StarDate

While many celebrate the arrival of the new year with champagne, the team that operates New Horizons may have a special reason to open a bottle of bubbly: The spacecraft is set to stage the most distant encounter ever. On New Year’s Eve night, it’ll fly about 2200 miles from 2014 MU69, a small chunk of ice and rock more than four billion miles away.

New Horizons flew by Pluto in July of 2015. It had enough fuel left to maneuver to a second encounter in the Kuiper Belt, a “doughnut” of iceballs beyond the major planets. It was targeted for MU69, which was discovered by Hubble Space Telescope in 2014.

The encounter has taken a lot of preparation. Last year, for example, astronomers set up telescopes at a couple of remote locations to watch the object pass in front of a star. The observations revealed details about its size and shape. At the same time, telescopes in the air and in space looked for dangerous debris near MU69.

Because the object is only about 20 miles across, it’s no more than a dot in any Earth-based telescope. That makes it hard to know its exact location. So New Horizons itself has been tracking it since August. Its images have allowed navigators to plot a precise path for the craft, which will fly past MU69 at about 30,000 miles per hour.

It’ll take months for New Horizons to transmit all of its data to Earth — stretching out the celebrations of this distant encounter.

Script by Damond Benningfield

The star Spica poses near the Moon at first light tomorrow. It’s the brightest star of the constellation Virgo, and one of the 20 brightest stars in the entire night sky.

When we look at Spica and the Moon, we’re actually seeing the same thing: starlight.

Spica is a ball of hot gas that produces its own light. In fact, Spica is especially hot — tens of thousands of degrees hotter than the Sun. That high temperature makes the star especially bright, and gives it a blue-white color.

The Moon, on the other hand, is a ball of rock. It produces no light of its own. Instead, what we call “moonlight” is actually reflected sunlight — light produced by our own star. The Moon isn’t a very good reflector, though. Its surface is quite dark, so it reflects only about a tenth of the sunlight that strikes it.

As the Moon orbits Earth, the Sun illuminates different parts of it. When the Moon is full, it lights up the entire hemisphere that faces Earth. And when the Moon is new, the Sun lights up the hemisphere that faces away from Earth.

At dawn tomorrow, the Sun will be lighting about a third of the visible hemisphere, so the Moon will be in a “crescent” phase. Over the next few days, the crescent will get smaller and smaller as the Moon moves toward the Sun. The Moon will be new in a week.

For now, look for the Moon near Spica in the early morning sky. They climb into good view by about 2 or 3 a.m., with Spica to the lower right of the Moon.

Script by Damond Benningfield

When the New Horizons spacecraft left Earth, George W. Bush was president, the first smartphone hadn’t even been announced, and Pluto was still a major planet — but one about which little was known. Two presidents, beau coup smartphone models, and one reclassification later, New Horizons is getting ready for its final port of call. On New Year’s Eve night, it’ll pass close to a chunk of ice and rock more than four billion miles from Earth — the most remote encounter with any object.

New Horizons was launched in early 2006 to explore Pluto. It flew by Jupiter to get a gravitational “kick,” then passed within 7800 miles of Pluto in July of 2015.

New Horizons revealed that Pluto is a remarkable world. It has mountains of ice, plains coated with frozen nitrogen, and a “cauldron” where blobs of warm ice may bubble to the surface. Its thin atmosphere doesn’t freeze out, as scientists had expected. And the north pole of its largest moon is coated with organic compounds that may have come from Pluto itself.

Now, New Horizons has set its sights on one last object in the Kuiper Belt — a vast “doughnut” of icy and rocky bodies that includes Pluto.

On Monday night, it’ll fly a couple of thousand miles from 2014 MU69. It’s about 20 miles in diameter, and it may consist of two bodies, not one.

New Horizons won’t have enough fuel to target another object. So this is its final encounter — a last act for a pioneering explorer.

Script by Damond Benningfield

The Sun and similar stars are steadily losing weight — they blow some of their gas into space through strong “winds.” And at the end, they blow away all of their outer layers of gas, leaving only their hot, dense cores, known as white dwarfs — tiny remnants of once glorious stars.

An example is Sirius B, the companion to the Dog Star, Sirius A, the brightest star in the night sky. Sirius climbs into view in the east-southeast by around 8:30 or 9, and arcs across the south during the night.

Sirius B is too small and faint to see without a telescope. But millions of years ago, that wouldn’t have been the case. The star probably was a few times as massive as the Sun, so it would have shined brighter than Sirius A is today.

Such a hot, bright star produces a much thicker wind than the Sun does, so it loses mass at a higher rate. And because the star was heavier than the Sun, it burned through the nuclear fuel in its core much faster. As a result, it burned out in a couple of hundred million years, while the Sun is still only half way through a 10 billion-year lifetime.

As it neared the end of its life, Sirius B puffed up like a giant balloon, then expelled its outer layers. Some of that gas probably piled on the surface of Sirius A, increasing its mass.

Today, Sirius B is as heavy as the Sun, but only as big as Earth. It still shines because it’s extremely hot. But it’s only a faint remnant of its former glory.

Script by Damond Benningfield

Over the centuries, we’ve given the visible stars many names — proper names, catalog designations, and others. But one star is best known not by any of its formal names, but by its nickname: the Dog Star. Its proper name is Sirius. It’s the leading light of Canis Major, the big dog — hence the nickname.

Sirius is so well known because it’s the brightest star in the night sky — its closest competition is only about half as bright. Part of that brilliance is because Sirius is a couple of dozen times brighter than the Sun. But part of it is because Sirius is a close neighbor — less than nine light-years away. Only five other stars systems are closer.

And thanks to the relative motions of Sirius and the Sun, Sirius is inching closer — at about 17,000 miles per hour — about as fast as the International Space Station orbits Earth. It’ll continue to close in for tens of thousands of years. But the distances between the stars are so huge that even at that speed, Sirius won’t get much brighter.

Astronomers discovered the star’s motion toward us by measuring its redshift — a slight change in the wavelengths of its light. That shift also allowed them to measure the orbit of a faint companion — a stellar corpse known as a white dwarf; more about that tomorrow.

In the meantime, look for Sirius climbing into good view in the east-southeast by about 8:30 or 9. It’s the brightest star in the night sky, so you can’t miss it.

Script by Damond Benningfield

A Japanese billionaire recently bought the first ticket to fly to the Moon aboard a new rocket being designed by SpaceX, a company headed by Elon Musk. But he’s not the first to make a reservation for a Moon flight. 50 years ago this week, in fact, people began booking flights in a hurry.

On Christmas Eve night in 1968, the crew of Apollo 8 staged a live TV broadcast from lunar orbit. It was viewed by what was then the largest audience in history.

By the next day, Pan American Airways began getting calls from people who wanted to reserve their own Moon flights. The company had started a “First Moon Flights” Club after an Austrian journalist booked a flight through a travel agency in 1964. Four years later, the movie “2001” featured a Pan Am shuttle ferrying passengers to space.

By the time of Apollo 8, the company had about a hundred reservations. After Apollo 8, the number climbed to a couple of thousand. And it really took off after Apollo 11 landed on the Moon the following year. When Pan Am stopped taking reservations, in 1971, it had 93,000 customers on its list. Alas, none of them ever made the trip. Pan Am folded in 1991, bringing dreams of lunar excursions to an end.

And while all we can do right now is dream about trips to the Moon, at least we can enjoy the Moon’s beauty from afar. Our satellite world climbs into good view late this evening. Regulus, the heart of Leo, follows it across the sky.

Script by Damond Benningfield

For 20 hours in December of 1968, three American astronauts watched the Moon pass outside their windows. Frank Borman, Jim Lovell, and Bill Anders were the first people to see the Moon from close range, as they orbited just 70 miles above the surface.

Their mission was to check out the Apollo mothership for future lunar-landing missions. But the crew of Apollo 8 also kept the world informed of its progress with several television broadcasts. On Christmas Eve night, the astronauts transmitted from lunar orbit, to what was then the largest television audience in history.

After the crew read the first verses from the Book of Genesis, Commander Borman closed with season’s greetings.

A few hours later, on Christmas morning, Apollo 8 fired its rocket engine to begin the trip home. As they emerged from behind the Moon with news of the successful firing, the astronauts were even jollier.

Apollo 8 splashed down on December 27th. The flight helped set the stage for the first lunar landing just seven months later.

Script by Damond Benningfield

During the early years of the Space Race, the Soviet Union and the United States had pulled off some daring feats: the first man in space, the first walks in space, the first docking between two spacecraft.

But a mission that was under way 50 years ago today was the most audacious of them all. Astronauts Frank Borman, Jim Lovell, and Bill Anders were on their way to the Moon — the first mission to our satellite world.

NASA had launched the first Apollo astronauts just a couple of months earlier. They stayed in Earth orbit. But their flight provided confidence in the Apollo mothership. At the same time, the CIA was reporting that the Soviets were planning to send a cosmonaut around the Moon before the end of the year. So the space agency decided to send Apollo 8 to lunar orbit.

LOI was a rocket firing to settle the craft into orbit. It took place behind the Moon, out of contact with Earth. But everything worked perfectly — allowing the crew to enjoy a sight that no human eye had ever seen before: a close-range view of the lunar surface.

Apollo 8 orbited the Moon 10 times, highlighted by a TV broadcast on Christmas Eve. More about that tomorrow.

Script by Damond Benningfield

Christmas is three days away. But for many astronomers, Santa came early. In April, he brought a bagful of presents — new observations of more than a billion stars. Astronomers began sorting through those goodies right away. And they’ve already found some treats.

The observations were provided by Gaia, a European space telescope. It was launched five years ago. Its mission is to measure the positions, motions, and other details of more than a billion objects. A catalog of its observations was released in April.

The catalog includes the 3-D motions of about seven million stars. Astronomers can trace the paths of those stars, and look for patterns in the way stars are moving.

One team found about 20 stars that are moving so fast that they’ll escape from the Milky Way galaxy. But many of the stars are moving into the galaxy’s disk. That suggests they came from somewhere else, and are just passing through. The stars might have been born in other galaxies, but were kicked out by close encounters with black holes, or when companion stars exploded.

Another team found a region of the galaxy where many stars are moving like ripples on a pond. They may have been set on that course by an encounter with a small galaxy hundreds of millions of years ago. The galaxy came even closer later on, and was grabbed by the Milky Way, which is now “ingesting” the galaxy.

Astronomers will continue to study Gaia’s bag of goodies for many years to come.

Script by Damond Benningfield

If you enjoy long nights under moonlight, then you’ll love the next couple of nights. That’s because it’s the time of the Long-Night Moon — the full Moon that’s in view longer than any other full Moon of the year.

And this long night of moonlight has a special appeal. Fifty years ago today, astronauts headed for the Moon for the first time. Frank Borman, Jim Lovell, and Bill Anders launched aboard Apollo 8:

The trio reached the Moon on Christmas Eve of 1968, and orbited until Christmas.

At the time of the flight, the Moon was a bare crescent. Now, though, it’s nice and full. That means it lines up opposite the Sun in our sky, so it does just the opposite of what the Sun does.

Since today is the winter solstice, it’s the shortest day of the year. So the Sun rises late, sets early, and scoots low across the sky during the short day.

The full Moon, on the other hand, rises around sunset, climbs high across the sky during the night, and sets around sunrise.

From the U.S., the time of the full Moon is around midday tomorrow. So that gives us tonight and tomorrow night to enjoy the brilliance of the full Moon — shining for hours and hours and hours.

And as you watch the Moon, look for two bright stars close to it. Aldebaran stands to the upper right of the Moon in early evening, with Betelgeuse to the lower right. The stars add to the beauty of a long winter’s night.

Script by Damond Benningfield