Comparison of ground-based and space-based light curves for hot exoplanet HAT P7b (Image credit: NASA Ames Research Center)

This is the morning of Kepler. I’m currently sitting in a the Marriot Ballroom watching the speaker, William J Borucki (NASA/Ames) gear up to announcing planets.

This amazing mission has been imaging the same rich stellar field over and over looking for planetary transits: the slight dimming of light from a star that comes from an orbiting planet passing between us and that distance star.

After 20 minutes of gearing up, he announced 5 new planets with orbital periods between 3.2 and 4.9 days orbiting stars larger than the sun at orbital distances 4.31 to 18.8 times the size of the Earth’s orbit. Because the stars are bigger than the Sun (by an amount not shown in the table), this is hard to quantify – they could be very near the stellar surfaces! – He referred to them as icy giants, but their surfaces are all hotter than 1500 Kelvin, with surfaces in 2 cases hotter than molten lead! These are large hot planets.

4 of these planets are all more massive than Jupiter, and one is smaller but still larger than Earth. There is a great table coming in a paper on Astro-PH going up later today (link to come)

In addition to these stars, they have also discovered several neat variable stars: binaries, oscillating stars, pulsating variables, and more. This is one of the great things about this mission: While it was designed to find earth-sized planets orbiting other stars (given more time – they require data over more time than Jupiter-sized planets), it also collects data on variable stars in the field that is of amazing quality. This means that Kepler’s throw away data is somebody else’s science.

Okay he just said something weird I’m going to have to look up. They have found small – Jupiter-ish sized in radius – that are hotter than the star they are orbiting. These look like tiny hot stars orbiting cooler stars BUT the hot object is too big to be a white dwarf and too hot to be anything else. He said there are more than one in the field and no one knows what they are.

The Kepler Press conference is coming up soon, and hopefully we’ll get more info there.

In a new pre-print over on arXive, astronomers Ignasi Ribas (ICE/CSIC-IEEC, Spain), Andreu Font-Ribera (ICE/CSIC-IEEC, Spain), and Jean-Philippe Beaulieu (IAP, France) announce they have found what may be the smallest planet yet discovered – a 5 Earth mass world – orbiting a cool red dwarf star. They found this potential new planet through its invisible tug-a-war on an already known gas giant.

Here’s how the game is played. Some astronomer (or 2 or 12) adopts a star and observers it over and over and over with a telescope equipped with a high-resolution spectrograph. If they are lucky they find something neat in the light.

The following is a long, forgive me I’m a prof, explanation of how astronomers study the light to look for planets using spectrographs.

If the star is moving at a constant velocity on its orbit around the galaxy, the lines in the spectra (caused by the emission and absorption of light by atoms) will always be at the same set of wavelengths – a specific set of measurable numeric values. This is easier to imagine if we mentally replace the light spectra with a rich cord sang by a choir being accompanied by a massive orchestra. If you record the sound and look at its acoustic spectra, you’ll see specific peaks that correspond to various pitches sung by individual people and instruments. While any sound is possible – we’ve all heard the slid whistle slide from high to low – a single cord sung by a specific set of voices will have a very limited set of acoustic peaks. A single star, with a specific set of atoms all humming at the same temperature, will have a specific set of light peaks and valleys in its light spectra.

Now imagine that you place that choir on a fire truck that drives straight toward you, misses you by 10 inches, and then tears away. As the fire truck goes from moving toward you to moving away, you hear the pitch go from abnormally high-pitched (soprano) to abnormally low-pitched (bass). In the same way, if you could stick a star on that fire truck without you dieing or it melting, instead of hearing the pitch change you would see the color go from abnormally blue to abnormally red.

If a star, on its orbit around the galaxy, has a planet orbiting around it, then it will develop this to and fro 2-step in which it the planet’s gravity causes the star to move a little faster and a little slower as the center of mass of the star+planet system moves at a steady velocity around the galaxy. This dance appears as a slight shifting of the star’s spectral lines from blue to red and back to blue again – a shift that is a measurable set of numerical values. We call this Doppler Shifting.

If a star with a planet with a shift that we can observe is adopted by an astronomer, it is possible to measure the orbital period of the planet by measuring how long it takes to get from blue to red and back to blue again. It is also possible to measure the size of the planet by the size of color shift (a large planet will produce a larger shift in colors). And in some cases, if we are lucky we can observe the planet directly by seeing it pass directly between us and the star, blocking a little bit of the light as it goes (the rest of the time, the orbit of the planet carries it above and below the star instead of in front of it). This is called a transit. If the orbit of the planet changes for any reason, any transits we see will also change – getting longer as the planet passes across the center of the star and getting shorter as the star grazes the planets edges alone, and also changing if the planets orbital shape or size changes. Using computers and complex numerical analysis software, it is possible to take what we see and figure out what it means by moving around digital models of the system until their behavior matches observed behavior.

Okay – I’m done with the background.

Within the light of a little star named GL 436, astronomers found the characteristic color shifting of a star with a planet. Initial discovery of a 23 Earth mass planet (something a bit bigger than Neptune) occurred in 2004. At that time, astronomers let by Butler (of 51 Peg fame), looked for and could not find any planetary transits. It happens. It’s sad, but hey, sometimes planets aren’t as exciting as one would want.

What was really weird, however, was that in another paper in 2007 by Gillon et al., they did see a transit – just a little grazing one – but it was there blocking 7/1000 of the star’s light. This (coupled with some weirdness in the stars Doopler shift), indicate that the star’s orbit isn’t perfectly repeating, but rather systematically changes over time. Using careful computer simulations, the team demonstrated that all the weirdnesses could be accounted for (more or less) by one tiny little planet – just 5 earth masses in size – orbiting twice  once for every one two times the gas giant orbits the star. (This means the gas planet is closer to the star than the rocky world – not something they teach you to expect in school books!)

What was really cool about this paper, and what lead to me want to write this post – was that their paper made specific predictions about how the observed transits will get longer if the inclination of the gas giant changes by just 0.1 degree – tiny amount that can be somewhat expected. This means, if the 5ish earth mass planet is there, we know what effects it will have on the system in the future.

I love science. One group of folks found a planet. Another group found a change in the planet’s transit behavior. A third group went ?!?!? and abused some computers to possibly sort it all out and make some predictions. I wouldn’t be at all surprised if it was a 4th group who made the follow up observations needed to prove the planet is there.

Astronomy is no longer a single man on the mountain science of individuals. Collaboration: it’s what all the cool kids are doing.

image credit: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF

So, when we look for planets directly, we need instruments that can look for the light the planets reflect from the star they orbit, instruments for detecting the infrared light they give off because they are warm, and design instruments that lest us do all of this while not getting blinded by the pesky central star. In his October 7 paper on arXiv, Steven Beckwith calculates that a space telescope of 10 meters or more (and preferably more like 16m) is required to detect terrestrial planets within the habitable zone of stars. (Fine point here, while the habitable zone moves as stars change in size, this doesn’t help – Big Stars are really bright and can can interfere with things at the larger radii where habitable planets must be located, and little stars have to keep their habitable planets really close in, which makes them hard to see even in the little star’s faint light).

To come up with his 10m and larger number, Beckwith asked, what diameter is needed to resolve the planet from the star when the star is farthest from its star. This number changes with wavelength, and larger telescopes are needed to resolve small features at longer wavelengths (in English, if I want to see details on Jupiter in an optical telescope, I only need something a few inches across, but if I want to resolve those same features with a radio telescope, I need a telescope a billion times bigger. He states, “A spectrum should extend to at least 1 micron to be analyzed for evidence of disequilibrium chemistry indicative of life, and longer wavelengths require lengths bring in even more interesting features.” In other words, to see the neat molecules that result from life (more below) we need to look at infrared light. To resolve 1 micron light from a planet 27 pc away, he estimates an 8-m space telescope is required. To see planets out to 54 pc, a 16-m space telescope is required. For reference, James Webb Space Telescope will be 6.5-m. The larger the telescope, the farther away we can resolve planets, and the farther away we are able to look, the more of space we can sample. Mathematically, this has the neat effect that for every doubling of the telescope’s size – that increase from 8-m to 16-m diameter – the number potential planets we can look for goes up by a factor of 10.

What makes Beckwith’s paper strong is how he details what happens as real world issues are taken into account – things like planets not generally being ideally located at their most distant point on the sky from their star, the effects of background stars, interference from dust and gas in the distant solar system and other annoying side effects.

He also discusses ways to detect planets by blocking out the light of the star instead of trying to resolve the planet in the glare of the star. This sounds like it should be easy – just throw a chronograph (a disc that blocks the star’s light) on the scope and go. The problem is, light waves coming around the disc can interfere with one another and cause diffraction. One possible solution, put forward by Webster Cash and a team at Colorado University, suggests using a flower shaped screen to block the star’s light from a distance. With this technique, a 60m screen 400,000 km away could allow a 4m telescope to efficiently find planets like the 8m mentioned above. This raises the awkward question, is it easier / more cost effective to build 8m telescopes with very precisely built chronographs or 4 m telescopes and 60 m screens that have to be separately controlled?

He also gives a detailed discussion of how planetary atmospheres can be observed in the spectra of their parent stars, making the key point “somewhat non-intuitively … the atmospheric signature for a planet in the habitable zone is independent of the planet’s size; … it depends only on the density and temperature” of the atmosphere. In the perfect storm of planets consistently having just the right atmosphere and crossing stars across the middle of their disk, an 8-m telescope will only be able to resolve organically interesting feature in a few (like 3) solar systems in the solar neighborhood. This isn’t good. Beckwith estimates that only 1 in 100 stars searched will have a planet that may have the right characteristics to look for life, and our imaginary 8-m telescope just isn’t likely to let us find it. He estimates that a telescope 16-m in diameter would have a chance to find 1000s of candidate stars and 100s of possible planets to remotely explore for life.

It’s in the second paper, by L. Kaltenegger of Harvard CfA dna F. Selsis of CRAL-ENS (France) that we learn what to look for when searching for life. This team follows up on the 1993 work of Sagan (yes, the Carl Sagan) and collaborators who directed the Galileo Space Probe to turn its detectors back on Earth to see if they could detect life on Earth as the probe flew toward Jupiter. Sagan and company detected molecular oxygen and methane gas in Earth’s atmosphere, as well as a distinctive absorption of red light that indictes biophotosynthesis. In this new work, they point out that in addition to these biomarkers, other gases including water vapor Nitrous Oxide, Hydrogen Sulfide, Carbon Dioxide and can also be used to find life. Methane and N20 are both produced by life on Earth, and N2O in particular isn’t produced by many natural processes. Seeing H20 and C02 can indicate a planet that could have life, and finding N20 probably means life is there.

This raises the question, what is required to find the molecular lines of these molecules? Well, as stated above, a big telescope. The US has proposed the construction of a satellite called Terrestrial Planet Finder (TPF) and Europe is considering a mission named Darwin. TPF will be able to see molecular oxygen and water vapor and Darwin will be able to see molecular oxygen, carbon dioxide and some water lines. It is a start. Unfortunately, many of the biomarkers can be easily lost or confused in the rich forest of molecular lines that appear in gases seeded with Carbon. But, its a start.

Ten years ago we were just starting to find exoplanets. Today we can can count over 200 of them out among the nearby stars. 5 years ago we were just starting to detect them via transits, and today amateur astronomers are in on finding the faint fluctuations that indicate planets. 3 years ago we just started to detect the light of planets separate from the light of stars. Each time, the first discovery has been a delightful surprise. While this is really hard work, technological breakthroughs keep surprising us and making it easier to find new worlds. We know what we need to look, in terms of technology, and we know what to look for in terms of molecular lines in spectra. Now, we just need the money to build the instruments that will allow us to go forward and discover.

Hat tip to Fraser Cain for pointing out these two great papers.

Living with a Red Dwarf: Dr. Ed Guinan (Villanova University) presented a clean bit of research that demonstrated that M dwarf stars may be capable of calmly illuminating their planets for 40 billion plus years, but before they do that they like to wreck havoc with X-ray and far ultraviolet emissions. When first born, these stars rotate very quickly (periods of hours), and then gradually slow to longer periods (measured in 10s of days). When the star is rotating faster, it has a stronger magnetic field, and also has stronger and more frequent coronal mass ejections. These events release vast amounts of high energy radiation that will destroy and blast off the atmospheres of any planets without a magnetic field. These high energy blasts continue for over 1 billion years. Unfortunately, any planet in the habitable zone of an M dwarf will become tidally locked to the star in less then 0.5 billion years, and thus will rotate only once per orbit. With this slow of a rotation, the planet will lose its magnetic field. This implies that any planet within the habitable zone of an M dwarf will be made uninhabitable.

28 planets announced: The second announcement was just a press release stating that there are 28 more planets on the exoplanet.org website than there were when they last had a press release. All but 2 of 3 of these planets had already been published, and coverage has already appeared in much of the media.

A-list planets: In the final presentation, Dr. John Asher Johnson (University of California, Berkeley) showed that it is possible to find planets around stars that were A-stars on the main sequence. These planets also helped to define a relationship that shows the frequency of planets being found around stars is directly related to their mass, with larger stars having planets more often. Oddly, the locations of the planets around these “retired A-stars” don’t follow the same distributions seen in smaller stars. For some unknown reason, planets around former A-stars avoid the inner solar system, and are found predominately outside of 0.8AU.

This piece of work showed an interesting way of diagnosing planetary populations in eone type of star using surrogate populations. We want to know how many main sequance A-type stars – stars hotter and more massive than the Sun – have planets. We can’t with current technology measure that directly. A stars are so hot that they have very few spectral lines (most of the atoms are completely ionized) and rotate very quickly, with broadens the spectral lines so much that doppler shifts caused by planets can’t be measured. When these stars evolve off the main sequence and begin burning hydrogen in a shell around their helium core, they expand, cool, and rotate slower. This means planets can be looked for using doppler shifts. We just have to assume the number and physical locations of the planets don’t change too much during the evolution, and this is a pretty big assumption.

From the Audience: It was this last bit that lead to one of the most fascinating exchanges of the press conference. During the questions session, several people asked “So what is new about this?” and then someone else clarified “No, what is new and hasn’t been in a journal article or pre-print.” This lead to a fascinating moment in which we, the journal reading press, got to educate a small group of scientists about how much we read what they are doing. In what was the sub-news of the day, it became very clear that the science that is reported isn’t limited to what comes out the press release engines, but rather we the press are, as a community, reading the journals to look for the next big thing, and reporting the results of peer-review without worrying if some press officer has or has not sent us pre-digested content for mass distribution. In that moment, I was really proud of the group of people I get to work with in the AAS press room.

A black hole press conference is about to happen, and I’ll have more on that in a little bit.

As we peer at stars in more wavelengths and in greater detail, we are beginning to find evidence of planetary systems around more and more objects.* As we witness this co-formation of stars and planets it is becoming impossible to stick stars in discrete boxes – Stars and planetary systems must be studied as a whole. This was brought home to me by a newly released Spitzer Space Telescope image of Helix nebula (above right, credit:NASA/JPL-Caltech/K. Su (Univ. of Ariz.)). This favorite object of amateur astronomers appears as a faint swirl of light through the eyepiece of a backyard telescope in a dark location. With Spitzer, it is resolved into concentric rings marking the location of a dead star. Around that dead star are the remnants of a cometary cloud.

At some point in the not too cosmologically distant past, a star not to different from our own Sun shut off. For billions of years, that star had first burned hydrogen to helium, and then helium into carbon. As it reached the end of its life, its atmosphere began to drift away and its light appeared to vary, until one day, the burning stopped. The helium fuel ran out, and with it the stars ability to keep burning ran out. What was left of the star’s outer atmosphere drifted away, and a carbon core was left behind. Today we see that carbon core as a white dwarf and that lost atmosphere the Helix planetary nebula. In this text book description of stellar evolution, however, we don’t see any discussion of what happened to any planetary objects that might have orbited the star.

In the Spitzer image we see a diffuse glow (appearing red in the above image) that comes from a dust disk extending from 35 AU to 150 AU from the central white dwarf. In our own solar system, this would place the inner edge of the disk slightly beyond Neptune and the outer edge well within the 526 AU orbit of the trans-Neptunian object Sedna. In our own solar system, the Kuiper Belt and a disk of scattered icy objects can be found in the same region we now observe a disk within the Helix nebula.

In a paper on this system, Dr. Kate Su (University of Arizona) and her team reason that the disk is generated by the collisions of comets. When the star that became the Helix nebula was young and stable it was surrounded by comets that were in stable orbits (and there could have been planets too – we just don’t have any evidence to say yes or no). When the star died, the comets’ orbits were disrupted, and now they are colliding in much the same way that comets (and everything else) in a still forming system collide. In a new born system, collisions between small objects can build big objects, and in the dieing system, collisions between big objects destroy big objects. From dust to dust.

This isn’t the first time a cometary disk has been found around a white dwarf. Last year a much smaller disk was found around G29-38. What makes this discovery so powerful is it is an object that is familiar, and that I can go outside and point to. I can say to my students – See that object? It used to be just like the Sun. It was surrounded by objects similar to things we have in our own solar system. We are watching it die. In 10,000 years that nebula will have drifted away. The comets are going to continue to destroy each other for a while, and the white dwarf in the center is going to slowly cool off and fade away for millions of years. Eventually, when man’s distant prodgeny look at that place in the sky it will be dark. And someday, when some entity looks at our solar system, it too will be dark. Everything is transitory, and when we look at the Helix, we see our future.

*Specifically, the Spitzer Space Telescope has allowed scientists to find asteroids belts around numerous nearby stars, to identify mega-planet forming disks around hypergiant stars, and finally start to directly measure such fundamental qualities as the day and night time temperatures on Jupiter-like planets circling sun-like stars.

Locally, COROT (vaguely rhymes with Inspector Perot), obtained first light today (image above, credit CNES 2006 – D. Ducros). This orbital observatory will dedicate it self to the search for rocky worlds around other stars. A product of the European Space Agency, COROT will study nearby stars with its 30cm telescope, looking for slight changes in brightness indicative of planetary transits. The images it takes will also be useful for asteroseismology, the study of how stars bump and wiggle in reaction to chemical and thermal processes deep beneath their surfaces. Pre-launch calculations predict that every 150 days (the time COROT will spend studying one area of the sky), COROT could discover 10-40 rocky planets and tens of gas giants. Since the first published discoveries of an extrasolar planet around a pulsar in 1992, and around a normal star in 1995, astronomers have only discovered 209 extrasolar worlds. With COROT, that number could double in as little as 1 year.

A little farther out, the STEREO spacecraft (left, credit: NASA/Johns Hopkins University Applied Physics Laboratory) are swinging past the moon on their way to their final orbital homes ahead of and behind the Earth. From these positions they will produce three dimensional images of the Sun in much the same way that your two eyes are able to give you a three-dimensional view of the world around you.

Out near Jupiter, the New Horizons (right, credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)) mission is zooming toward its first major science target. While zipping past our solar system’s largest gas giant, New Horizons will test its instruments. New Horizons images will be the first close ups on Jupiter since the Galileo spacecraft ended its life by plunging into Jupiter’s atmosphere on Sept 21, 2003 (I’m personally looking forward to seeing what New Horizons can learn about Red Spot Junior.)

Somewhere out past Mars, Stardust is waiting to learn if NASA will let it visit more comets. Launched in 1999, this little capsule that could imaged asteroid Annefrank in November 2002 , investigated comet Wild 2 in Jan 2004, and returned to Earth a sample of comet and interplanetary dust in January 2006.

Also on the go are Mars Express, Venus Express, Rosetta, SOHO, XMM-Newton, Integral, Hubble, Spitzer, Cassini, Voyager I, Voyager II, Spirit, Oppurtunity, and many many more space craft. In recent decades NASA and ESA have demonstrated over and over that while they have their moments of bad luck and stupidity (Mars Polar Lander, anyone?), they can very successfully get to objects all over the solar system and explore them in ways that both bring home good science and get the public interested in space.

At the same time, the private sector is getting in on the space gig as well. SpaceX is readying to test their Falcon 1. Virgin Galactic has a business plan and has partnered with Scaled Composited (the guys behind SpaceShipOne, GlobalFlyer and nospaces in names) to get everyday men and famous dudes into space starting sometime in the next couple years. Bigelow Aerospace has inflated modules on orbit and is aiming to start launching hotel pieces late this year. Along side these companies are roughly two dozen competitors, all aimed at making a buck off of space. Today, the sky isn’t a limit for companies seeking to get people and goods farther, faster and cheaper.

In my ideal fantasy universe, each agency and company is able to thrive doing what it does best. In the case of space, NASA and ESA and their international government run space agency brethren use tax dollars to explore with robots and probes, doing the science that serves to excite and inspire, but that doesn’t exactly do much to raise anyone’s financial bottom line. At the same time, the I dream of seeing some of the two dozen plus commercial space corporations becoming tomorrows PanAm and TWA or UPS and FedEx as they compete to get people and goods everywhere. In this perfect fantasy world, Mars gets explored by man, but it is paid for in the same commercial spirit that the Dutch and British East Indian Trade Companies paid to explore the Earth’s ocean’s.

But today’s space reality is far from my personal fantasy. Today, NASA’s space science budget is getting raped by the manned space program. With congress announcing that budgets will be flat in this first quarter of 2007, NASA Administrator Michael Griffin has said he will be compensating for a half-billion dollar funding hole by taking money from programs he believes are low priority to fund the International Space Station and Orion crew exploration vehicle programs. So far, money has been cut from weather and climate research budgets, and a lot of people are holding their breath as they wait to see what space exploration programs get put on hold and/or canceled.

So, here is my question for the people who figure out how NASA dollars should be calculated. When was the last time a press release from the International Space Station (ISS) took someone’s breath away the same way Cassini images so often do? When was the last time science results from the ISS made people think life the way the results of finding evidence on Mars so often do? What exactly has the ISS done for anyone lately? Our failure to be on time and on budget has got to be annoying our international collaborators. I’m not really sure what we’re learning, and I try to stay up to date on this stuff. I do think we need to replace the shuttle, but before we go building heavy-lift, Moon and Mars heading vehicles, shouldn’t we be asking, what do we need people doing in space? The Mars Rovers have demonstrated that we can reprogram robots to do new things from great distances. People are great construction workers. We can repair things really really well. Having the ability to go into orbit, grab a satellite and fix or update it is really useful. I can totally get behind that type of a project. But, we can’t take a person and put it in a parking orbit like we did with Stardust, and spend a few months trying to figure out what to do next.

But NASA is gearing up to make fewer StarDusts and to spend my tax dollars putting people on Mars. I don’t like this, so what can I do? Well, I can sign petitions, like the one put together by the Planetary Society, and I can write my congressional representatives. And I can ask you to think about what you feel NASA, ESA, or any other tax dollar spending space agency should be doing, and once informed, write to let the people spending your tax dollars know what you think they should be doing.

Space is the last great frontier, and while I don’t advocate filling it with garbage, I like to thinking that we are slowly decorating our corner of the universe with bits of science gleaning flying metal bits.

Its always good to be surprised.

In the first press conference of the American Astronomical Society meeting in Seattle Washington, astronomer James Graham of the University of California Berkeley described fluff found around the star AU Microscopii. This tiny red dwarf star is a baby at just 12 million years of age, and it is surrounded by a dust disk. The material in this disk may eventually grow into planets, but today it is simply forming snowballs.

Within the disk, parent bodies (snow balls) form via much the same physics that determines how dust bunnies form under your bed and lint balls form in the trash that you toss dryer lint into in your laundry room. When the parent bodies collide, dust particles break off. They examined the density of this material using scattered light. When light hits a surface it breaks off in a way that is directly related to the density of the material. Using polarized filters similar to the polarizers in ski goggles, they measured the materials refractive index and determined that the dust is roughly 97% empty space and 3% ice – a composition similar to snow powder.

It’s pretty neat to think that in some places pocket lint (admittedly made of frozen gases and dust) is the stuff behind the formation of planets.

I’m going to try to grab Dr. Graham to get a picture of his lint latter.