StarDate Billy Henry

Modern astronomy is a job for professionals. Amateurs discover comets and make many other contributions. But most of the cutting-edge research is done by professional scientists using expensive telescopes and other equipment.
In the not-so-distant past, though, many major discoveries were made by “gentleman astronomers” — rich men who built their own telescopes and shared a passion for the stars.
That was especially true in Britain. There wasn’t much public money for telescopes, and only a handful of men made their living as full-time astronomers.
In fact, the Royal Astronomical Society was dominated by amateurs — doctors, lawyers, clergymen, and industrialists who had the time, money, and desire to study the heavens. They built entire observatories — sometimes in England, sometimes in parts of the globe with better climates for skywatching.
In 1845, William Parsons, the Earle of Rosse, built the largest telescope in the world at his estate in Ireland. Its mirror was six feet across, and the 60-foot tube was maneuvered by ropes, pulleys, and cranes. With this behemoth, Parsons drew beautiful sketches of galaxies, and suggested they were “cities of stars” beyond the Milky Way.
And in 1846, beer baron William Lassell discovered Triton, the largest moon of the planet Neptune, with a telescope of his own design. We’ll have more about this “gentleman astronomer” tomorrow.
Script by Damond Benningfield

A pair of cat’s eyes glows just above the north-northwestern horizon as darkness falls. The glowing eyes drop from sight in a hurry. And they’ll drop even lower during the coming nights, before disappearing entirely in the evening twilight.
The “eyes” are the stars Pollux and Castor. They mark the heads of the constellation Gemini. The stars are described as “twins,” but that’s mainly because they’re so close together. Pollux is actually twice as bright as Castor, which is close to its right.
Like all the stars in the night sky, Pollux and Castor rise and set about four minutes earlier each day. They and the other distant stars return to the same point in the sky every 23 hours and 56 minutes. But during that time, Earth moves a little farther in its orbit around the Sun. So Earth has to turn a little bit longer for the Sun to return to the same spot. As a result, the entire background panorama shifts position from night to night.
Gemini is at its best during winter, when it’s in view for all or most of the night. In early spring, it’s in view for about half the night. And now, as spring gives way to summer, only the twins remain in view — but not for much longer. They’ll soon vanish from the evening sky once again. But they’ll return to view a couple of months from now — this time in the dawn twilight — beginning another year-long circle across the night sky.
Tomorrow: “gentlemanly” astronomy.
Script by Damond Benningfield

This might come as a bit of a surprise, but no star is perfectly round. A star’s rotation, and the gravitational tug of any companion stars, can distort the shape. So most stars are slightly flattened. The Sun, for example, is about six miles wider through the equator than through the poles. The Sun’s average diameter is about 865 thousand miles, though, so that slight flattening isn’t noticeable. But some stars are so squashed that they look like lozenges. And still others look like eggs.
Two egg-shaped stars form the system known as Spica, the leading light of the constellation Virgo.
Both of Spica’s stars are much bigger, brighter, and heavier than the Sun. And the stars are quite close together. Their surfaces are just a few million miles apart — so close that we can’t see them as individual stars even through the largest telescopes.
Because the stars are so big, their grip on their outer layers of gas is pretty weak. And at their tight range, the gravity of each star exerts a pretty good pull on the other. That distorts the shapes of both stars — it makes them “bulge” outward. So if we could see the system up close, both stars would look like eggs, with the narrow ends pointing toward each other.
Look for Spica close to the left or lower left of the Moon as darkness falls this evening. The bright star will stand about the same distance to the right of the Moon tomorrow night.
Script by Damond Benningfield

Archaeologists know of only a few major artifacts of the pharaoh Khufu, who ruled Egypt more than 4500 years ago. The list includes some small statuettes — some of which might have been created long after his reign. But one artifact is at the opposite end of the size scale: the Great Pyramid of Giza, one of the seven wonders of the ancient world.
The pyramid was built with the help of a guiding light — the star Thuban. At the time, it was the Pole Star. It marked due north in the sky, making it a good tool for laying out the pyramid. And as the Pole Star, it was the hub of the sky, with all the other stars rotating around it — a position that held great power for many cultures.
Thuban stands due north as the sky gets dark right now. It’s in Draco, the dragon, high above today’s Pole Star, Polaris. Thuban isn’t very bright, so it’s hard to see from light-polluted cities.
Thuban lost its position as the north celestial pole because of an effect known as precession. Earth wobbles on its axis like a gyroscope that’s running down. It takes 26,000 years to complete a single wobble. During that time, Earth’s axis draws a big circle on the northern sky, so different stars take turns marking the pole.
Thuban held that position for a couple of thousand years, including the time when Khufu’s pyramid was built. It’ll return to that celebrated spot in the sky again — in about 20,000 years.
Script by Damond Benningfield

Our universe appears to be “flat” — like a sheet of paper stretching to infinity. If so, that would mean it’s finely balanced — a sort of “just right.”
Albert Einstein’s theory of gravity, known as General Relativity, allows the universe to assume one of three basic shapes. One shape is “closed” — like a sphere. In such a universe, two lights beamed out parallel to each other eventually would circle all the way around to their starting point.
Another possible shape is “open” — curved like a saddle or a really big Pringles chip. The light beams in such a universe would move away from each other for all time.
Finally, there’s a “flat” universe. Two light beams would remain parallel to each other forever — never spreading apart or coming together.
The actual geometry is dictated by the density of the universe — how much matter is packed into its space. In a closed universe, there’s enough matter for its gravity to cause the universe to collapse. An open universe would expand forever. And a flat universe would be balanced — neither collapsing nor expanding without end.
So far, the evidence supports a flat universe, although the matter isn’t completely settled.
Not surprisingly, it’s all pretty complicated. The flat universe is flat in three dimensions — after all, we see galaxies in every direction. To a cosmologist, it all makes sense — a “flat” universe that’s the same every way we look at it.
Script by Damond Benningfield

When it comes to understanding a star, it’s all a matter of perspective. The angle at which you view the star makes a big difference in what you know about it.
Consider Vega, the leading light of the constellation Lyra and one of the brighter stars in the northern sky. It’s in the northeast at nightfall, and climbs high overhead later on.
For a long time, astronomers thought Vega was about three times as massive as the Sun, and no more than a hundred million years old. So when they discovered a cloud of dust grains around Vega, they thought it might be raw material for planets.
But it turns out they were seeing Vega from a different angle than thought. We’re looking almost directly down on one of the star’s poles. That perspective makes it more difficult to measure Vega’s details.
Once they knew the correct angle, astronomers determined that the star spins so fast that it’s almost ripping itself apart. They also found that Vega’s a bit smaller than thought, and hundreds of millions of years older.
Today, perhaps the best estimate puts Vega’s age at about 455 million years. That’s too old for the dust around Vega to be making new planets. In fact, Vega appears to already have at least one planet — a giant that’s much bigger than Earth, and much closer to its star. So the dust probably is debris from collisions between asteroids or other bodies — maybe even fully grown planets.
Script by Damond Benningfield