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Light Travel Time

All articles tagged with #light travel time

Naked-Eye Stars Aren’t Dead: Most Are Still Shining Within Reach
science13 days ago

Naked-Eye Stars Aren’t Dead: Most Are Still Shining Within Reach

The common claim that the night sky is full of dead stars is mistaken: the stars visible without a telescope lie within roughly 4,000–10,000 light-years and have lifetimes from millions to trillions of years, so the light we see is a snapshot of their past rather than evidence of their demise. Because the naked-eye sample is nearby and long-lived, only about one visible star is expected to die every ~10,000 years as a rough Milky Way estimate, far slower than stellar lifespans. Exceptions exist (e.g., Earendel at great distance and Betelgeuse, which is not due to explode for ~100,000 years), but for ordinary observers the sky remains largely “alive.”

Brisk Light: A New Middle-Ground Model for Black-Hole Imaging
science1 month ago

Brisk Light: A New Middle-Ground Model for Black-Hole Imaging

Physicists propose 'brisk light', an intermediate approach between fast-light (single emission time per image) and slow-light (full time-delay map) to model how photons from different moments reach us around black holes. Brisk light preserves the dominant time-delay structure while reducing computational costs, and while current Event Horizon Telescope images of M87* and Sgr A* are well captured with fast-light, the next generation of observatories aiming to resolve photon rings will need timing-accurate models.