Orion climbs into good view in the east and southeast by about 8 p.m. In European mythology, Orion was a hunter. But to the Maya, those stars probably represented a turtle and the “hearth” of the heavens, corresponding to the central fire in a Mayan household.

The letter X has a big reputation. It’s used to designate things that are powerful, scary, mysterious, or all of the above. So we have X-rays and X Men, the X Files and X planes, and in the movies, at least a couple of spies designated triple-X.

The Sun gets into the act, too, with X-class solar flares — eruptions that are powerful, scary, and a bit mysterious.

Solar flares are massive explosions. They occur when the lines of the Sun’s magnetic field tangle up, snap, then reconnect. They generate outbursts of particles and radiation that race into the solar system — and they can have dramatic impacts on Earth.

Scientists use five letters to designate the power of a solar flare. From weakest to strongest, they’re A, B, C, M, and X.

The first three categories are fairly mild. Class M flares can have some impact on Earth, but the really nasty ones are the X-class. The largest can produce as much energy as a billion hydrogen bombs.

They’re often accompanied by massive outbursts of charged particles. They can fry orbiting satellites, disrupt radio broadcasts, and knock out power grids. They can force airlines to reroute flights away from the north pole to avoid dangerous levels of radiation. And they can produce displays of the northern lights in places that seldom see them.

The Sun is getting more active these days, building toward the peak of its magnetic cycle in a couple of years — a lot of X-flares in our future.
 

Script by Damond Benningfield

An "X-class" solar flare erupts from the limb of the Sun in this 2014 image. X flares are the most powerful solar flares, which are giant eruptions of radiation and charged particles. Such flares can disrupt spacecraft, knock out power grids on Earth's surface, and cause other problems. Such flares are most common near the peak of the Sun's 11-year magnetic cycle. The next cycle currently is forecast to peak in 2024. [NASA/GSFC/SDO/Wiessinger]

Two birds wade low across the southern sky early tonight. They are the constellations Grus, the crane, and Phoenix, the firebird. They are best seen from the southern third of the country, with Grus standing a little taller than its cousin.

The Sun is getting brighter.

Not enough to notice, mind you. In fact, it’ll take more than a hundred thousand human lifetimes to tick up by even one percent. But that gradual change will add up. In a billion years or so, the extra energy should be enough to boil away Earth’s oceans and atmosphere, leaving nothing but a burned-out ball of rock.

The change is the result of changes deep inside the Sun.

Our star shines because its core is a giant nuclear reactor. It “fuses” lightweight hydrogen atoms to make heavier helium atoms — a process that produces enough energy to power the Sun.

As more hydrogen is converted to helium, the core shrinks and gets denser, which makes it hotter. And as the temperature goes up, so does the rate of nuclear reactions. That yields more energy, making the surface of the Sun brighter.

The Sun has already converted a large fraction of its hydrogen to helium. As a result, it beams about 25 percent more energy into space today than when it was born.

A billion years from now, it’ll shine about 10 percent brighter still — bright enough to heat Earth’s surface above the boiling point of water. And a few billion years after that, it’ll shine roughly twice as bright as when it was born.

By then, the Sun will have used up the hydrogen in its core, triggering changes that’ll make it shine hundreds of times brighter — a brilliant flare-up before it fades away for good.

More about the Sun tomorrow.
 

Script by Damond Benningfield