StarDate

The gods of ancient Greece weren’t great parents. One of the ancient gods known as the Titans, for example, swallowed his newborn children. Eventually, though, the kiddos escaped and overthrew him. Their victory is commemorated in the stars, as the altar where they swore allegiance to each other. It’s the constellation Ara, and it’s below the tail of the scorpion.

In the story, Cronus was the king of the Titans. He’d come to power by defeating his own father. A prophecy said that one of his children would defeat him. To prevent that, he swallowed each of his first five children.

But his wife, Rhea, got tired of that plan. When the last child was born, she hustled him away to an island and gave Cronus a rock wrapped in a blanket.

That child was Zeus. When he grew up, he returned home and forced his dad to cough up his brothers and sisters. They pledged to defeat the Titans, and won a 10-year war. Zeus became the king of the new gods and ruler of the sky. To celebrate the victory, he placed the altar among the stars.

The altar is so far south that most of it’s visible only from far-southern parts of the United States – places like Florida, South Texas, and especially Hawaii.

Ara is one of the smaller constellations, with only a couple of moderately bright stars. But it does have some good deep-sky objects, and we’ll talk about one of them tomorrow.

Script by Damond Benningfield

The formal name for a planet almost 50 light-years from Earth is Kua’Kua – a Costa Rican name that means “butterfly.” But there’s nothing beautiful or delicate about this world. Its surface is a desolate landscape of volcanic rock.

The planet is in the system LHS 3844. Its star is a cool, faint ember known as a red dwarf. Kua’Kua – LHS 3844 b – is a super-Earth. It’s bigger and heavier than Earth, and it’s made of rock and metal.

The planet is only about half a million miles from the star, and the same hemisphere always faces the star. So the dayside sizzles at more than 1300 degrees Fahrenheit.

Every 11 hours, the planet passes behind the star as seen from Earth. Astronomers have watched several passages with Webb Space Telescope.

Watching before and after a passage revealed the combined make-up of the star and planet. But when the planet disappeared, that left only the star in view. Comparing the readings revealed details about the surface of the planet. In fact, it’s the first “exoplanet” for which we have such a close look.

The surface appears to be made of dark volcanic rock that could have been deposited recently, making it fairly smooth and unbroken. But the surface also could be much older. In that case, a constant pounding by radiation and meteorites could have pulverized the surface. Either way, Kua’Kua is not a good place to go hunting for butterflies.

Script by Damond Benningfield

There’s just one place to catch a wave outside Earth: Titan, the largest moon of Saturn. It’s the only other world in the solar system with bodies of liquid on its surface. And the waves there could reach heights of 10 feet. But future surfers will need to dress carefully; the surface temperature is almost 300 degrees below zero.

Titan is half-again the size of Earth’s moon, and it has a dense atmosphere. Rain fills its lakes and seas with liquid methane, ethane, and nitrogen. The largest sea covers about 200,000 square miles – twice the area of all the Great Lakes combined. It could be several hundred feet deep.

The Cassini spacecraft used radar to measure Titan’s ponds. It saw waves of no more than an inch or so high. But a recent study says the waves could get a lot bigger.

Based on 20 years of observations of waves on Lake Superior, scientists built a computer model of how waves might work on other worlds. The model accounted for gravity, the pressure of the atmosphere, and the properties of the liquid. When the model was applied to Titan, it showed that even gentle breezes could whip up some big waves. But the waves would move more slowly than those on Earth – a slow-motion trip across the sea.

Saturn looks like a bright star close to our moon the next couple of mornings. It’ll stand to the left of the Moon at dawn tomorrow, and the lower right of the Moon on Tuesday.

Script by Damond Benningfield

The dawn twilight has a bright visitor the next few mornings – the planet Mercury. It’s farthest from the Sun for its current morning appearance. It looks like a bright star, but it’s so low in the sky that it’s tough to find.

Mercury holds an important spot in the history of astronomy and physics. It provided some of the first confirmation of General Relativity – Albert Einstein’s theory of gravity.

Mercury’s orbit around the Sun is lopsided, so the planet’s distance from the Sun varies. For a long time, astronomers had seen that the orbit’s closest point shifted a tiny bit over time. Isaac Newton’s laws of gravity explained most of the difference. But there was still a tiny amount that couldn’t be accounted for.

Einstein’s theory of gravity held that massive bodies warp the space around them. Since Mercury is the Sun’s closest planet, its orbit is influenced by that “warpage” more strongly than any other planet’s. In fact, general relativity accounted precisely for the shift in the orbit. So Mercury’s orbit provided some of the first evidence to support general relativity – a new way of thinking about gravity.

Look for Mercury quite low in the eastern sky during the waxing twilight. It’ll shine a little brighter each day over the next few mornings. But it’ll also drop a little closer to the Sun, so you’ll need a clear horizon to spot it.

Tomorrow: catching waves.

Script by Damond Benningfield

The Sun is getting bigger, hotter, and brighter. The change isn’t enough to notice during a human lifetime – or even a thousand lifetimes. It plays out over hundreds of millions of years. And it’s all the result of changes deep inside our star.

Like all stars in the prime phase of life, the Sun is “fusing” atoms of hydrogen in its core to make helium. That generates the energy that makes the Sun shine. As the amount of helium builds up, the core gets denser, so gravity squeezes it more tightly. That speeds up the fusion reactions, making the core even hotter.

Radiation from the hotter core pushes on the Sun’s outer layers, making the Sun bigger. It also makes its surface hotter. The combination of bigger and hotter makes the Sun brighter. So over its four-and-a-half-billion-year lifetime, our star has grown about 15 percent wider, and perhaps 40 percent brighter.

That should mean that the young Earth would have been an iceball. But studies suggest the atmosphere was much thicker when Earth was young. The atmosphere also contained much more carbon dioxide and other greenhouse gases. They trapped more heat, keeping Earth from freezing over.

The Sun’s bigger-hotter-brighter trend will continue. In perhaps a billion to two billion years, it’ll be so hot and bright that Earth’s air and oceans will boil away. That will reduce our planet to a bare cinder.

Script by Damond Benningfield