TEMPLATE DESIGN © 2008

www.PosterPresentations.com

Planetary Nebulae & Carbon Star (Death Star)Chicago Vocational Career Academy

Marlon Brown, Jackyln Olvera, Jonathan Richardson, Leshea SimmonsMade possible by the NASA CAPSTONE program and the University of Chicago.

Introduction

Our team decided to explore planetary nebulae because we wanted to know how were they formed, why they had so many colors, why they were called planetary nebulae, the significance of their names, their composition, how many possibly existed in the Milky Way galaxy, their approximate age, their first discovery and the aftermath of their eventual death. To address these questions, we oriented ourselves into using a large scientific database easily accessible to high school students.

These questions lead us to an exciting exploration of planetary nebulae.

The famous astronomer William Herschel discovered the first planetary nebulae called Dumbbell nebula (M27) in the 1870’s. The name was given because he found an apparent similarity to the disk of Uranus. So far, there are 2,000 planetary nebulae in our Milky Way galaxy and their average lifespan is about 50,000 years. A planetary nebula forms when a star has aged into a red giant (Mira star) with a dormant carbon core and an outer helium burning shell. It can no longer support itself by nuclear fusion reactions in its center. The gravity from the material in the outer part of the star takes its inevitable toll on the structure of the star, and forces the inner parts to condense and heat up. The unstable helium burning shell expands and breaks free. It becomes an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the last phases of their lives.

The hot central carbon core emits ultraviolet radiation and has a surface temperature of 100,000K which cools down to become a white dwarf. The high energy ultraviolet radiation is absorbed by the nebular material and is reemitted into spectral lines which give the ejected gas shell its glowing color.

The ejected matter of the shell contains carbon, nitrogen, oxygen which will eventually be recycled to form a new generation of stars.

A carbon star is a late-type, giant star that looks more likely to be a red giant whose atmosphere contains more carbon than oxygen.

References

Method

Earth nebula

Splash nebula

Smurf nebula

Owl nebula

Carbon star

Acknowledgments

ConclusionThe objects that we discovered were the Splash nebula, Smurf nebula, Earth nebula, and Owl nebula. An unusual object we discovered during our search was a carbon star which has a strange spectrum. Most of the planetary nebulae are glowing spheres of gas. After observing the spectrum we deduced that the planetary nebulae contained hydrogen and oxygen gas. We also learned how to calculate the approximate age of a planetary nebula.

With more time, we could have refined our search to discover more planetary nebulae or we could have looked for more strange objects like the carbon star.

We couldn’t get the distance for the other three planetary nebulae, we only got the distance for the owl nebula, and we calculated the age based on the distance to the owl nebula. It was impossible to calculate the age of the remaining nebulae because we did not know the distance to them.

In order to find possible planetary nebulae in the Milky Way galaxy, we used a database called “Sloan Digital Sky Survey” (SDSS). SDSS Database contains images obtained through a telescopic survey of the sky. We typed in a search code into a “SDSS Query Casjobs” to search the large database to get narrowed down results focusing on possible planetary nebulae. The results we obtained were coordinates called right ascension (ra) and declination (dec) . These coordinates were placed into another program called the navigate page of SDSS website which provided 52 images of possible planetary nebulae. These images were analyzed to confirm existing planetary nebulae.

Our group discovered a previously unseen nebula during the summer Capstone program at the University of Chicago and has been named “Earth nebula” due to its earth-like appearance. RA=119.42754,Dec=53.44425

In order to calculate the distance of the radius of the planetary nebula called Owl nebula, the equation utilized was the small angle formula. Using the navigate page on SDSS, a grid was placed on the image of Owl nebula to conclude the radius as 120 arc seconds. Using the triangle formula of two known sides and an unknown angle called the small angle formula (d/D = /206625 arcsec/rad). D is the distance from the center of the earth to the Owl nebula which is 500pc and is 120pc. After manipulating the equation algebraically, we were able to calculate d as 0.29 pc. This radius of the Owl nebula converted into 8.9*1012km. To find the age, t = d/v equation was used where v = 40 km/s which is the rate at which the outer helium shell expands away from the core and d = 8.9*1012km calculated above. The age of the Owl nebula was worked out to be 7050.5 years.

We think the Smurf nebula is an old nebula because every other nebula is formed in complete bright circle and the Smurf nebula is not as bright and looks as if it’s fading away. In the other spectra, there are very strong hydrogen lines, and as you see in our graph the hydrogen lines are not very strong, which shows us this nebula is very old and cool. Instead, the spectrum looks like it comes from a white dwarf. RA=275.4613DEC=64.36484

RA=185.86719,Dec=35.54775

The Splash nebula appeared in our search, and to decide if it was a planetary nebula, we looked for the white dwarf in the center, using the Galex telescope database.RA=194.86576, Dec=27.63631

A cool red-giant star in an advanced stage of evolution, displaying strong carbon features in the form of CN, CH, and C2 (Swan) bands in its spectrum; also known as spectral type C. In carbon stars, the abundance of carbon is greater Carbon stars, also known as C stars, have carbon/oxygen ratios that are typically four to five times higher than those of normal red giants and show little trace of the light metal oxide bands than that of oxygen

Margon et al. 2002, ApJ, 124,1651

RA=168.69134, Dec=55.00916

Professor Donald YorkJulia BrazasJustin JohnsenMercy Kurian & Bhavana KurianSean JohnsonAlan ZomblockiMitch Marks & Russell Revzan

1. Guerrero,M.A. et.al.2003, The Astronomical Journal2. Sloan Digital Sky Survey DR73. The Internet Encyclopedia of Science : Nebulae & Star Clusters4. Students for the Development and Exploration of Space : Planetary

Nebulae SDSS data

Galex data