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Outline:
Introduction
Body: I) the importance of
a comet:
-They are unpredictable
-They hold information going to the Big Bang time
-They have shaped life on Earth
-They are like a time machine
II) different information about comets:
- Comet’s orbit
- Meteor shower
- Parts of a comet
Conclusion
Introduction:
To a non astronomer a comet could be a fuzzy spot in the sky, sometimes, especially in the early ages it was seen as a bad sign. Natural catastrophe wars, diseases were seen as a consequence of the appearance of a comet in the sky.
I) the importance of a comet:
To astronomers, a comet is a frozen
body composed of various ices and dust. “It is a dirty snowball” (Fred
Whipple – astronomer). They are a mixture of ices (both frozen gases and
water) and dust that for some reason didn’t get incorporated into planets
when the solar system was formed. This makes them very interesting as they
give us information of the early history of the solar system. Comets are
exciting for many reasons:
1- They are unpredictable. They suddenly appear or fade in a matter of hours. They can lose their tail or develop multiple tails. Sometimes they can even split in 2 or more pieces.
2- Comets represent some of the oldest, untouched objects in the solar system. They hold information going to around the Big Bang time and because of that they help answering many questions when observing them.
3- Recent years have revealed comets have shaped
the progress of life, as we know it on Earth. Many astronomers are convinced
that early collisions between Earth and comets brought water that now make
the Earth’s Oceans. And these oceans enabled life on our planet. But comets
can also bring extinction to different life forms and that’s what happened
to the dinosaurs for example, 65 million years ago.
4- Comets are like a time machine. It is thrilling
to watch a comet like the famous Halley Comet with a 75 years period and
think about what life was like when the comet was last seen or imagine
the same with a comet that only passes near Earth several hundreds or thousands
or even millions of years ago.
II) different information about
comets:
Comets are invisible except when they are
near the sun and they are usually visible only at sunrise or sunset. Most
comets have highly eccentric orbits, which take them far beyond the orbit
of Pluto. These are seen once and then disappear for millennia. Only the
short and intermediate period comets (like Halley) stay within the orbit
of Pluto for a significant fraction of their orbits. After 500 or so passes
near the sun, a comet loses most of its ice and gas leaving a rocky object
very much like an asteroid in appearance. A comet whose orbit takes it
near the sun is also likely to either impact one of the planets or the
Sun or to be ejected out of the solar system.
Meteor shower sometimes occurs when the Earth passes through the orbit of a comet. The Perseid meteor shower occurs every year between August 9 and 13 when the Earth passes through the orbit of comet Swift-Tuttle. Comet Halley is the source of the orionid shower in October.
When they are neat the sun and active, comets
have several distinct parts:
- Nucleus: relatively solid and stable mostly
ice and gas with a small amount of dust and other solids.
- Coma: dense cloud of water, carbon dioxide and other neutral gases sublimed off of the nucleus.
- Hydrogen cloud: Huge (millions of km in diameter)
but very sparse envelope of neutral hydrogen.
- Dust tail: up to 10 million km long composed
of smoke-sized dust particles driven off the nucleus by escaping gases;
this is the most prominent part of a comet to the naked eye.
- Ion tail: up to 100 million km long composed
of plasma and laced with rays and streamers caused by interactions with
the solar wind.
Conclusion:
Our solar system began as a vast cloud of gas
and dust. Several billion years ago, this cloud slowly rotated around our
very young sun, and particles within the cloud collided one another. During
this time some objects were obliterated by these collisions, while others
grew in size and were later to become planets. Throughout this early period
comets probably filled the solar system. Their collisions with the early
planets played a major part n the growth and evolution of each planet.
Over the years, comets actually became rarer within our solar system. Today,
most comets are located outside our solar system in part of the original
cloud of dust and gas that has remained virtually untouched for billions
of years. These regions are the Oort Clout and the Kniper Blet.
References:
http://medecine.wustl.edu/~kronkg/comintro.html
http://seds.LpL.arizona.edu/billa/tnp/comets.html
Analysis on the research about COMETS:
In this research, I mainly talked about what is a comet, what is it made from, where it comes from etc.. Studying comets is really fascinating and searching for them is even more.
Imagine you’re on a hill, in the middle of a quiet summer night, with your telescope, a cold breeze passing by you while you are observing a wonderful, full of bright stars, black sky. What is interesting to mention is that most comets are discovered by amateurs. You just have to report your discovery and if you’re one of the lucky 1st 2 who reported their discovery the comet will be named after you. For example the comet that passed near Earth in 1997 (and is still visible from the southern hemisphere) was discovered by Alan Hale and Thomas Bopp and was named comet hale-bopp. This fact motivate amateurs to keep on looking for comets. I mean, can you imagine your name given to an object which have billions of years old and probably comes from the Big Bang?
As much fascinating as they could be, comets could be also deadly. A comet impact with Earth could at least make “local” damages, but it could also go to total extinction of life on Earth. It all depends on its size. Scientist Eugene Shoemaker (who died about 2 years ago) who was 1 of the rare persons to witness an impact, the only impact (collision of 2 solar system bodies) to be observed, (comet Shoemaker-Levy hit Jupiter in July 1994) believes that it’s only a matter of time before a comet hits (Earth) again. Earth has been impacted often by objects from space of various sizes in the past. When such objects hit us, it will cause such a global environmental catastrophe that all life, including man, will be extinct. When condition on the surface of the planet will improve, life will be born again but it will do so in other forms (Dinosaurs didn’t come back, man replaced them). At least 40% of all these large objects of 1 (or more) km will definitely hit the Earth at some point in time and that’s for sure. And if that’s wasn’t enough, Dr. Shoemaker confirm that all the comets and asteroids we know about only makes 7% of what exist out there. We know nothing about the other 93% and this make defending Earth in case of a possible impact ALMOST impossible. Scientists now believe that the Chicxulub crater in the Yucatan peninsula (Mexico) is the place where an impact occurred 65 million years ago, which exterminate the dinosaurs. This impact is known as K-T impact, it lead to a massive extinction. So it happened once, it will happen again. The only question is WHEN? Without knowing the time, we can’t prepare well to face this danger. Nevertheless, several theories are being studied like sending a nuclear bomb to the comet but this is a dangerous solution as the comet will be divided in many parts, which means we will have several impacts on earth. But let’s say we do this and we survive, there’s also the danger of being exposed to the nuclear radiation falling from the sky. Another theory, similar to the first, is to make a nuclear explosion next to the comet so that it will affect and change its trajectory and deviate it from Earth. But also in this case we would be exposed to nuclear radiation.
Another theory is to have a human hero who will give his life to defend Earth, like Bruce Willis in “Armageddon”, but this has small chances to work out, so better not to take it in consideration.
[I tried to look for other but I couldn’t find anything, so maybe we have no other solutions]
This extremely beautiful thing flying up there
is also extremely dangerous. Ok, it is dangerous if you look at it like
an incredibly huge, horrible icy rock that could provoke a total extinction
of life on Earth. But on the other hand, this thing has brought life on
Earth, as it was the reason of oceans and water on our planet. Besides,
if 65 million years ago the K-T impact didn’t happen, who knows, maybe
dinosaurs would still be here and us… Well maybe we would have never existed.
So if a similar impact would occur and exterminate life on Earth, it won’t
be the end, it will be the beginning of another life form that would appear
after our planet would recover from the impact. So comets are not only
a threat to life but in a way, they also are the reason for new lives to
come.
The test:
1) What are comets made of?
2) When can we see a comet?
3) Name the different parts of a comet.
4) Name one reason why comets are important to scientists.
5) Where do comets come from?
