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.