Posted on by Matt Williams

Astronomers Figure Out a New Way to Search for Planets at Alpha Centauri

Artist's impression of a hypothetical planet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Credit: ESO

At a distance of 4.37 light-years from Earth, Alpha Centauri is the nearest star system to our own. For generations, scientists and speculative thinkers have pondered whether it might have a planetary system like our own Sun, and whether or not life may also exist there. Unfortunately, recent efforts to locate extra-solar planets in this star system have failed, with potential detections later shown to be the result of artifacts in the data.

In response to these failed efforts, several more ambitious projects are being developed to find exoplanets around Alpha Centauri. These include direct-imaging space telescopes like Project Blue and the interstellar mission known as Breakthrough Starshot. But according to a new study led by researchers from Yale University, existing data can be used to determine the probability of planets in this system (and even which kind).

The study which detailed their findings recently appeared in The Astronomical Journal under the title “Planet Detectability in the Alpha Centauri System“. The study was led by Lily Zhao, a graduate student from Yale University and a fellow with the National Science Foundation (NSF), and was co-authored by Debora Fischer, John Brewer and Matt Giguere of Yale and Bárbara Rojas-Ayala of the Universidad Andrés Bello in Chile.

Artist’s impression of what the surface might look like on a planet orbiting Alpha Centauri system. Credit: Michael S. Helfenbein

For the sake of their study, Zhao and her team considered why efforts to locate planets within the the closest star system to our own have so far failed. This is surprising when one considers how, statistically speaking, Alpha Centauri is very likely to have a system if its own. As Prof. Fischer indicated in a recent Yale News press release:

“The universe has told us the most common types of planets are small planets, and our study shows these are exactly the ones that are most likely to be orbiting Alpha Centauri A and B… Because Alpha Centauri is so close, it is our first stop outside our solar system. There’s almost certain to be small, rocky planets around Alpha Centauri A and B.”

In addition to being a professor of astronomy at Yale University, Debora Fischer is also one of the leaders of the Yale Exoplanets Group. As an expert in her field, Fischer has devoted decades of her life to researching exoplanets and searching for Earth analogues beyond our Solar System. With partial funding provided by NASA and the National Science Foundation, the team relied on existing data collected by some of the latest exoplanet-hunting instruments.

These included CHIRON, a spectrograph mounted on the Small and Moderate Aperture Research Telescope System (SMARTS) at the Cerro Telolo Inter-American Observatory (CTIO) in Chile. This instrument was built by Fischer’s team, and the data it provided was combined with the High Accuracy Radial velocity Planet Searcher (HARPS) and the Ultraviolet and Visual Echelle Spectrograph (UVES) instruments on the ESO’s Very Large Telescope (VLT).

Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. The double star Alpha Centauri AB is visible to the upper right of Proxima itself. Credit: ESO

Using ten years of data collected by these instruments, Zhao and her colleagues then set up a grid system for the Alpha Centauri system. Rather than looking for signs of planets that did exist, they used the data to rule out what types of planets could not exist there. As Zhao told Universe Today via email:

“This study was special in that it used existing data of the Alpha Centauri system not to find planets, but to characterize what planets could not exist. By doing so, it returned more information about the system as a whole and provides guidance for future observations of this uniquely charismatic system. 

In addition, the team analyzed the chemical composition of the stars in the Alpha Centauri system to learn more about the kinds of material that would be available to form planets. Based on the different values obtained by observations campaigns conducted by different telescopes on Alpha Centauri’s three stars (Alpha, Beta and Proxima), they were able to place constraints on what kinds of planets could exist there. 

“We found that existing data rules out planets in the habitable zone above 53 Earth masses for alpha Centauri A, 8.4 Earth masses for Alpha Centauri B, and 0.47 Earth masses for Proxima Centauri,” said Zhao. “As for the chemical compositions, we found that the ratios of Carbon/Oxygen and Magnesium/Silicon for Alpha Centauri A and B are quite similar to that of the Sun.”

Artist’s impression of how the surface of a planet orbiting a red dwarf star may appear. Credit: M. Weiss/CfA

Basically, the results of their study effectively ruled out the possibility of any Jupiter-sized gas giants in the Alpha Centauri system. For Alpha Centauri A, they further found that planets that were less than 50 Earth masses could exist, while Alpha Centauri B might have planets smaller than 8 Earth masses. For Proxima Centauri, which we know to have at least one Earth-like planet, they determined that there might more that are less than half of Earth’s mass.

In addition to offering hope for exoplanet-hunters, this study carries with it some rather interesting implications for planetary habitability. Basically, the presence of rocky planets in the system is encouraging; but with no gas giants, a key ingredient in ensuring that planets remain habitable could be missing.

“[N]ot only could there still be habitable, Earth-mass planets around our closest stellar neighbors, but there also aren’t any gas giants that could endanger the survival of these potentially habitable, rocky planets,” said Zhao. “Furthermore, if these planets do exist, they are likely to have similar compositions to our very own Earth given the similarity in Alpha Cen A/B and our beloved Sun.”

At present, there are no instruments that have been able to confirm the existence of any exoplanets in Alpha Centauri. But as Zhao indicated, her and her teammates are optimistic that future surveys will have the necessary sensitivity to do it:

“[T]his very month has seen the commissioning of several next-generation instruments promising the precision necessary to discover these possible planets in the near future, and this analysis has shown that it is for sure worth it to keep looking!”

The ESO’s Paranal Observatory, located in the Atacama Desert of Chile. Credit: ESO

These include the ESO-built Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) – which was recently installed at the Paranal Observatory – and the EXtreme PREcision Spectrometer (EXPRES) built at Yale University. This latter instrument is currently conducting an observation run at the Lowell Observatory in Arizona, which Zhao is participating in.

“These instruments are promising a precision of down to 10-30 cm/s and should be able to detect many more smaller, and further away planets – such as habitable planets around the Centauri stars,” said Zhao. “The field of view of these two instruments are slightly different (ESPRESSO has the southern hemisphere, where Alpha Centauri is, while EXPRES covers the northern hemisphere, for instance where the Kepler and many of the K2 fields are).”

With new instruments at their disposal, and methods like the one Zhao and her team developed, the closest star system to Earth is sure to become a veritable treasure trove for astronomers and exoplanet-hunters in the coming years. And anything we find there will surely become targets for direct studies by groups like Project Blue and Breakthrough Starshot. If ET resides next door, we’re sure to hear about it soon!

Further Reading: Yale News, The Astronomical Journal

Posted on by Matt Williams

Maybe Mars and Earth Didn’t Form Close to Each Other

A new study by an international team of scientists considers whether Mars and Earth formed farther away from the Sun than previously thought. Credit: NASA/JPL-Caltech/USGS

In recent years, astronomers have been looking to refine our understanding of how the Solar System formed. On the one hand, you have the traditional Nebular Hypothesis which argues that the Sun, the planets, and all other objects in the Solar System formed from nebulous material billions of years ago. However, astronomers traditionally assumed that the planets formed in their current orbits, which has since come to be questioned.

This has come to be challenged by theories like the Grand Tack model. This theory states that Jupiter migrated from its original orbit after it formed, which had a big impact on the inner Solar System. And in a more recent study, an international team of scientists have taken things a step further, proposing that Mars actually formed in what is today the Asteroid Belt and migrated closer to the Sun over time.

The study, titled “The cool and distant formation of Mars“, recently appeared in the journal Earth and Planetary Science Letters. The study was led by Ramon Brasser of the Earth Life Science Institute at the Tokyo Institute of Technology, and included members from the University of Colorado, the Hungarian Academy of Sciences, and the University of Dundee in the UK.

Composite image showing the size difference between Earth and Mars. Credit: NASA/Mars Exploration

For the sake of their study, the team addressed one of the most glaring issues with traditional models of Solar System formation. This is the assumption that Mars, Earth and Venus formed closely together and that Mars migrated outward to its current orbit. In addition, the theory holds that Mars – roughly 53% as large as Earths and only 15% as massive – is essentially a planetary embryo that never became a full, rocky planet.

However, this has contradicted by bulk elemental and isotopic studies performed on Martian meteorites, which have noted key differences in composition between Mars and Earth. As Brasser and his team indicated in their study:

“This suggests that Mars formed outside of the terrestrial feeding zone during primary accretion. It is therefore probable that Mars always remained significantly farther from the Sun than Earth; its growth was stunted early and its mass remained relatively low.”

To test this hypothesis, the team conducted dynamical simulations that were consistent with the Grand Tack model. In these simulations, Jupiter moved a large concentration of mass towards the Sun at it migrated towards the inner Solar System, which had a profound influence on the formation and orbital characteristics of the terrestrial planets (Mercury, Venus, Earth and Mars).

The theory also holds that this migration pulled material away from Mars, thus accounting for the compositional differences and the planet’s smaller size and mass relative to Venus and Earth. What they found was that in a small percentage of their simulations, Mars formed farther from the Sun and that Jupiter’s gravitational pull pushed Mars into its current orbit.

The Grand Tack model (top) compared to the traditional theories about how the Inner Solar System formed. Credit: Sean Raymond/planetplanet.net

From this, the team concluded that either scientists lack the necessary mechanisms to explain Mars’ formation, or that of all the possibilities, this statistically rare scenario is indeed the correct one. As Stephen Mojzsis – a geological sciences professor at the University of Colorado and a co-author on the study – indicated in a recent interview with Astrobiology Magazine, the fact that the scenario is rare does not make it any less plausible:

“Given enough time, we can expect these events. For example, you’ll eventually get double sixes if you roll the dice enough times. The probability is 1/36 or roughly the same as we get for our simulations of Mars’ formation.”

In truth, a 2% probability (which is what they obtained from the simulations) is hardly poor odds when considered in cosmological terms. And when one considers that such a possibility would allow for the key differences between Mars and its terrestrial cousins (i.e. Earth and Venus), this slim probability appears rather possible. However, the idea that Mars migrated inward during the course of its history also carries with it some serious implications.

For starters, the researchers were pressed to explain how Mars could have possessed a thicker, warmer atmosphere that would have allowed for liquid water to exist on the surface. If Mars actually formed in the modern-day Asteroid Belt, it would have been subject to far less solar flux, and surface temperatures would have been significantly lower than if it had formed in its present-day location.

Scientists were able to gauge the rate of water loss on Mars by measuring the ratio of water and HDO from today and 4.3 billion years ago. Credit: Kevin Gill

However, as they go to indicate, if Mars had enough carbon-dioxide in its early atmosphere, then it is possible that impacts during the Late Heavy Bombardment could have allowed for intermittent periods where liquid water could exist on the surface. Or as they explain it:

“Unless, as our model shows, an intrinsically volatile-rich Mars possessed a strong and sustainable greenhouse atmosphere, its average surface temperature was unremittingly below 0 °C. Such a cold surface environment would have been regularly affected by early impact bombardments that both restarted a moribund hydrological cycle, and provided a haven for possible early life in the martian crust.”

Basically, while Mars would have been subject to less in the way of solar energy during its early lifespan, its possible it could have still been warm enough to support liquid water on its surface. And as Mojzsis stated in a paper he co-authored last year, the many bombardments it received (as attested to by its many craters) would have been enough to melt surface ice, thicken the atmosphere, and trigger a periodic hydrological cycle.

Another interesting thing about this study is how it predicts that Venus likely has a bulk composition (including its oxygen isotopes) that is similar to that of the Earth-Moon system. According to their simulations, this is due to the fact that Venus and Earth always shared the same building blocks, whereas Earth and Mars did not. These findings were consistent with recent ground-based infrared observations of Venus and its atmosphere.

Artist’s impression of the joint NASA-Roscosmos Venera-D mission concept, which wold include a Venus orbiter and a lander designed to survive on Venus’ surface for a few hours. Credit: NASA/JPL-Caltech

But of course, no definitive conclusions can be drawn about that until samples of Venus’ crust can be obtained. This could be accomplished if and when the proposed Venera-Dolgozhivuschaya (Venera-D) mission – a joint NASA/Roscomos plan to send a orbiter and lander to Venus – is launched in the coming decade. In the meantime, there are other outstanding issues in the Grand Tack model and Nebular Hypothesis that need to be addressed.

According to Mojzsis, these include how the gas/ice giants of the Solar System could have formed in their current locations. The idea that they formed in their current orbits beyond the Asteroid Belt seems inconsistent with models of the early Solar System, which show that there was not enough of the necessary material that far from the Sun. An alternative is that they formed closer to the Sun and also migrated outward.

As Mojzsis explained, this possibility is bolstered by recent studies of extra-solar planetary systems, where gas giants have been found to orbit very close to their stars (i.e. “Hot Jupiters”) and farther away:

“We understand from direct observations via the Kepler Space Telescope and earlier studies that giant planet migration is a normal feature of planetary systems. Giant planet formation induces migration, and migration is all about gravity, and these worlds affected each other’s orbits early on.”

If there’s one benefit to being able to look farther out into the Universe, its the way it has allowed astronomers to come up with better and more complete theories of how the Solar System came to be. And as our exploration of the Solar System continues to grow, we are sure to learn many things that will help advance our understanding of other star systems as well.

Further Reading: Astrobiology Magazine, Earth and Planetary Science Letters

Posted on by Matt Williams

Red Dwarf Star, Planet Orbiting at Right Angles. Mayhem.

Artist's impression of vessels floating near GJ436 its exoplanet, which orbits its star from pole to pole. Credit: University of Geneva/Denis Bajram

When we think of other planetary systems, we tend to think that they will operate by the same basic rules as our own. In the Solar System, the planets orbit close to the equatorial plane of the Sun – meaning around its equator. The Sun’s rotational axis, the direction of its poles based to its rotation, is also the same as most of the planets’ (the exception being Uranus, which rotates on its side).

But if the study of extra-solar planets has taught us anything, it is that the Universe is full of possibilities. Consider the star known as GJ436, a red dwarf located about 33 light-years from Earth. For years, astronomers have known that this star has a planet that behaves very much like a comet. But according to a recent study led by astronomers from the University of Geneva (UNIGE), this planet also has a very peculiar orbit.

The study, titled “Orbital Misalignment of the Neptune-mass Exoplanet GJ 436b With the Spin of its Cool Star“, recently appeared in the scientific journal Nature. The study was led by Vincent Bourrier of the Geneva University Observatory, and included members from the University of Grenoble Alpes, Tennessee State University, and the Center for Space and Habitability at the University of Bern.

Artist’s concept of the Neptune-sized planet Gliese 436b, surrounded by an envelop of hydrogen gas. Credit: NASA/ESA/STScI/G. Bacon

GJ436 has already been the source of much scientific interest, thanks in part to the discovery that its only confirmed exoplanet has a gaseous envelop similar a comet. This exoplanet, known as GJ436b, was first observed in 2004 using radial velocity measurements taken by the Keck Observatory. In 2007, GJ436b became the first Neptune-sized planet known to be orbiting very closely to its star (aka. a “Hot Neptune”).

And in 2015, GJ436 b made headlines again when scientists reported that its atmosphere was evaporating, resulting in a giant cloud around the planet and a long, trailing tale. This cloud was found to be the result of hydrogen in the planet’s atmosphere evaporating, thanks to the extreme radiation coming from its star. This never-before-seen phenomena essentially means that GJ436 b looks like a comet.

Another interesting fact about this planet is its orbital inclination, which astronomers have puzzled over for the past 10 years. Unlike the planets of the Solar System – whose orbits are largely circular – GJ436b follows a very eccentric, elliptical path. And as the research team indicated in their study, the planet also doesn’t orbit along the star’s equatorial plane, but passes almost above the its poles.

As Vincent Bourrier – a researcher at the Department of Astronomy of the UNIGE Faculty of Science, a member of the European Research Council project FOUR ACES, and the lead author of the study – explained in a UNIGE press release:

“This planet is under enormous tidal forces because it is incredibly close to its star, barely 3% of the Earth-Sun distance. The star is a red dwarf whose lifespan is very long, the tidal forces it induces should have since circularized the orbit of the planet, but this is not the case!”

Artist’s impression of JG436b, a hot Neptune located about 33 light years from Earth. Credit: Courtesy Space Telescope Science Institute

This was an especially interesting find for many reasons. On the one hand, it is the first instance where a planet was found to have a polar orbit. On the other, studying how planets orbit around a star is a great way to learn more about how that system formed and evolved. For instance, if a planet has been disturbed by the passage of a nearby star, or is being influenced by the presence of other massive planets, that will be apparent from its orbit.

As Christophe Lovis, a UNIGE researcher and co-author of the study, explained:

“Even if we have already seen misaligned planetary orbits, we do not necessarily understand their origin, especially since here it is the first time we measure the architecture of a planetary system around a red dwarf.”

Hervé Beust, an astronomer from the University of Grenobles Alpes, was responsible for doing the orbital calculations on GJ436b. As he indicated, the likeliest explanation for GJ436b’s orbit is the existence of a more massive and more distant planet in the system. While this planet is not currently known, this could be the first indication that GJ436 is a multi-planet system.

“If that is true, then our calculations indicate that not only would the planet not move along a circle around the star, as we’ve known for 10 years, but it should also be on a highly inclined orbit,” he said. “That’s exactly what we just measured!”

Artist impression of what GJ436b might look like. Credit: NASA

Another interesting takeaway from this study was the prediction that the planet has not always orbited so closely to its star. Based on their calculations, the team hypothesizes that the GJ436b may have migrated over time to become a “evaporating planet” that it is today. Here too, the existence of an as-yet-undetected companion is believed to be the most likely cause.

As with all exoplanet studies, these findings have implications for our understanding of the Solar System as well. Looking ahead, the team hopes to conduct further studies of this system in the hopes of determining if there is an elusive planetary companion to be found. These surveys will likely benefit from the deployment of next-generation missions, particularly the James Webb Space Telescope (JWST).

As Bourier indicated, “Our next goal is to identify the mysterious planet that has upset this planetary system.” Locating it will be yet another indirect way in which astronomers discover exoplanets – determining the presence of other planets based on orbital inclination of already discovered ones. The orbital inclination method, perhaps?

Further Reading: University of Geneva, Nature

Posted on by Matt Williams

Kilonova Neutron Star Collision Probably Left Behind a Black Hole

Artist's illustration of two merging neutron stars. The narrow beams represent the gamma-ray burst while the rippling spacetime grid indicates the isotropic gravitational waves that characterize the merger. Swirling clouds of material ejected from the merging stars are a possible source of the light that was seen at lower energies. Credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet

In February of 2016, scientists from the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced the first-ever detection of gravitational waves. A little over a century after they were first predicted by Einstein’s Theory of General Relativity, we finally had proof that this phenomenon existed. In August of 2017, another major breakthrough occurred when LIGO detected waves that were believed to be caused by a neutron star merger.

Shortly thereafter, scientists at LIGO, Advanced Virgo, and the Fermi Gamma-ray Space Telescope were able to determine where in the sky the neutron star merger occurred. While many studies have focused on the by-products of this merger, a new study by researchers from Trinity University, the University of Texas at Austin and Eureka Scientific, has chosen to focus on the remnant, which they claim is likely a black hole.

For the sake of their study, which recently appeared online under the title “GW170817 Most Likely Made a Black Hole“, the team consulted data from the Chandra X-ray Observatory to examine what resulted of the supernova merger. This data was obtained during Director’s Discretionary Time observations that were made on December 3rd and 6th, 2017, some 108 days after the merger.

This data showed a light-curve increase in the X-ray band which was compatible to the radio flux increase that was reported by a previous study conducted by the same team. These combined results suggest that radio and X-ray emissions were being produced at the same source, and that the rising light-curve that followed the merger was likely due to an increase in accelerated charged particles in the external shock – the region where an outflow of gas interacts with the interstellar medium.

As they indicate in their study, this could either be explained as the result of a more massive neutron star being formed from the merger, or a black hole:

“The merger of two neutron stars with mass 1.48 ± 0.12 M and 1.26 ± 0.1 M — where the merged object has a mass of 2.74 +0.04-0.01 M… could result in either a neutron star or a black hole. There might also be a debris disk that gets accreted onto the central object over a period of time, and which could be source of keV X-rays.”

The team also ruled out various possibilities of what could account for this rise in X-ray luminosity. Basically, they concluded that the X-ray photons were not coming from a debris disk, which would have been left over from the merger of the two neutron stars. They also deduced that they would not be produced by a relativistic jet spewing from the remnant, since the flux would be much lower after 102 days.

 

Collisions of neutron stars produce powerful gamma-ray bursts – and heavy elements like gold. Credit: Dana Berry, SkyWorks Digital, Inc.

All of this indicated that the remnant was more likely to be a black hole than a hyper-massive neutron star. As they explained:

“We show next that if the merged object were a hyper-massive neutron star endowed with a strong magnetic field, then the X-ray luminosity associated with the dipole radiation would be larger than the observed luminosity 10 days after the event, but much smaller than the observed flux at t ~ 100 days. This argues against the formation of a hyper-massive neutron star in this merger.”

Last, but not least, they considered the X-ray and radio emissions that were present roughly 100 days after the merger. These, they claim, are best explained by continued emissions coming from the merger-induced shock (and the not remnant itself) since these emissions would continue to propagate in the interstellar medium around the remnant. Combined with early X-ray data, this all points towards GW170817 now being a black hole.

The first-ever detection of gravitational waves signaled the dawn of a new era in astronomical research. Since that time, observatories like LIGO, Advanced Virgo, and GEO 600 have also benefited from information-sharing and new studies that have indicated that mergers are more common than previously thought, and that gravity waves could be used to probe the interior of supernovae.

With this latest study, scientists have learned that they are not only able to detect the waves caused by black hole mergers, but even the creation thereof. At the same time, it shows how the study of the Universe is growing. Not only is astronomy advancing to the point where we are able to study more and more of the visible Universe, but the invisible Universe as well.

Further Reading: LIGO, arXiv

Posted on by Matt Williams

Astronomers Find Another Solar System with 8 Planets. Uh, Pluto, About that Deplaneting…

In a series of papers, Professor Loeb and Michael Hippke indicate that conventional rockets would have a hard time escaping from certain kinds of extra-solar planets. Credit: NASA/Tim Pyle
In a series of papers, Professor Loeb and Michael Hippke indicate that conventional rockets would have a hard time escaping from certain kinds of extra-solar planets. Credit: NASA/Tim Pyle

With every passing year, more and more extra-solar planets are discovered. To make matters more interesting, improvements in methodology and technology are allowing for the discovery of more planets within individual systems. Consider the recent announcement of a seven-planet system around the red dwarf star known as TRAPPIST-1. At the time, this discovery established the record for most exoplanets orbiting a single star.

Well move over TRAPPIST-1! Thanks to the Kepler Space Telescope and machine learning, a team from Google AI and the Harvard-Smithsonian Center of Astrophysics (CfA) recently discovered an eighth planet in the distant star system of Kepler-90. Known as Kepler -90i, the discovery of this planet was made possible thanks to Google algorithms that detected evidence of a weak transit signal in the Kepler mission data.

Continue reading “Astronomers Find Another Solar System with 8 Planets. Uh, Pluto, About that Deplaneting…”

Posted on by Matt Williams

How Long Can a Rocky World Withstand the Blasts From a Red Dwarf Star?

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

Red dwarf stars have become a major focal point for exoplanet studies lately, and for good reason. For starters, M-type (red dwarf) stars are the most common type in our Universe, accounting for 75% of stars in the Milky Way alone. In addition, in the past decade, numerous terrestrial (i.e rocky) exoplanets have been discovered orbiting red dwarf stars, and within their circumstellar habitable zones (“Goldilocks Zones”) to boot.

This has naturally prompted several studies to determine whether or not rocky planets can retain their atmospheres. The latest study comes from NASA, using data obtained by the Mars Atmosphere and Volatile Evolution (MAVEN) orbiter. Having studied Mars’ atmosphere for years to determine how and when it was stripped away, the MAVEN mission is well-suited when it comes to measuring the potential habitability of other planets.

The study was shared on Dec. 13th, 2017, at the Fall Meeting of the American Geophysical Union in New Orleans, Louisiana. In a presentation titled “Spanning Disciplines to Search for Life Beyond Earth“, a team of NASA scientists and researchers from the University of California-Riverside and the University of Colorado-Boulder explained how insights from the MAVEN mission could be applied to the habitability of rocky planets orbiting other stars.

Artist’s rendering of a solar storm hitting Mars and stripping ions from the planet’s upper atmosphere. Credits: NASA/GSFC

Launched in November 18th, 2013, the MAVEN mission established orbit around Mars on September 22nd, 2014. The purpose of this mission has been to explore the Red Planet’s upper atmosphere, ionosphere and its interactions with the Sun and solar wind for the sake of determining how and when Mars’ atmosphere went from being thicker and warmer in the past (and thus able to support liquid water on the surface) to thin and tenuous today.

Since November of 2014, MAVEN has been measuring Mars’ atmospheric loss using its suite of scientific instruments. From the data it has obtained, scientists have surmised that the majority of the planet’s atmosphere was lost to space over time due to a combination of chemical and physical processes. And in the past three years, the Sun’s activity has increased and decreased, giving MAVEN the opportunity to observe how Mars’ atmospheric loss has risen and fallen accordingly.

Because of this, David Brain – a professor at the Laboratory for Atmospheric and Space Physics (LASP) at the CU Boulder is also a MAVEN co-investigator – and his colleagues began to think about how these insights could be applied to a hypothetical Mars-like planet orbiting around an red dwarf star. These planets include Proxima b (the closest exoplanet to our Solar System) and the seven planet system of TRAPPIST-1.

As Brain he explained in a recent NASA press release:

“The MAVEN mission tells us that Mars lost substantial amounts of its atmosphere over time, changing the planet’s habitability. We can use Mars, a planet that we know a lot about, as a laboratory for studying rocky planets outside our solar system, which we don’t know much about yet.”

At one time, Mars had a magnetic field similar to Earth, which prevented its atmosphere from being stripped away. Credit: NASA

To determine if this hypothetical planet could retain its atmosphere over time, the researchers performed some preliminary calculations that assumed that this planet would be positioned near the outer edge of the star’s habitable zone (as Mars is). Since red dwarf’s are dimmer than our Sun, the planet would have to orbit much closer to the star – even closer than Mercury does to our Sun – to be within this zone.

They also considered how a higher proportion of the light emanating from red dwarf stars is in the ultraviolet wavelength. Combined with a close orbit, this means that the hypothetical planet would be bombarded with about 5 times more UV radiation the real Mars gets. This would also mean that the processes responsible for atmospheric loss would be increased for this planet.

Based on data obtained by MAVEN, Brain and colleagues were able to estimate how this increase in radiation would affect Mars’ own atmospheric loss. Based on their calculations, they found that the planet’s atmosphere would lose 3 to 5 times as many charged particles through ion escape, while about 5 to 10 times more neutral particles would be lost through photochemical escape (where UV radiaion breaks apart molecules in the upper atmosphere).

Another form of atmospheric loss would also result, due to the fact that more UV radiation means that more charged particles would be created. This would result in a process called “sputtering”, where energetic particles are accelerated into the atmosphere and collide with other molecules, kicking some out into space and sending others crashing into neighboring particles.

To receive the same amount of starlight as Mars receives from our Sun, a planet orbiting an M-type red dwarf would have to be positioned much closer to its star than Mercury is to the Sun. Credit: NASA’s Goddard Space Flight Center

Lastly, they considered how the hypothetical planet might experience about the same amount of thermal escape (aka. Jeans escape) as the real Mars. This process occurs only for lighter molecules such as hydrogen, which Mars loses at the top of its atmosphere through thermal escape. On the “exo-Mars”, however, thermal escape would increase only if the increase in UV radiation were to push more hydrogen into the upper atmosphere.

In conclusion, the researchers determined that orbiting at the edge of the habitable zone of a quiet M-type star (instead of our Sun) could shorten the habitable period for a Mars-like planet by a factor of about 5 to 20. For a more active M-type star, the habitable period could be cut by as much as 1,000 times. In addition, solar storm activity around a red dwarf, which is thousands of times more intense than with our Sun, would also be very limiting.

However, the study is based on how an exo-Mars would fair around and M-type star, which kind of stacks the odds against habitability in advance. When different planets are considered, which possess mitigating factors Mars does not, things become a bit more promising. For instance, a planet that is more geologically active than Mars would be able to replenish its atmosphere at a greater rate.

Other factors include increase mass, which would allow for the planet to hold onto more of its atmosphere, and the presence of a magnetic field to shield it from stellar wind. As Bruce Jakosky, MAVEN’s principal investigator at the University of Colorado (who was not associated with this study), remarked:

“Habitability is one of the biggest topics in astronomy, and these estimates demonstrate one way to leverage what we know about Mars and the Sun to help determine the factors that control whether planets in other systems might be suitable for life.”

Multiple survey have revealed evidence of rocky planets orbiting a red dwarf stars, raising questions about their habitability. Credit: ESO/M. Kornmesser/N. Risinger (skysurvey.org).

In the coming years, astronomers and exoplanet researchers hope to learn more about the planets orbiting nearby red dwarf stars. These efforts are expected to be helped immensely thanks to the deployment of the James Webb Space Telescope, which will be able to conduct more detailed surveys of these star systems using its advanced infrared imaging capabilities.

These studies will allow scientists to place more accurate constraints on exoplanets that orbit red dwarf stars, which will allow for better estimates about their size, mass, and compositions – all of which are crucial to determining potential habitability.

Other panelists that took part in the presentations included Giada Arney and Katherine Garcia-Sage of NASA Goddard Space Flight Center and Stephen Kane of the University of California-Riverside. You can access the press conference materials by going to NASA Goddard Media Studios.

Further Reading: NASA, AGU

Posted on by Matt Williams

Gaia Looks Beyond our Galaxy to Other Islands of Stars

Color view of M31 (The Andromeda Galaxy), with M32 (a satellite galaxy) shown to the lower left. Credit and copyright: Terry Hancock.

The European Space Agency’s (ESA) Gaia mission is an ambitious project. Having launched in December of 2013, the purpose of this space observatory has been to measure the position and distances of 1 billion objects – including stars, extra-solar planets, comets, asteroids and even quasars. From this, astronomers hope to create the most detailed 3D space catalog of the cosmos ever made.

Back in 2016, the first batch of Gaia data (based on its first 14 months in space) was released. Since then, scientists have been poring over the raw data to obtain clearer images of the neighboring stars and galaxies that were studied by the mission. The latest images to be released, based on Gaia data, included revealing pictures of the Large Magellanic Cloud (LMC), the Andromeda galaxy, and the Triangulum galaxy.

The first catalog of Gaia data consisted of information on 1.142 billion stars, including their precise position in the night sky and their respective brightness. Most of these stars are located in the Milky Way, but a good fraction were from galaxies beyond ours, which included about ten million belonging to the LMC. This satellite galaxy, located about 166 000 light-years away, has about 1/100th the mass of the Milky Way.

Gaia’s view of the Large Magellanic Cloud. Click here for further details, full credits, and larger versions of the image. Credit: ESA/Gaia/DPAC

The two images shown above display composite data obtained by the Gaia probe. The image on the left, which was compiled by mapping the total density of stars detected by Gaia, shows the large-scale distribution of stars in the LMC. This image also delineates the extent of the LMC’s spiral arms, and is peppered with bright dots that represent faint clusters of stars.

The image on the right, on the other hand, reveals other aspects of the LMC and its stars. This image was created by mapping radiation flux in the LMC and is dominated by the brightest and most massive stars. This allows the bar of the LMC to be more clearly defined and also shows individual regions of star-formation – like 30 Doradus, which is visible just above the center of the galaxy in the picture.

The next set of images (shown below), which were also obtained using data from the first 14 months of the Gaia mission, depict two nearby spiral galaxies – the Andromeda galaxy (M31) and its neighbor, the Triangulum galaxy (M33). The Andromeda galaxy, located 2.5 million light-years away, is the largest galaxy in our vicinity and slightly more massive than our own. It is also destined to merge with the Milky Way in roughly 4 billion years.

The Triangulum galaxy, meanwhile, is a fraction the size of the Milky Way (with an estimated fifty billion stars) and is located slightly farther from us than Andromeda – about 2.8 million light-years distant. As with the LMC images, the images on the left are based on the total density of stars and show stars of all types, while images on the right are based on the radiation flux of each galaxy and mainly show the bright end of the stellar population.

Gaia’s view of the Andromeda galaxy. Credit: ESA/Gaia/DPAC

Another benefit of the images on the right is that they indicate the regions where the most intense star formation is taking place. For many years, astronomers have known that the LMC boasts a significant amount of star-forming activity, forming stars at five times the rate of the Milky Way Galaxy. Andromeda, meanwhile, has reached a point of near-inactivity in the past 2 billion years when it comes to star formation.

In comparison, the Triangulum Galaxy still shows signs of star formation, at a rate that is about four and a half times that of Andromeda. Thanks to the Gaia images, which indicate the relative rates of star formation from elevated levels of radiation flux and brightness, these differences between Andromeda, Triangulum and the LMC is illustrated quite beautifully.

What’s more, by analyzing the motions of individual stars in external galaxies like the LMC, Andromeda, or Triangulum, it will be possible to learn more about the overall rotation of stars within these galaxies. It will also be possible to determine the orbits of the galaxies themselves, which are all part of the larger structure known as the Local Group.

This region of space, which the Milky Way is part of, measures roughly 10 million light-years across and has an estimated 1.29 billion Solar masses. This, in turn, is just one of several collections of galaxies in the even larger Virgo Supercluster. Measuring how stars and galaxies orbit about these larger structures is key to determining cosmic evolution, how the Universe came to be as it is today and where it is heading.

The Triangulum galaxy (M33), based on data compiled by the Gaia mission. Credit: ESA/Gaia/DPAC

An international team of astronomers recently attempted to do just that using the CosmicFlows surveys. These studies, which were conducted between 2011 and 2016, calculated the distance and speed of neighboring galaxies. By pairing this data with other distance estimates and data on the galaxies gravity fields, they were able to chart the motions of almost 1,400 galaxies within 100 million light years over the course of the past 13 billion years.

In the case of the LMC, another team of astronomers recently attempted to measure its orbit using a subset of data from the first Gaia release – the Tycho–Gaia Astrometric Solution (TGAS). Combined with additional parallax and proper motion data from the Hipparcos mission, the team was able to identify 29 stars in the LMC and measure their proper motion, which they then used to estimate the rotation of the galaxy.

Gaia’s observations of the LMC and the Small Magellanic Cloud (SMC) are also important when it comes to studying Cepheid and RR Lyrae variables. For years, astronomers have indicated that these stars could be used as indicators of cosmic distances for galaxies beyond our own. In addition, astronomers working at the Gaia Data Processing and Analysis Consortium (DPAC) tested this method on hundreds of LMC variable stars in order to validate data from the first release.

Astronomers are eagerly awaiting the second release of Gaia data, which is scheduled for April of 2018. This will also contain measurements on stellar distances and their motions across the sky, and is expected to reveal even more about our galaxy and its neighbors. But in the meantime, there are still plenty of revelations to be found from the first release, and scientists expect to be busy with it for many years to come.

Further Reading: ESA

Posted on by Matt Williams

Are Little Blue Dots in the Hubble Frontier Fields Precursors to Globular Clusters?

The massive galaxy cluster Abell 370 as seen by Hubble Space Telescope in the final Frontier Fields observations. The lensing effect reveals details about a supernova in the distant universe. Credit: NASA/ESA/HFF

In 2012, the Hubble Space Telescope Frontier Fields program (aka. Hubble Deep Fields Initiative 2012) officially kicked off. The purpose of this project was to study the faintest and most distant galaxies in the Universe using the gravitational lensing technique, thus advancing our knowledge of early galaxy formation. By 2017, the Frontier Field program wrapped up, and the hard work of analyzing all the data it collected began.

One of the more interesting finds within the Frontier Fields data has been the discovery of low mass galaxies with high star formation rates. After examining the “parallel fields” for Abell 2744 and MACS J0416.1-2403 – two galaxy clusters studied by the program – a pair of astronomers noted the presence of what they refer to as “Little Blue Dots” (LBDs), a finding which has implications for galaxy formation and globular clusters.

The study which details their findings recently appeared online under the title “Little Blue Dots in the Hubble Space Telescope Frontier Fields: Precursors to Globular Clusters?“. The study team consisted of Dr. Debra Meloy Elmegreen – a professor of astronomy at Vassar College – and Dr. Bruce G. Elmegreen, an astronomer with the IBM Research Division at the T.J. Watson Research Center in Yorktown Heights.

The galaxy clusters Abell 2744, MACS J0416.1-2403, MACS J0717.5+3745, MACS J1149.5+2223, Abell S1063, Abell 370. Credit: NASA, ESA, STScI, and the HFF team

To put it simply, the Frontier Fields program used the Hubble Space Telescope to observe six massive galaxy clusters at optical and near-infrared wavelengths – with its Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3), respectively. These massive galaxies were used to magnify and stretch images of remote galaxies located behind them which were otherwise too faint for Hubble to see directly (aka. gravitational lensing).

While one of these Hubble cameras would look at a galaxy cluster, the other would simultaneously view an adjacent patch of sky. These adjacent patches are known as “parallel fields”, otherwise faint regions that provide some of the deepest looks into the early Universe. As Dr. Bruce Elmegreen told Universe Today via email:

“The purpose of the HFF program is to take deep images of 6 regions of the sky where there are clusters of galaxies, because these clusters magnify background galaxies through the gravitational lens effect. In this way, we can see further than just with direct imaging of the sky alone. Many galaxies have been studied using this magnification technique. The clusters of galaxies are important because they are big mass concentrations which make strong gravitational lenses.”

This six galaxy clusters used for the sake of the project included Abell 2744, MACS J0416.1-2403 and their parallel fields, the latter of which were the focal point in this study. These and the other clusters were used to find galaxies that existed just 600 to 900 million years after the Big Bang. These galaxies and their respective parallels had already been cataloged using computer algorithms that automatically found galaxies in the images and determined their properties.

Images of the MACS J0416.1–2403 and Abell 2744 galaxy clusters, taken as part of the Hubble Frontier Fields program. Credit: NASA/ESA/HST Frontier Fields team (STScI)

As the research duo go on to explain in their study, recent large-scale deep surveys have enabled studies of smaller galaxies at higher redshifts. These include “green peas” – luminous, compact and low mass galaxies with high specific star formation rates – and even lower-mass “blueberries”, small starburst galaxies that are a faint extension of the green peas that also show intense rates of star formation.

Using the aforementioned catalogues, and examining the parallel fields for Abell 2744 and MACS J0416.1-2403, the team went looking for other examples of low-mass galaxies with high star formation rates. The purpose of this was to measure the properties of these dwarf galaxies, and to see if any of their positions accorded with where globular clusters are known to have formed.

What they found was what they referred to as “Little Blue Dots” (LBSs), which are even lower-mass versions of “blueberries”. As Dr. Debra Elmegreen told Universe Today via email:

“When I was examining the images (there are about 3400 galaxies detected in each field), I noticed occasional galaxies that appeared as little blue dots, which was very intriguing because of Bruce’s previous theoretical work on dwarf galaxies. The published catalogs included redshifts and star formation rates and masses for each galaxy, and it turns out the little blue dots are low mass galaxies with very high star formation rates for their mass.”

Close-up view of a HFF parallel field, showing a LBD (upper right). Credit: Debra & Bruce Elmegreen

These galaxies didn’t show structure, so Debra and Bruce stacked the images of galaxies into 3 different ranges of redshift (which worked out to about 20 galaxies each) to create deeper images. “Still they showed no structure or faint extended outer disk,” said Debra, “so they are at the limit of resolution, with average sizes of 100-200 parsecs (about 300-600 light years) and masses of a few million times the mass of our sun.”

In the end, they determined that within these LBDs, star formation rates were very high. They also noted that these dwarf galaxies were very young, being less than 1% the age of the Universe at the time that they were observed. “So the tiny galaxies just formed,: said Bruce, “and their star formation rates are high enough to account for the globular clusters, maybe one in each LBD, when the star bursts in them wind down after a few tens of million years.”

Debra and Bruce Elmegreen are no strangers to high redshift galaxies. Back in 2012, Bruce published a paper that suggested that the globular clusters that orbit the Milky Way (and most other galaxies) formed in dwarf galaxies during the early Universe. These dwarf galaxies would have since been acquired by larger galaxies like our own, and the clusters are essentially their remnants.

Globular clusters are essentially massive star clusters that orbit around the Milky Way Halo. They are typically around 1 million Solar masses and are made up of stars that are very old – somewhere on the order of 10 to 13 billion years. Beyond the Milky Way, many appear in common orbits and in the Andromeda Galaxy, some even appear connected by a stream of stars.

The three groups of LBDs, where the dwarf galaxies were stacked based on their redshift. Credit: Debra & Bruce Elmegreen

As Bruce explained, his is a compelling argument for the theory that globular clusters formed from dwarf galaxies in the early Universe:

“This suggests that the metal-poor globular clusters are the dense remnants of little galaxies that got captured by bigger galaxies, like the Milky Way, and ripped apart by tidal forces. This idea for the origin of halo globular clusters goes back several decades… It would be only the metal-poor one that are like this, which are about half the total, because dwarf galaxies are metal poor compared to big galaxies, and they were also more metal poor in the early universe.”

This study has many implications for our understanding of how the Universe evolved, which was the chief aim of the Hubble Frontier Fields program. By examining objects in the early Universe, and determining their properties, scientists are able to determine how the structures that we are familiar with today – i.e. stars, galaxies, clusters, etc. – truly came from.

These same studies also allow scientists to make educated guesses about where the Universe is going and what will become of those same structures millions or even billions of years from now. In short, knowing where we’ve been lets us predict where we are headed!

Further Reading: arXiv

Posted on by Matt Williams

86 Stars Just got Official Names from the IAU

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

What springs to mind when we think of the most commonly-known stars in the night sky? Chances are, it would be stars like Sirius, Vega, Deneb, Rigel, Betelgeuse, Polaris, and Arcturus – all of which derive their names from Arabic, Greek or Latin origins. Much like the constellations, these names have been passed down from one astronomical tradition to another and were eventually adopted by the International Astronomical Union (IAU).

But what about the astronomical traditions of Earth’s many, many other cultures? Don’t the names they applied to heavens also deserve mention? According to the IAU, they do indeed! After a recent meeting by the Working Group on Star Names (WGSN), the IAU formally adopted 86 new names for stars drawn largely from the Australian Aboriginal, Chinese, Coptic, Hindu, Mayan, Polynesian, and South African peoples.

The WGSN is an international group of astronomers tasked with cataloging and standardizing the star names used by the international astronomical community. This job entails establishing IAU guidelines for the proposals and adoption of names, searching through international historical and literary sources for star names, adopting names of unique historical and cultural value, and maintaining and disseminating the official IAU star catalog.

Star map painting by Senior Wardaman Elder Bill Yidumduma Harney, featuring the Milky Way, the Moon, and ancestor spirits. Credit: IAU

Last year, the WGSN approved the names for 227 stars. With these latest additions, the catalog now contains the names of 313 stars. Unlike standard star catalogs containing millions or billions of stars designated using strings of letters and numbers, the IAU star catalog consists of bright stars with proper names derived from historical and cultural sources. As Eric Mamajek, chair and organizer of the WGSN, indicated in an IAU press release:

“The IAU Working Group on Star Names is researching traditional star names from cultures around the world and adopting unique names and spellings to avoid confusion in astronomical catalogues and star atlases. These names help ensure that intangible astronomical heritage from skywatchers around the world, and across the centuries, are preserved for use in an era of exoplanetary systems.”

A total of eleven Chinese star names were incorporated into the catalog, three of which are derived from the “lunar mansions” of traditional Chinese astronomy. This refers to vertical strips of the sky that act as markers for the progress of the Moon across the sky in the course of a year. In this sense, they provide a basis for the lunar calendar in the same way that the zodiac worked for Western calendars.

Two names were derived from the ancient Hindu lunar mansions as well. These stars are Revati and Bharani, which designate Zeta Piscium and 41 Arietis, respectively. In addition to being a lunar mansion, Revati was also the daughter of King Kakudmi in Hindu mythology and the consort of the God Balarama – the elder brother of Krishna. On the other hand, Bharani is the name for the second lunar mansion in Hindu astronomy and is ruled by Shurka (Venus).

Position of the Hindu Nakshatra Mandala, the “lunar mansions” in Hindu mythology. Credit: Wikipedia Commons/ Kishorekumar 62

Beyond the astronomical traditions of India and China, there are also two names adopted from the Khoikhoi people of South Africa and the people of Tahiti – Xamidimura and Pipirima. These names were approved for Mu¹ and Mu² Scorpii, the stars that make up a binary system located in the constellation of Scorpius. Xamidimura is derived from the Khoikhoi name for the star xami di mura – literally “eyes of the lion.”

Pipirima refers to the inseparable twins from Tahitian mythology, a boy and a girl who ran away from their parents and became stars in the night sky. Then you have the Yucatec Mayan name Chamukuy, a small bird that now designates the star Theta-2 Tauri, which is located in the Hyades star cluster in Taurus.

Four Aboriginal Australian star names were also added to the catalog, including the Wardaman names Larawag, Ginan, and Wurren and the Boorong name Unurgunite. These names now designate Epsilon Scorpii, Epsilon Crucis, Zeta Pheonicis, and Sigma Canis Majoris, respectively. Given that Aboriginal Australians have traditions that go back as far as 65,000 years, these names are some of the oldest in existence.

The brightest star to receive a new name was Alsephina, which was given to the star previously designated as Delta Velorum. The name stems from the Arabic name al-safinah (“the ship”), which refers to the ancient Greek constellation Argo Navis (the ship of the Argonauts). This name goes back to the 10th-century Arabic translation of the Almagest, which was compiled by Ptolemy in the 2nd century CE.

Artist’s concept of exoplanets orbiting a red dwarf star. Credit: NASA/JPL-Caltech

The new catalog also includes Barnard’s Star, a name that has been in common usage for about a century but was never an official designation. This red dwarf star, which is less than six light-years from Earth, is named after the astronomer who discovered it – Edward Emerson Barnard – in 1916. It now joins Alsafi (Sigma Draconis), Achird (Eta Cassiopeiae), and Tabit (Pi-3 Orionis) as being one of four nearby stars whose proper names were approved in 2017.

One of the hallmarks of modern astronomy is how naming conventions are moving away from traditional Western and Classical sources and broadening to become more worldly. In addition to being a more inclusive, multicultural approach, it reflects the spirit of modern astronomical research and space exploration, which is characterized by international cooperation.

Someday, assuming our progeny ever go forth and begin to colonize distant star systems, we can expect that the stars and planets they come to know will have names that reflect the diverse astronomical traditions of Earth’s many cultures.

Further Reading: IAU

Posted on by Matt Williams

New Map Shows the Motion of all the Galaxies in Our Supercluster

A mosaic of telescopic images showing the galaxies of the Virgo Supercluster. It's part of the cosmic web in which a galaxy can exist during part of its evolution. Credit: NASA/Rogelio Bernal Andreo
A mosaic of telescopic images showing the galaxies of the Virgo Supercluster. It's part of the cosmic web in which a galaxy can exist during part of its evolution. Credit: NASA/Rogelio Bernal Andreo

For almost a century, astronomers have understood that the Universe is in a state of expansion. This is a consequence of General Relativity, and the rate at which it is expanding is known as the Hubble Constant – named after the man who first noticed the phenomena. However, astronomers have also learned that withing the large-scale structures of the Universe, galaxies and clusters have also been moving closer and relative to one other.

For decades, astronomers have sought to track how these movements have taken place over the course of cosmic history. And thanks to the efforts of international team of astronomers, the most detailed map to date of the orbits of galaxies that lie within the Virgo Supercluster has been created. This map encompasses the past motions of almost 1,400 galaxies within 100 million light years of space, showing how our cosmic neighborhood has changed.

The study which details their research recently appeared in The Astrophysical Journal under the title “Action Dynamics of the Local Supercluster“. Led by Edward J. Shaya of the University of Maryland, the team included members from the UH Institute of Astronomy, the Racah Institute of Physics in Jerusalem, and the Institute for Research of the Fundamental Laws of the Universe (IRFU) in Paris.

Orbits of galaxies in the Local Supercluster. Credit: Brent Tully.

For the sake of their study, the team used data from the CosmicFlows surveys, a series of three studies that calculated the distance and speed of neighboring galaxies between 2011 and 2016. Several members of the study team were involved in these surveys, which they then paired with other distance and gravity field estimates to construct a massive flow study of the Virgo Supercluster.

From this, they were able to create computer models that charted the motions of almost 1,400 galaxies within 100 million light years, and over the course of 13 billion years (just 800 million years after the Big Bang). As Brent Tully, an astronomer with the UH Institute of Astronomy and a co-author on the study, explained in a UH press release:

“For the first time, we are not only visualizing the detailed structure of our Local Supercluster of galaxies but we are seeing how the structure developed over the history of the universe. An analogy is the study of the current geography of the Earth from the movement of plate tectonics.”

What they found was that their models fit the present day velocity flow well, meaning that the structures and speeds they observed in their models fit with what has been observed from galaxies in the present day. They also determined that within the area of space they mapped, the main gravitational attractor is the Virgo Cluster – which is located about 50 million light years away and contains between 1300 and 2000 galaxies.

Moreover, their study indicated that more than a thousand galaxies have fallen into the Virgo Cluster in the past 13 billion years, while all galaxies within 40 million light-years of the cluster will eventually be captured. At present, the Milky Way lies just outside this capture zone, but both the Milky Way and the Andromeda Galaxy are destined to merge in the next 4 billion years.

Once they do, the fate of the resulting massive galaxy will be similar to the rest of the galaxies in the area of study. This was another takeaway from the study, where the team determined that these merger events are merely part of a larger pattern. Basically, within the region of space they observed, there are two overarching flow patterns. Within one hemisphere of this region, all galaxies – including the Milky Way – are streaming towards a single flat sheet.

At the same time, every galaxy over the entire volume of space is moving towards gravitational attractors that are located far beyond the area of study. They determined that these outside forces are none other than the Centaurus Supercluster – a cluster of hundreds of galaxies, located approximately 170 million light years away in the Centaurus constellation – and the Great Attractor.

The Great Attractor is located 150 million light years away, and is a mysterious region that cannot be seen because of its location (on the opposite side of the Milky Way). However, for decades, scientists have known that our galaxy and other nearby galaxies are moving towards it. The region is also the core of the Laniakea Supercluster, a region that spans more than 500 million light-years and contains about 100,000 large galaxies.

In short, while the Universe is in a state of expansion, the dynamics of galaxies and galaxy clusters indicate that they still gravitate into tighter structures.  Within our cosmic neighborhood, the main attractor is clearly the Virgo Cluster, which is affecting all galaxies within a 40 million light-year radius. Beyond this, it is the Centaurus Supercluster and the Great Attractor (as part of the larger Laniakea Supercluster) that is tugging at our strings.

By charting this process of attraction that has been taking place over the past 13 billion years, astronomers and cosmologists are able to see just how our Universe has evolved over the course of the majority of its history. With time, and improved instruments that are capable of looking even deeper into the cosmos (such as the James Webb Space Telescope) we are expected to be able to probe even further back towards the beginning of the cosmos.

Charting how our Universe has changed over time not only confirms our cosmological models and verifies predominant theories about how matter behaves on the largest of scales (i.e. General Relativity). It also allows scientists to predict the future of our Universe with a fair degree of certainty, modelling how galaxies and superclusters will eventually come together to form even larger structures.

The team also created a video showing the results of their study, as well as an interactive model that let’s users examine the frame of reference from multiple vantage points. Be sure to check out the video below, and head on over to the UH page to access their interactive model.

Further Reading: University of Hawaii, The Astrophysical Journal