Are there any known star systems with 4 or 5 stars orbiting each other ?

Question

well, Alpha Centauri is as far as i know a trinary system, but are there known system cosisting of more than 3 stars ?

uh i do have difficulties to pick a best answer, cause you really digged into the matter far deeper than i did .. what can i do ?

Answer 1

In no particular order:

KAPPA-2 SAGITTARII

Kappa-2 Sagittarii is a quadruple system 371 light years from Earth. κ² Sagittarii A is a spectral type A3 dwarf with an apparent magnitude of +5.64. It is orbited by a close 7th magnitude companion, κ² Sagittarii B, which is 0.8 arcseconds, or approximately 90 Astronomical Units, away from the primary. Orbiting this pair are two more stars, the 15th magnitude κ² Sagittarii C, with a separation of 15.0 arcseconds, and the 14th magnitude κ² Sagittarii D, which is 29.3 arcseconds from the primary.

HATSYA (IOTA ORIONIS)

The brightest star in Orion's Sword and the eighth brightest in the constellation of Orion. Its apparent magnitude is 2.77 and it lies some 1300 light years away from us.

Its Arabic name, Na’ir al Saif, means “the Bright One of the Sword.” Iota Ori is actually a complex quadruple star dominated by a 15-solar-mass O star. At distances of 50" and 11", respectively, lie an 11th magnitude class A or F dwarf and a 7th magnitude B star, with true separations of at least 4,400 and 20,000 AU and orbital periods at least 75,000 and 700,000 years.

In addition, the O star has a B-type companion in a highly eccentric 29-day orbit that varies from 0.8 AU to 0.11 AU from the primary. At periastron, the centers of the stars are separated only by about 1.5 times the sum of the radii, which suggests that strong tidal forces will be generated and enhanced mass loss may be expected. Colliding stellar winds from the two giants generate powerful X-rays.

EPSILON LYRAE

Lying at a distance of 162 light years away, Epsilon Lyrae (ε Lyr / ε Lyrae) is a binary star in the constellation Lyra. Commonly known as the double-double, Epsilion Lyrae is one of the most well known of binary stars. It can be separated into two components when viewed through binoculars, or even the naked eye.

When viewed at higher magnifications, each component of the binary is further split into a binary, that is, two sets of binary stars orbiting each other, known as Epsilon1 and Epsilon2.

Epsilon1 consists of two stars of 4.7 (A3 spectral class) and 6.2 (A7) magnitude currently separated by 2.6". These stars are physically connected, orbiting slowly about their common center of gravity, taking something on the order of 1200 years for them to complete one orbit.

Epsilon2 consists of two 5.1 and 5.5 magnitude A5 stars currently separated by 2.3". They are also physically connected, orbiting once every 585 years.

Remarkably, each pair is also physically connected to the other. Separated by 0.16 light years they would take hundreds of thousands of years to complete an orbit.

MIZAR

Mizar (ζ UMa) is a star in the constellation Ursa Major and is the second star from the end of the Big Dipper's handle. Mizar has apparent magnitude 2.40 and spectral class A1 V.

With good eyesight one can make out a faint companion just to the east, called Alcor or 80 Ursae Majoris. Alcor has magnitude 3.99 and spectral class A5 V. The two are often called the horse and rider, and the ability to see the second is a traditional test of eyesight. The two stars lie more than a quarter of a light year apart and although proper motions show they move together, it is still not known whether they form a true binary star system, and not an optical binary as currently thought.

Mizar was the first telescopic binary discovered, most probably by Benedetto Castelli who in 1617 asked Galileo Galilei to observe it. Galileo then produced a detailed record of the double star. Later, around 1650, Riccioli wrote of Mizar appearing as a double.

The secondary star, Mizar B, has magnitude 4.0 and spectral class A7, and comes within 380 AU of the primary; the two take thousands of years to revolve around each other.

Mizar A then became the first spectroscopic binary to be discovered, by Pickering in 1889. The two components are both about 35 times as bright as the sun, and revolve around each other in about 20 days.

Mizar B (but not Alcor!) was later found to be a spectroscopic binary as well.

So Mizar is certainly a quadruple star system and may be a pentuple one if Alcor is able to be included.

CASTOR

Castor is 50 light years away and (with Pollux) one of the two brightest stars in the constellation Gemini, Castor was discovered to be a visual binary in 1678, with the magnitude of its components being 2.8 and 2.0. The separation of the components is about 6" and the period of revolution is around 350 years.

Each of the components of Castor is itself a spectroscopic binary, making Castor a quadruple star system. Castor has a faint companion separated from it by about 72" but having the same parallax and proper motion; this companion is also a spectroscopic binary with a period slightly less than 1 day. Castor can thus be considered to be a sextuple star system, with six individual stars gravitationally bound together. Component C has the variable star designation YY Geminorum.

The two brightest stars are in spectral class A and the remainder are in spectral class M.

A DIGRESSION INTO EXTRA-SOLAR PLANETS AND MULTIPLE STAR SYSTEMS.

It was generally thought that if stars have stellar companions, they would not have planetary ones as the other stars would inhibit the planet-forming process and tend to pull the planets out of orbit.

HD 188753 Ab

However, in July 2005, astronomers announced the discovery of a planet in a relatively tight triple star system, a finding that challenges current theories of planetary formation. The planet, a gas giant slightly larger than Jupiter, orbits the main star of the HD 188753 system, in the constellation Cygnus, and is hence known as HD 188753 Ab.

The stellar trio (yellow, orange, and red) is about 149 light years away from Earth. The planet orbits the main star (HD 188753 A) about once every 3.3 days, at a distance of about a twentieth the distance between Earth and the Sun.

The other two stars whirl tightly around each other in 156 days, and circle the main star every 25.7 years at a distance from the main star that would put them between Saturn and Uranus in our own Solar system. The latter stars call into question the leading hot Jupiter formation theory, which holds that these planets form at "normal" distances and then migrate inward through some debatable mechanism. Such migration could not have occurred here, since the outer star pair would have disrupted outer planet formation.

PSR B1620-26c

Also there is one known case of an extra-solar planet orbiting a binary star system. On July 10, 2003, using information obtained from the Hubble Space Telescope, a team of scientists led by Steinn Sigurdsson confirmed the oldest extrasolar planet yet. The planet is located in the globular star cluster M4, about 5,600 light years from Earth in the constellation Scorpius.

This is the only planet known to orbit around a stellar binary; one of the stars in the binary is a pulsar and the other is a white dwarf. The planet has a mass twice that of Jupiter, and is estimated to be 13 billion years old (alnost as old as the universe itself),

SUMMARY

An intriguing subject to research. I was fascinated to learn that two of these multiple star systems were realised to be binaries as long ago as 1617 and 1678. In the very early days of telescopes. I hope this has whetted your appertite to do some research yourself.

Answer 2

When you have two objects orbitting each other, or one object orbitting the other, they will gravitationally act on a third object as if they were a single object, if that third object is distant enough (which really isn't all that distant). So a stable orbit around a binary star system would be just as likely as around a single star at most distances. The possibility of life would be no different either, provided the interactions of the two stars aren't generating some intense radiation. As for a planet orbitting a single star in a binary system, it's theoretically possible. However, the stars would have to be unusually distant from each other to enable the planet to safely pass between them without getting swallowed up or pulled into a different orbit when passing between them. and considering the means by which star systems form, the planet would almost definitely have to be a captured object.

Answer 3

Here is a proof for such an instance..


Four star system gives planetary timescale
17:15 08 January 2002
From New Scientist Print Edition. Subscribe and get 4 free issues.
Eugenie Samuel


Astronomers investigating an unusual four star solar system have found one of the stars in the earliest stages of planetary formation yet seen. The discovery enables them to fix the timescale over which planets can form.

Ray Jayawardhana and colleagues at the University of California, Berkeley, and the Harvard Smithsonian Center for Astrophysics in Cambridge used the adaptive optics telescope on the Gemini North telescope in Hawaii to examine more closely a binary star system they were interested in.

To their surprise, they found the system actually contained four young stars orbiting each other. One of the stars is shrouded in proto-planetary dust disc that was just two million years old.

The disc is oriented edge on to the observers, so it was possible to measure its thickness. "It's very thin, which means dust particles have begun to stick together and settle into the middle of the disc," says Jayawardhana.

"One million year old dust discs are just like the dust in the molecular clouds, but by two million years we can see that these grains are already millimetres across," he says.

In 1998, Jayawardhana imaged a 10 million year old dust disc that was missing dust from the inner region, presumably because it had already clustered into asteroids and planets.

The new research was presented at the American Astronomical Society meeting in Washington DC.

Answer 4

The star Alpha Geminorum, known as Castor, is actually six stars gravitationally bound together in the form of three binary stars.

The four main stars are two close (~0.025 AU*) binary pairs, which are in a larger orbit (~100 AU) about each other. A binary pair of red dwarf stars orbits the main four at a greater distance.

*1 AU = 1 Astronomical Unit = the radius of Earth's orbit around the sun

Answer 5

Actually there are quite a few multiple star systems (about 10% of the stars in the known universe belong to multiple systems of 4 or more stars).

One very visible system is Castor, in the constellation Gemini. It appears as a first magnitude blue white star, but it contains a complex arrangement of six known stellar components.

Answer 6

Mizar (possibly) and Nu Scorpii are a 5 stars system.
Castor is a six star system.


There are assuredly more, but if the principal is too bright in comparison with the dimmer companions, resolving them become very quickly difficult as the distance increases.

Answer 7

it could be possible. There are millions and millions of star systems in the universe and there is, by chance, a star system that has more than 4 or 5 stars.

Answer 8

I think I'm reaching deep here but how about the seven sisters? By the way, you're pretty cute.