My Science School

The sun is a star, a hot ball of glowing gases at the heart of our solar system. Its influence extends far beyond the orbits of distant Neptune and Pluto. Without the sun's intense energy and heat, there would be no life on Earth. And though it is special to us, there are billions of stars like our sun scattered across the Milky Way galaxy. If the sun were as tall as a typical front door, the Earth would be the size of a U.S. nickel. The temperature at the sun's core is about 27 million degrees Fahrenheit.

The sun lies at the heart of the solar system, where it is by far the largest object. It holds 99.8% of the solar system's mass and is roughly 109 times the diameter of the Earth — about one million Earths could fit inside the sun. 

The surface of the sun is about 10,000 degrees Fahrenheit (5,500 degrees Celsius) hot, while temperatures in the core reach more than 27 million F (15 million C), driven by nuclear reactions. One would need to explode 100 billion tons of dynamite every second to match the energy produced by the sun, according to NASA.

The sun is one of more than 100 billion stars in the Milky Way. It orbits some 25,000 light-years from the galactic core, completing a revolution once every 250 million years or so. The sun is relatively young, part of a generation of stars known as Population I, which are relatively rich in elements heavier than helium. An older generation of stars is called Population II, and an earlier generation of Population III may have existed, although no members of this generation are known yet.

The sun was born about 4.6 billion years ago. Many scientists think the sun and the rest of the solar system formed from a giant, rotating cloud of gas and dust known as the solar nebula. As the nebula collapsed because of its gravity, it spun faster and flattened into a disk. Most of the material was pulled toward the center to form the sun.

The sun has enough nuclear fuel to stay much as it is now for another 5 billion years. After that, it will swell to become a red giant. Eventually, it will shed its outer layers, and the remaining core will collapse to become a white dwarf. Slowly, the white dwarf will fade, and will enter its final phase as a dim, cool theoretical object sometimes known as a black dwarf.

Credit : Space.com

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The speed of light is approximately 1,079,000,000 kilometers/hour (670,600,000 miles/hour). On average, the Sun is 150 million kilometers (93 million miles) away from Earth. This means that it takes a photon of light about 8 minutes and 20 seconds to travel from the Sun to Earth.

Objects in our universe are extremely far away. They’re so far away that kilometers or miles aren’t a useful measure of their distance. So we speak of space objects in terms of light-years, the distance light travels in a year. Light is the fastest-moving stuff in our universe. It travels at 186,000 miles per second (300,000 km/sec). And thus a light-year is 5.88 trillion miles (9.46 trillion kilometers).

But stars and nebulae – not to mention distant galaxies – are vastly farther than one light-year away. And, if we try to express a star’s distance in miles or kilometers, we soon end up with impossibly huge numbers. Yet miles and kilometers are what most of us use to comprehend the distance from one place on Earth to another. In the late 20th century astronomer Robert Burnham, Jr. – author of Burnham’s Celestial Handbook – devised an ingenious way to portray the distance of light-years in terms of miles and kilometers.

Credit : Earth Sky

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According to the World Meteorological Organization, Yuma (Arizona) is the sunniest place on earth. It has a total of 11 hours of sunlight in winter and up to 13 in summer. This means Yuma experiences an average of 4,015 hours of sunshine per year.

At first this sounds fantastic. But it really isn’t that pleasant, since its 90,000+ inhabitants have to combat an arid climate, typical of the Sonora desert, which it forms part of.

Rainfall does not exceed 200mm per year and temperatures exceed 40°C practically 100 days per year. It is a furnace that would leave you wishing for a winter’s rainy afternoon.

The wide-open spaces in and around Yuma lend themselves perfectly to outdoor adventures in the desert or on the Colorado River. Social distancing? No problem! Fresh air and nature? Lots of it! Sunny and warm weather? Undoubtedly, since Yuma is the Sunniest City on Earth, according to Guinness World Records.

If you want rugged outdoor adventure, Yuma's the perfect jumping-off spot to hundreds of square miles of wilderness in the Imperial, Kofa and Cibola National Wildlife Refuges.  Hiking, mountain biking, camping, bird watching, and learning more about desert plants and animals are all out there for exploring.

If in-town adventures are more to your liking, just steps from downtown, parklands next to the Colorado River are a gleaming necklace, studded with pearls of spacious and beautifully-tended attractions, monuments, beaches, and two must-see historic state parks. You can hike or jog on paved or woodchipped or dirt paths along the riverfront, and there are many family-friendly features such as a playground, beaches, and picnic ramadas. The East and West Wetlands are the pride of Yuma, having been restored to natural habitat from what had been a homeless camp and the city dump in the past century. Now a point of civic pride for local Yumans, the riverfront parks make it easy to experience Yuma naturally!

Credit : Visit Yuma

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An annular eclipse, though a rare and amazing sight, is far different from a total one. The sky will darken ... somewhat; a sort of weird "counterfeit twilight" since so much of the sun still shows. The annular eclipse is a subspecies of a partial eclipse, not total. The maximum duration for an annular eclipse is 12 minutes 30 seconds.

However, an annular solar eclipse is similar to a total eclipse in that the moon appears to pass centrally across the sun. The difference is, the moon is too small to cover the disk of the sun completely. Because the moon circles Earth in an elliptical orbit, its distance from Earth can vary from 221,457 miles to 252,712 miles. But the dark shadow cone of the moon's umbra can extend out for no longer than 235,700 miles; that's less than the moon's average distance from Earth.

So if the moon is at some greater distance, the tip of the umbra does not reach Earth. During such an eclipse, the antumbra, a theoretical continuation of the umbra, reaches the ground, and anyone situated within it can look up past either side of the umbra and see an annulus, or "ring of fire" around the moon. A good analogy is putting a penny atop a nickel, the penny being the moon, the nickel being the sun.

Credit : Space.com 

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It made history! On 24 September 2014, the Indian Space Research Organisation’s (ISRO) Mars mission, Mangalyaan, settled into its elliptical orbit around Mars as planned, with 40 kg of fuel to spare, 20 kg in excess of what was needed to complete its six-month planned mission!

Though over the next couple of months, the orbiter completed its mission objectives, it had enough fuel to remain operational, and its mission was extended. It continues to collect and transmit data to date, even on its seventh year in Mars orbit! Over this period, thanks to its autonomous functioning capabilities, Mangalyaan overcame an extended communications “blackout” in 2015 when Mars went out of the Earth’s sight behind the Sun in a solar conjunction, and a communications “whiteout” in 2016 when the Earth came in between the Sun and Mars with the solar radiation making it difficult for the spacecraft to receive signals from the Earth. Mangalyaan’s contribution to advancing the Indian space mission has been acknowledged in a unique way - a sketch of the spacecraft that features on the new Indian 2,000-Rupee note! It was also listed as one of the 25 best inventions of 2014 in Time magazine.

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Have you seen a film hero leap out of a moving car, and dash across the platform to board a running train? Don’t ever do it, because nothing can be more dangerous! For our spacecraft, they have no other choice. Because both their home and destination planets are racing around the Sun without ever stopping! To execute such a terrifying transit, different spacecraft use different manoeuvres. Mangalyaan did it in three phases - geocentric, heliocentric and areocentric phases.

In the first phase, Mangalyaan was carried by its rocket into an orbit around the Earth. Then by firing the spacecraft’s main engine in seven, carefully-planned stages, Mangalyaan’s orbit was made more and more elliptical, until it broke free of the Earth’s gravitational pull. The final firing launched Mangalyaan on a Sun-centric curved path to Mars, tangential to both planets. This space cruise stage from the Earth to Mars formed the second phase of the mission. The third phase began about ten months later with a precisely-timed manoeuvre, called Mars Orbit Insertion (MOI). The engines were fired once again to reduce the velocity of Mangalyaan just enough so that the gravitational field of Mars would pull the spacecraft into an orbit around it.

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The Mars Orbiter Mission (MOM), or Mangalyaan, was not just a scientific mission. It was also a chance to showcase the capabilities of Indian-made spacecraft, rockets and other instruments in the field of space technology!

As a technology demonstrator, Mangalyaan was to successfully cover all stages of an interplanetary journey - first go around the Earth in increasingly elliptical orbits, then cruise through space for the planned number of days, reach Mars and fall into an orbit around the planet, and continue orbiting it for the mission duration. The second goal of Mangalyaan was to image Mars, and collect data about its atmosphere and mineral composition. For this, Mangalyaan carried five payloads - Mars Colour Camera (MCC), Methane Sensor for Mars (MSM), Lyman Alpha Photometer (LAP), Mars Exospheric Neutral Composition Analyzer (MENCA), and Thermal Infrared Imaging Spectrometer (TIS).

While designing Mangalyaan, the Indian Space Research Organisation (ISRO) planned for all challenges it could foresee. Its engine was designed to restart smoothly after its ten-month space cruise.

Another aspect taken care of was the deep space communication system. The large distances separating the Earth and Mars mean that the Round-Trip Light Time, or RTLT (the time taken for a signal from Earth to travel to a spacecraft and back), will be anywhere between 6 and 43 minutes! So, it was also designed to independently manage many in-flight situations!

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On 24 September 2014, India joined the exclusive club of nations with a presence on a planet other than the Earth. The Indian Space Research Organisation’s (ISRO) first interplanetary attempt - Mars Orbiter Mission (MOM), also called Mangalyaan made it possible!

Built in a record time of just 15 months, Mangalyaan was launched on 5 November 2013 from the Satish Dhawan Space Centre at Sriharikota Range (SHAR), Andhra Pradesh. The rocket used for lift-off was a Polar Satellite Launch Vehicle (PSLV). The total project expense came only to around Rs.450 crores, a fraction of what it cost other nations to deploy a Mars orbiter, making Mangalyaan the least-expensive mission to Mars!

The success of Mangalyaan gave us a lot more “firsts” - it made India the first country in Asia with a presence on Mars, and the first nation in the world to succeed in a Mars mission at the very first attempt. Also, ISRO is the fourth space agency to reach Mars after the Soviet Union (present-day Russia), the U.S. National Aeronautics and Space Administration (NASA), and the European Space Agency (ESA).

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Within the last 20 years, the U.S. National Aeronautics and Space Administration (NASA) sent four missions to Mars - Mars Science Laboratory (MSL) mission (2011) which landed the Curiosity rover; Mars Atmosphere and Volatile Evolution (MAVEN) orbiter mission (2013); InSight mission (2018); and Mars 2020 mission (2020) that carried the Perseverance rover and the Ingenuity helicopter. All the four are operational to date.

After a precision landing in the Gale Crater in 2012, Curiosity has been collecting data about the Martian climate and geology, and searching for biosignatures on the planet. The rover found proof of an ancient mega-flood and organic chemicals in the crater.

The MAVEN orbiter has been zipping around Mars gathering details of the past and present of the Martian atmosphere since 2014. Meanwhile, the InSight lander, has been studying whatever goes on underneath! It does this by monitoring “marsquakes”, and using them to map the interior of the planet. Finally, Perseverance is also looking for signs of life on Mars.

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The last decade of the 20th century saw more mission failures than successes. Major among them were Mars 96 by Roscosmos (the space agency of the then-newly-constituted Russia) and Nozomi by Japan’s Institute of Space and Astronautical Science, or JAXA.

But the decade was saved by NASA’s Mars Global Surveyor or MGS (1996) and Mars Pathfinder (1996)! The MGS reached Mars in 1997, and by the time its mission ended in 2006, this orbiter had long achieved its primary goal of mapping Mars. It imaged potential landing sites for future missions.

The lander-rover mission, Mars Pathfinder, was a great achievement for two more reasons. Executed within three years, with a total cost of only 265 million dollars, the project was a success for NASA’s Discovery Program, which aimed to make space missions “cheaper, faster and better.” Additionally, on July 5 1997, Pathfinder’s rover, Sojourner, became the first to operate on a planet other than the Earth!

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The launch window of 1973 was dominated by the Soviet Union’s missions to Mars. By that time, the Space Race had also come to an end, and it was slowly replaced by growing cooperation between the two countries. In 1975, while the Soviet Union waited it out, the U.S. National Aeronautics and Space Administration (NASA) sent out a pair of identical missions to Mars, Viking 1 and Viking 2, together known as the Viking program.

Viking 1 was launched on 20 August 1975, and Viking 2 followed on 9 September. Both contained an orbiter and a lander each. While all four were successful, the lander of Viking 1 which touched down in the Martian terrain on 20 July 1976 became the first lander to successfully operate on the planet! Previous landers had all failed, except perhaps that of the Soviet Union’s Mars 2. But it too stopped working 110 seconds after landing, and transmitted only a partial image of the planet.

The pictures of Martian valleys captured by the Viking orbiters gave evidence of the massive floods that once used to flow across Mars, and completely changed the way we saw the planet. The landers, on either side of the planet (Viking 1 in Chryse Planitia, and Viking 2 in Utopia Planitia), collected data about the atmosphere and conducted experiments with the soil. They looked for biosignatures in the soil, but the results were not conclusive.

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After the launch failure of its Mariner 8 spacecraft on 9 May 1971, the U.S. National Aeronautics and Space Administration (NASA) launched Mariner 9 on the 30th of the same month. It was a late start compared to the Soviet Union’s (present-day Russia) Mars 2 and Mars 3 missions launched on 19 and 28 May, respectively. But Mariner 9 overtook them and became the first spacecraft to orbit another planet! It entered the orbit of Mars on 14 November 1971, with a lead of 13 days over its contender, Mars 2 of the Soviet Union.

But it was not ribbons and confetti that greeted the winner; it was a full – “blown” Martian dust storm that had hidden almost the entire planet from view! Imaging, therefore, was postponed for about two months by re-programming Mariner 9 from the Earth. Unfortunately, this was not an option for the Soviet Union’s Mars 2 and 3, and these orbiters wasted data resources by merely taking photographs of dust clouds that revealed none of the features of Mars.

In contrast, Mariner 9 out-performed its target of covering 70 per cent of the Martian surface by imaging 85 per cent instead! The whopping 7,329 photographs it took, including those of the most prominent features on Mars such as the Olympus Mons, Valles Marineris, and many other volcanoes and flow channels, improved our knowledge of the Red Planet by leaps and bounds! Mariner 9 also captured the Martian moons, Deimos, and Phobos. In fact, the Valles Marineris canyon is named in honour of the spacecraft!

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Riding on the success of Mariner 4, the U.S. National Aeronautics and Space Administration (NASA) planned a dual mission to the Red Planet for the near-Earth phase of Mars in 1969. The identical flyby missions were launched accordingly - Mariner 6 on 25 February 1969, and Mariner 7, just a month later, on 27 March 1969. On the 31st of July of the same year, Mariner 6 made its closest approach of Mars, passing by at a distance of around 3,400 kilometres from the surface. Just five days later, Mariner 7, which had caught up with its predecessor, also made its closest approach keeping about the same distance from Mars!

Mariner 6 and Mariner 7 took about 201 images, covering nearly 20 per cent of the surface of Mars! Some of them showed Martian craters containing ice, outlines of an ice cap at the South Pole, and dark features that had previously been mistaken for canals by astronomers. Data from the devices on the spacecraft also revealed that the atmosphere of Mars is thin, and made up of mainly carbon dioxide (about 98 per cent) and a small percentage of water vapour. They also detected minerals that indicated that the planet may have held liquid water in the past.

Together, the two Mariner spacecraft changed our understanding of the Red Planet. After successfully completing their mission in 1970, they are now spending their retired lives orbiting the Sun!

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In the period after the two World Wars, rivalry between the world’s two super-powers, the Soviet Union (the U.S.S.R. or the present-day Russia) and the U.S. was at its peak. Space was one of the frontiers both nations wanted to dominate, and thus began the Space Race, the golden age of space technology! The first artificial satellite, the first human to space, and the first mission to the Moon were all sent by the U.S.S.R, while the U.S. was the first to land a human on the Moon, and successfully complete a flyby of Venus. Next up for grabs was Mars!

After six failed missions to Mars (five by the Soviet Union, and one by the U.S.), the U.S. National Aeronautics and Space Administration (NASA) finally scored - its Mariner 4 became the first spacecraft to reach Mars! Launched on 28 November 1964, it travelled 112 million kilometres and completed a flyby of the Red Planet on 15 July 1965. The images it sent back became the first close-ups of the Martian terrain.

The absence of surface water on Mars, its heavily-cratered Moon-like surface, and its lack of a magnetic field came as a shock to many scientists of the day. From the data gathered by the mission, even those who thought Mars might have water or vegetation, had to accept that the planet was dry and barren (signs of water were detected only on later missions)!

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As on date, we have sent 82 spacecraft to Mars spanning over 49 missions. But almost 60 per cent of them ended in failure (or partial failure), sometimes before they could even start collecting useful data. In fact, our first attempt itself ended in a launch failure in 1960; the Soviet Union’s (present-day Russia) Mars 1M No.1 spacecraft, was destroyed after it suffered an equipment malfunction at an altitude of 120 kilometres above the Earth.

Over the first three launch windows (in 1960, 1962 and 1964), we suffered six losses before NASA’s Mariner 4 spacecraft became the first successful mission to Mars after completing a flyby of the planet on 15 July, 1965. But we have had unexpected successes also! NASA’s Mars Exploration Rovers (MER), called Spirit and Opportunity, launched separately in 2003, functioned much beyond their planned durations of operation (90 sols) by over 24 and 57 times! By the time we lost contact with them in 2010 and 2018, respectively, they had collected a wealth of data that are invaluable to our understanding of Mars.

As with everything else, every time a mission to Mars fails, we must let Thomas Edison’s words guide us – “I have not failed. I have just found 10,000 things that do not work!”

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