JWST reveals Milky Way-like galaxies in the young universe
New images from NASA’s James Webb Space Telescope (JWST) have revealed for the first time galaxies with stellar bars – elongated features of stars stretching from the centres of galaxies into their outer disks – existing farther back in time than any previously discovered.
The two barred galaxies (EGS-23205 and EGS-24268) are similar to our own Milky Way but come from a time when the universe was only a quarter of its current age.
“Bars solve the supply chain problem in galaxies,” explains Shardha Jogee, Professor of Astronomy at the University of Texas at Austin in the US.
“Just like we need to bring raw material from the harbor to inland factories that make new products, a bar powerfully transports gas into the central region where the gas is rapidly converted into new stars at a rate typically 10 to 100 times faster than in the rest of the galaxy.”
The discovery of their presence this early in the universe, about 11 billion years ago, will require astrophysicists to refine theories of how galaxies evolve.
“This discovery of early bars means galaxy evolution models now have a new pathway via bars to accelerate the production of new stars at early epochs,” Jogee says.
The article has been accepted for publication in The Astrophysical Journal Letters.
Turning a tentacle into a foot
The freshwater hydra – a small invertebrate only 1.4 cm long – is capable of regenerating any amputated part of its body throughout its life. This makes them perfect specimens to study trans differentiation – the process through which specialised (differentiated) cells change their identities.
All multicellular organisms – from humans to other animals, and plants – are made up of differentiated cells that have different functions. Scientists understand the mechanisms of differentiation well, but exactly how cells prevent both dedifferentiation (loss of identity) and trans differentiation is more mysterious.
According to a new study published in the journal Science Advances, geneticists have identified a key regulator of cell identity in Hydra and used this knowledge to successfully modify the structure and function of tentacle cells.
The regulator is a transcription factor called Zic4, which is responsible for regulating the expression of a series of target genes.
They found that when they reduced the expression of Zic4 so that there was less in the cell, the Hydra tentacle cells changed their identity and turned into foot cells. These cells formed functional feet… in the animals head!
‘‘In the hydra, the foot is called the basal disc of the animal. The cells that compose it are very specialised: they secrete mucus which allows it to attach to the surrounding environment,” explains Brigitte Galliot, Emeritus Professor at the Department of Genetics and Evolution at the University of Geneva, Switzerland, who supervised the study.
“After reduction of Zic4, it took only a few days for the process of trans differentiation of the tentacle cells to take place, leading to the development of feet in place of the tentacles.”
The results of the study raise questions about whether Zic4 plays the same role in other animals and whether it could allow the generation of other cell types.
NYC’s greenery absorbs a tremendous amount of its carbon emissions
A study of vegetation across New York City has found that, on many summer days, the photosynthesis by trees and other grasses absorbs all of the carbon emissions produced by transportation.
Most previous studies calculating carbon uptake of vegetation mainly look at contiguous forest and grassland. Instead, the researchers used fine-grained vegetation maps which documented the previously unrecognised greenery scattered in small spots in highly developed areas.
“Most people have assumed that New York City is just a grey box, that it’s biogenically dead,” says co-author Roísín Commane, an atmospheric chemist and Assistant Professor in the Department of Earth and Environmental Sciences at Columbia University in the US.
“But just because there’s a concrete sidewalk somewhere doesn’t mean there’s not also a tree that’s shading it.”
By modelling the carbon uptake of every tiny bit of this greenery and studying data from instrument towers that measure the air’s carbon dioxide content on a continuous basis, they found that the newly mapped vegetation areas offset up to 40% of atmospheric CO2 (due to anthropogenic emissions) on summer afternoons.
This result highlights the underappreciated importance of urban greenery in the carbon cycle. It’s published in the journal Environmental Research Letters.
How did early hunter-gatherers learn to make plates and bowls?
The knowledge of how to make and use pottery was probably shared between hunter-gatherer communities in Europe through kinship-driven, regional communication networks before the spread of agriculture – according to a new paper in Nature Human Behaviour.
The archaeologists propose that pottery traditions first originated in central Asia or western Siberia before being taken up by hunter-gatherer societies across the continent.
They analysed the remains of 1,226 pottery vessels from 156 hunter-gatherer sites across Eastern Europe and Russia using radiocarbon dating, data on the shape and decoration of the ceramic vessels, and analyses of the organic residues inside the pots.
Their findings suggest that the spread of pottery occurred relatively rapidly westwards from 5900 BCE onwards (approximately 8,000 years ago) and took only 300–400 years to advance over 3,000 kilometres.
The forms and decorations suggest that pottery spread through a process of cultural transmission and there is evidence that ceramics were used for cooking a wide range of food – so adoption wasn’t driven by any specific economic or environmental pressures.