- 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.”
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.
- 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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