The origins of the Moon have been the cause of many a scientific debate over the years but more recently we seem to have settled on a consensus. That a Mars-sized object crashed into Earth billions of years ago, with the debris coalescing into the Moon. The newly formed Moon drifted slowly away from Earth over the following eons but a new study suggests some surprising nuances to the accepted model.
According to current theory, the Moon formed around 4.5 billion years ago, shortly after the Solar System’s birth. It began with a massive collision between the early Earth and a Mars-sized protoplanet called Theia. The impact sent debris into orbit around the Earth which eventually coalesced to create the Moon. There is plenty of evidence to support this theory chiefly the composition of Earth’s mantle and lunar rocks.
Artist’s impression of the early Solar System, where collision between particles in an accretion disc led to the formation of planetesimals and eventually planets. Those early particles brought primitive minerals to each world. Credit: NASA/JPL-CaltechThe majority of the debris cloud settled back down on the Earth, a large proportion formed the Moon but some of it was ejected from the Earth-Moon system. In the paper recently authored by Stephen Lepp and his team from the University of Nevada they explored the dynamics of the material ejected from the impact.
Shortly after the Moon formed it was orbiting Earth at a distance about 5% of its current value (average distance – 384,400km) but slowly, due to tidal effects between Earth and Moon it drifted away to its current altitude. Its surface was largely molten magma which gradually cooled and solidified forming the familiar crust, mantle and core that we see today. Heavy bombardment scarred the lunar surface with impact basins and craters and volcanic activity led to the slow formation of the lunar maria.
The orbit of the Moon around the Earth has settled into a slightly elliptical one with an eccentricity of 0.0549. It is not a perfect circle and moves from 364,397km to 406,731km from Earth. The system wasn’t so stable in the early days of the Earth-Moon system and the particles in the accreting Moon had more erratic journeys.
The Moon on August 24, 2023, with the eQuinox 2 telescope by Unistellar. Credit: Nancy Atkinson.One of the terms that describes evolving orbits is nodal precession (where the orbital intersections slowly move around the orbit). There are two types and the first relates to where particles in an orbit slowly precess about the angular momentum vector of the Earth-Moon system. The other occurs around highly eccentric binary systems when the inclination of the orbiting object is large. The particle precesses about the binary eccentricity vector. Taking into account the Earth and orbits of particles in the debris cloud as the Moon started to form, such orbits described would be unstable.
The team showed that of all the possible orbits of particles, those in polar orbits were the most stable. They went further and showed that they existed around the Earth-Moon binary system after the Moon formed. As the separation of the Earth and Moon slowly increased through tidal interactions the region of space where polar orbits could exist decreased. Today, with the Moon at its current distance from Earth, there are no stable polar orbits since the nodal precession driven by the Sun is dominant
The team conclude that the presence of polar orbiting material can drive eccentricity growth of a binary system like the Earth and Moon. If a significant amount of material found its way into a polar orbit then the eccentricity of the Earth-Moon system would have increased.
Source : Polar orbits around the newly formed Earth-Moon binary system
The post When Earth Danced with Polar Moons appeared first on Universe Today.
Some galaxies experience rapid star formation hundreds or even thousands of times greater than the Milky Way. Astronomers think that mergers are behind these special galaxies, which were more abundant in the earlier Universe. But new results suggest no mergers are needed.
These galaxies are called Hyper Luminous Infrared Galaxies (HyLIRGs), and they emit most of their energy in the infrared. New research examined a HyLIRG that’s 10,000 times brighter than the Milky Way in infrared. Instead of a chaotic merger, they found an organized rotating ring of gas that they say is responsible for the galaxy’s abundant star formation.
Their results are in a paper in Nature Astronomy titled “Detailed study of a rare hyperluminous rotating disk in an Einstein ring 10 billion years ago.” The lead author is Daizhong Liu, a Research Professor at Purple Mountain Observatory near Nanjing, China.
HyLIRGs are the rarest type of starburst galaxy, and they’re the most extreme type. They’re found only in the distant, ancient Universe. The galaxy is named PJ0116-24 and has a redshift of z=2.125. That redshift value means the light we’re seeing was emitted about 10.5 billion years ago, and the distant galaxy is now about 16 billion light-years away. At that distance, astronomers had to use gravitational lensing to look at the galaxy. That not only magnified the galaxy, it created an Einstein Ring.
This image is a VLT MUSE image of PJ0116-24 distorted into an Einstein Ring by a gravitational lens. The foreground lens is not removed in this image. Image Credit: Liu et al. 2024.The researchers used a pair of telescopes to observe the galaxy. The Very Large Telescope traced the warm gas with its Enhanced Resolution Imager and Spectrograph (ERIS) instrument, and the Atacama Large Millimetre/submillimetre Array traced the cold gas. By combining the observations from both, the astronomers found an organized ring of rotating gas. If a merger had occurred and triggered the galaxy’s abundant star formation, an organized structure like this wouldn’t have been present. Instead, the galaxy’s morphology would be much more chaotic.
The authors write, “A widely accepted scenario is that HyLIRGs are the distant higher-luminosity tail of the local ultra-luminous IR galaxies with extreme starburst activities triggered by major mergers.” Another possibility is that these galaxies are very young and are experiencing their maximum star formation rates associated with youth. The problem is that astronomers haven’t observed enough of them to be certain exactly what’s going on.
This galaxy was identified by the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts project (PASSAGES), which found about 20 HyLIRGs. PJ0116-24 is the brightest one found in the southern sky.
This image from the research shows how the gravitational lensing created an Einstein Ring. It’s a distorted but still scientifically revealing image of the distant HyLIRG PJ0116-24. The gravitational lensing creates two images of the galaxy, with two AGN, labelled A1 and A2. The foreground lens has been removed from the image. Blue to green colours show stars, and red shows the cold gas out of which more stars form. (Note that the Einstein Ring is an artifact of gravitational lensing and is not the gaseous ring that the researchers found. That ring is revealed in velocity maps.) Image Credit: Liu et al. 2024.The authors write, “We found PJ0116-24 to be highly rotationally supported with a richer gaseous substructure than other known HyLIRGs. Our results imply that PJ0116-24 is an intrinsically massive and rare starburst disk probably undergoing secular evolution.” Its star formation rate (SFR) is 1,490 solar masses yr-1.
Simulations predict that the maximum SFR is greater than or equal to 1,000?solar masses yr-1. If these observations are correct, then they show that a galaxy can reach its maximum SFR even if it is alone and hasn’t been involved in a merger.
“Unlike almost all other extreme HyLIRGs, which are major mergers, PJ0116-24 does not obviously have massive companions or disturbed kinematics as evidence for major mergers,” the authors explain in their paper.
These velocity maps clearly show a coherent rotating gaseous ring structure in PJ0116-24. If the galaxy’s rapid SFR were because of a merger, no such orderly structure would be present. Image Credit: Liu et al. 2024.The galaxy also shows much higher metallicity than others in the early Universe. “These diagnostics indicate solar to supersolar metallicity,” the authors write. “This is much higher than in non-starburst galaxies at the same redshifts.”
Amit Vishwas is a postdoc at the Cornell Center for Astrophysics and Planetary Sciences. He’s a co-author of this paper and a previous paper in 2023 that used the JWST to observe another galaxy at an earlier epoch with similar gas conditions and metallicity. PJ0116-24 is about five times more massive and luminous than that one. Vishwas says both of these galaxies are helping astronomers build a better picture of how galaxies evolve.
“In both cases, gravitational lensing helped us zoom in to study the details of the interstellar medium of these galaxies,” Vishwas said in a press release. “I believe these new observations are helping us build an argument for the way galaxies evolve and build up – efficiently converting gas to stars in rapid growth spurts separated by long periods of relative calm.”
“The robust confirmation of PJ0116-24 as the most rotationally supported HyLIRG from this work is key evidence suggesting that secular evolution, that is, without recent major mergers, can be responsible for maximal star formation in the Universe,” the authors conclude in their work.
The post No Merger Needed: A Rotating Ring of Gas Creates A Hyperluminous Galaxy appeared first on Universe Today.
Labeled a silent epidemic by a growing number of therapists and researchers, estrangement is one of the most disorienting and painful experiences of a parent’s life. Popular opinion typically tells a one-sided story of parents who got what they deserved or overly entitled adult children who wrongly blame their parents. However, the reasons for estrangement are far more complex and varied. As a result of rising rates of individualism, an increasing cultural emphasis on happiness, growing economic insecurity, and a historically recent perception that parents are obstacles to personal growth, many parents find themselves forever shut out of the lives of their adult children and grandchildren.
As a trusted psychologist whose own daughter cut off contact for several years and eventually reconciled, Dr. Joshua Coleman is uniquely qualified to guide parents in navigating these fraught interactions. He helps to alleviate the ongoing feelings of shame, hurt, guilt, and sorrow that commonly attend these dynamics. By placing estrangement into a cultural context, Dr. Coleman helps parents better understand the mindset of their adult children and teaches them how to implement the strategies for reconciliation and healing that he has seen work in his forty years of practice. Rules of Estrangement gives parents the language and the emotional tools to engage in meaningful conversation with their child, the framework to cultivate a healthy relationship moving forward, and the ability to move on if reconciliation is no longer possible.
While estrangement is a complex and tender topic, Dr. Coleman’s insightful approach is based on empathy and understanding for both the parent and the adult child.
Joshua Coleman, PhD, is a psychologist in private practice and Senior Fellow with the Council on Contemporary Families. A frequent guest on NPR and Today, his advice has also appeared in The New York Times, The Atlantic, the Wall Street Journal, CNN, Chicago Tribune and other publications. A popular conference speaker, he has given talks to the faculties at Harvard, the Weill Cornell Department of Psychiatry and other academic institutions. Dr. Coleman is co-editor with historian Stephanie Coontz of seven online volumes of Unconventional Wisdom: News You Can Use: a compendium of noteworthy research on the contemporary family. He is the father of three adult children, has a teenage grandson and lives with his wife in the San Francisco Bay Area. He is the author of The Marriage Makeover: Finding Happiness in Imperfect Harmony. His latest book is Rules of Estrangement: Why Adult Children Cut Ties and How to Heal the Conflict.
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