A giant exoplanet with a massive mass equivalent to about 13.8 times that of Jupiter was announced in 2020. Orbiting an 81-light star of the Earth, which is relatively close in astronomical terms, It is the first exoplanet known to orbit a white dwarf.
Called WD 1856+534 B, it was detected in transit, that is, passing in front of its star from our point of view, which allows its indirect observation. The discovery surprised because when a star dies, she collapses and becomes a white dwarf, a process that destroys the nearby planets.
Now, in a recent article, not yet reviewed by peers, an international team of astronomers confirmed another record: WD 1856+534 B is the coldest exoplanet ever observed . The discovery was made using the James Webb Space Telescope (MIRI) infrared instrument (MIRI).
Current observations are part of the JWST General Observation Program – Cycle 3, which corresponds to the third year of planned scientific operations of the telescope, which began in 2025. This cycle includes proposals for studies submitted by researchers and selected by scientific merit.
These measurements represent one of the main purposes of JWST’s mission, which is the use of the direct image method to characterize exoplanets. Instead of detecting them in transit (as in the discovery of WD 1856+534 b), in this technique, the telescope captures the light coming directly from the planet.
How to capture the direct light of exoplanets?
Made by spectroscopic analysis, the direct image technique of exoplanets allows astronomers to identify bioassine such as oxygen, methane and water in these distant worlds, revealing details of their composition and formation. It is expected to be close to evidence of extraterrestrial life.
For this, emission spectra provides data on planetary composition and migration history. However, capturing light directly from exoplanets remains a difficult task because of the hanging glow of host stars, which limits direct observations.
Proof of this is that, to this day, no rock planet has been observed directly close to its star, nor exoplanets with temperatures below 1.85 ° C, comparable to that of the earth. Therefore, direct images have been limited to gaseous giants with wide orbits or superquent atmospheres.
The discovery of an exoplanet orbiting a white dwarf (WD) now comes as a unique opportunity to detect cooler worlds. This is because the low light of these stars reduces the so -called “contrast challenges”, which make it difficult to observe exoplanets in the sun -like stars.
As they are “dead” as they no longer produce energy by nuclear fusion, white dwarfs also offer insights on what happens to the planets after the death of their star. Therefore, studying them reveals information about orbital stability or migration, and possible survival of the planets.
Studying surviving planets in the orbit of dead stars
Studying planets around white dwarfs can help answer one of the great questions of Astrobiology: Do these worlds survive the death of their stars? If so, scientists assess whether these systems would still continue to maintain minimal conditions for habitability.
In the current study, astronomers led by Mary Anne Limbach confirmed the existence of the WD 1856+534 B Exoplanet, with the help of James Webb. For this, they used data from the Miri instrument and analyzed the excess infrared light emitted by the planet.
With this technique, it was possible to restrict the mass of the exoplanet and measure its atmospheric temperature. The data revealed an average of 186 Kelvins, the equivalent of –87 ° C, making WD 1856+534 BO Exoplanet cooler ever detected so far.
Using more recent data obtained by JWST, the authors have refined what has been known since the original discovery of the WD 1856+534 B in 2020. The mass, for example, is smaller than it thought and is just six times the mass of Jupiter.
But the great contribution of the new study was to present the first direct evidence that the planets manage to survive the death of their stars, and even migrate to orbits near the housing zones of white dwarfs. James Webb promises new observations in 2025.
The study is hosted on the Arxiv pre-impression platform.
This content was originally published in the coldest exoplanet ever found is confirmed by James Webb on CNN Brazil.
Source: CNN Brasil
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