Champaign-Urbana Astronomical Society
Hoag’s Object
Quote from David Berns on September 16, 2024, 3:57 pmHoag’s Object
This is my rendering of Hoag’s Object. The data for this render was obtained from The Mikulski Archive for Space Telescopes (MAST).
600 million light years from Earth, in the direction of the constellation of Serpens Caput (Serpent Head) lies one of the most amazing sights in the entire universe -- A Ring Galaxy. It is estimated that the galaxy has eight billion stars and spans a distance or nearly 100,000 light years.
In 1950, Arthur Hoag, an American astronomer, discovered a faint, 16th-magnitude ring surrounding a ball-like center. He assumed it was a planetary nebula, a shell of gas expelled from an average star at the end of its life. A far more exotic explanation that was proposed by Hoag was that this object could also possibly be an “Einstein Ring” from a faraway quasar, was also put forward by him. In this scenario, the quasar’s light is distorted into a halo by space-warping caused by a massive foreground spherical galaxy that it seems to surround. But later spectroscopic studies rejected this because the golden central ball and the blue ring have exactly the same redshift, indicating a whopping rush-away speed of 7,916 miles (12,740 kilometers) per second, which proves they’re both located exactly the same distance from us.
At one point Hoag suggested that the galaxy's ring formation was merely an optical illusion caused by gravitational lensing. This however, later proved to be incorrect. Hoag, not totally satisfied with his previous hypothesis, also conjectured that this strange object might be some sort of peculiar galaxy — his last surmise proved to be correct.
Many of the details of the galaxy formed remain a mystery. “Classic" ring galaxies are generally formed by the collision of a small galaxy with a larger disk-shaped galaxy. This collision produces a density wave in the disk that leads to a characteristic ring-like appearance. Such an event would have happened at least 2–3 billion years in the past and may have resembled the processes that form polar-ring galaxies.
However, there are no signs of any second galaxy that would have acted as the "bullet", and the likely older core of Hoag's Object has a very low velocity relative to the ring, making the typical formation hypothesis quite unlikely. Observations with one of the most sensitive telescopes have also failed to uncover any faint galaxy fragments that should be discoverable in a collision scenario. However, a team of scientists that analyzed the galaxy admits that "if the carnage happened more than 3 billion years ago, there might not be any detritus left to see."
There are a few other galaxies share several similarities with Hoag's Object, including a bright ring of detached stars, but their centers are elongated or barred. These galaxies may also exhibit some spiral structure. This small sampling of galaxies is known as Hoag-type galaxies.
Here is a link to my Facebook Group: https://www.facebook.com/groups/448595136986311
Processing summary:
The data (Red, Green and Blue exposures in FITS FILE format) were downloaded from Mikulski Archive for Space Telescopes (MAST).Filter f814w – 4 images, f606w – 2 images, and f450w - 5 images.
All images from the WFPC2 detector aboard the Hubble Space Telescope.
The images were opened and had their initial stretches applied using the software package “Siril” and were saved in 32 bit grayscale TIFF files. The TIFF files were then loaded into Photoshop. Where the data from each filter were aligned and stacked. The resultant image was saved as an aligned & Stacked (mean method) image. This image was then processed into the final render.
Hoag’s Object
This is my rendering of Hoag’s Object. The data for this render was obtained from The Mikulski Archive for Space Telescopes (MAST).
600 million light years from Earth, in the direction of the constellation of Serpens Caput (Serpent Head) lies one of the most amazing sights in the entire universe -- A Ring Galaxy. It is estimated that the galaxy has eight billion stars and spans a distance or nearly 100,000 light years.
In 1950, Arthur Hoag, an American astronomer, discovered a faint, 16th-magnitude ring surrounding a ball-like center. He assumed it was a planetary nebula, a shell of gas expelled from an average star at the end of its life. A far more exotic explanation that was proposed by Hoag was that this object could also possibly be an “Einstein Ring” from a faraway quasar, was also put forward by him. In this scenario, the quasar’s light is distorted into a halo by space-warping caused by a massive foreground spherical galaxy that it seems to surround. But later spectroscopic studies rejected this because the golden central ball and the blue ring have exactly the same redshift, indicating a whopping rush-away speed of 7,916 miles (12,740 kilometers) per second, which proves they’re both located exactly the same distance from us.
At one point Hoag suggested that the galaxy's ring formation was merely an optical illusion caused by gravitational lensing. This however, later proved to be incorrect. Hoag, not totally satisfied with his previous hypothesis, also conjectured that this strange object might be some sort of peculiar galaxy — his last surmise proved to be correct.
Many of the details of the galaxy formed remain a mystery. “Classic" ring galaxies are generally formed by the collision of a small galaxy with a larger disk-shaped galaxy. This collision produces a density wave in the disk that leads to a characteristic ring-like appearance. Such an event would have happened at least 2–3 billion years in the past and may have resembled the processes that form polar-ring galaxies.
However, there are no signs of any second galaxy that would have acted as the "bullet", and the likely older core of Hoag's Object has a very low velocity relative to the ring, making the typical formation hypothesis quite unlikely. Observations with one of the most sensitive telescopes have also failed to uncover any faint galaxy fragments that should be discoverable in a collision scenario. However, a team of scientists that analyzed the galaxy admits that "if the carnage happened more than 3 billion years ago, there might not be any detritus left to see."
There are a few other galaxies share several similarities with Hoag's Object, including a bright ring of detached stars, but their centers are elongated or barred. These galaxies may also exhibit some spiral structure. This small sampling of galaxies is known as Hoag-type galaxies.
Here is a link to my Facebook Group: https://www.facebook.com/groups/448595136986311
Processing summary:
The data (Red, Green and Blue exposures in FITS FILE format) were downloaded from Mikulski Archive for Space Telescopes (MAST).
Filter f814w – 4 images, f606w – 2 images, and f450w - 5 images.
All images from the WFPC2 detector aboard the Hubble Space Telescope.
The images were opened and had their initial stretches applied using the software package “Siril” and were saved in 32 bit grayscale TIFF files. The TIFF files were then loaded into Photoshop. Where the data from each filter were aligned and stacked. The resultant image was saved as an aligned & Stacked (mean method) image. This image was then processed into the final render.
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