Post by Andrei Tchentchik on Jun 22, 2019 14:08:45 GMT 2
(.#202).- A "hairy" exoplanet orbits in a strange way around its star.
A "hairy" exoplanet orbits in a strange way around its star.
By Tristan Vey - Published on 19/12/2017 at 15:34
The planet Gliese 436b does not orbit in the equatorial plane of its star, but rather passes over its poles, contrary to what this old artist's view suggests. Mark Garlick / University of Warwick.
The planet Gliese 436b describes an ellipse in a plane perpendicular to that of its star, which could betray the presence of another planet very massive but too far from its star to be detected.
The exoplanet Gliese 436b definitely combines the original features. Discovered in 2004, it was at the time the first "hot Neptune" ever discovered, a new class of exoplanets. With 22 land masses, this "little gas giant" is a little bigger than Neptune, but orbit thirty times closer to its star than the Earth of the Sun. The researchers then discover that its trajectory is not circular, but slightly elliptical. Very surprising for a planet that runs so close to its star.
In 2015, a new surprise: the planet is surrounded by an imposing "hair" of hydrogen and leaves in its wake a long tail of the same gas. Exactly like a comet, these dark ice balls that come to spray regularly passing near the Sun. In the case of Gliese 436b, the phenomenon at work is a little different a priori. It is not the sublimation of ice that gives rise to these gigantic clouds of gas, but its thick atmosphere that is gradually "blown" by the powerful X and UV radiation of its star.
But the story does not end there. Monday is an amazing new feature unveiled in Nature by the same team at the University of Geneva who discovered the "cometary" nature of this planet. Gliese 436b orbits in a plane perpendicular to the rotation of its star. It flies over the poles in short. This behavior is strange because the protoplanetary disks of gas and dust in which planets are formed are located logically enough in the equatorial plane of their star.
A hidden planet ?
Determining the direction of rotation of a star is not obvious. Researchers have studied very finely the light emitted by the star before, during and after the passage of the planet. They deduced what kind of light the planet masked as it passed. This light carries information on the speed of the stellar gas that emitted it. They found that the planet was rotating perpendicular to the plane in which the planet orbited. This technique has only been applied a handful of times. This is the most spectacular result she has achieved.
"To arrive at such a situation, we think that there is a fairly massive planet, Jupiter type, which orbits much further from its star," says Christophe Lovis, Master of Education and Research at the Department of Astronomy of the Faculty of Sciences of the University of Geneva. "It probably takes several decades to go around its star. So there is little chance that we can see it pass in front. For the same reason, it will probably be impossible to detect it by the method of radial velocities (by detecting the small movements back and forth of the star, caused by the gravitational attraction of the planet, Ed). Since this system is quite old, it is also probably too cold to be detected by direct imaging. "
F I N .
A "hairy" exoplanet orbits in a strange way around its star.
By Tristan Vey - Published on 19/12/2017 at 15:34
The planet Gliese 436b does not orbit in the equatorial plane of its star, but rather passes over its poles, contrary to what this old artist's view suggests. Mark Garlick / University of Warwick.
The planet Gliese 436b describes an ellipse in a plane perpendicular to that of its star, which could betray the presence of another planet very massive but too far from its star to be detected.
The exoplanet Gliese 436b definitely combines the original features. Discovered in 2004, it was at the time the first "hot Neptune" ever discovered, a new class of exoplanets. With 22 land masses, this "little gas giant" is a little bigger than Neptune, but orbit thirty times closer to its star than the Earth of the Sun. The researchers then discover that its trajectory is not circular, but slightly elliptical. Very surprising for a planet that runs so close to its star.
In 2015, a new surprise: the planet is surrounded by an imposing "hair" of hydrogen and leaves in its wake a long tail of the same gas. Exactly like a comet, these dark ice balls that come to spray regularly passing near the Sun. In the case of Gliese 436b, the phenomenon at work is a little different a priori. It is not the sublimation of ice that gives rise to these gigantic clouds of gas, but its thick atmosphere that is gradually "blown" by the powerful X and UV radiation of its star.
But the story does not end there. Monday is an amazing new feature unveiled in Nature by the same team at the University of Geneva who discovered the "cometary" nature of this planet. Gliese 436b orbits in a plane perpendicular to the rotation of its star. It flies over the poles in short. This behavior is strange because the protoplanetary disks of gas and dust in which planets are formed are located logically enough in the equatorial plane of their star.
A hidden planet ?
Determining the direction of rotation of a star is not obvious. Researchers have studied very finely the light emitted by the star before, during and after the passage of the planet. They deduced what kind of light the planet masked as it passed. This light carries information on the speed of the stellar gas that emitted it. They found that the planet was rotating perpendicular to the plane in which the planet orbited. This technique has only been applied a handful of times. This is the most spectacular result she has achieved.
"To arrive at such a situation, we think that there is a fairly massive planet, Jupiter type, which orbits much further from its star," says Christophe Lovis, Master of Education and Research at the Department of Astronomy of the Faculty of Sciences of the University of Geneva. "It probably takes several decades to go around its star. So there is little chance that we can see it pass in front. For the same reason, it will probably be impossible to detect it by the method of radial velocities (by detecting the small movements back and forth of the star, caused by the gravitational attraction of the planet, Ed). Since this system is quite old, it is also probably too cold to be detected by direct imaging. "
F I N .
