Friday, January 21, 2022

A tiny, incredibly dense exoplanet has just been discovered and is really close

A completely eccentric newly discovered exoplanet was discovered orbiting a star just 31 light years away.

It is called GJ 367b, and it is one of the smallest exoplanets ever discovered, slightly larger than Mars; but also one of the most compact, almost as dense as pure iron. In addition, it is insanely close to its host star, completing a full revolution in just eight hours.

Astronomers have yet to figure out how this planet might have formed, but they believe its discovery is important.

“Based on the precise definition of its radius and mass, GJ 367b is classified as a rocky planet,” said astronomer Christine Lam of the Institute for Planetary Research at the German Aerospace Center.

“It looks like it bears a resemblance to Mercury. This places it among the Earth-sized terrestrial planets and takes research one step further in search of a ‘second Earth’. “

The way we hunt exoplanets leads to certain biases in what we ultimately find; we have two main methods. The transit method is based on looking for very small dips in starlight as an exoplanet moves (or passes) between us and its star.

This tends to favor large exoplanets in close orbits, as a large exoplanet will result in more stellar fall (known as a light curve) and will more often pass in front of the star, which confirms a periodic orbit and allows astronomers to more accurately characterize this orbit.

The radial velocity or wobble method is based on changing the wavelength of light from a star, since the gravitational pull of a rotating exoplanet makes it move very little. Again, the more massive the exoplanet, the stronger the signal. Smaller exoplanets that generate less signal are more difficult to detect.

By all accounts, the discovery of the GJ 367b was accidental. Because it is so close (31 light years is pretty close, from a cosmic point of view), its passage was detected by the TESS space telescope, designed to hunt for exoplanets. TESS stares at regions of the sky for a long time, looking for precisely these dips in the starlight.

Falls can tell us how big a transiting exoplanet is; So a group of researchers found out that the diameter of the exoplanet is just over 9000 kilometers.

The scientists then used the line-of-sight velocity method to see how much the exoplanet’s gravitational pull affects the star. This allowed them to calculate the mass of GJ 367b and therefore its density at 8.106 grams per cubic centimeter. The density of the Earth is 5.51 grams per cubic centimeter; iron is 7.874 grams per cubic centimeter at room temperature.

This may tell us something about the composition of the exoplanet, since we have something very similar right here in the solar system.

“The high density indicates that the planet is dominated by an iron core,” said astronomer Szilard Chizmadia of the German Aerospace Center. “These properties are similar to those of Mercury, with its disproportionately large iron and nickel core, which distinguishes it from other terrestrial bodies in the solar system.”

To be clear, it is impossible that GJ 367b could be a second Earth. Despite the fact that it orbits a red dwarf star with a mass of about half the mass of the Sun – a star of a much colder type – its close proximity means that the exoplanet is tidally blocked, one side is always facing the star, and is exposed to absolutely scorching radiation. On the daytime side of the exoplanet, temperatures will be somewhere between 1300 and 1500 degrees Celsius (2372-2732 degrees Fahrenheit).

This is not a habitable climate.

But the very discovery of GJ 367b could lead us to other worlds that could very well be more hospitable.

“For stars of this class, the habitable zone will be somewhere between two to three weeks orbits,” said astronomer George Reeker of the Massachusetts Institute of Technology Institute of Astrophysics and Space Research at MIT.

“Because this star is so close and so bright, we have a good chance of seeing other planets in this system. It looks like a sign that says, “Look for additional planets here! “”

Team research published in The science

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