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Astronomers discover an Earth-sized ‘pi planet’ with a 3.14-day orbit

In a delightful alignment of astronomy and mathematics, scientists at MIT and elsewhere have discovered a “pi Earth” — an Earth-sized planet that zips around its star every 3.14 days, in an orbit reminiscent of the universal mathematics constant.

The researchers discovered signals of the planet in data taken in 2017 by the NASA Kepler Space Telescope’s K2 mission. By zeroing in on the system earlier this year with SPECULOOS, a network of ground-based telescopes, the team confirmed that the signals were of a planet orbiting its star. And indeed, the planet appears to still be circling its star today, with a pi-like period, every 3.14 days.

“The planet moves like clockwork,” says Prajwal Niraula, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), who is the lead author of a paper published today in the Astronomical Journal.

“Everyone needs a bit of fun these days,” says co-author Julien de Wit, of both the paper title and the discovery of the pi planet itself.

Planet extraction

The new planet is labeled K2-315b; it’s the 315th planetary system discovered within K2 data — just one system shy of an even more serendipitous place on the list.

The researchers estimate that K2-315b has a radius of 0.95 that of Earth’s, making it just about Earth-sized. It orbits a cool, low-mass star that is about one-fifth the size of the sun. The planet circles its star every 3.14 days, at a blistering 81 kilometers per second, or about 181,000 miles per hour.

While its mass is yet to be determined, scientists suspect that K2-315b is terrestrial, like the Earth. But the pi planet is likely not habitable, as its tight orbit brings the planet close enough to its star to heat its surface up to 450 kelvins, or around 350 degrees Fahrenheit — perfect, as it turns out, for baking actual pie.

“This would be too hot to be habitable in the common understanding of the phrase,” says Niraula, who adds that the excitement around this particular planet, aside from its associations with the mathematical constant pi, is that it may prove a promising candidate for studying the characteristics of its atmosphere.

“We now know we can mine and extract planets from archival data, and hopefully there will be no planets left behind, especially these really important ones that have a high impact,” says de Wit, who is an assistant professor in EAPS, and a member of MIT’s Kavli Institute for Astrophysics and Space Research.

Niraula and de Wit’s MIT co-authors include Benjamin Rackham and Artem Burdanov, along with a team of international collaborators.

Dips in the data

The researchers are members of SPECULOOS, an acronym for The Search for habitable Planets EClipsing ULtra-cOOl Stars, and named for a network of four 1-meter telescopes in Chile’s Atacama Desert, which scan the sky across the southern hemisphere. Most recently, the network added a fifth telescope, which is the first to be located in the northern hemisphere, named Artemis — a project that was spearheaded by researchers at MIT.

The SPECULOOS telescopes are designed to search for Earth-like planets around nearby, ultracool dwarfs — small, dim stars that offer astronomers a better chance of spotting an orbiting planet and characterizing its atmosphere, as these stars lack the glare of much larger, brighter stars.

“These ultracool dwarfs are scattered all across the sky,” Burdanov says. “Targeted ground-based surveys like SPECULOOS are helpful because we can look at these ultracool dwarfs one by one.”

In particular, astronomers look at individual stars for signs of transits, or periodic dips in a star’s light, that signal a possible planet crossing in front of the star, and briefly blocking its light.

Earlier this year, Niraula came upon a cool dwarf, slightly warmer than the commonly accepted threshold for an ultracool dwarf, in data collected by the K2 campaign — the Kepler Space Telescope’s second observing mission, which monitored slivers of the sky as the spacecraft orbited around the sun.

Over several months in 2017, the Kepler telescope observed a part of the sky that included the cool dwarf, labeled in the K2 data as EPIC 249631677. Niraula combed through this period and found around 20 dips in the light of this star, that seemed to repeat every 3.14 days.

The team analyzed the signals, testing different potential astrophysical scenarios for their origin, and confirmed that the signals were likely of a transiting planet, and not a product of some other phenomena such as a binary system of two spiraling stars.

The researchers then planned to get a closer look at the star and its orbiting planet with SPECULOOS. But first, they had to identify a window of time when they would be sure to catch a transit.

“Nailing down the best night to follow up from the ground is a little bit tricky,” says Rackham, who developed a forecasting algorithm to predict when a transit might next occur. “Even when you see this 3.14 day signal in the K2 data, there’s an uncertainty to that, which adds up with every orbit.”

With Rackham’s forecasting algorithm, the group narrowed in on several nights in February 2020 during which they were likely to see the planet crossing in front of its star. They then pointed SPECULOOS’ telescopes in the direction of the star and were able to see three clear transits: two with the network’s Southern Hemisphere telescopes, and the third from Artemis, in the Northern Hemisphere.

The researchers say the new pi planet may be a promising candidate to follow up with the James Webb Space Telescope (JWST), to see details of the planet’s atmosphere. For now, the team is looking through other datasets, such as from NASA’s TESS mission, and are also directly observing the skies with Artemis and the rest of the SPECULOOS network, for signs of Earthlike planets.

“There will be more interesting planets in the future, just in time for JWST, a telescope designed to probe the atmosphere of these alien worlds,” says Niraula. “With better algorithms, hopefully one day, we can look for smaller planets, even as small as Mars.”

This research was supported in part by the Heising-Simons Foundation, and the European Research Council.

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Enormous planet quickly orbiting a tiny, dying star

Thanks to a bevy of telescopes in space and on Earth — and even a pair of amateur astronomers in Arizona — a University of Wisconsin-Madison astronomer and his colleagues have discovered a Jupiter-sized planet orbiting at breakneck speed around a distant white dwarf star. The system, about 80 light years away, violates all common conventions about stars and planets. The white dwarf is the remnant of a sun-like star, greatly shrunken down to roughly the size of Earth, yet it retains half the sun’s mass. The massive planet looms over its tiny star, which it circles every 34 hours thanks to an incredibly close orbit. In contrast, Mercury takes a comparatively lethargic 90 days to orbit the sun. While there have been hints of large planets orbiting close to white dwarfs in the past, the new findings are the clearest evidence yet that these bizarre pairings exist. That confirmation highlights the diverse ways stellar systems can evolve and may give a glimpse at our own solar system’s fate. Such a white dwarf system could even provide a rare habitable arrangement for life to arise in the light of a dying star.

“We’ve never seen evidence before of a planet coming in so close to a white dwarf and surviving. It’s a pleasant surprise,” says lead researcher Andrew Vanderburg, who recently joined the UW-Madison astronomy department as an assistant professor. Vanderburg completed the work while an independent NASA Sagan Fellow at the University of Texas at Austin.

The researchers published their findings Sept. 16 in the journal Nature. Vanderburg led a large, international collaboration of astronomers who analyzed the data. The contributing telescopes included NASA’s exoplanet-hunting telescope TESS and two large ground-based telescopes in the Canary Islands.

Vanderburg was originally drawn to studying white dwarfs — the remains of sun-sized stars after they exhaust their nuclear fuel — and their planets by accident. While in graduate school, he was reviewing data from TESS’s predecessor, the Kepler space telescope, and noticed a white dwarf with a cloud of debris around it.

“What we ended up finding was that this was a minor planet or asteroid that was being ripped apart as we watched, which was really cool,” says Vanderburg. The planet had been destroyed by the star’s gravity after its transition to a white dwarf caused the planet’s orbit to fall in toward the star.

Ever since, Vanderburg has wondered if planets, especially large ones, could survive the journey in toward an aging star.

By scanning data for thousands of white dwarf systems collected by TESS, the researchers spotted a star whose brightness dimmed by half about every one-and-a-half days, a sign that something big was passing in front of the star on a tight, lightning-fast orbit. But it was hard to interpret the data because the glare from a nearby star was interfering with TESS’s measurements. To overcome this obstacle, the astronomers supplemented the TESS data from higher-resolution ground-based telescopes, including three run by amateur astronomers.

“Once the glare was under control, in one night, they got much nicer and much cleaner data than we got with a month of observations from space,” says Vanderburg. Because white dwarfs are so much smaller than normal stars, large planets passing in front of them block a lot of the star’s light, making detection by ground-based telescopes much simpler.

The data revealed that a planet roughly the size of Jupiter, perhaps a little larger, was orbiting very close to its star. Vanderburg’s team believes the gas giant started off much farther from the star and moved into its current orbit after the star evolved into a white dwarf.

The question became: how did this planet avoid being torn apart during the upheaval? Previous models of white dwarf-planet interactions didn’t seem to line up for this particular star system.

The researchers ran new simulations that provided a potential answer to the mystery. When the star ran out of fuel, it expanded into a red giant, engulfing any nearby planets and destabilizing the Jupiter-sized planet that orbited farther away. That caused the planet to take on an exaggerated, oval orbit that passed very close to the now-shrunken white dwarf but also flung the planet very far away at the orbit’s apex.

Over eons, the gravitational interaction between the white dwarf and its planet slowly dispersed energy, ultimately guiding the planet into a tight, circular orbit that takes just one-and-a-half days to complete. That process takes time — billions of years. This particular white dwarf is one of the oldest observed by the TESS telescope at almost 6 billion years old, plenty of time to slow down its massive planet partner.

While white dwarfs no longer conduct nuclear fusion, they still release light and heat as they cool down. It’s possible that a planet close enough to such a dying star would find itself in the habitable zone, the region near a star where liquid water can exist, presumed to be required for life to arise and survive.

Now that research has confirmed these systems exist, they offer a tantalizing opportunity for searching for other forms of life. The unique structure of white dwarf-planet systems provides an ideal opportunity to study the chemical signatures of orbiting planets’ atmospheres, a potential way to search for signs of life from afar.

“I think the most exciting part of this work is what it means for both habitability in general — can there be hospitable regions in these dead solar systems — and also our ability to find evidence of that habitability,” says Vanderburg.

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Unique supernova explosion

One-hundred million light years away from Earth, an unusual supernova is exploding.

That exploding star — which is known as “supernova LSQ14fmg” — was the faraway object discovered by a 37-member international research team led by Florida State University Assistant Professor of Physics Eric Hsiao. Their research, which was published in the Astrophysical Journal, helped uncover the origins of the group of supernovae this star belongs to.

This supernova’s characteristics — it gets brighter extremely slowly, and it is also one of the brightest explosions in its class — are unlike any other.

“This was a truly unique and strange event, and our explanation for it is equally interesting,” said Hsiao, the paper’s lead author.

The exploding star is what is known as a Type Ia supernova, and more specifically, a member of the “super-Chandrasekhar” group.

Stars go through a sort of life cycle, and these supernovae are the exploding finale of some stars with low mass. They are so powerful that they shape the evolution of galaxies, and so bright that we can observe them from Earth even halfway across the observable universe.

An image of the “Blue Snowball” planetary nebula taken with the Florida State University Observatory. The supernova LSQ14fmg exploded in a system similar to this, with a central star losing a copious amount of mass through a stellar wind. When the mass loss abruptly stopped, it created a ring of material surrounding the star. Courtesy of Eric Hsiao

Type Ia supernovae were crucial tools for discovering what’s known as dark energy, which is the name given to the unknown energy that causes the current accelerated expansion of the universe. Despite their importance, astronomers knew little about the origins of these supernova explosions, other than that they are the thermonuclear explosions of white dwarf stars.

But the research team knew that the light from a Type Ia supernova rises and falls over the course of weeks, powered by the radioactive decay of nickel produced in the explosion. A supernova of that type would get brighter as the nickel becomes more exposed, then fainter as the supernova cools and the nickel decays to cobalt and to iron.

After collecting data with telescopes in Chile and Spain, the research team saw that the supernova was hitting some material surrounding it, which caused more light to be released along with the light from the decaying nickel. They also saw evidence that carbon monoxide was being produced. Those observations led to their conclusion — the supernova was exploding inside what had been an asymptotic giant branch (AGB) star on the way to becoming a planetary nebula.

“Seeing how the observation of this interesting event agrees with the theory is very exciting,” said Jing Lu, an FSU doctoral candidate and a co-author of the paper.

They theorized that the explosion was triggered by the merger of the core of the AGB star and another white dwarf star orbiting within it. The central star was losing a copious amount of mass through a stellar wind before the mass loss was turned off abruptly and created a ring of material surrounding the star. Soon after the supernova exploded, it impacted a ring of material often seen in planetary nebulae and produced the extra light and the slow brightening observed.

“This is the first strong observational proof that a Type Ia supernova can explode in a post-AGB or proto-planetary-nebula system and is an important step in understanding the origins of Type Ia supernovae,” Hsiao said. “These supernovae can be particularly troublesome because they can mix into the sample of normal supernovae used to study dark energy. This research gives us a better understanding of the possible origins of Type Ia supernovae and will help to improve future dark energy research.”

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Meteorite strikes may create unexpected form of silica

When a meteorite hurtles through the atmosphere and crashes to Earth, how does its violent impact alter the minerals found at the landing site? What can the short-lived chemical phases created by these extreme impacts teach scientists about the minerals existing at the high-temperature and pressure conditions found deep inside the planet?

New work led by Carnegie’s Sally June Tracy examined the crystal structure of the silica mineral quartz under shock compression and is challenging longstanding assumptions about how this ubiquitous material behaves under such intense conditions. The results are published in Science Advances.

“Quartz is one of the most abundant minerals in Earth’s crust, found in a multitude of different rock types,” Tracy explained. “In the lab, we can mimic a meteorite impact and see what happens.”

Tracy and her colleagues — Washington State University’s (WSU) Stefan Turneaure and Princeton University’s Thomas Duffy, a former Carnegie Fellow — used a specialized cannon-like gas gun to accelerate projectiles into quartz samples at extremely high speeds — several times faster than a bullet fired from a rifle. Special x-ray instruments were used to discern the crystal structure of the material that forms less than one-millionth of a second after impact. Experiments were carried out at the Dynamic Compression Sector (DCS), which is operated by WSU and located at the Advanced Photon Source, Argonne National Laboratory.

Quartz is made up of one silicon atom and two oxygen atoms arranged in a tetrahedral lattice structure. Because these elements are also common in the silicate-rich mantle of the Earth, discovering the changes quartz undergoes at high-pressure and -temperature conditions, like those found in the Earth’s interior, could also reveal details about the planet’s geologic history.

When a material is subjected to extreme pressures and temperatures, its internal atomic structure can be re-shaped, causing its properties to shift. For example, both graphite and diamond are made from carbon. But graphite, which forms at low pressure, is soft and opaque, and diamond, which forms at high pressure, is super-hard and transparent. The different arrangements of carbon atoms determine their structures and their properties, and that in turn affects how we engage with and use them.

Despite decades of research, there has been a long-standing debate in the scientific community about what form silica would take during an impact event, or under dynamic compression conditions such as those deployed by Tracy and her collaborators. Under shock loading, silica is often assumed to transform to a dense crystalline form known as stishovite — a structure believed to exist in the deep Earth. Others have argued that because of the fast timescale of the shock the material will instead adopt a dense, glassy structure.

Tracy and her team were able to demonstrate that counter to expectations, when subjected to a dynamic shock of greater than 300,000 times normal atmospheric pressure, quartz undergoes a transition to a novel disordered crystalline phase, whose structure is intermediate between fully crystalline stishovite and a fully disordered glass. However, the new structure cannot last once the burst of intense pressure has subsided.

“Dynamic compression experiments allowed us to put this longstanding debate to bed,” Tracy concluded. “What’s more, impact events are an important part of understanding planetary formation and evolution and continued investigations can reveal new information about these processes.”

This research was supported by the Defense Threat Reduction Agency and the NSF. Washington State University (WSU) provided experimental support through awards from the U.S. Department of Energy (DOE)/National Nuclear Security Agency (NNSA).

This work is based on experiments performed at the Dynamic Compression Sector, operated by WSU under a DOE/ NNSA award. This research used the resources of the Advanced Photon Source, a Department of Energy Office of Science User Facility operated for the DOE Office of Science by the Argonne National .

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New insights for sun-gathering technologies

Every hour, the sun saturates the earth with more energy than humans use in a year. Harnessing some of this energy to meet global demand has become a grand challenge, with the world poised to double its energy consumption in just thirty years.

In a new study, researchers at the Biodesign Center for Applied Structural Discovery (CASD) and ASU’s School of Molecular Sciences take a page from Nature’s lesson book. Inspired by the way plants and other photosynthetic organisms collect and use the sun’s radiant energy, they hope to develop technologies that harvest sunlight and store it as carbon-free or carbon-neutral fuels.

“This article describes a general yet useful strategy for better understanding the role of catalysts in emerging technologies for converting sunlight to fuels,” says corresponding author Gary Moore.

The research appears in the current issue of the American Chemical Society (ACS) journal Applied Energy Materials.

Despite the advances in solar panel technologies, their limitations are apparent. Researchers would like to store accumulated energy from the sun in a concentrated form, to be used when and where it is needed. Catalysts — materials that act to speed up the rate at which chemical reactions occur — are a critical ingredient for harvesting sunlight and stockpiling it as fuels, through a process known as photoelectrosynthesis.

As the authors demonstrate, however, the effectiveness of catalysts is critically dependent on how they are used in new green technologies. The goal is to maximize energy efficiency and where possible, make use of earth-abundant elements.

According to Brian Wadsworth, researcher in the CASD center and lead author of the new study, a less-is-more approach to catalysts may improve the performance of photoelectrosynthetic devices:

“There is a traditional notion that relatively high loadings of catalyst are beneficial to maximizing the reaction rates and related performance of catalytic materials,” Wadsworth says. “However, this design strategy should not always be implemented in assemblies involving the capture and conversion of solar energy as relatively thick catalyst layers can hamper performance by screening sunlight from reaching an underlying light-absorbing material and/or disfavoring the accumulation of catalytically-active states.”

The new research provides a framework for better understanding catalytic performance in solar fuel devices and points the way to further discoveries.

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The most sensitive instrument in the search for life beyond Earth

The question of whether life exists beyond the Earth is one of humanity’s most fundamental questions. Future NASA missions, for example, aim to examine the ice moons of Jupiter and Saturn, which may potentially shelter life in the liquid oceans underneath the thick layer of ice, on the ground. Proving traces of life beyond the Earth is extremely challenging, however. Highly sensitive instruments which take measurements on the ground with the greatest possible degree of autonomy and with high precision — millions of kilometers from the Earth and thus without direct support from humankind — are required.

An international group of researchers under the leadership of Andreas Riedo and Niels Ligterink at the University of Bern have now developed ORIGIN, a mass spectrometer which can detect and identify the smallest amounts of such traces of life. They describe the instrument in a recently published article in the specialist journal Nature Scientific Reports. Niels Ligterink from the Center for Space and Habitability (CSH) is the lead author of the international study, and co-author Andreas Riedo from the Physics Institute at the University of Bern developed the instrument in the laboratories of the space research and planetary sciences divison of the Physics Institute. Various international space agencies, particularly NASA, have already expressed interest in testing ORIGIN for future missions.

New instrument required

Since the first Mars mission “Viking” in the 1970s, humanity has been searching for traces of life on Mars using highly specialized instruments which are installed on landing platforms and rovers. In its early years, Mars was Earth-like, had a dense atmosphere and even liquid water. However, as Niels Ligterink explains, Mars lost its protective atmosphere over the course of time: “As a result of this, the surface of Mars is subjected to high solar and cosmic radiation which makes life on the surface impossible.” NASA’s “Curiosity” rover is currently examining Mars in detail but with no concrete indications of traces of life to date.

Since the discovery by the Cassini and Galileo missions of the global oceans beneath kilometers of ice layers on Jupiter’s moon Europa and Saturn’s moon Enceladus, these two bodies have increasingly become the focus of the search for extraterrestrial life for researchers. According to current knowledge, the oceans have all of the properties which are not only needed for the occurrence of life, but also which provide environments in which life can exist in the long term. NASA therefore plans to land a mission on Jupiter’s moon Europa around 2030 and take measurements on the ground. The goal: Identification of life. Co-author Prof. Dr. Peter Wurz from the Physics Institute at the University of Bern says: “Concepts which were specially developed for Mars cannot be simply applied to other bodies in our solar systembecause they are very different. New instruments with higher sensitivity and simpler and more robust analysis systems must be designed and used.”

Unprecedented measurement sensitivity for proof of life in space

ORIGIN is one such new instrument which outperforms previous space instruments many terms over in terms of its measurement sensitivty. Various international space agencies have expressed great interest in the instrument for future missions. Andreas Riedo says: “NASA has invited us to particpaite and test our instrument in the Arctic. The Artic is the optimal test environment in the context of the EUROPA LANDER mission, which should start in 2025, which will allow us to demonstrate the performance of ORIGIN.”

Amino acids are key components of life as we know it on Earth. Contemporaneous proof of certain amino acids on extraterrestrial surfaces, such as those of Europa, allow conclusions to be drawn about possible life. The measurement principle developed by the Bern-based researchers is simple. Niels Ligterink explains: “Laser pulses are directed at the surface to be examined. In the process, small amounts of material are detached, the chemical composition of which is analyzed by ORIGIN in a second step.” Andreas Riedo adds: “The compelling aspect of our technology is that no complicated sample preparation techniques, which could potentially affect the result, are required. This was one of the biggest problems on Mars until now,” says Riedo. The amino acids which have been analyzed with ORIGIN to date have a specific chemical fingerprint which allows them to be directly identified. Niels Ligterink: “To be honest, we didn’t expect that our first measurements would already be able to identify amino acids.”

The discovery of traces of past or present life on bodies in our solar system beyond the Earth is of great importance for a better understanding of the existence of life in the universe and its genesis. Andreas Riedo says: “Our new measurement technology is a real improvement on the instruments currently used on space missions. If we are taken along on a future mission, we may be able to answer one of humanity’s most fundamental questions with ORIGIN: Is there life in space?.”

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Surprising number of exoplanets could host life

Our solar system has one habitable planet — Earth. A new study shows other stars could have as many as seven Earth-like planets in the absence of a gas giant like Jupiter.

This is the conclusion of a study led by UC Riverside astrobiologist Stephen Kane published this week in the Astronomical Journal.

The search for life in outer space is typically focused on what scientists call the “habitable zone,” which is the area around a star in which an orbiting planet could have liquid water oceans — a condition for life as we know it.

Kane had been studying a nearby solar system called Trappist-1, which has three Earth-like planets in its habitable zone.

“This made me wonder about the maximum number of habitable planets it’s possible for a star to have, and why our star only has one,” Kane said. “It didn’t seem fair!”

His team created a model system in which they simulated planets of various sizes orbiting their stars. An algorithm accounted for gravitational forces and helped test how the planets interacted with each other over millions of years.

They found it is possible for some stars to support as many as seven, and that a star like our sun could potentially support six planets with liquid water.

“More than seven, and the planets become too close to each other and destabilize each other’s orbits,” Kane said.

Why then does our solar system only have one habitable planet if it is capable of supporting six? It helps if the planets’ movement is circular rather than oval or irregular, minimizing any close contact and maintain stable orbits.

Kane also suspects Jupiter, which has a mass two-and-a-half times that of all the other planets in the solar system combined, limited our system’s habitability.

“It has a big effect on the habitability of our solar system because it’s massive and disturbs other orbits,” Kane said.

Only a handful of stars are known to have multiple planets in their habitable zones. Moving forward, Kane plans to search for additional stars surrounded entirely by smaller planets. These stars will be prime targets for direct imaging with NASA telescopes like the one at Jet Propulsion Laboratory’s Habitable Exoplanet Observatory.

Kane’s study identified one such star, Beta CVn, which is relatively close by at 27 light years away. Because it doesn’t have a Jupiter-like planet, it will be included as one of the stars checked for multiple habitable zone planets.

Future studies will also involve the creation of new models that examine the atmospheric chemistry of habitable zone planets in other star systems.

Projects like these offer more than new avenues in the search for life in outer space. They also offer scientists insight into forces that might change life on our own planet one day.

“Although we know Earth has been habitable for most of its history, many questions remain regarding how these favorable conditions evolved with time, and the specific drivers behind those changes,” Kane said. “By measuring the properties of exoplanets whose evolutionary pathways may be similar to our own, we gain a preview into the past and future of this planet — and what we must do to main its habitability.”

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New approach refines the Hubble’s constant and age of universe

Using known distances of 50 galaxies from Earth to refine calculations in Hubble’s constant, a research team led by a University of Oregon astronomer estimates the age of the universe at 12.6 billion years.

Approaches to date the Big Bang, which gave birth to the universe, rely on mathematics and computational modeling, using distance estimates of the oldest stars, the behavior of galaxies and the rate of the universe’s expansion. The idea is to compute how long it would take all objects to return to the beginning.

A key calculation for dating is the Hubble’s constant, named after Edwin Hubble who first calculated the universe’s expansion rate in 1929. Another recent technique uses observations of leftover radiation from the Big Bang. It maps bumps and wiggles in spacetime — the cosmic microwave background, or CMB — and reflects conditions in the early universe as set by Hubble’s constant.

However, the methods reach different conclusions, said James Schombert, a professor of physics at the UO. In a paper published July 17 in the Astronomical Journal, he and colleagues unveil a new approach that recalibrates a distance-measuring tool known as the baryonic Tully-Fisher relation independently of Hubble’s constant.

“The distance scale problem, as it is known, is incredibly difficult because the distances to galaxies are vast and the signposts for their distances are faint and hard to calibrate,” Schombert said.

Schombert’s team recalculated the Tully-Fisher approach, using accurately defined distances in a linear computation of the 50 galaxies as guides for measuring the distances of 95 other galaxies. The universe, he noted, is ruled by a series of mathematical patterns expressed in equations. The new approach more accurately accounts for the mass and rotational curves of galaxies to turn those equations into numbers like age and expansion rate.

His team’s approach determines the Hubble’s constant — the universe’s expansion rate — at 75.1 kilometers per second per megaparsec, give or take 2.3. A megaparsec, a common unit of space-related measurements, is equal to one million parsecs. A parsec is about 3.3 light years.

All Hubble’s constant values lower than 70, his team wrote, can be ruled out with 95 percent degree of confidence.

Traditionally used measuring techniques over the past 50 years, Schombert said, have set the value at 75, but CMB computes a rate of 67. The CMB technique, while using different assumptions and computer simulations, should still arrive at the same estimate, he said.

“The tension in the field occurs from the fact that it does not,” Schombert said. “This difference is well outside the observational errors and produced a great deal of friction in the cosmological community.”

Calculations drawn from observations of NASA’s Wilkinson Microwave Anisotropy Probe in 2013 put the age of the universe at 13.77 billion years, which, for the moment, represents the standard model of Big Bang cosmology. The differing Hubble’s constant values from the various techniques generally estimate the universe’s age at between 12 billion and 14.5 billion years.

The new study, based in part on observations made with the Spitzer Space Telescope, adds a new element to how calculations to reach Hubble’s constant can be set, by introducing a purely empirical method, using direct observations, to determine the distance to galaxies, Schombert said.

“Our resulting value is on the high side of the different schools of cosmology, signaling that our understanding of the physics of the universe is incomplete with the hope of new physics in the future,” he said.

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An origin story for a family of oddball meteorites

Most meteorites that have landed on Earth are fragments of planetesimals, the very earliest protoplanetary bodies in the solar system. Scientists have thought that these primordial bodies either completely melted early in their history or remained as piles of unmelted rubble.

But a family of meteorites has befuddled researchers since its discovery in the 1960s. The diverse fragments, found all over the world, seem to have broken off from the same primordial body, and yet the makeup of these meteorites indicates that their parent must have been a puzzling chimera that was both melted and unmelted.

Now researchers at MIT and elsewhere have determined that the parent body of these rare meteorites was indeed a multilayered, differentiated object that likely had a liquid metallic core. This core was substantial enough to generate a magnetic field that may have been as strong as Earth’s magnetic field is today.

Their results, published in the journal Science Advances, suggest that the diversity of the earliest objects in the solar system may have been more complex than scientists had assumed.

“This is one example of a planetesimal that must have had melted and unmelted layers. It encourages searches for more evidence of composite planetary structures,” says lead author Clara Maurel, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS). “Understanding the full spectrum of structures, from nonmelted to fully melted, is key to deciphering how planetesimals formed in the early solar system.”

Maurel’s co-authors include EAPS professor Benjamin Weiss, along with collaborators at Oxford University, Cambridge University, the University of Chicago, Lawrence Berkeley National Laboratory, and the Southwest Research Institute.

Oddball irons

The solar system formed around 4.5 billion years ago as a swirl of super-hot gas and dust. As this disk gradually cooled, bits of matter collided and merged to form progressively larger bodies, such as planetesimals.

The majority of meteorites that have fallen to Earth have compositions that suggest they came from such early planetesimals that were either of two types: melted, and unmelted. Both types of objects, scientists believe, would have formed relatively quickly, in less than a few million years, early in the solar system’s evolution.

If a planetesimal formed in the first 1.5 million years of the solar system, short-lived radiogenic elements could have melted the body entirely due to the heat released by their decay. Unmelted planetesimals could have formed later, when their material had lower quantities of radiogenic elements, insufficient for melting.

There has been little evidence in the meteorite record of intermediate objects with both melted and unmelted compositions, except for a rare family of meteorites called IIE irons.

“These IIE irons are oddball meteorites,” Weiss says. “They show both evidence of being from primordial objects that never melted, and also evidence for coming from a body that’s completely or at least substantially melted. We haven’t known where to put them, and that’s what made us zero in on them.”

Magnetic pockets

Scientists have previously found that both melted and unmelted IIE meteorites originated from the same ancient planetesimal, which likely had a solid crust overlying a liquid mantle, like Earth. Maurel and her colleagues wondered whether the planetesimal also may have harbored a metallic, melted core.

“Did this object melt enough that material sank to the center and formed a metallic core like that of the Earth?” Maurel says. “That was the missing piece to the story of these meteorites.”

The team reasoned that if the planetesimal did host a metallic core, it could very well have generated a magnetic field, similar to the way Earth’s churning liquid core produces a magnetic field. Such an ancient field could have caused minerals in the planetesimal to point in the direction of the field, like a needle in a compass. Certain minerals could have kept this alignment over billions of years.

Maurel and her colleagues wondered whether they might find such minerals in samples of IIE meteorites that had crashed to Earth. They obtained two meteorites, which they analyzed for a type of iron-nickel mineral known for its exceptional magnetism-recording properties.

The team analyzed the samples using the Lawrence Berkeley National Laboratory’s Advanced Light Source, which produces X-rays that interact with mineral grains at the nanometer scale, in a way that can reveal the minerals’ magnetic direction.

Sure enough, the electrons within a number of grains were aligned in a similar direction — evidence that the parent body generated a magnetic field, possibly up to several tens of microtesla, which is about the strength of Earth’s magnetic field. After ruling out less plausible sources, the team concluded that the magnetic field was most likely produced by a liquid metallic core. To generate such a field, they estimate the core must have been at least several tens of kilometers wide.

Such complex planetesimals with mixed composition (both melted, in the form of a liquid core and mantle, and unmelted in the form of a solid crust), Maurel says, would likely have taken over several million years to form — a formation period that is longer than what scientists had assumed until recently.

But where within the parent body did the meteorites come from? If the magnetic field was generated by the parent body’s core, this would mean that the fragments that ultimately fell to Earth could not have come from the core itself. That’s because a liquid core only generates a magnetic field while still churning and hot. Any minerals that would have recorded the ancient field must have done so outside the core, before the core itself completely cooled.

Working with collaborators at the University of Chicago, the team ran high-velocity simulations of various formation scenarios for these meteorites. They showed that it was possible for a body with a liquid core to collide with another object, and for that impact to dislodge material from the core. That material would then migrate to pockets close to the surface where the meteorites originated.

“As the body cools, the meteorites in these pockets will imprint this magnetic field in their minerals. At some point, the magnetic field will decay, but the imprint will remain,” Maurel says. “Later on, this body is going to undergo a lot of other collisions until the ultimate collisions that will place these meteorites on Earth’s trajectory.”

Was such a complex planetesimal an outlier in the early solar system, or one of many such differentiated objects? The answer, Weiss says, may lie in the asteroid belt, a region populated with primordial remnants.

“Most bodies in the asteroid belt appear unmelted on their surface,” Weiss says. “If we’re eventually able to see inside asteroids, we might test this idea. Maybe some asteroids are melted inside, and bodies like this planetesimal are actually common.”

This research was funded, in part, by NASA.

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Higher concentration of metal in Moon’s craters provides new insights to its origin

Life on Earth would not be possible without the Moon; it keeps our planet’s axis of rotation stable, which controls seasons and regulates our climate. However, there has been considerable debate over how the Moon was formed. The popular hypothesis contends that the Moon was formed by a Mars-sized body colliding with Earth’s upper crust which is poor in metals. But new research suggests the Moon’s subsurface is more metal-rich than previously thought, providing new insights that could challenge our understanding of that process.

Today, a study published in Earth and Planetary Science Letters sheds new light on the composition of the dust found at the bottom of the Moon’s craters. Led by Essam Heggy, research scientist of electrical and computer engineering at the USC Viterbi School of Engineering, and co-investigator of the Mini-RF instrument onboard NASA Lunar Reconnaissance Orbiter (LRO), the team members of the Miniature Radio Frequency (Mini-RF) instrument on the Lunar Reconnaissance Orbiter (LRO) mission used radar to image and characterize this fine dust. The researchers concluded that the Moon’s subsurface may be richer in metals (i.e. Fe and Ti oxides) than scientists had believed.

According to the researchers, the fine dust at the bottom of the Moon’s craters is actually ejected materials forced up from below the Moon’s surface during meteor impacts. When comparing the metal content at the bottom of larger and deeper craters to that of the smaller and shallower ones, the team found higher metal concentrations in the deeper craters.

What does a change in recorded metal presence in the subsurface have to do with our understanding of the Moon? The traditional hypothesis is that approximately 4.5 billion years ago there was a collision between Earth and a Mars-sized proto-planet (named Theia). Most scientists believe that that collision shot a large portion of Earth’s metal-poor upper crust into orbit, eventually forming the Moon.

One puzzling aspect of this theory of the Moon’s formation, has been that the Moon has a higher concentration of iron oxides than the Earth — a fact well-known to scientists. This particular research contributes to the field in that it provides insights about a section of the moon that has not been frequently studied and posits that there may exist an even higher concentration of metal deeper below the surface. It is possible, say the researchers that the discrepancy between the amount of iron on the Earth’s crust and the Moon could be even greater than scientists thought, which pulls into question the current understanding of how the Moon was formed.

The fact that our Moon could be richer in metals than the Earth challenges the notion that it was portions of Earth’s mantle and crust that were shot into orbit. A greater concentration of metal deposits may mean that other hypotheses about the Moon’s formation must be explored. It may be possible that the collision with Theia was more devastating to our early Earth, with much deeper sections being launched into orbit, or that the collision could have occurred when Earth was still young and covered by a magma ocean. Alternatively, more metal could hint at a complicated cool-down of an early molten Moon surface, as suggested by several scientists.

According to Heggy, “By improving our understanding of how much metal the Moon’s subsurface actually has, scientists can constrain the ambiguities about how it has formed, how it is evolving and how it is contributing to maintaining habitability on Earth.” He further added, “Our solar system alone has over 200 moons — understanding the crucial role these moons play in the formation and evolution of the planets they orbit can give us deeper insights into how and where life conditions outside Earth might form and what it might look like.”

Wes Patterson of the Planetary Exploration Group (SRE), Space Exploration Sector (SES) at Johns Hopkins University Applied Physics Laboratory, who is the project’s principal investigator for Mini-RF and a co-author of the study, added, “The LRO mission and its radar imager Mini-RF are continuing to surprise us with new insights into the origins and complexity of our nearest neighbor.”

The team plans to continue carrying out additional radar observations of more crater floors with the Mini-RF experiment to verify the initial findings of the published investigation.

This research project was funded through the University of Southern California under NASA award NNX15AV76G.

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Materials provided by University of Southern California. Original written by Ben Paul. Note: Content may be edited for style and length.

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