Could TRAPPIST-1 be home to life?
It turns out there wasn’t just dust on a telescope lens, the NASA Spitzer Space Telescope has spotted seven Earth-size planets around a nearby star, some or all of which could harbour water and possibly life. The exoplanetary system is named TRAPPIST-1.
What is TRAPPIST-1?
TRAPPIST-1 stands for Transiting Planets and Planetesimals Small Telescope. The discovery is a small, dim star in the constellation Aquarius, less than 40 light-years from Earth, or 235 trillion miles away, according to Nasa and the Belgian-led research team who announced its discovery on Wednesday. Seven planets circle TRAPPIST-1, with orbits ranging from one and a half to 20 days. If TRAPPIST-1 were our sun, all these planets would fit inside the orbit of Mercury. That’s how close they are to their star and why their orbits are so short. The planets have no real names. They’re only known by letters, “b” through “h.” The letter “A” refers to the star itself.
Can this newly discovered solar system support life?
Six of TRAPPIST-1’s “exoplanets” lie in a temperate zone where surface temperatures range from zero to 100C. Of these, at least three are thought to be capable of having watery oceans, greatly increasing the likelihood of life. No other star system known contains such a large number of Earth-sized and probably rocky planets. All are about the same size as Earth or Venus, or slightly smaller. Because the parent star is so dim, the planets are warmed gently despite having orbits much smaller than that of Mercury, the planet closest to the sun. Scientists said they need to study the atmospheres before determining whether these rocky, terrestrial planets could support some sort of life.
What do the planets and solar system look like?
As well as being in tight orbits, the TRAPPIST-1 planets are unusually close to one another, conjuring an image straight out of science fiction. If TRAPPIST-1 were our sun, all seven planets would be inside Mercury’s orbit. Mercury is the innermost planet of our own solar system.
Why all the excitement?
Three of TRAPPIST-1’s exoplanets are slap bang in the so-called habitable zone, also known as the Goldilocks zone, where conditions are just right for watery oceans – not too much and not too little stellar energy – greatly increasing the chance of life. Because the parent star is so dim, the planets are warmed gently despite having orbits much smaller than that of Mercury, the planet closest to the sun. Scientists said they need to study the atmospheres before determining whether these rocky, terrestrial planets could support some sort of life. Just because a planet is in this sweet spot, doesn’t mean life exists or ever did.
How did they find out about TRAPPIST-1?
The discovery, reported in the journal Nature, was made by astronomers using Nasa’s exoplanet-hunting Spitzer Space Telescope. The telescope operates at the infrared wavelengths which glow brightest from TRAPPIST-1 and can detect the tiny dimming that occurs when a passing or “transiting” planet blocks out light from its star. Spitzer’s data allowed the team to measure precisely the sizes of the seven planets and estimate the masses and densities of six of them. The Spitzer was launched in 2003 and was never meant to continue in space for this long but the telescope is still making discoveries beyond what was imagined. It follows the earth’s orbit around the sun, but travels slightly slower, so over time it gets further away from the earth. It is now in its “final” phase, which lasts until 2018.
What is an exoplanet?
An exoplanet is any planet that is outside of our solar system – ie anything that is not orbiting our star. The first exoplanet was discovered in 1988, but over 3,500 have been discovered since then. Only a tiny fraction of these have been deemed capable of supporting life in any way. Oceans and closeness to a star are two factors that scientists take into account.
Scientists need to study the atmospheres of these almost assuredly rocky planets before drawing any conclusions about water and life. The Hubble Space Telescope already is on the case and the still-under-construction James Webb Space Telescope will join in once it’s launched next year. The Webb will search for gases that might be a byproduct of life: oxygen, ozone and methane. Scientists say it should take five years to get a handle on all these atmospheres, and figure out whether water – and maybe life – are present.
What the experts are saying
Thomas Zurbuchen, associate administrator of the Science Mission Directorate at Nasa, said: This gives us a hint that finding a second earth is not just a matter of if, but when. You can just imagine how many worlds are out there that could have a habitable ecosystem that we can explore.
‘This is the first time so many planets of this kind are found around the same star. The TRAPPIST-1 planets make the search for life in the galaxy imminent,” said Sara Seager, an astronomer at the Massachusetts Institute of Technology who was not a member of the research team. “For the first time ever, we don’t have to speculate. We just have to wait and then make very careful observations and see what is in the atmospheres of the Trappist planets.
British astronomer Dr Chris Copperwheat, from Liverpool John Moores University, who co-led the international team, said:
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.
Amaury H. M. J. Triaud, an astronomer at the University of Cambridge and member of a research team said:
I think that we have made a crucial step toward finding if there is life out there. Here, if life managed to thrive and releases gases similar to that we have on Earth, then we will know.
Dr Seth Shostak, an astronomer at Seti Institute in Mountain View, California, said: If you’re looking for complex biology — intelligent aliens that might take a long time to evolve from pond scum — older could be better. It seems a good bet that the majority of clever beings populating the universe look up to see a dim, reddish sun hanging in their sky. And at least they wouldn’t have to worry about sunblock.
And if no life is ultimately found on any of the planets
It’s not all bad news – if no life is found, scientists will still have learned more about what has stopped it developing. And the search will continue.
Exoplanet: a planet that orbits a star other than our Sun
Habitable zone: a band of potential habitability, the right distance and temperature for liquid water to exist on the surface of a planet
Light year: a measure of distance, not time. It is the total distance that a beam of light, moving in a straight line, travels in one year
Orbital period: the time it takes a satellite to make one full orbit is called its period. For example, Earth has an orbital period of one year
TRAPPIST-1: a dim and ultra-cool dwarf star, much cooler and redder than the Sun and barely larger than Jupiter