StarDate

The Moon goes nose to nose with the bull this evening. It stands just below the V-shaped pattern of stars that outlines the head of Taurus the bull. The brightest member of that pattern is Aldebaran, the bull’s orange eye. The other members of the V, including the one at the nose, all belong to the Hyades, one of the most prominent star clusters in the sky.

Aldebaran looks so impressive because it’s a stellar giant. It’s at the end of its life, so it’s puffed up to many times its original size. It’s dozens of times wider than the Sun, and hundreds of times brighter.

Several of the stars of the Hyades are also giants. They don’t look as impressive as Aldebaran, though, in part because they’re more than twice as far away.

One of those giants is Gamma Tauri, the star that marks the bull’s nose. It’s heavier than Aldebaran, but not quite as big or bright. That may be because the two stars are in different phases of their “gianthood.”

Aldebaran has converted the original hydrogen fuel in its core to helium. Now, it’s getting ready to burn the helium to make even heavier elements. Changes in the star during this transition have caused it to expand and brighten.

When it starts burning the helium, it’ll get a little smaller and fainter — and that’s the stage that Gamma Tauri is already in. It’s still big and bright, but not as big and bright as it once was. But it’ll puff up again when the helium is gone — giving the bull a big, bright nose.

Script by Damond Benningfield

Mars is cold and dry, and its air is a bare wisp compared to Earth’s air. That’s not an especially comfortable environment for life. But it’s not an impossible one, either. Life on Earth can survive in conditions that are pretty inhospitable. So it’s possible that microscopic organisms could live below the Martian surface, perhaps in underground pools of water.

A recent study found that some of the simplest organisms on Earth could survive Mars-like conditions. That doesn’t mean we’ll actually find life on Mars — only that we can’t rule it out.

Scientists at the University of Arkansas tested several species of methanogens — microbes that produce methane. Observations have revealed traces of methane in the Martian atmosphere. They might come from geologic processes, but they could also be produced by life.

The scientists exposed the methanogens to conditions similar to those found below the Martian surface — similar chemistry and pressure, for example. And they found that the organisms survived the exposure just fine. So now they’re planning a new round of experiments that’ll factor in the Martian cold — new tests to see if microscopic life could survive on Mars.

And Mars huddles quite close to the crescent Moon this evening. It looks like a moderately bright orange star, and stands to the lower right of the Moon as they drop down the western sky.

We’ll talk about the Moon and another orange companion tomorrow.

Script by Damond Benningfield

Three small, rocky worlds put in an appearance this evening that makes them look more impressive than they really are. They’re low in the west as twilight fades away.

The brightest member of the trio is also the smallest: the Moon. It’s a beautiful crescent right now, with sunlight illuminating just five percent of the hemisphere that faces our way.

The Moon is a couple of thousand miles in diameter — roughly a quarter the size of Earth. It probably consists of a small iron core surrounded by thick layers of lighter rock.

To the lower right of the Moon, look for Mercury, which looks like a bright star.

At about three thousand miles in diameter, Mercury is the smallest planet in the solar system. But its core is massive — it accounts for more than three-quarters of the little planet’s diameter, and more than half its mass. Mercury may have been bigger in the distant past, with a thicker layer of rock around the core. But an impact with another body might have blasted away most of that material, leaving the core undisturbed.

Finally, look farther above the Moon for Mars. It’s the biggest of the three worlds by about a thousand miles. But it’s also the farthest, which makes it faint. It looks like a modest orange star.

Mars also has an iron core, although the iron is mixed with lighter elements. So even though Mars is bigger than Mercury, it’s less dense — a rocky planet with a difference.

More about Mars and the Moon tomorrow.

Script by Damond Benningfield

The list of worlds in the solar system where life could exist keeps growing. Studies show that conditions could be right for microscopic life on Mars, some of the moons of Jupiter and Saturn, and even in the clouds of Venus. And in recent months, one more world has been added to the list: Pluto.

When the New Horizons spacecraft flew past Pluto in 2015, it found evidence of an ocean beneath an ice-filled basin. The ocean could cover an area as big as Texas, and be up to 50 miles deep. And it could be heavy enough to act as a gravitational counterweight to the moon Charon, which always stays on the opposite side of Pluto.

Recent studies suggest that the ocean could be kept liquid, slushy, or even syrupy by heat from radioactive elements deep inside Pluto, or by being mixed with ammonia.

According to William McKinnon of Washington University in St. Louis, the ocean’s mixture of water, energy, and chemicals could be a good home for life. Not big life, like fish, or even relatively complex forms of microscopic life. Instead, it could be extremely simple organisms, much like the first life to appear on Earth.

So far, of course, talk about life on Pluto or any other world is just that — talk. We haven’t seen life of any kind beyond Earth. Right now, we really don’t have the technology to probe for life on any world other than perhaps Mars. But we can keep speculating — identifying places to begin looking for life elsewhere in the universe.

Script by Damond Benningfield

One of the most impressive galaxies around climbs high across the south on spring nights. M87 is a giant elliptical galaxy, so it looks like a fuzzy rugby ball, with no spiral arms or other major features. It’s in the east at nightfall, and is visible through a small telescope.

M87 contains several times as many stars as our home galaxy, the Milky Way. But like most other elliptical galaxies, it’s used up its supply of gas, so it doesn’t have the ingredients for making new stars.

But a galaxy that’s like a younger version of M87 is making lots of new stars. It’s called COSMOS 11494. It’s about 11 billion light-years away, so we see it as it looked when the universe was just three billion years old.

Despite its youth, the galaxy already has several times more stars than the Milky Way does today.

And it gave birth to those stars in a hurry. Astronomers came to this conclusion after measuring two elements in the galaxy: magnesium and iron.

Magnesium is cast into space when heavy but short-lived stars explode. In contrast, iron comes mostly from the explosions of longer-lived stars. The galaxy has the highest magnesium-to-iron ratio ever seen in a massive galaxy. That indicates the galaxy formed all of its stars in less than half a billion years.

Alas, we can’t see the galaxy as it looks today. But if we could, it might resemble M87 — a giant galaxy that probably also gave birth to many stars in its youth.

Script by Ken Croswell, Copyright 2016

M82 is one of the most vigorous galaxies around. It’s classified as a starburst galaxy. That means that, although it’s smaller than our galaxy, the Milky Way, it spawns far more stars. But new research suggests the star-making frenzy could soon come to an end.

A galaxy makes new stars from clouds of gas, which permeate the space between stars. The densest clumps of this gas collapse, heat up, and begin to glow, shining as new stars. Each year, enough gas in M82 comes together to make the equivalent of 13 stars as massive as the Sun — a rate that’s about five times faster than the Milky Way.

But M82’s star-making career can last only as long as its gas supply does. Each year, according to the new research, the galaxy adds just three and a half Sun’s worth of new gas from its surroundings. And each year, the galaxy’s own stars expel a lot more gas through stellar winds and supernova explosions.

As a result, M82’s future looks bleak. When astronomers compare its gas consumption rate with its current supply of gas, they conclude that it’ll run out in just eight million years — the blink of a cosmic eye.

Still, M82 could buy itself some time if additional gas falls onto it. So perhaps this amazing galaxy will keep on churning out bright new stars for a while longer.

And M82 is in Ursa Major, the big bear. It stands to the upper left of the bowl of the Big Dipper as night falls right now, and is visible through a small telescope.

Script by Ken Croswell, Copyright 2016

When healthy twins are born, they usually have the same life expectancy. Barring accidents or disease, they should live about the same amount of time.

When twin stars are born, though, it’s a different story. One of them is likely to expire long before its sibling. And it’s pretty easy for astronomers to tell which one will go first.

Consider Cor Caroli, the brightest star of Canes Venatici, the hunting dogs. It’s in the east-northeast at nightfall. It’s the first meagerly bright star to the right of the tip of the Big Dipper’s handle.

Cor Caroli consists of two stars, which probably were born together, from the same cloud of interstellar gas and dust.

One of the stars is about three times the mass of the Sun, while the other is only half that heavy. And when it comes to a star’s life expectancy, it’s all about the mass. Heavier stars consume the nuclear fuel in the cores at a much faster rate than less-massive stars, so they expire much more quickly.

The heavier star of Cor Caroli, for example, will live as a “normal” star for about 350 million years. After that, it’ll puff up to giant proportions, shining hundreds of times brighter than it is now. Then it’ll cast its outer layers into space, leaving only its hot but dead core.

When that happens, its lighter twin will still be going strong. The more leisurely rate of nuclear reactions in its core means that it’ll shine for a couple of billion years after its flashier twin expires.

Script by Damond Benningfield

Venus is losing its identity. After tonight, it will no longer be the “evening star.” Instead, it’ll be the “morning star,” as it crosses the line between Earth and the Sun.

This crossing is known as inferior conjunction, and it happens every 584 days — about 19 months. During that interval, the planet goes through a series of phases like the phases of the Moon.

At conjunction, Venus is “new” — the entire hemisphere that faces Earth is in the planet’s own shadow, so we’re looking at its nightside.

After conjunction, Venus becomes a thin crescent, which grows fatter as the weeks roll by. It’s during its crescent phase that Venus shines at its brightest. The planet is close to Earth then, so it forms a relatively large target in our sky. That proximity also means that more of the sunlight that Venus reflects into space reaches Earth. The combination makes the planet especially bright.

After that, Venus gets “fuller,” as sunlight illuminates more of its Earth-facing side. But it also moves farther away, so it doesn’t look as bright.

Venus is “full” at superior conjunction, when it lines up behind the Sun. After that, Venus begins to wane again as it once again prepares to cross between Earth and the Sun.

Venus is probably too close to the Sun for most of us to see it this evening. But it could be visible in the east shortly before sunrise tomorrow — and will definitely be putting in a great showing within a few days — as the “morning star.”

Script by Damond Benningfield

A major hurricane can cause tens of billions of dollars in direct damages. And it can cause tens of billions more in indirect damages — losses to the economy caused by destroyed businesses, fouled roads, power outages, and other problems.

A major storm on the Sun, however, has the potential to dwarf those losses. A recent study by the American Geophysical Union found that under the right circumstances, a solar storm could trigger economic damages of up to almost 50 billion dollars a day.

The Sun produces storms all the time — big eruptions of charged particles that race outward at millions of miles per hour. Most of the time, these storms miss Earth. But when they do hit, they can knock out satellites, disrupt communications and air travel, and even knock out power grids. In 1989, an especially big storm knocked out power to Quebec.

In recent years, there’s been concern that if a monster solar storm hit Earth, it could knock out power across most of the United States. Not only that, but the currents might fry equipment that could take months to replace. That could leave big chunks of the country powerless for weeks or months.

The recent report looked at the economic impact of such an outage. It found that damages could hit anywhere from a few billion dollars a day, up to 50 billion. About half of that loss comes from a ripple effect that impacts vendors, customers, and others — a major impact from a stormy Sun.

Script by Damond Benningfield

The next big space telescope, James Webb, is being prepared for launch next year. And the one after that, which will look like a twin of the venerable Hubble telescope, is being developed.

Yet even these instruments will leave many questions unanswered. So NASA is already planning the next generation of space telescopes. They’ll be bigger than anything launched before, and provide capabilities far beyond Hubble or Webb.

A year ago, NASA picked four teams to outline concepts for the next big space telescope. They’ll keep at it for two more years. After that, the National Academy of Sciences will review the ideas and recommend which one to develop.

One telescope would be like a super-sized version of Hubble. It would use a segmented mirror that could be as tall as a five-story building to look at a wide range of wavelengths. That would allow it to detect signs of life on planets in other star systems and watch the evolution of galaxies and black holes.

Another concept would also provide details on other planets. It could photograph planets in Earth-like orbits, and monitor their atmospheres for signs of life.

The other ideas would look only at wavelengths that are invisible to the human eye. That would allow them to study the earliest galaxies, or the disks of superhot gas around black holes.

All of this will take time, though. Whichever concept NASA eventually picks, the telescope won’t launch until at least the 2030s.

Script by Damond Benningfield