StarDate

Few objects in the universe are more beautiful than the final breath of a Sun-like star. The star expels its outer layers, forming a colorful cloud that’s lit up by the star’s hot core. The cloud can be sculpted into amazing shapes — from a butterfly to the heart of an atom.

One of those dying stars is the Blue Snowball Nebula. It’s high in the sky at nightfall, in Andromeda. Through a small telescope, it does look blue, and it has the slightly fuzzy outline of a snowball.

The system’s details are uncertain. That’s mainly because astronomers have had a hard time figuring out its distance. Measuring the distances to such nebulae is hard because most of them are far away, and they’re spread out — they’re not sharp points like stars are.

In recent years, though, astronomers have used several techniques to zero in on the distance. They suggest that the Blue Snowball is about 6,000 light-years away. If so, then the nebula spans the better part of a light-year.

The star began casting off its outer layers a few thousand years ago as seen from Earth. The nebula consists of two concentric shells of gas. The outer one is expanding faster than the inner one — more than a hundred thousand miles per hour.

The star is in the final stages of life. It’s about 60 percent the mass of the Sun, but about 200,000 degrees hotter. Its ultraviolet energy causes the nebula to glow like a neon bulb — revealing the last breath of a dying star.

Script by Damond Benningfield

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A faint but famous princess crowns the sky on November evenings. Andromeda is high in the east as night falls, and directly overhead by around 10 o’clock.

The constellation is marked by a slightly curved line of three equally bright stars. Alpheratz is at the top right of the line, and does double duty as one of the corners of the Great Square of Pegasus. Mirach is at the middle of the line, and is about the same brightness as Alpheratz.

Almach — also known as Gamma Andromeda — is at the bottom left of the line. It’s slightly fainter than the other two, but perhaps the most interesting of the bunch. That’s because it’s a family of at least four stars. A small telescope shows it as two stars — one that shines golden yellow, the other blue-white.

The golden yellow one is the brightest member of the quartet, and is known as Gamma 1 Andromeda. It’s bigger, heavier, and brighter than the Sun. The star is big because it’s at the end of its life, so it’s puffed up to many times its earlier size. Before long, it’ll cast off its outer layers, leaving behind only its tiny, hot, dead core — a white dwarf.

The other three stars in the system form Gamma 2 Andromeda. They’re pretty close together, so even through a small telescope their light blurs together into a single point. All three of the stars are hotter than the Sun, so they shine white or blue-white — forming a nice contrast to their golden companion.

More about Andromeda tomorrow.

Script by Damond Benningfield

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Arno Penzias and Robert Wilson had a problem. In the 1960s, the researchers at Bell Laboratories were studying radio waves reflected from a giant balloon in orbit. But the signal was noisy. They eliminated every source of interference they could think of — including pigeon droppings inside their radio telescope. But the noise remained.

When they talked to other scientists, though, they realized the “noise” was actually an important discovery: the “afterglow” of the Big Bang.

Astronomy contains many such instances of serendipity — chance discoveries made while working on a different topic.

In 1967, for example, graduate student Jocelyn Bell was using a radio telescope to study quasars — some of the brightest objects in the universe. She discovered several sources, though, that produced regular “pulses” of radio waves. She and her advisor ruled out many possible explanations for these “pulsars.” Another researcher eventually came up with the answer: They’re the spinning corpses of massive stars that “beam” energy into space.

As Bell was making her discovery, satellites were making another. They were looking for nuclear bomb tests, which were banned by a treaty. Instead, they found bursts of gamma rays from deep space. The discovery was declassified in 1973. But it took decades to work out the sources of the gamma-ray bursts: the explosions of massive stars, or the mergers of the corpses of such stars — serendipitous discoveries in the stars.

Script by Damond Benningfield

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20 years ago today, just two days after leaving Earth, an astronaut and two cosmonauts arrived at the International Space Station. The station has been occupied every day since then.

The crew of Expedition 1 consisted of American Bill Shepherd, the mission commander, and two Russians — Yuri Gidzenko and Sergei Krikalev.

When they arrived, the station was a barebones operation — only three modules and some solar panels had been put together. During Expedition 1’s four and a half months in orbit, though, another module and some giant solar panels were added to the complex.

Since then, the station has been expanded even more. It’s by far the largest object ever placed in space. It circles Earth 16 times a day, at an average altitude of about 250 miles. It hosts many research projects, including several that look out into the universe.

About 240 people from 20 countries have visited the station, with up to six living and working there for months at a time.

The station has been approved to continue through 2024. And NASA and other space agencies are talking about keeping it in orbit even longer — extending an occupation that began 20 years ago.

Script by Damond Benningfield

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The planet Uranus is windy. Winds have been clocked at up to 560 miles per hour. That’s three times faster than a category five hurricane here on Earth.

Uranus is one of the solar system’s giants — four times the diameter of Earth. Its atmosphere consists mainly of hydrogen and helium, the lightest chemical elements. But it’s topped by clouds and hazes made of water, ammonia, and methane. The methane absorbs red light, so the planet looks blue-green.

Only one spacecraft has ever flown past the planet, and that was 34 years ago. But better telescopes and instruments on Earth have allowed scientists to look into its atmosphere. They’ve plotted jet streams in the atmosphere’s upper and middle layers.

The calmest of the jet streams is at the equator. It blows at roughly 225 miles per hour. Winds get faster as you move away from the equator. They peak at about 60 degrees north and south of it. Wind speeds then drop to near zero at the poles. Scientists continue to ponder the reasons for high-speed winds on this giant planet.

Uranus is putting on its best showing of the year. The giant planet rises around sunset and is in view all night. Under especially clear, dark skies, those with good eyesight might just make it out, shining like a faint star. Most of us, though, will need binoculars to spot it — a tiny dot shining among the countless stars of the Milky Way.

Tomorrow: Day One of 20 years in space.

Script by Damond Benningfield

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A second planet is at its best this month. Mars was at its peak a couple of weeks ago, and is still shining brightly. And today, Uranus is at its peak. But while it’s a lot bigger than Mars, it’s also a lot farther away, so it isn’t nearly as bright. You need binoculars to pick it out.

Uranus is the third-largest planet in the solar system — about four times the diameter of Earth. In the odd jargon of science, it’s known as an ice giant.

That’s because most of the planet probably consists of a deep layer of water, ammonia, and methane — compounds that are classified as ices. On Uranus, though, they’re not what most of us would think of as ice — they form a hot, dense fluid.

The planet probably has a small, heavy core below the ices, and a thin layer of hydrogen and helium above them. The water and other compounds form clouds at the top of the atmosphere. Methane clouds absorb red light, so only bluer wavelengths pass through. That gives Uranus a blue-green color. It’s pale, though, because the planet’s average distance is 1.8 billion miles — making it a hard-to-see giant.

This is a good time to look for Uranus, though, because it lines up opposite the Sun. It’s in the sky all night, and it’s brightest for the year, too. Tonight, it’s due east at nightfall, above the Moon. It’s tough to see through the lunar glare. It’ll be a better target in a few days, when the Moon gives it a little more space.

More tomorrow.

Script by Damond Benningfield

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The Moon is full and bright the next couple of nights. And it has so many titles you might think it’s royalty. Since it’s officially full tomorrow, it’s a Halloween Moon. As the full Moon after the Harvest Moon, it’s the Hunter’s Moon. And as the second full Moon this month, it’s a Blue Moon. Put them all together, and it’s a Blue Hunter’s Halloween Moon.

The first full Moon this month came on the 1st. As the full Moon closest to the fall equinox, it was the Harvest Moon. And the Hunter’s Moon always comes next. In bygone times, the bare fields after the harvest made it easier for hunters to stock up on game for the winter.

A Blue Moon generally happens every two or three years. The Moon’s cycle of phases is 29 and a half days long, so the timing has to be just right to squeeze two full Moons into a single month. Back in 2018, we had two of them — in January and March — with no full Moon at all in February. And the next one won’t come along until August of 2023.

Although the full Moon is often associated with Halloween, the two don’t coincide all that often. In the 21st century, they happen an average of about once every 19 years. For most of the United States, the last one took place in 2001 — and it was a Blue Hunter’s Moon as well. And the next one won’t come around until 2039.

So enjoy the Blue Hunter’s Halloween Moon — lighting up the sky both tonight and tomorrow night.

Script by Damond Benningfield

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The trip to Mars won’t be easy. Astronauts might experience months of low gravity and exposure to cosmic rays. Big storms on the Sun could zap them with radiation. And that’s not including the dangers of actually landing on Mars.

It takes about six to 10 months to travel from Earth to Mars. A crew might spend most of that time with almost no gravitational pull. That could cause fluids to pool in their heads, creating vision changes and other problems.

One way to overcome those problems is to spin part of the spacecraft, creating artificial gravity. But that adds weight and complexity. As Plan B, Mars travelers might wear a device that pulls some of the fluids into their lower bodies.

Mars-bound astronauts would be zapped by cosmic rays — particles accelerated to almost the speed of light by exploding stars and other powerful objects. Earth’s magnetic field and atmosphere prevent them from reaching the surface. On the way to Mars, though, there’d be no such protection. The particles could cause cancer, heart disease, or other health problems.

And the Sun sometimes produces blasts of particles and radiation. A craft would need heavy shielding to protect its occupants from danger — adding even more weight and expense for a trip to Mars.

For now, look for Mars in the southeast in early evening, shining like a bright orange star. Tonight, it’s to the upper right of the Moon as they climb into view, and below the Moon at dawn tomorrow.

Script by Damond Benningfield

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Living on Mars would be both strange and familiar.

On the familiar side, a day on Mars is about the same length as a day on Earth — 24 hours and 37 minutes. Mars is tilted at the same angle that Earth is, so the planet experiences seasons in the same way. And many of its landscapes look like what you might see in the deserts of Earth, with mesas and sand dunes, along with dust devils whirling through the sky.

On the strange side, the surface gravity is only three-eighths as strong as Earth gravity. So if you weigh a hundred and fifty pounds on Earth, you’d weigh only 58 pounds on Mars. That means you’d probably need to walk much like Apollo astronauts did on the Moon, gently rocking from side to side. And if you dropped something, it would take longer to fall to the surface.

Mars has an atmosphere, as Earth does, but it’s less than one percent as thick as Earth’s. So you’d need an air supply to venture out across the surface. The thin air, and the greater distance from the Sun, make Mars much colder than Earth. Nighttime temperatures regularly plunge to 100 degrees below zero or lower, so you’d need to bundle up.

And two small moons race across the night sky — an unfamiliar sight on a somewhat familiar planet.

Mars stands close to our Moon tonight. It looks like a bright orange star to the left of the Moon in early evening, and above the Moon as they set, before dawn.

We’ll have more about Mars and the Moon tomorrow.

Script by Damond Benningfield

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An exploded star in Cassiopeia is a huge chemical factory. It’s surrounded by filaments of oxygen, iron, sulfur, and other elements. They were forged inside the star’s core, or in the blast that ripped it apart. Someday, they may be incorporated into new stars, planets — or even living organisms. In fact, the oxygen, iron, and many other elements in our own bodies were created in similar explosions.

Cassiopeia A began life as a heavy star — roughly 15 times the mass of the Sun. The core of such a star is extremely hot. At such high temperatures, it combines lighter atoms to make heavier ones — all the way up to iron.

At the end, the star can’t continue the process. The core collapses to form a neutron star. The star’s outer layers blast into space. The explosion is so hot that it creates many more new elements.

Astronomers have measured the amounts of different elements in the debris around Cas A. The debris forms a bubble that’s 10 light-years wide. It contains enough oxygen to make a star three times as massive as the Sun. There’s enough iron to make 70 thousand Earth-mass planets, and enough silicon to make 20 thousand Earths. All of that material is moving outward at millions of miles per hour — perhaps to form part of a future star system.

Cas A is in Cassiopeia, the queen, which is in the northeast as night falls and wheels high across the north during the night. Its stars form a big letter M or W.

Script by Damond Benningfield

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