Relative
sizes of the planets in the Solar System and several well-known stars:
Mercury <
Mars < Venus < Earth
Earth <
Neptune < Uranus < Saturn < Jupiter
Jupiter <
Wolf 359 < Sun < Sirius
Sirius <
Pollux < Arcturus < Aldebaran
Aldebaran
< Rigel < Antares < Betelgeuse
Betelgeuse
< Mu Cephei < VV Cephei A < VY Canis Majoris
ByANDY FLEMING
One of the really awesome
and mind-blowing aspects of astronomy is the sheer immense scale of the
distances between planets, stars, galaxies and galaxy clusters. Our everyday
terrestrial notions of scale, size, and distance must be discarded, even if we just
consider a transit between the Earth and Mars. Kilometres first fall as units
of measurement, then astronomical units (AU)(one AU is the distance between the
Earth and Sun) -- when we start to consider interstellar distances we have to
look at light years as units of measurement (the distance that light travels in
one year).
If distances become truly
'astronomical', then it comes as no surprise that likewise sizes and masses
follow suit. We all think that the Sun is massive, and it is, with a radius of
695,990km, this is 109 times that of the Earth. With a mass of 1.989x1030 kg,
the Sun has the equivalent of 333,000 Earth masses, and yet it is still just a
run-of-the-mill yellow dwarf class G2 star. As the diagram above shows,
although there are many considerably smaller than the Sun (very common red
dwarf stars) such as our nearest neighbour Proxima Centauri, there are also
stars very much more massive.
