Transcript CAPSTONE-poster

Planetary Nebulae & Carbon Star (Death Star)
Chicago Vocational Career Academy
Marlon Brown, Jackyln Olvera, Jonathan Richardson, Leshea Simmons
Made 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.
Method
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.
Guerrero,M.A. et.al.2003, The Astronomical Journal
Sloan Digital Sky Survey DR7
The Internet Encyclopedia of Science : Nebulae & Star Clusters
Students for the Development and Exploration of Space : Planetary
Nebulae
TEMPLATE DESIGN © 2008
www.PosterPresentations.com
RA=275.4613
DEC=64.36484
Carbon star
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
RA=185.86719,
Dec=35.54775
Earth nebula
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
Splash nebula
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
Galex data
References
1.
2.
3.
4.
Smurf nebula
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.
Owl nebula
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.
RA=168.69134,
Dec=55.00916
Margon et al.
2002, ApJ,
124,1651
Conclusion
The 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.
Acknowledgments
SDSS data
Professor Donald York
Julia Brazas
Justin Johnsen
Mercy Kurian & Bhavana Kurian
Sean Johnson
Alan Zomblocki
Mitch Marks & Russell Revzan