Our amazing universe

The universe is full of amazing objects of a massive scale, some very tiny, like the dust grains that burn up in our atmosphere, some massive like the supermassive blackholes at the centre of galaxies. In this article, we have a look at a selection of objects as a way comparing their sizes and attributes and also appreciating the variety of objects out there in the universe.

The Earth

We’ll start with our home, the Earth, the only one where people live and the most hospitable one for us humans, for the time being anyway. Given there’s 7 billion of us it’s quite good that it is rather big. It has a diameter of 12,756km and a density of 5.514 grams per cubic centimetre. It weighs 1 Earth mass, or 5,972,370,000,000,000,000,000,000kg and has a surface gravity of 1g (9.81 m/s2) and an average surface temperature of 15 degrees Celsius. Quite nice really.

The Moon

Other than the Sun, the Moon is the next most obvious object in the sky. It has a human population of zero, at the moment, and a diameter of 3474km (0.273 of the Earth). It’s a bit less dense than the Earth at 3.344 g/cc and it weighs 0.012 of the what the Earth does. The temperature ranges from -173 degrees C to +117 degrees C. The surface gravity is 0.1654g so quite a good weight (mass) loss programme and you can jump very high. Not the most pleasant environment without a spacesuit with some rather extreme temperature differences and no atmosphere.

The Moon, taken by the author


Rather than choose the Sun as a star to compare to the Earth and Moon, we thought Betelgeuse would be better to compare, to show just how huge these stars can get. The diameter varies a bit between 684 and 1090 times bigger than the Sun. The temperature is a nice balmy 3317 degrees C and the surface gravity is 0.0018747g and weighs a whooping big 3,862,174 times as much as the Earth. The low gravity is why the star is so bloated as it struggles to hang onto to its outer mass. It goes without saying, you really shouldn’t consider moving there.

Supermassive black hole

These objects are quite amazing, there’s one at the centre of our galaxy and its enourmous. It is really massive with the radius thought to be out to a distance of 6.25 light hours, or the distance of the sun to the orbit of Uranus, based on the behaviour of stars whizzing around this monster. Though the radius can be a little tricky to measure and scientists have calculated, based on it’s mass, the radius might also be about 41 light seconds – which gives an escape velocity of the speed of light. The weight of this giant is about 4.1 million solar masses or 1,365,078,600,000 times the weight of the Earth! Black holes are rather chilly being very close to 0K or -273 degrees Celsius. Clearly living on or near the surface of the supermassive black hole at the centre of our galaxy is not really ideal, property prices aren’t really going to be an issue. How these form is a bit of a mystery with some scientists thinking they started out as the collapsed remains of massive stars that formed in the early universe and over time they swallowed up more and more matter and slowly grew.

Some of these galaxies will have supermassive blackholes (picture by author)

Neutron Star

I think these are the most amazing objects in the universe, except maybe quark stars, if they are ever proved real. They are so dense and powerful these objects, that they are mind boggling to try and conceptualise. Neutron stars are not very big, often around 10km in radius but weighing a massive 1.4 to 3 time solar mass. They are the collapsed remains of stars that start off at about 10 to 29 solar masses. Neutron stars of 3 solar masses or less can’t collapse any further but if they are bigger than that then they collapse into black holes. These stars are very hot with surface temperatures in the vicinity of 6,000,000 degrees Celsius. These stars have monster gravity at about 200 billion g on their surface. They spin super fast as well, with the fastest observed spinning neutron star whizzing along at 43,000 revolution per minute – considerably faster than even a jet engine! Something quite interesting about neutron stars is that they are thought to have a solid surface that is very hard and very smooth.

The Sun is the featured image in this article and one of the most amazing objects in the Solar System. Some of the objects in the universe are truely bizarre with staggering properties and mind boggling scales that make our amazing Sun look very boring.