The hunt for exoplanets is getting better and better.
In fact, it's going so well that scientists just detected the signature of a faraway exoplanet's
magnetic field.
Without its magnetic field, life on Earth would be impossible, or at least a shadow
of what we know.
The Earth’s magnetic field protects its atmosphere and surface from the solar wind
and significantly impacts the evolution of life on Earth.
So the ability to detect the magnetic fields of exoplanets is a significant step toward
better understanding what these alien worlds may look like.
The disappearance of the Martian magnetic field was a major factor in the loss of atmosphere
on the planet, hence hunting for planetary magnetic fields is a fundamental aspect of
the search for life beyond our solar system.
For the first time, astronomers believe they have detected the signature of a magnetic
field in a planet outside the solar system.
Using the Hubble Space Telescope, an international team of astronomers observed the planet HAT-P-11b,
a Neptune-sized planet about 123 light-years away, pass in front of its host star six times
in what is known as a transit.
The observations were made in the ultraviolet light spectrum, which is beyond the human
eye’s ability to see.
The Hubble detected carbon ions, charged particles that interact with magnetic fields, surrounding
the exoplanet in the magnetosphere.
A magnetosphere is a region around a celestial object, like Earth, that is formed by the
object’s interaction with the solar wind emitted by its host star.
The discovery of HAT-P-11b’s magnetosphere is a significant step toward a better understanding
of an exoplanet’s habitability.
According to the researchers, not all planets and moons in our solar system have magnetic
fields of their own, and the relationship between magnetic fields and a planet’s habitat
needs to be investigated further.
HAT-P-11b proved to be a highly fascinating target because Hubble’s UV transit observations
showed a magnetic field that was seen as both an extended ion component around the planet
and a long tail of escape ions.
This general method could also be used to detect magnetic fields on various exoplanets
and evaluate their role in potential habitability.
Ballester, a primary investigator on one of the Hubble Space Telescope programs that observed
HAT-P-11b, helped to choose this particular target for UV research.
A significant discovery was the observation of carbon ions not just in a zone surrounding
the planet, but also in a long tail that streamed away from it at average speeds of 100,000
mph.
The tail reached space for at least one astronomical unit, the distance between Earth and the sun.
Researchers led by the first author of the study, Lotfi Ben-Jaffel at the Institute of
Astrophysics in Paris, then conducted 3D computer simulations to model interactions between
the planet’s topmost atmospheric regions and magnetic field with the incoming solar
wind.
Earth’s magnetic field and its immediate space environment interact with the solar
wind, which consists of charged particles traveling at about 900,000 mph.
And just like Earth, there are interactions between HAT-P-11b’s magnetic field and its
immediate space environment with the solar wind from its host star, and those are very
complex.
The physics in the magnetospheres of Earth and HAT-P-11b are similar.
However, the proximity of the exoplanet to its star, which is only about one-twentieth
of the distance from the Earth to the sun, causes its upper atmosphere to warm and basically
“boil off” into space, leading to the formation of a magnetotail.
In addition, the researchers also found that the atmospheric metallicity of HAT-P-11b,
the number of chemical elements in a substance heavier than hydrogen and helium, is lower
than expected.
The two icy gas planets, Neptune and Uranus, have high metallicity but weak magnetic fields,
while the two gas planets, Jupiter and Saturn, have low metallicity and high magnetic fields.
Therefore, the researchers claim that the low atmospheric metallicity of the exoplanet
challenges current models of exoplanet formation.
Even though the mass of HAT-P-11b is only 8% that of Jupiter, the exoplanet appears
to be more like a mini-Jupiter than Neptune.
The atmospheric system seen in the exoplanet suggests that further research needs to be
done to improve current theories regarding how exoplanets form in general.