Geochemical Detectives Use Lab Mimicry To Look Back In Time

New work from a research team led by Carnegie’s Anat Shahar contains some unexpected findings about iron chemistry under high-pressure conditions, such as those likely found in the Earth’s core, where iron predominates and creates our planet’s life-shielding magnetic field. Their results, published in Science, could shed light on Earth’s early days when the core was formed through a process called differentiation–when the denser materials, like iron, sunk inward toward the center, creating the layered composition the planet has today.

earth

Earth formed from accreted matter surrounding the young Sun. Over time, the iron in this early planetary material moved inward, separating from the surrounding silicate. This process created the planet’s iron core and silicate upper mantle. But much about this how this differentiation process occurred is still poorly understood, due to the technological impossibility of taking samples from the Earth’s core to see which compounds exist there.

Seismic data show that in addition to iron, there are “lighter” elements present in the core, but which elements and in what concentrations they exist has been a matter of great debate. This is because as the iron moved inward toward the core, it interacted with various lighter elements to form different alloyed compounds, which were then carried along with the iron into the planet’s depths.

Which elements iron bonded with during this time would have been determined by the surrounding conditions, including pressure and temperature. As a result, working backward and determining which iron alloy compounds were created during differentiation could tell scientists about the conditions on early Earth and about the planet’s geochemical evolution.

The team–including Carnegie’s Jinfu Shu and Yuming Xiao–decided to investigate this subject by researching how pressures mimicking the Earth’s core would affect the composition of iron isotopes in various alloys of iron and light elements. Isotopes are versions of an element where the number of neutrons differs from the number of protons. (Each element contains a unique number of protons.)

Because of this accounting difference, isotopes’ masses are not the same, which can sometimes cause small variations in how different isotopes of the same element are partitioned in, or are “picked up” by, either silicate or iron metal. Some isotopes are preferred by certain reactions, which results in an imbalance in the proportion of each isotope incorporated into the end products of these reactions–a process that can leave behind trace isotopic signatures in rocks. This phenomenon is called isotope fractionation and is crucial to the team’s research.

Before now, pressure was not considered a critical variable affecting isotope fractionation. But Shahar and her team’s research demonstrated that for iron, extreme pressure conditions do affect isotope fractionation.

More importantly, the team discovered that due to this high-pressure fractionation, reactions between iron and two of the light elements often considered likely to be present in the core–hydrogen and carbon–would have left behind an isotopic signature in the mantle silicate as they reacted with iron and sunk to the core. But this isotopic signature has not been found in samples of mantle rock, so scientists can exclude them from the list of potential light elements in the core.

Oxygen, on the other hand, would not have left an isotopic signature behind in the mantle, so it is still on the table. Likewise, other potential core light elements still need to be investigated, including silicon and sulfur.

“What does this mean? It means we are gaining a better understanding of our planet’s chemical and physical history,” Shahar explained. “Although Earth is our home, there is still so much about its interior that we don’t understand. But evidence that extreme pressures affect how isotopes partition, in ways that we can see traces of in rock samples, is a huge step forward in learning about our planet’s geochemical evolution.”

Cassini Explores A Methane Sea On Titan

Of the hundreds of moons in our solar system, Titan is the only one with a dense atmosphere and large liquid reservoirs on its surface, making it in some ways more like a terrestrial planet.

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Both Earth and Titan have nitrogen-dominated atmospheres — over 95 percent nitrogen in Titan’s case. However, unlike Earth, Titan has very little oxygen; the rest of the atmosphere is mostly methane and trace amounts of other gases, including ethane. And at the frigid temperatures found at Saturn’s great distance from the Sun, the methane and ethane can exist on the surface in liquid form.

For this reason, scientists had long speculated about the possible existence of hydrocarbon lakes and seas on Titan, and data from the NASA/ESA Cassini-Huygens mission does not disappoint. Since arriving in the Saturn system in 2004, the Cassini spacecraft has revealed that more than 620,000 square miles (1.6 million square kilometers) of Titan’s surface — almost two percent of the total — are covered in liquid.

There are three large seas, all located close to the moon’s north pole, surrounded by numerous of smaller lakes in the northern hemisphere. Just one large lake has been found in the southern hemisphere.

The exact composition of these liquid reservoirs remained elusive until 2014, when the Cassini radar instrument was first used to show that Ligeia Mare, the second largest sea on Titan and similar in size to Lake Huron and Lake Michigan combined, is methane-rich. A new study published in the Journal of Geophysical Research: Planets, which used the radar instrument in a different mode, independently confirms this result.

“Before Cassini, we expected to find that Ligeia Mare would be mostly made up of ethane, which is produced in abundance in the atmosphere when sunlight breaks methane molecules apart. Instead, this sea is predominantly made of pure methane,” said Alice Le Gall, a Cassini radar team associate at the French research laboratory LATMOS, Paris, and lead author of the new study.

The new study is based on data collected with Cassini’s radar instrument during flybys of Titan between 2007 and 2015.

A number of possible explanations could account for the sea’s methane composition, according to Le Gall. “Either Ligeia Mare is replenished by fresh methane rainfall, or something is removing ethane from it. It is possible that the ethane ends up in the undersea crust, or that it somehow flows into the adjacent sea, Kraken Mare, but that will require further investigation.”

In their research, the scientists combined several radar observations of heat given off by Ligeia Mare. They also used data from a 2013 experiment that bounced radio signals off Ligeia. The results of that experiment were presented in a 2014 paper led by radar team associate Marco Mastrogiuseppe at Cornell University, Ithaca, New York, who also contributed to the current study.

During the 2013 experiment, the radar instrument detected echoes from the seafloor and inferred the depth of Ligeia Mare along Cassini’s track over Ligeia Mare — the first-ever detection of the bottom of an extraterrestrial sea. The scientists were surprised to find depths in the sea as great as 525 feet (160 meters) at the deepest point along the radar track.

Le Gall and her colleagues used the depth-sounding information to separate the contributions made to the sea’s observed temperature by the liquid sea and the seabed, which provided insights into their respective compositions.

“We found that the seabed of Ligeia Mare is likely covered by a sludge layer of organic-rich compounds,” adds Le Gall.

In the atmosphere of Titan, nitrogen and methane react to produce a wide variety of organic materials. Scientists believe the heaviest materials fall to the surface. Le Gall and colleagues think that when these compounds reach the sea, either by directly falling from the air, via rain or through Titan’s rivers, some are dissolved in the liquid methane. The insoluble compounds, such as nitriles and benzene, sink to the sea floor.

The study also found that the shoreline around Ligeia Mare may be porous and flooded with liquid hydrocarbons. The data span a period running from local winter to spring, and the scientists expected that — like the seaside on Earth — the surrounding solid terrains would warm more rapidly than the sea.

However, Cassini’s measurements did not show any significant difference between the sea’s temperature and that of the shore over this period. This suggests that the terrains surrounding the lakes and seas are wet with liquid hydrocarbons, which would make them warm up and cool down much like the sea itself.

“It’s a marvelous feat of exploration that we’re doing extraterrestrial oceanography on an alien moon,” said Steve Wall, deputy lead of the Cassini radar team at NASA’s Jet Propulsion Laboratory in Pasadena, California. “Titan just won’t stop surprising us.”

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the US and several European countries.

Rainwater May Play An Important Role In Process That Triggers Earthquakes

Rainwater may play an important role in the process that triggers earthquakes, according to new research.

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Researchers from the University of Southampton, GNS Science (New Zealand), the University of Otago, and GFZ Potsdam (Germany), identified the sources and fluxes of the geothermal fluids and mineral veins from the Southern Alps of New Zealand where the Pacific and Australian Plates collide along the Alpine Fault.

From careful chemical analyses, they discovered that fluids originating from the mantle, the layer below Earth’s crust, and fluids derived from rainwater, are channelled up the Alpine Fault.

By calculating how much fluid is flowing through the fault zone at depth, the researchers showed for the first time that enough rainwater is present to promote earthquake rupture on this major plate boundary fault.

Lead researcher Dr Catriona Menzies, from Ocean and Earth Science at the University of Southampton, said: “Large, continental-scale faults can cause catastrophic earthquakes, but the trigger mechanisms for major seismic events are not well known. Geologists have long suspected that deep groundwaters may be important for the initiation of earthquakes as these fluids can weaken the fault zones by increasing pressures or through chemical reactions.

“Fluids are important in controlling the evolution of faults between earthquake ruptures. Chemical reactions may alter the strength and permeability of rocks, and if enough fluid is present at sufficiently high pressures they may aid earthquake rupture by ‘pumping up’ the fault zone.”

The Alpine Fault is a major strike-slip fault, like the San Andreas, that fails in very large (Magnitude 8+) earthquakes around every 300 years. It last ruptured in 1717 AD and consequently it is under intense scientific scrutiny because it is a rare example of a major fault that is late in the strain-build up before rupture.

Dr Menzies said: “We show that the Alpine Fault acts as a barrier to lateral fluid flow from the high mountains of the Southern Alps towards the Tasman Sea in the west. However, the presence of mantle-derived fluids indicates that the fault also acts as a channel for fluids, from more than 35 km depth, to ascend to the surface.

“As well as mantle derived fluids, our calculations indicate that 0.02-0.05 per cent of surface rainfall reaches around six kilometres depth but this is enough to overwhelm contributions from the mantle and fluids generated during mountain-building by metamorphic reactions in hot rocks. This rainwater is then focused onto the fault, forced by the hydraulic head of the high mountains above and the sub-vertical fluid flow barrier of the Alpine Fault.”

Funding for this research, published in Earth and Planetary Science Letters, was provided by the Natural Environmental Research Council (NERC), Deutsche Forschungsgemeinschaft, and GNS Science (New Zealand).

Light Echoes Give Clues To Planet Nursery Around Star

Imagine you want to measure the size of a room, but it’s completely dark. If you shout, you can tell if the space you’re in is relatively big or small, depending on how long it takes to hear the echo after it bounces off the wall.

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Astronomers use this principle to study objects so distant that they can’t be seen as more than points. In particular, researchers are interested in calculating how far young stars are from the inner edge of their surrounding protoplanetary disks. These disks of gas and dust are sites where planets form over the course of millions of years.

“Understanding protoplanetary disks can help us understand some of the mysteries about exoplanets, the planets in solar systems outside our own,” said Huan Meng, postdoctoral research associate at the University of Arizona’s Department of Astronomy and Steward Observatory. “We want to know how planets form and why we find large planets called ‘hot Jupiters’ close to their stars.”

Meng is the first author on a new study published in the Astrophysical Journal using data from NASA’s Spitzer Space Telescope and four ground-based telescopes to determine the distance from a star to the inner rim of its surrounding protoplanetary disk.

Making the measurement wasn’t as simple as laying a ruler on top of a photograph. Doing so would be as impossible as using a satellite photo of your computer screen to measure the width of the period at the end of this sentence.

Instead, researchers used a method called “photo-reverberation,” also known as “light echoes.” When the central star brightens, some of the light hits the surrounding disk, causing a delayed “echo.” Scientists measured the time it took for light coming directly from the star to reach Earth, then waited for its echo to arrive.

Thanks to Albert Einstein’s theory of special relativity, we know that light travels at a constant speed. To determine a given distance, astronomers can multiply the speed of light by the time light takes to get from one point to another.

To take advantage of this formula, scientists needed to find a star with variable emission — that is, a star that emits radiation in an unpredictable, uneven manner. Our own sun has a fairly stable emission, but a variable star would have unique, detectable changes in radiation that could be used for picking up corresponding light echoes. Young stars, which have variable emission, are the best candidates.

The star used in this study is called YLW 16B, which lies about 400 light-years from Earth. YLW 16B has about the same mass as our sun, but at one million years old, it’s just a baby compared to our 4.6-billion-year-old home star.

Astronomers combined Spitzer data with observations from ground-based telescopes: the Mayall telescope at Kitt Peak National Observatory in Arizona, the SOAR and SMARTS telescopes in Chile, and the Harold L. Johnson telescope in Mexico. During two nights of observation, researchers saw consistent time lags between the stellar emissions and their echoes in the surrounding disk. The ground-based observatories detected the shorter-wavelength infrared light emitted directly from the star, and Spitzer observed the longer-wavelength infrared light from the disk’s echo. Because of thick interstellar clouds that block the view from Earth, astronomers could not use visible light to monitor the star.

Researchers then calculated how far this light must have traveled during that time lag: about 0.08 astronomical units, which is approximately 8 percent of the distance between Earth and its sun, or one-quarter the diameter of Mercury’s orbit. This was slightly smaller than previous estimates with indirect techniques, but consistent with theoretical expectations.

Although this method did not directly measure the height of the disk, researchers were able to determine that the inner edge is relatively thick.

Previously, astronomers have used the light echo technique to measure the size of accretion disks of material around supermassive black holes. Since no light escapes from a black hole, researchers compare light from the inner edge of the accretion disk to light from the outer edge to determine the disk size. This technique is also used to measure the distance to other features near the accretion disk, such as dust and the surrounding fast-moving gas.

While light echoes from supermassive black holes represent delays of days to weeks, scientists measured the light echo from the protoplanetary disk in this study to be a mere 74 seconds.

The Spitzer study marks the first time the light echo method was used in the context of protoplanetary disks. The approach can be applied to other systems of stars with planet-forming disks around them, the scientists pointed out.

“Knowing the exact position of the inner boundary of a protoplanetary disk is important to anyone who wants to understand planet evolution,” Meng says.

Most stars are born with a protoplanetary disk around them, and astronomers have known for a long time that there is a gap between the star and its disk because of two competing processes: Close to the star, its strong radiation ionizes gas particles in the disk, diverting them along the star’s magnetic field lines above and below the plane of the disk. The other mechanism that prevents the disk from reaching all the way to the star’s surface is heat. Once a dust particle gets too close to the star, it simply vaporizes and either falls onto the star or gets blown out of the system.

“The predominant one of those two mechanisms plays an important role in the evolution of the disk, and right now, we don’t know which it is,” Meng says.

Until now, astronomers used a technique called interferometry to determine the position of the inner edge of protoplanetary disks, but that method requires assumptions about the shape of the disk, resulting in controversial findings.

“Our method provides a completely independent measurement of which mechanism plays the predominant role now and in the future,” Meng says.

Nearby Massive Star Explosion 30 Million Years Ago Equaled Detonation Of 100 Million Suns

A giant star that exploded 30 million years ago in a galaxy near Earth had a radius prior to going supernova that was 200 times larger than our Sun, according to astrophysicists at Southern Methodist University, Dallas.

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The sudden blast hurled material outward from the star at a speed of 10,000 kilometers a second. That’s equivalent to 36 million kilometers an hour or 22.4 million miles an hour, said SMU physicist Govinda Dhungana, lead author on the new analysis.

The comprehensive analysis of the exploding star’s light curve and color spectrum have revealed new information about the existence and sudden death of supernovae in general, many aspects of which have long baffled scientists.

“There are so many characteristics we can derive from the early data,” Dhungana said. “This was a big massive star, burning tremendous fuel. When it finally reached a point its core couldn’t support the gravitational pull inward, suddenly it collapsed and then exploded.”

The massive explosion was one of the closest to Earth in recent years, visible as a point of light in the night sky starting July 24, 2013, said Robert Kehoe, SMU physics professor, who leads SMU’s astrophysics team.

The explosion, termed by astronomers Supernova 2013ej, in a galaxy near our Milky Way was equal in energy output to the simultaneous detonation of 100 million of the Earth’s suns.

The star was one of billions in the spiral galaxy M74 in the constellation Pisces.

Considered close by supernova standards, SN 2013ej was in fact so far away that light from the explosion took 30 million years to reach Earth. At that distance, even such a large explosion was only visible by telescopes.

Dhungana and colleagues were able to explore SN 2013ej via a rare collection of extensive data from seven ground-based telescopes and NASA’s Swift satellite. The data span a time period prior to appearance of the supernova in July 2013 until more than 450 days after.

The team measured the supernova’s evolving temperature, its mass, its radius, the abundance of a variety of chemical elements in its explosion and debris and its distance from Earth. They also estimated the time of the shock breakout, the bright flash from the shockwave of the explosion.

The star’s original mass was about 15 times that of our sun, Dhungana said. Its temperature was a hot 12,000 Kelvin (approximately 22,000 degrees Fahrenheit) on the tenth day after the explosion, steadily cooling until it reached 4,500 Kelvin after 50 days. The sun’s surface is 5,800 Kelvin, while the Earth’s core is estimated to be about 6,000 Kelvin.

Shedding new light on supernovae, mysterious objects of our universe

Supernovae occur throughout the universe, but they are not fully understood. Scientists don’t directly observe the explosions but instead detect changes in emerging light as material is hurled from the exploding star in the seconds and days after the blast.

Telescopes such as SMU’s robotic ROTSE-IIIb telescope at McDonald Observatory in Texas, watch our sky and pick up the light as a point of brightening light. Others, such as the Hobby Eberly telescope, also at McDonald, observe a spectrum.

SN 2013ej is M74’s third supernova in just 10 years. That is quite frequent compared to our Milky Way, which has had a scant one supernova observed over the past 400 years. NASA estimates that the M74 galaxy consists of 100 billion stars.

M74 is one of only a few dozen galaxies first cataloged by the astronomer Charles Messier in the late 1700s. It has a spiral structure — also the Milky Way’s apparent shape — indicating it is still undergoing star formation, as opposed to being an elliptical galaxy in which new stars no longer form.

It’s possible that planets were orbiting SN 2013ej’s progenitor star prior to it going supernova, in which case those objects would have been obliterated by the blast, Kehoe said.

“If you were nearby, you wouldn’t know there was a problem beforehand, because at the surface you can’t see the core heating up and collapsing,” Kehoe said. “Then suddenly it explodes — and you’re toast.”

Distances to nearby galaxies help determine cosmic distance ladder

Scientists remain unsure whether supernovae leave behind a black hole or a neutron star like a giant atomic nucleus the size of a city.

“The core collapse and how it produces the explosion is particularly tricky,” Kehoe said. “Part of what makes SN 2013ej so interesting is that astronomers are able to compare a variety of models to better understand what is happening. Using some of this information, we are also able to calculate the distance to this object. This allows us a new type of object with which to study the larger universe, and maybe someday dark energy.”

Being 30 million light years away, SN 2013ej was a relatively nearby extragalactic event, according to Jozsef Vinko, astrophysicist at Konkoly Observatory and University of Szeged in Hungary.

“Distances to nearby galaxies play a significant role in establishing the so-called cosmic distance ladder, where each rung is a galaxy at a known distance.”

Vinko provided important data from telescopes at Konkoly Observatory and Hungary’s Baja Observatory and carried out distance measurement analysis on SN 2013ej.

“Nearby supernovae are especially important,” Vinko said. “Paradoxically, we know the distances to the nearest galaxies less certainly than to the more distant ones. In this particular case we were able to combine the extensive datasets of SN 2013ej with those of another supernova, SN 2002ap, both of which occurred in M74, to suppress the uncertainty of their common distance derived from those data.”

Supernova spectrum analysis is like taking a core sample

While stars appear to be static objects that exist indefinitely, in reality they are primarily a burning ball, fueled by the fusion of elements, including hydrogen and helium into heavier elements. As they exhaust lighter elements, they must contract in the core and heat up to burn heavier elements. Over time, they fuse the various chemical elements of the periodic table, proceeding from lightest to heaviest. Initially they fuse helium into carbon, nitrogen and oxygen. Those elements then fuel the fusion of progressively heavier elements such as sulfur, argon, chlorine and potassium.

“Studying the spectrum of a supernova over time is like taking a core sample,” Kehoe said. “The calcium in our bones, for example, was cooked in a star. A star’s nuclear fusion is always forging heavier and heavier elements. At the beginning of the universe there was only hydrogen and helium. The other elements were made in stars and in supernovae. The last product to get created is iron, which is an element that is so heavy it can’t be burned as fuel.”

Dhungana’s spectrum analysis of SN 2013ej revealed many elements, including hydrogen, helium, calcium, titanium, barium, sodium and iron.

“When we have as many spectra as we have for this supernova at different times,” Kehoe added, “we are able to look deeper and deeper into the original star, sort of like an X-ray or a CAT scan.”

SN 2013ej’s short-lived existence was just tens of millions of years

Analysis of SN 2013ej’s spectrum from ultraviolet through infrared indicates light from the explosion reached Earth July 23, 2013. It was discovered July 25, 2013 by the Katzman Automatic Imaging Telescope at California’s Lick Observatory. A look back at images captured by SMU’s ROTSE-IIIb showed that SMU’s robotic telescope detected the supernova several hours earlier, Dhungana said.

“These observations were able to show a rapidly brightening supernova that started just 20 hours beforehand,” he said. “The start of the supernova, termed ‘shock breakout,’ corresponds to the moment when the internal explosion crashes through the star’s outer layers.”

Like many others, SN 2013ej was a Type II supernova. That is a massive star still undergoing nuclear fusion. Once iron is fused, the fuel runs out, causing the core to collapse. Within a quarter second the star explodes.

Supernovae have death and birth written all over them

Massive stars typically have a shorter life span than smaller ones.

“SN 2013ej probably lived tens of millions of years,” Kehoe said. “In universe time, that’s the blink of an eye. It’s not very long-lived at all compared to our sun, which will live billions of years. Even though these stars are bigger and have a lot more fuel, they burn it really fast, so they just get hotter and hotter until they just gobble up the matter and burn it.”

For most of its brief life, SN 2013ej would probably have burned hydrogen, which then fused to helium, burning for a few hundred thousand years, then perhaps carbon and oxygen for a few hundred days, calcium for a few months and silicon for several days.

“Supernovae have death and birth written all over them,” Kehoe said. “Not only do they create the elements we are made of, but the shockwave that goes out from the explosion — that’s where our solar system comes from.”

Outflowing material slams into clouds of material in interstellar space, causing it to collapse and form a solar system.

“The heavy elements made in the supernova and its parent star are those which comprise the bulk of terrestrial planets, like Earth, and are necessary for life,” Kehoe said.

Hubble Discovers Moon Orbiting The Dwarf Planet Makemake

Peering to the outskirts of our solar system, NASA’s Hubble Space Telescope has spotted a small, dark moon orbiting Makemake, the second brightest icy dwarf planet — after Pluto — in the Kuiper Belt.

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The moon — provisionally designated S/2015 (136472) 1 and nicknamed MK 2 — is more than 1,300 times fainter than Makemake. MK 2 was seen approximately 13,000 miles from the dwarf planet, and its diameter is estimated to be 100 miles across. Makemake is 870 miles wide. The dwarf planet, discovered in 2005, is named for a creation deity of the Rapa Nui people of Easter Island.

The Kuiper Belt is a vast reservoir of leftover frozen material from the construction of our solar system 4.5 billion years ago and home to several dwarf planets. Some of these worlds have known satellites, but this is the first discovery of a companion object to Makemake. Makemake is one of five dwarf planets recognized by the International Astronomical Union.

The observations were made in April 2015 with Hubble’s Wide Field Camera 3. Hubble’s unique ability to see faint objects near bright ones, together with its sharp resolution, allowed astronomers to pluck out the moon from Makemake’s glare. The discovery was announced today in a Minor Planet Electronic Circular.

The observing team used the same Hubble technique to observe the moon as they did for finding the small satellites of Pluto in 2005, 2011, and 2012. Several previous searches around Makemake had turned up empty. “Our preliminary estimates show that the moon’s orbit seems to be edge-on, and that means that often when you look at the system you are going to miss the moon because it gets lost in the bright glare of Makemake,” said Alex Parker of Southwest Research Institute, Boulder, Colorado, who led the image analysis for the observations.

A moon’s discovery can provide valuable information on the dwarf-planet system. By measuring the moon’s orbit, astronomers can calculate a mass for the system and gain insight into its evolution.

Uncovering the moon also reinforces the idea that most dwarf planets have satellites.

“Makemake is in the class of rare Pluto-like objects, so finding a companion is important,” Parker said. “The discovery of this moon has given us an opportunity to study Makemake in far greater detail than we ever would have been able to without the companion.”

Finding this moon only increases the parallels between Pluto and Makemake. Both objects are already known to be covered in frozen methane. As was done with Pluto, further study of the satellite will easily reveal the density of Makemake, a key result that will indicate if the bulk compositions of Pluto and Makemake are also similar. “This new discovery opens a new chapter in comparative planetology in the outer solar system,” said team leader Marc Buie of the Southwest Research Institute, Boulder, Colorado.

The researchers will need more Hubble observations to make accurate measurements to determine if the moon’s orbit is elliptical or circular. Preliminary estimates indicate that if the moon is in a circular orbit, it completes a circuit around Makemake in 12 days or longer.

Determining the shape of the moon’s orbit will help settle the question of its origin. A tight circular orbit means that MK 2 is probably the product of a collision between Makemake and another Kuiper Belt Object. If the moon is in a wide, elongated orbit, it is more likely to be a captured object from the Kuiper Belt. Either event would have likely occurred several billion years ago, when the solar system was young.

The discovery may have solved one mystery about Makemake. Previous infrared studies of the dwarf planet revealed that while Makemake’s surface is almost entirely bright and very cold, some areas appear warmer than other areas. Astronomers had suggested that this discrepancy may be due to the sun warming discrete dark patches on Makemake’s surface. However, unless Makemake is in a special orientation, these dark patches should make the dwarf planet’s brightness vary substantially as it rotates. But this amount of variability has never been observed.

These previous infrared data did not have sufficient resolution to separate Makemake from MK 2. The team’s reanalysis, based on the new Hubble observations, suggests that much of the warmer surface detected previously in infrared light may, in reality, simply have been the dark surface of the companion MK 2.

There are several possibilities that could explain why the moon would have a charcoal-black surface, even though it is orbiting a dwarf planet that is as bright as fresh snow. One idea is that, unlike larger objects such as Makemake, MK 2 is small enough that it cannot gravitationally hold onto a bright, icy crust, which sublimates, changing from solid to gas, under sunlight. This would make the moon similar to comets and other Kuiper Belt Objects, many of which are covered with very dark material.

When Pluto’s moon Charon was discovered in 1978, astronomers quickly calculated the mass of the system. Pluto’s mass was hundreds of times smaller than the mass originally estimated when it was found in 1930. With Charon’s discovery, astronomers suddenly knew something was fundamentally different about Pluto. “That’s the kind of transformative measurement that having a satellite can enable,” Parker said.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Could Ferocious Lightning Storms On Other Planets Beam Radio Signals To Earth?

Ferocious lightning storms millions of times more powerful than those on Earth could be responsible for unexplained radio signals from planets orbiting other stars.

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That is the finding of researchers from the University of St Andrews School of Physics and Astronomy in a piece of work published today (25 April 2016).
In 2009 French astronomers observed what was thought to be a weak radio signal coming from the exoplanet HAT-P-11b, a “mini-Neptune” about five times bigger in size than the Earth and 26 times more massive. The following year the French team made an attempt to locate the signal again, but was unsuccessful leaving the phenomenon unexplained.

The St Andrews team set out to solve the mystery. Gabriella Hodosán, the Life, Electricity, Atmosphere, Planets (LEAP) Project PhD student leading the study said: “We assumed that this signal was real and was coming from the planet. Then we asked the question: could such a radio signal be produced by lightning in the planet’s atmosphere, and if yes, how many lightning flashes would be needed for it?”

Assuming that the underlying physics of lighting is the same for all Solar System planets, like Earth and Saturn, as well as on HAT-P-11b, the researchers found that 53 lightning flashes of Saturnian lightning-strength in a km2 per hour would explain the observed radio signal on HAT-P-11b.

Dr Paul Rimmer, LEAP researcher and co-author of the paper, said: “Imagine the biggest lightning storm you’ve ever been caught in. Now imagine that this storm is happening everywhere over the surface of the planet. A storm like that would produce a radio signal approaching 1% the strength of the signal that was observed in 2009 on the exoplanet HAT-P-11b.”

Miss Hodosán continued: “Such enormous thunderstorms are not unreasonable.

“Studies conducted by our group have also shown that exoplanets orbiting really close to their host star have very dynamic atmospheres, meaning that they change continuously, producing clouds of different sizes, even whole cloud systems, all over the planet’s surface.

“HAT-P-11b, being so close to the star, is likely to have such a dynamic, cloudy atmosphere, which would allow the formations of huge thunderclouds, focusing the lightning activity to a certain regime of the planetary surface, such as the face of the planet, which was observed in 2009.”

The team hoped that this intensity of lightning could be observed with optical telescopes but were thwarted by the powerful light emissions from the star around which HAT-P-11b orbits.

The process of lightning discharges involves plasma processes at very high temperatures and the release of a large amount of energy. This results in chemical reactions in the atmosphere that otherwise would not occur. These reactions produce molecules that can be used as lighting tracers.

The team considered whether such enormous thunderstorm clouds produce these tracer molecules, which then could be observed by Earth-telescopes, and suggested hydrogen cyanide (HCN) to be such a potential fingerprint of lightning. This molecule could be observable in the infrared spectral band, even years after the huge storm on HAT-P-11b would have occurred.

Miss Hodosán said: “In the future, combined radio and infrared observations may lead to the first detection of lightning on an extrasolar planet.
“The importance of the study is not just this prediction, but it shows an original scenario for the explanation of radio emission observable on extrasolar planets.”

Dr Christiane Helling, the LEAP Project principal investigator, said: “With all necessary caution, linking extraterrestrial lightning and radio emissions will open a new window to prove the presence of atmospheres and of clouds on extrasolar planets, both being essential for the existence of life as we know it.”