Aldebaran: The Red Giant

Aldebaran Properties:

Spectral Type: K5+ III
Distance: 65 light years
Age: ~ 6 billion years
Apparent Magnitude: 0.75 - 0.95 (slow irregular variable)
Mass: 1.16 M_☉
Radius: 45 R_☉
Luminosity: 440 L_☉
Surface Temperature: 3900 K

Size comparison: Aldebaran and Sun

Aldebaran is the brightest star in the zodiac constellation of Taurus. It is roughly 6 billion years old and is towards the later stages in its stellar life. The hydrogen fuel within its core has been depleted, having all fused into helium. Aldebaran has moved off the “main sequence” of stars and is a red giant.

Becoming a Giant

When Aldebaran’s hydrogen had mostly fused into helium in its core, the fusion process slowed and the force of gravity began compressing the core. This compression in turn heated the core and ignited the surrounding shell to begin nuclear fusion. The fusion process in the shell causes the star to balloon to a comparatively enormous size. Aldebaran’s mass is only 16% larger than the Sun but has swelled to a radius 45 times greater than the Sun (91,125 times the Sun’s volume)! This process has also caused Aldebaran to become 440 times brighter than the Sun.

End of Life

Since Aldebaran has a mass of greater than 0.6 solar masses, the core will continue to contract and heat up and the solar atmosphere will continue expanding outward into space. When the core temperature reaches 100 million Kelvin (degrees Celsius), the Helium core will reignite via nuclear fusion to begin forming carbon and oxygen. A significant fraction of the carbon and all of the oxygen in the universe is made by this process in giant stars.

After about 20,000 years, the surface temperature of the core reaches 30,000K and ultraviolet radiation is sent outward into space. The UV radiation ionizes the gas that has swelled outward from the central core and a planetary nebula is the result (planetary nebulae have nothing to do with planets other than being shaped like a sphere).

Aldebaran will end its life in this way in a few billion years. The resulting planetary nebula will shine for about 10,000 years until the ionized gas recombines and becomes transparent. The smoldering core will be all that remains visible - a white dwarf. The white dwarf will continue cooling for billions of years afterwards.

Aldebaran

Constellation: Taurus

Coordinates: RA: 4h 35m 55s Dec: +16° 30’ 33”

Dates Acquired: Feb. 20 & 24, 2024

Moon Illumination (average): 94%

Bortle Class: 6

Latitude: +43°

Equipment Info:

Telescope: William Optics Grand Tourismo 71 with 6AIII Flattener/Reducer

Focal Length: 335.2mm

f/4.2

Main Camera: ZWO 533MM-Pro

Guide Camera: ZWO 290MM-mini

Mount: Sky Watcher EQ6Ri-Pro

Filters: Astrodon 31mm (LRGB)

Integration:

Lum - 106 x 40s = 1h 11m

Red - 41 x 80s = 55m

Green - 30 x 80s = 40m

Blue - 32 x 80s = 43m

Calibrated with flats & dark flats

Total Light Integration: 3h 29m

Processing Techniques - PixInsight Workflow:

GraXpert
RGB - RGBCombination, SPCC
BlurXTerminator (LRGB)
GeneralizedHyperbolicStretch on L and RBG
StarXTerminator on L & RGB
- SCNR-Green , CorrectMagentaStars script, Curves on RGB-Stars
- Curves on RGB-Starless
- PixelMath to recombine stars & starless:
```
RGBK = combine(stars, starless, op_screen())
```
Apply L to RGB via LRBGCombination
Crurves on LRGB
NoiseXTerminator
Plate solved and annotated in PixInsight