For sound to travel there has to be something with molecules for it to travel through. Sound waves need to travel through a medium such as solids, liquids and gases. The sounds wave move through each of these mediums by vibrating the molecules present in the matter. But space, the large empty areas between stars and planets is vacuum. Therefore, sound does not travel in the vacuum because there are no molecules to vibrate. Sound travels in waves just like light or heat does, but unlike in those mediums, sound travels in space by making molecules vibrate through electromagnetic waves which can travel through the vacuum of outer space. Various space probes have recorded the interactions between the Solar Wind in our Solar System and our own planet, as well as Uranus, Jupiter, Saturn, and Neptune. Recordings have also been made of IO (a moon of Jupiter) and Miranda, and rings of planets Saturn and Jupiter. The recordings of these interactions come from several different sound environments.

The interaction between the Solar Wind and the planet’s magnetosphere, which releases charged ionic particles within the 20-20,000Hz range produces ‘sound’ on earth. Space sounds also come from the magnetosphere itself, and it is produced during trapped radio waves bouncing between Earth and the inner surface of its atmosphere. It comes also from electromagnetic field noise within space itself and from charged particle interactions from the planets, their satellites and the solar wind. The sounds also come from charged particle emitted from the rings around planets. We can listen to some of these sounds here. A massive black hole is sending out jets of particles that crash into the cloud, causing pressure waves to ripple outward. Some astronomers interpret these as sound waves. Certainly, even if we call it sound, it is too

low for anyone to hear. They estimate the note to be a “B flat”, about fifty-seven octaves lower than middle C. The deepest ‘note’ in space ever detected is a B flat though it is far, beyond the human range of hearing, detected in sound waves from a supermassive black hole in NGC 1275, in the Perseus cluster of galaxies 250 million light years from Earth.

The “note” is the deepest (a million billion times deeper) ever detected from any object in our Universe. NASA’s Voyager 1 recently passed the heliosphere (the bubble like region of space dominated by the Sun) and into the interstellar medium (the matter and radiation that exists in the space between the star systems in a galaxy). The vibrations of interstellar plasma detected by Voyager’s antennae so NASA knew the spacecraft had reached this point. The sounds were recorded using an onboard plasma wave instrument, which detected the vibrations of dense interstellar plasma, or ionized gas, from October to November 2012 and April to May 2013. The waves detected by the instrument antennae were simply amplified and played through a speaker. These frequencies are within the range of hearing by human ears. The Voyager I & II Spacecraft have sent back recordings from Jupiter, Saturn, Uranus and Neptune. Some more space sounds can be listened to here.

The Sun is ‘middle aged’ at 4.6 billion years old star. It’s surface temperature is of approximately 5778 K (5505°C) and its diameter is about 1,392,684 km. 620 million metric tons of hydrogen are transformed into helium each second by the Sun. The Sun will expand into a red giant and then die after running out the supply in about 5 billion years’ time leaving behind its core and a planetary nebula. A white dwarf will be left behind when the planetary nebula has dispersed into space, which will also cool and die someday. Helioseismology is the method of study the interior of the Sun used by the scientists. This study is similar to how geologists learn about the interior of the Earth by monitoring seismic waves emitted by earthquakes. Small oscillations of the surface caused by the waves in the Sun’s body that are observable. There are three layers that separates the surface of the Sun from its core. They are the photosphere, the convective zone and the radiative zone. The photosphere is made of hydrogen at 5500°C, and is where sunspots occur.

The convective zone contains currents which take heat to the photosphere, which is around 140,000 km thick. The energy from the core, which is where hydrogen is transformed into helium, goes through the radiative zone, about 380,000 km thick. The solar atmosphere refers to the parts of the Sun above the photosphere. The Sun’s atmosphere has five principal zones, they are the temperature minimum; the chromosphere; the transition region; the corona; and the heliosphere. The heliosphere extends past the orbit of Pluto to the heliopause; here it forms a shock front boundary with the interstellar medium. The chromosphere, transition region, and corona are all much hotter than the surface of the Sun. Solar flares occur in the chromosphere. NASA have developed a virtual tour of the Sun. We can click on features on the Sun to learn more about: sunspots; the Sun’s structure; the photosphere; solar active region; the corona; and the future of the Sun. We can also learn more about the current solar missions, ACRIMSAT and SORCE. There is also a video on the Sun’s role in climate change and some quick facts.