THE LONG and distinguished record of valuable astronomical observations made by Armagh Observatory has resumed following the capture of “first light” using a newly installed telescope there. The €118,000 instrument will help Armagh astronomers study variable stars whose light emissions do not remain constant.
The observatory’s astronomers will continue to utilise time acquired on remote telescopes based, for example, at the European Southern Observatory in Chile. But the installation of the 43cm reflecting instrument is the first major new telescope to be installed at the observatory for almost a century, according to Dr Simon Jeffery. This ends a decades-long period during which no deep-space images were captured at Armagh by its team of 30 astronomers and students.
Jeffery is a senior research astronomer there and an adjunct lecturer at Trinity College Dublin. He provided a tour of the observatory, including a look at the robotic telescope installed in its own compact dome. It captured its first image or “first light” on February 1st. “This was the first night that we acquired an image of stars,” he says.
Although it does not rank as the largest reflector telescope in Northern Ireland it is by far the most powerful, given its use of modern optics and an extremely sensitive 16-megapixel CCD (charge-coupled device) camera which delivers images like the one seen on this page.
Once development of the software that controls the telescope is completed it will become fully robotic and controllable from remote locations anywhere, Jeffery says. “The goal is that it will be operable from within the observatory and potentially from an astronomer’s home.”
It is also autonomous in that it will be able to cope with the unpredictable Irish weather. Typically, a set of observational instructions will be uploaded and, when it is time to make observations, the dome will open automatically. The camera will then lock itself on to an object, tracking it until the planned run is finished.
Before the dome opens, however, it will sample the weather, including humidity and the presence of precipitation. The run will only begin when the telescope determines that conditions are good enough for observations.
Although it may seem pointless to install a telescope under our rainy skies there are plenty of opportunities to make observations. “There are about 104 or 110 nights per year you can observe,” Jeffery says. Weather would be a problem if astronomers had to wait around for the skies to clear, but this telescope does its own checking. “If you get a computer that will check the sky and try to make the best use of those 100 nights, then you have got a great opportunity to use the sky you have and it is on your doorstep.”
The observatory’s director, Prof Mark Bailey, expressed his delight at the return of useful observations to Armagh, saying that “every observatory should observe”. Few observations were made between 1935 and 2000, because of both the weather and limitations to the equipment on site. “Now, with modern technology, you can have effective observations through the clouds.”
Nor has the Armagh site been rendered unusable by the ongoing increase in “light pollution” that is making observations more challenging right around the world.
“The light pollution from Armagh is not as bad as a big city,” says Jeffery, whose own main research area is the study of variable stars. “What you are aiming at is photometry, the measurement of light from particular variable stars. Many stars have variations in light output.”
Sometimes the output varies because of pulsing, or there may be a companion star in orbit around the variable star. “You can learn things about the properties of the star by measuring variations in the light,” Jeffery says.
This is akin to studying a bell and its properties by measuring its vibrations. A bell vibrates as soon as it is struck, but these stars might only dip in brightness once every five minutes or for a few days or even a year.
Studying the variability allows characteristics such as mass to be measured and means something can be learnt about a star’s external structure, according to Jeffery. The reason the comparatively compact new telescope is able to see sometimes minute changes in brightness – often as little as 1 or 2 per cent – is the extremely sensitive camera mounted on the end of the instrument. “With a small telescope we can study relatively faint stars,” Jeffery says.
The telescope is able to see objects 100,000 times fainter than the faintest star that can be seen with the naked eye, within a field of view of about one degree.
Funding for the telescope and for Armagh’s annual budget comes from the Northern Ireland Department of Culture, Arts and Leisure.
