34 | SCIENCE ILLUSTRATED
strong magnetic fields, which can bend the
particles around the worlds just like Earth’s
magnetic shield. However, the violent
outbreaks are most frequent during the first
billion years after the formation of a dwarf
star and the planetary system. If the planets
in the habitable zone by Trappist-1 have
oceans, the water will protect against the
particle radiation, so life could originate and
develop in the oceans and creep ashore, once
the worst part is over.
The planets will have major temperature
differences between the day sides and night
sides, which can make them too hot or too
cold for life, but a dense atmosphere and
cloud cover could level the differences and
allow for a large habitable zone around the
planets’ equators. Moreover, a dense
atmosphere would solve another problem, i.e.
that dwarf stars emit large quantities of
hazardous ultraviolet and X-radiation. Any life
forms must be able to tolerate this, but a
dense atmosphere would minimize the
quantity of radiation that reaches a planet’s
surface, improving living conditions.
So, the nature of the atmosphere is vital
for whether life could have originated on the
three rocky planets in the habitable zone
around Trappist-1. The observations of the
Spitzer space telescope fortunately indicate
that the planets of the small stellar system
could have dense atmospheres. The density
of the three planets is slightly smaller than
Earth’s, which is probably due to a larger
portion of volatiles such as atmospheric
gases, water in clouds, etc.
TELESCOPE SEARCHING FOR LIFE
Next year, NASA will launch the large James
Webb space telescope. With its keen glance,
the telescope will be able to study the
contents of the atmospheres surrounding
the three planets located in the habitable
zone by Trappist-1.
If the telescope finds life on one planet, it
probably also exists on the two other ones,
as they are so very much alike. And if the life
forms are also sophisticated, they have ideal
chances of continuing their development, as
the dwarf star will be shining with the exact
same brightness for trillions of years. In
comparison, life on Earth will only thrive for a
short while, as in 1.75 billion years, the Sun’s
brightness will have increased so much that
all water on Earth will evaporate.
The red dwarf star is 3-8 billion years old,
and the planets formed almost at the same
time as the star. If its age is at the high end of
the scale, life could have developed over a
much longer period of time than on Earth,
where life originated about four billion years
ago. So, the three habitable planets could
include civilizations, which are much older
and more sophisticated than ours.EARTH IS ALREADY IN TOUCH
Immediately after the discovery of the
planetary system, the US SETI Institute
(Search for Extraterrestrial Intelligence)
aimed several radio telescopes at Trappist-1
to look for artificial radio signals from a
sophisticated civilisation.
If the telescopes pick up signals, we can
send radio messages back and communicate
with the civilization, but we have to be
patient, as a radio signal travelling at the
speed of light would take 39 years to reach
the planetary system – and any answerThe conditions of animals and
plants living on a planet by a red
dwarf star are very different than
on Earth. Together with an
illustrator, a biologist specialising
in the environment’s effect on
evolution imagines what life might
look like around a red dwarf.
Red dwarfs: tough
living conditions
ANIMALS MUST RESIST RADIATION
Red dwarfs emit huge quantities of harmful
radiation. So, animals must be protected against
radiation – such as this guy with thick skin and
bone plate armour. The amphibian also has
powerful front legs, allowing it to dig itself in,
when the star emits showers of charged particles
during its frequent eruptions.PLANTS CREEP ALONG THE GROUND
Red dwarfs do not emit very much visible light.
So, plants have to use not only the visible light
from the star in their photosynthesis, but also
heat radiation. To capture the infrared
radiation, the leaves of plants will probably be
dark brown, dark red, or black, because dark
colours absorb more heat radiation.DENSE ATMOSPHERE: ISLANDS
IN SHALLOW WATER
Super-Earths have powerful gravity
and so a dense atmosphere, causing
heavy precipitation and erosion. This
levels the surface, so the planet gets a
shallow ocean with small groups of
islands. On Earth, life would thrive here.would take just as long to travel back to
Earth. Even if SETI gets in contact with the
civilization, it is highly unlikely that we can
send a spacecraft to the red dwarf star
within a foreseeable future, so we can
only imagine, just like Nature does:
“I love to aim the telescope at
our neighbouring planet of
Trappist-1f or Pangu. It is so
close that we can go there in a
week. The two closest
planets are almost like
neighbouring countries on
Earth. Trappist-1g or
Shennong is further
away. We know that it is
inhabited by an
ancient civilisation. I
am patiently waiting
for the opportunity
to go there and
meet them.”STEVE GRICE/SKETCFAB STEVE GRICE/SKETCFABARMOURED AMPHIBIAN CREEPING PLANT
SPACE EXOPLANETS