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Welcome to my site about stuff I find when searching for planets.   Just scroll down for the latest posts.  This is an exciting time for citizen scientists like me.  Why not join in the planet hunters’ project? Read the about page to learn more.

Exoplanet Analyser v 0.02a (alpha) Released

The spreadsheet comes in two versions:

• OpenOffice.org version
• Excel 95/2000/XP version (untested)

Both files zipped.

(Spreadsheet optimized for viewing on a 1600×900 monitor. Resizing necessary for other resolutions.)

Licence

Linkware: Use and distribute freely, as long as I’m credited as the author and a link is kept to this website. Otherwise © copyright 2012, by Ian Henderson, all rights reserved.

Features

• Copy and past data you download from the NASA exoplanets archive, after you first convert it to a CSV file. You’ll need the time and median-normalized flux data.
• Enter an orbital period to fine-tune a phase curve (also known as a folded light curve). Alongside is a list of possible harmonic periods to help narrow the actual orbital period down.
• Look at the phase curve from only part of the source data by entering the first and last days to view.
• Enter the target star’s surface gravity, radius and effective temperature from the NASA exoplanet archive, alongside your own observed transit data to calculate the system’s data.

Data output:

• Target star mass,
• Target star volume,
• Target star mean density,
• Target star luminosity.

• Transit time (hours),
• Target planet’s radius,
• Target planet’s volume,
• Target planet’s orbital period,
• Target planet’s orbital radius,
• Target planet’s orbital velocity,
• Target planet’s mean surface temperature.

• q-value for binary system,
• p1+p2 value for binary system.

Planet data also compared to Jupiter and Earth. Radius also compared to our sun.

• Data tested for our solar system, found to be accurate to Pluto for radius and orbit data; tested to Jupiter for temperature.
• Data tested for known exoplanets found to be reliable for larger planets; the degree of uncertainty rises as the exoplanet’s radius decreases.
• Data not yet tested for binary systems.

Changes from v 0.01a

• Minor changes to some data output formats from scientific to 3 decimal places.
• Correction of error to comparison of target star volume to number of solar volumes.
• Clarification on accuracy of output figures.
• Clarification that planet albedo is unknown for temperature output.
• Time series plot stepped at 10 day intervals and changed to flux* to allow zoom.
• Basic error warnings tweaked.

Equations used in Calculations

Assumptions

• Planetary orbit is circular
• Target star is spherical
• Target planet is spherical
• Target planet mass << target star mass

Conversions to SI Units

• star surface gravity (ms-2) = 10^cgs/100
• star radius (m) = solar radii*695500000
• orbital period (s) = P(days)*86400
• first contact (s) = Cf*P(days)*86400
• last contact (s) = Cl*P(days)*86400

Star Output Data

• star mass (kg) = (star surface gravity*star radius^2)/G (gravitational constant)
• star volume (m3) = 4/3*pi*star radius^3
• star mean density (kgm-3) = star mass/star volume
• star luminosity (W) = 4*pi*star radius^2*sigma*effective star temperature^4
• Comparisons also given to solar (sun) values

Planet Output Data (Untested for Binary Systems)

• planet mass (kg) = n/a
• delta flux = (fnotransit-ftransit)/fnotransit
• planet radius (m) = star radius*sqrt(delta flux)
• planet surface gravity = n/a
• planet volume (m3) = 4/3*pi*planet radius^3
• planet mean density (kgm-3) = n/a
• orbital period (s) = as calculated above
• orbital radius (m) = ((orbital period^2*G*star mass)/(4*pi^2))^(1/3)
• orbital velocity (ms-1) = 2*pi*orbital radius/orbital period
• planet temperature (K) = effective star temperature*sqrt(star radius/(2*orbital radius))

Binary System Output Data (Untested)

• q = star radius/companion radius
• p1+p1 = (star radius+companion radius)/orbital radius

Note: since the model assumes companion mass << star mass, and that a single, circular orbit, most orbital data are likely to be wrong for binary systems. But this has not yet been tested.

Sources for equations and explanations

• http://www.paulanthonywilson.com/exoplanets/exoplanet-transits-transmission-spectroscopy/the-transit-light-curve/
• http://arxiv.org/pdf/astro-ph/0206228v1.pdf
• http://www.phy.duke.edu/~kolena/invisible.html
• http://arxiv.org/pdf/astro-ph/0104450v1.pdf
• http://arxiv.org/pdf/?
• http://seagerexoplanets.mit.edu/ftp/Papers/Seager2007.pdf
• http://arxiv.org/abs/0810.5085
• http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_62/iss_5/46_1.shtml?type=PTALERT&bypassSSO=1
• Wikipedia

Planet Hunters Spreadsheet (alpha) Released

I have now finished my alpha testing of Exoplanet Data Analyser v 0.01a (alpha version). There are two versions as ZIP files:

• OpenOffice.org (created on v 3.2.0, portable apps version)
• Excel (exported from OpenOffice.org to Excel 97/2000/XP format)

This is all very much “alpha” or test-at-your-own-risk. I’m using a file download site I’ve not used before, and the spreadsheet needs more testing before knowing its full worth. Links are always available on the Resources page.

Licence

Linkware: Use and distribute freely, as long as I’m credited as the author and a link is kept to this website. Otherwise © copyright 2012, by Ian Henderson, all rights reserved.

Features

• Copy and past data you download from the NASA exoplanets archive, after you first convert it to a CSV file. You’ll need the time and median-normalized flux data.
• Enter an orbital period to fine-tune a phase curve (also known as a folded light curve). Alongside is a list of possible harmonic periods to help narrow the actual orbital period down.
• Look at the phase curve from only part of the source data by entering the first and last days to view.
• Enter the target star’s surface gravity, radius and effective temperature from the NASA exoplanet archive, alongside your own observed transit data to calculate the system’s data.

Data output:

• Target star mass,
• Target star volume,
• Target star mean density,
• Target star luminosity.

• Transit time (hours),
• Target planet’s radius,
• Target planet’s volume,
• Target planet’s orbital period,
• Target planet’s orbital radius,
• Target planet’s orbital velocity,
• Target planet’s mean surface temperature.

• q-value for binary system,
• p1+p2 value for binary system.

Planet data also compared to Jupiter and Earth. Radius also compared to our sun.

• Data tested for our solar system, found to be accurate to Pluto for radius and orbit data; tested to Jupiter for temperature.
• Data tested for known exoplanets found to be reliable for larger planets; the degree of uncertainty rises as the exoplanet’s radius decreases.
• Data not yet tested for binary systems.

Equations taken or derived from Wikipedia and published scientific papers.

Planet Hunter Spreadsheet Under Devolpment

Having spent the best part of four days struggling with some of the maths (only to find that the measurements of know data often aren’t good enough), I’m now starting the “aplha” testing of a spreadsheet to help identify possible exoplanets. The first version will estimate body radius and surface temperature, along with orbital radius and velocity. For now, I’ve found no reliable way to estimate body mass, density or surface gravity, or to classify as star, brown dwarf or planet based solely on body radius.

I’m now re-testing the spreadsheet with data for our solar system, and will then move on to data for “known” candidates for exoplanets and eclipsing binary systems. Initial testing suggests it can accurately estimate body radius, orbital radius and orbital velocity as long as the quoted star radius and surface gravity figures (and observed transit data) are accurate enough.

I’ll release the original OpenOffice.org and converted Excel versions for Beta testing soon. Watch this space.