Context: The European Space Agency’s (ESA) Euclid space telescope has discovered a rare ring of light (known as an Einstein ring) around a galaxy nearly 590 million light-years away from Earth.
Relevance of the Topic: Prelims: Einstein Ring; Gravitational lensing; Euclid space telescope.
What is an Einstein Ring?
- An Einstein ring is a ring of light around a form of dark matter, galaxy or cluster of galaxies. It is an example of strong gravitational lensing.
- Gravitational lensing is a phenomenon which occurs when a massive celestial object (such as a galaxy, cluster of galaxies or black hole) creates a strong gravitational field which distorts and amplifies the light (causes the light to bend/curve) from a distant object positioned directly behind it.
- The object causing the light to curve is called a gravitational lens.
- Gravitational lensing can result in several types of image configurations, including an Einstein ring.
Discovery of the recent Einstein Ring:
- The Einstein ring was discovered around NGC 6505, a galaxy that was first found in the 19th Century & is nearly 590 million light-years away from Earth.
- NGC 6505 acted as the gravitational lens. It distorted and amplified the light coming from a distant unnamed galaxy, located 4.42 billion light-years away.
- A light-year is the distance light travels in one year, which is 9.46 trillion kilometres.
- The photos taken by Euclid show a bright ball of light in the centre with a bright, cloudy ring around it.
- NGC 6505 acted as the gravitational lens. It distorted and amplified the light coming from a distant unnamed galaxy, located 4.42 billion light-years away.
Rarity of Einstein Rings:
- Einstein rings are named after mathematician and physicist Albert Einstein, whose general theory of relativity predicted that light could bend and brighten around objects across the cosmos.
- The first Einstein ring was discovered in 1987, and since then, several more have been discovered.
- Notably, they are extremely rare — less than 1% of galaxies have an Einstein ring.
- Einstein rings are not visible to the naked eye, and can be observed only through space telescopes such as Euclid.
Why do scientists study Einstein Rings?
- Probing dark matter:
- These rings help scientists investigate dark matter which has never been detected. Dark matter and dark energy together make up 95% of the universe.
- This dark matter does not interact with light, but it does have a gravitational effect. Gravitational lensing thus allows us to indirectly detect dark matter.
- Studying distant galaxies:
- Einstein rings enable scientists to learn about distant galaxies, which otherwise might not be visible.
- Expansion of Universe:
- They can also provide information about the expansion of the universe as the space between the Earth and other galaxies — both in the foreground and the background — is stretching.
About Euclid Space Telescope:
- The Euclid Space Telescope was launched in 2023 from Cape Canaveral in Florida on a SpaceX Falcon 9 rocket by the European Space Agency (ESA).
- The telescope is stationed 1.5 million km away from the Earth at the Lagrangian Point 2.
- It will observe the shapes, distances, and motions of billions of galaxies spanning over 10 billion light-years over the next six years.
- Objective:
- To create the largest cosmic 3D map of the universe to better understand the distribution of dark matter and reveal the influence of dark energy in the early universe.
- To understand the evolution of the Universe by looking at the light emitted from galaxies 10 billion years ago.