from earth to proxima centauri in 20
years the project breakthrough starshot
in 2016 the lasilla observatory in chile
identified proxima b the closest
exoplanet known to us today
it orbits in the habitable belt of its
own star proxima centauri a red dwarf
located 4.2 light years away from us in
the direction of the centaurus
constellation
proxima centauri is part of the alpha
centauri system a triple system
consisting of a yellow dwarf and an
orange dwarf very close to each other
and from proxima
proxima is a red dwarf probably the most
widespread stellar type in the milky way
dim and relatively cold
it's a little more than the age of the
sun about 4.8 billion years but a
diameter that is only 15 percent that of
the sun and a surface temperature of
only
2725 degrees celsius compared to
5725 degrees celsius of our star
consequently its habitable zone that is
the circumstellar belt in which a planet
could have liquid water on the surface
is very close it is located about 1 20th
of the earth's distance from the sun for
example proxima b which with an orbital
period of 11.2 earth days is within this
zone would be a hot world if it was
around the sun even if located inside
the habitability belt it is by no means
certain that proxima b is actually
habitable due to the intense activity of
its star proxima in fact red dwarfs are
known to manifest sudden and random
flares even very powerful ones
flares are violent eruptions of matter
that explode from a star's photosphere
releasing large amounts of energy they
are often accompanied by large plasma
ejections known as coronal mass
ejections
these elements determine the space
meteorology of the system and have a
fundamental role in the habitability of
a planet and the eventual evolution of
life on it as we know it under extreme
conditions super flares could wipe out a
planetary atmosphere and lash a
magnetosphere heavily pushing it back
until it leaves the planet's surface
exposed to deadly radiation
according to statistics it is estimated
that proxima centauri produces flares of
this magnitude at least five times a
year
every scope a series of small telescopes
that observed the stars in the southern
hemisphere detected a super flare that
made proxima 70 times brighter in 2016.
again a very intense flare by proxima
centauri was registered on march 24th
2017. the brightness of the star
increased by 1 000 times in only 10
seconds
the brightness increase was so big that
proxima became visible to the unaided
eye for a short period
given these premises if there was an
atmosphere around proxima b it probably
didn't survive the likely activity of
proxima while on our planet the ozone
layer absorbs harmful ultraviolet
radiation on proxima b assuming it has
no magnetic field ninety percent of the
atmospheric ozone would be lost after
only five years of stellar activity
the results of several simulations
carried out by a team of researchers led
by christophe lovis of the astronomy
department of the university of geneva
showed that without ozone the surface of
proxima b would be devoid of protection
against uv rays
during superflares such as those
observed the radiation dose without
protective ozone would be 65 times
greater than that needed to kill 90
percent of the most resistant organisms
to ultraviolet rays on earth
despite these features would you like to
visit proxima b let us know in the
comments
but what do we know about proxima b
today
it's probably a rocky planet whose
minimum mass could only be 1.17 earth
masses
this value together with other estimates
brings it to sixth position in the list
of exoplanets that are most likely to
have a rocky composition and keep liquid
water on the surface with earth
similarity index esi equal to 0.87
this value classifies alien worlds based
on their similarity to the earth as a
function of radius density escape
velocity and temperature but does not
take into account all the factors that
could affect their habitability in any
case we still know little about proxima
b its orbital inclination is not known
as well as its exact radius and
therefore also the mass could vary
considerably
this means that the planet might be
rocky like the earth or frozen like
neptune with a thick atmosphere of
hydrogen and helium
although proximity is about 20 times
closer to its star than earth is to the
sun it receives comparable energy this
means that the surface temperature could
favor the presence of water in a liquid
state if there is any and support the
development of life however it is likely
that the planet is stuck in synchronous
rotation due to the tight orbit around
its star that is to say it always shows
the same face to proxima as the moon
does to the earth
an important dichotomy between the two
hemispheres could arise from this
feature while the entire planet is
bombarded by the energy activity of the
red dwarf receiving an estimated amount
of x-rays about 400 times greater than
that which the earth receives from the
sun
nonetheless the proxima centauri system
remains one of the most intriguing to
study and one of the most coveted for
future extrasolar exploration
the planetary system of proxima centauri
has inspired several projects among the
best known the breakthrough star shot
also born from the breakthrough
initiatives starshot is a research and
engineering project announced in 2016
and born to develop a fleet of sailing
interstellar probes and laser propulsion
it was founded by yuri milner stephen
hawking and mark zuckerberg in 2017 nasa
also proposed a probe to look for bio
signatures on the planets around the
stars of the alpha centauri system the
launch taking place by 2069 would
celebrate the 100th anniversary of the
apollo 11 mission
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another idea to study proxima b more
closely is the starshot concept it
involves the launch of a mother ship
that transports small spacecraft a few
centimeters in size to the outside of
earth's orbit
from here a laser beam coming from the
ground will accelerate the four by four
meter sails connected to the micro
probes up to one hundred kilometers per
second to the power of two
thanks to these problems it will be
possible to reach and visit the planet
proxima centauri b in about 30 years and
capture an image of high quality
sufficient to fully understand the
surface characteristics of the planet
a swarm of about 1 000 units is assumed
to compensate for the losses caused by
interstellar dust collisions while
navigating to the planet of interest
in a recent detailed study
astrophysicist chai thiam hong and his
collaborators found that mitigating
collisions with dust hydrogen and cosmic
rays may not be as serious an
engineering problem as one might think
using our current technology a trip to
proxima centauri for a probe with the
same characteristics as the new horizons
the probe that recently visited pluto
ultima thul and is now entering the
kuiper belt would take about 78 000
years but projects like breakthrough
starshot or similar would give a big
boost to the development of new methods
of space propulsion and new technology
for miniaturization of cameras and other
electronic components because it is
certainly cool to travel to infinity and
beyond as buzz lightyear said in the
disney movie toy story but it is equally
sewn to look for applications that are
unthinkable today useful for improving
daily life
what if one day you want to send a human
crew to explore proxima centauri b
in this case the problems to be faced
would increase dramatically some
researchers have tried their hand by
analyzing some of them
as for the timing the theoretical speed
data of the next parker solar probe
launched on august 11 2018 were used it
is expected that this will be able to
reach a speed of about 724 000
kilometers per hour or 0.067 percent of
the speed of light only this data should
make us think a lot in fact a simple
mathematical calculation is enough to
understand that a possible trip based on
this technology of thrust could last
about 6 300 years
in the event that it is decided to send
a human expedition to proxima centauri b
it will be necessary to consider a
substantial generational change to be
hosted inside a spaceship designed for
colonization
according to the researchers the minimum
number of humans to send would be 98
people split equally between men and
women however this may not be as
accurate to calculate it the researchers
used a type of monte carlo simulation
called heritage which allows to identify
the most likely scenario obtaining it
through the consideration of various
iterations between the variables taking
into consideration the natural and
accidental deaths infertility and the
increase in consanguinity it turns out
the journey represents an unknown factor
especially in relation to its length
then there would be a serious problem of
crew sustenance in the long term which
would require a control in both
directions of the births with
restrictions based on the maximum number
of the population not to mention the
energy problem
the most critical element of all is
undoubtedly the creation of a habitat of
a few cubic meters in which astronauts
should spend the rest of their lives
it would be impossible for them to even
return to earth once the scientific
exploration of proxima b is finished
unless they radically increase the
capacity of the spaceship nuclear
reactor to supply energy
but this would most likely lead to
exceeding the limits of size and mass
useful for launch
if you were astronauts traveling to
proxima b how would you feel at the
thought that you will never return to
earth again let us know in the comments
in short a crew of heroes would be
needed for such a mission the astronauts
must be selected not only on the basis
of technical scientific preparation and
physical skills but above all on the
basis of character skills
it takes exceptional people to leave the
earth knowing they cannot go back ready
to spend decades locked up in a flying
box of a few cubic meters their solitude
would be absolute moving away from the
earth they would see the latency time
continuously increase between the
sending of a message and the arrival of
the relative response a time that would
gradually expand to become whole years
how would you feel to wait so long for a
response to your message to earth
write it in the comments
the effects on the human body of years
spent in space are unknown all the
experiments carried out so far have been
limited to a year or so spent in low
earth orbit aboard the international
space station
as in the case of the experiment
involving the astronaut twins mark and
scott kelly
we do not know what adaptations and
above all what physical cognitive and
psychological damage can affect human
beings forced to remain in space for
decades locked up with a narrow
environment without the earth's gravity
without the possibility of having
contact with other human beings without
direct exposure to sunlight and without
being able to breathe pure air
furthermore there is currently no
prototype of the space capsule capable
of creating an environment in which
astronauts can live for long years
an environment equipped for example with
artificial gravity micro greenhouses or
recreational facilities
it is very unlikely that something like
this could be produced within a few
years
above all it is very difficult if not
impossible that a home for astronauts
the supplies to survive in space for
decades and the scientific instruments
to explore new worlds can be crammed
within the limits of space and mass but
even a super rocket like the spacex
starship must comply
all this suggests that a manned
interstellar journey will not be
possible for at least 50 years perhaps
more and even when it has finally become
feasible it won't be at the paltry cost
of 100 million dollars but several tens
of billions of dollars considering the
preliminary decades spent on research
and development it will be an
undertaking that only a strong
international political will can
transform into reality
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