In June, central Ohioans will witness a nice arrangement of planets just after dark. Without staying up too late, we can watch Jupiter set in the southwest and Saturn and Mars rise in the southeast. It is a telescopic feast that we will gorge upon at our Friday-night public programs at Perkins Observatory.
Mars and Saturn are particularly close in the southwest. Add the star Antares, which is below Saturn and Mars right now in the constellation Scorpius, and you have a beautiful tableau that does not require a telescope to see.
Add to the mix that Antares and reddish Mars are quite similar in color. In fact, Antares got its name because of the similarity. Mars’ Greek name was Ares, and the Greeks noticed the color coordination. The best translation of “Antares” is “similar to Mars.”
But that fact doesn’t fully explain the name. Location has a lot to do with it, as well. Scorpius is a zodiacal constellation, one of the constellations that the planets pass through as they orbit the sun.
The Greeks were thus bound to notice the similarity if for no other reason that it’s easy to confuse the planet and the star when they are close together as they are, coincidentally, right now. Don’t believe me? Go out and take a look.
They are red for completely different reasons, however. Mars gets its rusty color from, well, rust, the high iron oxide content in its soil.
Antares’ redness is a sign that the star is simultaneously very young and very old. Astronomers estimate that Antares is a relative youngster at only 12 million years old. Consider that an average star like our sun will percolate for about 11 billion years before its thermonuclear nuclear fires are quenched. Compared to the lifetime of our sun, Antares has barely begun.
However, Antares had also reached a premature old age. Part of the problem is its enormous mass. The star has about 17 times more star stuff than old Sol. And that’s a problem if longevity is its aim.
So much star stuff generates a considerable amount of gravitational force. Stars convert the hydrogen deep in their core to helium in the same reaction that fuels our hydrogen bombs. The reaction occurs because the hydrogen at a star’s center is compressed and heated to temperatures that reach tens of millions of degrees.
Our puny star generates enough gravity to compress helium at a moderate rate. Our star has reached a respectable middle age after about five billion years. In about six billion years, it will stop exploding and collapse to a tiny white dwarf.
Antares’ enormous mass is compressing and converting hydrogen at a prodigious rate. After only 12 million years, it has reached decrepitude. In only a few hundred thousand years, it will die in a most spectacular way.
As part of the dying process, Antares has swelled to enormous size. At around 480 million miles wide, if it replaced our sun at the center of our solar system, it would engulf Earth and reach out past the orbit of Mars.
Its distinct redness tells us that it has also cooled down considerably. Earlier, when it was a yellow star like our sun, it reached a surface temperature of something over 10,000 degrees. As a red star, Antares has cooled to just under 6,000 degrees.
Like our sun, Antares will collapse when its thermonuclear nuclear fires are finally slaked. However, unlike our sun, the result will not be a white dwarf. Its core will collapse to an even smaller sphere and form a black hole. As it is collapsing, the star’s outer shell will explode away from the star in one of the most energetic events the universe has to offer.
If human beings are still around in a few hundred thousand years, they will be privileged to watch Antares briefly shine with a brightness that will rival the combined light of the full moon, except that the light will be condensed to a single point. It will briefly light up the night and be visible for a day or three during full daylight.
By the standards of supergiant stars like Antares, our star is distinctly below average. It is below average in mass. It generates a pitiful quantity of energy. But its puniness is a blessing in disguise. If the example of life on Earth teaches us anything, it is that life takes a long time to develop into anything as complex as humans. Even if Antares has suitable planets, life will not have had sufficient time to develop below the star dies.
There is a lesson in this, of course. Stars do not have the option of choosing their destinies, but you do. You can live a life of moderation like our sun and experience a long and productive life. Or you can live fast, die young, and leave a beautiful supernova. The choice is yours.
Tom Burns is director of the Perkins Observatory in Delaware.