StarDate

Tycho Brahe was one of astronomy’s most colorful characters. He lost his nose in a duel, built a great research center, and often quarreled with other scientists. And he made enemies in two royal courts.

Tycho died colorfully, too. Either he suffered a burst bladder after an evening of drinking — or he was murdered. To find out which, scientists exhumed his body 10 years ago today.

Tycho was born in 1546 — long before the invention of the telescope. Yet he compiled detailed records of the heavens. He proved that comets and the “new” stars known today as supernovae are in space, not inside Earth’s atmosphere. And his assistant, Johannes Kepler, later used Tycho’s catalogs to produce laws of planetary motion.

Tycho died in 1601, a few days after attending an event with his patron, the Holy Roman Emperor. It was believed that he refused to leave the table to relieve himself, so he died of a burst bladder.

But rumors developed that he was murdered by Kepler — perhaps by mercury poisoning. Tycho was an alchemist, so he often worked with the element. He was exhumed in 1901, and scientists found traces of mercury in his beard.

The newer analysis, though, found little of it — supporting the idea that he died of a ruptured bladder. And it found something else. After his duel, Tycho wore a false nose, which most thought was made of silver or gold. Instead, it was made of brass — a plain substance for a colorful character.

Script by Damond Benningfield

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Mars is coming to a halt for a bit. The planet is still orbiting the Sun, but its position against the background of stars will remain the same. That’s because our viewing angle is changing.

In astronomical parlance, Mars will be stationary. That’ll happen tomorrow. The planet will resume its normal motion across the sky right after that. But it’ll be slow at first, so it’ll take a day or two to notice any difference — and even then, you’ll have to be looking closely to see it.

As with all the other planets, Mars’s position in the night sky depends on both its motion and ours. Most of the time, Mars moves eastward against the starry background. Every couple of years, though, Earth begins to catch up to it in our smaller, faster orbit around the Sun. As we pass by Mars, it stops and reverses direction for a while. Then it stops again — which happens tomorrow — before resuming its normal course.

A planet puts on its best showing during the “reverse” part of its trek because that’s when it’s closest to Earth. Mars was at that point last month. And it’s still quite close now, so it’s quite a sight. It’s in the east-southeast as night falls, and looks like a brilliant orange star.

Incidentally, astrology assigns special meanings to a planet’s reverse track. Scientifically, though, there’s nothing to it. The brief “about face” is all part of a planet’s normal progression around the Sun — and across our night sky.

Script by Damond Benningfield

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The Milky Way forms a glowing arch in the western sky on November evenings. It stretches from Aquila and Cygnus in the west, through W-shaped Cassiopeia high in the northeast, and down near the bright stars Aldebaran and Capella.

The latter section aims away from the Milky Way Galaxy’s dense heart, and toward its thinly populated outer regions. But no one knows just how far those regions extend, or how thinly populated they really are.

The galaxy consists of two main parts. There’s a wide, thin disk that contains beautiful spiral arms. And there’s a “halo” of old, faint stars around the disk. It extends for hundreds of thousands of light-years.

Most studies have put the diameter of the disk at about 100,000 light-years, with our solar system roughly halfway between the center and the edge. And it’s certain that the vast majority of the stars in the disk lie within that span.

Yet there’s no fortress wall at the “edge” of the disk. So stars trickle from the disk out into the halo. Several studies have found stars out to about 60,000 light-years from the center of the Milky Way, making the disk 120,000 light-years across.

And one study found quite a few stragglers out to about 85,000 light-years from the center — and some that could be a hundred thousand light-years. That would make the disk 200,000 light-years in diameter — a giant family of stars spinning through the universe.

Script by Damond Benningfield

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A beautiful quartet greets early risers tomorrow: the Moon, two planets, and a star. All four of them are low in the east-southeast at the first blush of twilight.

The Moon will be a bare “fingernail” — only a small sliver will be lit up by the Sun. It’ll be nighttime across the rest of the lunar disk. Yet it won’t be anything like nighttime here on Earth. That’s because an almost-full Earth will hang in the sky. It shines dozens of times brighter than a full Moon, so it really brightens the night. And you can see that effect as “earthshine” — a ghostly glow on the dark portion of the Moon.

Mercury will stand directly below the Moon. It’s the closest planet to the Sun. As a result, our viewing angle on the little world usually isn’t very good.

It is good for the next few mornings, though. Mercury looks like a bright star, but it’s so low in the sky that you’ll need a clear horizon to spot it. And it will disappear from view quickly as the twilight begins to brighten.

Spica will stand to the right of the Moon. It’s the brightest star of the constellation Virgo. It’s easy to lose in the waxing twilight, although its proximity to the other bodies will help you pick it out.

Finally, Venus will perch above the other members of the quartet. The planet shines as the “morning star” — the brightest object in all the night sky other than the Moon. It completes a beautiful quartet in tomorrow’s dawn sky.

Script by Damond Benningfield

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Artemis Corona is the largest feature of its kind on the planet Venus. It’s a circular patch of rock that’s about 1300 miles wide. And it may still be growing — the result of activity far below the surface.

In fact, a recent study says Venus may still be an active world, with blobs of molten rock pushing up from deep inside the planet to change its surface.

Researchers created computer models to simulate the formation of coronae — round volcanic features found all across the planet. They compared the simulations to pictures of the surface. They found that 37 coronae match what the simulations say young features should look like. That suggests they formed recently, and are still being shaped today.

There’s little doubt that Venus was an active world in the past. Most of the rocks at its surface are volcanic. And it’s covered with volcanoes and similar features.

There’s been a debate about whether Venus is still active today. And the answer seems to be yes. Orbiting satellites have detected “hot spots” that could be erupting volcanoes. And images have revealed landscapes that must have been sculpted by recent activity. The new study adds to the evidence that the surface of Venus isn’t dead yet.

Right now, Venus is the brilliant “morning star.” Tomorrow, it’ll stand directly below the crescent Moon at first light. The star Spica and the planet Mercury will line up below them. More about this beautiful line-up tomorrow.

Script by Damond Benningfield

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For decades, the leading idea has said that the dinosaurs were killed off when a giant asteroid slammed into Earth. But some scientists disagree with that idea. They blame the demise on massive volcanic eruptions. A recent study, though, not only reaffirms the asteroid scenario, but says the volcanoes might have prevented even more extinctions.

Most of the dinosaurs died off about 66 million years ago. And they vanished quickly, indicating that something big happened to our planet then. And it did. An asteroid several miles wide slammed into the Gulf of Mexico, off the coast of Yucatan.

The impact blasted cubic miles of material into the atmosphere. The debris blotted out the Sun, making the entire planet much colder. The impact also created acid rain and had many other nasty effects. The combination could have changed the climate enough to destroy most of the dinosaurs.

On the other hand, massive eruptions were taking place at the same time at the Deccan Traps — massive volcanoes in India. The eruptions lasted for hundreds of thousands of years. They belched huge amounts of carbon dioxide and other gases into the air.

The recent study concluded that the effects of the asteroid impact were much more harmful. And the volcanoes actually made things better. Their gases warmed the atmosphere a bit — easing the effects of the asteroid impact by just a little. That may have helped some species survive the long global winter.

Script by Damond Benningfield

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NASA has sent some odd missions into space. Few sound stranger, though, than a craft that was launched 50 years ago today: OFO — Orbiting Frog Otolith. It carried a pair of male bullfrogs to study how their balance system adapted to life without gravity.

Over the decades, a whole menagerie of living organisms has been sent into space: dogs and cats, spiders and spider monkeys, hissing cockroaches, and many more. The list includes several species of frog.

But OFO was the first to carry bullfrogs. They were selected because their balance mechanism — built around a small rocky structure called an otolith — functioned in a similar way to the human system.

Scientists were interested because several Apollo astronauts had experienced space sickness. This nasty illness was caused by problems with the inner ear’s adaptation to microgravity. So learning more about it might help minimize the problem for future astronauts.

The frogs were inside a centrifuge that periodically spun up to create roughly half the pull of normal gravity.

Electrodes were inserted near the frog’s otoliths to record electrical impulses from the balance system. They found that the frogs had a tough time for the first few days in orbit. But their systems settled back to normal during the final day of the experiment.

Unfortunately, this was a one-way mission. The frogs perished when their capsule’s battery died — ending the first mission of bullfrogs in space.

Script by Damond Benningfield

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Mercury is putting in a pretty good appearance in the dawn sky. The planet is low in the east-southeast in the early glow of twilight, and looks like a bright star. The star Spica is close to its upper right, with much brighter Venus, the “morning star,” standing high above them.

Mercury is the closest planet to the Sun, so you might expect it to be the hottest planet as well — but it’s not. Venus is hotter. It has a thick atmosphere that traps the Sun’s heat. So temperatures are high enough to melt lead across the entire planet.

Instead, Mercury has the most extreme changes in temperature. And that takes a toll on the surface of the little planet.

Mercury has no atmosphere, so there’s nothing to block the Sun’s intense radiation. So noontime temperatures at the equator can top out at 800 degrees Fahrenheit. And Mercury rotates very slowly, so any point near the equator stays hot for weeks.

But since there’s no air to retain that heat, as a spot finally rotates over to Mercury’s nightside it gets cold — as low as 300 below.

That constant cycle of hot and cold causes Mercury’s surface to expand and contract. Over the eons, that’s cracked and pulverized some of its rocks.

Incidentally, not every spot on Mercury gets hot. Some craters at the north pole are so deep that sunlight never reaches their floors. So some of those craters hold large deposits of ice — perpetual cold spots on a hot-and-cold planet.

Script by Damond Benningfield

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A couple of bright stars with dead companions arc to the right of the Moon at midnight, and stairstep to the lower right of the Moon at first light.

Procyon is the one closer to the Moon, while Sirius is the brightest star in the entire night sky. Both stars are big and bright on their own, and they’re quite close by. And both of them have a “dead” companion — a white dwarf. Such stars are the leftover cores of once-normal stars. They’re small but hot, and they no longer produce the fusion reactions that create new elements.

The Big Bang created hydrogen, helium, and a smattering of a couple of other elements. Every other element was created by stars. That includes the oxygen we breathe, the iron in our blood, and the carbon that’s the basis of life on Earth.

Most of the carbon came from stars that were like the Sun. As such a star dies, it sheds its outer layers, leaving only its dead core — a white dwarf. The outer layers contain elements created during the star’s lifetime — including, in some cases, carbon.

A recent study concluded that there’s a “cut-off” line between stars that expel carbon into space and those that don’t. That line is about one and a half times the mass of the Sun. Stars that are born that big blow carbon out into space. Stars below that mass don’t. If confirmed, that means the Sun won’t pump out much carbon when it dies — so it won’t contribute much to possible life elsewhere in the galaxy.

Script by Damond Benningfield

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Most big spiral galaxies look calm and well ordered. Yet their histories are often just the opposite. The galaxies were built through a series of collisions, mergers, and close calls.

An example is M31, the Andromeda Galaxy. It’s our closest big galactic neighbor, at a distance of two-and-a-half million light-years. It’s high in the east in early evening, and looks like a small, faint, hazy patch of light.

Andromeda is a galactic giant. Its disk spans more than 200,000 light-years, and it contains hundreds of billions of stars. But it wasn’t born that way.

The original galaxy formed more than 10 billion years ago, from the merger of several smaller building blocks. There’s evidence that a few billion years later, it slammed into another large galaxy. That triggered an intense bout of star formation, giving birth to as many as a tenth of Andromeda’s present-day stars.

Since then, Andromeda has gobbled up several smaller galaxies. It’s also had encounters with a couple of nearby surviving galaxies, M32 and M33. M32 may have punched through Andromeda’s disk, while M33 may have sideswiped it. The encounters gave birth to more stars, pulled out ribbons of stars that reach far into space, and warped Andromeda’s rim.

Andromeda’s biggest galactic encounter is yet to come. In a few billion years, it will merge with our own galaxy, the Milky Way — giving birth to one of the most impressive galaxies in the universe.

Script by Damond Benningfield

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