The fate of the Sun, although it seems like a distant event, is a scientific certainty. The astronomical community has long sought to understand the exact consequences of the depletion of our star’s nuclear fuel, an event that will reshape the future of the Solar System and, consequently, the Earth.
Recently, research led by the University of St Andrews, in the United Kingdom, brought to light significant revelations, published in the renowned journal Nature. With the help of the James Webb Space Telescope, a global collaboration of scientists tracked a giant planet orbiting a white dwarf, allowing it to trace its trajectory. The findings indicate that the collapse of a star does not always mean the complete disappearance of all celestial bodies in its system.
What will the transformation of our Sun be like?
In approximately five billion years, the Sun will consume all the hydrogen present in its core. This process will mark the beginning of its phase as a red giant star, with a diameter that will exceed its current size by more than a hundred times.
Mercury and Venus are almost certain to be swallowed up, and Earth is at risk of following suit. Subsequently, the outermost layers of the Sun will be expelled into space, leaving behind only its center: a white dwarf. This object, although comparable in size to our planet, will be incredibly dense, containing approximately half the current solar mass compressed into a tiny space.
The most recent finding suggests that more distant planets, such as Jupiter, Saturn, Uranus and Neptune, have a great chance of resisting this devastating stellar transition.
Analysis of an exoplanet orbiting an extinct star
The central focus of the investigation is the giant exoplanet WD 1856 b, located approximately 80 light-years away from Earth. With dimensions similar to those of Jupiter, it has a mass between four and eleven times greater. However, what really intrigues is its extremely close orbit to a white dwarf, completing one revolution every 1.4 days, just 0.02 astronomical units (about 3 million kilometers) — a proximity that, at first glance, seemed unfeasible.
During the red giant phase, the system’s original star expanded far beyond the orbital path the planet currently occupies. If WD 1856 b had remained in this position from the beginning, it would certainly not have survived the stellar expansion.
For a long time, astronomers considered two main hypotheses: either the planet endured within the red giant’s atmosphere, or it formed in a much more distant orbit and subsequently migrated closer to the center of the system after the star’s demise.
Detailed observation from the James Webb Telescope
In their quest to unravel this enigma, scientists employed the James Webb telescope’s NIRSpec spectrograph. The tool was used during the planet’s rapid transit in front of the white dwarf, an event that lasted a mere eight minutes, highlighting the extraordinary precision required to collect such information.
Revelations about atmospheric composition
The analyzes brought a surprise: the planet’s atmosphere contains hydrocarbons, with a strong indication of methane, as well as fog and cloud formations. The data points to an exceptionally high carbon concentration. This is the first time that scientists have been able to detail the atmospheric composition of a planet that surrounds a lifeless star.
The chemical complexity detected is particularly valuable as it offers glimpses into the planet’s evolutionary trajectory. It is likely that part of these elements has been incorporated since its formation, but the hypothesis that it has accumulated carbon-rich components over billions of years cannot be ruled out.
However, the finding with the greatest impact was different. The planet exhibits a temperature of around 400 Kelvin (equivalent to approximately 127°C), a value significantly higher than the 160 Kelvin predicted if its only heat source were the faint white dwarf.
Models help reconstruct billion-year planetary history
Gas giant planets follow a cooling pattern that can be predicted throughout their existence. Using planetary cooling models, the research team traced the thermal history of WD 1856 b and determined the period in which the event that heated it occurred.
The result surprised astronomers: the planet’s warming occurred between three billion and 5.5 billion years after the main star had already completed its transformation into a white dwarf.
This data practically eliminates the theory that the planet managed to survive inside the red giant star. If this hypothesis were true, the heating process of the celestial body would have been temporally aligned with the period of stellar death.
The most accepted explanation, therefore, is that the planet remained for billions of years in a safe and distant orbit. Only after a long time, a phenomenon of planetary migration, caused by gravitational interactions, changed its route. During this displacement, intense tidal forces were responsible for generating vast amounts of heat inside.
The uncertain future of our Solar System
The revelation points out that the trajectory of a planetary system does not end with the death of its star, but can continue for billions of years. Gas giant planets that survive have the ability to change their orbits, undergo intense gravitational interactions and even move towards the remaining stellar core, long after the original star has disappeared.
Although it is uncertain whether a similar scenario will play out in our own Solar System, the existence of WD 1856 b proves that Jupiter and other gas giants could have a much longer-lasting and intricate evolution than previously thought.
For the first time in the history of astronomy, it was possible to observe and reconstruct a possible outcome for the Solar System. The conclusion is that the end of the Sun may not be a closure, but rather the starting point for a new and unexpected chapter.
