StarDate

If you’re looking to appreciate the faint beauty of the Milky Way, or perhaps catch some shooting stars, then the next few nights are likely to be a disappointment. That’s because the bright Moon gets in the way. It’ll be full on Tuesday, so it already fills the sky with its light. And it’s in view for most of the night. That just doesn’t leave much time to enjoy the subtleties of the night sky.

Fortunately, though, there are plenty of bright lights to shine through the pesky moonlight.

Three of those lights line up to the right of the Moon as darkness falls tonight. The planet Saturn is closest to the Moon. Antares — the supergiant star at the heart of the scorpion — is close below Saturn. And the brilliant planet Mars dazzles farther to their right. You might be able to make out its orange color even through the moonlight.

As these objects shine low in the south, another bright grouping stands high in the east: the Summer Triangle.

The brightest of its three stars is at the top of the triangle: Vega, in the constellation Lyra, the harp. It’s one of the brightest stars of summer nights, so you just can’t miss it.

Deneb, at the tail of Cygnus, the swan, stands to the lower left of Vega. And the triangle’s third point, to the lower right of the other two, is Altair. It’s in another bird, Aquila, the eagle.

These and several other bright stars and planets provide plenty to enjoy in the summer night sky — even through the moonlight.

Script by Damond Benningfield

If you’ve ever looked at a distant skyline on a smoggy day, you can understand the challenge of studying Titan, the largest moon of the planet Saturn. A layer of orange smog tops its cold, thick atmosphere, hiding the surface from view.

Over the last decade, though, scientists have had a set of eyes on Titan that can tune out the haze and see the surface. And they’ve recorded some amazing sights, including lakes and seas and tall mountains.

The eyes belong to the Cassini spacecraft. Its instruments can view Titan at wavelengths of light that penetrate the smog. Over a series of many close encounters, that’s allowed scientists to piece together a detailed picture of the big moon.

They’ve found that lakes and seas cover about two percent of the surface, for example, mostly around Titan’s north pole. The largest are as big as some of the Great Lakes here on Earth. And a recent analysis found that one of them is filled with methane — a substance that’s in liquid form only because Titan’s surface is extremely cold.

Mission scientists also reported that they’ve identified the tallest mountain on Titan, towering almost 11,000 feet high. It hints that something is going on in the ice below the surface that’s similar to the motions of molten rock below Earth’s crust. But that process is hidden from view — even from Cassini.

Saturn looks like a bright star quite close to our own Moon this evening, with Titan visible through good binoculars or a telescope.

Script by Damond Benningfield

The Moon anchors a rectangle of bright heavenly bodies tonight. The other points of the box are the planets Mars and Saturn and the star Antares, the heart of the scorpion.

That order describes the brightness of the four objects, as well as their relative distances from Earth. And there’s a direct correlation between the two.

The Moon looks brighter than the other three only because it’s our closest neighbor — just a quarter of a million miles away. The lunar surface is actually quite dark. But because the Moon is so close, it forms a big target in the night sky, and a lot of its light shines our way.

Mars stands below or to the lower right of the Moon as night falls, and looks like an orange star. It’s not a star at all, though. Instead, it’s a planet — and a close one at that. Earth passed closest to it just a couple of months ago, so it’s still a big target.

Saturn stands farther to the lower left of the Moon, and looks like a golden star. It’s the second-largest planet in the solar system, and its clouds reflect a lot of sunlight. But Saturn is hundreds of millions of miles away, so it looks fainter than Mars.

Antares is the faintest member of the rectangle, to the lower right of Saturn. But it only looks faint. In reality, it’s a supergiant star — billions of times brighter than the Moon and planets. But it’s hundreds of light-years away — a distance that dulls its magnificence.

More about the Moon and Saturn tomorrow.

Script by Damond Benningfield

We still have more than two long, hot months of summer here in the northern hemisphere. But the northern hemisphere of Mars is already headed into the cooler days of autumn, because the autumnal equinox was last week.

For parts of the southwestern United States, summer is monsoon season — the wettest time of year. Summer is the wettest time of year on Mars as well, but the dampness doesn’t come from rainfall. Instead, it comes from below ground.

At some latitudes, underground ice melts during summer, then squirts out onto the surface. Some of the liquid water trickles down slopes, forming dark streaks or small gullies.

And some recent research says that these trickles of water may alter the surface in more significant ways. In the vanishingly thin Martian atmosphere, the water quickly boils away. The boiling process may create turbulent streams that churn up grains of Martian sand like kernels of popcorn jumping around inside a popper. That kinetic flow can then trigger avalanches that rumble down hills and craters. So a small streamer of water may change the Martian surface in big ways.

And Mars is putting in a big showing over the next couple of nights. The planet looks like a bright orange star, and stands to the lower left of the Moon tonight. It’ll be even closer to the Moon tomorrow night. And a couple of other bright lights are near by: the golden planet Saturn and the orange star Antares.

We’ll have more about this lineup tomorrow.

Script by Damond Benningfield

The Sun sometimes pops off in dramatic fashion. It produces explosions known as solar flares — geysers of energy that can equal billions of one-megaton hydrogen bombs.

Our star may also pop off in less-dramatic fashion — the equivalent of only a few hundred H-bombs. But what these little blasts lack in power, they make up for in frequency — there could be thousands of them every second.

These “little” blasts are known as nanoflares. Astronomers first saw hints of their existence in the 1970s. But the first solid evidence for them came a couple of years ago, from two space telescopes.

Theory says the flares occur in the Sun’s outer atmosphere, known as the corona. The corona is millions of degrees hotter than the Sun, and nanoflares could generate the extra heat.

The Sun’s magnetic field frequently forms loops that extend far above the Sun’s visible surface. The surface itself is turbulent, so the loops wiggle around. That causes the lines of magnetic force to overlap. When they do, that may cause a short circuit — a nanoflare.

No one has seen nanoflares directly — perhaps because they don’t really exist, or perhaps because they’re too small and faint to spot against the Sun’s brilliant surface. But observations by ultraviolet and X-ray telescopes have provided hints that the flares are there.

Follow-up observations in the next year or two are planned to find out if the corona really does crackle with the constant explosions of nanoflares

Script by Damond Benningfield

Giant galaxies probably become giant galaxies through acts of cannibalism — they gobble up smaller galaxies. Our own Milky Way, for example, is ingesting at least one smaller galaxy right now, and there’s evidence that it has swallowed others in the past.

Another possible example is the massive elliptical galaxy M87. It’s one of the most impressive galaxies around. It’s 10 times wider than the Milky Way, and it contains a trillion stars. And quite a few of those stars may represent the remains of a smaller galaxy that M87 ingested within the last billion years.

European researchers reported the possible act of cannibalism last year. They discovered that many of the stars in M87 are quite blue, which means they’re also quite young. But M87 itself is an old galaxy that’s giving birth to almost no new stars. So the blue stars probably came from outside M87.

The researchers also looked at dying stars on the fringes of M87. The motions of these stars indicate that something stirred up the galaxy fairly recently.

From these observations, the researchers concluded that M87 gobbled up a smaller spiral galaxy within the last billion years — adding to M87’s considerable heft.

This galactic giant is a member of a large cluster of galaxies in the constellation Virgo. And the Moon is passing through Virgo right now. Tonight, the constellation’s brightest star, Spica, stands quite close to the lower left of the Moon as darkness falls.

Script by Damond Benningfield

Most constellations bear little resemblance to their namesakes. You need a great imagination to see a giraffe in the stars of Camelopardalis, for example, or a “sea goat” in Capricornus.

One constellation that does resemble its namesake is the dolphin, Delphinus. It’s a small grouping of stars that’s about a third of the way up the eastern sky as twilight fades away, and swims high across the south later on. And that group of stars really does look like a dolphin, jumping through the edge of the starry Milky Way.

In Greek mythology, Delphinus carried a poet to safety when he jumped overboard to escape some nasty sailors. The poet and the dolphin were commemorated in several coins that were issued around 500 B.C. And the dolphin gained longer-lasting recognition through its constellation.

None of the individual stars of Delphinus is particularly interesting. The brightest is known as Beta Delphini. It’s near the center of the constellation, and marks the end of the dolphin’s torso. The dolphin’s body stretches to the left as it climbs higher in the sky, and its tail to the right.

Beta Delphini is actually a binary. The two stars were born from the same cloud of gas and dust, and they remain bound to each other by their mutual gravitational pull. They orbit each other once every 27 years.

Look for the beautiful dolphin swimming into view in the east as darkness falls, and climbing high across the south during the night.

Script by Damond Benningfield

The Moon snuggles close to a bright light tonight, and even closer to a fainter light. In fact, from some parts of the country, the Moon will briefly extinguish the fainter one.

As night falls, look to the lower right of the Moon for Jupiter, the largest planet in the solar system. It outshines everything else at that hour except the Moon itself, so you won’t have any trouble spotting it.

The other light is Beta Virginis, the fifth-brightest star in the constellation Virgo. As seen from most of the United States, it’s quite close above or to the upper left of the Moon at nightfall. The star is pretty faint, though, so you need dark skies to see it, and binoculars will enhance the view.

As seen from a narrow strip of the southwest — from Texas to California — the Moon will pass directly between Earth and the star, blocking it from view. The exact time Beta Virginis disappears depends on your location, but it’s roughly 11 or 11:30 as seen from Texas, and around 8:30 or 9 as seen from California.

Beta Virginis is roughly similar to the Sun. It’s about 25 percent more massive, so it’s a little bigger than the Sun, and a few times brighter. It’s also a little younger. Still, as stars go, it’s a pretty good match. And it’s only about 35 light-years away, making it a close neighbor — one that’ll briefly hide behind the Moon.

Again, look for Beta Virginis quite near the Moon this evening, with brilliant Jupiter to the lower right.

Script by Damond Benningfield

You can’t go much of anywhere in the solar system without sniffing some water. There’s frozen water on Mars, in comets and asteroids, and on the surfaces of many moons. And there’s liquid water in the atmospheres of the giant planets, and below the icy crusts of some of their moons.

Water is especially prevalent at Jupiter, the largest planet. Jupiter stands close to the upper left of the Moon at nightfall, and shines like a brilliant star.

On Jupiter itself, water forms towering clouds that produce monster thunderstorms. But water also appears to be abundant on three of Jupiter’s moons.

There’s little doubt that an ocean lies below the crust of Europa. It contains much more water than Earth’s oceans. And there may well be “chimneys” at the bottom of the ocean that belch hot, mineral-rich fluids into the water, providing possible energy and nutrients for life.

There’s also evidence for an ocean on Callisto. It’s buried far deeper than the ocean on Europa. And there would be less energy in the ocean environment, making it a less likely home for life.

The third possible water world is Jupiter’s largest moon, Ganymede. Evidence for water there includes oddities in Ganymede’s magnetic field, cracks in the crust like those on Europa, and minerals on the surface that likely were deposited by salty water. Ganymede’s ocean would be the deepest of the three, though, so there’s little chance of splashing into this water world anytime soon.

Script by Damond Benningfield

The Sun has been exceptionally quiet for most of this year, with few sunspots marking its surface. In fact, the number of sunspots peaked more than two years ago. It’ll probably bottom out in about three more years — completing another cycle of magnetic activity.

The man who was the first to precisely plot the solar cycle was born 200 years ago today. Rudolf Wolf was born in Switzerland, and became one of Europe’s leading astronomers.

In the 1840s, Wolf became fascinated with the findings of another astronomer, who’d spent years counting sunspots. He found that the number of spots seemed to vary over a period of about a decade.

Wolf began counting sunspots himself — something he did for almost half a century. He also tracked down records of sunspots as far back as 1610. From that, he found that, on average, the number of sunspots peaked every 11 years. And later, Wolf was one of several astronomers to notice a link between spots on the Sun and auroras and other magnetic events on Earth.

At first, colleagues belittled Wolf’s idea of a solar cycle. But Wolf was able to stand behind his claims in part because he was an expert on statistics and probability, so he knew the numbers were solid.

The objections have long since melted away. Today, the sunspot cycle is much better understood. It reaches a peak when the Sun’s magnetic field becomes twisted and tangled, creating dark storms on the surface — storms that peak roughly every 11 years.

Script by Damond Benningfield