BLOGS

Topics: Astronomy, Astrophysics, Cosmology

Physicists have spent centuries grappling with an inconvenient truth about nature: Faced with three stars on a collision course, astronomers could measure their locations and velocities in nanometers and milliseconds and it wouldn’t be enough to predict the stars’ fates. 

But the cosmos frequently brings together trios of stars and black holes. If astrophysicists hope to fully understand regions where heavenly bodies mingle in throngs, they must confront the “three-body problem.” 

While the result of a single three-body event is unknowable, researchers are discovering how to predict the range of outcomes of large groups of three-body interactions. In recent years, various groups have figured out how to make statistical forecasts of hypothetical three-body matchups: For instance, if Earth tangled with Mars and Mercury thousands of times, how often would Mars get ejected? Now, a fresh perspective developed by physicist Barak Kol simplifies the probabilistic “three-body problem,” by looking at it from an abstract new perspective. The result achieves some of the most accurate predictions yet. 

Physicists Edge Closer to Taming the Three-Body Problem, Charlie Wood, Scientific American

Astronomers searched for candidate antimatter stars among nearly 6000 gamma-ray sources. After eliminating known objects and sources that lacked the spectral signature of an antistar, 14 possibles remained. (Courtesy: Simon Dupourqué/IRAP)

Topics: Astronomy, Astrophysics, Cosmology, High Energy Physics

Fourteen possible antimatter stars (“antistars”) have been flagged up by astronomers searching for the origin of puzzling amounts of antihelium nuclei detected coming from deep space by the Alpha Magnetic Spectrometer (AMS-02) on the International Space Station.

Three astronomers at the University of Toulouse – Simon Dupourqué, Luigi Tibaldo, and Peter von Ballmoos – found the possible antistars in archive gamma-ray data from NASA’s Fermi Gamma-ray Space Telescope. While antistars are highly speculative, if they are real, then they may be revealed by their production of weak gamma-ray emission peaking at 70 MeV, when particles of normal matter from the interstellar medium fall onto them and are annihilated.

Antihelium-4 was created for the first time in 2011, in particle collisions at the Relativistic Heavy Ion Collider at the Brookhaven National Laboratory. At the time, scientists stated that if antihelium-4 were detected coming from space, then it would definitely have to come from the fusion process inside an antistar.

However, when it was announced in 2018 that AMS-02 had tentatively detected eight antihelium nuclei in cosmic rays – six of antihelium-3 and two of antihelium-4 – those unconfirmed detections were initially attributed to cosmic rays colliding with molecules in the interstellar medium and producing the antimatter in the process.

Subsequent analysis by scientists including Vivian Poulin, now at the University of Montpellier, cast doubt on the cosmic-ray origin since the greater the number of nucleons (protons and neutrons) that an antimatter nucleus has, the more difficult it is to form from cosmic ray collisions. Poulin’s group calculated that antihelium-3 is created by cosmic rays at a rate 50 times less than that detected by the AMS, while antihelium-4 is formed at a rate 10⁵ times less.

The mystery of matter and antimatter

The focus has therefore turned back to what at first may seem an improbable explanation – stars made purely from antimatter. According to theory, matter and antimatter should have been created in equal amounts in the Big Bang, and subsequently, all annihilated leaving a universe full of radiation and no matter. Yet since we live in a matter-dominated universe, more matter than antimatter must have been created in the Big Bang – a mystery that physicists have grappled with for decades.

“Most scientists have been persuaded for decades now that the universe is essentially free of antimatter apart from small traces produced in collisions of normal matter,” says Tibaldo.

The possible existence of antistars threatens to turn this on its head. “The definitive discovery of antihelium would be absolutely fundamental,” says Dupourqué.

Are antimatter stars firing bullets of antihelium at Earth? Physics World, published in Physical Review D

Topics: Astrobiology, Astronomy, Astrophysics, SETI

Cultural references: The post title refers to NC A&T Alumni, and Civil Rights icon Reverend Jesse Jackson's appearance on Saturday Night Live, and the Wow! signal. Personal note: This signal appeared on the same day my granddaughter was born.

<p>On April 29, 2019, the Parkes Radio Telescope in Australia began listing to the radio signals from the Sun’s nearest neighbor, Proxima Centauri, just over 4 lightyears away. The telescope was looking for evidence of solar flares and so listened for 30 minutes before retraining on a distant quasar to recalibrate and then pointing back.

In total, the telescope gathered 26 hours of data. But when astronomers analyzed it in more detail, they noticed something odd — a single pure tone at a frequency of 982.02 MHz that appeared five times in the data.

The signal was first reported last year in The Guardian, a British newspaper. The article raised the possibility that the signal may be evidence of an advanced civilization on Proxima Centauri, a red dwarf star that is known to have an Earth-sized planet orbiting in its habitable zone.

But researchers have consistently played down this possibility saying that, at the very least, the signal must be observed again before any conclusions can be drawn. Indeed, the signal has not been seen again, despite various searches.

Now Amir Siraj and Abraham Loeb from Harvard University in Cambridge, Massachusetts, have calculated the likelihood that the signal came from a Proxima Centauri-based civilization, even without another observation. They say the odds are so low as to effectively rule out the possibility — provided the assumptions they make in their calculations are valid.</p>

Why The Recent Signal That Appeared to Come From Proxima Centauri Almost Certainly Didn't, Physics arXiv Blog, Discovery Magazine

Illustration of the main elements of the lattice confinement fusion process observed. In Part (A), a lattice of erbium is loaded with deuterium atoms (i.e., erbium deuteride), which exist here as deuterons. Upon irradiation with a photon beam, a deuteron dissociates, and the neutron and proton are ejected. The ejected neutron collides with another deuteron, accelerating it as an energetic “d*” as seen in (B) and (D). The “d*” induces either screened fusion (C) or screened Oppenheimer-Phillips (O-P) stripping reactions (E). In (C), the energetic “d*” collides with a static deuteron “d” in the lattice, and they fuse together. This fusion reaction releases either a neutron and helium-3 (shown) or a proton and tritium. These fusion products may also react in subsequent nuclear reactions, releasing more energy. In (E), a proton is stripped from an energetic “d*” and is captured by an erbium (Er) atom, which is then converted to a different element, thulium (Tm). If the neutron instead is captured by Er, a new isotope of Er is formed (not shown).

Topics: Astrophysics, NASA, Nuclear Fusion, Propulsion, Space Exploration, Spaceflight

A team of NASA researchers seeking a new energy source for deep-space exploration missions recently revealed a method for triggering nuclear fusion in the space between the atoms of a metal solid.

Their research was published in two peer-reviewed papers in the top journal in the field, Physical Review C, Volume 101 (April 2020): “Nuclear fusion reactions in deuterated metals” and “Novel nuclear reactions observed in bremsstrahlung-irradiated deuterated metals.”

Nuclear fusion is a process that produces energy when two nuclei join to form a heavier nucleus. “Scientists are interested in fusion because it could generate enormous amounts of energy without creating long-lasting radioactive byproducts,” said Theresa Benyo, Ph.D., of NASA’s Glenn Research Center. “However, conventional fusion reactions are difficult to achieve and sustain because they rely on temperatures so extreme to overcome the strong electrostatic repulsion between positively charged nuclei that the process has been impractical.

Called Lattice Confinement Fusion, the method NASA revealed accomplishes fusion reactions with the fuel (deuterium, a widely available non-radioactive hydrogen isotope composed of a proton, neutron, and electron, and denoted “D”) confined in the space between the atoms of a metal solid. In previous fusion research such as inertial confinement fusion, fuel (such as deuterium/tritium) is compressed to extremely high levels but for only a short, nano-second period of time, when fusion can occur. In magnetic confinement fusion, the fuel is heated in a plasma to temperatures much higher than those at the center of the Sun. In the new method, conditions sufficient for fusion are created in the confines of the metal lattice that is held at ambient temperature. While the metal lattice, loaded with deuterium fuel, may initially appear to be at room temperature, the new method creates an energetic environment inside the lattice where individual atoms achieve equivalent fusion-level kinetic energies.

NASA Detects Lattice Confinement Fusion

The stone circle of Nabta Playa marks the summer solstice, a time that coincided with the arrival of monsoon rains in the Sahara Desert thousands of years ago. (Credit: Wikimedia Commons)

Topics: African Studies, Astronomy, Astrophysics, Diversity in Science

For thousands of years, ancient societies all around the world erected massive stone circles, aligning them with the sun and stars to mark the seasons. These early calendars foretold the coming of spring, summer, fall, and winter, helping civilizations track when to plant and harvest crops. They also served as ceremonial sites, both for celebration and sacrifice.

These megaliths — large, prehistoric monuments made of stone — may seem mysterious in our modern era, when many people lack a connection with, or even view of, the stars. Some even hold them up as supernatural or divined by aliens. But many ancient societies kept time by tracking which constellations rose at sunset, like reading a giant, celestial clock. And others pinpointed the sun’s location in the sky on the summer and winter solstice, the longest and shortest days of the year, or the spring and fall equinox.

Europe alone holds some 35,000 megaliths, including many astronomically-aligned stone circles, as well as tombs (or cromlechs) and other standing stones. These structures were mostly built between 6,500 and 4,500 years ago, largely along the Atlantic and Mediterranean coasts.

The most famous of these sites is Stonehenge, a monument in England that’s thought to be around 5,000 years old. Though still old, at that age, Stonehenge may have been one of the youngest such stone structures to be built in Europe.

The chronology and extreme similarities between these widespread European sites lead some researchers to think the regional tradition of constructing megaliths first emerged along the coast of France. It was then passed across the region, eventually reaching Great Britain.

But even these primitive sites are at least centuries younger than the world’s oldest known stone circle: Nabta Playa.

Located in Africa, Nabta Playa stands some 700 miles south of the Great Pyramid of Giza in Egypt. It was built more than 7,000 years ago, making Nabta Playa the oldest stone circle in the world — and possibly Earth’s oldest astronomical observatory. It was constructed by a cattle worshiping cult of nomadic people to mark the summer solstice and the arrival of the monsoons.

“Here is human beings’ first attempt to make some serious connection with the heavens," says J. McKim Malville, a professor emeritus at the University of Colorado and archeoastronomy expert.

Nabta Playa: The World's First Astronomical Site Was Built in Africa and Is Older Than Stonehenge, Eric Betz, Discover Magazine

Topics: Astronomy, Astrophysics, Comets, Space Exploration

Invisible structures generated by gravitational interactions in the Solar System have created a "space superhighway" network, astronomers have discovered.

These channels enable the fast travel of objects through space and could be harnessed for our own space exploration purposes, as well as the study of comets and asteroids.

By applying analyses to both observational and simulation data, a team of researchers led by Nataša Todorović of Belgrade Astronomical Observatory in Serbia observed that these superhighways consist of a series of connected arches inside these invisible structures, called space manifolds - and each planet generates its own manifolds, together creating what the researchers have called "a true celestial autobahn."

This network can transport objects from Jupiter to Neptune in a matter of decades, rather than the much longer timescales, on the order of hundreds of thousands to millions of years, normally found in the Solar System.

Finding hidden structures in space isn't always easy, but looking at the way things move around can provide helpful clues. In particular, comets and asteroids.

There are several groups of rocky bodies at different distances from the Sun. There's the Jupiter-family comets (JFCs), those with orbits of less than 20 years, that don't go farther than Jupiter's orbital paths.

Centaurs are icy chunks of rocks that hang out between Jupiter and Neptune. And the trans-Neptunian objects (TNOs) are those in the far reaches of the Solar System, with orbits larger than that of Neptune.

Astronomers Just Found Cosmic 'Superhighways' For Fast Travel Through The Solar System, Michelle Starr (no kidding), Science Alert

Image Source: American Physical Society (APS) News

Topics: Astrophysics, Condensed Matter Physics, Diversity in Science, Women in Science

Dr. Joan Feynman was "Surely, You're Joking," Nobel laureate Dr. Richard Feynman's baby sister, and an impressive scientist in her own right. We lost her in July. She broke through a lot of barriers that her science progeny are now, rightfully, walking through.

Joan Feynman, an astrophysicist known for her discovery of the origin of auroras, died on July 21. She was 93.

Over the course of her career, Feynman made many breakthroughs in furthering the understanding of solar wind and its interaction with the Earth’s magnetosphere, a region in space where the planetary magnetic field deflects charged particles from the sun. As author or co-author of more than 185 papers, Feynman’s research accomplishments range from discovering the shape of the Earth’s magnetosphere and identifying the origin of auroras to creating statistical models to predict the number of high-energy particles that would collide with spacecraft over time. In 1974, she would become the first woman ever elected as an officer of the American Geophysical Union, and in 2000 she was awarded NASA’s Exceptional Scientific Achievement Medal.

Feynman’s choice in pursuing a career as a scientist was often at odds with the expectations for women, especially the expectations for a wife and mother, but she persisted to become an accomplished astrophysicist. During the 2018 APS April Meeting, where Feynman spoke at the Kavli Foundation Plenary Session, she recalled her mother discouraging her childhood interest in science, calling “women’s brains too feeble,” likely a common belief at the time.</em>

For her fourteenth birthday, Richard gave Feynman a copy of Astronomy by Robert Horace Baker, a college-level physics text, that both taught her about physics and what was possible: Feynman credited a figure attributed to Cecilia Payne-Gaposchkin for proving to her that women could indeed have a career doing science.

As part of her research at JPL, Feynman identified the mechanism that leads to the formation of auroras and developed a statistical model to determine the number of high-energy particles expelled from coronal mass injections that would hit a spacecraft during its lifetime. After her retirement from a senior scientist position in 2003, Feynman continued to conduct research on the impact of solar activity on the early climate of the Earth and the role of climate stabilization in the development of agriculture.

Joan Feynman 1927–2020, Leah Poffenberger, APS News

A 3D illustration of the interstellar object known as ‘Oumuamua. Credit: Getty Images

Topics: Astrophysics, Space Exploration, Spaceflight

‘Oumuamua—a mysterious, interstellar object that crashed through our solar system two years ago—might, in fact, be alien technology. That’s because an alternative, non-alien explanation might be fatally flawed, as a new study argues.

But most scientists think the idea that we spotted alien technology in our solar system is a long shot.

In 2018, our solar system ran into an object lost in interstellar space. The object, dubbed ‘Oumuamua, seemed to be long and thin—cigar-shaped—and tumbling end over end. Then, close observations showed it was accelerating as if something were pushing on it. Scientists still aren’t sure why.

One explanation? The object was propelled by an alien machine, such as a lightsail—a wide, millimeter-thin machine that accelerates as it’s pushed by solar radiation. The main proponent of this argument was Avi Loeb, a Harvard University astrophysicist.

Most scientists, however, think ‘Oumuamua’s wonky acceleration was likely due to a natural phenomenon. In June, a research team proposed that solid hydrogen was blasting invisibly off the interstellar object’s surface and causing it to speed up. 

Now, in a new paper published Monday (Aug. 17) in The Astrophysical Journal Letters, Loeb and Thiem Hoang, an astrophysicist at the Korea Astronomy and Space Science Institute, argue that the hydrogen hypothesis couldn’t work in the real world—which would mean that there is still hope that our neck of space was once visited by advanced aliens—and that we actually spotted their presence at the time.

Here’s the problem with ‘Oumuamua: It moved like a comet, but didn’t have the classic coma, or tail, of a comet, said astrophysicist Darryl Seligman, an author of the solid hydrogen hypothesis, who is starting a postdoctoral fellowship in astrophysics at the University of Chicago.

Mystery of Interstellar Visitor ‘Oumuamua Gets Trickier, Rafi Letzter, Live Science, Scientific American

Image Source: Link Below

Topics: Astrophysics, Interstellar, Plasma, Supernovae, Radiation

Scientists have found new evidence that Earth has been moving through the remains of exploded stars for at least the last 33,000 years.

In a new study published in the journal Proceedings of the National Academy of Sciences, a team of Australian researchers describes how they extracted a special isotope of iron called iron-60 from five deep-sea sediment samples using mass spectrometry.

That’s illuminating because as the researchers wrote in their paper, the isotope is “predominantly produced in massive stars and ejected in supernova explosions.” In other words, iron-60 is left over after a star explodes.

And because iron-60 is radioactive and decays in 15 million years, the theory is that our planet is continuously being dusted with the stuff as it’s moving through the “Local Interstellar Cloud,” a region of unclear origins made up of gas, dust, and plasma.

Scientists: Earth Moving Through Radioactive Debris of Exploded Stars, Victor Tangermann, Futurism

The first direct image of two exoplanets orbiting a Sun-like star, seen here, was captured by the SPHERE instrument on the ESO’s Very Large Telescope. The system is called TYC 8998-760-1 and is located some 300 light-years from Earth.

Topics: Astronomy, Astrophysics, Exoplanets

In another exoplanetary first, the European Southern Observatory's Very Large Telescope (VLT) in Chile's Atacama Desert has captured an image of two worlds orbiting a younger version of the Sun. The system, called TYC 8998-760-1, is located roughly 300 light-years away in the southern constellation Musca. And although it hides two gas giants orbiting a Sun-like star, we don’t have anything quite like these worlds in our own solar system.

The inner planet lies about 160 astronomical units from its host star (where one astronomical unit, or AU, is the average Earth-Sun distance) and is some 14 times the mass of Jupiter. With that amount of heft, the gas giant skirts the border between planet and brown dwarf, which is a type of almost-star. The more distant planet is located about 320 AU from its star and weighs in at about six Jupiter masses.

Two exoplanets seen dancing around Sun-like star for the first time, Mark Zastrow, Astronomy.com

Red-giant spotter: artist’s impression of the Kepler space telescope in Earth orbit. (Courtesy: NASA)

Topics: Astronomy, Astrophysics, Solar Physics

Some red-giant stars are rotating much faster than previously thought, according to a study led by Patrick Gaulme at Germany’s Max Planck Institute for Solar System Research. Using NASA’s Kepler space telescope, the astronomers found that about 8% of the red giants they observed are rotating fast enough to display starspots. The team reckons that the elderly stars acquire their rapid rotation by following one of three distinct routes in their evolution.

In main sequence stars like the Sun, the complex interplay that occurs between stellar rotation and the motions of plasma creates incredibly lively magnetic fields. When this magnetic activity is particularly strong, upwelling plumes of plasma in a star’s convective outer layers can be blocked, producing dark patches on its surface. To an observer on Earth, these starspots cause a periodic variation in the star’s brightness as it rotates, bringing the spots in and out of our field of view.

Until recently, starspots were not thought to be present on red giant surfaces. Since these older stars expand rapidly as they move out of the main sequence, while maintaining their angular momentum, previous theories had predicted that they must rotate more slowly than main sequence stars. Slower rotation should reduce magnetic activity, preventing starspots from forming.

Starspot study sheds light on why some red giants spin faster than others, Sam Jarman, Physics World

Comet NEOWISE over Mount Hood on July 11, 2020. Credit: Kevin Morefield Getty Images

Topics: Astronomy, Astrophysics, Comets

Comet NEOWISE has been entertaining space enthusiasts across the Northern Hemisphere. Although its official name is C/2020 F3, the comet has been dubbed NEOWISE after the Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE) space telescope that first noticed it earlier this year. This “icy snowball” with a gassy tail made its closest approach to the sun on July 3 and is now heading back from whence it came: the far reaches of the outer solar system. Its long, looping orbit around our star ensures that after passing closest to Earth on July 22, Comet NEOWISE will not return for some 6,800 years.

Even though the comet is now bright enough to observe with unaided eyes, inexperienced stargazers might have trouble knowing when and where to look. Scientific American spoke to Jackie Faherty, an astronomer at the American Museum of Natural History in New York City, for observing tips and a better appreciation of why comets are so special.

How does one prepare to watch Comet NEOWISE with the naked eye?

Find the darkest possible swath of sky and make sure your eyes are adjusted so that you give yourself the best possible opportunity to see faint objects. It means: don’t just walk outside after staring at lights or screens and expect to see [the comet] really well. You need 15 minutes or so to adjust your eyes, so that your pupils are adjusted, and they’re used to seeing fainter things. It’s the same as walking into a dark room, and everybody knows that [you] can’t see [things] first—and then, all of a sudden, you start seeing things. You need to do the same thing when you walk outside. And use the Comet NEOWISE app developed by astrophysicist Hanno Rein of University of Toronto Scarborough to see exactly where it is, so that you know what direction you need to look. And then the key would be to find yourself a place that is the darkest possible, that [has] no lights.

The Best Way to Watch Comet NEOWISE, Wherever You Are, Karen Kwon, Scientific American

This artist’s concept shows a hypothetical planet covered in water around the binary star system of Kepler-35A and B. The composition of such water worlds has fascinated astronomers and astrophysicists for years. (Image by NASA/JPL-Caltech.)

Topics: Astronomy, Astrobiology, Astrophysics, Cosmology, Exoplanets

Out beyond our solar system, visible only as the smallest dot in space with even the most powerful telescopes, other worlds exist. Many of these worlds, astronomers have discovered, may be much larger than Earth and completely covered in water — basically ocean planets with no protruding land masses. What kind of life could develop on such a world? Could a habitat like this even support life?

A team of researchers led by Arizona State University (ASU) recently set out to investigate those questions. And since they couldn’t travel to distant exoplanets to take samples, they decided to recreate the conditions of those water worlds in the laboratory. In this case, that laboratory was the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility at the DOE’s Argonne National Laboratory.

What they found — recently published in Proceedings of the National Academy of Sciences — was a new transitional phase between silica and water, indicating that the boundary between water and rock on these exoplanets is not as solid as it is here on Earth. This pivotal discovery could change the way astronomers and astrophysicists have been modeling these exoplanets, and inform the way we think about life evolving on them.

Dan Shim, associate professor at ASU, led this new research. Shim leads ASU’s Lab for Earth and Planetary Materials and has long been fascinated by the geological and ecological makeup of these distant worlds. That composition, he said, is nothing like any planet in our solar system — these planets may have more than 50% water or ice atop their rock layers, and those rock layers would have to exist at very high temperatures and under crushing pressure.

Beneath the surface of our galaxy’s water worlds, Andre Salles, Argonne National Laboratory

Vulcan from the link, also see Memory Alpha

Topics: Astronomy, Astrophysics, Exoplanets, Science Fiction, Star Trek

Note: 2018 article, but neat nonetheless.

One of the more interesting and rewarding aspects of astronomy and space exploration is seeing science fiction become science fact. While we are still many years away from colonizing the Solar System or reaching the nearest stars (if we ever do), there are still many rewarding discoveries being made that are fulfilling the fevered dreams of science fiction fans.

For instance, using the Dharma Planet Survey, an international team of scientists recently discovered a super-Earth orbiting a star just 16 light-years away. This super-Earth is not only the closest planet of its kind to the Solar System, it also happens to be located in the same star system as the fictional planet Vulcan from the Star Trek universe.

The study which details their findings, which recently appeared in the Monthly Notices of the Royal Astronomical Society, was led by Bo Ma and Jian Ge, a post-doctoral researcher and a professor of astronomy from the University of Florida, respectively. They were joined by researchers from Tennessee State University, the Instituto de Astrofisica de Canarias, the Universidad de La Laguna, Vanderbilt University, the University of Washington, and the University of Arizona’s Steward Observatory.

“The new planet is a ‘super-Earth’ orbiting the star HD 26965, which is only 16 light years from Earth, making it the closest super-Earth orbiting another Sun-like star. The planet is roughly twice the size of Earth and orbits its star with a 42-day period just inside the star’s optimal habitable zone.”

“Star Trek fans may know the star HD 26965 by its alternative moniker, 40 Eridani A,” he said. “Vulcan was connected to 40 Eridani A in the publications “Star Trek 2” by James Blish (Bantam, 1968) and “Star Trek Maps” by Jeff Maynard (Bantam, 1980).”

Astronomers find Planet Vulcan – 40 Eridani A – Right Where Star Trek Predicted it, Universe Today

A meme of past memes - seemed apropos.

Topics: Astrophysics, Humor, Science Fiction, SETI

Note: I use three sources for the commentary I've seen breathlessly displayed on the Internet speculating there may be 36 communicative (but, noticeably silent) civilizations in the Milky Way Galaxy. I grinned, and composed the combo meme above. Two words came to mind on my social media feed: click bait.

*****

The number 42 is, in The Hitchhiker's Guide to the Galaxy by Douglas Adams, the "Answer to the Ultimate Question of Life, the Universe, and Everything", calculated by an enormous supercomputer named Deep Thought over a period of 7.5 million years. Unfortunately, no one knows what the question is. Source: Wikipedia

*****

It's been a hundred years since Fermi, an icon of physics, was born (and nearly a half-century since he died). He's best remembered for building a working atomic reactor in a squash court. But in 1950, Fermi made a seemingly innocuous lunchtime remark that has caught and held the attention of every SETI researcher since. (How many luncheon quips have you made with similar consequence?)

The remark came while Fermi was discussing with his mealtime mates the possibility that many sophisticated societies populate the Galaxy. They thought it reasonable to assume that we have a lot of cosmic company. But somewhere between one sentence and the next, Fermi's supple brain realized that if this was true, it implied something profound. If there are really a lot of alien societies, then some of them might have spread out.

Fermi realized that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire Galaxy. Within ten million years, every star system could be brought under the wing of empire. Ten million years may sound long, but in fact it's quite short compared with the age of the Galaxy, which is roughly ten thousand million years. Colonization of the Milky Way should be a quick exercise.

So what Fermi immediately realized was that the aliens have had more than enough time to pepper the Galaxy with their presence. But looking around, he didn't see any clear indication that they're out and about. This prompted Fermi to ask what was (to him) an obvious question: "where is everybody?"

SETI Institute: Fermi Paradox, Seth Shostak, Senior Astronomer

*****

How many intelligent alien civilizations are out there among the hundreds of billions of stars in the spiral arms of the Milky Way? According to a new calculation, the answer is 36.

That number assumes that life on Earth is more or less representative of the way that life evolves anywhere in the universe — on a rocky planet an appropriate distance away from a suitable star, after about 5 billion years. If that assumption is true, humanity may not exactly be alone in the galaxy, but any neighbors are probably too far away to ever meet.

On the other hand, that assumption that life everywhere will evolve on the same timeline as life on Earth is a huge one, said Seth Shostak, a senior astronomer at the SETI Institute in Mountain View, California, who was not involved in the new study. That means that the seeming precision of the calculations is misleading.

"If you relax those big, big assumptions, those numbers can be anything you want," Shostak told Live Science.

The question of whether humans are alone in the universe is a complete unknown, of course. But in 1961, astronomer Frank Drake introduced a way to think about the odds. Known as the Drake equation, this formulation rounds up the variables that determine whether or not humans are likely to find (or be found by) intelligent extraterrestrials: The average rate of star formation per year in the galaxy, the fraction of those stars with planets, the fraction of those planets that form an ecosystem, and the even smaller fraction that develop life. Next comes the fraction of life-bearing planets that give rise to intelligent life, as opposed to, say, alien algae. That is further divided into the fraction of intelligent extraterrestrial life that develops communication detectable from space (humans fit into this category, as humanity has been communicating with radio waves for about a century).

The final variable is the average length of time that communicating alien civilizations last. The Milky Way is about 14 billion years old. If most intelligent, communicating civilizations last, say, a few hundred years at most, the chances that Earthlings will overlap with their communications is measly at best.

Solving the Drake equation isn't possible, because the values of most of the variables are unknown. But University of Nottingham astrophysicist Christopher Conselice and his colleagues were interested in taking a stab at it with new data about star formation and the existence of exoplanets, or planets that circle other stars outside our own solar system. They published their findings June 15 in The Astrophysical Journal.

Are there really 36 alien civilizations out there? Well, maybe. Stephanie Pappas, Live Science

Topics: Astrophysics, Atomic Physics, Cosmology, Philosophy

We are more alike than different. The atoms in our bodies are the same forged in distant stars; Carl Sagan said we are "made of star stuff."

Then: we evolve under ultraviolet light at degree inclinations on the globe, thereby changing the prominence of Melanin in our epidurals. Due to war and conquests, we craft a narrative of what is godly, who is "divine" and who is deviant. Good and evil has a hue or light and darkness. And thus, we craft the seeds of our own self-destruction from ignorance, hubris, racism, snobbery and xenophobia.

Star stuff should be better behaved.

View of the Alpha Centauri system. The bright binary star Alpha Centauri AB lies at the upper left. The much fainter red dwarf star Proxima Centauri is barely discernible towards the lower right of the picture. Credit: Digitized Sky Survey 2; Acknowledgement: Davide De Martin and Mahdi Zamani

Topics: Astronomy, Astrophysics, Exoplanets, Space Exploration

Astronomers May Have Captured the First Ever Image of Nearby Exoplanet Proxima C
Jonathan O'Callaghan, Scientific American

Burbidge, pictured with her husband and research partner, Geoffrey, was appointed to numerous leadership positions previously held only by men. | W.W. Girdner/Caltech Archives

Topics: Astronomy, Astrophysics, Diversity, Diversity in Science, Women in Science

In Memoriam:
Margaret Burbidge, Pioneering Astronomer and Advocate for Women in Science
Adam D. Cohen, American Association for the Advancement of Science

A cosmic homicide in action, with a wayward star being shredded by the intense gravitational pull of a black hole that contains tens of thousands of solar masses in an artist's impression obtained by Reuters April 2, 2020. NASA-ESA/D. Player/Handout via REUTERS.

Topics: Astrophysics, Black Holes, Cosmology, General Relativity, Hubble

Astronomers spot 'missing link' black hole - not too big and not too small
Will Dunham, Reuters Science

Over the past decade or so, astronomers have discovered a number of far-flung objects that all have very similar perihelia, meaning they make their closest approaches to the Sun at about the same location in space. One leading theory that attempts to explain the clustering is that a massive and unseen world known as Planet Nine hiding in the outer solar system. Fauxtoez/WikiMedia Commons

Topics: Astronomy, Astrophysics, Exoplanets, Space Exploration

Astronomers find 139 new minor planets in the outer solar system
Erica Naone, Astronomy