Tag Archive for 'Planethunters'

Planethunters: How to download Kepler Data from MAST and view it in Excel (for advanced users!)

In January, I posted some instructions telling Planethunters How To ID a PH Star in the Kepler dataset. Today, I’ll go further than that and tell you how to download the original Kepler Data from MAST and view it in Excel – though note that this requires that you have some knowledge of Excel, learning/installing software, and your own FTP software as well (e.g. Filezilla), so this is definitely for more advanced users. The instructions are quite lengthy, but I’m trying to explain a lot here – hopefully they’re clear though!

I’m assuming that people will be using Excel to plot the data, and fv to view the FITS data. If you don’t use these programs then you’ll have to translate the instructions to work for you (I have no idea how other FITS viewers work), but hopefully you’ll be able to figure it out!

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Planethunters: Kepler Q2 searchable star/planet spreadsheet now available!

Kepler-11 - a newly discovered system with six transiting planets!
Image credit: NASA/Tim Pyle

The Q2 Kepler data has been officially released, making at least another 90 days of data available! Now the planethunting community should be able to confirm or deny their discoveries more easily!

Quick summary of the news in case you missed it:

  • Kepler reveals 1200 new planet candidates – including 68 earth-sized planets, 5 of which are in their star’s habitable zone!
  • One system contains no less than SIX transiting planets!
  • Updated table of confirmed Kepler Discoveries, including the new 6-planet Kepler-11 system.

    The Kepler team have also released a scientific paper on the new planet candidates for anyone interested in the details (including lots of nice graphs showing the planet distributions too!).

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  • Planethunters: How to download Kepler lightcurve data! (for basic users)

    As promised, here’s the second part of my tutorial (following on from my previous post), explaining how to download Kepler lightcurve data for the stars on planethunters.org! Note however that this is intended for somewhat more advanced users than the previous one – you’ll need to know your way around Microsoft Excel for this!

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    Planethunters: How to ID a star on the Kepler Data Search site (updated to Q2)

    Kepler Search Page (screencap)


    A lot of people have asked how to identify a star that they see on the Planethunters website. Apparently the programming team will be adding something soon that says what the Kepler ID (KID) of the star is, but in the meantime I’ll show you how to track it down yourself!

    The good news is that it is possible to go to the Kepler Data Search page at http://archive.stsci.edu/kepler/data_search/search.php (shown in the screencap on the left) and find all the stars listed on the PH site, but it’s not quite as straightforward as typing the ID of the star into the search forms there – the stars on the PH site have their own ID numbers with APH or SPH in front of them, and these are not the same as the official Kepler IDs used in the Kepler catalogues. However, all the information you need to find a star is on the PH site.

    If you look at the source page for a star (e.g. http://www.planethunters.org/sources/SPH10052245 ) you’ll see on the right-hand side four “stats” for the star – “Type of star”, “Apparent visual magnitude”, “Teff“, and “Radius”. You don’t need the Type, but you’ll need the other three, so make a note of those numbers (or remember them).

    If you look at the Kepler Data Search Page, you’ll see a lot of places where you can enter numbers to search for things! It might seem a little intimidating at first, but don’t panic! Here’s what you need to do:

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    Planethunters: Planetary transit depths

    Is this a planet?

    ...or is this?

    Which of the two lightcurves shown above contains a planetary transit? If you’ve been following my blog then you’ll know the answer is the one on the right, since that’s the Kepler-5b graph from my last post about planetary transits! The graph on the left shows a detached eclipsing binary, which is consists of two stars orbiting eachother at a great enough distance that they are two distinct objects – as they orbit their centre of mass, the stars pass in front of eachother and reduce the total light coming from the system, which manifests as the dips in the lightcurve. So in that case, the transit is caused by a star and not a planet.

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    Planethunters: More examples of planetary transits

    One of the questions that comes up quite frequently on the planethunters.org forums is “what does a planetary transit look like”? That’s been partially answered by this post by Matt Giguere on the PH blog, but I’ve come across some more examples that planethunters might find useful.

    You may remember that in January 2010, the Kepler team announced the discovery of the first five exoplanets from Kepler data. The lightcurves for the stars that these planets orbit are actually available online, and they’re available in a text format that makes it easy to import into a spreadsheet program! So, this is what the lightcurves for the transits of these confirmed planets look like! (click on them to see a larger image):

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    Planethunters: Making sense of the lightcurves

    Over the past week I’ve been having a whale of a time looking at lightcurves at http:/www.planethunters.org (I’m on there as EDG) – well, actually I seem to be spending more time discussing them and trying to figure them out! I’ve learned a few things in the process that might be useful to other planet hunters out there:

    Making sense of Eclipsing Binaries

    I’ve learned a lot about the light curves of eclipsing binaries (EBs) this week, which consist of two stars orbiting eachother with one star passing in front of the other as seen from our perspective (which changes the light curve). If you’re looking through the data and want to see what the lightcurves for these EBs look like, then check out pages 18-22 of this Kepler paper (right-click the link and select “save as” to save it), which shows some typical examples of detached, semi-detached, over-contact, ellipsoid, and irregular binaries (there’s an explanation on page 17 for what these types mean – “detached” means that the stars are far enough away to be distinct from eachother, “semi-detached” means that one star has overflowed its roche lobe and is distorted, and “over-contact” means that the two stars are close enough to share a common envelope (i.e. both have overflowed their roche lobes). A dead giveaway for detached eclipsing binaries is that there may be two dips on the lightcurve, but one is shorter than the other.
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    Planethunters: Want to find an extrasolar planet? Now you can!

    Sample transit chart from planethunters.org (Simulated planet)

    Planet Hunters is a brand new “citizen science” site, like Galaxy Zoo (where participants identify galaxies from images) and Moon Zoo (where participants identify and catalogue craters on the moon) – it literally just went online a few hours ago. This time, your task (should you choose to accept it!) is to look through Kepler science data looking for tell-tale dips in brightness caused by planets transiting across the face of the target stars! (the Kepler spacecraft basically stares at a fixed point in the sky containing hundreds of thousands of stars, and it monitors the brightness of all of them, looking out for dips caused by transiting planets).

    It does take a while to get used to the brightness graphs, but you get the hang of it eventually. I’ve already found a couple of known transiting planets (it tells you whether it’s a “Kepler Favourite” or not, which presumably means it’s a known planetary system), correctly identified a simulated planet around a giant star (they throw some simulated data in occasionally to check that you’re finding things properly!).

    There might still be a few bugs and issues in the discussion forums, but they’re rapidly getting them sorted out. It’s a brillianty idea and it’s all very exciting – I’ve had a look at 50 systems so far and found a few interesting ones (I’ve collected them here, and I’ll be adding more as time goes on). They also have a Facebook page and a Twitter feed to follow as well!

    So here’s a perfect opportunity to join in and contribute to scientific discovery – and who knows, you might even find a planet! Head over to http://www.planethunters.org now and start looking! 🙂