Cosmic Symphony

While many of you might have pointed your telescopes to the sky to watch the stars on the 23rd May, have you ever thought about listening to the universe instead? While visually cosmic worlds are spectacular, their melodies can be magical.

Most of us assume that studying astronomy is observing the universe through telescopes with our eyes but, our ears can also “observe” the universe too! Instead of watching the distant stars and galaxies some scientists study the universe with sound!

The sound of the Cosmos

Scientists have been listening to the sound of the universe for some time now. In fact, Voyager 1, the spacecraft tasked with the mission to study the outer Solar system, has recorded the sounds of electrons in outer space. Waves of electrons in ionized gas (plasma) occur at frequencies that we can hear, by studying the pitch and frequencies of the sound scientists can know the position of Voyager 1. It has a lower pitch when Voyager 1 is still under the influence of the wind from the sun, while it has a higher pitch when it is in the outer most parts of space.

Mapping astronomical data into sound

Voyager 1 has debunked the tagline from the movie Alien, “In space, no one can hear you scream.” Other than recording the actual sound in outer space, scientists have found ways to convert data received from the cosmos into sound.

Our ears are actually better at recognizing and distinguishing patterns than our eyes. Our eyes can distinguish flashes of images at a frequency of 50Hz, but our ears can sense up to 20 kHz! Our ears are almost 400 times more sensitive than our eyes! So, scientists have made use of our hearing power and have translated astronomical data into sounds for investigations!

With the power of listening, not only can scientists analyze and find similarities and differences between galaxies from a large pool of data, people with limited knowledge in astronomy can also discern details of the data. Astronomy is not the world for scientists with good eyesight, people with visual impairment can also study the cosmic world and continue to bring advancement to the field!

So how is sound related to astronomical objects? Some scientists have developed strategies for mapping astronomical data into sound. For example, the high and low pitch of musical notes can represent the velocity and motion of stars, while the volume of sound can symbolize their energy.

An astounding auditory observation of the universe is the merging of black holes. When the two black holes collide, they produce gravity waves and they have the same frequency as sound waves! As the black holes come closer and closer together, the gravitational waves have a higher frequency and so we can hear a higher pitch when they merge. Scientists call these sounds “chirps” because they sound like a bird’s chirp.

Not only we can hear sound from deep space, we can also hear sound within our solar system! The largest planet in our solar system, Jupiter makes some weird noises. The fast-spinning metallic core of Jupiter creates a strong magnetic field, creating sounds of sea waves, and when one of its satellites, Io, interact with the magnetic field, we will hear sounds like popping popcorn!

Symphonies of the universe

Recently, scientists have brought the sound of the universe to life, converting data into a beautiful melodic symphony. Since different phases of gas in the galaxies have different features in their emission, scientists used different instruments to represent them; acoustic base represents gas atoms, wood blocks or piano represent gas molecules, and saxophone represents gas ions. In addition, since the motion of the gas is related to its frequency (Doppler shifts), the velocities of the gas correspond to the pitch of musical notes. The intensity of the emission determines the rhythm, with brighter emissions, having longer note durations. These all together result in “Milky Way Blues”, which describes how gas orbits around the centre of our galaxy. Scientists from the University of California have even launched the Astronomy Sound of the Month that features the melody produced from real astronomy data.

While new discoveries are expected to come, let’s sit back and watch and listen to the “wow” of the universe!

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