A really strange and very rare phenomenon


NASA / ESA Hubble Space Telescope image of GAL-CLUS-022058s, located in the Southern Hemisphere constellation Fornax (The Furnace). Credit: ESA / Hubble & NASA, S. Jha, Credit: L. Shatz

The narrow galaxy that twirls elegantly around its globular companion in this photo is a fantastic example of a truly strange and very rare phenomenon. This image, taken with the NASA/ ESA Hubble Space Telescope, shows GAL-CLUS-022058s, located in the constellation Fornax (The Furnace) in the Southern Hemisphere. GAL-CLUS-022058s is the largest and one of the most complete Einstein rings ever discovered in our universe. The object has been nicknamed by the principal investigator and his team who study this Einstein ring as the “molten ring,” which refers to its appearance and host constellation.

The unusual shape of this object, the theory of which first existed by Einstein in his general theory of relativity, can be explained by a process called gravitational lenses, whereby light shining from far away is bent and pulled by the gravity of an object between the source and the observer. In this case, the light from the background galaxy is distorted in the curve seen by the gravity of the galaxy cluster in front of it. The near-exact alignment of the background galaxy with the cluster’s central elliptical galaxy, seen in the center of this image, has distorted and enlarged the image of the background galaxy around itself into a near-perfect ring. The gravity of other galaxies in the cluster will soon cause additional distortions.

Objects like these are the ideal laboratory to investigate galaxies that are too dim and far away to see otherwise.

IAU Fornax chart

IAU Fornax chart. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg) CC BY 3.0

  • A Einstein ringalso known as an Einstein-Chwolson ring or Chwolson ring, is created when light from a galaxy or star passes a huge object on its way to Earth. Gravitational lenses divert the light, making it appear as if it is coming from different places. When the source, lens and observer are all aligned, the light appears as a ring.
  • General relativityalso known as the general theory of relativity, is the geometric theory of gravity published by Albert Einstein in 1915 and is the current description of gravity in modern physics. General relativity generalizes special relativity and refines Newton’s law of universal gravity, giving a uniform description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of the matter and radiation present. The relationship is specified by the Einstein field equations, a system of partial differential equations.
  • Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects ranging from the mass of a planet to the mass of a star, regardless of the light they emit. Astronomers can usually only detect bright objects that emit a lot of light (stars) or large objects that block background light (gas and dust clouds). These objects are only a small fraction of the mass of a galaxy. Microlensing makes it possible to study objects that emit little or no light.