Planet Hunters Talk

How is relative distance taken into consideration?

  • morkatog by morkatog

    Dear all,

    I was wondering how the relative distance of a planet in comparison to its star is taken into consideration.
    Recently I came across a screen explaining to me that currently the size of a planet is calculated by considering that the transit depth, d, is proportional to the radius of the planet, Rp.

    However this doesn't exactly explain how distance towards a star factures in. For example based on the explanation above a small planet further away from a star may lead to the same results as a larger planet located closer to a star.

    Could anyone give me an explanation how distance is compensated for, or otherwise give me a link to a paper explaining the process in more detail?

    Posted

  • mschwamb by mschwamb scientist in response to morkatog's comment.

    It matters if you're close to the star, but because we're so far away, we lose this geometric effect. We're so far away from these stars that it breaks down to the surface area of the planet's disk (actual size of the planet) blocking out area on the star.

    For the transit of Venus, since the Earth is very close to Venus and the Sun, the transit depth was actually larger because the relative size of Venus' projected shadow to that of the Sun's disk was larger. It was a 1% drop in light which is the same as what we observer for a Jupiter-sized planet transiting a sun-like star.

    This is a nicer primer on transits that should he explain the equations for transit depth.

    Cheers,

    ~Meg

    Posted