StarDate

The planet Venus has been showing some polite discretion the last few weeks. It’s stayed out of view, allowing one of its siblings to get all the attention. But now it’s beginning to return. It’s quite low in the southwest in the early evening twilight, and will climb a little higher each night throughout the month — beginning a long reign as the brilliant “evening star.” That means it’ll share the spotlight with bright orange Mars, which is putting in its best appearance of the year.

Venus has been out of view because it’s been passing “behind” the Sun as seen from Earth — a point called superior conjunction. It’s moved from the morning sky to the evening sky.

Superior conjunction happens every 19 and a half months. Venus is farthest from Earth at that point — about 160 million miles. So from our perspective, the planet moves across the sky quite slowly. That means it stays close to the Sun for several months — hidden from view in the sunlight.

The orbits of Venus and Earth are almost perfectly synchronized. Venus completes eight orbits around the Sun for every five orbits of Earth — give or take a couple of days. That means Venus appears at almost exactly the same point in the sky every eight years. So you can look for Venus just where it is now — low in the southwest at sunset — in early December of 2030.

For now, watch Venus throughout the month as it climbs higher into the sky — bookending the early evening with Mars.
 

Script by Damond Benningfield

Support McDonald Observatory

Scientists and engineers are working out plans for bringing samples of Mars to Earth in about a decade. But getting the material home is only the first step. We also need a place to study and store the samples — one that protects the samples from Earth, and Earth from the samples.

NASA built a lab for Moon rocks in the 1960s, and it’s still operating. Today, it also houses meteorites from Mars and the Moon, plus samples from a couple of asteroids.

But it’s not good enough to house samples from Mars. That’s because Mars is considered a much more likely home for microscopic life than the Moon was. The odds are extremely small. But no one wants to contaminate Earth with Martian “bugs.” And if the samples contain life — or evidence of life — no one wants to contaminate it by letting in anything from Earth.

So scientists are pondering what it will take to house the samples, do early studies on them, and parcel them out to researchers around the world. They know they’ll need clean rooms that provide a much more sterile environment than any hospital operating room. They’ll need special tools for handling the samples, and special cases to store them in.

It’ll take a few more years to lock down the details and get ready to receive pieces of Mars.

Mars is in great view right now. It’s low in the east-northeast as night falls, and looks like a bright orange star. It arcs high across the sky during the night.
 

Script by Damond Benningfield

Support McDonald Observatory

Brilliant Mars will vanish tonight. It’s not going anywhere — it’s just blocked out by something else.

Mars is at its biggest and boldest this month. It’s at opposition — it lines up opposite the Sun in our sky. It rises at sunset, is in view all night, and is closest to Earth for the year. As a result, it shines at its brightest — the fourth-brightest object in the night sky.

Tonight, though, around the moment of opposition, it will vanish for most of us in the United States. Another object at opposition — the full Moon — will occult the Red Planet, blocking it from view.

It’s just a coincidence that Mars and the Moon reach opposition at almost the same time. The Moon circles past Mars roughly once a month. As with lunar and solar eclipses, though, the conditions are usually a bit off for an occultation. The orbits of Mars and the Moon are tilted at different angles, so they don’t always overlap. The geometry has to be just right for the Moon to pass in front of Mars.

This occultation will be visible from all of the United States except the southeast, Hawaii, and most of Alaska. The timing depends on your location.

At most, the Moon will cover Mars for a little more than an hour. Mars looks like a bright star, although the moonlight will wash it out a bit and bleach its normal orange color — draining a bit of drama from the Red Planet’s best showing of the year.

We’ll have more about Mars tomorrow.
 

Script by Damond Benningfield

Support McDonald Observatory

Mars takes a pounding. The asteroid belt is just beyond it, so the planet gets hit by big space rocks that are kicked out of the belt and toward the Sun. We see the results of those impacts — big holes in the Martian landscape. Mars rovers have seen debris from the impacts — meteorites on the surface. And last year, another Mars mission “heard” an impact.

InSight arrived at Mars four years ago. It’s listened for marsquakes, and has recorded more than 1300 of them. The quakes generate waves that rumble through the planet, revealing details about how Mars is put together. The strongest quake was magnitude five — powerful enough to feel if you happened to be there.

Space rocks generate similar waves when they hit the surface. InSight recorded an impact on September 5th of last year. It heard the asteroid hit the upper atmosphere, split into three parts, then slam into the surface. The whole sequence took just a second or two.

A spacecraft in orbit later took a picture of the impact site — three fresh craters. Mission scientists dug through earlier observations and found that InSight had recorded three smaller impacts — evidence that Mars takes a pounding.

Look for Mars low in the east-northeast as night falls, to the lower left of the Moon, and climbing high across the sky later on. It looks like a bright orange star.

More about Mars and the Moon tomorrow.
 

Script by Damond Benningfield

Support McDonald Observatory

Mars is at its best this week. The planet is at opposition — it lines up opposite the Sun, so it’s closest to Earth and it’s in view all night. It’s low in the east-northeast at nightfall and looks like a brilliant orange star. It climbs high across the sky later on.

Opposition occurs every 26 months, when Earth sweeps past Mars in our smaller, faster orbit around the Sun.

No two oppositions are quite alike, though. That’s because Mars’s orbit around the Sun is lopsided. As a result, the distance between Mars and Earth varies depending on the time of year opposition takes place. With an opposition in early December, the distance is about 50 million miles — a good bit farther than when it happens in summer. So Mars isn’t quite as bright this year as it is at some other oppositions.

Even so, you just can’t miss it. In all the night sky, only the Moon and the planets Venus and Jupiter upstage it.

Tonight, Mars lines up far to the lower left of the Moon at nightfall. It forms a tall, skinny triangle with two other orange lights. Aldebaran, the star that marks the eye of Taurus, is directly to the right of Mars in early evening. The third orange dot climbs into view a couple of hours later, well below the other two: Betelgeuse, the star that marks the shoulder of Orion the hunter.

The Moon will creep closer to Mars tomorrow night, then pass in front of it on Wednesday night.

We’ll have more about Mars tomorrow.
 

Script by Damond Benningfield

Support McDonald Observatory

Rigel — the brightest star of Orion the hunter — is complicated. It’s going through some changes in its core that will make it much bigger and brighter. Its surface jiggles like a Jell-O mold. And it’s blowing a “wind” of hot gas into space — enough material every million years to make one or two stars as big as the Sun.

All of this activity is a result of Rigel’s great heft — more than 20 times the mass of the Sun. Such heavy stars burn through the nuclear fuel in their cores in a hurry, so their lives are short. Rigel is only a fraction of one percent of the age of the Sun, yet it’s already nearing the end of its life.

The star has consumed the hydrogen in its core to make helium. The core is now shrinking and getting hotter — perhaps hot enough to start burning the helium.

Nuclear reactions are taking place in a shell of hydrogen around the core. Some models say that makes the surface jiggle, with each jiggle lasting anywhere from a day to more than two months. But other models say the jiggles are created at the surface of the star.

That surface is extremely hot, so Rigel glows blue white. When the helium in the core ignites, though, the star’s outer layers will expand and cool, so Rigel probably will glow reddish orange.

All of that is a prelude to its final act: In the next few million years, Rigel will explode as a supernova.

Look for Rigel low in the east-southeast by about eight o’clock, to the right of Orion’s Belt.
 

Script by Damond Benningfield

Support McDonald Observatory

The longer, colder nights of late autumn bring one of the great skywatching treats of the year: the return of Orion to prime time. The hunter is in good view in the east and southeast by 9 o’clock, and climbs high across the sky later on.

The constellation’s most prominent feature is the hunter’s belt — a short line of three fairly bright stars. As Orion rises, the belt extends almost straight up from the horizon.

Two of the brightest and most impressive stars in all the night sky flank the belt. Orange Betelgeuse is to the left of the belt, with blue-white Rigel to the right.

Both stars are supergiants — they’re much bigger, heavier, and brighter than the Sun. Betelgeuse is the bigger of the two. If it took the Sun’s place in our own solar system, it would engulf half of the planets — Mercury, Venus, Earth, and Mars — and perhaps even the next one out, Jupiter.

Such massive stars burn through the nuclear fuel in their cores in a hurry. Betelgeuse is only about 10 million years old, compared to four-and-a-half billion years for the Sun. Yet it’s already near the end of its life. Within the next couple of million years, it probably will explode as a supernova, briefly looking as bright as the full Moon.

Rigel is about the same age as Betelgeuse, so it may soon puff up and get redder, just as Betelgeuse has. It, too, then will explode as a supernova — briefly adding to the luster of beautiful Orion.
 

Script by Damond Benningfield

Support McDonald Observatory

There’s no way to dive into the heart of a star to learn what’s going on. So scientists are creating their own stars here on Earth. The most recent experiment is creating the conditions found in the most common stars in the galaxy.

Scientists have been using a facility at Sandia National Laboratories in Albuquerque for years. It builds up a massive charge of electricity, which it discharges in an instant. That creates extremely high temperatures and pressures. Astronomers have used that to simulate conditions in several types of stars.

The current experiment is using the National Ignition Facility — the world’s most powerful laser. It’s at Lawrence Livermore National Laboratory in California. It generates almost 200 laser beams, which focus on a target area the size of a pencil eraser.

Scientists are using the lasers to create the conditions inside red dwarf stars. They account for more than two-thirds of all the stars in the galaxy — including our closest neighbor star. Yet they’re so small and faint that not a single one is visible to the unaided eye.

Conditions inside these stars are poorly understood. But they have a big impact on conditions at the surface. Many red dwarfs produce huge eruptions of radiation and charged particles. That could make it impossible for life to survive on any planets that orbit them. So understanding what’s happening inside red dwarfs can tell us a lot about whether anything could live near them.
 

Script by Damond Benningfield

Support McDonald Observatory

The biggest moon in the solar system is an ocean world. It may have as much liquid water as all of Earth’s oceans combined. Don’t start looking for beachfront property, though — the ocean is buried below a hundred miles of ice.

Ganymede is a moon of Jupiter. It’s about 3300 miles in diameter — half again the size of our moon. And it’s about three times farther from Jupiter than the Moon is from Earth. Some of its surface is covered by impact craters, while the rest features long, deep grooves.

Ganymede is the only moon in the entire solar system that produces its own magnetic field. And that’s key to the discovery of its buried ocean. As Ganymede rotates, the salty ocean creates an imprint on the moon’s magnetic field. The Galileo spacecraft measured hints of that as it orbited Jupiter. But it got only brief glimpses as it sped past Ganymede.

Hubble Space Telescope got a better idea by looking at Ganymede’s aurora — like the northern lights here on Earth. Interactions between the magnetic fields of Ganymede and Jupiter cause the aurora to rock back and forth. The size of that rocking motion hints at the internal ocean, and even provides some of the details about it — a deep ocean on a giant moon.

Jupiter is close to our Moon tonight. It looks like a brilliant star. Binoculars reveal Ganymede and Jupiter’s three other big moons. They look like tiny stars lined up near the solar system’s biggest planet.

Script by Damond Benningfield

Support McDonald Observatory

The Moon slides through a bright triangle this evening — the planets Jupiter and Saturn and the star Fomalhaut.

Jupiter is the triangle’s brightest point, to the upper left of the Moon. It’s the largest planet in the solar system — about 11 times the diameter of Earth. It’s a ball of hydrogen and helium gas with a dense, fuzzy core of heavier elements. It’s attended by about 80 known moons, four of which are easy to see with binoculars. The Moon will stand closer to Jupiter tomorrow night; more about that tomorrow.

Saturn is farther to the lower right of the Moon. It isn’t nearly as bright as Jupiter, but still looks like a bright star. It’s the second-largest planet, and it’s put together a lot like Jupiter. It also has a large entourage of moons, including the only one in the solar system with a dense atmosphere. And it’s best known for its bright, beautiful rings.

The final point of the triangle is Fomalhaut, the brightest star in Piscis Austrinus, the southern fish, below the Moon. It’s one of our closer stellar neighbors — just 25 light-years away. In other words, the light we see from the star tonight actually began its journey through space in 1997.

Fomalhaut is about twice the size and mass of the Sun. And its surface is thousands of degrees hotter. Its core is also hotter than the Sun’s. Because of that, Fomalhaut will live billions of years less than the Sun — a short life for a bright star.

Script by Damond Benningfield

Support McDonald Observatory