Hubble Captures Puzzling Galaxy NGC 2775
The NASA/ESA Hubble Space Telescope has captured an intriguing image of a galaxy that defies easy classification. This galaxy, known as NGC 2775, is located 67 million light-years away in the constellation Cancer, also called the Crab. What makes NGC 2775 so puzzling is its unusual combination of features. At its center, the galaxy has a smooth, featureless region that lacks gas, resembling an elliptical galaxy. Surrounding this center, however, is a dusty ring filled with patchy clusters of stars, a characteristic more typical of spiral galaxies. This raises the question: is NGC 2775 a spiral galaxy, an elliptical galaxy, or something else entirely?
Because astronomers can only observe NGC 2775 from a single viewpoint, determining its true nature is challenging. Some experts classify it as a spiral galaxy due to its delicate ring of stars and dust, which appears feathery in texture. Others argue that it is a lenticular galaxy, a type that shares traits with both spiral and elliptical galaxies. Lenticular galaxies are known for having a disk-like structure without the prominent spiral arms seen in classic spiral galaxies.
Understanding the Mystery of NGC 2775’s Classification
The origin and formation of lenticular galaxies remain uncertain, and they may form through various processes. One possibility is that lenticular galaxies begin as spiral galaxies that either merge with other galaxies or lose most of their star-forming gas, causing their spiral arms to fade. Another theory suggests that some lenticular galaxies start off more like elliptical galaxies and later accumulate gas that forms a disk around them.
In the case of NGC 2775, there is some evidence pointing to past galactic mergers. Although not visible in the Hubble image, NGC 2775 possesses a tail of hydrogen gas that extends nearly 100,000 light-years around the galaxy. This faint hydrogen tail could be the remnants of one or more smaller galaxies that ventured too close, were torn apart by gravitational forces, and eventually absorbed by NGC 2775. Such a history of mergers might explain the galaxy’s unusual appearance today.
Most astronomers currently classify NGC 2775 as a flocculent spiral galaxy. Flocculent spirals are known for having loosely defined, patchy spiral arms that look like tufts or feathers rather than continuous, well-formed arms. This classification fits with the feathery ring of stars and dust observed in NGC 2775.
New Insights from Hubble’s Latest Image
Hubble previously released an image of NGC 2775 in 2020. The latest image adds new details by including observations of a specific wavelength of red light emitted by clouds of hydrogen gas. These clouds surround massive young stars and appear as bright, pinkish clumps in the image. This additional wavelength helps astronomers pinpoint where new stars are forming within the galaxy.
By capturing this new data, the Hubble Space Telescope provides a clearer picture of the star formation activity in NGC 2775. This information is crucial for understanding the galaxy’s structure and evolution. The combination of a smooth, gas-poor center and a dusty, star-forming ring continues to make NGC 2775 a fascinating subject for astronomers trying to unravel its true nature.
In summary, the Hubble captures puzzling galaxy NGC 2775, a celestial object that challenges traditional galaxy classifications. Its unique features and possible history of mergers make it an important target for ongoing study. As astronomers continue to analyze data from Hubble and other observatories, they hope to better understand how galaxies like NGC 2775 form and evolve over time.
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Source: original article.