OK, first, the planet: called PH-1, it’s bigger than Earth, about six times our radius, or about half the diameter of Jupiter. The mass isn’t well known, but may be as high as 170 times our own mass, though far more likely it’s closer to 20 – 50 times our mass. That makes it closer physically to Uranus and Saturn than Earth, so it’s likely a gas giant. It’s also hot, with a probable cloud-top temperature of 400+ Celsius (800+° F). Even if it has Earth-sized moons they’re likely to be too hot to be hospitable. And since it’s 5000 light years away, we’re not headed there any time soon, anyway.
But the more interesting thing about this planet is its host stars: PJK-1 orbits a binary star, two stars that orbit each other (like Tatooine, if you like). Six other planets are known to orbit binary stars, but PH-1 is even cooler: the binary star is itself orbited by another binary pair much farther out, making it the first planet found in a four-star system.
So we have two stars orbiting each other, orbited by a planet, and also orbited by two other stars which orbit each other. Yegads.
But it gets better yet. This planet was not found by professional astronomers! It was discovered by two amateurs who participate in the Planet Hunters program. This project was started by astronomers using the orbiting Kepler Observatory, designed to stare at 100,000 stars and look for dips in light from them as any potential planets orbiting them block their light. These transits show up in graphs of the stars’ brightnesses, and actually our human eyes and brain are pretty good at picking them out. Planet Hunters puts Kepler data online for anyone to go in and poke around.
The two citizen scientists, Kian Jek and Robert Gagliano, are listed as authors on the scientific paper recently published. I love this: the digital nature of these data make it far, far easier to analyze the science than it was in the past, and also easier to get the data out to people. Because of this, we have an explosive growth in these kinds of projects. Planet Hunters is great, but then so is Galaxy Zoo, Moon Mappers, Ice Hunters, and so many others. You can find several of these collected at the CosmoQuest website.
And a word about this new planet; this isn’t the first planet found by Planet Hunters, but it’s the first ever found in a quaternary star system. In the image here, the central binary is the big blob in the middle, and the second pair the elongated double-blob to the lower left. The planet is far too close to the middle stars to be seen here – its orbit is smaller than Earth’s around the Sun, far smaller than a pixel in this image at that distance.
The central binary is made up of a bluish star hotter and brighter than the Sun, and one that’s cooler, fainter, and redder. The second binary is made of one star much like the Sun, and another dinky red one. Their distance from the planet – about 150 billion kilometers – means they’d both still be very bright, with the brighter of the two almost as bright as the full Moon as seen from Earth. What a sight that would be! The second star would be hard to pick out in the glare of the other, but with binoculars you could spot it.
Not that anyone could, since the planet is hot enough to melt tin and assuming it had a solid surface to start with. Still though, it’s not hard to imagine a smaller planet orbiting that binary farther out, in a cooler, more life-friendly position. And we know such a planet exists; Kepler recently revealed a planet orbiting a binary star at the right spot to have liquid water as well. Like PH-1, that planet is probably a gas giant, but it might have big moons…
And this shows us once again that nature just loves to make planets, even ones in really weird places that at first may seem inhospitable for planet formation. But there it is.
Every time we find a strange planet like this, it fills me with hope that the ultimate goal of this work is close: finding an Earth-sized planet in the habitable zone of another star. We’re getting closer every day to that announcement, I think. In fact, I strongly suspect that planet is already sitting in the Kepler data, faint and hard to tease out, but just waiting to be found.
Go sign up for Planet Hunters. Maybe you’ll be the one to find it.
Image credits: Haven Giguere/Yale; Keck Observatory/Megan E. Schwamb et al.
- Two exoplanets discovered by "citizen scientists"
- YOU can find extrasolar planets
- Astronomers discover a wretched hive of scum and villainy (and the followup, Exoplanet news Part 4: More wretched hives of scum and villany)
- Kepler finds a planet in a binary star’s habitable zone
Oh, this is too cool: scientists have found a planet orbiting a binary star (a pair of stars in tight orbit around each other) that is at the right distance to have liquid water! Let me be clear: this planet is much bigger than Earth, and is likely to be a gas giant. So it’s not Earth-like, and probably not itself habitable.
But it might have moons…
[Note: this image is artwork based on the science. Click to tatooineneate.]
OK, first: Kepler is an orbiting telescope that has been staring at one spot in the sky for about three years now. It’s looking at about 100,000 stars. If these stars have planets, and the orbits of these planets are seen edge-on, then they will occasionally pass directly between us and their parent star blocking a little bit of the light. This is called a transit, and if the planet is big enough it can block enough light from the star to be detected by Kepler. So far, 77 planets have been confirmed using Kepler, and over 2000 more have been detected and are awaiting confirmation.
The new discovery deals with a binary star called Kepler-47. It’s about 5000 light years away, which is pretty far for a Kepler system – it’s faint at that distance. Still, the observations look very good, and the conclusions convincing to me.
One of the two stars is very Sun-like, about the same size, temperature, and brightness as our home star. The second is fainter, smaller, and cooler. They comprise an eclipsing binary: their orbit is seen edge-on from Earth, so they pass in front of each other as seen by us as they circle each other. Their orbit is pretty tight: they’re only about 13 million kilometers (8 million miles) from each other, and their orbit is just 7.5 days long.
Two planets were actually found orbiting the stars. Kepler-47b is about 3 times the diameter of the Earth. Its mass isn’t known, but it’s likely 7 – 10 times ours. It’s hot: the orbit is just 50 million km (30 million miles) out, closer than Mercury is to the Sun. It takes about 50 days to orbit.
The second planet, Kepler-47c, is the interesting one. It’s even bigger, 4 – 6 times Earth’s diameter, roughly the size of Uranus, and most likely 20 times our mass. Its orbit is almost exactly the same size as Earth’s, coincidentally, taking 300 days to orbit the binary (its year is shorter than ours because the two stars together have more mass, and therefore more gravity, than the Sun).
Taking into account the orbital size and the physical properties of the stars, the scientists have determined that the planet is at the right distance to be in the stars’ habitable zone: the distance where liquid water could exist on a solid body.
As I pointed out, the planet is probably a gas giant. But it could have moons – in fact, given our own solar system configuration, it seems likely. It’s not crazy to think that these moons, should they exist, might be habitable. That’s amazing.
These two new worlds put the roster of confirmed circumbinary planets (that is, planets orbiting binary stars) to six. And we only just started looking a few years ago! Given the number of stars observed and the planets found, and applying a little statistics, it seems entirely possible that there are millions of such planets in our Milky Way galaxy alone.
That’s right: millions of possible Tatooines just waiting to be found! And we may yet find them. Finding gas giant planets is far easier than finding their much smaller moons, but one of the goals of exoplanet astronomy is to improve the technology and the techniques to the point where such moons can be detected as well. It may take bigger telescopes and more time, but there is nothing stopping us except our will to do so.
Think of that: we can detect potential Earths around stars quadrillions of kilometers away! And all we have to do is want it enough.
[P.S. If you want to keep up with exoplanet news, there's a wonderful iPhone/iPad app called Exoplanet that has info, diagrams, and updates when new planets are found. I use it myself and really like it.]
Image credit: NASA/JPL-Caltech/T. Pyle
- Astronomers discover a wretched hive of scum and villainy
- Exoplanet news Part 4: More wretched hives of scum and villany
- No, that’s not a picture of a double sunset on Mars
- New study: 1/3 of Sun-like stars might have terrestrial planets in their habitable zones
[The article below was originally posted on the BBC Future blog, and was titled "Will we ever… find life elsewhere in the universe?" I'm reposting it here because, oddly, the BBC page is only readable for people outside the UK! It has to do with the BBC rights and all that. But they gave me permission to post it here, and since I thought it was fun and provocative, I figure y'all would like it. Enjoy.]
Will we ever… find life in space?
One of the reasons I love astronomy is that it doesn’t flinch from the big questions. And one of the biggest is: are we alone?
Another reason I love astronomy: it has a good shot at answering this question.
Even a few decades ago hard-headed realists pooh-poohed the idea of aliens. But times change, and so does science. We’ve accumulated enough data that makes the question less far-fetched than it once was, and I’m starting to think that the question isn’t "Will we find life?" but rather "Which method will find it first?"
There are three methods that, to me, are the front-runners for finding life on other worlds. And I have an idea as to which one may find it first.
Life on Mars?
The first method follows the principle that when you’re looking for something, it’s best to start close to home.
We know of one planet that has life: Earth. So it makes sense to look for other places with Earth-like conditions: that is, liquid water, oxygen in the air, nutrients for growth, and so on.
The most obvious place to look is Mars. At first glance it appears dry, cold and dead. But if you can see past that, things start to look up. The polar caps, for example, have lots of frozen water, and we’ve directly seen ice at lower latitudes on the Red Planet as well – meteorite impacts have left behind shiny craters, digging up fresh ice from below the surface.
Several Mars rovers and landers have uncovered tantalising evidence that liquid water might flow just beneath the surface, but we still lack any conclusive evidence. However, if you broaden your timescale a bit, there is excellent evidence that in the past – perhaps a billion years or so ago – our neighbouring planet had oceans of liquid water and thicker air. In fact, conditions were pretty good to develop life as we know it even before it popped up here on Earth.
It’s entirely possible that life got a toehold (or pseudopod hold) there long ago, and died out. If that’s the case, we may yet find fossils in the Martian rocks. Again, there’s no conclusive evidence yet, but we’ve literally barely scratched the surface there. Now that it has successfully landed on Mars, we have the exciting possibility that the plutonium-powered, car-sized Curiosity rover will soon use its on-board laser and other tools to crack open and examine rocks in the Gale Crater, which were laid down billions of years ago in the presence of liquid water.
And Mars isn’t the only possibility in our solar system. Liquid water exists inside Saturn’s moon Enceladus, where geysers of liquid water erupt from deep canyons at its south pole. Energised by the gravitational tug of the giant ringed planet itself, the interior of Enceladus may be a vast ocean of liquid water even while the surface is frozen over. That doesn’t guarantee we’ll ever find alien fish swimming that moon’s seas, of course. But it’s an interesting place to look.
Europa, a moon of Jupiter, almost certainly has an undersurface ocean as well. If you relax your constraints even more, Saturn’s moon Titan has lakes of liquid methane and ethane on its surface, too. The chemistry for life would be different there – it’s a rather chilly -180C on the surface – but it’s not impossible to suppose life might arise there too.
Finding out whether this is the case means getting up close and personal. We’re doing that for Mars; however, the likes of Europa and Enceladus may have to wait a decade or four.
But maybe we don’t have to go anywhere. Instead, we might be able to sit here and wait for alien beings (of whatever form) to message us.
This is pretty cool: astronomer Alex Parker took all the planet candidates found by the Kepler telescope – nearly 2300 planets in all – and made an animation showing what they would look like if they all orbited one star.
Dr. Parker had to do some scaling to make this work. For example, the actual size of each planet is known relative to its parent star, which he then scaled to fit the star shown in the animation. He scaled the distance from the star in a similar way. He describes it all on the page for the video.
I have to admit, it’s hard to know if there’s anything scientific we can learn from this. It’s fun to play with data, and it does often happen that by doing so you can see hidden relationships, things that aren’t obvious when displayed in normal ways (I’ve had that happen to me as well just playing with data – and Parker is very good indeed at playing with data; see Related Posts below for more cool stuff he’s done). That may very well turn out to be true in this case, or it may simply turn out to be an interesting demonstration. But as he points out, since this is animation was done to scale using all the Kepler planet candidates, one thing you see immediately is that there is always at least one transit going on! In other words, looking at all the Kepler host stars, no matter when you look, there are probably a dozen transits or more occurring at that moment.
That to me is actually shocking. I mean, it makes sense, and given some thought I would’ve realized it on my own. However, the context I always put this in is that just a few years ago we didn’t know of any transiting planets, and in fact for a while after the first were found a lot of astronomers scoffed at the idea. Now, though, the evidence is so overwhelming there is no doubt these transiting exoplanets exist.
And yet in all that time we didn’t know these planets existed, in all that time astronomers were looking for them and didn’t see them, in all that time some were found and other astronomers scoffed, there was never a time when there wasn’t a planet transiting a star.
And that’s just in the tiny patch of sky Kepler looks at; the entire sky is over 300 times bigger. So if there are a dozen or so transits going on in just the Kepler field, as Parker states, that means there are thousands of them going on in the sky even as you read this. Every day, all day, for millions and billions of years.
All those planets, perhaps millions of them, hidden in plain sight. All we needed to do was actually look for them.
So the usefulness of Parker’s animation is clear to me; its impact on me was profound. It reminded me once again that science evolves, and that my own biases – all our biases – must evolve with it. Otherwise, who knows what we’ll miss?
Tip o’ the dew shield to the Scientific American blog.
- Piano sonata in the key of Kepler-11 (music by Alex Parker based on planet orbits)
- Music of the spheres (more music by Alex Parker, this time based on supernovae)
- New study: 1/3 of Sun-like stars might have terrestrial planets in their habitable zones
- Motherlode of potential planets found: more than 1200 alien worlds!
Via reddit (if you’re a redditor, go there and upboat!) I found a very interesting use of astronomical data in music. The composer [Update: Astronomer Alex Parker created this!] took the orbital information from the six-planet system called Kepler 11 and codified it into musical notes! From the YouTube notes:
Here, I’ve taken each transit seen by the observatory and assigned a pitch and volume to it. The pitch (note) is determined by the planet’s distance from its star (closer=higher), and they are drawn from a minor 11 chord. The volume is determined by the size of the planet (larger=louder).
The result is actually quite listenable!
That’s lovely, and oddly compelling. It’s like the notes are trying to reach some sort of coherence, straining to achieve a melody, but don’t quite make it. I find this interesting: after listening, and without having to check, I knew the planets weren’t in orbital resonance.
A resonance is when one planet’s orbit is a simple fraction of another’s; for example, one planet might circle the star every 2 days, and the next one out in 4 days. Resonances take many ratios, like 3:2, or 5:3. The planets in Kepler-11 don’t do this (though two of them are near a 5:4 resonance). If they did, then eventually the sonata’s melody, such as it is, would repeat. But I didn’t get a sense of that listening to it.
Isn’t that amazing? You can take data using light, convert it to sound, and actually be able to get insight into it. In this case, of course, you could just make a spreadsheet with the planetary periods in it and start dividing away, but that’s no fun!
Perhaps this is just an oddity with no real impact. But I wonder. We convert data into charts and graphs so that we can look for trends, correlations, compare one datum to another visually. In a sense — haha, "sense"! — this is just another case of that, appealing to hearing instead of sight. I’m not a musician per se* so I don’t know if this method has real use or not.
But it’s still cool. And rather pleasant, don’t you think?
* 20+ years of playing bass trombone may be used to argue my musicianship either way, I suspect.
I’m very excited about all the news we’re getting of planets orbiting other stars. For Q&BA I got a good question about them: How many exoplanets are there?
[Note: the aspect ratio on this video is messed up a bit, like it was on the last one. I understand the problem now, but cannot fix it in this video. They should be back to normal next time!]
I wonder how many of the thousands of candidate planets known will turn out to be real? Probably most of them. And there are billion, hundreds of billions, of planets in our galaxy alone! How many of those are like Earth? Maybe soon we’ll know.
I don’t care if it’s a curse or not. We do live in interesting times.
I have an archive of Q&BA links and videos. Take a look and see if there are other ones that tickle your imagination.
- Q&BA: Which moon has the best chance for life?
- Q&BA: Can we build a space habitat?
- Q&BA: The Science of Science Fiction
- Q&BA: How does a gravity slingshot work?
- Q&BA: Why spend money on NASA?
- Q&BA: What happens if you are exposed to the vacuum of space?
Well, this is some very welcome and happy news: NASA’s 2012 Senior Review for Operating Missions has recommended to NASA that eight of the nine operating space-based astrophysics missions be extended in funding through fiscal year 2016, and NASA has complied!
This really is great news! The missions extended through FY 2016 are Hubble, Chandra, Fermi, Planck, Suzaku, Swift, XMM-Newton, and Kepler. The exception is the infrared observatory Spitzer, which ran out of coolant a few years ago but is running in an extended "warm" phase, still able to do science. It will be extended through 2015, which is earlier than hoped, but it could be worse. The details are in the report issued by the Senior Review (PDF).
I’m very excited specifically about Swift — a gamma-ray burst mission that I worked on years ago, and which has been operating for more than 7 years so far. But I’m even more excited about Kepler. This is fantastic — it has found
hundreds dozens of planets orbiting other stars, and has thousands more candidates listed that await confirmation. The reason this extension is so great is that the longer Kepler looks, the more likely it is to find lower mass planets in longer orbits. Big, massive planets orbiting close to their stars are easy to find, but ones more like Earth are much tougher. Kepler is right on the thin hairy edge of being able to detect them now, and this extension means a much higher chance it will succeed.
I strongly suspect — based on what we’ve already seen from Kepler coupled with the statistics and physics of exoplanets — that the signal from an Earth-like planet orbiting a Sun-like star in the habitable zone is already in the data we’ve received. It may be very hard to tease out, though, so having even more data, years worth of extra data, is more than a boon. It’s like being given the key to a treasure chest.
So overall I’m pretty darn pleased with this. Given the semi-apocalyptic nature of the last budget news we heard about NASA, this is like an oasis in the desert. Congratulations to all the people involved with these missions, and I’m looking forward to many more years of great science from our orbiting fleet of observatories!
Tip o’ the lens cap to Travis Metcalfe for alerting me to this news.
There’s been a lot of exoplanet news lately! Part of that is due to the American Astronomical Society meeting recently — in fact, there was so much I wrote four articles just from that (Part 1, Part 2, and Part 3, and Part 4). This next story wasn’t released at the meeting, yet may honestly be the most mind-blowing of them all.
Astronomers have found what appears to be a planet literally boiling away from the blast-furnace heat of its star.
Holy cosmic oxyacetylene torch!
There’s a bit of a back story here. The star, KIC 12557548, is about 1500 light years away, and is one of many thousands being observed by the orbiting Kepler Observatory (KIC stands for Kepler Input Catalog, a list of stars under Kepler’s watchful eye). The observatory stares at one spot in the sky, looking for stars whose brightness dips periodically. There can be many causes of such behavior, one of which is the presence of planets orbiting the star and blocking the light from it as they pass in front of it. This is called a transit, and has proven to be wildly successful; hundreds of planets have been discovered this way.
What the authors of this new study are saying is that they see a periodic dip in the brightness of KIC 12557548 every 15.685 hours. Yes, hours. The star is a bit smaller and cooler than the Sun (a K star with about 0.7 times the mass of the Sun, if you want specifics), but even so, the planet must orbit the star a mere 1.5 million kilometers (900,000 miles) from its surface — that’s less than four times the distance of the Moon from the Earth!
That’s close. You’d expect the planet to be cooking… and you’d be right. It’s probably somewhere around 2000°C (3600°F).
Usually, with most planets, the amount of light blocked as the planet passes in front of the star is the same every time. That makes sense, because the planet itself isn’t changing. But not for KIC 12557548. What they saw was that every transit was different. Sometimes more than 1% of the light is blocked, sometimes they detect no dimming at all at the appointed time. That’s really weird.
They looked at and eliminated a few different scenarios, but the fact that the planet is that close to the star really leaves just one idea: a rocky world, probably half the diameter of Earth, being vaporized by the heat of its parent star*.
There’s been so much exoplanet news this week! I was in Texas the past couple of days giving a bunch of talks, so I’m trying to catch up. All the exoplanet news is way cool, but too much for one post, so I’ve split them up. I’ll post the other parts shortly.
Part 1: A trio of hot little rocks
First up? The three smallest exoplanets found so far. I usually don’t like to write about incremental discoveries, but this one is truly cool: all three orbit the same star, and all three are smaller than Earth! Any one of these would be a record breaker, but to find all three at once, in the same place? Amazing.
They orbit the star KOI-961 (short for Kepler Object of Interest), and were observed by the Kepler Observatory (details on how that all works can be found here). They all orbit the star extremely close in: the farthest one is a mere 2.3 million km (1.5 million miles) from the star! They’re so close they all take less than two days to circle it once. And even though the star is a red dwarf, and therefore relatively cool, they are so close to it that they probably resemble airless, heat-blasted Mercury more than Earth. They are almost certainly rocky/metallic bodies, since they are so small: 0.78, 0.73 and 0.57 times the diameter of the Earth. Although we’ve been surprised before, it’s hard to imagine anything that small could hold onto much atmosphere when they are so hot.
Funny, too: the star is tiny, only a bit bigger than Jupiter. And the planets are so close in the KOI-961 system looks more like Jupiter and its moons than our own solar system! The artwork above drives that point home. Everything there is to scale: the relative size of the star, the planets, Jupiter, and its moons. [Edited to add: Note that the distances are not to scale!]
Why is this news important? Well first, it adds more weight to the idea that planets smaller than Earth exist and can be found around other stars. Second, it shows that red dwarf stars can form and hold onto planets… which itself is important because red dwarfs are by far the most common kind of star in the Universe. They make up roughly 80% of the total number of stars! So finding multiple planets around one means, once again, planets are almost certainly common in the galaxy.
And third, it just shows once again that the Universe is a surprising place. This mini-solar system proves that nature is diverse, and will fill any niche it can. It also implies, very strongly, that we need to broaden our concepts of how solar systems form, what they look like, and how they behave.
Image credit: NASA/JPL-Caltech
- Kepler finds a mini solar system!
- Another Kepler milestone: Astronomers find two Earth-sized planets orbiting the same star!
- No, it’s *not* the smallest exoplanet found!
- A boiling superEarth joins the exoplanet roster
Last night, I started getting emails and tweets asking about a possible detection of a radio signal coming from two of the newly-discovered planets orbiting other stars.
Cutting to the chase: yes, a signal has been seen, but no, it’s not coming from some alien civilization. It’s almost certainly something much closer, like a satellite interfering with the observation.
So what’s the deal?
You talkin’ to me?
The Search For Extraterrestrial Intelligence (SETI) is a
privately-funded group of scientists and engineers who are trying* an ongoing effort to figure out ways to detect signals from space that could be coming from other intelligences: aliens. They focus (haha) mostly on radio signals, since it’s very easy to send radio waves across the vast light years separating stars, it’s easy to detect radio waves (so primitive life like us can pick up the call), and it’s easy to encode information that way. Heck, we’ve been broadcasting coded radio waves for over a century now!
Currently, no unambiguous alien "Hello there!" has been detected. The sky is big, there are a lot of stars out there, and the radio spectrum is really wide, too. Think of how many radio stations there are on a typical radio dial from top to bottom; now divide that up into a billion tiny slices and try to find the one that’s playing the song you want to hear. It’s something of a painstaking process.
Recently, astronomers came up with a clever idea: the Kepler space mission is finding tons of planets orbiting other stars. It may find an Earth-like planet orbiting a Sun-like star at just the right distance to allow life to evolve, though no such planet has been found just yet. Still, why look all over the sky when we know where there are lots of planets?
Can’t stop the signal
So a search targeting those stars with planets has been set up. And that’s where our story picks up: using the ginormous 100 meter Green Bank Telescope, astronomers from UC Berkeley found what look like artificial signals when observing two different stars. The stars are called Kepler Object of Interest 812 and 817 (or just KOI 812 and 817 for short). Here’s an example of a signal they found from KOI 817: