Space and astronomy news
Here’s a fun trip through the galaxy, put together by PhD student Tom Hands at the University of Leicester: In the above video, you can fly to of all the known exoplanets (around single stars only), ordered roughly by semi-major axis of largest orbit. Hands said the video is designed to give the viewer an overview of the current distribution of exoplanets.
Hands used data from the Open Exoplanet Catalogue.
There’s a lot you can learn by just staring at an object, watching how it changes in brightness. This is the technique of photometry, and it has helped astronomers discover variable stars, extrasolar planets, minor planets, supernovae, and much more.
Continue reading “Astronomy Cast Ep. 337: Photometry”
Trying to keep a low profile, to prevent the aliens from invading? Bad news. Life has actually been broadcasting our existence to the Universe for hundreds of millions of years.
Have you heard these crazy plans to send signals out into deep space? What if evil aliens receive them, come steal our water, enslave, eat, and use us as guinea pigs for their exotic probulators. How we could stop these madmen from announcing our presence to the galaxy? A petition on whitehouse.gov? An all caps Facebook group? An all pusheen protest? Somebody call Reddit, they’ll know what to do.
If this is a worry for you and your friends, I’ve got bad news, or possibly good news depending on which side you come down on. We’ve already been broadcasting our existence for hundreds of millions of years. If aliens wanted to know we were here, all they needed to do was look through their telescopes.
We’re in a golden age of extrasolar planet discovery, recently crossing the thousand-planets-mark thanks to Kepler and other space telescopes. With all these amazing planetary candidates, our next challenge will be to study the atmospheres of these planets, searching for evidence of life. There are chemicals which are naturally occurring, like water and carbon dioxide, and there are substances that can only be present if some source is replenishing them. Methane, for example, would only last only few hundred years in the atmosphere if it wasn’t for farting cows and colonies of bacteria eating dead things.
If we see methane or oxygen in the atmosphere of an extrasolar planet, we’ll have a good idea there’s life there. And if we see the byproducts of an industrial civilization, like air pollution, we can pinpoint exactly where they are in their technical development. It will work for us, and that means it would work for aliens.
For the first few billion years, oxygen was toxic. But then cyanobacteria evolved photosynthesis and figured out how to work with oxygen more than 2.4 billion years ago. This is known as the Great Oxidation Event.
For the first billion years, all this biologically generated oxygen was absorbed by the oceans and the rocks. Once those oxygen sinks filled up, oxygen began accumulating in the atmosphere. By 500 million years ago, there was enough oxygen in the atmosphere to support the kind of breathing we do today. And this much oxygen would have been obvious to the aliens. They would have known that life had evolved here on Earth, and they could have sent out their berserker spaceships to steal our water and made us watch while they ate all our small rodents.
If the aliens waited, we would have given them more signs. The Industrial Revolution began in the mid 1700’s. And this time, it was humans that filled the atmosphere with the pollution of our industrial processes. Again, aliens watching the planet with their space telescopes would know the moment we became a technological civilization.
In the 20th century, we harnessed the power of radio transmissions, and began sending our messages out into space. For about a hundred years now, our transmissions have been expanding into a bubble of space. And so, any aliens listening within this expanding sphere of space might have a chance of hearing us. They know we’re here, and they know some of us really like Ke$ha.
And finally, for the last few decades, a few groups have tried broadcasting messages using our powerful radio telescopes directly at other stars. These messages haven’t gotten very far, but I honestly wouldn’t worry. Life itself gave away our position hundreds of millions of years ago. And life will help us find other civilizations, if they’re out there.
What do you think? Should we turn out the lights and pretend like we’re not home or keep on actively broadcasting our presence to the Universe? Tell us what you think we should do in the comments below.
When astronomers first discovered other planets, they were completely unlike anything we’ve ever found in the Solar System. These first planets were known as “hot jupiters”, because they’re giant planets – even more massive than Jupiter – but they orbit closer to their star than Mercury. Dr. Heather Knutson, a professor at Caltech explains these amazing objects.
“My name is Heather Knutson, and I’m a professor in the planetary science department here at Caltech. I study the properties of extrasolar planets, which are planets that orbit stars other than the sun, so mostly these are our closest exoplanetary neighbors. We’re not talking about planets in other galaxies – we’re mostly talking about planets which are in the same part of our own corner of our galaxy. So these are around some of the closest stars to the sun.”
What is a hot jupiter?
“The planets that I’ve found the most surprising, out of all of the ones I’ve discovered so far, I guess the sort of classic example, is that we’ve see these sorts of giant planets which are very similar to Jupiter, but orbit very much closer in than Mercury is to our sun, so these planets orbit their sun every two or three days and are absolutely getting roasted. We know that they couldn’t have formed there – they had to have formed farther out and migrated in, so what we’re still trying to understand are what are the forces that caused them to migrate in, whereas Jupiter seems to have migrated a little bit but more or less stayed put in our own solar system.”
What do hot jupiters mean for our understanding our own Solar System?
“The implications of these “hot jupiters” as we call them are actually huge for our own solar system, because if you want to know how many potentially habitable earthlike planets are out there, having one of these giant planets just rampage their way though the inner part of the planetary system, and it could toss out your habitable earth and put it into either a much closer orbit or a much further orbit. So knowing how things have moved around will tell you a lot about where you might find interesting planets.”
What is their atmosphere like?
“So, the atmospheres of hot jupiters are very exotic, by solar system standards. They typically have temperatures of a thousand to several thousand Kelvin, so at these temperatures these planets could have clouds of molten rock, for example. They have atmospheric compositions that would seem very exotic to us – they’re actually more similar to the compositions of relatively cool stars, so we have to adapt to describe these planets – we actually use stellar models to describe their atmospheres. We think that they’re also probably also tidally locked, which is very interesting because it means that one side of the planet is getting all of the heat and the other side is sort of in permanent night. And one thing we do is to try and understand the effect that has on the weather patterns on these planets, so you have winds that are pretty good at carrying that around the night side and mixing everything up, or do these planets have these just extreme temperature gradients between the day side and the night side.”
How’d they get there?
“So, we have a couple of theories for how hot jupiters may have ended up in their present day orbits. One theory is, that after they formed, that they were still embedded in the gas disc where they formed, and maybe they interacted with the disc as such that it kind of torqued and pulled them and so that’s kind of an early migration theory. There’s also a late migration theory version where when after the disc had gone away, these planets had interacted with a third body in the system, so maybe you had another distant massive planet or maybe you had a planet that was part of a binary star system, and those three body interactions excited a large orbital eccentricity in the innermost planet, and once it starts coming in closer to the star, the tides start to damp out the eccentricities, so what you end up with is something which is a gas giant planet in a very short period circular orbit.
So that’s kind of a more complicated story, but there are some clues in the data that might be true for at least a subset of the hot jupiters that we study.”
Astronomers constantly probe the skies for the unexpected. They search for unforeseen bumps in their data — signaling an unknown planet orbiting a star, a new class of astronomical objects or even a new set of physical laws that will rewrite the old ones. They are willing to embrace new ideas that may replace the wisdom of years past.
But there’s one exception to the rule: the search for Earth 2.0. Here we don’t want to find the unexpected, but the expected. We want to find a planet so similar to our own, we can almost call it home.
While, we can’t exactly image these planets with great enough detail to see if one’s a water world with luscious green plants and civilizations, we can use indirect methods to find an “Earth-like” planet — a planet with a similar mass and radius to the Earth.
There’s only one problem: the current techniques to measure an exoplanet’s mass are limited. To date astronomers measure radial velocity — tiny wobbles in a star’s orbit as it’s tugged by the gravitational pull of its exoplanet — to derive the planet-to-star mass ratio.
But given that most exoplanets are detected via their transit signal — dips in light as a planet passes in front of its host star — wouldn’t it be great if we could measure its mass based on this method alone? Well, astronomers at MIT have found a way.
Graduate student Julien de Wit and MacArthur Fellow Sara Seager have developed a new technique for determining mass by using an exoplanet’s transit signal alone. When a planet transits, the star’s light passes through a thin layer of the planet’s atmosphere, which absorbs certain wavelengths of the star’s light. Once the starlight reaches Earth it will be imprinted with the chemical fingerprints of the atmosphere’s composition.
The so-called transmission spectrum allows astronomers to study the atmospheres of these alien worlds.
But here’s the key: a more massive planet can hold on to a thicker atmosphere. So in theory, a planet’s mass could be measured based on the atmosphere, or the transmission spectrum alone.
Of course there isn’t a one to one correlation or we would have figured this out long ago. The atmosphere’s extent also depends on its temperature and the weight of its molecules. Hydrogen is so light it slips away from an atmosphere more easily than, say, oxygen.
So de Wit worked from a standard equation describing scale height — the vertical distance over which the pressure of an atmosphere decreases. The extent to which pressure drops off depends on the planet’s temperature, the planet’s gravitational force (a.k.a. mass) and the atmosphere’s density.
According to basic algebra: knowing any three of these parameters will let us solve for the fourth. Therefore the planet’s gravitational force, or mass, can be derived from its atmospheric temperature, pressure profile and density — parameters that may be obtained in a transmission spectrum alone.
With the theoretical work behind them, de Wit and Seager used the hot Jupiter HD 189733b, with an already well-established mass, as a case study. Their calculations revealed the same mass measurement (1.15 times the mass of Jupiter) as that obtained by radial velocity measurements.
This new technique will be able to characterize the mass of exoplanets based on their transit data alone. While hot Jupiters remain the main target for the new technique, de Wit and Seager aim to describe Earth-like planets in the near future. With the launch of the James Webb Space Telescope scheduled for 2018, astronomers should be able to obtain the mass of much smaller worlds.
The paper has been published in Science Magazine and is now available for download in a much longer form here.
Growing up, my sister played video games and I read books. Now that she has a one-year-old daughter we constantly argue over how her little girl should spend her time. Should she read books in order to increase her vocabulary and stretch her imagination? Or should she play video games in order to strengthen her hand-eye coordination and train her mind to find patterns?
I like to believe that I did so well in school because of my initial unadorned love for books. But I might be about to lose that argument as gamers prove their value in science and more specifically astronomy.
Take a quick look through Zooniverse and you’ll be amazed by the number of Citizen Science projects. You can explore the surface of the moon in Moon Zoo, determine how galaxies form in Galaxy Zoo and search for Earth-like planets in Planet Hunters.
In 2011 two citizen scientists made big news when they discovered two exoplanet candidates — demonstrating that human pattern recognition can easily compliment the powerful computer algorithms created by the Kepler team.
But now we’re introducing yet another Citizen Science project: Disk Detective.
Planets form and grow within dusty circling planes of gas that surround young stars. However, there are many outstanding questions and details within this process that still elude us. The best way to better understand how planets form is to directly image nearby planetary nurseries. But first we have to find them.
“Through Disk Detective, volunteers will help the astronomical community discover new planetary nurseries that will become future targets for NASA’s Hubble Space Telescope and its successor, the James Webb Space Telescope,” said the chief scientist for NASA Goddard’s Sciences and Exploration Directorate, James Garvin, in a press release.
NASA’s Wide-field Infrared Survey Explorer (WISE) scanned the entire sky at infrared wavelengths for a year. It took detailed measurements of more than 745 million objects.
Astronomers have used complex computer algorithms to search this vast amount of data for objects that glow bright in the infrared. But now they’re calling on your help. Not only do planetary nurseries glow in the infrared but so do galaxies, interstellar dust clouds and asteroids.
While there’s likely to be thousands of planetary nurseries glowing bright in the data, we have to separate them from everything else. And the only way to do this is to inspect every single image by eye — a monumental challenge for any astronomer — hence the invention of Disk Detective.
Brief animations allow the user to help classify the object based on relatively simple criteria, such as whether or not the object is round or if there are multiple objects.
“Disk Detective’s simple and engaging interface allows volunteers from all over the world to participate in cutting-edge astronomy research that wouldn’t even be possible without their efforts,” said Laura Whyte, director of Citizen Science at the Adler Planetarium in Chicago, Ill.
The project is hoping to find two types of developing planetary environments, distinguished by their age. The first, known as a young stellar object disk is, well, young. It’s less than 5 million years old and contains large quantities of gas. The second, known as a debris disk, is older than 5 million years. It contains no gas but instead belts of rocky or icy debris similar to our very own asteroid and Kupier belts.
So what are you waiting for? Head to Disk Detective and help astronomers understand how complex worlds form in dusty disks of gas. The book will be there when you get back.
The original press release may be found here.
Host: Fraser Cain
Guests: +Brian Koberlein (@briankoberlein), David Dickinson (@Astroguyz), Pamela Gay (@starstryder)
Big thanks to Nicole Gugliucci (@noisyastronomer) for doing a wonderful job producing this past year!
Continue reading “Weekly Space Hangout – December 27, 2013: Year in Review & Looking Forward”
A team of European astronomers has discovered a second planetary system, the closest parallel to our own solar system yet found. It includes seven exoplanets orbiting a star with the small rocky planets close to their host star and the gas giant planets further away. The system was hidden within the wealth of data from the Kepler Space Telescope.
KOI-351 is “the first system with a significant number of planets (not just two or three, where random fluctuations can play a role) that shows a clear hierarchy like the solar system — with small, probably rocky, planets in the interior and gas giants in the (exterior),” Dr. Juan Cabrera, of the Institute of Planetary Research at the German Aerospace Center, told Universe Today.
Three of the seven planets orbiting KOI-351 were detected earlier this year, and have periods of 59, 210 and 331 days — similar to the periods of Mercury, Venus and Earth.
But the orbital periods of these planets vary by as much as 25.7 hours. This is the highest variation detected in an exoplanet’s orbital period so far, hinting that there are more planets than meets the eye.
In closely packed systems, the gravitational pull of nearby planets can cause the acceleration or deceleration of a planet along its orbit. These “tugs” cause the variations in orbital periods.
They also provide indirect evidence of further planets. Using advanced computer algorithms, Cabrera and his team detected four new planets orbiting KOI-351.
But these planets are much closer to their host star than Mercury is to our Sun, with orbital periods of 7, 9, 92 and 125 days. The system is extremely compact — with the outermost planet having an orbital period less than the Earth’s. Yes, the entire system orbits within 1 AU.
While astronomers have discovered over 1000 exoplanets, this is the first solar system analogue detected to date. Not only are there seven planets, but they display the same architecture — rocky small planets orbiting close to the sun and gas giants orbiting further away — as our own solar system.
Most exoplanets are strikingly different from the planets in our own solar system. “We find planets in any order, at any distance, of any size; even planetary classes that don’t exist in the solar system,” Cabrera said.
Several theories including planet migration and planet-planet scattering have been proposed to explain these differences. But the fact of the matter is planet formation is still poorly understood.
“We don’t know yet why this system formed this way, but we have the feeling that this is a key system in understanding planetary formation in general and the formation of the solar system in particular,” Cabrera told Universe Today.
The team is extremely hopeful that the upcoming mission PLATO will receive funding. If so, it will allow them to take a second look at this system — determining the radius and mass of each planet and even analyzing their compositions.
Follow-up observations will not only allow astronomers to determine how this planetary system formed, it will provide hints as to how our own solar system formed.
The paper has been accepted for publication in the Astrophysical Journal and is available for download here.
How common are planets like Earth? That’s been a question astronomers and dreamers have pondered for decades, and now, thanks to the Kepler spacecraft, they have an answer. One in five Sun-like stars in our galaxy have Earth-sized planets that could host life, according to a recent study of Kepler data.
“What this means is, when you look up at the thousands of stars in the night sky, the nearest sun-like star with an Earth-size planet in its habitable zone is probably only 12 light years away and can be seen with the naked eye. That is amazing,” said UC Berkeley graduate student Erik Petigura, who led the analysis of the Kepler and Keck Observatory data.
The Kepler telescope’s mission was to try and find small rocky planets with the potential for hosting liquid water and perhaps the ingredients needed for biology to take hold. For four years, the space telescope monitored the brightness of more than 150,000 stars, recording a measurement every 30 minutes.
Analysis by UC Berkeley and University of Hawaii astronomers shows that one in five sun-like stars have potentially habitable, Earth-size planets. (Animation by UC Berkeley/UH-Manoa/Illumina Studios)
For a recent focused study, scientists concentrated on 42,000 sun-like stars (G and K type stars), looking for periodic dimmings that occur when a planet transits — or crosses in front of — its host star. A team of scientists from the Kepler mission and the Keck telescope in Hawaii have announced that from that survey, they found 603 planets, 10 of which are Earth size and orbit in the habitable zone, where conditions permit surface liquid water.
Since there are about 200 billion stars in our galaxy, with 40 billion of them like our Sun, noted planet-hunter Geoff Marcy said that gives us about 8.8 billion Earth-size planets in the Milky Way.
But Marcy also cautioned that Earth-size planets in Earth-size orbits are not necessarily hospitable to life, even if they orbit in the habitable zone of a star where the temperature is not too hot and not too cold.
“Some may have thick atmospheres, making it so hot at the surface that DNA-like molecules would not survive. Others may have rocky surfaces that could harbor liquid water suitable for living organisms,” Marcy said. “We don’t know what range of planet types and their environments are suitable for life.”
All of the potentially habitable planets found in their survey are around K stars, which are cooler and slightly smaller than the sun, Petigura said. But the team’s analysis shows that the result for K stars can be extrapolated to G stars like the sun.
The Kepler spacecraft is now crippled because of faulty gyroscopes, but scientists say had Kepler survived for an extended mission, it would have obtained enough data to directly detect a handful of Earth-size planets in the habitable zones of G-type stars.
If the stars in the Kepler field are representative of stars in the solar neighborhood, then the nearest (Earth-size) planet is expected to orbit a star that is less than 12 light-years from Earth and can be seen by the unaided eye. Future instrumentation to image and take spectra of these Earths need only observe a few dozen nearby stars to detect a sample of Earth-size planets residing in the habitable zones of their host stars.
“For NASA, this number – that every fifth star has a planet somewhat like Earth – is really important, because successor missions to Kepler will try to take an actual picture of a planet, and the size of the telescope they have to build depends on how close the nearest Earth-size planets are,” said Andrew Howard, astronomer with the Institute for Astronomy at the University of Hawaii. “An abundance of planets orbiting nearby stars simplifies such follow-up missions.”
Further reading: Institute for Astronomy, University of Hawaii; UC Berkeley; Keck Observatory; NASA; PNAS.
Astronomers have now discovered one thousand extrasolar planets, reaching a milestone in modern astronomy. (See a recent Universe Today article on the subject.) While many have contributed to this achievement, Dr. Sara Seager of MIT has played a large role over the past two decades by contributing vastly to the field of exoplanet characterization. Her theoretical work led to the first detection of an exoplanet atmosphere.
The following is a condensed interview I held with Seager earlier this week.
What first pulled you in to the field of astronomy?
When I was 10 I got to see a really dark sky (well outside her hometown of Toronto, Canada). I stepped out in the middle of the night and I just saw so many stars. I wish you and everyone could see that. So many stars, I just couldn’t believe it.
You were working at Harvard for your PhD in the mid ‘90s when we first detected exoplanets. What was that like?
The mood was quite different. Today everybody wants to talk about it (exoplanets) and write about it. There’s a lot of hype. But back then it was very quiet.
There was a huge amount of skepticism too. People don’t like change. I want you to imagine a world where the gas giants like Jupiter and Saturn are very far from the star and the terrestrial planets like Earth, Mercury, Venus, and Mars are very close to the star. People had constructed theories on how planetary bodies form based on that one example.
So when the first planets around sun-like stars were found, they were Jupiter-mass planets, but they were several times closer to their star than Mercury is to our Sun. It offended all thoughts, theories, and paradigms … As scientists we’re supposed to be skeptical and push back on new discoveries and theories that are upsetting the system. There was huge skepticism.
How difficult was it during this time to work on exoplanets?
Many people, including my graduate student peers and faculty said, “Why are you doing this (working on exoplanet research)? This is not going to happen. And even if exoplanets are real we’re never going to be able to study their atmospheres,” which is what my PhD was on.
What pushed you through despite all the skepticism?
Ironically, I was not committed to a career in science. I didn’t feel like I needed to be involved with something that was at the 100 percent certainty level. I was free because I didn’t have a plan. I had nothing to lose by doing something I thought was really cool and exciting.
When you’re doing a PhD you’re really learning how to answer a tough question. Usually if you do a homework set in high school, or college, there’s already a known answer. But when you’re doing a PhD, if you’re asking a really hard question that has never been asked before you’re answering that question with your own tools that you’ve developed yourself.
At that time, I knew… the real thing is not just what you’re working on but it’s the tools that you’re using and the things that you’re learning. At the end of the day if you don’t stay in science you have gained a skill that most people don’t have.
What changed then? What kept you in science after graduate school?
I had freedom and really enjoyed what I was doing.
What is your motivation for studying exoplanets? Why should we study exoplanets?
We want to know: Are we alone? We want to know if there is life beyond earth. Eventually we will have dozens to hundreds of potential earth-like planets to study in detail. We want to look at their atmospheres for signs of life by way of biosignature gases.
What do you think is the likelihood that we will discover an earth-like planet orbiting a sun-like star?
Well, it really just depends if we can rally resources and interest in doing this problem. We think we know how to find an earth-like planet around a sun-like star. But it’s a very very very hard endeavor. We think that the earths are out there. It’s just a matter of building the sophisticated space telescopes that we need.
So what are the chances? It’s really more of a political and economical question more than anything else. I think it’s inevitable that eventually we will find one.
Do you have a favorite planet?
I always like to say my favorite planet is the next planet. We have a sort of ADD (attention deficit disorder) in this field where we’re propelled and motivated forward by finding the next exciting planet.
We’ve reached a huge milestone in astronomy of detecting one thousand exoplanets. What does this milestone mean to you?
There’s a caveat here, an uncertainty. We don’t know which one is going to be number one thousand because we don’t agree on the definition of a planet. And even if we did, there’s an uncertainty in the mass and size measurements such that some objects that are called planets probably aren’t planets depending on what definition you want. Occasionally a planet is retracted.
But in general, we’re about to pass the one thousandth mark. What do I think? I think it’s phenomenal. I mean I’m so excited.
The study of exoplanets really started as a field where no one wanted to work on it. People thought it was never going to happen, they thought even if there were real planets we’d never get any measurements beyond stamp collecting – a derogatory phrase we sometimes use in astronomy for science that is not that useful. You just find discoveries and they pile up because you don’t know what to do with them.
We’ve changed the paradigm of planet formation, found exotic types of planets, and we’re right on our way to finding another Earth. So I think it couldn’t be better.