When astronomers discovered the first worlds orbiting other stars thirty years ago, they also began to accept what might be called galactic planetary census, counting the number and types of exoplanets in the Milky Way. While it is impossible to carefully study all the hundreds of billions of stars in our galaxy, a representative sample of them can provide important information. By studying the planetary population of such a sample, researchers hope to learn which worlds are most common and which are rare, and how our own Earth and solar system relate to them.

But there are several different ways to find planets, and each works best on different types of worlds, which can lead to skewed results. The currently dominant methods infer the presence of a planet by looking for its subtle influence on its star, and they are most sensitive to giant planets very close to their stars. The orbital “years” of such worlds are only a few days or weeks, and they do not exist in the solar system. In contrast, direct viewing of planets—so-called direct imaging—needs to distinguish them from the blinding brilliance of a star, which is easiest to do for giant planets on the outskirts of the system. If such orbits revolved around our own Sun, most of these planets would be located far beyond Pluto.

Fortunately, new methods and larger datasets now allow scientists to bridge the gap between these extremes by combining results from multiple planet-searching methods to get a clearer picture of the Milky Way’s true planetary population. A new study published in The science is one of the first successes in this synergistic approach, which gives not only a newfound “in the middle of the road” planet, but also a broader strategy for finding and exploring many others. The largest and brightest of those planets to be discovered could also be good candidates for future direct studies, potentially allowing astronomers to discern their atmosphere and climate.

“When we unite [motion and imagery] together we get all three key properties of a planet — its orbit, its mass, and its atmosphere — so we learn a lot more,” says Thane Curry, planetary researcher at NASA’s Ames Research Center and lead author of the study.

catch a star

Curry and colleagues found their new planet, a giant world called HIP 99770 b, by comparing its star motion data collected in 2021 by the European Space Agency’s Gaia spacecraft with similar but less accurate measurements taken in the early 1990s. predecessor of Gaia. , an ESA Hipparcos satellite. Gaia and Hipparcos were intended to map the stars of the Milky Way (not its planets) using a technique called astrometry to accurately track stellar positions, distances, and movements. But astrometry can also reveal planets: a planet orbiting a star can cause a cyclic, very slight shift in the star’s position, oscillating back and forth in the plane of the sky. By determining the size and frequency of this shift, astronomers can determine the mass and orbit of the invisible planet.

The initial discovery of the planet and subsequent photographic observations were only possible thanks to several decades of Gaia-Hipparcos data, which made it possible to detect the long orbit of HIP 99770 b. The unified catalog itself has been in the making for years. After the first release of the Gaia data in 2016, Timothy Brandt, an astronomer at the University of California at Santa Barbara and co-author of the new study, published a list of tens of thousands of stars, reconciled and augmented by earlier Hipparcos data. observations, updating them again in 2021 after the last release of Gaia data. The result was an approximately 25-year window into how these stars moved across the sky.

Several teams have begun deepening a new database of stellar companions, “each in their own way determining exactly what information to consider when choosing a target,” says Caroline Morley, a researcher who studies exoplanet atmospheres at the University of Texas at Austin. part of a new study.

In the case of HIP 99770 b, the Gaia-Hipparcos data showed it to be a gas giant world orbiting its star at a distance slightly greater than Uranus from the Sun—large, bright, and far enough away from its stellar host to be within range of . reach of direct visualization. Subsequent observations with the SCExAO Direct Imaging Instrument on the Subaru Telescope at Mauna Kea in Hawaii confirmed these suspicions, revealing the planet as a dot obscured by molecules of water vapor and carbon monoxide. Climate models suggest that the temperature on the planet is between 1300 and 1400 kelvins (1880 to 2060 Fahrenheit). Although HIP 99770 b is clearly unearthly, its overall properties make it a relatively close relative of Earth.

“This is the first [finding from this database] it can actually state, “It’s probably a planetary mass,” says Beth Biller, who was not part of the research team. Biller, an astronomer at the University of Edinburgh in Scotland, further noted that the heavy world is in the gray zone between a planet and a brown dwarf, and that some may object to classifying it as a planet. Regardless, “this is definitely the least mass object detected by this method,” she says.

Worth a thousand words

Results like these could help fill in the remaining gaps in the galactic planetary census. In addition to being limited to very large planets in very wide orbits, current direct imaging efforts work best for very young worlds—10 to 100 million years old—and still glowing with the heat left over from their formation. The cumulative result of all these previous polls, according to Biller, was important but still underwhelming. “We found that [hot, young, wide-orbiting] giant planets are quite rare,” she says.

While many stars are expected to have some kind of planet in orbit, direct imaging studies have shown that far fewer stars have giant planets on their edges. Infrared images allow a better understanding of the atmosphere of these worlds, and models give an estimate of their mass. Of the dozens of exoplanets captured by direct images, astronomers have been able to more accurately narrow down the mass of only two using follow-up measurements with indirect planet detection techniques. Part of the problem is the pre-existing preference for observing young planets, which accordingly have young host stars that are much more active than more mature stars and therefore more damaging to stellar measurements of the companion’s mass.

“If you have a directly imaged planet, there is a certain amount of guesswork in confirming its physical properties,” says Brandt. Combining astrometry and direct imaging not only opens the door to detecting more targets; it also eliminates some of that guesswork by revealing the orbit and mass of each new planet, along with its atmosphere.

While Gaia targets two billion stars, Hipparcos has only studied 100,000, all relatively bright and close to Earth. Curry estimates that about a third of the stars studied in the combined catalog have companions, most of which are low-mass. If only one in 100 cataloged stars with satellites has a planet that can be photographed, a new confluence of planet detection methods should greatly increase the total number of worlds that astronomers will soon be able to see directly. The researchers say that by the end of their decade-long study, Gaia will be able to identify up to 100 additional planets as candidates for direct imaging with current instruments — more than four times as many directly imaged worlds as have been identified to date. And it will expand our knowledge of planetary systems beyond the youngest and brightest, perhaps showing more worlds like ours.

“The yield of new discoveries is higher than what we could get if we just did a blind search,” says Curry, “and the information we get is much richer than if we just did direct images.”

But snow – as much as possible – is at the heart of the Camman family business, North American Weather Consultants, based in Utah, which has cloud seeding contracts in the US west, centered in the Rocky Mountains.

Business has been on the rise lately. During two decades of drought in the Rocky Mountains, cloud seeding is gaining momentum, using aircraft or ground equipment to transfer rain and snow particles into clouds.

Colorado has added three new programs in the past five years. Wyoming, which began seeding in 2014, added an air program in 2018. Utah has been steadily increasing its fleet of cloud seeding equipment, and the state legislature just record funding to further expand programs and research.

Much of the growth is due to severe drought, which is putting pressure on the Colorado River and its tributaries, which supply water to millions of people from Wyoming to Los Angeles.

Not everyone thinks cloud filling is worth it. Some experts say conserving water is the best and more down to earth way to ensure you get enough water. Squeezing the juice out of the clouds to get a little more rainfall is a dubious alternative, they say.

“It’s always easier to talk about how to get more water than how to use less,” says Kathryn Sorensen of the Kyl Center for Water Policy at Arizona State University at Tempe. on the Colorado River, the numbers are so high that the solutions are actually to use less, especially in the agricultural sector. From a political standpoint, it’s really painful.”

But in the Rocky Mountains, cloud seeding these days has the full support of local and state officials looking to find a low-cost way to refill streams, rivers, and especially the large reservoirs of the Colorado River system, which hit record lows last year.

Their approach is to shoot silver iodide at clouds, where moisture binds to particles, forms ice, and falls as snow. This snowpack high in the mountains serves as a year-round cold storage for water that is released when it melts.

In Wyoming, cloud seeding by aircraft attempts to increase snow cover on the western side of the Wind River Mountains, so snowmelt flows into the Green River and downstream communities, eventually reaching the Colorado River and its reservoirs, including Lakes Powell and Lake Mead.

“Cloud seeding creates water that didn’t exist before,” said Brian Seppi, general manager of the United Water Council, which provides water to communities in southwestern Wyoming. “It’s just a benefit to the whole system.”

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When the weather is dry in the West and water is scarce—where they say whiskey is for drinking and water is for fighting—those who have long-established water rights are favored. And the sharing of increasingly limited water has led states to clash against each other.

However, filling in the clouds has become a partial solution that they can agree on.

Water suppliers in the lower Colorado River basin contribute about $1.5 million per year to the seeding of clouds in the Upper Basin, where melting snow feeds the river. The federal government recently announced a $2.4 million contribution to this effort, a nod to desperate times.

Despite increased attention, cloud seeding has been used worldwide and in the Rocky Mountains for over 50 years.

Cloud seeding in the US was “oversold” and federal funding dried up in the 1990s and early 2000s, said Frank McDonough, a scientist at the Desert Research Institute in Reno, Nevada.

“Water managers at the local level knew it was working, so they continued to fund it from the states,” McDonnow said. “Now there is new evidence that it actually works.”

A study Aerial seeding in Idaho in 2017 showed a clear pattern of snowfall on the radar, reflecting the seeding and indicating that the method was working.

Utah counted the number of additional water clouds formed there. In 2018, he added 186,000 acre feet of water, or nearly 12%, to the state’s water supply, according to the agency. analysis Department of Water Resources. The agency says the cost was $2.18 per acre-foot, a fraction of the $20 California farmers pay for that amount of water.

“That cost per acre foot was so low that it wasn’t a problem,” said Jake Serago, a water resources engineer with the division.

But Sarah Tessendorf of the National Center for Atmospheric Research said more research is needed to conclusively show how much extra water is being created through cloud seeding.

“People often want to know what extra percentage of precipitation has formed,” said Tessendorf, co-author of the Idaho cloud seeding study.

Silver iodide can have a minimal effect on some clouds and a strong effect on others, so the most important thing is how much is produced over the entire winter season, she says. “We do not yet have answers to this question, but we hope to have them in the next few years thanks to the results of our new computer model.”

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In the foothills north of Boulder, the first cloud seeding project is underway in the rapidly growing urban corridor of the Rocky Mountains north and south of Denver. This winter, two ground-based generators pumped silver iodine into the air for the St. Vrain and Left Hand areas.

Each is a two-wheeled trailer containing a tank of silver iodide released by a roaring propane-fueled flame on a metal mast. There is a communication antenna for signals to turn the generator on and off depending on the conditions.

The right conditions—wet weather blowing uphill from the east—happened a couple of times a month, according to Scott Griebling, the county’s water engineer.

The problem in the Rocky Mountains lately is not that there is too little snow. Due to the wet spring, some cloud seeding generators have been shut down due to concerns that heavy snowfall is already enough to cause flooding.

Among those idle are generators in the Sierra Madre range in southern Wyoming, where snow cover rivals the deepest on record, said Jonathan Bowler of the Savery Little Snake River Water Conservation District, which monitors runoff.

“You kind of live and die from the humidity here,” Bowler said. “Too dry is one extreme, and too wet is the other. But no matter what it gives you, you just have to do something.”

Long-term averages are important to the Wyoming Water Development Commission, which is responsible for the state’s cloud seeding program, according to Chairman Ron Cayley, Jr. “You have to consider the good years, the bad years, and everything in between to determine how successful the program is,” Kaylie said.

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North American Weather Consultants has been in the cloud seeding business for over 40 years. Cummans, who has a background in physics, chemistry and computer software, bought the company four years ago.

After expanding sites, including at the Colorado front for a pilot program in the Boulder area, North American Weather Consultants now has about 250 ground sites and two aircraft in use in the US west. Cammans now has about 20 employees, including meteorologists and his brothers. .

“As soon as favorable conditions arise, we will get to work,” he said. “We have a pilot who will take off and fly if conditions are favorable for aerial seeding. We have remote controlled equipment that meteorologists can control from their home offices.”

Many of the company’s ground-based generators are turned on and off manually by approximately 150 paid contractors, some of whom are on their own land.

Cummans often reserves these hardest jobs for his brothers Parker and Carver, who drive trucks with studded 35-inch (1-meter) tires suited to snow and mud.

“They do one of the most interesting and unreliable jobs,” he said.

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Follow Brittany Peterson on Twitter: @BrittanyPeters and Mid Grover: @meadgruber

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Now that we think about the future of the Earth, we know that there are two main factors that people need to live here.

First, the sun provides most of the energy that living things on Earth need to survive. Plants use sunlight to grow and produce oxygen. Animals, including humans, directly or indirectly rely on plants for food and oxygen.

Another thing that makes the Earth habitable is that the surface of our planet is constantly moving and shifting. This ever-changing surface environment creates weather patterns and chemical changes in the oceans and continents. allowed life to develop on Earth.

Movement giant chunks of the outer layer of the earth, which are called tectonic plates, move due to heat in the bowels of the Earth. This heat source will keep the Earth’s interior hot. for billions of years.

So what will change? Scientists have calculated that the sun will still shine 5 billion years. But gradually it will become brighter and brighter, warming the Earth more and more.

This warming is so slow that we would not notice it. In about 1 billion years, our planet will be too hot to support the oceans on its surface necessary for life. Considering that the average human life expectancy about 73 years old this is about 13 million human lives.

Many years later – in about 5 billion years – our Sun will grow into an even larger star, which astronomers call a “red giant”, which will eventually swallow the Earth. Just as our planet existed for more than 4 billion years before the appearance of man, it will exist for another 4 to 5 billion years after it becomes unsuitable for human life.

Shichun Huang is Associate Professor of Earth and Planetary Sciences at the University of Tennessee.

This article has been reprinted from Talk under a Creative Commons license. you can find original article Here.