“What Resides Within?” Hubble’s Epic Image of the Triangulum Galaxy

This wide-field view shows the Triangulum Galaxy — also known as Messier 33 — as seen from the ground. The extent of the new huge mosaic created with the NASA/ESA Hubble

 

The NASA/ESA Hubble Space Telescope  image of the Triangulum Galaxy, a spiral galaxy located at a distance of only three million light-years, inspires the question: “What amazing life forms reside there?” The NASA/ESA Hubble image is the most detailed image yet of a close neighbor of the Milky Way —  This panoramic survey of the third-largest galaxy in our Local Group of galaxies shown below provides a mesmerizing view of the 40 billion stars that make up one of the most distant objects visible to the naked eye.

This epic image of the Triangulum Galaxy — also known as Messier 33 or NGC 598 — has a staggering 665 million pixels and showcases the central region of the galaxy and its inner spiral arms. To stitch together this gigantic mosaic, Hubble’s Advanced Camera for Surveys needed to create 54 separate images. Wide-field view of the Triangulum Galaxy showing the extent of the survey is shown above.

Under excellent dark-sky conditions, the Triangulum Galaxy can be seen with the naked eye as a faint, blurry object in the constellation of Triangulum (the Triangle), where its ethereal glow is an exciting target for amateur astronomers.

 

At only three million light-years from Earth, the Triangulum Galaxy is a notable member of the Local Group — it is the group’s third-largest galaxy, but also the smallest spiral galaxy in the group. It measures only about 60 000 light-years across, compared to the 200 000 light-years of the Andromeda Galaxy; the Milky Way lies between these extremes at about 100 000 light-years in diameter.

The Triangulum Galaxy is not only surpassed in size by the other two spirals, but by the multitude of stars they contain. The Triangulum Galaxy has at least an order of magnitude less stars than the Milky Way and two orders of magnitude less than Andromeda. These numbers are hard to grasp when already in this image 10 to 15 million individual stars are visible.

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In contrast to the two larger spirals, the Triangulum Galaxy doesn’t have a bright bulge at its center and it also lacks a bar connecting its spiral arms to the center. It does, however, contain a huge amount of gas and dust, giving rise to rapid star formation. New stars form at a rate of approximately one solar mass every two years.

 

NGC 604 — a gigantic gas cloud in the Triangulum Galaxy

The image above shows NGC 604, located within the Triangulum Galaxy. Some 1500 light-years across, this is one of the largest, brightest concentrations of ionized hydrogen (H II) in our Local Group of galaxies, and it is a major center of star formation.

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The gas in NGC 604, around nine-tenths of which is hydrogen, is gradually collapsing under the force of gravity to create new stars. Once these stars have formed, the energetic ultraviolet radiation they emit excites the remaining gas in the cloud.

This image is only a tiny part of the large wide-field image of the Triangulum Galaxy created by the NASA/ESA Hubble Space Telescope. NASA, ESA, and M. Durbin, J. Dalcanton, and B. F. Williams (University of Washington)

The abundance of gas clouds in the Triangulum Galaxy is precisely what drew astronomers to conduct this detailed survey. When stars are born, they use up material in these clouds of gas and dust, leaving less fuel for new stars to emerge. Hubble’s image shows two of the four brightest of these regions in the galaxy: NGC 595 and NGC 604. The latter is the second most luminous region of ionized hydrogen within the Local Group and it is also among the largest known star formation regions in the Local Group.

These detailed observations of the Triangulum Galaxy have tremendous legacy value — combined with those of the Milky Way, the Andromeda Galaxy and the irregular Magellanic Cloud galaxies, they will help astronomers to better understand star formation and stellar evolution.

The Daily Galaxy via ESA/Hubble Space Telescope

Keywords Astrophysics Space/Planetary Science

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