November 3 Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 November 3

The Triangulum Galaxy, otherwise known as Messier 33, lies almost 3 million light-years from Earth, and is a near neighbor of the Andromeda Galaxy. The galaxy is imaged here by the Nicholas U. Mayall 4-meter Telescope, located at Kitt Peak National Observatory (KPNO), a Program of NSF’s NOIRLab.  The Triangulum Galaxy is the third-largest member of the Local Group, a cluster of galaxies that includes our Milky Way and its closest neighbors. The Andromeda Galaxy is the largest member. The Triangulum Galaxy and Andromeda Galaxy have history together, but astronomers are still investigating the details. Their close proximity has caused some researchers to suggest that Triangulum is a satellite of the Andromeda Galaxy, not unlike the way the Moon is a satellite of the Earth — just on a much, much bigger scale. Alternatively, some researchers propose that these two galaxies may be independent and have simply brushed past each other, as evidenced by streams of stars and neutral hydrogen gas linking the two galaxies. However they have interacted, it’s probable that they will dramatically collide in 2.5 billion years, resulting in their consolidation and eventual evolution into a lenticular galaxy.

M33: The Triangulum Galaxy

Image Credit & CopyrightProcessing – Robert Gendler
Data – Hubble Legacy ArchiveKPNONOIRLabNSFAuraAmateur Sources

Explanation: The small, northern constellation Triangulum harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy. M33 is over 50,000 light-years in diameter, third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the Andromeda Galaxy and astronomers in these two galaxies would likely have spectacular views of each other’s grand spiral star systems. As for the view from the Milky Way, this sharp image combines data from telescopes on and around planet Earth to show off M33’s blue star clusters and pinkish star forming regions along the galaxy’s loosely wound spiral arms. In fact, the cavernous NGC 604 is the brightest star forming region, seen here at about the 1 o’clock position from the galaxy center. Like M31, M33’s population of well-measured variable stars have helped make this nearby spiral a cosmic yardstick for establishing the distance scale of the Universe.