Comet Siding Spring is plunging toward the Sun along a roughly 1-million-year orbit. The comet, discovered in 2013, was within the radius of Jupiter's orbit when the Hubble Space Telescope photographed it on March 11, 2014. Hubble resolves two jets of dust coming from the solid icy nucleus. These persistent jets were first seen in Hubble pictures taken on Oct. 29, 2013. The feature should allow astronomers to measure the direction of the nucleus's pole, and hence, rotation axis. The comet will make its closest approach to our Sun on Oct. 25, 2014, at a distance of 130 million miles, well outside Earth's orbit. On its inbound leg, Comet Siding Spring will pass within 84,000 miles of Mars on Oct. 19, 2014, which is less than half the Moon's distance from Earth. The comet is not expected to become bright enough to be seen by the naked eye.
Scientists have for the first time witnessed the mechanism behind explosive energy releases in the Sun’s atmosphere, confirming new theories about how solar flares are created.
New footage put together by an international team led by University of Cambridge researchers shows how entangled magnetic field lines looping from the Sun’s surface slip around each other and lead to an eruption 35 times the size of the Earth and an explosive release of magnetic energy into space.
The discoveries of a gigantic energy build-up bring us a step closer to predicting when and where large flares will occur, which is crucial in protecting the Earth from potentially devastating space weather. The study is published in The Astrophysical Journal.
While solar flares have long been a spectacular reminder of our star’s power, they are also associated with Coronal Mass Ejections (CMEs) – eruptions of solar material with a twisted magnetic structure flying out of the Sun and into interplanetary space.
Space weather such as CMEs has been identified as a significant risk to the country’s infrastructure by the UK’s National Risk Register. Late last year The UK’s MET Office announced it would set up a daily space weather forecast to work with the USA’s Space Weather Prediction Center (SWPC).
The paper’s lead author, Dr Jaroslav Dudik, Royal Society Newton International Fellow at the University of Cambridge’s Centre for Mathematical Sciences, said: “We care about this as during flares we can have CMEs and sometimes they are sent in our direction. Human civilisation is nowadays maintained by technology and that technology is vulnerable to space weather. Indeed, CMEs can damage satellites and therefore have an enormous financial cost.”
“They can also threaten airlines by disturbing the Earth’s magnetic field. Very large flares can even create currents within electricity grids and knock out energy supplies.”
One such event hit the Earth before technology was as integrated into human civilization as it is now, but still had a marked effect. In 1859 the Carrington storm made night skies so bright that newspapers could be read as easily as in daylight and telegraph systems caught fire.
Knowing the standard scientific models are right is therefore very important. The standard 3D model of solar flares has shown that they occur in places where the magnetic field is highly distorted.
In these places, the magnetic field lines can continuously reconnect while slipping and flipping around each other. In doing so, new magnetic structures are created.
Long before the flare the magnetic field lines are un-entangled and they appear in a smooth arc between two points on the photosphere (the Sun’s visible surface) – areas called field line footpoints.
In a smooth, none-entangled arc the magnetic energy levels are low but entanglement will occur naturally as the footpoints move about each other. Their movement is caused as they are jostled from below by powerful convection currents rising and falling beneath the photosphere.
As the movement continues the entanglement of field lines causes magnetic energy to build up.
Like a group of straight cords which has been twisted, the lines will hold the energy until it becomes too great and then will release it, “straightening” back to the lower energy state.
Co-author Dr Helen Mason, Head of the Atomic Astro-Physics Group at the University of Cambridge, said: “You build the stress slowly until a point where they are no longer sustainable. The field lines say they have had enough and ‘ping’, they go back to something simple.”
That “ping” creates the solar flare and CME. The word “ping” belies its power of course. Temperatures in the hotspots of the ejection can reach almost 20 million Degrees Celsius.
The theory remained unconfirmed until Dudik was reviewing footage of the Sun for an unrelated project last year.
It is no surprise it has taken so long to make the discovery. The technology that created the video is part of the Solar Dynamics Observatory (SDO) satellite mission which was only launched in 2010 by NASA.
It watches the Sun in the ultra-violet with the Atmospheric Imaging Assembly (AIA) capturing ultra-high-definition images every 12 seconds.
The final piece of the theoretical jigsaw was put in place in 2012 by French scientists – a paper published just six days before the flare occurred. Dudik admits that the serendipity the discovery is hard to ignore. But in science, fortune favours the prepared: “Suddenly I knew what I was looking at,” he said.
What Dudik witnessed was the ultra-violet dance caused by the magnetic field lines slipping around each other, continuously “unzipping” and reconnecting as the footpoints of the flare loops move around on the surface. But during the flare, the footpoint slipping motion is highly ordered and much faster than the random motions entangling the field before the flare.
Dudik’s observations were helped by the sheer size of the flare he was looking at – it could encompass 35 Earths. Not only that, the flare was of the most energetic kind, known as an X Class flare, and it took around an hour to reach its maximum.
If it had happened in a smaller flare, the slipping motion might not have been visible, even with NASA’s technology to help.
Although only seen in an X Class flare to date, the mechanism might well be something which happens in all flares, said Dudik: “But we are not yet certain.”
The importance of seeing the evidence of theory cannot be underestimated said Dr Mason: “In recent years there have been a lot of developments theoretically but unless you actually tie that down with observations you can speculate widely and move further away from the truth, not closer, without knowing it.”
Video of magnetic field lines “slipping reconnection” bring scientists a step closer to predicting when and where large flares will occur.astrophysicsJaroslav DudikHelen MasonRoyal SocietyNASADepartment of Applied Mathematics and Theoretical PhysicsCentre for Mathematical SciencesHuman civilisation is nowadays maintained by technology and that technology is vulnerable to space weather.Dr Jaroslav Dudik Further information
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Solar System: Ring in the new
Nature 508, 7494 (2014). doi:10.1038/nature13218
Authors: Joseph A. Burns
Planets are no longer the only Solar System bodies sporting ring systems. Two dense rings have been detected encircling a Centaur object — a relatively small, icy interloper from the distant reaches of the Solar System. See Letter p.72
A ring system detected around the Centaur (10199) Chariklo
Nature 508, 7494 (2014). doi:10.1038/nature13155
Authors: F. Braga-Ribas, B. Sicardy, J. L. Ortiz, C. Snodgrass, F. Roques, R. Vieira-Martins, J. I. B. Camargo, M. Assafin, R. Duffard, E. Jehin, J. Pollock, R. Leiva, M. Emilio, D. I. Machado, C. Colazo, E. Lellouch, J. Skottfelt, M. Gillon, N. Ligier, L. Maquet, G. Benedetti-Rossi, A. Ramos Gomes, P. Kervella, H. Monteiro, R. Sfair, M. El Moutamid, G. Tancredi, J. Spagnotto, A. Maury, N. Morales, R. Gil-Hutton, S. Roland, A. Ceretta, S.-h. Gu, X.-b. Wang, K. Harpsøe, M. Rabus, J. Manfroid, C. Opitom, L. Vanzi, L. Mehret, L. Lorenzini, E. M. Schneiter, R. Melia, J. Lecacheux, F. Colas, F. Vachier, T. Widemann, L. Almenares, R. G. Sandness, F. Char, V. Perez, P. Lemos, N. Martinez, U. G. Jørgensen, M. Dominik, F. Roig, D. E. Reichart, A. P. LaCluyze, J. B. Haislip, K. M. Ivarsen, J. P. Moore, N. R. Frank & D. G. Lambas
Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur—that is, one of a class of small objects orbiting primarily between Jupiter and Neptune—with an equivalent radius of 124 9 kilometres (ref. 2). There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period. This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites.
Astrophysics: Early quasars ate like the rest
Nature 507, 7493 (2014). doi:10.1038/507403d
The giant black hole in the most distant-known quasar, which formed just 750 million years after the Big Bang, engulfed matter at the same rate as much younger quasars.Alberto Moretti of the Brera Astronomical Observatory in Milan, Italy, and his colleagues used the European
Solar System: Stranded in no-man's-land
Nature 507, 7493 (2014). doi:10.1038/507435a
Authors: Megan E. Schwamb
The discovery of a second resident in a region of the Solar System called the inner Oort cloud prompts fresh thinking about this no-man's-land between the giant planets and the reservoir of comets of long orbital period. See Letter p.471
A Sedna-like body with a perihelion of 80 astronomical units
Nature 507, 7493 (2014). doi:10.1038/nature13156
Authors: Chadwick A. Trujillo & Scott S. Sheppard
The observable Solar System can be divided into three distinct regions: the rocky terrestrial planets including the asteroids at 0.39 to 4.2 astronomical units (au) from the Sun (where 1 au is the mean distance between Earth and the Sun), the gas giant planets at 5 to 30 au from the Sun, and the icy Kuiper belt objects at 30 to 50 au from the Sun. The 1,000-kilometre-diameter dwarf planet Sedna was discovered ten years ago and was unique in that its closest approach to the Sun (perihelion) is 76 au, far greater than that of any other Solar System body. Formation models indicate that Sedna could be a link between the Kuiper belt objects and the hypothesized outer Oort cloud at around 10,000 au from the Sun. Here we report the presence of a second Sedna-like object, 2012 VP113, whose perihelion is 80 au. The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort cloud, whose objects could outnumber all other dynamically stable populations in the Solar System.