Revealed: Hundreds of billions of stars. Now we are looking for them for life | Louise Preston

TThis week, the James Webb Space Telescope made history, proving to be the most powerful space-based observatory mankind has ever built and revealing a tiny portion of the vast universe around us in stunning detail. Astronomers around the world were shown cheering, in tears and speechless. Astrobiologists like me who study the origin, evolution, distribution and future of life in the universe are also getting quite excited. By revealing images of galaxies from the dawn of time and chemical data of planetary atmospheres, JWST has the power to help us answer one of mankind’s oldest questions: Are we alone in the universe?

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

Given that we have multiple habitable (Earth) or potentially habitable (Mars, Europa, Enceladus, Titan) worlds in our solar system alone, chances are there are other planets or moons out there that have the potential to host life , as we know it has increased exponentially. The universe probably knows about 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 don’t contain much dust and older stars, while other objects, likely galaxies, appear red because they are shrouded in dust. I find the galaxies now colored green the most exciting. The green indicates that the dust in these galaxies contains a mixture of hydrocarbons and other chemical compounds – the chemical building blocks of life. ]

Imaged by Webb's First Deep Field, NASA's James Webb Space Telescope's first infrared image, galaxy cluster SMACS 0723 shows dust concentrations in galaxies identified by the colors blue, red, and green.
Imaged by Webb’s First Deep Field, NASA’s James Webb Space Telescope’s first infrared image, galaxy cluster SMACS 0723 shows dust concentrations in galaxies identified by the colors blue, red, and green. Photo: NASA/Reuters

The team has also released an infrared spectrum, taken with the Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph (FGS-NIRISS) instrument, analyzing starlight as it penetrated the atmosphere of Wasp-96b, a hot, Jupiter-like planet 1,150 , passed light-years away and orbits its star closer than Mercury to our Sun. These wavy lines showed us the presence of water vapor in its atmosphere (the planet is far too hot for liquid water). That’s a sensational result, and now the detective work really begins as we scour the smaller, rocky planets in hopes of finding worlds where the conditions are suitable for life.

How will we do that? We look for terrestrial atmospheres dominated by nitrogen, carbon dioxide, and water, since an terrestrial atmosphere is, by definition, our gold standard for habitability. But Earth’s atmosphere has not always been so composed throughout the history of life, and we are certain that other atmospheric mixtures can create habitable worlds. We call these “habitability markers,” and they also include the glint of light reflected off oceans and the effects of vegetation.

Astrobiologists are also looking for biosignature gases in these distant exoplanetary atmospheres – gases that indicate biological activity. For example, oxygen is a predominant gas in the Earth’s modern atmosphere, and most of it is produced by photosynthesis. Also, the main source of methane in our atmosphere is produced by methanogenesis, an ancient form of metabolism for some microorganisms. I should say here that identifying life’s unique signatures will not be easy. Many have abiotic (non-living) sources in addition to biological ones; They can be created by volcanoes, water-rock interactions, or even human activity.

At least for the time being, only such biosignatures with a global, planetary effect will probably be detectable. However, detecting these habitability markers or biosignature gases with the JWST will be tempting enough to make us stop and explore the worlds in question more deeply. And that’s more than exciting enough.

The JWST has already changed the way we see the universe in just a few days and will open our eyes to the chemical and, if we’re lucky, biological composition of other worlds in the future. Perhaps we’ll finally get proof that life is universal in one form or another and that, as I’ve always believed, we were never truly alone.

#Revealed #Hundreds #billions #stars #life #Louise #Preston

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