Astronomers confirm that an Earth-sized planet is moving through our Galaxy

Astronomers confirm that an Earth-sized planet is moving through our Galaxy

Not associated with any star or star system, what happens to the tiny planet flying carefree through interstellar space? What happens if a planet has no star system?

Scientists suspect that billions of free-flying or 'roaming' planets may exist in the Milky Way, but so far, among the roughly 4,000 worlds discovered outside our solar system, only a handful of candidates have been found.

Most of these potential rogue planets appear huge, with masses ranging from two to 40 times that of Jupiter (one Jupiter is equivalent to roughly 300 Earths). But now astronomers believe they have discovered an incomprehensible world unlike any other: a tiny, free-flying planet, roughly equal to the mass of the Earth, sweeping through the Milky Way.

The discovery, reported Oct. 29 in the Astrophysical Journal Letters, may help prove a long-standing cosmic theory.

According to the study authors, the small world may be the first real evidence that free-flying, Earth-sized planets can be among the most abundant objects in the galaxy.

(Jan Skowron / Astronomical Observatory, University of Warsaw).

“The chances of finding such a low-mass object are extremely low,” lead author Przhemek Mroz, a researcher at the California Institute of Technology, told Live Science.

'Either we are very lucky, or such objects are very common in the Milky Way. They can be as ordinary as the stars. '

Most of the planets in our galaxy are visible only because of the stars around which they revolve. In the literal sense, stars emit light that allows astronomers to directly observe alien worlds.

When a planet is too small or too distant to be seen directly, scientists can still detect it by the slight gravitational pull it exerts on its star (called the line-of-sight velocity method), or by the flicker that occurs when the planet passes in front of it (transit method).

Rogue planets, by definition, have no stars. Therefore, astronomers use an aspect of Einstein's general theory of relativity known as gravitational lensing.

Through this phenomenon, the planet (or even a more massive object) acts like a cosmic magnifying glass that temporarily deflects light from objects behind it from the Earth's perspective.

“If a massive object passes between a ground-based observer and a distant source star, gravity can deflect and focus light from the source,” Mroz explained in a statement. 'The observer will measure the short-term increase in brightness of the source star.'

The smaller this light bending object, the brighter the star will be perceived. While a planet several times the mass of Jupiter can create a lightening effect that lasts several days, a small planet with an Earth's mass will brighten the source star for only a few hours or less, the researchers said. This extremely rare occurrence is called 'microlensing'.

“The chances of observing microlensing are extremely small,” Mroz added in a statement. “If we only observed one source star, we would have to wait almost a million years to see the source under microlensing.”

Fortunately, Mroz and his colleagues have observed more than just one star in their study – they have observed hundreds of millions of them. Using observations from the Optical Gravitational Lensing Experiment (OGLE), a study of stars conducted at the University of Warsaw in Poland that has discovered at least 17 planets since 1992, the team carefully studied the center of the Milky Way for any signs microlensing.

In June 2016, they witnessed the shortest microlensing case ever seen. The star in question, located at a distance of about 27,000 light years from us in the densest part of the galaxy, has increased its brightness by only 42 minutes.

Calculations showed that the planet discovered in this way was not tied to any star within 8 astronomical units (AU, or eight times the average distance from the Earth to the Sun), which suggests that it is almost certainly a tiny planet thrown out of its solar system.

Depending on how far the planet is from the source star (this is impossible to tell with modern technology), the rogue world will have a mass between half and one Earth. According to Mroz, this is a 'huge milestone' for science.

“Planetary theories predict that most free-flying planets should be Earths or less, but this is the first time we've found a planet with such a low mass,” Mroz said.

“It's really amazing that Einstein's theory allows us to detect a tiny piece of rock flying through the galaxy.”

Article published by Live Science.

Sources: Photo: (Jan Skowron / Astronomical Observatory, University of Warsaw).

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