Re: [semi-OT] physics news update: extra-solar planet detected directly

On Wed, 22 Dec 1999, The next time you ask me a hypothetical question,
the answer is 'no' wrote:

> Somewhat off on a tangential line, got this from my boss, from
> a Physics News Update. Apparently a planet has been *seen* around
> Tau Bootis (~50 ly away). I haven't seen the actual article or
> paper yet, as this is just a 'news update', but it's interesting.

there's a paper in Nature; i can reproduce the abstract without breaking
copyright too hard, i think.

[!t] means a lowercase greek tau

[o:] means a lowercase o with two dots over it (a diaresis, in this
case,
i think)

<excerpt>

Nature 402, 751 - 755 (1999)

Probable detection of starlight reflected from the giant planet
orbiting [!t] Bo[o:]tis

ANDREW COLLIER CAMERON*, KEITH HORNE*, ALAN PENNY+ & DAVID JAMES*

* School of Physics and Astronomy, University of St Andrews, North
Haugh,
St Andrews, Fife KY16 9SS, UK
+ Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK

In the four years following the discovery of a planet orbiting the star
51
Pegasi, about 20 other planets have been detected through their
influence
on the radial velocities of lines in the stellar spectra. The orbital
motion of the planet is detected through the smaller 'reflex motion' of
the star, which can be measured using high-precision spectroscopy. This
indirect technique cannot investigate the radius or composition of the
planet, and can place only a lower limit on its mass. Here we report the
probable detection of Doppler-shifted starlight reflected from the
planet
known to orbit [!t] Bo[o:]tis with a period of just a few days. We find
that the orbital inclination is about i = 29, from which we infer that
the
mass is about eight times that of Jupiter. The planet has the size and
reflectivity expected for a gas-giant planet.

</excerpt>

the text of the paper suggests that there are several groups looking at
this planet with a variety of methods.

> (article on planet at bottom of news update)
> 
> >> STARLIGHT REFLECTED FROM AN EXTRASOLAR PLANET has
> >> been reported by University of St. Andrews astronomers.  Roughly 30
> >> planets have been detected around nearby stars through an indirect
> >> method which monitors fluctuations in the stars' positions.  More
> >> recently the shadow of an extrasolar planet was observed to transit
> >> across the face of its star (Update 458).	Now light has been
detected
> >> which apparently comes to us directly from a planet circling the
star
> >> tau Bootis, some 50 light years away.  The main difficulty was of
course
> >> discerning the reflected light while blocking out the  glare of the
star
> >> itself.   The planet seems to be blue-green in color, is twice the
size
> >> of Jupiter, and 8 times as massive.  (Cameron et al., Nature, 16
December
> >> 1999.)

i think it's a bit strong to say that the planet has been 'seen'; there
are no images of it as an object. what the astronomers did is analyse
the
spectrum of t bootis (if you'll excuse my spelling) and find a set of
lines which they believe to be light scattered from the planet rather
than
direct light from the star. the fact that they can figure out its mass,
size, orbital parameters and albedo from that tells you that these
people
are rather clever, i'd say. nice work, fellas!

tom