Supernova

November 1, 2007
Christine PulliamHarvard Smithsonian Center for Astrophysics
Astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) have found that a supernova discovered last year was caused by two colliding white dwarf stars. The white dwarfs were siblings orbiting each other. They slowly spiraled inward until they merged, touching off a titanic explosion. CfA observations show the strongest evidence yet of what was, until now, a purely theoretical mechanism for creating a supernova.
"This finding shows that nature may be richer than we suspected, with more than one way to make a white dwarf explode," said Harvard graduate student and first author Malcolm Hicken.
The paper describing this discovery appeared in the November 1st issue of The Astrophysical Journal Letters.
Astronomers characterize an observed supernova based on whether its spectrum shows evidence of hydrogen (Type II) or not (Type I). In Type II, a massive, short-lived star undergoes core collapse and explodes. In the conventional picture for Type Ia, the most common supernovae lacking hydrogen, a white dwarf star collects gas from a companion star until it undergoes catastrophic nuclear fusion and blasts itself apart.
The new find, supernova 2006gz, was classified as a Type Ia due to the lack of hydrogen and other characteristics. However, an analysis combining CfA data with measurements from The Ohio State University suggested that SN 2006gz was unusual and deserved a closer look.
Most importantly, SN 2006gz showed the strongest spectral signature of unburned carbon ever seen. Merging white dwarfs are expected to have carbon outside their densest regions. The powerful explosion from the inside then should push off the outmost carbon-rich layers.
The spectrum of SN 2006gz also showed evidence for compressed layers of silicon. Silicon was created during the explosion and then compressed by a shock wave that rebounded from the surrounding layers of carbon and oxygen.
Computer models for merging white dwarfs predict both the carbon and silicon spectral signatures.
Additionally, SN 2006gz was brighter than expected, indicating that its progenitor exceeded the 1.4 solar mass Chandrasekhar limit - the upper bound for a single white dwarf. Only one other potential example of a super-Chandrasekhar supernova has been seen: SN 2003fg. While observations of that event were suggestive, the data from SN 2006gz are much stronger.
"Our case is different. Although 2006gz is also extra bright, the chemistry we see, particularly unburned carbon, is well observed and very unusual," said Harvard astronomer Robert Kirshner, a member of the discovery team.
In addition to providing the first example of a new way to make supernovae, SN 2006gz holds implications for the field of cosmology. Type Ia supernovae typically have a narrow spread in brightness, which makes them useful as "standard candles" for calculating cosmic distances. It was the study of Type Ia supernovae that led to the discovery of dark energy, the mysterious force causing the expansion of the universe to accelerate.
If Type Ia supernovae are more varied than previously expected, then astronomers must be extra cautious when using them to study the cosmos.
"Supernova 2006gz stands out from normal Type Ia objects and wouldn't be included in cosmology studies," commented Hicken. "But we have to be careful not to mistake a double white dwarf explosion for a single white dwarf blast. SN 2006gz was easy to recognize, but there may be less clear-cut cases."
The full list of authors of the study is: Malcolm Hicken, Stéphane Blondin and Robert Kirshner (CfA); Peter Garnavich (University of Notre Dame); Jose Prieto and Darren DePoy (The Ohio State University); and Jerod Parrent (University of Oklahoma). This research was supported by the National Science Foundation.

"Halloween" and "Dead's day"

These are the differences between Halloween and Dead's Day:
The Halloween is an American tradition where one likes sweets and will not be granted if there is a mischief. Also people use costumes beings fantastic. In Mexico, children come to "calaverear" to ask too sweet, but first they have to pray at the altar or ofrenda that are deployed and are not required to be disguised. I think that the Dead's Day is more traditional and more real.

The Halloween

1.- What day of the month is Halloween?
October 31st
2.- Why is halloween celebrated?
Because it's an American tradition that has a lot of meaning and that to identify to the American people. The Mexicans celebrate the Halloween too, but here there is other tradition called "Dead's Day".
3.- Can you explain the history of Halloween?
Yes, the history of Halloween goes back since 3000 years, when the Celtics celebrated the day of the "Lord of the Dead" or the "Samhain" because they believe that the deads returns at the world for eat and to scare at the people. Later, the Romans changed the celebration because they used this day for the "day of harvest". After, the Christian church intervened to change the name and the day of the celebration and was called "All Hallow Day" and was celebrated on November 1st. The origin of the costumes was when the robbers used other dress for that the people don´t think that they was the robbers. This is the history of Halloween.
4.- How is Halloween celebrated in your country?
In Mexico, is celebrated the Dead's Day and the people have the tradition of to go to the cementeries and offering a "ofrenda" for to receive dead family . The ofrenda is colocated in the homes and they set bread, fruits and traditionals candys. The mexicans are very traditionals.
5.- Do you believe in ghosts?
Yes, I think in spirits and ghosts because are souls in penalty who live in solitude and that they have a mission on earth.
6.- What makes you afraid of ghosts?
Well, I'm afraid of alive people, not dead people.
7.- What are some of the symbols of Halloween?
Witches, pumpkins, bats, ghosts, skulls, spirits, black cats, superstition things, irreals worlds.
8.- What kind of costume are you going to wear to the Halloween party?
Like me the vampires that for my costume is going to be dark: a Vampireza
9.- Is your pumpkin still out ?
Well, I never asked calaverita.
10.- Are you still eating Halloween candy ?
Sweets are my weakness, taht for I eat candies all time.

Activity

1. The celebration of Samhain used to take two days.
False
2. Celtic tribes celebrated the end of summer on October 31st.
True
3. First jack-o-lanterns were carved from turnips.
True
4. Jack-o-lanterns were supposed to scare away evil spirits.
False
5. Samhain was the festival of satan.
False
6. Halloween was celebrated in America long before 1800's.
False
7. Irish settlers brought Halloween to America.
True
8. The souls of the dead were believed to be closest to this world on October 31st.
True
9.Burning twigs were used inside a pumpkin as a source of light.
True
10. Samhain meant "Summer's End".
True

Halloween's questionary

The questionary that I did was:
1.- Were is the Samhain celebration from?
It is from the Celtic civilization.
2.- Wath is the Samhain?
It's the name of the festival and mean "Summer's End"
3.- Satan was a creation of:
The Christian church.
4.- The people set jack-o-lenterns in a windows for:
To receive relatives familiars and as protection against malevolent spirits.
5.- The Europeans discovered the pumpkin on:
America.
6.- Moreover, Halloween is:
A celebration of the harvest.
7.- Halloween is a best moment for:
Be on contact with the dead to say good bye or ask for assistance.
8.- When is celebrate the Halloween?
Is celebrated since the sundown on October 31st.
9.- The Samhain have been to celebrated since:
3,000 years ago
10.- The jack-o-lenterns were carved on:
The pumpkins and turnips.

Comments

Hello, this is my comment of the topic of my friends:

Moraarredondo: He is a boy that chose a very good topic because the logic is wonderful for the person's life.
The puzzle about his family is interesting and his questionary was important. His work is good.

Kejikus: His work is about the Galapagos Islands and it will be interesting because this is a game. The homework is wonderful.

Victor Arrieta: his work is about the Salem Wiches and is exciting that somebody is interesting in this problem that to expresa a danger for the world.

Ricardo: his topic is the Galapagos Islands too and it's a game of animals. I think that his work is good.

Manuel: his topic is about the animals that live on the Ocean and I think that this topic is thge passion of Manuel because his topic is very interesting.

The topic of Ivonne is wonderful because choose the historic marc of the womens in the world.

Well, this is all and I think that my work is interesting because like me very much.
Bye , see you next class!!!!!!!!!!!

Cleopatra's Palace

Hello!!!!
This is my report of my favorite topic for the English class in the Mediateca.
My topic is about Cleopatra's Palace and I've made a Web Page that shows her life, her family, her love with César (Roman Imperor) and with Marc Antony (a Roman soldier). The Cleopatra's life was wonderful but dramatic too. This topic was my favorite because I love Egypt and it is my passion. Its palaces, piramids and monuments were fantastic and this culture is exciting for me.
My Web page will be read the next Thursday and I will send the address so that my friends can see it.
Bye!!!!!!!!!

Cleopatra's Palace

Hello teacher Marsella!!!!!!
This is my report of my favorite topic: Cleopatra's Palace.
In the page of Discovery Channel I read about the program for start an article of investigation for make a web page about the Cleopatra's Palace.
This is one of the most interestig topics for my person and I know that I will go to obtain make this web page.
In this page I have to talk of the Cleopatra's life and I have to recopiled information for make my work of investigation.

Well this is my plan for can to work and y will be to send you information about my topic.
Bye teacher. Have a nice day.

P.S. I remember you: my URL is guadalupe-egipto. O.K. Bye.