Abstract:
Are we alone in the Universe? Since the confirmation of the first planets outside our solar system in the 1990s, we have made tremendous progress towards answering this question. Yet, the confirmation of a true Earth-analogue still evades us. On top of this, if we are truly to understand the origins of life in the cosmos, we must also create a complete picture of planetary formation, evolution, and habitability. However, each of these aspects necessitates a detailed knowledge of Sun-like stars. This is because we study exoplanets indirectly by analysing their much more luminous host stars. For example, most planet confirmation relies on the Doppler wobble of the host star, induced by the presence of the planet. Moreover, we can learn about a planet's dynamical history from mapping its projected orbit as it transits its host star. Hence, if there are inhomogeneities on the stellar surface, they can impact planetary interpretations and even completely swamp the signals from rocky worlds. In this talk, I will discuss how we confirm and characterise planets outside our solar system and how our knowledge of their host stars poses a fundamental hurdle we must overcome on the pathway to rocky, temperate worlds.

It is our pleasure to welcome Dr Raphaëlle Haywood from the University of Exeter to the Centre for Exoplanets and Habitability seminar series. Dr Haywood will be giving a talk titled 'There’s No Place Like Home: Placing Earth in its Astronomical and Geological Contexts'.

Abstract:
Recent revolutionary discoveries in astronomy are showing that Earth is one of billions of planets, and that terrestrial, temperate planets are commonplace in our galaxy. Geological records indicate that Earth has been many different worlds over time, and life has shown extraordinary resilience through these planetary changes. If we could go to the stars and point our telescopes back at Earth, what would we see? How does life alter Earth's astronomical character? We will look at one of Earth's defining ecosystems: the Amazon rainforest, which is observable from cosmic distances. We will reflect on the impact of various human civilisations. Ultimately, we will draw on these astronomical and geological perspectives to demonstrate that humanity's flourishing is profoundly tied to maintaining this world, here, that we co-evolved with.

On 14 September 2020, a team of astronomers led by Dr Jane Greaves of Cardiff University announced the detection of phosphine, a potential biomarker, in the atmosphere of Venus. On Earth, phosphine can result from natural processes such as lightning and volcanic activity, but only in small amounts; by comparison, the amount of phosphine detected in Venus' atmosphere is relatively large. The only known processes that produce phosphine on Earth in similar quantities are biological in origin.

It must be stressed that this does not mean that there is life on Venus. What has been announced is a signal that is a possible sign of life, with a strength for which there are no plausible known abiotic explanations. There may, of course, be currently unknown methods of producing it in the amounts required. But this is still an exciting signal that warrants more investigation.

We are familiar with the idea that the twinkling pinpricks of light in the sky are stars, like our own Sun, but not all those stars are the same. There are many types of stars, and we can see most of these in the night sky, explains Dr Elizabeth Stanway.

Professor Tom Marsh from the Astronomy and Astrophysics Group explains how to make a sundial and what it can tell us about our Sun.