Tag Archives: rogue planet

An artist's impression of a gravitational microlensing event by a free-floating planet. (Jan Skowron / Astronomical Observatory, University of Warsaw)

‘Lonely’ Rogue Planet Discovered Wandering the Milky Way

Researchers believe that our galaxy is teeming with cosmic orphans, planets wandering free of a parent star. Though common, these rogue planets are difficult to spot, especially when they are in the size range of the earth. 

Despite this difficulty; an international team of astronomers including Przemek Mróz, a postdoctoral scholar at the California Institute of Technology (Caltech) and Radosław Poleski from the Astronomical Observatory of the University of Warsaw, have spotted what they believe to be a free-floating planet with a size and mass somewhere in the range of Mars and Earth, wandering the Milky Way. 

The discovery represents a major step forward in the field of exoplanet investigation as it is the first earth-sized ‘rogue planet’ ever observed.

An artist's impression of a gravitational microlensing event by a free-floating planet. (Jan Skowron / Astronomical Observatory, University of Warsaw)
An artist’s impression of a gravitational microlensing event by a free-floating planet. (Jan Skowron / Astronomical Observatory, University of Warsaw)

“We found a planet that seems extremely lonely and small, far away in the Universe,” Poleski tells ZME Science. “If you can imagine, Earth is in a sandbox surrounded by lots of other planets, and light from the Sun. This planet isn’t. It’s truly alone.”

The rogue planet the team found — OGLE-2016-BLG-1928 — is believed to be the smallest free-floating planet ever discovered. It was found in data collected by Optical Gravitational Lensing Experiment (OGLE), a Polish astronomical project based at the University of Warsaw. Previously discovered rogues — such as the first-ever recorded free-floating planet also found by OGLE in 2016 — are closer in size to Jupiter.

The gravity of a free-floating planet may deflect and focus light from a distant star when passing close in front of it. Due to the distorted image, the star temporarily seems much brighter. (v)

“We discovered the smallest free-floating planet candidate to date. The planet is likely smaller than Earth, which is consistent with the predictions of planet-formation theories,” Mróz — lead author of the team’s study published in Astrophysical Journal Letters — explains to ZME Science. “Free-floating planets are too faint to be observed directly — we can detect them using gravitational microlensing via their light-bending gravity.”

The Gravity of the Situation

The team spotted this wandering planet using the technique of gravitational microlensing, often utilised to spot exoplanets — planets outside our solar system. Exoplanets can’t often be observed directly, and when they can it’s a result of interaction with radiation from their parent star — for example, the dimming effect exoplanets have when they cross in front of their star and block some of the light it emits. Clearly, as rogue planets don’t have a parent star, they don’t have these interactions, making micro-lensing events the only way of spotting them.

“Microlensing occurs when a lensing object — a free-floating planet or star — passes between an Earth-based observer and a distant source star, its gravity may deflect and focus light from the source,” Mróz explains to ZME Science. “The observer will measure a short brightening of the source star, which we call a gravitational microlensing event.”

When the gravity of a free-floating planet deflects and focuses light from a distant star, we can observe temporary changes in star brightness. (temporary changes in star brightness.
Credit: Jan Skowron / Astronomical Observatory, University of Warsaw.)

Mróz continues by explaining that the duration of microlensing events depends on the mass of the object acting as a gravitational lens. “The less massive the lens, the shorter the microlensing event. Most of the observed events, which typically last several days, are caused by stars,” Mróz says. “Microlensing events attributed to free-floating planets usually last barely a few hours which makes them difficult to spot. We need to very frequently observe the same part of the sky to spot brief brightenings caused by free-floating planets.”

Changes of brightness of the observed star during the gravitational microlensing event by a free-floating planet. (Credit: Jan Skowron / Astronomical Observatory, University of Warsaw/ Robert Lea)

By measuring the duration of a microlensing event and shape of its light curve astronomers can estimate the mass of the lensing object. That is how the team were able to ascertain this free-floating planet is approximately Earth-sized. “Hence, we can discover very dim objects, like black holes, or free-floating planets,” says Poleski. “We found it an event, which has a timescale of 41 minutes. And it’s the shortest event ever discovered.”

Poleski explains that the lack of any other lensing body in the system told the team that it is a very strong candidate for a free-floating planet. He adds: “We know it’s a planet because of the very short timescale and we think it’s free-floating because we don’t see any star next to it.”

Going Rogue. How Free-Floating Planets Come to Wander the Universe Alone

Astronomers believe that free-floating planets actually formed in protoplanetary disks around stars in the same way that ‘ordinary’ planets are. At some point, they are ejected from their parent planetary systems, probably after gravitational interactions with other bodies, for example, with other planets in the system.

“Some low-mass planets are expected to be ejected from their parent planetary systems during the early stages of planetary system formation,” says Mróz. “According to planet formation theories, most of the ejected planets should be smaller than Earth. Theories of planet formation predict that typical masses of ejected planets should be between 0.3 and 1.0 Earth masses. Thus, the properties of this event fit the theoretical expectations.”

These free-floating rogue planets are believed to be fairly common, but researchers can’t be certain because they are so difficult to spot. “Our current studies indicate that the frequency of low-mass–in the Earth to super-Earth-mass range–free-floating or wide-orbit planets is similar to that of stars — there are about two-five such objects per each star in the Milky Way,” says Mróz. “These numbers are very uncertain because they are based on a few sightings of short-timescale microlensing events. However, if free-floating/wide-orbit planets were less frequent than stars, we would have observed much fewer short-timescale events than we do.”

The researcher adds that though these objects are relatively common, the chances of observing microlensing events caused by them are still extremely small. “Three objects — source, lens, and observer — must be nearly perfectly aligned,” Mróz says. “If we observed only one source star, we would have to wait almost a million year to see the source being microlensed.”

In fact, one of the extraordinary elements of the team’s study is that such a short duration lensing event wasn’t believed to be observable given the sensitivity of the current generation of telescopes.

“The surprise, in general, was that with current technology we could define such a short time event,” Poleski says. “It’s especially surprising if you beat the previous record by a factor of few.”

The Nancy Grace Roman Telescope and Future Rogue Reconnaissance

For Mróz, there are still questions that he would like to see answered about OGLE-2016-BLG-1928. Primarily, confirming that it definitely is a free-floating planet. 

“We aren’t fully sure whether our planet is free-floating or not. Our observations rule out the presence of stellar companions within 10 astronomical units–930 million miles–of the planet, but the planet may have a more distant companion,” Mróz says. “Let’s imagine that we’re observing microlensing events by a doppelganger of the Solar System. If Jupiter or Saturn caused a microlensing event, we would see a signature of the Sun in the microlensing event light curve. However, microlensing events by Uranus or Neptune would likely look like those of free-floating planets, because they are very far from the Sun.”

Fortunately, Mróz says that should be possible to distinguish between free-floating and wide-orbit planets. “The lens is moving relative to the source star in the sky and — a few years after the microlensing event — the lens and source should separate in the sky,” the researcher elaborates. “If the lens has a stellar companion, we will see some excess of light at its position. If it is a free-floating planet, we will not.” 

Whilst this method may seem simple, Mróz says we cannot apply it now, because the existing telescopes are not powerful enough. This includes the instrument that conducted the long-term observations that gave rise to the OGLE sky survey–the data from which the team found the micro-lensing event OGLE-2016-BLG-1928.

“[The discovery of OGLE-2016-BLG-1928] was part of the larger search for microlensing events in general, which we perform in a number of steps,” Poleski tells ZME. “In one step, I started looking at the wide orbit planets — planets similar to Uranus, or Neptune and on similar orbits. And while looking for those, I screened a list of candidate microlensing events in general and I found this one.”

Soon NASA’s Nancy Grace Roman Telescope will take over the search for microlensing events, but in the meantime, there is still data from OGLE and other projects to be examined. “We now have more data and other surveys are also collecting data. So we hope to analyze those,” Poleski says. “The longer-term future is the launch of the Nancy Grace Roman Space Telescope. It will be a telescope similar to the Hubble telescope, only with new infrared and infrared cameras and that camera field of view larger than the Hubble Space Telescope. 

“One of the main projects for the Raman telescope will be to observe galactic bulge in search for microlensing planets, including free-floating planets.”

Mroz, P., Poleski, R., Gould, A. et al., ‘A terrestrial-mass rogue planet candidate detected in the shortest-timescale microlensing event,’ Astrophysical Journal Letters, [2020] DOI: 10.3847/2041–8213/abbfad

This artist's conception illustrates a Jupiter-like planet alone in the dark of space, floating freely without a parent star. (NASA)

Rogue Planets Could Outnumber Stars in the Milky Way

Our galaxy is teeming with rogue planets either torn from their parent stars by chaotic conditions or born separate from a star. These orphan planets could be discovered en masse by an outcoming NASA project — Nancy Grace Roman Space Telescope. 

The Milky Way is home to a multitude of lonely drifting objects, galactic orphans — with a mass similar to that of a planet — separated from a parent star. These nomad planets freely drift through galaxies alone, thus challenging the commonly accepted image of planets orbiting a parent star. ‘Rogue planets’ could, in fact, outnumber stars in our galaxy, a new study published in the Astronomical Journal indicates. 

“Think about how crazy it is that there could be an Earth, a Mars, or a Jupiter floating all alone through the galaxy. You would have a perfect view of the night sky but stuck in an eternal night,” lead author of the study, Samson Johnson, an astronomy graduate student at The Ohio State University, tells ZME Science. “Although these planets could not host life, it is quite a place to travel to with your imagination. The possibility of rogue planets in our galaxy had not occurred to me until coming to Ohio State.”

This artist’s conception illustrates a Jupiter-like planet alone in the dark of space, floating freely without a parent star. (NASA)

Up to now, very few very of these orphan planets have actually been spotted by astronomers, but the authors’ simulations suggest that with the upcoming launch of NASA’s Nancy Grace Roman Space Telescope in the mid-2020s, this situation could change. Maybe, drastically so.

“We performed simulations of the upcoming Nancy Grace Roman Space Telescope (Roman) Galactic Exoplanet Survey to determine how sensitive it is to microlensing events caused by rogue planets,” Johnson says. “Roman will be good at detecting microlensing events from any type of ‘lens’ — whether it be a star or something else — because it has a large field of view and a high observational cadence.”

The team’s simulations showed that Roman could spot hundreds of these mysterious rogue planets, in the process, helping researchers identify how they came to wander the galaxy alone and indicating how great this population could be in the wider Universe.

Rogue by Name, Rogue by Nature: Mysterious and Missing

Thus far, much mystery surrounds the process that sees these planets freed from orbit around a star. The main two competing theories suggest that these stars either are thrown free of their parent star, or form in isolation. Each process would likely lead to rogue planets with radically different qualities. 

ESO’s New Technology Telescope at the La Silla Observatory captures the rogue planet CFBDSIR J214947.2-040308.9 in infrared light–appearing as a faint blue dot near the centre of the picture. This is the closest such object to the Solar System discovered thus far. (ESO/P. Delorme)

“The first idea suggests that rogue planets form like planets in the Solar System, condensing from the protoplanetary disk that accompanies stars when they are born,” Johnson explains. “But as the evolution of planetary systems can be chaotic and messy, members can be ejected from the system leading to most likely rogue planets with masses similar to Mars or Earth.”

 Johnson goes on to offer an alternative method of rogue planet formation that would see them form in isolation, similar to stars that form from giant collapsing gas clouds. “This formation process would likely produce objects with masses similar to Jupiter, roughly a few hundred times that of the Earth.”

“This likely can’t produce very low-mass planets — similar to the mass of the Earth. These almost certainly formed via the former process,” adds co-author Scott Gaudi, a professor of astronomy and distinguished university scholar at Ohio State. “The universe could be teeming with rogue planets and we wouldn’t even know it.”

The question is if these objects are so common, why have we spotted so few of them? “The difficulty with detecting rogue planets is that they emit essentially no light,” Gaudi explains. “Since detecting light from an object is the main tool astronomers use to find objects, rogue planets have been elusive.”

Astronomers can use a method called gravitational microlensing to spot rogue planets, but this method isn’t without its challenges, as Gaudi elucidates:

“Microlensing events are both unpredictable and exceedingly rare, and so one must monitor hundreds of millions of stars nearly continuously to detect these events,” the researcher tells ZME Science. “This requires looking at very dense stellar fields, such as those near the centre of our galaxy. It also requires a relatively large field of view.”

Additionally, as the centre of the Milky Way is highly obscured by requiring us to look at it in the near-infrared region of the electromagnetic spectrum — a task that is extremely difficult as the Earth’s atmosphere makes the sky extremely bright in near-infrared light.

“All of these points argue for a space-based, high angular resolution, wide-field, near-infrared telescope,” says Gaudi. “That’s where Roman — formally the Wide Field InfraRed Survey Telescope (WFIRST) — comes in.” 

Nancy Grace Roman Space Telescope (and Einstein) to the Rescue!

The Roman telescope — named after Nancy Grace Roman, NASA’s first chief astronomer, who paved the way for space telescopes focused on the broader universe–will launch in the mid-2020s. It is set to become the first telescope that will attempt a census of rogue planets — focusing on planets in the Milky Way, between our sun and the centre of our galaxy, thus, covering some 24,000 light-years.

An artist’s redition of the Nancy Grace Roman Space Telescope, named after ‘the Mother of Hubble’ (NASA)

The team’s study consisted of simulations created to discover just how sensitive the Roman telescope could be to the microlensing events that indicate the presence of rogue planets, finding in the process, that the next generation space telescope was 10 times as sensitive as current Earth-based telescopes. This difference in sensitivity came as a surprise to the researchers themselves. “Determining just how sensitive Roman is was a real shock,” Johnson says. “It might even be able to tell us about moons that are ejected from planetary systems! We also, found a new ‘microlensing degeneracy’ in the process of the study — the subject another paper that will be coming out shortly.”

Johnson’s co-author Gaudi echoes this surprise. “I was surprised that Roman was sensitive to rogue planets with mass as low as that of Mars and that the signals were so strong,” the researcher adds. “I did not expect that before we started the simulations.”

The phenomenon that Roman will exploit to make its observations stems from a prediction made in Einstein’s theory of general relativity, that suggests that objects with mass ‘warp’ the fabric of space around them. The most common analogy used to explain this phenomenon is ‘dents’ created in a stretched rubber sheet by placing objects of varying mass upon it. The heavier the object — thus the greater the mass — the larger the dent. 

This warping of space isn’t just responsible for the orbits of planets, it also curves the paths of light rays, the straight paths curving as they pass the ‘dents’ in space. This means that light from a background source is bent by the effect of the mass of a foreground object. The effect has recently been used to spot a distant Milky Way ‘look alike’. But in that case, and in the case of many gravitational lensing events, the intervening object was a galaxy, not a rogue planet, and thus was a much less subtle, more long-lasting, and thus less hard to detect effect than ‘microlensing’ caused by a rogue planet. 

This animation shows how gravitational microlensing can reveal island worlds. When an unseen rogue planet passes in front of a more distant star from our vantage point, light from the star bends as it passes through the warped space-time around the planet. The planet acts as a cosmic magnifying glass, amplifying the brightness of the background star. (NASA’s Goddard Space Flight Center/CI Lab)

“Essentially, a microlensing event happens when a foreground object — in this case, a rogue planet — comes into very close alignment with a background star. The gravity of the foreground object focuses light from the background star, causing it to be magnified,” Gaudi says. “The magnification increases as the foreground object comes into alignment with the background star, and then decreases as the foreground object moves away from the background star.”

As Johnson points out, microlensing is an important and exciting way to study exoplanets — planets outside the solar system — but when coupled with Roman, it becomes key to spotting planetary orphans.

“Roman really is our best bet to find these objects. The next best thing would be Roman 2.0 — with a larger field of view and higher cadence,” the researcher tells ZME, stating that rogue planets are just part of the bigger picture that this forthcoming space-based telescope could allow us to see. “I’m hoping to do as much work with Roman as possible. The next big project is determining what Roman will be able to teach us about the frequency of Earth-analogs — Earth-mass planets in the habitable zones of Sun-like stars.”

Original Research

Johnson. S. A., Penny. M, Gaudi. B. S, et al, ‘Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. II. Free-floating Planet Detection Rates*,’ The Astronomical Journal, [2020]. 

Artist impression of 2MASS J2126. Credit: Neil Cook, University of Hertfordshire

Lonely planet is actually part of the largest planetary system in the Milky Way

Astronomers used to think that a lonely planet called 2MASS J2126 was without a parent star, drifting like an orphan through interstellar space. A team now says the planet isn’t a rogue — it’s just that it has a really big orbit, about 7,000-times the size of Earth’s orbit around the sun. This makes the solar system it belongs to the largest in the Milky Way. Quite the plot twist.

Artist impression of 2MASS J2126. Credit: Neil Cook, University of Hertfordshire

Artist impression of 2MASS J2126. Credit: Neil Cook, University of Hertfordshire

A long distance relationship

“This is the widest planet system found so far and both the members of it have been known for eight years, but nobody had made the link between the objects before,” said lead author Dr Niall Deacon of the University of Hertfordshire in a statement about the findings.

When astronomers first spotted 2MASS J2126, they thought it was a rogue planet. These free floating planets are most intriguing for researchers. They are not orbiting a star but instead are wandering through the galaxy. These are either ancient planets formed in the early Universe or estranged daughters jettisoned out of their parent solar system. There could be 100,000 times more rogue planets than stars in our Milky Way galaxy alone, by some accounts, so 2MASS J2126 wasn’t that odd.

False colour infrared image. The arrows show the motion over the next 1,000 years. (Simon Murphy)

False colour infrared image. The arrows show the motion over the next 1,000 years. (Simon Murphy)

Upon closer inspection, a team from UK, U.S. and Australia found that 2MASS J2126 is associated with a dwarf star. The catch is that they’re spaced apart by 1 trillion kilometers and it takes a full 900,000 years for 2MASS J2126 to complete a revolution around its star, as reported in the paper.

“How such a wide planetary system forms and survives remains an open question,” Simon Murphy of Australian National University said in a statement.

The planet and its solar system are 104-light-years away from Earth. But the researchers’ findings shouldn’t be all that surprising. Last week, ZME Science reported how astronomers found what they think is the solar system’s ninth planet — and it’s not Pluto. Unceremoniously dubbed ‘Planet Nine’, it’s believed to be 10 times bigger than Earth and orbit 20 times farther from the sun than Neptune. The researchers didn’t actually find the planet, but reckoned it must be somewhere inside the Kuiper Belt based on the influence it exerts on other objects.

star flyby oort cloud

70,000 Years Ago, a Rogue Star Passed Through Our Solar System

Too close for comfort – a team of astronomers from the US, Europe, Chile and South Africa concluded that a dim star passed through the Oort cloud, our solar system’s distant cloud of comets. The star missed the Earth by less than one light year, and passed five times closer than the current closest star, Proxima Centauri.

star flyby oort cloud

Artist’s conception of Scholz’s star and its brown dwarf companion (foreground) during its flyby of the solar system 70,000 years ago. The Sun (left, background) would have appeared as a brilliant star. The pair is now about 20 light years away.
Credit: Michael Osadciw/University of Rochester.

In a paper published in The Astrophysical Journal Letters, lead author Eric Mamajek from the University of Rochester and his team studied the velocity and trajectory of a low-mass star system – WISE 0720-0846 (nicknamed “Scholz’s star”). Due to its low luminosity, the star was discovered only a year ago by astronomer Ralf Dieter-Scholz in Potsdam, Germany, through the use of NASA’s WISE (Wide Field Infrared Survey Explorer), which mapped the entire sky in infrared during the years 2010 and 2011.

Since it was discovered, it had some interesting characteristics. despite being fairly close (“only” 20 light years away), it showed very slow tangential motion, that is, motion across the sky. By studying its trajectory and velocity, astronomers found that the star was either moving towards, or away from our solar system. They reconstructed its past movement and quickly realized it was moving away from our solar system, which means that it passed through it (or very close to it) sometime in the past.

“Most stars this nearby show much larger tangential motion,” says Mamajek, associate professor of physics and astronomy at the University of Rochester. “The small tangential motion and proximity initially indicated that the star was most likely either moving towards a future close encounter with the solar system, or it had ‘recently’ come close to the solar system and was moving away. Sure enough, the radial velocity measurements were consistent with it running away from the Sun’s vicinity — and we realized it must have had a close flyby in the past.”

Scholz’s star moved much faster than expected, and missed Earth by “a whisker” – in astronomical terms, that is. It passed roughly 0.8 light years away from Earth, at 8 trillion kilometers; this happened 70,000 years ago. It may seem like a lot, but it’s really too close for comfort. This fits with an earlier theory, which proposed that such close flybys take place every 100,000 years or so. These encounters could hit the Oort cloud and trigger “comet showers” in the solar system.

“Sure enough, the radial velocity measurements were consistent with it running away from the sun’s vicinity — and we realized it must have had a close flyby in the past,” Mamajek said in a news release.

 

The star is a rogue star – a star that has escaped the gravitational pull of its home galaxy and is moving independently in or towards the intergalactic void; the movement of rogue stars is often hard to predict. A 2012 study claimed that rogue planets riddle the Milky Way, and while rarer, there are also rogue stars in our galaxy.

Currently, Scholz’s star is a small, inconspicuous red dwarf in the constellation of Monoceros, about 20 light years away. The star is part of a binary star system, composed of a low-mass red dwarf star (with mass about 8% that of the Sun) and a “brown dwarf” companion (with mass about 6% that of the Sun). Red dwarfs are by far the most common type of star in the Milky Way, at least in the neighborhood of the Sun, but due to their low luminosity, they are difficult to observe and study. Brown stars are “failed stars” – substellar objects not massive enough to sustain hydrogen-1 fusion reactions in their cores, unlike … well, stars.

Journal Reference:

  1. Eric E. Mamajek, Scott A. Barenfeld, Valentin D. Ivanov, Alexei Y. Kniazev, Petri Väisänen, Yuri Beletsky, Henri M. J. Boffin. THE CLOSEST KNOWN FLYBY OF A STAR TO THE SOLAR SYSTEM. The Astrophysical Journal, 2015; 800 (1): L17 DOI: 10.1088/2041-8205/800/1/L17

 

A strange, lonely planet found without a star

An international discovered a young, exotic, rogue planet – PSO J318.5-22, is just 80 light-years away from Earth and has a mass six times that of Jupiter; it was formed apporximately 12 million years ago – which makes it a newborn in terms of planets (the Earth was formed approximately 4.5 billion years ago.

ps1_lonely_planet-450

Multicolor image from the Pan-STARRS1 telescope of the free-floating planet PSO J318.5-22, in the constellation of Capricornus. Most of its energy is emitted in infrared.

“We have never before seen an object free-floating in space that that looks like this. It has all the characteristics of young planets found around other stars, but it is drifting out there all alone,” explained team leader Dr. Michael Liu of the Institute for Astronomy at the University of Hawaii at Manoa. “I had often wondered if such solitary objects exist, and now we know they do.”

During the past decade, the discovery of new exoplanet has developed at an exponential pace, without about 1.000 (!) new planet discovered through indirect methods. However, even with the astonishing development of technique, only a handful were observed through direct imaging.

“Planets found by direct imaging are incredibly hard to study, since they are right next to their much brighter host stars. PSO J318.5-22 is not orbiting a star so it will be much easier for us to study. It is going to provide a wonderful view into the inner workings of gas-giant planets like Jupiter shortly after their birth,” said Dr. Niall Deacon of the Max Planck Institute for Astronomy in Germany and a co-author of the study.

Astronomers have confirmed the existence of rogue planets only a few year ago, so this is also an exciting, new field of study. There is no current way of telling whether these are planets that have been ejected from orbiting a star or were originally formed on their own as sub-brown dwarfs.

Via University of Hawaii.

Eye of Sauron exoplanet

“Eye of Sauron” star hosts rogue planet

Eye of Sauron exoplanet

Back in 2008, Hubble released a stunning image of a very bright star called Fomalhaut which spanned a huge disk of matter around it. The whole picture bared an uncanny resemblance to the eye of Sauron from the Lord of the Rings movies. Also at the time, scientists caught the glimpse of a tiny speck of light deep in the debris disk which they believed was in fact an exoplanet.

Since then, however, followup observations had failed to find the distant world again. In 2010 the bleep of light appeared once again on the astronomers’ radar, but this time it was too far away in the right side of the start to orbit it, which lead many researchers to discount the find.

Newly-released Hubble images show that the debris belt is wider than previously known, spanning a section of space from 14 to nearly 20 billion miles from the star. Apparently, the planet Fomalhaut b follows a  highly eccentric path around the star coming in as close  as 4.6 billion miles, and as far away as 27 billion miles. Moreover, the planet’s orbit isn’t in the same plan as the huge disk, meaning it skews and passes above and below the disk.

“We are shocked. This is not what we expected,” says Paul Kalas of the University of California at Berkeley and the SETI Institute.

The findings suggest that Fomalhaut b is in fact a rogue planet, trailing away at a large distance from its parent star much in the same way as a comet. Its mass is believed to be comparable to that of an icy dwarf world, however its size is believed to be close to that of Jupiter.

“Hot Jupiters get tossed through scattering events, where one planet goes in and one gets thrown out,” says Mark Clampin of NASA’s Goddard Space Flight Center. “This could be the planet that gets thrown out.”

In the video below, astronomers show one possible orbit for Fomalhaut b derived from the analysis of Hubble Space Telescope data between 2004 and 2012. The findings were presented at the  American Astronomical Society 2013 conference.



Artist's impression of the "rogue planet" CFBDSIR2149 discovered in the AB Doradus group of moving stars. (European Southern Observatory/AFP)

Closest rogue planet discovered is just 100 light-years away

Like in a scene from a Sci-fi novel, about 100 light years away, somewhere in the constellation Doradus, a planet is travelling around the galaxy by itself, without orbiting a parent star. This “rogue planet“, has a temperature of about 400C and a mass between 4 to 7 times that of Jupiter – close to the mass limit beyond which it would have become a brown dwarf.

The object, that so far has the captivating name of CFBDSIR2149, has been discovered while observing a region of space occupied by a group of about 30 stars called the AB Doradus Moving Group – a group of stars that have formed at the same time – most likely from the same initial gaseous nebulae. This fact was derived from the similarities in the composition, age and the similar direction of movement through space of the stars – which place the age of this group somewhere between 50 and 120 million years old – a reasonably young star group.

Artist's impression of the "rogue planet" CFBDSIR2149 discovered in the AB Doradus group of moving stars. (European Southern Observatory/AFP)

Artist’s impression of the “rogue planet” CFBDSIR2149 discovered in the AB Doradus group of moving stars. (European Southern Observatory/AFP)

The initial observations placed the object in the category of brown dwarfs – a class of sub-stellar objects – that are more massive then the biggest planets – the gas giants, yet they don’t have enough mass to start nuclear fusion. However, further analyses revealed that our object was in fact smaller than this – making it a planet – a gas giant. The whole detection was possible due to the fact that our “rogue” emits light in the infrared wavelengths.

Astronomers said that based on its estimated age, through computer models of planetary evolution, they were able to make further deductions regarding the planet’s mass – 4 to 7 times the mass of Jupiter, and surface temperature of 400 degrees Celsius (750 degrees Fahrenheit).

The planet was discovered during a survey using the infrared cameras of the Canada-France-Hawaii Telescope on Hawaii’s Mauna Kea and the Very Large Telescope (VLT) in Chile, as study co-author Etienne Artigau of the University of Montreal said: “This object was discovered during a scan that covered the equivalent of 1,000 times the [area] of the full moon.

Of course, this is not the first time such a “nomad planet” has been spotted, but this observation is special because it found the closest such object discovered so far – only 100 light years away, the first such planet that is relatively close to our solar system, as study co-author Etienne Artigau put it: “We observed hundreds of millions of stars and planets, but we only found one homeless planet in our neighbourhood“.

A big question in the case of all such rogue planets is how this planet came to be? Maybe it formed inside a solar system, just as any other planet, and got ejected afterwards – through gravitational interaction perhaps with a more massive object entering that system. Or it formed separate from any solar system from the beginning, similar to the formation of a star – through progressive accretion of the gas of a dense nebulae. This question remains open – and perhaps will remain for some time to come.

Philippe Delorme of France’s Institute of Planetology and Astrophysics said: “these objects are important, as they can either help us understand more about how planets may be ejected from planetary systems, or how very light objects can arise from the star formation process.”

The findings were reported in the journal Solar and Stellar Astrophysics.

source: BBC

Stars capture and swap with one another nomad planets

Some time ago we told you about one of the most fascinating facts this blog has ever published, namely how there are “nomad” or “rogue” planets outside our solar system, which travel aimlessly through interstellar space without having to circle a certain star. It’s estimated that there are actually more such nomad planets haunting through space in the Milky Way than there are stars.

nomad planet A new study, authored by  Hagai Perets, of the Harvard-Smithsonian Center for Astrophysics and Thijs Kouwenhoven of China’s Peking University, found that there was a  3 to 6 percent chance a star would snag a free-floating planet and lock it into its orbit, after simulating the evolution of young star clusters. They studied young star clusters because capture is more likely when stars and free-floating planets are crowded together in a small space.

“Stars trade planets just like baseball teams trade players,” study lead author Hagai Perets said.

It seems rogue stars are a very natural consequence of star formation. When a new solar system is formed, it’s common for two planets to interact and thus one of them becomes ejected, doomed to free travel through interstellar space, until it may finally encounter a star massive enough to pull it in and hitch a ride. This explains why there are some solar systems with planets incredibly far away from the star their orbiting, in total discrepancy to the respective star’s mass. Also rogue stars orbiting a new home-star are likely to have orbits that are tilted relative to any “native” planets, and they may even revolve around their stars “backward,” researchers said.

Evidence

That’s the theory, but it’s very difficult for scientists to assert that a certain planet wasn’t actually formed in its current solar system, but instead hitched a long time after. One of the most conclusive piece of evidence astronomers have backing up the idea that rogue plants actually do happen to attach themselves to new solar system is a 2006 discovery. Then, scientists found a huge planetary duo – 14 and respectively 7 times more massive than Jupiter – orbiting each other without a star in their vicinity.

Concerning our own solar system, astronomers have scoured to the very outskirts and have yet to find any signs of a new planet, such a presence being deemed highly unlikely.

“There’s no evidence that the sun captured a planet,” Perets said. “We can rule out large planets. But there’s a non-zero chance that a small world might lurk on the fringes of our solar system.”

Well, let the Nibiru end of days conspiracy theories surface once more…

Nomad planets may litter Milky Way

According to a recent study published by researchers from the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), our galaxy may be ‘infested’ with nomad planets, which wander aimlessly instead of orbiting a star. Furthermore, the study concluded there may actually be 100,000 times more “nomad planets” in the Milky Way than stars.

If this theory is proven correct, it will severely affect our current understanding about planetary formation and will even affect what we think about the origin and abundance of life in our galaxy.

“If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist,” said Louis Strigari, leader of the team that reported the result in a paper submitted to the Monthly Notices of the Royal Astronomical Society.

The thing is, even though these planets don’t have the luxury of a star to offer them warmth, they might generate enough heat to support life through radioactive decay and tectonic activity. Past studies have shown more than 500 planets outside our solar system, almost all of which orbit stars, and last year alone, astronomers identified about a dozen nomad planets, through a technique called gravitational lensing, which analyzes stars whose light is momentarily refocused by the gravity of other passing planets.

The traditional belief was that roughly two nomads exist for every typical, so-called main-sequence star in our galaxy, but this new research showed that nomad planets may actually be 50.000 times more frequent than that.

“To paraphrase Dorothy from The Wizard of Oz, if correct, this extrapolation implies that we are not in Kansas anymore, and in fact we never were in Kansas,” said Alan Boss of the Carnegie Institution for Science, author of The Crowded Universe: The Search for Living Planets, who was not involved in the research. “The universe is riddled with unseen planetary-mass objects that we are just now able to detect.”

“Few areas of science have excited as much popular and professional interest in recent times as the prevalence of life in the universe,” said co-author and KIPAC Director Roger Blandford. “What is wonderful is that we can now start to address this question quantitatively by seeking more of these erstwhile planets and asteroids wandering through interstellar space, and then speculate about hitchhiking bugs.”

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