Four stories today. The whole ring of aurora around the Earth was imaged, daylit side included; a radio telescope in Canada caught the faint radio whisper of hydrogen from long ago; bundles of particles written down only as equations in 1931 were made in a cold atomic gas; and bacteria turn out to use a weapon the virus brings as their alarm bell.
Earth
SMILE, a satellite flown jointly by Europe and China, has imaged in ultraviolet the entire ring of aurora around the Earth's north pole — including the half in daylight.
An aurora is air glowing when particles from the Sun, caught by the Earth's magnetic field, pour into the sky near the poles. The glow forms a ring around the pole, and the ring is so large that from the ground you see only a slice of it. In daylight it is lost in the glare of the Sun altogether.
SMILE, flown by the European Space Agency with the Chinese Academy of Sciences, watches the Earth in ultraviolet from far out. In ultraviolet the aurora shows up even by day. The images just released hold the whole ring around the north pole, and over an hour you can watch it heave and change shape. The point of the satellite is to see at a glance how the wind blowing from the Sun shakes our magnetic field.
Through the eyes of the AtlasThe library piece on visible light and the electromagnetic spectrum says our eyes are a very narrow window. The daytime aurora was happening just beside that window, in the ultraviolet. This follows the story of the solar-wind watching satellite in this column on 26 September: that one measures the wind, this one watches the mark the wind leaves on the Earth.
A word of cautionThis is a new picture rather than a new discovery. The sequence was taken over about an hour in late July.
Source · NASA APOD (ESA · Chinese Academy of Sciences)
Space
CHIME, a radio telescope in Canada, has picked out the 21-centimetre radio emission of hydrogen gas from a time when the universe was less than half its present age.
The commonest stuff in the universe is hydrogen. Very occasionally a hydrogen atom changes state and gives out radio waves 21 centimetres long. Collect those waves into a map and you can see where the gas is gathered, rather than where the stars are — and it costs far less than counting galaxies one by one.
The trouble is how faint the signal is. It lies buried under radio waves from our own galaxy, from human transmitters, and from the instrument itself. Researchers at the University of British Columbia and elsewhere sifted ninety-four nights of CHIME data from 2019 and pulled out the hydrogen signal from light that set out some nine billion years ago. Checking that it was real took them more than a year. It is a first step showing the method works.
Through the eyes of the AtlasHubble saw that light from receding galaxies turns red, and knew the universe was growing. That is the library piece on redshift. If the same map can be drawn from the radio waves of gas instead of from galaxies, we can trace how fast the universe grew much further back.
A word of cautionNothing has been said here about dark energy. This is the stage of showing the method works, and only part of the gathered data was used.
Source · ScienceDaily (University of British Columbia)
Physics
Atoms held in extremely narrow tubes and made to attract one another formed bundles of six particles and more.
In a narrow world where things can move along one line only, particles can pull on each other and travel as a bundle. They are not joined by chemical bonds as in a molecule; the mutual pull alone holds them together. Hans Bethe showed such bundles in his equations in 1931, and they are called Bethe strings.
Researchers at the University of Innsbruck in Austria cooled caesium atoms to within a few billionths of a degree of absolute zero and split them among several thousand narrow tubes, so they could move in one direction only. Then they turned the force between the atoms from pushing to pulling, and bundles of several sizes appeared. To check that they were truly bound, the team let them spread out in two ways. Inside the tubes the bundles collided and survived; with the tubes removed, so the atoms spread in all directions, the bundles came apart and their binding energy showed up as motion.
Through the eyes of the AtlasThe library piece on quantisation says energy comes only in whole lumps. Squeeze those lumps into a narrow space where they pull on each other and they make a bundle of another kind — one that falls apart in three dimensions. The same particles follow different rules depending on how many dimensions they live in.
A word of cautionThe bundles were not photographed; they were inferred from the difference in energy between two ways of letting the gas spread. Similar states had been seen before in solid magnets; this is the first time in an atomic gas.
Source · ScienceDaily (University of Innsbruck)
Life
The moment a virus's protein-cutting enzyme snips a bacterial sensor protein turns out to be the signal that switches the defence on.
Bacteria catch viruses too. A virus that hunts bacteria is called a phage. Bacteria have several defences that switch on when a phage gets in, and one of them is fierce: the infected cell kills itself so the virus cannot spread to its neighbours. Since a false alarm kills a healthy cell, the signal has to be read correctly.
Researchers at the University of Utah found what that signal is. Inside the cell a phage uses an enzyme that works like scissors on proteins. The moment those scissors cut one of the bacterium's own sensor proteins is the alarm. That is unlike the usual way of spotting a virus by its genetic material: here the cell notices not what the virus brought with it, but what it is doing.
Through the eyes of the AtlasThe CRISPR of Doudna and Charpentier was also, to begin with, a device bacteria built in their fight with phages — one bacterial defence that became a human tool. As the library piece on penicillin and resistance says, bacteria learn faster than we do; and we keep rummaging through what they have learnt.
A word of cautionThis is basic research in bacteria. Using it to treat illness with phages is a possibility so far, and nothing has been tested in people.
Source · ScienceDaily (University of Utah Health)