StarDate Podcast

More Neptune at Opposition

Neptune at Opposition

Annular Eclipse

Galactic Grid

Dark Alternatives

Watching the Bear

Zenith

Sunflower Galaxy

Venus and Jupiter

Temperatures in the hearts of stars are tens of millions of degrees — hot enough to “fuse” hydrogen atoms together to make helium. This process converts almost one percent of the hydrogen to energy, which makes a star shine. Researchers have been trying for decades to re-create that process here on Earth, providing a source of safe, reliable power. So far, though, they haven’t had much luck. They have created fusion in the lab, but the reactions can’t be sustained. That’s because the gas is so hot that it flies apart, and no bottle can hold it. Most experiments use powerful magnetic fields to try to contain the nuclear reactions. But so far, more energy goes into the fusion process than comes out. Today, though, some scientists are trying a new approach using the Z machine at Sandia National Laboratories. It delivers a quick, powerful burst of electricity to create temperatures close to those inside stars. This burst of energy is combined with a high-power laser to heat the fuel and begin the fusion process. A magnetic field traps the particles created in the fusion reactions, so they feed back into the process and help sustain the reactions. Even with the new approach, though, it’s likely to be many years before we’re lighting our homes and offices with electricity generated by nuclear fusion — the power source of the stars. We’ll talk about how astronomers are using the Z machine to create the surfaces of stars tomorrow. Script by Damond Benningfield, Copyright 2013 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

JOEL LASH: This is the diagnostic package that’s going on this week’s experiments... Joel Lash manages the world’s largest X-ray machine. It doesn’t look for broken bones or bad teeth, though. Its main job is to help maintain America’s nuclear weapons. But some of its time has also been devoted to basic physics — understanding the properties of matter in extreme conditions. LASH: This has spectrometers on the top. They’re basically going to measure X-rays coming out of the machine. And from those X-rays we can then understand what’s going on with the physics down inside. It’s called the Z Machine. It sits inside a nondescript building at Sandia National Laboratories in Albuquerque. It stores energy taken from the city power grid in a bank of 36 giant capacitors. AUDIO: 85 KV. Charging complete, arming to fire....[bang] The capacitors fire together in a controlled short-circuit. That sends their power racing toward a vacuum chamber at the center of the machine. This jolt carries more than a thousand times the electricity of a typical lightning bolt, but it discharges in less than a millionth of a second. In that instant, it can produce more power than all the world’s power plants combined. The discharge produces a burst of X-rays, which zap samples of materials placed around the vacuum chamber. Instruments watch how the materials react. Astronomers use the Z Machine to study the stars; more about that tomorrow. Script by Damond Benningfield, Copyright 2013 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

Winter nights are filled with big, bold star pictures — constellations like Orion, Taurus, and Gemini, as well as Canis Major, home to Sirius, the brightest star in the night sky. Yet winter nights also feature some star patterns that are small and feeble — little slivers of stars between the brighter constellations. All of them were created in the 1750s by French astronomer Nicolaus Louis de Lacaille. At the time, the constellations consisted of the classical star pictures drawn in ancient times — figures like the hunter, the bull, and the twins. The stars between these well-known figures were orphans. De Lacaille set out to change that — especially in southern skies. He journeyed to the southern tip of Africa to map them. When he was done, he drew 14 new constellations. Most of them are so far south that they’re barely visible from much of the northern hemisphere. He named most of them for scientific instruments. Several of those constellations scoot low across the south tonight. All of them are quite faint, so they’re tough to see. And you need to be south of about Kansas City for them to climb very far above the horizon. As night falls, Fornax, the furnace, stands due south. Caelum, the chisel, takes that spot about an hour later. Pyxis, the compass, is due south around midnight, with Antlia, the air pump, following a couple of hours later — little slivers of stars between the bold lights of winter skies. Script by Damond Benningfield, Copyright 2013 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

The beautiful constellation Orion strides across the southern sky this evening. It’s in the southeast as night falls, with its brightest star, Rigel, to the lower right of its prominent three-star belt. If the hunter ever gets tired during his perpetual journey across the sky, he can always prop his feet up for a little rest. That’s because a “footstool” has been provided for him in the adjoining constellation Eridanus, the river. The stool is marked by the moderately bright star Cursa. Its name comes from an Arabic phrase that means “the footstool.” For the most part, Cursa is an unremarkable star. It’s a few times bigger and heavier than the Sun, and a few dozen times brighter. It’s used up the original hydrogen fuel in its core, so it’s undergoing a series of changes. The changes will cause its core to get smaller and hotter, igniting the next round of nuclear fusion. At the same time, its outer layers will get bigger and cooler. That will make Cursa shine much brighter than it does now. It’ll also give the star a definite orange hue. One remarkable thing did happen to the star more than a quarter of a century ago. For a couple of hours, it flared to more than 10 times its normal brightness. But it hasn’t repeated the flare-up, so astronomers can’t explain its sudden showiness. Cursa stands just above Orion’s foot — bright blue-white Rigel — in early evening, ready to give the hunter a break in his journey across the night sky. Script by Damond Benningfield, Copyright 2013 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

Rugged little Mercury, the smallest planet in the solar system, is putting in a quick but decent showing in the early evening sky right now. It’s especially easy to find tonight because it’s close to the upper left of the crescent Moon. Mercury’s surface resembles the Moon’s — a desolate landscape marked by countless impact craters. But observations by the orbiting MESSENGER spacecraft show a few differences. The main difference is the volcanic history of the two worlds. The Moon has been geologically “dead” for close to four billion years, so there’s been little volcanic activity. But Mercury stayed active for much longer. Relatively young volcanic plains fill much of the space between old craters — some of them formed just a couple of billion years ago. By then, Mercury’s interior had cooled quite a bit, causing the entire planet to shrink. Mercury’s crust got thicker and stronger, shutting off the flow of molten rock to the surface and ending the planet’s volcanic activity. The shrinking planet also created giant “wrinkles” in Mercury’s surface. These rounded cliffs can be up to a mile high and hundreds of miles long — features that are not found on the Moon. And Mercury and the Moon are in good view shortly after sunset this evening. The planet looks like a bright star close to the Moon. But they’re so low in the sky that you need a clear horizon to see them. They drop from sight not much more than an hour after sunset. Script by Damond Benningfield, Copyright 2013 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

There’s more than one way to look at the stars. With our eyes alone, we see only a tiny sliver of the spectrum of energy they release into space. But our instruments see the entire spectrum. And as we tune up and down that spectrum, different forms of energy become more prominent. Consider Adhara, the second-brightest star of Canis Major, the big dog, which is in the southeast by mid-evening. The constellation’s brightest star is Sirius — the brightest star in the night sky at visible wavelengths. Adhara is to its lower right. In reality, it’s thousands of times brighter than Sirius. It looks much fainter, though, because it’s hundreds of light-years farther. Even so, if you could tune your eyes to the ultraviolet, Adhara would far outshine Sirius. In fact, it would be the brightest star in the night sky. That’s because Adhara is quite hot. At such high temperatures, a star produces most of its energy not in the form of visible light, but as ultraviolet. Adhara is also big, so there’s a lot of surface area to radiate energy into space. The combination of size and temperature makes Adhara a brilliant ultraviolet beacon. That won’t always be the case, though. In a few million years, changes in the star’s core will cause its outer layers to puff up. As they do, they’ll get much cooler, so Adhara’s ultraviolet light will be extinguished. Instead, the star will blaze in another band of energy — one of the brightest infrared sources in the sky. Script by Damond Benningfield, Copyright 2013 For more skywatching tips, astronomy news, and much more, read StarDate magazine.