StarDate

The early universe was dark. The first stars and galaxies were embedded in a “fog” of atoms with no charge. By a billion years after the Big Bang, though, the fog was gone. The atoms had been “reionized” — charged up by something.

Much of the energy probably was provided by hot, massive stars. But some of it could have come from quasars — disks of superhot gas around supermassive black holes at the hearts of galaxies.

The biggest quasars are some of the brightest objects in the universe. Their black holes are billions of times the mass of the Sun, and they’re pulling in huge amounts of gas. But they’re rare — there just aren’t enough of them to reionize the universe.

So an astronomer at the University of Texas is looking to see if less-powerful quasars — powered by black holes perhaps a few million times the Sun’s mass — could have helped out.

Steven Finkelstein is using observations from the Hobby-Eberly Telescope Dark Energy Experiment. It uses a telescope at McDonald Observatory to study dark energy. But its observations can be used for many other studies.

The experiment is looking at hundreds of thousands of galaxies from when the universe was just a few billion years old — far more galaxies from that era than astronomers have seen before. A particular wavelength of light reveals what was going on inside the galaxies. It can even reveal if they had “little” quasars — possible engines for banishing the cosmic fog.
 

Script by Damond Benningfield

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Wolf 359 likes to snarl. The star produces huge outbursts of energy. That could be a problem for life on any planets that orbit the star.

Wolf 359 is one of our closest neighbors — less than eight light-years away. Only a few star systems are closer.

Other than those big outbursts, the star is amazingly meek. It’s less than one-tenth as massive as the Sun, and just one-tenth of one percent as bright.

But Wolf 359 generates a powerful magnetic field. Lines of magnetic force can tangle, then snap. That produces a flare — a powerful outburst of X-rays and gamma rays.

A recent study says the star probably produces outbursts as strong as anything ever seen from the Sun several times a day. And once a month or so, it can produce an outburst up to a hundred times stronger: a super-flare.

Astronomers have found evidence of two planets orbiting the star. Neither is likely to be a home for life. But if there are planets in the right location for life, the flares could be a problem. They could heat up and erode some of a planet’s atmosphere, and deliver a good jolt of energy to the surface. A planet might be able to handle the flares. But the flares wouldn’t make it any easier for life around this tiny star.

Wolf 359 is in Leo, which is high in the eastern sky at dawn. The star is well below Regulus, the lion’s bright heart. But despite all the snarling, you need a telescope to see this close neighbor.
 

Script by Damond Benningfield

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A big hole in the ground has helped scientists piece together the structure of the dwarf planet Ceres. It’s the largest member of the asteroid belt — about a quarter the size of the Moon. The hole shows that Ceres has layers, like a bigger planet or moon.

A spacecraft studied Ceres from orbit for three years. Its most impressive discovery was Occator Crater. It’s almost 60 miles wide and two miles deep. Big white blotches decorate its floor — deposits of salt.

Occator probably formed about 20 million years ago, when a space rock hit Ceres. Recent work suggests there was a layer of salty, muddy water about 30 miles below the site. The impact fractured the crust, allowing some of the brine to leak into the crater floor. The water evaporated, leaving the salt.

The crater also is marked by dozens of small rounded hills. They resemble features on Earth known as pingoes. They formed when water surged from below, pushing up the top layer of rocks and ice.

Occator Crater and other features reveal that Ceres has several layers. Two of those layers — the crust and mantle — are separated by a layer of muddy brine — which can sometimes leak onto the surface.

Ceres shines at its best for the year right now. It rises at sunset, is in view all night, and is brightest for the year. Through binoculars, it looks like a small, faint star to the lower left of the bright star Aldebaran as they climb into good view in the east by 9:30 or 10.
 

Script by Damond Benningfield

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One of the moons of Saturn is two-toned. One hemisphere is bright, while the other is as dark as coal. And the difference may be caused by another moon.

Iapetus was discovered 350 years ago today by Giovanni Cassini. The moon is about 900 miles in diameter and more than two million miles from Saturn. A ridge around its equator makes it look like a walnut.

As Cassini studied his discovery, he noticed something odd: He could see it only when it was on the western side of Saturn, not the eastern. He soon figured out that Iapetus always keeps the same hemisphere turned toward Saturn, just as the same hemisphere of our moon always faces Earth. Cassini also realized that half of the moon must be bright, the other dark.

We got a good look at that two-toned appearance from the Cassini spacecraft, which orbited Saturn for more than a decade. It showed that there’s a sharp line between light and dark.

The leading hemisphere of Iapetus probably gets coated with dust from Phoebe, another moon. The dust traps sunlight during the day, warming the ice below it. Some of the ice vaporizes and migrates to the trailing hemisphere, where it’s nighttime. Once there, it freezes — making the dark side darker and the bright side brighter.

Saturn is due south at nightfall and looks like a bright star, well to the right of brighter Jupiter. Iapetus is so faint that you need a telescope to see it — no matter which hemisphere is facing Earth.
 

Script by Damond Benningfield

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A NASA spacecraft is celebrating a major milestone today: 20 years in orbit around Mars. It’s the longest-operating Mars mission in history.

Mars Odyssey launched on April 7th, 2001. [launch audio: 3, 2, 1, we have ignition, and liftoff of a Delta II rocket carrying NASA on an odyssey back to Mars...] At launch, it was called 2001 Mars Odyssey in honor of the movie and novel “2001: A Space Odyssey.”

The craft entered orbit around Mars on October 23rd. It then spent months using a technique known as aerobraking to dip into the planet’s upper atmosphere and sculpt its final orbit.

Mars Odyssey’s instruments have mapped the entire Martian surface. They’ve also mapped the composition of the surface. Among other things, they’ve revealed salt, clay, and other compounds that formed in watery environments. The findings indicate that Mars was once much warmer and wetter than it is today — and perhaps even a comfortable home for life.

The orbiter also has detected vast layers of water ice buried beneath the red dirt all across the planet. Some of those deposits might someday provide drinking water, oxygen, and rocket fuel for human explorers.

Odyssey’s pictures have helped scientists pick out landing sites for Mars landers and rovers. And the craft has served as a relay station for those missions. It continues its work today — two decades after entering orbit around the Red Planet.

Tomorrow: a two-toned “walnut” at Saturn.
 

Script by Damond Benningfield

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It’s easy to see that the Moon moves across the sky. Compare its position to the background of stars from one night to the next, and that motion is obvious. Tonight, for example, the bright star Aldebaran rises to the lower right of the Moon. By tomorrow night, though, the Moon will have moved so much that Aldebaran will rise farther to its upper right.

The background stars are sometimes described as “fixed” because they don’t move from night to night — or at least not enough to notice. The stars are all in constant motion as they orbit the center of the galaxy, just as the Sun does. But the stars are so far away that the change from night to night — or even century to century — is imperceptible.

Aldebaran was the first to reveal that motion. In 1718, astronomer Edmond Halley studied records of Aldebaran’s position from more than 2,000 years earlier. He found that the star had moved — by about a quarter of the diameter of the Moon in our sky. Halley then studied the motions of two more stars, which confirmed the effect.

That shift is called proper motion. Aldebaran shows a large motion because it’s close — just 65 light-years away. So the relative motions of Aldebaran and the Sun combine to produce a large shift in the star’s position.

Today, Aldebaran marks the eye of Taurus. But thousands of years from now, the star will have moved away from that spot — depriving the bull of his bright orange eye.
 

Script by Damond Benningfield

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Pictures of Earth’s nightside shot from space show a lot of islands of light — the glow of cities and towns. When you add up all of that light, though, it isn’t much — the nightside is pretty dark.

But a study this year suggested that if there’s a civilization on a nearby exoplanet, it might produce enough nighttime light to see with a giant new space telescope.

Proxima Centauri b is one of the two planets known to orbit Proxima Centauri, our closest neighbor star. The star is so small and faint that you need a telescope to see it, even though it’s just four-and-a-quarter light-years away.

Proxima Centauri b is at a distance from the star where conditions are fairly comfortable for life. That makes the Earth-sized planet a candidate for studies by James Webb Space Telescope. It could look for compounds that are produced by life in the planet’s atmosphere, for example.

Abraham Loeb and Elisa Tabor suggested another way to hunt for life — in this case, an advanced civilization: Look for the glow of cities on the planet’s nightside.

The night would have to be really lit up — at least five percent as bright as Proxima Centauri. And the light would have to be concentrated in a narrow range of wavelengths.

The odds of such a civilization living there are tiny, so Webb isn’t likely to see any nightlights. But future space telescopes might extend the range to other stars — and look for the glow of alien cities.
 

Script by Damond Benningfield

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James Webb Space Telescope isn’t like any other telescope — in space or on the ground. Its main mirror, which will gather and focus starlight, is so big that it has to be folded for launch. The mirror is made of a material that’s rarely used in telescopes. And it’s coated with a thin layer of gold — the better to see the universe at infrared wavelengths.

The telescope is scheduled for launch this fall. It’ll travel to a point that’s a million miles “behind” Earth as seen from the Sun. That will give it a constant view of the universe, and eliminate any glare from Earth or the Moon.

Webb will be the biggest and most expensive space telescope ever launched. It’s taken more than a decade to develop, at a projected cost of about 10 billion dollars.

Webb’s main mirror spans about 21 feet. It consists of 18 hexagons that fit together like the tiles on a floor. They’re made of beryllium — a strong but lightweight metal. Small motors will fine-tune their position to create the right shape for the overall mirror. The shape has to be accurate to within one ten-thousandth of the width of a human hair.

A shield will protect the telescope from the Sun. That’s especially important for an infrared telescope, which studies some of the coldest objects in the universe.

After Webb is launched, it’ll take months to get it ready for work. But if everything goes as planned, we could see its first pictures and other results by late spring.

Script by Damond Benningfield

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Hubble Space Telescope has revealed some of the earliest galaxies in the universe — “cities” of stars as they looked when the universe was about half a billion years old. Astronomers would like to see even deeper, though — to the time when the first galaxies were taking shape. And if everything goes well, they’ll soon get a new tool for the search.

James Webb Space Telescope is being prepared for launch this fall. It’s the largest space telescope ever built. Its main mirror spans about 21 feet. And it will collect almost seven times as much light as Hubble. That will allow the telescope to see galaxies taking shape roughly a quarter of a billion years after the Big Bang. Those observations will help scientists understand how massive clouds of gas and dust came together to make stars and galaxies.

Webb is designed to study the universe at infrared wavelengths, which are invisible to the human eye. Most infrared comes from objects that are fairly cool. That includes clouds that are giving birth to stars, and disks around stars that are giving birth to planets. It also includes the planets themselves — those orbiting other stars, and those in our own solar system. Webb will try to measure the atmospheres of some of those distant worlds. If any of them have life, the telescope might be able to see some of the chemistry it produces — sniffing out signs of life with a giant new “eye” in space.

We’ll have more about the James Webb Space Telescope tomorrow.

Script by Damond Benningfield

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The space around a black hole can be busy. As gas funnels into a black hole, it can form a disk that’s heated to millions of degrees. And the spin of the disk and the black hole can create a strong magnetic field. The field can sculpt powerful “jets” that shoot gas from the disk into space at almost the speed of light.

Astronomers should learn more about that process with a space telescope that’s scheduled for launch this fall. It’s called IXPE — the Imaging X-Ray Polarimetry Explorer.

The craft will carry three telescopes that are sensitive to X-rays, which are produced by some of the most powerful objects and events in the universe. The telescopes will feed light to instruments that will detect X-rays that have been polarized — they move through space in sync, like members of a marching band. The X-rays can be polarized by magnetic fields, so studying them reveals how the fields align, how they’re created, and more.

The list of targets includes black holes large and small, plus the remnants of exploded stars. Among those remnants are magnetars. These tiny, ultra-dense corpses produce magnetic fields that are trillions of times stronger than Earth’s. IXPE should map those fields, helping scientists determine how magnetars are born, how they evolve, and how they affect the space around them.

IXPE isn’t the only space telescope being prepared for launch. We’ll talk about a much bigger one tomorrow.

Script by Damond Benningfield

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