UW News

January 8, 2019

Triangulum Galaxy shows stunning face in detailed Hubble portrait

An image of a nearby galaxy called M33.

This mosaic of the Triangulum Galaxy showcases the central region of the galaxy and its inner spiral arms. Millions of stars, hundreds of star clusters and bright nebulae are visible.NASA/ESA/Meredith Durbin/Julianne Dalcanton/Ben Williams/University of Washington

NASA’s Hubble Space Telescope has produced a stunningly detailed portrait of the Triangulum Galaxy, displaying a full spiral face aglow with the light of nearly 25 million individually resolved stars. It is the largest high-resolution mosaic image of Triangulum ever assembled, composed of 54 Hubble fields of view spanning an area 19,400 light-years across.

The project behind this mosaic is led by Julianne Dalcanton, a University of Washington professor of astronomy. Other major contributors include UW astronomy graduate student Meredith Durbin and UW astronomy professor Ben Williams.

The images show areas of star birth glow bright blue throughout the galaxy, particularly in nebulas of hot, ionized hydrogen gas.

Triangulum, also known as M33, is a spiral galaxy and one of our neighbors in a collection of dozens of galaxies called the Local Group. Triangulum is oriented with its face toward us, ideal for studying the distribution of stars and gas in its well-defined spiral structure. While astronomers are still delving into the immense trove of data collected by Hubble, a few characteristics stand out immediately, inviting comparisons and contrasts with our own Milky Way galaxy and the third large spiral galaxy in the Local Group, the Andromeda galaxy.

“My first impression on seeing the Hubble images was, wow, that really is a lot of star formation,” said Dalcanton. “The star formation rate intensity is 10 times higher than the area surveyed in the Andromeda galaxy in 2015.”

Astronomers think that Triangulum has been an introvert, avoiding disruptive interactions with other galaxies, instead spending the eons tending its well-ordered spiral and turning out new generations of stars. Further research may determine if Triangulum is actually a newer member of the Local Group of galaxies, and whether its quiet days will soon be over.

This mosaic was created from images taken by Hubble’s Advanced Camera for Surveys between February 2017 and February 2018. The panoramic image was presented at this week’s 233rd meeting of the American Astronomical Society in Seattle.


For more information, contact Dalcanton at jd@astro.washington.edu and Williams at ben@astro.washington.edu.

Adapted from press releases by the Space Telescope Science Institute and the European Space Agency.