A new study using a powerful JWST telescope has identified a planet 41 light years away that could have an atmosphere. The planet is located within a “household zone” and in the area around the star, liquid water can be present on the surface of a world filled with rocky temperatures. This is important because water is an important ingredient that supports the existence of life.
If confirmed by further observation, this is the first rocky habitable zone planet known to host the atmosphere. Findings come from two new studies published in the Journal Astrophysical Journal Letters.
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However, exoplanets that can host liquid water (a world that orbits stars outside our solar system) often require an atmosphere with sufficient greenhouse effect. The greenhouse effect generates additional heating for absorption and release from gases in the atmosphere, helping to prevent the evaporation of water into space.
With an international team of colleagues, we trained the largest telescope in the universe, the JWST of NASA, on a planet called Trapist-1 e. I wanted to determine whether this rocky world in the habitable zone of the stars has an atmosphere. This planet is one of seven rocky worlds known to orbit the small, cool “dwarf” star called Trapist-1.
Rocky exoplanets are all around our galaxy. The discovery of abundant rocky planets in the 2010s by Kepler and Tess’ space telescopes has had a major impact on our location in space.
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Most of the rocky exoplanets we have discovered so far are red dwarf stars (usually 2500°C/4,500°F compared to the Sun’s 5,600°C/10,000°F). This is not because planets around stars like the Sun are rare, but just because there is a technical reason why it’s easy to find and study planets orbiting small stars.
The red dwar star also offers many advantages when trying to measure the properties of a planet. Because the stars are cool, habitable zones where temperatures are preferred for liquid water are located much closer to the solar system, as the sun is much hotter. Therefore, a year on rocky planets with Earth’s temperature orbiting red stars is several days to a week compared to Earth’s 365 days.
Transit method
One way to detect an exoplanet is to measure the slight dimming of light as a planet passes or passes in front of it. Planets that put orbit into orbit take time to complete orbit. Astronomers can observe more passages in a shorter time and make it easier to collect data.
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During transport, astronomers can measure absorption from the planet’s atmosphere (if there is one). Absorption refers to the process by which a particular gas absorbs light at different wavelengths and prevents it from passing through. This provides scientists with a way to detect which gas is present in the atmosphere.
Importantly, the smaller the stars, the greater the proportion of light is blocked by the planet’s atmosphere in transit. Therefore, the red star is one of the best places to search for the atmosphere of rocky deplanets.
Located relatively close to 41 light years from Earth, the Trapist-1 system has been attracting a lot of attention since its discovery in 2016. Three planets, Trapist-1D, Trapist-1E, and Trapist-1F (3rd, 4th and 5th planets from the star) are located within the habitable zone.
JWST has been doing systematic searches of the atmosphere on the Trapist-1 planet since 2022. The results of the three inner planets, Trapist-1B, Trapist-1C, and Trapist-1D, show that these worlds are bare rocks with a thin atmosphere at best. However, planets attacked with less radiation and energy flare from the stars could potentially have an atmosphere.
We observed Trapist-1e, a planet located in the heart of the star’s habitable zone. This will be separate from the JWST between June and October 2023 on four occasions. Our data have found that the high and low temperature active regions of TRAPTIST-1 (similar to solar power generation) are strongly influenced by what is called “stellar contamination.” This required careful analysis to address it. In the end, it took me over a year to sift through the data and distinguish the signals coming from the stars from planetary signals.
There are two possible explanations of what is happening in Trapist-1E. The most exciting possibility is that planets have so-called secondary atmospheres containing heavy molecules such as nitrogen and methane. However, the four observations we have obtained are not accurate enough to eliminate alternative explanations of planets, bare rocks with no atmosphere.
If Trapist-1e actually has an atmosphere, it’s the first time I’ve found an atmosphere on a rocky planet in a habitable zone on another star.
Trappist-1e is firmly present in habitable zones, and a thick atmosphere with ample greenhouse effect can provide liquid water on the planet’s surface. To establish whether Trapist-1E is habitable, the concentration of greenhouse gases such as carbon dioxide and methane must be measured. These initial observations are an important step in that direction, but if Trapist-1E has an atmosphere and if so, more observations by JWST would be required to measure the concentration of these gases.
As we speak, 15 more Trapist-1E transits are ongoing and should be completed by the end of 2025. Follow-up observations use another observational strategy that targets consecutive transits of Trapist-1B (which is a bare rock) and Trapist-1E. This allows you to use exposed rocks to better “push out” the hot, cold, active areas of the stars. The excess absorption of gas seen only during the passage of trappist-1e is uniquely caused by the planet’s atmosphere.
Therefore, within the next two years, we need to take a much better photo of how Trapist-1E will be compared to the rocky planets of the solar system.
This edited article will be republished from the conversation under a Creative Commons license. Please read the original article.
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