Another video in the Big Science Observations series has been released. We’re filming a few more next week, so look forward to them.

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In all the cosmos there is only one planet known to harbor life. While Earth is special to us, there are countless similar worlds orbiting other stars. Since life arose early in Earth’s history, it seems likely that life could arise on other potentially habitable planets. But as we learn of both exoplanets and the history of life on Earth, we’ve found that things are a bit more complicated. 

In astronomy, “potentially habitable” simply means that the orbit of an exoplanet places it in a particular range of distance from its star. Close enough that its water wouldn’t deep freeze into a perpetual solid, and far enough away that its water doesn’t boil away leaving a dry husk of a world. Earth, as you would expect, lies within the habitable zone of the Sun.

But there are other things that make Earth so friendly to life. For one, our Sun is a stable main sequence star, so Earth has received a steady source of light and heat for billions of years. Earth also has a large moon, and the gravitational tug between the Earth and Moon creates tidal heating in Earth’s interior, producing volcanoes and other geologic activity that can bring rich material from the interior to Earth’s surface. In the outer solar system, the large moons of Jupiter experience similar tidal forces, warming their water to a liquid underneath their surface. Moons such as Europa might harbor life because of this tidal heating.

It turns out that our solar system is a bit unusual. Stars such as are much less common than smaller red dwarf stars. Most of the planets we’ve discovered orbit close to a red dwarf star. The Trappist-1 system, for example, has a least 7 Earth-sized worlds orbiting its star far more closely than Mercury orbits the Sun. Although Trappist-1 is about 90 times more massive than Jupiter, they are about the same size, and the planets orbit at a similar distance as the moons that orbit Jupiter. Since the orbits of these planets are not exactly circular, they experience tidal forces like the Jovian moons. So they could be geologically active in a life-friendly way.

Young red dwarfs can be rather hostile to life. They can produce large solar flares that can fry the atmosphere of a close planet, leaving them dry and arid. But Trappist-1 is an older, stable star, so its planets would have a steady stream of heat and light. In a recent paper, a team looked at the conditions for the Trappist planets, taking into account both the amount of heat they receive from their star, and the amount of tidal heating they generate. They found that planets d and e seem the most friendly for life, with moderate stellar heating and moderate tidal heating. They should be warm enough for liquid water, but cool enough to prevent a runaway greenhouse.

Of course the big question is whether these planets have ample water on their surface. That would depend critically on just how massive they are. While we have a good idea of their size, we aren’t as certain about their masses. So we’ll need more data to determine if life could survive on these nearby worlds.

Paper: A. C. Barr, et al. Interior structures and tidal heating in the TRAPPIST-1 planets. Astronomy & Astrophysics (2018)

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Einstein’s theory of gravity has been tested in lots of ways, from the slow precession of Mercury’s orbit, to the detection of gravitational waves. So far the theory has passed every test, but that doesn’t necessarily mean it’s completely true. Like any theory, general relativity is based upon certain assumptions about the way the universe works. The biggest assumption in relativity is the principle of general equivalence. 

The equivalence principle was proposed by both Galileo and Newton, and basically states that any two objects will fall at the same rate under gravity. Barring things like air resistance, a bowling ball and a feather should fall at the same rate. Experiments that have tested the principle of equivalence show it’s a good approximation at the very least.

In Newtonian gravity, this just means that the gravitational force on an object is proportional to its mass, so even if the equivalence principle is only an approximation we could still use Newtonian gravity. But Einstein’s theory of relativity, gravity isn’t a force, but simply an effect of the warp and weft of spacetime. In order for this to be true, the equivalence principle can’t be approximately true, it has to be exactly true. If objects “fall” due to the bending of space itself, then everything must fall at the same rate, because they are all in the same spacetime.

But there’s an interesting twist to this principle. One of the things relativity predicts is that mass and energy are related. This is where Einstein’s most famous equation, E = mc², comes into play. Normally the “relativistic mass” of an object is effectively the same as its regular mass, but objects like neutron stars have such strong gravitational and electromagnetic fields that their relativistic mass is a bit larger than the mass of their matter alone. If the gravitational force on an object is proportional to its mass-energy, then a neutron star should fall slightly faster than lighter objects. If Einstein is right, then a neutron star should fall at exactly the same rate as anything else.

A few years ago, astronomers discovered a system of three stars orbiting closely together. Two of them are white dwarf stars, while the third is a neutron star. The neutron star is also a pulsar, which means it emits regular pulses of radio energy. The timing of these pulses are determined by the rotation of the neutron star, which is basically constant. Any variation in the timing of the pulses is therefore due to the motion of the neutron star in its orbit. In other words, we can use the radio pulses to measure the motion of the neutron star very precisely.

Each of the stars in this system is basically “falling” in the gravitational field of the others. Recently a team of astronomers observed this system to see if the neutron star falls at a different rate different from Einstein’s prediction. Their result agreed with Einstein. To within 0.16 thousandths of a percent (the observational limit of their data) the neutron star falls at the same rate as a white dwarf.

Once again, Einstein’s gravitational theory is right.

Paper: A. Archibald et al. Testing general relativity with a millisecond pulsar in a triple system. 231st meeting of the American Astronomical Society, Oxon Hill, Md. (2018)

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While I don’t generally focus on alternative science models on this blog, I do like to talk about them from time to time. It’s a great way to show how we test scientific claims based on the evidence at hand. Fringe models aren’t rejected because they seem crazy. They’re rejected because the evidence doesn’t support them. So back in 2013 I started getting comments claiming astrophysics is wrong, and the truth is revealed in a new model called the Electric Universe, or EU for short. Over the next several months these comments got increasingly more common, so I figured I’d start looking into the model.

It’s a bit of an odd history. It’s origins can be traced back to The Electric Universe, published in 2007 by physicist Wallace Thornhill and comparative mythologist David Talbot. The broad claim is that traditional astrophysics is wrong, particularly in the way it deals with gravity, or prioritizes gravity in its models. As an alternative it presents a model where gravity plays a minor role. Planets, stars and galaxies are guided and even formed through electromagnetic forces. The universe is electric, not gravitational.

Dude, this plasma form looks like ancient artwork! Let’s rewrite physics!

Now it seems odd that a comparative mythologist would co-author a book on astrophysics, until you realize that The Electric Universe is a sequel to the 2005 book Thunderbolts of the Gods by the same authors. In this book the authors claim that many of the myths found in ancient civilizations were based on real astronomical events. As they write in the first chapter, after more than thirty years spent studying ancient history they have come to the shocking conclusion

The evidence suggests that only a few thousand years ago planets moved close to the earth, producing electrical phenomena of intense beauty and terror. Ancient sky worshippers witnessed these celestial wonders, and far-flung cultures recorded the events in the great myths, symbols, and ritual practices of antiquity.

They also write:

We contend that humans once saw planets suspended as huge spheres in the heavens. Immersed in the charged particles of a dense plasma, celestial bodies “spoke” electrically and plasma discharge produced heaven-spanning formations above the terrestrial witnesses. In the imagination of the ancient myth-makers, the planets were alive: they were the gods, the ruling powers of the sky.

That’s some pretty trippy stuff, but it seems to have roots in Immanuel Velikovsky’s 1950 book Worlds in Collision, where he claimed Venus was ejected from Jupiter thousands of years ago, passed by Earth changing its orbit and axial tilt, and the resulting geological catastrophes were recorded by early civilizations, such as Athena (not Venus, but close enough) springing out of the head of Zeus (Jupiter).

In other words, the electric universe began as a just-so story. The stories of ancient civilizations must be true, so the authors toss out established science to create a new field of astrophysics. One that can move Heaven and Earth to match their theory. But regardless of its origins, by 2014 the EU model was promoted as a legitimate scientific model. One based not on mythology, but on modern astronomical data. One that mainstream astronomers couldn’t accept because it would overturn their cherished cosmology.

Given its history, I could have just mocked the EU model as some kind of Chariots of the Gods kind of nonsense. But I wanted to give the model a fair shake. What are the actual claims of EU, and how do they compare to actual data? Weeding through various websites and videos can be a challenge, but fortunately EU had a great resource for beginners. A Beginner’s View of Our Electric Universe, by Tom Findlay. It was revised in 2013, making it reasonably up to date, and it was highly praised by Thornhill and other leading supporters of EU. As an extra bonus, the author made a PDF version freely available to the public, so anyone can check out the claims of EU for themselves. With this and other resources I was ready to write my post.

We will be returning to the idea of nuclear fusion-powered stars later to delve into why this, in fact, is not the way the Sun works and to take a close look at how all stars actually do work, electrically of course.

Image from Findlay’s book, showing the relation between current flow and stellar type.

In Chapter 6, Findlay explains that stars shine due to cosmic electric currents flowing through a star’s plasmasphere. Rather than nuclear fusion, stars are powered like an arc light. There are two big problems with this idea. One is that without nuclear fusion, the Sun would produce no neutrinos, but solar neutrinos have long been observed. The second is that plasma arc light doesn’t emit light in a continuous thermal spectrum, whereas the observed spectrum of the Sun is a thermal blackbody. Naturally, I pointed this out it my post, Testing the Electric Universe. And thus I sparked the fury of EU fans everywhere.

Their biggest complaint was that EU does not say fusion doesn’t occur. Which was evidence not only of my ignoble behavior, but also that scientists in general can’t be trusted. It doesn’t matter than Findlay clearly claims fusion doesn’t occur at all. Since other versions of EU say it might, I’m a lying liar. A couple of folks even tried to get me fired from my university position over this. To this day EU fans continue to demand I explain my unethical behavior, despite the fact that it’s been debated ad nauseam in the comments.

Of course the problem is that there isn’t just one EU model at this point, there are several conflicting versions of them. To my best current understanding, some EU models say fusion doesn’t occur at all, some EU supporters claim neutrinos don’t even exist, and some claim fusion occurs near stellar surfaces, but (as far as I know) all claim fusion does not occur in stellar cores. Again, to my understanding, if core fusion were shown to be valid, it would overturn the electric star claims of EU models, and thus most of EU in general.

If fusion occurred near a Sun’s surface, it would produce neutrinos, so the mere detection of solar neutrinos is consistent with both surface and core fusion models. However, we can do much more than detect solar neutrinos. We now have measurements of both the types (flavors) of neutrinos and their energy levels. We know the rate at which solar neutrinos are generated at various energy levels. What we find is that the energy of neutrinos follows a thermal distribution consistent with the thermal distribution we expect in the core (that is, produced by intense heat and pressure). Fusion produced by electromagnetic plasmas would have a different spectrum, which isn’t observed in solar neutrinos. We know this because we use particle accelerators (electromagnetic plasmas) to produce neutrinos in the lab. More recently we have finally detected neutrinos from the fundamental proton-proton collisions in the Sun’s core, which is consistent with core fusion.

Even if EU’s surface fusion model could be tweaked to mimic core fusion, there were still be the issue of high energy gamma rays. Any fusion of light elements produces not only neutrinos, but high energy photons (gamma rays). We’ve observed the Sun with gamma ray telescopes, and found no steady stream of gamma rays coming from the Sun. We sometimes observe bursts gamma rays coming from very intense solar flares, but this is not consistent with the electric Sun claims. The lack of observed gamma rays is consistent with the core fusion model. Gamma rays are produced in the solar core via fusion, but the photons soon collide with other nuclei in the core, transferring energy to the nuclei to generate heat. Thus the Sun is thermally heated through these gamma rays, which lose most of their energy before escaping the Sun.

The spectrum of a plasma arc is not a thermal blackbody.

Since the Sun is heated internally through nuclear fusion, its surface emits light with a thermal spectrum distribution. This is known as blackbody radiation. We see this effect in lots of things from heated metal to stars. Objects that have (close to) a blackbody spectrum produce their light through internal heat rather than electron band gaps and such. This is why if you look at light from an incandescent light bulb you will see a smooth rainbow (thermal light), but if you look at a fluorescent light or LED light through a prism you will see specific colors (non-thermal light). If sunlight were produced by surface fusion in the low-density outer layer of the Sun, the light produced wouldn’t be a thermal blackbody. Now, you could argue for some unspecified process that takes the light produced by surface fusion and heats the (more dense) photosphere to produce a thermal spectrum. That would be consistent with the sunlight we observe, because regardless of how the photosphere is thermally heated (core or surface) the spectrum would be pretty much the same.

But there’s a problem with a surface-heated photosphere model. If the Sun is surface heated rather than core heated, the surface should be hotter than the interior. Some EU folks actually claim this. But we know from observations that the deeper layers of the photosphere are hotter than the surface layer. So surface heating can’t be right given standard physics. To get around this, some folks such as Pierre-Marie Robitaille now claim that the blackbody law isn’t valid, and that the surface of the Sun is some kind of liquid metal. It gets pretty strange beyond that point. Basically you have to start tossing out well-proven physics left and right just to cobble together a model that can match observation, when the core fusion model already matches observation extremely well and in multiple ways.

As I wrote in 2014, the Electric Universe model is contradicted by observational evidence. Neutrinos or no, EU is provably wrong. That fact hasn’t changed over the years, and isn’t likely to.

If you’re an EU fan reading this, it’s probably because you tried to argue about my 2014 post, and I sent you this link in reply. Congratulations on making it to the end. It’s been four years since I wrote that post, and I’ve grown tired of constantly being asked to rebut your just-so story.

The post Just-So Story appeared first on One Universe at a Time.

One of the biggest challenges in astronomy is observing the cold, dark dust surrounding a young star. These planetary disks, as they are known, are the birthplace of planets. Understanding them helps us understand how planetary systems form. But much of the gas and dust is so cold that they emit light mostly in the microwave range, which is difficult to detect. But with the construction of the Atacama Large Millimeter/submillimeter Array (ALMA) we can finally start to see details. 

A common feature of these planetary disks is their ringed pattern. The disks often have rings or arcs of thick dust separated by gaps. It has been thought that these gaps are caused by young planets, which tug on the gas and dust to make patterns in the disk, similar to the way Jupiter created gaps in the asteroid belt known as Kirkwood gaps. But new research finds that these ringed patterns might not be evidence of planets after all.

Computer simulations from a team at NASA show these gaps could be caused by ultraviolet light. When ultraviolet light strikes grains of dust, it can free electrons from the dust grains through the photoelectric effect. The free electrons then collide with surrounding gas, heating it up. As the gas heats and expands it tends to trap more dust grains. This reinforcing cycle is known as photoelectric instability. The computer simulations show that photoelectric instability can combine with other interactions to create the type of arcs and rings we see in young planetary disks.

This doesn’t mean there aren’t young planets orbiting these young stars, but rather that the presence of rings in a planetary disk doesn’t prove there are planets. Planetary formation is complex, and we will need to do further study to understand it.

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Big Science is still working on the pilot video, but the Winter weather at Green Bank means we can’t finish until Spring. In the mean time look for a Big Science video series on YouTube.

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The New Horizons Pluto flyby was an ambitious mission. At the time of launch, its destination was known only as a blurry distant body.  We knew some of its properties, such as its mass and rough surface coloring, but we weren’t even certain of its exact size. But the laws of gravity are extremely precise, so we could ensure New Horizons would reach its target. The mystery was what it would find. 

What New Horizons discovered surprised us all. Rather than a cold inert world, we found Pluto has a thin atmosphere, that it has icy mountains, and is likely thermally active. The mission showed us just how strange and wondrous the solar system could be beyond Neptune. It piqued our interest in similar distant bodies.

Hubble image that discovered 2014 MU69. Credit: NASA, ESA, SwRI, JHU/APL, and the New Horizons KBO Search Team

We know even less about other worlds. Their tremendous distance and small sizes make them difficult to study. We have discovered lots of objects, some with rings, some with moons, and some even larger than Pluto. But each of these are seen only as small blurry dots even with our best telescopes. A mission to any of these worlds would be as costly as New Horizons, and would be a difficult sell in our current economic environment.

So the New Horizons team looked for distant worlds their spacecraft might be able to reach. They settled on a small body known as 2014 MU₆₉. Discovered eight years after the launch of New Horizons, it is a small world only about 20 to 30 kilometers wide. From the blurry images we have, it appears to be a close or contact binary, similar to the comet 67P/Churyumov-Gerasimenko. It’s difficult to tell, because 2014 MU₆₉ is about a billion miles further away from the Sun than Pluto, or about 25% more distant.  We do, however, know the path of its orbit, and with the equations of Newton’s gravity the New Horizons team knows it can reach it.

The date of the flyby is now scheduled for 1 January, 2019. To save power, the spacecraft is currently in hibernation until June. By August it will have woken up and will start taking images of 2014 MU₆₉. These will help pinpoint the exact path for New Horizons, and ensure a close and safe flyby.

This extended mission is a huge challenge. We’ve never attempted such a distant flyby, and even less is known about 2014 MU₆₉ than was known about Pluto. But the rewards promise to be huge. For the first time we will observe a body in the outer solar system close-up. It promises to be just as surprising as Pluto, if not more.

The post A Billion Miles Further appeared first on One Universe at a Time.

There is much we still don’t know about the origin of our Sun. We know that stars form within large clouds of gas and dust known as stellar nurseries. These clouds collapse under their own weight to form hundreds of stars at once. But something has to trigger that collapse. The most popular view is that it is triggered by supernovae, which sends shock waves through the cloud. But a new model argues that the birth of our Sun might have been triggered by the more subtle process of a Wolf-Rayet star.

A Wolf-Rayet star is an old massive star on its way to becoming a supernova. They are distinguished by extremely strong stellar winds and their spectral lines tend to show they are rich in helium, but don’t contain much hydrogen. They are often observed within a nebula produced when the outer layers of the star are pushed outward.

Wolf-Rayet stars cast off outer layers gradually, rather than through a single explosion like supernovae, so it was thought that they couldn’t trigger star formation within a stellar nursery. But new computer simulations show that they might encourage stars to form within the layers of the surrounding nebula. The strong stellar winds of a Wolf-Rayet star can cause the surrounding nebula to compress into a more dense layer surrounding the star. Known as a Wolf-Rayet bubble, simulations show that it could be dense enough to trigger star formation.

This idea would seem to be supported by the composition of the early solar system. Meteorites from the early solar system have higher levels of aluminum-26 and lower levels of iron-60 than the surrounding interstellar medium. Wolf-Rayet stars produce lots of aluminum-26, which would tend to get caught within the bubble.

There are other possible explanations for these elemental abundances, so the Wolf-Rayet model isn’t conclusive. It does show, however, that there is more than one way to trigger star formation, and the origin of our Sun may have a richer history than we once thought.

Paper: Vikram V. Dwarkadas et al. Triggered Star Formation inside the Shell of a Wolf–Rayet Bubble as the Origin of the Solar System. ApJ 851, 147 (2017)

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The life of a star is determined by its mass. Large stars live short lives that end in supernova explosions, while smaller stars live longer, ending their lives as white dwarfs. Knowing the mass of a star helps us understand not only the life of a star, but the evolution of galaxies. But determining the mass of a star can be difficult. 

The best way to weigh a star is to measure how strongly it pulls on another star. If two stars are a binary pair, the speed at which they orbit each other is governed by the gravitational pull between them. By measuring their orbits over time, we can determine the mass of each star. But many stars are solitary. The nearest star to them can be light years away, and its gravitational pull on these stars is too small to measure. So we need another way to determine its mass.

One alternative is to look at the temperature of a star. Larger mass stars burn hotter than smaller ones, so the higher a star’s temperature, the greater its mass. But this has a few downsides. For one, this relation between stellar temperature and mass is only true for main sequence stars. For another, stars get slightly hotter as they age. An old star with the Sun’s mass has a higher temperature than a young solar mass star.

A new way to measure a star’s mass looks at its surface gravity. A ball dropped near the surface of the Earth will fall at a rate of about 9.8 m/s². This is Earth’s surface gravity. Far away from the Earth gravity is weaker. The Moon, for example, “falls” around the Earth at  only about 2.7 mm/s². The surface gravity of a planet or star depends upon its mass and its diameter. By determining the distance to a star, we can use its apparent size to determine its diameter. Determining surface gravity is a bit more tricky.

If you bounce a ball against the ground, it takes a certain amount of time to rise to its maximum height and fall back to the ground. That time depends in part on surface gravity. If you were to bounce a ball in the same way on Mars, the time between bounces would be longer, because Mars has a smaller surface gravity. We can’t bounce balls on a star, but there are surface fluctuations that rise and fall. The surface of a star often churns a bit like boiling water, creating rising and falling pockets known as granules. The rate at which these granules rise and fall is determined by the star’s surface gravity. So by measuring the rate at which a star flickers in tiny ways, we can determine a star’s mass.

A recent paper looked at the observational limits of data from GAIA (currently gathering data) and TESS (planned to launch in March). They found that GAIA could determine a star’s mass give or take 25%, and TESS should be able to determine stellar mass to within 10%. Since these satellites will observe millions of stars, this could become a powerful tool in the study of stars.

Paper: Keivan G. Stassun, et al. Empirical, Accurate Masses and Radii of Single Stars with TESS and Gaia.  arXiv:1710.01460 (2017)

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Out of the vast sea of stars in the night sky, a few are special. Not because of their size, or color, or age, but because they have a name. When we name a star, we make it a part of our collective cultural heritage. Their names inspire epic stories, or remind us of our history.

Of course many stars have multiple names. The brightest star in the night sky is most commonly known as Sirus, from the Latin. But Geoffrey Chaucer referred to it as Alhabor. In Arabic it is Mirzam Al-Jawza, and in many cultures it is known as the dog-star or wolf-star. All human cultures have a history of astronomy, so lots of stars have multiple names. So how do we deal with this in astronomy? Traditionally we have relied upon the names from Western astronomy. That meant mostly Latin names for the bright stars and Arabic names for dimmer ones, since Arabic astronomers of the Middle Ages were so meticulous in their observations, and later Europeans relied upon their catalogs. Another way is to use the order of brightness within a particular constellation. So Rigel, in the constellation Orion, is Beta Orionis, since it is the second brightest star in Orion, after Betelgeuse. Some stars are most commonly known by this, such as the brightest star in the constellation Centaurus, Alpha Centauri. In Chinese astronomy it is known as Nán Mén Èr, or the second star of the southern gate.

The problem with this naming scheme is that the official constellations mainly derive from European tradition,  so they ignore the long history of astronomy in other parts of the world. We could just stop using names and instead use catalog numbers. But HD 172167 doesn’t appeal to us in the same way that Vega does. Names connect us both to the stars and our history, so why not use the names we have. The challenge is to use names that honor both the history of astronomy and the diverse cultures that have contributed to our common understanding of the stars. This is the goal of the International Astronomical Union (IAU) Division C Working Group on Star Names (WGSN). Over the past several years they have built a list of officially recognized names for stars. Recently they have added 86 new names to the list, bringing the total to 313.

Some of the list simply makes the most popular names official. Sirius, Betelgeuse, and Vega keep their names. Others change slightly, such as Alpha Centauri becoming Rigel Kentaurus (the foot of the Centaur). But other names are drawn from across the globe. The fifth brightest star in the constellation of the Southern Cross (Epsilon Crucis) now has the name Ginan. It derives from the astronomy of aboriginal Australia, which is perhaps the oldest culture of astronomy on Earth. A star in the Hyades cluster commonly called Theta-2 is now recognized as Chamukuy, from the Mayan. Zeta Piscium now has the Hindu name Revati. All of these names have been used in some circles of astronomy, but the IAU designation now recognizes them as the preferred name.

These names are just the beginning. The stars will continue to call to us. As we further understand them, learn of planets that orbit them, and perhaps even travel among them someday we will continue to give them names. They will continue to inspire stories of our history, wonder, past and future.

The post Naming Day appeared first on One Universe at a Time.

If an alien civilization wanted to study planet Earth, how might they do it? They could use powerful telescopes to measure the physical characteristics of our planet, or they could listen for signals from our TV and radio broadcasts. These are things we are doing in our search for alien civilizations. But a really advanced alien civilization might try something a bit more ambitious, such as an actual mission to Earth. One way to do this would be to build a probe within an asteroid, and send it on a journey across the stars. The asteroid could shelter the probe during it’s long trip through interstellar space. Once it arrived in our solar system, the probe could gather detailed information about Earth and the solar system. It might even try to communicate with humans by beaming a radio signal in Earth’s direction. Such an alien probe would look a lot like the recently discovered asteroid Oumuamua, which is why the Breakthrough Listen project wants to study it.

Oumuamua was discovered in October by the Pan-STARRS 1 telescope. Unlike any other asteroid, Oumuamua has an interstellar orbit. It is moving through our solar system so quickly that could not have originated in our solar system. Based on its trajectory, it came to our solar system from the general direction of the star Vega. Coincidentally, Vega is star aliens first communicated with humans from in Carl Sagan’s novel Contact. In addition to being the first confirmed interstellar object to enter our solar system, it also has a highly unusual cigar shape, with a length about 10 times longer than its width. Add to this the fact that Oumuamua made a relatively close approach to Earth, within 15 million miles of our planet, and it begins to look a bit alien.

Odds are this asteroid is just a chance visitor to our system. We’ve known that some asteroids can escape the solar system through close flybys of large planets like Jupiter, so it makes sense that asteroids from other star systems could travel between the stars. Such interstellar visitors might be rare, but they don’t require aliens to send them on their way. But Breakthrough Listen is interested in finding evidence of alien civilizations, no matter how long the odds. So when Oumuamua was discovered, it made for a promising target.

Oumuamua is currently about 2 astronomical units away from Earth. About twice as far as the Earth is from the Sun. That’s still much closer than many of the probes we’ve sent into space, such as Cassini and New Horizons. If it is an alien probe sending radio transmissions we should be capable of detecting them. So Breakthrough Listen will use the Green Bank Telescope to look for any evidence of alien technology, searching across four radio bands, from 1 to 12 GHz, for a total time of about 10 hours. If an alien probe wants to be detected, that’s a good frequency range to search.

Just to be clear, the odds of Breakthrough Listen finding anything are really slim. Studies so far haven’t found anything that would imply an artificial origin. But even if Breakthrough Listen doesn’t find anything, their observations will add to those we already have, and help us better understand asteroids that are rare, but natural, alien visitors.

The post The Search For Aliens On A Visiting Asteroid appeared first on One Universe at a Time.

Within most galaxies there lurks a supermassive black hole. Our own galaxy, for example contains a black hole 4 million times more massive than our Sun. One of the big mysteries of these black holes is just how they formed, and how long it took for them to reach such a massive size. Now a massive black hole at the edge of the observable universe challenges our understanding of them. 

We discovered this distant black hole because it is a quasar. When a black hole captures nearby material, the material becomes superheated and radiates powerful radio energy and x-rays. These beacons of light are so bright they can only be powered by supermassive black holes. By observing the brightness of distant quasar we can calculate the mass of its black hole engine.

Recently astronomers discovered the most distant quasar ever. Known as J1342+0928, it is so distant we see it from a time when the universe was only 690 million years old. At that time galaxies were just starting to form. But this quasar gives off so much light that its black hole must be 800 million times the mass of our Sun. So how did this particular black hole get so massive so soon? It’s possible that it exists in a rather dense region of space. Having lots of matter around would make it easier to grow quickly. But that isn’t enough to solve the mystery, because the faster a black hole consumes matter, the more light the matter would emit, and that pressure of light and heat would tend to push matter away from the black hole. It’s known as the Eddington limit, and it puts an upper bound on how fast a black hole can grow. To reach 800 million solar masses in such a short time, the black hole would have to consume matter fairly close to this limit.

The big question about this black hole is whether it is simply an unusually early bloomer, or if it is rather typical of black holes in the early universe. To answer that question we will need to find more examples of large quasars on the edge of the cosmos. So the race is on to find these most distant of beacons. If we can find them, they will help us understand how supermassive black holes and their galaxies formed.

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