Hubble captures vivid auroras in Jupiter’s atmosphere

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Auroras on Jupiter

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Timelapse of Jupiter’s auroras

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Timelapse of Jupiter’s auroras (2)

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Astronomers are using the NASA/ESA Hubble Space Telescope to study auroras — stunning light shows in a planet’s atmosphere — on the poles of the largest planet in the Solar System, Jupiter. This observation programme is supported by measurements made by NASA’s Juno spacecraft, currently on its way to Jupiter.

Jupiter, the largest planet in the Solar System, is best known for its colourful storms, the most famous being the Great Red Spot. Now astronomers have focused on another beautiful feature of the planet, using the ultraviolet capabilities of the NASA/ESA Hubble Space Telescope.

The extraordinary vivid glows shown in the new observations are known as auroras [1]. They are created when high energy particles enter a planet’s atmosphere near its magnetic poles and collide with atoms of gas. As well as producing beautiful images, this programme aims to determine how various components of Jupiter’s auroras respond to different conditions in the solar wind, a stream of charged particles ejected from the Sun.

This observation programme is perfectly timed as NASA’s Juno spacecraft is currently in the solar wind near Jupiter and will enter the orbit of the planet in early July 2016. While Hubble is observing and measuring the auroras on Jupiter, Juno is measuring the properties of the solar wind itself; a perfect collaboration between a telescope and a space probe [2].

“These auroras are very dramatic and among the most active I have ever seen”, says Jonathan Nichols from the University of Leicester, UK, and principal investigator of the study. “It almost seems as if Jupiter is throwing a firework party for the imminent arrival of Juno.”

To highlight changes in the auroras Hubble is observing Jupiter daily for around one month. Using this series of images it is possible for scientists to create videos that demonstrate the movement of the vivid auroras, which cover areas bigger than the Earth.

Not only are the auroras huge, they are also hundreds of times more energetic than auroras on Earth. And, unlike those on Earth, they never cease. Whilst on Earth the most intense auroras are caused by solar storms — when charged particles rain down on the upper atmosphere, excite gases, and cause them to glow red, green and purple — Jupiter has an additional source for its auroras.

The strong magnetic field of the gas giant grabs charged particles from its surroundings. This includes not only the charged particles within the solar wind but also the particles thrown into space by its orbiting moon Io, known for its numerous and large volcanos.

The new observations and measurements made with Hubble and Juno will help to better understand how the Sun and other sources influence auroras. While the observations with Hubble are still ongoing and the analysis of the data will take several more months, the first images and videos are already available and show the auroras on Jupiter’s north pole in their full beauty.

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Notes

[1] Jupiter’s auroras were first discovered by the Voyager 1 spacecraft in 1979. A thin ring of light on Jupiter's nightside looked like a stretched-out version of our own auroras on Earth. Only later on was it discovered that the auroras were best visible in the ultraviolet.

[2] This is not the first time astronomers have used Hubble to observe the auroras on Jupiter, nor is it the first time that Hubble has cooperated with space probes to do so. In 2000 the NASA/ESA/ASI Cassini spacecraft made its closest approach to Jupiter and scientists used this opportunity to gather data and images about the auroras simultaneously from Cassini and Hubble (heic0009). In 2007 Hubble obtained images in support of its sister NASA Mission New Horizons which used Jupiter's gravity for a manoeuvre on its way to Pluto (opo0714a).

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More Information 

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Image credit: NASA, ESA

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Links

• Images of Hubble
• Link to hubblesite release
• Juno mission webpage

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Contacts

Jonathan Nichols
University of Leicester
United Kingdom
Tel: +44 116 252 5049
Email: jdn4@leicester.ac.uk

Mathias Jäger
ESA/Hubble, Public Information Officer
Garching bei München, Germany
Cell: +49 176 62397500
Email: mjaeger@partner.eso.org

Source: ESA/Hubble - Space Telescope/News

Powerful Auroras Found at Brown Dwarf

This artist's concept shows an auroral display on a brown dwarf. If you could see an aurora on a brown dwarf, it would be a million times brighter than an aurora on Earth. Credit: Chuck Carter and Gregg Hallinan/Caltech.  › Larger view

Mysterious objects called brown dwarfs are sometimes called "failed stars." They are too small to fuse hydrogen in their cores, the way most stars do, but also too large to be classified as planets. But a new study in the journal Nature suggests they succeed in creating powerful auroral displays, similar to the kind seen around the magnetic poles on Earth.

"This is a whole new manifestation of magnetic activity for that kind of object," said Leon Harding, a technologist at NASA's Jet Propulsion Laboratory, Pasadena, California, and co-author on the study.

On Earth, auroras are created when charged particles from the solar wind enter our planet's magnetosphere, a region where Earth's magnetic field accelerates and sends them toward the poles. There, they collide with atoms of gas in the atmosphere, resulting in a brilliant display of colors in the sky.

"As the electrons spiral down toward the atmosphere, they produce radio emissions, and then when they hit the atmosphere, they excite hydrogen in a process that occurs at Earth and other planets," said Gregg Hallinan, assistant professor of astronomy at the California Institute of Technology in Pasadena, who led the team. "We now know that this kind of auroral behavior is extending all the way from planets up to brown dwarfs."

Brown dwarfs are generally cool, dim objects, but their auroras are about a million times more powerful than auroras on Earth, and if we could somehow see them, they'd be about a million times brighter, Hallinan said. Additionally, while green is the dominant color of earthly auroras, a vivid red color would stand out in a brown dwarf's aurora because of the higher hydrogen content of the object's atmosphere.

The foundation for this discovery began in the early 2000s, when astronomers began finding radio emissions from brown dwarfs. This was surprising because brown dwarfs do not generate large flares and charged-particle emissions the way the sun and other kinds of stars do. The cause of these radio emissions was a big question.

Hallinan discovered in 2006 that brown dwarfs can pulse at radio frequencies, too. This pulsing phenomenon is similar to what is seen from planets in our solar system that have auroras.

Harding, working as part of Hallinan's group while pursuing his doctoral studies, found that there was also periodic variability in the optical wavelength of light coming from brown dwarfs that pulse at radio frequencies. He published these findings in the Astrophysical Journal. Harding built an instrument called an optical high-speed photometer, which looks for changes in the light intensity of celestial objects, to examine this phenomenon.

The combination of results made scientists wonder: Could this variability in light from brown dwarfs be caused by auroras?

In this new study, researchers examined brown dwarf LSRJ1835+3259, located about 20 light-years from Earth. Scientists studied it using some of the world's most powerful telescopes -- the National Radio Astronomy Observatory's Very Large Array, Socorro, New Mexico, and the W.M. Keck Observatory's telescopes in Hawaii -- in addition to the Hale Telescope at the Palomar Observatory in California.

Given that there's no stellar wind to create an aurora on a brown dwarf, researchers are unsure what is generating it on LSRJ1835+3259. An orbiting planet moving through the magnetosphere of the brown dwarf could be generating a current, but scientists will have to map the aurora to figure out its source.

The discovery reported in the July 30 issue of Nature could help scientists better understand how brown dwarfs generate magnetic fields. Additionally, brown dwarfs will help scientists study exoplanets, planets outside our solar system, as the atmosphere of cool brown dwarfs is similar to what astronomers expect to find at many exoplanets.

"It's challenging to study the atmosphere of an exoplanet because there's often a much brighter star nearby, whose light muddles observations. But we can look at the atmosphere of a brown dwarf without this difficulty," Hallinan said.

Hallinan also hopes to measure the magnetic field of exoplanets using the newly built Owens Valley Long Wavelength Array, funded by Caltech, JPL, NASA and the National Science Foundation.

Caltech manages JPL for NASA.

Media Contact

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Hubble sees a flickering light display on Saturn

Saturn's aurorae

Credit: NASA, ESA
Acknowledgement: J. Nichols (University of Leicester)

Astronomers using the NASA/ESA Hubble Space Telescope have captured new images of the dancing auroral lights at Saturn’s north pole. Taken from Hubble’s perspective in orbit around the Earth, these images provide a detailed look at Saturn’s stormy aurorae — revealing previously unseen dynamics in the choreography of the auroral glow.

The cause of the changing patterns in Saturn's aurorae is an ongoing mystery in planetary science. These ultraviolet images, taken by Hubble’s super-sensitive Advanced Camera for Surveys, add new insight by capturing moments when Saturn’s magnetic field is affected by bursts of particles streaming out from the Sun.

Saturn has a long, comet-like magnetic tail known as a magnetotail — as do Mercury, Jupiter, Uranus, Neptune and Earth [1]. This magnetotail is present around planets that have a magnetic field, caused by a rotating core of magnetic elements. It appears that when bursts of particles from the Sun hit Saturn, the planet’s magnetotail collapses and later reconfigures itself, an event that is reflected in the dynamics of its aurorae.

Some of the bursts of light seen shooting around Saturn’s polar regions travelled at over three times faster than the speed of the gas giant’s rotation!

The new images also formed part of a joint observing campaign between Hubble and NASA's Cassini spacecraft, which is currently in orbit around Saturn itself. Between them, the two spacecraft managed to capture a 360-degree view of the planet’s aurorae at both the north and south poles. Cassini also used optical imaging to delve into the rainbow of colours seen in Saturn’s light shows. On Earth, we see green curtains of light with flaming scarlet tops. Cassini’s imaging cameras reveal similar auroral veils on Saturn, that are red at the bottom and violet at the top.

Notes

[1] A magnetosphere is the area of space around an astronomical object in which charged particles are controlled by that object’s magnetic field. The magnetosphere is compressed on the side of the sun, and on the other side it extends far beyond the object. It is this extended region of the magnetosphere that is known as the magnetotail.  

Source: ESA/Hubblle - Space Telescope

NASA Spacecraft Get a 360-Degree View of Saturn's Auroras

Ultraviolet and infrared images from NASA's Cassini spacecraft and Hubble Space Telescope show active and quiet auroras at Saturn's north and south poles. Full caption 

The dark region seen on the face of the sun at the end of March 2013 is a coronal hole (just above and to the right of the middle of the picture), which is a source of fast solar wind leaving the sun.  Image Credit: NASA/SDO/AIA. Full image and caption

While the curtain-like auroras we see at Earth are green at the bottom and red at the top, NASA's Cassini spacecraft has shown us similar curtain-like auroras at Saturn that are red at the bottom and purple at the top. Image Credit: NASA/JPL-Caltech/SSI.  Full image and caption

NASA trained several pairs of eyes on Saturn as the planet put on a dancing light show at its poles. While NASA's Hubble Space Telescope, orbiting around Earth, was able to observe the northern auroras in ultraviolet wavelengths, NASA's Cassini spacecraft, orbiting around Saturn, got complementary close-up views in infrared, visible-light and ultraviolet wavelengths. Cassini could also see northern and southern parts of Saturn that don't face Earth.

The result is a kind of step-by-step choreography detailing how the auroras move, showing the complexity of these auroras and how scientists can connect an outburst from the sun and its effect on the magnetic environment at Saturn.

"Saturn's auroras can be fickle -- you may see fireworks, you may see nothing," said Jonathan Nichols of the University of Leicester in England, who led the work on the Hubble images. "In 2013, we were treated to a veritable smorgasbord of dancing auroras, from steadily shining rings to super-fast bursts of light shooting across the pole."

The Hubble and Cassini images were focused on April and May of 2013. Images from Cassini's ultraviolet imaging spectrometer (UVIS), obtained from an unusually close range of about six Saturn radii, provided a look at the changing patterns of faint emissions on scales of a few hundred miles (kilometers) and tied the changes in the auroras to the fluctuating wind of charged particles blowing off the sun and flowing past Saturn.

"This is our best look yet at the rapidly changing patterns of auroral emission," said Wayne Pryor, a Cassini co-investigator at Central Arizona College in Coolidge, Ariz. "Some bright spots come and go from image to image. Other bright features persist and rotate around the pole, but at a rate slower than Saturn's rotation."

The UVIS images, which are also being analyzed by team associate Aikaterini Radioti at the University of Liege, Belgium, also suggest that one way the bright auroral storms may be produced is by the formation of new connections between magnetic field lines. That process causes storms in the magnetic bubble around Earth. The movie also shows one persistent bright patch of the aurora rotating in lockstep with the orbital position of Saturn's moon Mimas. While previous UVIS images had shown an intermittent auroral bright spot magnetically linked to the moon Enceladus, the new movie suggests another Saturn moon can influence the light show as well.

The new data also give scientists clues to a long-standing mystery about the atmospheres of giant outer planets.

"Scientists have wondered why the high atmospheres of Saturn and other gas giants are heated far beyond what might normally be expected by their distance from the sun," said Sarah Badman, a Cassini visual and infrared mapping spectrometer team associate at Lancaster University, England. "By looking at these long sequences of images taken by different instruments, we can discover where the aurora heats the atmosphere as the particles dive into it and how long the cooking occurs."

The visible-light data have helped scientists figure out the colors of Saturn's auroras. While the curtain-like auroras we see at Earth are green at the bottom and red at the top, Cassini's imaging cameras have shown us similar curtain-like auroras at Saturn that are red at the bottom and purple at the top, said Ulyana Dyudina, an imaging team associate at the California Institute of Technology, Pasadena, Calif.

The color difference occurs because Earth's auroras are dominated by excited nitrogen and oxygen molecules, and Saturn's auroras are dominated by excited hydrogen molecules.

"While we expected to see some red in Saturn's aurora because hydrogen emits some red light when it gets excited, we also knew there could be color variations depending on the energies of the charged particles bombarding the atmosphere and the density of the atmosphere," Dyudina said. "We were thrilled to learn about this colorful display that no one had seen before."

Scientists hope additional Cassini work will illuminate how clouds of charged particles move around the planet as it spins and receives blasts of solar material from the sun.

"The auroras at Saturn are some of the planet's most glamorous features – and there was no escaping NASA's paparazzi-like attention”, said Marcia Burton, a Cassini fields and particles scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., who is helping to coordinate these observations. "As we move into the part of the 11-year solar cycle where the sun is sending out more blobs of plasma, we hope to sort out the differences between the effects of solar activity and the internal dynamics of the Saturn system."

There is still more work to do. A group of scientists led by Tom Stallard at the University of Leicester is busy analyzing complementary data taken during the same time window by two ground-based telescopes in Hawaii -- the W.M. Keck Observatory and NASA's Infrared Telescope Facility. The results will help them understand how particles are ionized in Saturn's upper atmosphere and will help them put a decade of ground-based telescope observations of Saturn in perspective, because they can see what disturbance in the data comes from Earth's atmosphere.

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

Uranus auroras glimpsed from Earth

These composite images show Uranus auroras, which scientists caught glimpses of through the Hubble Space Telescope in 2011. CREDIT: Laurent Lamy. Hi-Res image

WASHINGTON—For the first time, scientists have captured images of auroras above the giant ice planet Uranus, finding further evidence of just how peculiar a world that distant planet is. Detected by means of carefully scheduled observations from the Hubble Space Telescope, the newly witnessed Uranian light show consisted of short-lived, faint, glowing dots – a world of difference from the colorful curtains of light that often ring Earth's poles.

In the new observations, which are the first to glimpse the Uranian aurora with an Earth-based telescope, the researchers detected the luminous spots twice on the dayside of Uranus – the side that’s visible from Hubble. Previously, the distant aurora had only been measured using instruments on a passing spacecraft. Unlike auroras on Earth, which can turn the sky greens and purples for hours, the newly detected auroras on Uranus appeared to only last a couple minutes.

In general, auroras are a feature of the magnetosphere, the area surrounding a planet that is controlled by its magnetic field and shaped by the solar wind, a steady flow of charged particles emanating from the sun. Auroras are produced in the atmosphere as charged solar wind particles accelerate in the magnetosphere and are guided by the magnetic field close to the magnetic poles – that’s why the Earthly auroras are found around high latitudes.

But contrary to the Earth – or even Jupiter and Saturn – “the magnetosphere of Uranus is very poorly known,” said Laurent Lamy, with the Observatoire de Paris in Meudon, France, who led the new research.

The results from his team, which includes researchers from France, the United Kingdom, and the United States, will be published Saturday in Geophysical Research Letters, a journal of the American Geophysical Union.

Auroras on Uranus are fainter than they are on Earth, and the planet is more than 4 billion kilometers (2.5 billion miles) away. Previous Earth-bound attempts to detect the faint auroras were inconclusive. Astronomers got their last good look at Uranian auroras 25 years ago when the Voyager 2 spacecraft whizzed past the planet and recorded spectra from of the radiant display.

“This planet was only investigated in detail once, during the Voyager flyby, dating from 1986. Since then, we’ve had no opportunities to get new observations of this very unusual magnetosphere,” Lamy noted.

Planetary scientists know that Uranus is an oddball among the solar system’s planets when it comes to the orientation of its rotation axis. Whereas the other planets resemble spinning tops, circulating around the Sun, Uranus is like a top that was knocked on its side – but still keeps spinning.

The researchers suspect that the unfamiliar appearance of the newly observed auroras is due to Uranus’ rotational weirdness and peculiar traits of its magnetic axis. The magnetic axis is both offset from the center of the planet and lists at an angle of 60 degrees from the rotational axis – an extreme tilt compared to the 11 degree difference on Earth. Scientists theorize that Uranus’s magnetic field is generated by a salty ocean within the planet, resulting in the off-center magnetic axis.

The 2011 auroras differ not only from Earth’s auroras but also from the Uranian ones previously detected by Voyager 2. When that spacecraft made its flyby decades ago, Uranus was near its solstice – its rotational axis was pointed toward the Sun. In that configuration, the magnetic axis stayed at a large angle from the solar wind flow, producing a magnetosphere similar to the Earth’s magnetosphere, although more dynamic. Under those 1986 solstice conditions, the auroras lasted longer than the recently witnessed ones and were mainly seen on the nightside of the planet, similar to what’s observed on Earth, Lamy said. Hubble can’t see the far side of the planet, however, so researchers don’t know what types of auroras, if any, were generated there.

The new set of observations, however, is from when the planet was near equinox, when neither end of the Uranian rotational axis aims at the Sun, and the axis aligns almost perpendicular to the solar wind flow. Because the planet’s magnetic axis is tilted, the daily rotation of Uranus during the period around the equinox causes each of its magnetic poles to point once a day toward the Sun, likely responsible for a very different type of aurora than the one that was seen at solstice, Lamy explained.

“This configuration is unique in the solar system,” added Lamy, who noted that the two transient, illuminated spots observed in 2011 were close to the latitude of Uranus’s northern magnetic pole.

Capturing the images of Uranus’s auroras resulted from a combination of good luck and careful planning. In 2011, Earth, Jupiter and Uranus were lined up so that the solar wind could flow from the Sun, past Earth and Jupiter, and then toward Uranus. When the Sun produced several large bursts of charged particles in mid-September 2011, the researchers used Earth-orbiting satellites to monitor the solar wind’s local arrival two to three days later. Two weeks after that, the solar wind sped past Jupiter at 500 kilometers per second (310 miles per second). Calculating that the charged particles would reach Uranus in mid-November, the team scrambled to scheduled time on the Hubble Space Telescope.

Ever since the Voyager 2 flyby demonstrated that Uranus was a “strange beast,” said Fran Bagenal, a planetary scientist with the University of Colorado in Boulder, “we’ve been really keen to get a better view. This was a very clever way of looking at that.”

A better understanding of Uranus’ magnetosphere could help scientists test their theories of how Earth’s magnetosphere functions, she added. “We have ideas of how things work on Earth and places like Jupiter and Saturn, but I don’t believe you really know how things work until you test them on a very different system.”


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Title

“Earth-based detection of Uranus' aurorae”


Authors

L. Lamy and R. Prange: LESIA, Obs. de Paris, CNRS, UPMC, Univ. Paris Diderot, Meudon, France;

K. C. Hansen: Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA;

J. T. Clarke: Center for Space Physics, Boston University, Boston, Massachusetts, USA;
P. Zarka, B. Cecconi, and J. Aboudarham: LESIA, Obs. de Paris, CNRS, UPMC, Univ. Paris Diderot, Meudon, France;

N. Andre: Institut de Recherche en Astrophysique, Toulouse, France;

G. Branduardi-Raymont: University College London, Mullard Space Science Laboratory, Dorking, UK;

R. Gladstone: Southwest Research Institute, San Antonio, USA;

M. Barthelemy: Institut de Planetologie et d’Astrophysique de Grenoble, Grenoble, France;

N. Achilleos and P. Guio: University College London, London, UK;

M. K. Dougherty: Blackett Laboratory, Imperial College London, London, UK;

H. Melin, S.W.H. Cowley, T.S. Stallard and J. D. Nichols: Department of Physics and Astronomy, University of Leicester, Leicester, UK;

G. Ballester: Lunar and Planetary Laboratory, University of Arizona, USA


Contact information for the author

Laurent Lamy
Telephone: +33 1-45-07-76-61
Email: laurent.lamy@obspm.fr


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Exoplanet Aurora: An Out-of-this-World Sight

This artist's conception shows a "hot Jupiter" and its two hypothetical moons with a sunlike star in the background. The planet is cloaked in brilliant aurorae triggered by the impact of a coronal mass ejection. Theoretical calculations suggest that those aurorae could be 100-1000 times brighter than Earth's. Credit: David A. Aguilar (CfA). High Resolution Image (jpg)

In this animation, stunning aurorae ripple around a "hot Jupiter." When a stellar eruption known as a coronal mass ejection hit the planet, it triggered these aurorae, which are the planetary equivalent of Earth's Northern and Southern Lights. However, this exoplanet's aurorae shine up to a thousand times brighter than Earth's, and extend from the equator to the poles. Animation created by Hyperspective Studios. Credit: CfA. Animation (mov)

Cambridge, MA - Earth's aurorae, or Northern and Southern Lights, provide a dazzling light show to people living in the polar regions. Shimmering curtains of green and red undulate across the sky like a living thing. New research shows that aurorae on distant "hot Jupiters" could be 100-1000 times brighter than Earthly aurorae. They also would ripple from equator to poles (due to the planet's proximity to any stellar eruptions), treating the entire planet to an otherworldly spectacle.

"I'd love to get a reservation on a tour to see these aurorae!" said lead author Ofer Cohen, a SHINE-NSF postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics (CfA).

Earth's aurorae are created when energetic particles from the Sun slam into our planet's magnetic field. The field guides solar particles toward the poles, where they smash into Earth's atmosphere, causing air molecules to glow like a neon sign. The same process can occur on planets orbiting distant stars, known as exoplanets.

Particularly strong aurorae result when Earth is hit by a coronal mass ejection or CME - a gigantic blast that sends billions of tons of solar plasma (electrically charged, hot gas) into the solar system. A CME can disrupt Earth's magnetosphere - the bubble of space protected by Earth's magnetic field - causing a geomagnetic storm. In 1989, a CME hit Earth with such force that the resulting geomagnetic storm blacked out huge regions of Quebec.

Cohen and his colleagues used computer models to study what would happen if a gas giant in a close orbit, just a few million miles from its star, were hit by a stellar eruption. He wanted to learn the effect on the exoplanet's atmosphere and surrounding magnetosphere.

The alien gas giant would be subjected to extreme forces. In our solar system, a CME spreads out as it travels through space, so it's more diffuse once it reaches us. A "hot Jupiter" would feel a stronger and more focused blast, like the difference between being 100 miles from an erupting volcano or one mile away.

"The impact to the exoplanet would be completely different than what we see in our solar system, and much more violent," said co-author Vinay Kashyap of CfA.

In the model, a CME hits the "hot Jupiter" and weakens its magnetic shield. Then CME particles reach the gas giant's atmosphere. Its aurora lights up in a ring around the equator, 100-1000 times more energetic than Earthly aurorae. Over the course of about 6 hours, the aurora then ripples up and down toward the planet's north and south poles before gradually fading away.

Despite the extreme forces involved, the exoplanet's magnetic field shields its atmosphere from erosion.

"Our calculations show how well the planet's protective mechanism works," explained Cohen. "Even a planet with a magnetic field much weaker than Jupiter's would stay relatively safe."

This work has important implications for the habitability of rocky worlds orbiting distant stars. Since red dwarf stars are the most common stars in our galaxy, astronomers have suggested focusing on them in the search for Earthlike worlds.

However since a red dwarf is cooler than our Sun, a rocky planet would have to orbit very close to the star to be warm enough for liquid water. There, it would be subjected to the sort of violent stellar eruptions Cohen and his colleagues studied. Their future work will examine whether rocky worlds could shield themselves from such eruptions.

This research has been accepted for publication in The Astrophysical Journal and is available online.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

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David A. Aguilar
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Source: Harvard-Smithsonian Center for Astrophysics