The origins of Omicron

The Omicron variant of the coronavirus SARS-CoV-2 has spread around the world faster than any previous version. It has more than 50 mutations when compared with the original SARS-CoV-2 virus that was first isolated in Wuhan, China. Some 30 of these contribute to changes in amino acids in the spike protein, which the coronavirus uses to attach to and fuse with cells; previous variants of concern have had no more than 10 such spike mutations. Our Feature this week examines where the “craziest SARS-CoV-2 genome” might have come from.

Most mutated: Scatter plot showing the number of mutations on spike protein S1 of the SARS-CoV-2 coronavirus over time.

Source: Nextstrain

Lagrange points explained

NASA’s James Webb Space Telescope, which is the most complex telescope ever built, last week arrived at its destination: a special spot in space known as the second Lagrange point, or L2. This point is on the opposite side of Earth from the Sun, about 1.5 million kilometres away, or four times the distance to the Moon. There, the gravitational pull of the Sun and Earth equals the centripetal force required for Webb to move with them. Only a handful of space missions have travelled to L2, which is one of five Lagrange points in the Sun–Earth system. The location is particularly good for sensitive astronomical observatories such as Webb.

Vantage points: Schematic showing the location of the Solar System's five Lagrange points.

Source: Adapted based on materials from NASA/WMAP Science Team

The wonder of gravitational waves

The first direct detection of gravitational waves was achieved in 2015 by the US Laser Interferometry Gravitational-Wave Observatory (LIGO), which measured waves produced in the final moments of the merger of two black holes. Since then, LIGO and its Italian counterpart Virgo have spotted dozens of similar bursts. Those waves peak in frequency at tens to thousands of cycles per second — similar to the lower frequencies of audible sound — and can be sensed for several seconds or, in some cases, minutes.

Now, an astronomy collaboration known as the International Pulsar Timing Array (IPTA) could be on the verge of detecting gravitational waves from distant supermassive black holes — millions or even billions of times larger than the black holes spotted so far. The groups’ pulsar technique aims to detect longer-lasting gravitational waves that oscillate at much lower frequencies, measured in cycles per year or even per decade, as this graphic explains.

The gravitational-wave spectrum: a graphic that shows the frequencies of waves emitted by objects and how to detect them.