Toliman Mission: is there life on Alpha Centauri?
Alpha Centauri is a triple star system, located at 4.36 light-years from our Sun.
The two main stars of this system are solar-type stars, while the third one
it's a red dwarf – the famous Proxima Centauri. Proxima Centauri is very famous, not only because
until now it is the nearest star to us (indeed, the word Proxima comes from Latin and means “the
nearest one”), but also because it may have at least two exoplanets that orbit around it.
We don't know really much more than this. However, this is something that needs to be
studied in more detail, because if such Earth-like planets existed in orbit around other stars,
they would be the most convenient destination for humanity, beyond our solar system.
That's why Toliman mission comes into play.
Follow me in this video to get to know more about the finding of life in our galaxy neighbourhood,
and to unveil the secrets of Alpha Centauri.
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Alpha Centauri is one of the brightest sources of our night sky,
and it can be easily seen by the naked eye.
You may recognize it in the direction of the Centaurus constellation.
Robert Innes was the first to discover it, in 1915 from South Africa.
It used photographic plates taken at different times during a study dedicated to monitoring the
proper motion of stars. The great proper motion and parallax of this seemingly
anonymous red star seemed perfectly compatible with those of the α Centauri AB system. Being at
a distance of 4.22 light-years from Earth, Proxima Centauri was thus recognized as the closest
star ever. The currently accepted distances derive from the parallax measurements
performed by the Hipparcos satellite and reported in the homonymous catalogue.
α Centauri A is the main (or primary ) member of the triple star system,
and appears slightly brighter than our Sun, in absolute terms. However, it is a star similar to
our star, of the main sequence, with colour tending to yellowish, whose classification
is G2 V. This star is about 10% more massive than our Sun, with a 23% larger radius; The
rotation speed of α Centauri A is about 2,7 km /s, which equates to a rotation period of 22 days.
Now. Stars are special objects. We all dream about
the stars and we always look at the sky with high admiration.
In the past, it was thought that the presence of exoplanets orbiting double stars was unlikely,
due to the gravitational perturbations induced by the stars making up the system.
But the discovery of planets around some double stars, such as γ Cephei, made it possible to
believe the existence of terrestrial-type planets in the α Centauri system. They can in fact orbit
around component A or component B, or possess a sufficiently large orbit to include both stars.
But wouldn't it be even more special if you knew that, somewhere over there, someone is looking
at the Sun in the same way we are looking at the stars? If someone out there is looking at you in
the same way you are looking at them? That would be amazing.
And this is what astronomers hope to find out in the future.
The good news is that...the future is already happening.
Scientists from Sidney University, in collaboration with Breakthrough
Initiative in California, Saber Astronautica in Australia and NASA's JPL,
are about to set up the future TOLIMAN mission, which will pave the way for the
hunting of planets in the goldilocks zone, which hopefully host live.
TOLIMAN is a weird and long name, but it stands for Telescope for Orbit Locus Interferometric
Monitoring of our Astronomical Neighbourhood.
Let's talk about it and see what kind of knowledge it will bring to us on Earth.
First of all, Toliman is an innovative low-cost mission that will be the first
capable of revealing potentially habitable planets
around a handful of the nearest solar-type stars to the sun.
Rocky planets in habitable orbits among our immediate
stellar neighbours will change our understanding of the universe,
not only from a physical perspective but also in philosophical and ethical ones.
If everything goes well, TOLIMAN will enable detailed characterisation of atmospheres
and surfaces, and prospecting for potential bio-signatures.
What are they for? Well, if you think about it,
science is made of small pieces that, together, form the Big Puzzle of the universe.
On long timescales, TOLIMAN's data may furnish targets for futuristic robotic probes.
These data will reveal the presence, orbit and mass of all orbiting exoplanets.
The primary target for this mission will be the detailed studying
of Alpha Centauri A & B, and objects down to one Earth mass will be accessible.
But how will the Toliman mission gain this data? It will use the astrometry method.
Astrometry is basically the only technology capable of detecting all Earth-Mass planets
in the Habitable zones of very nearby sun-like stars, such as Alpha Centauri.
Astrometry is the method that detects the motion of a star by making precise
measurements of its position in the sky. Planets orbiting around a star change their position,
and we can find them by measuring tiny changes in the star's position as it wobbles around
the centre of mass of the planetary system. However, the precision required to detect a planet
orbiting a star using this technique is extremely difficult to achieve and for this reason,
only one planet has been discovered by this method, although astrometry has
been used to make follow-up observations for planets detected via other methods.
Conventional astrometry measures the position of a star using bright field stars in the neighbouring
regions of the sky as references. This requires a wide field of view, as the distance between the
science target and sufficiently bright reference stars is typically on the order of a degree.
Space astrometry over wider angles has proved to be extremely productive delivering basic stellar
positions, distances and kinematics with the HIPPARCOS mission, and its ambitious successor
GAIA which is measuring a billion stars with precision up to the tens of micro-arcseconds.
With the help of this technique, we will be able to reveal important info such as masses of planets
and orbital parameters, for example, eccentricity and orbit's inclination.
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Do you know how many new planets are we discovering per day? The rate is
something like one new exoplanet per day. And yet, if we wish to know whether any
particular star hosts a rocky planet in the Habitable zone, we have a tiny
and remote chance of being able to find out. Most of these detections were just guided by luck.
Missions like Kepler gave us information on the statistical incidence of planets in various
stellar environments, but we still don't know if the nearest of sun-like stars such as Alpha
Centauri, Tau Ceti and Epsilon Eridani actually host a potentially-habitable rocky world.
Even worse, with present technologies, we have no way of finding out.
That's the reason why we need new improved instruments to do the job,
and TOLIMAN is exactly what we need.
Toliman will be actually a quite modest astrometric space telescope
designed to discover and perform dynamical characterization of rocky planets.
It is not so big, having a 30 cm diameter,
and it will be of course a space telescope, meaning that we'll need to launch it first.
The mission will yield immediate constraints on the orbit and mass of any detected planets from
the habitable zone out to the dynamical stability limit imposed by the binary.
If such a planet is found in the nearest solar-type star system,
it will be a game-changing discovery that will trigger intensive characterization efforts.
TOLIMAN will also observe a handful of F/G/K spectrum stellar targets within the
immediate solar neighbourhood, variously probing down to Earth or Super-Earth mass
(with limiting sensitivity depending on the specifics of each system).
At the centre of the TOLIMAN mission, there's a new type of telescope,
which makes use of a diffraction lens. This mirror diffuses the starlight captured by
nearby stars in a complex floral pattern which, paradoxically, makes it easier to
detect the perturbations of stellar movements, signs of the presence of planets in orbit.
But what makes TOLIMAN such a special instrument?
"Before finding out the answer to this question, be sure to like or dislike the
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What makes it so special is its empowered optical architecture.
It promises to deliver the required micro-arcsecond astrometric precision.
When trying to reference stellar positions at micro-arcsecond scales, a lot of small
imperfections and mechanical drifts, even the smallest defects, can create instabilities that
can be orders of magnitude larger than the true signal, since it is very low.
Rather than trying to directly contain all these errors, the Diffractive Pupil approach
sidesteps them by creating a new astrometric ruler to register the star’s position: one formed from
the starlight itself. The diffraction pattern from the pupil broadcasts a reference grid onto the
detector plane against which stellar locations are registered. The genius of this approach is
that the diffractive grid of starlight suffers identical distortions and aberrations to the
signal being measured (the binary separation). Drifts in the optical system, therefore, cause
identical displacements of both the object and the ruler is used to measure it, and so the
data are immune to a large class of errors that beset other precision astrometric experiments.
In this image, you can see how this fantastic idea works.
You can clearly see the diffraction pattern we were talking about.
Hopefully, Toliman will become an inspiring mission for future generations of astronomers
and scientists all over the world. Who knows, maybe in the next years
we will rewatch this video together with our new friends, the inhabitants
of the Alpha Centauri triple star system. Or it could be that our sons and daughters
will still be working on this mission because science takes time and effort.
The only important thing is that we will never stop trying: we will never quit.
Our curiosity is so strong that it overcomes difficulties.
And together we can make the difference.
"This video ends here! Thanks for watching everyone! What are your thoughts about this one?
Do you think we will find new forms of life in the Alpha Centauri System?
Let us know in the comment below! See you next time on the channel!