The spectacular barred spiral galaxy NGC 6872 has ranked among the biggest stellar systems for decades. Now a team of astronomers from the United States, Chile and Brazil has crowned it the largest-known spiral, based on archival data from NASA’s Galaxy Evolution Explorer (GALEX) mission.
Measuring tip-to-tip across its two outsized spiral arms, NGC 6872 spans more than 522,000 light-years, making it more than five times the size of our Milky Way galaxy.
“Without GALEX’s ability to detect the ultraviolet light of the youngest, hottest stars, we would never have recognized the full extent of this intriguing system,” said lead scientist Rafael Eufrasio, a research assistant at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The galaxy’s unusual size and appearance stem from its interaction with a much smaller disk galaxy named IC 4970 (circled in the image above), which has only about one-fifth the mass of NGC 6872. The odd couple is located 212 million light-years from Earth in the southern constellation Pavo.
The research included Fernanda Urrutia-Viscarra and Claudia Mendes de Oliveira at the University of São Paulo in Brazil and Dimitri Gadotti at the European Southern Observatory in Santiago, Chile.
For more on the research, see the NASA press release.