The Hubble Space Telescope has captured a stunning image of the unusual galaxy NGC 4694, located 54 million light-years away in the Virgo galaxy cluster.
Most galaxies fit into two main categories: spiral galaxies, which are young and full of energy, and elliptical galaxies, which have an older population of stars and appear more subdued.
However, some galaxies, like NGC 4694, don't fit neatly into either category.
At first glance, NGC 4694 has a smooth disk and no spiral arms, similar to an elliptical galaxy.
Elliptical galaxies are typically made up of older, redder stars, and they don't have much gas to form new stars.
But NGC 4694 is different.
While it lacks spiral arms, new stars are still forming in its bright core, giving it a younger and more energetic appearance than a typical elliptical galaxy.
In addition, NGC 4694 is rich in hydrogen gas and dust -- the key ingredients for star formation.
Most elliptical galaxies lack these materials, but this one is surrounded by a huge cloud of hydrogen gas, indicating that something unusual has happened to shape this galaxy.
Astronomers have discovered that NGC 4694 is connected to a nearby, faint dwarf galaxy called VCC 2062 by a long bridge of hydrogen gas.
This suggests that the two galaxies collided in the past, with NGC 4694 pulling gas from its smaller neighbor. This collision has likely caused the peculiar shape of NGC 4694 and triggered the star formation seen in its core.
Based on its structure, NGC 4694 is classified as a lenticular galaxy.
Lenticular galaxies are a mix of spirals and ellipticals: they have a central bulge and a disk but lack the spiral arms seen in younger galaxies. Despite their smooth appearance, lenticular galaxies, like NGC 4694, can still contain the gas needed to form new stars.
Thanks to Hubble's detailed observations, astronomers have been able to uncover the true nature of NGC 4694.
It's a reminder that not all galaxies are easy to classify, and sometimes, it takes a bit more investigation to understand their full story.