We already know that binary stars are double-star systems in which the components (individual stars) revolve around a common point situated between them, called their barycentre; that they are trapped in the system on account of bigger gravity of the two — once trapped, gravity keeps them together ‘till death do us part’. And they keep gnawing at each other for matter.

We also know that at least 50 per cent of galaxies stars are binaries; often two stars locked in a celestial embrace (anything from 40 million very near to one billion miles between them). Some are known to exist as near as 80,000 miles and some as far away as 100 billion miles! One of them went so close that it went inside its master star, eating away its matter like it came for free!

But most of them are billions of miles apart, still going around each other. The smaller, despite its size it causes perturbation in the orbit of bigger star.

You know what? Even our sun is thought by some astronomers to be the companion in a binary! There is a small brown star several times the size of planet Jupiter, going round the sun once in 40,000 years or so. The vast majority of astronomers reject this as a joke, which it evidently is.

Also, this strange phenomenon is not in human experience of the last 40,000 years. If true, the companion binary should remain in our skies for many thousand years causing perturbation and havoc both. Our ancestors have left no record in their folklore, not in their paintings, not anywhere. Also, any geologist will tell you that it is not possible, for reasons easy to perceive.

Besides, 40,000 years is too small a period. Multiply it by 10 (to sound more plausible!) and it is a small period again. So, in my opinion, as in the most other astronomers, the sun is a loner.

Now to pulsating stars or pulsars…

Pulsar actually is a misnomer. It is not quite true. Its periodic flashing is thought to be pulsation. It is so called because of its flashing, which is actually caused by its rotation. The spinning neutron star emits beams of radiation that sweep around the sky much like the ship where sailor sees a pulse of light when beam from a lighthouse sweeps over the ship. Likewise, when one of these beams sweeps over us, we detect a pulse.

The theory suggests that neutron stars spin so fast, and its magnetic field is so strong that it acts like a generator and creates an electric field around itself. The field is so strong that it rips charged particles, mostly electrons, out of the surface near the magnetic poles and accelerates them to high velocity. The electrons emit photons. Thus, photons leave the neutron star surface in narrow beams which sweep across the sky. Hence the “pulses”.Most of the pulsating stars, or pulsars, remain undetected but some 500 of them have been found and are being studied and observed by thousands of scientists to ascertain various laws and hypotheses going the rounds since 1920s after Einstein’s famous laws of 1916 — although the first pulsars were discovered decades later.

As you know only when pulsar beam sweeps across our planet do we detect its presence. For it to be ‘found’, the Earth must lie in its path. First pulsar was discovered in November 1967.

A neutron star rotates very fast. It may rotate 642 times in a second! It’s very hot and has a very strong magnetic field. These objects are identified as pulsars i.e. sources of ‘pulsed’ radio energy. But the rapidly spinning neutron star also slows a little as it radiates energy into space. Just as the law of angular momentum states, some of its energy will be lost in the process.

The interesting thing about a neutron star/pulsar is its crust. A standard pulsar is a star with a radius of 10km and a temperature of 1,000,000 Kelvin. Of 10km radius, one kilometre is crust which is very hard and compressed. If there is a mountain range on its surface, it is only a few millimetres high! Whenever an earthquake occurs in the crust, it sends glitches across the empty space which are recorded here as elsewhere in the galaxy. A glitch is a sudden change (surge) in the intensity of a pulse.

A neutron is a small, highly dense star composed almost entirely of tightly packed neutrons, with a radius of 10 km. Its size was too small to collapse into a black hole.

Compared to that a pulsar is a source of short, precisely timed radio bursts. They are believed to be spinning neutron stars.

Now the all-popular black holes… And also quasars!

But in the next issue!

The writer is a professional astronomer and a former head of PIA Planetaria. He can be reached at astronomerpreone@hotmail.com