StarDate

One of the most famous characters in the night sky takes a prominent position at this time of year: Hercules, the strongman. His relatively faint constellation is in view by the time it gets dark, and soars high overhead during the night.

Hercules is the Roman version of a character from Greek mythology. He was the son of a mortal woman and Zeus, the king of the gods. To appease his wife, who was angry at Zeus’s dalliance, Zeus named the boy Heracles, which means “glory to Hera.” But the strategy didn’t work. Hera tormented Heracles throughout his life. To atone for crimes committed while under Hera’s spell, Heracles was forced to perform 12 labors of strength and courage. His labors included killing a lion and a snake, which also stand in the stars.

The most prominent portion of the constellation Hercules is the Keystone — four stars that form a lopsided square. It’s above the northeastern horizon as darkness falls.

Along the line connecting the two stars that rise first, look for a beautiful globular star cluster known as M13. In dark skies, it’s visible to the unaided eye as a faint smudge of light. Binoculars reveal a swarm of stars, while telescopes reveal hundreds of them. In fact, M13 contains hundreds of thousands of stars packed into a tight ball. These stars are among the oldest in the galaxy.

Look for Hercules in the east and northeast at nightfall, and soaring high overhead after midnight.

Script by Damond Benningfield

A beautiful spiral galaxy in the constellation Coma Berenices has a black eye. And it may have the same cause as when a person gets a black eye: the galaxy ran into something else.

The galaxy is M64. It’s smaller than our own galaxy, the Milky Way, and it has fewer stars. But it’s well known because it has a prominent dark band below its nucleus. That gives M64 a couple of nicknames: the Black-Eye or the Evil-Eye galaxy.

The dark spot consists of dust grains, which block the light of the stars that are behind them. About 25 years ago, astronomers discovered that the lane of dust is rotating in the opposite direction from the stars and gas in the center of the galaxy. The dust probably is the residue from a smaller galaxy that collided with M64.

Where the oppositely spinning regions rub against each other, they squeeze clouds of gas and dust. The clouds break into smaller blobs, which collapse to give birth to new stars. Hubble Space Telescope has photographed many stellar nurseries in the galaxy. It’s also seen many hot, brilliant young stars, which shine bright blue.

These stars live short lives — no more than a few tens of millions of years. And since M64 is at least 17 million light-years away, we see it as it looked at least 17 million years ago. So many of those bright blue stars have already blasted themselves to bits as supernovae — temporary blemishes for the Black-Eye galaxy.

Script by Damond Benningfield

The Milky Way galaxy is home to about 160 globular clusters — ball-shaped collections of hundreds of thousands of stars. They’re spread all over. So it’s rare to see two of them close together in the sky.

Two that appear quite close to each other are high in the sky this evening, in Coma Berenices. M53 is easily visible through binoculars, while its companion, NGC 5053, is fainter. They’re separated by less than the width of your finger held at arm’s length.

NGC 5053 is about 54,000 light-years from Earth, with M53 a few thousand light-years farther. That closeness suggests the two clusters may be linked in some way. In fact, one set of observations detected a “bridge” of stars between them — stars that could have been pulled into space when the two clusters passed especially close together. Other studies have seen “tails” of stars but no bridge, so it’s not certain that the clusters have interacted with each other.

Researchers have also suggested that one or both clusters might belong to a dwarf galaxy that the Milky Way is gobbling up.

Some recent studies argue against that idea, though. For one thing, the chemistry of the stars in the clusters is a pretty good match for those in the Milky Way. And for another, the orbit of NGC 5053 doesn’t seem to match that of the dwarf galaxy. So the clusters may have been born with the Milky Way after all — two siblings that are high in the east at nightfall.

Script by Damond Benningfield

Gravity is a great organizer. It pulls things together to make them nice and neat. It pulls in gas to make stars. It pulls the stars together to make galaxies, galaxies to make galaxy clusters, and clusters to make superclusters.

One of the nearest superclusters is in the constellation Coma Berenices, which is high in the east at nightfall. The supercluster is centered about 300 million light-years away. It incorporates the galaxies of two clusters, known as Coma and Leo. Combined, they span about 20 million light-years.

Telescopes reveal that the clusters contain thousands of galaxies, each of which contains billions of stars. But no telescope can show us what makes up most of the mass of these galaxies — dark matter. It produces no detectable energy, but its gravity tugs at the visible matter around it.

Most dark matter is found outside the bright disks, balls, and blobs that make up the visible parts of galaxies. So in tightly packed clusters and superclusters, it mainly inhabits the dark regions between galaxies.

In fact, the existence of dark matter was first suspected in the Coma Cluster. In 1933, astronomer Fritz Zwicky found that the cluster’s galaxies were moving differently than they should be based on the gravity of their stars and gas. He proposed that some “dark matter” was altering their motion. It took decades to confirm the existence of dark matter — the “glue” that holds together vast collections of galaxies.

Script by Damond Benningfield

Astronomers love star clusters. All the stars in a cluster were born at the same time, from the same cloud of gas and dust. So any differences in the stars are the result of their evolution, which is a result of their mass. That makes it easier to learn what’s going on inside the stars.

One problem, though, is identifying which stars belong to a cluster. It takes detailed measurements of motion and brightness to distinguish cluster members from stars that just happen to line up in the same direction.

An example is Melotte 111, in Coma Berenices. The constellation is high in the east at nightfall. Under dark skies, the cluster is a good target for binoculars or a small telescope.

The cluster is about 280 light-years away. But it spans dozens of light-years, so its stars are spread out. That makes it harder to pick out its members. And it takes big telescopes to pick out its fainter stars.

So despite decades of study, astronomers are still locking down the census of stars in Melotte 111. A study a few years ago confirmed eight small, faint members — the first of their kind known to belong to the cluster. And another study found that about a quarter of the stars in the cluster are binaries or multiple-star systems.

These discoveries bring the total number of stars in Melotte 111 to about 60, with a few dozen more possible stars — members of a wide-spread stellar family.

We’ll talk about a family of galaxies in Coma Berenices tomorrow.

Script by Damond Benningfield

The constellations honor many individual people, almost all of them heroic: Hercules, Perseus, the twins of Gemini, and several others. But only one constellation is named for a real person. And the reason for her ascension to the stars may be a bit of propaganda.

Coma Berenices is high in the eastern sky at nightfall. Its stars are faint. But under a dark sky, they offer one of the prettiest sights in the heavens: streamers of stars that represent the hair of Queen Berenice of Egypt.

Berenice married her cousin, Ptolemy III, in 246 B.C. As king, Ptolemy later went to war. The tale says that to protect her husband, Berenice promised to cut her beautiful hair and offer it to the gods if Ptolemy returned safely. He did, so she did. She placed her locks in a temple, dedicated either to the goddess Aphrodite, or to all the gods, depending on the version of the story.

The hair soon disappeared, though. The court astronomer told the king that the locks had been taken by the gods and placed in the sky — streamers of stars near Leo, the lion.

The story might be true, or might have been created — or at least embellished — to raise the king’s profile.

Even then, Coma Berenices didn’t become a constellation until 1536. And it didn’t enter wide-spread use until 1602, when it was included in an atlas published by Tycho Brahe. Yet it’s filled with some wonderful sights, including the Coma Berenices Cluster. More about that tomorrow.

Script by Damond Benningfield

Whether it’s our own eyes, or just pictures of eyes, we always try to get the red out. And the planet Jupiter may be doing the same thing. Its giant red “eye” — the Great Red Spot — has been shrinking for decades. Eventually, it could disappear.

The spot is a giant storm. It towers about five miles above the surrounding clouds. The Sun’s ultraviolet light zaps chemical compounds at the top of the storm, turning them red. And the Juno spacecraft, which is orbiting Jupiter, found that the storm extends a couple of hundred miles down into the planet’s thick atmosphere.

The Great Red Spot has been around since at least 1831. It may also have been seen in the 1600s, although no one is sure if that sighting was the same feature. In the late 1800s, it was a wide oval that spanned at least three times Earth’s diameter. By the time the Voyager probes flew past Jupiter, the spot was about twice as wide as Earth. And today, it’s about one-and-a-third times Earth’s diameter.

That’s still huge. But the shrinking trend doesn’t seem to be slowing down. So one NASA scientist has speculated that the Great Red Spot could disappear in as little as a couple of decades — depriving Jupiter of its beautiful red “eye.”

And Jupiter is shining at its best right now. It’s low in the southeast at nightfall, and looks like a brilliant star. It slides across the south during the night, and sets at sunrise.

Script by Damond Benningfield

It’s amazing what a difference a few centuries can make.

Consider Jupiter, the largest planet in the solar system. It shines at its best for the year this week. It’s at opposition — it lines up opposite the Sun. It rises at sunset, scoots low across the south during the night, and sets around sunrise. It’s brightest for the year, too, outshining everything else in the night sky except the Moon and Venus.

When people first looked at Jupiter and the other planets, they saw bright lights moving across the background of stars. Over time, though, they noticed patterns in their motions. Combined with their brightness and color, that appeared to give each planet a personality.

Jupiter, for example, is quite bright, and it takes about 12 years to complete a circle against the background of stars. That gave it a regal quality. So early cultures thought of it as the most majestic of their gods. To the Greeks he was Zeus, the king of the gods. The Romans adopted him as Jupiter.

Centuries later, scientists realized the lights were heavenly bodies, moving along predictable paths. And in the 17th century, Galileo saw Jupiter as a world in its own right, orbited by its own moons.

In the centuries since, better telescopes have revealed that Jupiter is a giant ball of gas. Stripes of clouds and mammoth storms decorate its upper atmosphere. They give Jupiter its own appearance and personality — the king of the planets.

More tomorrow.

Script by Damond Benningfield

A star system in Virgo is headed for an act of cannibalism. In 250 million years or so, one object in the system will begin consuming the other.

The system was discovered by the Kepler spacecraft, which hunts for planets in other star systems. The system consists of two objects. One is a white dwarf — the dead core of a star. The other is a brown dwarf. It’s too massive to be a planet, but not massive enough to shine like a star.

The pair probably formed about three billion years ago. The star was more massive than the Sun, so it burned through the nuclear fuel in its core faster than the Sun does. As it used up that fuel, the star expanded. It got so big that its outer layers enveloped the brown dwarf. That caused the “failed star” to spiral closer to the true star’s core.

The star eventually expelled its outer layers into space, leaving only its hot, dead core. It’s about 40 percent as heavy as the Sun, but no bigger than Earth.

The brown dwarf is closer to the star than the Moon is to Earth. At that range, the two objects orbit each other quickly, emitting gravitational waves in the process. That causes them to spin closer together. In about 250 million years, they’ll be so close that the white dwarf will start pulling gas off the brown dwarf. Every million years or so, enough gas may build up to trigger an explosion, called a nova — a process that may continue until the brown dwarf has been consumed by its dead companion.

Script by Damond Benningfield

The “hot spots” in the search for life in the solar system are just that — hot spots. They’re places where hot, mineral-rich water bubbles up into seas or oceans. They provide the ingredients for life: water, energy, and the right chemistry. Known as hydrothermal vents, they’re common in Earth’s oceans, and are thought to exist on moons of Jupiter and Saturn.

And a recent study found possible hydrothermal vents on Mars as well — in a giant lake that existed almost four billion years ago.

The lake is in a region known as Eridania. The lake consists of several round basins that probably formed when big space rocks hit Mars. Water then bubbled up from below the ground, filling the basins and some of the surrounding land. The possible lake spans several hundred miles, and the water could have been up to three-quarters of a mile deep. In all, the lake held about nine times as much water as the Great Lakes here on Earth.

Scientists have found possible lakes and seas all across Mars. What makes this one special is that its basins are lined with volcanic rock. It’s likely that at least some of that rock pushed up into the basins when they were filled with water. If so, then the bottom of the lake was dotted with hydrothermal vents. That makes the lake a good place to look for evidence of ancient microscopic life.

And Mars is in great view early tomorrow. It looks like a bright orange star just to the lower right of the Moon at first light.

Script by Damond Benningfield