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Viewings: 5110High in the sky dancing, twinkling, giant colored ribbon. Good night for lovers of polar lights! Bands of red become blue and red again, fleeing clouds. In the night sky behind them stars shining. The full moon rises majestically up two Crescent...
Polar lights on Jupiter was first registered by its radio emission. In the same way you would find it on exoplanets.
Welcome to one of exoplanets. Those found more than 850 - mainly thanks to the observations of vibrations of the light of the stars, or a short eclipses of light. These methods can tell us about the mass of the planet and the radius of its orbit. Other details theoretically can be drawn from the analysis of the atmosphere of the few relatively large and proximity of planets.
The new idea is the study of Aurora. No its not there yet seen, because the light is too weak to go the distance even from the nearest to us exoplanets. But Aurora besides emit radio waves - that's what I would like to hunt researchers.
Radiation can give a huge amount of information that is inaccessible to other methods. Thus, one could discover, first, as yet unseen worlds. And secondly - to calculate the duration of day, to measure the strength of the magnetic field, to get an idea about the internal processes that control the magnetic field to find out how the planet interacts with a star, and even open her companions.
On Earth polar lights become a result of the collision of electrons accelerated by the solar wind, with the gas molecules in the upper atmosphere. Color Aurora depends on the wavelength of the emitted light: oxygen gives greenish-yellow, nitrogen - red or blue. And the radio waves are emitted before this when the electrons revolve around the lines of the magnetic field of the planet.
The Aurora seen also on Jupiter, Saturn, Uranus and Neptune. There is every reason to expect that at least some ekzamenah will be the same, because several times had a flare caused by the interaction of the magnetic fields of stars and planets.
The brightest avroramy in the Solar system has Jupiter. However, as seen from Earth, we can't because there prevails ultraviolet light not able to go through our atmosphere. For the first time we saw them because of the "Voyager 1 spacecraft in 1979. Today we help of a space telescope "Hubble" and orbiting x-ray Observatory Chandra.
But even before that we knew about polar lights on Jupiter for low frequency radio signals. They made it possible to calculate the magnetic field of the planet long before send "the Voyager 1 spacecraft" to the place of direct measurements.
Radio waves have the advantage that if the planet has a magnetic field, it can radiate radio signals stronger than the stars, while in the optical and infrared parts of the spectrum (where basically looking for exoplanets) she weaker bright and hot lights. And our understanding of Jupiter would interpret information received from other planets, especially since most of the discovered so far tel resembles Jupiter than Earth.
At low frequencies (in the area of several tens of megahertz) Jupiter's radiation becomes as bright as the sun, but this is not enough: if he were in another star, we would not see it. It is hoped that there is a planet where the radiation is even stronger.
But what and how can be defined on the radio? For example, the frequency with which they are emitted Aurora, depends on the magnetic field strength. Fortunately, they come in the form of a kind of cone of rays, which rotate with the planet. For the observer it looks like a ripple over which to calculate the period of rotation of the body around its axis.
Signal besides circularly polarized, because the electric field also rotates. Thus, we can distinguish radiation of the planet from that of the stars: the latter is not polarized, as is the emission of electrons through the outer atmosphere.
The first group, which was engaged in the search for exoplanets on the radio was headed by William Erickson of the University of Maryland (USA). Inspired by the successful detection of radio signals Jupiter researchers in 1977, started to monitor 22 nearest stars with radioobservatory Clark lake near Borrego springs in California. The sensitivity of the radio telescope have revealed the Aurora is not less than one thousand times stronger jupiterians, but nothing came out.
Now, 35 years later, interest in radioizluchenie Auror returns in connection with completion of construction of LOFAR telescope is the largest and most sensitive to frequencies below 250 MHz. Array, which left ten years, includes more than 45 thousand small antennas. The main part is set in a quiet conservation area in the North-East of the Netherlands, and the rest scattered in France, Germany, Sweden and the UK. Work began in December and to the search for exoplanets planned to start in the near future.
Planet like Jupiter, capable of powerful radio emission in two cases. First, the configuration of the magnetic field of a planet near the star, can strongly affected by the solar wind. The result is a flow of charged particles, which can lead to polar lights. The modelling performed by Philip Зарк? of the Paris Observatory and Sebastian Assam from the laboratory LATMOS (both from France), showed that in this way you can determine the slope of the "hot Jupiter" relative to the plane of the orbit, the tilt of the magnetic field relative to the rotation axis, the rotation period, the orbital period and the magnetic field strength. To identify all this other way is impossible.
Secondly, a strong surge of radio emission can be associated with the satellite of the planet, which is typical for our Jupiter. There Aurora arise in connection with the fact that the volcanoes of IO every second throw towards the planet ton of ionized gas. Jonathan Nichols from Leicester University (UK) has calculated that on the strength of radio emission of such polar lights affect the speed of rotation of the planet, the speed of the outflow of ionized gas with its satellites and orbital distance, as well as ultraviolet brightness of the stars. According to the expert, such outbursts on the massive and rapidly rotating planets can be detected at a distance of 150 light years.
While nothing like I couldn't tell, despite the constant search. Walid Majeed from the jet propulsion Laboratory of NASA and his colleagues reviewed the half-dozen exoplanets using GMRT radio telescope, located 80 km North of Pune (India). The main reason for the failure of researchers see the inability of tool to record relatively low frequencies. For example, Jupiter does not radiate intense radio waves at a frequency of 40 MHz, and the lower limit of GMRT - 50 MHz. From LOFAR, the average is 10 MHz, but the Earth's atmosphere blocks frequencies below 10 MHz, so you need a space antenna. Mr. Majid offers to put it on the moon.
The sensitivity of the telescope effect, of course, and on the ability to observe the radio signals of Aurora. To improve this indicator can install additional antennas, and by identifying and eliminating noise in the signal caused by other sources of radio waves. Mr. Majid sure that radio astronomy will cope with this task by running not only LOFAR, but the SKA telescope total area of about a square kilometer with antennas in South Africa and Australia. And if we in a few years, nothing ever find that thing, believes Mr. Zarqawi, this happens due to the fact that there is no bursts of appropriate capacity, and not due to imperfections of the equipment.
Not accidentally, the low frequency radio astronomy sometimes called the advanced science of the future decades.
Prepared according to NewScientist.
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