Category Astronomy

Mercury is the smallest planet in our solar system. Located closest to the Sun, it is also the fastest planet in our solar system, travelling at a speed of nearly 47 kilometres per second. In fact, the closer a planet is to the Sun, the faster it travels. Mercury completes one circle around the Sun in just about 88 Earth-days.

When observed from its surface, the Sun would appear more than three times as large as it does when viewed from Earth, and the sunlight is as much as seven times brighter. But despite this proximity to the Sun, Mercury is not the hottest planet in our solar system- it is Venus. The reason for this is Venus’ dense atmosphere.

Another interesting aspect of Mercury is that the Sun appears to rise briefly, set, and rise again from some parts of the planet’s surface due to its elliptical and egg-shaped orbit, and sluggish rotation. The same phenomenon happens in reverse during sunset.

Picture Credit : Google 

A protogalaxy is in simpler words a primeval galaxy. It refers to a galaxy that is undergoing the first generation of star formation. It is also defined as a cloud of gas that is forming into a galaxy. This particular celestial mass would just comprise hydrogen gas trapped in some dark matter prior to the initial stages of star formation. The stars are formed from the smaller clumps of gas in the protogalaxy.

Types of Galaxies

There are two types of galaxies viz. elliptical galaxies and spiral galaxies. The majority of the galaxies that you come across are elliptical galaxies and they are called so because they have an even, ellipsoidal shape. They also are comprised with a greater population of older stars when compared to spiral galaxies.

A spiral galaxy normally has a rotating disc replete with spiral ‘arms. The stellar orbits are circular in shape and they have a flattened disk system. Most spiral galaxies also contain in their centre a mini-elliptical galaxy. Our galaxy, the Milky Way, is a spiral galaxy.

So what determines the shape of a galaxy? The rate of star formation during galactic evolution determines whether it turns out into a spiral or elliptical galaxy. If the star formation is at a slower pace, then it turns into a spiral galaxy.

Milky Way

About 12.5 billion years ago, the Milky Way started to form. Several huge clusters of stars and clumps of gas fused together to form a protogalaxy. This was the building basis of our home!

It then collided with many galaxies, and after a lot of mergers, it acquired its present form.

Recently, scientists discovered a population of millions of stars at the center of our galaxy. Those were the remains of the ancient protogalaxy! These oldest stars that were found in the core area of our galaxy were analysed and the scientists found out that they were part of a protogalaxy.

The diameter of which extended to 18 thousand light-years, and with a mass that was 50-200 million times that of the Sun!

Picture Credit : Google 

The Centaur upper stage rocket is a family of high-energy rockets that has played a pivotal role in advancing global communications and furthering our knowledge of space. November 27, 1963 is an important day in its history as it marked the first in-flight burn of a liquid hydrogen/ liquid oxygen engine.

When we speak about successful space missions, we generally talk about the results they delivered – the satellites that now orbit the Earth or the probes that gathered invaluable data from other planets. There’s a lot of work and plenty of factors, however, that goes into reaching that point. One of them is the upper stage rocket that boosts satellites into orbit and propels probes into space.

Among upper stage rockets, Centaur is a significant achievement as it has served as America’s workhorse in space and has been involved in many success stories. Used for over 100 unmanned launches, Centaur has expanded the frontiers of space and revolutionised communication.

Where it all began

Centaur’s beginnings predate even the existence of NASA as the U.S. Air Force studied a proposal from General Dynamics/ Astronautics Corp. to develop a new booster stage in 1957. With the space race between the U.S. and the Soviet Union heating up during this period, the idea was to give the country an edge, providing a means of orbiting heavy payloads in a very short time.

In 1958, the year NASA was established, Centaur became an official hardware programme with the Air Force as its assigned development authority. While the heaviest Soviet satellite orbiting the Earth at this time was the 1,360-kg Sputnik III, the U.S. had plans for boosting payloads to up to 3,850 kg. They planned to achieve this using Centaur, which was to have a new propulsion system using liquid hydrogen, mixed with liquid oxygen.

By July 1959, Centaur moved from the jurisdiction of the Department of Defense to NASA. Centaurs planned schedule of testing and operation, however, proved too optimistic, as there were a mountain of problems, failures, and delays to overcome.

Silverstein provides the silver lining

In 1962, American engineer Abe Silverstein put his hand up and convinced NASA that his Lewis Research Center could debug the Centaur and manage its problems. Once the entire responsibility was assigned to Lewis under Silverstein, the Lewis engineers got to work, perfecting the booster, while carrying out complex research and development to ensure Centaurs reliability. The fact that Lewis had been involved in pioneering work on high-energy liquid propellants for rockets helped, as this meant that most engineers working with Centaur were already aware of safely handling the liquid hydrogen/ liquid oxygen cryogenic fuels that it used.

The original Centaur rocket measured 30 feet long and 10 feet in diameter. As it used very cold propellants (liquid oxygen at-297 degrees Fahrenheit and liquid hydrogen at -420 degrees Fahrenheit), its tanks required special construction. A doubled walled bulkhead not only served as a heat barrier, but also separated the two compartments containing liquid hydrogen and liquid oxygen. Made of stainless steel less than 200ths of an inch thick, the tank was extremely thin and light-weight even once pressurised.

Following successful assembly, inspection, and shipping to Cape Canaveral, engineers and technicians perform testing procedures that can last weeks. A special tiger team uses a checklist to go through it all once again in the days leading up to any launch, before putting the rocket into start condition for the flight.

Go Centaur!

On November 27, 1963, one such launch took place. While it only carried a dummy payload that was put into orbit, it was a significant milestone. This was NASA’s first successful launch of the Atlas Centaur, proving the compatibility of the Atlas rocket with the upper stage Centaur. Additionally, it had the first in-flight burn of a liquid hydrogen/liquid oxygen engine, showing that these could be safely fired in space. In the decades that followed, there were many more successes for Centaur and a few mishaps too. Centaur was involved in sending the unmanned Surveyor spacecraft, which collected data on the moon’s surface and paved the way for the Apollo missions. Along with Atlas and Titan boosters, Centaur featured as the upper for probes and flybys to all other planets in our solar system.

It didn’t stop there as Centaur also launched orbiting observatories that help expand our knowledge about the universe, peering at space beyond our solar system. Centaur was also involved in launching various satellites into geosynchronous orbits that have changed the face of communication on our planet. While its name might not be often mentioned along with successful missions, Centaur continues to be a workhorse that serves its purpose.

Picture Credit : Google 

The largest planet in our solar system, Jupiter, is located fifth from the Sun. It is more than two times the size of all the planets in our solar system combined. Jupiter has also been instrumental in our understanding of the universe and our place in it. In 1610, Galileo discovered Jupiter’s four large moons: lo, Europa, Ganymede and Callisto. This confirmed the Copernican view that the Earth was not the centre of the universe as these newly discovered celestial objects were revolving around another planet.

It is estimated that eleven Earths could fit across Jupiter’s equator. To put it in other words, if our planet is the size of a grape, then Jupiter is the size of a basket-ball. It has an iconic Great Red Spot, which is a giant storm that has been active in Jupiter’s atmosphere for hundreds of years. This storm is bigger than the Earth!

Jupiter’s orbit is about 778 million kilometres or 5.2 Astronomical Units (AU) from the Sun (Earth is one AU from the Sun). Jupiter is a gas giant, which lacks an Earth-like atmosphere. Even if it has a solid inner core at all, it would only be about the size of the Earth. Jupiter’s atmosphere contains mainly hydrogen (H) and helium (He) and has more than 75 moons. It rotates about its axis once every 10 hours (a Jovian day), and takes about 12 Earth years to complete one revolution about its orbit around the Sun (a Jovian year).

In the year 1979, NASA’s Voyager mission discovered Jupiter’s faint ring system. We have discovered that all the four giant planets of our solar system have ring systems. Till date, nine spacecraft have visited Jupiter. Of them, only the most recent one landed on Jupiter. Seven of them only flew by this gas giant and the other two just orbited it. Juno, the latest spacecraft, arrived on Jupiter in 2016.

Although it is the biggest planet in our solar system, Jupiter cannot support life as we know it. But we have come to know that some of its moons have oceans beneath their crusts, which could possibly support some form of life.

Picture Credit : Google