Tag: planetary systems (page 1 of 2)

Adam Kadmon Race – Part 3 – Metatron – August – 14 – 2016

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Guiding Our Search for Life on Other Earths

The James Webb Telescope

Excerpt from space.com

A telescope will soon allow astronomers to probe the atmosphere of Earthlike exoplanets for signs of life. To prepare, astronomer Lisa Kaltenegger and her team are modeling the atmospheric fingerprints for hundreds of potential alien worlds. Here's how:
The James Webb Space Telescope, set to launch in 2018, will usher a new era in our search for life beyond Earth. With its 6.5-meter mirror, the long-awaited successor to Hubble will be large enough to detect potential biosignatures in the atmosphere of Earthlike planets orbiting nearby stars.
And we may soon find a treasure-trove of such worlds. The forthcoming exoplanet hunter TESS (Transiting Exoplanet Survey Satellite), set to launch in 2017, will scout the entire sky for planetary systems close to ours. (The current Kepler mission focuses on more distant stars, between 600 and 3,000 light-years from Earth.) 

Astronomer Lisa Kaltenegger

While TESS will allow for the brief detection of new planets, the larger James Webb will follow up on select candidates and provide clues about their atmospheric composition. But the work will be difficult and require a lot of telescope time.
"We're expecting to find thousands of new planets with TESS, so we'll need to select our best targets for follow-up study with the Webb telescope," says Lisa Kaltenegger, an astronomer at Cornell University and co-investigator on the TESS team.
To prepare, Kaltenegger and her team at Cornell's Institute for Pale Blue Dots are building a database of atmospheric fingerprints for hundreds of potential alien worlds. The models will then be used as "ID cards" to guide the study of exoplanet atmospheres with the Webb and other future large telescopes.
Kaltenegger described her approach in a talk for the NASA Astrobiology Institute's Director Seminar Series last December.
"For the first time in human history, we have the technology to find and characterize other worlds," she says. "And there's a lot to learn."

Detecting life from space  

In its 1990 flyby of Earth, the Galileo spacecraft took a spectrum of sunlight filtered through our planet's atmosphere. In a 1993 paper in the journal Nature, astronomer Carl Sagan analyzed that data and found a large amount of oxygen together with methane — a telltale sign of life on Earth. These observations established a control experiment for the search of extraterrestrial life by modern spacecraft.
"The spectrum of a planet is like a chemical fingerprint," Kaltenegger says. "This gives us the key to explore alien worlds light years away."
Current telescopes have picked up the spectra of giant, Jupiter-like exoplanets. But the telescopes are not large enough to do so for smaller, Earth-like worlds. The James Webb telescope will be our first shot at studying the atmospheres of these potentially habitable worlds.
Some forthcoming ground-based telescopes — including the Giant Magellan Telescope (GMT), planned for completion in 2020, and the European Extremely Large Telescope (E-ELT), scheduled for first light in 2024 — may also be able to contribute to that task. [The Largest Telescopes on Earth: How They Compare]
And with the expected discovery by TESS of thousands of nearby exoplanets, the James Webb and other large telescopes will have plenty of potential targets to study. Another forthcoming planet hunter, the Planetary Transits and Oscillations of stars (PLATO), a planned European Space Agency mission scheduled for launch around 2022-2024, will contribute even more candidates.
However, observation time for follow-up studies will be costly and limited.
"It will take hundreds of hours of observation to see atmospheric signatures with the Webb telescope," Kaltenegger says. "So we'll have to pick our targets carefully."

Giant Magellan Telescope
Set to see its first light in 2021, The Giant Magellan Telescope will be the world’s largest telescope.

Getting a head start

To guide that process, Kaltenegger and her team are putting together a database of atmospheric fingerprints of potential alien worlds. "The models are tools that can teach us how to observe and help us prioritize targets," she says.
To start, they have modeled the chemical fingerprint of Earth over geological time. Our planet's atmosphere has evolved over time, with different life forms producing and consuming various gases. These models may give astronomers some insight into a planet's evolutionary stage.
Other models take into consideration the effects of a host of factors on the chemical signatures — including water, clouds, atmospheric thickness, geological cycles, brightness of the parent star, and even the presence of different extremophiles.
"It's important to do this wide range of modeling right now," Kaltenegger said, "so we're not too startled if we detect something unexpected. A wide parameter space can allow us to figure out if we might have a combination of these environments."
She added: "It can also help us refine our modeling as fast as possible, and decide if more measurements are needed while the telescope is still in space. It's basically a stepping-stone, so we don't have to wait until we get our first measurements to understand what we are seeing. Still, we'll likely find things we never thought about in the first place."

A new research center

The spectral database is one of the main projects undertaken at the Institute for Pale Blue Dots, a new interdisciplinary research center founded in 2014 by Kaltenegger. The official inauguration will be held on May 9, 2015.
"The crux of the institute is the characterization of rocky, Earth-like planets in the habitable zone of nearby stars," Kaltenergger said. "It's a very interdisciplinary effort with people from astronomy, geology, atmospheric modeling, and hopefully biology."
She added: "One of the goal is to better understand what makes a planet a life-friendly habitat, and how we can detect that from light years away. We're on the verge of discovering other pale blue dots. And with Sagan's legacy, Cornell University is a really great home for an institute like that."

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Young Jupiter wiped out solar system’s early inner planets, study says

(Photo : NASA/ESA) In early days of solar system, Jupiter destroyed everything that came in its way, researchers have found.

Excerpt from latimes.com

Before Mercury, Venus, Earth and Mars occupied the inner solar system, there may have been a previous generation of planets that were bigger and more numerous – but were ultimately doomed by Jupiter, according to a new study.

If indeed the early solar system was crowded with so-called super-Earths, it would have looked a lot more like the planetary systems found elsewhere in the galaxy, scientists wrote Monday in the Proceedings of the National Academy of Sciences.

Inner planets
As NASA’s Kepler space telescope has found more than 1,000 planets in orbit around other stars, along with more than 4,000 other objects that are believed to be planets but haven’t yet been confirmed. Kepler finds these planets by watching their host stars and registering tiny drops in their brightness – a sign that they are being ever-so-slightly darkened by a planet crossing in front of them.

In addition, ground-based telescopes have detected hundreds of exoplanets by measuring the wiggles of distant stars. Those stars wiggle thanks to the gravitational pull of orbiting planets, and the Doppler effect makes it possible to estimate the size of these planets.

The more planetary systems astronomers discovered, the more our own solar system looked like an oddball. Exoplanets – at least the ones big enough for us to see – tended to be bigger than Earth, with tight orbits that took them much closer to their host stars. In multi-planet systems, these orbits tended to be much closer together than they are in our solar system. For instance, the star known as Kepler-11 has six planets closer to it than Venus is to the sun.

Why does our solar system look so different? Astrophysicists Konstantin Batygin of Caltech and Greg Laughlin of UC Santa Cruz summed it up in one word: Jupiter.

Here’s what could have happened, according to their models:

In Solar System 1.0, the region closest to the sun was occupied by numerous planets with masses several times bigger than that of Earth. There were also planetesimals, “planetary building blocks” that formed within the first million years after the birth of the sun, Batygin and Laughlin wrote.

This is how things might have stayed if the young Jupiter had stayed put at its initial orbit, between 3 and 10 astronomical units away from the sun. (An astronomical unit, or AU, is the distance between the Earth and the sun. Today, Jupiter’s orbit ranges between 5 and 5.5 AUs from the sun.)

But Jupiter was restless, according to a scenario known as the “Grand Tack.” In this version of events, Jupiter was swept up by the currents of gas that surrounded the young sun and drifted toward the center of the solar system.

Jupiter, however, was too big to travel solo. All manner of smaller objects would have been dragged along too. With so many bodies in motion, there would have been a lot of crashes.

The result was “a collisional cascade that grinds down the planetesimal population to smaller sizes,” the astrophysicists wrote. For the most part, these planetary crumbs were swept toward the sun and ultimately destroyed, like disintegrating satellites falling back to Earth.

The planetesimals wouldn’t have been Jupiter’s only victims. Assuming the early solar system resembled the planetary systems spied by Kepler and other telescopes, there would have been “a similar population of first-generation planets,” the pair wrote. “If such planets formed, however, they were destroyed.”

Jupiter probably got about as close to the sun as Mars is today before reversing course, pulled away by the gravity of the newly formed Saturn. That would have ended the chaos in the inner solar system, allowing Earth and the other rocky planets to form from the debris that remained.

“This scenario provides a natural explanation for why the inner Solar System bears scant resemblance to the ubiquitous multi-planet systems” discovered by Kepler and other survey efforts, Batygin and Laughlin wrote.

Although their models show that this is what might have happened, they don’t prove that it actually did. But there may be a way to get closer to the truth.

The scientists’ equations suggest that if a star is orbited by a cluster of close-in planets, there won’t be a larger, farther-out planet in the same system. As astronomers find more exoplanetary systems, they can see whether this prediction holds up.

Also, if far-away solar systems are experiencing a similar series of events, telescopes ought to be able to detect the extra heat thrown off by all of the planetesimal collisions, they added.

Sadly for those hoping to find life on other planets, the pair’s calculations also imply that most Earth-sized planets are lacking in water and other essential compounds that can exist in liquid or solid form. As a result, they would be “uninhabitable,” they wrote.

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Water and Unique Lifeforms are Highly Possible in Countless Unexplored Planets Within our Galaxy

Excerpt from esbtrib.com 

Imagine the distinct possibility that among the billions of stars located in our vast Milky Way Galaxy, there might be a habitable zone where water probably exists and life as we know it as well.
Scientists have studied more than 150 exoplanetary systems with more than one planet circling the host star, thru the Kepler space telescope of NASA.
The new research, published in Monthly Notices of the Royal Astronomical Society, revealed the thousands of planets orbiting stars in our Milky Way galaxy.  Researchers were able to compute that the stars in the Milky Way have one to three planets orbiting the habitable zone.
PhD student in the research group Astrophysics and Planetary Science at the Niels Bohr Institute at the University of Copenhagen, Steffen Kjær Jacobsen said, “In these 31 planetary systems located near the habitable zone, our calculations showed that there was an average of two planets in the habitable zone. According to statistics and the indications we have, a good share of the planets in the habitable zone will be solid planets where there might be liquid water and where life could exist.”
He added,   “In 124 of the planetary systems, the Titius-Bode law fit with the position of the planets as good as or better than our own solar system. Using Titus-Bode’s law we tried to predict where there could be more planets further out in the planetary systems. But we only made calculations for planets where there is a good chance you can see them with the Kepler satellite,”
Researchers urged other scientist to look further  into the records from the Kepler satellite again for more signs of the planetary systems they have predicted, as a number  of them should be quite apparent.
Will this change our perception of religion? That we are not God’s only living creation?

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Have Aliens Left The Universe? Theory Predicts We’ll Follow

Excerpt from robertlanza.com

In Star Wars, the bars are bustling with all types of alien creatures. And then, of course, there’s Yoda and Chewbacca. Recently, renowned scientist Stephen Hawking stated that he too believes aliens exist: “To my mathematical brain, the numbers alone make thinking about aliens perfectly rational.”

Hawking thinks we should be cautious about interacting with aliens — that they might raid Earth’s resources, take our ores, and then move on like pirates. “I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach.”
But where are they all anyhow?

For years, NASA and others have been searching for extraterrestrial intelligence. The universe is 13.7 billion years old and contains some 10 billion trillion stars. Surely, in this lapse of suns, advanced life would have evolved if it were possible. Yet despite half a century of scanning the sky, astronomers have failed to find any evidence of life or to pick up any of the interstellar radio signals that our great antennas should be able to easily detect.

Some scientists point to the “Fermi Paradox,” noting that extraterrestrials should have had plenty of time to colonize the entire galaxy but that perhaps they’ve blown themselves up. It’s conceivable the problem is more fundamental and that the answer has to do with the evolutionary course of life itself.

Look at the plants in your backyard. What are they but a stem with roots and leaves bringing nutriments to the organism? After billions of years of evolution, it was inevitable life would acquire the ability to locomote, to hunt and see, to protect itself from competitors. 
Observe the ants in the woodpile — they can engage in combat just as resolutely as humans. Our guns and ICBM are merely the mandibles of a cleverer ant. The effort for self-preservation is vague and varied. But when we’ve overcome our struggles, what do we do next? Build taller and more splendid houses?

What happens after life completes its transition to perfection? Perhaps across space, more advanced intelligences have taken the next evolutionary step. Perhaps they’ve evolved beyond the three dimensions we vertebrates know. A new theory — Biocentrism — tells us that space and time aren’t physical matrices, but simply tools our mind uses to put everything together. These algorithms are the key to consciousness, and why space and time — indeed the properties of matter itself — are relative to the observer. More advanced civilizations would surely understand these algorithms well enough to create realities that we can’t even imagine, and to have expanded beyond our corporeal cage.

Like breathing, we take for granted how our mind puts everything together. I can recall a dream I had of a flying saucer landing in Times Square. It was so real it took awhile to convince myself that it was a dream (that I was actually at home in bed). I was standing in a crowd surrounded by skyscrapers when a massive spaceship appeared overhead. Everyone started running. My mind had somehow generated this spatio-temporal experience out of electrochemical information. I could feel the vibrations under my feet as the ship started to land, merging this 3D world with my inner thoughts and sensations.

Although I was in bed with my eyes closed, I was able to run and move my arms and fingers. My mind had created a fully functioning body and placed it in a virtual world (replete with clouds in the sky and the Sun) that was indistinguishable from the one I’m in right now. Life as we know it is defined by this spatial-temporal logic, which traps us in the universe of up and down. But like my dream, quantum theory confirms that the properties of particles in the “real” world are also observer-determined.

Other information systems surely exist that correspond to other physical realities, universes based on logic completely different from ours and not based on space and time as we know it. In fact, the simplest invertebrates may only experience existence in one dimension of space. Evolutionary biology suggests life has progressed from a one dimensional reality, to two dimensions to three dimensions, and there’s no scientific reason to think that the evolution of life stops there.

Advanced civilizations would certainly have changed the algorithms so that instead of being trapped in the linear dimensions we find ourselves in, their consciousness moves through the multiverse and beyond. Why would Aliens build massive ships and spend thousands of years to colonize planetary systems (most of which are probably useless and barren), when they could simply tinker with the algorithms and get whatever they want?

Life on Earth is just beginning to send its shoots upward into the heavens. We’ve even flung a piece of metal outside the solar system. Affixed to the spacecraft is a record with greetings in 60 languages. One can’t but wonder whether some civilization more advanced than ours will come upon it. Or will it just drift across the gulf of space? To me the answer is clear. But in case I’m wrong, I have a pitch fork guarding the ore in my backyard.

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Earth’s Moon May Not Be Critical to Life Afterall

Excerpt from space.com

The moon has long been viewed as a crucial component in creating an environment suitable for the evolution of complex life on Earth, but a number of scientific results in recent years have shown that perhaps our planet doesn't need the moon as much as we have thought.

In 1993, French astronomer Jacques Laskar ran a series of calculations indicating that the gravity of the moon is vital to stabilizing the tilt of our planet. Earth's obliquity, as this tilt is technically known as, has huge repercussions for climate. Laskar argued that should Earth's obliquity wander over hundreds of thousands of years, it would cause environmental chaos by creating a climate too variable for complex life to develop in relative peace.
So his argument goes, we should feel remarkably lucky to have such a large moon on our doorstep, as no other terrestrial planet in our solar system has such a moon. Mars' two satellites, Phobos and Deimos, are tiny, captured asteroids that have little known effect on the Red Planet. Consequently, Mars' tilt wobbles chaotically over timescales of millions of years, with evidence for swings in its rotational axis at least as large as 45 degrees. 

The stroke of good fortune that led to Earth possessing an unlikely moon, specifically the collision 4.5 billion years ago between Earth and a Mars-sized proto-planet that produced the debris from which our Moon formed, has become one of the central tenets of the 'Rare Earth' hypothesis. Famously promoted by Peter Ward and Don Brownlee, it argues that planets where everything is just right for complex life are exceedingly rare.

New findings, however, are tearing up the old rule book. In 2011, a trio of scientists — Jack Lissauer of NASA Ames Research Center, Jason Barnes of the University of Idaho and John Chambers of the Carnegie Institution for Science — published results from new simulations describing what Earth's obliquity would be like without the moon. What they found was surprising.

"We were looking into how obliquity might vary for all sorts of planetary systems," says Lissauer. "To test our code we began with integrations following the obliquity of Mars and found similar results to other people. But when we did the obliquity of Earth we found the variations were much smaller than expected — nowhere near as extreme as previous calculations suggested they would be."
Lissauer's team found that without the moon, Earth's rotational axis would only wobble by 10 degrees more than its present day angle of 23.5 degrees. The reason for such vastly different results to those attained by Jacques Laskar is pure computing power. Today's computers are much faster and capable of more accurate modeling with far more data than computers of the 1990s.

Lissauer and his colleagues also found that if Earth were spinning fast, with one day lasting less than 10 hours, or rotating retrograde (i.e. backwards so that the sun rose in the West and set in the East), then Earth stabilized itself thanks to the gravitational resonances with other planets, most notably giant Jupiter. There would be no need for a large moon. 

Earth's rotation has not always been as leisurely as the current 24 hour spin-rate. Following the impact that formed the moon, Earth was spinning once every four or five hours, but it has since gradually slowed by the moon's presence. As for the length of Earth's day prior to the moon-forming impact, nobody really knows, but some models of the impact developed by Robin Canup of the Southwest Research Institute, in Boulder, Colorado, suggest that Earth could have been rotating fast, or even retrograde, prior to the collision.

Tilted Orbits
Planets with inclined orbits could find that their increased obliquity is beneficial to their long-term climate – as long as they do not have a large moon.

"Collisions in the epoch during which Earth was formed determined its initial rotation," says Lissauer. "For rocky planets, some of the models say most of them will be prograde, but others say comparable numbers of planets will be prograde and retrograde. Certainly, retrograde worlds are not expected to be rare."

The upshot of Lissauer's findings is that the presence of a moon is not the be all and end all as once thought, and a terrestrial planet can exist without a large moon and still retain its habitability. Indeed, it is possible to imagine some circumstances where having a large moon would actually be pretty bad for life.

Rory Barnes, of the University of Washington, has also tackled the problem of obliquity, but from a different perspective. Planets on the edge of habitable zones exist in a precarious position, far enough away from their star that, without a thick, insulating atmosphere, they freeze over, just like Mars. Barnes and his colleagues including John Armstrong of Weber State University, realized that torques from other nearby worlds could cause a planet's inclination to the ecliptic plane to vary. This in turn would result in a change of obliquity; the greater the inclination, the greater the obliquity to the Sun. Barnes and Armstrong saw that this could be a good thing for planets on the edges of habitable zones, allowing heat to be distributed evenly over geological timescales and preventing "Snowball Earth" scenarios. They called these worlds "tilt-a-worlds," but the presence of a large moon would counteract this beneficial obliquity change.

"I think one of the most important points from our tilt-a-world paper is that at the outer edge of the habitable zone, having a large moon is bad, there's no other way to look at it," says Barnes. "If you have a large moon that stabilizes the obliquity then you have a tendency to completely freeze over."

Barnes is impressed with the work of Lissauer's team.
"I think it is a well done study," he says. "It suggests that Earth does not need the moon to have a relatively stable climate. I don't think there would be any dire consequences to not having a moon."

Mars' Changing Tilt
The effects of changing obliquity on Mars’ climate. Mars’ current 25-degree tilt is seen at top left. At top right is a Mars that has a high obliquity, leading to ice gather at its equator while the poles point sunwards. At bottom is Mars with low obliquity, which sees its polar caps grow in size.

Of course, the moon does have a hand in other factors important to life besides planetary obliquity. Tidal pools may have been the point of origin of life on Earth. Although the moon produces the largest tides, the sun also influences tides, so the lack of a large moon is not necessarily a stumbling block. Some animals have also evolved a life cycle based on the cycle of the moon, but that's more happenstance than an essential component for life.

"Those are just minor things," says Lissauer.

Without the absolute need for a moon, astrobiologists seeking life and habitable worlds elsewhere face new opportunities. Maybe Earth, with its giant moon, is actually the oddball amongst habitable planets. Rory Barnes certainly doesn't think we need it.
"It will be a step forward to see the myth that a habitable planet needs a large moon dispelled," he says, to which Lissauer agrees.
Earth without its moon might therefore remain habitable, but we should still cherish its friendly presence. After all, would Beethoven have written the Moonlight Sonata without it?

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Move Over Hubble, Meet the New High Powered Star Searcher

NASA'S James Webb Space Telescope

Excerpt from space.com

NASA's James Webb Space Telescope, scheduled for launch in 2018, will probe the cosmos to uncover the history of the universe from the Big Bang to alien planet formation and beyond.
Scientists are planning to use the infrared telescope to search for the first galaxies that formed at the beginning of the universe. The James Webb Space Telescope (JWST) will also have the ability to look through cosmic dust clouds to find newly forming planetary systems and seek out the chemical origins of life in the solar system.

The powerful $8.8 billion spacecraft is also expected to take amazing photos of celestial objects like its predecessor, the Hubble Space Telescope. 

Instruments on board

The JWST will come equipped with four science instruments.
  • Near-Infrared Camera (NIRCam) — Provided by the University of Arizona, this infrared camera will detect light from stars in nearby galaxies and stars within the Milky Way. It will also search for light from stars and galaxies that formed early in the universe's life. NIRCam will be outfitted with coronagraphs that can block a bright object's light, making dimmer objects near those stars (like planets) visible.
  • Near-Infrared Spectrograph (NIRSpec) — NIRSpec will observe 100 objects simultaneously, searching for the first galaxies that formed after the Big Bang. NIRSpec was provided by the European Space Agency with help from NASA's Goddard Space Flight Center.
  • Mid-Infrared Instrument (MIRI) — MIRI will produce amazing space photos of distant celestial objects, following in Hubble's tradition of astrophotography. The spectrograph that is a part of the instrument will allow scientists to gather more physical details about distant objects in the universe. MIRI will detect distant galaxies, faint comets, forming stars and objects in the Kuiper Belt. MIRI was built by the European Consortium with the European Space Agency and NASA's Jet Propulsion Laboratory.
  • Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS) — This Canadian Space Agency-built instrument is more like two instruments in one. The FGS component is responsible for keeping the JWST pointed in exactly the right direction during its science investigations. NIRISS will scope out the cosmos to find signatures of the first light in the universe and seek out and characterize alien planets.
The telescope will also sport a tennis court-size sunshield and a 21.3 foot (6.5 meter) mirror — the largest mirror ever launched into space. Those components will not fit into the rocket launching the JWST, so both will unfurl once the telescope is in space.

Infrared: Inside the huge space observatory that operates from a point in space four times further away than the moon.
NASA's James Webb Space Telescope is an $8.8 billion space observatory built to observe the infrared universe like never before. See how NASA's James Webb Space Telescope works in this Space.com infographic
James Webb the man

The JWST is named for former NASA chief James Webb. Webb took charge of the space agency from 1961 to 1968, retiring just a few months before NASA put the first man on the moon.

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The Best Bet for Alien Life May Be in Planetary Systems Very Different From Ours

Excerpt from wired.com

In the hunt for extraterrestrial life, scientists started by searching for a world orbiting a star just like the sun. After all, the steady warmth of that glowing yellow ball in the sky makes life on Earth possible.

But as astronomers continue to discover thousands of planets, they’re realizing that if (or when) we find signs of extraterrestrial life, chances are good that those aliens will orbit a star quite different from the sun—one that’s redder, cooler, and at a fraction of the sun’s size and mass. So in the quest for otherworldly life, many astronomers have set their sights on these small stars, known as red dwarfs or M dwarfs.

At first, planet-hunting astronomers didn’t care so much about M dwarfs. After the first planet outside the solar system was discovered in 1995, scientists began hunting for a true Earth twin: a rocky planet like Earth with an orbit like ours around a sun-like star. Indeed, the search for that kind of system drove astronomers through most of the 2000s, says astronomer Phil Muirhead of Boston University.

But then astronomers realized that it might be technically easier to find planets around M dwarfs. Detecting another planet is really hard, and scientists rely on two main methods. In the first, they look for a drop in a star’s brightness when a planet passes in front of it. In the second, astronomers measure the slight wobble of a star, caused by the gentle gravitational tug of an orbiting planet. With both of these techniques, the signal is stronger and easier to detect for a planet orbiting an M dwarf. A planet around an M dwarf also orbits more frequently, increasing the chances that astronomers will spot it.

M dwarfs got a big boost from the Kepler space telescope, which launched in 2008. By staring at small patch of the sky, the telescope searches for suddenly dimming stars when a planet passes in front of them. In doing so, the spacecraft discovered a glut of planets—more than 1,000 at the latest count—it found a lot of planets around M dwarfs. “Kepler changed everything,” Muirhead said. Because M-dwarf systems are easier to find, the bounty of such planets is at least partly due to a selection effect. But, as Muirhead points out, Kepler is also designed to find Earth-sized planets around sun-like stars, and the numbers so far suggest that M-dwarfs may offer the best odds for finding life.

“By sheer luck you would be more likely to find a potentially habitable planet around an M dwarf than a star like the sun,” said astronomer Courtney Dressing of Harvard. She led an analysis to estimate how many Earth-sized planets—which she defined as those with radii ranging from one to one-and-a-half times Earth’s radius—orbit M dwarfs in the habitable zone, the region around the star where liquid water can exist on the planet’s surface. According to her latest calculations, one in four M dwarfs hosts such a planet.

That’s higher than the estimated number of Earth-sized planets around a sun-like star, she says. For example, an analysis by astronomer Erik Petigura of UC Berkeley suggests that fewer than 10 percent of sun-like stars have a planet with a radius between one and two times that of Earth’s.

This illustration shows Kepler-186f, the first rocky planet found in a star's habitable zone. Its star is an M dwarf.
This illustration shows Kepler-186f, the first rocky planet found in a star’s habitable zone. Its star is an M dwarf. NASA Ames/SETI Institute/JPL-Caltech

M dwarfs have another thing going for them. They’re the most common star in the galaxy, comprising an estimated 75 percent of the Milky Way’s hundreds of billions of stars. If Dressing’s estimates are right, then our galaxy could be teeming with 100 billion Earth-sized planets in their stars’ habitable zones.

To be sure, these estimates have lots of limitations. They depend on what you mean by the habitable zone, which isn’t well defined. Generally, the habitable zone is where it’s not too hot or too cold for liquid water to exist. But there are countless considerations, such as how well a planet’s atmosphere can retain water. With a more generous definition that widens the habitable zone, Petigura’s numbers for Earth-sized planets around a sun-like star go up to 22 percent or more. Likewise, Dressing’s numbers could also go up.
Astronomers were initially skeptical of M-dwarf systems because they thought a planet couldn’t be habitable near this kind of star. For one, M dwarfs are more active, especially during within the first billion years of its life. They may bombard a planet with life-killing ultraviolet radiation. They can spew powerful stellar flares that would strip a planet of its atmosphere.

And because a planet will tend to orbit close to an M dwarf, the star’s gravity can alter the planet’s rotation around its axis. When such a planet is tidally locked, as such a scenario is called, part of the planet may see eternal daylight while another part sees eternal night. The bright side would be fried while the dark side would freeze—hardly a hospitable situation for life.

But none of these are settled issues, and some studies suggest they may not be as big of a problem as previously thought, says astronomer Aomawa Shields of UCLA. For example, habitability may depend on specific types and frequency of flares, which aren’t well understood yet. Computer models have also shown that an atmosphere can help distribute heat, preventing the dark side of a planet from freezing over.

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Do human bodies contain mega-ancient interstellar water?

This image shows water through time in the formation of the solar system, as scientists have revealed that water filling the Earth's oceans pre-date the formation of the sun

"Our findings show that a significant fraction of our Solar System’s water, the most-fundamental ingredient to fostering life, is older than the Sun," said Conel Alexander.

WASHINGTON, Sept. 25 (UPI) -- If you took a dip at the beach this summer, chances are you bumped up against some truly ancient water molecules -- water older than the sun. In fact, there's probably interstellar water hanging out inside all of us -- we are 60 percent water, after all.

A new study suggests as much as a third of Earth's ocean water was likely formed prior to the birth of the sun and sourced from deep space ice.

Like all planets in our solar system, most of the Earth and much of its water was formed from the debris floating around our young sun -- a hot cloud of gas and other cosmic material known as the solar nebula. Included in this nebula were ices, but we know there are also ices floating in interstellar space -- as evidenced by meteorite samples.

What scientists haven't been sure of, however, is exactly how much of our water is made of interstellar ice, and how much was formed locally in the solar nebula. To solve that quandary, a team of scientists led by L. Ilsedore Cleeves from the University of Michigan built a model to predict the answer. The model was based on the scientists' understanding of the chemical circumstances that enable the formation of "heavy" water molecules -- a molecule with a deuterium atom instead of a hydrogen atom.

About 1 in every 3,000 water molecules has a deuterium atom. The scientists' model, part chemistry part mathematics, showed that the solar nebula wasn't capable of forming all of Earth's heavy water on its own, and thus suggested roughly a third of Earth's water is really alien water.

"Our findings show that a significant fraction of our Solar System's water, the most-fundamental ingredient to fostering life, is older than the Sun, which indicates that abundant, organic-rich interstellar ices should probably be found in all young planetary systems," said Conel Alexander, a researcher at Carnegie Science institute in Washington.

As Alexander explained, the revelation suggests the materials necessary for life are probably not as rare as scientists previously thought.

"If water in the early Solar System was primarily inherited as ice from interstellar space, then it is likely that similar ices, along with the prebiotic organic matter that they contain, are abundant in most or all protoplanetary disks around forming stars," Alexander added.
The study was published this week in the journal Science.

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