TESS – or the Transiting Exoplanet Survey Satellite – will search for alien worlds. It will not help us find whether there is extraterrestrial life there, but it will go one step towards it.
And even before we find our potential galactic neighbours, we could discover thousands of exciting new planets.
What’s happening this week?
TESS will lift off from Cape Canaveral Air Force Station, starting the clock on a two-year, $337m (£235m) mission in one of astronomy’s newest fields of exploration.
Nasa’s latest space-bound astrophysics instrument will be carried aloft by a Falcon 9 rocket from the fleet of billionaire entrepreneur Elon Musk’s private launch service, Space Exploration Technologies, or SpaceX.
Are we about to find aliens?
Not immediately, and not directly. But TESS kicks off a process that could lead to the discovery extraterrestrial life, and that’s one reason why people are so excited about the launch, though not the only one.
But – if that happens – it will probably be a long time, and a long way, from now. There’s going to be a few steps to actually get there, and it will require other launches, other satellites and much more scientific work.
All the same, TESS could be the next stop on a long journey towards that ultimate goal. But it will help us find a lot more while it is doing so.
What are we actually going to find then?
TESS’s goal is to look out for exoplanets: other worlds, orbiting around stars far outside of our solar system. Until now, most of those have been found by the Kepler space telescope – but that is about to run out of fuel, and so TESS will take over.
How will it do that?
Roughly the size of a refrigerator with solar panels for wings and equipped with four special cameras, TESS will take about 60 days to reach a highly elliptical, first-of-a-kind orbit looping it between Earth and the moon every two and a half weeks.
Like Kepler, TESS will use a detection method called transit photometry, which looks for periodic, repetitive dips in the visible light from stars caused by planets passing, or transiting, in front of them.
But unlike Kepler, which fixed its gaze on a range of stars within a tiny fraction of the sky, TESS will scan a broader swath of the heavens to focus on 200,000 pre-selected stars that are closer and thus among the brightest as seen from Earth.
That makes them better suited for sensitive follow-up analysis for the exoplanet candidates TESS locates.
The TESS survey will concentrate on stars called red dwarfs, smaller, cooler and longer-lived than our sun. Red dwarfs also have a high propensity for Earth-sized, presumably rocky planets, making them potentially fertile ground for closer examination.
And because the planets circling them are bigger relative to the size of the star, and orbit at a closer distance, the slight disruptions of visible light from their transits are more pronounced, scientists said.
Measuring blips in starlight can determine the exoplanet’s size and orbital path. Further observations from ground telescopes can supply its mass and ultimately the planet’s density and composition – whether largely solid, liquid or gas.
And how will that help us find aliens?
If life is out there, then it will be out there on another planet. And the whole goal of this satellite is to find those.
In all, TESS is expected to find thousands of exoplanets. It will also help us discover things about those exoplanets: scientists will be able to judge how close they are to their star, for instance, helping them work out what the climate is like and whether it might be able to support life.
From that catalogue of distant worlds, scientists will be able to pick out the best candidates for further study. That will get us ready for when more advanced space satellites launch in the coming years – satellites that will allow us to “sniff” the atmosphere of those distant worlds, and assess whether they might be able to accommodate alien life.
Additional reporting by agencies
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