Posted on by Matt Williams

It Might Not be Planet 9 Causing Disruptions in the Kuiper Belt, Just the Collective Gravity of Everything Out There

Artist's concept of the hypothetical "Planet Nine." Could it have moons? Credit: NASA/JPL-Caltech/Robert Hurt

In January of 2016, astronomers Mike Brown and Konstantin Batygin published the first evidence that there might be another planet in our Solar System. Known as “Planet 9” (or “Planet X”, to those who contest the controversial 2006 Resolution by the IAU), this hypothetical body was believed to orbit at an extreme distance from our Sun, as evidenced by the fact that certain Trans-Neptunian Objects (TNOs) all seem to be pointing in the same direction.

Since that time, other lines of evidence have emerged that have bolstered the existence of Planet 9/Planet X. However, a team of researchers from CU Boulder recently proposed an alternative explanation. According to their research, it could be interactions between Kuiper Belt Objects (KBOs) themselves that might explain the strange dynamics of “detached objects” at the edge of the Solar System.

The researchers presented their findings at the 232nd meeting of the American Astronomical Society, which ran from June 3-7 in Denver, Colorado. The presentation took place on June 4th during a press conference titled “Minor Planets, Dwarf Planets & Exoplanets”. The research was led Jacob Fleisig, an undergraduate studying astrophysics at CU Boulder, and included Ann-Marie Madigan and Alexander Zderic – an assistant professor and a graduate student at CU Boulder, respectively.

Artist’s conception of Sedna, a dwarf planet in the Solar System that only gets within 76 astronomical units (AUs) of our Sun. Credit: NASA/JPL-Caltech

For the sake of their study, the team focused on icy bodies like Sedna, a minor planet that orbits the Sun at a distance ranging from 76 AU at perihelion to 936 AU at aphelion. Along with a handful of other objects at this distance, such as Eris, Sedna appears to be separated from the rest of the Solar System – something which astronomers have struggled to explain ever since it was discovered.

Sedna was also discovered by Michael Brown who, along with Chad Trujillo of the Gemini Observatory and David Rabinowitz of Yale University, spotted it on November 14th, 2003, while conducting a survey of the Kuiper Belt. In addition to orbiting our Sun with a period of over 11,000 years, this minor planet and other detached objects has a huge, elliptical orbit.

What’s more, this orbit does not take them Sedna or these other objects anywhere near to Neptune or any other gas giant. Unlike Pluto and other Trans-Neptunian Objects (TNOs), it is therefore a mystery how they achieved their current orbits. The possible existence of a as-yet-undiscovered planet (Planet 9/Planet X), which would be about 10 times the size of Earth, is one hypothetical explanation.

After years of searching for this planet and attempting to determine where its orbit would take it, astronomers have yet to find Planet 9/Planet X. However, as Prof. Madigan explained in a recent CU Boulder press release, there is another possible explanation for the gravitational weirdness going on out there:

“There are so many of these bodies out there. What does their collective gravity do? We can solve a lot of these problems by just taking into account that question… Once you get further away from Neptune, things don’t make any sense, which is really exciting.”

While Madigan and her team did not originally set out to find another explanation for the orbits of “detached objects”, they ended up pursuing the possibility thanks to Jacob Fleisig’s computer modelling. While developing simulations to explore the dynamics of the detached objects, he noticed something very interesting about the region of space they occupy.

Having calculated the orbits of icy objects beyond Neptune, Fleisig and the rest of the team noticed that different objects behave much like the different hands on a clock. Whereas asteroids move like the minute hand (relatively fast and in tandem), larger objects like Sedna move more slowly like the hour hand. Eventually, the hands intersect.  As Fleisig explained:

“You see a pileup of the orbits of smaller objects to one side of the sun. These orbits crash into the bigger body, and what happens is those interactions will change its orbit from an oval shape to a more circular shape.”

What Fleisig’s computer model showed was that Sedna’s orbit goes from normal to detached as a result of those small-scale interactions. It also showed that the larger the detached object, the farther it gets away from the Sun – something which agrees with previous research and observations. In addition to explaining why Sedna and similar bodies behave the way they do, these findings may provide clues to another major event in Earth’s history.

Artistic rendition of the Chicxulub impactor striking ancient Earth, which is believed to have caused the Cretaceous–Paleogene extinction event. Credit: NASA

This would be what caused the extinction of the dinosaurs. Astronomers have understood for a long time that the dynamics of the outer Solar System often end up sending comets towards the inner Solar System on a predictable timescale. This is the result of icy objects interacting with each other, which causes their orbits to tighten and widen in a repeating cycle.

And while the team is not able to say that this pattern was responsible for the impact that caused the Cretaceous–Paleogene extinction event (which resulted in the extinction of the dinosaurs 66 million years ago), it is a fascinating possibility. In the meantime, the research has shown just how fascinating the outer Solar System is, and how much remains to be learned about it.

“The picture we draw of the outer solar system in textbooks may have to change,” said Madigan. “There’s a lot more stuff out there than we once thought, which is really cool.”

The research was made possible thanks to the support of the NASA Solar System Workings and the Rocky Mountain Advanced Computing Consortium Summit Supercomputer.

Further Reading: University of Colorado Boulder

Posted on by Susie Murph

Astronomy Cast Ep. 495: Update on Asteroids & Prospects of Asteroid Mining

Our knowledge of space is starting to match up with our ability to get out there an explore it. There are several companies working on missions and techniques to harvest minerals from asteroids. What other resources are out there that we can use?

We usually record Astronomy Cast every Friday at 3:00 pm EST / 12:00 pm PST / 20:00 PM UTC. You can watch us live on AstronomyCast.com, or the AstronomyCast YouTube page.

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Posted on by Matt Williams

Does Climate Change Explain Why We Don’t See Any Aliens Out There?

A case study of the inhabitants of Easter Island served in part as the basis for a mathematical model showing the ways a technologically advanced population and its planet might develop or collapse together. Credit: University of Rochester illustration / Michael Osadciw

In the 1950s, famed physicist Enrico Fermi posed the question that encapsulated one of the toughest questions in the Search for Extra-Terrestrial Intelligence (SETI): “Where the heck is everybody?” What he meant was, given the age of the Universe (13.8 billion years), the sheer number of galaxies (between 1 and 2 trillion), and the overall number of planets, why has humanity still not found evidence of extra-terrestrial intelligence?

This question, which has come to be known as the “Fermi Paradox”, is something scientists continue to ponder. In a new study, a team from the University of Rochester considered that perhaps Climate Change is the reason. Using a mathematical model based on the Anthropocene, they considered how civilizations and planet systems co-evolve and whether or not intelligent species are capable of living sustainability with their environment.

The study, titled “The Anthropocene Generalized: Evolution of Exo-Civilizations and Their Planetary Feedback“, recently appeared in the scientific journal Astrobiology. The study was led by Adam Frank, a professor of physics and astronomy at the University of Rochester, with the assistance of Jonathan Carroll-Nellenback (a senior computational scientist at Rochester) Marina Alberti of the University of Washington, and Axel Kleidon of the Max Planck Institute for Biogeochemistry.

Today, Climate Change is one of the most pressing issues facing humanity. Thanks to changes that have taken place in the past few centuries – i.e. the industrial revolution, population growth, the growth of urban centers and reliance on fossil fuels – humans have had a significant impact on the planet. In fact, many geologists refer to the current era as the “Anthropocene” because humanity has become the single greatest factor affecting planetary evolution.

In the future, populations are expected to grow even further, reaching about 10 billion by mid-century and over 11 billion by 2100. In that time, the number of people who live within urban centers will also increase dramatically, increasing from 54% to 66% by mid-century. As such, the quesiton of how billions of people can live sustainably has become an increasingly important one.

Prof. Frank, who is also the author of the new book Light of the Stars: Alien Worlds and the Fate of the Earth (which draws on this study), conducted this study with his colleagues in order to address the issue Climate Change in an astrobiological context. As he explained in a University of Rochester press release:

“Astrobiology is the study of life and its possibilities in a planetary context. That includes ‘exo-civilizations’ or what we usually call aliens. If we’re not the universe’s first civilization, that means there are likely to be rules for how the fate of a young civilization like our own progresses.”

Using the Anthropocene as an example, one can see how civilization-planet systems co-evolve, and how a civilization can endanger itself through growth and expansion – in what is known as a “progress trap“. Basically, as civilizations grow, they consume more of the planet’s resources, which causes changes in the planet’s conditions. In this sense, the fate of a civilization comes down to how they use their planet’s resources.

In order to illustrate this process Frank and his collaborators developed a mathematical model that considers civilizations and planets as a whole. As Prof. Frank explained:

“The point is to recognize that driving climate change may be something generic. The laws of physics demand that any young population, building an energy-intensive civilization like ours, is going to have feedback on its planet. Seeing climate change in this cosmic context may give us better insight into what’s happening to us now and how to deal with it.”

The model was also based on case studies of extinct civilizations, which included the famous example of what became of the inhabitants of Rapa Nui (aka. Easter Island). According to archaeological studies, the people of the South Pacific began colonizing this island between 400 and 700 CE and its population peaked at 10,000 sometime between 1200 and 1500 CE.

Professor Adam Frank, who led the study in how civilization-planet systems evolve. Credit: University of Rochester photo / J. Adam Fenster

By the 18th century, however, the inhabitants had depleted their resources and the population declined to just 2000. This example raises the important concept known as “carrying capacity”, which is the maximum number of species an environment can support. As Frank explained, Climate Change is essentially how the Earth responds to the expansion of our civilization:

“If you go through really strong climate change, then your carrying capacity may drop, because, for example, large-scale agriculture might be strongly disrupted. Imagine if climate change caused rain to stop falling in the Midwest. We wouldn’t be able to grow food, and our population would diminish.”

Using their mathematical model, the team identified four potential scenarios that might occur on a planet. These include the Die-Off scenario, the Sustainability scenario, the Collapse Without Resource Change scenario, and the Collapse With Resource Change scenario. In the Die-Off scenario, the population and the planet’s state (for example, average temperatures) rise very quickly.

This would eventually lead to a population peak and then a rapid decline as changing planetary conditions make it harder for the majority of the population to survive. Eventually, a steady population level would be achieved, but it would only be a fraction of what the peak population was. This scenario occurs when civilizations are unwilling or unable to change from high-impact resources (i.e. oil, coal, clear-cutting) to sustainable ones (renewable energy).

Four scenarios for the fate of civilizations and their planets, based on mathematical models developed by Adam Frank and his collaborators. Credit: University of Rochester illustration / Michael Osadciw

In the Sustainability scenario, the population and planetary conditions both rise, but eventually come to together with steady values, thus avoiding any catastrophic effects. This scenario occurs when civilizations recognize that environmental changes threaten their existence and successfully make the transition from high-impact resources to sustainable ones.

The final two scenarios  – Collapse Without Resource Change and Collapse With Resource Change – differ in one key respect. In the former, the population and temperature both rise rapidly until the population reaches a peak and begins to drop rapidly – though it is not clear if the species itself survives. In the latter, the population and temperature rise rapidly, but the populations recognizes the danger and makes the transition. Unfortunately, the change comes too late and the population collapses anyway.

At present, scientists cannot say with any confidence which of these fates will be the one humanity faces. Perhaps we will make the transition before it is too late, perhaps not. But in the meantime, Frank and his colleagues hope to use more detailed models to predict how planets will respond to civilizations and the different ways they consume energy and resources in order to grow.

From this, scientists may be able to refine their predictions of what awaits us in this century and the next. It is during this time that crucial changes will be taking place, which include the aforementioned population growth, and the steady rise in temperatures. For instance, based on two scenarios that measured CO2 increases by the year 2100, NASA indicated that global temperatures could rise by either 2.5 °C (4.5 °F) or  4.4 °C (8 °F).

In the former scenario, where CO2 levels reached 550 ppm by 2100, the changes would be sustainable. But in the latter scenario, where CO2 levels reached 800 ppm, the changes would cause widespread disruption to systems that billions of humans depends upon for their livelihood and survival. Worse than that, life would become untenable in certain areas of the world, leading to massive displacement and humanitarian crises.

In addition to offering a possible resolution for the Fermi Paradox, this study offers some helpful advice for human beings. By thinking of civilizations and planets as a whole – be they Earth or exoplanets – researchers will be able to better predict what changes will be necessary for human civilization to survive. As Frank warned, it is absolutely essential that humanity mobilize now to ensure that the worst-case scenario does not occur here on Earth:

“If you change the earth’s climate enough, you might not be able to change it back. Even if you backed off and started to use solar or other less impactful resources, it could be too late, because the planet has already been changing. These models show we can’t just think about a population evolving on its own. We have to think about our planets and civilizations co-evolving.”

And be sure to enjoy this video that addresses Prof. Frank and his team’s research, courtesy of the University of Rochester:

Further Reading: University of Rochester, Astrobiology

Posted on by Matt Williams

There are Strange Objects Near the Center of the Galaxy. They Look Like Gas, but Behave Like Stars

The galactic core, observed using infrared light and X-ray light. Credit: NASA, ESA, SSC, CXC, and STScI

During the 1970s, astronomer became aware of a massive radio source at the center of our galaxy that they later realized was a Supermassive Black Hole (SMBH) – which has since been named Sagittarius A*. And in a recent survey conducted by NASA’s Chandra X-ray Observatory, astronomers discovered evidence for hundreds or even thousands of black holes located in the same vicinity of the Milky Way.

But, as it turns out, the center of our galaxy has more mysteries that are just waiting to be discovered. For instance, a team of astronomers recently detected a number of “mystery objects” that appeared to be moving around the SMBH at Galactic Center. Using 12 years of data taken from the W.M. Keck Observatory in Hawaii, the astronomers found objects that looked like dust clouds but behaved like stars.

The research was conducted through a collaboration between Randy Campbell at the W.M. Keck Observatory, members of the Galactic Center Group at UCLA (Anna Ciurlo, Mark Morris, and Andrea Ghez) and Rainer Schoedel of the Instituto de Astrofisica de Andalucia (CSIC) in Granada, Spain. The results of this study were presented at the 232nd American Astronomical Society Meeting during a press conference titled “The Milky Way & Active Galactic Nuclei”.

Pictured here are members of GCOI in front of Keck Observatory on Maunakea, Hawaii, during a visit last year. Credit: W.M. Keck Observatory

As Ciurlo explained in a recent W.M. Keck press release:

“These compact dusty stellar objects move extremely fast and close to our Galaxy’s supermassive black hole. It is fascinating to watch them move from year to year. How did they get there? And what will they become? They must have an interesting story to tell.”

The researchers made their discovery using 12 years of spectroscopic measurements obtained by the Keck Observatory’s OH-Suppressing Infrared Imaging Spectrograph (OSIRIS). These objects – which were designed as G3, G4, and G5 – were found while examining the gas dynamics of the center of our galaxy, and were distinguished from background emissions because of their movements.

“We started this project thinking that if we looked carefully at the complicated structure of gas and dust near the supermassive black hole, we might detect some subtle changes to the shape and velocity,” explained Randy Campbell. “It was quite surprising to detect several objects that have very distinct movement and characteristics that place them in the G-object class, or dusty stellar objects.”

Astronomers first discovered G-objects in proximity to Sagittarius A* more than a decade ago – G1 was discovered in 2004 and G2 in 2012. Initially, both were thought to be gas clouds until they made their closest approach to the supermassive black hole and survived. Ordinarily, the SMBHs gravitational pull would shred gas clouds apart, but this did not happen with G1 and G2.

3-D spectro-imaging data cube produced using software called OSIRIS-Volume Display ( OsrsVol) to separate G3, G4, and G5 from the background emission. Credit: W.M. Keck Observatory

Because these newly discovered infrared sources (G3, G4, and G5) shared the physical characteristics of G1 and G2, the team concluded that they could potentially be G-objects. What makes G-objects unusual is their “puffiness”, where they appear to be cloaked in a layer of dust and gas that makes them difficult to detect. Unlike other stars, astronomers only see a glowing envelope of dust when looking at G-objects.

To see these objects clearly through their obscuring envelope of dust and gas, Campbell developed a tool called the OSIRIS-Volume Display (OsrsVol). As Campbell described it:

“OsrsVol allowed us to isolate these G-objects from the background emission and analyze the spectral data in three dimensions: two spatial dimensions, and the wavelength dimension that provides velocity information. Once we were able to distinguish the objects in a 3-D data cube, we could then track their motion over time relative to the black hole.”

UCLA Astronomy Professor Mark Morris, a co-principal investigator and fellow member of UCLA’s Galactic Center Orbits Initiative (GCOI), was also involved in the study. As he indicated:

“If they were gas clouds, G1 and G2 would not have been able to stay intact. Our view of the G-objects is that they are bloated stars – stars that have become so large that the tidal forces exerted by the central black hole can pull matter off of their stellar atmospheres when the stars get close enough, but have a stellar core with enough mass to remain intact. The question is then, why are they so large?

Chandra data (above, graph) on J0806 show that its X-rays vary with a period of 321.5 seconds, or slightly more than five minutes. This implies that the X-ray source is a binary star system where two white dwarf stars are orbiting each other (above, illustration) only 50,000 miles apart, making it one of the smallest known binary orbits in the Galaxy. According to Einstein's General Theory of Relativity, such a system should produce gravitational waves - ripples in space-time - that carry energy away from the system and cause the stars to move closer together. X-ray and optical observations indicate that the orbital period of this system is decreasing by 1.2 milliseconds every year, which means that the stars are moving closer at a rate of 2 feet per year.
A binary star system potentially on the verge of a stellar collision. Credit: Chandra

After examining the objects, the team noticed that there was a great deal of energy was emanating from them, more than what would be expected from typical stars. As a result, they theorized that these G-objects are the result of stellar mergers, which occur when two stars that orbit each other (aka. binaries) crash into each other. This would have been caused by the long-term gravitational influence of the SMBH.

The resulting single object would be distended (i.e. swell up) over the course of millions of years before it finally settled down and appeared like a normal-sized star. The combined objects that resulted from these violent mergers could explain where the excess energy came from and why they behave like stars do. As Andrea Ghez, the founder and director of GCOI, explained:

“This is what I find most exciting. If these objects are indeed binary star systems that have been driven to merge through their interaction with the central supermassive black hole, this may provide us with insight into a process which may be responsible for the recently discovered stellar mass black hole mergers that have been detected through gravitational waves.”

Looking ahead, the team plans to continue following the size and shape of the G-objects’ orbits in the hopes of determining how they formed. They will be paying especially close attention when these stellar objects make their closest approach to Sagittarius A*, since this will allow them to further observe their behavior and see if they remain intact (as G1 and G2 did).

This will take a few decades, with G3 making its closest pass in 20 years and G4 and G5 taking decades longer. In the meantime, the team hopes to learn more about these “puffy” star-like objects by following their dynamical evolution using Keck’s OSIRIS instrument. As Ciurlo stated:

“Understanding G-objects can teach us a lot about the Galactic Center’s fascinating and still mysterious environment. There are so many things going on that every localized process can help explain how this extreme, exotic environment works.”

And be sure to check out this video of the presentation, which takes place from 18:30 until 30:20:

Further Reading: Keck Observatory

Posted on by Matt Williams

And NASA’s Big Announcement is: Ancient Organic Molecules Found on Mars!

This low-angle self-portrait of NASA's Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin" on lower Mount Sharp. Credits: NASA/JPL-Caltech/MSSS

Ever since Curiosity landed on Mars in 2012, the rover has made numerous groundbreaking discoveries about the Red Planet. These include confirming how Mars once had flowing water and lakes on its surface, evidence of how it lost its ancient atmosphere, and the discovery of methane and organic molecules. All of these discoveries have bolstered the theory that Mars may have once supported life.

The latest discovery came on Thursday, May 7th, when NASA announced that the Curiosity rover had once again discovered organic molecules. This time, however, the molecules were found in three-billion-year-old sedimentary rocks located near the surface of lower Mount Sharp. This evidence, along with new atmospheric evidence, are another indication that ancient life may have once existed on the Red Planet.

The new findings appear in two new studies – titled “Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars” and “Background levels of methane in Mars’ atmosphere show strong seasonal variations” – that were published in the June 8th issue of Science. As these studies indicate, these molecules – while not evidence of life in and of itself – have bolstered the search for evidence of past life.

MRO image of Gale Crater illustrating the landing location and trek of the Rover Curiosity since it landed in 2012. Credits: NASA/JPL, illustration, T.Reyes

As Thomas Zurbuchen, the associate administrator for the Science Mission Directorate at NASA Headquarters, explained in a recent NASA press release:

“With these new findings, Mars is telling us to stay the course and keep searching for evidence of life. I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet.”

In the first paper, the authors indicate how Curiosity’s Sample Analysis at Mars (SAM) suite detected traces of methane in drill samples it took from Martian rocks. Once these rocks were heated, they released an array of organics and volatiles similar to how organic-rich sedimentary rocks do on Earth. On Earth, such deposits are indications of fossilized organic life, which may or may not be the case with the samples examined by Curiosity.

However, this evidence is bolstered by the fact that Curiosity has also found evidence that the Gale Crater was once an ancient lakebed. In addition to water, this lakebed contained all the chemical building blocks and energy sources that are necessary for life. As Jen Eigenbrode of NASA’s Goddard Space Flight Center, and the lead author of the first study, explained:

“Curiosity has not determined the source of the organic molecules. Whether it holds a record of ancient life, was food for life, or has existed in the absence of life, organic matter in materials holds chemical clues to planetary conditions and processes… The Martian surface is exposed to radiation from space. Both radiation and harsh chemicals break down organic matter. Finding ancient organic molecules in the top five centimeters of rock that was deposited when Mars may have been habitable, bodes well for us to learn the story of organic molecules on Mars with future missions that will drill deeper.”

This image illustrates possible ways methane might get into Mars’ atmosphere and also be removed from it. Credit: NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan

In the second paper, the team described how Curiosity’s SAM suite also detected seasonal variations in methane in the Martian atmosphere. These results were obtained over the course of nearly three years on Mars, which works out to almost six Earth years. While the team admits that water-rock chemistry could have generated the methane, they cannot rule out the possibility that it was biological in origin.

In the past, methane and organic molecules have been detected in Mars’ atmosphere and in drill samples, the former of which appeared to spike unpredictably. However, these new results indicate that within the Gale Crater, low levels of methane peak during the warm summer months and drop in the winter months every year. As Chris Webster, a researcher from NASA’s Jet Propulsion Laboratory (JPL) and the lead author of the second paper, explained:

“This is the first time we’ve seen something repeatable in the methane story, so it offers us a handle in understanding it. This is all possible because of Curiosity’s longevity. The long duration has allowed us to see the patterns in this seasonal ‘breathing.'”

To find this organic material, Curiosity drilled into sedimentary rocks (known as mudstone) in four areas in the Gale Crater. These rocks formed over the course of billions of years as sediments were deposited at the bottom of the ancient lake by flowing water. The drill samples were then analyzed by SAM, which used its oven to heat the samples to over 500 °C (900 °F) to release organic molecules from the powdered rock.

Simulated view of Gale Crater Lake on Mars. This illustration depicts a lake of water partially filling Mars’ Gale Crater, receiving runoff from snow melting on the crater’s northern rim. Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

These results indicate that some of the drill samples contained sulfur (which could have preserved the organic molecules) as well as thiophenes, benzene, toluene, and small carbon chains – such as propane or butene. They also indicated organic carbon concentrations of about 10 parts per million or more, which is consistent with carbon concentrations observed in Martian meteorites and about 100 times what has been previously detected on Mars’ surface.

While this does not constitute evidence of past life on Mars, these latest findings have increased confidence that future missions will find more organics, both on the surface and slightly beneath the surface. But above all, they have bolstered confidence that Mars may have once had life of its own. As Michael Meyer, the lead scientist for NASA’s Mars Exploration Program, summarized:

“Are there signs of life on Mars? We don’t know, but these results tell us we are on the right track.”

In the coming years, additional missions will also be searching for signs of past life, including NASA’s Mars 2020 rover and the European Space Agency’s ExoMars rover.The Mars 2020 rover will also leave samples behind in a cache that could be retrieved by a future crewed mission for sample-return analysis. So if there was life on Mars (or, fingers crossed, still is) we are sure to find it soon enough!

And be sure to check out this video of this latest discovery by Curiosity, courtesy of NASA’s Jet Propulsion Laboratory:

Further Reading: NASA

Posted on by Matt Williams

Chandra Observatory Checks to Make Sure Alpha Centauri is Safe, You Know, in Case We Decide to Visit

The Alpha Centauri system, shown in the optical and X-ray wavelenghts (using Chandra data). Credit: chandra.harvard.edu

At distance of just 4.367 light years, the triple star system of Alpha Centauri (Alpha Centauri A+B and Proxima Centauri) is the closest star system to our own. In 2016, researchers from the European Southern Observatory announced the discovery of Proxima b, a rocky planet located within the star’s habitable zone and the closest exoplanet to our Solar System. However, whether or not Alpha Centauri has any potentially habitable planets remains a mystery.

Between 2012 and 2015, three possible candidates were announced in this system, but follow-up studies cast doubt on their existence. Looking to resolve this mystery, Tom Ayres – a senior research associate and Fellow at the University of Colorado Boulder’s Center for Astrophysics and Space Astronomy – conducted a study of Alpha Centauri based on over a decade’s worth of observations, with encouraging results!

The results of this study were presented at the 232rd meeting of the American Astronomical Society, which took place in Denver, Colorado, from June 3rd to June 7th. The study was based on ten years worth of monitoring of Alpha Centauri, which was provided the Chandra X-ray Observatory. This data indicated that any planets that orbit Alpha Centauri A and B are not likely to be bombarded by large amounts of X-ray radiation.

The two brightest stars of the Centaurus constellation – (left) Alpha Centauri and (right) Beta Centauri. The faint red star in the center of the red circle is Proxima Centauri. Credit: Wikipedia Commons/Skatebiker

This is good news as far as Alpha Centauri’s potential habitability goes since X-rays and related Space Weather effects are harmful to unprotected life. Not only can high doses of radiation be lethal to living creatures, they can also strip away planetary atmospheres. According to data provided by the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter, this  is precisely what happened to Mars between 4.2 and 3.7 billion years ago.

As Tom Ayres explained in a recent Chandra press release:

“Because it is relatively close, the Alpha Centauri system is seen by many as the best candidate to explore for signs of life. The question is, will we find planets in an environment conducive to life as we know it?”

The stars in the Alpha Centauri system (A and B) are quite similar to our Sun and orbit relatively close to each other. Alpha Centauri A, a G2 V (yellow dwarf) star, is the most Sun-like of the two, being 1.1 times the mass and 1.519 times the luminosity of the Sun. Alpha Centauri B is somewhat smaller and cooler, at 0.907 times the Sun’s mass and 0.445 times its visual luminosity.

As such, the odds that the system could support an Earth-like planet are pretty good, especially around Alpha Centauri A. According to the Chandra data, the prospects for life (based on X-ray bombardment) are actually better for any planet orbiting Alpha Centauri A than for the Sun, and Alpha Centauri B is only slightly worse. This is certainly good news for those who are hoping that a potentially habitable exoplanet is found in close proximity to the Solar System.

The respective habitable zones around Alpha Centauri A and B. Credit: Planetary Habitability Laboratory

When the existence of Proxima b was first announced, there was naturally much excitement. Not only did this planet orbit within it’s star’s habitable zone, but it was the closest known exoplanet to Earth. Subsequent studies, however, revealed that Proxima Centauri is variable and unstable by nature, which makes it unlikely that Proxima b could maintain an atmosphere or life on its surface. As Ayers explained:

“This is very good news for Alpha Cen AB in terms of the ability of possible life on any of their planets to survive radiation bouts from the stars. Chandra shows us that life should have a fighting chance on planets around either of these stars.”

Meanwhile, astronomers continue to search for exoplanets around Alpha Centauri A and B, but without success. The problem with this system is the orbit of the pair, which has drawn the two bright stars close together in the sky over the past decade. To help determine if Alpha Centauri was hospitable to life, astronomers began conducting a long-term observation campaign with Chandra in 2005.

As the only X-ray observatory capable of resolving Alpha Centauri A and B during its current close orbital approach, Chandra observed these two main stars every six months for the past thirteen years. These long-term measurements captured a full cycle of increases and decreases in X-ray activity, in much the same way that the Sun has an 11-year sunspot cycle.

What these observations showed was that any planet orbiting within the habitable zone of A would receive (on average) a lower dose of X-rays compared to similar planets around the Sun. For planets orbiting withing the habitable zone of B, the X-ray dose they received would be about five times higher. Meanwhile, planets orbiting within Proxima Centauri’s habitable zone would get an average of 500 times more X-rays, and 50,000 times more during a big flare.

In addition to providing encouraging hints about Alpha Centauri’s possible habitability, the X-ray observations provided by Chandra could also go a long way towards informing astronomers about our Sun’s X-ray activity. Understanding this is key to learning more about space weather and the threat they can pose to human infrastructure, as well as other technologically-advanced civilizations.

In the meantime, astronomers continue to search for exoplanets around Alpha Centauri A and B. Knowing that they have a good chance of supporting life will certainly make any future exploration of this system (like Project Starshot) all the more lucrative!

Some of the study’s results also appeared in the January issue in the Research Notes of the American Astronomical Society, titled “Alpha Centauri Beyond the Crossroads“. And be sure to enjoy this video about Alpha Centauri’s potential habitability, courtesy of the Chandra X-ray Observatory:

Further Reading: Chandra X-ray Observatory

Posted on by Matt Williams

Breakthrough Starshot is Now Looking for the Companies to Build its Laser-Powered Solar Sails to Other Stars

Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity's first interstellar voyage. Credit: breakthroughinitiatives.org

In 2015, Russian billionaire Yuri Milner established Breakthrough Initiatives, a non-profit organization dedicated to enhancing the search for extraterrestrial intelligence (SETI). In April of the following year, he and the organization be founded announced the creation of Breakthrough Starshot, a program to create a lightsail-driven “wafercraft” that would make the journey to the nearest star system – Proxima Centauri – within our lifetime.

In the latest development, on Wednesday May 23rd, Breakthrough Starshot held an “industry day” to outline their plans for developing the Starshot laser sail. During this event, the Starshot committee submitted a Request For Proposals (RFP) to potential bidders, outlining their specifications for the sail that will carry the wafercraft as it makes the journey to Proxima Centauri within our lifetimes.

As we have noted in several previous articles, Breakthrough Starshot calls for the creation of a gram-scale nanocraft being towed by a laser sail. This sail will be accelerated by an Earth-based laser array to a velocity of about 60,000 km/s (37,282 mps) – or 20% the speed of light (o.2 c). This concept builds upon the idea of a solar sail, a spacecraft that relies on solar wind to push itself through space.

An artist’s illustration of a light-sail powered by a radio beam (red) generated on the surface of a planet. Credit: M. Weiss/CfA

At this speed, the nanocraft would be able to reach the closest star system to our own – Proxima Centauri, located 4.246 light-years away – in just 20 years time. Since its inception, the team behind Breakthrough Starshot has invested considerable time and energy addressing the conceptual and engineering challenges such a mission would entail. And with this latest briefing, they are now looking to move the project from concept to reality.

In addition to being the Frank B. Baird, Jr. Professor of Science at Harvard University, Abraham Loeb is also the Chair of the Breakthrough Starshot Advisory Committee. As he explained to Universe Today via email:

“Starshot is an initiative to send a probe to the nearest star system at a fifth of the speed of light so that it will get there within a human lifetime of a couple of decades. The goal is to obtain photos of exo-planets like Proxima b, which is in the habitable zone of the nearest star Proxima Centauri, four light years away. The technology adopted for fulfilling this challenge uses a powerful (100 Giga-watt) laser beam pushing on a lightweight (1 gram) sail to which a lightweight electronics chip is attached (with a camera, navigation and communication devices). The related technology development is currently funded at $100M by Yuri Milner through the Breakthrough Foundation.”

In addition to outlining BI’s many efforts to find ETI – which include Breakthrough Listen, Breakthrough Message and Breakthrough Watch – the RFP focused on Starshot’s Objectives. As was stated in the RFP:

“The scope of this RFP addresses the Technology Development phase – to explore LightSail concepts, materials, fabrication and measurement methods, with accompanying analysis and simulation that creates advances toward a viable path to a scalable and ultimately deployable LightSail.”

A phased laser array, perhaps in the high desert of Chile, propels sails on their journey. Credit: Breakthrough Initiatives

As Loeb indicated, this RFP comes not long after another “industry day” that was related to the development of the technology of the laser – termed the “Photon Engine”. In contrast, this particular RFP was dedicated to the design of the laser sail itself, which will carry the nanocraft to Proxima Centauri.

“The Industry Day was intended to inform potential partners about the project and request for proposals (RFP) associated with research on the sail materials and design,” added Loeb. “Within the next few years we hope to demonstrate the feasibility of the required sail and laser technologies. The project will allocate funds to experimental teams who will conduct the related research and development work. ”

The RFP also addressed Starshot’s long-term goals and its schedule for research and development in the coming years. These include the investment in $100 million over the next five years to determine the feasibility of the laser and sail, to invest the value of the European Extremely Large Telescope (EELT) from year 6 to year 11 and build a low-power prototype for space testing, and invest the value of the Large Hardon Collider (LHC) over a 20 year period to develop the final spacecraft.

“The European Extremely Large Telescope (EELT) will cost on order of a billion [dollars] and the Large Hadron Collider cost was ten times higher,’ said Loeb. “These projects were mentioned to calibrate the scale of the cost for the future phases in the Starshot project, where the second phase will involve producing a demo system and the final step will involve the complete launch system.”

Artist’s impression of Proxima b, which was discovered using the Radial Velocity method. Credit: ESO/M. Kornmesser

The research and development schedule for the sail was also outlined, with three major phases identified over the next 5 years. Phase 1 (which was the subject of the RFP) would entail the development of concepts, models and subscale testing. Phase 2 would involve hardware validation in a laboratory setting, while Phase 3 would consist of field demonstrations.

With this latest “industry day” complete, Starshot is now open for submissions from industry partners looking to help them realize their vision. Step A proposals, which are to consist of a five-page summary, are due on June 22nd and will be assessed by Harry Atwater (the Chair of the Sail Subcommittee) as well as Kevin Parkin (head of Parkin Research), Jim Benford (muWave Sciences) and Pete Klupar (the Project Manager).

Step B proposals, which are to consist of a more detailed, fifteen-page summary, will be due on July 10th. From these, the finalists will be selected by Pete Worden, the Executive Director of Breakthrough Starshot. If all goes according to plan, the initiative hopes to launch the first lasersail-driven nanocraft in to Proxima Centauri in 30 years and see it arrive there in 50 years.

So if you’re an aerospace engineer, or someone who happens to run a private aerospace firm, be sure to get your proposals ready! To learn more about Starshot, the engineering challenges they are addressing, and their research, follow the links provided to the BI page. To see the slides and charts from the RFP, check out Starshot’s Solicitations page.

Further Reading: Centauri Dreams, Breakthrough Starshot

Posted on by Matt Williams

Are There Enough Chemicals on Icy Worlds to Support Life?

A montage of some of the "ocean worlds" in our Solar System. From top to bottom, left to right, these include Europa, Enceladus, TItan and Ceres. Credit: NASA/JPL

For decades, scientists have believed that there could be life beneath the icy surface of Jupiter’s moon Europa. Since that time, multiple lines of evidence have emerged that suggest that it is not alone. Indeed, within the Solar System, there are many “ocean worlds” that could potentially host life, including Ceres, Ganymede, Enceladus, Titan, Dione, Triton, and maybe even Pluto.

But what if the elements for life as we know it are not abundant enough on these worlds? In a new study, two researchers from the Harvard Smithsonian Center of Astrophysics (CfA) sought to determine if there could in fact be a scarcity of bioessential elements on ocean worlds. Their conclusions could have wide-ranging implications for the existence of life in the Solar System and beyond, not to mention our ability to study it.

The study, titled “Is extraterrestrial life suppressed on subsurface ocean worlds due to the paucity of bioessential elements?” recently appeared online. The study was led by Manasvi Lingam, a postdoctoral fellow at the Institute for Theory and Computation (ITC) at Harvard University and the CfA, with the support of Abraham Loeb – the director of the ITC and the Frank B. Baird, Jr. Professor of Science at Harvard.

Artist’s depiction of a watery exoplanet orbiting a distant red dwarf star. Credit: CfA

In previous studies, questions on the habitability of moons and other planets have tended to focus on the existence of water. This has been true when it comes to the study of planets and moons within the Solar System, and especially true when it comes the study of extra-solar planets. When they have found new exoplanets, astronomers have paid close attention to whether or not the planet in question orbits within its star’s habitable zone.

This is key to determining whether or not the planet can support liquid water on its surface. In addition, astronomers have attempted to obtain spectra from around rocky exoplanets to determine if water loss is taking place from its atmosphere, as evidenced by the presence of hydrogen gas. Meanwhile, other studies have attempted to determine the presence of energy sources, since this is also essential to life as we know it.

In contrast, Dr. Lingam and Prof. Loeb considered how the existence of life on ocean planets could be dependent on the availability of limiting nutrients (LN). For some time, there has been considerable debate as to which nutrients would be essential to extra-terrestrial life, since these elements could vary from place to place and over timescales. As Lingam told Universe Today via email:

“The mostly commonly accepted list of elements necessary for life as we know it comprises of hydrogen, oxygen, carbon, nitrogen and sulphur. In addition, certain trace metals (e.g. iron and molybdenum) may also be valuable for life as we know it, but the list of bioessential trace metals is subject to a higher degree of uncertainty and variability.”

Artist rendering showing an interior cross-section of the crust of Enceladus, which shows how hydrothermal activity may be causing the plumes of water at the moon’s surface. Credits: NASA-GSFC/SVS, NASA/JPL-Caltech/Southwest Research Institute

For their purposes, Dr. Lingam and Prof. Loeb created a model using Earth’s oceans to determine how the sources and sinks – i.e. the factors that add or deplete LN elements into oceans, respectively – could be similar to those on ocean worlds. On Earth, the sources of these nutrients include fluvial (from rivers), atmospheric and glacial sources, with energy being provided by sunlight.

Of these nutrients, they determined that the most important would be phosphorus, and examined how abundant this and other elements could be on ocean worlds, where conditions as vastly different. As Dr. Lingam explained, it is reasonable to assume that on these worlds, the potential existence of life would also come down to a balance between the net inflow (sources) and net outflow (sinks).

“If the sinks are much more dominant than the sources, it could indicate that the elements would be depleted relatively quickly. In other to estimate the magnitudes of the sources and sinks, we drew upon our knowledge of the Earth and coupled it with other basic parameters of these ocean worlds such as the pH of the ocean, the size of the world, etc. known from observations/theoretical models.”

While atmospheric sources would not be available to interior oceans, Dr. Lingam and Prof. Loeb considered the contribution played by hydrothermal vents. Already, there is abundant evidence that these exist on Europa, Enceladus, and other ocean worlds. They also considered abiotic sources, which consist of minerals leached from rocks by rain on Earth, but would consist of the weathering of rocks by these moons’ interior oceans.

Artist’s rendering of possible hydrothermal activity that may be taking place on and under the seafloor of Enceladus. Credit: NASA/JPL

Ultimately, what they found was that, unlike water and energy, limiting nutrients might be in limited supply when it comes to ocean worlds in our Solar System:

“We found that, as per the assumptions in our model, phosphorus, which is one of the bioessential elements, is depleted over fast timescales (by geological standards) on ocean worlds whose oceans are neutral or alkaline in nature, and which possess hydrothermal activity (i.e. hydrothermal vent systems at the ocean floor). Hence, our work suggests that life may exist in low concentrations globally in these ocean worlds (or be present only in local patches), and may therefore not be easily detectable.”

This naturally has implications for missions destined for Europa and other moons in the outer Solar System. These include the NASA Europa Clipper mission, which is currently scheduled to launch between 2022 and 2025. Through a series of flybys of Europa, this probe will attempt to measure biomarkers in the plume activity coming from the moon’s surface.

Similar missions have been proposed for Enceladus, and NASA is also considering a “Dragonfly” mission to explore Titan’s atmosphere, surface and methane lakes. However, if Dr. Lingam and Prof. Loeb’s study is correct, then the chances of these missions finding any signs of life on an ocean world in the Solar System are rather slim. Nevertheless, as Lingam indicated, they still believe that such missions should be mounted.

Artist’s concept of a Europa Clipper mission. Credit: NASA/JPL

“Although our model predicts that future space missions to these worlds might have low chances of success in terms of detecting extraterrestrial life, we believe that such missions are still worthy of being pursued,” he said. “This is because they will offer an excellent opportunity to: (i) test and/or falsify the key predictions of our model, and (ii) collect more data and improve our understanding of ocean worlds and their biogeochemical cycles.”

In addition, as Prof. Loeb indicated via email, this study was focused on “life as we know it”. If a mission to these worlds did find sources of extra-terrestrial life, then it would indicate that life can arise from conditions and elements that we are not familiar with. As such, the exploration of Europa and other ocean worlds is not only advisable, but necessary.

“Our paper shows that elements that are essential for the ‘chemistry-of-life-as-we-know-it’, such as phosphorous, are depleted in subsurface oceans,” he said. “As a result, life would be challenging in the oceans suspected to exist under the surface ice of Europa or Enceladus. If future missions confirm the depleted level of phosphorous but nevertheless find life in these oceans, then we would know of a new chemical path for life other than the one on Earth.”

In the end, scientists are forced to take the “low-hanging fruit” approach when it comes to searching for life in the Universe . Until such time that we find life beyond Earth, all of our educated guesses will be based on life as it exists here. I can’t imagine a better reason to get out there and explore the Universe than this!

Further Reading: arXiv

Posted on by David Dickinson

Astro Challenge: Spotting 4 Vesta at its Best for Decades

The asteroid Vesta, courtesy of NASA's Dawn spacecraft. Meteorites ejected from Vesta may have helped form Earth's water. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA
The asteroid Vesta, courtesy of NASA's Dawn spacecraft. Meteorites ejected from Vesta may have helped form Earth's water. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA
Vesta
The brave new world of 4 Vesta, courtesy of NASA’s Dawn spacecraft. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

Up for a challenge? Planetary action is certainly heating up this summer: Jupiter passed opposition last month, Saturn does so in June, and Mars reaches favorable viewing next month. And with dazzling Venus in the west and Mercury to joining it starting in late June, we’ll soon have all of the naked eye classical planets in the evening sky.

Now, I want to turn your attention towards a potential naked eye object, one you’ve probably never seen: asteroid 4 Vesta.

Vesta
Vesta and the planet(s)… looking east in early June, about 45 minutes after sunset. Stellarium.

Vistas of Vesta

Vesta reaches opposition in 2018 on the night of June 19th. At 1.14 Astronomical Units (AU, 170.8 million kilometers) distant, this year’s opposition is slightly more favorable than any other since 1989. We won’t get another pass nearly as close until May 2036. Vesta orbits the Sun once every 3.6 years, ranging from a perihelion of 2.15 AU to an aphelion of 2.57 AU.

Although Vesta was the fourth asteroid discovered, it’s actually the brightest, and the only one visible with the naked eye—that is, if you have dark skies, and know exactly where to look for it. This summer, Vesta loiters in the star rich realm of the astronomical constellation Sagittarius, “in the weeds” for viewers up north, but high in the sky for southern viewers.

Vesta
The path of 4 Vesta through mid-September. Credit: Starry Night Education software.

Early June finds Vesta about 5 degrees northwest of the +3.8 magnitude star Mu Sagittarii, threading between the deep sky objects Messier 24 and Messier 25. Vesta then loops westward through the constellation Ophiuchus the Serpent Bearer starting on July 1st, before heading back to Sagittarius on September 5th.

Vesta in 2018

Catching Vesta with the naked eye isn’t easy. You’ll need dark rural skies with a limiting magnitude down to about +5.5, and a good beforehand knowledge of the fixed stars in the region. Vesta also spends 2018 weaving around the star-dappled plane of the Milky Way galaxy, making it an especially challenging target.

Binoculars or a telescope can bring the challenge within reach of suburban and urban skies, making it a pleasure to trace the track of Vesta from night to night. Sketch the background star field and you just might tease out the presence of Vesta as it slowly moves about 30′ arcminutes per night (the diameter of a Full Moon) through June. Crank up the magnification a bit using a large (10 inches aperture or greater) light bucket telescope, and you just might see the faint hint of an oblong disk… 348 by 277 miles (560 by 446 kilometers) in size, Vesta’s apparent size is 0.7” arcseconds around opposition, 1/3 the size of Neptune at its best.

occultation vesta
The occultation footprint for the June 27th event. Credit: Occult 4.2 software.

The 99% illuminated, waxing gibbous Moon will actually occult 4 Vesta for Hawaii, Central America and the Galapagos Islands just eight days after opposition on the night of June 27th.

ceres vesta
Ceres (left) and Vesta (right) imaged by the Hubble Space Telescope. Credit: NASA/HST/STl

Discovered on the night of March 29th, 1807 by prolific asteroid hunter Heinrich Olber, the Hubble Space Telescope gave us our first blurry images of 4 Vesta back in 2007. NASA’s Dawn spacecraft gave us our first good views of Vesta as a world starting in mid- 2011, orbiting the potato-shaped asteroid for just over a year before departing for 1 Ceres in late 2012.

The south pole Rheasilvia impact basin. Based on images obtained by NASA’s Dawn spacecraft, the lower false color map shows the elevation scale scooped out by an ancient impact. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

Attack of the Vestoid(s)

And did you know: we actually have identified samples of Vesta to study, right here on Earth. Vesta sustained a massive impact about a billion years ago, raining debris through the inner solar system. Dawn chronicled the resulting Rheasilvia impact basin on Vesta’s south pole, and asteroids such as 1981 Midas match the spectral composition of Vesta and are collectively known as “Vestoids”.

Vesta Meteorites
Meteorites recovered on Earth, courtesy of 4 Vesta. Credit: NASA/University of Tennessee.

On Earth, meteorites such as QUE 97053 found in Antarctica and the 1913 Moore County fall in North Carolina also match up in composition to Vesta, and make up a subgroup known as Howardite-Eucrite-Diogenite (HED) meteorites. Collectively, space rocks from this single impact on 4 Vesta contribute to an amazing 5% of all the meteorites recovered on Earth.

Fascinating thoughts to ponder, as we follow the brightest asteroid through the summer sky.