Hunting for life, but not as we know it
Ammonia could be as important on other worlds as oxygen is on ours
Prof Lewis Dartnell is an astrobiologist at the University of Westminster
Over the coming years, as astronomers use spectroscopy to read the atmospheres of Earthsized, habitable planets, detecting the presence of one gas will be an important discovery: oxygen. On Earth, oxygen is released by life – specifically, by organisms using sunlight for energy.
Oxygen is a very reactive gas. Early in Earth's α history any oxygen released into the atmosphere was rapidly removed. It reacted with rocks, or was destroyed by photochemical reactions driven by ultraviolet rays in sunlight. Such processes are known as 'sinks', and oxygen only started to accumulate in Earth's atmosphere once its production had overwhelmed these sinks. An oxygen-rich atmosphere is thought to be a sign of flourishing life on a world, which is why astronomers would be so excited about discovering one on an exoplanet.
But is oxygen the only 'biosignature' gas that would indicate the presence of life? Might other gases produced by biochemistry also be able to overwhelm the sinks on their exoplanets and accumulate to detectable levels? Sukrit Ranjan, at Northwestern University, and his colleagues have been investigating this. The best candidate worlds for detecting such biosignature gases, they argue, are exoplanets orbiting small, cool M-class red dwarf stars. Such stars emit less ultraviolet radiation than larger, hotter stars like the Sun, and so the sinks on those planets are much weaker. Planets orbiting M-class red dwarfs offer favourable conditions for the accumulation of reactive gases to levels that we could hopefully detect with space telescopes. This is one of the reasons why the James Webb Space Telescope (JWST) will be targeting these stars.
هذه القصة مأخوذة من طبعة April 2022 من BBC Sky at Night Magazine.
ابدأ النسخة التجريبية المجانية من Magzter GOLD لمدة 7 أيام للوصول إلى آلاف القصص المتميزة المنسقة وأكثر من 9,000 مجلة وصحيفة.
بالفعل مشترك ? تسجيل الدخول
هذه القصة مأخوذة من طبعة April 2022 من BBC Sky at Night Magazine.
ابدأ النسخة التجريبية المجانية من Magzter GOLD لمدة 7 أيام للوصول إلى آلاف القصص المتميزة المنسقة وأكثر من 9,000 مجلة وصحيفة.
بالفعل مشترك? تسجيل الدخول
Could We Find Aliens by Looking for Their Solar Panels?- Designed to reflect ultraviolet and infrared, the panels have a unique fingerprint
Researchers searching for life beyond Earth spend a lot of time thinking about what telltale signs might be detectable astronomically. Forms of unambiguous evidence for the presence of life on another world are known as biosignatures. By extension, techno signatures are indicators of activity by intelligent, civilisation-building life.
Antimatter- In our continuing series, Govert Schilling looks at antimatter, the strange counterpart to most of the matter filling our Universe
Particles and corresponding antiparticles are very much alike, except they have opposite electrical charges. For instance, the antiparticle of the electron - known as the positron - has the same tiny mass, but while electrons carry a negative electrical charge, positrons are positively charged.
Where Have All The Milky Way's Early Stars Gone?- Our Galaxy has a curious lack of pristine stars
The Big Bang produced a Universe filled almost exclusively with hydrogen and helium; all other elements - what astronomers call metals - were produced by stars, supernovae and everything that happens later. So if you can pick out a pristine star with no metals polluting it from among the billions in the Milky Way, then you are likely to have a star dating from our Galaxy's earliest days.
Inside The Sky At Night - Two years ago, exoplanet scientist Hannah Wakeford received some of the first data from the JWST
Two years ago, exoplanet scientist Hannah Wakeford received some of the first data from the JWST. In July's Sky at Night, we discovered what she's learned since then.
How to stack DSLR data in Siril
Easily combine multiple frames to boost detailin your astro photos
Lunar occultation of Saturn
You'll need to strike a balance on 21 August to capture the Moon covering the ringed planet
How to plot a variable star light curve
A rewarding project to chart stars that change brightness
Smartphone photography with a telescope
Mary Mcintyre explains how to get impressive night-sky images using your phone
Once-a-century solar storm is overdue
If a Carrington Event struck today it would be catastrophic, says Minna Palmroth
The new era of human spaceflight
There's been a step-change in crewed space missions since the dawn of the 21st century. Ben Evans charts its course and looks ahead to future horizons