Amazingly, Uranus had been ‘seen’ at least 18 times before its actual discovery by William Herschel in 1781. But it was plotted on charts as a star and not a planet!

TODAY we shall take a look at the backyard of the Solar System. Like any backyard, it has a pretty happy, albeit secluded, populace. There are three giants, a single rocky planet, lately denigrated to planetoid category, hundreds of comets and about two dozen moons going about their business unperturbed in a neighbourhood where loneliness reigns supreme. Whatever craters there are, formed a long time back.

As you know, a long time in astronomy, or even geology, is a trifle longer than we can imagine. The last of the impacts must have scarred the surface some 100,000 years ago, if not earlier. Let us see the first of the giants, Uranus.

It is the seventh planet out from the Sun. It is named so for being the father of Saturn. In Greek mythology, the father of Kronos (Saturn) was Ouranous, the god of the skies. The Latin spelling of the name was Uranus. And it was adopted so. It is one of the four gas giants, the others being Jupiter, Saturn and Neptune. They are all called Jovian planets.

If we go by the solar nebula theory, the creation of planets came about from the nebula around the proto star (in fact, from the remains of a great and sprawling nebula, or an exploded star). In simple terms, planets are a by-product of star formation. That is to say that the Sun came into being first, followed soon after by planets. Not much later, or else the remaining gas and dust would have been lost into space. The time difference between the birth of the Sun and that of planets was not much to speak of. The nursery came alive almost simultaneously. In other words the planets and their moons are the scattered remains of the solar nebula. So are the comets, but more about them at a later stage.

As soon as the Sun became luminous, in other words, nuclear reactions set in motion in its centre, dust and gases in the outer nebula was blown away by the force of the solar wind and the debris quickly began to coalesce into planets, helped in no uncertain terms, by the ever increasing gravity.

Enter William Herschel (1738-1822), the German-born, self-educated English astronomical genius who toiled hard in searching the skies in the region of constellation Gemini, finding a hazy patch that he suspected was a new star — very faint and misty, yet a star, not finding enough courage to announce that he had perhaps found a new planet.

It was left to the Russian astronomer, Anders Lexell (1740-1784) to break the news. That it was the first time in recorded history that a planet had been discovered was no mean achievement. Originally a musician of repute in native Germany he took up a prestigious job as an organist in a chapel in Bath, Somerset, England, studying astronomy in his spare time. With the remarkable discovery, however, Herschel instantly became a celebrity across Europe, landing a lucrative job in the court of the English king George III.

Not just that, with this discovery, first mistaken for a comet by some, and a star by some others, Herschel became world famous. His discovery extended the classical universe and opened it to new speculation that there could be more for the taking. After all why stop at Uranus? He named the newly found planet after his benefactor, Georgium Sidus, i.e. George’s Star. This step did not find favour with Europe which did not like to accord immortality to an English king. Hence the change of name to Uranus.

At this point in time, the English King had begun to show signs of madness, but not before he had granted a handsome pension for William Herschel!

Curiously, it is on record that Uranus had been ‘seen’ at least 18 times before its actual discovery by Herschel in 1781. But it was plotted on charts as a star and not a planet! William teamed up with his sister, Caroline — a talented astronomer and observer of the skies herself — in an attempt to map the limits of the universe. Together they did a commendable job.

Planet Uranus has an equatorial diameter of 51,118km, more than four times the diameter of the Earth (12,756km), with its mass 14.54 times that of the Earth, with a low density of 1.19 gms/cubic centimetres, standing a poor comparison to the Earth’s 5.5. The orbital period of Uranus is 84.013 years, more than an average life span of humans on Earth. Its average orbital velocity is much less than the Earth’s: 6.81 km/sec to Earth’s 29.79. Because it is so far out, the surface temperature is -221C (-366F)!

As far as its distance from the Sun is concerned, it is at a whopping distance of 19.18 AUs. And did you know that Uranus has its own ring system? Thin and wiry, but they are there. Voyager’s rendezvous with Uranus in 1986, gave us a plethora of information about the beautiful light blue planet, which we shall save for the next issue.

Could you believe that so much is known about a planet hundreds of millions of miles away?

HOW MUCH DO YOU KNOW ABOUT SPACE?

Voyagers in space

LAUNCHED in 1977, Nasa’s Voyager 1 and Voyager 2 spacecraft have collectively explored Jupiter, Saturn, Uranus, and Neptune. Built to last only five years, they’re still going strong — closer than ever to the edge of the Solar System and now poised to enter interstellar space.

Ice volcanoes in Space

ENGLISH brewery mogul William Lassell used part of his fortune to build a telescope. Just 17 days after Neptune was found in 1846, he discovered Triton, its largest moon. Triton's ice volcanoes spew liquid chemicals and dust, which freeze and fall to the surface like snow.

An egg in the orbit:

NAMED after a Hawaiian goddess, dwarf planet Haumea has an elongated, egg-like shape because it rotates so quickly. It turns fully every four hours. This icy object orbits the sun once every 285 years and has two known moons, Hi’aka and Namaka, named for Haumea’s daughters.