Astronomy Archives

May 12, 2018 by Matt Williams

Evidence for Thousands of Black Holes Buzzing Around the Center of the Milky Way

On September 14th, 2013, astronomers caught the largest X-ray flare ever detected from the supermassive black hole at the center of the Milky Way, known as Sagittarius A* (Sgr A*). Credit: NASA/CXC/Stanford/I. Zhuravleva et al.

Since the 1970s, astronomers have understood that a Supermassive Black Hole (SMBH) resides at the center of the Milky Way Galaxy. Located about 26,000 light-years from Earth between the Sagittarius and Scorpius constellations, this black hole has come to be known as Sagittarius A* (Sgr A*). Measuring 44 million km across, this object is roughly 4 million times as massive as our Sun and exerts a tremendous gravitational pull.

Since that time, astronomers have discovered that most massive galaxies have SMBHs at their core, which is what separates those that have an Active Galactic Nuclei (AGN) from those that don’t. But thanks to a recent survey conducted using NASA’s Chandra X-ray Observatory, astronomers have discovered evidence for hundreds or even thousands of black holes located near the center of the Milky Way Galaxy.

The study which described their findings was recently published in the journal Nature under the title “A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy“. The study was led by Chuck Hailey, the Pupin Professor of Physics and the Co-Director of the Columbia Astrophysics Laboratory (CAL) at Columbia University, and including members from the Instituto de Astrofísica at the Pontificia Universidad Católica de Chile and the Harvard-Smithsonian Center for Astrophysics.

The center of the Milky Way Galaxy, with X-ray binaries circled in red, other X-ray sources circled in yellow, and Sagittarius A* circled in blue at the center. Credit: NASA/CXC/Columbia University/C. Hailey et al.

Using Chandra data, the team searched for X-ray binaries containing black holes that were in the vicinity of Sgr A*. To recap, black holes are not detectable in visible light. However, black holes (or neutron stars) that are locked in close orbits with a star will pull material from their companions, which will then be accreted onto the black holes’ disks and heated up to millions of degrees.

This will result in the release of X-rays which can then be detected, hence why these systems are called “X-ray binaries”. Using Chandra data, the team sought out X-ray of sources that were located within roughly 12 light years of Sgr A*. They then selected sources with X-ray spectra similar to those of known X-ray binaries, which emit relatively large amounts of low-energy X-rays.

Using this method, they detected fourteen X-ray binaries within about three light years of Sgr A*, all of which contained stellar-mass black holes (between 5 and 30 times the mass of our Sun). Two of these sources had been identified by previous studies and were eliminated from the analysis, while the remaining twelve (circled in red in the image above) were newly-discovered.

Other sources which relatively large amounts of high energy X-rays (labeled in yellow) were believed to be binaries containing white dwarfs. Hailey and his colleagues concluded that the majority of the dozen X-ray binaries were likely to contain black holes, based on their variability and the fact that their X-ray emissions over the course of several years was different from what is expected from binaries containing neutron stars.

*Artist”s impression of a black hole binary, consisting of a black hole siphoning material from its companion. Credit: ESO/L. Calçada*

Given that only the brightest X-ray binaries containing black holes are likely to be detectable around Sgr A* (given its distance from Earth), Hailey and his colleagues concluded that this detection implies the existence of a much larger population. By their estimates, there could be at least 300 and as many as one thousand stellar-mass black holes present around Sgr A*.

These findings confirmed what theoretical studies on the dynamics of stars in galaxies have indicated in the past. According to these studies, a large population of stellar mass black holes (as many as 20,000) could drift inward over the course of millions of years and collect around an SMBH. However, the recent analysis conducted by Hailey and his colleagues was the first observational evidence of black holes congregating near Sgr A*.

Naturally, the authors acknowledge that there are other explanations for the X-ray emissions they detected. This includes the possibility that half of the dozen sources they observed are millisecond pulsars – very rapidly rotating neutron stars with strong magnetic fields. However, based on their observations, Hailey and his team strongly favor the black hole explanation.

In addition, a follow-up study conducted by Aleksey Generozov (et al.) of Columbia University – titled “An Overabundance of Black Hole X-Ray Binaries in the Galactic Center from Tidal Captures” – indicated that there could be as many as 10,000 to 40,000 black holes binaries at the center of our galaxy. According to this study, these binaries would be the result of companions being captured by black holes.

In February 2016, LIGO detected gravity waves for the first time. As this artist's illustration depicts, the gravitational waves were created by merging black holes. The third detection just announced was also created when two black holes merged. Credit: LIGO/A. Simonnet. — *Artist’s impression of merging binary black holes. Credit: LIGO/A. Simonnet.*

In addition to revealing much about the dynamics of stars in our galaxy, this study has implications for the emerging field of gravitational wave (GW) research. Essentially, by knowing how many black holes reside at the center of galaxies (which will periodically merge with one another), astronomers will be able to better predict how many gravitational wave events are associated with them.

From this, astronomers could create predictive models about when and how GW events are likely to happen, and well as discerning what role they may play in galactic evolution. And with next-generation instruments – like the James Webb Space Telescope (JWST) and the ESA’s Advanced Telescope for High Energy Astrophysics (ATHENA) – astronomers will be able to determine exactly how many black holes reside near the center of our galaxy.

Further Reading: NASA

May 11, 2018 by Matt Williams

The Future of Our Sun is Still a Bit of a Puzzle. What Will Happen When it Dies?

Abell 39 is a good example of a planetary nebula, similar to the one discovered in M37. Credit: WIYN/NOAO/NSF

The life cycle of our Sun began roughly 4.6 billion years ago. In roughly 4.5 to 5.5 billion years, when it depletes its supply of hydrogen and helium, it will enter into its Red Giant Branch (RGB) phase, where it will expand to several times its current size and maybe even consume Earth! And then, when it has reached the end of its life-cycle, it is believed that it will blow off its outer layers and become a white dwarf.

Until recently, astronomers were not certain how this would take place and whether or not our Sun would end up as a planetary nebula (as most other stars in our Universe do). But thanks to a new study by an international team of astronomers, it is now understood that our Sun will end its life-cycle by turning into a massive ring of luminous interstellar gas and dust – known as a planetary nebula.

Their study, titled “The mysterious age invariance of the cut-off the Planetary Nebula Luminosity Function“, was recently published in the scientific journal Nature. The study was led by Krzysztof Gesicki, an astrophysicist from Nicolaus Copernicus University, Poland; and included Albert Zijlstra and M Miller Bertolami – a professor from the University of Manchester and an astronomer the Instituto de Astrofísica de La Plata (IALP), Argentina, respectively.

*The life cycle of a Sun-like star, from its birth (left side) to its evolution into a red giant (right side) after billions of years. Credit: ESO/M. Kornmesser*

Roughly 90% of all stars end up as a planetary nebula, which traces the transition they go through between being a red giant and a white dwarf. However, scientists were previously unsure if our Sun would follow this same path, as it was thought to not be massive enough to create a visible planetary nebula. To determine if this would be the case, the team developed a new stellar, data-model that predicts the lifecycle of stars.

This model – which they refer to as the Planetary Nebula Luminosity Function (PNLF) -was used to predict the brightness of the ejected envelope for stars of different masses and ages. What they found was that our Sun was just massive enough to end up as a faint nebula. As Prof. Zijlstra explained in a Manchester University press release:

“When a star dies it ejects a mass of gas and dust – known as its envelope – into space. The envelope can be as much as half the star’s mass. This reveals the star’s core, which by this point in the star’s life is running out of fuel, eventually turning off and before finally dying. It is only then the hot core makes the ejected envelope shine brightly for around 10,000 years – a brief period in astronomy. This is what makes the planetary nebula visible. Some are so bright that they can be seen from extremely large distances measuring tens of millions of light years, where the star itself would have been much too faint to see.”

This model also addressed an enduring mystery in astronomy, which is why the brightest nebulae in distant galaxies all appear to have the same luminosity. Roughly 25 years ago, astronomers began to observe this, and found that they could gauge the distance to other galaxies (in theory) by examining their brightest planetary nebulae. However, the model created by Gesicki and his colleagues contradicted this theory.

*Four different planetary nebulae from our galaxy. Credit: NASA/Chandra Observatory*

In short, the luminosity of a planetary nebula does not come down to the mass of the star creating it, as was previously assumed. “Old, low mass stars should make much fainter planetary nebulae than young, more massive stars,” said Prof. Zijlstra. “This has become a source of conflict for the past for 25 years. The data said you could get bright planetary nebulae from low mass stars like the Sun, the models said that was not possible, anything less than about twice the mass of the sun would give a planetary nebula too faint to see.”

Essentially, the new models demonstrated that after a star ejects its envelope, it will heat up three times faster than what older models indicated – which makes it much easier for low mass stars to form a bright planetary nebula. The new models also indicated that the Sun is almost exactly at the lower cut off for low mass stars that will still produce a visible, though faint, planetary nebula. Anything smaller, Prof. Zijlstra added, will not produce a nebula:

“We found that stars with mass less than 1.1 times the mass of the sun produce fainter nebula, and stars more massive than 3 solar masses brighter nebulae, but for the rest the predicted brightness is very close to what had been observed. Problem solved, after 25 years!”

In the end, this study and the model the team produced has some truly beneficial implications for astronomers. Not only have they indicated with scientific confidence what will happen to our Sun when it dies (for the first time), they have also provided a powerful diagnostic tool for determining the history of star formation for intermediate-age stars (a few billion years old) in distant galaxies.

It’s also good to know that when our Sun does reach the end of lifespan, billions of years from now, whatever progeny we leave behind will be able to appreciate it – even if they are looking across the vast distances of space.

Further Reading: University of Manchester, Nature

May 10, 2018May 10, 2018 by Matt Williams

The Giant Planets in the Solar System Stunted the Growth of Mars

A new study led by researchers from OU indicates that the outer planets could be why Mars is significantly smaller than Earth. Credit: NASA

For centuries, astronomers and scientists have sought to understand how our Solar System came to be. Since that time, two theories have become commonly-accepted that explain how it formed and evolved over time. These are the Nebular Hypothesis and the Nice Model, respectively. Whereas the former contends that the Sun and planets formed from a large cloud of dust and gas, the latter maintains the giant planets have migrated since their formation.

This is what has led to the Solar System as we know it today. However, an enduring mystery about these theories is how Mars came to be the way it is. Why, for example, is it significantly smaller than Earth and inhospitable to life as we know it when all indications show that it should be comparable in size? According to a new study by an international team of scientists, the migration of the giant planets could have been what made the difference.

For over a decade, astronomers have been operating under the assumption that shortly after the formation of the Solar System, the gas and ice giants of the outer Solar System (Jupiter, Saturn, Uranus and Neptune) began to migrate outward. This is the substance of the Nice Model, which asserts that this migration had a profound effect on the evolution of the Solar System and the formation of the terrestrial planets.

This model – named for the location of the Observatoire de la Côte d’Azur (in Nice, France), where it was initially developed – began as an evolutionary model that helped explain the observed distributions of small objects like comets and asteroids. As Matt Clement, a graduate student in the HL Dodge Department of Physics and Astronomy at the University of Oklahoma and the lead author on the paper, explained to Universe Today via email:

“In the model, the giant planets (Jupiter, Saturn, Uranus and Neptune) originally formed much closer to the Sun. In order to reach their current orbital locations, the entire solar system undergoes a period of orbital instability. During this unstable period, the size and the shape of the giant planet’s orbits change rapidly.”

For the sake of their study, which was recently published in the scientific journal Icarus under the title “Mars Growth Stunted by an Early Giant Planet Instability“, the team expanded on the Nice Model. Through a series of dynamical simulations, they attempted to show how, during the early Solar System, the growth of Mars was halted thanks to the orbital instabilities of the giant planets.

The purpose of their study was also to address a flaw in the Nice Model, which is how the terrestrial planets could have survived a serious shake up of the Solar System. In the original version of the Nice Model, the instability of the giant planets occurred a few hundred million years after the planets formed, which coincided with the Late Heavy Bombardment – when the inner Solar System was bombarded by a disproportionately large number of asteroids.

This period is evidenced by spike in the Moon’s cratering record, which was inferred from an abundance of samples from the Apollo missions with similar geological dates. As Clement explained:

“A problem with this is that it is difficult for the terrestrial planets (Mercury, Venus, Earth and Mars) to survive the violent instability without being ejected out of the solar system or colliding with one another. Now that we have better, high resolution images of lunar craters and more accurate methods for dating the Apollo samples, the evidence for a spike in lunar cratering rates is diminishing. Our study investigated whether moving the instability earlier, while the inner terrestrial planets were still forming, could help them survive the instability, and also explain why Mars is so small relative to the Earth.”

Clement was joined by Nathan A. Kaib, a OU astrophysics professor, as well as Sean N. Raymond of the University of Bordeaux and Kevin J. Walsh from the Southwest Research Institute. Together, they used the computing resources of the OU Supercomputing Center for Education and Research (OSCER) and the Blue Waters supercomputing project to perform 800 dynamical simulations of the Nice model to determine how it would impact Mars.

These simulations incorporated recent geological evidence from Mars and Earth that indicate that Mars’ formation period was about 1/10th that of Earth’s. This has led to the theory that Mars was left behind as a “stranded planetary embryo” during the formation of the Sun’s inner planets. As Prof. Kaib explained to Universe Today via email, this study was therefore intended to test how Mars emerged from planetary formation as a planetary embryo:

“We simulated the “giant impact phase” of terrestrial planet formation (the final stage of the formation process). At the beginning of this phase, the inner Solar System (0.5-4 AU) consists of a disk of about 100 moon-to-mars-sized planetary embryos embedded in a sea of much smaller, more numerous rocky planetesimals. Over the course of 100-200 million years the bodies making up this system collide and merge into a handful (typically 2-5) rocky planetary mass bodies. Normally, these types of simple initial conditions build planets on Mars-like orbits that are about 10x more massive than Mars. However, when the terrestrial planet formation process is interrupted by the Nice model instability, many of the planet building blocks near the Mars region are lost or tossed into the Sun. This limits the growth of Mars-like planets and produces a closer match to our actual inner solar system.”

*Size comparison between Earth and Mars. Credit: NASA*

What they found was that this revised timeline explained the disparity between Mars and Earth. In short, Mars and Earth vary considerably in size, mass and density because the giant planets became unstable very early in the Solar System’s history. In the end, this is what allowed Earth to become the only life-bearing terrestrial planet in the Solar System, and for Mars to become the cold, desiccated and thinly-atmosphered place that it is today.

As Prof. Kaib explained, this is not the only model for explaining the disparity between Earth and Mars, but the evidence all fits:

“Without this instability, Mars likely would have had a mass closer to Earth’s and would be a very different, perhaps more Earth-like, planet compared to what it is today,” he said. “I should also say that this is not the only mechanism capable of explaining the low mass of Mars. However, we already know that the Nice model does an excellent job of reproducing many features of the outer Solar System, and if it occurs at the right time in the Solar System’s history it also ends up explaining our inner Solar System.”

This study could also have drastic implications when it comes to the study of extra-solar systems. At present, our models for how planets form and evolve are based on what we have been able to learn from our own Solar System. Hence, by learning more about how gas giants and terrestrial planets grew and assumed their current orbits, scientists will be able to create more comprehensive models of how life-bearing planets could merge around other stars.

It certainly would help narrow the search for “Earth-like” planets and (dare we dream?) planets that support life.

Further Reading: University of Oklahoma, Icarus

May 8, 2018May 8, 2018 by Matt Williams

China is Working on Their Own Reusable Rocket: the First Stage of the Long March-8, Which Could Launch in 2021

China's brand-new heavy-lift Long March-5 rocket blasts off from Wenchang Space Launch on Nov. 3, 2016. Credit: Xinhua/Li Gang.

In recent decades, China’s space program has advanced considerably. In addition to deploying their first space station (Tiangong-1) and developing a modern rockets (the Long March 5), the nation has also sent robotic mission to the lunar surface and plans to conduct crewed missions there in the coming years. To this end, China is looking to create a new series of rockets that will enable them to explore the Moon and maybe even Mars.

One of the rockets they use to accomplish these goals is known as the Long-March 8, which is expected to make its maiden flight around 2021. According to a statement made by the chief rocket designer (Long Lehao) during a recent space conference in Harbin, China, the rocket will also include a reusable first stage. This latest announcement shows that China is also pursuing reusable launch vehicles to lower costs and increase their presence in space.

According to the China Space Report, the Long March 8 (Changzheng 8, or CZ-8) is a medium-lift vehicle intended for Sun-Synchronous Orbit (SSO) missions – i.e. where payloads are delivered to a nearly polar orbit around a planet. Consisting of two stages and two boosters, this rocket will reportedly have a payload capacity of 3000 to 4,500 kg (6600 to 9900 lbs) to SSO.

*The first Long March 5 rocket being rolled out for launch at Wenchang in late October 2016. Credit: Su Dong/China Daily*

The first stages on this rocket are believed to be based on the first-stage of the Long March 7, which are powered by two single-chamber YF-100, 1,200 kN-thrust engines fueled by LOX/kerosene. Based on Long’s statement, the first stages and boosters are expected to be retrieved through vertical landing (similar to SpaceX’s Falcon 9 and Falcon Heavy rockets).

However, according to Bao Weimin, the director of the Science and Technology Commission of the China Aerospace Science and Technology Corporation, the Long March 8 will use different technologies that those employed by SpaceX. The purpose of this rocket will be to provide commercial launch services to customers from around the world.

As Long indicated during the course of the conference (according to China Daily):

“China’s aerospace industry is making efforts to develop low-cost vehicles that can enter space rapidly to support future large-scale space exploration and promote a commercial space industry.”

In addition, Long also emphasized that China will be making efforts to address an ongoing problem with its younger Long March rockets, which is controlling where they fall. Currently, landing areas have to be are evacuated at every launch since these rockets rely on toxic chemicals. And with launches becoming more frequent, controlling where these rockets fall is becoming a major priority.

*Villagers gather around the debris of Long March 3A rocket carrier on December 31, 2014. Photo: Chinanews.com*

“As the current Long March 2, 3, 4 series rockets are fueled by toxic propellants, they cannot be recycled,” said Long. “But we are developing technologies to precisely control the fall of the rocket remains to ensure safety.”

Lastly, Long indicated what lies ahead for China’s space program and commercial spaceflight. By 2025, he claimed, reusable carriers will be developed for conducting suborbital space flights. By 2030, China National Space Agency will be conducting launches with rockets that rely on two reusable stages and will have achieved complete reusability by 2035. He also hinted how by 2040, China will be using reusable carrier rockets that will rely on hybrid-power sources.

All of this will allow for cheaper and more efficient launch services, facilitate spaceflight for private citizens, and allow for the commercialization of Low Earth Orbit (LEO). These goals are in keeping with what space agencies like NASA and private aerospace companies like SpaceX have in mind for the coming decades. In this sense, China is indicating that it intends to parallel other major powers in space by following a similar path.

Further Reading: China Daily

May 8, 2018March 16, 2020 by Matt Williams

How Many of Earth’s Moons Crashed Back Into the Planet?

Artist's concept of a collision between proto-Earth and Theia, believed to happened 4.5 billion years ago. Credit: NASA

For decades, scientists have pondered how Earth acquired its only satellite, the Moon. Whereas some have argued that it formed from material lost by Earth due to centrifugal force, or was captured by Earth’s gravity, the most widely accepted theory is that the Moon formed roughly 4.5 billion years ago when a Mars-sized object (named Theia) collided with a proto-Earth (aka. the Giant Impact Hypothesis).

However, since the proto-Earth experienced many giant-impacts, several moons are expected to have formed in orbit around it over time. The question thus arises, what happened to these moons? Raising this very question, a team an international team of scientist conducted a study in which they suggest that these “moonlets” could have eventually crashed back into Earth, leaving only the one we see today.

May 7, 2018 by Matt Williams

Breathing Lunar Dust Could Give Astronauts Bronchitis and Even Lung Cancer

Lunar footprint from the Apollo missions. Credit: NASA

It’s been over forty years since the Apollo Program wrapped up and the last crewed mission to the Moon took place. But in the coming years and decades, multiple space agencies plan to conduct crewed missions to the lunar surface. These includes NASA’s desire to return to the Moon, the ESA’s proposal to create an international Moon village, and the Chinese and Russian plans to send their first astronauts to the Moon.

For this reason, a great deal of research has been dedicated to what the health effects of long-duration missions to the Moon may be – particularly the effects a lower gravity environment would have on the human body. But in a recent study, a team of pharmacologists, geneticists and geoscientists consider how being exposed to lunar dust could have a serious effect on future astronauts’ lungs.

The study, titled “Assessing Toxicity and Nuclear and Mitochondrial DNA Damage Caused by Exposure of Mammalian Cells to Lunar Regolith Simulants“, recently appeared in GeoHealth – a journal of the American Geophysical Union. The study was led by Rachel Caston, a postdoctoral researcher from the Stony Brook University School of Medicine, and included members from Stony Brook’s Department of Pharmacological Sciences and the Department of Geosciences.

Geologist and astronaut Harrison Schmitt, Apollo 17 lunar module pilot, pictured using an adjustable sampling scoop to retrieve lunar samples during the Apollo 17 mission in December 1972. Credit: NASA.

Because it has no atmosphere, the Moon’s surface has been pounded by meteors and micrometeroes for billions of years, which have created a fine layer of surface dust known as regolith. In addition, the Moon’s surface is constantly being bombarded by charged particles from the Sun, which cause the lunar soil to become electrostatically charged and stick to clothing.

Indications that lunar dust could cause health problems first emerged during the Apollo missions. After visiting the Moon, astronauts brought lunar soil back with them into the command module as it clung to their spacesuits. After inhaling the dust, Apollo 17 astronaut Harrison Schmitt described having symptoms akin to hay fever, which including sneezing, watery eyes and a sore throat.

While the symptoms were short-lived, researchers wanted to know what the long-term effects of lunar dust could be. There have also been indications that exposure to lunar dust could be harmful based on research that has shown how breathing dust from volcanic eruptions, dust storms and coal mines can cause bronchitis, wheezing, eye irritation and scarring of lung tissue.

Previous research has also shown that dust can cause damage to cells’ DNA, which can cause mutations and eventually lead to cancer. For these reasons, Caston and her colleagues were well-motivated to see what harmful effects lunar soil could have on the human body. For the sake of their study, the team exposed human lung cells and mouse brain cells to samples of simulated lunar soil.

*After taking the first boot print photo, Aldrin moved closer to the little rock and took this second shot. The dusty, sandy pebbly soil is also known as the lunar ‘regolith’. Credit: NASA*

These simulants were created by using dust samples from Earth that resemble soil found on the Moon’s lunar highlands and volcanic plains, which were then ground to a fine powder. What they found was that up to 90% of human lung cells and mouse neurons died when exposed to the dust samples. The simulants also caused significant DNA damage to mouse neurons, and the human lung cells were so effectively damaged that it was impossible to measure any damage to the cells’ DNA.

The results show that breathing lunar dust (even in minute quantities) could pose a serious health hazard to astronauts traveling to any airless bodies in the future. This includes not only the Moon, but also Mars and other terrestrial bodies like Mercury. Until now, this health hazard has been largely overlooked by space agencies seeking to understand the long-term health risks of space travel.

“There are risks to extraterrestrial exploration, both lunar and beyond, more than just the immediate risks of space itself,” said Rachel Caston. According to Bruce Demple, a biochemist at Stony Brook University School of Medicine and senior author of the new study, their results (coupled with the experience of the Apollo astronauts) indicate that prolonged exposure to lunar dust could impair airway and lung function.

What’s worse, he also indicated that if the dust induces inflammation in the lungs, it could increase the risk of more serious diseases like cancer. “If there are trips back to the Moon that involve stays of weeks, months or even longer, it probably won’t be possible to eliminate that risk completely,” he said.

*Long-duration missions to the Moon, which could involve permanent bases, will have to contend with the hazard of breathing lunar dust. Credit: ESA/Foster + Partners*

Ergo, any attempts to mitigate the risks of mounting crewed missions to the Moon, Mars, and beyond will have to take into account exposure to not only low-gravity and radiation, but also electrostatically charged soil. Aside from limiting the duration of missions and the number of EVAs, certain protective counter-measures may need to be incorporated into any plans for long-duration missions.

One possibility is to have astronauts cycle through an airlock that would also spray their suits with water or a compound designed to neutralize the charge, thus washing them clean of dust before they enter the main habitat. Otherwise, astronauts working in the International Lunar Village (or any other off-world habitat for that matter) may have to wear breathing masks the entire time they are not in a spacesuit.

Further Reading: AGU, GeoHealth

May 7, 2018December 2, 2018 by Tammy Plotner

Messier 69 – the NGC 6637 Globular Cluster

The globular clusters M69 and M70, which lie in the Sagittarius Constellation. Image: Wikisky

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the globular cluster known as Messier 69.

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.

One of these objects is known as Messier 69 (NGC 6637), a globular cluster located in the constellation Sagittarius. Located about about 29,700 light-years away from Earth, this cluster lies close to Messier 70 (both of which were discovered Charles Messier on August 31st, 1780). Both objects lie close to the galactic center, and M69 is one of the most metal-rich globular clusters known. Continue reading “Messier 69 – the NGC 6637 Globular Cluster”

May 4, 2018May 4, 2018 by Matt Williams

NASA Has Tested a New Fission Space Reactor that Could be Used in Future Missions

Artist's concept of new fission power system on the lunar surface. Credits: NASA

Looking to the future of crewed space exploration, it is clear to NASA and other space agencies that certain technological requirements need to be met. Not only are a new generation of launch vehicles and space capsules needed (like the SLS and Orion spacecraft), but new forms of energy production are needed to ensure that long-duration missions to the Moon, Mars, and other locations in the Solar System can take place.

One possibility that addresses these concerns is Kilopower, a lightweight fission power system that could power robotic missions, bases and exploration missions. In collaboration with the Department of Energy’s National Nuclear Security Administration (NNSA), NASA recently conducted a successful demonstration of a new nuclear reactor power system that could enable long-duration crewed missions to the Moon, Mars, and beyond.

Known as the Kilopower Reactor Using Stirling Technology (KRUSTY) experiment, the technology was unveiled at a recent news conference on Wednesday, May 2nd, at NASA’s Glenn Research Center. According to NASA, this power system is capable of generating up to 10 kilowatts of electrical power – enough power several households continuously for ten years, or an outpost on the Moon or Mars.

*NASA and NNSA engineers lower the wall of the vacuum chamber around the Kilowatt Reactor Using Stirling TechnologY (KRUSTY system). Credits: Los Alamos National Laboratory*

As Jim Reuter, NASA’s acting associate administrator for the Space Technology Mission Directorate (STMD), explained in a recent NASA press release:

“Safe, efficient and plentiful energy will be the key to future robotic and human exploration. I expect the Kilopower project to be an essential part of lunar and Mars power architectures as they evolve.”

The prototype power system employs a small solid uranium-235 reactor core and passive sodium heat pipes to transfer reactor heat to high-efficiency Stirling engines, which convert the heat to electricity. This power system is ideally suited to locations like the Moon, where power generation using solar arrays is difficult because lunar nights are equivalent to 14 days on Earth.

In addition, many plans for lunar exploration involve building outposts in the permanently-shaded polar regions or in stable underground lava tubes. On Mars, sunshine is more plentiful, but subject to the planet’s diurnal cycle and weather (such as dust storms). This technology could therefore ensure a steady supply of power that is not dependent on intermittent sources like sunlight. As Marc Gibson, the lead Kilopower engineer at Glenn, said:

“Kilopower gives us the ability to do much higher power missions, and to explore the shadowed craters of the Moon. When we start sending astronauts for long stays on the Moon and to other planets, that’s going to require a new class of power that we’ve never needed before.”

*Artist’s impression of four KRUSTY generators providing power to an outpost on the surface of Mars. Credit: NASA/STMD*

The Kilopower experiment was conducted at the NNSA’s Nevada National Security Site (NNSS) between November and March of 2017. In addition to demonstrating that the system could produce electricity through fission, the purpose of the experiment was also to show that it is stable and safe in any environment. For this reason, the Kilopower team conduct in the experiment in four phases.

The first two phases, which were conducted without power, confirmed that each component in the system functioned properly. For the third phase, the team increased power to heat the core slowly before moving on to phase four, which consisted of a 28-hour, full-power test run. This phase simulated all stages of a mission, which included a reactor startup, ramp up to full power, steady operation and shutdown.

Throughout the experiment, the team simulated various system failures to ensure that the system would keep working – which included power reductions, failed engines and failed heat pipe. Throughout, the KRUSTY generator kept on providing electricity, proving that it can endure whatever space exploration throws at it. As Gibson indicated:

“We put the system through its paces. We understand the reactor very well, and this test proved that the system works the way we designed it to work. No matter what environment we expose it to, the reactor performs very well.”

*A Kilopower reactor could allow for permanent bases on the Moon and Mars and allow for the local production of fuel and other materials. Credit: ESA/Foster + Partners*

Looking ahead, the Kilopower project will remain a part of NASA’s Game Changing Development (GCD) program. As part of NASA’s Space Technology Mission Directorate (STMD), this program’s goal is to advance space technologies that may lead to entirely new approaches for the Agency’s future space missions. Eventually, the team hopes to make the transition to the Technology Demonstration Mission (TDM) program by 2020.

If all goes well, the KRUSTY reactor could allow for permanent human outposts on the Moon and Mars. It could also offer support to missions that rely on In-situ Resource Utilization (ISRU) to produce hydrazine fuel from local sources of water ice, and building materials from local regolith.

Basically, when robotic missions are mounted to the Moon to 3D print bases out of local regolith, and astronauts begin making regular trips to the Moon to conduct research and experiments (like they do today to the International Space Station), it could be KRUSTY reactors that provide them will all their power needs. In a few decades, the same could be true for Mars and even locations in the outer Solar System.

This reactor system could also pave the way for rockets that rely on nuclear-thermal or nuclear-electric propulsion, enabling missions beyond Earth that are both faster and more cost-effective!

And be sure to enjoy this video of the GCD program, courtesy of NASA 360:

Further Reading: NASA

May 3, 2018June 20, 2020 by Matt Williams

One of the TRAPPIST-1 Planets Has an Iron Core

Artist's impression of TRAPPIST-1e, which has a large iron core, according to a recent study. Credit: NASA/JPL-Caltech

In February of 2017, a team of European astronomers announced the discovery of a seven-planet system orbiting the nearby star TRAPPIST-1. Aside from the fact that all seven planets were rocky, there was the added bonus of three of them orbiting within TRAPPIST-1’s habitable zone. Since that time, multiple studies have been conducted to determine whether or not any of these planets could be habitable.

In accordance with this goal, these studies have focused on whether or not these planets have atmospheres, their compositions and their interiors. One of the latest studies was conducted by two researchers from Columbia University’s Cool Worlds Laboratory, who determined that one of the TRAPPIST-1 planets (TRAPPIST-1e) has a large iron core – a finding which could have implications for this planet’s habitability.

Continue reading “One of the TRAPPIST-1 Planets Has an Iron Core”

May 2, 2018May 2, 2018 by Matt Williams

NASA is Investigating a Self-Assembling Space Telescope

Graphic depiction of Modular Active Self-Assembling Space Telescope Swarms Credit: D. Savransky

NASA has some pretty advanced concepts in mind when it comes to the next generation of space telescopes. These include the Transiting Exoplanet Survey Satellite (TESS), which recently took to space, as well as the James Webb Space Telescope (JWST) (scheduled to launch in 2020) and the Wide-Field Infrared Survey Telescope (WFIRST), which is still in development.

Beyond these, NASA has also identified several promising proposals as part of its 2020 Decadal Survey for Astrophysics. But perhaps the most ambitious concept is one that calls for a space telescope made up of modules that would assemble themselves. This concept was recently selected for Phase I development as part of the 2018 NASA Innovative Advanced Concepts (NIAC) program.

The team behind this concept is led by Dmitri Savransky, an assistant professor of mechanical and aerospace engineering at Cornell University. Along with 15 colleagues from across the US, Savransky has produced a concept for a ~30 meter (100 foot) modular space telescope with adaptive optics. But the real kicker is the fact that it would be made up of a swarm of modules that would assemble themselves autonomously.

*On March. 23rd, 16 concepts received a Phase I award as part of the NASA Innovative Advanced Concepts (NIAC) program. Credit: NASA*

Prof. Savransky is well-versed in space telescopes and exoplanet hunting, having assisted in the integration and testing of the Gemini Planet Imager – an instrument on the Gemini South Telescope in Chile. He also participated in the planning of the Gemini Planet Imager Exoplanet Survey, which discovered a Jupiter-like planet orbiting 51 Eridani (51 Eridani b) in 2015.

But looking to the future, Prof. Savransky believes that self-assembly is the way to go to create a super telescope. As he and his team described the telescope in their proposal:

“The entire structure of the telescope, including the primary and secondary mirrors, secondary support structure and planar sunshield will be constructed from a single, mass-produced spacecraft module. Each module will be composed of a hexagonal ~1 m diameter spacecraft topped with an edge-to-edge, active mirror assembly.”

These modules would be launched independently and then navigate to the Sun-Earth L2 point using deployable solar sails. These sails will then become the planar telescope sunshield once the modules come together and assemble themselves, without the need for human or robotic assistance. While this may sound radically advanced, it is certainly in keeping with what the NIAC looks for.

“That’s what the NIAC program is,” said Dr. Savransky in recent interview with the Cornell Chronicle. “You pitch these somewhat crazy-sounding ideas, but then try to back them up with a few initial calculations, and then it’s a nine-month project where you’re trying to answer feasibility questions.”

*Artist’s concept of the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) space telescope. Credits: NASA/GSFC*

As part of the 2018 NAIC’s Phase I awards, which were announced on March 30th, the team was awarded $125,000 over a nine month period to conduct these studies. If these are successful, the team will be able to apply for a Phase II award. As Mason Peck, an associate professor of mechanical and aerospace engineering at Cornell and the former chief technology officer at NASA, indicated, Savransky is on the right track with his NIAC proposal:

“As autonomous spacecraft become more common, and as we continue to improve how we build very small spacecraft, it makes a lot of sense to ask Savransky’s question: Is it possible to build a space telescope that can see farther, and better, using only inexpensive small components that self-assemble in orbit?”

The target mission for this concept is the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR), a proposal that is currently being explored as part of NASA’s 2020 Decadal Survey. As one of two concepts being investigated by NASA’s Goddard Space Flight Center, this mission concept calls for a space telescope with a massive segmented primary mirror that measures about 15 meters (49 feet) in diameter.

Much like the JWST, LUVOIR’s mirror would be made up of adjustable segments that would unfold once it deployed to space. Actuators and motors would actively adjust and align these segments in order to achieve the perfect focus and capture light from faint and distant objects. The primary aim of this mission would be to discover new exoplanets as well as analyze light from those that have already been discovered to asses their atmospheres.

The Hubble Space Telescope on the left has a 2.4 meter mirror and the James Webb Space Telescope has a 6.5 meter mirror. LUVOIR, not shown, will dwarf them both with a massive 15 meter mirror. Image: NASA

As Savransky and his colleagues indicated in their proposal, their concept is directly in line with the priorities of the NASA Technology Roadmaps in Science Instruments, Observatories, and Sensor Systems and Robotics and Autonomous Systems. They also state that the architecture is a credible means to construct a giant space telescope, which would not be possible for previous generations of telescopes like Hubble and the JWST.

“James Webb is going to be the largest astrophysical observatory we’ve ever put in space, and it’s incredibly difficult,” he said. “So going up in scale, to 10 meters or 12 meters or potentially even 30 meters, it seems almost impossible to conceive how you would build those telescopes the same way we’ve been building them.”

Having been granted a Phase I award, the team is planning to conduct detailed simulations of how the modules would fly through space and rendezvous with each other to determine how large the solar sails need to be. They also plan to conduct an analysis of the mirror assembly to validate that the modules could achieve the required surface figure once assembled.

As Peck indicated, if successful, Dr. Savransky’s proposal could be a game changer:

“If Professor Savransky proves the feasibility of creating a large space telescope from tiny pieces, he’ll change how we explore space. We’ll be able to afford to see farther, and better than ever – maybe even to the surface of an extrasolar planet.”

On June 5th and 6th, NASA will also be conducting an NIAC Orientation Meeting in Washington D.C., where all the Phase I winners will have a chance to meet and discuss their ideas. Other proposals that received a Phase I award include shape-shifting robots for exploring Titan, lightweight aerial sensors to explore Venus’ atmosphere, flapping-wing swarm robots to explore Mars, a new form of beam propulsion for interstellar missions (similar to Breakthrough Starshot), a steam-powered robot for ocean worlds, and a self-replicating habitat made from fungus.

You can read more about these concepts, as well as those that were given Phase II award, here.

Further Reading: Cornell Chronicle, NASA