StarDate

A hypermassive neutron star defies gravity. Instead of instantly collapsing to form a black hole, it keeps itself puffed up. But only for a while. In the end, gravity always wins.

A neutron star is the ultra-dense corpse of a once mighty star. It’s more massive than the Sun, but smaller than the city limits of Chicago.

Neutron stars have a weight limit — about twice the mass of the Sun. If they pack on more, they collapse to form a black hole.

But there may be a way for a neutron star to hold up against that limit: from the merger of two neutron stars. If they come together in the right way, they might resist gravity by spinning extremely fast — up to 78 thousand times a minute.

That would churn up the surrounding space-time, producing tiny ripples known as gravitational waves. Future observatories should be able to “hear” those ripples as the stars approach each other, as depicted in this simulation. [audio]

The ripples would end with a “chirp” as the combined stars finally surrendered, forming a black hole. From merger to collapse, it should all be over in less than a second.

The black hole would “ring” like a bell for a while longer as it settled down, producing more waves. No one has yet “heard” that ringing. But a recent study found two candidate mergers from the 1990s. They were accompanied by intense bursts of gamma rays — bright flashes before the ultimate darkness.

More about gravitational waves tomorrow.
 

Script by Damond Benningfield

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A star that’s moving into the final stages of life arcs high across the south tonight. Although the star is bigger and heavier than the Sun, its fate is the same: It will end its life as a hot cosmic cinder called a white dwarf.

The star is Rasalhague, the brightest star in Ophiuchus, the serpent bearer. It climbs into view in the east shortly after darkness falls, but climbs high across the sky during the night.

Rasalhague is actually a binary — two stars that are bound by their mutual gravitational pull. But only one of the stars is visible to the unaided eye. It’s more than twice as massive as the Sun, and about 25 times brighter. It’s much hotter than the Sun as well.

From this profile, astronomers deduce that the star is moving into the penultimate phase of its life: It’s becoming a giant. The star has fused the hydrogen fuel in its core to make helium, so the core is shrinking and getting hotter. Right now, it’s fusing the hydrogen in a thin layer around the core. As part of that process, the star’s outer layers are puffing up, making Rasalhague many times larger — a stellar giant.

When the giant phase ends, the star will cast its outer layers into space, leaving only its dense core — a white dwarf. Rasalhague will no longer produce energy, but it will still shine faintly because it’s extremely hot — the remains of a once giant star.

The Sun will go through the same series of changes — in several billion years.
 

Script by Damond Benningfield

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The Moon looks like it’s rolling through a rack of bowling pins tonight — past the one-pin and heading for the next row, taking dead aim at the star Delta Scorpii. The whole group climbs into good view by about 11 or 11:30.

The one-pin is Antares, the brightest star of Scorpius. It’s close below the Moon. Despite our analogy, the Moon is actually moving toward the bright star, and will be even closer at dawn.

As seen from Earth, Delta Scorpii isn’t quite as bright as Antares. In reality, though, it’s just about as bright. In fact, it’s almost a twin to the Antares system.

Both Antares and Delta Scorpii are binaries — two stars linked by their gravitational pull. Each consists of a supergiant paired with a slightly less impressive star. The supergiants will explode as supernovas — probably within the next million years or so. The companion stars are right along the supernova mass limit, so they might explode, but they might not.

Pi Scorpii is to the right of the Moon. It’s a triple system. It consists of another Antares-like binary linked to a smaller star a long way away.

Antares and Delta and Pi Scorpii are all about the same age — roughly 11 million years to 15 million years. And they’re all members of the same huge complex of gas, dust, and stars. It’s given birth to many supergiants and near supergiants, plus thousands of smaller stars. And many more are taking shape — possible future “bowling pins” for the scorpion.
 

Script by Damond Benningfield

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The full Moon scoots low across the south tonight, shining on us from Libra, the balance scales.

A couple of years ago, astronomers snapped the sharpest pictures of the Moon ever taken from Earth. They showed details as small as a few feet across — shot with radar. The images were a demo for a project to develop the most powerful planetary radar system ever.

Astronomers have been using radar for six decades. It told them how fast Venus turns on its axis and revealed ice at the poles of the planet Mercury. It’s also tracked some asteroids that could one day threaten Earth.

The most powerful radar used the giant Arecibo radio telescope in Puerto Rico. But it collapsed a couple of years ago. NASA’s Deep Space Network does some of the work, too. But its main job of tracking missions across the solar system keeps it busier and busier.

So astronomers built a transmitter that used less power than a microwave oven to beam radio waves from the Green Bank Telescope in West Virginia. A network of other antennas caught the reflections. The demo produced the images of the Moon and tracked an asteroid that was more than five times farther than the Moon.

Now, astronomers want to make the system a thousand times more powerful. That would let them map other planets and moons, discover hazardous asteroids at much greater distances, and track junk around Earth and the Moon — making the space around our planet a little bit safer.
 

Script by Damond Benningfield

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TOI-5205b didn’t make astronomers work that hard to find it. But they did spend months learning the planet’s details, and they’re planning to learn even more.

Most of the more than 5,000 confirmed planets in other star systems were found when they passed across the face of their parent star, blocking some of its light. Often, that dip is so small that it can take a while to confirm that it’s real.

That wasn’t the case with TOI-5205b, which was discovered by a space telescope. The planet blocks seven percent of the star’s light — a huge fraction.

Astronomers followed up with several ground-based telescopes, including the Hobby-Eberly Telescope at McDonald Observatory.

The observations revealed that the planet is a little bigger and heavier than Jupiter, the giant of our own solar system. It’s huge compared to the star, which is about 40 percent the size and mass of the Sun, and it’s quite close in. The combination makes it unique among the exoplanets discovered so far.

Starlight filters through the planet’s atmosphere. Studying that light should reveal how and where the planet was born, how it’s moved, and more — details about a planet that doesn’t try to hide.

The TOI-5205 system is about 300 light-years away. It’s to the right of bright Cygnus, the swan, in the wee hours of the morning. But you need a telescope to see the star — even outside the dark passages of its giant planet.
 

Script by Damond Benningfield

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Those GPS numbers on your smartphone pinpoint your latitude and longitude — your position on Earth’s surface. Latitude is your position north or south of the equator, usually expressed in degrees, minutes, and seconds. And longitude is your position east or west, in hours, minutes, and seconds.

Astronomers use a projection of those coordinates to define locations in the sky. Instead of latitude, though, the north-south position is known as declination. And the east-west position is called right ascension.

There’s a difference in the land-based and sky-based coordinates, though — the celestial ones change position. Earth wobbles on its axis, which causes the stars to shift around the sky. So when astronomers use a star’s coordinates, they have to specify time as well.

As an example, consider Spica, the brightest star in Virgo. Today, it’s at right ascension 13 hours, 26 minutes, 12 seconds, and a declination of minus 11 degrees, 17 minutes, and four seconds. But astronomers frequently use the location from the year 2000 to provide a fixed time. In that system, Spica is 13 hours, 25 minutes, 12 seconds, by 11 degrees, nine minutes, and 42 seconds — a slight but well-understood difference.

Tonight, there’s an easy way for most of us to spot Spica: It’s quite close to the Moon at nightfall, and stays close throughout the night.
 

Script by Damond Benningfield

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A monster star appears to be taking shape in a cloud of gas and dust about 8,000 light-years from Earth. It may be more than 1300 times the mass of the Sun — one of the heavier “protostars” yet seen. What’s more, it’s feeding faster than any other protostar. So this amazing object could produce a monster star.

MIR 2 is in a stellar nursery in Centaurus. From the southern states, the constellation stands low in the south around midnight. The nursery is too faint to see without a telescope.

The nursery is young, so it contains few natal stars. But MIR 2 makes up for the lack of siblings. It accounts for about half of all the energy coming from the nursery.

Recent studies suggest the protostar is just 40,000 years old. So it offers a unique chance to study how such massive stars are born.

MIR 2’s birth is controlled by two forces. Gravity pulls in material from the surrounding cloud. Much of that infalling gas forms a ribbon that’s massive enough to form 500 stars the size of the Sun. At the same time, radiation and magnetic fields are pushing material away from the protostar. That may be blocking the birth of smaller stars.

MIR 2 won’t maintain its great heft. The heaviest stars yet seen are only a couple of hundred times the Sun’s mass. Even so, when the fires of nuclear fusion ignite, in a million years or so, MIR 2 should be a monster — one of the more impressive stars in the galaxy.
 

Script by Damond Benningfield

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The Sun isn’t behaving itself. Most forecasts for its current cycle said it should be quiet. But it hasn’t been. And the level of activity has been picking up.

The Sun goes through an 11-year magnetic cycle. At the cycle’s peak, the Sun is covered with more of the dark magnetic storms known as sunspots. It also produces more big outbursts of energy and particles.

Those outbursts can have a big impact on our technology. They can damage or destroy orbiting satellites, disrupt air traffic and radio transmissions, and knock out power grids on the surface. So scientists keep an eye on solar activity. And they produce both short-range and long-range forecasts to help operators know when to take precautions.

The last cycle was quiet. There were periods of days or weeks when there were no sunspots at all. That cycle ended in late 2019.

Forecasters expected the new cycle to be just as quiet. They expected it to peak in mid-2025, with an average maximum of about 115 daily sunspots — about a third less than the average peak.

From the beginning, though, the new cycle has been more active. There have been more sunspots, and more of the big outbursts known as solar flares. That includes several that are in the most powerful category — like category 5 hurricanes.

As with all forecasts, we can’t be sure what’ll happen next. But it sure looks like we can expect the Sun to be even more unruly over the next few years.
 

Script by Damond Benningfield

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High technology highlights the southern evening sky at this time of year — the technology of the 18th century. A couple of small, faint constellations are named for the high-tech devices of the time.

Pyxis, the compass, is in the south-southwest at nightfall, just above the horizon. Antlia, the air pump, is to its left.

Nicolas Louis de la Caille created these and other technology-themed constellations in the 1750s. He journeyed to Africa to map parts of the sky that were difficult or impossible to see from Europe. From that, he drew some new constellations that covered fairly barren regions of the sky.

His constellations honored the telescope and microscope, the pendulum clock, and an early instrument for navigating at sea.

In the case of Pyxis, several of its stars once were part of the giant constellation Argo Navis — the boat that carried Jason and the Argonauts. La Caille split the constellation into thirds, with each part representing a section of the boat.

He then took a few stars that were part of the ship’s mast and turned them into Pyxis — a magnetic compass. Its brightest stars form a line that aims almost due north and south. Those stars are faint, though, so you need a clear, dark sky to see them

The stars of Antlia are even tougher to spot. They represent an air pump that had been invented by a French engineer a few decades earlier — a bit of 18th-century technology in the modern night sky.
  

Script by Damond Benningfield

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The Moon is a giant among the more than 200 known moons of the solar system’s major planets. It’s the fifth-largest and -most massive. It’s the second-densest. And it’s the largest compared to its host planet. As a result, some scientists consider Earth and the Moon to be a double planet.

To bolster that picture, the Moon is put together in a similar way to Earth. It has a dense core, made mostly of iron with a smattering of other metals. The core is wrapped in a layer of molten iron. In turn, that layer is wrapped in a partially molten layer of metals and rock. Then there’s a thick mantle of rocky materials, topped by a thin crust.

The crust isn’t the same around the entire Moon, though. On average, it’s about 40 to 45 miles thick on the near side, but about twice as thick on the far side.

That may be a result of the Moon’s relationship with Earth. The same hemisphere of the Moon always faces Earth — the reason we always see the same features. Asteroids and comets are pulled in by Earth’s gravity. As they approach the Moon, they’re more likely to hit the far side. The extra impacts build up a thicker crust — one big difference between the Moon and Earth.

The Moon is in its gibbous phase now, so it’s nice and bright. It stands high in the south at nightfall. And it has a bright companion: Regulus, the star that marks the heart of the lion.

Tomorrow: 18th-century technology in the southern sky.
 

Script by Damond Benningfield

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