Identified as NGC 3808 and PGC 36227/8 in various catalogs, Arp 87 presents a captivating pair of interacting galaxies situated approximately 330 million light-years away in the Leo constellation. This cosmic spectacle was first discovered by William Herschel on April 10, 1785.
In the renowned Arp catalog of peculiar galaxies, meticulously compiled by Halton Arp, Arp 87 occupies a distinct place in the category of "spiral galaxies with large high surface brightness companions." The two galaxies, in the NGC catalog, are recognized as NGC 3808 (the larger, nearly face-on spiral galaxy) and NGC 3808A (the smaller companion), an edge-on spiral galaxy.
Through optical imaging, we can observe multiple conspicuous dust arms and a luminous ring of star formation on NGC 3808. Furthermore, elements such as stars, gas, and dust from NGC 3808 have collectively formed an arm that encircles its smaller companion. NGC 3808A is encased by a rotating ring of stars and interstellar clouds, oriented perpendicular to the plane of NGC 3808, a structure known as a polar ring.
Interacting galaxies like Arp 87 serve as valuable sources for multifaceted studies, providing critical insights into galactic interaction and evolution. Additionally, such environments are hotbeds for star formation, offering essential information on this topic.
The featured image is a composite optical snapshot of Arp 87 as captured by the Hubble Space Telescope. It was developed using broadband filters centered at 450 nm (B-band, blue), 555 nm (V-band, green), and 814 nm (I-band, red), along with a narrow band filter focusing on the emission of ionized hydrogen/nitrogen (Hα and [N II], red). This image clearly illustrates how both galaxies are distorted due to their gravitational interaction, with a strikingly visible arm from NGC 3808 encircling its smaller companion.
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