StarDate

With the Fourth of July coming up, we predict that you’ll soon be seeing fireworks in the night sky. And some astronomers in Michigan are predicting fireworks in the sky as well. They expect a star in Cygnus, the swan, to explode in about five years. If they’re right, the blast will be as bright as the North Star.

KIC 9832227 was first studied in detail by Kepler, a planet-hunting space telescope. Its observations showed that the system’s brightness was changing. Larry Molnar and Daniel van Noord of Calvin College were intrigued by the star, so they kept an eye on it for a while.

Van Noord concluded that the system is a contact binary — two stars that actually touch other. And their contact is getting more intimate — their cores are getting closer together.

By comparing the system to a contact binary that exploded a few years ago, Molnar predicts that the stars will merge in 2022, give or take a year. The merger will trigger an explosion. For a few weeks, the system will shine 10,000 times brighter than it does today.

Right now, the astronomers are watching the system with radio and infrared telescopes on the ground, and an X-ray telescope in space. These observations should confirm whether we’ll see some fireworks from the swan in the years ahead.

And Cygnus flies across the eastern sky on these early summer evenings. KIC 9832227 is near the middle of its top wing. But you need a telescope to see it — for now.

Script by Damond Benningfield

Two stars that recently merged into one threw up a thick veil of dust around themselves.

V1309 Scorpii first came to light in September of 2008, when a nova flared up in the beautiful constellation Scorpius, which is visible in the southern sky tonight. A nova is an exploding star, and most novae turn blue. But the nova in Scorpius was unusual, because it turned red instead.

By good luck, astronomers had been keeping an eye on this part of the sky. During the years leading up to the explosion, they’d made more than a thousand observations of the star. These observations revealed the star’s remarkable nature: it was really two stars that were stuck together, forming a contact binary. If Earth circled a contact binary, we’d see not a glowing sphere in the daytime sky, but a glowing peanut.

The pre-nova observations also indicated that the two stars were spiraling closer and closer together. They then merged into one, sparking the blast. At its peak brightness, it rivaled the most luminous stars in the entire galaxy.

Recent observations of V1309 Scorpii reveal that a thick blanket of dust formed shortly after the nova erupted. The single star born in the merger spun quickly, so it flung gas from its surface out into space. The gas cooled and turned red, accounting for the nova’s color. As the gas cooled, grains of dust also formed, blocking much of the light — almost as if the now-single star was seeking to block the view of outsiders like us.

Script by Ken Croswell, Copyright 2017

The bright star HD 87901 perches just a whisker away from the crescent Moon this evening. If that name isn’t familiar to you, try this one: 32 Leo. Still not ringing any bells? Try Regulus, the little king.

Regulus is the brightest star of Leo, the lion, so it’s known as the “heart” of the lion. But the name “Regulus” has nothing to do with the king of the beasts. Instead, it refers to human royalty — the “little king” or “prince.”

The name was adapted from an earlier name: Rex, the king. That name was bestowed in ancient times, and it indicated that the star ruled the heavens. That’s because the Sun appeared near the star at the summer solstice, one of the most important dates in many ancient calendars.

Like all bright stars, Regulus has a long list of names, titles, and other designations. As the leading light of Leo, for example, it’s known as Alpha Leonis, from a system devised four centuries ago by Johannes Bayer. Each star gets a letter of the Greek alphabet, followed by the name of the star’s constellation. A constellation’s brightest star usually gets the “alpha” designation.

“32 Leo” comes from a system that was created about a century later, by John Flamsteed, in which every star in a constellation gets a number.

Many “names” are actually catalog numbers. HD 87901, for example, comes from the Henry Draper catalog. It was compiled by Harvard Observatory in the 19th and 20th centuries — providing one more way to address the stars.

Script by Damond Benningfield

Astronomers are searching the distant precincts of the solar system for a possible Planet 9. The search was triggered by the odd orbits of several bodies in the Kuiper Belt — a band of icy objects beyond Neptune, the eighth planet. A team of astronomers suggested that the bodies were pushed by the gravity of a planet up to 10 times as massive as Earth.

If Planet 9 is found, it won’t be the first world discovered by its gravitational influence. Neptune was discovered through its effect on the orbit of Uranus. And the man who first suspected its existence was born 250 years ago tomorrow.

Alexis Bouvard was a French astronomer who came from a humble background. He was a shepherd boy who made his way to Paris at age 18. He was a gifted mathematician, so he got a job at an observatory as a computer.

Bouvard discovered several comets, and used his math skills to plot their orbits. And beginning in the early 1800s, he tried to calculate the orbit of the newly discovered Uranus. But his numbers didn’t add up — he couldn’t find an orbit that made sense.

Bouvard concluded that Uranus must be influenced by the gravity of another planet outside its own orbit. Bouvard died soon afterward, so he couldn’t follow up on his idea. But scientists in France and Britain did follow up. They calculated a possible location for the new planet. Using the work of the French astronomer, an astronomer in Germany found Planet 8 in 1846 — the planet known today as Neptune.

Script by Damond Benningfield

The sky offers plenty of calendar markers to help note the turning of the seasons. At the start of summer, for example, the Sun is farthest north in the sky for the entire year. And by the time the last rays of the Sun fade away, another marker is in good view: the Summer Triangle.

The brightest point of the triangle is Vega, in Lyra, the harp. It’s high in the east-northeast as darkness falls. It’s one of the brightest stars in all the night sky, so you just can’t miss it. And it’s a close neighbor, at a distance of just 25 light-years — one of the reasons it looks so bright.

Well to the lower left of Vega, look for the faintest point of the triangle, Deneb. It marks the tail of Cygnus, the swan. Its fainter appearance is deceiving, though. The star is a supergiant, so it’s tens of thousands of times brighter than the Sun. It looks fainter than Vega only because it’s about 1400 light-years farther — one of the most-distant stars that’s easily visible to the eye alone.

Finally, look far to the lower right of Vega and Deneb for the triangle’s southernmost point, Altair, in Aquila, the eagle. It’s the closest member of the triangle, just 17 light-years from Earth. It’s actually the least impressive member of the triangle. Even so, it’s bigger and heavier than the Sun, and a good bit brighter, helping it stand out as a member of the season’s signature star pattern: the Summer Triangle.

Tomorrow: noticing the tug of an unseen planet.

Script by Damond Benningfield

Stars come in all types. One of the most common types is the orange dwarf — which is also one of the hardest to see. Orange dwarfs are somewhat smaller and cooler than the Sun. And they’re not quite as bright, which is why so few are visible to the unaided eye. Tonight, though, you can see not one, not two, but three orange dwarfs all at once.

This triple star is known as 36 Ophiuchi. It’s just 19 light-years from Earth. Its two brightest stars each emit about a quarter as much visible light as the Sun does. The two stars orbit each other every 500 years, on a highly elongated path. Yet another orange star stands a good distance away from these two, giving 36 Ophiuchi a grand total of three orange dwarf stars.

Such stars account for about 10 percent of all the stars in the galaxy. They’re so faint, though, that none is prominent in the night sky. Fortunately, because 36 Ophiuchi is so close, it’s one of the few orange dwarfs you can see without binoculars or a telescope.

You will, however, need a star chart and a good, dark, moonless night, like tonight, away from city lights. 36 Ophiuchi is quite low in the south-southeast at nightfall, and due south around midnight, not far to the lower right of the bright planet Saturn. And if you can’t get away from the city, binoculars will bring the system into view — a triple orange dwarf that’s among our nearest neighboring stars.

Script by Ken Croswell, Copyright 2016

Solar storms can create all sorts of trouble. They can knock out power grids, cripple orbiting satellites, and disrupt airline schedules and radio communications. And a team of scientists is looking at one other possible form of trouble: stranding events for whales, dolphins, and porpoises.

These marine mammals, known as cetaceans, have internal compasses to help them navigate the world’s oceans. But solar storms are caused by short-circuits in the Sun’s own magnetic field. They can send massive clouds of charged particles toward Earth. These particles cause problems when they hit Earth’s magnetic field.

The researchers suggest that one of those problems is interfering with the navigation of cetaceans.

These animals sometimes strand themselves on the beach, either individually or in groups. There are many possible causes for the strandings, including diseases and storms. And sonar causes some strandings by interfering with the animals’ internal sonar, which they use to locate both prey and others of their own kind.

Because the animals have an internal compass to sense Earth’s magnetic field, though, the researchers suggest that solar storms could be another cause of strandings. The team will comb through many years of observations of strandings and solar storms. They’ll compare the two to see if there’s a relationship — perhaps identifying another threat to these beautiful creatures.

Tomorrow: three stars for the price of one.

Script by Damond Benningfield

The Sun has been unusually “quiet” in recent years — the quietest in more than a century. And forecasters say there’s a good chance it’ll be even quieter over the next few decades.

The Sun’s level of activity is determined by its magnetic cycle. On average, a cycle lasts about 11 years. The Sun is most active at the cycle’s peak, when it can be covered by dozens of sunspots and produce big outbursts of energy and charged particles. These outbursts can knock out power grids on Earth, damage orbiting satellites, and disrupt our technology in many other ways.

Astronomers have been watching the solar cycles for four centuries. And they’ve been counting them since 1755. Right now, we’re near the end of Cycle 24.

The most active solar cycle ever recorded peaked in the early 1960s. The cycles since then have been weaker. And the current one is the weakest since the early 1900s. Over the last few years, in fact, there have been dozens of days when there were no sunspots at all.

And scientists say that trend could continue. Early forecasts call for Cycle 25 to be even weaker than the current one, with Cycle 26 weaker still. In fact, we could be heading into a period of weakness that could rival the Maunder Minimum — a period in the 17th and 18th centuries where the Sun was almost comatose. If so, then the Sun could remain quiet through the end of the century — giving our technology a break from our star’s disruptive effects.

Script by Damond Benningfield

The Sun is one of the steadiest of all stars. Even so, its energy output does vary — by less than a tenth of one percent. This variation takes place over an 11-year cycle that’s tied to changes in the Sun’s magnetic field. But cycles aren’t the same. The most intense yet seen peaked in the early 1960s. And right now, we’re in the middle of the weakest cycle in more than a century.

The Sun is a big, spinning ball. Because it’s made of gas, different layers and different latitudes rotate at different rates. That causes the Sun’s magnetic field to get twisted and tangled. Lines of magnetic force poke through the surface, creating dark sunspots, giant eruptions, and other activity. When the cycle peaks, the Sun can be covered with dozens of sunspots.

Astronomers have been tracking sunspots for more than 400 years. In the late 1600s and early 1700s, they saw almost no sunspots at all — a period known as the Maunder Minimum. It corresponded to a period of unusually cold weather in North America and Europe. Four of the five busiest cycles they’ve seen have happened in the last 75 years or so.

By looking at tree rings, and at ice cores from Antarctica and Greenland, scientists have estimated the intensity of solar cycles going back more than 11,000 years. And they’ve found that the peaks of the mid-20th century are the strongest in at least 8,000 years.

Over the last few cycles, though, that intensity has faded. More about that tomorrow.

Script by Damond Benningfield

The modern calendar is one of the oldest and most basic astronomical instruments. It measures the relative motions of Earth and the Sun. A day, for example, is the average length of time it takes the Sun to return to the same place in the sky: 24 hours. And a year is the time it takes Earth to make one complete turn around the Sun.

So perhaps it’s not surprising that the calendar uses astronomical definitions for the seasons: key points in the Sun’s annual migration across the sky.

Summer, for example, begins tonight here in the northern hemisphere, when the Sun stands farthest north for the year — a moment known as the summer solstice. And the season lasts until the September equinox, when the Sun crosses the equator from north to south. The solstice also marks the longest day of the year.

For centuries, the calendar was timed to match the seasons as well. In Great Britain and its American colonies, for example, the year began at the spring equinox in March. It wasn’t until 1752 that the British calendar was changed to move the start of the year to January 1st.

Of course, astronomy isn’t the only way to mark the seasons. Meteorologists, for example, have a slightly different range for summer: from the first of June through the end of August. And families follow the school calendar, in which summer also spans June through August — different ways to mark the cycles of the Sun.

We’ll have more about the Sun tomorrow.

Script by Damond Benningfield