Scientists find evidence of two massive stars that exploded together

WASHINGTON — Scientists have discovered the first evidence of two massive stars from the same binary system that both ran out of fuel and exploded as supernovas within a relatively short period, leaving behind glowing clouds of gas known as nebulas.

Unlike the sun, which exists alone, many of the largest stars in the universe are born in pairs within binary systems. These stars remain connected by gravity throughout their lives, but even these cosmic partnerships eventually come to an end.

Researchers used more than 16 years of observations from NASA’s Fermi Gamma-ray Space Telescope to study two nearby nebulas and found evidence that they were created by separate supernova explosions from stars that once belonged to the same binary system.

One of the nebulas is the well-known Jellyfish Nebula, officially called IC 443, which earned its name because of its resemblance to the tentacles of a sea creature. Scientists believe it was created when a star between 15 and 25 times more massive than the sun exploded at the end of its life.

The second nebula, known as G189.6+3.3, is believed to have formed after the explosion of the star’s companion, which was at least 20 times more massive than the sun.

Both stars were believed to have been tens of thousands of times brighter than the sun during their lifetimes. After their violent deaths, they may have collapsed into dense remnants called neutron stars.

The two nebulas are located about 6,000 light-years from Earth in the constellation Gemini. A light-year is the distance light travels in one year, equivalent to about 5.9 trillion miles (9.5 trillion kilometers).

A Rare Look at a Massive Binary System

The discovery provides scientists with a rare opportunity to study the full life cycle of a massive binary system, from the formation of two giant stars to their eventual destruction.

“This system provides a rare opportunity to reconstruct the complete evolutionary history of a massive binary — from the birth and interaction of two massive stars, through both supernova explosions, to the remnants they left behind,” said Miltiadis Michailidis, a postdoctoral fellow in Stanford University’s physics department and lead author of the study published Tuesday in the journal Nature Communications.

Although most massive stars are born in binary systems, researchers said no pair had previously been confirmed where both stars exploded as supernovas and left behind observable remnants.

Some massive stars are also born in systems containing three or more stars.

The two nebulas are expanding clouds of hot gas, energetic particles and shocked interstellar material left behind by the supernova explosions.

Massive stars have relatively short lifespans compared with smaller stars like the sun. While the sun is expected to live for about 10 billion years, massive stars typically exist for only a few million years before ending in powerful explosions.

“Systems like this one can provide direct observational constraints on how the evolution of massive stars is modified by the presence of a binary companion — one of the major outstanding questions in stellar astrophysics,” Michailidis said.

Until now, scientists have relied largely on theoretical models and computer simulations to understand the final stages of massive stars in binary systems.

Two Explosions Separated by Thousands of Years

Researchers believe the star that created the newly identified nebula exploded first, disrupting the binary system and sending its surviving companion into space. The second star later reached the end of its life and exploded as well.

The researchers estimated that between 20,000 and 110,000 years passed between the two supernova explosions.

“The first explosion disrupted the binary, and the surviving companion continued moving through space until it also exploded,” Michailidis said.

Before the explosions, the two stars orbited each other at a very close distance, possibly only several times farther apart than Earth is from the sun.

Today, the centers of the two supernova remnants are separated by about 30 to 50 light-years.

Scientists believe the stars may have exchanged material through a process called mass transfer while they were still part of the same system.

However, it remains unclear whether the first supernova directly caused the second star to explode.

“By the time the first supernova occurred, the second star may already have been close to the end of its life,” Michailidis said.

— Reporting by Will Dunham; Editing by Daniel Wallis/Reuters