ALS 19653, a star with two nested shells

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ALS 19653 is a B0.5 Ib blue supergiant star located in the constellation Serpens cauda. This image is the result of a ProAm collaboration with Prof. Vasilii Gvaramadze (Sternberg Astronomical Institute, Moscow). The goal was to acquire a full color image of a mass ejection nebula around the star. This image was then captured with narrowband filters (Hydrogen alpha and OIII, 3nm bandpass). The total exposure was 42 hours in narrowband plus an additional 1.5 hours through RGB filters, to capture the stars with their natural color.


The processing was very simple with only a dual deconvolution in order to extract more signal and some detail on the external shell (Maximum Entropy) as well as detecting more detail in the inner shell (Positive Constraint). As a result, this image has two properties. On one side, it shows, in the inner nebula a similar amount of detail as the IPHAS (now merged with IGAPS) image, taken with the Isaac Newton Telescope (2.5m). On the other side, the external shell is a complete bubble, with a brighter NE side. Prof. Gvaramadze’s calculations, using the space velocity of the star, allowed him to determine that this shell is related to ALS 19653 and not a diffuse nebulosity that happened to be in the way.

This work was published as a Research Note of the American Astronomical Society (RNAAS) on 29 September 2020.


Additional Information


Name(s): ALS 19653

Type: Blue supergiant type B0.5 Ib

RA:  18h 47m 59s

Dec: +02º 54’ 47”

Constellation: Serpens Cauda

Size (arcmin): 6.2×5.9 arcmin

Magnitude: N/A



Date: 2020-04-23 to 2020-06-30

Location: Curiosity2 Observatory, New Mexico Skies, Mayhill, NM, USA

Size (arcmin): 26×26 arcmin

Telescope: 24” (61 cm) f/6.5 Reflector

Camera: FLI PL16803 (4096x4096pix)

Guiding: Astrodon MonsterMOAG off-axis guider

Total exposure: 43.5 hours (Ha: 24.7 h; OIII: 17.3h; RGB: 1.5h)

Processing: CCDStack, Photoshop CC 2020

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