By Ahmad Abu El-Hamd
Life may have evolved on at least three planets within a newly discovered solar system that is 39 light years from Earth, it was announced last night.
Astronomers at the National Aeronautics and Space Administration (Nasa) have detected no less than seven roughly Earth-sized worlds orbiting a dwarf star in the system, it was announced today. Scientists had previously only identified a tiny number of so-called “exoplanets”, which are believed to have the qualities needed to support life.
However, the new system contains an unprecedented number of Earth-sized, probably rocky planets, and is being hailed as an “accelerated leap forward” in the search for extraterrestrial life. Three of the new planets are said to be particularly promising because they could sustain oceans. Thomas Zurbuchen, associate administrator of Nasa’s Science Mission Directorate, told a press conference in Washington: “This gives us a hint that finding a second Earth is not a matter of ‘if’, but ‘when’.”
The planets were detected using Nasa’s Spitzer Space Telescope and several ground-based observatories. Lead researcher Michaël Gillon, of the University of Liège, said: “The planets are all close to each other and very close to the star, which is very reminiscent of the moons around Jupiter. “Still, the star is so small and cold that the seven planets are temperate, which means that they could have some liquid water – and maybe life, by extension – on the surface.”
The team determined that all the planets in the system are similar in size to Earth and Venus, or slightly smaller. And density measurements suggest that at least the innermost six planets are rocky. Because the star is so dim, the planets are warmed gently despite having orbits much smaller than that of Mercury, the planet closest to our Sun.
Key observations were made by the Trappist robotic telescope at La Silla, Chile which gives the system its name. Three planets – classified as Trappist-1e, f and g – orbit in the “habitable” or so-called “Goldilocks” zone where temperatures are suited to surface oceans of liquid water. The star at the centre of the solar system has a temperature of 2550K and is at least 500 million years old. In comparison, the Sun is about 4.6 billion years old and has a temperature of 5778K. The six inner planets lie in a temperate zone where surface temperatures range from zero to 100C.
Nasa’s Hubble Space Telescope is already being used to search for atmospheres around the planets. Future telescopes, including the proposed European Extremely Large Telescope and the James Webb Space Telescope, may be powerful enough to detect markers of life, such as oxygen, in the atmospheres of exoplanets.
Prof Sara Seager, an expert in planetary science and physics at the Massachusetts Institute of Technology, said: “In this planetary system, Goldilocks has many sisters. We have made a giant accelerated leap forward in the search for habitable worlds and life in other worlds,” she said. The Spitzer telescope, which uses infrared technology, was able to track how fast each of the planets crossed Trappist-1 and completed an orbit.
From this the research team calculated how far the planets were from their star, and therefore how likely they are to be habitable. They were assisted by astronomers from Liverpool John Moores University, operating a ground-based telescope in the Canary Islands. British astronomer Dr Chris Copperwheat, from Liverpool John Moores University, who co-led the international team said: “As a robotic telescope and the largest in the world, the Liverpool telescope is very sensitive to the small, less than 1 per cent, dips in brightness through which the planets are discovered.”
The new planets are very close to each other and Dr Gillon said a person standing on the surface of one would have a view of its neighbours, similar to seeing the Moon from Earth. The first exoplanet was confirmed to have been discovered in 1992, since when a total of 3,577 have been found. Of these, less than a dozen are thought to be well suited to supporting life, and Nasa said only three previously known exoplanets were as ideal as those in the new solar system.
Around a fifth of Sun-like stars are thought to have an Earth-sized planet in their habitable zones. Astronomers estimate there could be as many as 40 billion potentially habitable worlds in our galaxy, the Milky Way. Prof Zurbuchen said that now was a “gold-rush phase” in the search for these exoplanets. “This is going forward at a rapid pace not just because of the telescopes there, but the telescopes we are launching soon,” he said.
Dr Copperwheat, added: “The discovery of multiple rocky planets with surface temperatures which allow for liquid water make this amazing system an exciting future target in the search for life.”
A robotic telescope operated by Liverpool John Moores University played a major role in the discovery reported in the journal Nature.
It was one of a number of ground-based instruments that supported observations made by American space agency Nasa’s orbiting Spitzer telescope. The Liverpool telescope helped detect the planets as they passed in front of their star. The planets were found using the “transit” method that looks for tiny amounts of dimming caused by a world blocking light from its star. The Liverpool Telescope is located on La Palma in the Canary Islands.
Astronomer Royal Sir Martin Rees thinks he discovery of these new worlds is just the start.
