In the hunt for life on other worlds, astronomers scour over planets that are light-years away. They need ways to identify life from afar — but what counts as good evidence?
Stars are born when huge clouds of dust and gas collapse in on themselves and ignite. These clouds are made up of raw elements, like oxygen and titanium, and each cloud has a unique composition that imprints on the star. And within the stellar afterbirth – from the material that didn’t find its way into the star – planets are formed.
Europa, a frozen moon around Jupiter, is believed to be one of the most habitable worlds in the solar system. It was first imaged in detail by the Voyager 1 probe in 1979, revealing a surface almost devoid of large craters. This suggested that water regularly floods up from inside, resurfacing the satellite. Europa is also criss-crossed with long troughs, folds and ridges, potentially made of icebergs floating around in melt-water or slush.
In 1960, famed theoretical physicist Freeman Dyson made a radical proposal. In a paper titled “Search for Artificial Stellar Sources of Infrared Radiation” he suggested that advanced extra-terrestrial intelligences (ETIs) could be found by looking for signs of artificial structures so large, they encompassed entire star systems (aka. megastructures). Since then, many scientists have come up with their own ideas for possible megastructures.
Planetary systems can be harsh environments in their early history. The young worlds orbit suns in stellar nurseries, clusters of stars where violent encounters are commonplace. None of this makes it easy for life to get going, but now astronomers at the University of Sheffield find one positive of this tumultuous period. A model developed by undergraduate student Bethany Wootton and Royal Society Dorothy Hodgkin Fellow Dr Richard Parker looks at how the habitable zone – the region around a star where the temperature allows liquid water to exist – changes around pairs of stars, so-called binary systems.
In 1961, famed astronomer Frank Drake created a formula for estimating the number of extra-terrestrial intelligences (ETIs) that could exist within our galaxy. Known as the “Drake Equation“, this formula demonstrated that even by the most conservative estimates, our galaxy was likely to host at least a few advanced civilizations at any given time. About a decade later, NASA officially kicked of its search for extra-terrestrial intelligence (SETI) program.
NASA is targeting technosignatures in its renewed effort to detect alien civilizations. Congress asked NASA to re-boot its search for other civilizations a few months ago. Their first step towards that goal is the NASA Technosignatures Workshop, held in Houston from September 26th to 28th, 2018.
In recent decades, astronomers have discovered many planets that they believe are “Earth-like” in nature, meaning that they appear to be terrestrial (i.e. rocky) and orbit their stars at the right distance to support the existence of liquid water on their surfaces. Unfortunately, recent research has indicated that many of these planets may in fact be “water worlds“, where water makes up a significant proportion of the planet’s mass.
The Cassini orbiter revealed many fascinating things about the Saturn system before its mission ended in September of 2017. In addition to revealing much about Saturn’s rings and the surface and atmosphere of Titan (Saturn’s largest moon), it was also responsible for the discovery of water plumes coming from Enceladus‘ southern polar region. The discovery of these plumes triggered a widespread debate about the possible existence of life in the moon’s interior.
The study of exoplanets -- planets that lie outside our solar system -- could help scientists answer big questions about our place in the universe, and whether life exists beyond Earth. But, these distant worlds are extremely faint and difficult to image directly. A new study uses Earth as a stand-in for an exoplanet, and shows that even with very little light -- as little as one pixel -- it is still possible to measure key characteristics of distant worlds.
When it comes to the search for extra-terrestrial intelligence (SETI) in the Universe, there is the complicated matter of what to be on the lookout for. Beyond the age-old question of whether or not intelligent life exists elsewhere in the Universe (statistically speaking, it is very likely that it does), there’s also the question of whether or not we would be able to recognize it if and when we saw it.
It’s a staple of science fiction, and something many people have fantasized about at one time or another: the idea of sending out spaceships with colonists and transplanting the seed of humanity among the stars. Between discovering new worlds, becoming an interstellar species, and maybe even finding extra-terrestrial civilizations, the dream of spreading beyond the Solar System is one that can’t become reality soon enough!