Due to the necessity for long-term observations and the uncertainty in position and proper motion determinations, only a few binaries have been found astrometrically. With the next generation of space-based astrometric missions, this will undoubtedly alter. Sirius is the most well-known example of an astrometric binary system. It had a wobble in its proper motion, according to Friedrich Bessell in 1844. He deduced from this that the visible star, now known as Sirius A, must have an unseen (and so dim) partner, Sirius B.
Alvan Clark only saw this telescopically in 1862, and it is now recognized to be a dim white dwarf. Procyon, also known as A Canis Minoris, was discovered as an astrometric binary system. It, too, has a white dwarf companion, which may now be seen through telescopical observation.
“Exotic” type of binaries
The first-known binary pulsar, PSR J0737-3039, was one of the most fascinating celestial objects found in late 2003 on the Parkes radio telescope. It has a 23-millisecond pulsar, PSR J0737-3039A, and another pulsar, PSR J0737-3039B, which rotates every 2.8 seconds and orbits each other every 2.4 hours.
This unusual binary system has piqued the interest of astronomers all around the world because it serves as a fantastic test bed for General Relativity and the search for gravitational waves. It’s not only the first of its kind to be discovered, but it’s also an eclipsing binary system. However, because of relativistic influences on the orbit, it is only expected to remain in an eclipse orbit for another ten years or so.