Antares, the bright star at the heart of Scorpius, huddles quite close to the Moon early this evening. They set not long after the sky gets dark, so there’s not a lot of time to look for them.

The Moon is a thin crescent now, so it’s night across most of the lunar disk. But on the bright sliver that’s in daylight, you can still make out some of the dark lunar “seas” – vast plains of volcanic rock. They formed long ago, when giant asteroids slammed into the Moon. Molten rock bubbled up from below, then cooled and hardened.

A recent study found evidence of an especially big impact three-and-a-half billion years ago. The hit would have been powerful enough to melt the surface across a wide area.

Researchers discovered the evidence in a meteorite known as Northwest Africa 12593. It was found in Mali, in 2017. It contained some tiny crystals that form only under extreme heat. The chemistry of the meteorite suggested the impact happened three-and-a-half billion years ago.

A later impact shattered the lava plain, jumbling up the rocks. And a third impact blasted some of the fragments into space, including the one that fell to Earth. The initial impact happened at about the time of similar events on Earth and the asteroid Vesta. That suggests that the inner solar system was littered with many giant space rocks at the time – cosmic “missiles” that sometimes smashed into Earth and the other large worlds.

More tomorrow.

Script by Damond Benningfield

Some high-speed bullets are firing across the night sky this week. They’re the bits of debris that produce the Orionid meteor shower – small pebbles left behind by Comet Halley. They hit the atmosphere at about 150,000 miles per hour. They vaporize almost instantly, forming the glowing streaks known as meteors.

Halley visits the inner solar system once every 76 years or so. On each approach, the Sun’s heat vaporizes some of its frozen surface. That releases bits of rock and dirt. Over time, they spread out along the comet’s orbit. Earth flies through this path twice a year, sweeping up some of the particles.

But the comet dust isn’t evenly spread out. Halley produces a new “streamer” with each pass. So the strength of the shower depends on which of these ribbons we encounter, and how deeply we pass through it.

Most years, the Orionids produce up to a couple of dozen meteors per hour. But if we pass through a denser stream, or if we pass through its middle, the rate can go up. In 2006, for example, the shower produced up to a hundred meteors per hour.

Experts aren’t forecasting that kind of performance this year. Still, the shower is worth checking out. You need a dark skywatching site, far from city lights. And the best view comes in the wee hours of the morning, after the Moon has set. The meteors can appear anywhere in the sky, so sit back, look up, and enjoy the show.

Script by Damond Benningfield

The modern constellations offer a convenient way to appreciate the beauty of the night sky. Using the outline of a scorpion or a lion as a landmark makes it easier to find your way around. It’s also a good way to exercise your imagination.

Our imaginations don’t all show us the same pictures, though. The western constellations were passed down from ancient Greece and Rome. And many of them are even older – they came from ancient Babylon and Sumeria. But just about every culture had its own star pictures – its own map of the night sky.

An example is Capricornus. In western mythology, it represents a sea-goat – half goat and half fish – perhaps a story about the god Pan. But records from ancient China describe something different.

Six of the stars in that region formed an ox, known as Niu – a sacrifice for mid-winter. Three others formed dams to hold water for the emperor’s fields, which were also in Capricornus. And other stars formed parts of different pictures – different stories in the night sky.

Capricornus is low in the south at nightfall. The constellation isn’t especially bright, so it’s invisible from light-polluted cities. Under darker skies, you can see the outline of a wide triangle. Tonight, the gibbous Moon is near the triangle’s eastern point. That makes it easier to find where the sea-goat is, but harder to see its faint outline.

Script by Damond Benningfield