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Categories: Physics: Acoustics and Ultrasound, Space: The Solar System

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Scientists have solved a long-standing space mystery -- the origin of the 'theta aurora'. Auroras are the most visible manifestation of the Sun's effect on Earth. They are seen as colorful displays in the night sky, known as the Northern or Southern Lights. They are caused by the solar wind, a stream of plasma -- electrically charged atomic particles -- carrying its own magnetic field, interacting with the earth's magnetic field. Normally, the main region for this impressive display is the 'auroral oval', which lies at around 65-70 degrees north or south of the equator, encircling the polar caps. However, auroras can occur at even higher latitudes. One type is known as a 'theta aurora' because seen from above it looks like the Greek letter theta -- an oval with a line crossing through the center.

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The closest planet to the sun appears to get hit by a periodic meteor shower, possibly associated with a comet that produces multiple events annually on Earth. The clues pointing to Mercury's shower were discovered in the very thin halo of gases that make up the planet's exosphere, which is under study by NASA's MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft.

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The Voyager 1 spacecraft has experienced three shock waves. The most recent shock wave, first observed in February 2014, still appears to be going on. One wave, previously reported, helped researchers determine that Voyager 1 had entered interstellar space.

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The normally bland face of Uranus has become increasingly stormy, with enormous cloud systems so bright that for the first time, amateur astronomers are able to see details in the planet's hazy blue-green atmosphere. Astronomers first observed the storms in the infrared using the Keck telescope. When amateurs learned of the storms, they turned their optical telescopes on the planet and saw different but equally impressive storms.

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Several organizations are eligible to name one of 20 to 30 planets, and their host stars, in a unique competition organized by the International Astronomical Union (IAU). The scheme gives members of the public the chance to name the newly discovered ExoWorlds (which have all been identified and confirmed since 2008).

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On Oct. 18, 2014, a sunspot rotated over the left side of the sun, and soon grew to be the largest active region seen in the current solar cycle, which began in 2008. Currently, the sunspot is almost 80,000 miles across -- ten Earth's could be laid across its diameter.

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Venus is hiding something beneath its brilliant shroud of clouds: a first order mystery about the planet that researchers may be a little closer to solving because of a new re-analysis of twenty-year-old spacecraft data. Venus's surface can't be seen from orbit in visible light because of the planet's hot, dense, cloudy atmosphere. Instead, radar has been used by spacecraft to penetrate the clouds and map out the surface – both by reflecting radar off the surface to measure elevation and by looking at the radio emissions of the hot surface. The last spacecraft to map Venus in this way was Magellan, two decades ago.

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Our view of other solar systems just got a little more familiar, with the discovery of a planet 25,000 light-years away that resembles our own Uranus. Astronomers have discovered hundreds of planets around the Milky Way, including rocky planets similar to Earth and gas planets similar to Jupiter. But there is a third type of planet in our solar system -- part gas, part ice -- and this is the first time anyone has spotted a twin for our so-called "ice giant" planets, Uranus and Neptune.

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As the search for Earth-like planets wages on, a team of researchers may have found a way to speed up the process. The team is developing a new laser-based technology known as the green astro-comb to obtain information about the mass of a distant planet. Using this information, astronomers will be able to determine whether distant exoplanets are rocky worlds like Earth or less dense gas giants like Jupiter.

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Astronomers have just proposed a solution to the problematic chemical composition of Uranus and Neptune, thus providing clues for understanding their formation. The researchers focused on the positioning of these two outermost planets of the Solar System, and propose a new model explaining how and where they formed.

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Miranda, a small, icy moon of Uranus, is one of the most visually striking and enigmatic bodies in the solar system. Despite its relatively small size, Miranda appears to have experienced an episode of intense resurfacing that resulted in the formation of at least three remarkable and unique surface features -- polygonal-shaped regions called coronae.

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Underscoring the vast differences between Earth and its neighbor Venus, new research shows a glimpse of giant holes in the electrically charged layer of the Venusian atmosphere, called the ionosphere. The observations point to a more complicated magnetic environment than previously thought -- which in turn helps us better understand this neighboring, rocky planet.

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Blame the 'hot Jupiters.' These large, gaseous exoplanets can make their suns wobble when they wend their way through their own solar systems to snuggle up against their suns, according to new research.

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Astronomers have defined the 'Venus Zone,' the area around a star in which a planet is likely to exhibit the unlivable conditions found on the planet Venus. The research will aid Kepler astronomers searching for exoplanets, helping them determine which are likely to be similar to Earth and which are more likely to resemble Venus.

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The Atacama Large Millimeter/submillimeter Array (ALMA) has reached a major milestone by extending its vision fully into the realm of the submillimeter, the wavelengths of cosmic light that hold intriguing information about the cold, dark, and distant Universe.

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On the evening of Aug. 20, 2014, the International Space Station was flying past North America when it flew over the dazzling, green blue lights of an aurora. On board, astronaut Reid Wiseman captured this image of the aurora, seen from above.

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Mercury's interior is different from the Earth's interior in a way that explains Mercury's bizarre magnetic field, planetary physicists report. Measurements from NASA's Messenger spacecraft have revealed that Mercury's magnetic field is approximately three times stronger at its northern hemisphere than its southern one.

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Astronomers have discovered a transiting exoplanet with the longest known year. Kepler-421b circles its star once every 704 days. In comparison, Mars orbits our Sun once every 780 days. Most of the 1,800-plus exoplanets discovered to date are much closer to their stars and have much shorter orbital periods.

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Understanding the sun from afar isn't easy. NASA's MESSENGER spacecraft -- which orbits Mercury, and so is as close as 28 million miles from the sun versus Earth's 93 million miles -- is near enough to the sun to detect solar neutrons that are created in solar flares.

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New simulations show that Mercury and other unusually metal-rich objects in the solar system may be relics left behind by hit-and-run collisions in the early solar system. The origin of planet Mercury has been a difficult question in planetary science because its composition is very different from that of the other terrestrial planets and the moon.