Re: Number of low eccentricity distant planets

On 23 veebr, 22:43, Mike Williams <nos...@[EMAIL PROTECTED]
> wrote:
> Wasn't it Crown-Horned Snorkack who wrote:
>
> >Hot jupiters are easier to detect than the more distant planets like
> >Solar System giants. However, some planets on long period orbits have
> >been found.
>
> >Planets on circular orbits, like in Solar System, should be no harder
> >to find than planets on eccentric orbits. Yet most planetary systems
> >have eccentric orbits.
>
> >How rare are systems with low eccentricity orbits like Solar System -
> >excluding the hot jupiters?
>
> This page lists extrasolar planets detected by radial velocity ordered
> by eccentricity
>    http://exoplanet.eu/catalog-RV.php?&mode=5
> (You can order by any column by clicking on the column name).
>
> Decide what value you consider to be "low eccentricity" and count off
> the pro****tion. As a guide, the eccentricity of the Earth is 0.0167.
> About 16% of those extrasolar planets have orbits that are less
> eccentric than that of the Earth. I ignored exoplanets for which the
> eccentricity has not been calculated.
>
> This page allows you to display a histogram of exoplanet eccentricities.
>    http://exoplanet.eu/catalog-RV.php?mdAff=stats#tc
> Choose "Planet Ecc" as the "Ref" field.
>
Very nice.

Looking by the order of orbital period:

there are 22 planets with orbital periods from 95 days (HIP 14810 c)
to 228 days (HD8574 b) inclusive (that is, between the orbital periods
of Mercury and Venus). Those 22 include 1 with eccentricity - and 2
with eccentricity 0. Out of the remaining 19, just 7 have eccentricity
under 0,2 (the eccentricity of Mercury)

> You can also use that page to produce a correlation diagram. If you plot
> Planet Mass (log) vs Planet Eccentricity (linear) you'll see that
> there's a slight tendency for low mass planets to have more circular
> orbits.
>