[meteorite-list] Subject: Re: Habital Planet Discovery Announcement

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Fri, 1 Oct 2010 04:23:59 -0700 (MST)
Message-ID: <2181c295ecdb05f828e4dac53647ab89.squirrel_at_webmail.lpl.arizona.edu>

Hi Sterling:

I hope that I am not repeating something. Too many emails on too many
subjects (not all the metlist) the last few days and getting ready for a
conference.

One thing seems to be missing in these discussions; how the planets were
detected.

All of the planets in the Gliese 581 system were detected by spectroscopy.
You look at a spectral line from the star and, over time it shifts to the
blue and then to the red. This is the Doppler shift as the star moves
toward and away from you (respectively) as it is tugged on by it companion
planet. It take many orbits of the planet to verify this motion, not just
one "signal." The bigger the planet, the more the spectral line shifts,
the easier it is to see." The closer the planet is to the star, the
shorter the cycle is and the easier it is to see (if the period is a year,
it takes several years to see several cycles). This obviously gets very
complicated when you have multiple planets and are looking for cycles on
cycles.

This leads to a very important thing that seems to be left out of all of
these discussions.The numbers quoted are MINIMUM masses. The Doppler shift
is the shift in the direction of the viewer. These numbers assume that the
planet orbits are lined up with the Earth, which would be highly unlikely.
For the Gliese planetary system, the inclination of the planets is not
known. If their orbits are in reality tilted by say 45 degrees, their
masses would be about 1.4 times the numbers quoted. Still not bad. The
distance from the star is only dependent on the mass of the star and the
distance of the planet from the star (Kepler's Law, orbital period), but
the mass is dependent on the inclination of the orbits relative to the
Earth.

Again, I hope I am not repeating others on this.

Larry

> Not to doubt the scientific trustworthiness of
> the Daily Mail, but they state that the light pulse
> was seen December, 2008, "long before it was
> announced that the star Gliese 581 has habitable
> planets in orbit around it."
>
> But Gliese 581 c, the first low mass extrasolar
> planet found to be near its star's habitable zone,
> was discovered in April 2007, and Gliese 581 b,
> approximately Neptune-sized and the first planet
> detected around Gliese 581, was discovered in
> August 2005.
>
> Discovered at the same time as Gliese 581 c, a third
> planet, Gliese 581 d, has a mass of roughly 7 Earths,
> or half a Uranus, and an orbit of 66.8 Earth days. It
> orbits just within the outer limit of the habitable zone.
>
> The fourth planet, Gliese 581 e, was announced on
> 21 April 2009. This planet, at an estimated minimum
> mass of 1.9 Earths, is currently the lowest mass exoplanet
> identified around a "normal star." The more distant
> Gliese 581 f was found at the same time.
>
> Gliese 581 was much in the news by December, 2008.
> It was known that there were low-mass planets and that
> there were planets in the habitable zone. The BEBO
> message had been "sent" just two months before, in
> October, 2008.
>
> It is certainly not true that the pulse was "long before it was
> announced that the star Gliese 581 has habitable planets
> in orbit around it." It was well known.
>
> Unrepeated signals don't count. Basic rule of SETI.
>
>
> Sterling K. Webb
> --------------------------------------------------------------------------
> ----- Original Message -----
> From: <countdeiro at earthlink.net>
> To: <meteorite-list at meteoritecentral.com>
> Sent: Thursday, September 30, 2010 10:40 PM
> Subject: [meteorite-list] Subject: Re: Habital Planet Discovery
> Announcement
>
>
>> Listees,
>>
>> And now we have this to contemplate.
>>
>> http://www.dailymail.co.uk/sciencetech/article-1316538/Gliese-581g-mystery-Scientist-spotted-mysterious-pulse-light-direction-newEarth-planet-year.html
>>
>> Best to all,
>>
>> Count Deiro
>> IMCA 3536
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Received on Fri 01 Oct 2010 07:23:59 AM PDT