Artist’s impression of how an an Earth-like exoplanet might look. Credit: ESO.
The ongoing hunt for exoplanets has yielded some very interesting returns in recent years. All told, the Kepler mission has discovered more than 4000 candidates since it began its mission in March of 2009. Amidst the many “Super-Jupiters” and assorted gas giants (which account for the majority of Kepler’s discoveries) astronomers have been particularly interested in those exoplanets which resemble Earth.
And now, an international team of scientists has finished perusing the Kepler catalog in an effort to determine just how many of these planets are in fact “Earth-like”. Their study, titled “A Catalog of Kepler Habitable Zone Exoplanet Candidates” (which will be published soon in the AstrophysicalJournal), explains how the team discovered 216 planets that are both terrestrial and located within their parent star’s “habitable zone” (HZ).
The international team was made up of researchers from NASA, San Francisco State University, Arizona State University, Caltech, University of Hawaii-Manoa, the University of Bordeaux, Cornell University and the Harvard-Smithsonian Center for Astrophysics. Having spent the past three years looking over the more than 4000 entries, they have determined that 20 of the candidates are most like Earth (i.e. likely habitable).
Figure showing the habitable zone for different types of stars, as well as the location of terrestrial size Kepler candidates. Credit: Chester Harman
As Stephen Kane, an associate professor of physics and astronomy at San Fransisco University and lead author of the study, explained in a recent statement:
“This is the complete catalog of all of the Kepler discoveries that are in the habitable zone of their host stars. That means we can focus in on the planets in this paper and perform follow-up studies to learn more about them, including if they are indeed habitable.”
In addition to isolating 216 terrestrial planets from the Kepler catalog, they also devised a system of four categories to determine which of these were most like Earth. These included “Recent Venus”, where conditions are like that of Venus (i.e. extremely hot); “Runaway Greenhouse”, where planets are undergoing serious heating; “Maximum Greenhouse”, where planets are within their star’s HZ; and “Recent Mars”, where conditions approximate those of Mars.
From this, they determined that of the Kepler candidates, 20 had radii less than twice that of Earth (i.e. on the smaller end of the Super-Earth category) and existed within their star’s HZ. In other words, of all the planets discovered in our local Universe, they were able to isolate those where liquid water can exist on the surface, and the gravity would likely be comparable to Earth’s and not crushing!
Earlier today, NASA announced that Kepler had confirmed the existence of 1,284 new exoplanets, the most announced at any given time. Credit: NASA
This is certainly exciting news, since one of the most important aspects of exoplanet hunting has been finding worlds that could support life. Naturally, it might sound a bit anthropocentric or naive to assume that planets which have similar conditions to our own would be the most likely places for it to emerge. But this is what is known as the “low-hanging fruit” approach, where scientists seek out conditions which they know can lead to life.
“There are a lot of planetary candidates out there, and there is a limited amount of telescope time in which we can study them,” said Kane. “This study is a really big milestone toward answering the key questions of how common is life in the universe and how common are planets like the Earth.”
Professor Kane is renowned for being one of the world’s leading “planet-hunters”. In addition to discovering several hundred exoplanets (using data obtained by the Kepler mission) he is also a contributor to two upcoming satellite missions – the NASA Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency’s Characterizing ExOPLanet Satellite (CHEOPS).
These next-generation exoplanet hunters will pick up where Kepler left off, and are likely to benefit greatly from this recent study.
Artist's impression of an exoplanet orbiting a low-mass star. Credit: ESO/L. Calçada
The Fermi Paradox essentially states that given the age of the Universe, and the sheer number of stars in it, there really ought to be evidence of intelligent life out there. This argument is based in part on the fact that there is a large gap between the age of the Universe (13.8 billion years) and the age of our Solar System (4.5 billion years ago). Surely, in that intervening 9.3 billion years, life has had plenty of time to evolve in other star system!
An artist’s depiction of planets transiting a red dwarf star in the TRAPPIST-1 System. Credit: NASA/ESA/STScl
When Hubble first observed the atmospheric conditions of an extrasolar planet in 2000, it opened up that entire field of study. Now, Hubble has conducted the first preliminary study of the atmospheres of Earth-sized, relatively nearby worlds and found “indications that increase the chances of habitability on two exoplanets,” say the researchers.
The planets, TRAPPIST-1b and TRAPPIST-1c, were discovered earlier this year and are approximately 40 light-years away. At the time of their discovery, it was unknown if the worlds were gas planets or rocky worlds, but Hubble’s most recent observations suggest that both planets have compact atmospheres, similar to those of rocky planets such as Earth, Venus, and Mars instead of thick, puffy atmospheres, similar to that of the gas planets like Jupiter.
“Now we can say that these planets are rocky. Now the question is, what kind of atmosphere do they have?” said Julien de Wit of the Massachusetts Institute of Technology, who led a team of scientists to observe the planets in near-infrared light using Hubble’s Wide Field Camera 3. “The plausible scenarios include something like Venus, with high, thick clouds and an atmosphere dominated by carbon dioxide, or an Earth-like atmosphere dominated by nitrogen and oxygen, or even something like Mars with a depleted atmosphere. The next step is to try to disentangle all these possible scenarios that exist for these terrestrial planets.”
Structure of the TRAPPIST-1 exosystem. The green is the star’s habitable zone. Credit: Planetary Habitability Lab.
The exoplanets were originally discovered by the TRAPPIST telescope at ESO’s La Silla observatory in Chile, which, like the Kepler telescope, looks for planetary transits (TRAPPIST stands for Transiting Planets and Planetesimals Small Telescope) observing dips in a star’s light from planets passing in front of it from Earth’s point of view.
The star, TRAPPIST-1, is an ultracool dwarf star and is very small and dim. TRAPPIST-1b completes an orbit around the star in just 1.5 days and TRAPPIST-1c in 2.4 days, and the planets are between 20 and 100 times closer to their star than the Earth is to the sun. Both are tidally locked, where one side of these worlds might be hellish and uninhabitable, but conditions might permit a limited region of habitability on the other side. And because of the star’s faintness, researchers think that TRAPPIST-1c may be within the star’s habitable zone, where moderate temperatures could allow for liquid water to pool.
“A rocky surface is a great start for a habitable planet, but any life on the TRAPPIST-1 planets is likely to have a much harder time than life on Earth,” said Joanna Barstow, an astrophysicist at University College London, who was not involved with the research. “Of course, our ideas of habitability are very narrow because we only have one planet to look at so far, and life might well surprise us by flourishing in what we think of as unlikely conditions.”
The researchers used spectroscopy to decode the light and reveal clues to the chemical makeup of the planets’ atmospheres. While the content of the atmospheres is unknown and are scheduled for more observations, the low concentration of hydrogen and helium has scientists excited about the implications.
The team realized a rare double transit was going to take place, when the two planets would almost simultaneously pass in front of their star, but they only knew two weeks in advance. They took a chance, and taking advantage of Hubble’s ability to do observations on short notice, they wrote up a proposal in a day.
“We thought, maybe we could see if people at Hubble would give us time to do this observation, so we wrote the proposal in less than 24 hours, sent it out, and it was reviewed immediately,” de Wit said. “Now for the first time we have spectroscopic observations of a double transit, which allows us to get insight on the atmosphere of both planets at the same time.”
Using Hubble, the team recorded a combined transmission spectrum of TRAPPIST-1b and c, meaning that as first one planet then the other crossed in front of the star, they were able to measure the changes in wavelength as the amount of starlight dipped with each transit.
“The data turned out to be pristine, absolutely perfect, and the observations were the best that we could have expected,” de Wit says. “The force was certainly with us.”
“These initial Hubble observations are a promising first step in learning more about these nearby worlds, whether they could be rocky like Earth, and whether they could sustain life,” says Geoff Yoder, acting associate administrator for NASA’s Science Mission Directorate in Washington. “This is an exciting time for NASA and exoplanet research.”
The star system CVSO 30, which was found to have two exoplanets with extreme orbital periods. If you look closely, you can see 30c to the upper left of the star. Credit: ESO
Every planet in the Solar System has its own peculiar orbit, and these vary considerably. Whereas planet Earth takes 365.25 days to complete a single orbit about our Sun, Mars takes almost twice as long – 686.971 days. Then you have Jupiter and the other gas giants, which take between 11.86 and 164.8 years to orbit our Sun. But even with these serving as examples, astronomers were not prepared for what they found when they looked at CVSO 30.
This star system, which lies some 1200 light years from Earth, has been found in recent years to have two candidate exoplanets. These planets, which are many times the mass of Jupiter, were discovered by an international team of astronomers using both the Transit Method and Direct Imaging. And what they found was very interesting: one planet has an orbital period of less than 11 days while the other takes a whopping 27,000 years to orbit its parent star!
In addition to being a big surprise, the detection of these two planets using different methods was an historic achievement. Up until now, the vast majority of the over 2,000 exoplanets discovered have been detected thanks to indirect methods. These include the aforementioned Transit Method, which detects planets by measuring the dimming effect they cause when crossing their parent star’s path, and the Radial Velocity Method, which measures the gravitational effect planets have on their parent star.
In 2012, astronomers used the Transit Method to detect CVSO 30b, a planet with 5 to 6 times the mass of Jupiter, and which orbits its star at a distance of only 1.2 million kilometers (by comparison, Mercury orbits our Sun at a distance of 58 million kilometers). From these characteristics, CVSO 30b can be described as a particularly “hot-Jupiter”.
In contrast, Direct Imaging has been used to spot only a few dozen exoplanets. The reason for this is because it is typically quite difficult to detect the light reflected by a planet’s atmosphere due it being drowned out by the light of its parent star. It can also be quite demanding when it comes to the instrument involved. Still, compared to indirect methods, it can be more effective when it comes to exploring the remote regions of a star.
Thanks to the efforts of an international team of astronomers, who combined the use of the Keck Observatory in Hawaii, the ESO’s Very Large Telescope in Chile, and the Spanish National Research Council’s (CSIC) Calar Alto Observatory, CVSO 30c was spotted in remote regions around its parent star, orbiting at a distance of around 666 AU.
The details of the discovery were published in a paper titled “Direct Imaging discovery of a second planet candidate around the possibly transiting planet host CVSO 30“. In it, the researchers – who hail from such prestigious institutions as the Cerro Tololo Inter-American Observatory, the Jena Observatory, the European Space Agency and the Max Planck Institute for Astronomy – explained the methods used to find the exoplanet, and the significance of its discovery.
The star CVSO30, showing the two detection methods that revealed its exoplanet candidates. Credit: Keck Observatory/ESO/VLT/NACO
As Tobias Schmidt – of the University of Hamburg, the Astrophysical Institute and University Observatory Jena, and the lead author of the paper – told Universe Today via email:
“[30b and 30c] are both unusual on their own. CVSO 30b is the first transiting planet around a star as young as 2.5 million years. Published in 2012, all previously detected transiting planets were older than few hundred million years… It has been a surprise to find a planetary mass companion at 662 AU, or 662 times the distance from Earth to the Sun, from a primary star having only about 0.4 solar masses. According to the standard model, planets form in disks around the star. But none of the observed disks around such low-mass stars is large enough to form such an object.”
In other words, it is surprising to find two exoplanet candidates with several times the mass of Jupiter (aka. Super-Jupiters) orbiting a star as small as CVSO 30. But to find two exoplanets with such a disparity in terms of their respective distance from their star (despite being similar in mass) was particularly surprising.
Relying on high-contrast photometric and spectroscopic observations from the Very Large Telescope, the Keck telescopes and the Calar Alto observatory, the international team was able to spot 30c using a technique known as lucky imaging. This process, which is used by ground-based telescopes, involves many high-speed, quick exposure photos being taken to minimize atmospheric interference.
An artist’s conception of a T-type brown dwarf. Credit: Tyrogthekreeper/Wikimedia Commons.
What they found was an exoplanet with a wide orbit that was between 4 and 5 Jupiter masses, and was also very young – less than 10 million years old. What’s more, the spectroscopic data indicated that it is unusually blue for a planet, as most other planet candidates of its kind are very red. The researchers concluded from this that it is likely that 30c is the first young planet of its kind to be directly imaged.
They further concluded that 30 c is also likely the first “L-T transition object” younger than 10 million years to be found orbiting a star. L-T transition objects are a type of brown dwarf – objects that are too large to be considered planets, but too small to be considered stars. Typically they are found embedded in large clouds of gas and dust, or on their own in space.
Paired with its companion – 30 b, which is impossibly close to its parent star – 30 c is not believed to have formed at its current position, and is likely not stable in the long-term. At least, not where current models of planetary formation and orbit are concerned. However, as Prof. Schmidt indicated, this offers a potential explanation for the odd nature of these exoplanets.
“We do think this is a very good hint,” he said, “that the two objects might have formed regularly around the star at a separation comparable to Jupiter or Saturn’s separation from the Sun, then interacted gravitationally and were scattered to their current orbits. However this is still speculation, further investigations will try to prove this. Both have about the same mass of few Jupiter masses, the inner one might be even lower.”
The Very Large Telescoping Interferometer firing it’s adaptive optics laser. Credit: ESO/G. Hüdepohl
The discovery is also significant since it was the first time that these two detection methods – Transit and Direct Imaging – were used to confirm exoplanet candidates around the same star. In this case, the methods were quite complimentary, and present opportunities to learn more about exoplanets. As Professor Schmidt explained:
“Both Transit method and radial velocity method have problems finding planets around young stars, as the activity of young stars is disturbing the search for them. CVSO 30 b was the first very young planet found with these methods, currently a hand full of candidates exist. Direct imaging, on the other hand, is working best for young planets as they still contract and are thus self-luminous. It is therefore great luck that a far out planet was found around the very first young star hosting a inner planet…
“However, the real advantage of transit and direct imaging methods is that the two objects can now be investigated in greater detail. While we can use the direct light from the imaging for spectroscopy, i.e. split the light according to its wavelength, we hope to achieve the same for the inner planet candidate. This is possible as the light passes through the atmosphere of the planet during transits and some of the elements are absorbed by the composition material of the atmosphere. So we do hope to learn a lot about planet formation, thus also formation of the early Solar System and about young planets in particular from the CVSO 30 system.”
Since astronomers first began began to find exoplanet candidates in distant star systems, we have come to learn just how diverse our Universe really is. Many of the discoveries have challenged our notions about where planets can form around their parent star, while others have showed us that planets can take many different forms.
As time goes on and our exploration of the local Universe advances, we will be challenged to find explanations for how it all fits together. And from that, new and more comprehensive models will no doubt emerge.
The Jovian planets of the Solar System. Credit: bork.hampshire.edu
Beyond our Solar System’s “Frost Line” – the region where volatiles like water, ammonia and methane begin to freeze – four massive planets reside. Though these planets – Jupiter, Saturn, Uranus and Neptune – vary in terms of size, mass, and composition, they all share certain characteristics that cause them to differ greatly from the terrestrial planets located in the inner Solar System.
Officially designated as gas (and/or ice) giants, these worlds also go by the name of “Jovian planets”. Used interchangeably with terms like gas giant and giant planet, the name describes worlds that are essentially “Jupiter-like”. And while the Solar System contains four such planets, extra-solar surveys have discovered hundreds of Jovian planets, and that’s just so far…
Definition:
The term Jovian is derived from Jupiter, the largest of the Outer Planets and the first to be observed using a telescope – by Galileo Galilei in 1610. Taking its name from the Roman king of the gods – Jupiter, or Jove – the adjective Jovian has come to mean anything associated with Jupiter; and by extension, a Jupiter-like planet.
The giant planets of the Solar System (aka. the Jovians). Credit: spiff.rit.edu
Within the Solar System, four Jovian planets exist – Jupiter, Saturn, Uranus and Neptune. A planet designated as Jovian is hence a gas giant, composed primarily of hydrogen and helium gas with varying degrees of heavier elements. In addition to having large systems of moons, these planets each have their own ring systems as well.
Another common feature of gas giants is their lack of a surface, at least when compared to terrestrial planets. In all cases, scientists define the “surface” of a gas giant (for the sake of defining temperatures and air pressure) as being the region where the atmospheric pressure exceeds one bar (the pressure found on Earth at sea level).
Structure and Composition:
In all cases, the gas giants of our Solar System are composed primarily of hydrogen and helium with the remainder being taken up by heavier elements. These elements correspond to a structure that is differentiated between an outer layer of molecular hydrogen and helium that surrounds a layer of liquid (or metallic) hydrogen or volatile elements, and a probable molten core with a rocky composition.
Due to difference in their structure and composition, the four gas giants are often differentiated, with Jupiter and Saturn being classified as “gas giants” while Uranus and Neptune are “ice giants”. This is due to the fact that Neptune and Uranus have higher concentrations of methane and heavier elements – like oxygen, carbon, nitrogen, and sulfur – in their interior.
Interior models of the giant planets, showing rocky cores overlaid by solid and gaseous envelopes. Credit: NASA/JPL
In stark contrast to the terrestrial planets, the density of the gas giants is slightly greater than that of water (1 g/cm³). The one exception to this is Saturn, where the mean density is actually lower than water (0.687 g/cm3). In all cases, temperature and pressure increase dramatically the closer one ventures into the core.
Atmospheric Conditions:
Much like their structures and compositions, the atmospheres and weather patterns of the four gas/ice giants are quite similar. The primary difference is that the atmospheres get progressively cooler the farther away they are from Sun. As a result, each Jovian planet has distinct cloud layers who’s altitudes are determined by their temperatures, such that the gases can condense into liquid and solid states.
In short, since Saturn is colder than Jupiter at any particular altitude, its cloud layers occur deeper within it’s atmosphere. Uranus and Neptune, due to their even lower temperatures, are able to hold condensed methane in their very cold tropospheres, whereas Jupiter and Saturn cannot.
The presence of this methane is what gives Uranus and Neptune their hazy blue color, where Jupiter is orange-white in appearance due to the intermingling of hydrogen (which gives off a red appearance), while the upwelling of phosphorus, sulfur, and hydrocarbons yield spotted patches areas and ammonia crystals create white bands.
Jupiter and Saturn have similar appearances, owing to their similar compositions and atmospheres. Credit: NASA/GSFC
The atmosphere of Jupiter is classified into four layers based on increasing altitude: the troposphere, stratosphere, thermosphere and exosphere. Temperature and pressure increase with depth, which leads to rising convection cells emerging that carry with them the phosphorus, sulfur, and hydrocarbons that interact with UV radiation to give the upper atmosphere its spotted appearance.
Saturn’s atmosphere is similar in composition to Jupiter’s. Hence why it is similarly colored, though its bands are much fainter and are much wider near the equator (resulting in a pale gold color). As with Jupiter’s cloud layers, they are divided into the upper and lower layers, which vary in composition based on depth and pressure. Both planets also have clouds composed of ammonia crystals in their upper atmospheres, with a possible thin layer of water clouds underlying them.
Uranus’ atmosphere can be divided into three sections – the innermost stratosphere, the troposphere, and the outer thermosphere. The troposphere is the densest layer, and also happens to be the coldest in the solar system. Within the troposphere are layers of clouds, with methane clouds on top, ammonium hydrosulfide clouds, ammonia and hydrogen sulfide clouds, and water clouds at the lowest pressures.
Next is the stratosphere, which contains ethane smog, acetylene and methane, and these hazes help warm this layer of the atmosphere. Here, temperatures increase considerably, largely due to solar radiation. The outermost layer (the thermosphere and corona) has a uniform temperature of 800-850 (577 °C/1,070 °F), though scientists are unsure as to the reason.
Uranus and Neptune, the Solar System’s ice giant planets. Credit: Wikipedia Commons
This is something that Uranus shares with Neptune, which also experiences unusually high temperatures in its thermosphere (about 750 K (476.85 °C/890 °F). Like Uranus, Neptune is too far from the Sun for this heat to be generated through the absorption of ultraviolet radiation, which means another heating mechanism is involved.
Neptune’s atmosphere is also predominantly hydrogen and helium, with a small amount of methane. The presence of methane is part of what gives Neptune its blue hue, although Neptune’s is darker and more vivid. Its atmosphere can be subdivided into two main regions: the lower troposphere (where temperatures decrease with altitude), and the stratosphere (where temperatures increase with altitude).
The lower stratosphere is believed to contain hydrocarbons like ethane and ethyne, which are the result of methane interacting with UV radiation, thus producing Neptune’s atmospheric haze. The stratosphere is also home to trace amounts of carbon monoxide and hydrogen cyanide, which are responsible for Neptune’s stratosphere being warmer than that of Uranus.
Weather Patterns:
Like Earth, Jupiter experiences auroras near its northern and southern poles. But on Jupiter, the auroral activity is much more intense and rarely ever stops. These are the result of Jupiter’s intense radiation, it’s magnetic field, and the abundance of material from Io’s volcanoes that react with Jupiter’s ionosphere.
Reprocessed view by Bjorn Jonsson of the Great Red Spot taken by Voyager 1 in 1979 reveals an incredible wealth of detail. Credit: NASA/JPL
Jupiter also experiences violent weather patterns. Wind speeds of 100 m/s (360 km/h) are common in zonal jets, and can reach as high as 620 kph (385 mph). Storms form within hours and can become thousands of km in diameter overnight. One storm, the Great Red Spot, has been raging since at least the late 1600s.
The storm has been shrinking and expanding throughout its history; but in 2012, it was suggested that the Giant Red Spot might eventually disappear. Jupiter also periodically experiences flashes of lightning in its atmosphere, which can be up to a thousand times as powerful as those observed here on the Earth.
Saturn’s atmosphere is similar, exhibiting long-lived ovals now and then that can be several thousands of kilometers wide. A good example is the Great White Spot (aka. Great White Oval), a unique but short-lived phenomenon that occurs once every 30 Earth years. Since 2010, a large band of white clouds called the Northern Electrostatic Disturbance have been observed enveloping Saturn, and is believed to be followed by another in 2020.
The winds on Saturn are the second fastest among the Solar System’s planets, which have reached a measured high of 500 m/s (1800 km/h). Saturn’s northern and southern poles have also shown evidence of stormy weather. At the north pole, this takes the form of a persisting hexagonal wave pattern measuring about 13,800 km (8,600 mi) and rotating with a period of 10h 39m 24s.
Saturn makes a beautifully striped ornament in this natural-color image, showing its north polar hexagon and central vortex. Credit: NASA/JPL-Caltech/Space Science Institute
The south pole vortex apparently takes the form of a jet stream, but not a hexagonal standing wave. These storms are estimated to be generating winds of 550 km/h, are comparable in size to Earth, and believed to have been going on for billions of years. In 2006, the Cassini space probe observed a hurricane-like storm that had a clearly defined eye. Such storms had not been observed on any planet other than Earth – even on Jupiter.
Uranus’s weather follows a similar pattern where systems are broken up into bands that rotate around the planet, which are driven by internal heat rising to the upper atmosphere. Winds on Uranus can reach up to 900 km/h (560 mph), creating massive storms like the one spotted by the Hubble Space Telescope in 2012. Similar to Jupiter’s Great Red Spot, this “Dark Spot” was a giant cloud vortex that measured 1,700 kilometers by 3,000 kilometers (1,100 miles by 1,900 miles).
Because Neptune is not a solid body, its atmosphere undergoes differential rotation, with its wide equatorial zone rotating slower than the planet’s magnetic field (18 hours vs. 16.1 hours). By contrast, the reverse is true for the polar regions where the rotation period is 12 hours. This differential rotation is the most pronounced of any planet in the Solar System, and results in strong latitudinal wind shear and violent storms.
Reconstruction of Voyager 2 images showing the Great Dar Spot (top left), Scooter (middle), and the Small Dark Spot (lower right). Credit: NASA/JPL
The first to be spotted was a massive anticyclonic storm measuring 13,000 x 6,600 km and resembling the Great Red Spot of Jupiter. Known as the Great Dark Spot, this storm was not spotted five later (Nov. 2nd, 1994) when the Hubble Space Telescope looked for it. Instead, a new storm that was very similar in appearance was found in the planet’s northern hemisphere, suggesting that these storms have a shorter life span than Jupiter’s.
Exoplanets:
Due to the limitations imposed by our current methods, most of the exoplanets discovered so far by surveys like the Kepler space observatory have been comparable in size to the giant planets of the Solar System. Because these large planets are inferred to share more in common with Jupiter than with the other giant planets, the term “Jovian Planet” has been used by many to describe them.
Many of these planets, being greater in mass than Jupiter, have also been dubbed as “Super-Jupiters” by astronomers. Such planets exist at the borderline between planets and brown dwarf stars, the smallest stars known to exist in our Universe. They can be up to 80 times more massive than Jupiter but are still comparable in size, since their stronger gravity compresses the material into an ever denser, more compact sphere.
Artist’s concept of the “Hot Jupiter” exoplanet HD 149026b. Credit: NASA/JPL-Caltech
Those Super-Jupiters that have distant orbits from their parent stars are known as “Cold Jupiters”, whereas those that have close orbits are called “Hot Jupiters”. A surprising number of Hot Jupiters have been observed by exoplanet surveys, due to the fact that they are particularly easy to spot using the Radial Velocity method – which measures the oscillation of parent stars due to the influence of their planets.
In the past, astronomers believed that Jupiter-like planets could only form in the outer reaches of a star system. However, the recent discovery of many Jupiter-sized planets orbiting close to their stars has cast doubt on this. Thanks to the discovery of Jovians beyond our Solar System, astronomers may be forced to rethink our models of planetary formation.
Since Galileo first observed Jupiter through his telescope, Jovian planets have been an endless source of fascination for us. And despite many centuries of research and progress, there are still many things we don’t know about them. Our latest effort to explore Jupiter, the Juno Mission, is expected to produce some rather interesting finds. Here’s hoping they bring us one step closer to understanding those darn Jovians!
A new study announced the discovery of a system hosting five transiting planets (image credit: jhmart1/deviantart).
A new study announced the discovery of a system hosting five transiting planets (image credit: jhmart1/deviantart).
NASA’s planet-discovering Kepler mission suffered a major mechanical failure in May 2013, but thanks to innovative techniques subsequently implemented by astronomers the satellite continues to uncover worlds beyond our Solar System (i.e., exoplanets). Indeed, Andrew Vanderburg (CfA) and colleagues just published results highlighting a new system found to host five transiting planets, which include: two sub-Neptune sized planets, a Neptune sized planet, a sub-Saturn sized planet, and a Jupiter sized planet.
The four new, but as yet unconfirmed, exoplanets. Image: University of British Columbia
A student at the University of British Columbia (UBC), Canada, has discovered four new exoplanets hidden in data from the Kepler spacecraft.
Michelle Kunimoto recently graduated from UBC with a Bachelor’s degree in physics and astronomy. As part of her coursework, she spent a few months looking closely at Kepler data, trying to find planets that others had overlooked.
In the end, she discovered four planets, (or planet candidates until they are independently confirmed.) The first planet is the size of Mercury, two are roughly Earth-sized, and one is slightly larger than Neptune. According to Kunimoto, the largest of the four, called KOI (Kepler Object of Interest) 408.05, is the most interesting. That one is 3,200 light years away from Earth and occupies the habitable zone of its star.
“Like our own Neptune, it’s unlikely to have a rocky surface or oceans,” said Kunimoto, who graduates today from UBC. “The exciting part is that like the large planets in our solar system, it could have large moons and these moons could have liquid water oceans.”
Her astronomy professor, Jaymie Matthews, shares her enthusiasm. “Pandora in the movie Avatar was not a planet, but a moon of a giant planet,” he said. And we all know what lived there.
On its initial mission, Kepler looked at 150,000 stars in the Milky Way. Kepler looks for dips in the brightness of these stars, which can be caused by planets passing between us and the star. These dips are called light curves, and they can tell us quite a bit about an exoplanet.
“A star is just a pinpoint of light so I’m looking for subtle dips in a star’s brightness every time a planet passes in front of it,” said Kunimoto. “These dips are known as transits, and they’re the only way we can know the diameter of a planet outside the solar system.”
Michelle Kunimoto and her prof., Jaymie Matthews, at the University of British Columbia in Vancouver, Canada. Image: Martin Dee/UBC
One of the limitations of the Kepler mission is that it’s biased against planets that take a long time to orbit their star. That’s because the longer the orbit is, the fewer transits can be witnessed in a given amount of time. The “warm Neptune” KOI 408.05 found by Kunimoto takes 637 days to orbit its sun.
This long orbit explains why the planet was not found initially, and also why Kunimoto is receiving recognition for her discovery. It took a substantial commitment and effort to uncover it. Kepler has discovered almost 5,000 planet and planet candidates, and of those, only 20 have longer orbits than KOI 408.05.
Kunimoto and Matthews have submitted the findings to the Astronomical Journal. They may be the first of many submissions for Kunimoto, as she is returning to UBC next year to earn a Master’s Degree in physics and astronomy, when she will hunt for more planets and investigate their habitability.
The fun didn’t end with her exoplanet discovery, however. As a Star Trek fan (who isn’t one?) she was lucky enough to meet William Shatner at an event at the University, and to share her discovery with Captain James Tiberius Kirk.
It makes you wonder what other surprises might lie hidden in the Kepler data, and what else might be uncovered. Might a life-bearing planet or moon, maybe the only one, be found in Kepler’s data at some future time?
Special Guests:
Mike Brown is the Richard and Barbara Rosenberg Professor of Planetary Astronomy at CalTech. Konstantin Batygin is Assistant Professor of Planetary Science at CalTech. They’ll be here discussing their discovery of Planet 9 and what’s been happening since that amazing announcement.
We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we’ve started a new system. Instead of adding all of the stories to the spreadsheet each week, we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today or the Universe Today YouTube page.
Special Guest:
Arne Christer Fuglesang is a Swedish physicist and an ESA astronaut. He was first launched aboard the STS-116 Space Shuttle mission on December 10, 2006, making him the first Swedish citizen in space.
We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we’ve started a new system. Instead of adding all of the stories to the spreadsheet each week, we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
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The northern constellation Auriga, showing the brightest stars of Capella, Menkalinan, and proximate Deep Sky Objects. Credit: stargazerslounge.com
Welcome back to Constellation Friday! Today, in honor of our dear friend and contributor, Tammy Plotner, we examine the Auriga constellation. Enjoy!
In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of the then-known 48 constellations. His treatise, known as the Almagest, would serve as the authoritative source of astronomy for over a thousand years to come. Since the development of modern telescopes and astronomy, this list has come to be expanded to include the 88 constellation that are recognized by the International Astronomical Union (IAU) today.
One of these is the constellation of Auriga, a beautiful pentagon-shaped collection of stars that is situated just north of the celestial equator. Along with five other constellations that have stars in the Winter Hexagon asterism, Auriga is most prominent during winter evenings in the Northern Hemisphere. Auriga also belongs to the Perseus family of constellations, together with Andromeda, Cassiopeia, Cepheus, Cetus, Lacerta, Pegasus, Perseus, and Triangulum.
