2020-04-02_Science_Illustrated

4.2

light years is the

distance to the closest

potentially-inhabited

planet, Proxima Centauri b.

Large underground detectors

capture neutrinos. Astronomers

believe that aliens might use the

particles that are produced in

huge accelerators to send signals.

So to establish a more useful direct line
between planets, the messages must be sent
to exoplanets in our cosmic neighbourhood.
Since the first exoplanet was discovered in
1992, 4100 have been spotted by space tele-
scopes such as Hubble and Kepler. Based on
the sizes of exoplanets and stars, their
mutual distances and their atmospheric
make-up can be determined, so astronomers
can try to determine whether a planet is in
the inhabitable zone and is a rocky planet
that could include intelligent life.
The music bites sent by METI in two stages
in 2017 and 2018 are headed for GJ 273 b,
an exoplanet only 12.4 light years from
Earth, and the first message will arrive in
November 2030. If the planet includes an
intelligent civilisation that has radio tele-
scopes, a reply could reach Earth in 2043. As
of now, nobody knows if this planet
harbours any life, but new telescopes can
intensify METI’s search.
Since 2018, NASA’s Tess satellite has been
dicovering rocky planets near stars in our
neighbourhood. When the next large space
telescope, James Webb, is launched in 2021,
its 6.5m-wide mirror will be able to more
closely identify the molecular make-up of
atmospheres to find evidence of oxygen,
water, methane... and so life. METI’s long-
term ambition is to focus on the planets that
are most likely to include life, but also to send
signals to millions of other exoplanets close to
Earth, hoping for a relatively rapid reply.

Come and get us

In direct conflict with METI’s aim, you will

find a written agenda from 2015 signed by

scientists from the SETI Institute, SpaceX

founder Elon Musk, and others, expressing

concern about the potential hostility of

aliens: “A global, scientific, political, and

humanitarian discussion must take place

before any messages are sent,” it says.

But decades of emissions of waves for

radio and TV have already produced a

bubble of signals around our world that

travel away from us at the speed of light. In

principle, an alien civilisation some 85 light

years from Earth could pick up a weak radio

signal of a Bing Crosby hit from 1933.

“It is too late to conceal ourselves in the

universe, so we should decide how we want

to represent ourselves,” METI president

Douglas Vakoch said in an interview in 2018.

As the debate continues, METI plans its

next message: a visualisation of the periodic

table. The organisation hopes to send the

message from a powerful radio telescope

such as Arecibo.

The search continues

The ‘Wow!’ signal still remains the best chance

of being a sign of alien intelligence. Astron-

omer Antonio Paris in 2017 claimed that the

signal came from two comets, but Jerry

Ehman, who discovered the signal, does not

think that comets emit such a brief signal.

On the other hand, almost everybody agrees

that the signal is not from Earth.

The SETI Institute continues the search

for evidence of intelligent life. In the years to

come, the 350 telescopes of the American

Allen Telescope Arrays are to search more

than one million stars for evidence of radio

waves. Other astronomers are working on

expanding SETI’s search to signals other

than radio waves, such as infrared radiation

from lasers, or tiny neutrinos that could

come from particle accellerators.

According to Nobel Prize laureate Didier

Queloz, within 30 years we will have the

technology to find life on remote planets,

and within 100 years we will have found the

first aliens. Until then, we must enjoy our

alone time in the universe.

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58 | SCIENCE ILLUSTRATED
SPACE ALIENS