Messier 87 (M87), supergiant elliptical galaxy, has been seen growing even larger, as astronomers used a new astronomical technique to witness the action. This galaxy is seen in the constellation Virgo, laying in the center of a cluster of galaxies named after the star formation.

Galaxy M87 is growing as the family of stars absorbs other smaller collections of matter. This process is usually extremely difficult to record. The large number of stars within the supergiant galaxy makes it nearly impossible to see smaller galaxies being driven into the larger family of stars through the force of gravity.

Instead of looking directly at the crowded field of stars seen face-on through the galaxy, astronomers studied gas clouds surrounding the family of stars, floating like a galactic halo. They found evidence revealing that M87 merged with a smaller spiral galaxy at one point during the last billion years.

"This result shows directly that large, luminous structures in the Universe are still growing in a substantial way — galaxies are not finished yet! A large sector of Messier 87's outer halo now appears twice as bright as it would if the collision had not taken place," Alessia Longobardi, one of the researchers on the study, said.

Planetary nebulae, clouds of gas surrounding galaxies, shine in a specific wavelength of aquamarine light. Examining the area surrounding a galaxy for this frequency of light allows astronomers to easily see these formations apart from the light coming from the hundreds of billions of stars in such a galaxy. Examining this light through a spectrograph, which breaks light into its component colors, allowed investigators to determine the direction and velocity these clusters are traveling.  

The Very Large Telescope, operated by the European Southern Observatory (ESO) in Chile, was utilized to record the new data.

Astronomers believe most of the stars originally contained in the medium-sized galaxy that collided with Messier 87 scattered over an area roughly 100 times as large as the original gathering of stellar bodies. Study of these stars, using a spectrograph, revealed the bodies were originally part of the impacting galaxy.

"The green planetary nebulae are the needles in a haystack of golden stars. But these rare needles hold the clues to what happened to the stars," Magda Arnaboldi from the European Southern Observatory said.

Analysis of M87 and how the supergiant galaxy is growing through the accumulation of smaller collections of stars was profiled in the journal Astrophysical & Astrophysics.

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