hunting. Kepler settled into an Earth-trailing orbit, then fixed its gaze on a small patch of sky. It stared at that patch for four years. Within that small patch were some 150,000 stars. Kepler was waiting to catch tiny dips in the amount of light coming from individual stars, caused by planets crossing in front of them. The result: more than 2,000 confirmed exoplanets were sifted from the data, the bulk of the more than 3,300 confirmed so far, with more than 2,400 planetary candidates as scientists continue to mine Kepler’s observations. The Kepler mission faced its own skeptical audience in the 1990s. Four times, NASA rejected the designs proposed by William Borucki of the NASA Ames Research Center in Moffet Field, California. Borucki, now retired, finally won approval in 2001. His idea was proven right; Kepler’s four years of data are still revealing new planets.

But failure of two reaction wheels on the spacecraft ended its primary mission in 2013. From the left to right, the Spitzer, Kepler, and Hubble space telescopes have discovered over 1,000 planets outside our solar system. Credit: JPL-Caltech/R. Hurt (SSC); NASA Ames/ W. Stenzel; ESA Still, it’s hard to keep a good spacecraft down. The Kepler science team devised a clever fix: using the pressure of sunlight to stabilize one axis of the telescope. The instrument was rechristened "K2" and continues to discover planets, though at shorter observation times than its original four-year stare. Other instruments, on the ground and in space, continue to round out the tally of exoplanets bagged so far. The European CoRoT satellite preceded Kepler, and also used the transit method to find numerous planets during its functional period from 2006 to 2012. The Hubble Space Telescope not only has discovered a variety of transiting exoplanets, but has characterized the atmospheres of some of them. As a planet makes its transit across the face of its star, a sliver of starlight shines through the planet’s atmosphere.

Gases and chemicals in the atmosphere absorb different wavelengths of the light as it passes through. By looking for these missing slices of the star’s light spectrum, scientists can tell which constituents are present in that alien atmosphere. Another skywatcher, NASA’s Spitzer Space Telescope, observes transiting exoplanets in infrared wavelengths, and has helped to chart and characterize many, including puzzling out details of planetary atmospheres. Spitzer often works in conjunction with ground-based telescopes, including OGLE’s Warsaw Telescope at the Las Campanas Observatory in Chile. In 2015, a collaboration between Spitzer and Italy’s 3.6 meter Galileo National Telescope in the Canary Islands revealed the closest known rocky planet: HD 219134b, only 21 light-years away from Earth. Disappointingly, however, the planet orbits its star too closely to make it suitable for life. All but a handful of the thousands of exoplanets observed so far have been detected via indirect methods, such as watching for transits or measuring star wobbles. We’ve only just begun to enter a new era of planet hunting: direct imaging.

Hey exoplanets: Say 'cheese!' Astronomers say the future of exoplanet exploration is all about direct observation. Missions like the James Webb Space Telescope, now under construction, and the planned WFIRST (Wide-Field Infrared Survey Telescope) will expand and sharpen our ability to capture actual images of distant planets. New technology under development will boost these capabilities, allowing us to snap portraits of smaller and smaller exoplanets. The WFIRST mission, for example, will use an internal instrument called a coronagraph to selectively block and process incoming starlight to reveal the planets hidden in the glare. Something similar could be done outside the telescope by a device called the starshade, being developed at JPL. The starshade would deploy in deep space like a sunflower the size of a baseball diamond. Tens of thousands of miles away, a space telescope would point toward it; the starshade would block unwanted starlight, allowing the space telescope to capture images of the planets around the target star. In coming decades, as space telescopes grow larger and more refined, perhaps we’ll finally capture the iconic image of another Earth—a faraway world of continents, clouds and oceans. But what, exactly, makes a planet Earth-like?

Where should we look to find a habitable twin? To find out, read on to the next topic: Exoplanet Exploration: Planets Beyond our Solar System: Kepler's Mini Planetary System Galleries Kepler's Mini Planetary System This artist's concept depicts an itsy bitsy planetary system -- so compact, in fact, that it's more like Jupiter and its moons than a star and its planets. Astronomers using data from NASA's Kepler mission and ground-based telescopes recently confirmed that the system, called KOI-961, hosts the three smallest exoplanets known so far to orbit a star other than our sun. An exoplanet is a planet that resides outside of our solar system. The star, which is located about 130 light-years away in the Cygnus constellation, is what's called a red dwarf. It's one-sixth the size of the sun, or just 70 percent bigger than Jupiter. The star is also cooler than our sun, and gives off more red light than yellow. The smallest of the three planets, called KOI-961.03, is actually located the farthest from the star, and is pictured in the foreground.

This planet is about the same size as Mars, with a radius only 0.57 times that of Earth. The next planet to the upper right is KOI-961.01, which is 0.78 times the radius of Earth. The planet closest to the star is KOI-961.02, with a radius 0.73 times the Earth's. All three planets whip around the star in less than two days, with the closest planet taking less than half a day. Their close proximity to the star also means they are scorching hot, with temperatures ranging from 350 to 836 degrees Fahrenheit (176 to 447 degrees Celsius). The star's habitable zone, or the region where liquid water could exist, is located far beyond the planets. The ground-based observations contributing to these discoveries were made with the Palomar Observatory, near San Diego, Calif., and the W.M. Keck Observatory atop Mauna Kea in Hawaii. NASA's Ames Research Center in Moffett Field, Calif., manages Kepler's ground system development, mission operations and science data analysis. JPL managed the Kepler mission's development.

For more information about the Kepler mission visit . Credit

Question: An exoplanet is a planet which does what to a sun (outside of our own solar system)?
Answer: Orbits