[meteorite-list] OT: Plutonian Planets, Undiscovered Nearby Stars

From: Dawn & Gerald Flaherty <grf2_at_meteoritecentral.com>
Date: Mon Aug 1 20:06:01 2005
Message-ID: <022301c596f5$f08243f0$6502a8c0_at_GerryLaptop>

Thanks for the neat site Sterling. Jerry
"I can't wait", are we there yet?
----- Original Message -----
From: "Sterling K. Webb" <kelly_at_bhil.com>
To: "Meteorite List" <meteorite-list_at_meteoritecentral.com>
Sent: Sunday, July 31, 2005 6:55 PM
Subject: [meteorite-list] OT: Plutonian Planets, Undiscovered Nearby Stars


> Hi,
>
> An assortment of stuff about near(er)by stars, KBO's, and other
> topics of interest to somebody...
>
> A "zoomable" 3-D map of (known) stars within 12.5 light years. You
> can zoom it out to the entire galaxy in steps. Very neat.
> <http://anzwers.org/free/universe/12lys.html>
>
> Hipparchos data suggest:
> "a value of 11.7 +/- 1.3 stellar encounters per Myr within one pc of
> the Sun." or about one every 80,000 to 100,000 years.
>
> I poo-poohed a big KBO being an extra-solar object, but not
> everybody does. These guys say a 10% chance. A planet from another
> star?!
> Stellar encounters as the origin of
> distant solar system objects
> in highly eccentric orbits by:
> Kenyon, Scott J ; Bromley, Benjamin C.
> "Abstract: The discovery of Sedna places new constraints on the
> origin and evolution of our solar system. Here we investigate the
> possibility that a close encounter with another star produced the
> observed edge of the Kuiper belt, at roughly 50 AU, and the highly
> elliptical orbit of Sedna. We show that a passing star probably
> scattered Sedna from the Kuiper Belt into its observed orbit. The
> likelihood that a planet at 60-80 AU can be scattered into Sedna's orbit
> is roughly 50%; this estimate depends critically on the geometry of the
> flyby. Even more interesting, though, is the roughly 10% chance that
> Sedna was captured from the outer disk of the passing star. Most
> captures have very high inclination orbits; detection of these objects
> would confirm the presence of extrasolar planets in our own Solar
> System."
> Notice that they "thought" the edge of the KB was at 50 AU, Whoops!
> 2003 UB313 at 97, and 2003 EL61 at 51.
>
>
> Closest star passage in the future?
> Close Approaches of Stars
> to the Solar System, by
> P. R. Weissman, J. Garcia-Sanchez,
> R. A. Preston, D. L. Jones
> (Jet Propulsion Laboratory),
> J.-F. Lestrade Observatoire de Paris-Meudon/CNRS),
> D. W. Latham (Harvard-Smithsonian CfA)
> "Only one star, Gliese 710, is found with a predicted closest
> approach distance <100,000 AU (0.5 parsecs), although several stars
> come within about 1 parsec during a 8.5 Myr interval. The predicted
> minimum distance for Gliese 710 is 53,000 to 71,000 AU, approximately
> 1.0 to 1.4 Myr in the future. Gliese 710 is a late-type dwarf star (dM1
> or K7 V) with an estimated mass of 0.42 solar masses, and is currently
> about 19 parsecs from the Sun. The star may be a binary."
>
>
> Planets at all?
> Are stars with planets anomalous?
> Guillermo Gonzalez
> "The chemical-dynamical properties of stars with giant planets are
> compared to those of a nearby star sample within the framework of a
> stellar orbital diffusion model. The stars-with-planets sample includes
> recently discovered extrasolar planets and the Sun. We find that the
> planet-bearing stars, 14 Her, rho-1 Cnc and tau Boo, are much more
> metal-rich than stars of similar age and this cannot be easily explained
> by orbital diffusion. We also confirm previous claims that the motion of
> the Sun relative to the local standard of rest is very small compared to
> other G dwarfs of similar age, and we offer a possible explanation for
> this apparent anomaly."
>
>
> There's good news and bad news...
>
> The Close Approach of Stars in the Solar Neighbourhood Quarterly Journal
> of the Royal Astronomical Society 35 1-9 1994:
> "At present, 58 stars are known to lie within a radius of about 5
> parsecs of the Sun, and thus within the so-called "Solar Neighbourhood".
> In this paper, I calculate the trajectories and distances of those
> making the closest approach to the Sun over the next 50,000 years. I
> find that Proxima Centauri has been the closest star to the Sun for the
> last 32,000 years, but will lose this status to the dwarf star Ross 248
> in 33,000 years' time. We are approaching a period relatively rich in
> stellar encounters, with six stars coming closer to the Sun that
> Proxima's current distance within the next 45,000 years. Only the close
> approach of Alpha Centauri A/B - which has a combined mass more than
> twice that of our Sun - will have any noticeable dynamical effects,
> however. In particular, it has already begun to perturb the outer Oort
> Cloud of comets, and will put around 100,000 comets into potentially
> Earth-impacting orbits."
>
> 100,000 comets in Earth-impacting orbits? You did say 100,000,
> didn't you? I thought so. Do I start digging the shelter now?
>
> Update on Earth Trojans (subject of an earlier thread):
>
<http://www.rssd.esa.int/SA-general/Projects/GAIA_files/LATEX2HTML/node118.h
tml>
>
> They'll be searching Venus Trojan points for the first time ever,
> among other things.
> The same site about the dynamic properties of KBO's:
>
<http://www.rssd.esa.int/SA-general/Projects/GAIA_files/LATEX2HTML/node119.h
tml>
>
> This group hoped to find Pluto-sized KBO's. Good idea, but too late.
> They haven't launched yet. They explain the difficulties of finding them
> with earth-based telescopes, which are considerable.
> Brown did just fine, though...
>
> About the frequency of L class stars:
> "Class T and L could be more common than all the other classes
> combined, if recent research is accurate. From studying the number of
> proplyds (protoplanetary discs, clumps of gas in nebulae from which
> stars and solar systems are formed) then the number of stars in the
> galaxy should be several orders of magnitude higher than what we know
> about. It's theorised that these proplyds are in a race with each other.
> The first one to form will become a proto-star, which are very violent
> objects and will disrupt other propylids in the vicinity, stripping them
> of their gas. The victim propylids will then probably go on to become
> main sequence stars or brown dwarf stars of the L and T classes, but
> quite invisible to us. Since they live so long (no star below 0.8 solar
> masses has ever died in the history of the galaxy) then these smaller
> stars will accumulate over time."
>
>
> They're looking for that L class near the Sun, apparently:
> Announcement of New Spectral Class of Stars: L Dwarfs, by
> J. D. Kirkpatrick, R. M. Cutri, B. Nelson, C. A. Beichman (IPAC,
> Caltech), I. N. Reid (Caltech), J. Liebert (U.Arizona), C. C. Dahn, D.
> G. Monet (U.S.Naval Observatory, Flagstaff), M. F. Skrutskie
> (U.Massachusetts, Amherst)
> "Summary: A new spectral class of stars, L Dwarfs, has been defined
> that extends the previously-defined spectral classes of normal stars to
> cooler objects. 20 new sources have been found in only 1% of the 2MASS
> data, which was enough to define a temperature sequence with 9
> subdivisions for the L spectral class, L0-L8. At least 6 of these
> sources are brown dwarfs, objects formed like stars but which will never
> sustain hydrogen burning, and hence will fade from view much more
> rapidly than normal stars.
> The L Dwarfs do not contribute much matter to the Galaxy since they
> individually weigh typically perhaps one-twentieth the mass of the sun.
> However, they probably outnumber all other spectral classes of stars
> combined. This directly implies that there is a good chance that an L
> dwarf is the closest source to the Solar System, beating out Proxima
> Centauri, an M5 star 1.3 pc (4.3 light-years) distant. Further 2MASS
> work will find out whether such a source exists."
>
> Keep looking...
>
>
> Sterling K. Webb
>
>
>
>
>
>
>
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Received on Mon 01 Aug 2005 08:05:48 PM PDT