Comet

The comet’s periodicity was first determined in 1705 by English astronomer Edmond Halley, who it was eventually named after. Halley’s Comet last appeared in the inner in 1986 and won’t appear again until mid-2061. Although the nucleus of the comet itself is not that large, the coma can extend to a very large size. As the gas molecules in the coma are ionized by the solar ultraviolet radiation pressure from the solar wind, a stream of particles emitted by the Sun pulls the coma’s ions out into a long tail, which may extend more than 100 million kilometers into space. The nucleus itself is only 15 kilometers long, 8 kilometers wide, and 8 kilometers thick. In comparison, the earth has a diameter of 12,756 km and the sun has a diameter of 1,392,000 km.

This means that Halley’s Comet is only about 4% the size of earth but because of its coma, it appears much larger to the naked eye. While the orbit around the sun, Halley’s Comet orbits towards and away from the sun, all the way out to Jupiter, perpendicular to the ’s orbits. Halley is classified as a periodic or short-period comet, one with an orbit lasting 200 years or less. This contrasts it with long-period comets, whose orbits last for thousands of years. Most short-period comets, those with orbital periods shorter than 20 years and inclinations of 20–30 degrees or less, are called Jupiter family comets. Those like Halley, with orbital periods of between 20 and 200 years and inclinations extending from zero to more than 90 degrees, are called Halley type comets. Only 54 Halley-type comets have been observed, compared with almost 400 identified Jupiter family comets. The orbits of the Halley-type comets suggest that they were originally long-period comets whose orbits were altered by the gravity of the giant planets and directed into the inner Solar System. If Halley was once a long-period comet, it is likely to have originated in the Oort cloud a sphere of bodies that has an inner edge of 50,000 AU. Also, the Jupiter family comets are believed to originate from the Kuiper belt, a flat disc of icy masses between 30 AU and 50 AU, from the Sun. Another point of origin for the Halley type comets has been proposed.

In 2008, a new object with a retrograde orbit similar to Halley’s was discovered. Named Drac, its orbit takes it from just outside that of to twice the distance of Pluto. It may be a member of a new population of small Solar System bodies that serve as the source of Halley type comets. A few things make Halley’s Comet popular and unique. The obvious thing is that it is fairly easy to see when it does orbit, more so than most other orbiting comets. Also, it orbits every 70 years or so. This makes it unique because it means that most people have a chance to see it at least once. Every generation of people gets an equal opportunity to see it, which makes it special because now everybody can have a part in it. A lot of other comets only orbit every hundred years or so, so you just have to be lucky to be able to see them.

References:

1. http://csep10. phys.utk. edu/astr161/lect/comets/halley.html
2. http://nineplanets.org/halley.html
3. http://en.wikipedia.org/wiki/Halley%27s_Comet

Specific Purpose: To give honor and recognition for his scientific achievements. Thesis Statement: Through his early life experiences and with the knowledge he left behind, Sir Isaac Newton was able to develop calculus, natural forces, and optics. From birth to early childhood, Isaac Newton overcame many personal, social, and mental hardships. It is through these experiences that helped create him to be the person we know today, that is why he is worthy of the Scientist of the Century award. Introduction 1. Attention-getter: “What we know is a drop, what we don’t know is an ocean. said Isaac Newton 2. Establishment of ethos: As a former cell mate of Isaac Newton for 5 years with a 23 hour lock down, I really got to know the person. That’s why I believe I have the credibility to speak on behalf of Sir Isaac Newton. 3. Preview (each main point): First I will talk about Isaac Newton’s incredible inventions and discoveries. Next I will discuss the hardships of Newton’s life experience. Finally I will talk about the Scientist of the Year Award and provide reasons why Sir Isaac Newton is a well-deserved candidate of this award. Transition: To start with. . . ) Body I. Main idea 1: Isaac Newton is well known as one of the greatest scientists who ever lived. A. He studied and researched the binomial theorem, light, telescopes, calculus and theology. After supposedly seeing an apple fall in the garden, he investigated gravity, but was unable to solve the puzzle until some years later. 1. Newton applied his binomial theorem to infinite series and from there developed calculus, a new form of mathematics. For the first time it was ossible to accurately calculate the area inside a shape with curved sides, and to calculate the rate of change of one physical quantity with respect to another. 2. In Newton’s day, many people were superstitious or afraid of what they could not understand such as the appearance of a comet, which was considered a sign of coming disaster. In 1684, Newton again began to consider gravity. He developed his theory of universal gravitation, what is known as the inverse square law. B. Sir Isaac Newton used prisms to show that sunlight was made up of all the colors of the rainbow.

This proved that the ancient Greeks ideas about light were wrong. 1. Although he’s not the first to consider using a curved mirror instead of a lens, Newton was the first to successfully construct a telescope using this principle, a principle still used today in many telescopes (Internal summary/Transition: Now that I’ve provided a few examples of Isaac Newton’s many inventions and discoveries, I will now talk about Isaac Newton’s many personal, social, and mental hardships. ) II.

Main idea 2: After many years of hard work, little rest, and plenty of controversy, Newton’s health failed suffering some mental illnesses and his theories being rejected by many scientist of his time. A. He suffered his second nervous breakdown in 1693. He also suffered recurrent attacks of depression, a mental illness he must have suffered from throughout most of his life. B. Although he engaged in arguments with scientists who dared dispute the correctness of his ideas, he acquired more admirers than critics, both inside and outside the English scientific community. . Newton eventually won acceptance because his theories produced better practical results. For instance, his theory correctly predicted the return of Halley’s Comet. (Internal summary/Transition: Now that I’ve described some of the hardships Newton went through I will now go into the Scientist of the Year Award and why Sir Isaac Newton is a qualified candidate. ) II. Main idea 3: Scientist of the Year Award is a set of annual awards by the Royal Society committees in recognition of scientific advancement. A.

The Scientist of the Year Award has been presented every year since 1650. Many try to achieve this award but very few, if any receive it. B. Sir Isaac Newton is worthy to accept this award not only because of his theories that have changed mankind in today’s society but also because of his contributions to science, mathematics, optics, and physics (Internal summary/Transition to conclusion): Conclusion I. Summary of Speech Theme: Without Sir Isaac Newton’s theories it is not likely humanity would have reached the Moon or that the TV or even the radio would have been invented.

II. Review (each main point): First I have demonstrated a few of Newton’s discoveries and inventions. Second, I’ve explained many of the hardship of Newton’s life that helped shaped who he was. Finally, I provided substantial evidence for reasons why Sir Isaac Newton deserves the Scientist of the Year Award. III. End with Impact: On behalf of myself, every scientist lucky enough to have worked with him and every researcher who makes new discoveries using his theories, I am pleased to present to you this year’s candidate of the Scientist of the Year Award, Sir Isaac Newton.

The Oort Cloud The Oort cloud is a vast swarm of some 2 trillion comets orbiting our star in the most distant reaches of our solar system, extending from beyond the orbits of Neptune and Pluto out to 100,000 times the Earth-Sun distance. Almost one-third the distance to the nearest star. While the planets are confined to a flattened disk in the solar system, the Oort cloud forms a spherical shell centered on the Sun, which gradually flattens down to an extended disk in the inner region, called the Kuiper belt.

Bright comets observed through telescopes or with the naked eye get thrown out of the Oort cloud or Kuiper belt, and become visible when they get close to enough so that the Sun’s energy can transform the surface ices into gases. These gases drag off the embedded dust, and we see the light reflected from the dust as a tail. Comets are the leftover icy building blocks from the time of planet formation, which formed in the region of the outer planets. Essentially thesecomets are dirty snowballs, composed primarily of water ice, with some carbon monoxide and other ices, in addition to interstellar dust.

When their orbits passed close enough to the giant planets to be affected, some were thrown toward the Sun and some were tossed outward toward the distant reaches of the solar system, the spherical swarm we now call the Oort cloud. Some of the comets sent inward hit the inner rocky planets, and probably contributed a significant amount of ocean water and organic material, the building blocks of life, to Earth. Comets that live in the Oort cloud are especially important scientifically because they have been kept in a perpetual deep freeze since the formation of our solar system 4. 6 billion years ago.

This means that they preserve, nearly intact, a record of the chemical conditions during the first few million years of the solar system’s history, and can be used to unravel our solar system’s origins much like an archaeologist uses artifacts to decipher an ancient civilization. The Oort cloud is thought to occupy a vast space from somewhere between 2,000 and 5,000 AU (0. 03 and 0. 08 ly)[12] to as far as 50,000 AU (0. 79 ly)[3] from the Sun. Some estimates place the outer edge at between 100,000 and 200,000 AU (1. 58 and 3. 16 ly). [12] The region can be subdivided into a spherical outer Oort cloud of 20,000–50,000 AU (0. 2–0. 79 ly), and a doughnut-shaped inner Oort cloud of 2,000–20,000 AU (0. 03–0. 32 ly). The outer cloud is only weakly bound to the Sun and supplies the long-period (and possibly Halley-type) comets to inside the orbit of Neptune. [3] The inner Oort cloud is also known as the Hills cloud, named after J. G. Hills, who proposed its existence in 1981. [13] Models predict that the inner cloud should have tens or hundreds of times as many cometary nuclei as the outer halo;[13][14][15] it is seen as a possible source of new comets to resupply the relatively tenuous outer cloud as the latter’s numbers are gradually depleted.

The Hills cloud explains the continued existence of the Oort cloud after billions of year The outer Oort cloud is believed to contain several trillion individual objects larger than approximately 1 km (0. 62 mi)[3] (with many billions with absolute magnitudes brighter than 11—corresponding to approximately 20 km (12 mi) diameter), with neighboring objects typically tens of millions of kilometres apart. Its total mass is not known with certainty, but, assuming that Halley’s comet is a suitable prototype for all comets within the outer Oort cloud, the estimated combined mass is 3? 025 kg (7? 1025 lb or roughly five times the mass of the Earth). Earlier it was thought to be more massive (up to 380 Earth masses), but improved knowledge of the size distribution of long-period comets has led to much lower estimates. The mass of the inner Oort Cloud is not currently known. If analyses of comets are representative of the whole, the vast majority of Oort-cloud objects consist of various ices such as water, methane, ethane, carbon monoxide and hydrogen cyanide.

However, the discovery of the object 1996 PW, an asteroid in an orbit more typical of a long-period comet, suggests that the cloud may also contain rocky objects. Analysis of the carbon and nitrogen isotope ratios in both the Oort cloud and Jupiter-family comets shows little difference between the two, despite their vastly separate regions of origin. This suggests that both originated from the original protosolar cloud,a conclusion also supported by studies of granular size in Oort-cloud comets by the recent impact study of Jupiter-family comet.