Who is pioneer in the then developing science of astrophotography?



 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


How do astronomers know the size of the universe?



How big is the Universe? Many astronomers think it has no end, so its real size cannot be measured. But it is possible to measure the diameter of the observable Universe by calculating the distance between the farthest known objects in all directions.



The light from the most distant galaxies has travelled 15 to 20 million galaxies light years before it reaches the Earth. So the diameter of the Universe, as far as we can see, is as much as 40 million million light years, or 378 million million million million kilometres.



 



Picture Credit : Google


How Astronomers weigh stars?



The stars in any double-star system, such as Cygnus X-1 and HDE 226868, swing around their common centre of gravity. If the stars are equally massive, their centre of gravity lies halfway between them. If not, it lies closer to the heavier star. So a double-star system forms a natural balance which allows astronomers to ‘weigh’ stars. By studying the motion of the star HDE 226868, astronomers found that the centre of gravity lay so close to the star that it suggested its companion must be half the weight, or mass, of the star itself.



HDE 226868 is a type of the star called a blue super giant. It is 20 million miles (32 million km) across and shines 50,000 times more brilliantly than the Sun. A blue super giant is about 20 times heavier than the Sun. That is, it has 20 times the mass of the Sun. So if its invisible companion, the black hole Cygnus X-1, is half this weight, it must weigh as much as ten Suns.



The Sun itself weighs as much as 300,000 Earths or 1989 million million million million tons. Astronomers calculate this figure by using the theory of gravity. Careful experiments in the laboratory have revealed the gravitational pull between two large lead spheres of known masses. This force depends partly on the distance between them. This experiment can be ‘scaled up’ so that the distance between the spheres becomes the distance of the Earth from the Sun. It can then be deduced how massive the Sun must be in order to exert the gravitational pull needed to keep the Earth and the other planets in orbit around it.



 



Picture Credit : Google


Why does an astronaut need a space suit?


A space suit enables an astronaut to survive by providing him artificially with conditions like those he is used to on earth.



    These conditions can be reproduced in a large space craft or space station in orbit, but an astronaut still needs a space suit for operations outside the craft or for an emergency.



     In space men lack the air needed for breathing, the pressure required to stop their blood from boiling and the natural protection of the atmosphere against radiation. All these must be supplied by the space suit which also must withstand the cold of space.



     When an astronaut ventures into space, he leaves behind the safety of the atmospheric blanket which we, on earth, take for granted. His space suit becomes his own personal little world.



 



Picture credit: google


What are the main differences between astronomy and astrology?

In astrology (dating back to ancient times), only heavenly phenomena and movements visible to the naked eye are considered. Hence the planets beyond Saturn that can only be seen with telescopes do not figure in astrology. Astrology also places great importance on the visual pattern (constellations) of the heavenly objects in the night sky, whereas they are of least significance to astronomers. The heavenly objects recognized by astrologers also include objects like “Rahu” and “Ketu” considered non-existent by astronomers. The movements of the heavenly objects are believed by astrologer’s manner, whereas according to astronomers such a contention has no scientific basis and any astrological correlations are considered purely coincidental.