Exoplanet Search

In an effort to get my stuff together, I'm publishing a short whitepaper here...I know y'all are far too harsh to allow a partial understand, or explanation...

Exoplanet Search

Abstract
Exoplanet search has become an important part of astronomy, and is a task ideally suited for robots. Robots are by far, better suited to the tedium of relentless search than any Human that might want to engage in such an activity.

We will talk about three (3) techniques and how they may be implemented in modern computer and robotic technologies.

Transit Method
The Transit method watches for the passing of a planet in front of its star. The resulting decrease of stellar magnitude, while small can be rather easy to detect under the right conditions.

One issue here is the “twinkling” effect of the atmosphere, this “introduced” variability of the star’s magnitude is typically greater than the change we ae looking for. In order to remove this effect we can apply a method knows as Differential Photometry. In Differential Photometry a comparison star is located within the Field of View; the “corrected” and “averaged” magnitude of this comparison star is used to adjust the magnitude of the “Target star” at the time data is acquired. This allows us to collect data that is “normalized”, and stable for inclusion in our Acquired dataset.

Post-acquisition activities will include the updating of the selected “comparison star” so that we always have a valid comparison. The system should also maintain a dataset of comparison stars.

Stars of interest are visited frequently and data acquired, at any point in the process a report on that data, known as a “Lightcurve” may be produced from the acquired magnitude data. Regular “dips” or depressions of a target’s magnitude may indicate a “transiting” planet.

Subsequent “transit” events can be correlated to verify a planet.

Radial Velocity
As a planet orbits its star it also causes the star to “wobble”, this wobble manifests in a Doppler shift in the light from the star. From our vantage point we will experience a small “Red” or “Blue” shift depending on the direction of movement.

There are a couple of methods to detect and quantify this shift. The first is to use “real’ spectrometry. Placing a prism or diffraction grating in the light path, and analyzing the resulting spectra and specifically looking for these color shifts. Comparing wavelengths to saved data will indicate the magnitude, and direction of any shifts.

The second is via a sort of “software spectrograph”. A software method that converts the color, the actual “RGB” array values into a hue, comparing this new hue to the old and detecting both its direction, and magnitude.

These data and datasets can be used, as the magnitude datasets were, to produce reports. In this case we can compile “velocitycurves” that will allow us to detect and measure various aspects of an exoplanet.

Microlensing
Microlensing is based on the gravitational lens effect. A massive object (the lens) will bend the light of a bright background object (the source). This can generate multiple distorted, magnified, and brightened images of the background source; it is the brightening effect we are “looking” for, as this can produce a very distinctive lightcurve of our target star.

The sharp rise in magnitude verses time is relatively easy to distinguish in the data, and is wholly independent of distance to the target star. It does however, rely upon relatively rare events and alignments, though it is likely that the augmentation provided by software may ease this somewhat.

A microlensing event during a planetary transit is the holy grail of this kind of search. A microlensing event of this nature could reveal details about the transiting planet’s atmosphere if the spectra is captured during that event.

The search process employed at WRO will always have spectra data associated with every recorded event, thus if such a microlensing event did occur, the available spectra will be included with other event data.

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Please do your "worst"; it will help me understand.

I'm no astronomer, but this sort of stuff really interests me and I research it in my own time occasionally May I suggest the transit method? That way, astronomers can determine the atmospheric composition of a planet. This would make it easier to know if the exo-planet was capable of supporting life.

originally posted by: Tenebris
I'm no astronomer, but this sort of stuff really interests me and I research it in my own time occasionally

May I suggest the transit method? That way, astronomers can determine the atmospheric composition of a planet. This would make it easier to know if the exo-planet was capable of supporting life.

He does plan to do transit photometry using some open source Differential Photometry software NASA helped to develop which I hooked him up with.

Interesting. Let me know if you find anything good!

a reply to: tanka418

Lets face it given the modification to the Drake equation we are pretty confident as to their being a hell of a lot more habitable worlds in our Universe than originally suspected. Its only a matter of time until we find one of sufficient interest and a way of actually getting there. The search for exoplanets is one of the most interesting fields of study humanity has accomplished, i love the topic, just wish i understood the science behind it a whole lot better. Interesting thread.

originally posted by: JadeStar

originally posted by: Tenebris
I'm no astronomer, but this sort of stuff really interests me and I research it in my own time occasionally

May I suggest the transit method? That way, astronomers can determine the atmospheric composition of a planet. This would make it easier to know if the exo-planet was capable of supporting life.

He does plan to do transit photometry using some open source Differential Photometry software NASA helped to develop which I hooked him up with.

Indeed...I've found ways of using all three of these methods, though, sadly the microlensing will still be a rare be quite welcome event.

And, that initial introduction to OSCAAR started a small cascade of discovery. From there I found several papers specifically on differential photometry. And, now that I actually have an understanding of the process, and methods, should be able create a very nice system.

Twinkle, twinkle little star...Oh, I'm sorry I took your twinkle away...fear not, it only reveals your hidden beauty!

When I started thinking about Radial Velocity I realized I would need a "real" spectrograph, and pondered that for at least several minutes...until I remembered that a diffraction grating would give me what I needed...well along with a little software.

Later, I began to realize that I didn't need a high res image of a star field to analyze all the stars in the field, and that the initial image return by a CCD would work quite well for finding magnitudes, and even spectra...so only a few seconds are actually required to acquire the data...quite a bit longer to process though...so we do that "off-line".

Unfortunately the microlens will remain a rare event, fortunately, the way I'm planning to acquire this data will include both magnitude, and spectral data in "frames" with short latency, so IF there is a microlens event, I will be able to "see" both its magnitude, and spectra.

The open source differential photometry (OSCAAR) though is one of the best additions to this though. It allows me to stabilize the data I'm getting. The original system was written in a language called "Python", actually one of the more popular high level languages. It is known for its "clarity". Python was designed to use very "English like" statements and thus yields a program source that is very easy for Humans to understand. Though, it is an "interpreted" language, so it may not be well suited to "real time" operation...though, to do what it does, does not require "real time".

Since I'm an old dog software engineer, I'm probably going to build my own system, based on OSCAAR, and the several papers I've read, and I'll likely use a rather cryptic, but very powerful, language as well; something like a "C++" (C Plus), or "C#" (C Sharp).

This whole line of query has proven to be an exciting learning experience...

originally posted by: andy06shake
a reply to: tanka418

Lets face it given the modification to the Drake equation we are pretty confident as to their being a hell of a lot more habitable worlds in our Universe than originally suspected. Its only a matter of time until we find one of sufficient interest and a way of actually getting there. The search for exoplanets is one of the most interesting fields of study humanity has accomplished, i love the topic, just wish i understood the science behind it a whole lot better. Interesting thread.

Just yesterday I was watching an old video on the Drake Equation...it was almost funny...

They started off talking about how many stars there were...around 100 billion, except the current estimate is more like 300 billion...

Then they started on the "how many of these stars have planets". Again, slightly more modern view is that virtually all stars have planets, and it appears probable that most have 2 - 3 planets in the Habitable Zone...

It is kind of amazing what only a few years of search can do to old ideas...where once Drake has many possible places for ET, there are nearly exponentially more now. Where the equation once said there were only a small number of stars with planets, now to almost all.

When we get to the place holder for "how many places exist with in a solar system that can support life?" We find that where we once thought number was, at least for Earth, one, we have found that it may be as many as 6 or more.

It would almost seem, that as science learns more about the cosmos, the more probable life becomes.