Image source, Getty Images
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- Author, Jonathan O’Callaghan
- Role, BBC Future
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2 hours ago
The sight of auroras, magical lights that usually appear in the Arctic and Antarctic skies, is also found on other planets in the Milky Way Galaxy and outside the Milky Way. These findings provide astronomers with valuable new insights into this alien world.
The rays of light seemed to dance, moving from one shadow to another. The view is similar to the polar lights in the Arctic Circle. But this light is not on Earth, but on the planet Uranus.
Uranus is a planet in the solar system whose auroras have been studied in detail recently. Researchers at the University of Leicester, England, recently detected infrared aurora on the giant ice planet.
“We analyzed the planet for six hours to see if there were any variations in its infrared emission,” said Emma Thomas, the study’s lead researcher and a PhD student studying planetary auroras at the University of Leicester.
“We saw the peak of a very bright glow, which indicates the presence of aurora emissions,” he continued.
Although it cannot be seen by the human eye, a space probe passing around the poles of the planet Uranus captured another aspect of the aurora that shines there. It shows that the light produced alternates from ultraviolet to infrared, as well as radio waves.
However, this planet is not the only one that has auroras. Auroras on planets in our solar system appear to be quite common.
The eight main planets orbiting the Sun also display some kind of aurora, whether caused by magnetic fields or activity on their surfaces.
Observations of other solar systems also suggest the possibility of similar auroras.
For astronomers who detect these alien light shows, their presence can provide valuable insight into the world where they radiate, including about the aurora borealis and aurora australis on our planet.
Image credit: NASA/Getty Images
Caption,
Aurora-like light was seen on the planet Jupiter on December 19, 2000, which was captured by the Hubble Telescope
On Earth, auroras appear due to the interaction of magnetic fields with electrically charged particles from the Sun. When these particles traveled 149 million kilometers to our planet, they were trapped by magnetic fields that directed them towards the poles.
These particles then collide with atoms and molecules in the Earth’s atmosphere, producing a dramatic curtain of light, which we call the northern lights or southern lights.
Its dramatic color variations, and its long, visible wavelengths, depend on the interaction of atoms with a barrage of particles from the sun.
Atoms absorb energy from these encounters and release it at certain wavelengths of light.
Nitrogen, the most abundant gas found in our atmosphere, produces predominantly blue light. Meanwhile, oxygen produces green light.
The height of the point where the particles meet can also have an effect. Red light will appear when high-energy particles collide with oxygen atoms at an altitude of 200-500 kilometers above the Earth’s surface, while green light is released at an altitude of 100-250 kilometers. Pinks and purples appear at lower elevations.
On Uranus, the most abundant gases in the atmosphere are hydrogen and helium so the auroras are a little different. Auroras on Uranus are invisible to the human eye because they shine in the electromagnetic spectrum.
Ultraviolet and radio aurora on this planet were first discovered by NASA’s Voyager 2 spacecraft in 1986 during a flyby. However, the infrared aurora was not detected at that time.
This latest finding could be very valuable scientifically. The atmosphere at the top of Uranus is much hotter than researchers expected for a planet so cold and far from the sun.
Space probes that passed there showed that the temperature ranged between 220-420C, much hotter if this planet only depended on the heat of the Sun and when compared to its neighbor, Saturn, which is larger.
The latest findings suggest that the condition may be the result of heat radiated to the planet by auroras.
“Now that we can see the infrared aurora, we can start to figure out how it works,” Thomas said.
Image source, Getty Images
Aurora Uranus can also add important insight regarding the features of the Earth’s magnetic field, that the Earth’s magnetic field often reverses direction.
In the last 20 million years, the magnetic field has reversed about three to five times every million years, switching the magnetic pole north to south and vice versa (this is not a cycle, and it has been more than 780,000 years since the last reversal. Even in the Cretaceous, the magnetic field The Earth has not flipped at all for 37 million years).
Predicting when the next geomagnetic reversal will occur and what impact it will have on Earth is extremely difficult. However, Uranus, which has a strange orbit on its side and relative to its motion around the Sun, may provide some clues. This is because its magnetic field experiences a rotation that is much different from that of Earth.
“The big question is what happens when that reversal occurs?” Thomas said.
“Should we expect the magnetic field to vary, stronger, weaker, and how would that affect the satellite? Uranus is the right planet to observe that kind of thing.”
Although the magnetic field itself is not visible, the aurora rings around the poles make it possible to study how the magnetic field changes.
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However, Uranus is not the only other planet that has auroras.
The first aurora seen from another planet was on Jupiter. It was seen through radio wave observations in the 1950s, then by Nasa’s Voyager 1 spacecraft in 1979.
Auroras have been seen dancing at Jupiter’s poles by several telescopes since then, including the Hubble Telescope, and the James Webb Telescope.
“We’re seeing things we’ve never seen before,” said Henrik Melin, a planetary researcher at the University of Leicester who led the James Webb Telescope’s observations, including the structure of the planet’s upper atmosphere.
We also saw auroras in Saturn’s atmosphere, which showed very intense polar light, especially in the ultraviolet spectrum due to the high levels of hydrogen in its atmosphere. Likewise on Neptune.
Saturn’s aurora are also thought to increase the temperature of the atmosphere around its poles. Neptune’s complex magnetosphere appears to create a number of auroral regions throughout the planet’s atmosphere.
Although most auroras in the Solar System are caused by their planets’ strong magnetic fields, magnetic fields are not necessarily needed to produce auroras.
According to Melin, the planet Mars has long lost its magnetic field, but has auroras thanks to the magnetic field carried by the solar wind and covering the planet’s atmosphere.
Venus also has no magnetic field, but there are auroras triggered by the solar wind encountering the planet’s ionosphere.
These conditions form magnetic plasma bubbles that stretch thousands of miles, resulting in a process called magnetic reconnection. This is seen on Earth and other planets, where field lines converge and charged particles flow toward the planet.
Image source, Getty Images
On Mercury, an even stranger process occurs. This planet has a magnetic field, but no atmosphere. However, by channeling charged particles onto its surface, the planet glows with X-rays when electrons from the solar wind rain down on its surface.
This finding was confirmed by scientists in early 2023, using a European and Japanese space probe called BepiColombo.
“The particles settle on the surface like rain,” said planetary researcher at the Japan Space Agency (Jaxa), Sae Aizawa.
This effect occurs most often when dawn breaks on Mercury’s surface because the direction of the electric field in Mercury’s magnetosphere deflects particles coming from the Sun towards the part of the planet where dawn breaks.
Research related to auroras is not only carried out in our Solar System. In 2015, astronomers detected an extremely powerful aurora 20 light years away from a brown dwarf star, a failed star that does not have enough mass to allow fusion in its core.
Astronomers also look for auroras on exoplanets, planets that orbit other stars. So far, there are some interesting clues regarding this.
In April, researchers discovered radio emissions from the YZ Ceti star system 12 light years away, which suggested interactions between the star and the magnetic field of a rocky planet called YZ Ceti b. The radio emissions are caused by auroras on the star itself, but the planet also has its own aurora.
Looking for auroras on exoplanets through their radio emissions is one way that can be done.
“The observational problem is challenging,” said Sebastian Pineda, a planetary scientist at the University of Colorado, Boulder, US, who led the YZ Ceti research.
However, if we can find them, we could get important clues about the habitability of other planets.
“Exoplanet magnetic fields may be an important element that determines the evolution of habitability,” Pineda said.
Image source, Getty Images
Caption,
Aurora at Earth’s poles visible from space
Other observations also hint at ultraviolet emissions that could be the result of magnetic fields on the Neptune-like planet HAT-P-11b, which is more than 123 light years away.
However, such detections are only in the initial stages.
“We haven’t detected anything truly significant,” said Mary Knapp, an exoplanet scientist at the Massachusetts Institute of Technology.
By researching this, we can gain better insight into other worlds, as well as understand the uniqueness of Earth itself compared to other rocky planets.
“Are most planets like Earth – having thin, hospitable atmospheres – or like Venus?” Knapp said. “We really don’t know yet.”
2024-01-13 08:43:24
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