# Why can't we have trinary or multiple sytems, like binary systems?

We usually come across close binary systems in Astrophysics. Also, we can have hierarchical systems in which there is a close binary. The Alpha Centauri is an example of an hierarchical triple.

But why don't we have any trinary or multiple systems?

• en.wikipedia.org/wiki/HD_181068 is a system in which the orbital periods are not all that different (1 day for the two closest stars vs. 25 days for the third one). – probably_someone Nov 27 '19 at 13:08
• Who says we don’t? – Kyle Kanos Nov 27 '19 at 13:15
• – Kyle Oman Nov 27 '19 at 14:16
• Would you consider something like a globular cluster ($n$-body) to be a 'system'? – Jon Custer Nov 27 '19 at 18:08