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VIDEO: Two amazing views of Planet Earth

THESE TWO AMAZING NASA VIDEOS were taken by the astronauts aboard the International Space Station. The one above was made in mid March, and shows the view looking down as the Station sailed across Brazil and out into the Atlantic Ocean and across the Earth’s “terminator”. The terminator is the line dividing the half of the planet lit by the Sun and the half in shadow. The camera view also shows Soyuz (manned) and Progress (unmanned) spacecraft docked with the Station.

The video below was taken a little later in March and shows what it’s like to see an aurora from above. The Station was flying over the southern part of the Indian Ocean at the time. Toward the end of the video we can see daylight beginning to break across the horizon in the right-hand half of the screen.

Story by Jonathan Nally. Videos courtesy NASA.

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Solar storm reaches Earth

Illustration of space weather

Artist's illustration of events on the Sun changing the conditions in Near-Earth space

THIS WEEK SAW A HUGE solar disturbance that sent a storm of energy on a collision course with our planet.

The Sun erupted with one of the largest solar flares of this solar cycle on March 6. The flare was categorised as an X5.4, making it the second largest flare—after an X6.9 on August 9, 2011—since the Sun’s activity moved into a period of relatively low activity called solar minimum in early 2007. The current increase in the number of X-class flares is part of the Sun’s normal 11-year solar cycle, during which activity ramps up to solar maximum, which is expected to peak in late 2013.

About an hour later, the same region let loose an X1.3 class flare. An X1 is 5 times smaller than an X5 flare.

Space weather starts at the Sun. It begins with an eruption such as a huge burst of light and radiation called a solar flare or a gigantic cloud of solar material called a coronal mass ejection (CME). But the effects of those eruptions are felt at Earth, or at least near-Earth space. Scientists monitor several kinds of “space weather” events—geomagnetic storms, solar radiation storms, and radio blackouts—all caused by these immense explosions on the Sun.

Geomagnetic storms

One of the most common forms of space weather, a geomagnetic storm refers to any time Earth’s magnetic environment, the magnetosphere, undergoes sudden and repeated change. This is a time when magnetic fields continually re-align and energy dances quickly from one area to another.

Geomagnetic storms occur when certain types of CMEs connect up with the outside of the magnetosphere for an extended period of time. The solar material in a CME travels with its own set of magnetic fields. If the fields point northward, they align with the magnetosphere’s own fields and the energy and particles simply slide around Earth, causing little change. But if the magnetic fields point southward, in the opposite direction of Earth’s fields, the effects can be dramatic. The Sun’s magnetic fields peel back the outermost layers of Earth’s fields changing the whole shape of the magnetosphere. This is the initial phase of a geomagnetic storm.

The next phase, the main phase, can last hours to days, as charged particles sweeping into the magnetosphere accumulate more energy and more speed. These particles penetrate closer and closer to the planet. During this phase viewers on Earth may see bright aurora at lower latitudes than usual. The increase—and lower altitude—of radiation can also damage satellites travelling around Earth.

The final stage of a geomagnetic storm lasts a few days as the magnetosphere returns to its original state.

The movie below shows the March 6, 2012 X5.4 flare, captured by the Solar Dynamics Observatory (SDO) spacecraft. One of the most dramatic features is the way the entire surface of the Sun seems to ripple with the force of the eruption. This movement comes from something called EIT waves—because they were first discovered with the Extreme ultraviolet Imaging Telescope (EIT) on the Solar Heliospheric Observatory (SOHO).

Since SDO captures images every 12 seconds, it has been able to map the full evolution of these waves and confirm that they can travel across the full breadth of the Sun. The waves move at over a million miles per hour, zipping from one side of the Sun to the other in about an hour. The movie shows two distinct waves. The first seems to spread in all directions; the second is narrower, moving toward the southeast. Such waves are associated with, and perhaps trigger, fast coronal mass ejections, so it is likely that each one is connected to one of the two CMEs that erupted on March 6.

Geomagnetic storms do not always require a CME. Mild storms can also be caused by something called a co-rotating interaction region (CIR). These intense magnetic regions form when high-speed solar winds overtake slower ones, thus creating complicated patterns of fluctuating magnetic fields. These, too, can interact with the edges of Earth’s magnetosphere and create weak to moderate geomagnetic storms.

Geomagnetic storms are measured by ground-based instruments that observe how much the horizontal component of Earth’s magnetic field varies. Based on this measurement, the storms are categorized from G1 (minor) to G5 (extreme). In the most extreme cases transformers in power grids may be damaged, spacecraft operation and satellite tracking can be hindered, high frequency radio propagation and satellite navigation systems can be blocked, and auroras may appear much further south than normal.

Solar radiation storms

A solar radiation storm, which is also sometimes called a solar energetic particle (SEP) event, is much what it sounds like: an intense inflow of radiation from the Sun. Both CMEs and solar flares can carry such radiation, made up of protons and other charged particles. The radiation is blocked by the magnetosphere and atmosphere, so cannot reach humans on Earth. Such a storm could, however, harm humans travelling from Earth to the Moon or Mars, though it has little to no effect on airplane passengers or astronauts within Earth’s magnetosphere. Solar radiation storms can also disturb the regions through which high frequency radio communications travel. Therefore, during a solar radiation storm, airplanes travelling routes near the poles—which cannot use GPS, but rely exclusively on radio communications—may be re-routed.

Photo of an aurora

Aurorae occur primarily near Earth's poles. They are the most common and the only visual result of space weather. This aurora image associated with solar flares and CMEs on February 23-24, 2012 was taken over Muonio, Finland before sunrise on February 27, 2012.

Solar radiation storms are rated on a scale from S1 (minor) to S5 (extreme), determined by how many very energetic, fast solar particles move through a given space in the atmosphere. At their most extreme, solar radiation storms can cause complete high frequency radio blackouts, damage to electronics, memory and imaging systems on satellites, and radiation poisoning to astronauts outside of Earth’s magnetosphere.

Radio blackouts

Radio blackouts occur when the strong, sudden burst of X-rays from a solar flare hits Earth’s atmosphere, jamming both high and low frequency radio signals. The X-rays disturb a layer of Earth’s atmosphere known as the ionosphere, through which radio waves travel. The constant changes in the ionosphere change the paths of the radio waves as they move, thus degrading the information they carry. This affects both high and low frequency radio waves alike. The loss of low frequency radio communication causes GPS measurements to be off by feet to miles, and can also affect the applications that govern satellite positioning.

Radio blackouts are rated on a scale from R1 (minor) to R5 (extreme). The strongest radio blackouts can result in no radio communication and faulty GPS for hours at a time.

More information: Space Weather Frequently Asked Questions

Adapted from information issued by NASA. Images courtesy NASA and Thomas Kast. Video courtesy NASA / GSFC / SDO.

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Northern Lights put on a show

THE NORTHERN LIGHTS have been in the news lately, with some impressive displays reported this week. Here’s a plain-language Q&A on the Lights and when and where they can be seen.

Also called the “aurora borealis”, the Northern Lights are big patches of glowing air molecules high up in our atmosphere. The Southern Hemisphere equivalent is the “aurora australis” or Southern Lights.

To see the Northern Lights you have to be located in far northern latitudes, eg. UK, Scandinavia, northern Europe. Likewise, to see the Southern Lights you have to be located in far southern latitudes, eg. Tasmania, New Zealand and the tip of South America. The best view of the Southern Lights is to be had in Antarctica.

The Northern Lights get their name from the Roman goddess of dawn, Aurora, and the Greek name for the north wind, Boreas.

The video above shows what the aurora looks like from space.

What causes them?

They’re caused by an interaction between particles from the Sun, Earth’s magnetic field and Earth’s atmosphere.

The Sun sends out waves of electrically charged particles, sometimes in big clumps. Those particles get caught in Earth’s magnetic field and are funnelled downward from space and toward our north and south poles.

When they hit the molecules in our upper atmosphere, those molecules give off light—a bit like a giant fluorescent tube in the sky.

They occur very high up, in the upper layer of Earth’s atmosphere called the “thermosphere”—essentially, right on the edge of space

The different colours are caused by the different molecules in the air: oxygen produces a green or brownish glow, nitrogen produces a red or blue glow. The glows from oxygen and nitrogen can combine to produce a pink glow.

Here’s a very good video that explains how the aurora is produced:

Can we see them from Australia?

Yes, but you have be far south and away from city lights. During the time of solar maximum (see below), they’re often seen from Tasmania, southern Victoria and southern Western Australia. In the past, I’ve even heard reports of sightings from the Blue Mountains west of Sydney.

Because the Southern Lights occur down near Antarctica, from Australian latitudes they will be seen way down toward our southern horizon (if at all).

I understand that the next 12 months should be good to see them?

Yes. The Sun has an 11-year cycle of activity, and we’re coming up to “solar maximum” sometime in the next 12-18 months. So we can expect many more auroral reports.

Apart from a pretty light show, do they have any other effects on us?

The aurorae themselves don’t have any other effect, but the space weather that causes them can.

Those charged particles from the Sun, and the effect the solar wind can have on Earth’s magnetic field, can cause:

  • Damage or disruption to satellites, eg. GPS, communications, weather, military
  • Disruption to radio communications networks
  • Damage or disruption to electricity grids (due to currents induced into the grid by the changing magnetic field)
  • Damage or disruption to long pipeline systems (ditto)
  • Disruption to mineral exploration (which often relies on magnetic field information)

More information:

Space Weather.com

Aurora Watch

Aurora Alert

Aurora Forecast

Space Weather Prediction Centre

Ionospheric Prediction Service (Australian Government)

Story by Jonathan Nally.

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Astronaut’s view of Earth’s aurora

THIS VIDEO OF THE AURORA AUSTRALIS was created from a sequence of still shots taken by astronauts on board the International Space Station (ISS). The images were acquired on September 11, 2011 as the ISS orbit pass descended over eastern Australia.

The Aurora Australis is the glow produced by air molecules as charged particles from the Sun are deflected into the upper reaches of the atmosphere by Earth’s magnetic field.

Adapted from information issued by NASA.

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Exoplanets have unearthly light shows

Artist's concept of a 'hot Jupiter' planet

Artist's concept of a 'hot Jupiter' planet with two moons and a Sun-like star. The planet is cloaked in brilliant aurorae—100-1000 times brighter than Earth's—triggered by stellar storms.

BEINGS LIVING ON ‘HOT JUPITER’ PLANETS could be treated to a dazzling nightly light show a thousand times better than Earth’s Northern and Southern Lights.

Earth’s aurorae provide a dazzling light show to people living in the polar regions, with shimmering curtains of green and red undulating across the sky like a living creature.

But new research shows that aurorae on ‘hot Jupiter’ planets closely orbiting distant stars could be 100-1000 times brighter than Earthly aurorae. They also would ripple from equator to poles (due to the planet’s proximity to any stellar eruptions), treating the entire planet to an otherworldly spectacle.

“I’d love to get a reservation on a tour to see these aurorae!” said lead author Ofer Cohen, a SHINE-NSF postdoctoral fellow at the Harvard-Smithsonian Centre for Astrophysics (CfA).

Gigantic stellar blasts

Earth’s aurorae are created when energetic particles from the Sun slam into our planet’s magnetic field. The field guides the particles toward the poles, where they smash into Earth’s atmosphere, causing air molecules to glow like a neon sign.

The same process can occur on planets orbiting distant stars, known as exoplanets.

Aurora Australis seen from the International Space Station

The Southern Lights or Aurora Australis seen from the International Space Station on July 14, 2011.

Particularly strong aurorae result when Earth is hit by a coronal mass ejection or CME—a gigantic blast that sends billions of tonnes of solar plasma (electrically charged, hot gas) into the Solar System.

A CME can disrupt Earth’s magnetosphere—the bubble of space protected by Earth’s magnetic field—causing a geomagnetic storm. In 1989, a CME hit Earth with such force that the resulting geomagnetic storm blacked out huge regions of Quebec.

Planets in the firing line

Cohen and his colleagues used computer models to study what would happen if a gas giant planet in a close orbit, just a few million kilometres from its star, were hit by a stellar eruption.

He wanted to learn the effect on the exoplanet’s atmosphere and surrounding magnetosphere.

The alien gas giant would be subjected to extreme forces. In our Solar System, a CME spreads out as it travels through space, so it’s more diffuse once it reaches us.

Aurora planet animation

In this animation, stunning aurorae (pink/purple) ripple around a 'hot Jupiter' planet.

A ‘hot Jupiter’ would feel a stronger and more focused blast, like the difference between being 100 kilometres from an erupting volcano or one kilometre away.

“The impact to the exoplanet would be completely different than what we see in our Solar System, and much more violent,” said co-author Vinay Kashyap of CfA.

Yet despite the extreme forces involved, the exoplanet’s magnetic field would shield its atmosphere from erosion.

Too close for comfort

This work has important implications for the habitability of rocky worlds orbiting distant stars. Since red dwarf stars are the most common stars in our galaxy, astronomers have suggested focusing on them in the search for Earth-like worlds.

However since a red dwarf is cooler than our Sun, a rocky planet would have to orbit very close to the star to be warm enough for water to exist as a liquid. There, it would be subjected to the sort of violent stellar eruptions Cohen and his colleagues studied.

Their future work will examine whether rocky worlds could shield themselves from such eruptions.

Adapted from information issued by the Harvard-Smithsonian Centre for Astrophysics. Images courtesy David A. Aguilar (CfA). Animation produced by Hyperspective Studios.

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Amazing aurora videos

Saturn’s eerie polar light show

False-colour image of Saturn

This false-colour composite of 65 Cassini spacecraft images shows the glow of the aurora over Saturn's north polar region. The colours are: blue is sunlight reflecting from the rings and from one of Saturn's cloud levels; red shows where heat is coming from the interior of the planet; and green shows the aurora.

  • Mini-movie made of Saturn’s polar aurora
  • Uses data from NASA’s Cassini spacecraft
  • Aurora pulses in time with the Sun and Saturn’s spin

As if its rings weren’t spectacular enough, Saturn also puts on a light show for anyone who can see at the right wavelengths.

In this case, those eyes belong to NASA’s Cassini spacecraft, which has been orbiting the Ringed Planet since 2004.

Scientists using Cassini’s visual and infrared mapping spectrometer (VIMS) instrument have been studying Saturn’s aurora, the equivalent of Earth’s Northern and Southern Lights.

Aurorae occur when particles in the solar wind are directed along magnetic field lines towards a planet’s poles. Funnelling down into the atmosphere, they strike gas molecules and cause an eerie, but very pretty, glow.

“Cassini’s instruments have been imaging the aurora in magnificent detail, but to understand the overall nature of the auroral region we need to make a huge number of observations—which can be difficult because Cassini observation time is in high demand,” says Dr Tom Stallard of the University of Leicester in the UK.

Time-lapse video of Saturn's aurora

This time-lapse video covers 20 Earth hours—just under two whole Saturnian days. Parts of the aurora seem synchronised with the direction of the Sun (left-hand side), while other parts appear orchestrated with Saturn's magnetic field.

So Dr Stallard and his colleagues turned to other Cassini images that weren’t specifically targeted at the aurora—but which nevertheless happened to serendipitously capture it—to compile a short video that shows the aurora’s behaviour as Saturn rotates.

“Sometimes the aurora can be clearly seen, sometimes we have to add multiple images together to produce a signal,” Dr Stallard said.

The video shows the aurora changing considerably during the over the course of Saturn’s day, which is around 10 hours and 47 minutes in Earth time.

On the left-hand side of the video—the direction towards the Sun—the aurora brightens, indicating that it is being influenced by the Sun.

Other parts of the aurora seem more connected with the planet below; specifically, with the orientation of Saturn’s magnetic field as the planet spins.

“Saturn’s aurora are very complex and we are only just beginning to understand all the factors involved,” said Stallard.

Story by Jonathan Nally, editor SpaceInfo.com.au

Images courtesy NASA / JPL / University of Leicester / University of Arizona.

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How long is a day on Saturn?

  • Saturn’s northern and southern lights found to pulse
  • Pulsation pattern is same as radio emission from Saturn
  • Gives hints as to the planet’s so-far uncertain day length

A team of scientists led by Dr Jonathan Nichols of the University of Leicester has found that Saturn’s aurora—an ethereal ultraviolet glow near the planet’s poles (see video above)—pulses roughly once per Saturnian day.

The length of Saturn’s day has been under much discussion since it was discovered that the traditional ‘clock’ used to measure the planet’s rotation period, apparently does not keep good time.

Like all magnetised planets, Saturn—a gas giant with no visible solid surface for reference—emits radio waves into space from its polar regions. These radio emissions pulse with a period near to 11 hours, and the timing of the pulses was originally thought to represent the rotation of the planet.

However, over the years the period of the pulsing has varied. Since the rotation of a planet cannot be easily sped up or slowed down, the hunt for the source of the varying radio period has become one of the most perplexing puzzles in planetary science.

Now, in a paper published in the journal Geophysical Research Letters, Nichols and colleagues have used images from the Hubble Space Telescope of Saturn’s aurorae to show that, not only do the radio emissions pulse, but the aurorae vary in time with the radio.

Aurorae, more commonly known as the “northern lights” or “southern lights” on Earth, are caused when charged particles in space are funnelled along a planet’s magnetic field and into the planet’s upper atmosphere near the poles, whereupon they hit gas particles and cause them to glow.

Saturn’s radio waves were long-suspected to be emitted by the charged particles as they hurtle toward the poles, but no pulsing had been observed in the aurora…a puzzling difference between two supposedly related phenomena.

However, the team found that by using the radio pulsing to organise the auroral data, and stacking all the Hubble Saturn images from 2005-2009 on top of each other, the auroral pulsing finally revealed itself.

“This confirms that the auroras and the radio emissions are indeed physically associated, as suspected,” adds Dr Nichols.

But does this research finally answer the question of the length of the Saturnian day?

The answer is no, it doesn’t quite. But it does help feed into the best current estimate: 10 hours, 32 minutes and 35 seconds.

And here’s a NASA/JPL video clip with space scientist Andy Ingersoll, who discusses the causes and effects of the aurora on Saturn:

Adapted from information issued by Jonathan Nichols / University of Leicester NASA / ESA / J. Clarke (Boston University) / Z. Levay (STScI).

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Solar storm heading our way

Image of the Sun taken on August 1 by NASA’s Solar Dynamics Observatory

Image of the Sun taken on August 1 by NASA’s Solar Dynamics Observatory. The solar eruption can be seen as the dark area in the top right portion of the Sun's disc.

  • Eruption on the Sun last weekend
  • Swarm of charged particles heading toward Earth
  • Stargazers might see aurorae in the night sky

Sky viewers might get to enjoy some spectacular Northern and Southern Lights, or aurorae, Tuesday or Wednesday nights, depending on where you are in the world.

After a long slumber, the Sun is waking up.

On Sunday, the Sun’s surface erupted and blasted tons of plasma (ionised atoms) into interplanetary space. That plasma is headed our way, and when it arrives, it could create a spectacular light show.

“This eruption is directed right at us, and is expected to get here early in the day [US time] on August 4th,” said astronomer Leon Golub of the Harvard-Smithsonian Centre for Astrophysics (CfA). “It’s the first major Earth-directed eruption in quite some time.”

The eruption, called a coronal mass ejection, was caught on camera by NASA’s Solar Dynamics Observatory (SDO), a spacecraft that launched in February. SDO provides better-than-HD quality views of the Sun at a variety of wavelengths.

“We got a beautiful view of this eruption,” said Golub. “And there might be more beautiful views to come, if it triggers aurorae.”

Below is a very short, speeded-up movie from the Solar Dynamics Observatory, showing a 3.5-hour sequence of X-ray images of the Sun taken on Sunday, August 1. In the upper right can be seen a dark filament of plasma erupting outward.

When a coronal mass ejection reaches Earth, it interacts with our planet’s magnetic field, potentially creating a geomagnetic storm. Solar particles stream down the field lines toward Earth’s poles. Those particles collide with atoms of nitrogen and oxygen in the atmosphere, which then glow like miniature neon signs.

Aurorae normally are visible only at high latitudes. However, during a geomagnetic storm aurorae can light up the sky at lower latitudes. Sky watchers in the northern USA and other Northern Hemisphere countries should look toward the north on the evening of August 3rd/4th for rippling “curtains” of green and red light.

For those at far southern latitudes in the Southern Hemisphere, the idea is to look to the south.

“It should be emphasised, however, that there is no guarantee of seeing an aurora,” said Jonathan Nally, editor of space news web site SpaceInfo.com.au. “Most of the time, only those who live at latitudes very far north in the Northern Hemisphere, or very far south in the Southern, have any chance of seeing an aurora.”

Solar cycle

The Sun goes through a regular activity cycle about 11 years long on average. The last solar maximum occurred in 2001. Its latest minimum was particularly weak and long lasting. This eruption is one of the first signs that the Sun is waking up and heading toward another maximum.

Solar storms can other affects than just producing pretty sky shows. Their interaction with Earth’s magnetic field and atmosphere can cause disruption to satellite and long-distance radio communications.

The can also cause disruptions to long pipeline operations and power grids, as these facilities act light giant radio antennae, experiencing power surges that can knock them out of operation.

In 1989, a significant portion of Quebec experienced an hours-long blackout when a major power grid went down in the wake of a solar storm.

This type of things is not expected to occur with Sunday’s storm, as it is a relatively minor one. But in five or six years time, when the Sun will be reaching the maximum of its cycle, it might be a different story.

Sun facts:

  • The Sun is 109 times wider than the Earth
  • Its mass is about 330,000 times that of the Earth
  • The Sun contains just under 99.9% of all the matter in our Solar System (all the planets, asteroids, comets etc, make up the rest)
  • Its surface temperature is 5,500 degrees Celsius
  • But the temperature at the core is 13.6 million degrees Celsius
  • Nuclear reactions in the core convert matter into energy at the rate of over 4 million tonnes per second! Even at that rate, the Sun will live for 10 billion years.
  • The energy released in the core takes tens of thousands years to reach the surface – from there, it travels at the speed of light and only takes just less than 8.5 minutes to reach Earth, 150 million kilometres away. So when we see the Sun, we see it as it was almost 8.5 minutes ago!

Adapted from information issued by the Harvard-Smithsonian Centre for Astrophysics / NASA.

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Below is a very short, speeded-up movie from the Solar Dynamics Observatory, shows a 3.5-hour sequence of X-ray images of the Sun taken on Sunday, August 1. In the upper right can be seen a dark filament of plasma erupting outward.