Category Science

What are X-ray binaries?

An X-ray binary system is a contact binary system containing a collapsed star (a white dwarf, neutron star or possibly, a Black Hole) and a normal star. As the normal star expands (in the giant phase of evolution) material flows from it towards the collapsed star, giving rise to a kind of gravitational whirlpool in the form of an extremely thin hot disc orbiting round the collapsed star. This disc is a source of X-rays.

What are eclipsing binaries?

In eclipsing binaries each of the stars periodically passes in front of the other eclipsing it, resulting in the combined brightness of the two stars diminishing periodically.

What is a worm hole?

The theories of Black Holes and wormholes are derived from Einstein’s Theory of General Relativity. Einstein’s Theory of Gravity states that gravity exists because massive objects curve the space around them and things fall simply because they are following the shortest path through curved space. Wormholes and black holes have long been recognized as possible solutions to Einstein’s equations. Both are severe space warps, or intense gravitational fields. But there are two important differences between them. A black hole has a ‘bottom’- a ‘singularity’ at which its gravitational field becomes infinitely strong.

A wormhole in contrast does not have a bottom, but has two ‘mouths’ connected by a ‘throat’. The mouths may be very far apart in space even though the throat is short. Thus a worm hole might in principle serve as a kind of cosmic shortcut, like the one a worm takes when it burrows through an apple rather than crawling the long way around the surface. An object sucked into one mouth of a wormhole and down the throat might emerge from the second mouth only a few moments later, but possibly halfway across the universe. However there is no completely satisfactory theory that explains how worm holes are formed and maintained in nature. No wormholes have so far been detected.

What are visual binaries?

In visual binaries the two component starts are clearly visible.

What are astrometric binaries?

In astrometric binaries one of the stars is a dark companion (such as a black dwarf or a Black Hole) which emits little or no radiation. The existence of the dark companion star can therefore be deduced only from an observation of the minute perturbations in the motion of the visible star caused by the gravitational field of its dark companion.

What are contact binaries?

In contact binaries, the gravity of one star is so great that it is actually sucking out material from the other star in the form of a stream of matter continuously transferring from one star to the other.

What is the Time Dilation Effect?

According to Einstein’s special relativity theory, time slows down for a moving object as measured by an observer considered to be stationary. The theory predicts for example that if one member of a pair of identical twins travels at near light speed to a distant star and back, he will return to find that his clock has been running slow and that his homebound brother has aged more than he has. This “time dilation” effect has been confirmed by experiment: Atomic clocks taken on long rides in space have been found to lag a few billionths of a second behind clocks that remained on Earth.

Can neutron stars be detected from Earth?

It is thought that Pulsars are neutron stars which have an extraordinarily high speed of rotation caused by the sudden decrease in size following the supernova explosion. In theory a neutron star can rotate in periods as short as a millisecond. Pulsars can be detected from Earth.

Do Pulsars transit only radio pulses?

Some Pulsars transmit pulses at non-radio wavelengths also. For example, the Pulsar in the Crab Nebula transmits pulses in the X-ray and optical wavelengths also.

How rapidly are pulses from a pulsar transmitted?

The Pulsar in the Crab Nebula (one of the fastest) transmits pulses at intervals of 0.033 seconds and each pulse has duration of just 0.002 seconds.

What is the explanation of the behavior of a Pulsar?

A Pulsar is thought to be a type of rapidly rotating neutron star having an intense magnetic field. The radiation is tripped by the magnetic field and leaks out in narrow beams at the magnetic poles. As the star rotates the beam sweeps round like the beam of a light house and each time the beam points in the direction of Earth, a pulse signal is received.

Is the period of a Pulsar of a Pulsar constant?

The period of a Pulsar can suddenly increase and decrease due to turbulences in the neutron star which cause the rotation to change, to conserve the angular momentum.

The loss of energy of a Pulsar by radiation also causes it to slow down over a period. Hence a slowly pulsing Pulsar is likely to be an old Pulsar which has slowed down while a rapidly pulsing Pulsar is likely to be a young Pulsar that has not yet slowed down.

What is ‘Nemesis’?

There is an unproven theory that the Sun may be part of a binary star system containing a distant dark companion named ‘Nemesis’.

When was the first double (binary) Quasar discovered?

The first double Quasar(named 0957+56)  was discovered in 1980.

What is a Pulsar?

Pulsar is an abbreviation for Pulsating Radio Star, first discovered in 1967. Pulsars are radio sources which emit brief pulses of signals at very regular short intervals of typically one second or less.

What causes a star to become a nova?

Most, if not all, novae are members of binary systems of binary systems in which one member is a body like a white dwarf on Black Hole whose intense gravitation draws out a stream of matter from the other body. From time to time such matter is transferred from the second star to the first star which undergoes an unpredictable violent explosion called a nova, often periodically every few decades.

Can a nova be visible to the eye?

Yes. For example a nova visible to the naked eye occurred in August 1975 in the constellation Cygnus. Typically, a nova’s brightness increases by a factor of 10,000 to 100,000 in a few days or even in a few days or even in a few hours, and returns to its original brightness, more or less, over or period of many years.

How can Black Holes be detected?

Since nothing can radiate out of a Black Hole, it is invisible and cannot be directly observed. It can only be observed when the influence of its tremendous gravity is detected on some other visible object near it. For example, in a binary system if one star is an invisible Black Hole, it will certainly influence its visible companion star.

Have any Black Holes been detected?

The best example of a likely Black Hole is Cygnus X-1 which is an X-ray source containing an invisible object too massive to be a white dwarf or neutron star.

How is a Black Hole likely to influence its companion in a binary system?

If one star in a binary system is a Black Hole, its visible companion will be seen to be following an orbit around an invisible object. Moreover due to the Black Hole a steady stream of matter from the visible star will be flowing to the Black Hole, and this matter will emit X-rays when falling into the Black Hole. Hence an X-ray source containing a massive invisible object is likely to be the location of a Black Hole.