Neutron Stars Emit Radio Waves example essay topic

Crab Nebula Looking up at the night sky you see stars lying on a never-ending dark blanket. It is within this "blanket", called the interstellar medium, that new stars are formed. The interstellar medium consists of 99% gas and about 1% dust particles. Hydrogen is the predominant gas in both atomic and molecular forms.

While being the place where stars are born, the interstellar medium also creates beautiful nebulae. A reflection nebula is created when light from a nearby star reflects from the dust particles in the interstellar medium. There are two main types of nebulae and two other descriptions of what happens to the light that comes from nearby stars. One of the main types of nebulae is called a reflection nebula.

The particles around stars are about the same size as the wavelength of visible light and therefore they are able to reflect the visible light being emitted from the nearby star. However, most of the time these clouds of dust have a bluish color to them and that is due to the fact that the particles are at about the same size as the blue wavelengths and it is harder for them to interact with the longer red or orange wavelengths. The best reflections nebulae come around stars that are cooler than 25000 K. Another main type of nebula is an emission nebula and this type derives its light from the UV radiation being emitted from a nearby star. The light from the starts exits atoms in the dust cloud which in turn emit light...

When describing what happens to light coming from a star there are two things that refer to it. One would be extinction and this happens when the dust cloud around the star is so dense that the light cannot pass through it and it appears as if the light just stops or makes the star appear dimmer than it really is. Another one would be reddening and this happens when the dust particles in the interstellar medium pass the longer red or orange wavelengths. This process gives the clouds a reddish color and overpowers the blues, greens, and violets. A supernova remnant is a cloud of gas created in the explosion of a star as a supernova. Located 6,300 light years away, the Crab Nebula (M 1) is one of the most famous supernova remnants and is one of only a few historically observed supernovae in the Milky Way Galaxy.

It is specifically located at right ascension 5 hours and 34.5 minutes with declination +22 degrees and 1 minute, appearing above the southern horn of the constellation Taurus in the night sky. The supernova was first noted by Chinese astronomers, in either July or August of 1054, who saw and recorded the star's demise. The star itself was approximately 10 times more massive than our sun, and the supernova was about six times brighter than Venus and about as bright as the full Moon. It was so bright that people could actually see it in the sky during daylight hours for at least one month. During this time, the star was blazing with a light of about 400 million suns. The star continued to remain visible at night for over a year (History).

As one can tell, the energy from this supernova was extreme. Most of the star's mass was ejected at speeds of hundreds of kilometers per second. As the star's fragmented mass hurdles through space, it acts as a kind of vacuum, sweeping up all the gas it comes in contact with as it rushes outward. It slows down more when it hits other gases that are extremely concentrated.

Because of these pockets of gas, the nebula appears rather irregular, with the various wisps, knots, and filaments that we see today (Crab). However, the supernova was forgotten for more than 600 years, until the invention of the telescope, which revealed fainter celestial details than the human eye alone can detect. In 1731 John Beavis discovered the nebulous remnant and added it to his sky atlas. Charles Messier also found the nebula while looking for comets in 1758. It thus became the first entry into his now famous "Catalogue of Nebulae and Star Clusters" which he later published in 1774 (M 1). In 1844, the nebula was finally named the Crab Nebula by Lord Rose because he believed its tentacle like structure resembled the legs of a crab (History).

Because of their fascination with this somewhat mysterious object, astronomers continued to study the Crab Nebula in depth. In 1942, Walter Baade found a prominent star near the nebula's center and thought it might be related to its origin. Then, in 1948, astronomers noticed that the nebula was emitting some of the strongest radio waves of any celestial object. Four years later, Baade further noticed that that the nebula contained powerful magnetic fields, and in 1963, a high altitude rocket detected X-ray energy from the nebula (History).

Then, on November 9, 1968 the Crab pulsar, a pulsating radio source, was discovered by astronomers in Puerto Rico. The star is the right one of the pair visible near the center of the nebula (M 1). Later astronomers discovered that this pulsar was actually a rapidly rotating neutron star, spinning at 30 times per second. This neutron star actually powers radiation through the entire spectrum which we see from the Crab pulsar and the nebula (In Context). A neutron star is actually the star's dense, collapsed neutron core created by the compression of electrons and protons after a supernova explosion. Neutron stars are generally small in size with an extremely high density.

Because of this, neutron stars have a gravitational field about 300,000 times greater than that of the Earth (History). Furthermore, because the star is rotating, this gravitational field acts like a giant electric power generator. The Crab neutron star produces a total power output 100,000 times the power output of our own sun (In Context). Some neutron stars emit radio waves, light, and other forms of radiation that appear to pulse on and off like a lighthouse beacon.

Called pulsars, they only appear to turn radio waves on and off because the star is spinning. We can only pick up the radio waves when the pulsar's beam sweeps across Earth. Their rapid rotation makes them powerful electric generators, trapping and emitting charged particles though space as radio waves. It can charge these particles up to millions of volts. The Crab pulsar, produces enough energy to power the nebula and make it expand (History). Because a pulsar's energy output lights up and expands the nebula around it, it loses energy from the rotation, causing it to spin slower over time.

However, the rate of loss is so minimal that it will take about 10,000 years for the pulsar to slow to even half of its current speed. As time goes on, the Crab's pulses will become less and less intense, and its X-Ray emissions will eventually end. The nebula itself will disappear after only a few thousand years, leaving only the radio pulsar to beam every few seconds (History).