Hidden within the infinite space of the universe, there are countless numbers of celestial bodies that are drifting indefinitely across the Earth without our knowledge. These mysterious celestial bodies are known by astronomers as “wandering planets”, or “rogue planets” (Rogue planet).
Unlike normal planets that orbit a host star, wandering planets are not bound to any star. Like ghosts, they are drifting indefinitely in empty space, belonging to nothing but darkness.
A recent study found that more than one hundred billion wandering planets exist in the Milky Way. However, out of 4000 exoplanets discovered to date, only a very small number of wandering planets have ever been found.
Due to their floating in interstellar space, where the light from the stars is not strong enough to reach, the wandering planets are difficult to detect using conventional observation methods.
The discovered wandering planets themselves are enormous, with masses between 2 and 40 times that of Jupiter (Jupiter has 300 times the mass of the Earth).
But now astronomers believe they have discovered a wandering planet about the size and mass of Earth that is drifting indefinitely in the Milky Way. According to the team, this tiny world could be the first evidence that a huge number of Earth-sized wandering planets exist in the Milky Way.
“The rate of detecting such a low mass object is extremely low,” said Przemek Mroz, the study’s lead author.
“Either we have been very lucky, or such celestial bodies are very common in the Milky Way. They are as many as stars.”
Use Einstein’s ‘magnifying glass’ to detect the wandering planet
When an exoplanet is too small or too far to be directly observed, scientists can detect these planets from the light gravitational force it exerts on the host star (called the method radial velocity, or through transit signal technology, which measures the changes in light as exoplanets pass through their host star.
However, the detection of wandering planets by the two methods above is very difficult. Because they are floating in interstellar space, where the light from the stars is not strong enough, planets like ‘ghost’ are difficult to detect.
Thus, the researchers used a technique called “microlensing”, which measures the distortion of light as one star passes in front of another when viewed from the left. land.
Seen from Earth, a wandering planet bends the light of the star behind it
Accordingly, the light from a distant star will be amplified under the influence of the gravitational force of a massive object, such as a planet, according to Albert Einstein’s general theory of relativity. Astronomers will measure the distortion of light to get a closer look at celestial bodies passing by the star, including the wandering planets.
Worth mentioning, astronomers have little chance of searching for planets that roam by this method, because “microlensing” is very rare in the universe.
“The chances of seeing microlensing are extremely small. If we observe only one star, we will have to wait nearly a million years for this phenomenon to happen,” said astronomer Przemek Mroz.
Fortunately, Mroz and his colleagues did not observe a single star. Instead, they are tracking hundreds of millions of stars in the central region of the Milky Way for any signs of “microlensing”.
In June 2016, they discovered the shortest microlensing event ever observed in the center of the Milky Way, about 27,000 years from Earth.
Located in the densest part of the galaxy, a star has lit up in 42 minutes. This shows that some celestial body is passing through this star. Calculations show that this object is not bound to any host star within 8 astronomical units (AU, or eight times the average distance from Earth to the Sun).
This shows that this is a small exoplanet wandering through space, after being ‘shot’ out of their star system after an event. According to the team, it is a “big milestone” for the science of planet formation.
“Planetary formation theories have predicted that the majority of free-floating planets should have mass equal to Earth or less, but this is the first time we have ever found a planet with such low volume, “said the representative of the research team.
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