Re: A Question

[Stupendous Man <richmond@stupendous.cis.rit.edu>]

  Tom asked:

> How do you tell the difference between an eclipsing binary and an extra
> solar planet?
> 
> If the binary stars are different color, then I presume you can sort it out
> with color.  But what if they are near the same in color and magnitude?  Or
> does one presume that if the dip is periodic and small then it must be a
> planet?

  Yes, you have it: the signs of a transit by a planet are:

        a) a very small dip, of about the size you'd expect for a
                planet passing in front of a star (i.e. a few percent
                or less)

        b) the dip has a characteristic shape: steep walls and a
                flat bottom, indicating that the occulting object
                is completely within the outline of the background star
                (this helps to distinguish a planetary transit from
                a very partial eclipse by another star)

        c) periodic

        d) same amplitude in all passbands

                                                   Michael