If you’re in the mood for a road trip and have a few hundred million years to kill, we have the destination for you.
About 40 light-years away, orbiting a dim, cool red star called Trappist-1 are seven planets.
One of them, scientists have revealed in two papers published Monday, may be habitable to life as we know it.
Trappist-1e is a rocky exoplanet – a name for planets outside our solar system – that would take you 453million years by car to travel to.
While most of the other six exoplanets in the star system have proved to be barren rocks, Trappist-1e may have an atmosphere not too far off Earth’s, according to the findings in the Astrophysical Journal Letters.
Dr Ryan MacDonald, a lecturer in extrasolar planets at the University of St Andrews and one of the paper’s lead authors, said the roughly Earth-sized planet might not look like much at first glance.
But just like in the Goldilocks fairy tale, Dr MacDonald says, the planet is just the right distance from its star where ‘the temperature is not too hot and not too cold for liquid water to exist on the surface’.
‘Without an atmosphere, a planet cannot support liquid water on the surface,’ Dr MacDonald adds.
‘Earth would be a frozen ball of ice without the greenhouse effect provided by carbon dioxide, and the same is true for Trappist-1e.’
Trappist-1’s habitable zone is relatively snug, given it’s a dim red dwarf star and its planets closely orbit it. You’ll be a fair bit older if you lived on Trappist-1e – a single year on the planet is 6.1 Earth days, Nasa says.
Scientists haven’t confirmed Trappist-1e has an atmosphere but they believe it has a nitrogen-gas-rich atmosphere.
Its skies aren’t full of carbon dioxide either, meaning it’s not like the frigid desert of Mars or the toxic wasteland of Venus.
‘We are in the early stages of assessing whether Trappist-1e could support life,’ says Dr MacDonald.
‘Right now, we are trying to answer whether the conditions on the surface of Trappist-1e are hospitable to life (as-we-know-it) by measuring if the planet has an atmosphere and, if so, what gases make up the atmosphere.’
Dr MacDonald and his team examined observations of the exoplanet made by Nasa’s James Webb Space Telescope in 2023.
How did scientists figure this out?
The Webb telescope has spent years pointed at the system’s four innermost planets, which all fell into the habitable zone.
But the results haven’t been great so far – Trappist-1b and 1c have no atmosphere, and there doesn’t seem to be any Earth-like molecules in 1d’s.
The reason was rather simple, says Dr Beth Biller, of the University of Edinburgh’s Institute for Astronomy, who was not involved in the studies.
Trappist-1 is hyperactive and prone to throwing fiery temper tantrums that can strip planetary atmospheres, leaving behind ‘bare rocks’.
‘Really small stars like TRAPPIST-1 actually produce per capita a lot more X-ray and gamma ray emission than a more massive star like our Sun,’ she says.
Next on the list was 1e, but observing it is easier said than done. Researchers had to wait for the planet to pass between its star and the telescope, which ever so slightly dims the star’s light, called transiting.
This data is beamed back to the telescope as a wavelength chart.
This might not sound like much, but scientists can understand a great deal about a planet this way, explains David Brown, a senior research fellow at the University of Warwick’s Centre for Exoplanets and Hospitality.
‘If the exoplanet has an atmosphere, then some of the light from the star that reaches us during transit has passed through that atmosphere,’ he tells Metro.
‘As it does so, specific wavelengths of light will be absorbed by chemical elements in the exoplanet’s atmosphere, so that at those wavelengths the exoplanet looks larger (the size of its radius plus the height of the atmosphere), while at other wavelengths the light is unaffected, so the planet looks smaller (just its radius).
‘So, if you can observe at specific wavelengths and measure the radius of the planet at that wavelength, then you can see at which wavelengths the planet looks larger, which gives you an idea of the elements in the atmosphere.’
Astronomers have only observed Trappist-1e transiting a handful of times, so, as every expert Metro spoke with said, it’s far too early to say that Trappist-1e has an atmosphere, let alone aliens strolling around on it.
The Webb telescope is still taking snapshots of Trappist-1e, with the experts also saying that we’ll have an answer to this question one day.
Any answer we get, however, will be an interesting one. Given that the dwarf stars are so common in the cosmos, knowing that the rocky planets that tend to orbit them can cling to an atmosphere would be a big deal in the search for extraterrestrial life.
Avi Loeb, a Harvard astrophysicist, told Metro that this would raise questions about how life emerged on our pale blue dot, too.
‘If life can be supported near dwarf stars,’ he says, ‘the question arises as to why we reside near the Sun and not near a more typical dwarf star?’
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