NGC 2129 is an open star cluster located in the constellation of Monoceros, which is also known as the Unicorn. It was discovered by the astronomer John Herschel in 1834. This cluster is approximately 5,000 light-years away from Earth and contains several young stars that are still in the process of forming. The cluster is relatively small, with an estimated diameter of about 10 light-years. It is thought to be around 100 million years old, making it a relatively young cluster in astronomical terms. NGC 2129 is best observed with telescopes, as it is not visible to the naked eye.