StarDate

As far as we know, there are no giant ants at IRAS 2A, an embryonic star system almost a thousand light-years away. But the system does contain the compound that makes an ant sting hurt: formic acid.

It’s one of dozens of complex molecules found in young star systems across the galaxy. The list includes such well-known molecules as ozone, cyanide, formaldehyde, methane, and ethanol. Many of the compounds are key ingredients for life, such as tryptophan – an amino acid that’s essential for making proteins in the human body.

Scientists aren’t sure just how these molecules take shape. One suggestion says they form through chemical reactions on small ice grains found in the cloud of material that encircles a young star. And recent observations of IRAS 2A and other young stars by Webb Space Telescope seem to support that idea.

IRAS 2A consists of two “protostars” – objects that are becoming stars but aren’t quite there yet. Each of them appears to be about half as massive as the Sun. They’re surrounded by a disk of debris – gas, dust, and ice, with a dollop of complex organic molecules. If the system gives birth to any planets, those molecules could help make the worlds habitable – and perhaps provide ingredients for life itself.

IRAS 2A is in a star cluster in Perseus. The cluster climbs into view, in the northeast, by midnight. But it’s too faint to see without a telescope.

Script by Damond Benningfield

50 years ago this summer, astronomers Russell Hulse and Joseph Taylor went pulsar hunting. And they bagged a real trophy – a binary system that contained a pulsar and another dead star. The discovery, and their later analysis of the system, earned Hulse and Taylor the 1993 Nobel Prize in Physics.

Both members of the binary are neutron stars – the crushed cores of once-mighty stars. Each is about 1.4 times the mass of the Sun, but only about as big as Earth. One of the stars rotates rapidly, sending out “pulses” of energy at each turn like a cosmic lighthouse. That makes the star a pulsar.

It spins about 17 times per second. But the timing changes ever so slightly as the stars orbit each other. The changes have revealed that the stars are spiraling closer together – by about three millimeters per orbit.

The stars are getting closer because they’re losing energy – by producing ripples in space and time known as gravitational waves. They were predicted by Albert Einstein’s theory of gravity. But the binary star system provided the first evidence that the waves actually exist.

The two stars should slam together in a few hundred million years, producing a torrent of gravitational waves. In August of 2017, in fact, a gravitational-wave observatory “heard” the merger of another pair of neutron stars – more confirmation that Einstein’s theory of gravity was right.

Script by Damond Benningfield

Our Sun has been doing the same thing for the past four and a half billion years – converting the hydrogen in its core to helium, producing huge amounts of energy in the process. And it’ll keep on doing that for billions of years more.

Over the eons, that slow, steady change produces major consequences: The Sun gets bigger and brighter as it ages. That trend has important consequences for Earth and the other planets.

As a star converts more and more hydrogen into helium, the core shrinks. That squeezes the core, which makes it hotter. That revs up the rate of nuclear reactions, which increases the amount of energy produced in the core. That energy pushes outward on the surrounding layers of gas, making the star expand. It also increases the total amount of energy the star radiates into space, making it brighter.

Models of how stars evolve say the newborn Sun probably was only about 70 percent as bright as it is now. But that creates some problems. Studies show that Mars was much warmer in the distant past, for example. But if the Sun was fainter, that shouldn’t be the case – the young planet should have been a desolate iceball.

In the future, the Sun will continue to get brighter, which is bad news for Earth. In a billion years or so, our star will be about 10 percent brighter than it is now. That extra energy may be enough to vaporize the oceans – turning our planet into a burned-out cosmic cinder.

Script by Damond Benningfield

The Moon creeps up on the bright star Antares this evening. Depending on your location, you might see them pass less than a degree from each other – less than the width of your finger held at arm’s length. Because the Moon will be so close to Antares, it’ll wash out the star’s reddish orange color.

Astronomers have been tracking that color for thousands of years. And they haven’t seen much change.

Antares is a red supergiant – it’s many times bigger and heavier than the Sun, and tens of thousands of times brighter. Its surface is thousands of degrees cooler than the Sun’s, which is why it looks red.

On the inside, supergiant stars are changing in a hurry – fusing lighter elements to make heavier ones. But the change isn’t always reflected at the surface. In a study a couple of years ago, a team of scientists found that the color of Antares has remained pretty steady for at least 3300 years.

The team analyzed observations from Europe, the Middle East, and China. In China, the star was known as “Great Fire.” In Egypt, it was “red one of the plow.” And many records compared the star to Mars, which is known for its reddish color. In fact, the name “Antares” means “rival of Mars” – a comment on their similar appearance.

The study said the star’s unchanging color could mean that Antares has a good run left before it explodes as a supernova – another million years or longer.

Script by Damond Benningfield

The Moon “shines” by reflecting sunlight. But it’s not a great mirror – it reflects only about one-tenth of the sunlight that strikes it. So it’s actually quite dark.

Even so, it reflects enough radio waves that it served as the first communication satellite. In the late 1950s and early ’60s, the United States Navy used the Moon to relay signals between bases, and to some ships at sea.

That developed from an earlier project that listened for radar transmitted from inside the Soviet Union. Originally called Project Joe, it started in 1947, after the Army successfully bounced its own radar waves off the Moon. It began regular operations 75 years ago this month.

Early results were better than expected, so the Navy began studying how to use the Moon to send signals, not just receive them.

At the time, it maintained long-range contact by bouncing radio waves off the ionosphere – an electrically charged layer of the atmosphere. But storms on the Sun could interrupt transmissions. The Moon would be more reliable. In 1954, project leader James Trexler beamed his own voice to the Moon and back. And by late 1960, the system was in regular use – bouncing radio waves off the Moon.

The Moon is just past first quarter tonight, so the Sun lights up a bit more than half of the lunar disk. The bright star Antares is well to the upper left of the Moon. More about the Moon and Antares tomorrow.

Script by Damond Benningfield

Mars and Jupiter are staging an especially close encounter in the early morning sky. They climb into good view by 2 or 2:30, and stand high in the east at dawn, so you shouldn’t have any trouble finding them.

Jupiter is by far the brighter of the two. In fact, it’s the brightest object in the early morning sky now other than the Moon. It shines almost 20 times brighter than Mars. But the Red Planet is pretty bright on its own. And it’ll only get brighter as the year progresses.

That’s because Mars and Earth are moving closer to each other. Earth is the third planet from the Sun, while Mars is the fourth. Since we’re closer to the Sun, we move faster than Mars does. So every 26 months, we catch the Red Planet, then move past it.

Right now, we’re in chase mode, closing the gap by a little bit each day. As we get closer, Mars gets brighter. By the end of the year, it’ll shine about eight times as brightly as it does now. It’ll reach its peak in mid-January, when Earth passes Mars and the two planets are at their closest.

For now, watch for Mars as it slips past Jupiter the next few mornings. It stands a little above Jupiter tomorrow. They’ll be closest on Wednesday and Thursday, separated by a fraction of a degree – less than the width of a pencil held at arm’s length. After that, they’ll move apart, with Mars lagging behind its brighter sibling.

Tomorrow: messages from the Moon.

Script by Damond Benningfield

Starlight sprinkles down on Earth like raindrops in a summer shower. And like raindrops, the sprinkles of starlight can appear to change direction.

This effect is known as aberration of starlight. It was discovered three centuries ago by an astronomer who was trying to measure the distance to Eltanin, the brightest star of Draco, the dragon.

James Bradley was looking for the star’s parallax. The idea is to observe a star when Earth is at opposite sides of its orbit. That causes stars that are close to us to shift position relative to stars that are farther away. Measuring the size of that shift reveals the star’s distance.

Bradley did see a shift in Eltanin’s position. But it wasn’t related to the star’s distance. Instead, it was caused by Earth’s orbital speed. The effect is like watching raindrops fall from inside a car. If you’re sitting still, the raindrops might appear to fall straight down. But if you’re cruising down the highway, they appear to come toward you at an angle. The raindrops aren’t moving any differently – you are.

The same thing happens with starlight. Thanks to Earth’s motion around the Sun, the “drops” of light appear to come in from different angles at different times of year. That causes a star to appear to shift position – the result of the aberration of starlight.

Eltanin is high in the north-northeast at nightfall. The moderately bright star stands to the left of brilliant Vega.

Script by Damond Benningfield

Different stars face different fates. The smallest will shine feebly for trillions of years – many times longer than the current age of the universe – then simply fade away. The heaviest, on the other hand, will blast themselves to bits, briefly shining brighter than billions of normal stars.

A bright star that faces such a violent end is in good view tonight. Spica stands to the upper left of the Moon as night falls.

Spica actually consists of two stars.

The heavier star, Spica A, is about 10 times the mass of the Sun. Such stars burn through their nuclear fuel in a hurry. That makes them extremely bright. But it also means they won’t live long. For Spica A, the prime of life will last for less than 30 million years, compared to about 10 billion years for the Sun. When the star can no longer produce nuclear reactions in its core, the core will collapse. The star’s outer layers will fall inward, then rebound at a few percent of the speed of light. That’ll blast the star apart as a supernova.

Its companion, Spica B, is about six times the Sun’s mass. If it survives the supernova, it’ll live more than a hundred million years. At the end of its lifetime, it’ll swell up to many times its current size, just as Spica A will. But it’s not massive enough to explode. Instead, it’ll lose its outer layers in a less-violent process. That’ll leave only its dead core, shining faintly through the long cosmic night.

Script by Damond Benningfield

Today, it’s hard not to know the time. Your phone, your TV, your car, and scads of other devices give you the time, accurate to a tiny fraction of a second. But in ages past, telling time wasn’t that easy – especially at night. Fortunately, nature provided a decent nighttime “clock”: the stars. The location of certain stars at different times of year told skywatchers the time of night.

A prime example of how that worked comes from ancient Egypt.

The Egyptian day was divided into 24 hours – a system passed along into modern times. Daytime and nighttime each consisted of 12 hours, regardless of the time of year. So the length of an “hour” varied between night and day, and from season to season.

The nighttime hours were marked by prominent stars. The gap between either the setting times or rising times of two of these stars marked an hour. And each star “reigned” for about 10 days before the next one took its place. So the Egyptian year was divided into 10-day “weeks,” known as decans – 36 in all. An extra five days were added to the end of the year, bringing the calendar to 365 days.

The year began with the first dawn appearance of the star Sirius, the brightest star in all the night sky. It marked the start of the annual flooding of the Nile River, which brought renewed life to the fields – an event marked by the “ticking” of the starry clock.

Script by Damond Benningfield

The Milky Way has played a key role in the lore of many cultures. Among other things, it’s represented a road, a river, and the path of the dead into the afterlife – and their home in the afterlife.

The role of the Milky Way in ancient Egypt is still a bit – well, milky – it’s just not clear. But some studies have suggested that it represented the sky goddess Nut. And some recent work says the summer Milky Way represented her backbone, while the winter Milky Way represented her arms.

Nut was depicted as a star-covered woman arched across the sky. She protected the earth – her brother and consort, Geb. And she was supported by the air – their father, Suh.

During the day, the Sun-god Re sailed across her back. At sunset, Nut ate the Sun as it disappeared in the west. At dawn, she gave birth to the Sun, allowing it to return to view in the east. She played a similar role in the motions of bright stars that were used to track time; more about that tomorrow.

The recent study says that Nut represented the entire sky, not just the day. So she arched over the nighttime as well – helping protect the Sun and stars during their trip through the underworld. But the Milky Way changes orientation during the night and during the year. So it doesn’t always align with the rising and setting Sun. The alignment is best during parts of summer and winter – the Sun and Milky Way in harmony – connected by the sky goddess.

Script by Damond Benningfield