Scientists have been searching for dark matter for decades. They haven’t found it – every experiment they’ve devised has come up empty. But they haven’t given up. Among other ideas, they’re thinking about ways to use moons, planets, and stars as detectors.
Dark matter appears to make up about 85 percent of all the matter in the universe. We know it’s there because its gravity pulls on the visible stars and galaxies around it.
Dark matter may consist of a type of particle that almost never interacts with normal matter. But it should interact just enough to reveal its nature.
Experiments here on Earth haven’t seen any such interactions. So some scientists recommend using astronomical objects instead of lab experiments.
Blobs of dark matter might enfold a binary star system. The dark matter’s gravity could pull the two stars away from each other. And dark matter might clump together to make a special kind of star. Both of those might be detectable with current telescopes.
Smaller blobs might slam into an icy moon, creating a special kind of crater. Such craters could be visible on Ganymede, the largest moon of Jupiter. Two missions on their way to Jupiter might be able to see them.
And dark matter might fall into the center of a planet and hang around. If enough builds up, it could heat the planet’s interior. So by studying many planets in other star systems, we might see some that are unusually warm – heated up by encounters with dark matter.
Script by Damond Benningfield
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Toasty Future
Things are heating up for a planet that orbits the brightest star of Aries. The star is expanding to become a giant, so it’s pumping more energy into space. That will make temperatures extremely uncomfortable on the planet.
Hamal is at the end of its life. It’s converted the hydrogen in its core to helium. Now, it’s getting ready to fuse the helium to make other elements. That’s made the core hotter. And that’s caused the star’s outer layers to puff up – to more than a dozen times the diameter of the Sun. So Hamal is about 75 times brighter than the Sun.
Hamal has one known possible planet. It’s heavier than Jupiter, the giant of our own solar system. On average, the planet is about as far from Hamal as Earth is from the Sun – much closer in than Jupiter is. So every square foot of the planet’s surface receives dozens of times more energy than the same area on Jupiter does.
If the planet is a ball of gas like Jupiter, then the extra heat is causing its atmosphere to puff up – and causing a lot of it to stream away into space.
Over the next few million years, the planet will get even hotter, because Hamal will get even bigger. The extra energy may erode the planet’s atmosphere completely. On the other hand, the planet may spiral into the star. Either way, things are going to get much hotter for Hamal’s only known planet.
Look for Hamal in the east at nightfall, well to the left of the Moon.
Script by Damond Benningfield
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‘Minor’ Constellations
As most parents can tell you, coming up with names isn’t easy. It sometimes takes a while to settle on something that sounds just right. It wasn’t easy for the people who named the constellations, either. Some of the names sound like they just gave up. They picked a region of the sky with few stars, gave it the name of a nearby bright constellation, then added the word “minor.”
All three of these minor constellations are in good view at dawn: Ursa Minor, Canis Minor, and Leo Minor.
The most famous of the bunch is Ursa Minor – the little bear. Seven of its stars form the Little Dipper, which is in the north – directly below the Big Dipper, which is part of Ursa Major. The constellation is especially well known because its brightest star is Polaris, the Pole Star. It’s at the tip of the little bear’s tail.
Canis Minor is the little dog. It’s about half way up the sky in the west-southwest. It has only a couple of bright stars. The brightest is Procyon – a name that means “before the dog.” That’s because the little dog leads the big dog across the sky. In ancient Greece, in fact, the constellation was known as Procyon.
Finally, Leo Minor is high overhead. It’s the little lion, standing on the shoulder of Leo. That region of the sky wasn’t depicted as a separate constellation until 1687. Today, though, it’s one of the 88 official constellations – even if it is a “minor” one.
Script by Damond Benningfield
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Martian Equinox
The shortest season on the planet Mars begins today – autumn in the northern hemisphere, and spring in the southern hemisphere. It will last for 142 Mars days – almost eight weeks less than the longest season.
Mars has seasons for the same reason that Earth does – it’s tilted on its axis. And the tilt is at almost the same angle as Earth’s.
But the seasons on Mars are more exaggerated because the planet’s orbit is more lopsided. A planet moves fastest when it’s closest to the Sun, and slowest when it’s farthest from the Sun. That stretches out some seasons, and compresses others.
It also changes the intensity of the seasons. Mars is farthest from the Sun when it’s summer in the northern hemisphere. So northern summers are fairly mild, while southern winters are bitterly cold. On the flip side of that, northern winters are less severe, while southern summers are the warmest time on the whole planet.
The start of northern autumn also marks the beginning of dust-storm season. Rising currents of air can carry along grains of dust. Enough dust can be carried aloft to form storms that cover thousands of square miles. And every few Martian years, a storm gets big enough to cover the entire planet. The storms usually peak around the start of southern summer.
Mars is about to pass behind the Sun, so it’s hidden in the Sun’s glare. It’ll return to view, in the dawn sky, in early spring – on Earth.
Script by Damond Benningfield
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Moon and Saturn
The Moon slides by Saturn the next couple of nights. The planet looks like a bright star. It’s to the left of the Moon as night falls this evening, and to the lower right of the Moon tomorrow night.
Saturn is best known for its rings. They’re almost wide enough to span the distance from Earth to the Moon. Right now, we’re viewing them almost edge-on, so they look like a thin line across the planet’s disk.
Saturn isn’t the only world with rings. The solar system’s three other giant outer planets also have them. But they’re dark and thin, so they’re hard to see. Several asteroids and dwarf planets have rings, too. But the biggest set of rings yet seen may encircle a “rogue” planet about 450 light-years away.
The possible rings were discovered years ago. Over a period of eight weeks, the light of a star in Centaurus flickered – sometimes dropping to just five percent of its normal level. The most likely cause was the passage of a set of rings in front of the star. And it’s quite a set. The rings are more than a hundred million miles across – greater than the distance from Earth to the Sun.
The ringed planet appears to be traveling through the galaxy alone, and it just happened to pass in front of the star. It could be up to six times the mass of Jupiter, the giant of our own solar system. And moons could be orbiting inside the rings – the most impressive rings we’ve seen anywhere in the galaxy.
Script by Damond Benningfield
USA