The life of Aldebaran

Before Aldebaran was anything it started off as a large/ relatively cool mass of gas, part of a nebula. As gravity causes the gas to contract, its temperature rises, eventually becoming high enough to trigger a nuclear reaction in its atoms. When the gases and interstellar dust of the nebula contract, a protostar is formed. Gravity causes the protostar to condense further and heat up. Nuclear reactions occur when the temperature in the centre of the protostar reaches 10 million degrees, and the star is born. Further expansion and heating of the star’s exterior then led to the formation of a red giant, with a diameter 10 to 100 times that of the Sun. So now Aldebaran as we know it, is born. Aldebaran is a massive star, so it will generate heavy elements, like iron, and grow to form a supergiant. Then it will explode and its matter will be released into space. If the entire supergiant explodes it will evolve into a supernova. Depending on the mass, the supernova will give birth either to a neutron star or, if the exploded supergiant is of sufficiently high mass a black hole. If only the outer part of the supergiant will explode a nova forms. So the life cycle of Aldebaran is very advanced and extremely long, so we will end up looking at it for quite some time (depending on if humans stay alive that long). However, now Aldebaran is a K5 III Spectral Class orange giant and is currently fusing He to C/O in its core. 


Chemical Composition

Aldebaran has now evolved out of the main sequence, and has fully shifted from the fusion of hydrogen to helium at its core to the fusion to helium to carbon and oxygen, with trace activity of other nuclear processes. The surrounding shell of gas and dust around Aldebaran contains traces of the higher element magnesium this indicates that this shell is cooler. Aldebaran's surface temperature is 4000 degrees Kelvin gives it distinct orange colour.



The main Characteristics of Aldebaran

The main distinction of Aldebaran is that it is located in the Taurus constellation as the eye of Taurus. Aldebaran gets its name from Arabic as “the follower” which describes the way in which Aldebaran rises after the Pleiades. Aldebaran is most famous for being the brightest star in the constellation Taurus. It is also the 13 th brightest star in the night sky and is 360times the sun’s luminosity (Mv=0.49). This is probably due to the fact that it is 50 times the size of the sun and would almost fill out to mercury’s orbit. It can be viewed during the period of October through March from the northern middle latitudes. It is 72 light years away from earth and 65.1 light-years away from the sun. Aldebaran is also accompanied by Aldebaran B, (Alpha Tauri B) which is thought to contain a planet with water. Aldebaran also has a mass orbiting it but it is still to be found weather it is a planet or a brown dwarf. So Aldebaran is quite an original feature to this galaxy and hopefully these planets support life and we will one day get a chance to see them.

Star Map



Aldebaran (Alpha Tauri A) is in a binary star system with Alpha Tauri B. Both of these stars orbit around a fixed point. For this reason we decided to compare these two stars.

Alpha Tauri A is orange whereas Alpha Tauri B is red. Alpha Tauri A is brighter (150 times sols luminosity) than Alpha Tauri B, which is very dim (14/10,000 of sols luminosity). The larger of the two stars is Alpha Tauri A has a mass of 40 to 52 times its diameter whereas Alpha Tauri B has a mass of only 36% of its diameter. The temperature difference of the two stars is considerable. It is estimated that the surface temperature of Alpha Tauri A is 4000 degrees Kelvin, as a comparison our own sun’s temperature is thought to be 5800 degrees Kelvin. The smaller planet Alpha Tauri B appears to have a brown dwarf or planet orbiting it, well within the equivalent distance of Mercury from our sun. Temperatures on Mercury can reach over 350 ° C, which is too hot for the planet to have any liquid water but the possible planet orbiting Alpha Tauri B has water. The planet may be capable of sustaining life whereas Alpha Tauri is so hot any planet this close would be burnt to a cinder. The nearest object to Alpha Tauri A, still subject to confirmation, has a separation of 1.35 Aus. This takes almost 654 days to orbit, compared to the orbit of the planet near Alpha Tauri B of 6.5 days.

Practical Exercise to be used for Teaching

We have found out that Stars vary in their brightness with Aldebaran being one of the brightest stars in the night sky. When you look at the stars at night though they all seam to be the same. To make it easier to understand this it would be good to set up a way of demonstrating how the light intensity changes. You could attach bulbs to dimmer switches and set them at different brightness. The brightest bulb could represent stars like Aldebaran and the dimmer ones could be used to represent the less visible stars. It may even be possible to set up the bulbs in the shape of a constellation the pupils would recognise and could try to find.