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This NASA\/ESA Hubble Space Telescope<\/a> image features an uncommon\u00a0galaxy\u00a0with a striking appearance. NGC 7722 is a lenticular galaxy located about 187 million light-years away in the constellation\u00a0Pegasus.<\/p>\n A lenticular, meaning \u201clens-shaped,\u201d galaxy is a type whose classification sits between more familiar\u00a0spiral galaxies\u00a0and\u00a0elliptical galaxies. It is also less common than spirals and ellipticals \u2014 partly because these galaxies have a somewhat ambiguous appearance, making it hard to determine if it is a spiral, an elliptical, or something in between. Many of the known lenticular galaxies sport features of both spiral and elliptical. In this case, NGC 7722 lacks the defined arms of a spiral galaxy, while it has an extended, glowing halo and a bright bulge in its center like an elliptical galaxy. Unlike elliptical galaxies, it has a visible disk \u2014 concentric rings swirl around its bright nucleus. Its most prominent feature, however, is undoubtedly the long lanes of dark red dust coiling around the outer disk and halo.<\/p>\n This new Hubble image, the sharpest taken of NGC 7722, brings the galaxy\u2019s impressive dust lanes into sharp focus. Bands of dust like this are\u00a0not\u00a0uncommon\u00a0in lenticular galaxies, and they stand out against the broad, smooth halo of light that typically surrounds lenticulars. Astronomers think NGC 7722\u2019s distinctive dust lanes are the result of a past merger with another galaxy, similar to\u00a0other lenticular galaxies<\/a>. Researchers do not fully understand how lenticular galaxies form, but they think mergers and other gravitational interactions play an important part in reshaping galaxies and exhausting their supplies of gas while bringing new dust.<\/p>\n While it doesn\u2019t host as many new, young stars as a spiral galaxy, there\u2019s still activity in NGC 7722: in 2020 it was host to the explosion of a star that astronomers detected from Earth. SN\u00a02020SSF was a Type Ia\u00a0supernova, an event that occurs when a\u00a0white dwarf\u00a0star in a binary system siphons enough mass away from its companion star that it grows unstable and explodes. These explosions output a remarkably consistent level of light: by measuring how bright they appear from Earth and comparing that to how bright they intrinsically are, astronomers can tell how far away they must be. Type Ia supernovae are one of the best ways to measure distances to galaxies, so understanding exactly how they work is of great importance for astronomy.<\/p>\n Taken with Hubble\u2019s\u00a0Wide Field Camera 3<\/a>, this Hubble image was obtained as part of an observing program (#16691<\/a>, PI: R. J. Foley) that followed up on recent supernovae. SN 2020SSF, is not visible in this image. Researchers purposefully observed NGC 7722 two years after the supernova faded to witness the supernova\u2019s aftereffects and examine its surroundings, which can only be accomplished once the intense light of the explosion is gone. With Hubble\u2019s clear vision, astronomers can search for radioactive material created by the supernova, catalog its neighbors to help determine the original star\u2019s age, and look for the companion star it left behind \u2014 all from almost 200 million light-years away.<\/p>\n Text Credit: European Space Agency (ESA)<\/strong><\/p>\n Media Contact<\/span>:<\/strong><\/p>\n Claire Andreoli<\/strong>
NASA’s\u00a0<\/strong>Goddard Space Flight Center<\/strong><\/a>,\u00a0Greenbelt, MD<\/strong>
claire.andreoli@nasa.gov<\/strong><\/a><\/p>\n<\/div>\n