StarDate

Astronomers have discovered dozens of planets in other star systems that are in the “habitable zone” — the distance from the star where temperatures are just right for liquid water — a key ingredient for life. Yet so far, they haven’t actually seen a single one of them. The planets are all so close to their stars that they’re impossible to see through the starlight.

But scientists and engineers are working on a device that could bring some of these planets to light. Called Starshade, it would work in tandem with a space telescope to block a star’s light, allowing its planets to shine through.

The current design looks like a 10-story sunflower with spikes at the ends of its petals. It would be launched to a point in space where the gravity of Earth, Sun, and Moon are balanced.

There, it would be maneuvered to a spot about 25,000 miles from the telescope. The telescope would take aim at a star within a few dozen light-years that’s known to have a planet in the habitable zone. Starshade would line up in front of the star, blocking it from view. The telescope could then take pictures of the planet and measure the composition of its atmosphere, allowing scientists to look for evidence of life.

The concept has been tested on a telescope in Arizona, and the idea of a starshade is ranked highly by scientists. Even if it’s approved, though, it’ll take a decade or longer for this cosmic flower to bloom — and help look for evidence of life in other star systems.

Script by Damond Benningfield

Back in 2012, Christmas came a little early for NASA. In June, the National Reconnaissance Office gave the agency two space telescopes, each with a main mirror as big as that on Hubble Space Telescope. It took some time for the space agency to figure out what to do with the telescopes. But this year, it’s finalizing plans for one of them: It’ll study dark energy, the earliest galaxies, and planets in other star systems.

The mission is known as WFIRST — the Wide-Field InfraRed Space Telescope. It’ll take advantage of the fact that the would-be spy telescope has a much wider field of view than Hubble, allowing it to see an area of sky a hundred times larger.

With that expansive view, WFIRST will look at a billion galaxies across the cosmos. Precise measurements of the location and motion of these galaxies will allow astronomers to measure changes in dark energy over the eons. Dark energy is causing the universe to expand faster as it ages, but so far, it’s not certain what dark energy really is.

The telescope also will look at galaxies in the very early universe to learn more about the birth of the first stars.

And WFIRST will carry a special instrument to block out the light of a star. That will allow the telescope to probe the space around a star for planets — and even to take pictures of the planets.

Scientists and engineers are looking at another way to use WFIRST to take pictures of planets, and we’ll talk about that tomorrow.

Script by Damond Benningfield

When Hubble Space Telescope took its deepest look into the universe, it saw galaxies galore — big and small, near and far, young and old. Even with Hubble’s vision, though, the farthest galaxies of all were nothing more than tiny red dots — smudges of light from the newborn universe.

Astronomers are eager to study those smudges in detail, though, because they can reveal how the first stars were born and how they died, and how the galaxies themselves came together.

A tool for studying those galaxies is nearing completion — the James Webb Space Telescope. It’s undergoing final assembly this year, with testing next year and launch scheduled for 2018.

It’ll be the largest space telescope ever launched. Its main mirror will be as tall as a two-story building. The mirror will consist of 18 segments that’ll be folded up for launch. The segments are coated with gold — a substance that’s good at reflecting the wavelengths of light that Webb is designed to study: the infrared.

The first galaxies are so far away that their light has been stretched by the expansion of the universe. So what started out as visible light has been shifted to longer, infrared wavelengths.

Hubble is sensitive to some infrared wavelengths, but James Webb will see them all. Combined with its greater size and some new instruments, that’ll give astronomers their best view yet at the first galaxies in the universe.

We’ll talk about another future space telescope tomorrow.

Script by Damond Benningfield

Perhaps the most famous date in all of literature is the Ides of March. It’s immortalized by William Shakespeare’s play “Julius Caesar,” in which a soothsayer warns the Roman leader to “beware” the Ides. Caesar ignores the advice and visits the Senate — where he’s promptly assassinated.

The play, of course, is based on fact. Caesar really was murdered in the Senate on the Ides of March. In the modern calendar — created at the orders of Caesar himself — that date is March 15th.

The Roman calendar didn’t number the days of the month as we do today. Instead, days were reckoned in relation to three key points: the Kalends, which marked the start of the month; the Nones, which came on the 5th or 7th, depending on the month; and the Ides, which came on the 13th or 15th. The other days were counted backwards from these dates.

In every month, the Ides was the day that rents and other debts were due. And the Ides of March held special significance. For much of Roman history, the year began in March, not January. The Ides of March was a time of feasting and other celebrations. An early feast, for example, honored a goddess of the new year. And later on, the Ides kicked off a whole week of celebrations.

And the very first Roman calendar was based on the phases of the Moon. The Ides corresponded to the full Moon, so the Ides of March marked the first full Moon of the year.

So enjoy this year’s Ides of March — a famous date from an early calendar.

Script by Damond Benningfield

Most of the stars in the galaxy are born with companions — other stars that are gravitationally bound to them. And according to a recent study, there’s more than one way to make systems of two or more stars.

The study used an array of radio telescopes in New Mexico to examine a stellar nursery in the constellation Perseus, which is half-way up the northwestern sky at nightfall.

The nursery is one of the largest in the galaxy. It’s given birth to many new stars, and many more are being born even now. And the study found that most of these newborn or newly forming stars come in groups of two, three, or even more.

The groupings fall into a couple of different categories: stars that are quite close to each other, and stars that are much farther apart. And there seems to be different ways to make the two groups.

All the stars form when giant clouds of gas and dust collapse. In the case of the widely separated companions, the cloud just breaks apart into two or more clumps, and each clump continues its collapse independent of the others.

The closer companions, though, seem to follow a different path. A single star begins to form, surrounded by a disk of gas and dust. Disturbances in the disk cause large amounts of this material to stick together. If enough of it sticks together, it forms another star. In that case, the stellar siblings are so close that they’re likely to remain together — gliding through the galaxy as a tight-knit family.

Script by Damond Benningfield

A beautiful crescent Moon hangs high in the sky as darkness falls this evening. The crescent is bathed in sunshine, while the rest of the lunar disk is bathed in earthshine — sunlight reflected off our own planet.

The line between those regions, which divides day from night, is crossing the most famous feature on the lunar surface: the Sea of Tranquility. It’s where astronauts first set foot on the Moon, almost a half century ago.

The Sea of Tranquility covers more than 150,000 square miles — an area as big as Montana. And like all the other lunar seas, it’s a dark volcanic plain. It formed several billion years ago, when molten rock bubbled up to the surface. The rock is rich in iron, magnesium, and other elements that give it the dark color. In fact, that color reminded early lunar mapmakers of the seas here on Earth — hence the “watery” names of these features.

If you could zoom in on the Sea of Tranquility, though, you’d see that it’s not as smooth as it seems. Great ripples and mounds undulate across the surface. And like the rest of the Moon, it’s covered with impact craters — the scars of collisions with space rocks large and small.

Watch the Moon as it drops down the western sky this evening. A bright companion stands to its upper left: Aldebaran, the orange eye of Taurus, the bull. The Moon will move past Aldebaran by tomorrow night, so the star will stand about the same distance to the lower right of the Moon.

Script by Damond Benningfield

A small comet is racing toward Earth right now, heading for a close approach on March 21st. Despite what you might see online, though, it’s absolutely no threat to hit us — it’ll miss our planet by more than three million miles.

Comet 252P/LINEAR was discovered in the year 2000. It was picked up by an automated search for Near-Earth Objects — comets and asteroids whose orbits bring them close to Earth. Such objects could someday hit Earth. Finding them and tracking their orbits could provide enough lead time to deflect them from a collision course. Using telescopes at White Sands Missile Range in New Mexico, the LINEAR project has discovered more than 2500 of these objects.

Comet 252P isn’t very big, so it’s not expected to get very bright. In fact, even at its peak, you’ll probably need a telescope to see it — even though it’s one of the closest comets ever recorded.

Right now, it’s below the horizon for most northern-hemisphere skywatchers. It’ll begin climbing into view soon, though. On March 25th, it’ll cross the tail of Scorpius, which will be quite low in the south shortly before dawn. After that, it’ll climb higher in the sky in a hurry. It’ll pass close to the left of the triangle formed by bright Mars, Saturn, and Antares. And in early April, the comet will move into Ophiuchus, which stands above Scorpius — beginning its journey back into the outer solar system. It’ll return to the inner solar system in 2021.

Script by Damond Benningfield

A pair of spacecraft is getting ready to head for Mars, while another probe has been grounded for at least two years.

The launch window opens Monday for ExoMars, a joint mission of the European and Russian space agencies. It’ll consist of two spacecraft that’ll share a ride to the Red Planet. They’ll separate a few days before arrival, with one craft entering orbit while the other heads for the surface.

The Trace Gas Orbiter will sniff the Martian atmosphere for signs of methane and related gases. Methane can be produced by volcanoes and other types of geologic activity. But it also can be produced by living organisms, so traces of it in the atmosphere could hint at the presence of life. In fact, several observations from the ground and by other spacecraft have shown methane on Mars. But so far, scientists haven’t been able to trace its origin.

The lander, Schiaparelli, is designed to test the technologies for future missions. It’ll use parachutes and rockets to touch down, then carry out a few days of scientific observations before its batteries die.

The two craft are scheduled to arrive at Mars in mid-October. A NASA mission was planned to arrive then as well, also after a launch this month. InSight is designed to probe the planet’s interior by listening for Marsquakes. But a problem with its main scientific instrument scuttled the launch. The next launch window won’t open until 2018 — the next chance for a trip to Mars.

Script by Damond Benningfield

A thin crescent Moon highlights the western sky the next couple of evenings. It’s quite low as darkness falls this evening, but a little higher by Friday.

Sunlight illuminates only a small fraction of the lunar hemisphere that faces our way. Such a pronounced crescent is sometimes described as a “fingernail” Moon — the crescent looks like the curved edge of a fingernail.

And in a surprising way, that’s an appropriate description for the Moon itself. It’s moving away from Earth at a rate of about an inch-and-a-half per year. According to a study a few years ago, an adult’s fingernail grows at that same rate.

The Moon is inching away from us because it “steals” a bit of momentum from Earth through the tides. The Moon’s gravity raises tides in Earth’s oceans, and smaller tides in the solid crust. That causes Earth to spin slower on its axis. To maintain the overall balance in the Earth-Moon system, the Moon’s orbital speed increases, which pushes the Moon farther away.

Eventually, the Moon will move far enough away, and Earth will spin slowly enough, that the two will match. At that point, the system will be gravitationally locked, so the Moon will stop moving away from Earth. When that happens, the same side of Earth will always face the Moon, just as the same side of the Moon always faces Earth. So the Moon will always hover in the same spot in the sky from one side of Earth, while the other side never sees the Moon at all.

Script by Damond Benningfield

Jupiter is known for greatness: its great mass, its great entourage of moons, and most of all, its Great Red Spot. There’s one characteristic, though, which isn’t so great: its rings. They’re far smaller and fainter than the rings of Saturn, another of the solar system’s giant planets. In fact, they’re so faint that they were discovered only a few decades ago.

Jupiter’s rings are of a completely different nature from Saturn’s. The main part of Saturn’s rings probably formed when a small moon was pulverized, either when it passed too close to Saturn or it was hit by another body. The rings consist of chunks of rock and ice, plus a large amount of dust.

Jupiter’s rings, on the other hand, are made almost entirely of dust. The dust comes from several of Jupiter’s moons. Space rocks hit the moons, blasting grains of dust out into space. The tiny dust grains then spread out around the planet to form rings.

There are four major rings. A couple are pretty narrow, while two others are fairly wide. None of the rings contains much material, though. And the material that is there quickly spirals down into Jupiter. That means the rings are being constantly fed by fresh impacts — adding to Jupiter’s not-so-great rings.

The great planet itself is in great view right now. It’s putting in its best showing of the year. It looks like a brilliant star, low in the east at sunset and scooting across the southern sky during the night.

Script by Damond Benningfield