[Originally written for New Zenith, newsletter of the Vectis Astronomical Society, 3 January 2019]
Early on New Year’s Day [2019], the New Horizons spacecraft successfully achieved its long anticipated flyby of Ultima Thule. At about 43 times the distance from the Earth to the Sun, this was the furthest encounter yet with an object in our Solar System. From that far out the messages from New Horizon take over 6 hours to reach Earth! These are exciting times of what one NASA scientist called “pure exploration”. Each pixelated image of Ultima Thule shows more detail than the last. By the time you are reading this, no doubt, these pictures will be superseded, and questions are already being settled daily: it is a contact binary object rather than a close binary; and the mysterious absence of a detectable light curve amplitude (almost unchanging brightness over time) from an irregularly-shaped rotating object is due to the orientation of the axis of rotation. And other questions will answered and others posed as the data streams in.
The BBC heralded the event by an interview with Professor Brian May. The rock guitarist-cum-astrophysicist was excited not only about the brilliant scientific feat, but was speaking over the soundtrack of a song called “New Horizons” which he had written specially. On the back of an all-night party at NASA Mission Control, he was heady with anticipation for the images that will be received over the coming weeks and months, as well as about possibly re-launching his solo career!
This combination of music and science led me to think about other music inspired by astronomy. The multi-talented US musician Anna Coogan (a visitor to the IW in 2018) has albums The Birth of the Stars and The Lonely Cry of Space and Time, the title track written about the first gravitational wave detection by the LIGO observatory in 2017. And we can all recall numerous other pop songs inspired by manned space flight, such Elton John’s Rocket Man and David Bowie’s Space Oddity. These artists were more drawn towards the human experience of isolation and the new perspective of a person looking down on the Earth.
Perhaps we can imagine musicians actually looking up at the night sky in titles like The Moon and Seven Stars, a lively jig in the English folk tradition, and which we may guess was conceived on a starlit summer evening of song and dance as the Pleiades hung over the harvest fields. This idea was later revisited by experimental composer John Cage in the early 1960s – his piece Atlas Eclipicalis asks an orchestra to play from a score constructed directly from a star map. In classical music it is more often mythology than the real science that feeds composers’ imaginations. For example Gustav Holst’s Planets Suite (including the incomparable Mars – the Bringer of War) was inspired by the astrological associations of the planets rather than an appreciation of the night sky itself. By contrast, Joseph Haydn’s Creation was conceived in 1798 after he discussed music and astronomy with William Herschel who played the oboe (when he wasn’t busy discovering Uranus).
Why music and astronomy? Encounters with the wonders of nature often inspire an artistic response to express a sense of awe or wonder, just as they excite the curiosity that that has led to further observations and theories to make sense of what we see. And with music and astronomy there is a commonality in the mathematics underlying both harmony and orbital motion. The “Music of the Spheres” was an early model of the Cosmos (solar system) mapped from musical ideas. Regularities in the movement of the planets have been known from ancient times. Then closer observation reinforced the expectation of finding simple ratios between planets’ orbits.
Pythagoras is credited with first observing the mathematics underpinning musical harmony – first (and erroneously) in the notes of different sized anvils, and later finding the simple relationships between lengths of strings and the “pleasant” combinations of musical pitches heard when they are plucked or bowed. String lengths of ratio 2:1 give pitches which are an octave apart; a ratio of 3:2, a perfect fifth; 4:3, a perfect fourth, etc. These pure harmonic patterns became in the Middle Ages a model which was imposed on the planetary orbital periods by none other than Johannes Kepler. In his 1619 book Harmonices Mundi (“The Harmony of the World”) it was this music of the spheres, together with careful observations, that led to the formulation of his three laws of planetary motion that revolutionised astronomy by introducing elliptical orbits into a heliocentric system.
What may be less well known is that Kepler was so keen to make the data fit the patterns that he fudged some of the facts, including the inconvenience that the relationship between the orbital periods of Mars and Jupiter didn’t fit his all-too-perfect ideas. However real physical patterns of “orbital resonances” – simple harmonic ratios between orbital periods – do emerge in many different places and are key to our understanding the formation and evolution of the solar system. Resonances can explain the distribution of asteroids in the asteroid “belt”, the clockwork 4:2:1 ratio of the orbits of moons Ganymede, Europa and Io around Jupiter, and the patterns in the rings around Saturn. And finally, returning to Ultima Thule in the Kuiper Belt, far beyond the orbit of Pluto, this is the region where orbital resonances will be key to identifying the suspected Planet X (Planet 9) which so far can only be detected by its gravitational effect on other objects.
This New Year 2019 will continue to bring more discoveries and open up new questions about the Universe. And over the next 20 months, while we wait for the precious data to return from New Horizons, bear in mind the Old Harmonies of the Music of the Spheres.
New Horizons – Old Harmonies (Revisited)
Two years on from the extraordinary encounter of the New Horizons spacecraft with what was then the most distant and ancient object seen at close quarters. But it is now known as Arrakoth, because the popular nickname at the time “Ultima Thule” proved to be problematic as it was associated with the mythical Aryan race beloved of 19th century racists. So its official name is now a word (meaning ‘sky’ or ‘cloud’) in the now-extinct language of Powhatan, formerly spoken by indigenous American people in Maryland, where the object was discovered.
So much more is now known about Arrakoth because of the data collected from the various cameras and instruments aboard New Horizons and then downloaded until September 2021. The surface has been mapped, the shape and composition closely studied and theories developed about its formation since the early days of the Solar System.
New Horizons continues on its journey and the mission team continue to search for more potential encounters with Kuiper Belt Objects. Even as it cruises on it has been instrumental in an important demonstration of the first easily measured interstellar parallax experiment, further strengthening one of the rungs on the cosmological distance ladder. The New Horizons mission may continue until 2030, by which time the spacecraft will – like Voyager 1 – eventually turn its camera back to take a picture towards the Earth, another “Pale Blue Dot”. And eventually New Horizons will follow Pioneers 10&11 and Voyagers 1&2 into the outer reaches of the Solar System and beyond.
Links
- The Vectis Astronomical Society webpage
- See forthcoming post on Kepler’s “The Harmony of the World”…
- Musica Universalis – The Music of the Spheres (no, not the Coldplay album…)
- … OK here is Coldplay’s 2021 album Music of the Spheres
- For more astronomical thoughts, see Star of Wonder, Star of Light
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