Stellar flyby refers to the close passage of two or more

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

s, which remain unbound after their passage

Close encounters with the Sun

The Sun resides in a region of relatively low stellar density in the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

. Thus, close stellar flybys are relatively rare. However, once in a while a star can come relatively close. One example is

Scholz's star Scholz's Star (Wide-field Infrared Survey Explorer, WISE designation WISE 0720−0846 or fully WISE J072003.20−084651.2) is a dim Binary star, binary stellar system from the Sun in the constellation Monoceros near the galactic plane ...

( WISE designation WISE 0720−0846 or fully WISE J072003.20−084651.2), which is a dim binary stellar system 22

light-years A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astro ...

(6.8

parsecs The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

) from the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Monoceros Monoceros ( Greek: , "unicorn") is a faint constellation on the celestial equator. Its definition is attributed to the 17th-century cartographer Petrus Plancius. It is bordered by Orion to the west, Gemini to the north, Canis Major to the s ...

near the

galactic plane The galactic plane is the plane (geometry), plane on which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms ''galactic plane'' and ''galac ...

. The system passed through the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

Oort cloud The Oort cloud (pronounced or ), sometimes called the Öpik–Oort cloud, is scientific theory, theorized to be a cloud of billions of Volatile (astrogeology), icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 A ...

roughly 70,000 years ago.

Gliese 710 Gliese 710, or HIP 89825, is an orange star in the constellation Serpens Cauda. It is projected to pass near the Sun in about 1.29 million years at a predicted minimum distance of 0.051 parsecs— (about 1.6 trillion km)—about 1/25th o ...

or HIP 89825, an orange 0.6 M_☉

in the

Serpens Serpens () is a constellation in the northern celestial hemisphere. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations designated by the International Astronomical Union. It ...

Cauda, is projected to pass near the

in about 1.29 million years at a predicted minimum distance of 0.051

—0.1663

(10,520

astronomical units The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its mode ...

) (about 1.60 trillion km) – about 1/25th of the current distance to

Proxima Centauri Proxima Centauri is the nearest star to Earth after the Sun, located 4.25 light-years away in the southern constellation of Centaurus. This object was discovered in 1915 by Robert T. A. Innes, Robert Innes. It is a small, low-mass st ...

Close flybys in different environments

Close flybys are usually relatively rare among field stars, but are more common in

star cluster A star cluster is a group of stars held together by self-gravitation. Two main types of star clusters can be distinguished: globular clusters, tight groups of ten thousand to millions of old stars which are gravitationally bound; and open cluster ...

s In these groups of stars the stellar density is much higher, so that close passages of between stars are more common. In particular in young star clusters,

open cluster An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

s and

globular cluster A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...

s stellar flybys are thought to be common. In young clusters, such close stellar flybys might influence the frequency and size of protoplanetary discs, and influence the

planet formation The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting t ...

process in these environments.

References

{{reflist Astronomy