Now that spring has arrived, we bid farewell once again to our friend Orion as it inches closer to the Sun in our sky each day. By mid-May, the fabled hunter is mostly below the horizon by the time dusk fades and the stars begin making their appearance.
Orion occupies a portion of the sky that is a treasure trove for astronomers and astrophotographers. The disk of our Milky Way galaxy stretches through the region, and within it lie rich star clusters and nebulae that amaze and delight. In early 2025, Dyer released a long-exposure image of one of Orion’s most famous regions – the Great Orion Nebula. Found within the “sword” of the hunter, the star-forming nebula is bright enough to be observed with just a pair of binoculars.
Found next to bright Alnitak, the leftmost star of Orion’s three belt stars, are another collection of photogenic celestial clouds that exemplify three general types of nebulae. Located at distances on the order of 1,500 light-years or so (about the same distance as the Orion Nebula), these nebulae appear much fainter and require dark skies and large telescopes to be able to spy them through an eyepiece. Over the span of five evenings in late February and March, Dyer Observatory director Billy Teets used a 16″ astrograph telescope, on loan from Vanderbilt Board of Trust alumnus Mark Dalton, to image the region.
Likely the most famous of the nebulae is the Horsehead Nebula. Discovered photographically by Williamina Fleming in 1888, the Horsehead is an example of a dark nebula, a large cloud rich in dust. The nebula appears in silhouette against a glowing red ribbon of hydrogen gas (an emission nebula) fluorescing as a result of the intense ultraviolet light emitted by the naked-eye star Sigma Orionis (out of frame in the featured image). Nashville astronomer Edward Emerson Barnard provided one of the first professional descriptions of the Horsehead Nebula as he scoured the sky, cataloging this (listed as B33 in his catalog) and other dark regions that pervade our galaxy. Of course, it’s hard to rival the detail highlighted in images of the Horsehead Nebula from the Hubble Space Telescope and James Webb Space Telescope.
Dominating the featured image is the bright star Alnitak, 31st-brightest star of the night sky, and just below it is the Flame Nebula. Appearing somewhat similar to the torch flame of Lady Liberty, this is not just another example of an emission nebula — it is also a stellar nursery where stars and other objects, such as brown dwarfs, are actively forming. Due to the large amount of dust present, it is difficult to observe and study the star cluster that resides within. The Hubble and Webb telescopes have imaged portions of the nebula in recent years to get a better understanding of the stars that call this region home.
Finally, appearing to the lower-left the Horsehead Nebula is another region of nebulosity designated NGC 2023. In contrast to the redder nebulosity seen in other areas, this region has a notably bluer appearance and is known as a reflection nebula. The bluer coloration is due to the presence of dust within the nebula. In this case, the hot blue star HD 37903 that lights up the region is in front of much of the dust, and the dust particles scatter its light. Thanks to the extremely small size of the particles, they scatter shorter wavelengths of light (bluer colors) more easily than longer wavelengths (redder colors), giving rise to the observed appearance.
If you want to try to spot any of these regions or try your hand at some astrophotography, you’ll need to wait until late summer for Orion to regain an appreciable height in the early morning sky before the Sun begins making its presence known. Good luck!