For the first time, astronomy discovered a planet with half of its hemisphere in eternal darkness

Imagine if this happened to Earth, Americans would have to go to Vietnam just to see the Sun.

In a new report published in The Astrophysical Journal, scientists provide the clearest evidence to date of the possibility of a planet with two hemispheres immersed in eternal light/darkness.

This phenomenon is named by experts as ' tidal synchronization ', roughly translated as ' tidal synchronization ' or ' 1:1 tidal locking ', roughly translated as ' 1:1 tidal locking ' . According to astronomers, many exoplanets (planets outside the Solar System) are also 'trapped' like that , including many planets that are believed to be able to support life.

' What was still a hypothesis has now become more real than ever. It turns out that this is the appearance of planets of this type ,' said Nicolas Cowan, study co-author, an astronomer working at McGill University, Canada.

Half-dark illustration of planet LHS 3844b - (Photo: NASA/JPL-Caltech/R. Hurt)

Two sides of one planet

When a planet orbits very close to the system's central star, the planet's near-star half will experience a much greater gravitational pull than the other half. Over time, the imbalance will cause the planet's rotation speed to slow until its orbit is fully synchronized. The scientific community has another name used to refer to the force that creates this phenomenon, which is 'tidal force'.

When synchronization occurs, the time it takes a planet to complete one revolution around its axis will be equal to the time it takes to complete an orbit around the central star. In fact, scientists believe that our Moon is influenced by tidal forces created by the Earth, so the other half of the Moon never points towards the Earth.

The vast majority of us have never seen the "back" of the Moon - (Photo: Shutterstock).

As for the long list of exoplanets, many of them are located so close to their central star that scientists think they are tidally locked . However, until now, we still have no evidence to prove that. Modern instruments can easily observe a planet's stellar rotation, but its axial rotation is much more difficult to observe, especially when the atmosphere can obscure the planet's surface.

To find evidence of tidal locking, researchers turned their eyes to planets located very close to their central star. One such effort came in 2019, when the Spitzer Space Telescope pointed toward LHS 3844b - a super-Earth orbiting the red dwarf star LHS 3844 located 48.5 light years away.

Researcher Cowan and his co-authors realized that they could determine the temperature of LHS 3844b's Earth-facing surface, because the exoplanet has no atmosphere.

Planets that are not tidally locked will heat up due to a conflict between their ability to rotate on their axis and the tidal forces generated by the central star . The team found that the surface of LHS 3844b is quite cool, satisfying one of the signs of a tidally locked planet.

The most convincing evidence to date

' This is the clearest evidence we can get, based on the information we have and the equipment we have ,' said Emily Rauscher, an astrophysicist at the University of Michigan. , speak.

Another researcher disagrees with the assertion that LHS 3844b has no atmosphere. Ms. Emily Whittaker cited a scientific report she co-published in 2022, pointing out that LHS 3844b possesses a very thin layer of atmosphere. However, Ms. Whittaker agrees that the evidence presented by Cowan and colleagues is highly convincing that LHS 3844b is tidally locked.

Planet LHS 3844b, nicknamed Kua'kua and star LHS 3844 - (Photo: Space Telescope Science Institute).

According to researcher Cowan, future data from the James Webb Space Telescope (JWST) will soon provide more evidence that LHS 3844b has half of its hemisphere in darkness . Originally, JWST allowed astronomers to study a planet's rotation around its axis.

As for the question of whether LHS 3844b can support life, researcher Cowan could not comment. According to him, planets of this type ' have no tides, no seasons, no day-night cycle ', so it is unclear whether they can support the evolutionary capacity for ' diverse and complex life'. as complex as that of Earth.