The universe is teeming with brothers and sisters of the earth.
About less than 40 light years away from Earth there have seven Earth-like planets been discovered surrounding a red dwarf. What does the discovery of these planets mean and can we go there?
1. What does this discovery say about the number of Earth-like planets?
Outside our solar system we discovered more than 3,500 planets, of which about fifty have the conditions that may be favorable for life. Small Earth-like planets are difficult to detect. They reflect very little starlight; and if they pass in front of their star, they hold back very little light. Not surprising that therefore most of the planets that are discovered so far around other stars are larger and heavier than the Earth.
The investigation by the Belgian ‘TRAPPIST’ telescope focuses specifically on red dwarf stars. With such a small star an Earth-like planet is much easier to discover. Only our own galaxy contains a few hundred billion planets that are similar in size, composition and temperature of the earth. With this of course, it is not known if there will be life on these planets.
2. How do we find out what is happening on those planets?
Step 1: Obtain the most important properties of the planets. The latest measurements of the dwarf star TRAPPISTS-1 they can already see how big and how heavy the planets are. It is to calculate the density; which lies in most cases, slightly lower than the density of the earth. That means that the planets to a large extent consist of stones, probably mixed with ice.
Step 2: Measure the amount of infrared radiation emitting planets. the heat radiation provides information on the temperature of the upper layers of clouds (if there is one atmosphere), or surface. How to find out if there may be water, and you can create climate models. Such measurements may be possible from earth, and certainly with the future James Webb Space Telescope. Which will be launched end of 2018.
Step 3: Determine the composition of the atmosphere. Due to the relatively small distance from the system should also be OK with the James Webb telescope, or the future European Extremely Large Telescope. If a planet contains methane and oxygen in it’s atmosphere, it could hardly be that there is biological activity.
3. Can we get there, or only do the research on a distance?
The seven sisters of the Earth orbiting a star 39 light-years away in the constellation Aquarius. A beam of light will have to travel a distance that takes 39 years at a speed of 300,000 km per second. Even if a spaceship could be accelerated to ten percent of the speed of light, and go on a trip to TRAPPIST-1 it will take nearly four centuries.
Russian billionaire Yuri Milner hopes with his Breakthrough ‘Star Shot’ Initiative in a few decades to send a swarm of nano-space ships to Proxima Centauri, the star that is closest to our sun. Also at Proxima last year a planet was discovered, which, incidentally, is larger and heavier than the Earth. How feasible the project is is not really clear. It will probably take centuries before a terrestrial spacecraft can visit TRAPPIST-1, and then it is certainly an unmanned unit.
Studying by distance offers many more opportunities, only because you also can examine a much larger number of stars and planets. Belgian researchers are already working on a successor to TRAPPIST, named SPECULOOS. NASA launches next year’s space telescope TESS, which will also hunt for planets around nearby stars.
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