Physics

 Do you feel a sense of wonderment every time you are confronted with an image that depicts distant celestial objects or galaxies? For even though what they show is way beyond our reach, and sometimes even beyond our naked-eye vision, these photographs give us an opportunity to gaze at them or even print and hold them in our hands.

Astrophotography (the use of photography in astronomy), however, wasn’t always as good as how we have it today. It obviously had to wait for the advent of photography and even after that, it required advancements that let people aim at things way beyond what humans can see. Even if you look at the usage of the word “astrophotography”, you will notice that it picks up only from the 1880s. One of those who contributed to the rise of this field is Isaac Roberts.

Born in 1829 in Groes, Denbighshire, Wales, Roberts was the son of a farmer. Following a few formative years here, he moved to Liverpool, where he apprenticed with a building firm of mechanical engineers.

Works as an engineer

Having started out as an apprentice in 1844, he became a partner and then the manager in the years that followed and turned out to be one of the best engineers in his locality, until he retired from business in 1888.

The success in his professional life meant that he had both the time and the means to indulge in his interests. Roberts was keen to take to the sciences and even though he was initially drawn towards geology, it was astronomy that held his undivided attention from 1878.

Roberts had a seven-inch refractor at his home in Rock Ferry, Birkenhead in 1878 and though he started out as an observer, he quickly realised his potential as a photographer. He began experimenting with astrophotography and pleased with what he was able to produce, decided to invest in better telescopes.

Moves for better views

To better his photography and observations with the aid of larger telescopes and clearer atmosphere, Roberts moved twice. In 1882, he moved from Rock Ferry to Maghull, Sefton and in 1890 he shifted again, this time to Crowborough in Sussex.

While at Maghull, Roberts ordered a 20-inch diameter reflecting telescope from Howard Grubb, an optical designer from Dublin and an authority on the subject. Having built an observatory to house it by 1885, Roberts set about his work.

Piggyback technique

In order to avoid loss of light, which occurs when using a second mirror, Roberts mounted photographic plates directly at the prime focus of the telescope. As astrophotography required extended exposure times to record faint objects in the plate, Roberts also developed a piggyback technique. In this technique, Roberts mounted the camera on a larger equatorial mounted telescope as the combination meant that the camera’s aim was accurate throughout, despite the long exposure time during the Earth’s rotation.

Using his methods, Roberts was able to capture plenty of images of celestial objects, including the constellation Orion and the star cluster Pleiades. His greatest work, however, is the photograph of the Great Nebula in Andromeda that he took on December 29, 1888. Roberts’ image of the Andromeda Galaxy or M31 showed its arrangement and revealed that the nebula had a spiral structure.

He published his photos in the form of a book, one of the first popular works on celestial photography. By revealing through his images how nebulae and clusters look , Roberts provided his inputs for grand theories about galaxies that soon developed.

Picture Credit : Google

The factors that determine the magnitude of a volcanic eruption are the viscosity of the molten rock of magma, the gases and material spewed out of the volcano, and the proximity of lives to a volcano. The magma viscosity depends on temperature, dissolved gases and chemical; make-up.

• Explosive eruptions can create a number of deadly natural events. They can shoot particles 32km high, hurl boulders more than a km away, and cause massive landslides. On the other hand, effusive eruptions cause lava to flow out slowly. People can easily run away from the lava. The flowing lava may destroy everything it comes into contact with.
• An explosive eruption can create ash clouds, carried in the atmosphere for tens of km. ash clouds can cause suffocation and serious aircraft damage. They destroy crops, contaminate water, and damage property.
• In the New Zealand incident, the eruption was identified to be phreatic in nature. A phreatic eruption occurs when magma heats ground or surface water. The extreme temperature of the magma causes instantaneous evaporation of water to steam, resulting in an explosion of steam, water, ash, and rock. The victims suffered severe burns and many were found buried under the ash and debris.

Picture Credit : Google