A graviton ellipse (designated as spatial anomaly 521 by the Borg) is a stable pocket of normal space moved by a surrounding elliptical gravimetric distortion perimeter measuring millions of terajoules of subspace energy.
Graviton ellipses travel through subspace, emerging into normal space and extra-dimensional realms only when they are in proximity of objects that emit electromagnetic energy, such as spacecraft and dark matter asteroids. The ellipses themselves generate an electromagnetic radiation field of dangerous levels to humanoids that make the anomaly react like a magnet drawn to another magnet, relative to its target. The Borg had discovered that cutting down power and simultaneously reversing the polarity of deflector shields will result in the anomaly no longer being attracted to the ship. The anomalies remain outside of subspace for some hours only.
In addition to the electromagnetic field,these anomalies emit level 9 gravimetric distortions through subspace to the space around them, creating severe turbulence. As an ellipse emerges from subspace, the initial target it was drawn to is already in range of the distortions and will no longer be capable of forming warp fields to escape. In addition, the target ship will experience a ship-wide power drain. An ellipse could overtake the ship even if it was traveling at maximum impulse.
The stress caused by the gravimetric interference is higher closer to the perimeter and can tear some starships apart. Some ships can, however, survive the ordeal intact. The actual elliptical perimeter of the anomaly is composed of gravimetric currents of increasing gravimetric shear intensity closer to the interior of the phenomenon. As the anomaly changes course or devours objects, it discharges gravimetric surges in the perimeter that travel outward and even affect objects thousands of kilometers away.