Cosmic Collisions: How to Witness the Birth of Planets express

Original: "Can giant impacts be directly detected in other star systems?"

· Pavan Tanna, Simon Lock, Amy Bonsor, Simon Hodgkin, Cathie. J. Clarke

arXiv:2606.26026 · 2026-06-24 · CC BY 4.0 · 1 min

Giant impacts between planets light up the cosmic forge with flashes now within reach of new telescopes.

The birth of planets resembles the workings of a cosmic forge. Rocky blocks collide and fuse together. A powerful impact strikes a spark — material heats to white-hot and glows like cooling metal. Computer simulations show: the flash is visible from days to years, peaking at a tenth of the sun's light. Modern telescopes monitoring millions of stars can catch it. New sky surveys like Gaia and LSST will gather precise brightness data of stars. Scientists anticipate up to 14 such events: they will reveal how often worlds collide in the Milky Way.

Dozens of collisions occur in the Galaxy each year. An impact of such power not only births a planet — a moon can coalesce from the debris cloud. Earth's satellite likely formed this way.

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The temperature at the impact site skyrockets to thousands of degrees in minutes — debris glows like a blacksmith's workpiece.

In Lars von Trier’s film ‘Melancholia,’ Earth collides with a rogue planet, producing a blinding flash akin to this effect.

Scientists

Christian Doppler D. B. McLaughlin Didier Queloz Michel Mayor R. A. Rossiter David Charbonneau

Concepts

asteroid impact impact collision magma ocean galaxy merger signatures red giant gas giant lsst transit planetesimal formation gravitational effects on small bodies progenitor massive star interstellar object ejection stellar explosion direct imaging supernova remnant formation prominence transit method particle collision

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Cosmic Collisions: How to Witness the Birth of Planets express