astronomy (42)

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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Modified Gravity...

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Rotation curve of the typical spiral galaxy M 33 (yellow and blue points with error bars) and the predicted one from the distribution of the visible matter (white line). The discrepancy between the two curves is accounted for by adding a dark matter halo surrounding the galaxy. Credit: Wikipedia

Topics: Astronomy, Astrophysics, Cosmology, Dark Matter

Although dark matter is central to the standard cosmological model, it's not without issues. There continue to be nagging mysteries about the stuff, not the least of which is the fact that scientists have found no direct particle evidence of it.

Despite numerous searches, we have yet to detect dark matter particles. Some astronomers favor an alternative, such as modified Newtonian dynamics (MoND) or the modified gravity model. And a new study of galactic rotation seems to support them.

The idea of MoND was inspired by galactic rotation. Most of the visible matter in a galaxy is clustered in the middle, so you'd expect that stars closer to the center would have faster orbital speeds than stars farther away, similar to the planets of our solar system. We observe that stars in a galaxy all rotate at about the same speed. The rotation curve is essentially flat rather than dropping off. The dark matter solution is that a halo of invisible matter surrounds galaxies, but in 1983 Mordehai Milgrom argued that our gravitational model must be wrong.

At interstellar distances, the gravitational attraction between stars is essentially Newtonian. So rather than modifying general relativity, Milgrom proposed modifying Newton's universal law of gravity. He argued that rather than the force of attraction as a pure inverse square relation, gravity has a small remnant pull regardless of distance. This remnant is only about ten trillionths of a G, but it's enough to explain galactic rotation curves.

New measurements of galaxy rotation lean toward modified gravity as an explanation for dark matter, Brian Koberlein, Universe Today/Phys.org.

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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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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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Yonder Water Worlds...

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Hot and humid The surface of a Hycean planet as interpreted by an artist. (Courtesy: Amanda Smith, University of Cambridge).

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

Hot, ocean-covered exoplanets with hydrogen-rich atmospheres could harbor life and may be more common than planets that are Earth-like in size, temperature, and atmospheric composition. According to astronomers at the University of Cambridge, UK, this newly defined class of exoplanets could boost the search for life elsewhere in the universe by broadening the search criteria and redefining which biosignatures are important.

Astronomers define the habitable or “Goldilocks” zone as the region where an exoplanet is neither too close nor too far from its host star to have liquid water on its surface – water being the perfect solvent for many forms of life. Previous studies of planetary habitability have focused primarily on searching for Earth-like exoplanets and evidence that they could harbor the kind of chemistry found in life on Earth. However, it has so far proven difficult to detect atmospheric signatures from Earth-like planets orbiting Sun-like stars.

Potentially habitable mini-Neptunes

Larger exoplanets are easier to detect than smaller, Earth-sized ones, and exoplanets around 1.6‒4 times bigger than the Earth, with masses of up to 15 Earth masses and temperatures that in some cases exceed 2000 K, are relatively common. These planets are known as mini-Neptune's as they are similar to the ice giant planets in our solar system.

Previous studies suggested that the high pressures and temperatures beneath these planets’ hydrogen-rich atmospheres were incompatible with life. However, based on their analysis of an exoplanet called K2-18b, exoplanet scientist Nikku Madhusudhan and colleagues at Cambridge say that life could, in fact, exist on a subset of mini-Neptunes that meet specific criteria.

This subset, which the researchers dub “Hycean” (hydrogen + ocean) planets, consists of planets that have radii up to 2.6 times larger than Earth’s and are capable of harboring vast oceans under atmospheres dominated by molecular hydrogen and water vapor. Such oceans could cover the whole planet and reach depths greater than the Earth’s oceans, and the researchers say that the conditions within them could be compatible with some forms of Earth-based microbial life. Hycean planets tidally locked with their host star could also exhibit habitable conditions on their permanent night side.

Astronomers define new class of potentially habitable ocean worlds, Chaneil James, Physics World

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Ganymede...

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A global view of Ganymede, based on data gathered by NASA’s Voyager 1, Voyager 2, and Galileo spacecraft. Credit: USGS Astrogeology Science Center, Wheaton, NASA and JPL-Caltech

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

Ganymede, get ready for your close-up.

No probe has gotten a good view of Jupiter’s largest moon since 2000 when NASA’s Galileo spacecraft swung past the strange world, which is the largest moon in the whole solar system. But on Monday (June 7),  at 1:35 p.m. EDT (1735 GMT), NASA’s Juno spacecraft will skim just 645 miles (1,038 kilometers) above Ganymede’s surface, gathering a host of observations as it does so.

“Juno carries a suite of sensitive instruments capable of seeing Ganymede in ways never before possible," principal investigator Scott Bolton, a space scientist at the Southwest Research Institute in San Antonio, said in a NASA statement. “By flying so close, we will bring the exploration of Ganymede into the 21st century.”

Ganymede is a fascinating world for scientists. Despite its status as a moon, it’s larger than the tiny planet Mercury and is the only moon to sport a magnetic field, a bubble of charged particles dubbed a magnetosphere. Until now, the only spacecraft to get a good look at Ganymede were NASA’s twin Voyager probes in 1979 and the Galileo spacecraft, which flew past the moon in 2000.

NASA’s Juno Set for Close Encounter with Jupiter’s Moon Ganymede, Meghan Bartels, SPACE.com, Scientific American

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Sun Quake...

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The first coronal mass ejection, or CME, observed by the Solar Orbiter Heliospheric Imager (SoloHI) appears as a sudden gust of white (the dense front from the CME) that expands into the solar wind. This video uses different images, created by subtracting the pixels of the previous image from the current image to highlight changes. The missing spot in the image on the far right is an overexposed area where light from the spacecraft solar array is reflected into SoloHI’s view. The little black and white boxes that blip into view are telemetry blocks – an artifact from compressing the image and sending it back down to Earth.
Credits: ESA & NASA/Solar Orbiter/SoloHI team/NRL

Topics: Astronomy, Astrophysics, ESA, Heliophysics, NASA

For the new Sun-watching spacecraft, the first solar eruption is always special.

On February 12, 2021, a little more than a year from its launch, the European Space Agency, and NASA’s Solar Orbiter caught sight of this coronal mass ejection or CME. This view is from the mission’s SoloHI instrument — short for Solar Orbiter Heliospheric Imager — which watches the solar wind, dust, and cosmic rays that fill the space between the Sun and the planets.

It's a brief, grainy view: Solar Orbiter’s remote sensing won’t enter full science mode until November. SoloHI used one of its four detectors at less than 15% of its normal cadence to reduce the amount of data acquired. Still, a keen eye can spot the sudden blast of particles, the CME, escaping the Sun, which is off-camera to the upper right. The CME starts about halfway through the video as a bright burst – the dense leading edge of the CME – and drifts off-screen to the left.

For SoloHI, catching this CME was a happy accident. At the time the eruption reached the spacecraft, Solar Orbiter had just passed behind the Sun from Earth’s perspective and was coming back around the other side. When the mission was being planned, the team wasn’t expecting to be able to record any data during that time.

A New Space Instrument Captures Its First Solar Eruption, Miles Hatfield, NASA

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Volume of Chaos...

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Topics: Astronomy, Astrophysics, Cosmology

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

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

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

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

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Antistars...

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

Topics: Astronomy, Astrophysics, Cosmology, High Energy Physics

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

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

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

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

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

The mystery of matter and antimatter

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

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

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

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

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