We’ve found hundreds of planets outside the solar system, but taking a picture of one is still something quite special. The light of the parent star tends to greatly overwhelm the faint light of the alien planet. (So usually we learn about planets by tracking the effects each planet has on its star, like dimming light when it passes in front or making the star slightly wobble.)
This picture (above) shows HD95086 b, which astronomers believe is one of only about a dozen exoplanets ever imaged. It’s 300 light-years from Earth. The planet candidate is about four to five times the mass of Jupiter and orbiting a very young star that is probably only 10 million to 17 million years old. That’s a baby compared to our own solar system, estimated at 4.5 billion years old.
We still have a lot to learn about this object (and the observations from the Very Large Telescope will need to be confirmed independently), but so far astronomers say they figure that planet formed in the gas and dust surrounding star HD 95086. But the planet is actually very far away from the star now, about twice the distance as the Sun-Neptune orbital span in our own solar system.
“Its current location raises questions about its formation process,” stated team member Anne-Marie Lagrange, who is with the Grenoble Institute of Planetology and Astrophysics in France.
“It either grew by assembling the rocks that form the solid core and then slowly accumulated gas from the environment to form the heavy atmosphere, or started forming from a gaseous clump that arose from gravitational instabilities in the disc.
“Interactions between the planet and the disc itself,” she added, “or with other planets may have also moved the planet from where it was born.”
Astronomers estimate the planet candidate has a surface temperature of 1,292 degrees Fahrenheit (700 degrees Celsius), which could allow water vapor or methane to stick around in the atmosphere. It will take more VLT observations to figure this out, though.
The results from this study will be published in Astrophysical Journal Letters. The paper is also available on prepublishing site Arxiv.
We don’t have the budget yet to send Star Trek‘s U.S.S. Enterprise to probe the surface of strange new worlds, but luckily for humanity, astronomers are figuring out techniques to do that without even needing to leave Earth.
One of Earth’s prolific planet-hunters, the Kepler Space Telescope, has found a lot of planet candidates with rocky surfaces. That’s exciting for astronomers, as rocky planets tend to be smaller than their gas giant counterparts. Also, learning more about rocky planets could give us more clues as to Earth’s history, and that of other planets in our solar system.
But how the heck, from so far away, can we begin to understand the surface? One idea: Check the heat signature, or in more scientific words, look at exoplanets in the infrared part of the light spectrum.
NASA’s Astrobiology Magazine recently published an article about this method, which we encourage you to check out. In summary, the team behind a new research paper (submitted to the Astrophysical Journal) proposes to check out “airless” exoplanets that have surface temperatures below 3,140 degrees Fahrenheit (1,726 Celsius or 2,000 Kelvin.)
Because different kinds of rocks emit “signature” spectrums in different wavelengths, it’s possible we could pick up the signs of silicate rocks or other types of material. There’s a caveat, though.
“With current technology, however, the team cautions that determining surface composition of exoplanets is a very different process than studying their solar system counterparts,” the magazine wrote. “Due to the limits of technology, the team proposes to concentrate on the most prominent mineral signatures detected from exoplanets.”
Check out more details in the scientific journal article here, or the entire Astrobiology Magazine article at this link.
When you sit back and think about how far away exoplanets are — and how faint — it’s a scientific feat that we can find these distant worlds outside our Solar System at all. It’s even harder to learn about the world if the exoplanet is orbiting a dim star — say, about two-thirds the size of the Sun — that is faint through even the largest telescope.
In response to this problem, there’s one science team that thinks it’s found a way to solve it. Their research bumped a planet from the habitable zone to the not-so-friendly zone of a star. Here’s how it happened:
The usual way to measure a distant star is this: look at the light. A Sun-sized star, for example, would have its light waves measured at different wavelengths. Scientists then match what they see to spectra (light bands) that are created artificially.
This method doesn’t work so well for smaller stars, though. “The challenge is that small stars are incredibly difficult to characterize,” stated Sarah Ballard, a post-doctoral researcher at the University of Washington, in a press release. Worse, these small guys make up about two-thirds of the stars in the universe.
Ballard led a multi-university team describing a “characterization by proxy” method accepted for publication in The Astrophysical Journal and now available online.
The science team based their work on previous research performed by astronomer Tabetha Boyajian, who is currently at Yale University.
Boyajian combined the resources of several telescopes that measured wavelengths of light, wavelengths that are slightly longer than visible light. This technique allowed the interferometer (the combined telescopes) to figure out the size of stars that are close by.
With that data on hand, Ballard and her colleagues looked out into the universe. Their target was Kepler-61b (Kepler Object 1361.01), a “candidate” planet about double the size of Earth spotted by the planet-hunting Kepler space telescope. The candidate, if proven, is orbiting a low-mass star 900 light-years away that is hard to measure in a telescope.
Next, the scientists picked four nearby stars that have similar light patterns, reasoning that they would be spectroscopially close enough to Kepler-61b’s parent star to make accurate measurements. The four stars are located in Ursa Major and Cygnus, ranging between 12 to 25 light years away from Earth.
When the scientists compared the measurements to Kepler 61’s star, a surprise emerged.
“Kepler-61 turned out to be bigger and hotter than expected,” the University of Washington stated. “This in turn recalibrated planet Kepler-61b’s relative size upward as well — meaning it, too, would be hotter than previously thought and no longer a resident of the star’s habitable zone.”
The newly refined planetary radius for Kepler-61b is 2.15 times the radius of Earth (plus or minus 0.13 radii). Astronomers estimate it orbits its star about once every 59.9 days and has a temperature of 273 Kelvin (plus or minus 13 Kelvin.)
Just to wrap up, here’s a note about how likely it is that Kepler-61b is actually a planet — and not a planetary candidate.
The candidate was first described in this 2011 scientific paper. Kepler-61b is just one in a long list of 1,235 planetary candidates catalogued in that paper, all discovered in just four months — between May 2 and Sept. 16, 2009.
While the NASA Exoplanet Archive still lists Kepler-61b as a candidate planet — one that must be confirmed by independent observations — this 2011 paper says that most Kepler candidates have a strong possibility of being actual planets because the Kepler software is technologically apt.
In other words, Ballard and her co-authors write in the research, Kepler-61b is very likely to be a planet itself — with only 4.8 percent possibility of being a “false positive”, to be exact.
Maybe it’s because Jurassic Park is in theaters again, but we at Universe Today sometimes worry about how one person can mess up an otherwise technologically amazing system. It took just one nefarious employee to shut down the dinosaur park’s security fences in the movie and cause havoc. How do we ensure science can fight against that, especially when everyday citizens are getting more and more involved in the scientific process?
But perhaps, after talking to Chris Lintott, that view is too suspicious. Lintott is in charge of a collaborative astronomy and science project called the Zooniverse that uses public contributions to fuel some of the science he performs. Basically, anyone with an Internet connection and a desire to contribute can hunt for planets or examine astronomical objects, among many other projects.
Lintott, an astrophysicist at the University of Oxford, says the science requires public contributions. Moreover, he hasn’t had a problem yet despite 800,000 individual contributors to the Zooniverse. He told Universe Today about how that’s possible in an e-mail interview.
1) Zooniverse has already produced tangible scientific results in space through collaborating with ordinary folks. Can you talk about some of the papers/findings that have been produced in your various projects?
There’s a long, long list. I’m particularly excited at the minute about our work on bulgeless galaxies; most spiral galaxies have a bulge full of old stars at their centre, but we’ve found plenty that don’t. That’s exciting because we think that means that they’re guaranteed not to have had a big merger in the last 10 billion years or so, and that means we can use them to figure out just what effect mergers have on galaxies. You’ll be hearing more about them in the next year or so as we have plenty of observing time lined up.
I’m also a big fan of Planet Hunters 1b, our first confirmed planet discovery – it’s a planet in a four-star system, and thus provides a nice challenge to our understanding of how planets form. We’ve found lots of planet candidates (systems where we’re more than 90% sure there’s a planet there) but it’s nice to get one confirmed and especially nice for it to be such an interesting world.
2) What benefits have you received from involving the public in space projects, in terms of results as well as raising awareness?
We couldn’t do our research any other way. Astronomers have got very good in the last few decades at collecting information about the universe, but we’re not always so good at learning how to use all of that information. The Zooniverse allows us to collaborate with hundreds of thousands of people so that we can scale our efforts to deal with that flood of data, and many of those volunteers go much further than just clicking on buttons we provide. So really our research is now driven in collaboration with thousands of people, spread all around the world – that’s an inspiring thought.
3) How many people do you manage in your space projects, approximately? How do you keep track of them all?
We have more than 800,000 registered volunteers – luckily, the computer keeps track of them (when they log in!).
4) How do you ensure their results meet the standards of scientific publication?
We carefully design projects so that we’re sure they will produce scientifically useful results before they’re launched; this usually means running a test with a small amount of data and comparing work done by volunteers with that of professionals. We usually find the volunteers are better than us! It helps that we have several people complete each task, so collectively we don’t make accidental mistakes.
5) How do you guard against somebody deliberately or accidentally altering the results?
The system insists that every classification is independent, and as we have several people look at each classification finding any deliberate attack would be easy – in any case, we’ve never seen any evidence of such a thing. Despite popular reports, most people are nice!
Dwarf star HD 40307 is now thought to host at least 6 exoplanet candidates… one of them well within its habitable zone. (G. Anglada/Celestia)
Located 43 light-years away in the southern constellation Pictor, the orange-colored dwarf star HD 40307 has previously been found to hold three “super-Earth” exoplanets in close orbit. Now, a team of researchers poring over data from ESO’s HARPS planet-hunting instrument are suggesting that there are likely at least six super-Earth exoplanets orbiting HD 40307 — with one of them appearing to be tucked neatly into the star’s water-friendly “Goldilocks” zone.
HARPS (High Accuracy Radial velocity Planet Searcher) on ESO’s La Silla 3.6m telescope is a dedicated exoplanet hunter, able to detect the oh-so-slight wobble of a star caused by the gravitational tug of orbiting planets. Led by Mikko Tuomi of the UK’s University of Hertfordshire Centre for Astrophysics Research, a team of researchers reviewed publicly-available data from HARPS and has identified what seems to be three new exoplanets in the HD 40307 systems. The candidates, designated with the letters e, f, and g, all appear to be “super Earth” worlds… but the last one, HD 40307 g, is what’s getting people excited, as the team has calculated it to be orbiting well within the region where liquid water could exist on its surface — this particular star’s habitable zone.
In addition, HD 40307 g is located far enough away from its star to likely not be tidally locked, according to the team’s paper. This means it wouldn’t have one side subject to constant heat and radiation while its other “far side” remains cold and dark, thus avoiding the intense variations in global climate, weather and winds that would come as a result.
“The star HD 40307, is a perfectly quiet old dwarf star, so there is no reason why such a planet could not sustain an Earth-like climate.”
– Guillem Anglada-Escudé, co-author.
“If the signal corresponding to HD 40307 g is a genuine Doppler signal of planetary origin, this candidate planet might be capable of supporting liquid water on its surface according to the current definition of the liquid water habitable zone around a star and is not likely to suffer from tidal locking.” (Tuomi et al.)
If HD 40307 g is indeed confirmed, it may very well get onto the official short list of potentially habitable worlds outside our Solar System — although those others are quite a bit closer to the mass of our own planet.
UPDATE: HD 40307 g has been added to the Planetary Habitability Laboratory’s Habitable Exoplanets Catalog, maintained by the PHL at the University of Puerto Rico at Arecibo. It’s now in 4th place of top exoplanets of interest based on similarity to Earth. According to Professor Abel Mendez Torres of the PHL, “Average temperatures might be near 9°C (48°F) assuming a similar scaled-up terrestrial atmosphere. It might also experience strong seasonal surface temperature shifts between -17° to 52°C (1.4° to 126°F) due to its orbital eccentricity. Nevertheless, these extremes are tolerable by most complex life, as we know it.” (Read more here.)
While the other planetary candidates in the HD 40307 system are positioned much more closely to the star, with b, c, d, and e within or at the equivalent orbital distance of Mercury, g appears to be in the star’s liquid-water habitable zone, orbiting at 0.6 AU in an approximately 200-day-long orbit. At this distance the estimated 7-Earth-mass exoplanet receives around 62-67% of the radiation that Earth gets from the Sun.
Representation of the liquid water habitable zone around HD 40307 compared to our Solar System (Tuomi et al., from the team’s paper.)
Although news like this is exciting, as we’re always eagerly anticipating the announcement of a true, terrestrial Earthlike world that could be host to life as we know it, it’s important to remember that HD 40307 g is still a candidate — more observations are needed to not only confirm its existence but also to find out exactly what kind of planet it may be.
“A more detailed characterization of this candidate is very unlikely using ground based studies because it is very unlikely [sic] to transit the star, and a direct imaging mission seems the most promising way of learning more about its possible atmosphere and life-hosting capabilities,” the team reports.
Still, justfinding potential Earth-sized worlds in a system like HD 40307’s is a big deal for planetary scientists. This system is not like ours, yet somewhat similar planets have still formed… that in itself is a clue to what else may be out there.
“The planetary system around HD 40307 has an architecture radically different from that of the solar system… which indicates that a wide variety of formation histories might allow the emergence of roughly Earth-mass objects in the habitable zones of stars.”
Illustration of 55 Cancri e, a super-Earth that’s thought to have a thick layer of diamond (Yale News/Haven Giguere)
If diamonds are forever then this planet should be around for a very, very long time; it appears to be literally made of the stuff.
55 Cancri e — an exoplanet discovered in 2004 — is more than twice Earth’s diameter and over eight times more massive, making it a so-called “super Earth.” Earlier this year it made headlines by being the first Earth-sized exoplanet whose light was directly observed via the infrared capabilities of NASA’s Spitzer Space Telescope.
Using information about 55 Cancri e’s size, mass and orbital velocity, as well as the composition of its parent star 55 Cancri (located 40 light years away in the constellation Cancer) a research team led by scientists from Yale University created computer models to determine what the planet is most likely made of.
They determined that 55 Cancri e is composed primarily of carbon (as graphite and diamond), iron, silicon carbide, and possibly some silicates. The researchers estimate that at least a third of the planet’s mass — the equivalent of about three Earth masses — could be diamond.
“This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth. The surface of this planet is likely covered in graphite and diamond rather than water and granite.”
– Nikku Madhusudhan, Yale postdoctoral researcher and lead author
So what would one expect to find on a world made of diamond?
“On this planet there would basically be a thin layer below the surface which will have both graphite and diamond,” Madhusudhan told Universe Today in an email. “But, below that there will be a thick layer (a third of the radius) with mostly diamond. For a large part the diamond will be like the diamond on Earth, except really, really pure.
“But at greater depths the diamond could also be in liquid form,” Madhusudhan added.
Scientists had previously thought that 55 Cancri e might have a lot of water — superheated water, due to the planet’s incredibly high 4,000-degree (F) temperatures — based on the assumption that its composition is similar to Earth’s. But this new research indicates that it doesn’t have much water at all.
“By contrast, Earth’s interior is rich in oxygen, but extremely poor in carbon — less than a part in thousand by mass,” said Kanani Lee, Yale geophysicist and co-author of the paper.
This study shows that we can’t assume that planets in other systems are made of the same stuff that ours is, even if they are of similar size (and also that diamonds aren’t necessarily a valuable commodity on all worlds!)
The team’s paper “A Possible Carbon-rich Interior in Super-Earth 55 Cancri e” was accepted for publication in the journal Astrophysical Journal Letters. Read more on Yale News here.
Top image by Haven Giguere. Inset image shows visible location of 55 Cancri, by Nikku Madhusudhan using Sky Map Online.
Astronomers have found four nearby white dwarf stars surrounded by disks of material that could be the remains of rocky planets much like Earth — and one star in particular appears to be in the act of swallowing up what’s left of an Earthlike planet’s core.
The research, announced today by the Royal Astronomical Society, gives a chilling look at the eventual fate that may await our own planet.
Astronomers from the University of Warwick used Hubble to identify the composition of four white dwarfs’ atmospheres, found during a survey of over 80 such stars located within 100 light-years of the Sun. What they found was a majority of the material was composed of elements found in our own Solar System: oxygen, magnesium, silicon and iron. Together these elements make up 93% of our planet.
In addition, a curiously low ratio of carbon was identified, indicating that rocky planets were at one time in orbit around the stars.
Since white dwarfs are the leftover cores of stellar-mass stars that have burnt through all their fuel, the material in their atmosphere is likely the leftover bits of planets. Once held in safe, stable orbits, when their stars neared the ends of their lives they expanded, possibly engulfing the innermost planets and disrupting the orbits of others, triggering a runaway collision effect that eventually shattered them all, forming an orbiting cloud of debris.
This could very well be what happens to our Solar System in four or five billion years.
“What we are seeing today in these white dwarfs several hundred light years away could well be a snapshot of the very distant future of the Earth,” said Professor Boris Gänsicke of the Department of Physics at the University of Warwick, who led the study. “During the transformation of the Sun into a white dwarf, it will lose a large amount of mass, and all the planets will move further out. This may destabilise the orbits and lead to collisions between planetary bodies as happened in the unstable early days of our solar systems.”
One of the white dwarfs studied, labeled PG0843+516, may even be actively eating the remains of an once-Earthlike world’s core.
The researchers identified an abundance of heavier elements like iron, nickel and sulphur in the atmosphere surrounding PG0843+516. These elements are found in the cores of terrestrial planets, having sunk into their interiors during the early stages of planetary formation. Finding them out in the open attests to the destruction of a rocky world like ours.
Of course, being heavier elements, they will be the first to be accreted by their star.
“It is entirely feasible that in PG0843+516 we see the accretion of such fragments made from the core material of what was once a terrestrial exoplanet,” Prof. Gänsicke said.
It’s an eerie look into a distant future, when Earth and the inner planets could become just some elements in a cloud.
Located 880 light-years away, a massive gas giant called CoRoT-2b orbits its star at a mere 2 million miles – less than a tenth the distance of Mercury’s orbit from the Sun. At this cozy proximity the star, CoRoT-2a, continually assaults the hot, gassy exoplanet with high-powered stellar winds and magnetic storms, stripping it of millions of kilograms of mass every day… and undoubtedly creating global auroras that rival even the most energetic seen on Earth.
But CoRoT-2b isn’t merely a tragic player in this stormy stellar performance; the planet itself may also be part of the cause.
Almost 3 1/2 times the mass of Jupiter, CoRoT-2b (so named because it was discovered by the French Space Agency’s Convection, Rotation and planetary Transits space telescope, or CoRoT) orbits its star very rapidly, completing an orbit every 1.7 days. This in turn actually speeds up the rotation of the star itself thus generating even more magnetic activity, via a dynamo effect.
Caught up in this deadly dance, CoRoT-2b is losing mass at an estimated rate of 150 million billion kilograms of material every year! The planet would likely have a long comet-like tail of this stripped material trailing behind it.
Although this sounds like a lot, CoRoT-2b has enough mass to keep “spinning up” its star for thousands of billions of years.
It’s a given. It won’t be long until human technology will expand our repertoire of cataloged exoplanets to astronomical levels. Of these, a huge number will be considered within the “habitable zone”. However, isn’t it a bit egotistical of mankind to assume that life should be “as we know it”? Now astrobiologists/scientists like Dirk Schulze-Makuch with the Washington State University School of Earth and Environmental Sciences and Abel Mendez from the University of Puerto Rico at Aricebo are suggesting we take a less limited point of view.
“In the next few years, the number of catalogued exoplanets will be counted in the thousands. This will vastly expand the number of potentially habitable worlds and lead to a systematic assessment of their astrobiological potential. Here, we suggest a two-tiered classification scheme of exoplanet habitability.” says Schulze-Makuch (et al). “The first tier consists of an Earth Similarity Index (ESI), which allows worlds to be screened with regard to their similarity to Earth, the only known inhabited planet at this time.”
Right now, an international science team representing NASA, SETI,the German Aerospace Center, and four universities are ready to propose two major questions dealing with our quest for life – both as we assume and and alternate. According to the WSU news release:
“The first question is whether Earth-like conditions can be found on other worlds, since we know empirically that those conditions could harbor life,” Schulze-Makuch said. “The second question is whether conditions exist on exoplanets that suggest the possibility of other forms of life, whether known to us or not.”
Within the next couple of weeks, Schulze-Makuch and his nine co-authors will publish a paper in the Astrobiology journal outlining their future plans for exoplanet classification. The double approach will consist of an Earth Similarity Index (ESI), which will place these newly found worlds within our known parameters – and a Planetary Habitability Index (PHI), that will account for more extreme conditions which could support surrogate subsistence.
“The ESI is based on data available or potentially available for most exoplanets such as mass, radius, and temperature.” explains the team. “For the second tier of the classification scheme we propose a Planetary Habitability Index (PHI) based on the presence of a stable substrate, available energy, appropriate chemistry, and the potential for holding a liquid solvent. The PHI has been designed to minimize the biased search for life as we know it and to take into account life that might exist under more exotic conditions.”
Assuming that life could only exist on Earth-like planets is simply narrow-minded thinking, and the team’s proposal and modeling efforts will allow them to judiciously filter new discoveries with speed and high level of probability. It will allow science to take a broader look at what’s out there – without being confined to assumptions.
“Habitability in a wider sense is not necessarily restricted to water as a solvent or to a planet circling a star,” the paper’s authors write. “For example, the hydrocarbon lakes on Titan could host a different form of life. Analog studies in hydrocarbon environments on Earth, in fact, clearly indicate that these environments are habitable in principle. Orphan planets wandering free of any central star could likewise conceivably feature conditions suitable for some form of life.”
Of course, the team admits an alien diversity is surely a questionable endeavor – but why risk the chance of discovery simply on the basis that it might not happen? Why put a choke-hold on creative thinking?
“Our proposed PHI is informed by chemical and physical parameters that are conducive to life in general,” they write. “It relies on factors that, in principle, could be detected at the distance of exoplanets from Earth, given currently planned future (space) instrumentation.”
Original News Source: WSU News. For Further Reading: A Two-Tiered Approach to Assessing the Habitability of Exoplanets.
Earlier this month astronomers released news of the darkest exoplanet ever seen: discovered in 2006, the gas giant TrES-2b reflects less than 1% of the visible light from its parent star… it’s literally darker than coal! Universe Today posted an article about this intriguing announcement on August 11, and now Dr. David Kipping of the Harvard-Smithsonian Center for Astrophysics is featuring a podcast on 365 Days of Astronomy in which he gives more detail about the dark nature of this discovery.
“TrES-2b is similar in mass and radius to Jupiter but Jupiter reflects some 50% of the incident light. TrES-2b has a reflectivity less than that of any other planet or moon in the Solar System or beyond. The reflectivity is significantly less than even black acrylic paint, which makes the mind boggle as to what a clump of this planet would look like in your hand. Perhaps an appropriate nickname for the world would be Erebus, the Greek God of Darkness and Shadow. But what really is causing this planet to be so dark?”
– Dr. David Kipping
David Kipping obtained a PhD in Astrophysics from University College London earlier this year. His thesis was entitled ‘The Transits of Extrasolar Planets with Moons’ and David’s main research interest revolves around exomoons. He is just starting a Carl Sagan Fellowship at the Harvard-Smithsonian Center for Astrophysics.
The paper on which the the podcast is based can be found here.
Jason Major is a graphic designer, photo enthusiast and space blogger. Visit his website Lights in the Dark and follow him on Twitter @JPMajor and on Facebook for more astronomy news and images!