PAM KILMARTIN / ALAN GILMORE
On July 26, 2020, an unknown object was detected in the night sky. Scientists at the University of Arizona made the discovery as part of anasa-funded project to search space for near-earth objects (NEOS).
That night, New Zealand astronomers Pam Kilmartin and Alan Gilmore were also watching the skies and were able to provide measurements that allowed the Minor Planet Center in Cincinnati, Ohio, to determine the object’s distance. At its nearest it came within 50,000 kilometres of Earth – which in astronomical terms is close.
Kilmartin, 70, and Gilmore, 76, have been studying the skies for more than 50 years. From the University of Canterbury’s Mt John Observatory, in Tekapo, they have produced several thousand observations and discovered more than 40 asteroids, mostly in the main belt betweenmars and Jupiter. And in 2003, they were the first to identify the optical counterparts of two gamma-ray bursts.
Despite retiring in 2014, the couple still spend nights studying NEOS. They are part of an international network of astronomers who search for objects that cross the orbit of Mars, but they insist they are not part of Earth’s last line of defence. ‘‘ Guardians of the Galaxy we are not,’’ Kilmartin says.
New Zealand’s location means their observations can help determine the precise location of comets and asteroids, when compared to measurements taken in the northern hemisphere. ‘‘If they get a follow-up from New Zealand, you get a parallax and that immediately gives them a distance. So we can be very useful,’’ Gilmore says.
NEOS can range in size from small rocks to larger bodies, several kilometres across.
While most burn up in Earth’s atmosphere, they can still cause considerable damage.
In June 1908, an asteroid is believed to have destroyed a 2000 square kmarea in remote Siberia, flattening as many as 80 million trees. Known as the Tunguska Event, the incident could have been disastrous had it occurred a few hours later.
In 2013, ameteor created a powerful airburst as it fell over Chelyabinsk, Russia. The energy that was released damaged buildings, injuring more than a thousand people, most due to falling glass.
Kilmartin and Gilmore established an international reputation for studying asteroids in the 1970s, having both been fascinated by space since they were children.
Gilmore was born in Greymouth in 1944 and grew up in Lowerhutt. He remembers seeing a falling star when he was 4 or 5 years old, and his dad explaining it was a ‘‘rock in space’’.
He also witnessed a solar eclipse in the early 1950s, viewing the Moon’s passage across the Sun through a piece of glass that had been blackened over a candle.
Shortly afterwards his dad took him to Wellington’s Carter Observatory for the first time. ‘‘They used to run public sessions on Friday evenings. We went along and had a look through the 9-inch (22.9cm) telescope, at the Moon and I think Venus.’’
While there, his dad bought him a collection of reprinted articles written by respected New Zealand astronomer Algernon Charles Gifford, which he read his way through.
In his school library he found a book about observational astronomy and decided to build his own telescope, saving his money to buy a 6-inch (15.2cm) mirror.
At 15, he wrote to the Carter Observatory to see if there was anything useful he could do and was advised by the director Ivan Thompson that he could observe variable stars. ‘‘They are stars that for various reasons change their brightness,’’ he says. ‘‘That taught me an awful lot about handling a telescope and identifying what you can see in the eyepiece and what’s on the chart. It’s a lot harder than it looks.’’
In the sixth form (now year 12) he was enlisted tomake observations from various mountain sites on his school holidays.
It was in December 1962 that he ‘‘first met Mt John’’ and spent the summer living in a musterer’s caravan on the summit. ‘‘I had a telescope in a tin shed and used to walk down to the general store every couple of days to pick up supplies.’’
Pam Kilmartin was born in 1949 and grew up in Manunui, west of Taupo¯. She says living in a small town allowed her to see lots of ‘‘starry views’’ at night.
She recalls observing the early American satellite Echo flying overhead and even the low glow of the Aurora Australis. ‘‘To see an aurora like that was quite rare.’’
Her parents bought her a Time Life book called The Universe, which she read cover to cover. She was advised that if shewanted to pursue astronomy at university she should study physics but her school didn’t teach the subject, so she enrolled at the University of Auckland to read languages.
She discovered the Auckland Astronomical Society by chance.
She signed up for an introductory course and met fellow enthusiasts, including other female astronomers. Kilmartin and the other women formed a ladies’ group. They were allowed to use the telescope once amonth.
Gilmore completed a degree in physics from Victoria University and in 1970 he began working as a senior assistant at the Carter Observatory. His early observations involved pencil and paper measurements, using photographic plates and a programmable calculator, the size of a typewriter.
Gilmore and Kilmartin briefly met at a Royal Astronomical Society of New Zealand conference in Christchurch in 1971 but it wasn’t until Kilmartin also moved to Wellington to study to be a librarian that they got together. Their first date was in June 1972, and they went to a concert, then stayed up talking until late. ‘‘I just knew I had found my soulmate,’’ Gilmore says.
Kilmartin also joined the Carter Observatory as an information officer and the pair established a programme tracking southern comets and NEAS.
They said the observatory’s board members were ‘‘a little dubious’’ about the couple working together in case they separated.
As it was, their work would be published by the International Astronomical Union and attract the attention of the Minor Planet Center.
Using cables and telex messages, they liaisedwith US scientists and made several important discoveries, gaining an international reputation.
T‘‘From time to timewe are remarkably useful, as in cases like [the near-earth object in July] ...’’
he couple married in March 1974 and have two sons. They left the Carter Observatory but frequently travelled to Mt John to use the 24-inch telescope, the largest in New Zealand.
At the time the sitewas shared by the University of Canterbury (UC) and the US Air Force, which operated a base to track American and Soviet satellites.
In 1980, the couple were offered a job at the UC observatory supporting UC researchers and launching their NEA programme.
When Gilmore was made Mt John superintendent (sitemanager) in 1996 they moved to a house on top of Mt John, a stone’s throw from the telescope domes.
They lived there until their retirement in 2014, but they still travel up to the observatory to carry out their observations.
At 1029m, the summit can be bitterly cold, with the temperature dropping to a bonechilling -14 degrees Celsius on one occasion.
Despite being in their 70s, Gilmore says a 10-hour shift is not unusual. ‘‘We try to get up there by dusk. You want to get objects low in the western sky before they’re too low,’’ he says.
‘‘There have been occasions when we’ve done a 12-hour night because there are objects in the dawn we want to see.’’
The pair are Adjunct Fellows at UC and continue to assist the university’s public outreach by hosting school and alumni visits and producing monthly star chart.
Both are members of the International Astronomical Union and since 1997 Kilmartin has been on the committee that vets the proposed names of asteroids.
Gilmore was heavily involved in the foundation of Aoraki Mackenzie International Dark Sky Reserve – the region’s internationally recognised dark-sky status.
The pair still get excited to make new discoveries but Gilmore modestly describes theirwork as a ‘‘worthwhile contribution’’.
‘‘From time to timewe are remarkably useful, as in cases like [the NEO in July], but most of the time, it’s just handy to have us here,’’ he says. ‘‘There’s quite a lot to it and you don’t realise how much you know, until you start to explain it to someone else. After 50 yearswe’re still learning.’’