Artist's impression of red dwarf star TVLM 513-46546.
Artist's impression of red dwarf star TVLM 513-46546. ALMA observations suggest that it has an amazingly powerful magnetic field (shown by the blue lines), potentially associated with a flurry of solar-flare-like eruptions.
NRAO/AUI/NSF; Dana Berry / SkyWorks
Epic Auroras Throughout the Solar System: Photos
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When you live in the extreme north or south regions of Earth, there is a special astronomical phenomenon to enjoy besides an extra-long winter. That's auroras (or aurorae), sometimes called the northern or southern lights. This happens when charged particles from the sun interact with Earth's magnetic field lines, and "excite" molecules high in the atmosphere. Luckily for future explorers of the solar system, they will have similar light shows to enjoy on other planets and moons. Here's a brief overview of some of the aurora research going on around our planetary neighborhood. (We should note that auroras or associated magnetic activity for them are discussed as possibilities in some locations, such as Venus , but this will focused on confirmed observations.) PHOTOS: Epic Aurora Photos From the Space Station
Image: A view of an auroral display over Earth as seen from the International Space Station during a solar storm in September 2015. Credit: NASA/Scott Kelly
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Because Mars doesn't have a global magnetic field like Earth, we don't expect to see auroras that often. But the Red Planet does happen to have "residual magnetism" in its crust, which is just enough to create the light show, according to the European Space Agency. During about 10 years of observations reported earlier this month, a handful of auroras were detected near where open and closed magnetic field lines intersect. Auroras, which shine on Mars in the ultraviolet, were also detected for five days before Dec. 25, 2014 by NASA's MAVEN (Mars Atmosphere and Volatile Evolution Mission) spacecraft. In this case, the auroras seem to have been sparked by an outburst on the sun with energetic particles deep enough to penetrate into the atmosphere of the planet, further down than what you would see on Earth. PHOTOS: Solar Storm Leads to Stunning Aurora Displays
Image: Aurora detections made by the Mars Express spacecraft between 2004 and 2014. Credit: Based on data from J-C. Gérard et al (2015)
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A decade after NASA's Galileo mission, which ended in 2003, scientists are keen to further research the mysteries of Jupiter's magnetic field. Luckily, NASA's Juno spacecraft is on its way there, scheduled to arrive in 2016. Among its instruments is an ultraviolet spectrometer that will give a detailed look at auroras on the planet. There should be a nice light show if past research is any indication. An amazing picture (above) from the Hubble Space Telescope shows auroras dancing around Jupiter's north pole, built on emissions from its largest moons -- Io (left), Ganymede (center) and Europa (right). The emissions happen as the moons create electric current that interacts with Jupiter's magnetic field. Some of Jupiter's moons also have aurora-like features. Galileo spotted collisions between charged particles and Io's atmosphere that created emissions similar to aurora. Auroral features on Europa happen because Jupiter has such a strong magnetic field; these are just visible by Hubble. And we can't forget years of observations on Ganymede, which not only has a magnetic field, but also a stable location where auroras are located . PHOTO: Sun Storm Supercharges Northern Lights
Image: This picture from the Hubble Space Telescope shows auroras coiled around Jupiter's north pole. Credit: John Clarke (University of Michigan) and NASA
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Saturn has been under a long-time watch from NASA's Cassini spacecraft, which arrived there in 2004. And what a view we've had. Last year, Cassini and Hubble teamed up to provide a 360-degree view of auroras on the planet, which you can view above ( and in this video ). "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," NASA wrote at the time . A couple of the major findings: It appears there is a strong link between solar activity, specifically the amount of charged particles making its way into Saturn's magnetic environment. Storms are likely also sustained as magnetic field lines forge connections between each other, which are linked to movements of the moons Enceladus and Mimas. PHOTOS: Spectacular Displays of Dancing Aurora
Image: A NASA Cassini mission view of an aurora on Saturn as seen in ultraviolet light. Credit: NASA
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The Voyager 2 spacecraft captured some information about auroras on Uranus when it zoomed by in 1986, but little is known to this day about the planet's magnetosphere. It is so far away, and was only visited by the one spacecraft very briefly, so it is difficult to get much information about auroras and other signs of magnetic activity. A brief exception to that came in 2011, when auroras shone so brightly on the planet that they were captured by Hubble. "The ultraviolet images were taken at the time of heightened solar activity in November 2011 that successively buffeted the Earth, Jupiter, and Uranus with a gusher of charged particles from the Sun," NASA wrote at the time . "Because Uranus' magnetic field is inclined 59 degrees to its spin axis, the auroral spots appear far from the planet's north and south poles." PHOTOS: Stunning Auroras Seen Over Swedish Mountains
Image: Auroras spotted on Uranus in 2011. This image is a combination of Hubble's view of the aurora, 2011 Gemini Observatory pictures of Uranus' ring system in infrared light, and 1986 Voyager 2 pictures of Uranus in visible light. Credit: NASA, ESA, and L. Lamy (Observatory of Paris, CNRS, CNES)
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Neptune is another planet that we know little about. It's far away from Earth and telescope time is precious, so we only have relative glimpses here and there into the gas giant's science. Our best close-up look came from a single spacecraft flyby in 1989, when Voyager 2 briefly zoomed by the cool, blue planet. Voyager 2 found a much different magnetic field on Neptune than on Earth. "Because of Neptune's complex magnetic field, the auroras are extremely complicated processes that occur over wide regions of the planet, not just near the planet's magnetic poles," NASA wrote in a summary page about the planet . "The auroral power on Neptune is weak, estimated at about 50 million watts, compared to 100 billion watts on Earth."
Image: While you can't see storms in this Voyager 2 image of Neptune, the spacecraft did gather data in 1989 showing auroras at the large planet. Credit: NASA
Some stars are just born with extremely magnetic personalities.
Take TVLM 513-46546 for example. It’s a small M-class red dwarf, a star that belongs to the most populous stellar group in the galaxy. But TVLM 513-46546 would find it hard blending in with the crowd.
As observed by the Atacama Large Millimeter/submillimeter Array (ALMA), this little star was found to have an extremely powerful magnetic field, rivaling the most powerful magnetically active regions on our sun. It is so active, argue astronomers, that if our planet was in orbit around this star, satellites would not function.
“If we lived around a star like this one, we wouldn’t have any satellite communications. In fact, it might be extremely difficult for life to evolve at all in such a stormy environment,” said Peter Williams, of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. and lead author of the study published in the Astrophysical Journal.
TVLM 513-46546 is located some 35 light-years from Earth in the constellation Boötes. It is a teeny tiny star is only 10 percent the mass of our sun, so tiny in fact that it is on the cusp of the bridging gap between what constitutes a star and what constitutes a planet. If the star were any smaller, there would be insufficient pressure in its core to ignite fusion, making it a brown dwarf, or a “failed star.” But a brown dwarf TVLM 513-46546 is not, it is a magnetic powerhouse and one of the most violent stellar objects we’ve seen in the Milky Way.
The red dwarf is spinning rapidly, taking only 2 hours to spin a full rotation — by comparison, our sun takes 25 days to complete one rotation — and this rotation rate could be the root as to why TVLM 513-46546′s magnetic field is so strong.
“This star is a very different beast from our sun, magnetically speaking,” said coauthor Edo Berger, also from the CfA.
When studying the object with ALMA, the researchers detected powerful radio signals that betrayed the star’s magnetic personality. They measured a signal at 95 GHz, a high-frequency radiation produced by a process known as synchrotron emission, which is generated by high-energy electrons rapidly accelerated by intense magnetic fields. From this measured frequency, the researchers realized the star had a global magnetic field hundreds of times more powerful than the average magnetic field observed in our sun. Although our sun can muster the strength to occasionally generate synchrotron emissions at these frequencies, only the most powerful solar flares can generate them.
As ALMA only observed TVLM 513-46546 for a short, 4 hour period, and it was generating these powerful radio emissions for the entire time, astronomers were able to deduce that this star is constantly erupting, blasting superflares into space.
This is yet another example of why red dwarfs may not be the best locations for potentially habitable planets to spawn life. The constant stellar flare ups would wash the local interplanetary environment with radiation, continually destroying hypothetical atmospheres and any biospheres that have the potential to evolve within. Also, as TVLM 513-46546 is so tiny and cool, any planet orbiting within the star’s habitable zone (the region surrounding a star that is neither too hot or too cold for liquid water to persist on the planet’s surface) would be extremely close to the red dwarf, making the likelihood of life (at least, life as we know it) extremely slim.
Source: CfA press release