We already knew about the ability of the James Webb Space Telescope to record unprecedented images, both deep sky as of our planets neighbors in the Solar System. But it is not only capable of obtaining these instants: it was also designed to analyze the infrared emission of objects cold very distant. For example, extrasolar planets or exoplanets.
After studying the emission spectrum of the exoplanet VHS 1256b (located 40 light years from Earth and 19 times more massive than Jupiter), an international team of researchers has come to the following conclusion: this giant extrasolar planet contains grains of sand in its atmosphere, as well as water, methane, and carbon monoxide.
This is the first time that it will be possible to identify such a large number of molecules on a planet outside the Solar System at the same time.
Before commenting on the new results, let’s delve into the world of extrasolar planets.
Beyond the Solar System
Since school we study the planets of the Solar System (even sung their namesordering them according to their proximity to the Sun).
Of this select group of eight (Pluto came to be considered a dwarf planetalthough still there is controversy), four are rocky planets (Mercury, Venus, Earth and Mars) and the other four, the furthest from the Sun, are gas giants (Jupiter, Saturn, Uranus and Neptune). In ancient times they were called wandering starsbecause its position in the firmament was not constant as in the case of the fixed stars.
Although astronomers assumed the existence of planets outside the Solar System, it was not until October 6, 1995 that the first exoplanet was discovered, orbiting a main sequence star. Its about exoplanet 51 Pegasi blarger than Jupiter and revolving around the helvetii starabout 50 light years from us.
The findings did not stop increasing. For example, the super earth Gliese 876 d (one of the first terrestrial exoplanets) and the TRAPPIST-1 planetary system.
The image above is curious: seven rocky exoplanets (similar in size to Earth) orbit around a red dwarf star. As a significant fact, the distance of these planets from their star is much less than that of the planet Mercury from the Sun.
United Nations year on the farthest planet (TRAPPIST-1h) it lasts 18.8 Earth days, while the closest one (TRAPPIST-1b) completes a revolution in just 1.5 days.
Precisely, a recent study of TRAPPIST-1b (based on infrared emission data collected by James Webb) shows an exoplanet no significant atmosphere with a temperature of up to 230 degrees Celsius on its day side.
Until the year 2022 NASA had about 5000 confirmed exoplanets out of the hundreds of billions that our galaxy can host. Recently, the discovery of exoplanet TOI 700e (similar in size to Earth and within the so-called habitable zone) has gained importance, as it could host liquid water on its surface. are the planets perfect for the development of life as we know it.
But how have astronomers been able to detect these exoplanets?
Methods to detect exoplanets
It is likely that we have in mind an image of a planet in the Solar System captured by powerful terrestrial or space telescopes (capable of capturing the light reflected by such objects). cold). For example, in this snapshot of Jupiter taken by the hubble space telescope (and recorded in the visible, infrared, and ultraviolet) unprecedented detail of this gas giant can be seen.
The problem with this detection method direct lies in the difficulty of capturing the dim light reflected by a distant exoplanet (where, in most cases, they were dazzled by the parent star).
Still, astronomers have been able to photograph an extrasolar planet (2M1207b) orbiting around its star (2M1207).
On the other hand, there are indirect detection methods widely used in astronomy. Two stand out:
Radial speeds: based on the speed variations of a central star due to the gravitational effect of a planet (in principle, invisible) orbiting around it. This method has been very useful for detecting larger exoplanets close to their central star.
Transits: consists of observing the decrease in the intensity of light from a star when an exoplanet orbits in front of it. It has also been very successful in finding large extrasolar planets.
The turbulent exoplanet VHS 1256b
Returning to our exoplanet VHS 1256b, this gas giant orbits its two stars at four times the distance that Pluto does around the Sun, completing one revolution in about 10,000 years.
Consequently, the light emitted by its atmosphere will not mix with that of its parent stars. This allows very reliable results of its composition and dynamics to be obtained.
On the other hand, Webb has not analyzed this planet using the indirect methods described above. Instead, he has recorded the emission spectrum of its turbulent atmosphere (reaching temperatures of 815 ⁰C) using two of the instruments aboard it.
In this way, the graph of the upper figure shows the radiation emitted by VHS 1256b, against the infrared wavelengths in which the NIRSpec instruments operate (horizontal axis, from 1 to 5 microns) and MIRI (from 5 to 28 microns).
It is notorious that, for specific ranges of wavelengths, the curve presents emission maxima (associated with the different chemical compounds present in the exoplanet’s atmosphere). In particular, James Webb has been able to identify water, methane, carbon monoxide, and silicates in the atmosphere of VHS 1256b.
The presence of these larger silicate grains is what the scientists behind this finding classify as very hot sand particles. On the other hand, the finer grains could resemble tiny particles in the smoke.
This is the largest number of molecules identified at the same time on an extrasolar planet (due to the wide range of infrared wavelengths that the NIRSpec and MIRI instruments can measure).
Will the James Webb be able to detect other molecules such as oxygen or carbon dioxide in the atmosphere of very distant planets? It is almost certainly a question of timing.