A long time ago, in a galaxy far, far away … there were some weird things happening. They are still happening—in our own galaxy and in many, many others. There are the cannibal stars that snack on their neighbors, the discovery of a “diamond” exoplanet, and light, fluffy snow found on the moons of Saturn. These things may sound like they’re straight out of science fiction, but they’re not. They’re the cold, hard, weird truth.
Was Earth’s water delivered from above? Astronomers believe they know the answer.
For the first time, astronomers have found water on a comet that’s a chemical match for water on Earth, a new study says. The discovery backs up theories that water-rich comets helped fill ancient Earth’s oceans.
A close-up of peanut-shaped Hartley 2 (Photo Credit 7.2)
Planet-formation models indicate that early Earth was much too hot to sustain liquid water on its surface, making the origin of Earth’s oceans a mystery. So scientists speculated that our planet’s surface water came from comets that slammed into Earth once the planet had cooled.
This theory was dealt a serious blow in the 1980s, however, due to measurements of the ratio of normal to “semiheavy” molecules—the D/H ratio—in comet water. In a semiheavy water molecule, one hydrogen atom (H) is replaced with a heftier version called deuterium (D). All water in nature has a D/H ratio, and since deuterium is a very stable atom, this ratio can go unchanged for eons.
Since the 1980s, researchers have found that several comets in our solar system have D/H ratios that are very different from that of Earth’s water. Those results indicated that, at best, only about 10 percent of Earth’s water could have come from comets, with the rest probably coming from water-rich asteroids, explained study leader Paul Hartogh, an astronomer at the Max Planck Institute for Solar System Research in Germany.
“The reservoir of Earth ocean-like material is much larger than we thought, and it encompasses cometary material, which we hadn’t recognized. We have to think really hard and try to get a better understanding of what is going in our Solar System, and whether you can really rule out comets as the source of Earth’s water.”
Ted Bergin
University of Michigan
In the new study, Hartogh and his team used the European Space Agency’s Herschel Space Observatory to examine the D/H ratio of the comet 103P/Hartley 2. Hartley 2 is a so-called Jupiter family comet because its orbit takes the comet close to the orbits of Jupiter and the other gas giants.
The results show that Hartley 2’s water is very similar to that of Earth. Importantly, computer simulations suggest that Hartley 2 originated from the Kuiper belt, a region beyond the orbit of Neptune that is filled with comets and other icy remnants from the formation of our solar system.
This would suggest that the larger group of comets that helped form Earth’s oceans originally came from the Kuiper belt. By contrast, the comets with D/H ratios that didn’t match Earth’s are thought to have originated in the Oort cloud, a reservoir of billions of comets that astronomers think exists far beyond the Kuiper belt.
TRUTH:
IT WOULD TAKE A STACK OF MORE THAN NINE EMPIRE STATE BUILDINGS TO EQUAL THE AVERAGE DEPTH OF THE OCEAN.
Finding a comet that’s a match for Earth suggests more such matches may be out there, which means much more of our planet’s water could have come from comets after all, Hartogh said. But exactly how much is still unclear and will require further studies.
“We cannot give a number,” Hartogh said. “In principle, all of Earth’s water may [have] come from comets. However, it is still possible that a large—or the largest—fraction came from asteroids.” 
A new planet found about 36 light-years away could be one of the most Earthlike worlds yet—if it has enough clouds, a new study says.
The search for Earthlike planets is one of the most exciting challenges facing astronomers today, and the clouds on one of the latest discoveries, the unpoetically named HD85512b, have captured their attention.
An artist’s impression of a “Super Earth” orbiting the sunlike star HD85512b (Photo Credit 7.3)
HD85512b was discovered orbiting an orange dwarf star in the constellation Vela. Astronomers found the planet using the European Southern Observatory’s High Accuracy Radial velocity Planet Searcher, or HARPS, instrument in Chile.
Radial velocity is a planet-hunting technique that looks for wobbles in a star’s light, which can indicate the gravitational tugs of orbiting worlds. The HARPS data show that the planet is 3.6 times the mass of Earth, and the new world orbits its parent star at just the right distance for water to be liquid on the planet’s surface—a trait scientists believe is crucial for life as we know it.
“The distance is exactly the limit where you want to be to have liquid water,” said study leader Lisa Kaltenegger of the Harvard-Smithsonian Center for Astrophysics and the Max Planck Institute for Astronomy. “If you scale it to our system, it’s a bit farther out than Venus is to our sun.” At that distance, the planet likely receives a bit more solar energy from its star than Earth does from the sun.
Earths Galore?
HD85512b is one of 16 super-Earths that the European Southern Observatory recently discovered using the High Accuracy Radial velocity Planet Searcher (HARPS). Super-Earths are planets whose mass is between one and ten times that of Earth, but whether life exists there requires exploration. Michel Mayor, who led the HARPS team, says, “In the coming 10 to 20 years we should have the first list of potentially habitable planets in the sun’s neighborhood. Making such a list is essential before future experiments can search for possible spectroscopic signatures of life in the exoplanet atmospheres.”
But Kaltenegger and colleagues calculate that a cloud cover of at least 50 percent would reflect enough of the energy back into space to prevent overheating. On average, Earth has 60 percent cloud cover, so partly cloudy skies on HD85512b are “not out of the question,” she said.
Of course, clouds of water vapor depend on the presence of an atmosphere similar to Earth’s, something that can’t be detected on such distant planets with current instruments. Models of planet formation predict that planets with more than ten times Earth’s mass should have atmospheres dominated by hydrogen and helium, Kaltenegger said. Less massive worlds—including HD85512b—are more likely to have Earthlike atmospheres, made mostly of nitrogen and oxygen.
So far, the newly detected planet is the second rocky world outside our solar system to be confirmed in its star’s habitable zone—the region around a star that’s not too hot and not too cold for liquid water. The first, planet Gliese 581d, was previously discovered using the HARPS instrument. This world lies just on the cool edge of its star’s habitable zone.
Another promising planet, Gliese 581g, was discovered in 2010 and dubbed the most Earthlike planet yet. But controversy surrounds the claim, with some experts declaring that the entire planet is actually a data glitch. Manfred Cuntz, director of the astronomy program at the University of Texas, Arlington, noted that more information is needed before anyone can speculate whether aliens are wandering around the newfound planet. “It’s not their fault no extra information [about the planet’s atmosphere] is available right now,” Cuntz said of the research team. “It looks like this is a strong candidate, in principle.”
TRUTH:
DAYS ARE LONGER THAN YEARS ON THE PLANET MERCURY.
In addition to size and location, HD85512b has two other points in its favor for potentially harboring life, Cuntz said. The planet’s orbit is nearly circular, which would provide a stable climate, and its parent star, HD85512, is older—and therefore less active—than our sun, which would lower the likelihood of electromagnetic storms damaging the planet’s atmosphere.
Not only that, but in principle, the age of the system—5.6 billion years—“gives life a chance to originate and develop,” he said. By contrast, our own solar system is thought to be about 4.6 billion years old.
Given current limits on space travel, it’s unlikely for now that humans will get to visit HD85512b. But if we could get there, the newfound planet might seem like a fairly alien world: muggy, hot, and with a gravity 1.4 times that of Earth’s, study leader Kaltenegger said. On the bright side, “Hot yoga might be one of the things you don’t have to pay for there,” she quipped.
There’s been a recent flurry of sunspot activity, but scientists believe it’s the storm before the calm. The sun may be going on a break.
Enjoy our stormy sun while it lasts. When our star drops out of its latest sunspot activity cycle, the sun is most likely going into hibernation, scientists announced.
A quiet sun: Very few active regions are visible in this 2009 satellite picture. (Photo Credit 7.4)
Three independent studies of the sun’s insides, surface, and upper atmosphere all predict that the next solar cycle will be significantly delayed—if it happens at all. Normally the next cycle would be expected to start roughly around 2020. The combined data indicate that we may soon be headed into what’s known as a grand minimum, a period of unusually low solar activity.
The predicted solar “sleep” is being compared to the last grand minimum on record, which occurred between 1645 and 1715. Known as the Maunder Minimum, the roughly 70-year period coincided with the coldest spell of the Little Ice Age, when European canals regularly froze solid and Alpine glaciers encroached on mountain villages.
TRUTH:
ABOUT A MILLION EARTHS COULD FIT INSIDE THE SUN.
“We have some interesting hints that solar activity is associated with climate, but we don’t understand the association,” said Dean Pesnell, project scientist for NASA’s Solar Dynamics Observatory (SDO). Also, even if there is a climate link, Pesnell doesn’t think another grand minimum is likely to trigger a cold snap.
“With what’s happening in current times—we’ve added considerable amounts of carbon dioxide and methane and other greenhouse gases to the atmosphere,” said Pesnell, who wasn’t involved in the suite of new sun studies. “I don’t think you’d see the same cooling effects today if the sun went into another Maunder Minimum-type behavior.”
Sunspots are cool, dark blemishes visible on the sun’s surface that indicate regions of intense magnetic activity. For centuries, scientists have been using sunspots—some of which can be wider than Earth—to track the sun’s magnetic highs and lows. For instance, 17th-century astronomers Galileo Galilei and Giovanni Cassini separately tracked sunspots and noticed a lack of activity during the Maunder Minimum.
In the 1800s, scientists recognized that sunspots come and go on a regular cycle that lasts about 11 years. We’re now in Solar Cycle 24, heading for a maximum in the sun’s activity sometime in 2013.
Recently, the National Solar Observatory’s Matt Penn and colleagues analyzed more than 13 years of sunspot data collected at the McMath-Pierce Telescope at Kitt Peak, Arizona. They noticed a long-term trend of sunspot weakening, and if the trend continues, the sun’s magnetic field won’t be strong enough to produce sunspots during Solar Cycle 25, Penn and colleagues predict.
“The dark spots are getting brighter,” Penn said. Based on their data, the team predicts that, by the time it’s over, the current solar cycle will have been “half as strong as Cycle 23, and the next cycle may have no sunspots at all.”
TRUTH:
A VOLCANIC ERUPTION IN 1883 MADE THE SUN LOOK GREEN.
Separately, the National Solar Observatory’s Frank Hill and colleagues have been monitoring solar cycles via a technique called helioseismology. This method uses surface vibrations caused by acoustic waves inside the star to map interior structure.
Specifically, Hill and colleagues have been tracking buried “jet streams,” called torsional oscillations, encircling the sun. These bands of flowing material first appear near the sun’s poles and migrate toward the equator. The bands are thought to play a role in generating the sun’s magnetic field.
Sunspots tend to occur along the pathways of these subsurface bands, and the sun generally becomes more active as the bands near its equator, so they act as good indicators for the timing of solar cycles.
“The torsional oscillation … pattern for Solar Cycle 24 first appeared in 1997,” Hill said. “That means the flow for Cycle 25 should have appeared in 2008 or 2009, but it has not shown up yet.” According to Hill, their data suggest that the start of Solar Cycle 25 may be delayed until 2022—about two years late—or the cycle may simply not happen.
Adding to the evidence, Richard Altrock, manager of the U.S. Air Force’s coronal research program for the National Solar Observatory (NSO), has observed telltale changes in a magnetic phenomenon in the sun’s corona—its faint upper atmosphere.
Known as the “rush to the poles,” the rapid poleward movement of magnetic features in the corona has been linked to an increase in sunspot activity, with a solar cycle hitting its maximum around the time the features reach about 76 degrees latitude north and south of the sun’s equator.
The rush to the poles is also linked to the sun “sweeping away” the magnetic field associated with a given solar cycle, making way for a new magnetic field and a new round of sunspot activity.
This time, however, the rush to the poles is more of a crawl, which means we could be headed toward a very weak solar maximum in 2013—and it may delay or even prevent the start of the next solar cycle.
Taken together, the three lines of evidence strongly hint that Solar Cycle 25 may be a bust, the scientists reported during a 2011 meeting of the American Astronomical Society in Las Cruces, New Mexico. But a solar lull is no cause for alarm, NSO’s Hill said: “It’s happened before, and life seems to go on. I’m not concerned but excited.”
In many ways a lack of magnetic activity is a boon for science. Strong solar storms can emit blasts of charged particles that interfere with radio communications, disrupt power grids, and can even put excess drag on orbiting satellites. “Drag is important for people like me at NASA,” SDO’s Pesnell said, “because we like to keep our satellites in space.”
What’s more, a decrease in sunspots doesn’t necessarily mean a drop in other solar features such as prominences, which can produce aurora-triggering coronal mass ejections. In fact, records show that auroras continued to appear on a regular basis even during the Maunder Minimum, Pesnell said.
Seeing Spots
Sunspots have been observed from Earth for centuries. Chinese astronomers first recorded seeing them with the naked eye more than 2,800 years ago. In the early 1600s, astronomers Thomas Harriot and Galileo Galilei were the first to observe them through a new invention, the telescope.
Instead, he said, the unusual changes to the sun’s activity cycles offer an unprecedented opportunity for scientists to test theories about how the sun makes and destroys its magnetic field. “Right now we have so many sun-watching satellites and advanced ground-based observatories ready to spring into action,” Pesnell said. “If the sun is going to do something different, this is a great time for it to happen.”
Star light. Star bright. First star I eat tonight …
A tiny cannibal star has been caught munching on another star, thanks to a superbright flash of x-rays spied by cosmic hunters.
The culprit is what’s known as a neutron star, the tiny but very dense corpse of a massive star that died in a supernova blast. Sitting 16,000 light-years away, this particular neutron star is normally among the faintest objects in the x-ray sky.
But during recent observations with the European Space Agency’s XMM-Newton space telescope, the star unexpectedly surged to 10,000 times its original brightness. “A companion blue supergiant star is believed to have thrown off a gigantic clump of super-heated gas from its surface, [which] got attracted by the intense gravitational field of the much smaller and denser neutron star orbiting nearby,” said study leader Enrico Bozzo, an astronomer with the ISDC Data Centre for Astrophysics in Geneva, Switzerland.
TRUTH:
THERE ARE MORE STARS IN THE UNIVERSE THAN GRAINS OF SAND ON EARTH.
A clump of matter from a blue supergiant star (left) heads toward a smaller companion neutron star. (Photo Credit 7.5)
The lump of wayward stellar matter measured an estimated 9.9 million miles (16 million kilometers) across and took up about a hundred billion times the volume of the moon. As it became part of the neutron star, the material was heated to millions of degrees, generating a brilliant x-ray flare that lasted for four hours.
“I really could not believe this was true that we were so lucky! I didn’t sleep for days. We are finally able to provide direct evidence for the existence of these clumps of matter.”
Enrico Bozzo
astronomer, describing his reaction upon discovering the cannibal star
Astronomers previously knew that the neutron star and the blue super-giant are part of a stellar odd couple known as a Supergiant Fast X-ray Transient, or SFXT. These usually faint binary stars are prone to occasional flare-ups that cause them to rival the brightest x-ray sources in the sky.
Unfortunately for astronomers, these flares take place randomly only a few times a year, and they last just a couple hours, making them practically impossible to catch from beginning to end. What makes this event even harder to see is that most space-based observatories with sensitive x-ray detectors can observe only a tiny fraction of the sky at a time, and they can’t be swung into action fast enough when these flares go off.
“What usually ends up happening is that these events are detected by instruments that can move very fast or have much larger fields of view, but which suffer from reduced sensitivity, so that they just can’t provide a clear understanding of what caused such an event,” Bozzo said.
One theory was that the flares are caused by the neutron star devouring matter cast off by its hefty companion. Most massive stars generate a constant “wind” of charged particles, which pushes large quantities of stellar material in all directions into space.
Instead of a steady outflow of gas, the blue supergiant in an SFXT system may be emitting winds studded with large “bullets” of material, according to the theory. Flares happen when the neutron star gets shot by one of these clumps.
However, existing observations couldn’t offer clear proof for this theory—until now. By chance, XMM-Newton caught such a flare in 2010 during a scheduled 12.5-hour observation of the SFXT system known as IGR J18410–0535.
TRUTH:
THE BRIGHTER THE STAR, THE SHORTER ITS LIFE SPAN.
“I really could not believe this was true that we were so lucky! I didn’t sleep for days,” Bozzo said. “We are finally able to provide direct evidence for the existence of these clumps of matter.”
Bozzo and his team now hope to make observations of other SFXTs with XMM-Newton, to better understand the unusual flares. “We think it’s the right time,” he said, “to ask for an unprecedented large observational time with the space observatory and provide a final clear answer to the nature of these sources.”
It’s a winter wonderland on Saturn’s moon Enceladus, where scientists have found 330 feet (100 meters) of snow on the surface.
Skiers, get your poles ready: Saturn’s moon Enceladus appears to be cloaked in drifts of powdery snow, scientists announced.
The researchers think superfine snowflakes are blasted out of geyser-like jets, which emanate from long fissures called tiger stripes on the moon’s southern hemisphere. Some of the snow from these plumes falls back to the moon’s surface, coating older fractures and craters in a slow process of accumulation.
“The particles are only a fraction of a millimeter in size … even finer than talcum powder,” study leader Paul Schenk, a planetary scientist at the Lunar and Planetary Institute in Houston, Texas, said in a statement. “This would make for the finest powder a skier could hope for.”
The finding is based on new high-resolution pictures of Enceladus from NASA’s Cassini orbiter, as well as global maps of color patterns that help reveal the ages of surface features.
“The particles are only a fraction of a millimeter in size … even finer than talcum powder. This would make for the finest powder a skier could hope for.”
Paul Schenk
planetary scientist, Lunar and Planetary Institute, Houston
In 2005, Enceladus’s icy geysers were first seen spewing from the moon’s south polar region in pictures from the Cassini spacecraft. Further Cassini data have since shown that the active tiger-stripe fissures are warmer than the surrounding icy terrain, hinting that the jets are being driven by a subsurface liquid ocean. Cassini’s close flybys of the moon also revealed that Enceladus’s geysers may contain the chemical ingredients for life. Enceladus is so far from the sun, however, that its surface temperature is about -330 degrees Fahrenheit (-200 degrees Celsius), causing water vapor spewed from its geysers to condense into ice crystals.
TRUTH:
SATURN HAS MORE THAN 60 MOONS.
According to the new study, as Enceladus’s powdery snow falls back to the surface, it softens the contours of the underlying landscape. The rims of older craters and fissures appear to have been smoothed by the blanket of snow, while the edges of newer fractures are more distinct. Based on such images, Schenk estimates that snow has accumulated to depths of 250 to 400 feet (75 to 125 meters) in places.
Scientists estimate that Enceladus’s low gravity—about 1 percent that of Earth—allows some of the ice emitted by the polar geysers to jet into space rather than falling back to the moon’s surface. Enough material escapes to form an entire ring of Saturn, called the E ring. The wispy E ring is so tenuous that astronomers didn’t see it until 1967.
Scientists previously estimated that if Enceladus’s geysers were to shut off, Saturn’s E ring would dissipate within a few hundred to a few thousand years. This would mean that the entire E ring—and the geysers that feed it—could be quite recent features that we just happen to be seeing at the right time.
But the large accumulations of snow on Enceladus’s surface prove otherwise, Schenk argued at a joint meeting of European and American planetary scientists. That’s because the snowfall on Enceladus is incredibly light, with accumulations of less than a thousandth of a millimeter a year. For snow to build up to depths of hundreds of feet would require tens of millions of years, he said—indicating that the geysers have been active for a very long time.
How rude. Young sunlike stars have been seen spitting water out into space. Is it just a phase that all protostars go through?
Seven hundred and fifty light-years from Earth, a young, sunlike star has been found with jets that blast epic quantities of water into interstellar space, shooting out droplets that move faster than a speeding bullet.
The discovery suggests that protostars may be seeding the universe with water. These stellar embryos shoot jets of material from their north and south poles as their growth is fed by infalling dust that circles the bodies in vast disks.
“If we picture these jets as giant hoses and the water droplets as bullets, the amount shooting out equals a hundred million times the water flowing through the Amazon River every second,” said Lars Kristensen, a postdoctoral astronomer at Leiden University in the Netherlands.
TRUTH:
COLD STARS ARE RED, WHILE HOT STARS ARE BLUE.
“We are talking about velocities reaching 200,000 kilometers [124,000 miles] per hour, which is about 80 times faster than bullets flying out of a machine gun,” said Kristensen, lead author of the new study detailing the discovery, which has been accepted for publication in the journal Astronomy & Astrophysics.
Located in the northern constellation Perseus, the protostar is no more than a hundred thousand years old and remains swaddled in a large cloud—gas and dust from which the star was born.
Using an infrared instrument on the European Space Agency’s Herschel Space Observatory researchers were able to peer through the cloud and detect telltale light signatures of hydrogen and oxygen atoms—the building blocks of water—moving on and around the star.
After tracing the paths of these atoms, the team concluded that water forms on the star, where temperatures are a few thousand degrees Celsius. But once the droplets enter the outward-spewing jets of gas, 180,000-degree-Fahrenheit (100,000-degree-Celsius) temperatures blast the water back into gaseous form.
A star is born in this illustration: Gas and dust swirl inward, while polar jets spurt outward. (Photo Credit 7.6)
Once the hot gases hit the much cooler surrounding material—at about 5,000 times the distance from the sun to Earth—they decelerate, creating a shock front where the gases cool down rapidly, condense, and reform as water, Kristensen said.
“If we picture these jets as giant hoses and the water droplets as bullets, the amount shooting out equals a hundred million times the water flowing through the Amazon River every second. We are talking about velocities reaching 200,000 kilometers (124,000 miles) per hour, which is about 80 times faster than bullets flying out of a machine gun.”
Lars Kristensen
postdoctoral astronomer, Leiden University, Netherlands
What’s really exciting about the discovery is that it appears to be a stellar rite of passage, the researchers say, which may shed new light on the earliest stages of our own sun’s life—and how water fits into that picture.
“We are only now beginning to understand that sunlike stars probably all undergo a very energetic phase when they are young,” Kristensen said. “It’s at this point in their lives when they spew out a lot of high-velocity material—part of which we now know is water.”
Like a celestial sprinkler system, the star may be enriching the interstellar medium—thin gases that float in the voids between stars. And because the hydrogen and oxygen in water are key components of the dusty disks in which stars form, such protostar sprinklers may be encouraging the growth of further stars, the study says.
The water-jet phenomenon seen in Perseus is “probably a short-lived phase all protostars go through,” Kristensen said. “But if we have enough of these sprinklers going off throughout the galaxy—this starts to become interesting on many levels.”
Uranus’s cool turquoise exterior appears tranquil and serene, but astronomers have spotted a new stormy spot.
In a surprise to astronomers, Uranus recently presented onlookers with a new spot on its northern hemisphere.
Near-infrared pictures from the 8.1-meter Gemini North telescope in Hawaii have revealed a region on the giant planet that’s much brighter than its surroundings. The spot is likely a tall methane cloud that reaches high enough for us to see sunlight scattered by its icy particles, said Uranus expert Heidi Hammel, executive vice president of the Association of Universities for Research in Astronomy (AURA).
The Uranian cloud is probably similar to an anvil cloud, the type of towering cumulonimbus cloud that’s associated with severe thunderstorms on Earth. The cloud is also at a lower latitude on Uranus than any that have been observed before. That could mean the spot is a storm that has migrated south.
TRUTH:
THE NORTH POLE OF URANUS GETS NO SUNLIGHT FOR ABOUT 42 YEARS AT A TIME.
A Hubble picture of Uranus in 2005, shortly before the planet’s equinox (Photo Credit 7.7)
Hammel first saw bright spots on Uranus a few years before the planet’s spring equinox in 2007. She was turned on to the spots’ presence thanks to a photo of Uranus in another researcher’s presentation on the ice giant’s moons. “I said, ‘Wow, what’s this?’ And he said, ‘I don’t know, it’s just the way Uranus looks.’ I said, ‘No it’s not!’ ”
Subsequent observations made with the Hubble Space Telescope and ground-based telescopes revealed that the spots were most likely storms, similar to Jupiter’s Great Red Spot. Storms are unusual on Uranus because the planet has very little large-scale atmospheric circulation—movements that are driven mostly by temperature differences.
That’s because, unlike the other seven planets in our solar system, Uranus’s axis of rotation is tilted on its side. In addition, at an average of 1.7 billion miles (2.8 billion kilometers) from the sun, the planet completes an orbit every 84 years.
The Oddly Tilted Planet
Uranus is a bit of an oddball planet, and scientists are intrigued by its curiosities:
1. Uranus spins on its side. It’s the only planet with a rotational axis that’s tilted almost into its orbital plane.
2. Unlike the other gas giants, Uranus doesn’t emit much heat.
3. Uranus has the most powerful known winds in the solar system, blowing at more than 500 miles an hour (805 kilometers an hour).
During an equinox on Uranus, the planet is “completely sideways to the sun,” Hammel said. Uranus’s exposure to light and dark is therefore more similar to that experienced by the other planets, and the resulting temperature differences allow the icy giant’s atmosphere to “turn on” and see more circulation.
Hammel and other astronomers have been studying the planet’s cloud activity since the last equinox to track how seasonal changes affect the weather. Until this new spot was observed, researchers had thought Uranus’s spring period was over. Now astronomers aren’t sure just how long the planet will continue to form such clouds.
Hammel is hoping more astronomers will study Uranus’s new spot, and that enough independent confirmation of the feature will prompt Hubble managers to once again look at Uranus. After all, the last time this planet experienced a change in seasons was 1965. “This is the first opportunity in modern astronomy to look at Uranus with this detail,” she said.
A planetary “roller derby” may be playing out around the supermassive black hole at the heart of the Milky Way, according to a new theory that could help solve a dusty mystery.
For planets and asteroids, life near a black hole can be nasty, brutish, and short. But astronomers believe that in their demise may be found the origin of giant cosmic dust clouds.
Almost all of the large galaxies observed so far have central black holes, each billions of times the mass of our sun. But about half of these cosmic monsters are obscured by dense rings of dust, and astronomers have been uncertain where all this dust comes from and how it’s remained intact over time.
According to the new theory, it’s possible that newly formed planets and asteroids whirling close to these giant black holes are continually being smashed to smithereens, creating the thick, donut-shaped clouds of debris.
TRUTH:
NOTHING CAN ESCAPE FROM A BLACK HOLE.
“Near a supermassive black hole, velocities are hundreds to a few thousand kilometers per second,” said study leader Sergei Nayakshin of the University of Leicester in the United Kingdom. At such speeds, “hitting an Earth-size planet with a solid object a few kilometers across could fragment [the planet] into lots of smaller fragments that, over time, become nothing more than dust.”
Supermassive Attack
Supermassive black holes are the largest black holes in a galaxy, and recently, one was caught eating a star. Astronomers observed a burst of high-energy gamma rays emanating from the center of a dwarf galaxy 3.8 billion light-years away. The flash, one of the brightest and longest gamma ray bursts ever seen, was believed to be caused by a supermassive black hole destroying a star that got too close to its gravitational pull. While supermassive black holes are thought to exist in most large galaxies, such an event may happen only once every hundred million years in any given galaxy.
In 2006, astronomers discovered a population of stars in two rotating disks around the Milky Way’s central black hole. Nayakshin’s team believes these stars may have also formed their own planets and asteroids, similar to the objects in our solar system. Such planets would have to be orbiting their host stars extremely closely to be able to form under the intense gravitational forces that exist near a black hole.
At the same time, stellar densities are very high near the giant black hole, so its possible that the gravitational pull of closely passing stars frequently causes planets to unbind from their host stars and smash into each other, according to the new theory.
The dust created by these pulverized worlds might be similar to the zodiacal dust in our solar system—the result of ancient collisions between newborn planets, asteroids, and comets. A similar mechanism could be at work across the universe, filling other galaxies with dust near their central black holes.
For the study, Nayakshin and his colleagues looked at existing observations of dust clouds around supermassive black holes and compared them with computer models of dust-cloud creation in planetary systems. “If you know this process to actually work on a smaller scale in a somewhat similar setting, then chances are that it may work in the bigger system you’re studying,” Nayakshin said.
The team found that the type of microscopic dust generated as planets and asteroids collided would in fact block light even from actively feeding black holes, which spew intense radiation as matter falls toward the black hole, compresses, and heats up.
Of course, the future for any newly formed planet orbiting a galactic black hole may seem bleak. But the violent demise of star systems could have a protective effect for other parts of some galaxies. If the resulting clouds of dust are massive enough, Nayakshin believes, they can obscure much of the lethal x-rays and gamma rays that are constantly bellowing out from the edges of an actively feeding supermassive black hole.
While much of the area surrounding such a black hole would be sterile, Nayakshin said, “parts of the galaxy that are shielded by the ring of dust—about 50 percent of it—will have a safer and quieter environment for star and planet formation.” Overall, he added, the theory raises some interesting new possibilities for the exotic environments close to supermassive black holes.
TRUTH:
THERE IS NO TIME AT THE CENTER OF A BLACK HOLE.
People used to think all that existed around such black holes was gas and dust, Nayakshin said. “But if we are right, then there are also planets, asteroids, and comets that exist there too—so it is a much more diverse environment than people ever thought.”
Everyone loves to show off baby pictures, and astronomers are no exception. When they got a snapshot of the youngest planet, they were proud to share it with the world.
A new picture of a Jupiter-like world swaddled in gas and dust is a direct image of what may be the youngest planet yet seen, astronomers report. The newborn gas giant, dubbed LkCa 15b, orbits a sunlike star 450 light-years away in the northern constellation Taurus. The planet orbits inside a disk of material around the star that’s no more than two million years old.
The big baby planet may be up to six times the mass of Jupiter, according to theory-based calculations, and it appears to orbit 11 times farther from its parent star than Earth does from our sun. The new picture was made in near-infrared light, but “the planet would probably appear a deep red to our eye, since it’s still glowing from the heat of being formed,” said Adam Kraus, lead study author and an astronomer at the University of Hawaii.
TRUTH:
MORE THAN 500 CONFIRMED PLANETS HAVE BEEN DISCOVERED ORBITING OTHER STARS.
Kraus and colleagues zeroed in on the young star based on previous observations that showed a conspicuous gap in the star’s surrounding debris disk. Such gaps are thought to be telltale signs that massive, newly formed planets are circling inside the disks—a protoplanet’s gravity would clear away a wide swath of gas and dust as it accumulates matter.
“This [gap] is a huge benefit for astronomers who want to find planets—we know a planet is probably there, and we even know approximately where to look,” Kraus said. “We just needed to find a way to distinguish the very faint planet from its very bright parent star.”
For this, the team turned to the Keck II 10-meter telescope on the summit of Hawaii’s Mauna Kea. First off, the telescope’s deformable mirror was able to correct for distortions in the collected starlight caused by Earth’s atmosphere. The team then used a small mask with several holes placed over the light-collecting mirrors, a method called aperture mask interferometry. This technique allowed the team to block out the light from the host star while capturing the fainter glow of the disk and its embedded planet.
Theories of Planet Formation Debunked!
Just when scientists thought they had planets all figured out, new discoveries pop up that change their thinking about just how planets behave. Here are some theories that are being overturned:
THEORY 1: All planetary orbits are roughly circular. In fact, only about one in three of the known exoplanets has a circular or near-circular orbit.
THEORY 2: With minor exceptions, everything in a star system orbits in the same plane and in the same direction. One in three exoplanets’ orbits are “misaligned.” Some orbit in the opposite directions of their stars’ rotations, and others are tilted well out of the ecliptic.
THEORY 3: Giants the size of Neptune are rare. The size range where theory suggested there should be the fewest planets—3 to 15 times the size of Earth—has been the most commonly found.
Kraus and his team plan to continue observing LkCa 15b so they can pin down its temperature and orbital characteristics, such as the shape and orientation of its path around the star. The team also hopes to expand the search to other stars that have surrounding disks with gaps—and perhaps begin to answer some basic questions about early planet formation.
“We’d been looking for this kind of planet for several years, specifically because we know that observing planet formation in action would tell us a lot about how it actually works,” Kraus said. “My first reaction was that this is finally going to tell us how planets really form!”
An exotic planet as dense as diamond has been found in the Milky Way. Astronomers think the world is a former star that got transformed by its orbital partner.
“In terms of what it would look like, I don’t know I could even speculate. I don’t imagine that a picture of a very shiny object is what we’re looking at here.”
Ben Stappers
University of Manchester, on the “diamond” planet
An odd planet was discovered orbiting what’s known as a millisecond pulsar—a tiny, fast-spinning corpse of a massive star that died in a supernova. Astronomers estimate that the newfound planet is 34,175 miles (55,000 kilometers) across, or about five times Earth’s diameter.
In addition, “We are very confident it has a density about 18 times that of water,” said study leader Matthew Bailes, an astronomer at the Swinburne Centre for Astrophysics & Supercomputing in Melbourne, Australia. “This means it can’t be made of gases like hydrogen and helium like most stars but [must be made of] heavier elements like carbon and oxygen, making it most likely crystalline in nature, like a diamond.”
In this depiction, the newfound “diamond” planet orbits the pulsar so closely that the entire system would fit inside the sun. (Photo Credit 7.8)
The new millisecond pulsar, dubbed PSR J1719–1438, lies about 4,000 light-years away in the southern constellation Serpens. Bailes and his team found the star during a pulsar survey using the radio telescope at Australia’s Parkes Observatory. A pulsar is a type of stellar corpse that emits powerful beams of radio waves from its poles. If these beams sweep across Earth’s field of view as the star rotates, radio telescopes on Earth can detect the star’s regular pulses.
A millisecond pulsar is thought to form when the pulsar is siphoning material from a companion star. The action of eating matter speeds up the pulsar’s spin to hundreds of rotations a second. So far it seems millisecond pulsars are rare, with only about a hundred found in the last 30 years. The study team found PSR J1719–1438 by using supercomputers to comb through almost 200,000 gigabytes of data—enough to fill more than 23,500 standard DVDs.
The data show that the pulsar spins more than 10,000 times a minute. The astronomers also noticed that the star’s radio pulses have an unusual modulation, which the team concluded must be due to the gravitational pull of a small orbiting object.
About 70 percent of the known millisecond pulsars have orbital companions, but PSR J1719–1438 is only the second thought to have a planetary partner. That’s probably because planets don’t form around millisecond pulsars in the usual way, Bailes said.
Diamonds Are Forever
The diamond planet, dubbed J1719–1438, has a stable system, with no evidence that it will change for billions of years. “Of course,” notes Michael Keith of the Australia Telescope National Facility, “this also means that it could well have been around for a long time, just waiting for us to find it. Since it’s likely to last for longer than the Earth or the sun, I would say that in this case, a diamond really is forever.”
Astronomers think planets are created from dusty disks of material swirling around newborn stars. As this material orbits the star, gravitational interactions cause clumps to form, and the clumps build mass as they sweep through the disk. By contrast, the new study hints that pulsars can strip material away from their companions until all that’s left of the consumed star is enough mass for a planetlike object.
The newfound “diamond” planet probably formed from a white dwarf star—the core of a dead sunlike star—that was being stripped of matter by the pulsar. The leftover object likely represents just 0.1 percent of the white dwarf’s original mass, Bailes said. Based on their data, the team calculates that the planet orbits the pulsar in just two hours and ten minutes at a distance of about 372,822 miles (600,000 kilometers).
Bailes and his team would now like to know exactly how rare their discovery really is. In all likelihood, this weird method of planet production requires special circumstances that rely on the white dwarf companion having a particular mass and chemical composition.
But even if the diamond planet is a result of a perfect storm of special circumstances, there should be more such worlds out there, Bailes said.
“The most exciting aspect to me is that we’ve only processed a small fraction of space so far,” he said. “With the new supercomputers coming online, we should be in a strong position to possibly make many more discoveries like this one.”
In a galaxy 250 million light-years from Earth, astronomers have spotted a record-breaking seven supernovae, and they were all found at the same time.
Astronomers have spotted a record-breaking seven supernovae in a prodigious galaxy known as Arp 220. This galaxy is thought to have formed from the merger of two smaller galaxies and is well known to host a very intense burst of star formation, easily seen in visible wavelengths.
The galaxy Arp 220, where the seven supernovae were found (Photo Credit 7.9)
“As far as we know, only three supernovae in a single galaxy were found at once so far, which is already an impressive number,” said study leader Fabien Batejat, a Ph.D. student at Chalmers University of Technology in Onsala, Sweden. “But we can confirm seven supernovae [in a single galaxy], thanks to a 17-year monitoring of the radio sources in Arp 220.”
The unprecedented find may offer a unique cosmic laboratory for studying galaxy evolution. The new data also confirm that Arp 220 is a very efficient factory for explosive star deaths, giving scientists a glimpse of how the earliest galaxies in the universe may have behaved.
Rogue Planets
A new theory suggests that when a star dies in a violent supernova, some of its planets may survive the blast but be ejected from orbit and sent wandering the galaxy. This would offer an explanation for some of the free-roaming planets that have been found and it could mean that more exist across the Milky Way. In rare cases, some survivor planets may remain bound to supernova remnants, finding new orbits around the neutron stars or black holes left behind by the explosions.
Each of the supernovae found in Arp 220 spans less than a light-year, and at such a great distance, each radio signal covers an angle in the sky less than 0.5 milliarcseconds across, Batejat said. “To give you an idea of how small this is, this size corresponds to what you would see if you would look into a straw of about 1,500 kilometers [932 miles] long,” Batejat said.
“In order to see such small objects, we would need a telescope of 10,000 kilometers [6,214 miles] across, which is a bit less than the diameter of the Earth itself. But since we can’t build such gigantic telescopes, we use interferometry to simulate them.” In astronomy, interferometry uses the combined power of an array of telescopes—rather than a single, huge telescope—to create high-resolution images that can probe deep into the universe.
Batejat’s team used 57 of the largest radio telescopes on Earth, which are spread across two continents and five countries. The project included data from the European VLBI Network, the Very Long Baseline Array, the Green Bank Telescope, and the Arecibo Observatory.
The heart of Arp 220 is highly obscured by dust that can’t be penetrated by visible wavelengths. But radio waves can travel through such a dense environment to reach telescopes on Earth.
TRUTH:
INTERFEROMETRY USES THE COMBINED POWER OF MANY TELESCOPES, AS OPPOSED TO A SINGLE, HUGE TELESCOPE, TO CREATE HIGH-RESOLUTION IMAGES THAT CAN PROBE DEEP INTO THE UNIVERSE.
Ultimately the data revealed about 40 radio sources near the center of Arp 220. By watching how these sources changed over time in two different radio wavelengths, astronomers could tell that seven of the objects were stars that had exploded around the same time.
Astronomers estimate that our Milky Way galaxy sees only a single supernova every hundred years, on average, Batejat said. But the highly active Arp 220, with its dynamic cycles of star birth and death, behaves more like how young galaxies probably did more than ten billion years ago.
“We hope this might lead to interesting discoveries on how stars formed [and died] in the early universe,” Batejat said. What’s more, such relatively fresh supernovae “are rare, and they have short lives of a few decades maximum” before they settle into supernova remnants, he said. “So discovering seven such supernovae at once is something amazing.”
“There’s gold in them thar meteors!” says a new study that supports the theory that meteors delivered gold and other metals to Earth billions of years ago.
Not all that glitters is gold. But Earth would have a lot less of the glittery stuff if not for a massive rain of meteors about 3.9 billion years ago, according to a new study.
Based on analysis of some of the world’s oldest rocks, scientists have the first direct evidence that a cataclysmic meteor shower changed early Earth’s chemical composition. The find offers support for the theory that meteors delivered gold and other precious metals to infant Earth.
The presence of precious metals in Earth’s mantle and crust poses a puzzle because these elements are attracted to iron. When Earth first formed roughly 4.5 billion years ago, the planet was basically a ball of magma. As the planet cooled, denser material sank toward the center, eventually producing a core made mostly of iron.
But that means any iron-loving—or siderophile—elements present in the primordial magma should have also retreated toward the core. In fact, based on the composition of meteorites thought to be akin to early Earth, our planet should have enough gold in its present-day core to cover the entire globe with a 12-foot-thick (4-meter-thick) layer of the precious metal.
“All that stuff disappeared into the core, but we still find some gold around [the surface],” said study co-author Matthias Willbold of the University of Bristol. One possible answer for where the precious metals came from is that a “firestorm” of meteors called the terminal bombardment added a veneer of material to Earth’s surface some 650 million years after the planet’s formation.
“Our work shows that most of the precious metals on which our economies and many key industrial processes are based have been added to our planet by lucky coincidence when the Earth was hit by about 20 billion billion tonnes of asteroidal material.”
Matthias Willbold
study co-author, University of Bristol
To find proof for this theory, Will-bold and colleagues studied rock samples from the Isua Greenstone Belt in Greenland. Although the Greenstone rocks date to about 3.8 billion years ago—close to the time of the terminal bombardment—“the mantle source from which these rocks are coming is from 4.5 billion years ago,” Willbold said. That means the rocks should retain chemical signatures that predate the massive meteor shower.
By comparing those ancient rocks with modern ones, the researchers found that the two samples have different tungsten isotope ratios. Tungsten-182 was produced only in the first 50 million years of the solar system. But the Greenland rocks have more tungsten-182 than tungsten-184, the version of the element more commonly found in modern rocks.
“These rocks that we found on Greenland are the only ones that show an anomalous tungsten condition,” Willbold said—a sign that meteor impacts did in fact change Earth’s surface composition.
In general, based on the rate of impacts during the terminal bombardment, meteors slamming into Earth may have added about half a percent of the material now in the planet’s mantle, Willbold said. That may not seem like much, but it works out to about 20 billion billion tons, he added.
Coal-black, reflecting almost no light, this newfound world is off-the-charts dark—and the cause is a mystery, experts say.
It may be hard to imagine a planet blacker than coal, but that’s what astronomers say they’ve discovered in our home galaxy with NASA’s Kepler space telescope.
Orbiting only about three million miles out from its star, the Jupiter-size gas giant planet, dubbed TrES-2b, is heated to 1,800 degrees Fahrenheit (980 degrees Celsius). Yet the apparently inky world appears to reflect almost none of the starlight that shines on it, according to a new study.
“Being less reflective than coal or even the blackest acrylic paint—this makes it by far the darkest planet ever discovered,” lead study author David Kipping said. “If we could see it up close it would look like a near-black ball of gas, with a slight glowing red tinge to it—a true exotic amongst exoplanets,” added Kipping, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
“Being less reflective than coal or even the blackest acrylic paint—this makes it by far the darkest planet ever discovered.”
David Kipping
astronomer, Harvard-Smithsonian Center for Astrophysics
The Earth-orbiting Kepler spacecraft was specifically designed to find planets outside our solar system. But at such distances—TrES-2b, for instance, is 750 light-years from us—it’s not as simple as snapping pictures of alien worlds.
Instead, Kepler—using light sensors called photometers that continuously monitor tens of thousands of stars—looks for the regular dimming of stars. Such dips in stellar brightness may indicate that a planet is transiting (passing in front of a star, relative to Earth), blocking some of the star’s light; in the case of the coal-black planet, blocking surprisingly little of that light.
When a planet passes in front of its star, the world’s shaded side faces Kepler. But as the planet begins orbiting to the side of and “behind” its star, its star-facing side comes to face the viewer. The amount of starlight grows until the planet, becoming invisible to Kepler, passes fully behind its star.
Watching TrES-2b and its star, Kepler detected only the slightest such dimming and brightening, though enough to ascertain that a Jupiter-size gas giant was the cause. The light reflected by the newfound extrasolar planet, or exoplanet, changed by only about 6.5 parts per million, relative to the brightness of the host star.
Experts believe the newfound gas-giant is black with a slight red glow. (Photo Credit 7.10)
“This represents the smallest photometric signal we have ever detected from an exoplanet,” Kipping said. What’s more, as the coal-black planet passed in front of its star, the starlight’s dimming was “so small that it’s like the dip in brightness we would see with a fruit fly going in front of a car headlight.”
Current computer models predict that hot-Jupiter planets—gas giants that orbit very close to their stars—could be only as dark as Mercury, which reflects about 10 percent of the sunlight that hits it. But TrES-2b is so dark that it reflects only 1 percent of the starlight that strikes it, suggesting that the current models may need tweaking, Kipping said.
Assuming the new study’s measurements are sound, what exactly is making the new planet’s atmosphere so dark? “Some have proposed that this darkness may be caused by a huge abundance of gaseous sodium and titanium oxide,” Kipping said. “But more likely there is something exotic there that we have not thought of before. It’s this mystery that I find so exciting about this discovery.”
TrES-2b may even represent a whole new class of exoplanet—a possibility Kipping and company hope to put to the test with Kepler, which has so far detected hundreds of planets outside our solar system.
Go Kepler, Go!
The primary goal of NASA’s Kepler space telescope mission is to find rocky, Earthlike planets orbiting in stars’ habitable zones—the regions in which planets receive enough heat from their stars for liquid water to exist. While the finds haven’t quite yet met those criteria, they do show that Kepler is working as expected, offering a “tantalizing hint at what we can expect in a few years’ time,” says Greg Laughlin, an astronomer at the University of California, Santa Cruz.
“As Kepler discovers more and more planets by the day, we can hopefully scan through those and work out if this is unique or if all hot Jupiters are very dark,” Kipping said. Meanwhile, the very darkness of the new exoplanet suggests perhaps a catchier moniker for TrES-2b, Kipping said. “Maybe an appropriate nickname would be Erebus”—ancient Greece’s god of darkness.
Astronomers are still quarreling over Pluto’s status. The debate rages on as new finds continue to fuel the arguments over whether little Pluto should regain its planetary status—or not.
Officially, Pluto is still not a planet.
But years after the ruling that demoted the icy object to dwarf planet, people continue struggling with the definition, and the debate over what exactly should be called a planet remains as contentious as any political divide. “Maybe it’s just an argument over semantics, but we ought to be worried about semantics. We learned that lesson when the definition was changed,” said Marc Kuchner, a planetary scientist at NASA’s Goddard Space Flight Center in Maryland.
TRUTH:
IF YOU WEIGH 150 POUNDS ON EARTH, YOU WOULD WEIGH ABOUT 10 POUNDS ON PLUTO.
“After the ruling, astronomers everywhere were besieged by complaints from everyone big and small. A planet is a very personal thing—we think of the Earth, the moon, and the other planets as part of our home, and maybe that’s why we got so upset about Pluto.”
Since the 2006 ruling, astronomers have also made a number of scientific advances that further cloud the issue, from discoveries of planets that don’t orbit stars to new models of how our own solar system may have rearranged itself since birth.
The issue of whether Pluto should be a planet first arose in the 1970s, when scientists were able to refine their estimates for the mass and size of the distant body. With each new measurement, Pluto got lighter and tinier, until astronomers realized that the object is in fact smaller than Earth’s moon and has a very low density.
Then in 1978, scientists announced they’d found a moon of Pluto—but one that’s almost half its size, making it the largest moon in relation to its parent body. During the ensuing decades, scientists continued to find similarly large objects in Pluto’s neighborhood, a region of the solar system beyond the orbit of Neptune called the Kuiper belt.
“You don’t know how you’re supposed to feel about it at first. I’d like us all to think about the dwarf planets out there as new siblings that we have to get to know and learn to love.”
Marc Kuchner
planetary scientist, NASA’s Goddard Space Flight Center
The biggest challenge for Pluto came in 2005, when Caltech astronomer Mike Brown announced that he’d found a Kuiper belt object more massive than Pluto—a potential tenth planet provisionally called 2003 UB313. The discovery prompted the IAU to convene a committee to decide on an official definition of a planet.
“It was a bureaucratic problem, as it had to do with naming rights for these kinds of things,” said Owen Gingerich, the Harvard-Smithsonian astronomer who chaired the committee. After all, if 2003 UB313 really was a new planet, it would need a proper name on which everyone could agree.
The committee initially proposed that there be two categories of planets: the classical planets and the group of planetlike bodies beyond Neptune, to be called plutons, “as a way of tipping our hat to Pluto,” Gingerich said. The planetlike object Ceres would have to be in a separate class because it resides in the main asteroid belt, between the orbits of Mars and Jupiter. So the committee suggested it be called a dwarf planet.
An artist’s depiction of Pluto and its largest moon, Charon, are seen from one of the dwarf planet’s smaller moons. (Photo Credit 7.11)
The draft definition was put to a vote in 2006 at the IAU general assembly in Prague, the Czech Republic. What emerged from the session is that, to be a planet, an object must
1. be in orbit around the sun,
2. have sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
3. have cleared the neighborhood around its orbit.
Instead of plutons, the IAU members present voted that Pluto, Ceres, and 2003 UB313—now known as Eris—would all be called dwarf planets, and that this term is not for a subclass of planets but is for a unique category of solar system objects.
At the time of the ruling, the IAU noted that the new definition does not apply to anything outside the solar system, leaving it unclear how the organization defines the planetary objects found orbiting other stars.
Since 2006, there’s been an explosion in the number of these extrasolar planets, or exoplanets, known to exist, with the current count at more than 700 and rising. Many are bigger than the gas giant Jupiter, but astronomers have found an increasing number of worlds close to Earth’s mass, some of which may be habitable. And in the past few years astronomers have even found rocky planets akin to Earth’s mass that don’t orbit stars at all.
By the current IAU definition, none of these objects are official planets because they violate the first rule about orbiting the sun. “I was disappointed when I learned that exoplanets were not included in the definition,” said NASA’s Kuchner.
The second part of the definition, that planets must be massive enough to be nearly round, helped draw a line between bodies such as Pluto and large asteroids such as 433 Eros, a 21-mile-long (34-kilometer-long) space rock shaped somewhat like a peanut; the third rule, whether an object has cleared its orbital neighborhood, has proved the most controversial.
Search for Planet X
A self-taught astronomer from Kansas, Clyde Tombaugh built powerful homemade telescopes in the 1920s to scan the night skies. Hoping to get some feedback, he sent his findings to astronomers at the Lowell Observatory. Instead of a critique, he got a job offer and joined the staff at Lowell as part of their team searching for “Planet X,” the elusive planet beyond Neptune. After ten months of observations and photographing 65 percent of the sky, Tombaugh’s persistence paid off when he discovered the body we now know as Pluto.
Kuchner, who was a graduate student under Caltech’s Brown, thinks this part of the definition is the most subjective. In baseball, he said, “If you have a foul ball, it’s because the ball landed on one side of the line—that’s pretty clear. But it’s harder to say if something’s a strike … That relies on someone calling it.” In the case of defining a planet, IAU made the call, and “now we have to use this definition and try to play the game.”
Overall, he added, the ruling was crucial for limiting the number of things in the solar system that deserve to be called planets. “We really didn’t have a choice,” he said. “It was either going to be eight planets or a whole lotta planets. Nature sort of forced our hand.”
But other astronomers aren’t in favor of placing those kinds of limits. “There are more than 200 bones in the human body. Does that mean we should redefine bones to make life easier for medical students?” argued Timothy Spahr, head of the IAU’s Minor Planet Center based in Cambridge, Massachusetts.
Instead the IAU definition makes life more complicated for astronomers, he said, because the notion of whether an orbital neighborhood has been cleared remains hazy. As an example, Spahr points to the increased number of known Earth-crossing asteroids, including roughly 8,000 that are considered near-Earth objects. While these space rocks don’t exactly share our planet’s orbit, they do cross it, in the sense that when they are closest to the sun, they are inside Earth’s orbital path.
“There’s certainly no big donut where Earth is, just a big mass of objects” that could be said to share our neighborhood, he said. This mass of objects will probably always exist, as asteroids in the main belt collide, break apart, and send new material on orbits closer to Earth’s. “In 50 million years our orbital neighborhood will look pretty much the same.” By some counts, that means Earth will not ever clear its orbit of debris.
For his part, Spahr favors a simpler definition than the current version. “Orbiting a star and round is a good way to start,” he said. Planetary scientist Alan Stern at the Southwest Research Institute calls it the Star Trek criteria. He added: “If you can look out the viewfinder of the Enterprise and see it’s round, it’s a planet.”
From there, Spahr said, planets could be grouped into subclasses: terrestrial planets like Earth, gas giants like Jupiter, and icy outer planets like Pluto. “We could even have a category for rogue planets, to account for the worlds that don’t orbit stars.”
While NASA’s Kuchner thinks the current definition should stand for now, he says he’s “happy that we are constantly updating our definitions and revising our vision of universe—that’s what science is all about.”
TRUTH:
AN 11-YEAR-OLD GIRL NAMED THE DWARF PLANET PLUTO.
And of course, no matter what you call it, many astronomers will continue to see Pluto as one of the most fascinating objects in the solar system, the Minor Planet Center’s Spahr said. The IAU definition “doesn’t change the fact that we’re going to visit Pluto with [the New Horizons] spacecraft, and scientists are still going to go hog wild over all the data we collect.”
To help maintain a youthful appearance, stars may steal energy from other stars, draining their energy away.
The stellar version of vampires—stars that drain life away from other stars—has been discovered for the first time in the heart of our Milky Way galaxy.
Called blue stragglers, these cannibal stars have been spotted in other parts of the Milky Way. They seem to lag in age next to the other stars with which they formed—appearing hotter, and thus younger and bluer. Astronomers suspect blue stragglers look so youthful because they’ve stolen hydrogen fuel from other stars, perhaps after colliding into their victims.
These cannibal stars are routinely found in dense star clusters, where stars have many chances to feed off each other. Now, however, scientists have found blue stragglers in the Milky Way’s galactic bulge, a dense region of stars and gas surrounding the galaxy’s center.
TRUTH:
STELLAR VAMPIRISM HAS BEEN GOING ON FOR 500,000 YEARS, AND SHOULD CONTINUE FOR 200,000 MORE.
“For a long time, it was suspected there were blue stragglers in the bulge, but no one knew how many there might be,” said Will Clarkson, an astronomer at Indiana University Bloomington and the University of California, Los Angeles. “At long last, we’ve shown they’re there.”
Using NASA’s Hubble Space Telescope, astronomers looked at 180,000 stars in and near the bulge. The team discovered 42 unusually blue stars that appeared much younger than the other stars.
From these 42 stars, researchers estimate that 18 to 37 of them are likely real blue stragglers that are about 10 billion to 11 billion years old. The remainder may be genuinely young stars in the bulge, or stars not actually in the bulge.
It’s also possible the blue stragglers did not form by slamming into other stars and absorbing extra hydrogen fuel, as occurs in other parts of the universe. Instead, the blue stragglers in the galactic bulge may have formed by ripping hydrogen off their companion stars. This possibly occurred either when one star fed off its partner in a two-star system, or perhaps after gravitational interactions in a triple-star system had caused two of its members to merge into one.
“We think we have a good understanding of stellar evolution, but it doesn’t predict blue stragglers … now we have the detailed observations needed to identify how they were created. I’ve always enjoyed trying to get to the bottom of a mystery.”
Aaron M. Geller
astronomer, Northwestern University
“There’s still a lot we don’t know about the details of how blue stragglers form,” Clarkson said. “Finding them in the bulge provides another set of constraints that can help refine models of their formation.”