An exoplanet so close to its star that its surface is a sea of magma has just become a study that may reveal how these complex worlds exist.
The “world of hell” in question is called 55 Cancri e (aka Janssen) and a new analysis of its orbit and the paths of other exoplanets that orbit the star shows that Janssen may have made it very far from the star, moving slowly towards it. over time and dissolved in the process.
“We’ve learned how the multiplanetary system — one of the most multiplanetary systems we’ve ever discovered — got into the way it is,” says astronomer Lily Zhao of the Flatiron Institute in New York.
All planets have their problems, but the Copernicus system, which is 41 years away (closer to the nearest door), has its own problems. Besides Janssen, five exoplanets orbit the star: Galileo, Brahe, Harriot, and Lipperhey, all of which are much further away from Copernicus than their mysterious cousin.
With its closest orbit, Janssen orbits the star, named Copernicus (the orange branch slightly smaller than the Sun), about once every 18 hours. It is 1.85 times the length of the earth and 8 times its circumference. This means that it is slightly closer to Earth and could be a Super-Earth at a greater distance from its star.
But it is not. Of course not.
The temperature of the side facing the star is 2,573 Kelvin (2,300 degrees Celsius, or 4,172 degrees Fahrenheit), and at night looking away 950 Kelvin. It is much hotter and higher than molten magma.
What Janssen is like inside is anyone’s guess, but research shows that its interior is very different from rocky worlds in our Sun.
We have very little data to collect on exoplanets, even the closest ones to the Copernicus system, so to find out how Janssen got there, Zhao and his team began measuring the orbits of five orbiting exoplanets. stars.
We already knew that Janssen’s method was different from the other four. That’s because there are two main ways we can identify exoplanets based on how they interact with their star.
The first is a transit, when an exoplanet passes between us and a star, it dims its light a bit. Constantly drenched in starlight probably means the surrounding sky.
The second is the radial velocity. This is related to gravity. Every planet orbiting a star has a gravitational force. Gravity is not as strong as a star’s, of course, but it causes the star to “wobble” a little on the spot.
This is reflected in the change in the wavelength of the star’s light: a little stretching when the star is moving away from us (redshifted) and compression when the star is moving towards us (blueshifted).
All five Copernicus exoplanets were detected by radial velocity, but later observations confirmed that Janssen and Galileo were the only ones observed to be moving.
This means that it is possible that the two are not on the same orbital plane as Brahe, Harriot, and Lipperhey, and Galileo’s journey is so difficult that astronomers have failed to measure its height and temperature, so it is not shared with Janssen. or orbital plane.
Researchers discovered more about Janssen’s method. When a star rotates, the light coming from the direction it is rotating towards us is bent a little, and the light coming from the direction it is rotating is stretched a little. Using a powerful new instrument, the EXtreme PREcision Spectrometer (EXPRES) at the Lowell Observatory in Arizona, the team can see the movement of Janssen across the star, from the blue side to the red, following its path with great precision.
This revealed that the exoplanet follows a path around the star’s equator. Previous studies have found that Copernicus’ companion, a slightly redder one, may have disrupted the system, pulling exoplanets into an orbital plane that is focused from the star’s orbit.
Zhao and his colleagues believe that interactions between exoplanets may push Janssen into a decaying orbit around the star, bringing it closer. Because Copernicus orbits, it collapses a bit, creating a small hole around the equator, where gravity is strongest. The exoplanet, naturally, was drawn to this region.
It is possible that Galileo is doing the same on the shorter 14.7 day orbit, although further observations will be needed to determine this. (Brahe has an orbit of 44.4 days, Harriot 260 days, and Lipperhey 5,574 days.)
This work presents a method for studying the history of exoplanets in close orbits with their stars.
Of particular interest are exoplanets called hot Jupiters: gas giants with orbits of less than a day. These worlds present an interesting paradox because they are too close to their stars to allow the formation of a dense atmosphere. Inward migration is one way these bright exoplanets can get very close to the star.
This work shows that the model can be transparent.
“The spin-orbit coupling of [Janssen] the researchers write, “they prefer the deep belief of long-term planetary migrations,” meaning that the termination of the tides is due to global incompatibility and/or planetary tides.
Research has been published in Nature Astronomy.
