My Science School

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.

 

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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.

 

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In the 17th century, the English physicist Sir Isaac Newton recognised that there were problems with the traditional refracting telescope, which used glass lenses to focus light from a star.

The lenses produced a fringe of false colours around the star. This happened because when a beam of light coming through when a beam of light coming through glass is bent, its waves, being of different lengths, are bent at, different angles. Blue light, for example, which has short waves, is bent (or refracted) more sharply than red light, which has longer waves.

So newton designed a reflecting telescope which collected and focused light by means of two mirrors. (These mirrors were made from an alloy of tin and copper, known as speculum metal.) the front of the mirror which collected the light was curved, rather like a shaving mirror. As a result, it could focus light just like a lens.

Large modern telescopes all use mirrors to collect light, although they have grown in size from Newton’s 1in (25mm) mirror to  Soviet monster 236in (6m) in diameter.

 

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A rendezvous in space

Imagine being out in space in a spacecraft. You are likely to have a few others for company, but for your spacecraft as such, it will mostly be lonely in the region of space it inhabits. How would you feel when another spacecraft with people on board come close by, almost within touching distance? The first such human rendezvous in space was conducted on December 15,1965, by those aboard the Gemini VI and Gemini VII spacecraft.

Gemini VI and VII, however, were never meant to fly together at the same time. What with the moon mission coming ever closer, Gemini VI was set to test rendezvous manoeuvres, while Gemini VII was to carry out extended space-flight experiments.

A target explodes

Even though Gemini VI was ready to fly on its intended launch date of October 25, 1965, it did not take off as the Gemini Agena Target vehicle it was supposed to rendezvous with exploded. It was then that a “rapid-fire” launch proposal was considered again.

According to this proposal, a Gemini spacecraft would target another Gemini spacecraft in space. Even though such an idea was explored previously, it was considered to be extremely unsafe to fly two manned spacecraft at the same time. But it was approved in the end, and it was decided that Gemini VI would rendezvous with Gemini VII, while experiments.

Seven before six

Gemini VII was to be launched first and it took off on December 4, 1965. The crew members- commander Frank Borman and pilot James Lovell – were scheduled to perform 20 experiments during their 14-day stay in space, apart from providing a target for Gemini VI.

For a second time, Walley Schirra and Thomas Stafford – crew members of Gemini VI – were suited up and ready for mission on December 12. Even though the engines ignited, the vehicle didn’t take off. Engineers worked on the failure and realized that a plastic cover left on the gas generator port of a check value had caused an electrical anomaly.

The NASA staff replaced the generator but were now racing against time to ensure that Gemini VI was launched before Gemini VII’s scheduled return. The third launch that took place on December 15, 1965 finally turned out to be successful.

Once Gemini VI was in Orbit, Schirra and Stafford were tasked with the role of catching up with Gemini VII. It took them a good six hours before they could get anywhere close to Borman and Lovell.

No relative motion

After a few careful manoeuvres Gemini VI and VII achieved their rendezvous, the first such manned activity performed in space. As they revolved around the Earth, there was no relative motion between the two spacecraft. Gemini VI and Gemini VII got as close as 0.30 matrefrom each other during their next three revolutions around the Earth.

Having achieved what it set out to – a successful rendezvous mission – it was Gemini VI that splashed down first – Schirra and Stafford getting out safely on December 16. Borman and Lovell continued their scientific, technological and medical experiments for a couple of days, before they also made a successful landing on December 18.

Human space-flight improved by leaps and bounds in a single year in 1965. Apart from this successful human rendezvous in space, the year also saw human being put in orbit and brought back, achieve long-duration stay and perform extravehicular activity in space, apart from controlling their re-entry. The mission to the moon was getting ever closer.

 

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The race to the moon in the first decades of the second half of the 20th Century is littered with many firsts. While some of these are extremely popular and known to almost everyone, there are others that are not as famous, but equally important in the grand scheme of things. Among the latter is the Surveyor 6 spacecraft, achieved the first lift-off from a celestial body.

The Surveyor series of spacecraft were robotic landers, managed by NASA, whose objectives included making soft landings on the surface of the moon, studying the lunar surface and in general, aiding the planned human landings in the future. While lunar orbiters had provided orbital imagery, those were to be combined with ground-level data gathered by the Surveyor spacecraft at potential Apollo landing sites, thereby making ourselves mission-ready for the grand challenge ahead.

An elusive target

Surveyor 6 was the sixth in a series of seven crew-less spacecraft that proved to be highly successful. The intended target for this spacecraft was nearly in the centre of the moon’s Earth-facing hemisphere, a small lunar mare (any flat, dark plain of lower elevation on the moon) that went by the name Sinus Medii (Latin for “Bay of the Centre”)

Apollo mission planners were looking for a close-up of this area as it appeared rougher than other proposed sites for landing. NASA’s two previous attempts to land here using Surveyor spacecraft hadn’t been successful.

While Surveyor 2, launched on September 20, 1966, went out of control following a mid-course correction, Surveyor 4, launched on July 14, 1967, crashed and failed during the final descent to the lunar surface after an otherwise faultless mission. With only two approved Surveyor flights, including Surveyor 6, remaining, the onus was on the planners to succeed this time.

Basaltic surface

The Surveyor 6 was launched from Cape Canaveral, which contains NASA’s launch pads, on an Atlas-Centaur rocket on November 7, 1967. Landing was scheduled to occur 65 hours after lift-off and Surveyor 6 managed a safe landing on Sinus Medii on November 10, 1967. After routine post-landing checks and routine and reconfiguration for surface operations, it started sending images of the site where it had landed on the moon.

The images showed scientists that it had landed on a relatively level surface and also allowed them to determine the landing site based on orbital imagery. The site was found to be very similar to the previous three Surveyor mare landing sites and that it would support human landing.

The crucial experiments to measure the surface chemistry with an alpha scattering detector showed that landing area was basaltic. This showed that the surface measurements where Surveyor 6 landed were remarkably similar to Surveyor 5’s measurements obtained two months earlier over 700 km away. In effect, it further validated that the terrestrial area of the moon was made of basalt, an important detail for the Apollo mission planners.

First to land twice

On November 17, 1967, Surveyor 6 performed another important experiment. The NASA engineers commanded the Surveyor 6 engine to fire its three main liquid propellant thrusters briefly. As a result, Surveyor 6 not only became the first spacecraft to lift-off from the moon, but also the first to be launched from any celestial body. Not to mention, it was the first to land twice on the surface of the moon.

Even though the Surveyor rejected the first shut-down command, the second command from the ground controllers turned off the engines. All this happened inside 7 seconds, during which time the Surveyor 6 reached an estimated peak altitude of about 10 feet, before landing about eight feet west of its original landing point.

The engineering test successfully demonstrated that rockets could be restarted on the moon, providing another tick in a huge list prepared with a human mission in mind. Following this small lunar hop, Surveyor 6 employed its cameras to study its original landing footprints and determine the soil’s mechanical properties.

Before the onset of the lunar night on November 24, 1967, Surveyor 6 had returned close to 30,000 images of the lunar surface. Even though controllers were able to regain contact on December 14, 1967 and the spacecraft had survived the two week lunar night, no significant data was returned, primary landing operations ceased and the mission ended. By then, however, Surveyor 6 had completed the data acquisition needed for the Apollo missions, freeing up Surveyor 7 to be sent to a site of greater scientific interest and getting us closer to making one small step on the moon.

 

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It is an interstellar message that was beamed into space in 1974 with the hope of making contact with extra-terrestrial life. It was transmitted on November 16, 1974 from the Arecibo radio telescope in Puerto Rico to the globular start cluster M13 about 25,000 light years away. The event marked the remodeling of what was then the world’s largest single-aperture telescope. The cluster M13 was chosen because it was at the right place at the right time.

The Arecibo message was the most powerful broadcast ever beamed deer space at the time. It contained 1679 binary digits, arranged in 73 lines of 23 characters per line. It was transmitted at a frequency of 2,380 MHz. the ‘phone call’ to the universe was less than three minutes long.

The message was created by Frank Drake, (an American astronomer and astrophysicist) with the help of Carl Sagan, (American astronomer-author) and the observatory staff. The message had seven components:

1. The numbers one to ten


2. The atomic numbers of the elements which make up our DNA – hydrogen, carbon, nitrogen, oxygen and phosphorous


3. The formulas for the sugars and bases in the nucleotides of DNA


4. The number of nucleotides in DNA and a graphic of the double helix structure of DNA


5. The human figure along with its average height and the population of Earth


6. The solar system


7. The Arecibo Observatory and the diameter of the transmitting antenna dish.

It will take nearly 25,000 years for the message to reach its intended destination and an additional 25,000 years for any reply. The message was more a display of the achievement of human technology than an expectation of contact with aliens.

To mark the event’s 45th anniversary in November 2019, the Arecibo Observatory has asked young people around the world to devise an updated version of the message.

 

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           After Chandrayaan 2, sending Man into space is India’s next biggest dream. The ISRO has already made plans for the Indian Human Spaceflight Programme and is working on a crewed orbital spacecraft- Gaganyaan.

          Gaganyaan is expected to be launched in 2020 and its manufacturing is carried out in co-operation with Hindustan Aeronautics Ltd. Gaganyaan is designed to carry three people into space and is supposed to orbit the Earth at an altitude of 400 kilometres for seven days. It is planned to be launched by GSLV Mk III, the same launch vehicle that put Chandrayaan 2 in its course to the Moon.

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          After the Vikram lander had a crash landing, the ground control lost contact with it. For two weeks, both ISRO and NASA tried to locate it. Though it was later located by the orbiter of Chandrayaan 2, the communication hasn’t been restored. Efforts are made to establish communication with the lander.

          K Sivan, the chairman of ISRO had set up a Failure Analysis Committee to look into the causes of failure. This committee is headed by P S Goel, senior scientist at ISRO.

          The orbiter remains intact and is expected to remain functional for seven years. All the payloads in the orbiter remain operational and their initial trials were completed successfully. The orbiter continues to perform the scheduled scientific experiments.

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          Since the conception of Mangalyaan, ISRO had made significant efforts to involve more women in their project. Thirty per cent of the Chandrayaan 2 crew is constituted by women. Ritu Karidhal is one among them and is known as the ‘Rocket Woman of India’.

          Ritu Karidhal is an aerospace engineer and she now works as the Mission Director of Chandrayaan 2. She had played a crucial role in the development of the Mangalyaan project, holding the position of the Operations Director. Recognizing her work and potential, Ritu Karidhal was awarded the ISRO Young Scientist Award in 2007.

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          ‘Better late than never.’ This saying is true in the case of Chandrayaan 2. Though India was ready with all the payloads for the mission as per the schedule, it had to be first postponed to January 2013 and then to 2016. This happened because Russia was unable to develop the lander on time.

          Later, Russia withdrew from the project following the failure of Fobos-Grunt, a Russian mission to one of the moons of Mars. The technology used in Fobos-Grunt was also used in the lunar project and needed reviewing. Finally, Russia backed out, failing to deliver the lander by 2015. Following this, ISRO decided to go ahead with the project independently.

          After the development of the lander, Chandrayaan 2 was scheduled to be launched in March 2018. But, it was further delayed to conduct relevant tests and was planned for the first half of 2019.

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