StarDate

Earth’s magnetic field sometimes does a flip. The north magnetic pole becomes the south pole, and vice versa. On average, it happens once every few hundred thousand years.

But sometimes, it’s more of a flip flop — the field flips right back over.

One flip-flop took place about 42,000 years ago. Known as the Laschamps Excursion, the flip lasted only a few hundred years. And a recent study said the transition could have been a major ...

Earth’s magnetic field is a protective blanket. It keeps charged particles from the Sun and beyond from hitting the surface and much of the atmosphere, where they could cause a lot of problems. But it’s a lumpy blanket. It doesn’t provide the same level of protection for the whole planet. Instead, the magnetic field has peaks and valleys.

Today, there’s a deep “valley” over parts of South America and the South Atlantic Ocean. Known...

Be careful what you say — a single phrase can define a legacy.

Consider Frances Baily. He served four terms as president of the Royal Astronomical Society and compiled some of the most important star catalogs in history. But he’s best known for five little words: “like a string of beads.”

Baily was born 250 years ago today, in England. As a young man, he traveled to the wilds of North America, then joined the London Stock Exchange....

Russian astronomer Friedrich Wilhelm von Struve discovered and catalogued thousands of binary stars — pairs of stars that are gravitationally bound to each other. But a system that he first saw in 1829 was so striking that he gave it a special name: Pulcherrima — “the most beautiful.” It honors the contrasting colors of the two stars. One looks pale orange, while the other looks blue-white or even green.

The system is also known by...

The brightest star in the night sky is getting ready to leave it for a while. Sirius, the Dog Star, is low in the southwest as night falls. Over the next few weeks, it’ll sink deeper into the twilight, then disappear from view.

Sirius is almost nine light-years away. And it actually consists of two stars, not one. The one we see is a good bit bigger, brighter, and heavier than the Sun. The other is about the same mass as the Sun, b...

Stars are huge — anywhere from about 10 times the diameter of Earth to a hundred thousand times or more. Such a scale is just hard to fathom. One way to envision it is to consider how long it would take you to make one turn around such a giant body.

An extreme example is Antares, the bright orange heart of Scorpius. It’s to the lower left of the Moon as they climb into good view tonight, after midnight, and about the same distance ...

Over the millennia, stars acquire a lot of names. Some make sense, some don’t. And some of them might have gotten mixed up along the way.

An example is the fourth-brightest star of Leo, the lion, which is about 58 light-years away. It represents the lion’s hip. A few centuries ago, it was assigned the name “Delta Leonis” — an indication of its ranking within the constellation. But it also has some older names, including Zosma and D...

Immanuel Kant is best known for his ideas about philosophy, from ethics to the nature of knowledge. But he also played a role in the development of an idea about how planets are born. And while many of the details were off, his basic idea was sound.

Kant was born 300 years ago this week, in the German state of Konigsberg. And during his 80 years, he never left it.

He enrolled in the University of Konigsberg at age 16. But his fathe...

Few constellations have as many backstories as Virgo, the virgin. In ancient Greece and Rome, it was linked with several goddesses, each with her own story.

In one story, she was Dike, the goddess of justice. She lived when the gods known as the Titans ruled the land. Everything was peaceful, it was always spring, and living was easy. But after Zeus and the Olympians defeated the Titans, life got much more complicated. The goddess ...