Revealed: hundreds of billions of stars. Let us now seek them for life Louisa Preston

This week it James Webb Space Telescope wrote history and proved to be the most powerful space-based observatory that humanity has ever built, revealing a small piece of the vast universe around us in breathtaking detail. Astronomers all over the world have proved jubilant, in a flood of tears and missing words. Astrobiologists like myself, who study the origin, evolution, distribution and future of life in the universe, also get quite excited. By revealing images of galaxies from the dawn of time and chemical data from planetary atmospheres, JWST has the power to help us answer one of humanity’s oldest questions: are we alone in the universe?

The first spectacular image released was of the galaxy cluster SMACS 0723, known as Webb’s first deep field. This image covers only a part of the sky that is about the size of a grain of sand held at arm’s length by someone on the ground – and yet it is crowded with galaxies, literally thousands of them. Within each galaxy, there may be an average of 100 billion stars, each with its own family of planets and moons orbiting them.

Given the fact that we only have in our solar system several habitable (Earth) or potentially habitable (Mars, Europe, Enceladus, Titan) worlds, the odds are to find other planets or moons out there with the potential to house life as we know it has increased exponentially. The universe is probably full of them.

Using another instrument called MIRI (Mid-Infrared Instrument) on the same view reveals even more about the nature of these stars and galaxies. Some appear blue because they do not have much dust and older stars, while other objects, probably galaxies, look red because they are covered in dust. For me, the most exciting galaxies are now green. The green indicates that the dust in these galaxies contains a mixture of hydrocarbons and other chemical compounds – the chemical building blocks of life. ]

Galaxy cluster SMACS 0723 taken from Web's First Deep Field, the first infrared image from NASA's James Webb space telescope, shows dust levels in galaxies indicated by the colors blue, red and green.
Galaxy cluster SMACS 0723 taken from Web’s First Deep Field, the first infrared image from NASA’s James Webb space telescope, shows dust levels in galaxies indicated by the colors blue, red and green. Photo: NASA / Reuters

The team has also released an infrared spectrum included Fine-tuning sensor and near-infrared image camera and slit-free spectrograph (FGS-NIRISS) instruments, which analyzed starlight as it passed through the atmosphere of Wasp-96b, a hot, Jupiter-like planet 1,150 light-years away, orbiting its star closer than Mercury does to our Sun. This bunch of wavy lines revealed to us the presence of water vapor in its atmosphere (the planet is far too hot for liquid water). This is a sensational result, and now the detective work really begins when we search through the smaller, rocky planets in the hope of finding worlds where the conditions are suitable for life.

So how do we do this? We are looking for earth-like atmospheres, such as those dominated by nitrogen, carbon dioxide and water, because an earth-like atmosphere is by definition our gold standard for habitability. But the Earth’s atmosphere during the history of life has not always been composed in this way, and we are sure that other atmospheric mixtures can create habitable worlds. We call these “viability markers”, and they also include flashes of light reflected from the oceans and the effects of vegetation.

Astrobiologists are also looking to find biosignature gases in these distant exoplanetary atmospheres – that is, gases that indicate biological activity. For example, oxygen is a dominant gas in the Earth’s modern atmosphere, and most of it is produced from photosynthesis. The dominant methane source in our atmosphere is also produced via methanogenesis, an ancient form of metabolism for certain microorganisms. I should say here that it will not be easy to identify unambiguous signatures of life. Many have abiotic (non-living) sources as well as biological ones; they can be produced by volcanoes, water-mountain interactions or even human activity.

At least for now, only those biosignatures with a global, planetary impact will probably be discovered. However, the detection of these habitable markers or biosignature gases with JWST will be tempting enough to make us pause and explore the worlds in question more deeply. And it’s more than exciting enough at the moment.

JWST has already, in just a few days, changed the way we look at the universe and will in the future open our eyes to the chemical and, if we are lucky, biological composition of other worlds in it. Maybe we will finally get the proof that life in one form or another is universal, and, as I have always believed, that we have never actually been alone.

#Revealed #hundreds #billions #stars #seek #life #Louisa #Preston

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