The Universe According to Richard Pearson
We
are on the eve of a truly historic occasion, because physicists are about to announce
the detection of Gravitational Waves (if the recent hype can be believed). I can
remember a similar occasion that occurred 30 years ago, and I also sense the
rising excitement as we await the announcement on Thursday.
Back in 1981 I had a 15 Cm
reflector and my main interest was variable stars. At that time extrasolar
planets were in the future, and the Infrared Astronomical Satellite, IRAS, was
two years away from launch.
For a number of years there was conversation
among amateur and professional astronomers about T Tauri type stars because they
displayed a peculiar nature, which was a bit of a mystery.
T Tauri is a variable star in the
constellation Taurus. It was discovered in October 1852 by English astronomer John
Russell Hind. T Tauri appears amongst the Hyades cluster, not far from Epsilon
Tauri. Like all T Tauri stars, it is very young, being only a million years
old. Its distance from Earth is about 460 light years, and its apparent
magnitude varies unpredictably from about 9.3 to 14.
Importantly, they are generally found
near molecular clouds, and T Tauri stars are pre-main-sequence, about 3 times
more massive than our Sun, in the process of contracting onto the main sequence
as seen in the famous HR Diagram.
Careful analysis of the star’s
variable observations suggested that T Tauri itself was associated with a Protoplanetary
disk, a young alien solar system in the process of formation. However, there
was no evidence, and Infrared astronomy was then in its infancy.
In 1983 IRAS -- The Infrared Astronomical Satellite -- was launched into
Earth orbit; it was the first
observatory to perform an all-sky survey at infrared wavelengths. It imaged the
star Beta Pictoris, and resolved a Protoplanetary disk for the very first time.
As infrared techniques improved more discoveries of circumstellar disks
followed. So T Tauri itself holds a special place in the history of extra solar
planets.
Since 1988 over 2000 exoplanets have been discovered, and with better
infrared telescopes, more are being added to the list with the passage of time.
Wanting to learn more about the topic of the discovery of alien planets
around distant stars, I have begun reading ‘The Exoplanet Handbook’ by Michael
Perryman, published in 2011 by Cambridge University Press. The book is
extremely detailed, and covers the main discovery techniques used by astronomers
along with analysis of their observations.
In the introduction Michael Perryman notes:
1 Astronomical Unit = the Earth/Sun distance of 93 million miles, or 150 milion Km.
“As of the cut-off date for this
review, 2010 November 1, almost 500 exoplanets were known, with more than 50
multiple systems. Diversity continuing the trend established by the earliest
discoveries, exoplanets does not adhere to the individual or system properties
extrapolated from the known architecture of the solar system.
Orbital properties vary widely.
Around one third have very elliptical orbits, with e > 0.3, compared with
the largest eccentricities in the solar system, of about 0.2 for Mercury and
Pluto (and just 0.05 for Jupiter). More than half are around the mass of
Jupiter (0.3 - 3Mj), and many of these orbit their host star much closer than
Mercury orbits the Sun (0.39 AU): hot highly-irradiated giants piled up towards
0.03 AU that cannot have formed in situ. Others are located far out, at
distances of 100 AU or more from their host star. Planets with orbits highly
inclined to the star's equatorial plane occur frequently, some even with
retrograde orbits.
“Exoplanets are being discovered
around a wide variety of stellar types. Host stars are not only main sequence
stars like the Sun, but they include very low- mass stars, low metallicity
stars, giant stars, and other advanced evolutionary stages such as white dwarfs
and pulsars. Their internal structure and composition vary widely too. Gas
giants with stripped outer envelopes, water worlds formed beyond the snow line,
and carbon- dominated terrestrial planets may all exist. The first Exoplanet
atmospheres have been probed through secondary eclipse photometry and
spectroscopy.
“Of the multiple Exoplanet
systems, massive planets
orbiting in mean motion resonance are common, presenting a certain challenge to
explain their ubiquity. The
first triple-planet Laplace resonance has been discovered, as have prominent
transit time variations in a
two-planet transiting system. Systems with multiple lower-mass planets are
being found in increasing numbers
as the radial velocity surveys improve their detection threshold and increase
their temporal baseline. The fire-planet system 55 Cnc has been overtaken by
the (possible) six-planet system GJ 581 with a 3.1M® planet in the habitable zone, and up to seven
planets with five Neptune-mass in the case of HD 10180.”
In my opinion, as we move into 2016 It will not be long before astronomers
discover an Earth like planet similar to our own, and then speculation will
focus on finding the tell tale signs of intelligent life. The gigantic
reflector telescopes now under construction in Chile will help astronomers discover
the very first Earth-like planet, and you will then be the first to witness another
truly historic occasion.
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