Comparison between Thuban and other celestial elements

 

Due to its features, it is rather difficult to compare Thuban with other objects. No other element has coincidences or differences with it as to brightness, size, temperature or distance from our planet. This is an average star with very common features. This is why we compare each of those parameters either with other very similar ones or with other extremely different ones.

BRIG H TNESS

According to Bayer’s Uranometry, Alpha Draco (magnitude +3.7) should be the brightest star in the constellation. Nevertheless, Eltanin, which is “gamma”, is much brighter (magnitude +2.42). Even Rastaban -beta Draconis- (2.79) is much brighter. These two have the same brightness intensity as the “Eyes of Dragon”. Epsilon Eridano (3.7 K2V), for example, has the same magnitude as Thuban. Another star with a similar magnitude is tau Whale (3.5 G8V).

On the other hand, if we search celestial objects with much more brightness we can find the Sun (magnitude –26.8) or the Moon (magnitude -13). If we are talking about visual luminosity, then Deneb (alpha Swan) is certainly much brighter. We can also find objects much less brightness than Thuban, as is the case of  Pluto (+13.8).

SIZE

Thuban (A0III) is a white giant, with an appearance similar to Arcturus (K2III) and also to Agena (B1III).

There also much smaller stars like Vega (A0V) or the Sun (G2V). And there exist, too, stars with an incomparable bigger size like the supergiants Rigel (B8la), Betelegeuse (M2lb) o Antares (M1lb).

TEMPERATURE ON THE SURFACE

As for its temperature, Thuban (A0) looks much like Sirius (A0), Vega (a0), Altair (A7) and Deneb (A2). Their temperature is between 7500 and 10000 degrees Kelvin.

If we look for M type stars, the coldest ones, we can come across Betelgeuse (M2), Antares (M1), Gacrux (M4) and Mirach (M0), whose temperature is below that of Thuban. However, there also exist much hotter stars like Alnitak (09.5), Naos (05), Hatsya (09) or Meissa (08).

DISTANCE BETWEEN THU B AN AND THE EARTH

Thuban is about 309 light years from our planet. At a similar distance is Beta Centaurus (300 light years).

There exist much nearer stars like the Sun, about 149,597,870 km, or our Moon, about 384,399 km.

Some other stars at a bigger distance from the Earth are, for example, about 2,000 light years from our planet.

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