Posted on by Matt Williams

Thanks to a Gravitational Lens, Astronomers Can See an Individual Star 9 Billion Light-Years Away

Hubble image of a luminous red galaxy (LRG) gravitationally distorting the light from a much more distant blue galaxy, a technique known as gravitational lensing. The shape of the galaxy doing the lensing created an almost circular image. An oblong galaxy would create more of an Einstein Ring effect. Credit: ESA/Hubble & NASA
Hubble image of a luminous red galaxy (LRG) gravitationally distorting the light from a much more distant blue galaxy, a technique known as gravitational lensing. The shape of the galaxy doing the lensing created an almost circular image. An oblong galaxy would create more of an Einstein Ring effect. Credit: ESA/Hubble & NASA

When looking to study the most distant objects in the Universe, astronomers often rely on a technique known as Gravitational Lensing. Based on the principles of Einstein’s Theory of General Relativity, this technique involves relying on a large distribution of matter (such as a galaxy cluster or star) to magnify the light coming from a distant object, thereby making it appear brighter and larger.

This technique has allowed for the study of individual stars in distant galaxies. In a recent study, an international team of astronomers used a galaxy cluster to study the farthest individual star ever seen in the Universe. Although it normally to faint to observe, the presence of a foreground galaxy cluster allowed the team to study the star in order to test a theory about dark matter.

The study which describes their research recently appeared in the scientific journal Nature Astronomy under the title “Extreme magnification of an individual star at redshift 1.5 by a galaxy-cluster lens“. The study was led by Patrick L. Kelly, an assistant professor the University of Minnesota, and included members from the Las Cumbres Observatory, the National Optical Astronomical Observatory, the Harvard-Smithsonian Center for Astrophysics (CfA), the Ecole Polytechnique Federale de Lausanne (EPFL), and multiple universities and research institutions.

For the sake of their study, Prof. Kelly and his associates used the galaxy cluster known as MACS J1149+2223 as their lens. Located about 5 billion light-years from Earth, this galaxy cluster sits between the Solar System and the galaxy that contains Icarus. By combining Hubble’s resolution and sensitivity with the strength of this gravitational lens, the team was able to see and study Icarus, a blue giant.

Icarus, named after the Greek mythological figure who flew too close to the Sun, has had a rather interesting history. At a distance of roughly 9 billion light-years from Earth, the star appears to us as it did when the Universe was just 4.4 billion years old. In April of 2016, the star temporarily brightened to 2,000 times its normal luminosity thanks to the gravitational amplification of a star in MACS J1149+2223.

As Prof. Kelly explained in a recent UCLA press release, this temporarily allowed Icarus to become visible for the first time to astronomers:

“You can see individual galaxies out there, but this star is at least 100 times farther away than the next individual star we can study, except for supernova explosions.”

Kelly and a team of astronomers had been using Hubble and MACS J1149+2223 to magnify and monitor a supernova in the distant spiral galaxy at the time when they spotted the new point of light not far away. Given the position of the new source, they determined that it should be much more highly magnified than the supernova. What’s more, previous studies of this galaxy had not shown the light source, indicating that it was being lensed.

Icarus, the farthest individual star ever seen, shown at left. Panels at right show the view in 2011, without Icarus visible, compared with the star’s brightening in 2016. Credit: NASA, ESA and Patrick Kelly/University of Minnesota

As Tommaso Treu, a professor of physics and astronomy in the UCLA College and a co-author of the study, indicated:

“The star is so compact that it acts as a pinhole and provides a very sharp beam of light. The beam shines through the foreground cluster of galaxies, acting as a cosmic magnifying glass… Finding more such events is very important to make progress in our understanding of the fundamental composition of the universe.

In this case, the star’s light provided a unique opportunity to test a theory about the invisible mass (aka. “dark matter”) that permeates the Universe. Basically, the team used the pinpoint light source provided by the background star to probe the intervening galaxy cluster and see if it contained huge numbers of primordial black holes, which are considered to be a potential candidate for dark matter.

These black holes are believed to have formed during the birth of the Universe and have masses tens of times larger than the Sun. However, the results of this test showed that light fluctuations from the background star, which had been monitored by Hubble for thirteen years, disfavor this theory. If dark matter were indeed made up of tiny black holes, the light coming from Icarus would have looked much different.

Since it was discovered in 2016 using the gravitational lensing method, Icarus has provided a new way for astronomers to observe and study individual stars in distant galaxies. In so doing, astronomers are able to get a rare and detailed look at individual stars in the early Universe and see how they (and not just galaxies and clusters) evolved over time.

When the James Webb Space Telescope (JWST) is deployed in 2020, astronomers expect to get an even better look and learn so much more about this mysterious period in cosmic history.

Further Reading: UCLA

Posted on by Matt Williams

The Universe’s Missing Matter. Found!

A simulation of the cosmic web, diffuse tendrils of gas that connect galaxies across the universe. Credit: Illustris Collaboration

In the 1960s, astronomers began to notice that the Universe appeared to be missing some mass. Between ongoing observations of the cosmos and the the Theory of General Relativity, they determined that a great deal of the mass in the Universe had to be invisible. But even after the inclusion of this “dark matter”, astronomers could still only account for about two-thirds of all the visible (aka. baryonic) matter.

This gave rise to what astrophysicists dubbed the “missing baryon problem”. But at long last, scientists have found what may very well be the last missing normal matter in the Universe. According to a recent study by a team of international scientists, this missing matter consists of filaments of highly-ionized oxygen gas that lies in the space between galaxies.

The study, titled “Observations of the missing baryons in the warm–hot intergalactic medium“, recently appeared in the scientific journal Nature. The study was led by Fabrizio Nicastro, a researcher from the Istituto Nazionale di Astrofisica (INAF) in Rome, and included members from the SRON Netherlands Institute for Space Research, the Harvard–Smithsonian Center for Astrophysics (CfA), the Instituto de Astronomia Universidad Nacional Autonoma de Mexico, the Instituto Nacional de Astrofísica, Óptica y Electrónica, the Instituto de Astrofísica de La Plata (IALP-UNLP) and multiple universities.

Artist’s impression of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun. Credit: ESO/M. Kornmesser

For the sake of their study, the team consulted data from a series of instruments to examine the space near a quasar called 1ES 1553. Quasars are extremely massive galaxies with Active Galactic Nuclei (AGN) that emit tremendous amounts of energy. This energy is the result of gas and dust being accreted onto supermassive black holes (SMBHs) at the center of their galaxies, which results in the black holes emitting radiation and jets of superheated particles.

In the past, researchers believed that of the normal matter in the Universe, roughly 10% was bound up in galaxies while 60% existed in diffuse clouds of gas that fill the vast spaces between galaxies. However, this still left 30% of normal matter unaccounted for. This study, which was the culmination of a 20-year search, sought to determine if the last baryons could also be found in intergalactic space.

This theory was suggested by Charles Danforth, a research associate at CU Boulder and a co-author on this study, in a 2012 paper that appeared in The Astrophysical Journal – titled “The Baryon Census in a Multiphase Intergalactic Medium: 30% of the Baryons May Still be Missing“. In it, Danforth suggested that the missing baryons were likely to be found in the warm-hot intergalactic medium (WHIM), a web-like pattern in space that exists between galaxies.

As Michael Shull – a professor of Astrophysical and Planetary Sciences at the University of Colorado Boulder and one of the co-authors on the study – indicated, this wild terrain seemed like the perfect place to look.“This is where nature has become very perverse,” he said. “This intergalactic medium contains filaments of gas at temperatures from a few thousand degrees to a few million degrees.”

Close-up of star near a supermassive black hole (artist’s impression). Credit: ESA/Hubble, ESO, M. Kornmesser

To test this theory, the team used data from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope to examine the WHIM near the quasar 1ES 1553. They then used the European Space Agency’s (ESA) X-ray Multi-Mirror Mission (XMM-Newton) to look closer for signs of the baryons, which appeared in the form of highly-ionized jets of oxygen gas heated to temperatures of about 1 million °C (1.8 million °F).

First, the researchers used the COS on the Hubble Space Telescope to get an idea of where they might find the missing baryons in the WHIM. Next, they homed in on those baryons using the XMM-Newton satellite. At the densities they recorded, the team concluded that when extrapolated to the entire Universe, this super-ionized oxygen gas could account for the last 30% of ordinary matter.

As Prof. Shull indicated, these results not only solve the mystery of the missing baryons but could also shed light on how the Universe began. “This is one of the key pillars of testing the Big Bang theory: figuring out the baryon census of hydrogen and helium and everything else in the periodic table,” he said.

Looking ahead, Shull indicated that the researchers hope to confirm their findings by studying more bright quasars. Shull and Danforth will also explore how the oxygen gas got to these regions of intergalactic space, though they suspect that it was blown there over the course of billions of years from galaxies and quasars. In the meantime, however, how the “missing matter” became part of the WHIM remains an open question. As Danforth asked:

“How does it get from the stars and the galaxies all the way out here into intergalactic space?. There’s some sort of ecology going on between the two regions, and the details of that are poorly understood.”

Assuming these results are correct, scientists can now move forward with models of cosmology where all the necessary “normal matter” is accounted for, which will put us a step closer to understanding how the Universe formed and evolved. Now if we could just find that elusive dark matter and dark energy, we’d have a complete picture of the Universe! Ah well, one mystery at a time…

Further Reading: UCB, Nature

Posted on by David Dickinson

Planetpalooza: All Bright Planets Visible in the July Dusk Sky

Moon and Venus
Venus and the waxing crescent Moon above the Grand Palais in Paris, France from May 17th. Image credit: Gwenael Blanck
Moon and Venus
Venus and the waxing crescent Moon above the Grand Palais in Paris, France from May 17th. Image credit: Gwenael Blanck

Missed the planets in the dusk sky in early 2018? This summer’s astronomical blockbuster sees the return of all the classical naked eye planets in the dusk sky, in a big way.

The Sky Scene in July

This coming July 2018 features a rare look at the solar system in profile: you can see Mercury and Venus low in the dusk looking westward immediately after sunset, with Jupiter high to the south, Saturn rising in the east, and Mars rising just behind. This isn’t a true grouping or grand conjunction, as the planets span a 170 degree swath of the ecliptic from Mercury to Mars (too bad they’re not in orbital order!) but a product of our Earthly vantage point looking out over the swath of inner solar system in the evening sky.

Can you manage a “planetary marathon” and collect all five this coming Fourth of July weekend? Here’s a quick rundown of all the planetary action from west to east:

Mercury
An amazing view – Mercury through the telescope from May 5th. Image credit and copyright: Roger Hutchinson.

Mercury’s July apparition – fleeting Mercury is always the toughest of the planets to catch, low to the west. -0.3 magnitude Mercury actually forms a straight line with the bright +1st/2nd magnitude stars Castor and Pollux in Gemini the Twins later this week on the evening of June 27th. Mercury reaches greatest elongation 26 degrees east of the Sun on July 12th, presenting a half illuminated, 8” disk. The angle of the evening ecliptic is canted southward in July, meaning that the position of the planets in the evening sky also favors southern viewers. July also presents another interesting mercurial challenge, as Mercury passes in front of the Beehive Open cluster (Messier 44) in the heart of the constellation Cancer on the night of July 3rd/4th.

planets
The span of the planets through late-July at dusk. Credit: Stellarium.

Venus this summer – higher up at dusk, brilliant Venus rules the evening sky, shining at magnitude -4. Venus is so bright that you can easily pick it up this month before sunset… if you know exactly where to look for it. Venus reaches greatest elongation 46 degrees east of the Sun on August 17th, presenting a featureless half-illuminated disk 25” in diameter near a point known as dichotomy. Venus also flirts with the bright star Regulus (Alpha Leonis) in July, passing a degrees from the star on July 10th. Fun fact: Venus can actually occult (pass in front of) Regulus and last did so on July 7th, 1959 and will do so next on October 1st, 2044.

Jupiter
Jupiter, with the shadow of Europa in transit from June 6th. Image credit and copyright: Ralph Smyth.

Jupiter Rules – The King of the Planets, Jupiter rules the sky after darkness falls, crossing the astronomical constellation Libra the Scales. Fresh off of its May 9th opposition, Jupiter still shines at a respectable magnitude -2 in July, with a disk 36” across. Jupiter heads towards quadrature 90 degrees east of the Sun on August 6th, meaning the planet and its retinue of four Galilean moons cast their respective shadows off to one side. In fact, we also see a series of fine double shadow transits across the Jovian cloud tops involving Io and Europa starting on July 29th.

saturn
The glorious planet Saturn. Image credit and copyright: Paul Stewart

…and Saturn makes five: Stately Saturn never fails to impress. Also just past its June 27th opposition, the rings are still tipped open narrowing down only slightly from last year’s widest angle of 27 degrees, assuring an amazing view. Shining at magnitude 0 and subtending 42” (including rings) in July, Saturn traverses the star-rich fields of the astronomical constellation Sagittarius the Archer this summer. Look at Saturn, and you’re glimpsing the edge of the known solar system right up until William Herschel discovered Uranus on the night of March 13th, 1781.

The origins of a dust storm: Mars from late May. Image credit and copyright: Efrain Morales.

Enter Mars: We saved the best for last. The Red Planet races towards a fine opposition on July 27th. This is the best approach of Mars since the historic 2003 opposition, and very nearly as favorable: Mars shines at magnitude -2.8 at the end of July, and presents a 24.3” disk. More to come as Mars approaches!

And as with many an opposition, dust storm season has engulfed Mars. Be vigilant, as the ‘Red’ Planet often takes on a sickly yellowish tint during a large dust storm, and this cast will often be apparent even to the naked eye. NASA’s aging Opportunity rover has fallen silent due to the lack of sunlight and solar power, and it’s to be seen if the rover can ride out the storm.

The path of the Moon – The Moon makes a good guidepost as it visits the planets in July. The first eclipse season of 2018 also begins in July, with a partial solar eclipse for Tasmania, SE Australia and the extreme southernmost tip of New Zealand on July 13th and wrapping up with a fine total lunar eclipse favoring Africa, Europe, Asia and Australia on July 27th. Note that this eclipse is only 14 hours after Mars passes opposition… we expect to see plenty of pictures of a ruddy Mars near a Blood Moon eclipse.

The Moon also makes a handy guide to catch each of the planets in the daytime sky… though you’ll need binoculars or a telescope to nab Mercury or Saturn (also, be sure the Sun is physically blocked out of view while hunting for Mercury in the daytime sky!) Here are the respective passes of the Moon near each planet in July:

Planet Date Time Moon Phase/illumination Distance
Mercury July 14th 23UT/7PM EDT Waxing crescent/5% 2.1 degrees
Venus July 16th 4UT/00AM EDT Waxing crescent/14% 1.5 degrees
Jupiter July 21st 2UT/10PM EDT Waxing gibbous/63% 4.2 degrees
Saturn July 25th 5UT/1AM EDT Waxing gibbous/94% 2 degrees
Mars July 27th 16UT/12 EDT Full Moon/100% 8 degrees

Unfortunately, the telescopic planets Uranus and Neptune are left out of the July evening view; Uranus is currently crossing the constellation Aries and Neptune resides in Aquarius, respectively. Pluto is, however, currently in the direction of Sagittarius, and you can also wave to NASA’s New Horizons spacecraft en route to its New Year’s Day 2019 KBO destination Ultima Thule (nee 2014 MU69) near the waxing gibbous Moon on the night of July 26th.

The Moon, Pluto and New Horizons on the evening of July 26th. Credit: Starry Night

And finally, another solar system destination in Ophiuchus the Serpent Bearer beckons telescope owners in July: asteroid 4 Vesta.

All of this is more than enough planetary action to keep planetary observers and imagers up late on forthcoming July evenings.

Posted on by Matt Williams

The Martian Dust Storm Has Covered the Entire Planet

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

Martian dust storms, which occur during the summer season in the planet’s southern hemisphere, can get pretty intense. Over the course of the past few weeks, a global dust storm has engulfed Mars and forced the Opportunity rover to suspend operations. Given that this storm is much like the one that took place back in 2007, which also raged for weeks, there have been concerns over how this development could affect rover operations.

Meanwhile the Curiosity rover managed to snap pictures of the thickening haze caused by the storm. Though Curiosity is on the other side of the planet from where Opportunity is currently located, atmospheric dust has been gradually increasing over it. But unlike Opportunity, which runs on solar power, Curiosity will remain unaffected by the global storm thanks to its nuclear-powered battery, and is therefore in a good position to study it.

As already noted, Martian storms occur during summer in the southern hemisphere, when sunlight warms dust particles and lifts them higher into the atmosphere, creating more wind. The resulting wind kicks up yet more dust, creating a feedback loop that NASA scientists are still trying to understand. Since the southern polar region is pointed towards the Sun in the summer, carbon dioxide frozen in the polar cap evaporates.

Global map of Mars produced by the Mars Color Imager (MARCI) camera on NASA’s Mars Reconnaissance Orbiter (MRO), which shows a growing dust storm as of June 6th, 2018. The blue dot indicates the approximate location of Opportunity. Credit: NASA/JPL-Caltech/MSSS

This has the effect of thickening the atmosphere and increasing the surface pressure, which enhances the process by helping suspend dust particles in the air. In some cases, the dust clouds can reach up to 60 km (40 mi) or more in elevation. Though they are common and can begin suddenly, Martian dust storms typically stay contained to a local area and last only about a weeks.

By contrast, the current storm has lasted for several weeks and is currently covering an area that would span North America and Russia combined. While smaller than the storm that took place back in 2007, this storm has intensified to the point where it created a perpetual state of night over the rover’s location in Perseverance Valley and led to a level of atmospheric opacity that is much worse than the 2007 storm.

When dust storms occur, scientists measure them based on their opacity level (tau) to determine how much sunlight they will prevent from reaching the surface. Whereas the 2007 storm had a tau level of about 5.5, this most recent storm reached an estimated tau of 10.8 earlier this month over the Perseverance Valley – where Opportunity is located.

The intensity of the storm also led Bruce Canton, deputy principal investigator of the Mars Color Imager (MARCI) camera onboard NASA’s Mars Reconnaissance Orbiter (MRO), to declare that the storm has officially become a “planet-encircling” (or “global”) dust event. Above the Gale Crater, where Curiosity is located, the tau reading is now above 8.0 – the highest ever recorded by the mission.

In June 2018 NASA’s Curiosity Rover used its Mast Camera, or Mastcam, to snap photos of the intensifying haziness the surface of Mars, caused by a massive dust storm. The photos span about a couple of weeks, starting with a shot of the area before the storm appeared. Credits: NASA

While the storm has some worried about the fate of Opportunity, which is Mars’ oldest active rover (having remained in operation for over 14 years), it is also an chance to address one of the greatest questions scientists have about Mars. For example, why do some storms span the entire planet and last for months while others are confined to small areas and and last only a week?

While scientists don’t currently know what the answer is, Curiosity and a fleet of six scientific spacecraft in orbit of Mars are hoping this most recent storm will help them find out. These spacecraft include NASA’s Mars Reconnaissance Orbiter (MRO), 2001 Mars Odyssey and Mars Atmosphere and Volatile EvolutioN (MAVEN) missions, India’s Mars Orbiter Mission (MOM) and the ESA’s Mars Express and ExoMars Trace Gas Orbiter.

The animation (shown above) consists of a series of daily photos captures by Curiosity’s Mast Camera (Mastcam), which show the sky getting hazier over time. While taking these pictures, Curiosity was facing the crater rim, about 30 km (18.6) away from where it stands inside the crater. This sun-obstructing wall of haze is about six to eight times thicker than normal for this time of season.

Nevertheless, Curiosity’s engineers – which are based at NASA’s Jet Propulsion Laboratory in Pasadena, California – have studied how the growing dust storm could affect the rover’s instruments and concluded that it poses little risk. Ironically enough, the largest impact will be on the rover’s cameras, which require extra exposure time due to the low lighting conditions.

Two images from the Mast Camera (Mastcam) on NASA’s Curiosity rover depicting the change in the color of light illuminating the Martian surface since a dust storm engulfed Gale Crater. Credits: NASA/JPL-Caltech/MSSS

As Jim Watzin, the director of NASA’s Mars Exploration Program at the agency’s headquarters in Washington, explained in a NASA press release earlier this month:

“This is the ideal storm for Mars science. We have a historic number of spacecraft operating at the Red Planet. Each offers a unique look at how dust storms form and behave – knowledge that will be essential for future robotic and human missions.”

However, all dust events, regardless of size, help to shape the Martian surface. As such, studying their physics is critical to understanding the Martian climate, both past and present. As Rich Zurek, the chief scientist for the Mars Program Office at NASA’s Jet Propulsion Laboratory, indicated:

“Each observation of these large storms brings us closer to being able to model these events – and maybe, someday, being able to forecast them. That would be like forecasting El Niño events on Earth, or the severity of upcoming hurricane seasons.”

The ability to understand the causes and dynamics of Martian dust storms would not only lead to a better understand of how weather works on other planets, it would also be of immense importance if and and when humans begin traveling to the Red Planet on a regular basis. For instance, if SpaceX really does intend to bring tourists to Mars in the future, said tourists will want to avoid booking during “storm season”.

And if humans should choose to someday make Mars their home, they will need to know when planet-spanning dust storms are coming, especially since their habitats will likely be relying on wind and solar power. In the meantime, NASA and other space agencies will continue to monitor this storm and the Opportunity rover is expected to come through (fingers crossed!) unscathed!

Further Reading: NASA

Posted on by Susie Murph

Astronomy Cast Ep. 497: Update on Globular Clusters

Is it globular clusters or is it globeular clusters? It doesn’t matter, they’re awesome and we’re here to update you on them.

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

Visit the Astronomy Cast Page to subscribe to the audio podcast!

If you would like to support Astronomy Cast, please visit our page at Patreon here – https://www.patreon.com/astronomycast. We greatly appreciate your support!

If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!

Posted on by Matt Williams

The Tools Humanity Will Need for Living in the Year 1 Trillion

A new study considers what life could be like for civilizations 1 trillion years from now, when every star in the Universe will expand beyond the cosmic horizon. Credit: ESO/S. Brunier

Since the 1990s, astrophysicists have known that for the past few billion years, the Universe has been experiencing an accelerated rate of expansion. This gave rise to the theory that the Universe is permeated by a mysterious invisible energy known as “dark energy”, which acts against gravity and is pushing the cosmos apart. In time, this energy will become the dominant force in the Universe, causing all stars and galaxies to spread beyond the cosmic horizon.

At this point, all stars and galaxies in the Universe will no longer be visible or accessible from any other. The question remains, what will intelligent civilizations (such as our own) do for resources and energy at this point? This question was addressed in a recent paper by Dr. Abraham Loeb – the  Frank B. Baird, Jr., Professor of Science at Harvard University and the Chair of the Harvard Astronomy Department.

The paper, “Securing Fuel for our Frigid Cosmic Future“, recently appeared online. As he indicates in his study, when the Universe is ten times its current age (roughly 138 billion years old), all stars outside the Local Group of galaxies will no be accessible to us since they will be receding away faster than the speed of light. For this reason, he recommends that humanity follow the lesson from Aesop’s fable, “The Ants and the Grasshopper”.

This classic tale tells the story of ants who spent the summer collecting food for the winter while the grasshopper chose to enjoy himself. While different versions of the story exist that offer different takes on the importance of hard work, charity, and compassion, the lesson is simple: always be prepared. In this respect, Loeb recommends that advanced species migrate to rich clusters of galaxies.

These clusters represent the largest reservoirs of matter bound by gravity and would therefore be better able to resist the accelerated expansion of the Universe. As Dr. Loeb told Universe Today via email:

“In my essay I point out that mother Nature was kind to us as it spontaneously gave birth to the same massive reservoir of fuel that we would have aspired to collect by artificial means. Primordial density perturbations from the early universe led to the gravitational collapse of regions as large as tens of millions of light years, assembling all the matter in them into clusters of galaxies – each containing the equivalent of a thousand Milky Way galaxies.”

Dr. Loeb also indicated where humanity (or other advanced civilizations) should consider relocating to when the expansion of the Universe causes the stars of the Local Group to expand beyond the cosmic horizon. Within 50 million light years, he indicates, likes the Virgo Cluster, which contains about a thousands times more matter than the Milky Way Galaxy. The second closest is the Coma Cluster, a collection of over 1000 galaxies located about 336 million light years away.

Diagram showing the Virgo Supercluster. Credit: Wikipedia Commons/Andrew Z. Colvin

In addition to offering a solution to the accelerating expansion of the Universe, Dr. Loeb’s study also presents some interesting possibilities when it comes to the search for extra-terrestrial intelligence (SETI). If, in fact, there are already advanced civilizations migrating to prepare for the inevitable expansion of the Universe, they may be detectable by various means. As Dr. Loeb explained:

“If traveling civilizations transmit powerful signals then we might be able to see evidence for their migration towards clusters of galaxies. Moreover, we would expected a larger concentration of advanced civilization in clusters than would be expected simply by counting the number of galaxies there. Those that settle there could establish more prosperous communities, in analogy to civilizations near rivers or lakes on Earth.”

This paper is similar to a study Dr. Loeb conducted back in 2011, which appeared in the Journal of Cosmology and Astroparticle Physics under the title “Cosmology with Hypervelocity Stars“. At the time, Dr. Loeb was addressing what would happen in the distant future when all extragalactic light sources will cease to be visible or accessible due to the accelerating expansion of the Universe.

This study was a follow-up to a 2001 paper in which Dr. Loeb addressed what would become of the Universe in billions of years – which appeared in the journal Physical Review Letters under the title “The Long–Term Future of Extragalactic Astronomy“. Shortly thereafter, Dr. Loeb and Freeman Dyson himself began to correspond about what could be done to address this problem.

An artist’s conception of a hypervelocity star that has escaped the Milky Way. Credit: NASA

Their correspondence was the subject of an article by Nathan Sanders (a writer for Astrobites) who recounted what Dr. Loeb and Dr. Dyson had to say on the matter. As Dr. Loeb recalls:

“A decade ago I wrote a few papers on the long-term future of the Universe, trillions of years from now. Since the cosmic expansion is accelerating, I showed that once the universe will age by a factor of ten (about a hundred billion years from now), all matter outside our Local Group of galaxies (which includes the Milky Way and the Andromeda galaxy, along with their satellites) will be receding away from us faster than light. After one of my papers was posted in 2011, Freeman Dyson wrote to me and suggested to a vast “cosmic engineering project” in which we will concentrate matter from a large-scale region around us to a small enough volume such that it will stay bound by its own gravity and not expand with the rest of the Universe.”

At the time, Dr. Loeb indicated that data gathered by the Sloan Digital Sky Survey (SDSS) indicated that attempts at “super-engineering” did not appear to be taking place. This was based on the fact that the galaxy clusters observed by the SDSS were not overdense, nor did they exhibit particularly high velocities (as would be expected). To this, Dr. Dyson wrote: “That is disappointing. On the other hand, if our colleagues have been too lazy to do the job, we have plenty of time to start doing it ourselves.”

A similar idea was presented in a recent paper by Dr. Dan Hooper, an astrophysicist from the Fermi National Accelerator Laboratory (FNAL) and the University of Chicago. In his study, Dr. Hooper suggested that advanced species could survive all stars in the Local Group expanding beyond the cosmic horizon (100 billion years from now), by harvesting stars across tens of millions of light years.

Artist impression of the 14 galaxies detected by ALMA as they appear in the very early, very distant universe. These galaxies are in the process of merging and will eventually form the core of a massive galaxy cluster. Credit: NRAO/AUI/NSF; S. Dagnello

This harvesting would consist of building unconventional Dyson Spheres that would use the energy they collected from stars to propel them towards the center of the species’ civilization. However, only stars that range in mass of 0.2 to 1 Solar Masses would be usable, as high-mass stars would evolve beyond their main sequence before reaching the destination and low-mass stars would not generate enough energy for acceleration to make it in time.

But as Dr. Loeb indicates, there are additional limitations to this approach, which makes migrating more attractive than harvesting.

“First, we do not know of any technology that enables moving stars around, and moreover Sun-like stars only shine for about ten billion years (of order the current age of the Universe) and cannot serve as nuclear furnaces that would keep us warm into the very distant future. Therefore, an advanced civilization does not need to embark on a giant construction project as suggested by Dyson and Hooper, but only needs to propel itself towards the nearest galaxy cluster and take advantage of the cluster resources as fuel for its future prosperity.”

While this may seem like a truly far-off concern, it does raise some interesting questions about the long-term evolution of the Universe and how intelligent civilizations may be forced to adapt. In the meantime, if it offers some additional possibilities for searching for extra-terrestrial intelligences (ETIs), then so much the better.

And as Dr. Dyson said, if there are currently no ETIs preparing for the coming “cosmic winter” with cosmic engineering projects, perhaps it is something humanity can plan to tackle someday!

Further Reading: arXiv, Journal of Cosmology and Astroparticle Physics, astrobites, astrobites (2)

Posted on by Matt Williams

Strange Landscapes on Mars were Created by Explosive Volcanoes

A 13-kilometer (8-mile) diameter crater being infilled by the Medusae Fossae Formation. Credit: High Resolution Stereo Camera/European Space Agency.

Scientists first observed the Medusae Fossae Formation (MFF) in the 1960s, thanks to the efforts of the Mariner spacecraft. This massive deposit of soft, sedimentary rock extends for roughly 1,000 km (621 mi) along the equator and consists of undulating hills, abrupt mesas, and curious ridges (aka. yardangs) that appear to be the result of wind erosion. What’s more, an unusual bump on top of this formation also gave rise to a UFO conspiracy theory.

Needless to say, the formation has been a source of scientific curiosity, with many geologists attempting to explain how it could have formed. According to a new study from Johns Hopkins University, the region was the result of volcanic activity that took place on the Red Planet more than 3 billion years ago. These findings could have drastic implications for scientists’ understanding of Mars’ interior and even its past potential for habitability.

The study – which recently appeared in the Journal of Geophysical Research: Planets under the title “The Density of the Medusae Fossae Formation: Implications for its Composition, Origin, and Importance in Martian History” – was conducted by Lujendra Ojha and Kevin Lewis, a Blaustein scholar and an assistant professor in the department of Earth and Planetary Science at Johns Hopkins University, respectively.

Perspective view of Medusa Fossae looking south-east. Copyright: ESA/DLR/FU Berlin (G. Neukum)

Ojha’s past work includes finding evidence that water on Mars occurs in seasonal brine flows on the surface, which he discovered in 2010 as an undergraduate student. Lewis, meanwhile, has dedicated much of his academic carreer to the in-depth study of the nature of sedimentary rock on Mars for the sake of determining what this geological record can tell us about that planet’s past climate and habitability.

As Ojha explained, the study of the Medusa Fossae Formation is central to understanding Mars geological history. Much like the Tharsus Montes region, this formation was formed at a time when the planet was still geologically active. “This is a massive deposit, not only on a Martian scale, but also in terms of the solar system, because we do not know of any other deposit that is like this,” he said.

Basically, sedimentary rock is the result of rock dust and debris accumulating on a planet’s surface and becoming hardened and layered over time. These layers serve as a geological record, indicating what types of processes where taking place on the surface at the time that the layers were deposited. When it comes to the Medusae Fossae Formation, scientists were unsure whether wind, water, ice or volcanic eruptions were responsible for the deposits.

In the past, radar measurements were made of the formation that suggested that Medusae Fosssae had an unusual composition. However, scientists were unsure whether the formation was made of highly porous rock or a mixture of rock and ice. For the sake of their study, Ojha and Lewis used gravity data from various Mars orbiters to measure the formation’s density for the first time.

An isolated hill in the Medusae Fossae Formation. The effect of wind erosion on this hill is evident by its streamlined shape. Credit: High Resolution Stereo Camera/European Space Agency

What they found was that the rock is unusually porous and about two-thirds as dense as the rest of the Martian crust. They also used radar and gravity data to show that the Formation’s density was too great to be explained by the presence of ice. From this, they concluded that the heavily-porous rock had to have been deposited by volcanic eruptions when Mars was still geologically active – ca. 3 billion years ago.

As these volcanoes exploded, casting ash and rock into the atmosphere, the material would have then fallen back to the surface, building up layers and streaming down hills. After enough time, the ash would have cemented into rock, which was slowly eroded over time by Martian winds and dust storms, leaving the Formation scientists see there today. According to Ojha, these new findings suggest that Mars’ interior is more complex than previously thought.

While scientists have known for some time that Mars has some volatiles – i.e. water, carbon dioxide and other elements that become gas with slight increases in temperature –  in its crust that allow for periodic explosive eruptions to occur on the surface, the kind of eruption needed to create the Medusa Fossae region would have been immense. This indicates that the planet may have massive amounts of volatiles in its interior. As Ojha explained:

“If you were to distribute the Medusae Fossae globally, it would make a 9.7-meter (32-foot) thick layer. Given the sheer magnitude of this deposit, it really is incredible because it implies that the magma was not only rich in volatiles and also that it had to be volatile-rich for long periods of time.”

An artist's impression of the ancient Martian ocean. When two meteors slammed into Mars 3.4 billion years ago, they triggered massive, 400 ft. tsunamis that reshaped the coastline. Image: ESO/M. Kornmesser, via N. Risinger
According to Ojha and Lewis’ study, the eruption that created the Medusa Fossae Formation would have covered Mars in a global ocean. Image: ESO/M. Kornmesser, via N. Risinger

In addition, this activity would have had a drastic impact on Mars’ past habitability. Basically, the formation of the Medusae Fossae Formation would have occurred during a pivotal point in Mars’ history. After the eruption occurred, massive amounts of carbon dioxide and (most likely) methane would have been ejected into the atmosphere, causing a significant greenhouse effect.

In addition, the authors indicated that the eruption would have ejected enough water to cover Mars in a global ocean more than 9 cm (4 inches) in thickness. This resulting greenhouse effect would have been enough to keep Mars’ surface warm to the point that the water would remain in a liquid state. At the same time, the expulsion of volcanic gases like hydrogen sulfide and sulfur dioxide would have altered the chemistry of Mars’ surface and atmosphere.

All of this would have had a drastic impact on the planet’s potential habitability. What’s more, as Kevin Lewis indicated, the new study shows that gravity surveys have the potential to interpret Mars’ geological record. “Future gravity surveys could help distinguish between ice, sediments and igneous rocks in the upper crust of the planet,” he said.

Studying Mars surface features and geological history is a lot like peeling an onion. With every layer we peel back, we get another piece of the puzzle, which together adds up to a rich and varied history. In the coming years and decades, more robotic missions will be studying the Red Planet’s surface and atmosphere in preparation for an eventual crewed mission by the 2030s.

All of these missions will allow us to learn more about Mars warmer, wetter past and whether or not may have existed there at some time (or perhaps, still does!)

Further Reading: AGU, Journal of Geophysical Research

Posted on by Matt Williams

New Model Predicts That We’re Probably the Only Advanced Civilization in the Observable Universe

Using information from Gaia's second data release, a team of scientists have made refined estimates of the Milky Way's mass. Credit: ESA/Gaia/DPAC

The Fermi Paradox remains a stumbling block when it comes to the search for extra-terrestrial intelligence (SETI). Named in honor of the famed physicist Enrico Fermi who first proposed it, this paradox addresses the apparent disparity between the expected probability that intelligent life is plentiful in the Universe, and the apparent lack of evidence of extra-terrestrial intelligence (ETI).

In the decades since Enrico Fermi first posed the question that encapsulates this paradox (“Where is everybody?”), scientists have attempted to explain this disparity one way or another. But in a new study conducted by three famed scholars from the Future of Humanity Institute (FHI) at Oxford University, the paradox is reevaluated in such a way that it makes it seem likely that humanity is alone in the observable Universe.

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Posted on by Matt Williams

How an Advanced Civilization Could Stop Dark Energy From Preventing Their Future Exploration

This illustration shows the evolution of the Universe, from the Big Bang on the left, to modern times on the right. Image: NASA

During the 1930s, astronomers came to realize that the Universe is in a state of expansion. By the 1990s, they realized that the rate at which it is expansion is accelerating, giving rise to the theory of “Dark Energy”. Because of this, it is estimated that in the next 100 billion years, all stars within the Local Group – the part of the Universe that includes a total of 54 galaxies, including the Milky Way – will expand beyond the cosmic horizon.

At this point, these stars will no longer be observable, but inaccessible – meaning that no advanced civilization will be able to harness their energy. Addressing this, Dr. Dan Hooper  – an astrophysicist from the Fermi National Accelerator Laboratory (FNAL) and the University of Chicago – recently conducted a study that indicated how a sufficiently advanced civilization might be able to harvest these stars and prevent them from expanding outward.

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