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Searching for an exoplanet - Printable Version

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Searching for an exoplanet - Roland Van Kerschaver - 08-30-2018

I have bought me a new smartphone.
A LG G6.
Al sensors are present.
I controlled the lightsensor and got a good result.
And then I remembered a lesson from a retired american prof with PocketLab to simulate the search for an exoplanet.
The PocketLab can be replaced with an Android smartphone + Phyphox.
With the PocketLab you get a picture of the experience + graph.
If you have a iPhone you need a PocketLab + Bluetooth+ Phyphox (beta).

RE: Searching for an exoplanet - Sebastian Staacks - 08-30-2018

Hey Roland, thanks for sharing.

I would like to add two things:

1. This might be difficult on some phones with a low resolution light sensor. Some phones should work just like with the PocketLab, but some only give a coarse reading that updates in too big steps. You need to try it to know if a phone works well for this.

2. Phyphox will support the PocketLab One and PocketLab Voyager among other Bluetooth Low Energy devices with the upcoming major update. In fact, Rich (who might be the professor you mentioned) has already developed several experiments with multiple PocketLab Voyagers and phyphox (you can find them by searching for phyphox in their site). A working beta version of the upcoming update will be released for Android next week, although this one will not (yet) support the light sensor on PocketLab devices.

RE: Searching for an exoplanet - sphynx74 - 07-01-2020

Hi, this project is very interesting. Along the same lines, (and because I use an iphone -so no light sensor-) I was wondering if you know of an external light sensor that can maybe be plugged in (USB?) for which your scripts could run on?
There is a wealth of optical experiments which could be performed with a photometry capability (i.e. simple light integration).

RE: Searching for an exoplanet - Jens Noritzsch - 07-01-2020

The original post referred to PocketLab that is now fully supported by phyphox, see Any other BLE capable sensor (box) might do, too. I would be not so sure about any USB sensor as this bus is rather restricted in i(Pad)OS.

RE: Searching for an exoplanet - Jens Noritzsch - 07-01-2020

… and check out this thread: (TI SensorTag)

RE: Searching for an exoplanet - sphynx74 - 07-01-2020

Hi Jens, many thanks.
So if I understood correctly, you are suggesting that rather than plugging in a sensor in the phone and have phyphox access it... use a sensor that communicates with the phone via Bluetooth. Is that right?
I also checked out the TI item in the link above... it seems to have a whole range of sensors (some redundant with ones already supported by phyphox native to the phone). I guess this is a marketing issue and trying to find specifically an optical one isn't straightforward? (something like a USB photodiode of sorts)

RE: Searching for an exoplanet - Jens Noritzsch - 07-02-2020

That's right. We have quite some good experience with bluetooth sensors, more precisely bluetooth low energy sensors providing a GATT server:

As you see, we have not looked so much into the direction of single purpose sensors (yet)…

As far as I know, USB sensors are already not supported on OS level (for instance, even mass storage devices could not been accessed until last summer). So they would not been available to phyphox.

RE: Searching for an exoplanet - SJS - 07-02-2020

Hi everyone,

based on the idea of how to "detect" exoplanets with the pocket lab, which Roland described above, we are currently working on an article with different (DIY) setups and teaching materials for student experiments on the transit method (at school).

We basically started with the optical stopwatch experiment and based on the maximum/minimum illuminance we calculate the transit depth.

The optical stopwatch itself can easily be used to determine the transit time and the duration of a year. This can be achieved by first measuring the illuminance of the "star" and then setting the lower threshold to slightly less than the illuminance of the "star" so that the stopwatch starts and ends according to the eclipse.

So far the results are quite good. We are currently working on a function to calculate the "planet" radius based on a given "star" radius, using the transit depth from above, the given radius of the "star" and the Stefan-Boltzmann law. Since the proportions in our lab situation are quite different from those in space, this does not (and might never) give us any useful results.

Of course we work with strong idealizations and the students get to know the transit method on a qualitative rather than on a quantitative level. However, the phyphox experiment is suitable to explain the basic principle of the transit method and to give an outlook on what information can be derived from it.

Attached the work-in-progresss for Smartphone or SensorTag use. As soon as I can get back to the lab, I will provide some images and curves!

PS: the experiment is currently labeled to match our student lab, so that students can find it faster and find their way around the teaching materials more easily. Feel free to adapt it to your needs! I also will provide the teaching materials, as soon as we are finished.