Despite the vast distance between us and Saturn’s gleaming moon Enceladus, the icy ocean moon is a prime target in our search for life. It vents water vapour and large organic molecules into space through fissures in its icy shell, which is relatively thin compared to other icy ocean moons like Jupiter’s Europa. Though still out of reach, scientific access to its ocean is not as challenging as on Europa, which has a much thicker ice shell.
The presence of large organic molecules isn’t very controversial. But they don’t necessarily signify that something alive lurks in its ancient, unseen ocean. Instead, hydrothermal processes could produce them. The complexity arises because hydrothermal processes are also linked to the emergence of life.
Understanding the abiotic processes that produce these molecules is important not just for Enceladus. It could serve as a baseline for understanding the results of a future mission to the frozen moon and any biosignatures it might detect.
New research in the journal Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences examines this issue. It’s titled “Laboratory characterization of hydrothermally processed oligopeptides in ice grains emitted by Enceladus and Europa.” The lead author is Dr. Nozair Khawaja from the Institute of Space Systems (IRS) at the University of Stuttgart.
Scientists postulate the life on Earth got started at hydrothermal events on the ocean floor. These vents provide mineral-rich fluids. At deep ocean vents under extreme pressure, these minerals can react with seawater to produce the building blocks of life.
“In research, we also speak of a hydrothermal field,” explains lead author Khawaja. “There is convincing evidence that conditions prevail in such fields that are important for the emergence or maintenance of simple life forms.”
Much of what we know about Enceladus comes from the Cassini mission. Scientists are still working with Cassini’s data even though it ended in 2017. Although much of the data was low resolution, it’s still valuable.
Professor Frank Postberg from the Freie Universität (FU) Berlin is one of the study’s co-authors. “In 2018 and 2019, we encountered various organic molecules, including some that are typically building blocks of biological compounds,” Postberg said. “And that means it is possible that chemical reactions are taking place there that could eventually lead to life.”
There’s a missing link between the hydrothermal vents and the molecules vented into space. Scientists aren’t certain if the vents are responsible for the molecules or in what way. Is life involved?
To answer these questions, the researchers simulated an Enceladus hydrothermal vent in their laboratory.
“To this end, we simulated the parameters of a possible hydrothermal field on Enceladus in the laboratory at the FU Berlin,” said lead author Khawaja. “We then investigated what effects these conditions have on a simple chain of amino acids.” Amino acids are the basic building blocks of proteins and the basis of all Earth life. There are hundreds of them, and 22 of them are in all living cells. They’re the precursors to proteins and they show that life on Earth is all connected.
The researchers subjected amino acids to conditions thought to persist at Encledadus’ ocean floor. “Here, we present results from our newly established facility to simulate the processing of ocean material within the temperature range 80–150°C and the pressure range 80–130 bar, representing conditions suggested for the water-rock interface on Enceladus,” they write in their paper. Under those conditions, the chains of amino acids behaved characteristically.
But that’s in a lab. Can we devise a space probe that can detect these types of changes on Enceladus? The changes themselves are obscured, but do they produce byproducts or markers that are emitted into space?
Cassini’s Cosmic Dust Analyzer (CDA) detected the organic molecules in Enceladus’ plumes by watching collisions between rapidly moving particles that shatter molecules and vapourize their contents. Some particles, stripped of their electrons, become positively charged and are attracted to a negative electrode on the instrument. The less massive they are, the faster they reach the electrode.
By combining a large amount of this type of data, the CDA revealed a lot about the original molecules.
But this can’t be replicated in a lab.
“Instead, we employed an alternative measurement method called LILBID for the first time on ice particles containing hydrothermally altered material,” Khawaja explains. LILBID stands for laser-induced liquid beam ion desorption, a different type of mass spectrometry than the CDA performs. Though the method is different, it produces results similar to Cassini’s CDA instrument.
“This delivers very similar mass spectra to the Cassini instrument. We used this to measure an amino acid chain before and after the experiment. In the process, we came across characteristic signals that were caused by the reactions in our simulated hydrothermal field,” Khawaja said.
Specifically, the researchers examined the hydrothermal processing of the triglycine (GGG) peptide. GGG is a tripeptide, the most common one. Scientists often use GGG to study amino acids, peptides, and proteins, analyzing the molecular interactions and physicochemical parameters of all three.
“Differences observed between mass spectra of hydrothermally processed and unprocessed triglycine can be regarded as a spectral fingerprint to identify processed GGG in ice grains from icy moons in the solar system,” the authors wrote in their research.
“This delivers very similar mass spectra to the Cassini instrument. We used this to measure an amino acid chain before and after the experiment. In the process, we came across characteristic signals that were caused by the reactions in our simulated hydrothermal field,” Khawaja said.
The researchers intend to repeat this experiment with other organic molecules under extended geophysical conditions in Enceladus’ ocean. “With this new laboratory setup, we will simulate a range of hydrothermal conditions, from the high pressures and temperatures associated with greater depths into the core, to the milder conditions in the ocean water near the water-rock interface,” the authors write in their paper.
The results will allow them to search through Cassini’s data for similar markers. It can also work for future missions to Enceladus and would be further proof of hydrothermal activity on the frozen ocean moon.
If scientists can confirm hydrothermal vents on Enceladus, the excitement that moon generates will only increase.
The post Linking Organic Molecules to Hydrothermal Vents on Enceladus appeared first on Universe Today.
Astronomers were surprised in 1937 when a star in a binary pair suddenly brightened by 1,000 times. The pair is called FU Orionis (FU Ori), and it’s in the constellation Orion. The sudden and extreme variability of one of the stars has resisted a complete explanation, and since then, FU Orionis has become the name for other stars that exhibit similar powerful variability.
The star in question is called Orionis North, and it’s the central star of the pair. Astronomers see its brightening behaviour in old stars but not in young stars like FU Ori. The young star is only about 2 million years old.
Astronomers working with ALMA (Atacama Large Millimetre-submillimetre Array) have discovered the reason behind Fu Ori’s variability. They’ve published their research in the Astrophysical Journal. It’s titled “Discovery of an Accretion Streamer and a Slow Wide-angle Outflow around FU Orionis,” and the lead author is Antonio Hales, deputy manager of the North American ALMA Regional Center and scientist with the NRAO.
Here’s what scientists do know about FU Ori (FUor) stars and their variability. They brighten when they attract gas gravitationally into an accretion disk. Too much mass at once can destabilize the disk, and as material falls into the star, it brightens. But what they didn’t understand was why and how this happened.
“FU Ori has been devouring material for almost 100 years to keep its eruption going. We have finally found an answer to how these young outbursting stars replenish their mass,” explained lead author Hales. “For the first time we have direct observational evidence of the material fueling the eruptions.”
ALMA is the world’s largest radio telescope. It’s an interferometer with 66 separate antennae, which can be moved across the ground to give the observatory a ‘zoom-in’ effect. This powerful observatory has driven a lot of astronomical science.
In this research, ALMA identified a long streamer of carbon monoxide that appears to be falling into FU Ori. The researchers don’t think this streamer has enough material to sustain the star’s current outburst. But it could be the remnant from a past episode. “It is possible that the interaction with a bigger stream of gas in the past caused the system to become unstable and trigger the brightness increase,” explained Hales.
The current outburst creates strong stellar winds that interact with a leftover envelope of material from the star’s formation. The wind shocks the envelope, sweeping up carbon monoxide with it. The CO is what ALMA detected.
ALMA’s ability to operate in different configurations and wavelengths played a role in this work. It allowed the team to detect different types of emissions and to detect the mass flowing into FU Ori. They compared the observations to models of mass flow and accretion streamers. “We compared the shape and speed of the observed structure to that expected from a trail of infalling gas, and the numbers made sense,” said Aashish Gupta, a Ph.D. candidate at European Southern Observatory (ESO). Gupta is a co-author of this work, and he developed the methods used to model the accretion streamer.
The researchers measured the amount of material flowing into FU Ori through the streamer. About 0.07 Jupiter Masses per Myr?1 flow into the young star. Jupiter is about 318 times more massive than Earth. This means that FU Ori’s infall streamer rate is lower than infall around other Class 0 protostars. “This would suggest that the observed streamer will require ?100 Myr to replenish disk masses, which is at least an order of magnitude greater than the typical disk lifetimes,” the authors point out.
The infall streamer and its effect on the star are complex. Not enough material comes in via the streamer to trigger the outbursts. “The streamer needs to be more massive to sustain FU Ori’s outburst accretion rates (by several orders of magnitude). The estimated streamer mass infall rate is not even sufficiently massive to sustain quiescent stellar accretion rates,” the authors explain.
Instead, the infalling material causes disk instability, which in turn delivers enough material to FU Ori to trigger outbursts. “Anisotropic infall, cloudlet capture events, the inhomogeneous delivery of material, and the building up of material around dust traps can all lead to the disk instabilities that could trigger accretion outbursts,” Hales and his co-authors write. They can’t say for sure if this is what’s happening. That would require more modelling, which is outside the scope of this work.
ALMA also spotted another streamer of slow-moving CO. This one is coming from the star rather than falling into it. Hales and his colleagues think this streamer is similar to streamers coming from other young protostellar objects and isn’t related to the brightening. “The ALMA observations reveal the presence of large-scale, wide-angle bipolar outflows for the first time around the class prototype FU Ori,” the researchers write in their paper.
Curiously, astronomers have detected these outflows from other FUor stars but never at FU Ori itself. It’s coming from Fu Ori North, the star that experiences the powerful brightening.
“Prior searches for molecular outflows around FUors, mainly using single-dish telescopes, reported outflowing material from many FUors but failed to detect flows emerging from the FUor class prototype,” the researchers write in their paper. “These nondetections instigated the belief that there were no molecular outflows around the FU Ori system. Our discovery ends the mystery by clearly demonstrating the presence of a molecular outflow from FU Ori itself.”
Understanding young stars is critical because their behaviour governs planet formation. FU Ori’s brightening could have a defining effect on the planets that form around the star.
“By understanding how these peculiar FUor stars are made, we’re confirming what we know about how different stars and planets form,” Hales explained. “We believe that all stars undergo outburst events. These outbursts are important because they affect the chemical composition of the accretion discs around nascent stars and the planets they eventually form.”
For the authors, their research demonstrates how the powerful ALMA observatory makes a unique contribution to astronomical research. “These results demonstrate the value of multiscale interferometric observations to enhance our understanding of the FU Ori outbursting system and provide new insights into the complex interplay of physical mechanisms governing the behaviour of FUor-type and the many other kinds of outbursting stars,” the authors conclude.
The post A Star Became 1,000 Times Brighter, and Now Astronomers Know Why appeared first on Universe Today.
Planetary scientists perk up whenever methane is mentioned. Methane is produced by living things on Earth, so it’s considered to be a potential biosignature elsewhere. In recent years, MSL Curiosity detected methane coming from the surface of Gale Crater on Mars. So far, nobody’s successfully explained where it’s coming from.
NASA scientists have some new ideas.
Ever since Curiosity landed on Mars in 2012, it’s been sensing methane. But the methane displays some odd characteristics. It only comes out at night, it fluctuates with the seasons, and sometimes, the amount of methane jumps to 40 times more than the regular level.
The ESA’s ExoMars Trace Gas Orbiter entered a science orbit around Mars in 2018, and scientists fully expected it to detect methane in the planet’s atmosphere. But it didn’t, and it has never been detected elsewhere on Mars’ surface.
If life was producing the methane, it appears to be restricted to the subsurface under Gale Crater.
There’s no convincing evidence that life exists on Mars. It may have in the past, and it’s possible that some extant life clings to a tenuous existence in subsurface brines or something. But we lack evidence, so life is basically ruled out as the methane source. Especially since the evidence shows life would have to be under Gale Crater and nowhere else.
Scientists have been trying to determine the source of methane, but so far, they haven’t come up with a specific answer. It has something to do with subsurface geological processes involving water, most likely.
“It’s a story with a lot of plot twists,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California, which leads Curiosity’s mission.
Alexander Pavlov is a planetary scientist at NASA’s Goddard Space Flight Center who leads a group of NASA scientists studying the Martian Methane Mystery. In recent research, they suggested that the methane is stored underground. They didn’t explain what produced it, but they showed that methane can be sealed underground by salt solidified in the Martian regolith.
They suggested that the methane could be released from its subsurface reservoir by the weight of the Curiosity rover itself. The rover’s weight could break the salt seal and release methane in puffs. That’s an interesting proposition, but it doesn’t explain the seasonal and diurnal fluctuations. That makes sense since the Gale Crater is one of only two regions where a rover is working. The other is Jezero Crater, where the Perseverance Rover is working, but it doesn’t have a methane detector. (Neither will the ESA’s Rosalind Franklin rover, which is scheduled to land on Mars in 2029.)
The research group addressed those fluctuations by suggesting that seasonal and daily heating could also break the seal and release methane.
Their potential explanations stem from research Pavlov conducted in 2017. He grew bacteria called halophiles, which grow in salty conditions, in simulated Martian permafrost. The simulated soil was infused with salt, replicating conditions on much of Mars. The microbe growth was inconclusive, but the researchers noticed something else. As the salty ice sublimated, a layer of solidified salt remained, forming a crust.
“We didn’t think much of it at the moment,” Pavlov said.
But he remembered it when MSL Curiosity detected an unexplained burst of methane on Mars in 2019.
“That’s when it clicked in my mind,” Pavlov said. Then, he and a team of researchers began testing conditions that could form the hardened salt seals and then break them open.
Perchlorate is a chemical salt that’s widespread on Mars. Pavlov and his fellow researchers recreated different simulated Martian permafrosts with varying amounts of perchlorate. Inside a Mars simulation chamber, they subjected the samples to different temperatures and atmospheric pressures to see if they would form seals.
In their experiments, they used neon as a methane analog and injected it under the soil. Then, they measured the gas pressure below and above the soil. They found that the pressure was higher under the soil, meaning the gas was being trapped by the salty permafrost. Furthermore, they found that seals formed in samples containing as little as 5% or 10% perchlorate, and they formed within 3 to 13 days. Those are compelling results.
While 5-10% perchlorate doesn’t sound like much, it’s actually a higher concentration than in Gale Crater, where the methane has been detected. But perchlorate isn’t the only salt in Martian regolith. It also contains sulphates, another type of salt mineral. Pavlov says he and his team will test sulphates next for their ability to form a seal.
The Martian Methane Mystery is commanding a lot of attention. It’s a juicy mystery, and once it’s solved, our understanding of methane as a biosignature or false positive will be much improved. NASA’s 2022 Planetary Mission Senior Review recommended that the issue of methane production and destruction at Mars be investigated further.
The type of work that Pavlov and his colleagues are doing is important, but it’s being held back. Pavlov says that they need more consistent methane measurements. The problem is that Curiosity’s SAM (Sample Analysis at Mars) instrument, which senses the methane, is busy with other tasks. It only checks for methane a few times per year. It’s mostly occupied with drilling samples and testing them, a critical and time-consuming part of the rover’s mission.
“Methane experiments are resource intensive, so we have to be very strategic when we decide to do them,” said Goddard’s Charles Malespin, SAM’s principal investigator.
Curiosity’s mission wasn’t designed to measure methane fluctuations. In 2017, NASA said its SAM instrument only sampled the atmosphere 10 times in 20 months. That’s a very inconsistent sample that leaves lots of unanswered questions.
Scientists think another mission is needed to advance their understanding of Martian methane. Rather than one sensor taking irregular methane readings from one location, we need multiple testing stations on the surface that regularly monitor the atmosphere. Nothing like it is in the works.
“Some of the methane work will have to be left to future surface spacecraft that are more focused on answering these specific questions,” Vasavada said.
The post New Answers for Mars’ Methane Mystery appeared first on Universe Today.
Mention the Milky Way and most people will visualise a great big spiral galaxy billions of years old. It’s thought to be a galaxy that took shape billions of years after the Big Bang. Studies by astronomers have revealed that there are the echo’s of an earlier time around us. A team of astronomers from MIT have found three ancient stars orbiting the Milky Way’s halo. The team think these stars formed when the Universe was around a billion years old and that they were once part of a smaller galaxy that was consumed by the Milky Way.
The Milky Way is our home galaxy within which our entire Solar System and an estimated 400 billion other stars. It measures 100,000 light years from sided to side and is home to almost everything else we can see in the sky with our naked eyes. On a clear dark night we can see the combined light from all the stars in the galaxy forming a wonderful band of hazy light arching across the sky from horizon to horizon. If you could view the Galaxy from the outside its broad shape would resemble two fried eggs stuck back to back.
The story of the discovery takes us back to 2022 during a new Observational Stellar Archaeology course at MIoT when students were learning how they can analyse ancient stars. They then applied them to stars that have not yet been analysed. They worked with data from the 6.5m Magellan-Clay telescope at Las Campanas Observatory and were searching for stars that had formed soon after the Big Bang. At this time in the evolution of the Universe, there was mostly hydrogen and helium with trace amounts of strontium and barium. The team therefore searched for stars with spectra indicating these elements.
They honed in on just three stars that had been observed in 2013 and 2014 but they had not been previously analysed so were a great study for the students. On completion of their analysis (which took several hundred hours at a computer), the team identified that the stars had very low levels of strontium and barium as predicted if they were ancient stars. The stars they studied were estimated at having formed between 12 and 13 billion years ago. What wasn’t clear was the origin of the stars. How did they come to be in the Milky Way given that it was relatively new and young.
The team decided to analyse the orbital characteristics of the stars to see how they moved. The stars were all in different locations through the Milky Way’s halo and all thought to be about 30,000 light years from Earth. Comparing the motion with data from the Gaia astrometric satellite they discovered the stars were going in the opposite direction to the majority of other stars in the Milky Way. We call this retrograde motion and it suggests the stars came from somewhere else, not having formed with the Milky Way. The chemical signatures of the stars coupled with their motion give strong credibility to the liklihood these ancient stars are not native to the Milk Way.
Now they have developed there approach to identify ancient stars, the students are keen to expand their search to see if any others can be located. However with 400 billion stars in the Milky Way, a slightly more efficient method needs to be found.
Source : MIT researchers discover the universe’s oldest stars in our own galactic backyard
The post Three of the Oldest Stars in the Universe Found Circling the Milky Way appeared first on Universe Today.
If you watch astronauts in space then you will know how they seem to float around their spaceship. Spaceships in orbit around the Earth are in free-fall, constantly falling toward surface fo the Earth with the surface constantly falling away from it. Any occupant is also in free-fall but living like this causes muscle tone to degrade slowly. One solution is to generate artificial gravity through acceleration in particular a rotating motion. A new paper makes the case for a rotating space station and goes so far that it is achievable now.
Acceleration is a change in either direction or speed. In a lift you can feel a deceleration as you feel heavier when the lift slows at the bottom of its descent. It would certainly be possible to generate an artificial force of gravity in a box travelling through space if it constantly accelerates. This would produce a sense of a floor and pin the occupants to the rear wall. This is however, a fairly inefficient way to produce gravity as significant amounts of fuel would be required to continually accelerate the box.
A recent paper published in Science Direct by lead author Jack J.W.A. van Loon shows how a spaceship that continuously rotates will produce an artificial gravity on the inner skin of the outer shell. The benefits to such an approach are significant; improved crew health and wellbeing, safety improvements, cost reductions and the simplification of numerous flight operations.
There are many ways that astronauts attempt to limit the impacts on health from micro-gravity. Treadmills with straps to pull the astronauts down onto the running platform are just one of the ways they attempt to keep bones and muscles in tip top condition. If they don’t then bone and muscle density declines. Research has sown that for every month in space, an astronauts’ weight bearing bones become 1% less dense. Muscles wean too and this causes problems on their return to Earth and ‘normal gravity’ so it is a vitally important part of their routine.
The team go on to explore a number of options such as a short arm centrifuge. These would certainly generate artificial gravity but the short arm would mean the gravity gradient from foot to head of occupants would be too great and have a negative health impact. An alternate solution, and more efficient feasible solution is to build a large rotating spacecraft. Such a craft would have benefits for long term missions such as trips to Mars but also benefit those in orbit around Earth for months on end. Savings would be impressive as significant investments are made combatting the effect of microgravity.
The team discuss what would be needed to simulate and Earth-like 1g environment on a spacecraft. A donut shaped spacecraft with a 25 m radius would need to be spun 6 times per minute to generate a 1g environment. Larger spacecraft could be revolved at a slower rate. Doing so not only benefits the astronauts but nearly every aspect of life in space would be enhanced and safer; liquids would behave in a normal way, flames too would behave in a more familiar way, toilets can of a more normal design as can self care systems. The benefits are significant so I don’t think it will be long before we see astronauts walking around in revolving spacecraft enjoying the luxury of normal gravity again.
Source : Benefits of a rotating – Partial gravity – Spacecraft
The post A Rotating Spacecraft Would Solve So Many Problems in Spaceflight appeared first on Universe Today.
When stars exhaust their hydrogen fuel at the end of their main sequence phase, they undergo core collapse and shed their outer layers in a supernova. Whereas particularly massive stars will collapse and become black holes, stars comparable to our Sun become stellar remnants known as “white dwarfs.” These “dead stars” are extremely compact and dense, having mass comparable to a star but concentrated in a volume about the size of a planet. Despite being prevalent in our galaxy, the chemical makeup of these stellar remnants has puzzled astronomers for years.
For instance, white dwarfs consume nearby objects like comets and planetesimals, causing them to become “polluted” by trace metals and other elements. While this process is not yet well understood, it could be the key to unraveling the metal content and composition (aka. metallicity) of white dwarf stars, potentially leading to discoveries about their dynamics. In a recent paper, a team from the University of Colorado Boulder theorized that the reason white dwarf stars consume neighboring planetesimals could have to do with their formation.
The research team consisted of Tatsuya Akiba, a Ph.D. candidate at UC Boulder with the Joint Institute for Laboratory Astrophysics (JILA) at UC Boulder. He was joined by Selah McIntyre, an undergraduate student in the Department of Chemistry, and Ann-Marie Madigan, a JILA Fellow and a professor in the Department of Astrophysical and Planetary Sciences. Their research was reported in a paper titled “Tidal Disruption of Planetesimals from an Eccentric Debris Disk Following a White Dwarf Natal Kick,” which recently appeared in The Astrophysical Journal.
Despite their prevalence in our galaxy, the chemical makeup of white dwarfs has puzzled astronomers for years. The presence of heavy metal elements like silicon, magnesium, and calcium on the surfaces of many of these stellar remnants defies what astronomers consider conventional stellar behavior. “We know that if these heavy metals are present on the surface of the white dwarf, the white dwarf is dense enough that these heavy metals should very quickly sink toward the core,” said Akiba in a recent JILA press release. “So, you shouldn’t see any metals on the surface of a white dwarf unless the white dwarf is actively eating something.”
Madigan’s research group at JILA focuses on the gravitational dynamics of white dwarfs and how these affect surrounding material. For their study, the team created computer models that simulated a white dwarf experiencing a rare phenomenon known to occur during its formation. This consisted of an asymmetric mass loss caused by a “natal kick” that altered its motion and the dynamics of the surrounding material. As Professor Madigan explained:
“Simulations help us understand the dynamics of different astrophysical objects. So, in this simulation, we throw a bunch of asteroids and comets around the white dwarf, which is significantly bigger, and see how the simulation evolves and which of these asteroids and comets the white dwarf eats. Other studies have suggested that asteroids and comets, the small bodies, might not be the only source of metal pollution on the white dwarf’s surface. So, the white dwarfs might eat something bigger, like a planet.”
In 80% of their test runs, the team observed that the orbits of comets and planetesimals within 30 to 240 AU (the distance between the Sun and Neptune and well into the Kuiper Belt) of the star became elongated and aligned. They also found that in about 40% of their simulations, the consumed planetesimals came from retrograde orbits. Lastly, they extended their simulations to 100 million years after formation and found that these planetesimals still had elongated orbits and moved as one coherent unit.
These new findings also shed light on the origin, chemistry, and future evolution of stars, including our Solar System. In about 5 billion years, our Sun will exit its main sequence phase and grow to become a Red Giant. Roughly 2 billion years later, it will blow off its outer layers in a supernova, leaving behind a white dwarf remnant. Looking ahead, the researchers hope to take their simulations to greater scales to examine how white dwarfs interact with larger planets. These simulations could reveal what will become of the outer planets in our Solar System once our Sun is in its “dead” phase. Said Madigan:
“This is something I think is unique about our theory: we can explain why the accretion events are so long-lasting. While other mechanisms may explain an original accretion event, our simulations with the kick show why it still happens hundreds of millions of years later. The vast majority of planets in the universe will end up orbiting a white dwarf. It could be that 50% of these systems get eaten by their star, including our own solar system. Now, we have a mechanism to explain why this would happen.”
The post White Dwarfs are Often Polluted With Heavier Elements. Now We Know Why appeared first on Universe Today.
We have discovered over 5,000 planets around other star systems. Amongst the veritable cosmic menagerie of exoplanets, it seems there is a real shortage of Neptune-sized planets close to their star. A new paper just published discusses a Saturn-sized planet close to its host star which should be experiencing mass loss, but isn’t. Studying this world offers a new insight into exoplanet formation across the Universe.
Exoplanets really are fascinating. Ever-since their discovery the race has been on to discover and catalogue them. It gives us a great opportunity to explore a far more statistically significant set of data to understand planetary system formation rather than just studying are own system.
The absence of Neptune-mass exoplanets closer to the host stars in exoplanetary systems has been a bit of a mystery. Their lack has been attributed to one of two things; photoevaporation – mass is lost through ionisation of gas by radiation which then disperses away form the ionising source or high-eccentricity migration – where the planets move through the planetary system as we have seen with some of the giant planets in our Solar System.
To distinguish between these two possibilities a team of astronomers led by Morgan Saidel from the California Institute of Technology investigated the origins of TOI-1259 A b which is a Saturn mass exoplanet. It is in a 3.48 day orbit around a K type star at a distance putting it on the edge of the so called Neptune desert. A region around a star wherein there are no Neptune sized planets.
In the case of TOI-1259 A b, it is thought that its low density means it is especially vulnerable to photoevaporation. Transit methods were used, observing with the Hale Telescope at Palomar Observatory in the 1083nm helium line to probe the upper levels of the atmosphere. The near-infrared spectrograph on Keck II was also used and showed that there was indeed atmosphere escaping but at a rate lower than expected. The rate of gas loss through photoevaporation (1010.325 g s?1)is too low to significantly have altered the planets mass even if it had formed in its current location.
Instead, the team believe that the presence of a white dwarf companion (TOI-1259 B) may have caused the planet to migrate inwards after formation. Analysing the orbital parameters of the planet and the binary star system reveal that high-eccentricity migration is a far more likely explanation.
Planetary migrations of this sort may leave a trace through accretion of elements in the planetary atmosphere. Quantities of H2O, CO, CO2 , SO2 and CH4 should be at detectable levels in the atmosphere of TOI-1259 A b. If they are observed through transmission spectroscopic studies, will reveal where in protoplanetary disk the planet formed in. Further studies will be required to finally answer this question.
Source : Atmospheric Mass Loss from TOI-1259 A b, a Gas Giant Planet With a White Dwarf Companion
The post Saturn-Sized Exoplanet Isn’t Losing Mass Quickly Enough appeared first on Universe Today.
Gravitational wave astronomy has been one of the hottest new types of astronomy ever since the LIGO consortium officially detected the first gravitational wave (GW) back in 2016. Astronomers were excited about the number of new questions that could be answered using this sensing technique that had never been considered before. But a lot of the nuance of the GWs that LIGO and other detectors have found in the 90 gravitational wave candidates they have found since 2016 is lost.
Researchers have a hard time determining which galaxy a gravitational wave comes from. But now, a new paper from researchers in the Netherlands has a strategy and developed some simulations that could help narrow down the search for the birthplace of GWs. To do so, they use another darling of astronomers everywhere—gravitational lensing.
Importantly, GWs are thought to be caused by merging black holes. These catastrophic events literally distort space-time to the point where their merger causes ripples in gravity itself. However, those signals are extraordinarily faint when they reach us—and they are often coming from billions of light-years away.
Detectors like LIGO are explicitly designed to search for those signals, but it’s still tough to get a strong signal-to-noise ratio. Therefore, they’re also not particularly good at detailing where a particular GW signal comes from. They can generally say, “It came from that patch of sky over there,” but since “that patch of sky” could contain billions of galaxies, that doesn’t do much to narrow it down.
But astronomers lose a lot of context regarding what a GW can tell them about its originating galaxy if they don’t know what galaxy it came from. That’s where gravitational lensing comes in.
Gravitational lenses are a physical phenomenon whereby the signal (in most cases light) coming from a very faraway object is warped by the mass of an object that lies between the further object and us here on Earth. They’re responsible for creating “Einstein Rings,” some of the most spectacular astronomical images.
Light is not the only thing that can be affected by mass, though—gravitational waves can, too. Therefore, it is at least possible that gravitational waves themselves could be warped by the mass of an object between it and Earth. If astronomers are able to detect that warping, they can also tell which specific galaxy in an area of the sky the GW sign is coming from.
Once astronomers can track down the precise galaxy, creating a gravitational wave, the sky is (not) the limit. They can narrow down all sorts of characteristics not only of the wave-generating galaxy itself but also of the galaxy in front of it, creating the lens. But how exactly should astronomers go about doing this work?
That is the focus of the new paper from Ewoud Wempe, a PhD student at the University of Groningen, and their co-authors. The paper details several simulations that attempt to narrow down the origin of a lensed gravitational wave. In particular, they use a technique similar to the triangulation that cell phones use to determine where exactly they are in relation to GPS satellites.
Using this technique can prove fruitful in the future, as the authors believe there are as many as 215,000 potential GW lensed candidates that would be detectable in data sets from the next generation of GW detectors. While those are still coming online, the theoretical and modeling worlds remain hard at work trying to figure out what kind of data would be expected for different physical realities of this newest type of astronomical observation.
Learn More:
Wempe et al. – On the detection and precise localization of merging black holes events through strong gravitational lensing
UT – After Decades of Observations, Astronomers have Finally Sensed the Pervasive Background Hum of Merging Supermassive Black Holes
UT – A Neutron Star Merged with a Surprisingly Light Black Hole
UT – When Black Holes Merge, They’ll Ring Like a Bell
Lead Image:
Example of a gravitational lens.
Credit – Hubble Telescope / NASA / ESA
The post Gravitational Lenses Could Pin Down Black Hole Mergers with Unprecedented Accuracy appeared first on Universe Today.
The TRAPPIST-1 solar system generated a swell of interest when it was observed several years ago. In 2016, astronomers using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) at La Silla Observatory in Chile detected two rocky planets orbiting the red dwarf star, which took the name TRAPPIST-1. Then, in 2017, a deeper analysis found another five rocky planets.
It was a remarkable discovery, especially because up to four of them could be the right distance from the star to have liquid water.
The TRAPPIST-1 system still gets a lot of scientific attention. Potential Earth-like planets in a star’s habitable zone are like magnets for planetary scientists.
Finding seven of them in one system is a unique scientific opportunity to examine all kinds of interlinked questions about exoplanet habitability. TRAPPIST-1 is a red dwarf, and one of the most prominent questions about exoplanet habitability concerns red dwarfs (M dwarfs.) Do these stars and their powerful flares drive the atmospheres away from their planets?
New research in the Planetary Science Journal examines atmospheric escape on the TRAPPIST-1 planets. Its title is “The Implications of Thermal Hydrodynamic Atmospheric Escape on the TRAPPIST-1 Planets.” Megan Gialluca, a graduate student in the Department of Astronomy and Astrobiology Program at the University of Washington, is the lead author.
Most stars in the Milky Way are M dwarfs. As the TRAPPIST-1 makes clear, they can host many terrestrial planets. Large, Jupiter-size planets are comparatively rare around these types of stars.
It’s a distinct possibility that most terrestrial planets are in orbit around M dwarfs.
But M dwarf flaring is a known issue. Though M dwarfs are far less massive than our Sun, their flares are way more energetic than anything that comes from the Sun. Some M dwarf flares can double the star’s brightness in only minutes.
Another problem is tidal locking. Since M dwarfs emit less energy, their habitable zones are much closer than the zones around a main sequence star like our Sun. That means potentially habitable planets are much more likely to be tidally locked to their stars.
That creates a whole host of obstacles to habitability. One side of the planet would bear the brunt of the flaring and be warmed, while the other side would be perpetually dark and cold. If there’s an atmosphere, there could be extremely powerful winds.
“As M dwarfs are the most common stars in our local stellar neighbourhood, whether their planetary systems can harbour life is a key question in astrobiology that may be amenable to observational tests in the near term,” the authors write. “Terrestrial planetary targets of interest for atmospheric characterization with M dwarf hosts may be accessible with the JWST,” they explain. They also point out that future large ground-based telescopes like the European Extremely Large Telescope and the Giant Magellan Telescope could help, too, but they’re years away from being operational.
Red dwarfs and their planets are easier to observe than other stars and their planets. Red dwarfs are small and dim, meaning their light doesn’t drown out planets as much as other main-sequence stars do. But despite their lower luminosity and small size, they present challenges to habitability.
M dwarfs have a longer pre-main-sequence phase than other stars and are at their brightest during this time. Once they’re on the main sequence, they have heightened stellar activity compared to stars like our Sun. These factors can both drive atmospheres away from nearby planets. Even without flaring, the closest planet to TRAPPIST-1 (T-1 hereafter) receives four times more radiation than Earth.
“In addition to luminosity evolution, heightened stellar activity also increases the stellar XUV of M dwarf stars, which enhances atmospheric loss,” the authors write. This can also make it difficult to understand the spectra from planetary atmospheres by creating false positives of biosignatures. Exoplanets around M dwarfs are expected to have thick atmospheres dominated by abiotic oxygen.
Despite the challenges, the T-1 system is a great opportunity to study M dwarfs, atmospheric escape, and rocky planet habitability. “TRAPPIST-1 is a high-priority target for JWST General and Guaranteed Time Observations,” the authors write. The JWST has observed parts of the T-1 system, and that data is part of this work.
In this work, the researchers simulated early atmospheres for each of the TRAPPIST-1 (T-1 hereafter) planets, including different initial water amounts expressed in Terrestrial Oceans (TO.) They also modelled different amounts of stellar radiation over time. Their simulations used the most recent data for the T-1 planets and used a variety of different planetary evolution tracks.
The results are not good, especially for the planets closest to the red dwarf.
“We find the interior planets T1-b, c, and d are likely desiccated for all but the largest initial water contents (>60, 50, and 30 TO, respectively) and are at the greatest risk of complete atmospheric loss due to their proximity to the host star,” the researchers explain. However, depending on their initial TO, they could retain significant oxygen. That oxygen could be a false positive for biosignatures.
The outer planets fare a little better. They could retain some of their water unless their initial water was low at about 1 TO. “We find T1-e, f, g, and h lose, at most, approximately 8.0, 4.8, 3.4, and 0.8 TO, respectively,” they write. These outer planets probably have more oxygen than the inner planets, too. Since T1-e, f, and g are in the star’s habitable zone, it’s an intriguing result.
T-1c is of particular interest because, in their simulations, it retains the most atmospheric oxygen regardless of whether the initial TO was high or low.
The potential habitability of T-1 planets is an important question in exoplanet science. The type of star, the number of rocky planets, and the ease of observation all place it at the top of the list of observational targets. We’ll never really understand exoplanet habitability if we can’t understand this system. The only way to understand it better is to observe it more thoroughly.
“These conclusions motivate follow-up observations to search for the presence of water vapour or oxygen on T1-c and future observations of the outer planets in the TRAPPIST-1 system, which may possess substantial water,” the authors write in their conclusion.
The post TRAPPIST-1 Outer Planets Likely Have Water appeared first on Universe Today.
I can remember when Perseverance was launched, travelled out into the Solar System and landed on Mars in February 2021. In all the time since it arrived, having clocked up 1000 days of exploration, it has collected 23 samples from different geological areas within the Jezero Crater. The area was once home to an ancient lake and if there is anywhere on Mars to find evidence of ancient (fossilised) life, it is here.
The date was 30 July 2020 when a gigantic Atlas V-541 rocket roared off the launchpad from Cape Canaveral in Florida. On board was the Perseverance rover, on its way to Mars. It arrived around 7 months later, entered the Martian atmosphere and successfully landed using a complex sequence of parachutes, retrorockets and for the first time, a sky crane to lower it from a hovering platform. Its chief purpose on Mars was to explore the geology, climate and atmospheric conditions as a precursor to human exploration.
The landing site, the Jezero Crater, was chosen because previous orbital studies revealed clear evidence of an ancient lake that once filled the crater. It is thought that water is a key ingredient to the evolution of life so if there had been a body of water, then there is a greater chance of life evolving. Studying the rocks here is like taking a flick through the history books as it preserves signs of ancient life and also ancient environmental conditions.
The crater had been formed, like the majority of other craters in the Solar System from some form of impact event. In the case of Jezero it was an asteroid impact around 4 billion years ago. On its arrival at the crater the floor was soon discovered to be made of igneous rock, formed from a huge underground chamber of magma and bought to the surface through volcanic activity. Since then, other types of rock from sand and mud were found providing evidence of the presence of water in Mars’ distant past.
By the time Perseverance had hit the 1000 day anniversary of its exploration of the red planet it had collected the rock samples, safely packaged them up ready for collection and by and large, completed its exploration of the ancient lake bed. One sample in particular which has been called ‘Lefroy Bay’ has been found to contain fine grained silica. This material is commonly found on Earth and known to preserve fossils. Another of the samples contains phosphate which, on Earth is most definitely associated with biological processes. Both of these contain carbon which can be used to study the environmental conditions from when the rock formed.
Jezero crater is a big place, 45 kilometres across so deciding on where to collect the samples was challenging. When a target site had been identified, Perseverance would first use its abrasion tool to wear away the surface and then use the onboard instruments such as PIXL, the Planetary Instrument for X-ray Lithochemistry. The instruments on board have the ability to detect both microscopic, fossil-like structures and also to identify chemical changes left behind by ancient microbes. Alas to date, whilst Perseverance has achieved an amazing amount, the detection of signs of life have alluded the rover.
Source : NASA’s Perseverance Rover Deciphers Ancient History of Martian Lake
The post Perseverance Wraps Up Over 1,000 Days on Mars. Still Going Strong appeared first on Universe Today.
