3591 - EXOPLANETS - many new discovery tools!

  -  3591  -  EXOPLANETS  -  many new discovery tools!  As May, 2022,  NASA has indicated that 5,030 extrasolar planets have been confirmed in 3,772 systems, with another 8,974 candidates awaiting confirmation. Let me repeat that over 5,000 planets outside our solar system.  And, nearly 9,000 more being investigated as exoplanets.

---------------------  3591  -    EXOPLANETS  -  many new discovery tools!

---------The “Closeby Habitable Exoplanet Survey” (CHES) could detect exoplanets within a few dozen light-years of Earth using “astrometry”.

-

-  With next-generation instruments like the James Webb Space Telescope (JWST) coming online, the number and diversity of confirmed exoplanets are expected to grow exponentially. Wow!!

-

-  Astronomers anticipate that the number of known terrestrial planets and Super-Earths will drastically increase.  A team led by the “Chinese Academy of Sciences” (CAS) described a new space-telescope concept known as the “Closeby Habitable Exoplanet Survey” (CHES). This observatory will search for Earth-like planets in the habitable zones (HZs) of Sun-like stars within approximately 33 light-years (10 parsecs) using a method known as “micro-arcsecond relative astrometry“.

-

-  The branch of astronomy known as “astrometry” consists of taking precise measurements of the positions and proper motions of celestial bodies by comparing them to background reference stars. 

-

-  The Europe’s “Gaia Observatory“, which has been measuring the motion of 1 billion stars in the Milky Way (as well as 500,000 distant quasars) since 2013. This data will be used to create the most precise three-dimensional map of our Galaxy ever made.

-

-  The proposed CHES mission will operate at the Sun-Earth L2 Lagrange point, where NASA’s James Webb Space Telescope (JWST) currently resides, and observe target stars for five years. These targets will include 100 stars within 33 light-years of the Solar System that fall into the F, G, and K types.

-

-   F-type stars (yellow-white dwarfs) are hotter, brighter, and more massive than our Sun,

-

-   G-type stars (yellow dwarf) are consistent with our Sun – a main-sequence G2V star.

-

-    K-type stars (orange dwarf) are slightly dimmer, cooler, and less massive than our Sun.

-

-   For each star it observes, CHES will measure the small and dynamical perturbances induced by orbiting exoplanets, which will provide accurate estimates of their masses and orbital periods.  CHES will not be subject to interference due to Earth’s precession and atmosphere and will be able to make astrometry measurements accurate enough to fall into the micro-arcsecond domain. 

-

-  For an Earth-mass planet at 1 Astronomical Unit distance around a solar-type star at 10 pc, the astrometry wobble of the star caused by the Earth Twin is 0.3 micro-arcsecond. Thus the micro-arcsecond level measurement is required. 

-

-  The relative astrometry for CHES can accurately measure micro-arcsecond level angular separation between one target star and 6-8 reference stars. Based on the measurements of these tiny changes, astronomers can detect whether there are terrestrial planets around them.

-

-   CHES will make the first direct measurements of the true masses and inclinations of Earth analogs and super-Earths that orbit within their stars’ HZ and are considered “potentially habitable“.

-

-   The primary payload for this mission is a high-quality mirror with a diameter of 1.2 meters (ft) and a field of view (FOV) of 0.44° x 0.44°. This mirror is part of a coaxial three-mirror anastigmat (TMA) system, where three curved mirrors are used to minimize optical aberrations.

-

-  CHES also relies on “Mosaic Charge-Coupled Devices” (CCDs) and the laser metrology technique to conduct astrometric measurements in the 500nm to 900nm range encompassing visible light and the near-infrared spectrum. 

-

-  These capabilities will offer significant advantages compared to the Transit Method, which remains the most widely-used and effective means for detecting exoplanets. In this method, stars are monitored for periodic dips in luminosity, which are possible indications of planets passing in front of the star ( transiting) relative to the observer.

-

-  CHES will conduct an extensive survey of the nearby solar-type stars at 10 PC away from us and detect all the Earth-like planets in the habitable zone via astrometry, in the case where the Transit Method cannot do (such as TESS or PLATO).  This requires the edge-on orbits for the planets with respect to the line of sight of the observers.

-

-   CHES will offer the first direct measurements of true masses for ‘Earth Twins’ and super-Earths orbiting our neighbor stars, in which the planetary mass really matters to characterize a planet. In comparison, the Transit Method can generally provide the radius of the planet and should be confirmed by other ground-based methods, such as radial velocity.

-

-  CHES will provide three-dimensional orbits ( inclinations ) of terrestrial planets, which also act as another crucial index involved in planetary formation and characterization. These capabilities will help astronomers vastly expand the current census of exoplanets, which consists predominantly of Gas Giants (Jupiter or Saturn-like), mini-Neptunes, and Super-Earths.

-

-   With the improved resolution and sensitivity of next-generation instruments, astronomers anticipate that the number of Earth analogs will grow exponentially. It will also improve our understanding of the diverse nature of planets that orbit Sun-like stars and shed light on the formation and evolution of the Solar System.

-

-  The benefits of a next-generation space-based astrometry mission will be able to assist with surveys that rely on the second-most-popular and effective exoplanet detection method, known as the “Radial Velocity Method” (or,  Doppler Spectroscopy). For this method, astronomers observe stars for signs of apparent motion back and forth (“wobble”) resulting from the orbiting planets’ gravitational influence.

-

-  CHES can conduct joint measurements with high-precision radial-velocity instruments such as the “Extremely Large Telescope” (ELT) and “Thirty Meter Telescope” (TMT).  It can also verify habitable planet candidates discovered by this method, and accurately characterize planetary masses and orbital parameters.

-

-   CHES will be aiding in the search for dark matter, the study of black holes, and other research fields. This research will provide new insights into the physics that govern our Universe, the formation and evolution of planetary systems, and the origins of life itself. 

-

-  The “Nancy Grace Roman Space Telescope” (and the ELT and TMT), will be able to conduct Direct Imaging studies of smaller exoplanets that orbit more closely to their stars This is precisely where rocky HZ planets are expected to be found.

-

-  Combined with astrometry measurements that could reveal hundreds of rocky exoplanets in neighboring systems, astronomers could be on the verge of finding life beyond Earth!

-

May 30, 2022      EXOPLANETS  -  many new discovery tools!                      3591                                                                                                                                           

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---   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, May 31, 2022  ---------------------------

3590 - JAMES WEBB - and Event Horizon telescopes.

  -  3590 -  JAMES  WEBB -   and Event Horizon telescopes.    James Webb Space Telescope is now experiencing all seasons – from hot to cold – as it undergoes the thermal stability test, May, 2022.   To complete the telescope’s commissioning, astronomers will measure the detailed performance of the science instruments before they start routine science operations in the summer.

---------------------  3590  -    JAMES  WEBB -   and Event Horizon telescopes

-

-  James Webb Space Telescope is now experiencing all seasons – from hot to cold – as it undergoes the thermal stability test, May, 2022.   To complete the telescope’s commissioning, astronomers will measure the detailed performance of the science instruments before they start routine science operations in the summer.

-

-  With the telescope aligned and the observatory near its final cryogenic temperature, astronomers are ready to begin the last group of activities;

-

----------------  The instruments, the Near-Infrared Camera (NIRCam), 

-

----------------  Near-Infrared Spectrometer (NIRSpec),

-

 ---------------  Near-Infrared Imager and Slitless Spectrometer (NIRISS), 

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----------------  Mid-Infrared Instrument (MIRI),

-

-  The Fine Guidance Sensor (FGS) have been powered up and safely cooled. They have operated their mechanisms and detectors, including filter wheels, grating wheels, and the NIRSpec microshutter assembly. 

-

-  The Webb optics team used images of isolated stars taken with each of the instruments to align the primary and secondary mirrors.

-

-  They will begin an extensive suite of calibrations and characterizations of the instruments using a rich variety of astronomical sources. They will measure the instruments’ throughput, that is, how much of the light that enters the telescope reaches the detectors and is recorded. 

-

-  There is always some loss with each reflection by the mirrors of the telescope and within each instrument, and no detector records every photon that arrives. They will measure this throughput at multiple wavelengths of light by observing standard stars whose light emission is known from data obtained with other observatories combined with theoretical calculations.

-

-  The “astrometric calibration” of each instrument maps the pixels on the detectors to the precise locations on the sky, to correct the small but unavoidable optical distortions that are present in every optical system. 

-

-  They do this by observing the Webb astrometric field, a small patch of sky in a nearby galaxy, the Large Magellanic Cloud. This field was observed by the Hubble Space Telescope to establish the coordinates of about 200,000 stars to an accuracy of 1 milli-arcsec (less than 0.3 millionths of a degree). 

-

-  Calibrating this distortion is required to precisely place the science targets on the instruments’ field of view.   To get the spectra of a hundred galaxies simultaneously using the “NIRSpec microshutter assembly“, the telescope must be pointed so that each galaxy is in the proper shutter, and there are a quarter of a million shutters!

-

-  They measure the sharpness of the stellar images, that astronomers call the ‘point spread function.’   They already know the telescope is delivering to the instruments image quality that exceeds prelaunch expectations, but each instrument has additional optics.

-

-   These optics perform a function, such as passing the light through filters to get color information about the astronomical target or using a diffraction grating to spread the incoming light into its constituent colors. Measuring the point spread function within each instrument at different wavelengths provides an important calibration for interpreting the data.

-

-  For some observations, it is sufficient to point the telescope using the position of a guide star in the “Fine Guidance Sensor” and know the location of the science target relative to that guide star. This places the science target to an accuracy of a few tenths of an arcsecond. 

-

-  However, in some cases more precision is necessary, approximately a hundredth of an arcsecond.  For coronagraphy, the star has to be placed behind a mask so its light is blocked, allowing the nearby exoplanet to shine through.

-

-   In time series observations, they measure how an exoplanet’s atmosphere absorbs the stellar light during the hours it takes to pass in front of its star, allowing us to measure the properties and constituents of the planet’s atmosphere. Both of these applications require that the instrument send corrections to the telescope pointing control system to put the science target precisely in the correct location within the instrument’s field of view.

-

-   Most astronomical objects are so far away that they appear to be stationary on the sky. However, this is not true of the planets, satellites and rings, asteroids, and comets within our own solar system. Observing these requires that the observatory change its pointing direction relative to the background guide stars during the observation.  

-

-  When the commissioning is complete by July, 2022,  JAMES is fully ready for its scientific mission. 

-

-  There is another new telescope, the “Event Horizon Telescope”  that is collecting data to create new images of the Milky Way's supermassive blackhole.   A legion of other telescopes including three NASA X-ray observatories in space was also watching.

-

-  Astronomers are using these observations to learn more about how the black hole in the center of the Milky Way galaxy, Sagittarius A * (Sgr A* for short), interacts with, and feeds off, its environment some 27,000 light years from Earth.  You are just this far away fro a blackhole.  

-

-  When the Event Horizon Telescope (EHT) observed Sgr A* to make the new image, scientists in the collaboration also peered at the same black hole with facilities that detect different wavelengths of light. 

-

-  With this multiwavelength observing campaign astronomers assembled X-ray data from:

----------------  NASA's Chandra X-ray Observatory, 

-

----------------  Nuclear Spectroscopic Telescope Array (NuSTAR), 

-

----------------  Neil Gehrels Swift Observatory;

-

---------------   radio data from the East Asian Very Long-Baseline Interferometer (VLBI) network 

---------------   radio data from the Global 3-millimeter VLBI array;

-

---------------   infrared data from the European Southern Observatory's Very Large Telescope in Chile.

-

-  The Event Horizon Telescope has captured yet another remarkable image, this time of the giant black hole at the center of our own home galaxy.   One important goal was to catch X-ray flares, which are thought to be driven by magnetic processes similar to those seen on the Sun, but can be tens of millions of times more powerful. 

-

-  These flares occur approximately daily within the area of sky observed by the EHT, a region slightly larger than the event horizon of Sgr A*, the point of no return for matter falling inward.

-

-   Another goal was to gain a critical glimpse of what is happening on larger scales. While the EHT result shows striking similarities between Sgr A* and the previous black hole it imaged, M87*, the wider picture is much more complex.

-

-  If the new EHT image shows us the eye of a black hole hurricane, then these multiwavelength observations reveal winds and rain the equivalent of hundreds or even thousands of miles beyond.

-

-  One of the biggest ongoing questions surrounding black holes is exactly how they collect, ingest, or even expel material orbiting them at near light speed, in a process known as "accretion." This process is fundamental to the formation and growth of planets, stars, and black holes of all sizes, throughout the universe.

-

-  “Chandra” images of hot gas around Sgr A* are crucial for accretion studies because they tell us how much material is captured from nearby stars by the black hole's gravity, as well as how much manages to make its way close to the event horizon. 

-

-   Astronomers can largely agree on the basics that black holes have material swirling around them and some of it falls across the event horizon forever.   The comparison of the models with the measurements gives hints that the magnetic field around the black hole is strong and that the angle between the line of sight to the black hole and its spin-axis is low, less than about 30 degrees.

-

-   If this is confirmed this means that from our vantage point we are looking down on Sgr A* and its ring more than we are from side-on, surprisingly similar to EHT's first target M87*.

-

-  The researchers managed to catch X-ray flares from Sgr A* during the EHT observations: a faint one seen with Chandra and Swift, and a moderately bright one seen with Chandra and NuSTAR. X-ray flares with a similar brightness to the latter are regularly observed with Chandra, but this is the first time that the EHT simultaneously observed Sgr A*, offering an extraordinary opportunity to identify the responsible mechanism using actual images.

-

-  The millimeter-wave intensity and variability observed with EHT increases in the few hours immediately after the brighter X-ray flare, a phenomenon not seen in millimeter observations a few days earlier. 

-

-  These are not ordinary telescopes.  Galileo would be proud.

-

May 30, 2022       JAMES  WEBB -   and Event Horizon telescopes             3590                                                                                                                                           

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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, May 31, 2022  ---------------------------

3589 - STARS - chemical elements in Stars?

   3589  -  STARS  -  chemical elements in Stars?   Astronomers find a star that contains 65 different “Elements”.  Chemical elements are listed in the “Periodic Table of Elements“.  There are 88 natural elements and up to some 103 that can be created in radioactive research. 

-

---------------------  3589  -  STARS  -  chemical elements in Stars?   

-  We know that gold comes from stars. All stars are comprised primarily of hydrogen and helium. But they contain other elements, which astrophysicists refer to as a star’s metallicity. Our Sun has a high metallicity and contains 67 different elements, including about 2.5 trillion tons of gold.  That’s right 2,500,000,000,000 tons.

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-   Astronomers have found a distant star that contains 65 elements, the most ever detected in another star. Gold is among the elements discovered.  This star was a fairly bright star in our neighborhood of the Milky Way, named” HD 222925“. 

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-  It is close to the southern sky’s Tucana (Toucan) constellation. Astronomers are calling it the “gold standard” star because it’s their best opportunity to study how stars create some of the heavy elements in the Universe. That process is called the “r-process“, or “rapid neutron capture process“.

-

-    HD 222295 is an r-process enhanced but metal-poor star. It has high metallicity, meaning it contains many elements other than hydrogen and helium, but not much of those elements by mass. 

-

-  It’s not the first one discovered. “CS 22892–052“,  “Sneden’s star“, namedd after the scientist who first identified 53 chemical elements in it. But HD 222295 is much brighter in UV than Sneden’s star, making it much easier to observe spectroscopically. Spectroscopy is how the researchers were able to identify these 65 different elements.

-

-  Each element in the periodic table will absorb or emit light at different wavelengths depending the orbits of that elements electrons.  If you measure the absorption lines in the elements spectrum you can identify that element.  This process is called spectroscopy.

-

-  What makes this star so unique is that it has a very high relative proportion of the elements listed along the bottom two-thirds of the periodic table. These heavier elements were made by the “rapid neutron capture process“.   Astronomers are trying to study the physics to understanding how, where and when those heavier elements were created.

-

-  There are two types of neutron capture: the “slow neutron capture process“, or “s-process“, and the “r-process“. The s-process is reasonably well-understood, but scientists still have significant questions about the r-process. Astrophysicists have a good theoretical understanding of the r-process, but it wasn’t observed directly until 2019 when observers saw strontium in a kilonova explosion.  Kilonova is a more explosive type of supernova explosion.

-

-  Rapid neutron capture allows an atomic nucleus to capture neutrons quicker than the neutrons can decay, creating heavy elements. The r-process begins with elements lighter than iron. In an environment with lots of neutrons and lots of energy, these lighter elements can capture neutrons since they’re neutral and have no charge. 

-

-  When an atom captures a neutron, it emits an electron, converting the neutron into another proton. That raises the atomic number, and the lighter element becomes a heavier element.

-

- These heavier elements, including gold, are rarely detected in stars because the astrophysical sites that have the r-process are rare.  You need lots of neutrons that are free and a very high energy set of conditions to liberate them and add them to the nuclei of atoms.

-

-  This rarity makes the r-process challenging to study, and also what makes the heavier elements, like gold, rare.   Neutron star mergers and the resulting kilonova explosions are one of the environments that foster the r-process. 

-

-  Supernovae explosions of massive stars are the other. Nailing down the astrophysical environments that allow the r-process is critical in understanding the r-process. 

- 

-  HD 222295 didn’t produce the heavy elements it contains. They were produced earlier in the Universe and then spread into space by either supernovae or kilonovae. Then they were taken up in another generation of star formation, in this case by HD 222295.

-

-  Scientists know that the r-process is one of the main ways stars and their remnants produce heavier elements with atomic numbers greater than 30.  Observations have confirmed that the r-process occurs in neutron star mergers and the resulting kilonova explosions. But there are still some open questions that have persisted for a long time, like which elements it produces and in what abundances?

-

-  In 2019, a team of European researchers found signatures of strontium formed in a neutron-star merger. Researcher’s questions have led to the creation of the “R-Process Alliance“, a group of scientists trying to find answers. 

-

-   The researchers think that HD 222295 is one of a group of stars that formed in an environment enriched by the r-process. The star’s metallicity is higher than most known stars enriched by the r-process. That suggests that multiple supernovae enriched it. HD 222295 likely didn’t form as part of the Milky Way but was captured by our galaxy at some point in the past.

-

-   Now that astrophysicists have identified a bright star containing elements from the r-process, it can act as a proxy for what supernovae and kilonovae produce. As researchers create models of the r-process inside these events that creates the heavy elements, those models must have the same signature as HD 222295.

-

-  Gold has always held a certain mystique for humanity. It’s unique among the elements and made regular appearances in the world’s myths. In ancient Greece, the Gods dressed in gold and golden apples conferred mortality on those who ate them if they could get past the dragon that guarded them. In Hindu mythology, gold is the source of power and can transmit divine consciousness. 

-

-  The ancients treasured gold, but they couldn't have guessed at its origins. King Tut's mask  and his inner coffin. The inner coffin is solid gold and weighs almost 243 pounds. 

-  

-  Those beliefs are wiped away now, lost to time. But the science that replaces them is even more fascinating. The ancients could never have imagined that their myths would be replaced by science and that stars could explode and create gold and other elements. 

-

-  They could never have envisioned gigantic mountain-top telescopes that peer vast distances into space. They could never have imagined that we could cut up a star’s light and determine that the star holds gold.

-

-  And they could never have guessed that our own Sun contains 2.5 trillion tons of gold.

- 

May 28, 2022         STARS  -  chemical elements in Stars?                 3589                                                                                                                                           

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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, May 29, 2022  ---------------------------

3587 - MILKY WAY - black hole centers our galaxy?

  -  3587  -  MILKY WAY  -   black hole centers our galaxy?   The first image of our Galaxy’s supermassive black hole, released May, 2022, has already begun to explain some enduring mysteries about the heart of our Milky Way.  The wealth of new information about the black hole, called Sagittarius A*, joins many other lines of evidence that are now painting a detailed picture of the center of our galaxy. 

---------------------  3587  -   MILKY WAY  -   black hole centers our galaxy?

-   Sagittarius A* black hole is sucking in matter at a slow pace, making it unusually dim compared with the central black holes of other galaxies.   Sagittarius A* could have been spectacularly active only a few million years ago. 

-

-  The blackhole picture shows a glowing ring of radio emissions surrounding a dark shadow. This shadow lies just beyond the black hole’s event horizon which is the intangible sphere that marks a point of no return for anything that crosses it. 

-

-  As matter spirals into the black hole at nearly the speed of light, it forms an ‘accretion disk’ that emits radiation across the electromagnetic spectrum, including radio waves that the telescopes can detect. 

-

-  This data show that the accretion disk is shaped more like a puffed-up doughnut than a flat pancake. This fattened shape means that the disk supplies the black hole with scraps of matter at a leisurely pace, which makes it relatively dim compared with other, greedier black holes.

-

-  Although the shape of the accretion disk met expectations, many astrophysicists were surprised that the data showed the disk ‘face on’. This means its axis of rotation is angled at less than 50° degrees from our line of sight from Earth.

-

-  Scientists had expected that the disk’s axis of rotation would instead point vertically, showing the accretion disk ‘edge on’ from Earth’s point of view. This orientation would arise from the interplay of three separate rotations: the stately turn of the Galaxy’s spiral arms, the infalling matter supplying the accretion disk, and the rapidly spinning black hole itself.

-

-  Sagittarius A* probably formed from the merger of two black holes, when a pair of galaxies combined to formed the Milky Way. Initially, the spin of the new black hole could have pointed in any direction. But as it grew by feeding on dust and gas, the momentum of infalling matter would have slowly aligned the black hole’s spin with that of the Galaxy.

-

-  This study ruled out a vertical spin axis for the accretion disk, and perhaps also for the black hole itself. This matches observations made in 2018 by the Very Large Telescope (VLT), a facility on the mountain Cerro Paranal in Chile, which saw flares from matter orbiting very close to the black hole’s event horizon in a clockwise direction, just where the “Event Horizon Telescope“, EHT saw its ring. 

-

-  The “GRAVITY instrument“ collects infrared light from the VLT’s four 8-metre dishes to achieve a resolution comparable to that of a single 130-meter-wide telescope. Like the EHT, GRAVITY found that the accretion disk has a face-on orientation, with its axis of rotation angled 20 to 30° degrees from our line of sight.

-

-  This face-on orientation is also consistent with decades of observations of the structure of the Milky Way’s central region. The black hole’s accretion disk is supplied by matter flowing from stars that orbit Sagittarius A* in a disk about one light year across. So the orientation of the accretion disk should match the disk of stars, rather than the larger-scale structure of the Galaxy.

-

-  Zooming out from the center of the Galaxy, astronomers have previously mapped several other larger structures up to a few parsecs across. These include a ‘mini-spiral’ made of streams of gas that are reminiscent of the Milky Way’s spiral arms, but 10,000 times smaller. 

-

-  There does not seem to be much matter falling inwards from the spiral, but in the past it could have fed the black hole during periods of much more intense activity.  This spiral does not align with the disk of stars around Sagittarius A*, nor with its accretion disk or with the Galaxy itself.

-

-  Models predict a gradual alignment of the black hole’s spin might apply only to galaxies that supply a steady stream of matter to the black hole over a long time.  That doesn’t seem to be the case for the Milky Way, nor for many other galaxies that seem to contain misaligned central black holes.  

-

-  The reason must be that the gas feeding the black hole is not directed in an orderly way, but comes in separate episodes whose directions are arranged completely randomly compared with the black-hole spin axis.

-

-  This kind of chaotic feeding could keep the black hole spinning at a fairly slow rate, which would allow it to accrete enough matter to grow rapidly. That could help to explain how some black holes grew so big, so quickly: some were already billions of times as massive as the Sun when the Universe was one-tenth of its current age.

-

-  Although all of these pieces of evidence seem to agree on the orientation of Sagittarius A*, there are still big questions about a possible connection between the black hole and other huge features seen around the Galaxy’s center.

-

-  In 2010, astronomers using NASA’s Fermi Gamma-ray Space Telescope mapped two enormous lobes of gas extending directly above and below the central region of the Galaxy, each 7,700 parsecs long. 

-

-  These lobes glow in X-rays, and have become known as the “Fermi bubbles“. And in 2020, the “eROSITA X-ray telescope”  detected even larger bubbles in the same region of space.

-

-  This suggests that these bubbles are the afterglow from shock waves that jutted out of the Galactic Center in the past 20 million years. A plausible source for such a shock wave could be a burst of star-forming activity, leading to a large number of stellar explosions,  supernovae.   Another major suspect is a period of intense feeding from Sagittarius A*.

-

-   Researchers have also found glowing columns of gas extending more than 150 parsecs from the Galactic Center, which might indicate that Sagittarius A* created the Fermi bubbles. Like a chimney that’s still hot from smoke and heat that just went through it, these chimneys could be a relic of the outflow that inflated the Fermi and eROSITA bubbles.

-

-  But the bubbles seem to be aligned vertically with the Milky Way’s axis, so it’s unclear how they could have originated from a black hole that is tilted in a different direction. One possibility is that the bubbles are the end result of many separate periods of intense feeding, each spewing out matter in a different direction. 

-

-  A super-sensitive South African telescope has studied these two giant ‘radio bubbles’ above and below the central region of the Milky Way. The features stretch over a total of 430 parsecs (1,400 light years), about 5% of the distance between the Solar System and the Galaxy’s center.

-

-  The bubbles are gas structures that can be observed because electrons stirring inside them produce radio waves as they are accelerated by magnetic fields. This activity suggests that the bubbles are the remnants of an energetic eruption of hot gas several millions years ago.

-

-  One possible explanation is that the super-massive black hole at the center of the Galaxy underwent a period of intense matter-gobbling that created the outburst. 

-

-    Another could be a ‘starburst’ event, the near-simultaneous formation and subsequent fiery death of around 100 large stars. The shock waves of their explosions could have combined to blow a hole through the thick interstellar matter of the Galaxy’s central region.

-

-   Both starburst and black-hole activity might have been at play, even reinforcing each other. And researchers know of a starburst that took place in the region around 7 million years ago. 

-

-  The bubbles could also solve an old puzzle in radio astronomy. It’s possible that the electrons accelerating inside them are the source of bright ‘filaments’ of matter tens of parsecs long that stretch out of the Galactic center. Even larger bubbles, towering over those seen by MeerKAT’s, have been seen in the γ-ray part of the spectrum , and could have a similar origin.

-

-  The $330-million MeerKAT is an array of 64 radio dishes, each 13.5 meters across, at a remote site in Northern Cape province. It will form the core of the South African part of the SKA, due to be built in the 2020s. The observatory’s second section will be in Australia.

-

May 26, 2022       MILKY WAY  -   black hole centers our galaxy?             3587                                                                                                                                           

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

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

--------------------- ---  Friday, May 27, 2022  ---------------------------

3588 - NEPTUNE and URANUS - spacecraft to visit?

  -  3588  -  NEPTUNE  and  URANUS  -  spacecraft to visit?  -   Uranus is the least-explored planet of our solar system alongside Neptune.  Understanding how and where these two planets formed has direct implications for the evolution of our own planet.

-----------  3588  -     NEPTUNE  and  URANUS  -  spacecraft to visit?

------------------------------------  NEPTUNE  

-  Earth formed about 4,600,000,000  years ago as a result of a violent process where thousands of baby planets over 62 miles diameter in size collided with each other and accreted over a few million years. Scientists think early Earth would have lost most of its water to space due to the high heat from this process.

-

-  Our water instead likely came during a brief period roughly 4 billion years ago when the grand migration of the giant planets of our solar system, Jupiter, Saturn, Uranus and Neptune, scattered large asteroids and comets all over. Many of these bombarded Earth, depositing water and organic materials which are  essential ingredients for life as we know it.

-

-  Yet beyond the existence of such a critical period we don’t know exactly how the giant planets formed, how they migrated and where from.  What's the difference between gas giants and ice giants?

-

-  Jupiter and Saturn (the gas giants) and Uranus and Neptune (the ice giants) represent two different classes of planets. The gas giants are primarily made up of hydrogen and helium; ice giants contain those substances as well as heavier ones such as oxygen, nitrogen, carbon and sulfur. While their cores were forged from rapidly accreting rock-metal baby planets in the outer disk of material surrounding the Sun, their outer layers accumulated differently.

-

-  Since Jupiter and Saturn were the first and most massive planets to form, they gobbled up most of the outer solar disk’s hydrogen and helium to create their mantles and outer atmospheres. This left the still-growing mantles of Uranus and Neptune with more fractions of ices like water and ammonia, and only a relatively thin hydrogen and helium atmosphere.

-

-   Figuring out the origin of ice giants is key to understanding not only our own solar system but countless others across the galaxy. Even though planets around other stars are incredibly far away, astronomers can use certain techniques to infer their masses and sizes, and thus their densities, to tell a gas giant apart from an icy one.

-

-  In the thousands of exoplanets discovered to date (> 5,000), Uranus- and Neptune-scale worlds are the most common, followed by the gas giants. The giant planets are thus key to understanding planetary formation across the Universe.

-

-  Clues to the origin and evolution of giant planets lie in the specific elements that make up their atmospheres, ones other than the hydrogen were inherited from the Sun’s disk. For example, noble gases like helium undergo very few chemical reactions inside giant planets so measuring their abundance compared to other gases will tell scientists how and where each planet acquired its heavy elements over time.

-

-  The trouble is that other than the direct gas measurements from inside Jupiter’s atmosphere by NASA’s Galileo probe in 1995, we lack such information on Saturn, Uranus and Neptune. This is particularly pressing for the ice giants because their noble gases are the most unaltered reflections of the planet-forming materials in the early outer solar disk. 

-

-   Neptune and Uranus are the least-explored planets of our solar system, only flown past once by NASA’s Voyager 2 spacecraft in the last century, which also flew by Jupiter and Saturn.

-

-   The most recent gravity data from NASA’s Juno spacecraft, which entered Jovian orbit in 2016, provided evidence that Jupiter doesn’t have a distinct rock-metal core. Jupiter's core is larger and fuzzier than expected, likely caused by the intense gas pressures in its mantle dissolving the core into an exotic substance called “metallic hydrogen“, or due to Jupiter absorbing a planet with 10 Earth masses during its formation.

-

-  Data from NASA’s Cassini mission suggests Saturn has a fuzzy core too, spanning 60% of the planet’s diameter. These discoveries have led scientists to think that Uranus and Neptune might also have large diluted cores. The only way to know is to send a mission to the ice giants.

-

-  The 2023-2032 Planetary Science Decadal Survey produced every 10 years by the U.S. scientific community to guide future NASA missions recommends sending a spacecraft to Uranus as the highest priority. 

-

-  If commissioned, the “Uranus Orbiter and Probe” (UOP) mission will measure the planet’s complex and unique magnetic field, map gravity variations,  and note the nature of its atmospheric wobbles to determine if the planet really sports a fuzzy core and what it is made of. A probe would enter Uranus’ atmosphere and precisely measure gases and their relative abundance.

-

-  The UOP mission would thus paint us a clear picture of where and how Uranus formed, and how it subsequently evolved. Because of the two ice giants' similarity, these insights would also likely apply to Neptune. 

-

-   The mission would also provide us with missing information necessary to understand the migration of the gas giants and the connected evolution of our solar system and early Earth.

-

-   The UOP could launch on a SpaceX Falcon Heavy rocket in 2031 or 2032 and reach Uranus 12 to 13 years later.  

-

-  ESA is also considering a Uranus orbiter mission. China is considering a Voyager-like mission to interstellar space that would launch in 2024 and fly past Neptune in 2038. The spacecraft would include an atmospheric probe.

-

-   In the meanwhile, observing Jupiter-like and Neptune-like planets in different star systems lets us witness snapshots of planets forming, migrating and evolving. The next generation of telescopes, like the “Nancy Grace Roman Space Telescope“, will advance such studies by letting us observe ice giant worlds in various stages of formation.

-

-  The ice giants in our backyard are essential to understanding how planets form and evolve. It’s time we give them a visit.

-

May 27, 2022     NEPTUNE  and  URANUS  -  spacecraft to visit?               3588                                                                                                                                           

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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, May 27, 2022  ---------------------------

3586 - UNIVERSE - Einstein’s theory of the universe?

  -  3586  -    UNIVERSE  -  Einstein’s  theory of the universe?    Is Einstein’s cosmological constant the same as dark energy? Why has, over time, the term “dark energy” replaced the original term “cosmological constant?” Are the two terms identical or not, and why?

----------------  3586  -    UNIVERSE  -  Einstein’s  theory of the universe? 

-  One of the most mysterious components in the entire Universe is “dark energy“. Modern astronomers had assumed, quite reasonably, that the Universe was a balancing act, with the expansion of the Universe and the gravitational effects of everything within it fighting against one another.

-

-   If gravity won, the Universe would recollapse; if the expansion won, everything would fly away into oblivion. And yet when we made the critical observations in the 1990s and beyond, we found that not only is the expansion winning, but the distant galaxies we see speed away from us at faster and faster rates as time goes on. 

-

-   We now know that a large fraction of galaxies beyond the Milky Way are spiral-shaped in nature, and that all of the spiral nebulae we were considering in 1920 are indeed galaxies beyond our own. 

-

-   When Einstein was working on a theory of gravity to replace and supersede Newton’s law of universal gravitation, we didn’t yet know very much about the Universe.  We had measured stars, comets, asteroids, and nebulae; we had witnessed novae and supernovae; we had discovered variable stars and knew about atoms; and we had revealed intriguing structures in the sky, like spirals and ellipticals.

-

-  But we didn’t know that these spirals and ellipticals were “galaxies” all unto themselves. In fact, that was only the second-most popular idea; the leading idea of the day was that they were entities, perhaps proto-stars in the process of forming, contained within the Milky Way, which itself comprised the entire Universe. 

-

-  Einstein was looking for a theory of gravity that could be applied to anything and everything that existed, and that included the known Universe as a whole.

-

-  The gravitational behavior of the Earth around the Sun is not due to an invisible gravitational pull, but is better described by the Earth falling freely through “curved space” dominated by the Sun. 

-

-  The shortest distance between two points isn’t a straight line, but rather a “geodesic“: a curved line that’s defined by the gravitational deformation of spacetime. 

-

-  The problem became apparent when Einstein succeeded in formulating his theoretical  “General Relativity“”.   Instead of being based on masses exerting forces on one another infinitely fast across infinite distances, Einstein’s conception was vastly different. First, because space and time were relative for each and every observer, not absolute, the theory needed to give identical predictions for all observers: what physicists call “relativistic invariant.” 

-

-  That meant instead of separate notions of space and time, they needed to be woven together into a four-dimensional fabric: “spacetime“. And instead of propagating at infinite speeds, gravitational effects were limited by the speed of gravity, which in Einstein’s theory equals the speed of light.

-

-  The key advance that Einstein made was that, instead of masses pulling on each other, gravity worked by both matter and energy curving the fabric of spacetime. That curved spacetime, in turn, then dictated how matter and energy moved through it.

-

-   At each instant in time, the matter and energy in the Universe tells spacetime how to curve, the curved spacetime tells matter how to move, and then it does: the matter and energy moves a tiny bit and the spacetime curvature changes. And then, when the next instant arrives, the same equations of General Relativity tell both the matter and energy and the spacetime curvature how to evolve into the future.

-

-  If Einstein had stopped there, he would have instigated a cosmic revolution.  One side of the equation,  had all the matter and energy in the Universe, while on the other side of the equals sign in the equation, you had the curvature of spacetime.   Whatever the equations predict should tell you what happens next.

-

-  When Einstein solved those equations a large distance away from a small mass, he got Newton’s law of universal gravitation back. When he got closer to the mass, he started to get corrections, which both explained the orbit of Mercury and predicted that starlight passing near the Sun during a total solar eclipse would be deflected. This was how General Relativity was first validated when put to the test.

-

-  But,  there was another problem that arose in a different situation. If we assumed that the Universe was filled roughly evenly with matter, we could solve that scenario. What Einstein discovered was disconcerting: the Universe was unstable. If it began in a stationary spacetime, the Universe would collapse in on itself. So Einstein, to fix this, invented a “cosmological constant“.

-

-  In a Universe that isn’t expanding, you can fill it with stationary matter in any configuration you like, but it will always collapse down to a black hole. Such a Universe is unstable in the context of Einstein’s gravity, and must be expanding to be stable, or we must accept its inevitable fate.

-

-  You have to understand where the idea of a cosmological constant comes from. There’s a very powerful mathematical tool that we use all the time in physics: a differential equation.   Something as simple as Newton’s F = ma is a differential equation. All it means is that this equation tells you how something will behave in the next moment, and then, once that moment has elapsed, you can put those new figures back into the same equation, and it will go on to tell you what happens in the next moment.

-

-  A differential equation will tell you what happens to a ball rolling down a hill on the Earth. It tells you what path it will take, how it will accelerate, and how its position will change at every moment in time. Just by solving the differential equation describing the ball rolling down the hill, you can know precisely what trajectory it will take.

-

-  The differential equation tells you almost everything you’d want to know about the ball rolling down the hill, but there’s one thing it can’t tell you: how high the base level of the ground is. You have no way of knowing whether you’re on a hill atop a plateau, on a hill that ends at sea level, or on a hill that ends in a hollowed-out volcanic crater. An identical hill at all three elevations will be described by the exact same differential equation.

-

-  When we see something like a ball balanced precariously atop a hill, this appears to be what we call a finely-tuned state, or a state of unstable equilibrium. A much more stable position is for the ball to be down somewhere at the bottom of the valley. But is the valley at zero, or some non-zero positive or negative value? The mathematics of a ball rolling down the hill is identical up to this additive constant. 

-

-  That same problem shows up in calculus when you first learn how to do an “indefinite integral“; anyone who’s taken calculus will remember the infamous “plus C” that you have to add at the end. Well, Einstein’s General Relativity isn’t just one differential equation, but a matrix of 16 differential equations, related in such a way that 10 of them are independent of one another.

-

-   But to each of those differential equations, you can add a constant in a particular way: what became known as the “cosmological constant“. Perhaps surprisingly, it’s the only thing you can add to General Relativity besides another form of matter or energy that won’t fundamentally alter the nature of Einstein’s theory.

-

-  Einstein put a cosmological constant into his theory not because it was allowed, but because, for him, it was preferred. Without adding a cosmological constant in, his equations predicted that the Universe should either be expanding or contracting, something that clearly wasn’t happening.

-

-   Instead of going with what the equations said anyway, Einstein threw the cosmological constant in there in order to “fix” what appeared to be an otherwise broken situation. If he had listened to the equations, he could have predicted the expanding Universe. 

-

-  While matter (both normal and dark) and radiation become less dense as the Universe expands owing to its increasing volume, dark energy, and also the field energy during inflation, is a form of energy inherent to space itself. As new space gets created in the expanding Universe, the dark energy density remains constant.

-

-  The cosmological constant is unlike the types of energy we know of otherwise. When you have matter in the Universe, you have a fixed number of particles. As the Universe expands, the number of particles stays the same, so the density goes down over time.

-

-  With radiation, not only are the number of particles fixed, but as the radiation travels through the expanding Universe, its wavelength stretches relative to an observer that will someday receive it: its density goes down, and each individual quantum also loses energy with time.

-

-  But for a cosmological constant, it’s a constant form of energy that’s “intrinsic to space“.  There’s no way to “know” what the value of the cosmological constant is; we’ve simply assumed that it would be zero. But it doesn’t have to be; it could take on any value at all: positive, negative, or zero.

-

-  Various components of and contributors to the Universe’s energy density, and when they might dominate.  Radiation is dominant over matter for roughly the first 9,000,000,000 years, then matter dominates, and finally, a cosmological constant emerges. 

-

-  If we extrapolate back in time to when the Universe was younger, hotter, denser, and smaller the cosmological constant wouldn’t have been noticeable. It would have been swamped by the much larger effects of matter and radiation early on. Only after the Universe has expanded and cooled so that the matter and radiation density drops to a low enough value can the cosmological constant finally appear.

-

-  When we talk about dark energy, it might turn out to be a cosmological constant.  When we take all of the observations we have so far, it appears that dark energy is consistent with being a cosmological constant, as the way the expansion rate changes over time agrees, within the uncertainties, with what a cosmological constant would be responsible for. But there are uncertainties there, and dark energy could be:

-

-------------------  Increasing or decreasing in strength over time,

-------------------  Changing in energy density, unlike a cosmological constant,

-------------------   Evolving in a novel, complicated fashion.

-

-  Although we have constraints on how much dark energy could be evolving by over the past 6 billion years or so, we cannot definitively say it’s a “constant“.

-

-  We would like to know whether it is a constant or not. The way we’re going to make this determination, as is always the case in science, is with superior and subsequent observations. Large data sets are the key, as is sampling the Universe at a wide variety of distances, as it’s the way the light evolves as it travels through the expanding Universe that allows us to determine how the expansion rate has changed over time. If it’s exactly equal to a cosmological constant, there’s a particular curve it’ll follow; if not, it’ll follow a different curve, and we’ll be able to see that.

-

-  By the end of the 2020s, we’ll have an enormous and comprehensive ground-based survey of the Universe thanks to the “Vera C. Rubin observatory“, which will supersede everything that surveys like ‘Pan-STARRS” and the “Sloan Digital Sky Survey” have done. 

-

-  We’ll have an enormous suite of space-based data thanks to the “ESA’s Euclid observatory” and NASA’s “Nancy Roman telescope“, which will see more than 50 times as much Universe as Hubble presently sees. With all of this novel data, we should be able to determine whether dark energy, which is a general term for any novel form of energy in the Universe, is truly identical to what the very specific “cosmological constant” predicts, or whether it varies in any way at all.

-

-  Instead of adding in a cosmological constant, modern dark energy is treated as just another component of energy in the expanding Universe. This generalized form of the equations clearly shows that a static Universe is out, and helps visualize the difference between adding a cosmological constant and including a generalized form of dark energy. 

-

-  It’s extremely tempting to assume that dark energy is nothing more complex than a cosmological constant. It’s understandable why we’d do this: the cosmological constant is already allowed as part of General Relativity without additional explanation. 

-

-  Furthermore, we don’t know how to calculate the zero-point energy of empty space in quantum field theory, and that contributes to the Universe in exactly the same fashion as a cosmological constant would as well. 

-

-  And, when we make our observations, they’re all consistent with dark energy being a cosmological constant, with no need for anything more complicated.

-

-  But,  that underscores exactly why it’s so vitally important to make these novel measurements. If we didn’t bother to measure the Universe in a careful, precise, intricate fashion, we’d never have discovered the need for Einstein’s relativity in the first place. 

-

-  We never would have discovered quantum physics, nor would we have conducted most of the Nobel-winning research that’s driven society forward over the 20th and 21st centuries. Years from now, we’ll have the data to know whether dark energy differs from a cosmological constant by as little as 1%.

-

-  The cosmological constant may be the same thing as dark energy, but it doesn’t need to be. Even if it is, we’d still like to understand why it behaves this particular way and not any other.

-

-   As 2022 dawns, it’s important to remember the most vital lesson of all: the answers to our deepest cosmic questions are written on the face of the Universe. If we want to know them, the only way is to put the question to our physical reality itself.

-

May 24, 2022        UNIVERSE  -  Einstein’s  theory of the universe?                   3586                                                                                                                                           

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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, May 24, 2022  ---------------------------

3585 - PLANET NINE - is it out there? -

 

 -  3585  -  PLANET  NINE   -  is it out there?  A new method for hunting minor planets uncovered more than a hundred small, distant worlds.  The discovery of 139 new minor planets in the outer solar system, and especially the new method used to find them, might eventually help astronomers determine whether “Planet Nine” exists past Neptune.

---------------------  3585  -  PLANET  NINE   -  is it out there?

-

-  We all learned that Pluto was “planet nine“.  But, astronomy experts have reduced Pluto to a dwarf planet.  So our Solar System has 8 planets now.   And many dwarfs farther out.  The decision occurred because astronomers kept discovering smaller planets orbiting outside the orbit of Neptune. 

-

-  As of 2022, astronomers have discovered 139 new minor planets orbiting the Sun beyond Neptune by searching through data from the Dark Energy Survey. The new method for spotting small worlds is expected to reveal many thousands of distant objects in coming years, meaning these first hundred or so are likely just the tip of the iceberg.

-

-  Taken together, the newfound distant objects, as well as those to come, could resolve one of the most fascinating questions of modern astronomy: Is there a massive and mysterious world called “Planet Nine” lurking in the outskirts of our solar system?

-

-  Neptune orbits the Sun at a distance of about 30 astronomical units, 1 AU is the Earth-Sun distance.  Beyond Neptune lies the “Kuiper Belt” , a comet-rich band of frozen, rocky objects (including Pluto) that holds dozens to hundreds of times more mass than the asteroid belt.

-

-   Both within the Kuiper Belt and past its outer edge at 50 AU orbit distant bodies called trans-Neptunian objects (TNOs). Currently, we know of nearly 3,000 TNOs in the solar system, but estimates put the total number closer to 100,000.

-

-  As more and more TNOs have been discovered over the years, some astronomers have noticed a small subset of these objects have peculiar orbits. They seem to bunch up in unexpected ways, as if an unseen object is herding these so-called “extreme TNOs”  into specific orbits. Astronomers think these bizarrely orbiting TNOs point to the existence of a massive, distant world called “Planet Nine“.

-

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

-

-  This Planet Nine is to be 5 to 15 times the mass of Earth and to orbit some 400 AU (or farther) from the Sun.  The proposed Planet Nine would have enough of a gravitational pull that it could orchestrate the orbits of the extreme TNOs, causing them to cluster together as they make their closest approaches to the Sun.

-

-  The problem is that the evidence for Planet Nine is so far indirect and sparse. There could be something else that explains the clumped orbits, or perhaps researchers stumbled on a few objects that just happen to have similar orbits.

-

-   Discovering more TNOs, particularly beyond the Kuiper Belt, will allow astronomers to find more clues that could point to the location of the proposed Planet Nine, or,  deny its existence altogether. Of the 139 newly discovered minor planets found in this study, seven are extreme TNOs.

-

-  The new TNOs were found by astronomers at the University of Pennsylvania using data from the “Dark Energy Survey“, (DES), which was not originally designed to look for distant minor planets.

-

-  “The Blanco Telescope” at the Cerro Tololo Inter-American Observatory in Chile houses the Dark Energy Camera, the primary tool of the Dark Energy Survey. Designed to reveal mysteries of dark energy in the universe, data from the survey could also help resolve the mystery of Planet Nine.

-

-   DES, an international effort to understand dark energy, began observing the southern skies in 2013, using an extremely sensitive camera mounted on the Blanco 4-meter telescope in the Chilean Andes. 

-

-  Most astronomers trying to find TNOs have a dedicated way of looking at the sky where they take images a few hours apart and you can see the objects move very easily. The DES data didn’t work that way.

-

-  DES uses novel algorithms that could identify moving objects by connecting the dots between DES images, helping identify whether TNOs were present. The researchers then validated their movement-spotting algorithm against known TNOs and also confirmed that they could filter out fake objects.

-

-   Astronomers expect to find as many as 500 or more TNOs. Then, if the same method is applied to data from even more sensitive surveys on the horizon, such as by the new “Vera C. Rubin Observatory“, they expect discoveries of new TNOs to number in the thousands. And with those numbers, astronomers might finally get a definitive answer to whether or not our solar system is harboring a giant planet in its distant reaches.

-

-  It’s a fantastic example of how a survey designed for one area of astronomy,  to study the expansion history of the universe, can also produce great science in a completely unrelated area.

-

-  

The hypothetical world called Planet Nine is expected to be a super-Earth or sub-Neptune planet with an orbit that potentially takes it dozens of times farther from the Sun than the dwarf planet Pluto.   TNOs are difficult to detect, and so each one we find tells us that there is a much more massive underlying population of objects out there.

-

-   The more TNOs we discover, the more we can tell if there’s evidence for Planet Nine.

-

May 21, 2022              PLANET  NINE   -  is it out there?              3584                                                                                                                                           

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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”  -----------

--------------------- ---  Sunday, May 22, 2022  ---------------------------

3583 - BLACKHOLE BINARIES - not many detected?

  -  3583  - BLACKHOLE  BINARIES -   not many detected?   Astronomers have not directly detected gamma or X-ray emissions from the pulsar in this binary star.   The binary was discovered because we see a star with a day side that’s much hotter than the night side, orbiting around something every 62 minutes.  This seems to point to it being a “black widow binary“. 

---------------------  3583  -  BLACKHOLE  BINARIES -   not many detected?

-  See Review 3582 about binary stars in general  This review is about those special cases where one of the binaries is a blackhole.

-

-  A binary system 3,000 light years from Earth is a stellar oddity.  It is called a  “black widow binary” because a rapidly spinning neutron star, or pulsar, that is circling and slowly consuming a smaller companion star.

-

-  Astronomers know of about two dozen black widow binaries in the Milky Way. This newest candidate,  “ZTF J1406+1222“, has the shortest orbital period yet identified, with the pulsar and companion star circling each other every 62 minutes. The system is unique in that it appears to host a third, far-flung star that orbits around the two inner stars every 10,000 years.

-

-  This likely triple black widow is raising questions about how such a system could have formed.  As with most black widow binaries, the triple system likely arose from a dense constellation of old stars known as a globular cluster. This particular cluster may have drifted into the Milky Way’s center, where the gravity of the central black hole was enough to pull the cluster apart while leaving the triple black widow intact.

-

-  To detect the triple system astronomers used a new approach.   While most black widow binaries are found through the gamma and X-ray radiation emitted by the central pulsar, the team used visible light, and specifically the flashing from the binary’s companion star.

-

-   Black widow binaries are powered by “pulsars” which are rapidly spinning neutron stars that are the collapsed cores of massive stars. Pulsars have a rotational period, spinning around every few milliseconds, and emitting flashes of high-energy gamma and X-rays in the process.

-

-  Normally, pulsars spin down and die quickly as they burn off a huge amount of energy. But every so often, a passing star can give a pulsar new life. As a star nears, the pulsar’s gravity pulls material off the star, which provides new energy to spin the pulsar back up. The “recycled” pulsar then starts reradiating energy that further strips the star, and eventually destroys it.

-

-  These systems are called “black widows” because of how the pulsar consumes the thing that recycled it.

-

-   The companion star’s day side, the side perpetually facing the pulsar, can be many times hotter than its night side, due to the constant high-energy radiation it receives from the pulsar.

-

-   Optical data was taken by the “Zwicky Transient Facility“, an observatory based in California that takes wide-field images of the night sky. The brightness of stars were changing dramatically by a factor of 10 or more, on a timescale of about an hour or less.  These were signs that indicate the presence of a companion star orbiting tightly around a pulsar.

-

-  Astronomers then spotted this star whose brightness changed by a factor of 13, every 62 minutes, indicating that it was likely part of a new black widow binary.

-

-  Astronomers have not directly detected gamma or X-ray emissions from the pulsar in the binary, which is the typical way in which black widows are confirmed.  The one thing that was discovered is that we see a star with a day side that’s much hotter than the night side, orbiting around something every 62 minutes.  This seems to point to it being a black widow binary. 

-

May 20, 2022          BLACKHOLE  BINARIES -   not many detected?         3583                                                                                                                                            

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