Your hair collects space dust from comets
Every day, several tonnes of material falls to Earth from space. Some of it is witnessed on arrival, as a bright meteor may result in a meteorite – a fragment of rock and metal crashing into the ground.But a great deal of this cosmic material doesn’t make such a spectacular entrance to our planet. Rather, it falls gently through the atmosphere in the form of space dust that is all but invisible to our eyes. A surprisingly large quantity of space dust lands on our planet: about 5,200 tonnes per year, 100 tonnes per week, or 14 tonnes per day. This dust is made up of tiny particles of rock and metal that have been chipped off asteroids and comets, either in large collisions or by micrometeoroids. About 80 per cent of all this dust originates from Jupiter-family comets, which have orbital periods of less than 20 years. The particles are so small – at most a few tenths of a millimetre across – that they are not generally visible to the naked eye and can only be detected using specialised instruments. Every time you’re outside, you stand a chance of catching some of this space dust in your hair. It’s very likely you’ve already caught some and later washed it out without knowing it.
Some stars are so cool, you could touch them without scalding your hand
In understanding that the Sun is a star, we’ve come to think of all stars as blazing hot, fiery balls of plasma that could melt any material or alloy we could create. But this isn’t true of all stars, and, in fact, there is a category of fascinating, supercool stars lurking within the Galaxy. Brown dwarfs are colder than any known star and are classified as sub-stellar objects. They are often referred to as ‘failed stars’ because they are too small to sustain nuclear fusion in their cores, which is the process that powers the Sun. As a result, brown dwarfs emit very little light and heat, making them quite challenging to detect. The surface temperatures of brown dwarfs vary, but one particular subclass – Y-type stars – are the coldest of all. Their surface temperatures are typically only a few hundred degrees Celsius above absolute zero. That corresponds to a temperature of some tens of degrees Celsius. Your skin has a temperature of around 35 °C and a warm mug of tea is just a bit hotter. Were it possible to touch the surfaces of these Y-type stars, you would be able to feel the warmth without even scalding your hand!
There could be as many as 10 billion Earth-like planets in the Milky Way
In 2019, astronomers combined data from the Kepler Space Telescope with new results from the European Space Agency’s Gaia mission, concluding that, on average, as many as one in six stars hosts an Earth-sized planet in its habitable zone. Potentially tens of billions of such worlds are strewn across the Milky Way. While the search for Earth-like planets continues, the range of environments that can be considered habitable is widening. An exact Earth analogue may not be necessary for complex life and the number of life-supporting havens may be higher than we think.
Saturn's rings are incredibly thin
Saturn, the sixth planet from the Sun, is known for its spectacular rings that encircle the gas giant. While they appear to be solid and continuous from afar, the reality is that they are made up of trillions of individual pieces of ice and small amounts of rock, ranging in size from tiny dust-like particles to giant boulders. One of the most remarkable things about Saturn’s rings is their incredible thinness. Despite stretching out to a distance of nearly 140,000 km from Saturn’s equator, the rings are only a few hundred metres thick at most. Put another way, the rings are hundreds of thousands of times wider than they are tall. For comparison, a Blu-ray disc is 120 mm wide and 1.2 mm thick. To match the scale of Saturn’s rings at this thickness, the Blu-ray disc would need to be about 1 km wide!
Precious metals like silver and gold are forged when dead stars collide
The remnants of exploding stars – neutron stars – will sometimes collide, producing and releasing vast quantities of precious metals among many other elements. The energy involved in these collisions is far greater than that released by a supernova. As a result, the heaviest naturally occurring elements, including uranium, are produced almost exclusively by these extreme events. Both supernovae and neutron star collisions fuse heavy elements through ‘r-process’ nucleosynthesis. They create sufficient temperatures and pressures for atomic nuclei to undergo a rapid neutron capture. These nuclei are forced to absorb neutrons, bulking up their atomic numbers. Merging neutron stars can reach numbers like 47 (silver), 78 (platinum), 79 (gold) and 92 (palladium), making them forges for precious metals. If you invest in these metals, think about where they came from. Perhaps they’ll seem more valuable in light of their extreme origins!
