Halloween 2003 will live forever in the annals of solar history. In the space of two weeks centred around the spooky celebration, solar physicists witnessed the most sustained bout of solar activity since satellites took to the skies.

The Solar and Heliospheric Observatory (SOHO) was monitoring it all. The ultraviolet telescope captured the climax of activity on 4 November 2003, showing a blistering solar flare bursting from active region 10486 at 19:29 GMT. Solar flares are the near-instantaneous release of energy caused by a loop of magnetism snapping into a more stable configuration.

In this process, the energy of up to a thousand billion Hiroshima-sized atomic bombs can be released in just a few minutes. That release is seen here. The horizontal white streak is where the camera has been blinded by the brightness of the flare.

Things began when a giant sunspot, fully ten times the diameter of Earth, hove into view around the western limb of the Sun in late October. It was followed by another, equally large, spot and together they moved across the face of the Sun generating flares on an almost daily basis. This image shows the second spot’s parting volley.

Solar flares are classed according to the energy they release at X-ray wavelengths. There are three major categories: C, M and X, further divided into 10 subclasses. M1 flares are ten times more powerful than C1, and X1 flares are ten times more powerful than M1 flares, or 100 times more powerful than C1.

This 2003 flare was so powerful that it broke right through the top of the X-class range, which is usually given as X10. Analysis showed that it clocked in at X28, making it 28 times more powerful than an X1.

A billion tonnes or so of the solar atmosphere was propelled into space at a speed of 2300 km/s – a staggering 8.2 million km/h.

Credit: ESA/NASA

Tags:   SOHO Sun Solar and Heliospheric Observatory solar flare

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This image shows the Musca molecular clouds based on a combination of data from ESA’s Herschel and Planck space telescopes. The bright areas in the picture shows the emission by interstellar dust grains in three different wavelengths observed by Herschel (250, 350, and 500 microns) and the lines crossing the image in a ‘drapery pattern’ represent the magnetic field orientation (based on the Planck data.)

The Musca clouds are part of the Chamaeleon cloud complex, where the vast star-forming region overlaps with the constellation of Musca, the Fly. Resembling a streak of lightning, the well-defined, elongated molecular cloud spans three degrees across the sky. It is also sometimes called the Dark Doodad Nebula.

Magnetic field lines clearly appear to be perpendicular to the main filament in the cloud. Striations are present, although not necessarily connected to the main filament, and there are also denser hair-like strands – structures attached to the main filament. Strands are distributed all along the main filament.

Musca is similar to the B213 filament in the Taurus Molecular Cloud in terms of perpendicular striations, however Musca lacks the fine substructure of the Taurus filament.

Credits: ESA/Herschel/Planck; J. D. Soler, MPIA

Tags:   ESA European Space Agency Space Universe Cosmos Space Science Science Space Technology Tech Technology Space Science Image of the Week Herschel Planck Gas clouds Dust Taurus Ophiuchus Lupus Corona Australis Chamaeleon-Musca Aquila Rift Perseus Orion magnetic field

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This Cassini image shows Jupiter from an unusual perspective. If you were to float just beneath the giant planet and look directly up, you would be greeted with this striking sight: red, bronze and white bands encircling a hazy south pole. The multicoloured concentric layers are broken in places by prominent weather systems such as Jupiter’s famous Great Red Spot, visible towards the upper left, chaotic patches of cloud and pale white dots. Many of these lighter patches contain lightning-filled thunderstorms.

Jupiter has very dramatic weather – the planet’s axis is not as tilted (towards or away from the Sun) as much as Earth’s so it does not have significant seasonal changes, but it does have a thick and tumultuous atmosphere filled with raging storms and chaotic cloud systems.

These clouds, formed from dense layers of ammonia crystals, are tugged, stretched and tangled together by Jupiter’s turbulence and strong winds, creating vortices and hurricane-like storms with wind speeds of up to 360 km per hour.

The Great Red Spot is actually an anticyclone that has been violently churning for hundreds of years. It was at one stage large enough to contain several Earth-sized planets but recent images from the Hubble Space Telescope show it to be shrinking. There are other similarly striking storms raging in both Jupiter’s cool upper atmosphere and hotter lower layers, including a Great Dark Spot and Oval BA, more affectionately nicknamed Red Spot Jr.

Jupiter’s south pole is at the very centre of this image, visible as a murky grey-toned circle. This patch is not as detailed as the rest of the planet because Cassini had to peer through a lot more atmospheric haze in the polar region, making it harder to see.

This polar map is composed of 18 colour images taken by the narrow-angle camera on NASA’s Cassini spacecraft during a flyby on 11–12 December 2000. This map is incredibly detailed; the smallest visible features in this image are about 120 km across. There is also an accompanying map of the planet’s north pole. In 2016, NASA’s Juno spacecraft will arrive at Jupiter and start to beam back images of the planet’s poles.

The Cassini–Huygens mission, launched in 1997 as a joint endeavour of ESA, NASA and Italy’s ASI space agency, flew past Venus, Earth and Jupiter en route to observe Saturn, its moons and rings. Observations with Cassini have given us an unprecedented understanding of the Saturnian system. ESA’s Juice mission aims to do the same for Jupiter. Planned for launch in 2022, the spacecraft will reach Jupiter in 2030 and begin observing the planet and three of its moons – Ganymede, Callisto and Europa. Previous flybys of these moons have raised the exciting prospect that some of them might harbour subsurface liquid oceans and conditions suitable to support some forms of life.

Juice was recently given the green light to continue to the next stage of development.

Credit: NASA/JPL/Space Science Institute

Tags:   JUICE Cassini Jupiter

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Space Science image of the week:

In the early hours of Saturday morning, the international Cassini–Huygens mission made its final close flyby of Saturn’s largest moon, Titan, coming within 1000 km of the atmosphere-clad world.

The image presented here is a raw image sent back to Earth yesterday, taken on Saturday at 18:42 GMT. It is one of many that can be found in the Cassini raw image archive.

The latest flyby used Titan’s gravity to slingshot Cassini into the final phase of its mission, setting it up for a series of 22 weekly ‘Grand Finale’ orbits that will see the spacecraft dive between Saturn’s inner rings and the outer atmosphere of the planet. The first of these ring plane dives occurs on Wednesday.

Cassini will make many additional non-targeted flybys of Titan and other moons in the Saturnian system in the coming months, at much greater distances. Non-targeted flybys require no special manoeuvres, but rather the moon happens to be relatively close to the spacecraft’s path.

A final, distant, flyby of Titan will occur on 11 September, in what has been nicknamed the ‘goodbye kiss,’ because it will direct Cassini on a collision course with Saturn on 15 September. This will conclude the mission in a manner that avoids the possibility of a future crash into the potentially habitable ocean-moon Enceladus, protecting that world for future exploration.

A press conference will be held on 25 April at 13:30 GMT (15:30 CEST), at the European Geosciences Union meeting in Vienna, to preview the Grand Finale, as well as celebrate the scientific highlights of Cassini’s incredible 13-year odyssey at Saturn.

Just today a new result was published in Nature Astronomy finds that when viewed from Cassini's orbit, Titan's nightside likely shines 10-200 times brighter than its dayside. Scientists think that this is caused by efficient forward scattering of sunlight by its extended atmospheric haze, a behaviour unique to Titan in our Solar System.

Cassini–Huygens is a cooperative project of NASA, ESA and ASI, the Italian space agency.

Credit: NASA/JPL-Caltech/Space Science Institute

Tags:   Space Science Cassini-Huygens Flyby Titan Saturn gravity slingshot Image of the Week ESA NASA ASI

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Jupiter’s moon Europa is brimming with water. Although it is thought to be mostly made up of rocky material, the moon is wrapped in a thick layer of water – some frozen to form an icy crust, some potentially pooled in shallow underground lakes or layers of slush, and vast quantities more lurking even deeper still in the form of a giant subsurface ocean.

This false-colour image from NASA’s Galileo spacecraft shows a disrupted part of Europa’s crust known as Conamara Chaos. The long criss-crossing grooves etched into the shattered chunks of ice are a perfect example of “chaos terrain” – a feature seen most prominently in our Solar System on Europa, Mars and Mercury.

Although the exact ways chaos regions form are not completely understood, in the case of Europa scientists have a few ideas. One possibility is fast-moving impactors that smash through the moon’s brittle crust. As a liquid layer lies immediately beneath the crust, the shards are more mobile and can refreeze in different configurations, creating a fractured terrain with young scars carved into the icy plains.

Many chaos regions have small impact craters clustered nearby. In the case of Conamara Chaos, for example, a large 26 km-diameter crater named Pwyll lies 1000 km to the south, and a handful of smaller, 500 m-diameter craters are scattered throughout the region, likely formed by lumps of ice thrown up by the impact that created Pwyll.

Another suggestion is that Europa harbours an intricate system of shallow subsurface lakes. Instead of an object slamming into the Jovian moon, a lake system could influence and stress the crust from below to cause the thin ice sheets to fracture and collapse.

This patch of Europa’s crust takes on an iridescent appearance in this false-colour image, which strongly enhances subtle colour differences present in the scene. Areas of blue and white stand out distinctly from areas of rusty orange and bronze. This colouration is thought to be caused by material from Pwyll: when the crater formed it threw up a blanket of fine ice particles that settled over parts of Conamara Chaos, colouring parts of the landscape in dark blue (coarser particles of ice), light blue (smaller particles) and white (very fine particles). The bronze patches are regions of ice that have been stained by minerals from beneath the disrupted crust.

Although astronomers have studied Europa intensively, the only way to confirm the structure and composition of the moon is to probe its shell and interior with a space probe. ESA’s JUpiter ICy moons Explorer (Juice) mission aims to do just that when it arrives in the Jovian system in 2030. Alongside detailed studies of Jupiter itself, Juice will explore and characterise three of the gas giant’s potentially habitable icy moons: Ganymede, Europa and Callisto. The mission is in development, on track for launch in 2022.

North is to the top of the picture and the Sun illuminates the surface from the right side of the frame. The image is centred at 9ºN / 274ºW, and covers an area of some 70 km by 30 km. The image combines data taken by Galileo’s Solid State Imaging system during three orbits through the Jovian system in 1996 and 1997.

Credit: NASA/JPL/University of Arizona

Tags:   Jupiter moon Europa NASA’s Galileo spacecraft Conamara Chaos JUpiter ICy moons Explorer Juice

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