Together, these galaxies are known as ARP 143. A galactic collision created an unusual triangle pattern of star formation.
NASA, ESA, STScI, Julianne Dalcanton Center for Computational Astrophysics, Flatiron Inst./UWashington)/Joseph DePasquale (STScI)You can think of it as a star-birthing frenzy, but galaxies NGC 2445 and NGC 2444 sure know how to make a splash in space. A newly released Hubble Space Telescope image shows the pair, known collectively as Arp 143, creating an unusual triangle-shaped region of active star formation.
NGC 2445 (the distorted, sparkly spiral galaxy) and NGC 2444 (the more diffuse galaxy on the left) had a head-on collision and likely passed through each other, triggering an area of star birth that looks like a cosmic version of a fat slice of pizza.
Astronomer Julianne Dalcanton of the Flatiron Institute and the University of Washington in Seattle said that rings of star formation aren’t uncommon, but that this triangle shape is “weird.”
“Part of the reason for that shape is that these galaxies are still so close to each other and NGC 2444 is still holding on to the other galaxy gravitationally,” Dalcanton said in a NASA statement on Tuesday. “NGC 2444 may also have an invisible, hot halo of gas that could help to pull NGC 2445’s gas away from its nucleus. So, they’re not completely free of each other yet, and their unusual interaction is distorting the ring into this triangle.”
If you see a space object labeled “Arp,” chances are you’re in for a fun time. Arp objects are part of astronomer Halton Arp’s 1966 Atlas of Peculiar Galaxies, a catalog of oddballs that don’t fit the mold of most galaxies.
The two galaxies of Arp 143 are pulling away from each other. Newer stars (around 1 million to 2 million years old) are forming near the center of NGC 2445. Older ones dating back to 50 million to 100 million years ago can be found in the blue “streamers” of stars that look like tendrils between the galaxies.
“It’s a fantastic sandbox to understand star formation and interacting galaxies,” said Elena Sabbi of the Space Telescope Science Institute.
Hubble, a joint project from NASA and the European Space Agency, is still cranking despite a series of technical glitches and its impressive age. NASA hopes it will continue to thrive and send back more spectacular observations like this one.
