Topic: Mid August Astronomy Bulletin

[Clive]

EARTH SMASHES RECORD FOR SHORTEST DAY

Earth Sky

On July 29, the Earth broke its record for the shortest day as it completed a full spin in 1.59 milliseconds less than its standard 24-hour rotation. The planet recently has been increasing its speed. Back in 2020, the Earth saw its shortest month that has ever been recorded since the 1960s. On July 19 of that year, the shortest of all time was measured. It was 1.47 milliseconds shorter than a typical 24-hour day. The next year, the planet continued to spin at a generally increased rate, but it did not break any records. However, according to some scientists a 50-year phase of shorter days may be starting right now. The cause of the differing speed of Earth's spin is still unknown. But scientists speculate that this could be because of processes in the inner or outer layers of the core, oceans, tides or even changes in climate. Some researchers also believe that this could be related to the movement of Earth's geographic poles across its surface, known as the "Chandler wobble". In simpler words, this is similar to the quiver one sees when a spinning top starts gaining momentum or slows down.

If the Earth continues to spin at an increasing rate it could lead to the introduction of the negative leap seconds, in a bid to keep the rate that the Earth orbits the Sun consistent with the measurement from atomic clocks. However, the negative leap second would have potentially confusing consequences for smartphones, computers and communications systems. Citing a Meta blog, the outlet reported that the leap second "mainly benefits scientists and astronomers" but that it is a "risky practice that does more harm than good". This is because the clock progresses from 23:59:59 to 23:59:60 before resetting to 00:00:00. A time jump like this can, therefore, crash programmes and corrupt data due to the timestamps on the data storage. Should a negative leap second occur, the clock will change from 23:59:58 to 00:00:00, and this could have a "devastating effect" on the software relying on timers and schedulers. According to IE, to solve this, international timekeepers may need to add a negative leap second - a "drop second". Notably, Coordinated Universal Time (UTC), the primary time standard by which the world regulates clocks and time, has already been updated with a leap second 27 times.



SUPER-EARTH SKIMMING HABITABLE ZONE OF RED DWARF

National Institutes of Natural Sciences

A super-Earth planet has been found near the habitable zone of a red dwarf star only 37 light-years from the Earth. This is the first discovery by a new instrument on the Subaru Telescope and offers a chance to investigate the possibility of life on planets around nearby stars. With such a successful first result, we can expect that the Subaru Telescope will discover more, potentially even better, candidates for habitable planets around red dwarfs. Red dwarfs, stars smaller than the Sun, account for three-quarters of the stars in the Milky Way Galaxy, and are abundant in the neighbourhood around the Sun. As such, they are important targets in the search for nearby extra-solar planets and extraterrestrial life. But red dwarfs are cool and don't emit much visible light compared to other types of stars, making it difficult to study them. In the infrared wavelengths red dwarfs are brighter. So the Astrobiology Center in Japan developed an infrared observational instrument mounted on the Subaru Telescope to search for signs of planets around red dwarf stars. The instrument is called IRD for Infrared Doppler, the observational method used in this search. The first fruits of this search are signs of a super-Earth four times the mass of the Earth circling the star Ross 508, located 37 light-years away in the constellation Serpens. This planet, Ross 508 b, has a year of only 11 Earth-days, and lies at the inner edge of the habitable zone around its host star. Interestingly, there are indications that the orbit is elliptical, which would mean that for part of the orbit the planet would be in the habitable zone, the region where conditions would be right for liquid water to exist on the surface of the planet. Whether or not there is actually water or life are questions of further study.

AREAS ON THE MOON WHERE THE TEMPERATURE IS 15c :

University of California - Los Angeles

A team of planetary scientists has discovered shady locations within pits on the Moon that always hover around a comfortable 15 degrees centigrade. The pits, and caves to which they may lead, would make safer, more thermally stable base camps for lunar exploration and long-term habitation than the rest of the Moon's surface, which heats up to 127 degrees during the day and drops to 138 degrees below zero at night. Pits were first discovered on the Moon in 2009, and since then, scientists have wondered if they led to caves that could be explored or used as shelters. About 16 of the more than 200 pits are probably collapsed lava tubes. Two of the most prominent pits have visible overhangs that clearly lead to some sort of cave or void, and there is strong evidence that another's overhang may also lead to a large cave. Lava tubes, also found on Earth, form when molten lava flows beneath a field of cooled lava or a crust forms over a river of lava, leaving a long, hollow tunnel. If the ceiling of a solidified lava tube collapses, it opens a pit that can lead into the rest of the cave-like tube. Scientists processed images from the Diviner Lunar Radiometer Experiment -- a thermal camera and one of six instruments on NASA's robotic Lunar Reconnaissance Orbiter -- to find out if the temperature within the pits diverged from those on the surface. Focusing on a roughly cylindrical 100-metre-deep in Mare Tranquillitatis, the team used computer modelling to analyse the thermal properties of the rock and lunar dust and to chart the pit's temperatures over a period of time. The results revealed that temperatures within the permanently shadowed reaches of the pit fluctuate only slightly throughout the lunar day, remaining at around 15 degrees. If a cave extends from the bottom of the pit, as images taken by the Lunar Reconnaissance Orbiter Camera suggest, it too would have this relatively comfortable temperature.

A day on the Moon lasts nearly 15 Earth days, during which the surface is constantly bombarded by sunlight and is frequently hot enough to boil water. Unimaginably cold nights also last about 15 Earth days. Inventing heating and cooling equipment that can operate under these conditions and producing enough energy to power it nonstop could prove an insurmountable barrier to lunar exploration or habitation. Solar power -- NASA's most common form of power generation -- doesn't work at night, after all. (NASA currently has no plans to establish an exploration base camp or habitations on the Moon.) Building bases in the shadowed parts of these pits allows scientists to focus on other challenges, like growing food, providing oxygen for astronauts, gathering resources for experiments and expanding the base. The pits or caves would also offer some protection from cosmic rays, solar radiation and micrometeorites. Diviner has been mapping the Moon continuously since 2009, producing NASA's second largest planetary dataset and providing the most detailed and comprehensive thermal measurements of any object in our solar system, including Earth. The team's current work on lunar pits has improved data from the Diviner experiment. Data from the early stages of this lunar pit thermal modelling project were used to help develop the thermal management system of the rover for NASA's proposed Moon Diver mission.

HEAVIEST KNOWN NEUTRON STAR CONSUMING COMPANION

University of California - Berkeley

Millisecond pulsars spin far more rapidly than expected for a collapsed star. The best chance to study these neutron stars is to find a black widow system where the pulsar has evaporated and eaten much of its companion star. The Keck I telescope was just able to capture spectra of one such companion, allowing astronomers to weigh its pulsar. It's the heaviest found to date, and perhaps near the upper limit for a neutron star. A dense, collapsed star spinning 707 times per second -- making it one of the fastest spinning neutron stars in the Milky Way galaxy -- has shredded and consumed nearly the entire mass of its stellar companion and, in the process, grown into the heaviest neutron star observed to date. Weighing this record-setting neutron star, which is 2.35 times the mass of the Sun, helps astronomers understand the weird quantum state of matter inside these dense objects, which -- if they get much heavier than that -- collapse entirely and disappear as a black hole. A neutron star is like one giant nucleus, but when you have one-and-a-half solar masses of this stuff, masses of nuclei all clinging together, it's not at all clear how they will behave. Neutron stars are so dense -- 1 cubic inch weighs over 10 billion tons -- that their cores are the densest matter in the Universe short of black holes, which because they are hidden behind their event horizon are impossible to study. The neutron star, a pulsar designated PSR J0952-0607, is thus the densest object within sight of Earth. The measurement of the neutron star's mass was possible thanks to the extreme sensitivity of the 10-meter Keck I telescope on Maunakea in Hawai'i, which was just able to record a spectrum of visible light from the hotly glowing companion star, now reduced to the size of a large gaseous planet. The stars are about 3,000 light years from Earth in the direction of the constellation Sextans.

If 2.35 solar masses is close to the upper limit of neutron stars, the researchers say, then the interior is likely to be a soup of neutrons as well as up and down quarks -- the constituents of normal protons and neutrons -- but not exotic matter, such as "strange" quarks or kaons, which are particles that contain a strange quark. Astronomers generally agree that when a star with a core larger than about 1.4 solar masses collapses at the end of its life, it forms a dense, compact object with an interior under such high pressure that all atoms are smashed together to form a sea of neutrons and their subnuclear constituents, quarks. These neutron stars are born spinning, and though too dim to be seen in visible light, reveal themselves as pulsars, emitting beams of light -- radio waves, X-rays or even gamma rays -- that flash Earth as they spin, much like the rotating beam of a lighthouse. "Ordinary" pulsars spin and flash about once per second, on average, a speed that can easily be explained given the normal rotation of a star before it collapses. But some pulsars repeat hundreds or up to 1,000 times per second, which is hard to explain unless matter has fallen onto the neutron star and spun it up. But for some millisecond pulsars, no companion is visible. One possible explanation for isolated millisecond pulsars is that each did once have a companion, but it stripped it down to nothing. The pulsar PSR J0952-0607 and its faint companion star support this origin story for millisecond pulsars. Finding black widow pulsars in which the companion is small, but not too small to detect, is one of few ways to weigh neutron stars. In the case of this binary system, the companion star -- now only 20 times the mass of Jupiter -- is distorted by the mass of the neutron star and tidally locked, similar to the way our Moon is locked in orbit so that we see only one side. The neutron star-facing side is heated to temperatures of about 6,200 Kelvin, a bit hotter than our Sun, and just bright enough to see with a large telescope.

DETECTION OF GAS IN CIRCUMPLANETARY DISK

National Radio Astronomy Observatory

Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) have made the first-ever detection of gas in a circumplanetary disk. What's more, the detection also suggests the presence of a very young exoplanet. Circumplanetary disks are an amassing of gas, dust, and debris around young planets. These disks give rise to moons and other small, rocky objects, and control the growth of young, giant planets. Studying these disks in their earliest stages may help shed light on the formation of our own Solar System, including that of Jupiter's Galilean moons, which scientists believe formed in a circumplanetary disk of Jupiter around 4.5 billion years ago. While studying AS 209 -- a young star located roughly 395 light-years from Earth in the constellation Ophiuchus -- scientists observed a blob of emitted light in the middle of an otherwise empty gap in the gas surrounding the star. That led to the detection of the circumplanetary disk surrounding a potential Jupiter-mass planet. Scientists are watching the system closely, both because of the planet's distance from its star and the star's age. The exoplanet is located more than 200 astronomical units, or 18.59 billion miles, away from the host star, challenging currently accepted theories of planet formation. And if the host star's estimated age of just 1.6 million years holds true, this exoplanet could be one of the youngest ever detected. Further study is needed, and scientists hope that upcoming observations with the James Webb Space Telescope will confirm the planet's presence. Scientists have long suspected the presence of circumplanetary disks around exoplanets, but until recently were unable to prove it. In 2019, ALMA scientists made the first-ever detection of a circumplanetary, moon-forming disk while observing the young exoplanet PDS 70c, and confirmed the find in 2021. The new observations of gas in a circumplanetary disk at AS 209 may shed further light on the development of planetary atmospheres and the processes by which moons are formed.

DISTURBANCE IN NEARBY DWARF GALAXIES INDICATE ALTERNATIVE GRAVITY THEORY

University of Bonn

Dwarf galaxies are small, faint galaxies that can usually be found in galaxy clusters or near larger galaxies. Because of this, they might be affected by the gravitational effects of their larger companions. Tides arise when gravity from one body pulls differently on different parts of another body. These are similar to tides on Earth, which arise because the Moon pulls more strongly on the side of Earth which faces the Moon. The Fornax Cluster has a rich population of dwarf galaxies. Recent observations show that some of these dwarfs appear distorted, as if they have been perturbed by the cluster environment. Scientists analysed the expected level of disturbance of the dwarfs, which depends on their internal properties and their distance to the gravitationally powerful cluster centre. Galaxies with large sizes but low stellar masses and galaxies close to the cluster centre are more easily disturbed or destroyed. They compared the results with their observed level of disturbance evident from photographs taken by the VLT Survey Telescope of the European Southern Observatory. The comparison showed that, if one wants to explain the observations in the standard model, the Fornax dwarfs should already be destroyed by gravity from the cluster centre even when the tides it raises on a dwarf are sixty-four times weaker than the dwarf's own self-gravity. Not only is this counter-intuitive, it also contradicts previous studies, which found that the external force needed to disturb a dwarf galaxy is about the same as the dwarf's selfgravity.

From this, the team concluded that, in the standard model, it is not possible to explain the observed morphologies of the Fornax dwarfs in a self-consistent way. They repeated the analysis using Milgromian dynamics (MOND). Instead of assuming dark matter halos surrounding galaxies, the MOND theory proposes a correction to Newtonian dynamics by which gravity experiences a boost in the regime of low accelerations. It is not certain that the dwarf galaxies would be able to survive the extreme environment of a galaxy cluster in MOND, due to the absence of protective dark matter halos in this model, but the results show a remarkable agreement between observations and the MOND expectations for the level of disturbance of the Fornax dwarfs. This is not the first time that a study testing the effect of dark matter on the dynamics and evolution of galaxies concluded that observations are better explained when they are not surrounded by dark matter. The number of publications showing incompatibilities between observations and the dark matter paradigm just keeps increasing every year.

DARK MATTER AROUND GALAXIES 12 BILLION YEARS AGO

Nagoya University

Japanese scientists have investigated the nature of dark matter surrounding galaxies seen as they were 12 billion years ago, billions of years further back in time than ever before. Seeing something that happened such a long time ago is difficult. Because of the finite speed of light, we see distant galaxies not as they are today, but as they were billions of years ago. But even more challenging is observing dark matter, which does not emit light. Consider a distant source galaxy, even further away than the galaxy whose dark matter one wants to investigate. The gravitational pull of the foreground galaxy, including its dark matter, distorts the surrounding space and time, as predicted by Einstein's theory of general relativity. As the light from the source galaxy travels through this distortion, it bends, changing the apparent shape of the galaxy. The greater the amount of dark matter, the greater the distortion. Thus, scientists can measure the amount of dark matter around the foreground galaxy (the "lens" galaxy) from the distortion. However, beyond a certain point scientists encounter a problem. The galaxies in the deepest reaches of the Universe are incredibly faint. As a result, the further away from Earth we look, the less effective this technique becomes. The lensing distortion is subtle and difficult to detect in most cases, so many background galaxies are necessary to detect the signal. Most previous studies have remained stuck at the same limits. Unable to detect enough distant source galaxies to measure the distortion, they could only analyze dark matter from no more than 8-10 billion years ago. These limitations left open the question of the distribution of dark matter between this time and 13.7 billion years ago, around the beginning of our Universe.

To overcome these challenges and observe dark matter from the furthest reaches of the Universe, a research team used a different source of background light, the microwaves released from the Big Bang itself. First, using data from the observations of the Subaru Hyper Suprime-Cam Survey (HSC), the team identified 1.5 million lens galaxies using visible light, selected to be seen 12 billion years ago. Next, to overcome the lack of galaxy light even further away, they employed microwaves from the cosmic microwave background (CMB), the radiation residue from the Big Bang. Using microwaves observed by the European Space Agency's Planck satellite, the team measured how the dark matter around the lens galaxies distorted the microwaves. After a preliminary analysis, the researchers soon realized that they had a large enough sample to detect the distribution of dark matter. Combining the large distant galaxy sample and the lensing distortions in CMB, they detected dark matter even further back in time, from 12 billion years ago. This is only 1.7 billion years after the beginning of the Universe, and thus these galaxies are seen soon after they first formed. One of the most exciting findings of the researchers was related to the clumpiness of dark matter. According to the standard theory of cosmology, the Lambda-CDM model, subtle fluctuations in the CMB form pools of densely packed matter by attracting surrounding matter through gravity. This creates inhomogeneous clumps that form stars and galaxies in these dense regions. The group's findings suggest that their clumpiness measurement was lower than predicted by the Lambda-CDM model.

RUSSIA TO STAY WITH ISS UNTIL 2028

Verge

After insinuating that it planned to leave the International Space Station partnership after 2024, Russia’s state space corporation Roscosmos has told NASA that it intends to remain in the program until at least 2028. Roscosmos plans to stay involved with the ISS until it gets a new Russian space station up and running, with 2028 as the target date. NASA and Roscosmos are the two biggest partners on the International Space Station, and both entities are tasked with operating the vehicle and maintaining a continuous human presence on the ISS while in orbit. However, growing tensions between the United States and Russia over the latter’s invasion of Ukraine have prompted concern about the future of the ISS partnership. NASA still plans to operate the vehicle until 2030, and it appears that Roscosmos will be on board for most of that time.

CURIOSITY MARS ROVER STILL GOING STRONG

JPL

Despite signs of wear, the intrepid spacecraft is about to start an exciting new chapter of its mission as it climbs a Martian mountain.  Ten years ago, a jetpack lowered NASA’s Curiosity rover onto the Red Planet, beginning the SUV-size explorer’s pursuit of evidence that, billions of years ago, Mars had the conditions needed to support microscopic life.  Since then, Curiosity has driven nearly 18 miles and ascended 2,050 feet as it explores Gale Crater and the foothills of Mount Sharp within it. The rover has analysed 41 rock and soil samples, relying on a suite of science instruments to learn what they reveal about Earth’s rocky sibling. And it’s pushed a team of engineers to devise ways to minimize wear and tear and keep the rover rolling: In fact, Curiosity’s mission was recently extended for another three years, allowing it to continue among NASA’s fleet of important astrobiological missions. It’s been a busy decade. Curiosity has studied the Red Planet’s skies, capturing images of shining clouds and drifting moons. The rover’s radiation sensor lets scientists measure the amount of high-energy radiation future astronauts would be exposed to on the Martian surface, helping NASA figure out how to keep them safe. But most important, Curiosity has determined that liquid water as well as the chemical building blocks and nutrients needed for supporting life were present for at least tens of millions of years in Gale Crater. The crater once held a lake, the size of which waxed and waned over time. Each layer higher up on Mount Sharp serves as a record of a more recent era of Mars’ environment.  Now, out, leaving behind salty minerals called sulphates. Curiosity has made striking progress up the mountain. Back in 2015, the team captured a “postcard” image of distant buttes. A mere speck within that image is a Curiosity-size boulder nicknamed “Ilha Novo Destino” – and, nearly seven years later, the rover trundled by it last month on the way to the sulphate-bearing region. The team plans to spend the next few years exploring the sulphate-rich area. Within it, they have targets in mind like the Gediz Vallis channel, which may have formed during a flood late in Mount Sharp’s history, and large cemented fractures that show the effects of groundwater higher up the mountain.

DON MACHHOLZ 1952-2022

EarthSky

Don Machholz visually discovered 12 comets that bear his name. He was one of the inventors of the Messier marathon, which amateur astronomers around the world use to test their skill. It’s sad to announce the passing of Don Machholz on August 9, 2022, at his home – Stargazer Ranch, Arizona. Don became interested in astronomy at age 8. With this in mind, he received his first telescope on October 7, 1965, a 2-inch (5-cm) refractor. Later, he received a 6-inch (15-cm) Criterion Dynascope and found all the Messier Objects in one year (1969-70). Consequently, he decided to attempt a comet hunting program, which he began on January 1, 1975. He found his first comet on September 12, 1978, after 1,700 hours of searching. Subsequently, his second find took an additional 1,742 hours. Eventually, he spent 8,900 hours comet hunting, during which he discovered a total of 12 comets which bear his name. He was, in fact, the number one living visual comet discoverer.