ScienceAlert.com
MICHELLE STARR
9 JULY 2021 The way a planet is tilted on its rotational axis with respect to its orbital plane around a star - what we know as 'axial tilt' - could be key to the emergence of complex life. 

According to a new study, a modest axial tilt, like Earth's, helps increase the production of oxygen, which is vital for life as we know it - and planets with tilts that are too small or too large might not be able to produce enough oxygen for complex life to thrive.
"The bottom line is that worlds that are modestly tilted on their axes may be more likely to evolve complex life," said planetary scientist Stephanie Olson of Purdue University. "This helps us narrow the search for complex, perhaps even intelligent life in the Universe."
It's possible that life may emerge outside the parameters we know here on Earth, of course, but this pale blue dot is the only world which we know for a certainty harbors life. Therefore, it's expedient to model our searches accordingly.
When looking for habitable worlds elsewhere in the galaxy, the first things we look for are: is it relatively small and rocky, like Earth? And does it orbit the star at a distance called the habitable zone, the Goldilocks region of not too hot, not too cold, where temperatures allow liquid water on the surface?

Those questions are good, but the contributing factors to the emergence of life are likely a lot more complex.
The presence of a magnetic field, for instance, is thought to be pretty important, because it protects the planetary atmosphere from stellar winds. The eccentricity of the planet's orbit, and what kind of other planets are present in the system might also be key.
Olson and her team went a little more granular, looking at the presence and production of oxygen; specifically, the conditions on the planet that may impact the amount of oxygen produced by photosynthetic life.
Most organisms (although not all) on Earth require oxygen for respiration - we can't live without it. Yet early Earth was low in oxygen. Our atmosphere only became rich in oxygen about 2.4 to 2 billion years ago, a period known as the Great Oxidation Event. It was triggered by a boom in cyanobacteria, which pumped out vast amounts of oxygen as a metabolic waste product, enabling the rise of multicellular life.
Olson and her team sought to understand how the conditions arose in which cyanobacteria could thrive, using modelling.



"The model allows us to change things such as day length, the amount of atmosphere, or the distribution of land to see how marine environments and the oxygen-producing life in the oceans respond," Olson explained.
Their model showed that several factors could have influenced the transport of nutrients in the oceans in a way that contributed to the rise of oxygen-producing organisms like cyanobacteria.
Over time, Earth's rotation slowed, its days lengthened, and the continents formed and migrated. Each of these changes could have helped increase the oxygen content, the researchers found.
Then they factored in axial tilt. Earth's axis isn't exactly perpendicular to its orbital plane around the Sun; it's tilted at an angle of 23.5 degrees from the perpendicular - think of a desktop globe.
This tilt is why we have seasons - the tilt away from or towards the Sun influences seasonal variability. Seasonal temperature changes also influence the oceans, resulting in convective mixing and currents, and the availability of nutrients.
So perhaps it's not surprising that axial tilt had a significant effect on oxygen production in the team's study.
"Greater tilting increased photosynthetic oxygen production in the ocean in our model, in part by increasing the efficiency with which biological ingredients are recycled," explained planetary scientist Megan Barnett of the University of Chicago.
"The effect was similar to doubling the amount of nutrients that sustain life."
But there's a limit. Uranus, for example, is tilted at 98 degrees from the perpendicular. Such an extreme tilt would result in seasonality that may be too extreme for life. A small tilt, also, might not produce enough seasonality to encourage the right level of nutrient availability. This suggests there may be a Goldilocks zone for axial tilt, too - neither too extreme, nor too small.
It's another parameter we can use to help narrow down planets elsewhere in the galaxy that are likely to harbor life as we know it.
"This work reveals how key factors, including a planet's seasonality, could increase or decrease the possibility of finding oxygen derived from life outside our Solar System," said biogeochemist Timothy Lyons of the University of California Riverside.
"These results are certain to help guide our searches for that life."
The research has been presented at the 2021 Goldschmidt Geochemistry Conference.

500 Discovered Exoplanets in one image-mentalfloss.com
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by Michelle Starr, 1 July 2021 @  ScienceAlert.com
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It's not the first such impending cosmic smash-up that we've seen, but it does seem to confirm the theory that these filaments of gas are "matter roads", guiding galaxy cluster mergers.
The new research has been submitted to Astronomy & Astrophysics and is available on preprint server arXiv.
The filament itself, spanning 50 million light-years and faintly glowing in X-rays, was identified and described last year. Such filaments make up the strands of the cosmic web; they clumped together under gravity in the Universe's early stages, and they span vast intergalactic distances between galaxies and clusters of galaxies.
Filaments like these can tell us a lot about the Universe, such as how it formed and continues to evolve, where dark matter is concentrated (the mysterious invisible substance responsible for extra gravity in the Universe), and where we can find normal matter, too.
But the threads of diffuse gas are very faint, compared to all the very bright stuff out there, like stars and galaxies. We've only just started finding them. So astronomers were very interested in this vast cosmic filament, and were taking a closer look.
Vast filaments of intergalactic gas are the highways along which galaxies are hurtling towards a certain collision.
In new, extremely detailed images of an enormous cluster of galaxies, astronomers have identified that the cluster is moving along a vast thread of gas, inexorably drawn by gravity towards two other clusters of galaxies.

Specifically, one of the things they were looking at was a feature known as the Northern Clump, a cluster of galaxies found in the filament.
By combining data from a number of X-ray and radio telescopes, the researchers were able to identify a galaxy at the centre of the Northern Clump, with an active supermassive black hole at its center.
That the supermassive black hole is active, devouring material swirling around it in a dense disc, is key. As material from this disc feeds into the black hole, some is channeled around the outside along magnetic field lines, researchers think, where it is launched from the poles into space at speeds approaching the speed of light.
These jets of material can travel tremendous distances into space, which allows astronomers to make observations about the intergalactic environment. And this proved to be the case with the galaxy at the heart of the Northern Clump.
Its jets, according to astrophysicist Angie Veronica of the University of Bonn in Germany, are streaming away as the Northern Clump hurtles through space "like the braids of a running girl".



This, the researchers believe, suggests that the Northern Clump is traveling at great velocity along the filament, towards two other galaxy clusters that are also aligned along the filament - Abell 3391 and Abell 3395.
We can't see that motion, of course - it's simply occurring on scales that are too vast and too distant - but we can see its effects.
"We are currently interpreting this observation such that the Northern Clump is losing matter as it travels," explained astrophysicist Thomas Reiprich of the University of Bonn. "However, it could also be that even smaller clumps of matter in the thread are falling toward the Northern Clump."
Eventually, the clusters will meet and merge, forming an even larger cluster of galaxies - a cosmic pile-up on a mind-blowing scale. This scenario matches simulations performed by a separate team of astronomers.
It's thought that filaments of the cosmic web are responsible for feeding star-forming material into nodes, where it can form galaxies and clusters of galaxies. Without the cosmic web, the Universe as we know it may not even exist. So understanding how and why it works is fundamental to cosmology.
The new findings are consistent with current theory about the cosmic web, including the idea that dark matter gravitationally binds the filaments. And they're leading us ever closer into understanding how everything in the Universe is connected.
The research has been submitted to Astronomy & Astrophysics and is available on arXiv.

You may not be all that familiar with planet LHS 3844b, but it now has its own particular distinction: It's the first planet outside of our Solar System where astronomers think they might have evidence of tectonic activity.

That evidence is a set of advanced simulations based on observations of the rocky planet, which is slightly larger than Earth. Importantly for this particular piece of research, it doesn't look as though the exoplanet has an atmosphere.

That leaves half of LHS 3844b permanently exposed to its sun and could mean temperatures of up to roughly 800 degrees Celsius (1,472 degrees Fahrenheit) on the 'daytime' side, and about minus 250 degrees Celsius (minus 418 degrees Fahrenheit) on the 'night-time' side.

"We thought that this severe temperature contrast might affect material flow in the planet's interior," says astronomer Tobias Meier, from the University of Bern in Switzerland.

Based on phase curve observations of the planet's brightness and possible temperatures, and computer models simulating various possible tectonic materials and heat sources, Meier and his colleagues think a hemisphere-scale flow of subsurface material is happening.

Most of the simulations the researchers ran showed only upwards flow on one side of the planet and only downwards flow on the other, but in some scenarios that was reversed – a surprising find, and one that doesn't match tectonic movement on Earth.

​"Based on what we are used to from Earth, you would expect the material on the hot dayside to be lighter and therefore flow upwards and vice versa", says geophysicist Dan Bower, from the University of Bern
The underlying reason is the changing temperature of the mantle material as it moves, with colder rock stiffening up and becoming less mobile, and warmer rock becoming much more liquid-like as it heats up. The scientists say that shifting surface and material could lead to some rather incredible tectonic activity.
"On whichever side of the planet the material flows upwards, one would expect a large amount of volcanism on that particular side," says Bower.
As a result, scientists suggest that LHS 3844b could have one entire hemisphere covered in volcanoes, while the other side shows hardly any volcanic activity – all because of the intense temperature contrast around the planet.
The sort of upwelling that would cause these volcanoes does match what we see on Earth, but only in specific places, such as Hawaii and Iceland. In more general terms, the tectonic movement that these models suggest is unlike anything in our Solar System.
As more powerful space telescopes come online and our understanding of exoplanets improves, further observations and research should help confirm what's happening across the surface of LHS 3844b – and whether it really is half covered in volcanoes.
"Our simulations show how such patterns could manifest, but it would require more detailed observations to verify," says Meier.
"For example, with a higher-resolution map of surface temperature that could point to enhanced outgassing from volcanism, or detection of volcanic gases. This is something we hope future research will help us to understand."
The research has been published in the Astrophysical Journal Letters.

Photo:  FU Orionis resides near the imaginary shoulder of the great hunter constellation of Orion, at a location of about 3 degrees NW of Betelgeuse,  Here:  The constellation of Orion, as it can be seen by the naked eye. Lines have been drawn.

These planets are the first four from the sun: Mercury, Venus, Earth and Mars. They’re mostly made of rock and iron – whose particles don’t readily stick together.

They could have been sticky enough if they had a coating of snow and organic goo, Hubbard says. But despite all Earth’s oceans and carbon-based life, our planet has too little water or carbon to support this explanation.

Now Hubbard has suggested an intriguing solution to Earth’s difficult birth. In 1936, an infant star began to brighten, eventually shining over 100 times more brightly than it did originally. Now named FU Orionis, this star has stayed bright ever since. And several other stellar youngsters have done the same thing.

BLINDED BY BEAUTY
​ How each culture views the Universe is guided by its beliefs in, for example, mathematical beauty or the structure of reality. If these ideas are deeply rooted, people tend to interpret all data as supportive of them — adding parameters or performing mathematical gymnastics to force the fit. Recall how the belief that the Sun moves around Earth led to the mathematically beautiful (and incorrect) theory of epicycles advocated by the ancient Greek philosopher Ptolemy. Similarly, modern cosmology is augmented by unsubstantiated, mathematically sophisticated ideas — of the multiverse, anthropic reasoning and string theory. The multiverse idea postulates the existence of numerous other regions of space-time, to which we have no access and in which the cosmological parameters have different values. The anthropic argument is then often applied. It holds that our own region has the parameters it does (including those of dark energy and dark matter) because other, more likely values would not have allowed life to develop near a star like the Sun in a galaxy such as the Milky Way. An overlooked problem with this argument is that, accord¬ing to one analysis, life is 1,000 times more likely to exist 10 trillion years from now around stars that weigh one-tenth the mass of the Sun. This means that terrestrial life might be premature and not the most likely form of life, even in our own Universe.

A vibrant scientific culture encourages many interpretations of evidence, argues Avi Loeb. 

Abraham Loeb Frank B. Baird Jr. Professor of Science, Harvard University Chair, Harvard Astronomy Department Director, Institute for Theory and Computation (ITC) Founding Director, Black Hole Initiative (BHI) Chair, Breakthrough Starshot Advisory Committee Vice Chair, Board on Physics and Astronomy, National Academies​

Photo: No known restrictions on publication.2015.This planetary nebula is called PK 329-02.2 and is located in the constellation of Norma in the southern sky. It is also sometimes referred to as Menzel 2, or Mz 2, named after the astronomer Donald Menzel who discovered the nebula in 1922. When stars that are around the mass of the Sun reach their final stages of life, they shed their outer layers into space, which appear as glowing clouds of gas called planetary nebulae. The ejection of mass in stellar burnout is irregular and not symmetrical, so that planetary nebulae can have very complex shapes. In the case of Menzel 2 the nebula forms a winding blue cloud that perfectly aligns with two stars at its centre. In 1999 astronomers discovered that the star at the upper right is in fact the central star of the nebula, and the star to the lower left is probably a true physical companion of the central star. For tens of thousands of years the stellar core will be cocooned in spectacular clouds of gas and then, over a period of a few thousand years, the gas will fade away into the depths of the Universe. The curving structure of Menzel 2 resembles a last goodbye before the star reaches its final stage of retirement as a white dwarf. A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Serge Meunier.

"...Now, for the first time, researchers have seen this scenario unfold. Andrew Vanderburg, an astronomer at the Harvard-Smithsonian Center for Astrophysics, was analyzing data from Kepler, which detects planets when they block the light of their sun. "One of the white dwarfs suddenly popped up with this really intriguing signature," Vanderburg says. As his team reports online today in Nature, the white dwarf, located in the constellation Virgo and named WD 1145+017, has at least one, and probably several, asteroids that are disintegrating. As a debris cloud from each asteroid passes between us and the star, Kepler detects a dimming of the star's light.

"It's fascinating," says astronomer Michael Jura of the University of California, Los Angeles, who was not part of the discovery team. "They've actually caught in the act the process of some asteroid breaking into pieces, being disrupted by the white dwarf host star."

Indeed, the star itself is the asteroids' enemy. Its gravity has torn them asunder, and its light is vaporizing their rock. The asteroids are so close to the star that they revolve in just 4.5 to 4.9 hours; Vanderburg estimates they are roughly the size of Ceres, the largest asteroid between the orbits of Mars and Jupiter...."