StarDate

Just about every telescope is an amazing scientific instrument — an “eye” on the universe. But some are much more: They’re works of art. An example is the Great Refractor, at Harvard College Observatory. It took its first peek at the heavens 175 years ago today.

Astronomy was still a young American science then. But a brilliant comet had spurred interest in the field. Harvard took advantage to build a new telescope. It raised almost $26,000 from 94 donors, including former president John Quincy Adams.

The telescope’s heart was a 15-inch primary lens — the largest in the United States for 20 years. It was housed in a 20-foot tube with a veneer of polished mahogany. Some of the fittings were made of brass. The combination made the telescope look like a sculpture as much as a scientific tool.

The telescope first looked at the sky on the afternoon of June 24th, 1847 — a view of the gibbous Moon. At first, astronomers actually looked at the sky through the telescope. Later, they used it to take pictures. In fact, it took the first daguerreotype of a star — Vega, one of the bright highlights of the summer sky.

The Great Refractor remained a busy scientific instrument until the early 1930s. After that, it was used for education and public outreach. It was finally retired in the 1970s. But it’s still there, and still occasionally peeks at the night sky — a beautiful instrument for observing the stars.
 

Script by Damond Benningfield

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The Moon lines up between two bright planets tomorrow morning. And it practically runs over another planet, which is too faint to see with the eye alone.

At first light, Venus stands to the lower left of the Moon. It’s the “morning star,” so you can’t miss it. Mars is about the same distance to the upper right of the Moon. The orange planet isn’t nearly as bright as Venus, but it’s still an easy target.

The third planet is Uranus. It’s to the lower left of the Moon, and is visible through binoculars. Uranus and the Moon will appear closer together from the western United States than from the east. And from some other parts of the world, the Moon will pass in front of Uranus, blocking it from view.

Such an event is called an occultation. Another occultation, more than four decades ago, led to the discovery of the planet’s rings. In that case, though, Uranus occulted a star. Astronomers noticed that the star’s light flickered several times shortly before and after the star disappeared from view. That meant its light was being partially blocked — by rings.

Since then, the number of known rings has climbed to 13. All of them are faint, and most of them are thin — no more than a few miles across. Most are made of solid chunks of rock up to a few dozen feet across. At least one, though, appears to be made of ice. Today, astronomers continue to study the rings — with the help of more occultations.
 

Script by Damond Benningfield

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A star in the constellation Leo is a carbon factory. And it’s blowing a lot of the stuff out into the galaxy, providing a key ingredient for future stars, planets — and perhaps even life.

CW Leonis is producing so much carbon that it’s known as a carbon star. It’s the closest one — perhaps 400 light-years away.

The star long ago used up the hydrogen fuel in its core to make helium. Now, it’s fusing the helium to forge carbon, some of which works its way to the surface.

The surface layers have puffed up to hundreds of times the diameter of the Sun. And much of their material is being blown into space in a thick “wind.” That’s surrounded the star with giant shells, rings, and arcs, which are continuing to move outward.

Those structures contain a lot of carbon, plus oxygen, nitrogen, and silicon. And they even contain a lot of water — perhaps created by chemical reactions powered by ultraviolet light from the star.

Before long, CW Leonis will expel all of its outer layers. That will leave only its hot but dead core — a white dwarf — which will slowly cool and fade away. But its carbon and other elements will continue to expand into the galaxy — perhaps to be incorporated into future stars and planets.

CW Leonis is due west at nightfall, to the lower right of Regulus, the heart of Leo. CW Leonis is big and bright, but the carbon around it blocks a lot of its light, so you need a telescope to see it.
 

Script by Damond Benningfield

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The longest season of the year for those of us in the northern hemisphere begins today — the summer solstice. It’s the first day of summer and the longest day of the year. The season will last about 93 days — about four days longer than winter, the shortest season.

The lengths of the seasons are uneven on most of the other planets in the solar system, too. Their disparities can be much more dramatic. And the prime example is Mars.

It takes the Red Planet almost two years to orbit the Sun. So, on average, the seasons are almost twice as long as those on Earth. Northern summer, for example, lasts for 183 days.

But there’s a greater difference in the length of the seasons on Mars. That’s because the planet’s orbit is more stretched out than Earth’s orbit. When Mars is close to the Sun it moves faster than when it’s farther away, so it completes a larger portion of its orbit in less time.

Right now, Mars is closest to the Sun for the year. And it’s late in the planet’s northern fall season. That makes fall the shortest season of all — about 147 Earth days. On the other hand, Mars will be farthest from the Sun during northern spring. So it will last about 194 days — a difference of more than seven weeks — on a planet with lopsided seasons.

Look for Mars close to the left of the Moon at first light tomorrow. It looks like a bright orange star. Much brighter Jupiter stands to their upper right.
 

Script by Damond Benningfield

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A beautiful sight greets early risers on the first day of summer tomorrow: a conjunction between the Moon and the planet Jupiter. Jupiter looks like a brilliant star to the upper left of the Moon. As a bonus, orange Mars is not far to their left.

Summer actually arrives at just about the same time — 4:14 a.m. Central Daylight Time. That moment is the summer solstice in the northern hemisphere. The Sun is farthest north for the entire year, so it’s the longest day of the year.

Despite all that sunlight, the solstice is not the warmest day of the year. That usually comes in July or August for most of the hemisphere. And there are a couple of reasons for that.

Since the Sun stays high in the sky long after the solstice, it continues to shine almost directly down on us. So its rays pass through a thinner layer of atmosphere than at other times of the year. That means the atmosphere doesn’t filter out much of the Sun’s energy, so things continue to heat up.

And we still have more hours of daylight than darkness, so there’s more sunlight to heat things up. It’s kind of like putting a roast in the oven at a high temperature, then turning it down a bit. The roast can keep on warming up until it reaches the same temperature as the oven. In the case of the atmosphere, it reaches that point in mid to late summer — when we’re thoroughly “baked” by the heat of the Sun.

We’ll have more about the solstice tomorrow.
 

Script by Damond Benningfield

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There’s one star in the night sky that you should never need help to find. In fact, it can help find you. It’s Polaris, the North Star. It always stands due north — every night of the year. And it’s always at the same altitude in the sky — an altitude that reveals your latitude in the northern hemisphere. If you’re at 40 degrees, for example, Polaris is 40 degrees above the horizon.

Polaris won’t always be the North Star, though. In a couple of thousand years, that honor will go to a fainter star, in Cepheus, the king.

Gamma Cephei is about 45 light-years away. It’s a good bit bigger, heavier, and brighter than the Sun. It has a small, faint companion star, plus a giant planet.

Gamma Cephei will take over “North Star” honors because Earth wobbles on its axis like a spinning gyroscope. As it does so, the north pole aims at different stars. Right now, it aims at Polaris. But around the year 4100, it’ll aim at Gamma Cephei. And around 7500, it’ll aim at Alpha Cephei, the constellation’s brightest star. Eventually, it’ll return to Polaris — in about 23,000 years.

Cepheus is to the lower right of Polaris as darkness falls. Its brightest stars form an outline that looks like a child’s drawing of a house, with Gamma Cephei at the peak. At nightfall, the house is turned on its side, so Gamma Cephei is the first star you come to as you head away from Polaris.
 

Script by Damond Benningfield

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The Sun is a fairly big, middle-aged star. And as sometimes happens in those middle years, it moves a little more slowly than it did when it was younger — it takes almost a month to complete one full turn on its axis.

Many other stars spin much faster than the Sun does. An example is Altair, the brightest star of the constellation Aquila, the eagle.

Altair is almost twice as wide and heavy as the Sun. Despite its bulk, it makes a complete turn in only about 10 hours. At that rate, a point at its equator moves at about 150 miles per second — fast enough to cross from New York to Los Angeles in less than half a minute.

One reason Altair spins so fast is that it’s much younger than the Sun. The Sun probably turned much faster when it was younger, too. But its magnetic field acts as a brake, slowing it down.

One of the effects of Altair’s high-speed rotation is that its gas is forced outward at the equator, making the star look a bit like a flattened beachball. It’s about 14 percent wider through the equator than through the poles. There’s a limit to how flattened the star can get, though; if Altair twirled about half again as fast as it does now, it would fly apart.

Altair is low in the east as darkness falls. It forms the southern point of the Summer Triangle. The highest and brightest point is the star Vega, with Deneb forming the triangle’s left point. The triangle is high in the west at first light.
 

Script by Damond Benningfield

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The Moon has played many roles. It’s escorted lovers, inspired music and poetry, served as both god and goddess, and become a destination for people and machines. And in recent decades, it’s taken on another role: scientific instrument. It helps scientists refine their ideas about gravity. And researchers have proposed a new way for it to do that — by helping detect gravitational waves.

The waves are ripples in space-time. But they’re extremely difficult to sense. Scientists have discovered waves from the mergers of ultra-dense corpses of stars — black holes and neutron stars. But they’re looking for waves from bigger black holes, and even from the birth of the universe.

A team recently proposed a way to use the Moon to help find those waves. It would bounce laser beams off special reflectors on the Moon to measure the Earth-Moon distance. As the waves pass through Earth and the Moon, they could change that distance by a tiny amount. That could confirm the presence of gravitational waves from sources other than those already discovered.

Scientists have actually been doing that work since the Apollo missions. But new missions are expected to take more and better reflectors. That would improve the accuracy of the measurements — providing a new way to find ripples in space and time.

The Moon rises after midnight, with the bright planet Saturn to its upper left. Saturn is above the Moon at first light.
 

Script by Damond Benningfield

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The stars at night, are big and bright, deep in the heart of Texas — or at least in West Texas. A new “dark skies reserve” encompasses about 15,000 square miles of western Texas and northern Mexico. It acknowledges that the night sky is already dark, and can help keep it dark in the years ahead.

Proper nighttime lighting provides a lot of advantages. It’s good for the ecosystem, because too much light can interfere with the migrations of birds and other animals. It’s good for public safety because light is directed where it’s needed — on the ground. It’s good for astronomy because extra light can spoil the view of stars and galaxies. And it’s good for astro-tourism because dark skies attract stargazers from the world over.

McDonald Observatory and other groups in West Texas and northern Mexico have helped keep the night sky dark. They’ve worked with governments to enact rules that require good nighttime lighting, and with the oil industry and others to change the way they light their operations.

That led to the creation of the Greater Big Bend International Dark Sky Reserve. It was certified by the International Dark-Sky Association, which works to preserve dark night skies around the world. It’s the largest dark sky reserve in the world. It recognizes the work done to keep the night sky dark. And it provides a model for other regions of the world — keeping the night skies dark well beyond the heart of West Texas.
 

Script by Damond Benningfield

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Every couple of decades, the star system V2487 Ophiuchi produces a massive explosion. Gas that’s piled up on one of its stars is blasted into space, making the system shine thousands of times brighter than average. The last such outburst was seen 24 years ago today, in fact.

But you don’t have to wait that long to see fireworks from the system. About once a day, it produces a “superflare” — a deadly outburst of radiation that dwarfs anything seen from the Sun.

The system consists of two stars. One is similar to the Sun, while the other is a white dwarf — the dead core of a once normal star. They’re so close together that the white dwarf “steals” gas from the other star. The gas forms a disk around the white dwarf.

Because the stars are so close, the companion spins rapidly. That generates a powerful magnetic field. And according to a study by astronomers at LSU, that’s the source of the superflares. Magnetic field lines extend into the disk around the white dwarf — or even to the white dwarf itself. The lines quickly become twisted and tangled. Then they snap, releasing huge amounts of energy — a superflare.

The largest one yet seen was 20 million times more powerful than the largest flare ever seen on the Sun. And a typical flare is about 10 times larger than those seen from any other star. The flares would strip away the atmospheres of orbiting planets, and destroy any life — making V2487 Ophiuchi a place to avoid.
 

Script by Damond Benningfield

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