Speaker: Ralf Klessen (ITA, Heidelberg)

Title: The astronomical odds for a starry night, or how unique is our place in the Universe?

Abstract: The star-filled night sky that inspired Vincent van Gogh’s Starry Night has guided human navigation, art, and scientific inquiry throughout history. Yet it remains unclear whether such a view is typical across the Milky Way or the result of unusually favorable cosmic circumstances. Using stellar catalogues, Gaia-based three-dimensional reconstructions of interstellar dust, and high-resolution simulations of a Milky Way–like galaxy, we quantify how the local interstellar medium regulates the visibility of stars for an Earth-like observer. A central aspect of this investigation is our knowledge of our local Galactic environment. Our solar system is currently located in the middle of a large cavity of tenuous, hot gas, the Local Bubble. We believe this structure originated from the energy and momentum released by 15–20 supernova explosions over the past 15 million years or so, which displaced the nearby interstellar medium, like a snowplow pushing snow from the street to pile it up along the sidewalk. This environment may not be unique and there are likely thousands of similarly large bubbles in the Milky Way, a view that is supported by recent observations with the James Webb Space Telescope in nearby galaxies. Better understanding the Local Bubble is important, not only because it defines our place in the Milky Way and many of the nearby star-forming regions are associated with the walls of the Local Bubble, but also because essentially all extragalactic observations pass through this cavity and are thus subject to veiling effects from the bubble walls. Accurately assessing the impact of this foreground, for example, is important for the scientific success of future experiments measuring the cosmic microwave background and its polarization properties at high angular resolution. In this presentation, I will report the current efforts at Heidelberg University to address this challenge and share some of the many failures and the (much fewer) successes we had.

• Date:
  Feb. 19, 2026, 2:30 p.m. – 3:30 p.m.
  
  
• Location:

  AIP; Kirch building, Conference room

  
  
• Contact:
  Ewald Puchwein
  epuchwein@aip.de