Artifacts In Space

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Voyager 2 entered interstellar space last month, becoming a space “artifact” of our civilization. (NASA)

 

All of a sudden, we have spacecraft and objects coming into our solar system and leaving for interstellar space. This is highly unusual, and very intriguing.

The departing spacecraft is Voyager 2, which launched in 1977 and has traveled spaceward some 11 billion miles.  It has now officially left the heliosphere, the protective bubble of particles and magnetic fields created by the sun.  In this it follows Voyager I – which left our solar system in 2012 — and managers of the two craft have reason to think they can travel until they cross the half-century mark.

This is taking place the same time that scientists are puzzling over the nature of a cigar-shaped object that flew into the solar system from interstellar space last year.

Nobody knows what the object – called Oumuamua, Hawaiian for “first messenger,” or “scout” – really is. The more likely possibilities of it being a comet or an solar system asteroid have been found to be inconsistent with some observed properties of the visitor, and this has led some senior scientists to even hypothesize that it just might be an alien probe.

The likelihood may be small, but it was substantial enough for Harvard University Astronomy Department Chairman Avi Loeb to co-author a paper presenting the possibility.  In the Astrophysical Journal Letters, Loeb and postdoc Shmuel Bialy wrote that the object “may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization.”

They also say the object has some characteristics of a “lightsail of artificial origins,” rather like the one that Loeb is working on as chairman of the Breakthrough Starshot advisory committee.  The well-funded private effort is hoping to develop ways to send a fleet of tiny lightsail probes to the star system nearest to us, Alpha Centauri.

 

This artist’s impression of the first detected interstellar visitor: Oumuamua. This object was discovered in October 2017 by the Pan-STARRS 1 telescope in Hawaii. Subsequent observations from ESO’s Very Large Telescope in Chile and other observatories around the world show that it was traveling through space for millions of years before its seemingly chance encounter with our star system.  But some scientists wonder:  might it be instead a probe sent into the cosmos by intelligent creatures?(NASA)

 

Put the two phenomenon together — the coming into our solar system and the going out — and you have a pathway into the world of alien “artifacts,” products of civilizations near and far.  They are the kind of “technosignatures,” the potential or actual handwork of intelligent beings, that NASA is now interested in learning about more.

We know this because during a fall conference in Houston convened by NASA at the request of members of Congress, scientists were brought together to discuss many different kinds of potential signs of intelligent extraterrestrial life.  While artifacts were one of many topics discussed, the term carries a quite magnetic pedigree.

So far, that meaning is of course fictional, or a misreading of actual features.  There is perhaps most famously the monoliths from the movie “2001: A Space Odyssey” and then the myriad sightings of alien spacecraft that turn out to be anything but that.

This image taken by VIking 1 in the mid 1970s led to years of discussion about Martian beings having at one time carved what appeared to be a gigantic face. (NASA)

 

And then there’s the “Face on Mars.”

The original image taken by Viking 1 looked somewhat like a human face. The feature, found in the region where the highlands meet the northern plains of Mars, was subsequently broadly popularized as a potential “alien artifact,” with even a major motion picture.

So many people were convinced that an image had been sculpted on the surface of Mars that NASA ultimately put out a substantial release in 2001 to make clear that the face was actually a mountain.

That was after the Mars Global Surveyor orbiter determined that the “face” was created by unusual reflections in an otherwise ordinary Martian mountain.

This high-resolution image from the Mars Orbiter Camera about the Mars Global Surveyor spacecraft shows the famous “Face on Mars” in detail, clearly showing it to be a natural geological formation. (NASA/MSSS)

 

 

So alien artifacts surely and properly have a steep hill to climb before they can be taken at all seriously.

But does that mean they shouldn’t be taken seriously at all?  Loeb clearly says no, that they are a potential source of important and compelling science, even if they are natural phenomena.

And then there’s the question raised in the Houston “technosignatures” conference:  What actually is meant by an artifact?

Longtime SETI scientist and advocate Jill Tarter, for instance, wondered if the signatures of intelligent civilizations could be imprinted on neutrinos.  She said that a leak of the radioactive isotope tritium, which has a short 12-year half-life,  could also signal the presence of advanced life because (unless it’s near a supernova) it would have to come quite recently from a nuclear reactor.

Taking it further, she and others argued that artifacts of intelligent life would include many atmospheric and planetary changes that could only be accomplished by intelligent beings.  For instance, the presence of unnatural pollutants such as chloroflurocarbons (CFCs) or sulfur hexafluoride (SF6) in an exoplanet atmosphere would, in this view, be an “artifact” of civilization.

Back, now, to Voyager 2, which is for sure an extraterrestrial artifact.

 

Rendering of Voyager 2 in deep space. (NASA/JPL)

 

Voyager 2 was launched by NASA in August, 1977 to study the outer planets.  Part of the larger Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune.

Both have traveled far their original destinations. The spacecraft were built to last five years and conduct close-up studies of Jupiter and Saturn.  With the spacecraft holding up despite the rigors,  additional flybys of the two outermost giant planets, Uranus and Neptune, proved possible, and then the Voyagers were directed to interstellar space.

Their five-year lifespans have stretched to 41 years, making Voyager 2 NASA’s longest running mission ever.

At the on-going American Geophysical Union annual meeting, NASA project manager Suzanne Dodd said she believed that Voyager 2 can keep functioning for 5 to 10 more years in this new region of space, though not with all its instruments operating.

The greatest concerns about keeping the probes operating, she said, involve power and temperature. The  nuclear-powered Voyager 2 loses about 4 watts of power a year, and mission scientists have to shut off systems to keep instruments operating.

Voyager 2 is very cold — about 3.6 degrees Celsius and close to the freezing point of hydrazine — leading to concerns about the probe’s thruster that uses this fuel.  Dodd says she’s set a personal goal of keeping at least one of the Voyagers going until 2027, making it a 50-year mission.

The cameras for both probes are no longer on. But before the camera on Voyager 1 was decommissioned, it took the iconic “Pale Blue Dot” picture of the Earth.

 

 

This “Pale Blue Dot” image was captured in 1990, when Voyager 1 was about 4 million miles from Earth.  The spacecraft is now more than 13 billion miles from where it launched. (NASA)

 

In preparation for the potentially deep space travels for the Voyager spacecrafts, both were fitted with a greeting for any intelligent life that might be encountered.

The message is carried by a phonograph record – -a 12-inch gold-plated copper disk containing sounds and images selected to show the diversity of life and culture on Earth. The contents of the record were selected for NASA by a committee chaired by space scientist and popularizer Carl Sagan.  He and his associates assembled 115 images and a variety of natural sounds to give a sense of what Earth and Earthlings are like.

So are the Voyagers now artifacts from our civilization, messengers awaiting discovery by some distant beings?

Perhaps.  But they actually have not even left the solar system, and won’t be leaving anytime soon. They are in what is considered interstellar space, but the boundary of our solar system is beyond the outer edge of the Oort Cloud, a collection of small objects that are still under the influence of the sun’s gravity.

The width of the Oort Cloud is not known precisely, but it is estimated to begin at about 1,000 astronomical units (AU) from the sun and to extend to about 100,000 AU. One AU is the distance from the sun to Earth. It will take about 300 years for Voyager 2 to reach the inner edge of the Oort Cloud and possibly 30,000 years to fly beyond it.

 

The path of Oumuamua since it entered the solar system in 2017. (NASA)

 

Astronomers have long predicted that objects from other solar systems get shot out into space and arrive in our system.

The first identified interstellar object to visit our solar system, Oumuamua, was discovered in late 2017 by the University of Hawaii’s Pan-STARRS1 telescope as part of a NASA effort to search for and track asteroids and comets in Earth’s neighborhood.

While originally classified as a comet, observations revealed no signs of cometary activity after it was slingshotted around the sun at a remarkable 196,000 miles per hour.

Oumuamua seems to be a dark red highly-elongated metallic or rocky object that (at last analysis) is somewhere between 400 and 100 meters long and is unlike anything normally found in the solar system.  Researchers hypothesize that the shape and size suggest that the object has been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years.

Karen Meech of the University of Hawaii first identified Oumuamua. Here she is giving a TED Talk.

Immediately after its discovery, telescopes around the world were called into action to measure the object’s trajectory, brightness and color.  Combining the images from several large telescopes,  a team of astronomers led by Karen Meech of the Institute for Astronomy in Hawaii found that Oumuamua varies in brightness by a factor of 10 as it spins on its axis every 7.3 hours.

 

Avi Loeb, chair of the Harvard Astronomy Department and an advocate of thinking way outside the box about Oumuamua.

 

No known asteroid or comet from our solar system varies so widely in brightness, with such a large ratio between length and width. The most elongated objects we have seen to date are no more than three times longer than they are wide.

“This unusually big variation in brightness means that the object is highly elongated: about ten times as long as it is wide, with a complex, convoluted shape,” said Meech. “We also found that it had a reddish color, similar to objects in the outer solar system, and confirmed that it is completely inert, without the faintest hint of dust around it.”

Oumuamua is headed out of the solar system now, so it’s unlikely more will be learned about it.  And with its odd shape and features, it clearly remains something of a mystery.

And that’s where Harvard’s Avi Loeb comes in.  Especially due to the remarkably fast speed with which Oumuamua entered the solar system, he argues that a probe sent by intelligent others cannot be ruled out, that science must be open minded.

“There is data on the orbit of this object for which there is no other explanation” than that it is the product of intelligent others,” he has said.  “The approach I take to the subject is purely scientific and evidence-based.”

Others strongly disagree.  But the views of the chairman of the Harvard astronomy department are nonetheless an intriguing part of the story.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Does Proxima Centauri Create an Environment Too Horrifying for Life?

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Artist’s impression of the exoplanet Proxima Centauri b. (ESO/M. Kornmesser)

 

In 2016, the La Silla Observatory in Chile spotted evidence of possibly the most eagerly anticipated exoplanet in the Galaxy. It was a world orbiting the nearest star to the sun, Proxima Centauri, making this our closest possible exoplanet neighbour. Moreover, the planet might even be rocky and temperate.

Proxima Centauri b had been discovered by discerning a periodic wobble in the motion of the star. This revealed a planet with a minimum mass 30% larger than the Earth and an orbital period of 11.2 days. Around our sun, this would be a baking hot world.

But Proxima Centauri is a dim red dwarf star and bathes its closely orbiting planet in a level of radiation similar to that received by the Earth. If the true mass of the planet was close to the measured minimum mass, this meant Proxima Centauri b would likely be a rocky world orbiting within the habitable zone.

 

Comparison of the orbit of Proxima Centauri  b with the same region of the solar system. Proxima Centauri is smaller and cooler than the sun and the planet orbits much closer to its star than Mercury. As a result it lies well within the habitable zone. (ESO/M. Kornmesser/G. Coleman.)

Sitting 4.2 light years from our sun, a journey to Proxima Centauri b is still prohibitively long.

But as our nearest neighbor, the exoplanet is a prime target for the upcoming generation of telescopes that will attempt to directly image small worlds. Its existence was also inspiration for privately funded projects to develop faster space travel for interstellar distances.

Yet observations taken around the same time as the La Silla Observatory discovery were painting a very different picture of Proxima Centauri. It was a star with issues.

This set of observations were taken with Evryscope; an array of small telescopes that was watching stars in the southern hemisphere. What Evryscope spotted was a flare from Proxima Centauri that was so bright that the dim red dwarf star became briefly visible to the naked eye.

Flares are the sudden brightening in the atmosphere of a star that release a strong burst of energy. They are often accompanied by a large expulsion of plasma from the star known as a “coronal mass ejection”. Flares from the sun are typically between 1027 – 1032 erg of energy, released in a few tens of minutes.

For comparison, a hydrogen bomb releases the equivalent of about 10 megatons of TNT or a mere 4 x 1023 erg. Hitting the Earth, energy from solar flares and coronal mass ejections can disrupt communication equipment and create a spectacular aurora.

A solar flare erupting from the right side of the sun. (NASA/SDO)

But the Proxima super-flare spotted by Evryscope was well beyond a regular stellar flare.

On March 18 in 2016, this tiny red dwarf emitted an energy belch of 1033.5 erg. The flare consisted of one major event and three weaker ones and lasted approximately one hour, during which time Proxima Centauri became 68 times brighter.

A sudden, colossal increase in the brightness of a star does not bode well for any closely orbiting planets.

However, such a major flare might well be rare. If the star was normally fairly quiet, perhaps a planet could recover from a single very disruptive flare in the same way the Earth has survived mass extinction events.

Led by graduate student Ward Howard at the University of North Carolina, Chapel Hill, the discovering team used Evryscope to monitor Proxima Centauri for flares for a total of 1344 hours between January 2016 and March 2018. What they found was a horrifying environment, as reported in The Astrophysical Journal Letters.

While an event on the scale of the Proxima super-flare was only seen once, 24 large eruptions were spotted from the red dwarf, with energies from 1030.5 to 1032.4 erg. Allowing for the fact the star had only been observed for a small part of the year, this pattern of energy outbursts meant that a massive super-flare (1033 erg) was likely to occur at least five times annually.

 

Artist’s impression of the surface of the planet Proxima Centauri b. But what would conditions be like so close to a flaring star? (ESO/M. Kornmesser)

 

But how important is this for the planet?

The Earth is protected from flares from our sun by our atmosphere. The ozone layer absorbs harmful ultraviolet radiation with wavelengths between about 2400 – 2800 Angstroms (10-10 m), preventing it reaching the surface. So what if Proxima Centauri b had a similar protective layer of gases as the Earth?

To answer this question, Howard and his team ran simulations of an Earth-like atmosphere on Proxima Centauri b.

As is the case for the sun, the team assumed that large flares would be frequently accompanied by a coronal mass ejection. Radiation and stellar material then flooded over an Earth-like Proxima Centauri b at the observed rate. And the atmosphere crumbled.

 

Ward Howard, astrophysicist at the University of North Carolina.

High energy particles in the coronal mass ejections split the nitrogen molecules (N2) in the atmosphere, which reacted with the ozone (O3) to form nitrogen oxide (NO2). After just 5 years, 90% of the ozone in the atmosphere was lost and the amount was still decreasing.

Without ozone, the surface of Proxima Centauri b would be stripped of its protection from UV radiation. During the Proxima super-flare, the radiation dose without the protective ozone would be 65 times larger than that needed to kill 90% of one of the most UV-resilient organisms on Earth.

“Life would have to undergo extreme adaptation to UV or exist underground or underwater,” Howard notes. “Only the most resistant organisms could survive on the surface in this environment.”

The simulation does assume that Proxima Centauri b does not have a magnetic field. Such a shield could channel the particles from the coronal mass ejection to the poles, forming the aurora as on Earth and reducing the damage to the atmosphere.

However, orbiting so close to the star, Proxima Centauri b is likely to be in tidal lock as the moon is to the Earth. This is expected to weaken the magnetic field, as the slower rotation makes it harder to create a magnetic dynamo within the planet.

So if the protective shields are lowered on Proxima Centauri b, is our nearest planet a world populated by highly resistant UV organisms? Or have we seen evidence that rather than warming the planet to allow life to exist, this star has snuffed it out?

 

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Elizabeth Tasker
Elizabeth Tasker is an astrophysicist and science communicator at the Japan Aerospace Exploration Agency (JAXA). Her research explores the formation of stars and planets, while her science articles have covered topics from Egyptian coffins to deep sea drilling (but mainly focus on exoplanets and space missions!). While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

InSight Lands on Mars For Unique Mission

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NASA’s InSight Lander has returned its first picture from Mars via the MarCO CubeSat mission. (NASA)

 

NASA’s InSight lander touched down at 11:54 Pacific Time and followed a seven-month, 300 million-mile (485 million kilometer) journey from Southern California that started back in May.

InSight will spend the next few hours cleaning its camera lens and unfurling its solar arrays.

Once NASA confirms that the solar arrays have been properly deployed, engineers will spend the next three months preparing the lander’s science instruments to begin collecting data.

The touchdown continues NASA’s good fortunes with Mars landings, and is the fifth successful landing in a row.

Only 40% of missions by any agency sent to pass by, orbit or land on Mars have been successful, and NASA has certainly had some failures, too.

This is by way of saying that any successful mission to Mars is a great accomplishment.

The European Space Agency, the Indian Space Research Organisation and the team of ESA and Russia’s Roscosmos currently have satellites orbiting the planet, and Japan, China. Russia and the United Arab Emirates have Mars missions planned for the next decade.  The next NASA mission to the planet is the Mars 2020 rover, a follow-up to the still exploring Curiosity rover which landed in 2012.

 

For those who might have missed it, here is our recent Many Worlds column about the novel science planned for InSight:

 

An artist illustration of the InSight lander on Mars. InSight, short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, is designed to look for tectonic activity and meteorite impacts, study how much heat is still flowing through the planet, and track Mars’ wobble as it orbits the sun. While InSight is a Mars mission, it will help answer key questions about the formation of the other rocky planets of the solar system and exoplanets beyond. (NASA/JPL-Caltech)

In the known history of our 4.5-billion-year-old solar system,  the insides of but one planet have been explored and studied.  While there’s a lot left to know about the crust, the mantle and the core of the Earth, there is a large and vibrant field dedicated to that learning.

Sometime next month, an extensive survey of the insides of a second solar system planet will begin.  That planet is Mars and, assuming safe arrival, the work will start after the InSight lander touches down on November 26.

This is not a mission that will produce dazzling images and headlines about the search for life on Mars.  But in terms of the hard science it is designed to perform, InSight has the potential to tell us an enormous amount about the makeup of Mars, how it formed, and possibly why is it but one-third the size of its terrestrial cousins, Earth and Venus.

“We know a lot about the surface of Mars, we know a lot about its atmosphere and even about its ionosphere,” says Bruce Banerdt, the mission’s principal investigator, in a NASA video. “But we don’t know very much about what goes on a mile below the surface, much less 2,000 miles below the surface.”

The goal of InSight is to fill that knowledge gap, helping NASA map out the deep structure of Mars.  And along the way, learn about the inferred formation and interiors of exoplanets, too.

Equitorial Mars and the InSight landing site, with noting of other sites. (NASA)

The lander will touch down at Elysium Planitia, a flat expanse due north of the Curiosity landing site.  The destination was selected because it is about as safe as a Mars landing site could be, and InSight did not need to be a more complex site with a compelling surface to explore.

“While I’m looking forward to those first images from the surface, I am even more eager to see the first data sets revealing what is happening deep below our landing pads.” Barerdt said. “The beauty of this mission is happening below the surface. Elysium Planitia is perfect.”

By studying the size, thickness, density and overall structure of the Martian core, mantle and crust, as well as the rate at which heat escapes from the planet’s interior, the InSight mission will provide glimpses into the evolutionary processes of all of the rocky planets in the inner solar system.

That’s because in terms of fundamental processes that shape planetary formation, Mars is an ideal subject.

It is big enough to have undergone the earliest internal heating and differentiation (separation of the crust, mantle and core) processes that shaped the terrestrial planets (Earth, Venus, Mercury, our moon), but small enough to have retained the signature of those processes over the next four billion years.

So Mars may contain the most in-depth and accurate record in the solar system of these processes. And because Mars has been less geologically active than the Earth — it does not have plate tectonics, for example —  it has retains a more complete evolutionary record in its own basic planetary building blocks.  In terms of deep planet geophysics,  it is often described as something of a fossil.

 

An artist rendering of the insides of rocky body like Mars.  The manner in which the different layers form and differentiate is seen as a central factor in whether the planet can become habitable.  (NASA)

 

By using geophysical instruments like those used on Earth, InSight will measure the fingerprints of the processes of terrestrial planet formation, as well as measuring the planet’s “vital signs.” They include the  “pulse” (seismology), “temperature” (heat flow probe), and “reflexes” (precision tracking).

One promising way InSight will peer into the Martian interior is by studying motion underground — what we know as marsquakes.

NASA has not attempted to do this kind of science since the Viking mission. Both Viking landers had their seismometers on top of the spacecraft, where they produced noisy data. InSight’s seismometer will be placed directly on the Martian surface, which will provide much cleaner data.

As described by the agency, “NASA have seen a lot of evidence suggesting Mars has quakes. But unlike quakes on Earth, which are mostly caused by tectonic plates moving around, marsquakes would be caused by other types of tectonic activity, such as volcanism and cracks forming in the planet’s crust.

“In addition, meteor impacts can create seismic waves, which InSight will try to detect.

“Each marsquake would be like a flashbulb that illuminates the structure of the planet’s interior. By studying how seismic waves pass through the different layers of the planet (the crust, mantle and core), scientists can deduce the depths of these layers and what they’re made of. In this way, seismology is like taking an X-ray of the interior of Mars.”

 

The InSight seismometer, developed by European partners and JPL, consists of a total of six seismic sensors that record the vibrations of the Martian soil in three directions in space and at two different frequency ranges. ges allows them to be mathematically combined into a single extremely broadband seismometer.  In order to protect the seismometer against wind and strong temperature fluctuations, a protective dome (Wind and Thermal Shield, WTS) will be placed over it. (German Aerospace Center)

 

Scientists think it’s likely they’ll see between a dozen and a hundred marsquakes over the course of two Earth years. The quakes are likely to be no bigger than a 6.0 on the Richter scale, which would be plenty of energy for revealing secrets about the planet’s interior.

Another area of scientific interest involves whether or not the core of Mars is liquid. InSight’s Rotation and Interior Structure Experiment, RISE, will help answer that question by tracking the location of the lander to determine just how much Mars’ North Pole wobbles as it orbits the sun.

These observations will provide information on the size of Mars’ iron-rich core and will help determine whether the core is liquid.  It will also help determine which other elements, besides iron, may be present.

The InSight science effort includes a self-hammering heat probe that will burrow down to 16 feet into the Martian soil and will for the first time measure the heat flow from the planet’s interior. Combining the rate of heat flow with other InSight data will reveal how energy within the planet drives changes on the surface.

This is especially important in trying to understand the presence and size of some of the solar system’s largest shield volcanoes in the solar system, a region known as Tharsis Mons.  Heat escaping from deep within the planet drives the formation of these types of features, as well as many others on rocky planets.

 

The Tharsis region of Mars has some of the largest volcanoes in the solar system. They include Olympus Mons, which is 375 miles in diameter and as much as 16 miles high. (U.S. Geological Survey)

InSight is not an astrobiology mission — no searching for life beyond Earth.

But it definitely is part of the process by which scientists will learn what planet formation and the dynamics of their interiors says about whether a planet can be home to life.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Barnard’s Star, The “Great White Whale” of Planet Hunting, Has Surrendered Its Secret

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Barnard’s Star is the closest single star to our sun, and the most fast moving. It has long been attractive to planet hunters because it is so close and so bright, especially in the infared section of the spectrum. But until now, the exoplanets of this “great white whale” have avoided detection.

 

Astronomers have found that Barnard’s star — a very close, fast-moving, and long studied red dwarf — has a super-Earth sized planet orbiting just beyond its habitable zone.

The discovery relied on data collected over many years using the tried-and-true radial velocity method, which searches for wobbles in the movement of the host star.

But this detection was something big for radial velocity astronomers because Barnard-b was among the smallest planet ever found using the technique, and it was the furthest out from its host star as well — orbiting its star every 233 days.

For more than a century, astronomers have studied Barnard’s star as the most likely place to find an extrasolar planet.

Ultimately, said Ignasi Rablis of Spain’s Institute of Space Studies of Catalonia, lead author of the paper in journal Nature, the discovery was the result of 771 observations, an extremely high number.

And now, he said, “after a very careful analysis, we are over 99 percent confident the planet is there.”

The planet is at least 3.2 times the size of Earth and orbits near the snowline of the system, where water cannot be expected to ever be liquid.  That means is it a frozen world (an estimated -150 degrees Celsius) and highly unlikely to support life.

But Rablis and others on the large team say it also an extremely good candidate for future direct imaging and next-generation observing.

 

An artist’s rendering of the Barnard’s star planet at sunset. (Martin Kornmesser/ESO)

 

Thousands of exoplanets have been identified by now, and hundreds using the radial velocity method.  But this one is different.

“Barnard’s star is the ‘great white whale’ of planet hunting,” said Paul Butler, senior scientist at the Carnegie Institution, a radial velocity pioneer, and one of the numerous authors of the paper.

Because the star is so close (but 6 light-years away) and as a result so tempting, it has been the subject of exoplanet searches for 100 years, Butler said.  But until the radial velocity breakthroughs of the mid 1990s, the techniques used could not find a planet.

Nonetheless, an early exoplanet hunter, the Dutch-American astronomer Peter van de Kamp of Swarthmore College, thought that he had indeed found two gas giant planets around Barnard’s star in the 1960s.  He used a different technique based on the movement of the host star, and the findings even made it into some textbooks.  But later the detection was found to be incorrect.

Even after the modern exoplanet era began Barnard’s star kept its planetary secret close.

As Butler explained it, the combination of the planet’s size and distance from the star ultimately pushed the technology (and astronomers) to the very limit — requiring a measurement of  1.2 meters per second of “wobble.”

In contrast, the first planets were found by radial velocity that would detect 70 meter per second of wobble caused by the gravitational pull of a planet, and 30 years ago the best instruments could detect only 300 meters per second.

 

The radial velocity technique identifies planets via the shift in the wavelength of the light of a star as it wobbles due to the presence of a planet.  When a celestial object moves away from us, the light we observe becomes slightly less energetic and redder.  The opposite — light becomes slightly more energetic and bluer — happens when the star moves toward us.

 

The detected planet (which remains a “candidate” until further confirmed) was ultimately found following concerted effort by a large team of astronomers around the world.  It was co-led and organized by Guillem Anglada-Escudé of the Queen Mary University of London.  The young astronomer had made a major splash in 2016 with the detection of a planet orbiting Proxima Centauri, the closest star to our own.

That discovery was part of the “Pale Red Dot” campaign, which had the goal of detecting rocky planets around red dwarf stars.  After the Proxima discovery Barnard’s star went to the top of Anglada-Escudé list with the renamed “Red Dots” collaboration — which is supported by the European Southern Observatory and universities in Chile, the United Kingdom, Spain and Germany.

The Red Dots campaign is a collaboration including the European Southern Observatory, Queen Mary University of London, and several European and South American institutions.

By 2015, there was already almost 18 years of modern data collected regarding a possible planet orbiting the star, and a faint but clearly present signal had been detected.  But more was needed to confidently report a discovery, and the Red Dots effort took up the challenge.

To see if the result could be confirmed, astronomers regularly monitored Barnard’s star with high precision spectrometers such as the CARMENES (Calar Alto Observatory in Spain), and also the HARPS  (High Accuracy Radial velocity Planet Searcher.)

Ultimately, the team used observations from seven different instruments taken over 20 years, making this one of the largest and most extensive datasets ever used for precise radial velocity studies.

“We all have worked very hard on this result,” said Anglada-Escudé. “This is the result of a large collaboration organized in the context of the Red Dots project, which is why it has contributions from teams all over the world including semi-professional astronomers.”

Cristina Rodríguez-López, researcher at the Instituto de Astrofísica de Andalucía and co-author of the paper, said of the significance of the finding grow over decades.

Guillem Anglada-Escudé was a leader of the Barnard’s star collaboration, as he was in the successful campaign to detect a planet orbiting of Proxima Centauri.

“This discovery means a boost to continue on searching for exoplanets around our closest stellar neighbors, in the hope that eventually we will come upon one that has the right conditions to host life,” she said.

The next pr0ject for the Red Dots campaign is to study the star Ross 154, at 9.69 light-years away another of the closest stars to us.

The dramatically increased (and increasing) precision in radial velocity measurements is expected to continue with the next generation of ground-based telescopes and spectrometers.

Butler, for instance,  said that Carnegie is in the process of upgrading its Planet Finding Spectrograph at the Las Campanas Observatory in Chile to reach a 0.5-meters-per-second measurement. Other groups including the European Southern Observatory and American teams based at Pennsylvania State and Yale Universities have similar efforts under way.

If they succeed, Butler said, it may well be possible to find potentially habitable planets around sun-like and other categories of stars using the radial velocity method.

 

 

Barnard’s star is the fourth closest to our sun, and the closest single star. It lies 6 light-years from us, as opposed to a little more than 4 light-years for the Alpha Centauri/Proxima Centauri threesome. (NASA Photojournal)

 

Barnard’s a very-low-mass red dwarf star in the constellation of Ophiuchus. It is the fourth-nearest-known individual star to the sun (after the three components of the Alpha Centauri system) and the closest star in the Northern Celestial hemisphere.

Despite its proximity, the star is too faint to be seen with the unaided eye, though it is quite visible with an amateur 8-inch telescope.  It is much brighter in the infrared than in visible light.  Although Barnard’s Star is an ancient star, it still experiences star flare events, one being observed in 1998.

The star is named after the American astronomer E. E. Barnard.  He was not the first to observe the star (it appeared on Harvard University plates in 1888 and 1890), but in 1916 he measured its proper motion –the apparent angular motion of a star across the sky with respect to more distant stars — as 10.3 arcseconds per year relative to the sun.

This is likely to be the fastest star in terms of proper motion, as its proximity to the sun, as well as its high velocity, make it unlikely any faster object will be discovered.

Barnard’s Star is among the most studied red dwarfs because of its proximity and favorable location for observation near the celestial equator. Historically, research on Barnard’s Star has focused on measuring its stellar characteristics and its astrometry — which involves precise measurements of the positions and movements of stars and other celestial bodies on the plane of the sky.

When planet hunters use astrometry, they look for a minute but regular wobble in a star’s position as seen in images.  Van de Kamp, for instance, used astrometry to study Barnard’s star and (incorrectly) detected those two gas giants around it.

In contrast, radial (or Doppler) velocities look for the wobble of the star perpendicular to the plane sky, and astronomers have regularly, and now once again, made history with that method.

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Probing The Insides of Mars to Learn How Rocky Planets Are Formed

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An artist illustration of the InSight lander on Mars. InSight, short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, is designed to look for tectonic activity and meteorite impacts, study how much heat is still flowing through the planet, and track Mars’ wobble as it orbits the sun. While InSight is a Mars mission, it will help answer key questions about the formation of the other rocky planets of the solar system and exoplanets beyond. (NASA/JPL-Caltech)

In the known history of our 4.5-billion-year-old solar system,  the insides of but one planet have been explored and studied.  While there’s a lot left to know about the crust, the mantle and the core of the Earth, there is a large and vibrant field dedicated to that learning.

Sometime next month, an extensive survey of the insides of a second solar system planet will begin.  That planet is Mars and, assuming safe arrival, the work will start after the InSight lander touches down on November 26.

This is not a mission that will produce dazzling images and headlines about the search for life on Mars.  But in terms of the hard science it is designed to perform, InSight has the potential to tell us an enormous amount about the makeup of Mars, how it formed, and possibly why is it but one-third the size of its terrestrial cousins, Earth and Venus.

“We know a lot about the surface of Mars, we know a lot about its atmosphere and even about its ionosphere,” says Bruce Banerdt, the mission’s principal investigator, in a NASA video. “But we don’t know very much about what goes on a mile below the surface, much less 2,000 miles below the surface.”

The goal of InSight is to fill that knowledge gap, helping NASA map out the deep structure of Mars.  And along the way, learn about the inferred formation and interiors of exoplanets, too.

Equitorial Mars and the InSight landing site, with noting of other sites. (NASA)

The lander will touch down at Elysium Planitia, a flat expanse due north of the Curiosity landing site.  The destination was selected because it is about as safe as a Mars landing site could be, and InSight did not need to be a more complex site with a compelling surface to explore.

“While I’m looking forward to those first images from the surface, I am even more eager to see the first data sets revealing what is happening deep below our landing pads.” Barerdt said. “The beauty of this mission is happening below the surface. Elysium Planitia is perfect.”

By studying the size, thickness, density and overall structure of the Martian core, mantle and crust, as well as the rate at which heat escapes from the planet’s interior, the InSight mission will provide glimpses into the evolutionary processes of all of the rocky planets in the inner solar system.

That’s because in terms of fundamental processes that shape planetary formation, Mars is an ideal subject.

It is big enough to have undergone the earliest internal heating and differentiation (separation of the crust, mantle and core) processes that shaped the terrestrial planets (Earth, Venus, Mercury, our moon), but small enough to have retained the signature of those processes over the next four billion years.

So Mars may contain the most in-depth and accurate record in the solar system of these processes. And because Mars has been less geologically active than the Earth — it does not have plate tectonics, for example —  it has retains a more complete evolutionary record in its own basic planetary building blocks.  In terms of deep planet geophysics,  it is often described as something of a fossil.

 

An artist rendering of the insides of rocky body like Mars.  The manner in which the different layers form and differentiate is seen as a central factor in whether the planet can become habitable.  (NASA)

 

By using geophysical instruments like those used on Earth, InSight will measure the fingerprints of the processes of terrestrial planet formation, as well as measuring the planet’s “vital signs.” They include the  “pulse” (seismology), “temperature” (heat flow probe), and “reflexes” (precision tracking).

One promising way InSight will peer into the Martian interior is by studying motion underground — what we know as marsquakes.

NASA has not attempted to do this kind of science since the Viking mission. Both Viking landers had their seismometers on top of the spacecraft, where they produced noisy data. InSight’s seismometer will be placed directly on the Martian surface, which will provide much cleaner data.

As described by the agency, “NASA have seen a lot of evidence suggesting Mars has quakes. But unlike quakes on Earth, which are mostly caused by tectonic plates moving around, marsquakes would be caused by other types of tectonic activity, such as volcanism and cracks forming in the planet’s crust.

“In addition, meteor impacts can create seismic waves, which InSight will try to detect.

“Each marsquake would be like a flashbulb that illuminates the structure of the planet’s interior. By studying how seismic waves pass through the different layers of the planet (the crust, mantle and core), scientists can deduce the depths of these layers and what they’re made of. In this way, seismology is like taking an X-ray of the interior of Mars.”

 

The InSight seismometer, developed by European partners and JPL, consists of a total of six seismic sensors that record the vibrations of the Martian soil in three directions in space and at two different frequency ranges. ges allows them to be mathematically combined into a single extremely broadband seismometer.  In order to protect the seismometer against wind and strong temperature fluctuations, a protective dome (Wind and Thermal Shield, WTS) will be placed over it. (German Aerospace Center)

 

Scientists think it’s likely they’ll see between a dozen and a hundred marsquakes over the course of two Earth years. The quakes are likely to be no bigger than a 6.0 on the Richter scale, which would be plenty of energy for revealing secrets about the planet’s interior.

Another area of scientific interest involves whether or not the core of Mars is liquid. InSight’s Rotation and Interior Structure Experiment, RISE, will help answer that question by tracking the location of the lander to determine just how much Mars’ North Pole wobbles as it orbits the sun.

These observations will provide information on the size of Mars’ iron-rich core and will help determine whether the core is liquid.  It will also help determine which other elements, besides iron, may be present.

The InSight science effort includes a self-hammering heat probe that will burrow down to 16 feet into the Martian soil and will for the first time measure the heat flow from the planet’s interior. Combining the rate of heat flow with other InSight data will reveal how energy within the planet drives changes on the surface.

This is especially important in trying to understand the presence and size of some of the solar system’s largest shield volcanoes in the solar system, a region known as Tharsis Mons.  Heat escaping from deep within the planet drives the formation of these types of features, as well as many others on rocky planets.

 

The Tharsis region of Mars has some of the largest volcanoes in the solar system. They include Olympus Mons, which is 375 miles in diameter and as much as 16 miles high. (U.S. Geological Survey)

InSight is not an astrobiology mission — no searching for life beyond Earth.

But it definitely is part of the process by which scientists will learn what planet formation and the dynamics of their interiors says about whether a planet can be home to life.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.