Re: smallest planet to date found

But that is exactly the point.

The albedo of rocky planets is lower than the gas giants, Earth's for
example is roughly 0.4. Mercury is only 0.12.

But even if you assume an albedo of 1, i.e. the planet is as bright as the
star it revolves around, (which is absurd at best you would consider an
albedo of 0.5) there is no way that the apparent magnitude of an object the
size of Neptune is within the resolution of naked eye 50 light years away.

And, since albedo is the ratio of light radiation hitting the surface
divided by what is reflected. For the planets' absolute magnitude to even
approach the stars absolute magnitude, it would have to be very close to the
star, and that alone would make it indistinguishable from the star itself at
that distance.

----- Original Message -----
From: "Howard J. Van Till" <hvantill@sbcglobal.net>
To: <billyates@billyates.com>; <asa@calvin.edu>
Sent: Wednesday, August 25, 2004 6:04 PM
Subject: Re: smallest planet to date found

> On 8/25/04 5:17 PM, "Bill Yates" <billyates@billyates.com> wrote:
>
> > No, Howard--
> >
> > Our own planet Neptune is not visible to the naked eye. This one is 50
> > light-years away. Planets are seen by reflected light and are thousands
> > of times dimmer than the illuminating star. Even if somehow the
> > illuminating star were not there and the planet were as bright as if the
> > star were there, you still couldn't see it with the naked eye. In fact,
> > it took a very sophisticated instrument on a very large telescope to
> > discern its existence.
>
> Well, so much for my attempt to allow the possibility that the journalists
> got at least part of the comment right. I was holding out for the
> possibility that a Neptune-sized planet VERY close to the parent star (as
> this one seems to be) might be bright enough to make naked eye visibility
> (absent the star) remotely possible. I didn't do any computation to check
it
> out.
>
Received on Wed Aug 25 18:47:03 2004