An Abu Dhabi scientist was part of a team of researchers who mapped temperatures on a planet 400 light years away – and found that some areas are as hot as 3,500°C.
Dr Jasmina Blecic, from New York University Abu Dhabi, and her fellow researchers produced what is described as the first three-dimensional temperature map of an exoplanet – a planet that orbits a star other than the Sun.
The work on an exoplanet called Wasp-18b, described in a new paper in Nature Astronomy, forms part of wider efforts to better understand the universe and to develop techniques to study potentially habitable worlds.
Temperatures on exoplanets can vary wildly. The coldest known exoplanet experiences temperatures as low as minus 223°C, with the hottest topping 4,000°C.
While Wasp-18b itself is unsuitable for life, Dr Blecic, who is part of NYU Abu Dhabi’s Centre for Astrophysics and Space Science, said analysis of exoplanets could indicate which ones may be home to life.
“What motivates us when we study exoplanets is to answer the question, ‘Are we alone? Are there habitable planets out there?’” Dr Blecic told The National.
To help find answers, the first thing that scientists must understand, Dr Blecic said, is the temperature of the planet. “We expect the habitable planets that host life will have temperatures similar to what we have on Earth, which allow water to be liquid,” she added.
Too hot to handle
Although some other exoplanets may be habitable, Wasp-18b unquestionably is not: it is far too hot to have liquid water and it is purely gaseous. “It is not just that the temperatures are not appropriate for life to evolve in the form that we know it. The planet also should have a solid surface to be habitable,” Dr Blecic said.
Indeed, while there is some water vapour in the planet’s atmosphere, the temperatures are so extreme that most water molecules have been split into their chemical components, namely ions.
Dr Blecic and her co-researchers believe these charged particles move between north and south in the planet’s atmosphere, a consequence of Wasp-18b having a very strong magnetic field.
Wasp-18b’s temperatures are so high because it orbits its star 20 times closer than Mercury orbits the sun, forcing the planet to be, like our moon, tidally locked. This means a full rotation and a full orbit take the same length of time, so the same side always faces the larger planet.
Some areas of Wasp-18b are as much as 2,000°C cooler than others, with the variation depending on how much exposure to the star that part of the planet receives.
Producing a three-dimensional temperature map of an exoplanet is important because, Dr Blecic said, the temperature heavily dictates what conditions on the planet are like, in terms of both the climate and the atmosphere’s chemical composition.
The map was created from data from Nasa’s James Webb Space Telescope by a technique called 3D eclipse mapping, which involves measuring light changes associated with different parts of the atmosphere as a planet moves behind its star.
Analysing these variations in wavelengths allowed researchers to create a map showing how temperature varies with latitude, longitude and altitude.
Unravelling mysteries of the universe
There are thousands of known exoplanets and the researchers say their 3D mapping model could be applied to many of them.
Scientists have been observing Wasp-18b since 2009, but the quality of the data from the James Webb Space Telescope far exceeds that from previous analysis.
More than two years ago, again using data from the James Webb Space Telescope, Dr Blecic and her co-researchers revealed that they had found water on Wasp-18b.
This indicated to the scientists that they would also be able to detect water on other exoplanets, including some that might be habitable.
Despite being gaseous, Wasp-18b is very dense, with a mass that is about 3,000 times of Earth, even though its radius (the distance from the centre to the surface) is only about 10 times that of Earth. It is one of the densest planets that Dr Blecic and her colleagues have analysed.
Although the distance from Wasp-18b to Earth, at about 400 light years, is difficult to comprehend, given that light travels at just under 300,000km per second, it is tiny in relation to the universe as a whole.
Our galaxy, the Milky Way, is about 100,000 light years across, while the observable universe stretches to about 94 billion light years.
As well as Wasp-18b, Dr Blecic has previously published findings on a planet called Wasp-39b, which is around 700 light years away and is notable for being the first exoplanet where carbon dioxide has been detected in the atmosphere.
