NGC 5694 is an extremely distant globular cluster in the constellation Hydra, and appears to be moving so fast that it is destined to escape from our Galaxy into intergalactic space.
Globular cluster NGC 5694 was discovered on May 22, 1784 by William Herschel, and catalogued as H II.196. Herschel did not resolve it, but cataloged it as a "faint nebula." The object was first resolved and recognized as a globular cluster by C. O. Lampland and Clyde W. Tombaugh at Lowell Observatory in 1932.
At 113,200 light years from the Sun, NGC 5694 is one of the most remote globulars known. At this distance, the cluster's apparent diameter of 3.6' corresponds to a true diameter of almost 120 light-years. NGC 5694's location on the far side of the galaxy has made magnitude estimates difficult due to the unknown amount of obscuring dust and gas, but its apparent magnitude of 10.17 corresponds to an absolute magnitude of -7.81, or an intrinsic luminosity of about 120,000 times the Sun's.
NGC 5694 has an estimated mass of about 100,000 solar masses; thus it is a small globular - compare this to M22's estimated mass of 7 million Suns. Its ten brightest stars appear about magnitude 16.5; its integrated spectral type is now estimated at F4. Burnham reports that up to 1977, no variable stars had been detected in this remote globular. Exhaustive searches for variable stars within the cluster through 1994 failed to find any.
NGC 5694 is approaching us at about 144 km/sec, but has a true space velocity of at least 273 km/sec with respect to the galactic center. At a distance of 94,900 light years from the galactic center, escape velocity from the Milky Way is 190 km/sec - thus NGC 5694 must be leaving the Galaxy and will never come back.
A 1976 study by William Harris and James Hesser postulates that NGC 5694 may have been pushed into a higher-energy orbit at some point in its lifetime. The Magellanic Clouds appear to be the only obvious candidates with the right distance and sufficient mass to throw NGC 5694 into a hyperbolic orbit. Harris and Hesser also theorize that NGC 5694 may have once belonged to the cluster system of the Magellanic Clouds, and not of the Milky Way.