Part of our what-is-a-professional-astronomer assignment is to research the topic online. Since Cassi and I have already interviewed a grad student on the process of becoming a professional astronomer and she is planning on doing another interview with an astrophysics professor to see what a career in academia is actually like, I thought I would research what other sorts of jobs you can do with an astrophysics degree besides being a professor.
From the American Astronomical Society's career pamphlet: A New Universe to Explore: Careers in Astronomy, I found that about 55% of professional astronomers are faculty at a university or work at university affiliated laboratories. Around 33% of professional astronomers are employed in national or government labs. This may involve working for something like National Aeronautics and Space Administration (NASA), the Naval Research Laboratory, or the National Radio Astronomy Observatory. But what do you do if you are not doing research?
Approximately 10% of astronomers have some sort of industry job. Some work in astronomy industry. This includes companies such as SpaceX, which is working to privatize the space flight industry. Other companies may build satellites or develop remote sensing instrumentation. Some astronomers go into finance or consulting due to their strong math backgrounds. Others may apply what they learned about instrumentation or computer modeling to work in other areas of industry or business.
Astronomers can also go into a career in public education. This may involve being the director of a museum or planetarium, teaching high school classes, or writing popular science articles or books. These astronomers need to have a thorough background in astronomy, and science in general, and also should be able to communicate technical or abstract ideas to the public effectively.
Alternatively, you could be like Brian May and combine astrophysics research with playing guitar and writing songs for Queen. But you should probably find another band to lend your talents to.
Saturday, November 26, 2011
Transiting Planets and Stellar Radial Velocities
Ay 20 – Transiting Planets
Problem 1
Primary author: Joanna Robaszewski
Secondary author: Cassi Lochhaas
Abstract
This problem looks into one of the equation governing the relationship between the masses of a planet and a star orbiting their center of mass and the radial velocity of the star.
Introduction
As a planet orbits a star, the planet has some effect on the motion of the star. The change in the motion of the star can be inferred through the Doppler effect. When the star moves away from the observer, its emissions are measured to have a longer wavelength. When the star moves toward the observer, its emissions have a shorter wavelength. Measuring the differences caused by the planet in the radial velocity of the star allows observers to better estimate the mass of the planet, provided the star’s mass is already known.
Questions and Results
where Mp is the mass of the planet, M* is the mass of the star, V* is the maximum radial velocity of the star found in the plots, P is the period of the planet around the star, and G is Newton’s gravitational constant, we want to find the mass of the planets of the two systems.
In the case of the 1.8 solar mass star we have:
For the 1.7 solar mass star, we find that the planet has a mass of:
Once again, my calculations don’t quite match up with what Cassi and I found in class. This might just be from me estimating the period of the planet’s orbit from the graphs slightly differently than before. While working this problem out in class, we found that both the planets had masses on the order of 1030 grams, which is the mass of Jupiter. This is reasonable because many exoplanets discovered are about Jupiter size. In either case, the equation shows that the larger the ratio of the planet’s mass over the star’s mass, the larger the star’s maximum radial velocity. The period also plays a part in determining the radial velocity of the star, but I’m not entirely sure as to why an increase in the period would also cause an increase in the radial velocity. It may have something to do with the fact that the planet has more time to pull the star in one direction, because it is spending more time in one general direction from the star. I’ll think about it.
Wednesday, November 23, 2011
Astronomy Cast
Astronomy Cast (http://www.astronomycast.com/) is a weekly podcast put on by Fraser Cain, the editor of Universe Today, and Pamela Gay, professor of astronomy at Southern Illinois University - Edwardsville. Each show is about 30 minutes long and explains some sort of astronomical phenomenon or idea. Fraser and Pamela not only explain some astronomy facts, but they also try to clear up common myths and misconceptions. Additionally, they try to explain "how we know what we know", so the listener ends up learning about common astronomy techniques and various aspects of the scientific method.
This might make it sound as if Astronomy Cast is intended for somebody without an astronomy background, and it is appropriate for people who are curious about astronomy, but haven't had any formal training; however, it is definitely not boring if you have already have some background knowledge. In fact, I just listened to their episode about the sun, solar flares and cycles, and and the effects they might have on the Earth, and I found that I could appreciate it more now that I've taken most of Ay 20. They actually covered many of the same basic stellar principals that we have in class, including the idea that the sun is approximately made out of an ideal gas and how hydrostatic equilibrium plays a part in governing the sun's behavior. So having a bit of an astronomy background actually made the show even better!
Some of my favorite episodes have been on particular astronomy missions, like the Kepler mission. Fraser and Pamela tend to do a two part series for prominent or future missions. The first episode in the series is about the scientist the mission or technology is named after and the history of his or her research. The second episode then covers what the mission is and how it works. They generally try to explain the link between the scientist's historical contributions and how it inspired a new mission or new technology, and so why the mission was named after that particular scientist.
For the Kepler mission episodes (numbers 189 and 190) they didn't have a particularly strong link between the name of the mission and the scientist, but they did go into detail on how Kepler became interested in astronomy, why he had to become a theorist instead of an experimentalist, how astronomy had been progressing until he met Tycho Brahe, and how he developed his theories. And in the second episode they did a great job explaining the objective of the Kepler mission, how stars are eliminated as candidates for hosting Earth-sized planets, and how the telescope utilizes the transit method to discovers planets. If you want the actual information I guess you'll just have to go listen to the podcast yourself at http://www.astronomycast.com/.
This might make it sound as if Astronomy Cast is intended for somebody without an astronomy background, and it is appropriate for people who are curious about astronomy, but haven't had any formal training; however, it is definitely not boring if you have already have some background knowledge. In fact, I just listened to their episode about the sun, solar flares and cycles, and and the effects they might have on the Earth, and I found that I could appreciate it more now that I've taken most of Ay 20. They actually covered many of the same basic stellar principals that we have in class, including the idea that the sun is approximately made out of an ideal gas and how hydrostatic equilibrium plays a part in governing the sun's behavior. So having a bit of an astronomy background actually made the show even better!
Some of my favorite episodes have been on particular astronomy missions, like the Kepler mission. Fraser and Pamela tend to do a two part series for prominent or future missions. The first episode in the series is about the scientist the mission or technology is named after and the history of his or her research. The second episode then covers what the mission is and how it works. They generally try to explain the link between the scientist's historical contributions and how it inspired a new mission or new technology, and so why the mission was named after that particular scientist.
For the Kepler mission episodes (numbers 189 and 190) they didn't have a particularly strong link between the name of the mission and the scientist, but they did go into detail on how Kepler became interested in astronomy, why he had to become a theorist instead of an experimentalist, how astronomy had been progressing until he met Tycho Brahe, and how he developed his theories. And in the second episode they did a great job explaining the objective of the Kepler mission, how stars are eliminated as candidates for hosting Earth-sized planets, and how the telescope utilizes the transit method to discovers planets. If you want the actual information I guess you'll just have to go listen to the podcast yourself at http://www.astronomycast.com/.
Saturday, November 19, 2011
Stellar Formation
Ay 20 – The Formation of Stars
Problem 5
Primary author: Joanna Robaszewski
Secondary authors: Cassi Lochhaas and Daniel Lo
Abstract
This problem investigates the initial mass function that regulates mass distribution in star forming regions. It looks at the number of stars that fall into certain mass ranges and how much each mass group contributes to the overall luminosity and color of the star forming region.
Introduction
The initial mass function describes the distribution of stellar mass at the birth of the star. It takes on the form:
N is the number of stars that are forming, M is the mass, and A is a proportionality constant to be determined in the problem. We will be dividing the stars into three groups based on mass. One will be the low mass stars with a mass range of 0.1M⊙ to 1M⊙. Another will be the intermediate mass group with a range of 1M⊙ to 8M⊙. The last group will contain the high mass stars which fit into the 8M⊙ and greater range. M⊙ is one solar mass and is equal to 2 * 1033 grams. Luminosity is a measure of a star’s power output. The sun has a luminosity of 4 * 1033 ergs/s.
Questions and Results
5.a Consider a newly formed globular cluster with total mass of 106 M⊙ and the initial mass function in the mass range 0.1M⊙ to 20M⊙. Find the proportionality constant A.
We can think of dN/dM as being somewhat similar to a probability density. From it, we can determine how likely it is that a star forming in this cluster will have a certain mass. To find the total number of stars in some mass range we use the integral:
To find the total mass of all the stars forming for some mass range, we use the following integral:
In this case we know the total mass of the cluster is 106M⊙ and the mass range is 0.1 M⊙ to 20 M⊙. So let’s set up the integral:
So we found the proportionality constant A. If anybody has any ideas as to what the units mean, I’d be happy to hear them.
5.b What is the fractional number of stars that are fit in the high mass category, the intermediate mass category, and the low mass category (where the categories are defined in the introduction)? How much mass is contained in each of these mass bins?
We can use the integrals we found in the first part to find the number and mass of the stars in the various mass bins. All we have to do is pick appropriate boundaries for the mass.
For the high-mass category:
For the intermediate-mass stars:
For the low-mass stars:
So in total we have 3.08 * 1016 stars in the cluster. 0.19% of these stars are in the high-mass range. The intermediate-mass range contains 4.2% of the stars in the cluster. And the low-mass category has 95.5% of the stars in the cluster. The total mass in the high-mass bin is 1.41*1048 grams. The total mass of all the stars in the intermediate-mass range is 5.49*1048 grams. The total mass found in the low-mass range is 1.31*1049 grams.
5.c The luminosity of a star scales with mass differently for different mass ranges. The scaling relationships are below:
Low-Mass Stars: L = M5
Intermediate-Mass Stars: L = M3
High-Mass Stars: L = 64M
What is the total luminosity of the cluster? What are the fractional contributions to the total luminosity from each mass range?
First, let’s calculate the luminosity from the low-mass stars. We can use the same integrals we used to find total mass, but we have to make some substitutions. An integral for total luminosity would look like this:
So for the low-mass stars:
We also want to convert the boundaries from 0.1 M⊙ and 1 M⊙ to (0.1 M⊙)5 and (1 M⊙)5.
For those of you paying attention, you’ll notice that the units aren’t correct for luminosity. Ok, so I lied a bit when I said we were calculating the total luminosity contributed by the low-mass stars. What we actually have is proportionally how much the low-mass stars will contribute to the overall luminosity of the cluster. Once we calculate the luminosity contributions from the other mass ranges we can find the total contributions toward the cluster’s luminosity. After that we can find the actual percentages that each mass category contributes to the total luminosity. So we don’t need to calculate the actual luminosity. We can just find the proportions based on how luminosity scales with mass for various ranges of mass.
Now we need to calculate the luminosity contribution from the intermediate-mass stars. The new integral boundaries are now 1M⊙ and 8M⊙.
Now to calculate the luminosity contribution from the high-mass stars with integral boundaries 8M⊙ and 20M⊙:
Unfortunately these numbers are very far from those that we calculated during class, but I’ve already spent a week and a half trying to get the calculations to work out so I’m just posting what I have. Please let me know what I’ve left out in my calculations if you figure it out. In class, my group did the calculations and found a very interesting result. Even though the stars in the high-mass category were extraordinarily few in number in comparison to other types of stars, they contributed about 55% of the luminosity. The intermediate-mass stars contributed about 45%, while the low-mass stars contributed less than 1% of the luminosity. We were all quite surprised and intrigued by this result.
5.d Would you expect and active star forming galaxy to look more blue or more red? What about a very old, inactive, elliptical galaxy?
As was stated in the previous section, the high-mass stars contribute the most to the luminosity of the cluster, despite hardly contributing to the number of total stars. The larger stars that form are blue, while the smaller stars are red. So since the largest stars are contributing the most to the luminosity of star-forming region, an active star forming galaxy would look blue. The largest stars are also the ones the die off first, leaving behind the smaller, red stars. So in an old, inactive galaxy, all the large blue stars are gone. This leaves the small red stars to contribute most to the luminosity of the galaxy, thereby making it look red.
Wednesday, November 16, 2011
What is a Professional Astronomer? - Part II
A little while ago, I wrote down what my thoughts were on what it means to be a professional astronomer prior to researching the topic. My partner in this investigation is Cassi Lochhaas. She and I sat down with Kunal Mooley, a third year grad student in astrophysics at the California Institute of Technology, to interview him about his experiences and thoughts related to becoming a professional astronomer. Our questions and Kunal's answers can be found at Cassi's blog, Life and Its Relation to Astronomy (or Vice Versa). While you're reading that, Cassi and I will continue our research on what it means to be a professional astronomer.
Sunday, November 6, 2011
What is a Professional Astronomer? - Part I
One of the goals my astrophysics professor has for our class is for us to come away with an understanding of what it means to be a professional astronomer. But before doing any research or interviews on the subject, we are supposed to record our own assumptions and impressions on what it is professional astronomers do and how somebody gets to be a professional astronomer in the first place. So here is "What is a Professional Astronomer? - Part I" More parts will follow after I have been hit with a dose of professional astronomer reality.
Ever since I was 12 or so, I believed I wanted to be a physicist. Eventually it dawned on me that I had no idea what a physicist did. I've slowly built up an idea since then, but beyond knowing that there are two sorts of physicists, theoretical and experimental, I still don't know what these physicists actually do from day to day. I know that astrophysics is not the same as physics, but I still think this assignment will be tremendously helpful for me to figure out the general evolution of a professional scientist's career.
Let's start with how you become a professional astronomer. I assume that at some point before or during your undergraduate studies, you somehow become interested in astronomy. This could be through pictures, lectures, natural curiosity, whatever. Something about astronomy just sticks with you. Then comes an undergraduate program in astronomy, astrophysics, or physics. This involves taking the courses that your school deems necessary to be an astronomer. Perhaps you will do some astronomy research during the summer or get the chance to use a telescope. Eventually you'll graduate from the undergrad program, and most likely move on the graduate school in astronomy, although physics may still be acceptable at this point depending on what kind of physics you specialize in.
In grad school you'll pick an adviser and start specializing. I suppose astronomy may also be split between experiment and theory. If you do theory, you'll probably be doing lots of computer simulations and math to make predictions. If you do experiment, you'll probably be doing lots of observing and data analysis to test those predictions. You may also have to specialize in a type of instrumentation and wavelength, for example spectral, optical, x-ray imaging, and so on. In either case, you will have to narrow your focus to one or a few closely related astronomical phenomena. This does not mean that you have to stop studying everything else, but you'll start to become a specialist in one area, such as star formation or extra solar planets or black holes. As an astronomy grad student, you'll probably go to many, many conferences and observing sessions in less enchanting places, like Arizona, while your adviser goes to all of the observing runs in Hawaii. After 4 or 5 or 6 or 7 or 8 years you'll probably defend your thesis and get your Ph. D. Then you'll get to be a postdoc somewhere!
I actually have no idea what postdocs are. I think they sort of float in limbo between being a grad student and being an assistant professor. They probably continue their grad research, or maybe start to branch off in a slightly different direction. The have probably switched advisers, but now have to do some research on their own. I'm not sure what astronomy grad students do after they have finished grad school if they do not go into academia and become postdocs. Guess I'll find out later!
Continuing down the academia sequence, after you're done with your postdocs, you'll probably be an assistant prof somewhere. I'm not actually sure what makes an assistant prof an assistant. I guess you may be allowed to lecture occasionally and you still have to do you own research and you don't have tenure yet. That's pretty much all I have for the life of an assistant professor.
Eventually you'll be an astronomy professor! You'll have classes to teach, your own group of grad students to manage, and you'll be the one going to observe in Hawaii. You'll also have to write lots and lots of grant proposals. You'll continue to gather data and publish papers until you're either disproved by another group of astronomers or your ideas become widely accepted. In the latter case there will be much cake and celebration, hooray!
If you do not become a professor, you may still spend your time doing research and writing grant proposals at labs or observatories. You may spend your time as the director of a telescope. Maybe you'll design planetarium exhibits. As I said before, I don't really know what astronomers do outside of academia.
I suppose the ultimate goal of an astronomer is the same as the ultimate goal of any scientist, just applied to the field of astronomy. This may include deepening the understanding of the phenomena that make up the universe, and simply investigating questions that are interesting to them. Astronomers have to be well-organized and hard-working, but also creative and able to look for solutions in brand new ways, just like any scientist. I also think that astronomy is a highly collaborative field. I find the projects that publicly publish information directly after discovery, like the Catalina Real-Time Transient Sky Survey and projects that encourage at-home interaction, like Galaxy Zoo, to be an interesting new way of doing science, and I wonder if other fields have projects like these as well.
Well, those are my initial assumptions of what it would be like to be a professional astronomer and what it takes to get to that position. Most of my hypothesis comes from knowledge gained from PhD comics: http://www.phdcomics.com/comics.php. Stay tuned as I gather data on what it actually takes to be a professional astronomer!
Ever since I was 12 or so, I believed I wanted to be a physicist. Eventually it dawned on me that I had no idea what a physicist did. I've slowly built up an idea since then, but beyond knowing that there are two sorts of physicists, theoretical and experimental, I still don't know what these physicists actually do from day to day. I know that astrophysics is not the same as physics, but I still think this assignment will be tremendously helpful for me to figure out the general evolution of a professional scientist's career.
Let's start with how you become a professional astronomer. I assume that at some point before or during your undergraduate studies, you somehow become interested in astronomy. This could be through pictures, lectures, natural curiosity, whatever. Something about astronomy just sticks with you. Then comes an undergraduate program in astronomy, astrophysics, or physics. This involves taking the courses that your school deems necessary to be an astronomer. Perhaps you will do some astronomy research during the summer or get the chance to use a telescope. Eventually you'll graduate from the undergrad program, and most likely move on the graduate school in astronomy, although physics may still be acceptable at this point depending on what kind of physics you specialize in.
In grad school you'll pick an adviser and start specializing. I suppose astronomy may also be split between experiment and theory. If you do theory, you'll probably be doing lots of computer simulations and math to make predictions. If you do experiment, you'll probably be doing lots of observing and data analysis to test those predictions. You may also have to specialize in a type of instrumentation and wavelength, for example spectral, optical, x-ray imaging, and so on. In either case, you will have to narrow your focus to one or a few closely related astronomical phenomena. This does not mean that you have to stop studying everything else, but you'll start to become a specialist in one area, such as star formation or extra solar planets or black holes. As an astronomy grad student, you'll probably go to many, many conferences and observing sessions in less enchanting places, like Arizona, while your adviser goes to all of the observing runs in Hawaii. After 4 or 5 or 6 or 7 or 8 years you'll probably defend your thesis and get your Ph. D. Then you'll get to be a postdoc somewhere!
I actually have no idea what postdocs are. I think they sort of float in limbo between being a grad student and being an assistant professor. They probably continue their grad research, or maybe start to branch off in a slightly different direction. The have probably switched advisers, but now have to do some research on their own. I'm not sure what astronomy grad students do after they have finished grad school if they do not go into academia and become postdocs. Guess I'll find out later!
Continuing down the academia sequence, after you're done with your postdocs, you'll probably be an assistant prof somewhere. I'm not actually sure what makes an assistant prof an assistant. I guess you may be allowed to lecture occasionally and you still have to do you own research and you don't have tenure yet. That's pretty much all I have for the life of an assistant professor.
Eventually you'll be an astronomy professor! You'll have classes to teach, your own group of grad students to manage, and you'll be the one going to observe in Hawaii. You'll also have to write lots and lots of grant proposals. You'll continue to gather data and publish papers until you're either disproved by another group of astronomers or your ideas become widely accepted. In the latter case there will be much cake and celebration, hooray!
If you do not become a professor, you may still spend your time doing research and writing grant proposals at labs or observatories. You may spend your time as the director of a telescope. Maybe you'll design planetarium exhibits. As I said before, I don't really know what astronomers do outside of academia.
I suppose the ultimate goal of an astronomer is the same as the ultimate goal of any scientist, just applied to the field of astronomy. This may include deepening the understanding of the phenomena that make up the universe, and simply investigating questions that are interesting to them. Astronomers have to be well-organized and hard-working, but also creative and able to look for solutions in brand new ways, just like any scientist. I also think that astronomy is a highly collaborative field. I find the projects that publicly publish information directly after discovery, like the Catalina Real-Time Transient Sky Survey and projects that encourage at-home interaction, like Galaxy Zoo, to be an interesting new way of doing science, and I wonder if other fields have projects like these as well.
Well, those are my initial assumptions of what it would be like to be a professional astronomer and what it takes to get to that position. Most of my hypothesis comes from knowledge gained from PhD comics: http://www.phdcomics.com/comics.php. Stay tuned as I gather data on what it actually takes to be a professional astronomer!
Friday, November 4, 2011
The Cosmos According to Linux
Sorry I've been running slightly behind in writing. It's been midterms week, so I've been taking tests for a while. I'll try to catch up on posts this weekend.
I have a Windows/Linux dual-partition for my computer and every time I log-in to the Linux partition I am greeted by one of nine or so majestic astronomy pictures. The "Cosmos" desktop background is a slide show of various astronomical phenomena and it periodically changes from image to image while you work. I've had this background for a few years now, but I only recently wondered about the identities of the objects I was looking at. Some are easy to identify, such as Earth and Jupiter, but some were a mystery. I looked into the details of a few of the images. For some I could only find what type of object it was and not the name of the object, but the information that I found on the others I will share below. All the images are from http://hqwalls.blogspot.com/2010/07/cosmos-wallpapers-2560x1600.html. The majority of the information was gathered from http://www.spacetelescope.org/, http://www.universetoday.com/, and http://apod.nasa.gov/apod/.
Image 1: The Helix Nebula
The Helix Nebula is a planetary nebula approximately 700 light-years away, making it one of the closest planetary nebulae to Earth. The star at the center of the nebula is very old (and by "very old" I mean older than the sun and already past the red giant stage), and has already blown away its original outer-most gas and dust. Eventually, the star will become a white dwarf and the gas we can see now will have also been blown away. The structure of the Helix Nebula is interesting because there are "knots" in the shells of gas and dust. These knots are dense, intense patches of glowing gas. They have comet-like tails that point away from the star at the center of the nebula. Knots of nebulosity were first discovered in the Helix Nebula and have been found in other nebulae since then. The Helix Nebula got its name because the angle from which we view the nebula makes it look as if we are looking down the center of a helix.
Image 2: The Sombrero Galaxy
The Sombrero Galaxy is an unbarred spiral galaxy about 29 million light-years away from Earth. It has an unusually large central bulge and an extraordinarily well-defined dust lane. These characteristics, along with the fact that we view it edge on, make it look a bit like a sombrero. The ring contains mostly hydrogen gas and dust, and most of the stellar formation within the Sombrero Galaxy happens there. The Sombrero Galaxy also has one of the highest instances of globular clusters and one of the most massive black holes at its center. The black hole is estimated to have a mass of at least one billion solar masses. The galaxy cannot be seen with the naked eye, but it can be observed using only a 4-inch telescope.
Image 3: NGC 3370
NGC 3370 is also known as the Silverado Galaxy. It is a spiral galaxy about 98 million light-years away from Earth. It has well-defined spirals without a prominent central bulge. Both Cepheid stars, which vary in brightness in a predictable, periodic way, and type Ia supernovae have been found in this galaxy. Since Cepheids and type Ia supernovae have very distinctive light curves, they can be used to calculate the distance to the object they are found in. The age of the universe can then be estimated based on the distances to galaxies. This is possible because of the expansion of the universe. The farther away a galaxy is, the longer it has had to move away from our point of observation, and so the older it is. Once we know how distance and age correlate, we can convert distance to age, and the farthest galaxies can give us clues about how old the oldest objects in the universe are, thereby putting a lower bound on the age of the universe itself. Due to the presence of the Cepheid stars and type Ia supernovae, the distance to NGC 3370 could be measured quite accurately. So NGC 3370 would be a good galaxy to use in a study that was trying to find the relationship between distance and age, and in fact was used in such a study in 1994. You can also see many background galaxies in this image.
Image 4: The Whirlpool Galaxy
The Whirlpool Galaxy is a spiral galaxy about 23 million light-years away from Earth. We observe it almost directly face on, which gives us a magnificent view of its spiral structure. The smaller galaxy on the right side of the image is NGC 5195. The Whirlpool Galaxy is gravitationally interacting with NGC 5195, giving astronomers a chance to study galaxy interactions. The pink spots along the spiral arms are star-forming regions. The blue spots are star clusters. The other material in the arms is mostly dust and hydrogen gas. NGC 5195 is believed to help increase the number of star-forming regions. As NGC 5195 passes behind the Whirlpool Galaxy, NGC 5195's gravity ripples and compresses the gas in the spirals of the Whirlpool Galaxy. Once the gas is compressed enough, it starts to collapse under its own gravity and star-forming regions begin to form.
The only problem with knowing the identities and some of properties of the objects from the Linux Cosmos wallpaper is now every time somebody is near me and I'm working with Linux, he has to hear all about the image on my desktop. And 30 minutes later it changes to a new slide, and he has to listen to a new explanation all over again. On the other hand, I'm not so sure that a short, spontaneous astronomy lesson should be considered a problem. Either way, it's nice to be able see one of the images and no longer have to think "Oh, that's pretty, but what is it?" Now I know.
I have a Windows/Linux dual-partition for my computer and every time I log-in to the Linux partition I am greeted by one of nine or so majestic astronomy pictures. The "Cosmos" desktop background is a slide show of various astronomical phenomena and it periodically changes from image to image while you work. I've had this background for a few years now, but I only recently wondered about the identities of the objects I was looking at. Some are easy to identify, such as Earth and Jupiter, but some were a mystery. I looked into the details of a few of the images. For some I could only find what type of object it was and not the name of the object, but the information that I found on the others I will share below. All the images are from http://hqwalls.blogspot.com/2010/07/cosmos-wallpapers-2560x1600.html. The majority of the information was gathered from http://www.spacetelescope.org/, http://www.universetoday.com/, and http://apod.nasa.gov/apod/.
Image 1: The Helix Nebula
The Helix Nebula is a planetary nebula approximately 700 light-years away, making it one of the closest planetary nebulae to Earth. The star at the center of the nebula is very old (and by "very old" I mean older than the sun and already past the red giant stage), and has already blown away its original outer-most gas and dust. Eventually, the star will become a white dwarf and the gas we can see now will have also been blown away. The structure of the Helix Nebula is interesting because there are "knots" in the shells of gas and dust. These knots are dense, intense patches of glowing gas. They have comet-like tails that point away from the star at the center of the nebula. Knots of nebulosity were first discovered in the Helix Nebula and have been found in other nebulae since then. The Helix Nebula got its name because the angle from which we view the nebula makes it look as if we are looking down the center of a helix.
Image 2: The Sombrero Galaxy
The Sombrero Galaxy is an unbarred spiral galaxy about 29 million light-years away from Earth. It has an unusually large central bulge and an extraordinarily well-defined dust lane. These characteristics, along with the fact that we view it edge on, make it look a bit like a sombrero. The ring contains mostly hydrogen gas and dust, and most of the stellar formation within the Sombrero Galaxy happens there. The Sombrero Galaxy also has one of the highest instances of globular clusters and one of the most massive black holes at its center. The black hole is estimated to have a mass of at least one billion solar masses. The galaxy cannot be seen with the naked eye, but it can be observed using only a 4-inch telescope.
Image 3: NGC 3370
NGC 3370 is also known as the Silverado Galaxy. It is a spiral galaxy about 98 million light-years away from Earth. It has well-defined spirals without a prominent central bulge. Both Cepheid stars, which vary in brightness in a predictable, periodic way, and type Ia supernovae have been found in this galaxy. Since Cepheids and type Ia supernovae have very distinctive light curves, they can be used to calculate the distance to the object they are found in. The age of the universe can then be estimated based on the distances to galaxies. This is possible because of the expansion of the universe. The farther away a galaxy is, the longer it has had to move away from our point of observation, and so the older it is. Once we know how distance and age correlate, we can convert distance to age, and the farthest galaxies can give us clues about how old the oldest objects in the universe are, thereby putting a lower bound on the age of the universe itself. Due to the presence of the Cepheid stars and type Ia supernovae, the distance to NGC 3370 could be measured quite accurately. So NGC 3370 would be a good galaxy to use in a study that was trying to find the relationship between distance and age, and in fact was used in such a study in 1994. You can also see many background galaxies in this image.
Image 4: The Whirlpool Galaxy
The Whirlpool Galaxy is a spiral galaxy about 23 million light-years away from Earth. We observe it almost directly face on, which gives us a magnificent view of its spiral structure. The smaller galaxy on the right side of the image is NGC 5195. The Whirlpool Galaxy is gravitationally interacting with NGC 5195, giving astronomers a chance to study galaxy interactions. The pink spots along the spiral arms are star-forming regions. The blue spots are star clusters. The other material in the arms is mostly dust and hydrogen gas. NGC 5195 is believed to help increase the number of star-forming regions. As NGC 5195 passes behind the Whirlpool Galaxy, NGC 5195's gravity ripples and compresses the gas in the spirals of the Whirlpool Galaxy. Once the gas is compressed enough, it starts to collapse under its own gravity and star-forming regions begin to form.
The only problem with knowing the identities and some of properties of the objects from the Linux Cosmos wallpaper is now every time somebody is near me and I'm working with Linux, he has to hear all about the image on my desktop. And 30 minutes later it changes to a new slide, and he has to listen to a new explanation all over again. On the other hand, I'm not so sure that a short, spontaneous astronomy lesson should be considered a problem. Either way, it's nice to be able see one of the images and no longer have to think "Oh, that's pretty, but what is it?" Now I know.
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