ESA's Gaia is currently on a five-year mission to map the stars of the Milky Way. Image credit: ESA/ATG medialab; background: ESO/S. Brunier.
Early on the morning of Dec. 19, 2013, the pre-dawn sky above the coastal town of Kourou in French Guiana was briefly sliced by the brilliant exhaust of a Soyuz VS06 rocket as it ferried ESA’s “billion-star surveyor” Gaia into space, on its way to begin a five-year mission to map the precise locations of our galaxy’s stars. From its position in orbit around L2 Gaia will ultimately catalog the positions of over a billion stars… and in the meantime it will also locate a surprising amount of Jupiter-sized exoplanets – an estimated 21,000 by the end of its primary mission in 2019.
And, should Gaia continue observations in extended missions beyond 2019 improvements in detection methods will likely turn up even more exoplanets, anywhere from 50,000 to 90,000 over the course of a ten-year mission. Gaia could very well far surpass NASA’s Kepler spacecraft for exoplanet big game hunting!
“It is not just the number of expected exoplanet discoveries that is impressive”, said former mission project scientist Michael Perryman, lead author on a report titled Astrometric Exoplanet Detection with Gaia. “This particular measurement method will give us planet masses, a complete exoplanet survey around all types of stars in our Galaxy, and will advance our knowledge of the existence of massive planets orbiting far out from their host stars”.
Artist’s impression of a Jupiter-sized exoplanet orbiting an M-dwarf star
The planets Gaia will be able to spot are expected to be anywhere from 1 to fifteen times the mass of Jupiter in orbit around Sun-like stars out to a distance of about 500 parsecs (1,630 light-years) from our own Solar System. Exoplanets orbiting smaller red dwarf stars will also be detectable, but only within about a fifth of that distance.
While other space observatories like NASA’s Kepler and CNES/ESA’s CoRoT were designed to detect exoplanets through the transit method, whereby a star’s brightness is dimmed ever-so-slightly by the silhouette of a passing planet, Gaia will detect particularly high-mass exoplanets by the gravitational wobble they impart to their host stars as they travel around them in orbit. This is known as the astrometric method.
A select few of those exoplanets will also be transiting their host stars as seen from Earth – anywhere from 25 to 50 of them – and so will be observable by Gaia as well as from many ground-based transit-detection observatories.
After some issues with stray light sneaking into its optics, Gaia was finally given the green light to begin science observations at the end of July and has since been diligently scanning the stars from L2, 1.5 million km from Earth.
With the incredible ability to measure the positions of a billion stars each to an accuracy of 24 microarcseconds – that’s like measuring the width of a human hair from 1,000 km – Gaia won’t be “just” an unprecedented galactic mapmaker but also a world-class exoplanet detector! Get more facts about the Gaia mission here.
The team’s findings have been accepted for publication in The Astrophysical Journal.
This artist’s view shows an extrasolar planet orbiting a star (the white spot in the right). Image Credit: IAU/M. Kornmesser/N. Risinger (skysurvey.org)
Is our Solar System normal? Or is it weird? How does the Solar System fit within the strange star systems we’ve discovered in the Milky Way so far?
With all the beautiful images that come down the pipe from Hubble, our Solar System has been left with celestial body image questions rivaling that of your average teenager. They’re questions we’re all familiar with. Is my posture crooked? Do I look pasty? Are my arms too long? Is it supposed to bulge out like this in the middle? Some of my larger asteroids are slightly asymmetrical. Can everyone tell? And of course the toughest question of all… Am I normal?
The idea that stars are suns with planets orbiting them dates back to early human history. This was generally accompanied by the idea that other planetary systems would be much like our own. It’s only in the last few decades that we’ve had real evidence of planets around other stars, known as exoplanets. The first extrasolar planet was discovered around a pulsar in 1992 and the first “hot jupiter” was discovered in 1995.
Most of the known exoplanets have been discovered by the amazing Kepler spacecraft. Kepler uses the transit method, observing stars over long periods of time to see if they dim as a planet passes in front of the star. Since then, astronomers have found more than 1700 exoplanets, and 460 stars are known to have multiple planets. Most of these stellar systems are around main sequence stars, just like the Sun. Leaving us with plenty of systems for comparison.
Artist’s impression of the solar system showing the inner planets (Mercury to Mars), the outer planets (Jupiter to Neptune) and beyond. Credit: NASA
So, is our Solar System normal? Planets in a stellar system tend to have roughly circular orbits, just like our Solar system. They have a range of larger and smaller planets, just like ours. Most of the known systems are even around G-type stars. Just like ours.….and we are even starting to find Earth-size planets in the habitable zones of their stars. JUST LIKE OURS!
Not so fast…Other stellar systems don’t seem to have the division of small rocky planets closer to the star and larger gas planets farther away. In fact, large Jupiter-type planets are generally found close to the star. This makes our solar system rather unusual.
Computer simulations of early planetary formation shows that large planets tend to move inward toward their star as they form, due to its interaction with the material of the protoplanetary disk. This would imply that large planets are often close to the star, which is what we observe. Large planets in our own system are unusually distant from the Sun because of a gravitational dance between Jupiter and Saturn that happened when our Solar System was young.
55 Cancri. Image credit: NASA/JPL
Although our Solar System is slightly unusual, there are some planetary systems that are downright quirky. There are planetary systems where the orbits are tilted at radically different angles, like Kepler 56, and a sci-fi favorite, the planets that orbit two stars like Kepler 16 and 34. There is even a planet so close to its star that its year lasts only 18 hours, known 55 Cancri e.
And so, the Kepler telescope has presented us with a wealth of exoplanets, that we can compare our beautiful Solar System to. Future telescopes such as Gaia, which was launched in 2013, TESS and PLATO slated for launch in 2017 and 2024 will likely discover even more. Perhaps even discovering the holy grail of exoplanets, a habitable planet with life…
And the who knows, maybe we’ll find another planet… just like ours.
What say you? Where should we go looking for habitable worlds in this big bad universe of ours? Tell us in the comments.
And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!
SETI's Allen Telescope Array monitor the stars for signs of intelligent life (SETI.org)
During a hearing last week before the U.S. House Science and Technology Committee SETI scientists Seth Shostak and Dan Werthimer asserted that solid evidence for extraterrestrial life in our galaxy — or, at the very least, solid evidence for a definitive lack of it — will come within the next two decades. It’s a bold claim for scientists to make on public record, but one that Shostak has made many times before (and he’s not particularly off-schedule either.) And with SETI’s Allen Telescope Array (ATA) continually scanning the sky for any signals that appear intentional, exoplanets being discovered en masse, and new technology on deck that can further investigate a select few of their (hopefully) Earth-like atmospheres, the chances that alien life — if it’s out there — will be found are getting better and better each year.
Would you put your bet on E.T. being out there? Actually, you can.
Thanks to the internet and the apparently incorrigible human need to compete you can actually place a wager on when alien life will be discovered, via an Irish online betting site.
Illustration of Kepler-186f, a recently-discovered, possibly Earthlike exoplanet that could be a host to life. (NASA Ames, SETI Institute, JPL-Caltech, T. Pyle)
Typically focused on the results of international sporting matches, PaddyPower.com has also included the announcement of extraterrestrial life in its novelty bet section, hinging on “the sitting President of the USA making a statement confirming without doubt the existence of alternative life beings from another planet.” The odds of such an announcement being made in the years 2015-2018 are currently listed at 100 to one. After that they drop significantly… probably because by then the JWST will be in operation and we will “have the technology.” Stranieri.com also has offered a chance for Italian players of chance to bet on the sitting president discussing life from other planets, with betting open until 2025 for long-term gamblers!
Of course, whether you personally would place a wager on such things is purely personal preference, and neither I nor Universe Today condones or supports gambling, for aliens or otherwise. (And the legalities of doing so and any and all results thereof are the sole responsibility of the reader.) But it is interesting that we now live in a time when wagering on the discovery of alien life sits just a click away from the results of the Kentucky Derby, French Open, or World Cup.
Now if you really want to support the science that will make such a discovery possible — maybe even within our own Solar System — you can “stand up for space” and write your representatives to tell them you want NASA’s planetary science budget to be funded, and rather than gamble your money you can make a donation to support SETI’s ongoing mission here (or even help out yourself via SETI@home.)
And even if all else fails, you could end up with a free coffee courtesy of Dr. Shostak…
Artist's conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech
After several months with their telescope on the sidelines, the Kepler space telescope team has happy news to report: the exoplanet hunter is going to do a new mission that will compensate for the failure that stopped its original work.
Kepler’s exoplanet days were halted last year when the second of its four reaction wheels (pointing devices) failed, which meant the telescope could not gaze at its “field” of stars in the Cygnus constellation for signs of exoplanets transiting their stars.
Results of a NASA Senior Review today, however, showed that the telescope will receive the funding for the K2 mission, which allows for some exoplanet hunting, among other tasks. The telescope will essentially change positions several times a year to do its new mission, which is funded through 2016.
“The approval provides two years of funding for the K2 mission to continue exoplanet discovery, and introduces new scientific observation opportunities to observe notable star clusters, young and old stars, active galaxies and supernovae,” wrote Charlie Sobeck, the mission manager for Kepler, in a mission update today (May 16).
Artist’s rendering of the Earth-sized Kepler-186f (Credit: NASA Ames/SETI Institute/Caltech)
“The team is currently finishing up an end-to-end shakedown of this approach with a full-length campaign (Campaign 0), and is preparing for Campaign 1, the first K2 science observation run, scheduled to begin May 30.”
While Kepler itself was not being used for planet hunting, scientific discoveries continue because the telescope has a legacy of observations stretching between 2009 and 2013. One notable find: 715 exoplanets were announced in one swoop earlier this year using a new technique called “verification by multiplicity”, which is useful in multiple-planet systems.
Kepler also spotted the first known Earth-sized planet in a habitable zone outside of our solar system, which achieves the mission’s stated goal of finding extrasolar Earths.
Artist's rendering of Kepler-186f (Credit: NASA Ames/SETI Institute/Caltech)
It wasn’t so long ago that we found out there is an Earth-sized planet in a habitable zone of a star. But how many others are out there, and do we know if planets like this are truly habitable?
“Looking towards the future, what we really want to do eventually is transform our knowledge from planets in the habitable zone to [characterizing] planetary environments,” said Natalie Batalha, a co-investigator on NASA’s Kepler Space Telescope, in a webcast presentation today (April 28) .
This means that astronomers will be able to, from a distance, look at “biosignatures” of life in the atmosphere. What a biosignature would be is still being characterized, but it could be something like an unusually high proportion of oxygen — as long as abiotic processes are not accounted for, of course.
Batalha identified these parameters for finding other Earths in a presentation at the “Habitable Worlds Across Time and Space” conference presented by the Space Telescope Science Institute:
Detections of planets in the habitable zone: other telescopes (left) vs. the Kepler space telescope. Credit: Natalie Batalha / NASA (screenshot)
– The telescope must be sensitive to an Earth-sized planet in the habitable zone of a G, K or M-type star (which are stars that are like the sun);
– A uniform and reliable detection catalog with well-understood sizes, orbital periods and insolation fluxes (energy received from the sun);
– Knowledge of Kepler’s detection efficiency and the planetary catalog’s reliability;
– Well-documented and accessible data products for other community members to analyze.
What would also be helpful to planetary scientists is learning more about how a planet forms in the habitable region of its star.
Meet Kepler-22b, an exoplanet with an Earth-like radius in the habitable zone of its host star. Unfortunately its mass remains unknown. Image Credit: NASA
In a presentation at the same conference, the University of Toronto’s Diana Valencia (an astrophysicist) pointed out there is no single predictor for how large a planet will get. It depends on how close a planetesimal disc is to its star, the rate of accretion in the area and dust opacity, among other factors.
She also gave a brief overview of processes that demonstrate how hard it is to predict habitability. Earth had at least two atmospheres in its past, presentation slides said, with the first atmosphere lost and the second built from volcanism and impacts. Valencia also pointed to complexities involving the Earth’s mantle and plate tectonics.
Artist's rendering of Kepler-186f (Credit: NASA Ames/SETI Institute/Caltech)
It’s truly a “eureka” moment for Kepler scientists: the first rocky Earth-sized world has been found in a star’s habitable “Goldilocks” zone, the narrow belt where liquid water could readily exist on a planet’s surface without freezing solid or boiling away. And while it’s much too soon to tell if this really is a “twin Earth,” we can now be fairly confident that they do in fact exist.
The newly-confirmed extrasolar planet has been dubbed Kepler-186f. It is the fifth and outermost planet discovered orbiting the red dwarf star Kepler-186, located 490 light-years away. Kepler-186f completes one orbit around its star every 130 days, just within the outer edge of the system’s habitable zone.
The findings were made public today, April 17, during a teleconference hosted by NASA.
“This is the first definitive Earth-sized planet found in the habitable zone around another star,” says lead author Elisa Quintana of the SETI Institute at NASA Ames Research Center. “Finding such planets is a primary goal of the Kepler space telescope. The star is a main-sequence M-dwarf, a very common type. More than 70 percent of the hundreds of billions of stars in our galaxy are M-dwarfs.”
A visualization of the many “unseen” red dwarfs in the night sky. (CLICK FOR ANIMATION) Credit: D. Aguilar & C. Pulliam (CfA)
Unlike our Sun, which is a G-type yellow dwarf, M-dwarf stars (aka red dwarfs) are much smaller and dimmer. As a result their habitable zones are much more confined. But, being cooler stars, M-dwarfs have long lifespans, offering planets in their habitable zones — like Kepler-186f — potentially plenty of time to develop favorable conditions for life.
In addition, M-dwarfs are the most abundant stars in our galaxy; 7 out of 10 stars in the Milky Way are M-dwarfs, although most can’t be seen by the naked eye. Finding an Earth-sized planet orbiting one relatively nearby has enormous implications in the hunt for extraterrestrial life.
“M dwarfs are the most numerous stars,” said Quintana. “The first signs of other life in the galaxy may well come from planets orbiting an M dwarf.”
Still, there are many more conditions on a planet that must be met for it to be actually habitable. But size, composition, and orbital radius are very important first steps.
“Some people call these habitable planets, which of course we have no idea if they are,” said Stephen Kane, an assistant professor of physics and astronomy at San Francisco State University in California. “We simply know that they are in the habitable zone, and that is the best place to start looking for habitable planets.”
Scale comparison of the Kepler-186 system and the inner Solar System (NASA Ames/SETI Institute/Caltech)
As far as the planetary system’s age is concerned — which relates to how long life could have potentially had to evolve on Kepler-186f’s surface — that’s hard to determine… especially with M-dwarf stars. Because they are so stable and long-lived, once they’re formed M-dwarfs essentially stay the same throughout their lifetimes.
“We know it’s probably older than a few billion years, but after that it’s very difficult to tell,” BAERI/Ames scientist Tom Barclay told Universe Today. “That’s the problem with M-dwarfs.”
A comparison of the Kepler 186 and Solar systems (Presentation slide, NASA/Ames)
The exoplanet was discovered via the transit method used by NASA’s Kepler spacecraft, whereby stars’ brightnesses are continually monitored within a certain field of view. Any dips in luminance reveal the likely presence of a passing planet.
Because of its small size — just slightly over 1 Earth radius — and close proximity to its star, Kepler-186f can’t be observed directly with current telescope technology.
The Gemini North telescope on the summit of Mauna Kea (Gemini Observatory/AURA)
“However, what we can do is eliminate essentially all other possibilities so that the validity of these planets is really the only viable option,” said Steve Howell, Kepler project scientist and a co-author on the paper.
Using the latest advanced imaging capabilities of the Gemini North and Keck II observatories located atop Mauna Kea in Hawaii, astronomers were able to determine that the signals detected by Kepler were from a small orbiting planet and not something else, such as a background or companion star.
“The Keck and Gemini data are two key pieces of this puzzle,” Quintana said. “Without these complementary observations we wouldn’t have been able to confirm this Earth-sized planet.”
Kepler-186f joins the other 20 extrasolar worlds currently listed in the Habitable Exoplanets Catalog, maintained by the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo. To date 961 exoplanets have been confirmed through Kepler observations, with 1,696 total confirmed altogether. (Source)
Artist’s conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech
Whether Kepler-186f actually resembles Earth or not, this discovery provides more information on the incredible variety of planetary systems to be found even in our little corner of the galaxy.
“The diversity of these exoplanets is one of the most exciting things about the field,” Kane said. “We’re trying to understand how common our solar system is, and the more diversity we see, the more it helps us to understand what the answer to that question really is.”
The SETI Institute’s Allen Telescope Array has surveyed the Kepler-186 system for any potential signals but so far none has been detected. Further observations are planned.
“Kepler-186f is special because we already know that a planet of its size and distance is capable of supporting life.”
– Elisa Quintana, research scientist, SETI Institute
The team’s paper, “An Earth-sized Planet in the Habitable Zone of a Cool Star” by Elisa V. Quintana et al., will be published in the April 18 issue of Science.
Meet Kepler-22b, an exoplanet with an Earth-like radius in the habitable zone of its host star. Unfortunately its mass remains unknown. Image Credit: NASA
Planet-watchers, some exciting news: you know how we keep talking about planet candidates, those planets that have yet to be confirmed, when we reveal stories about other worlds? That’s because verifying that the slight dimming of a star’s light is due to a planet takes time – -specifically, to have other telescopes verify it through examining gravitational wobbles on the parent star.
Turns out there’s a way to solve the so-called “bottleneck” of planet candidates vs. confirmed planets. NASA has made use of a new technique that they say will work for multi-planet systems, one that already has results: a single Kepler release of data today (Feb. 26) yielded 715 new planets in one shot. That almost doubles the amount of known planets found before today, which was just under 1,000, officials said.
“This is the largest windfall of planets, not exoplanet candidates, but actual verified exoplanets announced at one time,” said Doug Hudgins, a NASA exoplanet exploration program scientist based in Washington, D.C., at a press conference today. What’s more, among the release were four planets (about double to 2.5 times the size of Earth) that could be considered habitable: Kepler-174 d, Kepler-296 f, Kepler-298 d, Kepler-309 c.
The findings were based on scouring the first two of Kepler’s four years of data, so scientists expect there will be a lot more to come once they go through the second half. Most of the discoveries were planets close to Earth’s size, showing that small planets are common in multiplanetary systems.
These planets, however, are crowded into insanely compact multiple planet systems, sometimes within the reaches of the equivalent of Mercury’s or Venus’ orbits. It’s raising questions about how young systems would have enough material in those reaches to form planets. Perhaps planetary migration played a role, but that’s still poorly understood.
Verification by multiplicity is a new method for finding planets in multiple-planet systems. In cases where astronomers see several objects transiting a star in regular orbits, the assumption is it must be planets. A set of stars in a similar configuration would have orbits too unstable for regular transits. Credit: NASA
Discoveries of these worlds was made with a new technique called “verification by multiplicity”. The challenge with the method Kepler uses — watching for starlight dimming when a planet passes in front of it — is there are other ways that same phenomenon can occur. One common reason is if the star being observed is a binary star and the second star is just barely grazing the first.
This is how the technique works: If you can imagine a star with a bunch of other stars around it, the mutual gravities of each object would throw their relative orbits into chaos. A star with a bunch of planets, however, would have a more stable orbital configuration. So if scientists see multiple transits of objects across a star’s face, the assumption is that it would be several planets.
“This physical difference, the fact you can’t have multiple star systems that look like planetary systems, is the basis of the validation by multiplicity,” said Jack Lissauer, a planetary scientist at the NASA Ames Research Center who was involved in the research.
Although this is a new technique, the astronomers said there has been at least one published publication talking about this method, and they added that two papers based on their own research have been accepted for publication in the peer-reviewed Astrophysical Journal.
Sizes of verified planets just after a release of 715 confirmed planets from Kepler data in February 2014. Credit: NASA
There’s been a lot of attention on Kepler lately, not only because of its planetary finds, but also its uncertain status. In May 2013, a second of its four reaction wheels (or gyroscopes) went down, robbing the probe of its primary mission: to seek planets transiting in front of their stars in a spot in the Cygnus constellation. Since then, scientists have been working on a new method of finding planets with the spacecraft.
The spacecraft is good to go for K2 physically, NASA added, as the spacecraft only has four major malfunctions: the two reaction wheels, and 2 (out of 21) “science modules” that are used for science observing. The first module failed early in the mission, while the second died during a recent K2 test. While the investigation is ongoing, NASA said that they expect it will be due to an isolated part failure and that it will have no measurable impact on doing K2.
Edit, 8:30 p.m. EST: The two papers related to the Kepler discovery are available here and here on the prepublishing site Arxiv. Both are accepted for publication in the Astrophysical Journal. (Hat tip to Tom Barclay).
