Scientists spot two huge companion stars that blew up

Unlike our sun, most of the largest stars in the cosmos are not solo acts, but rather are born together with another star in what is called a binary system, destined to spend their lives gravitationally bound in a cosmic marriage. But not even the best marriage - on Earth or in space - lasts forever.

Scientists now for the first time have discovered evidence of two such massive stars from a binary system that both ran out of fuel and exploded violently within a relatively short time, each leaving behind a telltale cloud of glowing gas called a nebula. Such stellar explosions are called supernovas.

One of these two nebulas is among the best known in our Milky Way galaxy, called the Jellyfish Nebula for its superficial resemblance to the tentacled sea creature.

Guided by more than 16 years of observations by NASA's Fermi Gamma-ray Space Telescope, the researchers found

evidence of a second nebula relatively nearby that has now

helped put the Jellyfish Nebula in its proper context as part of a dual calamity.

They believe that the Jellyfish Nebula, formally called IC 443, was produced when a star roughly 15 to 25 times more massive than the sun exploded at the end of its life cycle. They believe the other nebula, formally called G189.6+3.3, was produced by the explosion of the binary companion star, which had been at least 20 times more massive than the sun.

During their lifetimes, both stars are believed to have been at least tens of thousands of times more luminous than

the sun. After the explosions, both may have been reduced to dense stellar leftovers called neutron stars.

Both are located about 6,000 light-years from Earth in the constellation Gemini. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).

The discovery may offer insight into binary systems composed of massive stars