4545 - LIFE ON EXOPLANETS?

 

-    4545 -   LIFE  ON  EXOPLANETS?  -    We have gained so much powerful knowledge in the past few hundred years. But there’s still so much that we don’t know.  There are limits to our current knowledge of the universe. In astronomy, we have recently discovered that 95% of the matter and energy contents of the universe, dubbed dark matter and dark energy, are of a form completely unknown to modern science.

------------------------------------------  4545  -    LIFE  ON  EXOPLANETS?

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-    Everything we have ever studied and learned in our exploration of atoms, chemicals, and forces, every star we see in the night sky and every galaxy we observe in the distant cosmos, makes up less than 5% of the entire universe.

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-   We have pushed our understanding of the history of the universe into the earliest moments of the big bang, with a firm grasp of the physics underlaying the first few minutes of the existence of the cosmos. But beyond that is murky haze, a tangled mess of unsolved mathematics and over-complicated physics. We do not understand the origins of our universe, or even if that question makes sense, if our knowledge of time and space even apply at such extreme scales.

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-   We do not know how to merge our knowledge of gravity, as expressed through general relativity, with our understanding of quantum physics, which governs the other forces of nature. We do not know how gravity operates at extremely small scales, preventing us from understanding the big bang itself and the true nature of black holes.

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-  Despite cracking the code of DNA and the role that genetics plays in the evolutionary process, we do not understand how life first arose on the Earth, and whether we are truly alone in the cosmos. We do not know how sexual reproduction arose, or where viruses originated from, or the full extent of life on Earth. We do not understand the full variety of molecular interactions that power our own biochemistry, or how the components of our cells came to find themselves working together.

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-   We do not know if superconductors, which allow for the transmission of electricity with no resistance, is possible at room temperature. We do not know the full tectonic history of the Earth, or even if duplicates of the Earth’s climate system exist on other worlds orbiting alien stars.

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-    We do not even understand the origins, or even nature, of our own conscious thoughts, the source of our thirst for knowledge and our capacity to access it.    We do not even know how we are able to ask these questions.

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-   However we have learned the existence of extrasolar plane.  The census recently passed a major milestone, with 5500 confirmed candidates in 4,243 solar systems astronomers have learned a great deal about the types of planets that exist in our galaxy and have been rethinking several preconceived notions. These include the notion of “habitability” and whether Earth is the standard by which this should be measured.

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-   Traditionally, astronomers have defined habitable zones based on the type of star and the orbital distance where a planet would be warm enough to maintain liquid water on its surface. But in recent years, other factors have been considered, including the presence of planetary magnetic fields and whether they get enough ultraviolet light. 

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-   On Earth, the presence of an intrinsic magnetic field has been vital to the emergence and evolution of life as we know it. Without it, our atmosphere would have been stripped away long ago by energetic particles emanating from the Sun, which was the case with Mars. In addition to Earth’s atmosphere, our planet’s magnetic field ensures that a limited amount of solar radiation and cosmic rays reach the surface. For this reason, astrobiologists consider a planetary magnetic field essential for determining whether or not an exoplanet is habitable.

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-   Another factor is how the strength of a planet’s magnetic field and its interaction with its parent star’s magnetic field affect habitability. Not only does an exoplanet require a strong field to shield it against stellar activity (solar flares, etc.), but it must also orbit far enough to avoid a direct magnetic connection with its star.

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-    The magnetic interactions between planets and their parent stars are known as “space weather”.   The team examined 1,546 exoplanets to determine if they orbited inside or outside their host star’s Alfvén radius, the distance where stellar wind decouples from the star. This consisted of characterizing the stars’ activity known using their Rossby number (Ro), the ratio between a star’s rotational period to their convective turnover time.

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-   Planets orbiting within this radius would directly interact magnetically with the star’s corona, leading to significant atmospheric stripping, ruling them out as viable candidates for habitability. This phenomenon has been observed with TRAPPIST-1 and its system of seven exoplanets. After examining the exoplanets in their study, they found that only two planets met all the conditions for potential habitability. These were K2-3 d and Kepler-186 f, two Earth-sized exoplanets 144 and 579 light-years from Earth.

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-   These planets have strong enough magnetic fields to protect them from stellar activity.  These findings are also indicative of current efforts among astronomers and astrobiologists to refine the definition of “Habitable Zone” and create a more nuanced understanding.

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August 30, 2024                            4500

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--------  Comments appreciated and Pass it on to whomever is interested. ---

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--  email feedback, corrections, request for copies or Index of all reviews

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--------------------- ---  Friday, August 30, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4544 - EXOPLANET LIFE

 

-    4544 -  EXOPLANET LIFE  -    Perseverance Mars rover finds possible signs of ancient Red Planet life.  On Earth, these types of features in rocks are often associated with the fossilized record of microbes living in the subsurface.

---------------------------------------------  4544  -  EXOPLANET LIFE

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-   NASA's Perseverance rover has discovered a rock on Mars that may have once hosted microbial life. The rock, nicknamed “Cheyava Falls”, has chemical compositions and structures that could have been formed by ancient life, although non-biological processes cannot yet be ruled out.

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-   The rover has come across an intriguing, arrowhead-shaped rock that hosts chemical signatures and structures that could have been formed by microbial life billions of years ago, when Mars was significantly wetter than it is today. Inside the rock Perseverance's instruments detected organic compounds, which are precursors to the chemistry of life as we know it. Wisping through the length of the rock are veins of calcium sulfate, which are mineral deposits that suggest water, essential for life, once ran through the rock.

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-    The rover also found dozens of millimeter-sized splotches, each surrounded by a black ring and mimicking the appearance of leopard spots. These rings contain iron and phosphate, which are also seen on Earth as a result of microbe-led chemical reactions.

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-    On Earth, these types of features in rocks are often associated with the fossilized record of microbes living in the subsurface.  Cheyava Falls sits at the edge of an ancient, 400-meter-wide river valley named “Neretva Vallis”. Scientists suspect this ancient channel was carved out long ago due to water gushing into Jezero Crater; Neretva Vallis runs along the inner wall of this region.

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-    In one possible scenario, mud that already possessed organic compounds got dumped into the valley and later cemented into the Cheyava Falls rock, which Perseverance sampled on July 21, 2024.  A second episode of water oozing into the formed rock would have created the object's calcium sulfate veins and black-ringed spots the team sees today.

-

-   The rock's visible features aren’t irrefutable evidence of ancient microbial life on Mars, not yet, at least. It is possible, for instance, that the observed calcium sulfate entered the rock at uninhabitably high temperatures, perhaps during a nearby volcanic event. However, whether such non-biological chemical reactions could have resulted in the observed black-ringed spots is an open question.

-

-    We have zapped that rock with lasers and X-rays and imaged it literally day and night from just about every angle imaginable.

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-    Scientists are keen to get the Cheyava Falls sample to Earth, where it can be scrutinized with powerful instruments that Perseverance’s limited suite doesn't have.   The complex Mars Sample Return effort, however, has run into many snags in recent months after its costs spiked to $11 billion.

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-    In its current form, the program requires multiple launches to Mars to place a vehicle on the Red Planet, after which either Perseverance will travel to the vehicle and drop off its collected samples, or pop those samples over to a retrieval helicopter that can complete the handoff. Then, an ascender would launch the samples into orbit, where a spacecraft would collect them and return them to Earth.

-

-   On Earth, these types of features in rocks are often associated with the fossilized record of microbes living in the subsurface.   The arrowhead-shaped rock that hosts chemical signatures and structures that could have been formed by microbial life billions of years ago, when Mars was significantly wetter than it is today.

-

-    Inside the rock Perseverance's instruments detected organic compounds, which are precursors to the chemistry of life as we know it. Wisping through the length of the rock are veins of calcium sulfate, which are mineral deposits that suggest water once ran through the rock.

-

-   The rover also found dozens of millimeter-sized splotches, each surrounded by a black ring and mimicking the appearance of leopard spots. These rings contain iron and phosphate, which are also seen on Earth as a result of microbe-led chemical reactions.  On Earth, these types of features in rocks are often associated with the fossilized record of microbes living in the subsurface.

-

-    Cheyava Falls sits at the edge of an ancient, 400-meter-wide  river valley.  Scientists suspect this ancient channel was carved out long ago due to water gushing into Jezero Crater; Neretva Vallis runs along the inner wall of this region. In one possible scenario, mud that already possessed organic compounds got dumped into the valley and later cemented into the Cheyava Falls rock.  A second episode of water oozing into the formed rock would have created the object's calcium sulfate veins and black-ringed spots the team sees today.

-

-  It is possible that the observed calcium sulfate entered the rock at uninhabitably high temperatures, perhaps during a nearby volcanic event. However, whether such non-biological chemical reactions could have resulted in the observed black-ringed spots is an open question.

-

-

August 29, 2024          EXOPLANET   LIFE                  4544

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--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Friday, August 30, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4543 - EXOPLANETS - with large moons?

 

-    4543 -  EXOPLANETS  -  with large moons?  -  If we want to find life-supporting worlds, we should focus on small planets with large moons. Every planet-hunting method has some type of bias.

-------------------------------------------  4543  -  EXOPLANETS  -  with large moons?

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-    We’ve found most exoplanets using the “transit method”, which is biased toward larger planets. Larger planets closer to their stars block more light, meaning we detect large planets transiting in front of their stars more readily than we detect small ones.

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-  That’s a problem because some research says that life-supporting planets are more likely to be small, like Earth. It’s all because of moons and streaming instability.  Consider Earth’s Moon. While there’s no consensus on every aspect of the Moon and its role, there’s evidence that it helps make life on Earth possible and has helped life sustain itself for so long. As natural satellites go, it’s massive. Of the approximately 300 (and counting) moons in our Solar System, the Moon is the fifth largest.

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-   The Moon’s diameter is about one-quarter of Earth’s diameter, and its mass is about 1.2% of Earth’s. The four natural satellites in the Solar System that are larger than the Moon orbit the gas giants Jupiter and Saturn. Those moons are tiny compared to their planets.

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-    This means that the Moon has different effects on Earth than other moons do on their planets.  The Moon stabilizes Earth’s orbital tilt, which helps keep the climate stable and allows life to flourish and organisms to adapt. It creates tides, which may have played a role in the formation of nucleic acids and life. The Moon may even help Earth maintain its protective magnetosphere.  Earth would be a very different place without its huge Moon.

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-   We should look for small planets if we want to find life-supporting worlds because small planets are more likely to host larger moons.   Relatively small planets similar to the size of Earth are more difficult to observe and they have not been the major focus of the hunt for moons.  These planets are actually better candidates to host moons.

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-   The leading theory for the Moon’s formation is the “Giant Impact Hypothesis”. It states that when the Earth was very young, about 4.5 billion years ago, a Mars-sized protoplanet named “Theia” slammed into Earth. The collision created a rotating torus of molten rock that orbited the Earth. Some fell back down to Earth, and the rest coalesced into the Moon.

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-   The research questions the role of “streaming instability” in moon formation. Some scientists think that planet formation is the same as moon formation. However, while streaming instability is important for planet formation, it may not be for the formation of large moons like Earth’s, which help make planets habitable.

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-    Simulations were used to examine the role of streaming instability in moon formation. Streaming instability describes the effect that drag has on the accretion of matter in a protoplanetary disk that leads to planetesimals. Inside a disk, drag rapidly drives solid particles to concentrate spontaneously into clumps. These clumps can then collapse and form planetesimals.

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-   The question is, does streaming instability play the same role in the formation of moons around planets? In our case, the disk isn’t a protoplanetary disk but a disk of debris resulting from a collision.

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-   Research has found that this instability can quickly form 100 km-sized moonlets.  However, these moonlets are not large enough to avoid strong drag, and they still fall onto Earth quickly.  These moonlets could grow further once the disk cools enough and the vapor mass fraction of the disk becomes small.  However, by this time a significant amount of the disk mass is lost, and the remaining disk could make only a small moon.

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-   For a large moon like Earth’s to form, the collision has to be less energetic than one between much more massive planets. If “Theia” had been more massive, the heat from the impact would’ve created a completely vapourized disk. Only a much smaller moon could’ve formed in such a disk.

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-    Streaming instability may not help large moons form in vapour-rich disks. Fractionally large moons like Earth’s Moon, which may be necessary for life, might only form in vapour-poor disks. More massive planets have more energetic collisions, which creates vapour-rich disks. Smaller planets have vapour-poor disks where larger moons can form.

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-   So, if we want to find life-supporting planets, look for small worlds where larger moons are more likely to form.

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-    Astronomers have confirmed the existence of exoplanets with extremely small orbits around their stars. But what about exoplanets that get close enough to be devoured by their star, and what if it’s an Earth-sized exoplanet?

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-    Known as “ultra-short-period” (USP) exoplanets could eventually experience what’s known as tidal disruption, resulting in its devourment by its star.  Tidal disruption could be a potential fate of rocky planets.  It seems like about 10 percent of sun-like stars might have engulfed their rocky planets.

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-    Researchers analyzed “TOI-6255 b”, whose radius is 1.08 and mass is 1.44 of Earth’s and located just over 65.2 light-years from Earth. However, while being Earth-sized holds promise for life, TOI-6255 b’s 5.7-hour orbit not only make this exoplanet far too hot for life as we know it to exist, but this also means its orbit takes it dangerously close to what’s known as Roche limit.

The “Roche Limit” is the distance a smaller object can orbit a larger object until the larger object’s gravity tears the smaller object to pieces, along with TOI-6255 b also experiencing the tidal disruption, which is a common occurrence throughout the cosmos, including black holes.

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-   This particular planet is doomed for tidal disruption in 400Myr which is short on cosmic scale (13Gyr). The planet is also tidally distorted to be football like in shape (10 percent deviation from sphere), in comparison Earth’s tidal distortion due to the moon is only 1e-7 [0.0000001] level.

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-    USPs are exoplanets whose orbits are less than one day and whose masses are less than 2x the Earth. While intriguing, only about 100 USPs have been discovered with a 2014 study estimating approximately 0.5 percent exist around Sun-like stars and a 2019 study discussing their bulk composition (i.e., mass of its iron core and mantle).

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-     Given their extremely short orbit, these worlds are likely too hot for life as we know it to exist, and along with USPs are the familiar “hot Jupiters” who orbit their stars in only a few days and astronomers estimate their population is in the hundreds.   These worlds are Jupiter-sized or larger gas planets and are also potentially far too hot for life as we know it to exist. But what is the significance of TOI-6255 b being an Earth-sized planet as opposed to a Jupiter-sized planet, or larger?

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-    Planets similar to Earth in size are most likely rocky i.e. mostly made of iron core and silicate mantle. They show us what terrestrial planets in other planetary systems are made of. Jupiter-sized planets are most certainly covered by thick hydrogen and helium atmospheres. Jupiter-sized planets are unlikely to harbor life.

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-    While TOI-6255 b isn’t due for disassembly for another 400 million years, watching any exoplanet get ripped to shreds by its host star could provide important insights regarding the planet’s exterior and interior compositions, thus helping us better understand the similarities between exoplanets and planets within our own solar system.

-

-     These unique worlds and their extremely tight orbits have challenged our understanding of solar system architecture throughout our Milky Way Galaxy, as Mercury is the closest planet to our Sun, and it still takes 88 days to complete one orbit.

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-    One similarity between our solar system and exoplanetary systems is the Roche limit. However, the study also focuses on tidal disruption that is physically distorting TOI-6255 b. Tidal disruption could be a potential fate of rocky planets.

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-    Tidal disruption of planets is minimal in our solar system. However, the rings of Saturn are thought to originate from tidal disruption of satellites around Saturn. Tidal forces are strongly dependent on orbital separation, only objects with the shortest orbital period experience significant tides.

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August 20, 2024                 EXOPLANETS  -  with large moons?               4543

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--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Sunday, August 25, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4542 - ASTEROID HITS EARTH?

 

-    4542 -   ASTEROID  HITS  EARTH?  -     A large asteroid impacting Earth was the “Chicxulub event” that caused the end-Cretaceous mass extinction, 66 million years ago.  But there is an intense debate surrounding this rock that killed the dinosaurs has stirred scientists for decades.

------------------------------------------  4542  -  ASTEROID  HITS  EARTH?

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-   Researchers used an innovative technique to demonstrate that the apocalyptic culprit which slammed into the Earth's surface 66 million years ago, causing this most recent mass extinction, had formed beyond Jupiter's orbit.  They also refute the idea that it was a comet.

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-   The new insights into the apparent asteroid that cratered into Chicxulub, in what is present-day Mexico's Yucatan Peninsula, could improve the understanding of celestial objects that have struck our planet.  This asteroid initially formed beyond Jupiter.

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-   The new findings are based on analysis of sediment samples formed at the period between the Cretaceous and Paleogene eras, the time of the asteroid's cataclysmic impact.  Researchers measured the isotopes of the element ruthenium, not uncommon on asteroids but extremely rare on Earth.   By inspecting the deposits in multiple geological layers that mark the debris from the impact at Chicxulub, they could be sure that the ruthenium studied came "100 percent from this asteroid."

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-    This was the first time new study techniques were used on impact debris layers.  Ruthenium isotopes can be used to distinguish between the two main groups of asteroids: C-type, or carbonaceous, asteroids that formed in the outer solar system, and S-type silicate asteroids from the inner solar system, nearer the sun.

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-   The study affirms that the asteroid that triggered a mega-earthquake, precipitated a global winter and wiped out the dinosaurs and most other life, was a C-type asteroid that formed beyond Jupiter.  The conclusions are striking, because most meteorites, pieces of asteroids that fall to Earth are S-types.

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-   Does that mean the Chicxulub impactor formed beyond Jupiter and made a beeline for our planet? Not necessarily.  We cannot be really sure where the asteroid was hiding just before it impacted on Earth.  It may have made a stopover in the asteroid belt, located between Mars and Jupiter and where most meteorites originate.

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-     This study dismisses the idea that the destructive impactor was a comet, an icy rock from the very edge of the solar system.   Sample analyses now show that the celestial object was far different in composition from a subset of meteorites which are believed to have been comets in the past.

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-    Defining the nature of asteroids that have struck Earth since its beginnings some 4.5 billion years ago could help solve the enigma of the origin of our planet's water.  They believe water may have been brought to Earth by asteroids, likely of the C-type like the one that struck 66 million years ago, even though they are less frequent.

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-   If we find that earlier mass extinction events could also be related to C-type asteroid impacts, then... if there's ever going to be C-type asteroid on an Earth-crossing orbit, we have to be very careful because it might be the last one we witness.

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-   This asteroid initially formed beyond Jupiter.  These new findings are based on analysis of sediment samples formed at the period between the Cretaceous and Paleogene eras, the time of the asteroid's cataclysmic impact.

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-    Researchers measured the isotopes of the element ruthenium, not uncommon on asteroids but extremely rare on Earth. So by inspecting the deposits in multiple geological layers that mark the debris from the impact at Chicxulub, they could be sure that the ruthenium studied came "100 percent from this asteroid."

-

-   Ruthenium isotopes can be used to distinguish between the two main groups of asteroids:    C-type, or carbonaceous, asteroids that formed in the outer solar system, and S-type silicate asteroids from the inner solar system, nearer the sun.

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-    The study affirms that the asteroid that triggered a mega-earthquake, precipitated a global winter and wiped out the dinosaurs and most other life, was a C-type asteroid that formed beyond Jupiter.   Most meteorites, pieces of asteroids that fall to Earth, are S-types.

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-    If there's ever going to be C-type asteroid on an Earth-crossing orbit, we have to be very careful, because it might be the last one we witness.

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August 20, 2024                ASTEROID  HITS  EARTH?               4542

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--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Thursday, August 22, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4541 - HABITABLE PLANETS - getting closer to a find?

 

-    4541 -  HABITABLE  PLANETS  -  getting closer to a find?  -     The search for habitability elsewhere in the universe can be reduced to the search for water. We haven't yet found lifeforms that detach this substance from our conception of "life" itself, so we have no choice but to accept the water trail as our north star in the quest to find worlds that mirror our own.

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--------------------------  4541  -    HABITABLE  PLANETS  -  getting closer to a find?

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-    Researchers just announced that a tantalizing planet outside the solar system may have a temperate water ocean about half the size of the Atlantic.    Of all currently known temperate exoplanets, “LHS 1140 b” could well be our best bet to one day indirectly confirm liquid water on the surface of an alien world beyond our solar system.  This would be a major milestone in the search for potentially habitable exoplanets.

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-    “LHS 1140 b” exoplanet orbits a red dwarf star about a fifth the size of the sun and sits 48 light-years away from Earth in the constellation Cetus which, as luck would have it, translates to "the whale." But most important about LHS 1140 b is the fact that it lives in its star's habitable zone, otherwise known as its "Goldilocks zone."

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-    As that nickname would suggest, this is the area around a star where it's neither too hot nor too cold for a world to host liquid water, but rather fits the standard by which the fairy tale character Goldilocks lives.

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-   This is the first time we have ever seen a hint of an atmosphere on a habitable zone rocky or ice-rich exoplane with the analysis of LHS 1140 b's atmosphere.  The team might have even found evidence of "air" on it.

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-    The exoplanet could be either rocky or icy.   Though it has been making headlines now due to the new study involving JWST data, LHS 1140 b has actually been on planetary hunters' radars for some time. In fact, experts had already theorized that this could be a water world in the past, and even shared similar sentiments about how it could offer humanity the first-ever direct evidence of exoplanetary liquid water.

-

-   There was something like a gap in the literature about LHS 1140 b. Basically, the trouble was that scientists couldn't quite confirm whether the exoplanet is a mini-Neptune — a planet less massive than our original Neptune, but one that still has Neptunian characteristics — or a super Earth. A super Earth is a world that's larger than Earth, but still either rocky or water-rich. -

-    This work not only "strongly excluded" the mini-Neptune scenario, but also confirmed the world may have a nitrogen-laced atmosphere like Earth does.   The presence of a nitrogen-rich atmosphere would suggest the planet has retained a substantial atmosphere, creating conditions that might support liquid water.

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-   There are also a variety of other habitable-zone exoplanets scientists are drawn to. The most obvious are probably the seven worlds of the TRAPPIST-1 system, a planetary lineup that looks almost disturbingly similar to our solar system's structure. 

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-     However, a very interesting JWST study actually complicated the search for habitability in TRAPPIST-1 quite recently. It revealed that the system's anchor star is incredibly active in such a way that it could skew our observations, making us believe a world in the system is habitable when it really isn't.

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-    The star LHS 1140 appears to be calmer and less active, making it significantly less challenging to disentangle LHS 1140 b's atmosphere from stellar signals caused by starspots. The JWST data further suggests the exoplanet's mass might be made of between 10 percent and 20 percent liquid water, and, it paints a fantastical picture of what the planet might look like in simple terms.

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-     It could look like a snowball, essentially, that orbits its star while rotating in such a way that one side always faces that star. It's like the moon's orbit around Earth; we can't ever see the far side of the moon because the moon rotates at the same rate it revolves around Earth. One side never faces us, and the other always does.

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-   Similarly, this would mean that, if the JWST's illustration of the LHS 1140 b scene is correct, the side of the planet always facing its sun would be exposed to lots of heat. This would be the part of the snowball that's "melted" into a liquid ocean. 

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-    Current models indicate that if LHS 1140 b has an Earth-like atmosphere, it would be a snowball planet with a bull's-eye ocean about 2,485 miles in diameter.  The surface temperature of the ocean may very well even be a  "comfortable" 68 degrees Fahrenheit.

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August 21, 2024        HABITABLE  PLANETS  -  getting closer to a find?                     4541

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Tuesday, August 20, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4540 - HOW TO WEIGH A NEUTRON STAR?

 

-    4540 -  HOW  TO  WEIGH A  NEUTRON  STAR?  -   Neutron stars are some of the most extreme objects in the universe. Formed from the collapsed cores of supergiant stars, they weigh more than our Sun and yet are compressed into a sphere the size of a city.

----------------------------------  4540  -   HOW  TO  WEIGH A  NEUTRON  STAR?

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-   Neutron stars are some of the most extreme objects in the universe. Formed from the collapsed cores of supergiant stars, they weigh more than our Sun and yet are compressed into a sphere the size of a city.

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-   The dense cores of these exotic Neutron stars contain matter squashed into unique states that we can’t possibly replicate and study on Earth. That’s why NASA is on a mission to study neutron stars and learn about the physics that governs the matter inside them.

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-  Astronomers used radio signals from a fast-spinning neutron star to measure its mass. This enabled scientists working with NASA data to measure the star’s radius, which in turn gave us the most precise information yet about the strange matter inside.

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-    Matter in the core of neutron stars is even denser than the nucleus of an atom. As the densest stable form of matter in the universe, it is squashed to its limit and on the brink of collapse into a black hole. Understanding how matter behaves under these conditions is a key test of our theories of fundamental physics.

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-    NASA’s “Neutron star Interior Composition ExploreR” (NICER) mission is trying to solve the mysteries of this extreme matter.   NICER is an X-ray telescope on the International Space Station. It detects X-rays coming from hot spots on the surface of neutron stars where temperatures can reach millions of degrees.

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-    Scientists model the timing and energies of these X-rays to map the hot spots and determine the mass and size of the neutron stars.  Knowing how the sizes of neutron stars relate to their masses will reveal the “equation of state” of the matter in their cores. This tells scientists how soft or hard, how “squeezeable”, the neutron star is, and therefore what it is made of.

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-   A softer equation of state would suggest that neutrons in the core are breaking apart into an exotic soup of smaller particles. A harder equation of state might mean neutrons resist, leading to larger neutron stars.  The equation of state also dictates how and when neutron stars get ripped apart when they collide.

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-   One of NICER’s primary targets is a neutron star called “PSR J0437-4715”, which is the nearest and brightest millisecond pulsar.  A pulsar is a neutron star that emits beams of radio waves that we observe as a pulse every time the neutron star rotates.

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-   This particular pulsar rotates 173 times per second (as fast as a blender). We have been observing it for almost 30 years with Murriyang, CSIRO’s Parkes radio telescope in New South Wales.

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-    This pulsar's X-rays coming from a nearby galaxy made it hard to accurately model the hot spots on the neutron star’s surface.   Fortunately, we were able to use radio waves to find an independent measurement of the pulsar’s mass. Without this crucial information, the team would not have recovered the correct mass.

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-   To measure the neutron star’s mass, they rely on an effect described by Einstein’s theory of general relativity, called the “Shapiro delay”.   Massive and dense objects such as pulsars – and in this case its companion star, a white dwarf – warp space and time. The pulsar and this companion orbit one another once every 5.74 days. When pulses from the pulsar travel to us across the compressed spacetime surrounding the white dwarf, they are delayed by microseconds.

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-    Such microsecond delays are easy to measure with Murriyang from pulsars like              “PSR J0437-4715”. This pulsar, and other millisecond pulsars like it, are observed regularly by the Parkes Pulsar Timing Array project, which uses these pulsars to detect gravitational waves.

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-    Because PSR J0437-4715 is relatively close to us, its orbit appears to wobble slightly from our point of view as Earth moves around the Sun. This wobble gives us more details about the geometry of the orbit. We use this together with the Shapiro delay to find the masses of the white-dwarf companion and the pulsar.

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-    They calculated that the mass of this pulsar as typical of a neutron star, at 1.42 times the mass of our Sun. That’s important because the size of this pulsar should also be the size of a typical neutron star.

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-    Scientists working with the NICER data were then able to determine the geometry of the    X-ray hot spots and calculate that the neutron star’s radius is 11.4 kilometers. These results give the most precise anchor point yet found for the neutron star equation of state at intermediate densities.

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-   Our new picture already rules out the softest and hardest neutron star equations of state. Scientists will continue to decode exactly what this means for the presence of exotic matter in the inner cores of neutron stars. Theories suggest this matter may include “quarks” that have escaped their normal homes inside larger particles, or rare particles known as “hyperons”.

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-     This new data adds to an emerging model of neutron star interiors that has also been informed by observations of gravitational waves from colliding neutron stars and an associated explosion called a “kilonova”.

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August  21, 2024              HOW  TO  WEIGH A  NEUTRON  STAR?               4540

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--------  Comments appreciated and Pass it on to whomever is interested. ---

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--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Tuesday, August 20, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4539 - MILKYWAY and ANDROMEDA GALAXIES COLLIDE?

 

-    4539 -  MILKYWAY  and  ANDROMEDA  GALAXIES COLLIDE?  -    Are Andromeda and the Milky Way doomed to collide? Maybe not.  There is a predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy to unfold over the next several billion years.

-----------------------------  4539  -    MILKYWAY  and  ANDROMEDA  GALAXIES COLLIDE?

-    Scientists discovered the Andromeda galaxy, known as M31, hundreds of years ago, and around a century ago, we realized that it had negative radial velocity toward the Milky Way. In other words, eventually, the two galaxies would merge spectacularly. That has been common knowledge for astronomers since then, but is it really true?

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-   There are several confounding factors, including the gravitational influence of other galaxies in our local group, and these tell us there is a 50% chance that the Milky Way will merge with the Andromeda galaxy in the next 10 billion years.

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-  That seems like a pretty big thing to get the physics wrong on. So, how did the authors come to that conclusion? They accounted for a problem that has been popularized in media as of late—the three-body—or in this case, four-body—problem. And with that problem comes a lot of uncertainty, which is why there's still a 50% chance that this huge event might still happen.

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-   Thinking of Andromeda and the Milky Way in isolation doesn't account for the other galaxies in what we know as the "Local Group." This comprises approximately 100 smaller galaxies at various orientations, distances, and speeds.

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-   The largest of the remaining galaxies is the Triangulum galaxy, M33, which is about 2.7 million light-years away and consists of upwards of a 40 billion stars. That's about 40% of the approximately 100 billion stars in the Milky Way but a mere 4% of the nearly 1 trillion stars estimated to exist in Andromeda. Still, they would have their own gravitational pull, contorting the simplistic dynamic between Andromeda and the Milky Way.

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-   Further confounding that dynamic is the Large Magellanic Cloud, which is either the second or third closest galaxy to our own at a distance of only 163,000 light years. This is slightly larger than the Milky Way's diameter, at 105,700. It also houses around 20 billion stars, so while it's even less massive than M33, it still exerts a hefty gravitational pull.

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-   The authors accounted for the gravitational pull of both of those other galaxies in their calculations of the paths of the Milky Way and Andromeda over the next few billion years. They found that the complicated dance of astronomical giants could potentially result in a scenario where the two galaxies don't merge. However, there was another significant factor in their calculations: uncertainty.

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-    Scientists never like uncertainty. In fact, much of their research tries to place bounds on certain parameters, like the rotational speed of galaxies or the distances between them. Unfortunately, despite their proximity, there are many uncertainties surrounding the four galaxies used in the study, and those uncertainties make precise calculations of the effects of their gravitational and rotational pull difficult.

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-    If it happens at all, a merger between the Milky Way and Andromeda will happen long after our own sun has burned out, and humans will either die out with it or find a way to expand to new stars.

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-    Andromeda and the Milky Way Galaxies doomed to collide?   Maybe Not.  Scientists discovered the Andromeda galaxy, known as M31, hundreds of years ago, and around a century ago, we realized that it had negative radial velocity toward the Milky Way. In other words, eventually, the two galaxies would merge spectacularly.

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-    That has been common knowledge for astronomers since then, but is it really true? A new paper from researchers at the University of Helsinki looks at several confounding factors, including the gravitational influence of other galaxies in our local group, and finds only a 50% chance that the Milky Way will merge with the Andromeda galaxy in the next 10 billion years.

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-   That seems like a pretty big thing to get the physics wrong on. So, how did the authors come to that conclusion? They accounted for a problem that has been popularized in media as of late – the three-body – or in this case, four-body – problem. And with that problem comes a lot of uncertainty, which is why there’s still a 50% chance that this huge event might still happen.

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-   The “Local Group.” of galaxies comprises approximately 100 smaller galaxies at various orientations, distances, and speeds. The largest of the remaining galaxies is the “Triangulum galaxy”, M33, which is about 2.7 million light-years away and consists of upwards of a mere 40 billion stars. That’s about 40% of the approximately 100 billion stars in the Milky Way but a mere 4% of the nearly 1 trillion stars estimated to exist in Andromeda.

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-   Further confounding that dynamic is the Large Magellanic Cloud, which is either the second or third closest galaxy to our own at a distance of only 163,000 light years. This is slightly larger than the Milky Way’s diameter, at 105,700. It also houses around 20 billion stars, so while it’s even less massive than M33, it still exerts a hefty gravitational pull.

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-   The authors accounted for the gravitational pull of both of those other galaxies in their calculations of the paths of the Milky Way and Andromeda over the next few billion years. They found that the complicated dance of astronomical giants could potentially result in a scenario where the two galaxies don’t merge. However, there was another significant factor in their calculations: uncertainty.

-   Developing estimates rather than concrete numbers is one-way scientists often deal with uncertainty, and in this case, that estimate fell right at the 50% mark in terms of whether or not the two galaxies would collide. However, there is still a lot of uncertainty in that estimate, and plenty more confounding factors, including the other galaxies in the local group, will influence the final outcome.

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-    Ultimately, time will help solve the mystery, but that is a very long time on the scale of galaxy mergers. If it happens at all, a merger between the Milky Way and Andromeda will happen long after our own Sun has burnt out, and humans will either die out with it or find a way to expand to new stars. And if, at that point, we get easy access to an additional galaxy’s worth of resources, it would be all the better for us.

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August 19, 2024      MILKYWAY  and  ANDROMEDA  GALAXIES COLLIDE?        4539

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--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Tuesday, August 20, 2024  ---------------------------------