The Fate of Companion Stars in a Binary System During a Supernova

The intriguing question of what happens when there are two stars in close proximity and one has a supernova can be complex and multi-faceted. This article aims to provide a detailed overview of the various outcomes that can result from such an event, considering numerous factors and scenarios.

Introduction to Supernovas in Binary Systems

When a star in a binary system undergoes a supernova, the outcome for its companion star is not always clear-cut. A variety of factors, including the size and type of the exploding star, its distance from the supernova, and the nature of the binary system itself, all play significant roles in determining the fate of the companion.

Factors Influencing the Outcome

The strength and nature of the supernova explosion are directly influenced by the characteristics of the star that undergoes the explosion. The most common scenario is a Type II supernova, where a massive star depletes its fuel for nuclear fusion, leading to a catastrophic collapse and explosion.

However, there are other variations of supernovas. For example, in a Type Ia supernova, a white dwarf star siphons matter from a companion star, leading to a runaway fusion reaction. The type and size of the companion star also matter. Brown dwarfs, with masses ranging from about 12-75 times Jupiter's mass, are the smallest stars and pose different challenges compared to larger, more massive stars.

The distance between the two stars in the binary system is another critical factor. If the companion star is far enough from the explosion, it may survive the shockwave with minimal damage. Neutron stars, which are much denser and compact, are generally more resilient to the force of a supernova explosion.

Final Outcomes for the Companion Star

Depending on the specific circumstances, the companion star may experience a range of outcomes:

Survival

The companion star may survive the eruption, albeit with some changes. Even in cases where the supernova leaves a neutron star or a black hole, the remaining companion might still be intact but altered, potentially losing some of its mass due to the shockwave.

Escape Velocity

In some instances, the supernova explosion can impart enough energy to accelerate the companion star to escape velocity. This means the companion could potentially be ejected from the binary system entirely, becoming a rogue star wandering through space.

Orbital Velocity and Unbinding

Non-symmetric supernova explosions can cause the supernova to be expelled with a certain velocity, leaving the companion star with enough orbital velocity to also escape the system's gravitational pull. This process can happen even if the companion star is not initially moving at the escape velocity, as long as the conditions are right.

Unpredicted Outcomes

There are rare cases where a star can survive its own supernova. These so-called zombie stars are extremely rare and typically occur when a white dwarf star, having stolen matter from a companion, undergoes a Type Ia supernova but retains a significant portion of its mass.

Unexpected Survival and Planetary Survival

It's surprising, but in some cases, even planets can survive a nearby supernova. While supernovas are typically catastrophic events, the actual outcome depends on the precise conditions and timing. For planets, their survival often hinges on their distance from the supernova and the nature of the explosion itself.

The study of these rare events provides valuable insights into the dynamics of binary star systems and the explosive nature of stellar transformations. Understanding these processes is crucial for comprehending the diversity of stellar evolution and the potential for strange and unexpected outcomes in the cosmos.

Keywords: binary star, supernova, companion star, escape velocity, neutron star