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Small Telescopes, Big Science (Astronomy)

A quest to open up the dynamic, infrared sky begins

Our Milky Way galaxy is chock-full of dust. Stars are essentially dust-making factories that infuse the galaxy with a haze of dusty elements required for making planets and even life. But all that dust can make viewing the cosmos difficult. Telescopes that detect visible, or optical, light cannot see through the murkiness, and thus some of what goes on in the universe remains enshrouded.

Luckily for astronomers, infrared light, which has longer wavelengths than optical light, can sneak past dust. Several infrared-sensing telescopes, such as NASA’s Spitzer Space Telescope, have taken advantage of this fact and revealed much of the so-called infrared sky, including hidden planets, stars, supermassive black holes, and more. The next frontier for infrared astronomy involves watching how the infrared sky changes over time, an effort that Mansi Kasliwal (MS ’07, PhD ’11), an assistant professor of astronomy at Caltech, refers to as opening up the dynamic infrared sky.

To that end, Kasliwal has planned a series of four small ground-based infrared telescopes that will reveal everything from never-before-seen star explosions, asteroids, and even infrared counterparts to stellar collisions that send ripples through space and time known as gravitational waves.

The ambitious plan begins with Palomar Gattini-IR, a robotic instrument now in operation at Palomar Observatory, and will eventually include two additional instruments, called WINTER (Wide-field Infrared Transient Explorer) and DREAMS (Dynamic Red All-Sky Monitoring Survey), both of which are under construction. The final step in the plan is to build an instrument destined for Antarctica, where the chilly temperatures lead to even crisper views of the infrared sky.

“We are changing the game,” says Kasliwal. “We are building little telescopes that do big science.”

The little structure at Palomar Observatory where Gattini is housed.Credit: Caltech

Palomar Gattini-IR, or just Gattini for short, refers to the Italian word for kittens, gattini, and came from Kasliwal’s collaborator Anna Moore, a professor of astronomy at Australian National University, who used the term to casually refer to her own fleet of small telescopes in the Antarctic. “The name just stuck,” explains Kasliwal. Palomar Gattini-IR has been busy robotically scanning the skies from its perch in a small dome at Palomar Observatory since 2019 and has already produced some interesting results.

Stars That Go Bang

One recent paper accepted in The Astrophysical Journal reports the first real estimate of the number of nova explosions, or novae, that go off in our Milky Way galaxy per year (the answer is about 46). Novae are not as bright as supernovae, but powerful nonetheless and can briefly shine brighter than one million suns. They occur when a white dwarf, the burned-out core of a star, siphons enough material off a companion star to cause an explosion. These bursts are thought to seed our universe with many of the elements that make up our periodic table; in fact, novae are thought to be the main producers of lithium in our galaxy.

But novae can be hard to find because they often lie within the thick and dusty band of our Milky Way. Previous estimates of the rate of novae in our galaxy were wildly uncertain, with only about a dozen novae discovered each year.

“There was little consensus before now on the rate of novae in our galaxy,” says Kishalay De (MS ’18), a graduate student at Caltech and lead author of the Gattini study on novae. “The novae can be hidden behind huge columns of dust, so optical surveys could not find them.”

The novae results demonstrate the power of an infrared survey like Gattini, which scans the whole Northern sky every two nights. The newfound novae were “insanely easy to pick out,” according to Kasliwal, because they glow brightly when viewed in infrared light.

Mansi Kasliwal with members of her team who helped build the Gattini telescope. From left to right: Kishalay De, Scott Adams, Alex Delacroix, and Timothee Greffe of Caltech; Jamie Soon of Australian National University, and Kasliwal. Credit: Caltech

“This is truly a ground-breaking study,” says Allen Shafter, a nova expert at San Diego State University. “Dust limits the reach of optical nova surveys to a relatively small volume of space near the sun. As a result, optical estimates of the Galactic nova rate require a large and uncertain extrapolation of the nova rate in the solar neighborhood to the full extent of our Milky Way galaxy. The new Gattini infrared nova study has greatly increased the volume of space that can be directly surveyed, thereby reducing the extent of the required extrapolation and resulting in a more accurate estimate of the Galactic nova rate than has been hitherto possible.”

An Infrared Legacy

Caltech is a pioneer in the field of infrared astronomy. The late astronomy professors Gerry Neugebauer (PhD ’60) and Robert Leighton (BS ’41 and PhD ’47) designed and built one of the world’s first infrared telescopes. Later, Neugebauer and Tom Soifer (BS ’68), the Harold Brown Professor of Physics, Emeritus, helped create the first space mission to perform an all-sky infrared survey mission, called IRAS (Infrared Astronomical Satellite), which launched in 1983 and led to the creation of Caltech’s Infrared Processing and Analysis Center, now called simply IPAC.

Other IPAC infrared projects include the ground-based 2MASS (Two Micron All-Sky Survey), which scanned the entire sky from 1997 to 2001; NASA’s Spitzer Space Telescope, a sister telescope to the Hubble Space Telescope that ceased operations in 2020; and NASA’s WISE (Wide-field Infrared Survey Explorer), now called NEOWISE (Near-Earth Object WISE) and dedicated primarily to the search for asteroids.

These previous infrared surveys catalogued millions of never-before-seen asteroids, stars, galaxies, and other objects, and had better resolutions than Gattini, but they did not scan the whole sky as quickly.

“We’re doing a large chunk of what 2MASS did every night,” says De. “Gattini is the first-ever survey of the dynamic, or changing, infrared sky. We have traded in resolution for a wide field of view to enable us to regularly capture the whole night sky.” Gattini’s telescope is only 30 centimeters in size but its field of view is a whopping 25 square degrees, 40 times larger than any past or current infrared telescopes.

“Caltech is a pioneer for both infrared astronomy and time-domain astronomy, so it only makes sense that we would combine the two in the first dynamic infrared sky survey,” says Kasliwal. Time-domain astronomy refers to nightly surveys of the changing sky; Caltech’s Zwicky Transient Facility (ZTF) is a key instrument in this growing field, but unlike Gattini, it detects optical light.

From the Ground Up

The Gattini instrument was built at Caltech by Kasliwal and her team, including both graduate and undergraduate students. It was first installed at Palomar in 2018 and took some time to calibrate and set up to work automatically. “We left the telescope on its own to operate robotically,” says De. “Then the data came pouring down from the sky to our computers thanks to our data pipeline.”

One of the challenges in designing a survey instrument like Gattini is the development of software. Gattini’s software automatically sifts through enormous amounts of data to detect changes in the sky every night. De spent six months developing the software and data pipeline for the project as part of his PhD thesis.

“These software techniques are of prime importance to future space-based telescopes as well,” says De, “because they remove the blurring caused by the earth’s atmosphere and hence can in principle get extremely sharp images.”

Now that Gattini is up and running, astronomers have been mining its data for use in various projects. For instance, Caltech professor of astronomy Lynne Hillenbrand and her team used the instrument’s data to help discover a rare bursting young star hidden by clouds of dust. Hillenbrand’s group had previously discovered a similar star with the help of NEOWISE.

“Gattini can uniquely detect objects that are so buried in dust to not be seen in visible light, and which brighten so rapidly that only Gattini scans the sky fast enough to pick them out,” says Hillenbrand.

Next-Generation “Kittens”

Next up in Kasliwal’s plan to open the dynamic infrared skies are WINTER and DREAMS. WINTER, which is currently being built at MIT under the leadership of Kasliwal’s collaborator Rob Simcoe (PhD ’04), a professor of physics, is scheduled to begin operations at Palomar in the fall of 2021. DREAMS is being built by a team led by Moore in Australia and is scheduled to begin operations at Siding Springs Observatory in 2022. Both telescopes will use next-generation infrared detectors that are more efficient than those on Gattini.

The final step is to build an infrared survey telescope in Antarctica that will take advantage of the frigid air. “The night sky is blindingly bright in infrared light, but it’s 40 times darker in Antarctica at infrared wavelengths, which is partly due to the cold temperatures,” explains Kasliwal.

Another reason for building a survey telescope at the South Pole is because, together with those in the North, they will cover the entire sky. “It’s always nighttime somewhere,” she says.

A Goldmine of a Find

One of Kasliwal’s dreams is to be able to identify cataclysmic mergers of neutron stars, dramatic events that produce what astronomers call kilonovas. These explosions are even more powerful than novae, and are thought to generate a significant amount of the universe’s heaviest elements, including gold and platinum. Kasliwal’s team identified one such explosion along with other groups back in 2017, when LIGO (Laser Interferometer Gravitational-wave Observatory) first identified the gravitational waves produced by the collision. The occasion marked the first time that both gravitational waves and light were detected from the same event, and helped usher in the field of multi-messenger astronomy (where gravitational waves, light, and neutrinos are the messengers).

Since that time, LIGO has detected dozens of additional gravitational-wave events, but none have been seen simultaneously in light. Kasliwal suspects this may be due to the fact that kilonovas inherently produce much more infrared than optical light and are thus being missed by optical telescopes. Each step in Kasliwal’s plan—Gattini, WINTER, DREAMS, and a future instrument in Antarctica—has the ability to sleuth out the hidden kilonovas with increasing sensitivities. It is also possible that one of the telescopes may even catch a long-sought neutron star and black hole merger, which could be even more luminous in infrared light than neutron star collisions.

“There is a lot you can do with small ground-based telescopes,” she says. “Our small teams are very agile, and enable us to have some fun, take risks, and try something new. We have the freedom to dream big.”

Palomar Gattini-IR is funded by Caltech, Australian National University, the Mt. Cuba Foundation, the Heising-Simons Foundation, and the US-Israel Binational Science Foundation. The instrument is a collaborative project among Caltech, Australian National University, University of New South Wales, Columbia University, University of Chinese Academy of Sciences, and the Weizmann Institute of Science.

Featured image: The Gattini telescope. Credit: Caltech


Reference: De, Kishalay and Kasliwal, Mansi M. and Hankins, Matthew J. and Sokoloski, Jennifer L. and Adams, Scott M. and Ashley, Michael C. B. and Babul, Aliya-Nur and Bagdasaryan, Ashot and Delacroix, Alexandre and Dekany, Richard and Greffe, Timothee and Hale, David and Jencson, Jacob E. and Karambelkar, Viraj R. and Lau, Ryan M. and Mahabal, Ashish and McKenna, Daniel and Moore, Anna M. and Ofek, Eran O. and Sharma, Manasi and Smith, Roger M. and Soon, Jamie and Soria, Roberto and Srinivasaragavan, Gokul and Tinyanont, Samaporn and Travouillon, Tony D. and Tzanidakis, Anastasios and Yao, Yuhan (2021) A population of heavily reddened, optically missed novae from Palomar Gattini-IR: Constraints on the Galactic nova rate., ArXiv, pp. 1-25, 2021. https://arxiv.org/abs/2101.04045


Provided by Caltech

Which Conspiracy Theory Do You Believe In? (Psychology)

Everyone believes in at least one conspiracy theory, according to conspiracy researchers. Conspiracy theories aren’t reserved for angry Republicans in the United States. Do you think Biden stole the election?

Joe Biden is the new president of the United States, although half of the country’s Republicans believe he stole the election. A lot of people believe conspiracy theories on the other side of the Atlantic. But they aren’t only found there.

Joe Biden. Are you among those who think he stole the election? Photo: Andrew Cutraro, White House

Conspiracy theories are not exclusive to people who storm the U.S. Capitol.

“Everyone believes at least one conspiracy theory,” says Asbjørn Dyrendal, a professor in NTNU’s Department of Philosophy and Religious Studies who specializes in conspiracy theories.

The more conspiracy theories you bring up, the more people answer yes to one of them.

That fact leads American conspiracy researcher Joseph Uscinski at the University of Miami to posit that all people believe in at least one conspiracy theory. Dyrendal basically agrees, but he modifies Uscinski’s statement slightly, saying all people believe some conspiracy theory “a little.”

Referee has it out for your team

Maybe you don’t think that the earth is flat or that the moon landings were faked and kept under wraps by all the 400 000 individuals involved. Maybe you don’t believe that vaccines cause autism and that the authorities are doing this on purpose, or that 5G is messing up your head, even if you’re not exactly alone in that case.

We are all more vulnerable to believing what we think is right, especially when our identity is at stake and emotions are strong. It can be a bit like the emotions associated with football.

“Maybe you think the referee is out to get your football team, especially when one of your team’s players gets fouled in the box and no penalty is called,” says Dyrendal.

“These examples activate the same mechanisms that come into play when our thoughts build on themselves and turn into more entrenched conspiracy beliefs.”

Maybe you even think a lot of referees are against your team, especially if you believe you’re seeing a pattern, like your team never or only rarely getting a penalty kick.

This thinking doesn’t usually amount to a conspiracy theory in and of itself. But the same mechanisms come into play when thoughts build on themselves and turn into more entrenched conspiracy beliefs.

People can have degrees of conspiracy thinking as well. There’s a difference between yelling at the ref in a heated moment and believing that the earth is flat.

Donald Trump. Is he really a savior? Photo: Michael Vadon, Wikimedia Commons

Common traits

You can find people who believe in the most unusual conspiracy theories everywhere, perhaps even in your own mirror.

“But several common characteristics recur often,” says Dyrendal.

Conspiracy theorists typically:

  • tend to have a little less education.
  • more often live in societies that have less successful democracies, which influences trust in others and in the authorities.
  • belong to groups that feel they should have more power and influence.
  • belong to special political organizations or religious groups a little more often.
  • more often use intuition – their “gut feeling” – when making decisions.
  • see connections more often than most people do, also where such connections do not exist, and they are more likely to see intention as the cause of events.
  • are a little more narcissistic and paranoid than others.
  • more often obtain their information from social media.

We can take a closer look at some of these points.

Chemtrails or contrails? Are the stripes after a plane really chemicals that the authorities spray us with? No. It’s condensation. Water vapour. Photo: Shutterstock, NTB

Role of social media

“We’ve noticed that conspiracy theorists are somewhat more likely to find their news sources on social media,” says Dyrendal.

This has a bit to do with how social media works.

Social media can create echo chambers. The media is structured in such a way that you mostly hear from friends and other sources that you already agree with. “Likes” and posts that you click on influence what you see later. This makes it easy to confirm suspicions and perceptions that you already have. And you’ll always find a community of other individuals who feel and think a little like you do.

However, just blaming Twitter and Facebook for this phenomenon is a gross oversimplification. It may seem as if more people than before believe in the strangest conspiracy theories, but in fact we don’t know if there are more than before.

A majority of Americans do not believe that Lee Harvey Oswald was alone in killing John F. Kennedy. Photo: Victor Hugo King

Gender distribution

You may think that men are conspiracy theorists more often than women, but that’s actually not true.

“When we look at a large number of different conspiracy theories, we find no reliable gender differences in the average scores,” says Dyrendal.

But who believes in which theories can be different, although the differences don’t necessarily revolve exclusively around gender. They may have more to do with dominance.

“People who dislike equality and prefer hierarchy see themselves and their group as superior to others and believe more in conspiracy theories that are specifically about social out-groups,” Dyrendal says.

The United States Congress. More open to welcoming uninvited guests than we thought. Photo: Shutterstock, NTB

This kind of preference for clear social ranking expresses itself in general prejudices against groups that are seen as lower in the social hierarchy or which are perceived as a threat to the social hierarchy.

“These individuals tend to believe more easily in conspiracies like immigration, Jewish dominance, Muslims or the like, and this preference is a little stronger in men,” Dyrendal says.

Group belonging

The most prominent characteristic of conspiracy theorists is that they are often part of various groups that distrust the government and the way most of us live today.

“If you belong to a group that already believes in doomsday scenarios and a future saviour, it’s probably easier to believe in some of the conspiracy theories,” Dyrendal says.

Evangelical Christians in the United States, for example, will find it easier to adopt conspiracy theories that fit with their other beliefs. If you’re convinced that the world as we know it will soon end with the battle between good and evil at Armageddon, it’s not that big a jump to believe that politicians in recent decades are actually emissaries of Satan himself.

QAnon not that big

Among people who stormed the U.S. Capitol were several members of QAnon. This is a group that believes Donald Trump has been fighting a secret war against a powerful group of Satan-worshipping paedophiles, which includes Hillary Clinton.

Hillary Clinton. Probably not part of a Satan-worshiping network of paedophiles. Photo: US Department of State

But the followers of QAnon don’t number as many people some media might suggest, at least in proportion to the population of the United States. QAnon may seem widespread because many of the conspiracy theories adopted by QAnon were already well established and far more popular before.

“But in a country with 330 million inhabitants, numbers quickly grow to a good size anyway,” Dyrendal says.

Conspiracy researcher Uscinski in Miami has studied QAnon for a long time and believes the group hasn’t grown in recent years. He should know, since he’s been asking people about it since about the group’s beginnings.

Most aren’t extreme

But most of the people who stormed the Capitol were completely different people. And when half of the Republicans allege electoral fraud that was overwhelmingly rejected by election officials, we’re not exactly talking about belonging to some extremist group.

These aren’t just poor people who believe the powers-that-be and the rich are looking to oppress them, either. The connections are tangled.

“Conspiracy beliefs are also about a lot of people wanting more. Trump supporters may be less educated than the average population, but they have higher salaries,” says Dyrendal.

The media often portray most Trump supporters as slightly backward, disadvantaged people from rural areas, but this is simply not true.

Lingering beliefs

Most of us aren’t as far out as the strangest few are. Ninety-six per cent of Norwegians vaccinate their children.

But some perceptions and suspicions can linger. Isn’t Manchester United having a lot of penalties called at the moment? Didn’t Rosenborg have all the referees on their side when they won 13 league championships in a row?

Dyrendal admits he hasn’t yet forgiven the referee in the match between Leeds and Bayern Munich in 1975.

Bayern Munich won the European Cup final 2-0 after the referee disallowed Peter Lorimer’s goal, when he ruled Billy Bremner offside and twice failed to call a penalty against Bayern Munich.

French judges. They hate British teams, everyone knows that. And they’re really easy to bribe, right?


More reading: (1) Anastasiya Astapova, Eirikur Bergmann, Asbjørn Dyrendal, Annika Rabo, Kasper Grotle Rasmussen, Hulda Thórisdóttir, Andreas Önnerfors. Conspiracy Theories and the Nordic Countries. (2) Asbjørn Dyrendal, Leif Edward Ottesen Kennair, Mons Bendixen. Predictors of belief in conspiracy theory: The role of individual differences in schizotypal traits, paranormal beliefs, social dominance orientation, right wing authoritarianism and conspiracy mentality. Personality and Individual Differences Volume 173, April 2021, 110645. https://doi.org/10.1016/j.paid.2021.110645


Provided by Norwegian Sci-tech news

Discovery Could Lead to Self-propelled Robots (Engineering)

Army-funded researchers discovered how to make materials capable of self-propulsion, allowing materials to move without motors or hands.

Researchers at the University of Massachusetts Amherst discovered how to make materials that snap and reset themselves, only relying upon energy flow from their environment. This research, published in Nature Materials and funded by the U.S. Army, could enable future military robots to move from their own energy.

“This work is part of a larger multi-disciplinary effort that seeks to understand biological and engineered impulsive systems that will lay the foundations for scalable methods for generating forces for mechanical action and energy storing structures and materials,” said Dr. Ralph Anthenien, branch chief, Army Research Office, an element of the U.S. Army Combat Capabilities Development Command, now known as DEVCOM, Army Research Laboratory. “The work will have myriad possible future applications in actuation and motive systems for the Army and DOD.”

Researchers uncovered the physics during a mundane experiment that involved watching a gel strip dry. The researchers observed that when the long, elastic gel strip lost internal liquid due to evaporation, the strip moved. Most movements were slow, but every so often, they sped up.

Scientists discover how to make materials that snap and reset themselves, only relying upon energy flow from their environment. This research could enable future military robots that are able to move off their own energy. © Yongjin Kim, UMass Amherst

These faster movements were snap instabilities that continued to occur as the liquid evaporated further. Additional studies revealed that the shape of the material mattered, and that the strips could reset themselves to continue their movements.

“Many plants and animals, especially small ones, use special parts that act like springs and latches to help them move really fast, much faster than animals with muscles alone,” said Dr. Al Crosby, a professor of polymer science and engineering in the College of Natural Sciences, UMass Amherst. “Plants like the Venus flytraps are good examples of this kind of movement, as are grasshoppers and trap-jaw ants in the animal world.”

Snap instabilities are one way that nature combines a spring and a latch and are increasingly used to create fast movements in small robots and other devices as well as toys like rubber poppers.

“However, most of these snapping devices need a motor or a human hand to keep moving,” Crosby said. “With this discovery, there could be various applications that won’t require batteries or motors to fuel movement.”

Scientists discover how future military robots may be able to move off just their own energy. © Yongjim Kim, UMass Amherst

After learning the essential physics from the drying strips, the team experimented with different shapes to find the ones most likely to react in expected ways, and that would move repeatedly without any motors or hands resetting them. The team even showed that the reshaped strips could do work, such as climb a set of stairs on their own.

“These lessons demonstrate how materials can generate powerful movement by harnessing interactions with their environment, such as through evaporation, and they are important for designing new robots, especially at small sizes where it’s difficult to have motors, batteries, or other energy sources,” Crosby said.

The research team is coordinating with DEVCOM Army Research Laboratory to transfer and transition this knowledge into future Army systems.

Featured image: Army-funded researchers discover how to make materials capable of self-propulsion, allowing materials to move without motors or hands. © Yongjin Kim, UMass Amherst


Reference: Kim, Y., van den Berg, J. & Crosby, A.J. Autonomous snapping and jumping polymer gels. Nat. Mater. (2021). https://doi.org/10.1038/s41563-020-00909-w


Provided by US Army Research Laboratory

Why Massive Stars are More Prone to Form Massive Planets? (Planetary Science)

Summary:

○ According to Flor-Torres and colleagues, massive stars rotating faster than low-mass stars, had more massive protoplanetary disks (PPDs) with higher angular momentum, explaining why they formed more massive planets rotating faster around their stars.

○ They also found that most stars and planets lost their angular momentum due to the fact that there are interactions of the planets with their PPDs and that massive PPDs dissipates more angular momentum than lower mass PPD.

○ Thus, high mass exoplanets (HMEs) to have higher orbital angular momentum than the LMEs and to have lost more angular momentum through migration.


The discovery of gas giant planets rotating very close to theirs stars (hot Jupiter, or HJs) has forced Flor-Torres and colleagues to reconsider their model for the formation of planets around low mass stars by including in an ad hoc way large scale migration. Since this did not happen in the solar system, it brings the natural question of understanding under what conditions large scale migration could be triggered in a proto-planetary disk (PPD). By stating such question, they adopted the simplest view that there is only one universal process for the formation of planets, following the collapse of dense regions in a molecuar cloud.


This reduces the problem to a more specific one which is: how do we include migration in a well developed model like the core collapse scenario (the standard model), which explains in details how the solar system formed

— said Flor-Torres, lead author of the study.

In the literature, two migration mechanisms are favored for HJs. The first is disk migration, which proposes that a planet looses its orbit angular momentum by tidal interactions with the PPD, while the second, high-eccentricity migration, suggests a planet interacting with other planets gains a higher eccentricity, which brings it close to its star where it reaches equilibrium by tidal interactions (a process known as circularization). In terms of migration, these two mechanisms might suggest massive disks somehow amplified the level of migration compared to what happened in the solar system, because more massive PPDs either increase the intensity of interactions of the planets with their disks or favor the formation of a higher number of planets. Within the standard model this would suggest that what counts is whether the PPD follows the minimum mass model, with a mass between 0.01 to 0.02 M⊙, or the maximum mass model with a mass above 0.5 M⊙. There are few clues which could help determining which path the PPD of the solar system followed (and strong difficulties compared to direct observations of PPD). One is the total mass of the planets, which represents only 0.1% the mass of the Sun. This implies the solar system PPD have lost an important amount of its mass after the formation of the planets. Another clue is that 99% of the angular momentum of the solar system is located in the planets, suggesting that the initial angular momentum of the PPD might have been conserved in the planets. However, this is obviously not the case when large scale migration occurs, so what was the difference?

Fig. 1. Star rotational velocity vs. temperature, distinguishing between stars hosting HMEs and LMEs. The position of the Sun is included as well as the star with a BD as companion. © Flor-Torres et al.

If the initial angular momentum of the PPD passes to the planets, then one could use the orbital rotation momentum in exoplanetary systems to test different scenarios connecting the formation of the planets to the formation of their stars. For example, how is the angular momentum of the PPD coupled to the angular momentum of the stars? Since large scale migration represents a loss of angular momentum of the planets (at least by a factor 10), what was the initial angular momentum of the PPD when it formed and how does this compared to the initial mass of the PPD? Does this influence the masses of the planets and their migration? The answers are not trivial, considering that the physics involved is still not fully understood.


In particular, we know that the angular momentum is not conserved during the formation of stars. This is obvious when one compares how fast the Sun rotates with how fast its rotation should have been assuming the angular momentum of the collapsing molecular cloud where it formed was conserved.

— said Jack, co-author of the study.

Actually, working the math (a basic problem, but quite instructive; see course notes by Alexander 2017), the Sun effective angular momentum, j⊙ = J⊙/M⊙, is ∼ 10^6 times lower than expected. Intriguingly, j⊙ is also 10³ lower than the angular momentum of its breaking point, jb, the point where the centripetal force becomes stronger than gravity. If that was not true, then no stars whatever massive would be able to form. In fact, observations revealed that, in general, the angular momentum of stars with spectral type O5 to A5 trace a power law, J ∝ Mα, with α ∼ 2, with typical J∗ values that are exactly ten times lower than their breaking point. How universal is this “law”and how stars with different masses get to it, however, is unexplained. To complicate the matter, it is clear now that lower mass stars, later than A5, do not follow this law, their spin going down exponentially (cf. Fig.6 in Paper I). For low-mass stars, McNally, Kraft and Kawaler suggested a steeper power law, J ∝ M5.7, which suggests they loose an extra amount of angular momentum as their mass goes down. What is interesting is that low-mass stars are also those that form PPDs and planets, which had led some researchers to speculate there could be a link between the two.

To explain how low-mass stars loose their angular momentum, different mechanisms are considered. The most probable is stellar wind, which is related to the convective envelopes of these stars. This is how low-mass stars would differ from massive ones. However, whether this mechanism is sufficient to explain the break in the J – M relation is not obvious, because it ignores the possible influence of the PPD (the formation of a PPD seems crucial). This is what the magnetic braking model takes into account. Being bombarded by cosmic rays and UV radiation from ambient stars, the matter in a molecular cloud is not neutral, and thus permeable to magnetic fields. This allows ambipolar diffusion (the separation of negative and positive charges) to reduce the magnetic flux, allowing the cloud to collapse. Consequently, a diluted field follows the matter through the accretion disk to the star forming its magnetic field. This also implies that the accretion disk (or PPD) stays connected to the star through its magnetic field as long as it exists, that is, a period that although brief includes the complete phase of planet formation and migration. According to the model of disk-locking, a gap opens between the star and the disk at a distance Rt from the star, and matter falling between Rt and the radius of corotation, Rco (where the Keplerian angular rotation rate of the PPD equals that of the star), follow the magnetic field to the poles of the star creating a jet that transports the angular momentum out. In particular, this mechanism was shown to explain why the classic T-Tauri rotates more slowly than the weak T-Tauri. How this magnetic coupling could influence the planets and their migrations, on the other hand, is still an open question.

To investigate further these problems, Flor-Torres and colleagues started a new observational project to observe host stars of exoplanets using the 1.2 m robotic telescope TIGRE, which is installed near their department at the LA Luz Observatory (in central Mexico). In paper I, they explained how they succeeded in determining in an effective and homogeneous manner the physical characteristics ( Teff , log g, [M/H], [Fe/H], and V sin i) of a initial sample of 46 bright stars using iSpec. In this study, they explored the possible links between the physical characteristics of these 46 stars and the physical characteristics of their planets, in order to gain new insight about a connection between the formation of stars and their planets.


Our main goal is to check is there could be a coupling between the angular momentum of the planets and their host stars.

— said Flor-Torres, lead author of the study.

Table 1: Physical parameters of the High Mass Exoplanets (HME) & Low Mass Exoplanets (LME) in their samples. © For-Torres et al.

Separating our sample in two, stars hosting high-mass exoplanets (HMEs) and low-mass exoplanets (LMEs), we found the former to be more massive and to rotate faster than the latter.

– said Schmitt, co-author of the study.

They found that there is a connection between the stars and their exoplanets, which passes by their protoplanetary disks (PPDs). Massive stars rotating faster than low-mass stars, had more massive PPDs with higher angular momentum, explaining why they formed more massive planets rotating faster around their stars. However, in terms of stellar spins & planets orbit angular momentum, they found that both the stars and their planets have lost a huge amount of angular momentum (by more than 80% in the case of the planets), a phenomenon which could have possibly erased any correlations expected between the two. The fact that all the planets in their sample stop their migration at the same distance from their stars irrespective of their masses, might favor the views that the process of migration is due to the interactions of the planets with their PPDs and that massive PPDs dissipates more angular momentum than lower mass PPD. Consistent with this last conclusion, authors proposed that HMEs might have different structures than LMEs which made them more resilient to circularization.

We also found the HMEs to have higher orbital angular momentum than the LMEs and to have lost more angular momentum through migration. These results are consistent with the view that the more massive the star and higher its rotation, the more massive was its protoplanetarys disk and rotation, and the more efficient the extraction of angular momentum from the planets.

— concluded authors of the study.

Reference: (1) L. M. Flor-Torres, R. Coziol, K.-P. Schröder, D. Jack, J. H. M. M. Schmitt, S. Blanco-Cuaresma, “Connecting the formation of stars and planets. I — Spectroscopic characterization of host stars with Tigre”, ArXiv, 27 Jan 2021. https://arxiv.org/abs/2101.11666v1 (2) L. M. Flor-Torres, R. Coziol, K.-P. Schröder, D. Jack, J. H. M. M. Schmitt, “Connecting the formation of stars and planets. II: coupling the angular momentum of stars with the angular momentum of planets”, ArXiv, 27 Jan 2021. https://arxiv.org/abs/2101.11676v1


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Science of Sandcastles is Clarified, Finally (Physics)

Science of building sandcastles mysteriously explained for 150 years by the ‘Kelvin equation’ is finally understood by a Manchester team led by graphene pioneer Andre Geim.

Water vapor from ambient air will spontaneously condense inside porous materials or between touching surfaces. But with the liquid layer being only a few molecules thick this ubiquitous and important phenomenon has lacked understanding, until now.

A sandcastle on the beach which is held together by the universal process called capillary condensation. Photo by ‘Hello I’m Nik’ on Unsplash

Researchers at The University of Manchester led by Nobel Laureate Andre Geim – who, with Kostya Novoselov, was awarded the Nobel Prize for Physics 10 years ago this month – have made artificial capillaries small enough for water vapour to condense inside them under normal, ambient conditions.

The Manchester study is entitled ‘Capillary condensation under atomic-scale confinement’ and will be published in Nature. The research provides a solution for the century-and-half-old puzzle of why capillary condensation, a fundamentally microscopic phenomenon involving a few molecular layers of water, can be described reasonably well using macroscopic equations and macroscopic characteristics of bulk water. Is it a coincidence or a hidden law of nature?

Capillary condensation, a textbook phenomenon, is omnipresent in the world around us, and such important properties as friction, adhesion, stiction, lubrication and corrosion are strongly affected by capillary condensation. This phenomenon is important in many technological processes used by microelectronics, pharmaceutical, food and other industries – and even sandcastles could not be built by children if not for capillary condensation.

Scientifically, the phenomenon is often described by the 150-year-old Kelvin equation that has proven to be remarkably accurate even for capillaries as small as 10 nanometres, a thousandth of human hair’s width. Still, for condensation to occur under normal humidity of say 30% to 50%, capillaries should be much smaller, of about 1 nm in size. This is comparable with the diameter of water molecules (about 0.3 nm), so that only a couple of molecular layers of water can fit inside those pores responsible for common condensation effects.

The macroscopic Kelvin equation could not be justified for describing properties involving the molecular scale and, in fact, the equation has little sense at this scale. For example, it is impossible to define the curvature of a water meniscus, which enters the equation, if the meniscus is only a couple of molecules wide. Accordingly, the Kelvin equation has been used as a poor-man’s approach, for the lack of a proper description. The scientific progress has been hindered by many experimental problems and, in particular, by surface roughness that makes it difficult to make and study capillaries with sizes at the required molecular scale.

To create such capillaries, the Manchester researchers painstakingly assembled atomically flat crystals of mica and graphite. They put two such crystals on top of each other with narrow strips of graphene, another atomically thin and flat crystal, being placed in between. The strips acted as spacers and could be of different thickness. This trilayer assembly allowed capillaries of various heights. Some of them were only one atom high, the smallest possible capillaries, and could accommodate just one layer of water molecules.

The Manchester experiments have shown that the Kelvin equation can describe capillary condensation even in the smallest capillaries, at least qualitatively. This is not only surprising but contradicts general expectations as water changes its properties at this scale and its structure becomes distinctly discrete and layered.

“This came as a big surprise. I expected a complete breakdown of conventional physics,” said Dr Qian Yang, the lead author of the Nature report. “The old equation turned out to work well. A bit disappointing but also exciting to finally solve the century old mystery.

“So we can relax, all those numerous condensation effects and related properties are now backed by hard evidence rather than a hunch that ‘it seems to work so therefore it should be OK to use the equation’.”

The Manchester researchers argue that the found agreement, although qualitative, is also fortuitous. Pressures involved in capillary condensation under ambient humidity exceed 1,000 bars, more than that at the bottom of the deepest ocean. Such pressures cause capillaries to adjust their sizes by a fraction of angstrom, which is sufficient to snugly accommodate only an integer number of molecular layers inside. These microscopic adjustments suppress commensurability effects, allowing the Kelvin equation to hold well.

“Good theory often works beyond its applicability limits,” said Geim.

“Lord Kelvin was a remarkable scientist, making many discoveries but even he would surely be surprised to find that his theory – originally considering millimetre-sized tubes – holds even at the one-atom scale. In fact, in his seminal paper Kelvin commented about exactly this impossibility.

“So, our work has proved him both right and wrong, at the same time.”

Reference: Yang, Q., Sun, P.Z., Fumagalli, L. et al. Capillary condensation under atomic-scale confinement. Nature 588, 250–253 (2020). https://www.nature.com/articles/s41586-020-2978-1 https://doi.org/10.1038/s41586-020-2978-1

Provided by University of Manchester

Why Do Some People Believe The Earth is Flat? (Planetary Science)

“Although scientific evidence says the Earth is a sphere orbiting the Sun, there are some people around who still think our planet is flat… and social media plays a role”, said Anders Furze of University of Melbourne.

©NASA

If you type ‘flat Earth’ into Google, you’d be joining a group of people that have helped to triple the search term over the last couple of years. In fact, a recent YouGov poll found that only around two-thirds of Americans aged between 18 and 24 believe that the Earth is round.

Although the idea the Earth is flat has been scientifically discredited, there seems to be a growing belief in the conspiracy theory.

And it’s getting more traction than some of the other conspiracies out there, like chemtrails (which proposes that a plane’s long-lasting condensation trail is actually made up of chemical or biological agent).

A third of Americans polled by YouGov believe the Earth is flat. Picture: Getty Images

Interest in most of these other far-fetched theories remains stable but the flat-Earth movement is growing, particularly in America. And it has some high-profile supporters.

From basketball players to musicians, rappers to TV hosts, a number of celebrities are jumping on the flat Earth bandwagon.

So what’s causing a renewed interest in something that’s been scientifically disproven for the past two thousand years or more? What does it say about social media? And how did we actually establish that the world is round in the first place?

ROUNDING OUT THE WORLD

Once upon a time, it made sense for people to believe that the Earth was flat, says University of Melbourne cartographer Chandra Jayasuriya. Ships would sail off toward the horizon and often never return, and those people left behind didn’t really have access to information outside of their communities.

“Their view was egocentric and geocentric. They lived in a village that was the centre of their existence,’’ she says. “The further away from the village they travelled, the more hostile the environment became.”

Greek philosophers established that the Earth was round as far back as the third century BC, but it wasn’t until the 15th century that it became commonly accepted.

A 15th century manuscript copy of Ptolemy world map, reconstituted from Ptolemy’s Geography. Picture: Getty Images

The first scientific estimates of the Earth’s circumference were made by the Greek mathematician and geographer Eratosthenes in 240 BC. He noted that on the 21st of June that year, in a town called Syene (near modern day Aswan), the reflection of the sun could be seen in a deep well, meaning that it was directly overhead.

But in Alexandria, around 800 kilometres away and almost directly north of Syene, at noon on the same day, the angle of the sun was about seven degrees – or one-50th of a circle.

If the Earth was actually flat, the angle would be identical in both places.

“From this, he concluded that the circumference of the Earth must be 50 times the distance between Syene and Alexandria,” Ms Jayasuriya adds. “This gave him a figure that was very close to the actual circumference as we know it now.”

In 150 AD, Ptolemy’s treatise Geographia laid out a revolutionary system of assigning co-ordinates, expressed in degrees of latitude and longitude, to locations around the world. The mathematician and astronomer assigned these coordinates to more than 8000 places across the known world.

Even though many of the measurements weren’t accurate, Ptolemy’s concept of ‘global mapping co-ordinates’ – used to this day – was based on the theory that the Earth was and is, indeed, round.

“Although Ptolemy’s original map didn’t survive, the text was rediscovered around 1300 AD and cartographers were able to recreate the map”, says Ms Jayasuriya.

A flat Earth map drawn by Orlando Ferguson in 1893. Picture: Wikimedia

As well as observations of the sun and its shadows, Ms Jayasuriya says many scientists throughout history continued to gather observations and evidence that the Earth is spherical including:

  • That we see the top of a ship’s mast coming into port and not the entire ship
  • That all other planets and celestial objects are spheres
  • That during a lunar eclipse, the Earth’s shadow on the moon is curved

DISTRUSTING THE EXPERTS

So why, despite overwhelming scientific evidence that the Earth is an “oblate spheroid” – a sphere that’s squashed at its poles and swollen at the equator – is the flat-Earth movement gaining traction in the 21st century?

Well, in part, according to School of Culture and Communication lecturer Dr Jennifer Beckett, it’s due to a general shift towards populism and a distrust in the views of experts and the mainstream media.

“It’s really about the power of knowledge, and that increasing distrust in what we once considered to be the gatekeepers of knowledge – like academics, scientific agencies, or the government,” Dr Beckett says.

In this kind of environment, “it becomes really easy for once-fringe views to gain traction. You get a bunch of people around you who are constantly reaffirming your belief.”

Circa 1600, A terrestrial and a celestial globe, side by side, engraved for Bankes’s New System of Geography. Picture: Getty Images

Dr Beckett also notes that the burgeoning movement speaks to how so-called social media “influencers” can now hold more sway than an expert in the field.

“That’s often because they tend to be better storytellers,” Dr Beckett says.

“And there’s an element of authenticity there – people naively think, ‘Oh, they’re a real person, so it must be true’.”

THE FLAT EARTH ECOSYSTEM

Dr Beckett notes that the flat Earth community uses various social media platforms in distinct, overlapping ways in order to create a kind of ecosystem around their beliefs.

“Youtube becomes a content hub, Facebook becomes an administrative one-stop shop for that hub, and Twitter continually pushing out the messaging,” she says, likening Youtube to a sort of alternative documentary channel for flat earthers.

“It’s a really interesting beast … they can have their daily or weekly TV show in the same way that we go to David Attenborough.”

It’s a more powerful social media tool than Facebook or Twitter because it’s a “high context” platform, Dr Beckett says, where users can stream themselves with an immediacy and intimacy that’s lacking from text or image-based platforms.

“It’s kind of like feeling like you have direct access to David Attenborough, after watching one of his documentaries. Being able to have a conversation with him then have him respond in the next episode to your concerns or your question.”

And unlike TV, on Youtube you can go searching for videos by people who agree with your view of the world. Or in this case, the Earth.

Dr Beckett says that as we increasingly rely on social media for entertainment, we are becoming “affect addicts” – looking for the next hit of anger, happiness or other intense emotions.

And it’s very easy for misinformation to circulate in this environment. Many flat earthers endorse the idea that the UN logo is actually a flat Earth map, for example.

But Ms Jayasuriya adds its appearance is the result of a way of ‘projecting’ a 3D sphere onto a 2D plane.

Because there’s “no perfect way to project a 3D sphere onto a 2D surface”, cartographers produce maps using different ‘projections’ for different uses. The UN logo is a particular projection centred on the North Pole.

GETTING THE FACTS FOR CRITICAL THINKING

So, the question remains: why is this a theory that still persists in 2018 in the face of science, and even photographic evidence?

Well, it also comes back to thinking critically about information that’s out there. Particularly online.

“Look, flat earthers’ are actually employing Cartesian doubt; this a philosophical idea that the world outside the self is subject to uncertainty,” Dr Beckett says, referring to a method of sceptical thinking popularised by René Descartes, the French philosopher, mathematician, and scientist.

“But, I’d say the best way to do your research on whether a story is correct is to actually go to the mainstream media, to go to those scientific agencies and see what they’re saying.

“Academics are academics not because they’re trying to pull the wool over people’s eyes, but because we spend a lot of time training and thinking deeply about these issues,” says Dr Beckett.

“You know, a lot of time, work and effort has gone into perpetuating the notion that the Earth is a globe… perhaps, that’s a sign that it is.”

This article was first published on Pursuit. Read the original article.

We Now Know, What Generates Polar Hexagonal Storm On Saturn (Planetary Science)

With its dazzling system of icy rings, Saturn has been a subject of fascination since ancient times. Even now the sixth planet from the sun holds many mysteries, partly because its distance away makes direct observation difficult and partly because this gas giant (which is multiple times the size of our planet) has a composition and atmosphere, mostly hydrogen and helium, so unlike that of Earth. Learning more about it could yield some insights into the creation of the solar system itself.

The smaller storms on Saturn interact with the larger system and as a result effectively pinch the eastern jet and confine it to the top of the planet. The pinching process warps the stream into a hexagon. Credit: Jeremy Bloxham and Rakesh K. Yadav

One of Saturn’s mysteries involves the massive storm in the shape of a hexagon at its north pole. The six-sided vortex is an atmospheric phenomenon that has been fascinating planetary scientists since its discovery in the 1980s by the American Voyager program, and the subsequent visit in 2006 by the U.S.-European Cassini-Huygens mission. The storm is about 20,000 miles in diameter and is bordered by bands of winds blowing up to 300 miles per hour. A hurricane like it doesn’t exist on any other known planet or moon.

Two of the many scientists-turned-interplanetary-storm-chasers working to uncover the secrets of this marvel are Jeremy Bloxham, the Mallinckrodt Professor of Geophysics, and research associate Rakesh K. Yadav, who works in Bloxham’s lab in Harvard’s Department of Earth and Planetary Sciences. In a recently published paper in PNAS, the researchers began to wrap their heads around how the vortex came to be.

“We see storms on Earth regularly and they are always spiraling, sometimes circular, but never something with hexagon segments or polygons with edges,” Yadav said. “That is really striking and completely unexpected. [The question on Saturn is] how did such a large system form and how can such a large system stay unchanged on this large planet?”

By creating a 3D simulation model of Saturn’s atmosphere, Yadev and Bloxham believe are they closing in on an answer.

In their paper, the scientists say that the unnatural-looking hurricane occurs when atmospheric flows deep within Saturn create large and small vortices (aka cyclones) that surround a larger horizontal jet stream blowing east near the planet’s north pole that also has a number of storms within it. The smaller storms interact with the larger system and as a result effectively pinch the eastern jet and confine it to the top of the planet. The pinching process warps the stream into a hexagon.

“This jet is going around and around the planet, and it has to coexist with these localized [smaller] storms,” said Yadav, the study’s lead author. Think of it like this: “Imagine we have a rubber band and we place a bunch of smaller rubber bands around it and then we just squeeze the entire thing from the outside. That central ring is going to be compressed by some inches and form some weird shape with a certain number of edges. That’s basically the physics of what’s happening. We have these smaller storms and they’re basically pinching the larger storms at the polar region and since they have to coexist, they have to somehow find a space to basically house each system. By doing that, they end up making this polygonal shape.”

The model the researchers created suggests the storm is thousands of kilometers deep, well beneath Saturn’s cloud tops. The simulation imitates the planet’s outer layer and covers only about 10 percent of its radius. In a monthlong experiment the scientists ran, the computer simulation showed that a phenomenon called deep thermal convection — which happens when heat is transferred from one place to another by the movement of fluids or gases — can unexpectedly give rise to atmospheric flows that create large polar cyclones and a high-latitude eastward jet pattern. When these mix at the top it forms the unexpected shape, and because the storms form deep within the planet, the scientists said it makes the hexagon furious and persistent.

Convection is the same force that causes tornadoes and hurricanes on Earth. It’s similar to boiling a pot of water: The heat from the bottom transfers up to the colder surface, causing the top to bubble. This is what is believed to cause many of the storms on Saturn, which, as a gas giant, doesn’t have a solid surface like Earth’s.

“The hexagonal flow pattern on Saturn is a striking example of turbulent self-organization,” the researchers wrote in the June paper. “Our model simultaneously and self-consistently produces alternating zonal jets, the polar cyclone, and hexagon-like polygonal structures similar to those observed on Saturn.”

What the model didn’t produce, however, was a hexagon. Instead, the shape the researchers saw was a nine-side polygon that moved faster than Saturn’s storm. Still, the shape serves as proof of concept for the overall thesis on how the majestic shape is formed and why it has been relatively unchanged for almost 40 years.

Interest in Saturn’s hexagon storm goes back to 1988, when astronomer David A. Godfrey analyzed flyby data from the Voyager spacecraft’s 1980 and 1981 Saturn passes and reported the discovery. Decades later, from 2004 to 2017, NASA’s Cassini spacecraft captured some of the clearest and best-known images of the anomaly before plunging into the planet.

Relatively little is known about the storm because the planet takes 30 years to orbit the sun, leaving either pole in darkness for that time. Cassini, for instance, only took thermal images of the storm when it first arrived in 2004. Even when the sun shines on Saturn’s northern pole, the clouds are so thick that light doesn’t penetrate deep into the planet.

Regardless, many hypotheses exist on how the storm formed. Most center on two schools of thought: One suggests that the hexagon is shallow and only extends hundreds of kilometers deep; the other suggests the zonal jets are thousands of kilometers deep.

Yadev and Bloxham’s findings build on the latter theory, but need to include more atmospheric data from Saturn and further refine their model to create a more accurate picture of what’s happening with the storm. Overall, the duo hope their findings can help paint a portrait of activity on Saturn in general.

“From a scientific point of view, the atmosphere is really important in determining how quickly a planet cools. All these things you see on the surface, they’re basically manifestations of the planet cooling down and the planet cooling down tells us a lot about what’s happening inside of the planet,” Yadav said. “The scientific motivation is basically understanding how Saturn came to be and how it evolves over time.”

References: Rakesh K. Yadav and Jeremy Bloxham, “Deep rotating convection generates the polar hexagon on Saturn”, PNAS June 23, 2020 117 (25) 13991-13996; first published June 8, 2020; https://doi.org/10.1073/pnas.2000317117 link: https://www.pnas.org/content/117/25/13991

Provided by Harvard University

Chaco Canyon Has Been An Astronomy Hotspot For More Than 1000 Years (Astronomy)

Plenty has changed in the course of human history, but there are some things that will always be there. The stars in the sky, for example. That’s what Chaco Canyon, New Mexico is known for: It’s designated as an International Dark Sky Park for its dazzling view of the heavens, and it’s one of the only sites in the National Park system with its own astronomical observatory. That makes perfect sense, seeing as the Chaco culture has been charting the stars there for more than 1,000 years. What is it about the canyon’s nighttime sky that has ancient and modern astronomers so captivated?

Chaco canyon milky way ©gettyimages
Time lapse photo of Casa Rinconada With star paths ©National park service

Chaco Canyon is a shallow, 10-mile gorge slashed into the earth in the northwest corner of modern-day New Mexico. At an elevation of 6,200 feet (1,900 meters), its weather is harsh, with blazing summer heat and bitterly cold winters. Still, people have been calling this place home for thousands of years: Evidence of nomadic civilizations date back to 2900 B.C., and the first farmers were believed to have settled there around A.D. 200.

But it was A.D. 850 when things really got going: The Chacoan people laid more than 120 miles (200 km) of road and erected massive stone and wood buildings — we’re talking as much as five stories tall with up to 700 rooms. But it wasn’t the size that was the most interesting part of these structures; it was their position. They were precisely aligned to astronomical “landmarks” like the celestial meridian — that is, the imaginary line in the sky that connects the North Pole and the South Pole — along with the solar and lunar azimuth (the paths in the sky that the sun and moon follow, respectively). These alignments are important to astronomers because they make it easier to keep track of where things are in the sky.

There was plenty of other evidence pointing to the Chacoans’ impressive knowledge of astronomy, too. Carvings in the ground known as petroglyphs marked the cycles of the sun and moon, the most famous of which is known as the Sun Dagger: a spiral design believed to track the moon’s 18.6-year cycle. Those grand buildings are also strangely over-embellished, which some scholars think was an expression of Chacoan “concepts of the cosmos.”

It’s clear that the stars were important to the Chacoans, and why wouldn’t they be? That impossibly huge, incredibly dark sky just begs people to look up. Thanks to recent conservation efforts, modern society hasn’t diminished its beauty: More than 99 percent of Chaco Culture National State Park has been designated as a “natural darkness zone,” where there’s no permanent outdoor lighting. That led to its certification as an International Dark Sky Park by the International Dark-Sky Association — a designation given to areas “possessing an exceptional or distinguished quality of starry nights” that specifically protect them for the benefit of research, education, culture, and public enjoyment.

Bernard 33 or Horse head Nebula taken from Chaco observatory ©National Park Service

Until 2016, it was also the only National Park with its own astronomical observatory. Built in 1998, the Chaco Observatory is used mostly for science outreach. Visitors can peer through the telescopes, participate in astronomy programs, and learn about the way ancient cultures in the area thought about the cosmos. The technology might be more advanced, but in the end, modern fans of astronomy are no different than the ancient Chacoans. We’re all fascinated by the stars above us.

Some Planets May Be Better For Life Than Earth (Planetary Science)

Earth is not necessarily the best planet in the universe. Researchers have identified two dozen planets outside our solar system that may have conditions more suitable for life than our own. Some of these orbit stars that may be better than even our sun.

©gettyimages

A study led by Washington State University scientist Dirk Schulze-Makuch recently published in the journal Astrobiology details characteristics of potential “superhabitable” planets, that include those that are older, a little larger, slightly warmer and possibly wetter than Earth. Life could also more easily thrive on planets that circle more slowly changing stars with longer lifespans than our sun.

The 24 top contenders for superhabitable planets are all more than 100 light years away, but Schulze-Makuch said the study could help focus future observation efforts, such as from NASA’s James Web Space Telescope, the LUVIOR space observatory and the European Space Agency’s PLATO space telescope.

“With the next space telescopes coming up, we will get more information, so it is important to select some targets,” said Schulze-Makuch, a professor with WSU and the Technical University in Berlin. “We have to focus on certain planets that have the most promising conditions for complex life. However, we have to be careful to not get stuck looking for a second Earth because there could be planets that might be more suitable for life than ours.”

For the study, Schulze-Makuch, a geobiologist with expertise in planetary habitability teamed up with astronomers Rene Heller of the Max Planck Institute for Solar System Research and Edward Guinan of Villanova University to identify superhabitability criteria and search among the 4,500 known exoplanets beyond our solar system for good candidates. Habitability does not mean these planets definitely have life, merely the conditions that would be conducive to life.

The researchers selected planet-star systems with probable terrestrial planets orbiting within the host star’s liquid water habitable zone from the Kepler Object of Interest Exoplanet Archive of transiting exoplanets.

While the sun is the center of our solar system, it has a relatively short lifespan of less than 10 billion years. Since it took nearly 4 billion years before any form of complex life appeared on Earth, many similar stars to our sun, called G stars, might run out of fuel before complex life can develop.

In addition to looking at systems with cooler G stars, the researchers also looked at systems with K dwarf stars, which are somewhat cooler, less massive and less luminous than our sun. K stars have the advantage of long lifespans of 20 billion to 70 billion years. This would allow orbiting planets to be older as well as giving life more time to advance to the complexity currently found on Earth. However, to be habitable, planets should not be so old that they have exhausted their geothermal heat and lack protective geomagnetic fields. Earth is around 4.5 billion years old, but the researchers argue that the sweet spot for life is a planet that is between 5 billion to 8 billion years old.

Size and mass also matter. A planet that is 10% larger than the Earth should have more habitable land. One that is about 1.5 times Earth’s mass would be expected to retain its interior heating through radioactive decay longer and would also have a stronger gravity to retain an atmosphere over a longer time period.

Water is key to life and the authors argue that a little more of it would help, especially in the form of moisture, clouds and humidity. A slightly overall warmer temperature, a mean surface temperature of about 5 degrees Celsius (or about 8 degrees Fahrenheit) greater than Earth, together with the additional moisture, would be also better for life. This warmth and moisture preference is seen on Earth with the greater biodiversity in tropical rain forests than in colder, drier areas.

Among the 24 top planet candidates none of them meet all the criteria for superhabitable planets, but one has four of the critical characteristics, making it possibly much more comfortable for life than our home planet.

“It’s sometimes difficult to convey this principle of superhabitable planets because we think we have the best planet,” said Schulze-Makuch. “We have a great number of complex and diverse lifeforms, and many that can survive in extreme environments. It is good to have adaptable life, but that doesn’t mean that we have the best of everything.”

References: Dirk Schulze-Makuch, René Heller, and Edward Guinan, “In Search for a Planet Better than Earth: Top Contenders for a Superhabitable World”, Astrobiology, 2020 doi: https://doi.org/10.1089/ast.2019.2161 link: https://www.liebertpub.com/doi/10.1089/ast.2019.2161

Provided by Washington University