34 light reductions revealed planets
A small telescope discovered the two innermost planets orbiting Trappist-1. But when the Spitzer telescope took a look at the star, the last five Earth-like planets became visible.
stabilised their wild orbits. The seven rocky planets orbit the star in the same plane, and their orbits are synchronised. As the innermost planet orbits the star eight times, the next three planets take five, three, and two orbits respectively during the same period of time. The seven planets are all located so close to the star that they are probably locked by tidal forces, so the same side will always be facing the dwarf star. The planets also have warm day sides, where temperatures can rise above the boiling point of water, and cold night sides, which could be completely covered in ice. Under such conditions, the border regions between the day sides and the night sides will offer the best chances of finding life.
THE ATMOSPHERE IS IMPORTANT
Together with the previous discovery of a rocky planet in the habitable zone of the Solar System’s closest neighbour, the dwarf planet of Proxima Centauri, the discovery of the seven Earth-like planets has made astronomers more interested in red dwarfs. Next year, NASA will launch the TESS satellite, which is to search for planets near 10,000 close dwarf stars. Red dwarfs are the most common stars of the universe, and in our galaxy, the Milky Way, they make up 85 % of the stars.
Astrobiologists are currently working hard to estimate the possibilities of finding life in small, compact, planetary systems orbiting faint dwarf stars. Preliminary investigations have revealed several factors, which are unfavourable for life to exist on rocky planets close to red dwarfs.
Dwarf stars have frequent outbreaks, by which they eject large quantities of charged particles into space, such as protons and electrons. The outbreaks can be so intense that they cause magnetic storms, which might be thousands of times more powerful than the worst geomagnetic solar storms on Earth. The radiation will pose a threat to all life forms, unless the planets are protected by
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 answer 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 i nhabited by an ancient civilisation. I am patiently waiting for the opportunity to go there and meet them.”