40 Korea Institute for Advanced Study

In June 2012, astronomers across the world celebrated the very rare phenomenon of a transit of Venus the last

such example visible from the Earth until 2117. At the University of Glasgow in the UK, as the launch event for

Glasgow Science Festival 2012, a group of nearly 100 enthusiasts maintained an optimistic vigil throughout the

night of June 5th hoping to catch a brief glimpse of the transit just before it ended shortly after dawn the next

morning. Unfortunately the Scottish weather was poor, and the Glasgow transit-watchers had to make do with a

live link to Hawaii. However Glasgow’s all-night event featured an exhibition that celebrated the crucial place of

Venus transits in the history of astronomy. It was the globally coordinated observations of the 1769 transit of

Venus that provided the first reliable measurement of

the mean distance from the Earth to the Sun: the

astronomical unit that provides the first rung on the

cosmic distance ladder.

For astronomers in the UK 2012 marked another

auspicious anniversary: the diamond jubilee of

Elizabeth II who became Queen in 1952. The sixty

years since that date have seen remarkable scientific

progress, not least because our ability to study the

cosmos has been transformed by the opening of

observational windows across the entire

electromagnetic spectrum and indeed now even

beyond it. From the iconic Lovell radio telescope at

Jodrell Bank, which began operations in 1957, to

NASA’s Fermi gamma-ray satellite, launched in

“Powers of 60” Exhibition: Multi-messenger Astronomy andthe Scale of the Universe

Martin A. Hendry

School of Physics and Astronomy, University of Glasgow

Relationship between the sexagenary cycle and recent

Common Era years

2008, the past six decades have witnessed discoveries at every wavelength that have helped to revolutionise our

understanding of the cosmos. Moreover the next decade holds the promise of an entirely new window opening on

the Universe with the first direct detections of gravitational waves the so-called ripples in spacetime predicted by

Albert Einstein and produced by some of the most violent events in the cosmos: exploding stars, colliding black

holes, even the Big Bang itself.

For our East Asian colleagues the number 60 holds an different significance. The Chinese sexagenary cycle, also

known as the Stemsand-Branches, is a cycle of sixty terms used for recording days or years. It appears, as a

means of recording days, in the first Chinese written texts, the Shang dynasty oracle bones from the late second

millennium BC. Its use to record years began around the middle of the 3rd century B.C. The cycle, and variations

on it, have been an important part of historical calendrical systems in China, Japan and Korea.

The “Powers of 60” exhibition (www.tinyurl.com/powersof60), which premiered at the 2012 Glasgow Science

Festival, seeks to highlight these exciting advances in multi-wavelength and multi-messenger astronomy, linking

them (along with the Queen’s Diamond Jubilee and the 2012 transit of Venus) to the immense scale of the

Universe.

While radio waves, gamma rays and all forms of

electromagnetic radiation in between may differ hugely in the

energy that they convey to us from cosmic sources, they share

the common property that they propagate through the Universe

at the speed of light. As we look out into the cosmos, then,

astronomers are accustomed to the notion that they are looking

back in time: they are seeing the Universe as it was in the past.

This idea is key to the central conceit behind the “Powers of 60”

exhibition: that the radio and television signals broadcast around

the world from the coronation of Queen Elizabeth II have been

spreading out across the galaxy at the speed of light, and will by

now have reached stars within sixty light years of the Solar

System. Thus, we can think of that first sixty light-year sphere as

the first “stepping stone” on a cosmic journey: remarkably in

only five more steps, each sixty times further than the last, we

reach the edge of the observable Universe.

The six milestones on the cosmic ladder spanned by the “Powers

of 60” exhibition also feature observations in six different

windows of the electromagnetic spectrum. The first milestone, at

Science Café

2nd Milestone: ~3600 lightyears - Butterfly Nebula

Credit: NASA, ESA and the Hubble SM4 ERO Team

THE KIAS Newsletter 2013 41

1st Milestone: 60 lightyears - Beta Pictoris

Credit: ESO

42 Korea Institute for Advanced Study

60 lightyears from Earth, is the star Beta Pictoris, which infra-red observations have shown to be surrounded by a

large debris disk of gas and dust in which planets are still forming. In 2006 NASA’s FUSE satellite, observing in

the ultra-violet, discovered large amounts of carbon in the Beta Pictoris system, fuelling the fascinating

speculation that a carbon planet made mostly from compounds like silicon carbide and diamond might be

formed there.

The second milestone features an iconic Hubble Space Telescope optical image of the Butterfly Nebula, about

3600 light years distant. It is a stunning example of a bipolar planetary nebula: the remnant of a Sun-like star

which long ago shed its outer atmosphere, revealing the tiny, hot white dwarf star at its core.

The third milestone takes us beyond the Milky Way to the Ursa Minor dwarf satellite galaxy about 200,000 light

years from the Earth. This galaxy is so small and faint that astronomers believe it contains mainly dark matter.

Astronomers are using NASA’s Fermi Gamma-ray Space Telescope to look for tiny bursts of gamma rays

emitted by dark matter particles, in galaxies like the

Ursa Minor dwarf, as they annihilate each other.

The fourth milestone is Centaurus A, about 13 million

light years distant and the fifth brightest galaxy in our

skies. Centaurus A is one of the closest radio galaxies

to the Milky Way: the supermassive black hole at its

centre produces strong X-rays, as detected by NASA’s

Chandra Space Telescope.

The fifth milestone lies over 700 million light years

distant: Cygnus A, which (despite its vast distance) is

the brightest radio galaxy we can see-its colossal radio

jets spanning more than half a million light years,

produced by its supermassive black hole “engine”

accelerating charged particle close to the speed of

light.

The sixth and final milestone, more than 45 billion

light years from the Earth, is the Cosmic Microwave

Background Radiation: the faint echo of the Big Bang

itself that comes to us from when the Universe was

only about 380,000 years old. By studying the CMBR

we can trace the history of how the Universe has4th Milestone: ~13M lightyears - Centaurus A

Credit: NASA (CXC) and ESO

3rd Milestone: ~200,000 lightyears - Ursa Minor

Credit: NASA Extragalactic Database

THE KIAS Newsletter 2013 43

expanded, and perhaps better understand how it

might evolve in the future.

The “Powers of 60” exhibition was conceived and

designed by Prof. Martin Hendry of the School of

Physics and Astronomy at the University of

Glasgow. Between October 2010 and November

2012 Martin held a prestigious “Science in Society”

Fellowship from the UK’s Science and Technology

Facilities Council and led a worldwide project

entitled “Exploring the Dark Side of the Universe”

aimed at engaging schools and public audience with

some of the biggest questions in cosmology.

Martin’s goal was always to seek to link science

and art, in order to reach out to as wide an audience

as possible, and “Powers of 60” certainly helped

him to achieve that. The images featured in the

exhibition were aesthetically beautiful, as well as

scientifically thought-provoking, and the key

messages that they conveyed about the scale of the

cosmos and the changing ways in which we can

study it resonated with audiences of all ages and

backgrounds. After its premiere at Glasgow Science

Festival it was subsequently displayed at various venues around the city and across the country, and was also

featured as part of the BBC’s Stargazing Live regional events in January 2013 attracting an audience of more

than 4000 visitors in one evening. And of course the exhibition’s website provides a lasting legacy through which

visitors can explore the immense scale, and beauty, of the cosmos.

5th Milestone: ~700M lightyears - Cygnus A

Credit: National Radio Astronomy Observatory, C. Carilli

Science Café

6th Milestone: ~45 Billion lightyears - CMB

Credit: NASA WMAP Science Team

Martin A. Hendry

Martin A. Hendry FRSE FInstP, is Professor of Gravitational Astrophysics and

Cosmology in the School of Physics and Astronomy at the University of Glasgow,

Scotland. He was was first appointed a faculty member in 1998, and is currently Head of

School.