StarDate

Earth will reach its farthest point from the Sun for the entire year around midday tomorrow. We’ll be about 3.1 million miles farther than we were at closet approach, in early January.That far point is known as aphelion or ap-helion. The term comes from a mash-up of Latin and Greek. “Ap” is from a Latin word that means “far away,” while “helion” is a Greek word for the Sun.The changing distance...

Bellatrix, Spica, and Omega Herculis have something in common. They’re all good “semiquincentennial” stars. That has nothing to do with the stars themselves – only their distance. All three of them are roughly 250 light-years away. In other words, we see them as they looked roughly 250 years ago – around the time of the American Declaration of Independence.One light-year is the distance light...

The next big meteor shower is weeks away – at least, here on Earth. But some predictions say that a big shower could take place this weekend on the planet Venus – a result of the long-ago break-up of an asteroid.Regardless of where it takes place, a meteor shower happens when a planet flies through the orbital path of a comet or asteroid. Bits of rock and dust shed by the small body ram into the...

The planets Mars and Uranus will stage an especially close encounter the next couple of mornings. Uranus is quite faint, but its proximity to Mars can help you pick it out.Uranus is a giant – about four times the diameter of Earth. But it’s so far away that it’s faint. Under especially dark skies, people with good eyesight can just make it out. Moonlight or light pollution mask it from view, so...

A Japanese spacecraft is scheduled to pay a call on an asteroid this weekend. The encounter won’t last long – the craft will buzz by at about 12,000 miles per hour.This is the second asteroid encounter for Hayabusa2, which launched in 2014. Its main mission was a detailed study of the asteroid Ryugu. It orbited the asteroid for a year and a half. It gathered a few grams of dust and pebbles and...

The bright star that marks the tail of the swan is big, bright, and heavy. If you want to know how big, bright, and heavy, well, the most precise answer we can give you is “very.”We know for sure that Deneb is one of the more imposing stars around. But the details are a little hazy because the star’s distance is hazy. In part, that’s because of Deneb’s impressiveness.The most accurate stellar...

When the Moon covers the Sun during a total eclipse, a couple of rare sights greet viewers. One is the corona – the Sun’s hot but thin outer atmosphere, which looks like a silvery halo. The other is the short red or pink tendrils known as prominences – eruptions of gas into the corona. They’re actually there all the time, but they’re impossible to see against the brilliance of the Sun’s...

To predict the lifespan of a star, you don’t need a crystal ball – a bathroom scale will do just fine. Heavier stars age faster, so if you know the star’s mass, you have a good idea of its future.Consider Tarazed, the second-brightest star of the eagle. It’s only about six percent the age of the Sun. But because it’s about three and a half times the Sun’s mass, it’s already completed the “prime”...

Altair is one of the highlights of summer. It’s at one point of the Summer Triangle, and it’s the twelfth-brightest star in the night sky. And it’s just 16.7 light-years away.Because Altair is so close and bright, we know quite a bit about it. And we’re learning more all the time. A study a couple of years ago, for example, refined the likely age of the star – 88 million years, give or take 10...

A wave of starbirth is sweeping through Scorpius and some nearby constellations. It started about 20 million years ago, and is continuing today. It’s triggered the birth of thousands of stars, including some of the most impressive in our part of the galaxy.The complex is called the Scorpius-Centaurus association. It consists of three distinct regions that appear to be related. Giant clouds of gas...