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About the item
- Author, Jonathan O’Callaghan
- Role, BBC Future
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37 minutes ago
The sight of auroras, magical lights that usually appear in Arctic and Antarctic skies, are also found on other planets in the Milky Way and outside the Milky Way. These discoveries provide astronomers with valuable new information about 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 in England recently detected an infrared aurora on the giant icy planet.
“We scanned the planet for six hours to see if there were any changes 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, indicating 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 has captured another aspect of the aurora shining 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 to have auroras. Auroras on planets in our solar system appear to be quite common.
The eight major planets orbiting the Sun also show some sort of aurora, caused by magnetic fields or activity on their surfaces.
Observations from other solar systems also suggest the possibility of similar auroras.
For astronomers detecting these alien light shows, their presence can provide valuable information about the world they radiate into, including the northern and southern lights on our planet.
Image credit: NASA/Getty Images
Caption,
An aurora-like light was seen on the planet Jupiter on December 19, 2000, 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 towards our planet, they became trapped by magnetic fields that directed them towards the poles .
These particles then collide with atoms and molecules in Earth’s atmosphere, producing a dramatic curtain of light, which we call the Northern Lights or Southern Lights.
Its dramatic color variations and 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 in our atmosphere, produces predominantly blue light. Meanwhile, oxygen produces the green light.
The height of 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. Pink and purple appear at lower altitudes.
On Uranus, the most abundant gases in the atmosphere are hydrogen and helium, so the auroras are slightly different. The auroras on Uranus are invisible to the human eye because they shine in the electromagnetic spectrum.
Ultraviolet and radio auroras 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 discovery could be very valuable from a scientific point of view. The atmosphere at the top of Uranus is much warmer than researchers expected for a planet so cold and far from the sun.
Space probes that passed by showed that the temperature ranged between 220-420°C, much hotter if this planet depended only on the heat of the Sun and compared to its larger neighbor, Saturn.
The latest findings suggest that the condition may be the result of heat radiating onto the planet from the auroras.
“Now that we can see the infrared aurora, we can start to understand how it works,” Thomas said.
Image source, Getty Images
Aurora Uranus can also add important information about the characteristics of the Earth’s magnetic field, that is, the fact that the Earth’s magnetic field often reverses direction.
Over the last 20 million years, the magnetic field has reversed three to five times every million years, moving the magnetic pole from north to south and vice versa (this is not a cycle, and more than 780,000 years have passed since the last reversal Even in the Cretaceous, the Earth’s magnetic field did not flip 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 lateral orbit relative to its motion around the Sun, may provide some clues. This is because its magnetic field undergoes a rotation very different from that of the Earth.
“The big question is what happens when this 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 this kind of thing.”
Although the magnetic field itself is not visible, the aurora rings around the poles allow us to study how the magnetic field changes.
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However, Uranus is not the only other planet to have auroras.
The first aurora seen from another planet was on Jupiter. It was observed through radio wave observations in the 1950s, then by NASA’s Voyager 1 spacecraft in 1979.
Auroras have since been seen dancing at Jupiter’s poles by several telescopes, 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 is also believed to increase the temperature of the atmosphere around its poles. Neptune’s complex magnetosphere appears to create a series of auroral regions throughout the planet’s atmosphere.
Although most auroras in the Solar System are caused by the strong magnetic fields of their planets, magnetic fields are not necessarily necessary to produce auroras.
According to Melin, the planet Mars has long lost its magnetic field, but produces auroras thanks to the magnetic field carried by the solar wind and covering the planet’s atmosphere.
Venus also does not have a magnetic field, but there are auroras triggered by the solar wind encountering the planet’s ionosphere.
These conditions form bubbles of magnetic plasma that extend across thousands of kilometers, resulting in a process called magnetic reconnection. This is visible on Earth and other planets, where field lines converge and charged particles flow towards the planet.
Image source, Getty Images
An even stranger process occurs on Mercury. This planet has a magnetic field, but no atmosphere. However, by funneling charged particles onto its surface, the planet glows with X-rays as electrons from the solar wind rain down on its surface.
This discovery 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 Japanese Space Agency (Jaxa) planetary researcher 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 from the Sun toward 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 lacks 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 about it.
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. Radio emissions are caused by auroras on the star itself, but the planet also has its own auroras.
Searching for auroras on exoplanets through their radio emissions is one possible way.
“The observation 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 gain important clues about the habitability of other planets.
“The magnetic fields of exoplanets may be an important element determining the evolution of habitability,” Pineda said.
Image source, Getty Images
Caption,
Aurora at the Earth’s poles visible from space
Other observations also suggest ultraviolet emissions that may be the result of magnetic fields on the Neptune-like planet HAT-P-11b, more than 123 light-years away.
However, such detections are only in the early stages.
“We haven’t detected anything really significant,” said Mary Knapp, an exoplanet scientist at the Massachusetts Institute of Technology.
By researching this, we can gain a better view of other worlds, as well as understand the uniqueness of Earth itself compared to other rocky planets.
“Are most planets like Earth – with thin, hospitable atmospheres – or like Venus?” Knapp said. “We don’t really know yet.”
2024-01-13 08:43:24
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