StarDate

Mars and Jupiter are siblings – planets born at the same time, from the same disk of debris around the infant Sun. And they’re fairly close together – the fourth and fifth planets out. But other than that, they don’t seem to have much in common. They don’t look alike, their composition is different, and they’re wildly different sizes.The two planets will huddle close together in the morning sky...

Our solar system is filled with millions of leftovers – the chunks of rock and ice that weren’t incorporated into the planets and moons. The icy ones are known as comets, while the rocky ones are asteroids. But there’s not that much difference between them. They have similar ingredients, but in different amounts. How we classify them has more to do with where they were born and how close they get...

If anyone ever makes it to Pluto, they might want to stay away from the bottoms of steep craters. Occasional jiggling and shaking on the surface might trigger big, fast landslides – some of them big enough to bury a small city.Planetary scientists recently found evidence of several massive pileups in images snapped by New Horizons. The spacecraft flew past Pluto in 2015, giving us our only close...

Two “super-puff” planets appear to orbit a bright star about 1100 light-years from Earth. They’re as big as Jupiter, the giant of our own solar system. But they’re only a few percent the mass of Jupiter. That makes them extremely puffy – the least-dense worlds yet seen – less dense than cotton candy. Such planets are called super-puffs.The planets orbit the star TOI 791. It’s a little bigger and...

You can forget about sending a welcome basket to any neighbors on the planets orbiting Barnard’s Star, the second-closest star system to Earth. Conditions on all four of its planets are likely to be hostile to life.Barnard’s Star is just six light-years away – only the triple-star system Alpha Centauri is closer. The star is much smaller and lighter than the Sun. And at visible wavelengths, it’s...

The planet Venus is climbing higher into the morning sky day by day. It’ll reign as the “morning star” until summer, when it passes behind the Sun. It’ll return to view as the evening star in the fall.Just about every major culture figured out that the morning star and evening star are really a single object. The people of Sumeria probably knew it as far back as 5,000 years ago. But that didn’t...

Two planetary siblings are headed for a family reunion. They’re moving toward one another, and will be at their closest in a little more than a week. And they’re both bright, so you can follow their progress day by day.Jupiter and Mars climb into good view in the east by about 1:30 or 2. They’re high in the sky at dawn. Jupiter is the brightest object in the night sky after the Moon and Venus, so...

Early risers are in for a treat tomorrow – a tight triangle formed by the Moon, the planet Venus, and the star Spica. It’s in the east-southeast as dawn twilight paints the sky. But the group is quite low, so there’s not much time to look for it. And you’ll need a clear eastern horizon.The Moon is about as close to the Sun as it can get and still be visible. The Sun will light up only about three...

Two crescents hang out in the twilight the next couple of mornings: the Moon and the planet Venus. They’re quite low in the east at dawn. Venus is the “morning star.” It’s below the Moon tomorrow, but will be closer above the Moon on Saturday.Venus and the Moon appear as crescents for the same reason – both of them are passing between Earth and the Sun. That means their daylit sides are facing...

Two Mars-bound spacecraft have been just loitering about. They were launched a year ago. But the timing wasn’t right for them to reach Mars. So they were sent to a point in space where the gravity of Earth and the Sun are balanced – a place where they could “loiter.” But now, their time has come. They’ll leave that spot in a few days, beginning their trip to the Red Planet.Escapade consists of...