astrophysics (82)

Ancient Astronomy...

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Antikythera mechanism (Image), website, and publisher: Encyclopædia Britannica, https://www.britannica.com/topic/Antikythera-mechanism#/media/1/1334586/238592, access date: February 20, 2023

Topics: Archaeology, Astronomy, Astrophysics, History

In 1900 diver Elias Stadiatis, clad in a copper and brass helmet and a heavy canvas suit, emerged from the sea shaking in fear and mumbling about a “heap of dead naked people.” He was among a group of Greek divers from the Eastern Mediterranean island of Symi who were searching for natural sponges. They had sheltered from a violent storm near the tiny island of Antikythera, between Crete and mainland Greece. When the storm subsided, they dived for sponges and chanced on a shipwreck full of Greek treasures—the most significant wreck from the ancient world to have been found up to that point. The “dead naked people” were marble sculptures scattered on the seafloor, along with many other artifacts. Soon after, their discovery prompted the first major underwater archaeological dig in history.

One object recovered from the site, a lump the size of a large dictionary, initially escaped notice amid more exciting finds. Months later, however, at the National Archaeological Museum in Athens, the lump broke apart, revealing bronze precision gearwheels the size of coins. According to historical knowledge at the time, gears like these should not have appeared in ancient Greece or anywhere else in the world until many centuries after the shipwreck. The finding generated huge controversy.

The lump is known as the Antikythera mechanism, an extraordinary object that has befuddled historians and scientists for more than 120 years. Over the decades, the original mass split into 82 fragments, leaving a fiendishly difficult jigsaw puzzle for researchers to put back together. The device appears to be a geared astronomical calculation machine of immense complexity. Today we have a reasonable grasp of some of its workings, but there are still unsolved mysteries. We know it is at least as old as the shipwreck it was found in, which has been dated to between 60 and 70 B.C.E., but other evidence suggests it may have been made around 200 B.C.E.

One of the central researchers in the early years of Antikythera research was German philologist Albert Rehm, the first person to understand the mechanism as a calculating machine. Between 1905 and 1906, he made crucial discoveries that he recorded in his unpublished research notes. He found, for instance, the number 19 inscribed on one of the surviving Antikythera fragments. This figure referenced the 19-year period relation of the moon known as the Metonic cycle, named after Greek astronomer Meton but discovered much earlier by the Babylonians. On the same fragment, Rehm found the numbers 76, a Greek refinement of the 19-year cycle, and 223, for the number of lunar months in a Babylonian eclipse-prediction cycle called the saros cycle. These repeating astronomical cycles were the driving force behind Babylonian predictive astronomy.

The second key figure in the history of Antikythera research was British physicist turned historian of science Derek J. de Solla Price. In 1974, after 20 years of research, he published an important paper, “Gears from the Greeks.” It referred to remarkable quotations by the Roman lawyer, orator, and politician Cicero (106–43 B.C.E.). One of these described a machine made by mathematician and inventor Archimedes (circa 287–212 B.C.E.) “on which were delineated the motions of the sun and moon and of those five stars which are called wanderers ... (the five planets) ... Archimedes ... had thought out a way to represent accurately by a single device for turning the globe those various and divergent movements with their different rates of speed.” This machine sounds just like the Antikythera mechanism. The passage suggests that Archimedes, although he lived before we believe the device was built, might have founded the tradition that led to the Antikythera mechanism. It may well be that the Antikythera mechanism was based on a design by Archimedes.

An Ancient Greek Astronomical Calculation Machine Reveals New Secrets, Tony Freeth, Scientific American

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Planet Video...

 

Topics: Astronomy, Astrophysics, Exoplanets, Space Exploration

In 2008, HR8799 was the first extrasolar planetary system ever directly imaged. Now, the famed system stars in its very own video.

Using observations collected over the past 12 years, Northwestern University astrophysicist Jason Wang has assembled a stunning time-lapse video of the family of four planets — each more massive than Jupiter — orbiting their star. The video gives viewers an unprecedented glimpse into planetary motion.

“It’s usually difficult to see planets in orbit,” Wang said. “For example, it isn’t apparent that Jupiter or Mars orbit our sun because we live in the same system and don’t have a top-down view. Astronomical events happen too quickly or slowly to capture in a movie. But this video shows planets moving on a human time scale. I hope it enables people to enjoy something wondrous.”

An expert in exoplanet imaging, Wang is an assistant professor of physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).

Watch distant worlds dance around their sun, Amanda Morris, Northwestern University.

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Reimagining ET...

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Life on other planets might not look like any beings we’re used to on Earth. It may even be unrecognizable at first to scientists searching for it. Credit: William Hand

Topics: Astrobiology, Astronomy, Astrophysics, Planetary Science, SETI, Space Exploration

Sarah Stewart Johnson was a college sophomore when she first stood atop Hawaii’s Mauna Kea volcano. Its dried lava surface differed from the eroded, tree-draped mountains of her home state of Kentucky. Johnson wandered away from the other young researchers she was with and toward a distant ridge of the 13,800-foot summit. Looking down, she turned over a rock with the toe of her boot. To her surprise, a tiny fern lived underneath it, sprouting from ash and cinder cones. “It felt like it stood for all of us, huddled under that rock, existing against the odds,” Johnson says.

Her true epiphany, though, wasn’t about the hardiness of life on Earth or the hardships of being human: It was about aliens. Even if a landscape seemed strange and harsh from a human perspective, other kinds of life might find it quite comfortable. The thought opened up the cosmic real estate and the variety of life she imagined might be beyond Earth’s atmosphere. “It was on that trip that the idea of looking for life in the universe began to make sense to me,” Johnson says.

Later, Johnson became a professional at looking. As an astronomy postdoc at Harvard University in the late 2000s and early 2010s, she investigated how astronomers might use genetic sequencing—detecting and identifying DNA and RNA—to find evidence of aliens. Johnson found the work exciting (the future alien genome project!), but it also made her wonder: What if extraterrestrial life didn’t have DNA, RNA, or other nucleic acids? What if their cells got instructions in some other biochemical way?

As an outlet for heretical thoughts like this, Johnson started writing in style too lyrical and philosophical for scientific journals. Her typed musings would later turn into the 2020 popular science book The Sirens of Mars. Inside its pages, she probed the idea that other planets were truly other. So their inhabitants might be very different, at a fundamental and chemical level, from anything in this world. “Even places that seem familiar—like Mars, a place that we think we know intimately—can completely throw us for a loop,” she says. “What if that’s the life case?”

The Search for Extraterrestrial Life as We Don’t Know It, Sarah Scoles, Scientific American

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At Horizon's Edge...

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An artist’s concept of New Horizons during the spacecraft’s planned encounter with Pluto and its moon Charon. The craft’s miniature cameras, radio science experiments, ultraviolet and infrared spectrometers, and space plasma experiments would characterize the global geology and geomorphology of Pluto and Charon, map their surface compositions and temperatures, and examine Pluto’s atmosphere in detail. Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

Topics: Astronomy, Astrophysics, NASA, Planetary Science, Space Exploration

Only two spacecraft have ever left our solar system and lived to tell the tale. In 2012 and 2019, NASA’s Voyager 1 and 2 spacecraft respectively broke through the heliopause, the boundary at which our sun’s sphere of influence gives way to the interstellar medium. They have sent back remarkable riches from this distant location, humanity’s first foray into the limitless bounds beyond our solar system’s edge. Hot pursuit is a far more advanced vehicle, sporting improved instruments, updated optics, and even a means to sample the interstellar medium itself. New Horizons was launched from Earth in 2006 on a mission to visit Pluto, arriving in 2015 and revealing incredible details during its all-too-brief flyby. The spacecraft has continued its cruise toward interstellar frontiers ever since. It has now begun its second extended mission. It is soon set to wake up from a deep hibernation, opening a wealth of new scientific opportunities in the outer solar system. “It takes a long time to get to where our spacecraft is,” says Alice Bowman, mission operations manager for New Horizons at the Johns Hopkins University Applied Physics Laboratory (JHUAPL) in Maryland. “When you have a spacecraft that is out in that part of the solar system, it is a huge asset to the scientific community. There are so many unique things that a spacecraft that is out that far can do. We definitely want to take advantage of that.”

For New Horizons, those “unique things” include unprecedented studies of the planets Uranus and Neptune, sampling of the local dust, studies of the background light in the universe, and more. The sum total will be a new phase of the mission that is “really unique and interdisciplinary in nature,” says Alan Stern, the lead on the mission at the Southwest Research Institute (SwRI) in Texas. In October, this two-year second extended mission officially began, but in 2023 it will pick up the pace as the spacecraft exits hibernation and begins its scientific program in earnest. “There were lots of good ideas for how to do things in astrophysics, heliophysics, and planetary science,” Stern says. “We took the very best of those.” There is even the tantalizing possibility of visiting another object in the Kuiper Belt, the region of asteroids and icy objects that lurks beyond Neptune, in which New Horizons has already visited one object—Arrokoth in 2019—after its Pluto encounter. Even without such a possibility, there was more than enough reason for NASA to extend the mission. “New Horizons is at a unique location in the solar system with an amazing suite of functioning instruments on board,” says Becky McCauley Rench, New Horizons program scientist at NASA Headquarters in Washington, D.C. “[It] can provide valuable insights to the heliosphere and the solar wind, astronomical observations of the cosmic background radiation, and valuable data about Uranus and Neptune that can be applied to our knowledge about ice giant planets.”

NASA’s Pluto Spacecraft Begins New Mission at the Solar System’s Edge, Jonathan O'Callaghan, Scientific American

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Cosmic Family Portraits...

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Credit: NASA, ESA, CSA, and Jupiter ERS Team; Image processing by Ricardo Hueso/UPV/EHU and Judy Schmidt

Topics: Astronomy, Astrophysics, Planetary Science, Space Exploration

Jupiter's rings, its moons Amalthea (the bright point at left), Adrastea (the faint dot at the left tip of rings), and even background galaxies are visible in this image from JWST's NIRCam instrument. Whiter areas on the planet represent regions with more cloud cover, which reflects sunlight, especially Jupiter's famous Great Red Spot; darker spots have fewer clouds. Perhaps the most stunning feature is the blue glow of the planet's auroras at the north and south poles. This light shows results when high-energy particles streaming off the sun hit atoms in Jupiter's atmosphere. Auroras are found on any planet with an atmosphere and a magnetic field, which steers the sun's particles to the poles; besides Earth and Jupiter, telescopes have seen auroras on Saturn, Uranus, and Neptune.

The Best of JWST’s Cosmic Portraits, Clara Moskowitz, Scientific American

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Dinosaurs and Dodos...

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Credit: Andrzej Puchta/Alamy Stock Photo

Topics: Asteroids, Astronomy, Astrophysics, Civilization, Computer Modeling

The following article, since it simulated the destruction of my hometown, two days after my sixtieth birthday, is a little personal.

*****

On August 16, 2022, an approximately 70-meter asteroid entered Earth’s atmosphere. At 2:02:10 P.M. EDT, the space rock exploded eight miles over Winston-Salem, N.C., with the energy of 10 megatons of TNT. The airburst virtually leveled the city and surrounding area. Casualties were in the thousands.

Well, not really. The destruction of Winston-Salem was the storyline of the fourth Planetary Defense Tabletop Exercise, run by NASA’s Planetary Defense Coordination Office. The exercise was a simulation where academics, scientists, and government officials gathered to practice how the United States would respond to a real planet-threatening asteroid. Held February 23–24, participants were both virtual and in-person, hailing from Washington D.C., the Johns Hopkins Applied Physics Lab (APL) campus in Laurel, Md., Raleigh, and Winston-Salem, N.C. The exercise included more than 200 participants from 16 different federal, state, and local organizations. On August 5, the final report came out, and the message was stark: humanity is not yet ready to meet this threat.

On the plus side, the exercise was meant to be hard—practically unwinnable. “We designed it to fall right into the gap in our capabilities,” says Emma Rainey, an APL senior scientist who helped to create the simulation. “The participants could do nothing to prevent the impact.” The main goal was to test the different government and scientific networks that should respond in a real-life planetary defense situation. “We want to see how effective operations and communications are between U.S. government agencies and the other organizations that would be involved, and then identify shortcomings,” says Lindley Johnson, planetary defense officer at NASA headquarters.

NASA Asteroid Threat Practice Drill Shows We’re Not Ready, Matt Brady, Scientific American

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Death of Chrysalis...

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A view of Saturn from NASA's Hubble Space Telescope captures details of its ring system and atmospheric details on June 20, 2019. NASA, ESA, A. Simon (GSFC), M.H. Wong (University of California, Berkeley), and the OPAL Team/Handout via REUTERS

Topics: Astronomy, Astrophysics, NASA, Planetary Science

WASHINGTON, Sept 15 (Reuters) - Call it the case of the missing moon.

Scientists using data obtained by NASA's Cassini spacecraft and computer simulations said on Thursday the destruction of a large moon that strayed too close to Saturn would account both for the birth of the gas giant planet's magnificent rings and its unusual orbital tilt of about 27 degrees.

The researchers named this hypothesized moon Chrysalis and said it may have been torn apart by tidal forces from Saturn's gravitational pull perhaps 160 million years ago - relatively recent compared to the date of the planet's formation more than 4.5 billion years ago.

About 99% of the Chrysalis wreckage appears to have plunged into Saturn's atmosphere while the remaining 1% stayed in orbit around the planet and eventually formed the large ring system that is one of the wonders of our solar system, the researchers said. They chose the name Chrysalis for the moon because it refers to a butterfly's pupal stage before it transforms into its glorious adult form.

"As a butterfly emerges from a chrysalis, the rings of Saturn emerged from the primordial satellite Chrysalis," said Jack Wisdom, a professor of planetary science at the Massachusetts Institute of Technology and lead author of the study published in the journal Science.

Violent death of moon Chrysalis may have spawned Saturn's rings, Will Dunham, Reuters Science

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WASP-39b and CO2...

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Researchers detected carbon dioxide in WASP-39b’s atmosphere when the exoplanet crossed in front of its star. The data plot shows a telltale blip where infrared wavelengths from the star’s light were absorbed by carbon dioxide on the exoplanet. Credit: NASA, ESA, CSA, Leah Hustak (STScI), Joseph Olmsted (STScI)

Topics: Astrophysics, Chemistry, ESA, Exoplanets, James Webb Space Telescope, NASA

The James Webb Space Telescope — already famous for its mesmerizing images of the cosmos — has done it again. The telescope has captured the first unambiguous evidence of carbon dioxide in the atmosphere of a planet outside the Solar System.

The finding not only provides tantalizing hints about how the exoplanet formed but is also a harbinger for what’s to come as Webb studies more and more alien worlds. It was reported in a manuscript posted on the preprint server arXiv1, ahead of peer review, and is expected to be published in Nature in the coming days. (Nature’s news team is independent of its journals team.)

The discovery is presented in a data plot with none of the luster of Webb’s previous images — which showed galaxies locked in a cosmic dance and radiant clouds in a stellar nursery. But Jessie Christiansen, an astronomer at the NASA Exoplanet Science Institute at the California Institute of Technology in Pasadena, describes the data as “gorgeous”.

The plot, or spectrum, reveals detailed information about the atmosphere of the exoplanet WASP-39b, called a hot Jupiter by scientists because it has a diameter similar to Jupiter’s but orbits its star much more closely than Mercury orbits the Sun, making it incredibly hot. The planet, which is more than 200 parsecs from Earth, was initially discovered during ground-based observations2 and later detected by NASA’s Spitzer Space Telescope, which operated between 2003 and 2020. Data from the latter suggested3 that WASP-39b’s atmosphere might contain carbon dioxide, but they were inconclusive.

Webb telescope spots CO2 on exoplanet for first time: what it means for finding alien life, Sharron Hall, Nature

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Studying UAPs...

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Searches for alien civilizations often involve listening for radio transmissions from distant stars, but the possible extraterrestrial origins of UFOs have some scientists looking closer to home. Credit: Luc Novovitch/Alamy Stock Photo

Topics: Astrophysics, NASA, SETI

I was startled, to say the least, that this story appears in Scientific American, and that NASA and theoretical astrophysicist Avi Loeb is interested in it. The nut job "giggle factor" has given way to curiosity about things humans cannot explain, and that bothers us as a species.

My concern is if the question "are we alone?" has the answer "we are not," the next question is "why Earth?" What if the answer is "because we're someone's territory," and they regard Homo Sapiens (the only race we truly are) as a bipedal herd? That gives for the pilots of UAPs (if any found) humanity the same regard as we give a frog on a dissecting table.

On June 9, with only a few hours' notice, NASA held a press conference to announce a study it was commissioning on unidentified aerial phenomena (UAPs). The acronym is a rebranding of what is more popularly known as unidentified flying objects, or UFOs, a topic usually associated with purported extraterrestrial visitations and government conspiracy theories. The question on the public’s mind was why one of the U.S.’s premier scientific agencies was getting involved in something often considered to be at the farthest fringes of respectability.

Yet the pronouncement also fit in with the suddenly more open-minded zeitgeist regarding UAPs. Last year saw the publication of a much-anticipated report on the Department of Defense’s own investigations into the subject, following the release of first-person accounts and video from U.S. fighter pilots claiming to show encounters with strange objects in the skies. High-profile coverage in mainstream media and open congressional hearings about UAPs have kept the matter circulating in the public realm. A month after the Pentagon’s report came out, theoretical astrophysicist Avi Loeb, former chair of Harvard University’s astronomy department, announced a private initiative called the Galileo Project, which is aimed at searching for potential evidence of alien technology here on Earth.

What NASA can bring to this discussion is as yet unclear. The agency has set aside a slim $100,000 for the nine-month study—less than the typical funding it provides for exploratory studies of unconventional technologies such as space telescopes with kilometer-scale mirrors or interstellar probes propelled by giant laser beams. Helmed by the well-respected Princeton University astrophysicist David Spergel, the investigation intends to identify existing and future data sets scientists could use to advance their understanding of UAPs. Even if it uncovers little of interest, the study’s existence suggests that something the agency once avoided talking about at all costs is on the cusp of becoming an appropriate topic of inquiry.

With New Study, NASA Seeks the Science behind UFOs, Adam Mann, Scientific American

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Martians and Vulcans...

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(Credit: ktsdesign/Shutterstock)

Topics: Astrobiology, Astrophysics, Civilization, Existentialism, Philosophy, Special Relativity

The Cold War was a genesis of angst about the future due to the detonation of the atomic bomb by the Soviet Union in Kazakstan in 1949. After WWII (WWI was originally called, "the war to END all wars," until the sequel), the existential nervousness is understandable. Extraterrestrials, or musings about them, let humans off the hook if the Earth is rendered dystopic, and uninhabitable (with respect to "War of the Worlds" Martians), and some more advanced species to come to save us from our screw-ups (Star Trek Vulcans). Trek aliens that aren't that hospitable are the Gorn and Klingons. Neither of which I'd prefer to see on first contact. However, the vast distance between stars, relativistic speeds, and the drag of mass on even reaching a fraction of the speed of light make that possibility remote.

*****

In September 1961, Barney and Betty Hill were driving late at night in the mountains of New Hampshire when they saw a flying object whizzing in the sky. Barney thought it was a plane until he saw it swiftly switch directions.

According to The Interrupted Journey, the couple nervously continued driving until a spacecraft confronted them. They remembered seeing “humanoid-like” creatures and hearing pinging sounds reverberating off their car trunk. And then, they found themselves 35 miles further along on the highway with almost no memory of what had just transpired. They believed they had been abducted.

Scholars mark 1947 as the start of the UFO fascination. A pilot flying in the Cascade Mountains in Washington state reported seeing disc-shaped objects. In the next decade, aliens were primarily seen as benevolent, intelligent beings who came to Earth to offer advice or warnings.

In 1961, the Hills reported their abduction, and stories about aliens became more sinister. Social scientists, like famed psychologist Carl Jung, analyzed the UFO obsession and found it fit neatly with humans’ long fascination with heavenly ascents. Whereas past societies looked for angels, saints, or Gods to descend from the heavens, modern Americans were looking for “technological angels.”

Starting in the 1960s, aliens were both benign angels and menacing demons, which prompted some religious scholars to see UFO fixation as a modern religious movement.

Our Fascination With Aliens and When it All Started, Emilie Le Beau Lucchesi, Discover Magazine

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Heart of Darkness...

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The first direct image of the Milky Way's supermassive black hole shows an orange glowing ring — gas heated as it falls into the singularity — with the shadow of the black hole at the center. EHT Collaboration

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

In a triumph of observation and data processing, astronomers at the Event Horizon Telescope have captured the first-ever picture of the supermassive black hole at the center of the Milky Way Galaxy.

The black hole is named Sagittarius A* (pronounced “A-star”), and the reveal of its image received an international rollout this morning in simultaneous press conferences held by the National Science Foundation (NSF) at the National Press Club in Washington, D.C., and the European Southern Observatory headquarters in Garching, Germany.

The image represents 3.5 million gigabytes of data taken at millimeter wavelengths by eight radio telescopes around the world. “It took several years to refine our image and confirm what we had,” said Feryal Özel, an astronomer at the University of Arizona in Tucson, at the NSF press conference. “But we prevailed.”

Blackhole at the center of Milky Way imaged for the first time, Mark Zastrow, Astronomy

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Rogue Singularity...

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A lone black hole gives off no light - but its gravity does distort the path of light traveling around it. Ute Kraus (background Milky Way panorama: Axel Mellinger), Institute of Physics, Universität Hildesheim

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

Each second, a brand new baby black hole is born somewhere in the cosmos as a massive star collapses under its own weight.

But black holes themselves are invisible. Historically, astronomers have only been able to detect these stellar-mass black holes when they are acting on a companion.

Now, a team of scientists has made the first-ever confirmed detection of a stellar-mass black hole that’s completely alone. The discovery opens up the possibility of finding even more — an exciting prospect, considering there should be around 100 million such “rogue” black holes drifting through our galaxy unseen.

Relying on the neighbors

Black holes are difficult to find because they don’t shine like stars. Anything with mass warps the fabric of space-time, and the greater the mass, the more extreme the warp. Black holes pack so much mass into such a tiny area that space folds back in on itself. That means that if anything, even light, gets too close, its path will always bend back toward the center of the black hole.

Astronomers have found a couple hundred of these ghostly goliaths indirectly, by seeing how they influence their surroundings. They’ve identified around 20 black holes of the small, stellar-mass variety in our galaxy by watching as stars are devoured by invisible companions. As the black hole pulls matter from its neighbor, the material forms a swirling, glowing accretion disk that signals the black hole’s presence.

Astronomers detect the first potential 'rogue' black hole, Ashley Balzer, Astronomy Magazine

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Proxima Oceans...

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An artist’s impression of the newly discovered planet orbiting Proxima Centauri.Credit: ESO/L. Calçada

Topics: Astronomy, Astrophysics, Exoplanets, Space Exploration, Spaceflight

Astronomers have discovered a third planet orbiting Proxima Centauri, the star closest to the Sun. Called Proxima Centauri d, the newly spotted world is probably smaller than Earth and could have oceans of liquid water.

“It’s showing that the nearest star probably has a very rich planetary system,” says Guillem Anglada-Escudé, an astronomer at the Institute of Space Sciences in Barcelona, Spain, who led the team that, in 2016, discovered the first planet to be seen orbiting Proxima Centauri.

Astronomer João Faria and his collaborators detected Proxima Centauri d by measuring tiny shifts in the spectrum of light from the star as the planet’s gravity pulled at it during orbit. The team used a state-of-the-art instrument called the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) at the Very Large Telescope, a system of four 8.2-meter telescopes at the European Southern Observatory in Cerro Paranal, Chile. The results were published on 10 February in Astronomy & Astrophysics.

Earth-like planet spotted orbiting Sun’s closest star, Davide Castelvecchi, Nature

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Cosmic Existentialism...

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An illustration of a black hole and its event horizon. (Image credit: Nicholas Forder/Future Publishing)

Topics: Astronomy, Astrophysics, Black Holes, Cosmology, Einstein, General Relativity

"Small" black holes are estimated to make up 1% of the universe's matter.

Scientists have estimated the number of "small" black holes in the universe. And no surprise: It's a lot.

This number might seem impossible to calculate; after all, spotting black holes is not exactly the simplest task. Because there are as pitch-black as the space they lurk in, the light swallowing cosmic goliaths can be detected only under the most extraordinary circumstances — like when they're bending the light around them, snacking on the unfortunate gases and stars that stray too close, or spiraling toward enormous collisions that unleash gravitational waves.

But that hasn't stopped scientists from finding some ingenious ways to guess the number. Using a new method, outlined Jan. 12 in The Astrophysical Journal, a team of astrophysicists has produced a fresh estimate for the number of stellar-mass black holes — those with masses 5 to 10 times that of the sun — in the universe.

And it's astonishing: 40,000,000,000,000,000,000, or 40 quintillions, stellar-mass black holes populate the observable universe, making up approximately 1% of all normal matter, according to the new estimate.

So how did the scientists arrive at that number? By tracking the evolution of stars in our universe they estimated how often the stars — either on their own or paired into binary systems — would transform into black holes, said first author Alex Sicilia, an astrophysicist at the International School of Advanced Studies (SISSA) in Trieste, Italy.

40 quintillion stellar-mass black holes are lurking in the universe, a new study finds, Ben Turner, Space.com

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Dyson Sphere Feedback...

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Image: Artist’s impression of a Dyson sphere under construction. Credit: Steve Bowers.

Topics: Astronomy, Astrophysics, Dyson Sphere, SETI

Although the so-called Dysonian SETI has been much in the air in recent times, its origins date back to the birth of SETI itself. It was in 1960 – the same year that Frank Drake used the National Radio Astronomy Observatory in Green Bank, West Virginia to study Epsilon Eridani and Tau Ceti – that Freeman Dyson proposed the Dyson sphere. In fiction, Olaf Stapledon had considered such structures in his novel Star Maker in 1937. As Macy Huston and Jason Wright (both at Penn State) remind us in a recent paper, Dyson’s idea of energy-gathering structures around an entire star evolved toward numerous satellites around the star rather than a (likely unstable) single spherical shell.

We can’t put the brakes on what a highly advanced technological civilization might do, so both solid sphere and ‘swarm’ models can be searched for, and indeed have been, for in SETI terms we’re looking for infrared waste heat. And if we stick with Dyson (often a good idea!), we would be looking for structures orbiting in a zone where temperatures would range in the 200-300 K range, which translates into searching at about 10 microns, the wavelength of choice. But Huston and Wright introduce a new factor, the irradiation from the interior of the sphere onto the surface of the star.

This is intriguing because it extends our notions of Dyson spheres well beyond the habitable zone as we consider just what an advanced civilization might do with them. It also offers up the possibility of new observables. So just how does such a Dyson sphere return light back to a star, affecting its structure and evolution? If we can determine that, we will have a better way to predict these potential observables. As we adjust the variables in the model, we can also ponder the purposes of such engineering.

Think of irradiation as Dyson shell ‘feedback.’ We immediately run into the interesting fact that adding energy to a star causes it to expand and cool. The authors explain this by noting that total stellar energy is a sum of thermal and gravitational energies. Let’s go straight to the paper on this. In the clip below, E* refers to the star’s total energy, with Etherm being thermal energy:

When energy is added to a star (E increases), gravitational energy increases and thermal energy decreases, so we see the star expand and cool both overall (because Etherm is lower) and on its surface (because being larger at the same or a lower luminosity its effective temperature must drop). A larger star should also result in less pressure on a cooler core, so we also expect its luminosity to decrease.

Dyson Sphere ‘Feedback’: A Clue to New Observables? Paul Gilster, Centauri Dreams

Evolutionary and Observational Consequences of Dyson Sphere Feedback, Macy Huston, Jason Wright, Astrophysical Journal

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Exomoon Two...

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Artist’s impression of an exomoon (left) orbiting a giant planet around a distant star. Credit: Helena Valenzuela Widerström

Topics: Astronomy, Astrophysics, Exomoon, Exoplanets

And then there were two—maybe. Astronomers say they have found a second plausible candidate for a moon beyond our solar system, an exomoon, orbiting a world nearly 6,000 light-years from Earth. Called Kepler-1708 b-i, the moon appears to be a gas-dominated object, slightly smaller than Neptune, orbiting a Jupiter-sized planet around a sunlike star—an unusual but not wholly unprecedented planet-moon configuration. The findings appear in Nature Astronomy. Confirming or refuting the result may not be immediately possible, but given the expected abundance of moons in our galaxy and beyond, it could further herald the tentative beginnings of an exciting new era of extrasolar astronomy—one focused not on alien planets but on the natural satellites that orbit them and the possibilities of life therein.

There are more than 200 moons in our solar system, and they have an impressive array of variations. Saturn’s moon Titan possesses a thick atmosphere and frigid hydrocarbon seas on its surface, possibly an analog of early Earth. Icy moons such as Jupiter’s Europa are frozen balls that hide subsurface oceans, and they may be prime habitats for life to arise. Others still, such as our own moon, are apparently barren wastelands but could have water ice in their shadowed craters and maze-like networks of tunnels running underground. An important shared trait among these worlds, however, is their mere existence: six of the eight major planets of our solar system have moons. Logic would suggest the same should be true elsewhere. “Moons are common,” says Jessie Christiansen of the California Institute of Technology. “In our solar system, almost everything has a moon. I am very confident that moons are everywhere in the galaxy.”

Astronomers Have Found Another Possible ‘Exomoon’ beyond Our Solar System, Jonathan O'Callaghan, Scientific American

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Moments and Metaphors...

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Credit: Pete Saloutos/Getty Images

Topics: Astronomy, Astrophysics, Comets, Philosophy, Science Fiction

On a recent morning, in Lower Manhattan, 20 scientists, including me, gathered for a private screening of the new film Don’t Look Up, followed by lunch with the film’s director, Adam McKay.

The film’s plot is simple. An astronomy graduate student, Kate Dibiasky (Jennifer Lawrence), and her professor, Randall Mindy (Leonardo DiCaprio), discover a new comet and realize that it will strike the Earth in six months. It is about nine kilometers across, like the one that wiped out the dinosaurs 66 million years ago. The astronomers try to alert the president, played by Meryl Streep, to their impending doom.

“Let’s just sit tight and assess,” she says, and an outrageous, but believable comedy ensues, in which the astronomers wrangle an article in a major newspaper and are mocked on morning TV, with one giddy host asking about aliens and hoping that the comet will kill his ex-spouse.

At last, mainstream Hollywood is taking on the gargantuan task of combatting the rampant denial of scientific research and facts. Funny, yet deadly serious, Don’t Look Up is one of the most important recent contributions to popularizing science. It has the appeal, through an all-star cast and wicked comedy, to reach audiences that have different or fewer experiences with science.

Don’t Look Up isn’t a movie about climate change, but one about planetary defense from errant rocks in space. It handles that real and serious issue effectively and accurately. The true power of this film, though, is in its ferocious, unrelenting lampooning of science deniers.

After the screening, in that basement theater in SoHo, McKay said: “This film is for you, the scientists. We want you to know that some of us do hear you and do want to help fight science denialism.”

Hollywood Can Take On Science Denial: Don’t Look Up Is a Great Example, Rebecca Oppenheimer, curator, and professor of astrophysics at the American Museum of Natural History/Scientific American

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From Redshift to Enlightenment...

Topics: Astrobiology, Astronomy, Astrophysics, Carl Sagan, James Webb Space Telescope, SETI

The relief was as deep as the stakes were high. At 7:20 A.M. (ET), the rocket carrying the largest, most ambitious space telescope in history cleared the launchpad in French Guiana, and the members of mission control at the Space Telescope Science Institute in Baltimore roared their elation.

The suspense was not quite over. Half an hour postlaunch, the telescope still needed to decouple from its host rocket, after which it had to deploy solar panels to partly power its journey. Only after that first deployment proved successful, said a NASA spokesperson in a statement to Scientific American, would “we know we have a mission.”

Astronomers have more riding on the rocket than the James Webb Space Telescope (JWST). Also at risk is the viability of NASA’s vast space-science portfolio, if not the future of astronomy itself. As the successor to the Hubble Space Telescope (HST), JWST is one of those once-in-a-generation scientific projects that can strain the patience of government benefactors, as well as the responsible agency’s credibility, but also define a field for decades to come—and possibly redefine it forever.

The telescope that would become JWST was already under discussion even before HST launched in April 1990. By orbiting Earth, HST would have a line of sight free of the optical distortions endemic to our planet’s atmosphere. It would therefore be able to see farther across the universe (and, given that the speed of light is finite, farther back in time) than any terrestrial telescope.

The James Webb Space Telescope Has Launched: Now Comes the Hard Part, Richard Panek, Scientific American

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Kilonovas and Gold...

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Artist's impression of a neutron-star merger (Courtesy: NASA)

Topics: Astronomy, Astrophysics, Chemistry, Materials Science, Neutron Stars

The amounts of heavy elements such as gold created when black holes merge with neutron stars have been calculated and compared with the amounts expected when pairs of neutron stars merge. The calculations were done by Hsin-Yu Chen and Salvatore Vitale at the Massachusetts Institute of Technology and Francois Foucart at the University of New Hampshire using advanced simulations and gravitational-wave observations made by the LIGO–Virgo collaboration. Their results suggest that merging pairs of neutron stars are likely to be responsible for more heavy elements in the universe than mergers of black holes with neutron stars.

Today, astrophysicists have an incomplete understanding of how elements heavier than iron are made. In this nucleosynthesis process, lighter nuclei must be able to capture neutrons from their surroundings. Astrophysicists believe this can happen in two ways, each producing about half of the heavy elements in the universe. These are the slow process (s-process) that occurs in large stars and the rapid process (r-process), which is believed to occur in extreme conditions such as the explosion of a star in a supernova. However, exactly where the r-process can take place is hotly debated.

One event that could support the r-process is the merger of a pair of neutron stars, which can result in a huge explosion called a kilonova. Indeed, such an event was seen by LIGO–Virgo in 2017, and simultaneous observations using light-based telescopes suggest that heavy elements were created in that event.

Merging neutron stars create more gold than collisions involving black holes, Sam Jarman, Physics World

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J0030...

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The pulsar J0030 appears to have two to three hotspots on its southern hemisphere only – finding astronomers didn’t expect.
NASA’s Goddard Space Flight Center/CI Lab
(animation on the page link below)

Topics: Astronomy, Astrophysics, NASA, Neutron Stars, Pulsars

NASA’s NICER instrument reveals that neutron stars are not as simple as we thought.

Pulsars are the lighthouses of the universe. These tiny, compact objects are neutron stars — the remnants of once-massive stars — that spin rapidly, beaming radiation into space. Now, for the first time, astronomers have mapped the surface of a 16-mile-wide pulsar in exquisite detail. The discovery calls into question astronomers’ textbook depiction of pulsar appearance and opens the door to learning more about these extreme objects.

The Neutron star Interior Composition Explorer, or NICER, searches for X-rays from extreme astronomical objects such as pulsars from its perch on the exterior of the International Space Station. Researchers used NICER to observe the pulsar J0030+0451, or J0030 for short, which is located 1,100 light-years away in the constellation Pisces, in a series of papers published in The Astrophysical Journal Letters. Two teams, one led by researchers at the University of Amsterdam and the other by researchers at the University of Maryland, used X-ray light from J0030 to map the pulsar’s surface and calculate its mass. Both teams arrived at a conclusion that was unexpected.

A New Picture

What the teams found presented a different picture: J0030 has two or three hotspots, all of which are located in the southern hemisphere. The researchers at the University of Amsterdam believe the pulsar has one small, circular spot and one thin, crescent-shaped spot spinning around its lower latitudes. The University of Maryland team discovered that the X-rays could be coming from two oval spots in the star’s southern hemisphere, as well as one cooler spot near the star’s south pole.

Neither result is the simple picture astronomers expected, indicating that the pulsar’s magnetic field, which causes the hotspots, is likely even more complex than originally assumed. While the result certainly leaves astronomers wondering, “It tells us NICER is on the right path to help us answer an enduring question in astrophysics: What form does matter take in the ultra-dense cores of neutron stars?” NICER science lead and study co-author Zaven Arzoumanian said in a press release.

Astronomers Map a Neutron Star’s Surface for the First Time, Ignat, I Love the Universe

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