This supernova shock wave slammed into its companion star

A one-day-old supernova revealed clues about a companion star 20 times the Sun’s size.

Key Takeaways

  1. Astronomers captured a supernova shock wave colliding with a companion star for the first time.
  2. SN 2017cbv’s light curve showed an early bump, revealing the shock’s interaction with the star.
  3. The supernova occurred in galaxy NGC 5643, 55 million light-years away, detected hours after exploding.
  4. The findings support the theory that white dwarfs can explode by stealing material from a companion.
  5. Continuous monitoring with advanced telescopes like Las Cumbres Observatory is revolutionizing supernova studies.

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A Supernova’s Early Explosion Caught in Action

Astronomers have recorded unprecedented details of a supernova just hours after its explosion. Named SN 2017cbv, the event was discovered in March by David Sand at the University of Arizona as part of the DLT40 survey, which targets objects within 40 megaparsecs (about 120 million light-years). SN 2017cbv occurred in galaxy NGC 5643, located 55 million light-years away, making it one of the closest type Ia supernovae observed in recent years. The early detection, within a day of its explosion, enabled a global network of telescopes to document the event in real-time.

A Stellar Collision

The supernova’s light curve revealed a “bump” within its first few days, a signal attributed to the explosion’s shock wave colliding with a nearby companion star. Type Ia supernovae originate from white dwarfs, stellar remnants of Sun-like stars. These white dwarfs can explode if their mass surpasses 1.4 times that of the Sun, either by merging with another white dwarf or by pulling material from a companion star.

Astronomers believe SN 2017cbv originated in a system like this, where the white dwarf stole matter from a normal companion star. ESO, M. Kornmesser

For SN 2017cbv, the bump indicates the shock wave hitting a companion star, estimated to be 20 times the Sun’s radius. As the white dwarf siphoned material from this star, it gained enough mass to trigger the explosion. The collision caused the shock wave’s material to glow in ultraviolet light, creating the early bump observed in the supernova’s brightness. This phenomenon, predicted in 2010, was documented for the first time with SN 2017cbv, offering critical evidence for the single-degenerate (white dwarf-companion star) explosion scenario.

Expanding Our Understanding

The discovery adds weight to one theory of type Ia supernova origins but doesn’t discount the other possibility—two white dwarfs merging. Griffin Hosseinzadeh, leader of the study and a Ph.D. student at the University of California, Santa Barbara, emphasizes that both processes likely occur. To determine which is more common, astronomers must continue capturing supernovae in their earliest stages.

This groundbreaking observation was made possible by advanced tools like the Las Cumbres Observatory’s network of 18 telescopes, which tracked SN 2017cbv continuously after its detection. With these capabilities, astronomers can analyze supernovae in greater detail, paving the way for new insights into the universe’s expansion and the stars’ life cycles.

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