On July 20, 1969, the world sat in anticipation around radios and TV screens when Neil Armstrong became the first man to set foot on the moon. The Apollo 11 launch stood as an American triumph in the legacy of human fascination with the moon and stars. Recent Chinese explorations of the dark side of the moon show that we are still preoccupied with the mysteries and secrets of Earth’s first cousin. There are many surprising facts about the moon, some well-known and others less so.
Birth of the moon
Measures of lunar rocks show that the moon is roughly the same age as the earth, but these measures are taken on the scale of billions of years where a few hundred thousand is the blink of an eye. The leading theory regarding the formation of the moon is that it was created in the wake of a collision between young Earth and a large foreign body, causing debris from the impact to float into space.
The moon has a thin atmosphere incapable of shielding it from cosmic rays and colliding objects. Because of this, the planet is regularly bombarded with asteroids and comets that have led to the many craters on its surface and a thin layer of space dust coating the entire surface of the moon. The dark areas are impact sites known as maria, derived from the Latin word “mare” meaning sea. The lighter areas are called highlands. While the moon has no naturally occurring water sources, there are deposits of frozen water from comets and meteoroids around the poles of the moon.
Humans have long been fascinated with the moon’s ability to influence the tides and climate. These curiosities have been embodied from early astronomy to modern agriculture. Medieval societies believed that lunar cycles influenced behaviors to the point of inducing madness in some individuals. This is why the prefix “luna” in lunatic is the Latin word for moon. That the moon could induce madness was such a strong belief that it was once included in English law. While we no longer believe this, modern studies do show that lunar cycles can influence human sleep patterns.
Dark side of the moon
The moon completes one complete rotation around its own axis during the same period of time (27.3 days) that it takes to orbit the earth once. This is why the moon always shows the same face to the earth. The most recent explorations have been to the opposite side, known as the “dark side of the moon.” In actuality, both sides of the moon experience two weeks of sunlight and two weeks of darkness. Because of this, the “dark side” is more accurately known as the “far side of the moon.”
Adrift in space
The earth’s gravitational field is responsible for both the formation of the moon and its stable orbit around Earth. However, Earth is not a perfect sphere and exerts non-uniform gravitational pull on the moon. This phenomenon is responsible for the shift in tides as a result of lunar cycles, and it’s also causing the moon to expand its orbit ever so slightly. Each year, the moon drifts roughly 4 cm away from the earth. After 500 million years, this slight drift will place the moon about 14,600 miles away from Earth.
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At the annual meeting of the American Astronomical Society in St. Louis, Missouri, Allison Kirkpatrick, assistant professor of physics and astronomy at the University of Kansas, will announce her discovery of “cold quasars”—galaxies featuring an abundance of cold gas that still can produce new stars despite having a quasar at the center—a breakthrough finding that overturns assumptions about the maturation of galaxies and may represent a phase of every galaxy’s lifecycle that was unknown until now.
Her news briefing, entitled “A New Population of Cold Quasars,” takes place Wednesday, June 12, on the 2nd floor of the St. Louis Union Station Hotel.
A quasar, or “quasi-stellar radio source,” is essentially a supermassive black hole on steroids. Gas falling toward a quasar at the center of a galaxy forms an “accretion disk” which can cast off a mind-boggling amount of electromagnetic energy, often featuring luminosity hundreds of times greater than a typical galaxy. Typically, formation of a quasar is akin to galactic retirement, and it’s long been thought to signal an end to a galaxy’s ability to produce new stars.
“All the gas that is accreting on the black hole is being heated and giving off X-rays,” Kirkpatrick said. “The wavelength of light that you give off directly corresponds to how hot you are. For example, you and I give off infrared light. But something that’s giving off X-rays is one of the hottest things in the universe. This gas starts accreting onto the black hole and starts moving at relativistic speeds; you also have a magnetic field around this gas, and it can get twisted up. In the same way that you get solar flares, you can have jets of material go up through these magnetic field lines and be shot away from the black hole. These jets essentially choke off the gas supply of the galaxy, so no more gas can fall on to the galaxy and form new stars. After a galaxy has stopped forming stars, we say it’s a passive dead galaxy.”
But in Kirkpatrick’s survey, about 10 percent of galaxies hosting accreting supermassive black holes had a supply of cold gas remaining after entering this phase, and still made new stars.
“That in itself is surprising,” she said. “This whole population is a whole bunch of different objects. Some of the galaxies have very obvious merger signatures; some of them look a lot like the Milky Way and have very obvious spiral arms. Some of them are very compact. From this diverse population, we then have a further 10 percent that is really unique and unexpected. These are very compact, blue, luminous sources. They look exactly like you would expect a supermassive black hole to look in the end stages after it has quenched all of the star formation in a galaxy. This is evolving into a passive elliptical galaxy, yet we have found a lot of cold gas in these as well. These are the population that I’m calling ‘cold quasars.'”
The KU astrophysicist suspected the “cold quasars” in her survey represented a brief period yet to be recognized in the end-phases of a galaxy’s lifespan—in terms of a human life, the fleeting “cold quasar” phase may something akin to a galaxy’s retirement party.
“These galaxies are rare because they’re in a transition phase—we’ve caught them right before star formation in the galaxy is quenched and this transition period should be very short,” she said.
Kirkpatrick first identified the objects of interest in an area of the Sloan Digital Sky Survey, the most detailed digital map of the universe available. In an area dubbed “Stripe 82,” Kirkpatrick and her colleagues were able to visually identify quasars.
“Then we went over this area with the XMM Newton telescope and surveyed it in the X-ray,” she said. “X-rays are the key signature of growing black holes. From there, we surveyed it with the Herschel Space Telescope, a far infrared telescope, which can detect dust and gas in the host galaxy. We selected the galaxies that we could find in both the X-ray and in the infrared.”
The KU researcher said her findings give scientists new understanding and detail of how the quenching of star formation in galaxies proceeds, and overturns presumptions about quasars.
“We already knew quasars go through a dust-obscured phase,” Kirkpatrick said. “We knew they go through a heavily shrouded phase where dust is surrounding the supermassive black hole. We call that the red quasar phase. But now, we’ve found this unique transition regime that we didn’t know before. Before, if you told someone you had found a luminous quasar that had a blue optical color—but it still had a lot of dust and gas in it, and a lot of star formation—people would say, ‘No, that’s not the way these things should look.'”
Next, Kirkpatrick hopes to determine if the “cold quasar” phase happens to a specific class of galaxies or every galaxy.
“We thought the way these things proceed was you have a growing black hole, it’s enshrouded by dust and gas, it begins to blow that material out,” she said. “Then it becomes a luminous blue object. We assumed when it blew out its own gas, it would blow out its host gas as well. But it seems with these objects, that’s not the case. These have blown out their own dust—so we see it as a blue object—but they haven’t yet blown out all of the dust and gas in the host galaxies. This is a transition phase, let’s say of 10 million years. In universal timescales, that’s really short—and it’s hard to catch this thing. We’re doing what we call a blind survey to find objects we weren’t looking for. And by finding these objects, yes, it could imply that this happens to every galaxy.”
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Launched in November 2011, the Curiosity Rover was sent to Mars to collect data and, hopefully, answer the question “Did Mars ever have the right conditions to support life?” Curiosity answered this question early on, when it discovered chemical and mineral evidence of past habitable environments on the Red Planet. Though other missions have been sent to Mars, Curiosity carries the most advanced scientific instruments of any of them and can travel farther on Mars’ surface due to increased power capacity.
Right now, somewhere in the world, children stand at the edge of a lake counting the hops of stones skidding across the surface of the water. It’s hard to explain the tranquil pleasure of watching the ripples emanate farther and farther till nearly out of sight, but it’s even more of a challenge to fathom the distances to which we’ve launched objects into the dark ocean of space. As of February 2018, the Voyager 1 drifts 13 billion miles away from the surface of the earth, 42 years since its launch. It is one of five man made objects that has ever left our solar system.
Five years before the launch of the Voyager probes, on March 2, 1972, NASA launched the Pioneer 10 to investigate the surface of Jupiter. Weighing 569 pounds, the Pioneer 10 was the first spacecraft to cross the asteroid belt between Mars and Jupiter and, eventually, escape our solar system by nature of its velocity. It was also the first spacecraft to launch from the three-stage Atlas-Centaur launch vehicle to achieve its launch speed of 32,400 mph. It took the Pioneer 10 twelve weeks to cross the orbit of Mars. On December 3, 1973, the Pioneer 10 passed by the cloud tops of Jupiter to obtain the first close-up images of the planet.
Following its flyby of Jupiter, Pioneer 10 continued to gather data for NASA of the outer solar system until the end of its mission in March 31, 1977. The last faint signal from Pioneer 10 was received on January 23, 2003, as its radioisotope power source had decayed to the point of being unable to send further signals.
The launch of Pioneer 10 was succeeded just a year later on April 5, 1973. The launch this time was accelerated by an additional 210 ft/sec and aimed to pass Jupiter at a point closer to its surface. The closer proximity to Jupiter caused the spacecraft to accelerate by gravitational pull to the muzzle velocity of a rifle (110,000 mph), allowing it to obtain the velocity and direction necessary to approach Saturn.
On September 1, 1979, Pioneer 11 flew to within 13,000 miles of Saturn to obtain the first close-up images of the planet and discover two previously-unobserved moons. By September of 1995, the spacecraft could no longer make observations and by November, the last communication with the spacecraft was made.
Voyager 1 & 2
The Voyager spacecrafts were initially tasked with observing the properties and magnetospheres of our neighboring planets using their onboard instrumentation. Target planets included Jupiter, Saturn, and Saturn’s moon Titan. Data from the Pioneer 10 mission was used to create more robust spacecraft to tolerate the intense radiation around Jupiter. Voyager 1 started its observation of Saturn, the final phase of its initial mission, on August 22, 1980, whereas the Voyager 2 was sent on a longer trajectory to observe Uranus and Neptune, reaching Neptune on August 25, 1989.
In addition to their planetary observations, both Voyager spacecrafts were also tasked with interstellar missions. They were designed to continue scientific observations and signal transmission after escaping the heliosphere and exiting our solar system. They are both still active, with a projected lifetime of about five more years.
In 2006, NASA launched the New Horizons spacecraft with a primary mission of observing the dwarf planet Pluto. New Horizons was launched as the fastest man-made object ever launched from Earth with a speed of 36,400 mph. New Horizons started its flyby of Pluto on July 14, 2015. Three years later, in August of 2018, it confirmed the existence of a hydrogen wall previously observed by the Voyager launch.
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Astronomers have discovered a third planet in the Kepler-47 system, securing the system’s title as the most interesting of the binary-star worlds. Using data from NASA’s Kepler space telescope, a team of researchers, led by astronomers at San Diego State University, detected the new Neptune-to-Saturn-size planet orbiting between two previously known planets.
With its three planets orbiting two suns, Kepler-47 is the only known multi-planet circumbinary system. Circumbinary planets are those that orbit two stars.
The planets in the Kepler-47 system were detected via the “transit method.” If the orbital plane of the planet is aligned edge-on as seen from Earth, the planet can pass in front of the host stars, leading to a measurable decrease in the observed brightness. The new planet, dubbed Kepler-47d, was not detected earlier due to weak transit signals.
As is common with circumbinary planets, the alignment of the orbital planes of the planets change with time. In this case, the middle planet’s orbit has become more aligned, leading to a stronger transit signal. The transit depth went from undetectable at the beginning of the Kepler Mission to the deepest of the three planets over the span of just four years.
The SDSU researchers were surprised by both the size and location of the new planet. Kepler-47d is the largest of the three planets in the Kepler-47 system.
“We saw a hint of a third planet back in 2012, but with only one transit we needed more data to be sure,” said SDSU astronomer Jerome Orosz, the paper’s lead author. “With an additional transit, the planet’s orbital period could be determined, and we were then able to uncover more transits that were hidden in the noise in the earlier data.”
William Welsh, SDSU astronomer and the study’s co-author, said he and Orosz expected any additional planets in the Kepler-47 system to be orbiting exterior to the previously known planets. “We certainly didn’t expect it to be the largest planet in the system. This was almost shocking,” said Welsh. Their research was recently published in the Astronomical Journal.
With the discovery of the new planet, a much better understanding of the system is possible. For example, researchers now know the planets in in this circumbinary system are very low density – less than that of Saturn, the Solar System planet with the lowest density.
While a low density is not that unusual for the sizzling hot-Jupiter type exoplanets, it is rare for mild-temperature planets. Kepler-47d’s equilibrium temperature is roughly 50 degrees F (10 degrees C), while Kepler-47c is 26 degrees F ( 32 degrees C). The innermost planet, which is the smallest circumbinary planet known, is a much hotter 336 degrees F (169 degrees C).
The inner, middle, and outer planets are 3.1, 7.0, and 4.7 times the size of the Earth, and take 49, 187, and 303 days, respectively, to orbit around their suns. The stars themselves orbit each other in only 7.45 days; one star is similar to the Sun, while the other has a third of the mass of the Sun. The entire system is compact and would fit inside the orbit of the Earth. It is approximately 3340 light-years away in the direction of the constellation Cygnus.
“This work builds on one of the Kepler’s most interesting discoveries: that systems of closely-packed, low-density planets are extremely common in our galaxy,” said University of California, Santa Cruz astronomer Jonathan Fortney, who was not part of the study. “Kepler 47 shows that whatever process forms these planets – an outcome that did not happen in our solar system – is common to single-star and circumbinary planetary systems.”
Correction: A prior version of this article contained inaccuracies regarding the orbits of the Kepler-47 planets. This article has been updated to reflect the correct number of days it takes the inner, middle, and outer planets to orbit their suns: 49, 187 and 303 days respectively.
(THIS ARTICLE IS COURTESY OF THE NORTH CAROLINA NEWS AGENCY, THE VERGE)
A new discovery is strengthening the idea that a large, mysterious planet — known as Planet 9 or Planet X — may be lurking unseen at the Solar System’s edge. Astronomers say they have found a tiny object orbiting far out from the Sun that fits with the Planet X theory. In fact, the object may have even been pushed onto the path it takes now by this hidden planet’s gravity.
The tiny rock — eloquently named TG387 and nicknamed “The Goblin” — was spotted by astronomers at the Carnegie Institution of Science using a giant Japanese observatory in Hawaii called Subaru. The Carnegie team first spotted the object in 2015 and then followed it on its journey around the Sun for the last four years. Those observations revealed an incredibly distant target. TG387 takes a whopping 40,000 years to complete just one orbit around the Sun. And it’s on a very elliptical path far from the inner Solar System; the closest it ever gets to the Sun is 65 Astronomical Units (AU), or 65 times the distance between the Sun and the Earth. For reference, Pluto only gets as far as 49 AU’s from the Sun.
This orbit is particularly enticing since it puts TG387 in a select group of distant Solar System objects that all point to the possible existence of Planet X. Right now, there are 14 far-out space rocks that all share similar orbit patterns, suggesting that this planet is out there. Their paths are all super elongated, and they all cluster together in the same area when they approach the Sun. Plus, their orbits are all tilted alike, and they point in the same general direction, as if something big has pushed them into similar places. These objects are the strongest lines of evidence astronomers have for Planet X, and finding a new one that matches this pattern reinforces that idea that this planet is more than just a theory.
Plus, each new find helps astronomers narrow down where to look for Planet X. “Each time we find another one of these smaller objects, it will lead us to constrain where the bigger planet could be,” Scott Sheppard, an astronomer at Carnegie Science and the lead author of a study in The Astronomical Journal detailing the discovery, tells The Verge. “They’re all on very similar orbits, but their orbits are all slightly different, which [limits] where the planet could be.”
The idea that a giant planet is lurking beyond Neptune is an idea that astronomers have speculated for the last century. However, the hunt for this planet turned much more serious in 2012, when Sheppard and his team found a far-flung object that was truly unique. It was an object called VP113, and it currently holds the record for the most distant object orbiting the Sun. The closest it ever gets to the star is 80 AU’s, or 80 times the Earth-Sun distance. Sheppard noticed that this object also followed a path similar to those of a few other distant space rocks, as well as a far-off dwarf planet called Sedna. “They all have this clustering, and so that suggested that something was pushing them into similar types of orbits,” says Sheppard.
Then, in 2016, a pair of researchers from Cal Tech, Mike Brown and Konstantin Batygin, did the math. Based on the orbits of six of these objects, they estimated that there’s a planet roughly 10 times the mass of Earth orbiting far beyond Neptune. Their calculations showed that it possibly takes 10,000 to 20,000 years to orbit the Sun. Brown and Batygin dubbed the phantom planet “Planet 9,” though others had been calling it Planet X years before.
Since then, more and more objects have been found that fit this orbit pattern. The idea is that these objects are in just the right orbits needed to survive Planet X’s gravitational wrath. If they followed any other path, they would likely collide with the big planet or the planet’s gravity would send them hurtling out of the Solar System. However, all of these very distant extreme objects orbit in such a way that they never get close to Planet X when it crosses their orbits. “Whenever the planet is crossing the orbit of one of these objects, these objects are on the other side of the Solar System. So they never get close to each other,” says Sheppard.
But not all of these objects are as reliable narrators as they could be. “Among these 14 objects, some tell a more precise story than others,” Batygin, who was not involved with today’s study, tells The Verge. For one thing, some of the objects cross the orbit of Neptune, and that planet’s gravity might have some influence on the objects and warp their routes. “Neptune has the effect of muddying things up, even if you have an orbit carefully sculpted by Planet 9.” That makes it hard to know whether or not the object is truly pushed about by this unseen planet.
But this new discovery, TG387, is special because its orbit is so distant. When it’s farthest from the Sun, the rock will be at an extreme 2,300 AU’s away. In fact, it’s remarkable that astronomers found it all since it’s about seven times smaller than Pluto and so far off. But because of its extreme distance, TG387 is not influenced in any way by the large objects in the inner Solar System. Jupiter, Saturn, Uranus, and Neptune don’t have any effect on its orbit. That means if this object was truly batted around by Planet X, it might hold more information about the planet’s orbit than other objects do. And when the team ran simulations of the Solar System with a Planet X in it, they found that this object’s orbit isn’t subject to change. “This one joins an elite group of six objects that are stable,” says Batygin.
Of course, Planet X is nowhere near a done deal. There are only 14 objects that potentially support its existence. That’s a super low number by statistical standards. “We don’t have tens of these objects,” Michele Bannister, an astronomer studying distant small bodies at Queen’s University Belfast, who was not involved with this research, tells The Verge. “I’d be very happy if we had tens, but there’s barely even a handful.” Additionally, Bannister says it’s important to remember that astronomers still don’t have a comprehensive snapshot of the distant Solar System. The time of year, the weather, and the part of the sky a telescope observes all influence the kind of objects that are discovered out there, adding bias to the sample.
Plus, the objects that we find are typically on their closest approaches to the Sun on their super distant orbits, and that skews our discoveries a bit. For instance, TG387 was found when it was around 80 AU’s away, not thousands of AU’s away. That means we may not have a good idea of what all is out there because we can’t see the objects that are super far out on their orbits. “Each of these objects we detect is the tip of an iceberg for a larger population,” says Bannister. For every new discovery made, there must be hundreds of thousands of more objects that astronomers can’t see. And those objects could tell a different story than the Planet X one.
However, Bannister, who predicted that an object like TG387 could exist in the Solar System, does say this discovery is instrumental in helping to shape our understanding of the distant Solar System. We still don’t understand why there are objects like this one that are completely detached from the rest of the planets. “They’ve made a great discovery,” she says. “These are exactly the objects we need to be finding to understand the formation and history of our Solar System.”
Meanwhile, our best hope in the search for Planet X is to find more objects that corroborate its existence. “We don’t expect every object we find to fit this pattern, though that is what is happening right now,” says Sheppard. Better yet, finding Planet X would be pretty convincing, too. The problem is that there’s a lot of sky to scour and our telescopes don’t cover that much area at a time. The Subaru telescope in Hawaii is perhaps the best tool since it can observe the area of about six full Moons at a time. But it’s still tough to pinpoint the exact location of such a faraway, faint planet. “It’s a lot like looking for your target with a sniper rifle,” says Batygin. “You have to know where to look.”
But TG387 does help point astronomers in a slightly better direction. Before this discovery, there were about 30 orbits that Sheppard and his team thought Planet X could be on. Now, there are only 25 or so, he says. And the astronomers will be back at Subaru in mid-October to pick up the search. “We’ve covered about 30 percent of the prime area, and we hope by the end of this year, we’ll have covered 60 to 70 percent of that prime area,” says Sheppard.
If Planet X is found, then a whole new crop of questions will arise. Perhaps the biggest one of all is where did it come from? Most don’t think it’s possible for this planet to have formed where it is now. It likely formed in the inner Solar System and got flung outward, perhaps by Jupiter or Saturn. “That would suggest a lot of big things formed in our Solar System, and it was a very chaotic place in the formation era,” says Sheppard.
But before those questions can be answered, Planet X must be found. And those on the hunt are sure it will happen. “I’m really quite confident — about a 99 percent level of confidence — that Planet 9 is really out there,” says Batygin. “It might take on the order of a decade to find, but I’m quite confident it’s there.”
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Follow-up observations, detailed today in Nature, have found that the asteroid is dark and reddish, similar to the objects in the outer Solar System. It doesn’t have any gas or dust surrounding it like comets do, and it’s stretched long and skinny, looking a bit like an oddly shaped pen. It’s thought to be about a quarter-mile long, and about 10 times longer than it is wide. That makes it unlike any asteroids seen in our Solar System, none of which are so elongated.
Astronomers also think this object — nicknamed `Oumuamua, Hawaiian for “a messenger from afar arriving first”— traveled for millions of years before stumbling upon our Solar System. It seems to have come from the direction of the constellation Lyra, but the asteroid’s exact origin is still unknown. More answers might come soon, as NASA’s Hubble Space Telescope is observing `Oumuamua this week. “Our plan is to look at it through the end of the year, so we can get the very best pass possible and figure out where it came from,” Karen Meech, lead author of the study at the University of Hawaii’s Institute of Astronomy, tells The Verge.
`Oumuamua was first spotted on October 19th by astronomers working on the Pan STARRS telescope in Hawaii. The telescope is used to scan the sky for objects orbiting near Earth, looking for any that might pose a threat to our planet. But one of the rocks in the latest observations looked as if it might not belong in our neck of the Universe.
The team at Pan STARRS continued observing the object over the next couple of days. Based on their measurements, they were fairly certain that they were watching the first ever interstellar asteroid. Up until then, such a distant visitor had never been seen before, so observatories all over the world started following the object, too, in order to calculate its path and figure out its shape.
Interstellar asteroids are thought to be rejects from other planetary systems. When our Solar System first formed, for instance, the giant planets tossed around all the smaller bits of material circulating around the Sun, some of which landed in the outer edges of the Solar System while others were ejected from our neighborhood completely. These outcasts then traveled through interstellar space, possibly passing by other stars. Conceivably, ejected material from other planetary systems must make their way to our Solar System once in a while, says Meech.
Such interstellar objects are thought to pass through our Solar System pretty frequently, but they’re usually moving too fast, and they’re usually too faint to see. With `Oumuamua, astronomers got lucky: the asteroid entered our Solar System at an angle, coming in close by the Sun, and then passed by Earth on its way out of the Solar System. That gave astronomers the chance to catch it with ground-based telescopes. “I think it’s really neat that we had this visitor, however briefly, and we had a chance to look at it up close,” says Meech.
After it was first spotted, dozens of observatories all over the world continued to follow it over the next week and a half. Speed was crucial, since `Oumuamua is getting progressively farther away and growing fainter every day. “We had about a window of 10 days or two weeks to do anything practical,” says Meech. Through those quick observations, astronomers found that `Oumuamua had large fluctuations in brightness, indicating an unusually elongated, spinning object that makes one complete rotation every 7.3 hours.
Now, `Oumuamua is 124 million miles from Earth, zooming away at 85,700 miles per hour. It passed by Mars’ orbit on November 1st, and will reach Jupiter’s orbit sometime in 2018. Soon, it’ll be too hard to track, even with Hubble. “It’s really getting much too faint to do anything at all,” says Meech.
But in the next few years, we may be able to spot more interstellar objects like `Oumuamua. Once bigger telescopes start to come online, like the Large Synoptic Survey Telescope that’s being built in Chile, astronomers will be able to see even more visiting rocks. “I predict there will be a lot of these detected in the future,” says Meech.
By all accounts, the exoplanet known as WASP-19b is a pretty inhospitable place. As one of the closest known hot-Jupiters to its star—orbiting just two percent of the distance between the Earth and the Sun—it’s home to a scorchingly hot, violent atmosphere. The side of the planet which always faces the star churns with massive convection currents, dredging up heavier molecules from the planet’s lower layers.
Unsuitable for life as it may be, WASP-19b’s proximity to its star happened to make it a perfect candidate for atmospheric observation. A paper published Wednesday in the journal Nature has found the very first evidence of titanium oxide on any known exoplanet, in the upper atmosphere of WASP-19b. And that’s significant for a number of reasons.
“We will be able to constrain models and understand the structure of these atmospheres [and] where they were formed,” Elyar Sedaghati, European Southern Observatory astronomer and co-author of the study, told Gizmodo. “Because if we know what’s in the atmosphere, we can turn the clock back a little bit.”
WASP-19 is a pretty average star about 815 light years away from us, located in the Vela constellation. Its only known planet, WASP-19b, was detected by the Wide Angle Search for Planets in 2009, and it only takes three quarters of a day to orbit its star. That proximity made it a perfect target for a spunky little spectrograph called FORS2 (FOcal Reducer and low dispersion Spectrograph), which was originally installed to the Very Large Telescope in Chile in 1999, almost 20 years ago. But there was work to do before observations could begin.
“[The instrument] had to be upgraded,” said Sedaghati. “All that meant was basically replacing these two prisms that correct for some atmospheric distortions as the star goes near the horizon. These were causing some issues in the exoplanet observations that we were doing with this. So, in November 2014 we made the exchange.” He also hopes with these initial promising results, they go back and do even more improvements on the venerable device.
The researchers began peering at WASP-19b around that time, and they got some intriguing data in something called a light curve, which is the measure of how much the light dims when a planet transits a star. Spectrographs work by observing the light emitted by an object and breaking it into its spectra, much like when you shine white light through a prism and it turns into a rainbow. Using this data, you can determine what kind of chemicals are present in whatever the light is shining through. Because this particular planet is so close to its star, the researchers could see the spectra of its ferociously roiling atmosphere, which extends way further into space than, say, the atmosphere of a more distant gas giant like Jupiter does.
Getting better at decoding the atmospheres of exoplanets, even inhospitable ones like WASP-19b, will contribute to the holy grail of exoplanet research: hunting for signs of life. “Methane — that could be in combination with other molecules, a sign of life — will have very similar absorption features with titanium oxide. This basically gives us hope for future observations for example with the James Webb Telescope,” said Sedaghati.
“It’s a very nice result,” said Sara Seager, a professor of planetary sciences and physics at MIT, in an email. “I can say this is an outstanding achievement from a ground-based telescope and nature delivered us a fantastic hot planet atmosphere. So far, too many planets are literally “clouded out” and we can’t observe any spectral features. [Titanium Oxide] seems obscure, but is actually a very strong absorber—kind of like a skunk smell, only a tiny amount can make a difference.”
Seager says planets like WASP-19b have a “treasure trove” of features which are really useful to observe.
“It’s an amazing relief to see that planet atmospheres are behaving as expected. Hot planet atmospheres can be nearly as hot as cool star atmospheres and the cool stars are dominated by TiO,” she said.
Jonathan Fortney, an expert in exoplanet atmospheres at UC Santa Cruz, actually predicted that metal oxides would be present in nearby hot-Jupiters. But he admits discoveries in the field will be slow for now because most “general use” instruments can’t pick up the level of detail required for terrestrial exoplanetary atmospheric analysis. Even though the FORS2 tool has been really successful in this project, it was installed before we had even discovered exoplanets using the transit method.
“To me this shows that understanding exoplanet atmospheres is an extremely challenging observational field,” he said. “We must be thoughtful in how we design instruments to detect and understand exoplanet atmospheres. And we must be patient. I really think that this long time lag will be repeated, likely on an even longer time scale, for the atmospheres of temperate terrestrial planets.”
As the study of exoplanet atmospheres continues, be prepared to see stories of successful characterization where the evidence is a little sketchy, Fortney warns.
“People will make claims about these atmospheres, some will end up being correct, some will end up not being correct, and it will take a lot of time for the field to settle out, to correct itself. It will be exciting, but not clear-cut in the first findings,” said Fortney.
Bryson is a freelance storyteller who wants to explore the universe with you.
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