Close Distance: Short Film About Hunting for Planets
Close Distance is a short film created by Stefano Nurra & Florian Schwarz. It compares the lives of citizen scientist Caroyln Bol, who has taken part in Planet Hunters, and Dr Martin Dominik at the University of St Andrews, who uses technique called gravitational microlensing to detect exoplanets.
It’s a really nice look at what amateur and professional planet hunters have in common, which more than anything may be enthusiasm and a hopeful outlook on planet hunting. A lovely 10-minute documentary that you can find here on YouTube.
[This blog post is part of the 2013 Zooniverse Advent Calendar]
Comet ISON and the Best Studied Planetary System
This Thursday, the Solar System put on a celestial performance, and we had a front row seat to the spectacle. Long period Comet ISON made its closest approach to the Sun entering the Sun’s atmosphere. This sun-grazing comet was making its first entry into the inner Solar System after spending most of its lifetime in the outer reaches of the Solar System in the Oort Cloud (a spherical shell of icy bodies residing at ~10,000-20,000 AU and the repository of long period comets). For most of the Solar System’s history ISON has resided out in the Oort Cloud, but the gravitational tug from a chance passing star or the gravitational pull from the gravitational tides with the center of the Milky Way nudged ISON onto an orbit straight for the Sun.
Comet ISON was discovered in November 2012 and has sometimes been touted as potentially being the ‘Comet of the Century’ with some predictions that it might become so bright to be visible with the naked eye if it survived perihelion (its closest approach to the Sun). Since ISON was discovered with such warning before perihelion, astronomers were able to organize observing campaigns with ground-based and space-based telescopes to study how the comet changes as it got ever closer and closer to the Sun. Planetary scientists and astronomers will be pouring over the data for months and likely many years to come.
On Thursday the spacecraft monitoring the Sun including Solar Dynamics Observatory (SDO) and Solar and Heliospheric Observatory (SOHO) were poised to capture ISON as it made it’s closest approach. Comets are a conglomeration of ice, rock, dust, and frozen gases, and many don’t survive the fiery perihelion passage; the nucleus disintegrating with only dust and a rocky rubble pile remaining. It wasn’t sure if ISON would survive. It looks like something has indedeed survived perihelion passage, but ISON is providing more questions than answers. It appears to have completely lost its coma and tail which were blasted away as it skimmed the Sun’s million-degree corona. As you’ve probably seen the contradictory statements that ISON was dead and then alive (ISON is not behaving like any sungrazing comet seen before and if you were following twitter and the news reports you were seeing science in progress. Conclusions were changing as more data came down in live time). The current word on the street is that likely a small chunk of ISON’s nucleus made it through perihelion, but it’s still not 100% clear what survived. ISON appears to be behaving like a comet albeit a very small and dusty comet, but time will tell. Future observations over the coming days and weeks will confirm whether gas is being produced which would be the tell-tale sign that there is ice and frozen gases in from some part of the nucleus still around. If there is no gas, then it’s just a rubble of rock and dust left in orbit that will slowly dissipate. Chances are that at this point ISON won’t be naked eye visible but either way, ISON has left us with more learned about comets in the Oort Cloud and added many many many questions for astronomers and planetary scientists to solve while putting on a spectacular show for us.
Snapshots from SOHO’s C2 chronograph monitoring of the Sun showing Comet ISON after its closest approach with the Sun (left) and before (right) on its way to perihelion Image Credit:ESA/NASA/SOHO/Jhelioviewer
For full coverage and the latest on Comet ISON and how it is doing after it’s fiery encounter with the Sun, check out NASA Comet ISON Observing Campaign blog run by Karl Battams and the Planetary Society’s Comet ISON Live Blog by Emily Lakdawalla and Bruce Betts.
What am I doing talking about a comet on the Planet Hunters blog? I do have having a soft spot in my heart for icy outer Solar System bodies, that’s the area of research I worked on for my thesis, but Comet ISON is a good reminder that we should think about these exoplanets we’re finding with Kepler and Planet Hunters as members of a larger planetary system. The transiting planets are the ones we detect, but there is much more there that we don’t see. We know in some transiting exoplanet systems there are unseen (‘invisible’) non-transiting planets, perturbing the orbits of the transiting planets changing the timings and durations of the observed transits. There is also likely the building blocks of planet formation left over as debris hanging around in many of the planetary systems found in the Kepler field. Perhaps some of the material is trapped in belts like the asteroid belt and Kuiper belt in our own Solar System. Many of them likely have Oort Clouds (distant repository of icy bodies of their own). Debris disks likely the equivalent to our own Kuiper belt have been spotted around stars. One of the famous examples is Fomalhaut shown below.
Image credit: NASA/Spitzer
With all the stunning images from SOHO and the confounding behavior of Comet ISON, it reminds us that our Solar System remains the best studied planetary system and that we have still so much more to learn and understand about the Solar System’s formation and evolution. What happened to ISON is probably happening to many other icy bodies around other stars in our Milky Way. We just happened to have a front row seat, but what a show did ISON put on for us! So the next time you look for transits on http://www.planethunters.org take a moment and think about the planetestimals, dwarf planets, and minor planets likely residing around the planet host stars too.
Planet Hunters at Girls Do Hack
Today we have a guest post by Lauren Kelly. Lauren is an Educator for STEM Student Experiences at the Adler Planetarium in Chicago, IL, and holds a degree in Science Journalism from Columbia College Chicago. She loves working with young people and encouraging them to explore science.
Image credit- Adler Planetarium
On November 9th, 65 young women participated in Girls Do Hack at the Adler Planetarium, where they explored science, technology, engineering and math skills and fields as future career options. It was a incredibly fun, inspiring day.
As an Adler educator, I had the wonderful opportunity of leading a session about detecting exoplanets that many of the girls participated in. During the session, participants discovered how scientists find exoplanets using the transit method by doing a hands-on experiment creating and measuring light curves, practicing categorizing transits on Planet Hunters and working with the help of a postdoc Astronomer to explore real systems using NASA’s Eyes on Exoplanets program.
Image credit- Adler Planetarium
Image Credit: Adler Planetarium
K2 – Kepler’s (Proposed) 2nd Exoplanet Mission
K2 mountain, the 2nd highest peak in the world Image credit: Wikipedia (http://en.wikipedia.org/wiki/File:K2_2006b.jpg)
In May, Kepler lost its 2nd reaction wheel halting continuing observations of the Kepler field and its original exoplanet mission. Later this summer, NASA announced that attempts to revive the broken reaction wheels had failed, and that was the official end to the observations of the Kepler field with the 30 ppm (parts per million) precision obtained with the 3-wheel pointing. Other than the bum leg, the spacecraft and imager were in good condition. NASA issued a call for white papers soliciting ideas for potential use cases for a 2-wheeled Kepler.
It was announced two weeks ago at the 2nd Kepler Science Conference, that the Kepler team has a plan to return Kepler to exoplanet hunting that they will be proposing to NASA to give the go ahead and fund. They are dubbing this new 2-wheeled mission for Kepler ‘K2’. You might be inclined to call ‘K2’ Zombie Kepler, but in reality Kepler hasn’t gone anywhere. After the 2nd reaction wheel failure, the spacecraft has just been resting while NASA and Ball Aerospace engineers have been working on ways they could use the remaining two reaction wheels and thrusters to do exoplanet science. In the past few weeks Kepler has been taking engineering data to test stability and photometric precision in this K2 pointing/observing scheme.
Here’s how K2 works. With the loss of the 3rd reaction wheel, Kepler lost fine tuning in one of three spatial directions. If Kepler is pointed keeping the Sun in the X-Y plane, there’s a pointing ridge where they can balance the spacecraft and use the remaining wheels and thrusters to keep pointing. That means fields have to be in the ecliptic (plane of the Earth’s orbit). With that pointing very little changes to the current Kepler team data pipeline are needed to produce light curves with the same 29.4 minute cadence. The photometric precision is predicted to be better than 300 ppm (measured from preliminary engineering runs and testing). So there is a loss of sensitivity, 3-wheeled Kepler had 30 ppm photometric precision. Still Kepler can detect giant planets and for both bright and small stars, Kepler can detect rocky planets.
Kepler will not be able to stare at any one field for very long. The fields on the ecliptic would change as the Kepler orbits the Sun. Each field would get ~40 days worth of observations with some craft pointings able to extend the baseline to ~70-80 days. Also the number of pixels per star needs to be increased significantly, and since Kepler has a limited memory on board to store all of this data, the number of stars observed needs to significantly decreased from the over 160,000 stars monitored when observing the Kepler field. 10,000-20,000 stars would be monitored in K2. The K2 data, like that in the Kepler extended mission, would be available to the public and scientific community after it was downloaded and reduced.
The exciting prospect is that Kepler would observe different populations of stars than the Kepler field, which will be interesting to see how the frequencies of planets compares to the Kepler field. Not to forget, the prospect of having many many more new planets/planet candidates to characterize and study. There will be also be observing of cooler M dwarf stars where the habitable zone (the goldilocks region where water might exist on a rocky planet’s surface) is close to the star, and thus Kepler will find many more rocky planets in the habitable zone to further study. Also bright stars will be targeted which will enable ground-based follow-up with the radial velocity technique, which for gas giant planets can actually measure masses and confirm these planets. Also there’s a wealth of stellar astrophysics (and even potentially microlensing monitoring ) that could be done with K2, including observing stars in open clusters (conglomeration of stars loosely bound together that were all formed from the same molecular cloud) where we know their ages.
K2 is a mission concept at this point. The Kepler team is working hard, and has achieved or on track to finish software upgrades needed to enable Kepler to point and track on ecliptic fields for K2. Test data is starting to coming down from the spacecraft. The Kepler scientists and engineers are analyzing the data and assessing the data quality from K2-like observing. In the next few weeks the Kepler team will propose K2 to NASA, in December NASA will decide if K2 is viable and then give the go ahead for the Kepler team to propose for K2 in the senior review in April, where Kepler as well as other NASA missions will be examined and funding will be decided. Let us hope that K2 gets the full go ahead with (cross our fingers) observations starting some time in 2014.
The prospects for K2 are exciting, and I hope the missions gets the green light. I think the place for Planet Hunters in the K2 era is interesting. I think there will be a niche for Planet Hunters, especially with the short time span on each field, identifying single transits will be important for follow-up of the planetary systems discovered. There will be new eclipsing binaries monitored, and the prospect for more circumbinary planets which is also where I can see Planet Hunters contributing. Plus don’t forget the unexpected discoveries waiting to be found, as we’ve learned from the Kepler field data. So bring on K2!
Want to know more about the proposed K2 mission? Watch the 2nd Kepler Science Conference talks by Charlie Sobeck and Steve Howell detailing the specifics about K2.
20 million classifications and counting!
Planet Hunters has just crossed the 20 million classification mark, a milestone to be celebrated! Thinking back to this time three years ago, the the Zooniverse development team and Planet Hunters science team were hard at work on the design and building of the site. We didn’t know if people would come to the website to help find planets by reviewing Kepler light curves; we were showing graphs of a star’s brightness over time, not the beautiful galaxies in the stunning images on Galaxy Zoo. Since the day the project launched in December 2010, we’ve been blown away by the response. It’s been truly overwhelming. I know I couldn’t have comprehended reaching 20 million classifications back then, and here were are with over 260,000 volunteers worldwide participating in Planet Hunters!
A big thank you to the Planet Hunters community, to all of you who have contributed to the project. Thank you for your time, hard work, and dedication. With your help, Planet Hunters has discovered more than 30 planet candidates, a seven planet solar system, and two confirmed planets: PH1 b, a transiting circumbinary planet in a quadruple star system, and PH2 b, a confirmed Jupiter-sized planet in the habitable zone of a Sun-like star. Your classifications and efforts have resulted in 6 published papers and our 7th paper was just recently submitted to a scientific journal and currently in review. The science team is currently working hard on several new papers, and we’re looking forward to sharing the results with you in the coming months.
On to the next 20 million classifications and to uncovering the discoveries awaiting in the Kepler light curves! Keep the clicks coming at http://www.planethunters.org .
Whose planet is it anyway?
Since we announced, via this blog and via a paper we submitted to the Astrophysical Journal and released on the arXiv, there’s been a lot of talk about our wonderful seven planet system. If you remember, amongst the other discoveries we claimed to add a seventh planet to the six already known in a system going by the name of KOI-351.
One of the responses was by a team of astronomers in Europe, who released a paper on the same system, which they nicely describe as ‘a compact analogue to the Solar System’. In that paper, they claim to discover four of the seven planets in the system, including the same one that the Planet Hunters had identified. To make things more complicated, in news from the Kepler science conference yesterday, the Kepler team announced that they’d assigned the system the name ‘Kepler-90’.
Exploring the Tiny Planetary System of Kepler-90
We recently posted news of a Planet Hunters planet discovered as part of a seven-planet system. Dubbed Kepler-90 this system is a peculiar microcosm of our own Solar System, with small (probably rocky) worlds in the middle, and larger (probably gaseous) worlds on the outside. The major different being that the outermost planet in this system is as far from the star as Earth is from the Sun. The other six planets in this system were already known about, but thanks to volunteers on Planet Hunters (http://planethunters.org) we now think that there are seven worlds circling this stars, which is just a little brighter than our Sun.
To celebrate this fact I have created a model of the whole planetary system in Celestia, an awesome, cross-platform, open-source package that lets you explore space. You can download the Celestia files model directly here or watch the video below to be taken on a tour of Kepler-90 and it’s seven worlds.
http://vimeo.com/orbitingfrog/seven-planets
In this video, I’ve given the newly discovered Planet Hunters candidate some fetching green rings – which we do not have any evidence for or against. Also keep in mind that we know very little about what most exoplanets look like, so we’ve used artistic license to give them all different appearances, often using the surface of what might be analogue worlds in our Solar System. Maybe you can spot some familiar surfaces amongst them!
This system has some great features that make it interesting. The outermost world is roughly the the size of Jupiter but orbits at almost exactly the Earth-Sun distance of 1AU. A Jupiter-like world in an Earth-like orbit has been seen before in Planet Hunters discoveries. The middle planet in this system is at the same distance from this star as Mercury is from our Sun, but is six times as large. The rest of the planets whizz around in even smaller orbits. This star is a little hotter than our Sun so they are pretty scorching places with surfaces temperatures in the hundreds of degrees – nearly a thousand for the innermost planets.
The two innermost planets are roughly Earth sized and are really cool. The innermost one is 1.02x the diameter of Earth and the next is 1.18x. We assume that they are both rocky since they are so small. They orbit the star in just 7 days and 9 days respectively and are very close together. So close in fact that if you’re living on the inner, smaller planet then every few weeks, for about a week, the second planet appears in the sky about half the size of our full Moon.
Every year I see the rumour going round that Mars is going to be as big as the full moon. It will never happen for us – but on the tiny worlds circling Kepler-90, it happens all the time.
Update: The system used to be called KOI-351 but was given the name Kepler-90 just a day after this post went live. I have updated the name of the system in the text.
[Cross-posted on Orbiting Frog]
Seventh heaven with our sixth exoplanet paper
In total, we announce the discovery of 14 planet candidates, all of which were identified by volunteers through the Planet Hunters Talk page. Of these, eight reside in their host star’s habitable zone, but none of them approach Earth or super-Earth size. Additionally, five of these new candidates met the requirements to have been detected by the Kepler team’s automated Transit Planet Search algorithm, but were undetected, including KOI-351.07, the newly discovered seventh candidate.
What to do with a 2-wheeled Kepler?
Now that Kepler is officially 2-wheeled, NASA and the Kepler team are looking at what Kepler could be re-purposed to do. Except for having a bum leg, the rest of Kepler is in good shape. NASA put out a call for white papers, detailed proposals for ideas for what to potentially do next with Kepler. There was no shortage of ideas. In total there were 42 white papers. The proposed ideas ranged from studying the photometric variability of Active Galactic Nuclei (AGN) to a microlensing planet search. There is even a white paper from Kepler’s Principal Investigator (PI) Bill Borucki on how Kepler could continue exoplanet observations (though perhaps not at the same precision before the wheel failure). There are also other proposed options to do an exoplanet transit search by targeting new fields where the Kepler pointing would be better than going back to the the current Kepler field, though likely the observation span would be different from that before the reaction wheel failure. There are even proposals to stay the course and continue to follow-up the Kepler field even with the reduced sensitivity to transit depth with the aim of monitoring known Kepler planetary systems for transit timing variations (TTVs) and also look for long period giant planets.
If you’re interested in reading about all the proposed ideas in gory detail, all the white papers are online and freely available on the Kepler Guest Observer website. If you’re interested in the abridged version, Astrobites has an excellent summary by Nick Ballering highlighting the main categories of use cases proposed.
Some time in the Spring of 2014, NASA will decide on an alternative plan for Kepler and hopefully if there is funding, Kepler will be taking data in the Fall of 2014 whether it’s looking for exoplanets, searching for Near Earth Asteroids, or something else.
Spotting RR Lyrae Stars
RR Lyrae stars are a special type of variable star that changes in brightness due to radial pulsations that increase and decrease the radius of the star . Over the past 3 years, Planet Hunters volunteers on Talk have keenly spotted several previously unknown RR Lyrae stars in the Kepler field, that were nearby neighbors on the CCDs to Kepler targets and were contaminating the photometric aperture used to produce the light curve of the real Kepler target star. You read more about some of these discoveries here. These discoveries have been passed on to collaborators in the Kepler Cepheid & RR Lyrae Working Group who have continued to study those stars including sometimes having the contaminating RR Lyrae added to the Kepler list of targets to get its full light curve.
Katrien Kolenberg who is a member of the Kepler Cepheid & RR Lyrae Working Group, recently wrote a chapter for the conference proceedings of the ’40 Years of Variable Stars: A Celebration of Contributions by Horace A. Smith’ Conference’, and she presented a similarly titled talk at the conference this past May. In the chapter, she gives a summary of the science from the now over 55 RR Lyrae stars known in the Kepler field. She includes a shout out to Planet Hunters to acknowledge the project’s contribution to discovery. Congratulations to all involved in the RR Lyrae discoveries. You can read the chapter from the conference proceedings here.
Planet Hunters 
