Quintuple Star System Facts for Kids

Five Stars, One System!

1SWASP J093010.78+533859.5 is the first quintuple star system ever discovered that contains two eclipsing binary stars! It has five stars all bound together by gravity, located about 250 light-years away in the constellation Ursa Major (the Great Bear).

Two Pairs and a Loner!

The system is arranged as two pairs of stars — Binary A and Binary B — orbiting around their common center of mass, plus a fifth star tagging along with Binary A. Think of it like two dancing couples circling a ballroom, with a solo dancer following one couple!

Stars That Touch!

Binary B is a "contact binary" — its two stars orbit so close together (just 3 million km apart!) that they actually share an outer atmosphere! They orbit each other in just 5½ hours — one of the shortest orbital periods ever found.

Blazing Fast Orbit!

Binary B's two stars whip around each other in just 5 hours and 28 minutes! That's faster than a school day. In the time it takes Earth to orbit the Sun once, these two stars complete over 1,500 orbits around each other.

The Unequal Pair!

In Binary B, one star is 0.86 solar masses and the other is only 0.34 solar masses — the smaller star has less than half the mass! Despite this, they share a common surface temperature of about 4,700°C because their atmospheres are merged together.

The Detached Duo!

Binary A is a "detached binary" — its two stars orbit each other at a comfortable distance of about 5.8 solar radii apart (about 4 million km). Unlike Binary B, these stars keep their own separate atmospheres!

A Day and a Third!

Binary A's two stars orbit each other every 1.3 days — about 31 hours. So while you sleep, wake up, go through a full day and most of the next night, these two stars complete one full dance around each other!

Binary A's Residents!

Binary A contains stars of 0.84 and 0.67 solar masses — both smaller and cooler than our Sun. The bigger star is about 5,185°C at its surface (our Sun is 5,500°C), while the smaller one is a cooler 4,325°C.

The Fifth Wheel!

The mysterious fifth star orbits Binary A at a distance of up to 2 billion km! It's an early K-type star at about 5,000°C. It was detected through an extra set of spectral lines that didn't move with either binary pair — a stationary signature hiding in plain sight.

Far Apart Together!

The two binary pairs (A and B) are separated by about 21 billion km — roughly 140 AU, or about 3.5 times the distance from the Sun to Pluto! Despite this vast distance, gravity keeps them permanently bound together.

The Great Orbit!

The two binary pairs take centuries to orbit around their common center of mass. While each inner binary spins in hours or days, the outer orbit of the two pairs around each other takes an estimated thousands of years to complete!

A Gravitational Hierarchy!

The system is "hierarchical" — meaning gravity works at multiple scales. Each binary pair is tightly bound internally, the 5th star orbits Binary A at a medium distance, and the whole AB system orbits at the largest scale. If it weren't hierarchical, the system would be chaotic and fly apart!

Double Eclipse!

Both binary pairs produce eclipses visible from Earth! As each pair of stars orbits, one star passes in front of the other and blocks some light. This "doubly eclipsing" behavior is what made the system detectable — and it's the first known quintuple system with this property.

Same Plane, Same Origin!

Both binaries orbit at nearly the same inclination angle (~87-88° from our line of sight). This suggests all five stars formed from the same spinning disk of gas about 9-10 billion years ago — they're older than our entire Solar System!

Smaller Than the Sun!

All five stars are smaller, cooler, and dimmer than our Sun. They're all K-type or late G-type stars with surface temperatures between 4,300°C and 5,200°C. Despite having five stars, the whole system is only 9th magnitude — invisible to the naked eye!

Five Sunsets!

If a planet existed in this system, you could see up to five suns in the sky! Close binary pairs would look like one bright merged light, while the distant pair would appear as a bright star. The view would change hour by hour as the stars orbited.

Tidal Forces!

The close stars in each binary exert tremendous tidal forces on each other — just like the Moon causes tides on Earth, but millions of times stronger! These tidal forces have circularized both orbits (made them perfectly round) and synchronized the stars' rotations.

Sharing an Atmosphere!

In the contact binary (B), gas flows between the two stars through their shared envelope! The larger star is slowly feeding material to the smaller one. Over billions of years, this mass transfer can dramatically change both stars' evolution.

How It Was Found!

The system was discovered by Marcus Lohr and colleagues at the Open University in 2015. They first noticed one set of eclipses in the light curve, then found a second set of unexpected eclipses hiding in the data — revealing the extraordinary double-binary nature!

Billions of Years Stable!

At 9-10 billion years old, this system has survived for over twice as long as our Solar System has existed! The hierarchical arrangement — with widely separated tight binaries — is the secret to its stability. A non-hierarchical five-body system would self-destruct in just thousands of years.