The Moon stalks the heart of the lion tonight. And seen from Hawaii, it’ll catch it. The Moon will “occult” the heart, blocking it from view.

The lion’s heart is Regulus, the brightest star of Leo. The name Regulus means “the little king.” It was introduced 500 years ago. But the star’s association with royalty goes back much farther.

In ancient Persia, Regulus was one of the four “royal” stars – four especially bright stars near the ecliptic – the Sun’s path across the sky. The stars are roughly evenly spaced around the ecliptic. That means each star is at its best during a different season. So each star was considered the “guardian” of its season. Regulus is closer to the ecliptic than the other three guardians, so it was the most important of them all – a king among kings.

The Moon stays close to the ecliptic as well, straying only a few degrees to either side. So it circles past the same stars every month – including Regulus. Right now, the Moon’s path carries it especially close. And that’s easy to see tonight.

Regulus is below the Moon as night falls. But as the hours roll by, the Moon will creep closer and closer to the bright star. As seen from the continental United States, they’ll be separated by no more than about one degree as they set, before dawn – the width of a pencil held at arm’s length. And from Hawaii, the Moon will catch the star – “eclipsing” the little king.

Script by Damond Benningfield

The planets in our solar system fit into two groups. Four of the planets are small and rocky; Earth is the largest. The other four are big and bloated; Neptune is the smallest. But there’s nothing between the sizes of Earth and Neptune. And that’s a bit odd. Two of the most common types of planets elsewhere in the galaxy are somewhere in the middle: super-Earths and mini-Neptunes.

Astronomers have confirmed more than 6,000 planets in other star systems. Only one system has as many known planets as the solar system does. And the planets in almost all the known systems are packed in much closer to their stars than the worlds of the solar system – in part because close-in planets are the easiest to find.

But the biggest difference between our system and all the others appears to be the lack of super-Earths and mini-Neptunes.

A super-Earth is up to twice the diameter of Earth, and two to ten times Earth’s mass. Such worlds probably are dense and rocky. They may have thick atmospheres of hydrogen and helium, and perhaps deep oceans of liquid water.

Mini-Neptunes are larger than super-Earths, but no bigger than Neptune. They probably have a solid core as well, but thicker layers of gases and liquids.

The distinction between the two types of planets isn’t always clear. They probably have a lot in common – including the fact that we don’t have either of them in our own solar system.

Script by Damond Benningfield

You might forgive Pollux if it feels disrespected. It’s the brightest star of Gemini – twice as bright as Castor, its “twin.” But the designation that’s most often used by astronomers is Beta Geminorum. And the Greek letter “Beta” usually is applied to a constellation’s runner-up.

That naming system was created by German astronomer Johann Bayer, in 1603. He used the Greek alphabet to name most of the stars in a constellation. Usually, the brightest star was given the first letter, Alpha. The next-brightest was Beta, and so on.

But in some cases, Bayer switched things up. He labeled the stars based on their location in the constellation’s classical outline, or on some other category. So for Gemini, Pollux became the “Beta” star even though it’s clearly brighter than “Alpha.”

Pollux really is an impressive star. It’s moved into the red-giant phase of life. In fact, it’s the closest red giant to the Sun, at a distance of just 34 light-years.

It’s puffed up to about nine times the diameter of the Sun, so it shines almost 40 times brighter than the Sun. And it has a distinctively orange tint – a beautiful look for an impressive star.

Pollux and Castor line up to the upper left of the Moon at nightfall this evening. Pollux is closer to the Moon. The planet Jupiter is farther to the upper right of the Moon. Jupiter outshines all the true stars in the night sky – even the brightest light of Gemini.

Script by Damond Benningfield