Stellar collision
Encyclopedia
A Stellar collision is the coming together of two astronomical bodies, which through the force of gravity, merge into one larger unit. In a more basic sense, a stellar collision is a collision of star
s. Astronomers predict that over several hundred such collisions can take place somewhere in our galaxy, where events of this type occur about once every 10,000 years.. It is also predicted, that under the correct conditions, even three or four stars can collide and merge into a single star. While much is unknown about this theory, there are new strides being made every day in order to try to prove that this phenomenon occurs in the universe. Scientist have not yet been able to physically see a collision due to technological constraints, but they are able to detect the gravitational waves created by these collisions, allowing them to make predictions about what really occurs.
can be involved in a stellar collision; whether it is 'alive' (meaning fusion is still active in the star) or dead (with fusion no longer taking place.) Examples would include White Dwarf
stars, Neutron Stars, Black holes, Main Sequence Stars
, Giant stars, and Supergiants. Differerent types, masses, temperatures, and radiuses will result in different collisions or mergers. All astronomical bodies have different reactions in the way they collide due to forces such as gravity, and due to the physical parameters of the star.
, in which carbon fusion begins in the core increasing the interior temperature. Since the white dwarf consists of degenerate matter, there is no safe relation between pressure and temperature. Because of this, the reactions spreads outward at runaway speed with no barrier to stop it. This causes a collapse of outside layers causing a supernova
shockwave, and in a matter of seconds, all of the white dwarfs mass is thrown into space.
was discovered by astronomer Charles Messier
. After years of observation, fellow astronomers concluded that the cluster was approximately 13 billion years old.. Around 250 years later, the Hubble Telescope resolved the individual stars of Messier 30. With this new technology, astronomers discovered that some stars, known as “blue stragglers”, were younger than other stars in the cluster. Astronomers then hypothesized that stars may have “collided”, or “merged”, giving them more fuel so they continued fusion while fellow stars around them started going out.
The likelihood of close encounters with the Sun is also small. The rate is estimated as follows:
where N is the number of encounters per million years that come within a radius D of the Sun in parsec
s. For comparison, the mean radius of the Earth's orbit, 1 AU
, is .
Even though our star will likely not be directly affected by such an event, the Earth may very easily be impacted by a nearby collision. Astronomers say that if a stellar collision happens within 100 light years of the Earth, it could possibly result in the planet's destruction. This is still very unlikely though because there are no stellar clusters this close to the Solar system.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s. Astronomers predict that over several hundred such collisions can take place somewhere in our galaxy, where events of this type occur about once every 10,000 years.. It is also predicted, that under the correct conditions, even three or four stars can collide and merge into a single star. While much is unknown about this theory, there are new strides being made every day in order to try to prove that this phenomenon occurs in the universe. Scientist have not yet been able to physically see a collision due to technological constraints, but they are able to detect the gravitational waves created by these collisions, allowing them to make predictions about what really occurs.
Astronomical bodies Involved
Any star in the universeUniverse
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...
can be involved in a stellar collision; whether it is 'alive' (meaning fusion is still active in the star) or dead (with fusion no longer taking place.) Examples would include White Dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
stars, Neutron Stars, Black holes, Main Sequence Stars
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
, Giant stars, and Supergiants. Differerent types, masses, temperatures, and radiuses will result in different collisions or mergers. All astronomical bodies have different reactions in the way they collide due to forces such as gravity, and due to the physical parameters of the star.
Type Ia Supernova
White Dwarfs are the remnants of low mass stars, and if they form a binary system with another star, they can cause large stellar explosions known as type 1a supernovae. When a white dwarf comes near a "live star", they get caught in each other's gravity and begin a slow revolution around each other. While this happens, the white dwarf is rotating and begins sucking gas from its companion star until it reaches the Chandrasekhar limitChandrasekhar limit
When a star starts running out of fuel, it usually cools off and collapses into one of three compact forms, depending on its total mass:* a White Dwarf, a big lump of Carbon and Oxygen atoms, almost like one huge molecule...
, in which carbon fusion begins in the core increasing the interior temperature. Since the white dwarf consists of degenerate matter, there is no safe relation between pressure and temperature. Because of this, the reactions spreads outward at runaway speed with no barrier to stop it. This causes a collapse of outside layers causing a supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
shockwave, and in a matter of seconds, all of the white dwarfs mass is thrown into space.
Neutron Star Collisions
Neutron star collisions occur in a similar fashion to type 1a supernovae. When two neutron stars travelling through the galaxy get caught inside each other's gravity, they begin to revolve around each other, moving in closer as time passes. Once the two neutron stars meet in the middle, a huge collision occurs. This creates a magnetic field that is trillions times stronger than that of Earth, in a matter of one or two milliseconds. Astronomers believe that this event is what creates certain kinds of gamma-ray bursts.Discovery
While the theory of stellar collision has been around for several generations of astronomers, only the development of new technology has made it possible for it to be proven. The theory of stellar collisions started in 1764 when a cluster of stars known as Messier 30Messier 30
Messier 30 is a globular cluster in the Capricornus constellation. It was discovered by Charles Messier in 1764. M30 is at a distance of about 28,000 light-years away from Earth, and about 90 light-years across....
was discovered by astronomer Charles Messier
Charles Messier
Charles Messier was a French astronomer most notable for publishing an astronomical catalogue consisting of deep sky objects such as nebulae and star clusters that came to be known as the 110 "Messier objects"...
. After years of observation, fellow astronomers concluded that the cluster was approximately 13 billion years old.. Around 250 years later, the Hubble Telescope resolved the individual stars of Messier 30. With this new technology, astronomers discovered that some stars, known as “blue stragglers”, were younger than other stars in the cluster. Astronomers then hypothesized that stars may have “collided”, or “merged”, giving them more fuel so they continued fusion while fellow stars around them started going out.
Stellar Collisions and our Solar System
While stellar collisions may occur very frequently in certain parts of the galaxy, the likelihood of a collision involving the Sun is very small. A probability calculated predicts the odds of a stellar collision involving the Sun is 1 in 10 trillion, trillion years.The likelihood of close encounters with the Sun is also small. The rate is estimated as follows:
- N ~ 4.2 · D2 Myr−1
where N is the number of encounters per million years that come within a radius D of the Sun in parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
s. For comparison, the mean radius of the Earth's orbit, 1 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, is .
Even though our star will likely not be directly affected by such an event, the Earth may very easily be impacted by a nearby collision. Astronomers say that if a stellar collision happens within 100 light years of the Earth, it could possibly result in the planet's destruction. This is still very unlikely though because there are no stellar clusters this close to the Solar system.