The Tribune, Chandigarh, India

A diamond in the sky!
Amar Chandel

Diamonds are forever. But they are not for everyone, given their fabulous cost. Just because you love them does not mean you can have them.

For all those who dream of possessing a real large rock, Valentine Day this year came with a wish fulfilment. Scientists have discovered a huge sparkler. It is a 10,000,000,000,000,000,000,000,000,000,000,000 carat giant (that is 1 followed by 34 zeroes). Definitely too big to wear but still real enough!

By way of comparison it can be said that the largest diamond on earth happens to be the 530-carat Star of Africa which is party of the Crown Jewels of England. It was cut form the largest diamond ever found on earth, a 3,100-carat gem.

This 10 billion trillion trillion carat cosmic jewel is a chunk of crystallised carbon 4000 km across and weighing five million trillion trillion pounds.

It is 50 light-years from the earth in the constellation Centaurus. That means that if you can somehow rig up a rocket which travels at a speed of about three lakh km per second – an impossibility, considering that the space shuttles of today travel at about 5 km per second — you can reach the gem in half a century.

At today’s achievable speed, the coveted star is only 30 lakh years away, if you can find enough fuel, that is.

“It’s the mother of all diamonds!” says astronomer Travis Metcalfe of Harvard-Smithsonian Center for Astrophysics, who leads a team of researchers that discovered the giant gem. “Some people refer to it as ‘Lucy’ in a tribute to the Beatles song ‘Lucy In The Sky With Diamonds’.”

The newly discovered cosmic gem technically known as BPM 37093 is actually a crystallised white dwarf, the hot core of a star left over after the star uses up its nuclear fuel and dies.

It is made mostly of carbon and is coated by a thin layer of hydrogen and helium gases.

Our sun will become a white dwarf when it dies five billion years from now. About two billion years after that, the sun’s ember core will crystallise as well, leaving a giant diamond in the centre of our solar system, which will truly be forever.

Astronomers have postulated for more than four decades that the interiors of white dwarfs crystallise but have obtained direct evidence only recently.

The white dwarf studied by Metcalfe, Michael Montgomery (University of Cambridge) and Antonio Kanaan (UFSC Brazil), is not only radiant but also harmonious. It rings like a gigantic gong, undergoing constant pulsations.

“By measuring those pulsations, we were able to study the hidden interior of the white dwarf, just like seismograph measurements of earthquakes allow geologists to study the interior of the earth. We figured out that the carbon interior of this white dwarf has solidified to form the galaxy’s largest diamond,” says Metcalfe.

A paper announcing this discovery has been submitted to The Astrophysical Journal Letters for publication.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory.

CfA scientists, organised into six research divisions, study the origin, evolution and ultimate fate of the universe.

Space researchers have made another interesting discovery this month. It is a new photograph from the Spitzer Space Telescope showing a cluster of newborn stars.

These bright young stars are found in a rosebud-shaped (and rose-colored) nebulosity known as NGC 7129. The star cluster and its associated nebula are located at a distance of 3300 light-years in the constellation Cepheus. The shape and colour are turning even staid scientists into romanticists.

A recent census of the cluster reveals the presence of 130 young stars. The stars formed from a massive cloud of gas and dust that contains enough raw materials to create a thousand sun-like stars.

In a process that astronomers still poorly understand, fragments of this molecular cloud became so cold and dense that they collapsed into stars. Most stars in our Milky Way galaxy are thought to form in such clusters.

“The diameter of the cluster is equal to the distance between the sun and the nearest star, Proxima Centauri.

Within that distance, we find 130 stars. By combining data from the Smithsonian’s MMT Telescope in Arizona with Spitzer data, we find that roughly half of these stars are surrounded by disks of gas and dust.

Each of these disks is a forming solar system,” says CfA researcher Tom Megeath.

UNDERSTANDING THE UNIVERSE
WITH PROF YASH PAL

What is the circumference of earth? How was it measured?

Imagine that you are located at a point on earth where at some time of the day the length of the shadow cast by a vertical pole is zero. You also have a friend located some 500 kilometers due north of you monitoring the length of the shadow of a vertical pole of the same height. If you ask your friend over the telephone to measure the length of the shadow he is monitoring, then a simple geometric calculation would give you the circumference of the earth and hence its diameter! This is more or less what Eratosthenes seems to have done over two centuries before Christ.

You would notice that all you need is the distance between two points located on the same meridian and the valid assumption that the rays of the sun at the two locations are parallel. Of course a telephone connection would be useful. Eratosthenes avoided the need of a telephone by making his measurements at the time of the year when the shadows at the two points were minimum. In other words he chose the day of the summer solstice. The story goes that Eratosthenes knew that at Syene in Egypt the summer solstice sun shone vertically down into a well. He then proceeded to measure the angle to the vertical of the rays causing the minimum shadow at Alexandria, located 787 kilometers to the north and came out with a remarkable result, still nearly valid. Incidentally, the present value of the average radius of the earth is 6,380 kilometers. If true this is a story depicting extreme creativity in science.

The constellation Ursa Major (Saptarishi) revolves clockwise around the pole star. Then what will be the revolving speed of these stars?

Ursa Major or other constellations do not actually revolve around the Pole Star. They appear to be so revolving because our earth rotates around its axis and the northern side of this axis points close to an ordinary star that we started calling the Pole Star! It is no more fixed than any other star! Its special importance or prestige is recognised only on earth. Billions of other stars in our galaxy, including the Saptarishis, are not aware of its distinction!

But the stars do move. Besides their random motions they partake in the general rotation of the galaxy itself. Our sun is believed to complete one rotation in about 225 million years. Nearer to centre of the galaxy the rotation is faster while at the outer fringes it is much slower. Therefore as the galactic disc rotates in this differential manner the constellations of stars visible from any location and stellar neighborhoods also keep changing. Human history is not long enough for us to have become aware of this.

The mass and distance of the moon from the earth remains nearly same on full moon and on new moon day. Then what is the reason behind high and low tides?

In simple terms a high tide is the bulge of sea towards the direction of the moon. As the moon travels this bulge moves under it. When we have a bulge it must be accompanied by a dip - that is from where the water moves to the place where bulge is being formed. When the sun and the moon work together in the same direction, the tides are higher. This happens during the full moon and the new moon. In between these times the moon and the sun do not work in unison. Indeed, one might say the sun even acts as a spoil-sport in restricting the flow of waters to or from the lunar bulge; the tides are not, therefore, so spectacular.