Gathering the Wrong Light July 21, 2012
Posted by pjhsscience in Astronomy, Observatory, telescopes.Tags: Astronomy, cosmology, Light Pollution, Observatory, science, space, stars, telescope
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Imagine for a moment, driving at night through the vast and unpopulated expanses of the western deserts of North America. Frequently, some of the most amazing photos of our night sky are taken from locations such as these and for very good reason. The only light visible is that which is being projected from the stars above. Back to yourself in the car now, you are approaching a town, a rather large town. As you get closer the lights from above start to fade as your eyes are drawn toward the glowing city. It’s not that street lamps and stoplights are more of an amazing site than our celestial blanket; it’s just that those lights are quickly becoming the only thing visible. You are experiencing the plague of metropolitan exorbitance, a form of pollution, light pollution.
Light pollution is one of the newest forms of pollution plaguing modern society. Before electric grids the night sky, even in large cities, was still an intriguing sight. As technology evolved and electricity flowed we were able to combat our limited night vision by lighting the night. As the world at night become brighter we covered the sky by uncovering what lies beneath us at night.
Lighting too has evolved throughout time. We are becoming more familiar with the glow of HID, or high intensity discharge lights, while becoming less familiar with the arrangement of the heavens. To get a view of just how encroaching light pollution can be we need only look at the animal kingdom. Lighting areas where light is not naturally present at night is having a major effect on nocturnal animals. Sea turtle hatchlings are often confused by brightly lit beaches and wander away from safe havens. Migration patterns of many species of waterfowl have been altered due to excess lighting. Feeding is a naturally performed at night for nocturnal creatures and feeding patterns have brought unwanted guests to our doorsteps due to light pollution. Lights attract bugs and bugs attract bats.
Astronomers from amateur to professional can all agree that light pollution is a great disturbance. Before even viewing a star astronomers without an enclosure cannot expect to have full dark adaption at night. The tools of astronomy are also plagued by light pollution. For instance, the Mt. Wilson Observatory just outside of Los Angeles is now operating at 11% of its original capacity due to the glowing L.A. night sky. While some stars may be visible in areas of high light pollution galaxies and nebula are greatly dimmed and very difficult to see even with advanced telescopes. New observatories are increasingly being constructed in remote areas in order combat light pollution but remote construction brings higher costs.
Limiting magnitude can be described as the faintest apparent magnitude of a celestial body capable of being detected and dependent upon equipment. Light pollution has a direct and sustained impact on the limiting magnitude in a given area. The limiting magnitude of the human eye under a completely dark sky is somewhere in the range of 7.6-8.0. At the other side of this scale, imagine yourself staring up at the night sky in a brightly lit inner-city setting. The limiting magnitude of your eye has been reduced by fifty percent to 4.0 or less. That comparison is simply applied to eyeball astronomy though, what about astronomers looking to make an observation. Under a dark sky with a 32 centimeter reflecting telescope you might just make some observations at the 18th magnitude. Again, we travel to the city where you set up your scope and find that you will only be making observations at the 13th magnitude.
For those in areas affected by light pollution there are some methods of circumventing it. Astronomers often employ narrow or high-band filters that do not allow light of certain spectral lines to pass through a telescope. The spectral lines targeted are those emitted by common vapor lamps including mercury and sodium. Though a good tool, these filters do limit the use of higher magnification.
If you wish to calculate how much light pollution will affect your astronomy work there is a simple equation to employ. The equation, I=0.01Pd-2.5 where I is the increase in sky glow, P is the population of the targeted city and d is the distance to the center of the city, works very well. This law is commonly referred to as Walker’s Law. Merle Walker proposed this relation after taking measurements of sky glow in several California cities. If you used this calculation and yielded a value of .03 that would mean that at the midway point between the horizon and zenith angle in the direction of the city the current sky would be 3% brighter than the natural background.
It is easy to see that combating light pollution would be of great benefit to society in general, the cost savings alone are staggering. Every year we waste one billion dollars lighting the night sky. Remediation of this problem is not as difficult as one might think; in fact, light pollution is the easiest of all forms of pollution to fix. Replacing old style lamps that radiate light in all directions with lamps that focus light downward is one remediation tactic. Also, we have to realize that lighting is not always necessary and we should take steps to remove lighting where it is not needed. Changing output is another effective method. Extremely bright bulbs are used in a number of lighting applications where they are not needed, limiting energy output not only reduces light pollution but also saves money.
We often light outdoor areas without a thought as to what we are losing. We may gain a little extra ease of night time navigation but we lose light at the same time. The light we lose is the light from nebula, galaxies and stars. This light has traveled a great distance, often many light years. This light has traveled those great distances through the vast reaches of outer space. This light ends its journey within our atmosphere at the hands of our lighting. Light pollution is a problem we have created but a problem that we can fix. Take a moment to look at the heavens through a dark sky and ask yourself if it is worth saving. My answer is yes.
Astronomy Club Meeting Wednesday! March 1, 2011
Posted by jcconwell in Astronomy, stars.Tags: Eastern Illinois University, EIU, stars
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“The Life and Death of Stars.”
by Bob Gacki
March 2 at the Physical Science Building
Room 2153 at 8:00PM.
THE SIZE OF STARS February 22, 2011
Posted by jcconwell in stars.Tags: Size of Stars, stars
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This was posted today on astronomy picture of the day, but it’s so well done I just had to put it here also.
The Secrets of Star Birth: A New Podcast Sponsored by EIU Physics September 19, 2010
Posted by jcconwell in Podcast, stars.Tags: Eastern Illinois University, EIU, Podcast, stars
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http://365daysofastronomy.org/2010/09/18/september-18th-the-secrets-of-star-birth/
Description: Everyone knows where babies come from — but what about baby stars? NASA science writer and blogger Daniel Pendick talks to astrophysicist Jennifer Wiseman about the hidden process of star formation and what we will learn from new observatories and instruments now coming online. The Herschel Space Observatory, for example, recently confirmed that stars form along ragged filaments of collapsing gas cloud, “like beads on a string.” And a massive radio telescope under construction in the Atacama Desert of Chile will give us our first close long at the planet-forming zone of young solar systems.
Bio: Daniel Pendick is a science writer and blogger at Goddard Space Flight Center. His “Geeked On Goddard” blog takes an irreverent insider’s look at science and engineering at Goddard. [If you want more…] His writing has appeared in Astronomy, New Scientist, Earth, Scientific American Presents, and many other science and medical publications and websites.
Jennifer Wiseman, a NASA astrophysicist, currently heads the Laboratory for Exoplanets and Stellar Astrophysics at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, where she is the incoming senior project scientist for the Hubble Space Telescope. From 2003 to 2006, she served as the program scientist for the Hubble at NASA Headquarters in Washington, D.C. She received her bachelor’s degree in physics from MIT and her Ph.D. in Astronomy from Harvard University in 1995. Wiseman discovered periodic comet 114P/Wiseman-Skiff while working as an undergraduate research assistant in 1987.
Extreme Universe: 300 Solar Mass Star Uncovered July 21, 2010
Posted by jcconwell in Extreme Universe, stars.Tags: Extreme Universe, R136, stars
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A team of astronomers led by Paul Crowther, Professor of Astrophysics at the University of Sheffield, has used ESO’s Very Large Telescope (VLT), as well as archival data from the NASA/ESA Hubble Space Telescope, to study two young clusters of stars, NGC 3603 and RMC 136a in detail. NGC 3603 is a cosmic factory where stars form frantically from the nebula’s extended clouds of gas and dust, located 22 000 light-years away from the Sun (eso1005). RMC 136a (more often known as R136) is another cluster of young, massive and hot stars, which is located inside the Tarantula Nebula, in one of our neighbouring galaxies, the Large Magellanic Cloud, 165 000 light-years away (eso0613).
Cluster R136a1 in the Large Magellanic Cloud (Credit ESO
Spectroscopic analyses of hydrogen-rich WN5–6 stars within the young star clusters NGC 3603 and R136 are presented, using archival Hubble Space Telescope and Very Large Telescope spectroscopy, and high spatial resolution near-IR photometry, including Multi- Conjugate Adaptive Optics Demonstrator (MAD) imaging of R136.
Comparisons with stellar models calculated for the main-sequence evolution of 85 – 500 M⊙ accounting for rotation suggest ages of ∼1.5 Myr and initial masses in the range 105 – 170 M⊙ for three systems in NGC 3603, plus 165 – 320 M⊙ for four stars in R136.
Original paper at:
http://www.eso.org/public/archives/releases/sciencepapers/eso1030/eso1030.pdf
Hypervelocity Stars: A New Podcast May 26, 2010
Posted by jcconwell in Astronomy, Podcast, stars.Tags: EIU, Podcast, stars
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We all know about stars in the galaxy – but did you know about some of the fastest stars observed? They are called Hypervelocity Stars. In todays podcast we hear Dr Ross Church, he tells us all what they are, and how they form.
http://365daysofastronomy.org/2010/05/25/may-25th-hypervelocity-stars/
Movie of Chi Cygni pulsating over 408 days December 21, 2009
Posted by jcconwell in stars.Tags: Astronomy, stars
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At a distance of 550 light years away, Chi Cyni is a classic example of a red supergiant, and a variable star. It’s the last stage of a star that has exhausted it supply of Hydrogen in its core and has started to burn Helium. When its diameter is a minimum at 300 million miles, the star’s surface becomes splotchy with bright spots of hot plasma boil to its surface. Then, as it expands, Chi Cygni cools and dims, growing to a diameter of 480 million miles. The new images taken by the now closed IOTA (Infrared Optical Telescope Array) where arranged as a movie of the pulsating star, and shows that the pulsation is not only radial, but comes with inhomogeneities, for example, a giant hotspot that appeared when the star approaches minimum.
The IOTA, was a Michelson stellar interferometer located on Mt. Hopkins in southern Arizona. It operated with three 45 cm collectors that can be located at different stations on each arm of an L-shaped array (15 m X 35 m) and reaches a maximum baseline of 38 m. These IOTA pictures have 15 time the resolution of the Hubble space telescope.
Formation of the Elements July 20, 2009
Posted by jmegenhardt in Astronomy, stars, supernova.Tags: Astronomy, stars, supernova
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James Megenhard has his blog at: http://eastrichlandchemistry.wordpress.com/
Stardust, the Building Block of Everything?
At the birth of our universe the only elements formed in any substantial amount was helium and hydrogen. There were some heavier elements like lithium and beryllium, but these were so minor that they are not even considered. So where did the carbon that all life is made of, the oxygen that all animals need to breathe, or the iron that makes up some of our strongest buildings come from? Hydrogen and helium were formed during the Big Bang, while all of the other elements come from small bangs; the death of stars.
At this time, there are 118 known elements. The simplest element is hydrogen which has only 1 proton and 1 electron.
In order to make hydrogen into another element, protons need to be added; which in turn requires the addition of electrons and neutrons. For example, add a proton, an electron, and two neutrons, and hydrogen has become helium.
Adding a proton, electron, and two neutrons creates lithium. Adding yet another proton, electron, and neutron gives beryllium. By simply adding more protons, electrons, and neutrons, heavier and heavier elements can be formed. It seems reasonable for helium to form, after all, what else is to be done with the neutrons that hydrogen did not use from the Big Bang? The question is, why would more protons, neutron, and electrons come together to make any elements past helium?
The Big Bang roughly states that everything that would one day form the physical universe began as a super hot, super condensed mass. This mass reached a critical point which resulted in the mass exploding. As the material from this mass cooled hydrogen and helium were formed. The hydrogen and helium started pooling together into various gas clouds. These gas clouds were pulled in towards their center, resulting in an increase of mass at center, which created more gravity, which resulted in more hydrogen and helium being pulled in.
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In the Center of Star More mass in center → More gravity in center ↑ ↓ More gravity in center ← More mass in center
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The increasing density of that material resulted in more gas atoms colliding. Each time there was a collision, some of that energy was converted to heat. As more gas was pulled in, there were more collisions resulting in heat increasing, until the temperature reaches around 10 million degrees Kelvin at which point nuclear fusion of hydrogen begins; a star is born. To sum it up…
More gravity in center → More density in center → More collisions in center → More heat in center until nuclear fusion is reached.
Nuclear fusion is the process by which two atoms are combined to form a new atom. When two hydrogen atoms fuse they produces helium and energy. Click here to see how hydrogen becomes helium. It is the energy produced by nuclear fusion that runs a star. Since hydrogen is the simplest element with only a proton and electron, the star begins the process of fusion with it, but as hydrogen is used up and temperature increases, the helium produced can undergo nuclear fusion of its own to produce carbon, oxygen, or neon. Carbon can further fuse to form metals like sodium or magnesium, until nuclear fusion produces iron.
Layers of Fusion in a Star
But why did these elements not form during the Big Bang? The answer is repulsion. Hydrogen is a proton and electron, so its formation is easy since opposites attract. Helium, on the other hand, was a little tougherto form since it needs two positive protons in its center; but like charges repel. The only reason the two protons in helium did not repel away from each other was the pressure within the expanding material from the Big Bang was higher than the repulsive force. But this force was not great enough for more than two protons to come together. The only place in our universe where the force is so great that multiple protons cannot repel from each other is in the heart of a star.
The first 26 elements on the periodic table are formed by stars as they produce energy. The remaining elements are formed from a star dying. When a star dies, the gravitational pull upon that star causes the iron center to collapse. As the center collapses, it reaches a point where the energy build-up causes the collapse to stop and reverse just like a rubber ball will collapse so far before it rebounds. In other words, the center implodes and then explodes out. As the center is blown back outwards, it collides with the outer material surrounding the star; which was also being pulled in to the center. Just like in the birth of a star, this increase of collisions results in even more heat and pressure, which means even more nuclear fusion. The net result being that as the star is being blown apart, further nuclear fusion is occurring resulting in elements even heavier then iron. Not only does the stars death form these heavy elements, but it also causes those elements to be blasted out into space, where they can collect and form other astronomical bodies like planets and asteroids.
External resources:
Solar Flares – What, effects, and the end of the world…? July 14, 2009
Posted by dgsphysics in Astronomy, Solar and Space weather.Tags: Solar, stars
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Steve Zownorega has his blog at: http://dgsphysics.wordpress.com/
What They Are:
Solar flares are an amazing phenomenon in astronomy. Originating from a star, the solar flare has some interesting properties that can make a strong connection to physics as well as make you wonder if we will survive the year of 2012.
A solar flare occurring on the sun. Notice the magnetic field lines that are emerging from the surface.
A solar flare originates within the sun, and is caused by a build up of magnetic energy. When this magnetic energy (stored in a magnetic field) is released, a large amount of plasma is fired from the surface, usually directly over a sun spot. This magnetic field energy is transferred into many different types of energy, one of which is stored in waves (Gamma rays, x-rays, AKA Solar radiation). The amount of this energy that is in a typical solar flare is equivalent to millions of 100-megaton hydrogen bombs going off at the same time. Hard to wrap your head around that? That is about 10^20 joules per second. Still wondering what that is? It would be like having 1,600,000,000,000,000,000 (1.6 quintillion) light bulbs all on at the same time. It seems like a lot of energy, but this solar flare has less energy than the actual amount of energy that the sun creates during its fusion reaction. Just think of a solar flare as a ‘burst’ of this energy.
Effects:
So with all of this energy being released, why doesn’t it effect us on earth? Well thanks to the earths atmosphere, we never get hit directly with this solar radiation. The atmosphere will deflects most of the electromagnetic radiation. However, NASA has major concerns with these solar flares due to the fact that anything outside of the atmosphere such as satellites, space crafts, and even astronauts can be effected by this mass amount of energy.
Satellites and space crafts do have to be worried about a solar flare. These electromagnetic waves (gamma/x-rays) can burn out circuitry causing many systematic failures. This is a very similar situation to an EMP (electromagnetic pulse) that is used in destroying all electronic devices. With that, any electronic device sent out into space has a fail safe system which can be controlled to protect circuitry and draw large currents away from the main components in the device.
On that note, solar flares have a capability of effecting human beings. NASA is currently running a test on an artificial human being with an artificial solar flare. The reason for this test is to understand what type of safety systems we might have to give astronauts if we travel to the Moon or Mars. In this test, they will emulate what a solar flare would do to a person by having short exposures of radiation strikes to a plastic torso. This torso will have all the elements of a human by scientists placing blood in tubes and within organs through out the body. They also want to run a test where they expose this torso to 18 months (about as long as a mars mission might last) of normal radiation from the sun. Results are still pending, keep a watch on this website:
End of the World….?
You might ask yourself after reading this: When am I ever going to be effected by a solar flare? Well it may soon come. Records have indicated that in 1859 a large amount of solar radiation rained down on the earth. Richard Carrington, an English astronomer at this time, was observing sun spots when all of a sudden a bright white flash appeared on a piece of the sun for about 5 minutes. The northern lights, a common solar event that resembles this solar radiation coming down to earth, was the brightest ever recorded during this time in 1859. In 1859 journal entries through out the US (commonly seen only by the north pole) as well as many captains logs across many different oceans have indicated seeing a green glow so luminous that they could read the newspaper at 1:00AM. This is one of the largest northern light activity ever shown, and it was due to this large eruption in the sun.
A image of the northern lights
During this beauty came many other effects. One that came with the 1859 solar activity was technological problems. The telegraph system, the communication device at that time, went out of service for about 14 hours. Also, many measurement devices were also effected by having readings that were off the charts. This is due to the major effect that electromagnetic waves can have on electronic devices, which you can get more information here.
So you might be asking yourself why this concerns you? We live under the umbrella of technology. Power grids, information, communication, and basically any other part of technology could be effected by an event of this magnitude. Satellites alone in space might be greatly damaged, if not destroyed, by the solar energy.We have invested upwards to 60 billion dollars in these satellites – and these are the exact ones that help us communicate, receive and send information, and go about our daily life.
Your next question might be when will this happen again? It is estimated that something of this magnitude happens once every 500 years. An event of half of this magnitude happens once every 50 years. And the last one recorded was in 1960 – so one is on deck to happen within the next few years.
On that note, we can investigate one of the more interesting ideas that has been proposed. The Mayan’s predicted that the world is to end in 2012. One of the predictions is that it would be done by a large amount of solar activity. Now, solar flares are known to originate from sun spots, and currently there are no sun spots. Sun spot activity follows a cycle of 11 years, and we are about to enter the new cycle of sun spots. This may describe why we get these major events as described in 1859, however, I do want to remind everyone that the magnetic field (our atmosphere) of the earth is what protects us from this solar radiation. So to make a claim that we would die from solar radiation would be false.
So to give you a little recap:
I would like to leave you with a thought. Y2K was thought of as being the end of man kind, and this was due to technology. Many people were frightened due to…..yes, if you remember, it was due to a date change. Comparing Y2K to a solar flare, I just want to say that a solar flare (not properly prepared for) can do a lot more damage than a single date change.
The Strange case of Epsilon Aurigae July 12, 2009
Posted by jcconwell in Astronomy, Epsilon Aurigae, IYA 2009, Observatory, stars.Tags: EIU, Epsilon Aurigae, International Year of Astronomy, IYA 2009, Observatory, stars
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When I was a freshman in high school and first developed my interest in Astronomy, two of the more fascinating sources of knowledge I had were the books, “The Universe” by Issac Asimov and the “Guinness book of World Records”.
I still remember running across, in Guinness, the record “the largest star” ….which refers to the diameter of the star, not the mass of the star. Back then the record holder, according to Guinness, was Epsilon Aurigae B, the second member of the binary system (hence the B). The brighter member of the system, Epsilon Aurigae A , is a FO supergiant star visible to the naked eye as a 3.0 magnitude star. Given the temperature from its spectra, and at a distance of about 700 parsecs or 2300 light years, that means its about 100 times the diameter of the Sun and about 50,000 time more luminous.
Epsilon Aurigae in mid July before dawn
You can find the star in the East before dawn, just to the right and slightly above the bright star Capella.
The real interesting object , is not the FO star, but its companion. The system is what astronomers call an eclipsing binary. The system first caught the eye of astronomers when it was noticed that it was a variable star. A star that varied in brightness. In this case, it change between 3.0, and dims to 3.8 magnitude and back again to 3.0, over a cycle of 27.1 years. Now some star are what are called intrinsic variables, meaning the stars pulsate and actually change in brightness, not so here.
Light Curve from the last eclipse
The companion of the FO star happens have its orbit alligned to our eye so it passes in front of the primary star, blocking some of the light … hence eclipsing binary. Now eclipsing binary stars not uncommon, but in this case, the eclipse last for over 2 years! Meaning, whatever the companion is, it’s VERY big.
Notice I’ve stopped calling the companion a star, since it’s also very dark. Much darker than any star it’s size has a right to be. So dark, that astronomers don’t know for sure what it is. The best theory is it’s a large disk of gas and dust surrounding a hidden star that orbits Epsilon Aurigae. If you look at the light curve, above, you’ll notice it brightens in mid-eclipse. Some speculate there might be a double star rotating in the center of the disk that clears out a hole for the light of the main star to shine through.
Much of this is speculations, since 27 years ago astronomers weren’t able to get a good spectra of the object. So one of the projects, at the EIU observatory, are students trying to get spectra before and going into the eclipse. We hope the edges of the disk will be thin enough that we can see a change in the spectra as light starts to dim. You don’t need a big telescope since at 3rd magnitude the object is quite bright. So wish us luck, and if we see something we’ll let you know.
Listen to the PODCAST about Epsilon Aurigae at 365 days of astronomy
For More information on how you can contribute go to web site: citizensky.org
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