NGC 2775, a galaxy 67 million light-years away, is puzzling astronomers with its mix of traits.
The Hubble Space Telescope has released a new Picture of the Week, and this time the spotlight is on a galaxy that refuses to fit neatly into any category. The subject, known as NGC 2775, is located about 67 million light-years away in the constellation Cancer (The Crab). At its center lies a smooth, gas-free core that looks strikingly similar to an elliptical galaxy. Surrounding it, however, is a dusty ring sprinkled with uneven clusters of young stars, giving it the appearance of a spiral galaxy. So what is it exactly: spiral, elliptical — or something in between?
Because astronomers can only observe NGC 2775 from a single perspective, its true nature remains uncertain. Some scientists argue that it should be considered a spiral galaxy due to its delicate ring of dust and stars. Others, however, classify it as a lenticular galaxy, a transitional type that shares characteristics of both spirals and ellipticals.
The Mystery of Lenticular Galaxies
How lenticular galaxies form is still an open question, and several possibilities exist. They may have started out as spiral galaxies that either collided with other galaxies or used up most of their star-forming gas, leaving their spiral arms to fade away. Another theory suggests they could have been more like elliptical galaxies at first, later pulling in enough gas to build a disk around them.
Some evidence suggests that NGC 2775 has merged with other galaxies in the past. Invisible in this Hubble image, NGC 2775 has a tail of hydrogen gas that stretches almost 100,000 light-years around the galaxy. This faint tail could be the remnant of one or more galaxies that wandered too close to NGC 2775 before being stretched apart and absorbed. If NGC 2775 merged with other galaxies in the past, it could explain the galaxy’s strange appearance today.
A Fresh Look With Hubble
A Hubble image of NGC 2775 was previously released in 2020 (see above). The new version adds observations of a specific wavelength of red light that is emitted by clouds of hydrogen gas surrounding massive young stars.
Never miss a breakthrough: Join the SciTechDaily newsletter.