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 program is supported by measurements made by NASA's Juno spacecraft, currently on its way to Jupiter. 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 using the ultraviolet capabilities of the NASA/ESA Hubble Space Telescope.

This observation program 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.

"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.

The Daily Galaxy via ESA/Hubble

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The central regions of many glittering galaxies, our own Milky Way included, harbor cores of impenetrable darkness -- black holes with masses equivalent to millions, or even billions, of suns. What's more, these supermassive black holes and their host galaxies appear to develop together, or "co-evolve." Theory predicts that as galaxies collide and merge, growing ever more massive.

Researchers have developed a new method for detecting and measuring one of the most powerful, and most mysterious, events in the Universe - a black hole being kicked out of its host galaxy and into intergalactic space at speeds as high as 5000 kilometers per second.

"When the detection of gravitational waves was announced, a new era in astronomy began, since we can now actually observe two merging black holes," said study co-author Christopher Moore, a Cambridge University PhD student who was also a member of the team which announced the detection of gravitational waves earlier this year. "We now have two ways of detecting black holes, instead of just one - it's amazing that just a few months ago, we couldn't say that. And with the future launch of new space-based gravitational wave detectors, we'll be able to look at gravitational waves on a galactic, rather than a stellar, scale."

The method, developed by researchers from the University of Cambridge, could be used to detect and measure so-called black hole superkicks, which occur when two spinning supermassive black holes collide into each other, and the recoil of the collision is so strong that the remnant of the black hole merger is bounced out of its host galaxy entirely. Their results are reported in the journal Physical Review Letters.

Earlier this year, the LIGO Collaboration announced the first detection of gravitational waves - ripples in the fabric of spacetime - coming from the collision of two black holes, confirming a major prediction of Einstein's general theory of relativity and marking the beginning of a new era in astronomy. As the sensitivity of the LIGO detectors is improved, even more gravitational waves are expected to be detected - the second successful detection was announced in June.

As two black holes circle each other, they emit gravitational waves in a highly asymmetric way, which leads to a net emission of momentum in some preferential direction. When the black holes finally do collide, conservation of momentum imparts a recoil, or kick, much like when a gun is fired. When the two black holes are not spinning, the speed of the recoil is around 170 kilometres per second. But when the black holes are rapidly spinning in certain orientations, the speed of the recoil can be as high as 5000 kilometres per second, easily exceeding the escape velocity of even the most massive galaxies, sending the black hole remnant resulting from the merger into intergalactic space.

The Cambridge researchers have developed a new method for detecting these kicks based on the gravitational wave signal alone, by using the Doppler Effect. The Doppler Effect is the reason that the sound of a passing car seems to lower in pitch as it gets further away. It is also widely used in astronomy: electromagnetic radiation coming from objects which are moving away from the Earth is shifted towards the red end of the spectrum, while radiation coming from objects moving closer to the Earth is shifted towards the blue end of the spectrum. Similarly, when a black hole kick has sufficient momentum, the gravitational waves it emits will be red-shifted if it is directed away from the Earth, while they will be blue-shifted if it's directed towards the Earth.

"If we can detect a Doppler shift in a gravitational wave from the merger of two black holes, what we're detecting is a black hole kick," said study co-author Davide Gerosa, a PhD student from Cambridge's Department of Applied Mathematics and Theoretical Physics. "And detecting a black hole kick would mean a direct observation that gravitational waves are carrying not just energy, but linear momentum as well."

Detecting this elusive effect requires gravitational-wave experiments capable of observing black hole mergers with very high precision. A black hole kick cannot be directly detected using current land-based gravitational wave detectors, such as those at LIGO. However, according to the researchers, the new space-based gravitational wave detector known as eLISA, funded by the European Space Agency (ESA) and due for launch in 2034, will be powerful enough to detect several of these runaway black holes. In 2015, ESA launched the LISA Pathfinder, which is successfully testing several technologies which could be used to measure gravitational waves from space.

The researchers found that the eLISA detector above will be particularly well-suited to detecting black hole kicks: it will be capable of measuring kicks as small as 500 kilometres per second, as well as the much faster superkicks. Kick measurements will tell us more about the properties of black hole spins, and also provide a direct way of measuring the momentum carried by gravitational waves, which may lead to new opportunities for testing general relativity.

The Daily Galaxy via University of Cambridge and NASA/JPL

Image credit top of page: ligo.caltech.edu

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The Vanishing Planet

“Red dwarfs the dim bulbs of the cosmos have received scant attention by SETI scientists in the past,” SETI Institute engineer Jon Richard said last week in a news release announcing the initiative. “That's because researchers made the seemingly reasonable assumption that other intelligent species would be on planets orbiting stars similar to the sun.”

The srtistic representation shows the potentially habitable world Kapteyn b with the globular cluster Omega Centauri in the background. It is believed that the Omega Centauri is the remaining core of a dwarf galaxy that merged with our own galaxy billions of years ago bringing Kapteyn's star along. (PHL @ UPR Arecibo, Aladin Sky Atlas).

The SETI Institute belives that planetary systems orbiting red dwarfs — dim, long-lived stars that are on average billions of years older than our sun — are worth investigating for signs of advanced extraterrestrial life. The star that's closest to our sun, Proxima Centauri, is a red dwarf. A variety of observing efforts, including Cornell's Pale Red Dot initiative, are looking for habitable planets around Proxima Centauri (shown above).

The two-year project involves picking from a list of about 70,000 red dwarfs and scanning 20,000 of the nearest ones, along with the cosmic bodies that circle them using the SETI Institute's Allen Telescope Array in the High Sierras of northern California, a group of 42 antennas that can observe three stars simultaneously.

“We'll scrutinize targeted systems over several frequency bands between 1 and 10 GHz,” said SETI scientist Gerry Harp. “Roughly half of those bands will be at so-called ‘magic frequencies' — places on the radio dial that are directly related to basic mathematical constants. It's reasonable to speculate that extraterrestrials trying to attract attention might generate signals at such special frequencies.”

For a long time, scientists ruled out searching around red dwarfs because habitable zones around the stars are small, and planets orbiting them would be so close that one side would be constantly facing the star, making one side of the planet very hot and the other quite cold and dark.

But more recently, scientists have learned that heat could be transported from the light side of the planet to the darker side, and that much of the surface could be amenable to life.

“In addition, exoplanet data have suggested that somewhere between one sixth and one half of red dwarf stars have planets in their habitable zones, a percentage comparable to, and possibly greater than, for Sun-like stars,” said the statement.

The brightest of Red Dwarfs are a tenth as luminous as the sun, and some are just 0.01 percent as bright, but account for three-quarters of all stars, with 6 percent or more of all red dwarfs having potentially habitable, Earth-sized planets.

The Daily Galaxy via SETI Institute, and AFP

Image credits: NASA/Chandra X-Ray Space Observatory

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Traditional Basque dancers at the 2016 Smithsonian Folklife Festival on the National Mall in Washington, D.C. (Flickr photo by Victoria Pickering)

Martha Gonzalez is doing double-duty during the Folklife Festival, playing with the band Quetzal and with the FandangObon group. Today she danced on the tarima platform with her son jarocho group. You can find them each day at the Sounds of California Stage & Plaza. (Photo by Walter Larrimore, Ralph Rinzler Folklife Archives)

Salar Nader is a master of the tablas. He, along with rubâb player Homayoun Sakhi, performed in the opening ceremony and again in the afternoon at the Sounds of California Stage & Plaza. (Photo by Ronald Villasante, Ralph Rinzler Folklife Archives)

Demonstration of a rural Basque sportthe object is to cut 6 slices of no more than 3 centimeters thick, as fast as possible. At the 2016 Smithsonian Folklife Festival on the National Mall. (Flickr photo by Victoria Pickering)

Irati Anda and Xabier Paya are bertsolariak, Basque poets who improvise songs on given topics. In today's “Berto Workshop,” they sang about arriving in Washington, their favorite sports, and Xabi's amuma (grandmother). (Photo by Maureen Spagnolo, Ralph Rinzler Folklife Archives)

FandangObon got the audience circling around the Sounds of California Stage & Plaza with a mix of Japanese and Mexican dance traditions. Want to join in? You have no choice! Just dance! (Photo by Francisco Guerra, Ralph Rinzler Folklife Archives)

he day evening with an evening concert by Basque accordion virtuoso Kepa Junkera. Dancers from Aukeran and visitors joined in kalejira, the Basque festival tradition of “going around singing and dancing.” Photo by Josh Weilepp, Ralph Rinzler Folklife Archives