The search for a second Earth somewhere in the Milky Way continues, but the newly discovered world is far from complete.
The star comes with about 1.9 times the mass of Earth and orbits it at about twice the distance from the sun as Earth…but the star is a white dwarf, which means it could have been on an exoplanet. This means that sexual life probably disappeared during the Great BC or AD. The death throes of a red giant star.
However, this finding is nevertheless exciting. It’s like looking into the future of our solar system and the fate of Earth after the sun dies and completes its own evolution into a white dwarf star.
And this study, led by University of California astronomer Kemin Zhang, shows a possible way to discover it. phenomenon Known as microlensing – finding hard-to-find Earth-like worlds elsewhere in the galaxy.
White dwarfs change when a star like our Sun dies. It runs out of hydrogen fuel to fuse within its core, becomes less stable, and grows larger. This is the red giant phase.
Eventually, the star will completely eject its outer material and the core will collapse under gravity to form a dense object. That bright light is not produced by nuclear fusion, but by the residual heat of the decay process. Its hot core is a white dwarf star, which takes trillions of years to cool to complete darkness.
The red giant phase is pretty crazy. A star’s outer atmosphere can expand hundreds of times its initial size. Some predictions about the Sun’s future predict that it will begin to become a red giant in about 5 billion years or so, but could grow to a size large enough to outrun the Sun’s orbit. Mars,swallow mercury, Venusand the Earth in the process.
We don’t know what this means for the planet. Its destruction is possible. But the new discovery of an Earth-like world orbiting a white dwarf suggests that survival is an option.
“The simplest explanation is that the planet survived through a red giant host star,” Zhang told ScienceAlert.
This system was discovered due to an anomaly in gravity and the position of objects in space known as microlensing. The white dwarf system is approximately 4,200 light years away. About 26,100 light-years away, very large and bright stars lined up for a moment along the same line of sight from Earth.
As light from more distant stars passes through the white dwarf, its path is bent by the gravitational field, creating a magnifying effect.
“During the event, the lens of the white dwarf was almost perfectly aligned with the background source star, resulting in a magnification of more than 1,000 times,” Zhang explained.
“In these rare, very high-magnification microlensing events, companion stars as small as terrestrial planets can have a large effect on the magnification pattern, allowing us to accurately infer the lensing configuration over a wide range of masses and orbital spacings.” It will be.”
This allowed the researchers to determine not only the masses and orbital spacings of Earth-like or Earth-like exoplanets, but also the presence of brown dwarfs orbiting white dwarfs. Jupiter.
It’s a weird thing in between, too big to be a planet but too small to be a star. It is large enough to fuse deuterium at its center, but not large enough for the hydrogen fusion that defines a star.
The white dwarf’s mass is about half that of the Sun, suggesting that it was originally quite close to the Sun’s mass before being eviscerated. And the current orbital distance between terrestrial exoplanets and white dwarfs is similar to the distance between Earth and white dwarfs, which was once roughly the same as the distance between Earth and the sun, before being pushed further away as stars died. This suggests that it was in an astronomical unit.
“The planet’s current orbit is 2.1 astronomical units, around where Earth is expected to be found after the sun becomes a white dwarf,” Zhang told Science Alert.
“Models currently disagree on whether Earth can avoid being engulfed because the Sun’s mass loss rate in red giant stars is not known precisely enough. Our findings therefore , suggests that some of the models predicting Earth’s survival may be too pessimistic.”One day, Earth may narrowly avoid being engulfed like the star systems we discovered. . ”
By the time the Sun’s red giant phase begins, life on Earth will have long been extinct or changed dramatically. The sun is getting hotter and brighter over time, but not so much that we notice it right now. About 1 billion years laterhot enough that all the water on Earth evaporates. The world left behind will be extremely inhospitable to life as we know it.
But perhaps by then we’ll have found a way to make a living elsewhere.
“When the Sun becomes a red giant, the habitable zone will move around Jupiter, Saturnmany of these moons will become ocean planets. ” Zhang said.. “In that case, I think humans could migrate there.”
The team’s research natural astronomy.
