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Messier 109 (NGC 3992)
Joel Stehouwer

NGC 3992

In 1783, Charles Messier, a well known French astronomer, appended a new astronomicic object to his astronomical catalogue of nebulae and star clusters. This object became known as the Messier 109 galaxy and is the most distant object in the Messier Catalog. This galaxy is located just outside of the bottom of the bowl in the Big Dipper (Ursa Major) constellation. Messier 109 is a barred spiral galaxy because the central core of the galaxy appears to be stretched into a bar-like shape. A current question of research concerning Messier 109 asks how it has such a flat rotation curve, meaning the average orbital velocity of visible dust and stars increases only slightly farther from the galactic center, even though it has a low-mass galactic halo (the collection of dust and stars not located in the spiral arm disk or galactic nucleus). This is a valuable question to answer because discrepancies between the rotational curve and mass distribution in spiral galaxies are used as evidence for dark matter. Hence, research concerning Messier 109 may help us to better understand this mysterious and intruiging "invisible" matter.

Wondering why Messier 109 appears differently in the above image than other spiral galaxies you've seen? First, it is a barred spiral galaxy. This means that the galactic nucleus is oblong (bar-shaped) rather than spherical. Also, visible on the left edge of the above image is one (UGC 6969) of the three dwarf satellite galaxies of Messier 109. From only the visual image provided above, it would be reasonable to assume Messier 109 is a fairly symmetric spiral galaxy, however, the below infrared images shows us otherwise. The galaxy appears to have mostly blue arms and a white nucleus because of the typs of stars in these regions. The nucleus contains such a dense pocket of stars (and a quasar) that are of various types, and so emits light from the entire spectrum, which appears white. Toward the end of the bars the light appears quite red, meaning these regions are likely new star forming regions rich in heavier elements such as carbon and iron that have been produced and ejected by the older populations of stars. The arms are likely also new star forming regions, because they are emitting mostly blue light which is indicative of very hot and very dense gas - the perfect location for a new star to form.

NGC 3992 NGC 3992

Left: J-Band (near-infrared) image of NGC3992 image captured using the MAGIC camera using the 2.2m-MPIA-telescope at Calar Alto (Spain) by Wilke et al.

Right: Image taken by T. H. Jarrett, IPAC/Caltech using J-Band (infrared 1.2um) wavelengths as part of the 2MASS (Two Micron All Sky Survey) project using a 1.3m telescope at Mt Hopkins, AZ and CTIO, Chile. This image has not been modified visually but instead shows a true infrared observation of Messier 109.

Easily visible in the colored image is the barred shape of the galactic nucleus and the assymetry of the spiral arms. This also shows a leading curve of the ends of the bar in the direction of rotation. Another prominent result of the colored image is the ability to notice that the bar does not "connect" with the spiral arms, but instead these regions are separated by a buffer where very little light is emitted. Visible in the uncolored image is the skewed offset between the orientation of the major axis of the galaxy and the orientation of the barred nucleus.

Messier 109 has an inclination of approximately 60 degrees (see calculations below) when viewed from earth and so we see it from a relatively oblique perspective but can still easily distinguish its spiral arms. William Herschel independently discovered Messier 109 in 1789, but mislabelled it as a nebula, saying, "Considerably bright. Bright resolvable [mottled, not resolved] nucleus with very faint extended branches to position angle 30deg north preceding to south following. 7 or 8' long, 4 or 5' broad."

Above, I claimed that Messier 109 is the most distant of the objects in the Messier Catalog. This distance is estimated to be 20.9 Mpc (NED) or is approximately 68 million light years. Its maximum angular size is 6.54 arcminutes, which corresponds to a linear size of 12175 lightyears across its major axis. Using some generous estimation (see below), we can then conclude that it would take the Millenium Falcon (Star War's "fastest ship in the galaxy") approximately 11 hours and 41 minutes for the Millenium Falcon to traverse across Messier 109.

Data Reduction:

The first image was produced as a composite of 24 images taken using different filters from the visible light spectrum. Multiple images were captured over a period of two hours in order to eliminate error due to regions of the image that experienced interference. Also taken were flats, images used to correct for any potential errors in the telescope or caused by significant, nearby light sources. After being corrected using the flats, all of the images from each filter were combined to create a master image in that filter. Then each of the masters were combined using scale factors to modify the colors displayed. These factors were R=1.25, G=1.5, B=9.5, and the saturation and gamma values were also used to produce the most visually appealing and physically accurate image possible.


Calculations for Inclination Angle:

Minor Axis: 20.08 kpc (measured using the pixel scale value and number of pixels from end to end)

Major Axis: 39.71 kpc (measured using the pixel scale value and number of pixels from end to end)

Inclination Angle: arccos(minor/major) = 1.04 radians -> 60 degrees

Calculations for the Millenium Falcon:

Assumed top speed: 9,130,000C (9,130,000 times the speed of light!) -> 2.739*10^15 meters/second

Linear size of Messier 109's major axis: 12175 lightyears -> 1.15*10^20 meters

Time Required: Distance / Speed = 42055 seconds -> 11 hours and 41 minutes


Frommert, Hartmut, and Christine Kronberg. "Messier 109." Students for the Exploration and Development of Space, SEDS, 14 Oct. 2013. <>

"Messier 109." Messier Objects, 26 Sept. 2015. <>

Redington, Troy. "Fastest Ship in the Universe: How Sci-Fi Ships Stack Up." Fat Wallet, 1 July 2015. <>

Wikipedia, "Messier 109".

Wilke, K. , C. Möllenhoff, and M. Matthias. "Mass Distribution and Kinematics of the Barred Galaxies NGC3992 and NGC7479", Astronomy and Astrophysics (2000), 361, 507. <>

This research utilized NED ( the NASA/IPAC Extragalactical Database) which is provided by the California Institute of Technology in cooperation with NASA.

Right Ascension (J2000) 11:57:35
Declination (J2000) +53:22:25
Filters used B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter B, C, R, and V (300s)
Image dimension 727x512 pixels; 20.0x11.3 arcminutes
Date/time observed March 15, 2017, 3:02 UT



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