StarDate

A modest meteor shower should be at its best the next couple of nights. You need dark skies to see it – the glow of city lights will erase it from view. And even at its peak, the shower produces no more than a dozen or so meteors per hour. But the Moon won’t get in the way, so if you have good weather and a good viewing spot, it’s worth a look.

The Lyrid shower occurs at this time every year as Earth passes through a trail of comet dust – debris from Comet Thatcher.

The comet last visited the inner solar system in 1861, and it won’t return for almost three centuries. But each time it approaches the Sun, it sloughs off bits of rock and dirt. They spread out along the comet’s orbital path. When Earth flies through that path, some of the grains ram into the atmosphere at a hundred thousand miles per hour. They vaporize, forming the glowing streaks of light known as meteors.

The shower is named for the constellation Lyra, the harp. That’s because its meteors all appear to “rain” into the sky from near Vega, Lyra’s brightest star. They can fly across any part of the sky, though, so you don’t need to be looking at Lyra to see them.

The best view comes after Lyra climbs into good view, after midnight. The Moon sets a little later, making the skies nice and dark. That will provide several good hours to watch the meteors – reminders of a comet that’s billions of miles from Earth.

Script by Damond Benningfield

The Moon passes through the bull tonight. The bull’s “eye” – the star Aldebaran – is off to the left of the Moon. The bull’s face and shoulder are even closer, represented by a pair of star clusters – the Hyades and the Pleiades.

For the most part, you can’t tell the distance to an astronomical object just by its appearance. Something that looks quite bright might be close, but it might also be far away and especially bright.

But you can tell something about the distances to the objects around the Moon tonight by their appearance.

The Pleiades looks like a tiny dipper close below the Moon. It contains hundreds of young stars, some of which are hot and bright. But the cluster’s small size is a good indication of its distance – almost 450 light-years.

The Hyades looks bigger. It forms a letter V that outlines the bull’s face. It looks a good bit more spread out than the Pleiades. But that’s largely because it’s only a third as distant.

Aldebaran stands at the top left point of the V. It outshines all the other points. In part, that’s because it’s less than half as far – just 65 light-years away.
So these prominent features really do tell us something about their distances.

One other bright light stands directly below the Moon in early evening, and it’s the brightest of all: Venus, the “evening star.” Right now, it’s closer to us than anything else except the Moon.

Script by Damond Benningfield

You might want to have the butter and the Mrs. Butterworth’s handy for this one – it’s all about pancakes. Some of them are as big as a major city. There are only two problems: They’re made out of dense volcanic rock, and they’re on the planet Venus.

Venus is covered with many thousands of volcanic features – lava plains, cone-shaped mountains, and structures that look like crowns and spiders. Most of the features are old, but there are hints that the planet is still volcanically active today.

The list of features includes pancake domes. There are scores of them – some by themselves, but many in groups. They’re almost perfectly round and flat. They can be up to a few dozen miles across, and more than half a mile tall. And their edges are steep – almost-sheer cliffs.

The domes probably formed when thick molten rock bubbled to the surface. It spread out in all directions. And it continued to spread well after the lava spigot was turned off.

A study published last year said that some of the pancakes dented the surface below them – perhaps one reason they’re so flat. That dimple created a moat around one of the domes, with a raised rim around the moat – a good arrangement for catching all that butter and syrup.

Venus is the brilliant “evening star.” It’s quite close to the crescent Moon this evening. The Moon will stand above the planet tomorrow night; more about that on our next program.

Script by Damond Benningfield

There’s a frustrating meeting of planets in the early morning sky right now. It’s frustrating because the planets are quite low in the sky in the dawn twilight, so they’re hard to see.

The participants in this meet-up are Mercury, Mars, and Saturn. Tomorrow, they’ll form a tight triangle. They’ll form a straight line on Monday before they begin to separate. Mercury is the brightest of the trio, followed by Saturn, then Mars.

The planets aren’t actually anywhere close to each other – they just happen to line up in the same direction. Mercury is the closest, at a distance of a bit more than a hundred million miles. Mars is more than twice that far. And Saturn is farther still – almost a billion miles.

Mercury is making a small loop across the dawn before dropping back into the solar glare. It’s the closest planet to the Sun, so it never moves far from the Sun in our sky. That means our chances to see it are limited.

Mars and Saturn are farther from the Sun than Earth is, so they move all the way across the sky. Both are slowly working higher into the dawn. As the months pass, they’ll rise earlier and remain in view longer.

For now, Mercury, Mars, and Saturn are quite low in the east as twilight paints the sky. They’re tough to see, especially from farther north. From the U.S., the best views are from places like Miami and Honolulu. The best place to watch the meet-up is the southern hemisphere.

Script by Damond Benningfield

Every time that two or more planets congregate in the night sky, fear mongers crank up the volume on their predictions of doom. They say the combined gravity of the planets will cause everything from earthquakes and storms to boils and hangnails.

Don’t listen to them.

All of the planets are so small or so far away that their short-term effects on Earth are negligible.

Jupiter, the largest and heaviest planet in the solar system, is only one-tenth of one percent as massive as the Sun. And, on average, it’s about five times farther. When combined, those numbers tell us that Jupiter’s gravitational tug on Earth is just one-25,000th as strong as the Sun’s. The pull of the other planets is even weaker. So even if you lined up all of the planets in the same direction from Earth, their combined pull would be insignificant.

That’s not the case on longer terms, though. The gravity of Jupiter and Venus change the shape of Earth’s orbit and the planet’s tilt on its axis. Mars may play a role as well. That influence creates cycles of warmer and colder climate. But the cycles play out over tens of thousands of years or longer – not over days, weeks, or even centuries.

Planetary alignments are common. In fact, there’s one right now. Mars, Saturn, and Mercury are close together in the dawn twilight. But they’re so low in the sky that they’re tough to see. We’ll have more about their alignment tomorrow.

Script by Damond Benningfield