StarDate

For skywatchers, tonight’s a time for old friends. There’s an almost-full Moon, so its glare overpowers most of the stars in the night sky. But the brighter stars shine through – the most familiar ones. That includes the stars of the Big Dipper, which are in the northeast at nightfall.

The dipper’s leading light is Alioth. It’s the first star in the handle. It’s about 80 light-years away. But it’s an easy target because it’s about a hundred times brighter than the Sun. That’s because it’s bigger and hotter than the Sun.

Alioth is classified as a “peculiar” star – its chemical makeup is unusual. Astronomers measure its chemistry by breaking the star’s light into its individual wavelengths. Each element in the star imprints its own “barcode” in that pattern of light. But the mixture of elements in Alioth is different from most stars.

Some elements are especially common, while others are unusually rare. And the mixture changes as the star turns on its axis.

That behavior is caused by the star’s odd magnetic field. It’s tilted so far that the magnetic poles lie roughly along the star’s equator. Thanks to that alignment, the magnetic field pulls some elements to the surface, and concentrates them in specific locations. It pushes other elements down, so we can’t see them.

So Alioth is both familiar and peculiar – an old friend that’s easy to pick out through the glare of the full Moon.

Script by Damond Benningfield

Astronomers have been trying to hear from other civilizations for two-thirds of a century. So far, not a peep. But finding E-T might be the easy part. Actually having a conversation might be a lot harder. We wouldn’t know what the other folks were saying – or whether they were interested in talking at all.

To gain some insight, scientists have been studying some “non-terrestrial” intelligences here on Earth – whales and dolphins – species that live in the oceans instead of on land. Many of them have complex communications with each other. And some of them interact with humans.

One example is humpback whales. They’re playful and curious, and they often approach boats and divers. And a recent study suggested that they might be trying to have a conversation.

Researchers found a dozen times when humpbacks blew special bubbles while they were near people. The bubbles looked like smoke rings, a few feet across. The bubbles were different from those associated with other behavior, such as courting or “corraling” fish. In most cases, a whale first approached the people, then moved away a bit and blew one or more rings. Some of the whales poked their heads up through the rings.

The researchers said the whales might have been trying to play, or to see how the people responded. But the bubbles could have been an attempt to communicate – starting a conversation between terrestrial and non-terrestrial life.

Script by Damond Benningfield

The star Regulus leads the Moon across the sky tonight. The bright heart of the lion is close to the upper right of the Moon at nightfall, with the gap increasing as the hours roll by.

Regulus is about 79 light-years away. That means the light you see from Regulus tonight actually left the star about 79 years ago. So when a particle of light from Regulus hits your eye, it’s ending a journey of 79 years.

As with many things astronomical, though, it’s all relative. For the particle of light itself – a photon – the trip took literally no time at all.

That’s because the photon was traveling at the speed of light – 670 million miles per hour. Nothing can travel faster than that. And only photons can travel at that speed. That’s because photons have no mass – they weigh nothing at all. If anything else were to travel at lightspeed, it would become infinitely massive. So physical objects are limited to just below lightspeed.

As an object moves faster, time appears to slow down for it as viewed by an outside observer – its clock would tick more slowly. So if you could accelerate a starship to just a fraction below lightspeed, it could travel for thousands of years as measured by a clock back on Earth – but just a few years or even less as measured by its own clock.

So as you look at Regulus tonight, remember that the photons are completing a journey of both 79 years – and no time at all.

Script by Damond Benningfield

A young planet is getting greedy. It’s gobbling up gas and dust from its surroundings. And observations last summer showed that its appetite got a lot bigger – it was consuming as much as eight times more material than in the spring.

The planet is known by a catalog designation – Cha 1107. That indicates it’s in the constellation Chamaeleon, which is too far south to see from the United States. It’s hundreds of light-years away.

Most planets are born in disks of material that encircle newborn stars. But this one appears to be on its own. That makes it a “rogue” world. It’s roughly five to ten times the mass of Jupiter, the largest planet in our own solar system, and about three times Jupiter’s diameter.

It’s encircled by its own disk of material. That’s because it’s in a giant complex of gas and dust that’s giving birth to many new stars. As it pulls in material from its disk, it gets heavier – just like a newly forming star. The planet won’t get big enough to shine as a true star. But it’s possible that it could become a “failed” star known as a brown dwarf – a sort of missing link between stars and planets.

Last summer’s outburst wasn’t the first for Cha 1107. It flared up in 2016 as well. So its growth process may be choppy – short feeding frenzies between longer periods of quieter appetite.

Script by Damond Benningfield

If you’re looking for a world like Tatooine, good luck. Of the more than 6,000 known planets in other star systems, fewer than 20 orbit both stars of a binary system. So those double sunsets are few and far between.

Just to refresh your memory, Tatooine is the home world of Luke Skywalker in Star Wars. Such planets are called “circumbinaries” because they circle around both stars in the system.

Over the past decade, astronomers have searched for such worlds in a project with a rhythmic name: Bebop – Binaries Escorted by Orbiting Planets. The project looks for tiny “wiggles” in the motions of the stars caused by orbiting planets. It’s found a few planets, with several more candidates.

One of those discoveries is Bebop-3b. The system’s two stars are quite close together. One of them is similar to the Sun. The other is only about a quarter of the Sun’s mass, and a tiny fraction of its brightness.

The planet is about half the mass of Jupiter, the giant of our own solar system. It orbits the two stars once every 18 months, at a bit more than Earth’s distance to the Sun. We don’t know how fast Bebop-3b rotates, so we don’t know how often it sees sunrises and sunsets. All we know for sure is that there are two of each – one featuring a bright star, the other a faint cosmic ember.

The system is about 400 light-years away. It’s high overhead at nightfall – but much too faint to see without a telescope.

Script by Damond Benningfield