The European Space Agency's (ESA) decision to adopt the Arrakihs mission is a significant step forward in our understanding of the universe. This mission, set to launch by the end of 2030, aims to capture the faint light from nearby galaxy haloes, shedding light on the formation and evolution of galaxies like our own. But what makes this mission particularly fascinating is its potential to reveal the unseen, and in doing so, challenge our current understanding of the cosmos.
Uncovering the Unseen
One thing that immediately stands out is the focus on the galaxy halo, a region often overlooked in favor of the more visually striking central disc. The halo, primarily composed of dark matter and normal matter, holds the key to understanding the formation and evolution of galaxies. By studying the stellar streams and diffuse stellar haloes, Arrakihs will provide insights into the history of past mergers and the role of dark matter in galaxy formation.
What many people don't realize is that the halo is a treasure trove of information, offering a glimpse into the past of galaxies. The faint light from the halo can reveal the remnants of small galaxies that were torn apart by gravity, providing a detailed record of the cosmic history of our own Milky Way. This is a crucial aspect of the mission, as it aims to estimate the number of 'lonely' stars that were ripped away from their galaxies during mergers, offering a more accurate understanding of the Milky Way's formation.
A Unique Galactic Archaeology Mission
Arrakihs is a groundbreaking and unique galactic archaeology mission, according to Professor Carole Mundell, ESA's Director of Science. Its rapid development showcases the flexibility and breadth of ESA's Science Programme. The mission's ability to uncover hard-to-see galaxy haloes is a significant achievement, as it will provide new details about how galaxies form and whether the Milky Way galaxy is unique. This is a crucial aspect of the mission, as it aims to estimate the number of 'lonely' stars that were ripped away from their galaxies during mergers, offering a more accurate understanding of the Milky Way's formation.
The Instrument: Two Pairs of 'Binocular Telescopes'
The instrument at the heart of Arrakihs is a marvel of engineering. It consists of two pairs of 'binocular telescopes', a total of four cameras, each sensitive to a different band of wavelengths. This allows the instrument to capture images in the near-ultraviolet, visible spectrum, and near-infrared, providing a comprehensive view of the faint light from the galaxy halo. The design and development of this instrument is a collaborative effort led by Spain, with contributions from Switzerland, Austria, Belgium, Norway, Portugal, and Sweden.
A Step Towards Understanding the Universe
Arrakihs will join ESA's fleet of Cosmic Observers, addressing two top-level science themes of ESA's Cosmic Vision 2015–2025: What are the fundamental physical laws of the Universe? and How did the Universe originate and what is it made of? By mapping stellar streams and investigating at least 80 galaxies with a similar mass to the Milky Way, Arrakihs will provide a statistical understanding of galaxy formation, offering a more accurate picture of the universe's history.
Personal Perspective
In my opinion, the adoption of Arrakihs is a significant milestone in space exploration. It represents a step towards a deeper understanding of the universe, challenging our current models and offering new insights into the formation and evolution of galaxies. The mission's ability to uncover the unseen is particularly fascinating, as it will provide a more accurate picture of the cosmic history of our own Milky Way. As we look forward to the launch of Arrakihs, I am excited to see the new discoveries and insights that will emerge from this groundbreaking mission.
