StarDate

Jupiter is the “big boy” of the solar system. It’s more than twice the mass of all the other planets combined. In many other star systems, though, Jupiter wouldn’t seem quite so impressive. Astronomers have discovered hundreds of planets that are heavier than Jupiter – up to 80 times Jupiter’s mass.

Astronomers aren’t sure how such monster planets get to be so heavy. But they have a couple of main ideas. One says they grow from the mergers of smaller planets. The other says it depends on the environment in which a planet is born.

Almost all planets take shape in disks of gas and dust around infant stars. The more material there is in the disk, the more there is for making planets.

But there’s a limit on how massive a planet can become. Anything more than about 30 times the mass of Jupiter might become a brown dwarf – an intermediate step between planets and stars. And at more than 80 times Jupiter’s mass, it becomes a true star.

The heavy planets don’t get much bigger than Jupiter, no matter how massive they are. As an object gains mass its gravity gets stronger. That squeezes it tighter, making it more compact. So while these “super-Jupiter” planets might outweigh Jupiter, they’d look a lot like the big boy of the solar system.

Look for Jupiter near the Moon tonight. It looks like a brilliant star, so you can’t miss it. The twin stars of Gemini are close by, and we’ll have more about that tomorrow.

Script by Damond Benningfield

Elnath has dual citizenship. Officially, it’s the second-brightest star of Taurus, so it’s known as Beta Tauri. It marks the tip of one of the bull’s horns. But it’s also known as Gamma Aurigae – one of the bright stars that outlines Auriga, the charioteer. That designation is un-official – it’s been considered defunct for almost a century.

The dual identity is a result of changes in how astronomers define the constellations. At first, the constellations were vaguely defined. Each one encompassed the connect-the-dots pattern that outlined the classical figure. But there weren’t hard borders.

In 1603, German astronomer Johannes Bayer published a new naming scheme for all the stars. In it, he assigned Elnath to both Taurus and Auriga. That worked fine for centuries. But in the early 20th century, astronomers decided to assign precise boundaries for each constellation – like the borders of states or nations. Elnath was just inside the border of Taurus. So, officially, Elnath belongs to the bull. But it still forms part of the classical outline of Auriga – giving Elnath a dual citizenship.

Elnath is about 130 light-years away. It’s about five times the size and mass of the Sun, and it’s hundreds of times brighter. It’s easy to pick out tonight because it’s close to the Moon. As night falls, they’re no more than one or two degrees apart – right along the border between the bull and the charioteer.

Script by Damond Benningfield

Just about every star is born in a cluster – a family of dozens to thousands of stars. Most of these families fall apart, with the individual stars going their own way. The Sun’s cluster, for example, dissipated billions of years ago.

One cluster that’s in the process of dissipating is the Hyades, which outlines the face of Taurus, the bull. It’s the nearest cluster, at a distance of about 150 light-years.

Today, the Hyades contains several hundred stars – probably less than half its original population. The other stars were pulled away by the gravitational tug of the rest of the galaxy.

The cluster’s heaviest stars reside in its tightly packed center. None of them is much more than about twice as massive as the Sun. That’s because of the cluster’s age – 625 million years. All of its heavier stars have already burned out. All that remains is their dead cores.

The least-massive stars have migrated to the outskirts of the cluster. Over the next few hundred million years, those stars will all drift away. That will leave only a sad little remnant of this impressive family of stars.

The Hyades stands to the lower left of the Moon this evening. Its stars form a “V” shape. The brightest star in the outline is bright orange Aldebaran, the bull’s eye. But it’s not a member of the cluster – it simply lines up in the same direction as the stars of the Hyades.

We’ll have more about the Moon and Taurus tomorrow.

Script by Damond Benningfield

For the kings of ancient Egypt, the Sun was much more than just a glowing orb in the daytime sky. It was the god Ra, one of the most important of all the gods. Ra was a creator of life, the king’s father, and a representation of the king as a god himself.

So the kings of the Fifth Kingdom, about 4500 years ago, built temples to honor the Sun. Archaeologists have recently excavated about half of the largest one yet discovered – a massive complex that might have been topped by a spot for watching the Sun and stars.

The temple is named “Joy of Ra” or “Joy of the Heart of Ra.” It’s at Abu Gorab, about 10 miles from Cairo, near the ancient capital, Memphis. It was built by King Nyuserre, who reigned for two or three decades. At the time, the kings identified themselves with Ra – as eternal gods. So the temple was a place to honor both Ra and the king.

Excavations have uncovered two large enclosures. The upper level was discovered 125 years ago, but the lower one was found just recently. The upper level included an altar for making offerings to Ra. And one end featured an obelisk that would have towered high above the courtyard and the surrounding landscape. It had a perfect east-west alignment – the directions of the rising and setting Sun.

The recent work also uncovered a stairway to the roof. The rooftop probably served as an observatory – helping Nyuserre follow his “father” across the sky.

Script by Damond Benningfield

An astronomer greets visitors to a science museum in Canberra, Australia. He’s made of riveted iron plates, and he stands atop a wide ring, gazing skyward through a smaller ring in his right hand. He’s the last remnant of an historic telescope that was destroyed in a massive wildfire.

The fire blazed across Australia in January of 2003. It destroyed most of Mount Stromlo Observatory, one of the major astronomy research centers in the southern hemisphere. The fire consumed five telescopes, plus a laboratory where scientists and engineers built astronomical instruments.

One of the casualties was the Yale-Columbia Telescope. It was a 26-inch refractor – a type of telescope that uses lenses to gather and focus starlight. It was built in 1924, and had been operating at Mount Stromlo for half a century. Astronomers had used it to measure the distances to stars, to study double stars, and more.

After the fire, an Australian science institute commissioned a sculptor, Tim Wetherell, to create an artwork from the telescope’s remains. The result was “The Astronomer” – the piece on display in Canberra.

The figure stands on a setting circle – a wide ring that indicated where the telescope was pointing. It has numbers at 10-degree intervals, from zero to 180. The astronomer is holding a smaller version of the ring in his hand – continuing to look at the stars long after the telescope’s demise.

Script by Damond Benningfield