Re: Life on Zeta Reticuli?


In Article <9n599f$rql$1@neptunium.btinternet.com> Onion wrote:
> I think the Anglo Australian Obvervatory has measured radial velocity shift
> in Zeta2 Reticuli but, as I understand it, they haven't measured the shifts
> for long enough to say whether or not there is a planetary system causing
> it.
>
> There was a story some years ago about the European Southern Observatory
> detecting a candidate planet around HD20807 (Zeta2 Reticuli) which was one
> of a list of 30 other candidate stars that they measured which might have
> planets. The funny thing about the story is that the list was revised in a
> very short time ~48 hours, and the new list was missing 1 entry. You've
> guessed it, Zeta 2 Ret was off the list!
>
> One guy mailed ESO and asked why they had withdrawn HD20807 from the list
> and was told a lame excuse about accuracy or certainty issues. The obvious
> question being why would there be only accuracy and certainty issues with
> just this one star and none of the others??
>
> I'll keep an open mind on this issue.

There seem to be a number of odd things about astronomical research on this
star, and with the star itself.

I've found my notes from when I was researching the star. The purported
planet had a mass of .27 Jupiter, and a 18.9 day orbit, and was .14 au from 
the star. It imposed a radial velocity variation of 20.3 m/sec, while the 
detection limit was 14 m/sec.

I was in contact with Jean Schneider, who runs the Extrasolar Planets
Encyclopedia for a while, and I asked him why Zeta 2 was removed. He 
said it was discovered to be the result of pulsation of the star, rather than a 
planet.

In addition, there was a report of a companion to the star in: "Speckle
Interferometric Measurements of Binary Stars" by Bonneau, Blazit, Foy, 
and Labeyrie (A&A Supp. 42, 185-188 1980). The companion was at a 
distance of .046 arc seconds, or .55 au, and a position angle of 11°,
but no other information about it was provided.

This companion was also withdrawn, in a causal, mentioned-in-passing 
manner, in "Zeta 1 and Zeta 2 Reticuli: A Puzzling Solar-Type Twin 
System" by Foy and DaSilva (A&A 177, 204 1987). An attempt to find it 
again 334 days after detection had failed, so it was decided to be an artifact
of the telescope's spider.

However, a distance of .55 au means an orbital period of 144 days, so it 
would have made 2.3 orbits in the meantime. It wouldn't have been 
detected again because it would have been in front of (or behind) the star.

Robert