The speck of light that you see in these images represents 3C 273. Interesting? Maybe not. What if I tell you that 3C 273 is the first quasar to be discovered by us? Curious? Likely yes. Add to it the fact that quasars * are the most luminous and energetic objects in the entire universe and can be a trillion times brighter than our Sun, and we have a story in our hands.
The discovery of the first quasar and its effect on our understanding of the universe have been profound. It didn’t happen overnight though and it involved the work of a number of scientists through decades in the middle of the 20th century. For the discovered quasars, however, that time might as well be like the blink of an eye. *
The universe opens up
The universe, to us, was largely restricted to objects that emitted light in the visible spectrum even up until the 1940s. It was only during the period that radio astronomy was developed that astronomers began discovering objects emitting radio waves. When they went on to detect points in distant space that emitted visible light and radio frequencies, the excitement was palpable.
Astronomers Allan Sandage and Thomas Mathews entered the picture in 1960 and scoured the skies with the help of the 200-inch Hale telescope. They were able to identify one of the radio sources, but the emission lines from the star-like object was nothing like anything they had encountered with stars.
Hazard has an idea
A breakthrough was achieved in 1962 when another radio source, 3C 273, was expected to undergo five occultations (an event that occurs when object is hidden by another object passing between it and the observer) by the moon. British astronomer Cyril Hazard, stationed then at the University of Sydney, decided to take advantage of this.
Hazard booked observation time on the 210-foot Parkes Radio Telescope on August 5, 1962. A bout of absent-mindedness, however, meant that he missed the chance altogether, as he boarded the wrong train on the night he had to be at the observatory.
Mystery deepens
Science, however, often is a collective, collaborative exercise. John Bolton, the director of the observatory, took charge of the observation along with his staff. It wasn’t easy as the radio source appeared low on the horizon. Bolton and his mates had to cut down some trees and even remove some of the telescope’s safety bolts before they could catch hold of 3C 273. When they did, it was obvious that the source was emitting a large amount of energy and an unusual spectrum, adding further to the mystery of what these objects were.
The solution came the next year from Maarten Schmidt, a Dutch astronomer working with the Hale telescope at Mt. Palomar Observatory, California. Puzzled at the spectrum of 3C 273 and unable to figure out how these spectral lines were produced, he suddenly came to a realisation. For it dawned on him that these lines were in fact bright emission lines from hydrogen gas, only that they had been shifted an astonishing 16% towards the red wavelength, making them unrecognisable.
Billions of light years away
A red shift of that magnitude, according to Hubble’s law, meant that the object was billions of light years away. He published his work in March 1963, stating that 3C 273 is in fact about 2.5 billion light years away from Earth. Many more such sources have been identified since then.
The class of objects to which 3C 273 belongs to are called quasars, and they are among the brightest objects in the universe. They spelled the end to the already declining Steady State theory of the universe, which proposed the universe is more or less uniform, and by showing that the universe is not the same everywhere, supported the Big Bang theory. By allowing us to look back in time * , these quasars help us raise more questions that will unlock more mysteries and eventually enable us to better understand our universe.
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*Quasars, QSOs and time machines
The word quasar was short for “quasi-stellar radio source”. It is a misnomer as scientists are now aware that only about one in ten quasars emit strong radio waves. Apart from radio waves and visible light, quasars also emit ultraviolet rays, infrared rays, X-rays and gamma rays. Even though they are still referred to as quasars, they are now called quasi-stellar objects or QSOs.
This might be a bit confusing, and you might even have to re-read it, but quasars, in a way, are like time machines. This is because most of the quasars that have been identified are billions of light years (a light year is the distance travelled by light in a year) away. Since light has taken billions of years to reach us, it implies that what we see of a quasar is how it was when light left it, billions of years ago.
Therefore, the farther away a quasar is, the farther back in time a scientist is seeing. The farthest quasar as yet discovered gives us a glimpse of the universe as it was less than a billion years after the Big Bang (the age of the universe is 13.8 billion years).
Published - August 05, 2018 01:23 am IST
