March 7 – Star Light, Star Bright

Today’s Factismal: A single solar flare can release as much energy as 10,000,000 50 megaton bombs; that’s 500 times the total number of nuclear weapons on Earth.

If you’ve ever seen Star Wars, then you know how Vader feels about “technological terrors” – they are insignificant compared to the power of the force. And Vader was right; even the largest weapon designed by man is pretty puny when compared to the power of the Sun. That flaming mass of incandescent gas (plasma, actually) not only holds 99% of the matter in the Solar System but also creates 99.999% of the energy (the rest is released by radioactive decay in planets and fossil heat from the formation of the planets).

The Sun generates energy by making big atoms out of little ones (Image courtesy NASA)

The Sun generates energy by making big atoms out of little ones (Image courtesy NASA)

But how does the Sun generate all of that power? It turns out that we didn’t know the basics of the process until 1938 and we are still discovering new facets of how the process works. The fundamental process is fairly simple. Six hydrogen atoms are stripped of their electrons by the immense heat in the Sun’s interior, leaving six “naked” nuclei formed of a single proton. Four of the hydrogen nuclei are forced together and form two new atomic nuclei with two protons in each. Each of the new atomic nuclei gets one of the remaining protons and forms helium-3. The two helium-3 nuclei fuse together to form beryllium-6. But beryllium-6 is unstable and splits apart into helium-4 and two spare protons, along with some energy. Because four of the protons end up snuggled close together, they have less energy than the protons had when they were flying around by themselves (some astronomers refer to this as the “married couples effect”). That spare energy is what powers the Sun.

But raw energy isn’t all that the Sun creates. Those protons are charged particles, moving around in big bunches. As you probably remember from your high school physics, when you start moving charged things around, you create magnetic fields. And, because the magnetic fields can interact with the charged particles, the paths that the particles take are changed by the fields that they generate (a similar process happens in the Earth’s core and is responsible for creating the magnetic field). Astrophysicists call this “applied magnetohydrodynamics”; everybody else calls it “darn complicated”. And, as you might expect, in a process this complicated, things can and do go wrong.

A time-lapse photo of a solar flare (Image courtesy NASA)

A time-lapse photo of a solar flare (Image courtesy NASA)

Sometimes the magnetic fields get twisted around each other, forming cool areas on the Sun’s surface; we know these as sunspots. And sometimes the fields get really, really twisted and snap, releasing an enormous surge of energy known as a flare. Flares spew more than energy, too; they also throw huge clouds of atoms and atom pieces (electrons, protons, and ions) into space. When the charged particles hit the Earth’s atmosphere, they trigger the massive light shows known as the Aurora Borealis and Australis.

A composite image showing lots of flares on the Sun's surface (Image courtesy NASA)

A composite image showing lots of flares on the Sun’s surface (Image courtesy NASA)

Flares can also trigger coronal mass ejections, which is a really boring name for a really cool problem. CMEs (as the cool astronomers call them) are solar flares writ large. These violent episodes can dump ten billion tons of highly charged particles into space at speeds of a million miles an hour or more; think of an armada of 200,000flaming battleships going from London to New York in twelve seconds and you’ve got the idea. When CMEs hit the atmosphere, their effects can range from boring but pretty (“Ooh, look at the aurora!”) to disastrous; some experts blame the 1989 power failure in Canada on a CME.

The first space telescope OSO1 (Image courtesy NASA)

The first space telescope OSO1 (Image courtesy NASA)

Though we’ve been watching solar flares since 1859, there’s still a lot to learn. That’s why NASA launched the first space telescope on March 7, 1962. Called OSO1 (for Orbiting Solar Observatory), it was used to detect solar flares and other oddities by looking at the Sun in the gamma ray, X-ray, and ultraviolet parts of the spectrum. Though it only operated for a few months, it opened the way to other space-based telescopes, such as the Hubble and SOHO.

If you’d like to help scientists learn more about solar flares, then why not join the scientists at Solar Storm Watch and help them spot solar flares, sunspots, and CMEs?

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