BLOGS

Source: Same source for the Dark Matter definition below.

Topics: Astronomy, Astrophysics, Cosmology, Dark Matter, Einstein, General Relativity

Note: Your "secret decoder ring" for reading the Abstract.

Dark matter: It makes up about 85% of the universe, is invisible, and doesn't interact with matter except for gravitational effects. See: Center for Astrophysics, Harvard

"Tachyonic": Of, or referring to tachyons, (Greek for swift) theoretical particles that already travel faster-than-light and backward in time. Their rest mass, m₀ⁱ, is assumed to be imaginary. As it loses energy, it's assumed to become infinitely fast, so you can see why it's a favorite science fiction trope, along with dark matter, literally tableau rasas.

ΛCDM assumes that the universe is composed of photons, neutrinos, ordinary matter (baryons, electrons), and cold (non-relativistic) dark matter, which only interacts gravitationally, plus "dark energy," which is responsible for the observed acceleration in the Hubble expansion. Source: Goddard Spaceflight Center: Lambda

H₀ defines the Hubble constant, or, the rate at which the universe is expanding, determined by Hubble in the way back year of 1929 to be 500 km/s/Mpc. I'm going to defer to Wikipedia for this one.

km/s/Mpc = kilometers/second/megaparsec. Megaparsec is 1 million parsecs = 3,260,000 light years, or 3.26 x 10⁶ light years.

t₀ = the present age of the universe, t₀ = 2tH/3, where "tH" is the Hubble time. t₀ is roughly 13.7 × 10⁹ years, or 4.32 × 10¹⁷ seconds.

Gyr = giga years, or 1 billion years = 1 x 10⁹ years (a lot).

Abstract

An open or hyperbolic Friedmann-Robertson-Walker spacetime dominated by tachyonic dark matter can exhibit an “inflected” expansion—initially decelerating, later accelerating—similar but not identical to that of now-standard ΛCDM models dominated by dark energy. The features of the tachyonic model can be extracted by fitting the redshift-distance relation of the model to data obtained by treating Type Ia supernovae as standard candles. Here such a model is fitted to samples of 186 and 1048 Type Ia supernovae from the literature. The fits yield values of H₀ = (66.6±1.5) km/s/Mpc and H₀ = (69.6±0.4) km/s/Mpc, respectively, for the current-time Hubble parameter, and t₀ = (8.35 ± 0.68) Gyr and t₀ = (8.15 ± 0.36) Gyr, respectively, for the comoving-time age of the Universe. Tests of the model against other observations will be undertaken in subsequent works.

Subject headings: cosmology, dark matter, tachyons, distance-redshift relation, supernovae

Testing Tachyon-Dominated Cosmology with Type Ia Supernovae, Samuel H. Kramer, Ian H. Redmount, Physics arXiv

Topics: Astronomy, Astrophysics, Carl Sagan, Civilization, Existentialism, Star Wars, Star Trek, STEM

Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon. Commander Neil Armstrong and Lunar Module Pilot Buzz Aldrin landed the Apollo Lunar Module Eagle on July 20, 1969, at 20:17 UTC, and Armstrong became the first person to step onto the Moon's surface six hours and 39 minutes later, on July 21 at 02:56 UTC. Aldrin joined him 19 minutes later, and they spent about two and a quarter hours together exploring the site they had named Tranquility Base upon landing. Armstrong and Aldrin collected 47.5 pounds (21.5 kg) of lunar material to bring back to Earth as pilot Michael Collins flew the Command Module Columbia in lunar orbit, and were on the Moon's surface for 21 hours, 36 minutes before lifting off to rejoin Columbia.

Apollo 11 was launched by a Saturn V rocket from Kennedy Space Center on Merritt Island, Florida, on July 16 at 13:32 UTC, and it was the fifth crewed mission of NASA's Apollo program. The Apollo spacecraft had three parts: a command module (CM) with a cabin for the three astronauts, the only part that returned to Earth; a service module (SM), which supported the command module with propulsion, electrical power, oxygen, and water; and a lunar module (LM) that had two stages—a descent stage for landing on the Moon and an ascent stage to place the astronauts back into lunar orbit. Source: Wikipedia/Apollo_11

The first communal experience I recall is one now doubted by people swearing they "have the proof" in grainy YouTube videos and that I should "do my research!" Yeah.

June 3, 1969, the third and final season of Star Trek: The Original Series aired "Turnabout Intruder," its 24th and last episode. There was no "final curtain" or neatly wrapped-up script tying plot points. Many of us fans were left adrift. Syndication made the franchise a legend.

In July of 1969, I was six, one month from turning seven years old. In my maturity, then, there were a few priorities: eating, sleeping, playing, and cartoons.

My cartoons were interrupted on July 19, 1969, a Saturday ritual that any kids born after 2014 are bereft of the experience. It was my "chill time" to not think of the pending school year starting a few days after my birthday in August, which is probably why I've never made a big deal about my birthday. My cartoons were interrupted. I was missing "Tom and Jerry," "Woody Woodpecker," "Bugs Bunny," "The Herculoids," and I was pissed!

I calmed down, seeing that my parents were transfixed to the black and white TV.

A year and a few months before, we were transfixed after the assassination of Dr. Martin Luther King, Jr., the cities burning with the rage I would later see in Los Angeles with Rodney King. We were transfixed in our communal mourning.

This transfixion has been repeated over and over again, as if society has us as sadistic voyeurs in a play, we are constantly made to see in a culturally communal act of PTSD.

I started recognizing that Apollo 11 didn't have Nacelles that combined matter-antimatter for faster-than-light space travel. Before Star Wars, George Lucas, and Industrial Light and Magic, warp speed was indicated by a theatrical "swooshing" sound as the Enterprise's saucer section sped by intro and exit credits. The silvery capsule and landing module were attached to each other, and it detached with mechanical efficiency and elegance. No sound travels in space, and none was needed to communicate to me that before Zephram Cochrane, or someone like him, is to be born, this is the first small step.

I tried to communicate this feeling to my youngest son. He sent a video of how dark it momentarily got in Dallas, Texas. He and his girlfriend spoke briefly about how dark it became. My oldest was geeked and profoundly moved as our daughter-in-law made sure they had similar safety shades in Texas that we used to view it. In Greensboro, we got about 84% of the eclipse: it was dim but not dark, but my Texas box turtle, Speedy, went to sleep instinctively. My wife is now determined to follow the next eclipse on the planet so long as we can afford it. Our granddaughter is days from turning five, and the daycare opted to keep the children inside for safety concerns. She is sure to ask "Mimi and Paw-Paw" about it.

I lament that this is the last season of Star Trek: Discovery, just as I will lament the last season of Star Trek: Strange New Worlds. As a "Trekkie," I watched the franchise's iterations on free network TV. It made Trek accessible, at least to people who were channel-surfing that they might stop and peek into the future, exposure to STEM through fictional drama. I think this exposure to the possible created the communal experience that a boy in East Winston could share with his parents and people in Rural Hall, North Carolina, during a time before forced busing when I would meet others who didn't look like me.

I begrudgingly bought subscriptions to view it and the other iterations on Paramount Plus.

But streaming services, newsfeeds on social media, AM Talk Radio, and Podcasts do not create "communal experiences": they create silos, isolation, and tribalism.

Posting on Facebook, I said: "A communal experience. The universe experienced and witnessed itself." I said it without context regarding the eclipse. Here is the context:

"The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of 'star-stuff.'"

"The cosmos is within us. We are made of star stuff. We are a way for the universe to know itself."

Carl Sagan, "Cosmos"

“Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there-on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot.

Our posturing's, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.”
― Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space

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

There will be a partial eclipse here in Greensboro. I purchased these glasses (six pairs) in 2017 for ANOTHER partial eclipse that I missed due to working in the lab during my first year in grad school. Nano took precedence over Astro. According to Time and Date dot com, the current show starts around 1:56 p.m. and ends around 4:28 p.m.

I will look particularly at my Texas box turtle, "Speedy," to see how she reacts when the show starts. Animals tend to go into their shelters (which she has a faux log she likes to go under) during the eclipse because it looks like night. She's far more accurate than Punxsutawney Phil. I've never fully understood the legend and lore, but like many practices that make the world scratch its heads, this is a "thing" in America.

Oh, and its not a sign of the Apocalypse. Solar and lunar eclipses are natural occurrences that, unfortunately, superstition has promoted for whatever reason to disastrous results. It comes with the territory of having a moon. Venus, an oven that would make Hell blush, as far as we know, doesn't have a moon, and if we were to colonize Mars, it has two.

(Image: (c) Alan Dyer/VW Pics/UIG Getty Image)

On April 8, 2024, a total solar eclipse will be visible across North America. 

Our total eclipse 2024 guide tells you everything you need to know about the phenomenon from where to see it it to why it's so special. If you can't catch the eclipse in person you can watch the total solar eclipse live here on Space.com. 

During a total eclipse, the moon appears almost exactly the same size as the sun and blocks the entire disk for a few minutes — known as totality. 

The 115-mile-wide (185 kilometers) path of totality will cross three states in Mexico, 15 U.S. states and four states in southeast Canada.

A total solar eclipse is coming to North America. Daisy Dobrijevic, Contributions from Brett Tingley, Space.com

A new image from the Event Horizon Telescope has revealed powerful magnetic fields spiraling from the edge of a supermassive black hole at the center of the Milky Way, Sagittarius A*.

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

Physicists have been confident since the 1980s that there is a supermassive black hole at the center of the Milky Way galaxy, similar to those thought to be at the center of most spiral and elliptical galaxies. It has since been dubbed Sagittarius A* (pronounced A-star), or SgrA* for short. The Event Horizon Telescope (EHT) captured the first image of SgrA* two years ago. Now the collaboration has revealed a new polarized image (above) showcasing the black hole's swirling magnetic fields. The technical details appear in two new papers published in The Astrophysical Journal Letters.

"The new picture of Sgr A* compared to the old one shows the advantages of using a paintbrush rather than a crayon," Maynooth University cosmologist Peter Coles said on BlueSky. The new image is also strikingly similar to another EHT polarized image of a larger supermassive black hole, M87*, so this might be something that all such black holes share.

The only way to "see" a black hole is to image the shadow created by light as it bends in response to the object's powerful gravitational field. As Ars Science Editor John Timmer reported in 2019, the EHT isn't a telescope in the traditional sense. Instead, it's a collection of telescopes scattered around the globe. The EHT is created by interferometry, which uses light in the microwave regime of the electromagnetic spectrum captured at different locations. These recorded images are combined and processed to build an image with a resolution similar to that of a telescope the size of the most distant locations. Interferometry has been used at facilities like ALMA (the Atacama Large Millimeter/submillimeter Array) in northern Chile, where telescopes can be spread across 16 km of desert.

Event Horizon Telescope captures stunning new image of Milky Way’s black hole, Jennifer Ouellette, Ars Technica.

Avi Loeb, a Harvard University astrophysicist, displays a small vial of material recovered from the floor of the Pacific Ocean. The material, Loeb says, includes fragments of a meteorite that he claims came from another star system—and perhaps even from an alien spacecraft. Credit: Anibal Martel/Anadolu Agency via Getty Images

Topics: Astronomy, Astrophysics, Civilization, Cosmology, Existentialism, Theoretical Physics

Reanalysis of a meteor that fell to Earth has cast some doubt on its origin—and its final destination.

This much is certain: on January 8, 2014, an object now cataloged as CNEOS 2014-01-08 entered Earth’s atmosphere somewhere overhead off the northern coast of Papua New Guinea in the South Pacific, heating to become a blazing, shockwave-generating fireball during its plunge from space. Such events are not rare; meteors enter our atmosphere all the time. But estimates of the object’s speed, touted at some 45 kilometers per second, led to suggestions that it might be interstellar in origin—a space rock from some alien and distant planetary system. While we have seen interstellar objects passing through our solar system before, no such objects were known to have ever made planetfall on Earth. So interest in CNEOS 2014-01-08 was piqued, given that its fragments could potentially offer a first direct sample of material sourced from another star.

In June 2023 Avi Loeb—a theoretical physicist at Harvard University—mounted a $1.5-million expedition to find pieces of the meteor. Loeb has been the leading proponent of the notion that this meteor was indeed interstellar in origin—and has even speculated that it may be linked to putative alien spacecraft. His recovery expedition—which was part of his UFO-studying Galileo Project—became a public sensation, further padding Loeb’s already long list of high-profile media spots, which included interviews on prime-time national television shows and with the easily enraptured podcast host Joe Rogan. Loeb has written countless blog posts and a bestselling book on his unorthodox approach to studying extraterrestrial life and intelligence. He has even gone so far as to appear on a giant billboard in Times Square promoting the Galileo Project’s efforts to find the interstellar meteor fragments.

His approach to the topic has, at times, been abrasive, and many other astrobiology-inclined researchers have found his sensational claims too difficult to parse and potentially damaging to their field. But as with any scientific investigation, particularly with findings as provocative as those suggested by Loeb, there is invariably interest in trying to find flaws in the methodology and to offer alternative, more plausible solutions. This latest episode is no exception; it focuses on one very specific data point from this purported interstellar object.

Loeb’s recovery expedition used a boat-dragged magnetic “sled” to scrape samples of sediments from strips of seafloor in an 11-kilometer-wide square where the team believed the meteor had fallen. That zone of inquiry primarily emerged from triangulating the meteor’s presumptive debris field using sensor data from a classified network of U.S. military satellites that were scrubbed of sensitive details and made public as part of NASA’s Center for Near Earth Object Studies (CNEOS). Loeb’s pinpointing also used a local seismometer on Manus Island, Papua New Guinea, which recorded vibrations from an event around the time the meteor supposedly entered the atmosphere to reduce the search area to a strip that was one-kilometer wide.

After studying those seismometer data, however, Benjamin Fernando, a planetary scientist at Johns Hopkins University, has concluded that Loeb’s analysis was flawed. The seismometer, Fernando says, recorded not a celestial object but something much more mundane and closer to home—a passing heavy truck—meaning that the location Loeb and his team searched would not have been in the path of the falling object. “We think that what they picked up from the seafloor is nothing to do with this meteor at all,” says Fernando, who posted the research on the preprint server arXiv.org and presented it at the Lunar and Planetary Science Conference (LPSC) in Texas on Tuesday, March 12.

Fernando and his colleagues maintain that the seismic spike used by Loeb’s team was decidedly similar to other signals likely caused by “cultural noise”—that is, vibrations from vehicles and other hefty, human-made sources. A signal’s polarization can be used to estimate the direction of the source, and in this case, it suggested a movement from “southwest to north over about 100 seconds,” Fernando says. That matches the orientation of a road near the seismometer that runs to a local hospital and aligns with another matching signal that perhaps came from the same vehicular source that was detected earlier in the day (when no known fireballs were overhead). “It’s actually just a truck driving by,” he says. Using information from a separate network of infrasound sensors meant to look for clandestine atomic explosions as part of the Comprehensive Nuclear-Test-Ban Treaty, Fernando and his team provide a different entry point for the meteor some 170 kilometers from where Loeb’s group searched. They also argue that the meteor mostly burned up in the atmosphere anyway, scattering few, if any, notable pieces onto the land or sea below. “You wouldn’t go looking for bits of a firework,” Fernando says.

In the list of logical fallacies, I found unfortunately two (depending on the source, the total list can number 20, 24, more, etc.), that I reflected on as I read this article: "Hasty Generalization," and "Ought-Is."

Hasty Generalization means what this looks like, drawing some really spectacular conclusions on what appears to be limited evidence. The second, "Ought-Is," along with the recent scandal of 10,000 papers retracted in 2023 due to (I think) the pressure to "see your name(s)" in high-impact journals, has taken on the similitude of getting "likes" on social media, and has put the scientific enterprise, the hallmark of the Enlightenment, in crisis. "Ought-Is" fallacies are another word for wishful thinking. At that point, scientific progress grinds to a halt, and we slowly start limping back to the dark ages.

"The Demon-Haunted World: Science as a Candle in the Dark," by Carl Sagan (1995).

The demons appear to be winning.

‘Interstellar’ Meteor Signal May Have Been a Truck—So What Was Collected from the Ocean Floor? Jonathan O'Callaghan, Scientific American

Topics: Astronomy, Astrophysics, Dark Matter, Research, Theoretical Physics

Dark matter, composed of particles that do not reflect, emit, or absorb light, is predicted to make up most of the matter in the universe. However, its lack of interactions with light prevents its direct detection using conventional experimental methods.

Physicists have been trying to devise alternative methods to detect and study dark matter for decades, yet many questions about its nature and its presence in our galaxy remain unanswered. Pulsar Timing Array (PTA) experiments have been trying to probe the presence of so-called ultralight dark matter particles by examining the timing of an ensemble of galactic millisecond radio pulsars (i.e., celestial objects that emit regular millisecond-long radio wave pulses).

The European Pulsar Timing Array, a multinational team of researchers based at different institutes that are using 6 radio-telescopes across Europe to observe specific pulsars, recently analyzed the second wave of data they collected. Their paper, published in Physical Review Letters, sets more stringent constraints on the presence of ultralight dark matter in the Milky Way.

"This paper was basically the result of my first Ph.D. project," Clemente Smarra, co-author of the paper, told Phys.org. "The idea arose when I asked my supervisor if I could carry out research focusing on gravitational wave science, but from a particle physics perspective. The main aim of the project was to constrain the presence of the so-called ultralight dark matter in our galaxy."

Ultralight dark matter is a hypothetical dark matter candidate, made up of very light particles that could potentially address long-standing mysteries in the field of astrophysics. The recent study by Smarra and his colleagues was aimed at probing the possible presence of this type of dark matter in our galaxy via data collected by the European Pulsar Timing Array.

"We were inspired by previous efforts in this field, especially by the work of Porayko and her collaborators," Smarra said. "Thanks to the longer duration and the improved precision of our dataset, we were able to put more stringent constraints on the presence of ultralight dark matter in the Milky Way,"

The recent paper by the European Pulsar Timing Array makes different assumptions than those made by other studies carried out in the past. Instead of probing interactions between dark matter and ordinary matter, it assumes that these interactions only occur via gravitational effects.

"We assumed that dark matter interacts with ordinary matter only through gravitational interaction," Smarra explained. "This is a rather robust claim: in fact, the only sure thing we know about dark matter is that it interacts gravitationally. In a few words, dark matter produces potential wells in which pulsar radio beams travel. But the depth of these wells is periodic in time; therefore, the travel time of the radio beams from pulsars to the Earth changes with a distinctive periodicity as well."

New constraints on the presence of ultralight dark matter in the Milky Way, Ingrid Fadelli, Phys.org.

Artist's depiction of an extra-solar system that is crowded with giant planets. Credit: NASA/Dana Berry

Topics: Astronomy, Astrophysics, Planetary Science, Space Exploration

Giant gas planets can be agents of chaos, ensuring nothing lives on their Earth-like neighbors around other stars. New studies show in some planetary systems, the giants tend to kick smaller planets out of orbit and wreak havoc on their climates.

Jupiter, by far the biggest planet in our solar system, plays an important protective role. Its enormous gravitational field deflects comets and asteroids that might otherwise hit Earth, helping create a stable environment for life. However, giant planets elsewhere in the universe do not necessarily protect life on their smaller, rocky planet neighbors.

An Astronomical Journal paper details how the pull of massive planets in a nearby star system is likely to toss their Earth-like neighbors out of the "habitable zone." This zone is defined as the range of distances from a star that are warm enough for liquid water to exist on a planet's surface, making life possible.

Unlike most other known solar systems, the four giant planets in HD 141399 are farther from their star. This makes it a good model for comparison with our solar system, where Jupiter and Saturn are also relatively far from the sun.

"It's as if they have four Jupiters acting like wrecking balls, throwing everything out of whack," said Stephen Kane, UC Riverside astrophysicist and author of the journal paper.

Taking data about the system's planets into account, Kane ran multiple computer simulations to understand the effect of these four giants. He wanted specifically to look at the habitable zone in this star system and see if an Earth could remain in a stable orbit there.

Giant planets cast a deadly pall: How they can prevent life in other solar systems, Jules Bernstein, University of California - Riverside, Phys.org.

Image source: Link below

Topics: Applied Physics, Astrophysics, Computer Modeling, Einstein, High Energy Physics, Particle Physics, Theoretical Physics

In the search for new physics, a new kind of scientist is bridging the gap between theory and experiment.

Traditionally, many physicists have divided themselves into two tussling camps: the theorists and the experimentalists. Albert Einstein theorized general relativity, and Arthur Eddington observed it in action as “bending” starlight; Murray Gell-Mann and George Zweig thought up the idea of quarks, and Henry Kendall, Richard Taylor, Jerome Freidman and their teams detected them.

In particle physics especially, the divide is stark. Consider the Higgs boson, proposed in 1964 and discovered in 2012. Since then, physicists have sought to scrutinize its properties, but theorists and experimentalists don’t share Higgs data directly, and they’ve spent years arguing over what to share and how to format it. (There’s now some consensus, although the going was rough.)

But there’s a missing player in this dichotomy. Who, exactly, is facilitating the flow of data between theory and experiment?

Traditionally, the experimentalists filled this role, running the machines and looking at the data — but in high-energy physics and many other subfields, there’s too much data for this to be feasible. Researchers can’t just eyeball a few events in the accelerator and come to conclusions; at the Large Hadron Collider, for instance, about a billion particle collisions happen per second, which sensors detect, process, and store in vast computing systems. And it’s not just quantity. All this data is outrageously complex, made more so by simulation.

In other words, these experiments produce more data than anyone could possibly analyze with traditional tools. And those tools are imperfect anyway, requiring researchers to boil down many complex events into just a handful of attributes — say, the number of photons at a given energy. A lot of science gets left out.

In response to this conundrum, a growing movement in high-energy physics and other subfields, like nuclear physics and astrophysics, seeks to analyze data in its full complexity — to let the data speak for itself. Experts in this area are using cutting-edge data science tools to decide which data to keep and which to discard and to sniff out subtle patterns.

Opinion: The Rise of the Data Physicist, Benjamin Nachman, APS News

The sample return capsule from NASA's OSIRIS-REx mission is seen shortly after touching down in the desert at the Department of Defense's Utah Test and Training Range. Keegan Barber/NASA

Topics: Asteroids, Astrobiology, Astrophysics, NASA, Space Exploration

Scientists are exulting over the safe arrival of a canister containing about a cup's worth of asteroid rocks, collected 200 million miles away, that landed in a Utah desert after a 7-year NASA mission sent to retrieve them.

The black pebbles and dirt are older than Earth and are undisturbed remnants of the solar system's early days of planet formation. As part of an asteroid named Bennu, these rocks traveled unsullied through space for eons.

While bits of asteroids regularly fall to our planet as meteorites, scientists want to study pristine asteroid material, stuff that's uncontaminated by our planet, to understand the early chemistry that might have contributed to the emergence of life.

NASA asteroid sample lands safely in Utah before being whisked away by helicopter, Nell Greenfieldboyce, NPR

Artist's conception of the dwarf planet Sedna in the outer edges of the known solar system. (Image credit: NASA/JPL-Caltech/R. Hurt (SSC))

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

Astronomers are racing to explain the peculiar orbits of faraway objects at the edge of our solar system.

Among the many mysteries that make the furthest reaches of our solar system, well, mysterious, is the exceptionally egg-shaped path of a dwarf planet called 90377 Sedna.

Its 11,400-year orbit, one of the longest of any resident of the solar system, ushers the dwarf planet to seven billion miles (11.3 billion km) from the sun, then escorts it out of the solar system and way past the Kuiper Belt to 87 billion miles (140 billion km), and finally takes it within a loose shell of icy objects known as the Oort cloud. Since Sedna's discovery in 2003, astronomers have struggled to explain how such a world could have formed in a seemingly empty region of space, where it is too far to be influenced by giant planets of the solar system and even the Milky Way galaxy itself.

Now, a new study suggests that a thus far undetected Earth-like planet hovering in that region could be deviating orbits of Sedna and a handful of similar trans-Neptunian objects (TNOs), which are the countless icy bodies orbiting the sun at gigantic distances. Many TNOs have oddly inclined and egg-shaped orbits, possibly due to being tugged at by a hidden planet, astronomers say.

Could an 'Earth-like' planet be hiding in our solar system's outer reaches? Sharmila Kuthunur, Space.com

A University of Minnesota Twin Cities-led team used a first-of-its-kind technique to measure the Universe's expansion rate, providing insight that could help more accurately determine the Universe’s age and help physicists and astronomers better understand the cosmos. Credit: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)

Topics: Astronomy, Astrophysics, Cosmology, General Relativity

Thanks to data from a magnified, multiply-imaged supernova, a team led by University of Minnesota Twin Cities researchers have successfully used a first-of-its-kind technique to measure the universe's expansion rate. Their data provide insight into a longstanding debate in the field and could help scientists more accurately determine the universe's age and better understand the cosmos.

The work is divided into two papers published in Science and The Astrophysical Journal.

In astronomy, there are two precise measurements of the expansion of the universe, also called the "Hubble constant." One is calculated from nearby observations of supernovae, and the second uses the "cosmic microwave background," or radiation that began to stream freely through the universe shortly after the Big Bang.

However, these two measurements differ by about 10 percent, which has caused widespread debate among physicists and astronomers. If both measurements are accurate, that means scientists' current theory about the makeup of the universe is incomplete.

"If new, independent measurements confirm this disagreement between the two measurements of the Hubble constant, it would become a chink in the armor of our understanding of the cosmos," said Patrick Kelly, lead author of both papers and an assistant professor in the University of Minnesota School of Physics and Astronomy.

First-of-its-kind measurement of the universe's expansion rate weighs in on a longstanding debate. University of Minnesota, Phys.org.

Multiple images of a background image created by gravitational lensing can be seen in the system HS 0810+2554. Credit: Hubble Space Telescope / NASA / ESA

Topics: Astronomy, Astrophysics, Dark Matter, Einstein, General Relativity

Physicists believe most of the matter in the universe is made up of an invisible substance that we only know about by its indirect effects on the stars and galaxies we can see.

We're not crazy! Without this "dark matter," the universe as we see it would make no sense.

But the nature of dark matter is a longstanding puzzle. However, a new study by Alfred Amruth at the University of Hong Kong and colleagues, published in Nature Astronomy, uses light's gravitational bending to bring us a step closer to understanding.

Invisible but omnipresent

We think dark matter exists because we can see its gravity's effects on galaxies' behavior. Specifically, dark matter seems to make up about 85% of the universe's mass, and most of the distant galaxies we can see appear to be surrounded by a halo of the mystery substance.

But it's called dark matter because it doesn't give off light or absorb or reflect it, which makes it incredibly difficult to detect.

So what is this stuff? We think it must be some kind of unknown fundamental particle, but beyond that, we're not sure. All attempts to detect dark matter particles in laboratory experiments have failed, and physicists have debated its nature for decades.

Scientists have proposed two leading hypothetical candidates for dark matter: relatively heavy characters called weakly interacting massive particles (or WIMPs) and extremely lightweight particles called axions. Theoretically, WIMPs behave like discrete particles, while axions behave more like waves due to quantum interference.

It has been difficult to distinguish between these two possibilities—but now light bent around distant galaxies has offered a clue.

New look at 'Einstein rings' around distant galaxies just got us closer to solving the dark matter debate, Rossana Ruggeri, Phys.org.

The Artemis 2 crew, from left to right: Jeremy Hansen, Reid Wiseman, Victor Glover, and Christina Koch. (NASA TV)

Topics: Astronautics, Astrophysics, International Space Station, NASA, Space Exploration

NASA has selected the four astronauts that will travel to the Moon during the upcoming Artemis 2 mission, which will be humanity’s first crewed return to the Moon in more than 50 years.

The four astronauts are Reid Wiseman, Victor Glover, and Christina Koch of NASA, and Jeremy Hansen of the Canadian Space Agency.

“The Artemis 2 crew represents thousands of people working tirelessly to bring us to the stars,” said NASA Administrator Bill Nelson before announcing the crew during a live event broadcast on NASA TV. “This is their crew. This is our crew. This is humanity’s crew.”

Meet the Four Astronauts Who Will Soon Take a Trip to the Moon, Jake Parks, Discovery Magazine

Related: NC astronaut Christina Koch will be part of NASA Artemis II moon mission, Korie Dean, The Charlotte Observer

Images of six candidate massive galaxies, seen 500-800 million years after the Big Bang. One of the sources (bottom left) could contain as many stars as our present-day Milky Way but is 30 times more compact. Credit: NASA, ESA, CSA, I. Labbe (Swinburne University of Technology); Image processing: G. Brammer (Niels Bohr Institute’s Cosmic Dawn Center at the University of Copenhagen)

Topics: Astronomy, Astrophysics, Cosmology, Research

Nobody expected them. They were not supposed to be there. And now, nobody can explain how they had formed. 

Galaxies nearly as massive as the Milky Way and full of mature red stars seem to be dispersed in deep-field images obtained by the James Webb Space Telescope (Webb or JWST) during its early observation campaign. They are giving astronomers a headache. 

These galaxies, described in a new study based on Webb's first data release, are so far away that they appear only as tiny reddish dots to the powerful telescope. By analyzing the light emitted by these galaxies, astronomers established that they were viewing them in our universe's infancy, only 500 million to 700 million years after the Big Bang.

Such early galaxies are not in themselves surprising. Astronomers expected that the first star clusters sprung up shortly after the universe moved out of the so-called dark ages — the first 400 million years of its existence when only a thick fog of hydrogen atoms permeated space. 

But the galaxies found in the Webb images appeared shockingly big, and the stars in them were too old. The new findings are in conflict with existing ideas of how the universe looked and evolved in its early years and don't match earlier observations made by Webb's less powerful predecessor, the Hubble Space Telescope.

JWST Discovers Enormous Distant Galaxies That Should Not Exist, Tereza Pultarova, Scientific American/Space.com.

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

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.

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

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

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

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