We look at another ‘simulation’ plot this week 🙂
What if you had a forming protoplanet close to a young star and this planet accretes material? This means a large fraction of the volume around the planet (its Hill sphere) might be filled with gas and dust. If this material transits in front of the star we might be able to detect it. This works similar to exoplanet transits, but because the Hill sphere can be much larger than the planet itself, it will dim the stellar light by much more than the fraction of a percent a planet would, and it would also cause a much longer dimming – several days in fact.
We are trying to work out the best way to detect such events. One needs to determine for each kind of planet (mass and orbital radius) how to do this optimally. For example, one needs to smooth the light curves over a given timescale (‘Smoothing Length’) and then search for start and end of the dimming on a different timescale (‘Array Shift’). We simulate such dimming events in the light curves of our young stars, and determine what fraction we recover as a function of the two timescales. In the above plot the results are shown for a Saturn-like planet in a Venus-like orbit around a Sun-like star.
The interesting results are not the two timescales (though they are needed to search for such events in the real light curves), but the actual detection rate. For the optimum choice of timescales it is about nine percent. One can combine this with the probability of the transit happening (assuming all orbits are randomly orientated) and the number of young stars we can investigate. This allows us to determine what fraction of objects have such a planet if we find a certain number. In the above case, if we assume we do not find any such transit event in our light curves, it would mean that at most nine percent of the young stars have such a planet. Note that it is coincidence that the simulated detection rate and the maximum occurrence rate if no event is found are the same. 🙂