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Astronomy Club Meeting Wednesday! March 1, 2011

Posted by jcconwell in Astronomy, 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.

 

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THE SIZE OF STARS February 22, 2011

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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.

Solar eruption aimed at Earth February 17, 2011

Posted by jcconwell in Astronomy, Solar and Space weather, stars.
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We are coming off the bottom of the 11 year sunspot cycle, so the sun is getting more active. As the internal magnetic field of the sun winds up, the field bursts out of the surface in regions known as sunspots.  Sunspots are cooler regions, hence they look darker, on the solar surface that have large magnetic fields. They can form in groups, and as part of their dynamics, they can release solar flares . Sunspot 1158 is a group of 4 sunspots that just had such a flare. The eruption can be seen in the video above taken by the SDO satillite and the optical image is below.

SOHO image from 2/17/2012

Sunspot 1158 in the lower right (OHO image from 2/17/2012)

Two forms of radiation come from an eruption, the electromagnetic radiation arrives first, just 500 seconds after the eruption. Then come the particles (mostly protons, with some Helium nuclei ) called the solar mass ejection. Since the particles travel much slower it can take up to several days to get to the Earth …and that is only if the spots are aimed at us.

The Chinese have reported some disruption in shortwave radio traffic. Very intense flares can cause damage to some satellites and power grids. This one however should just produce a light show, the aurora for people in more northern latitudes.

The NOAA space weather prediction site has aurora  maps to check if you can see the Northern lights.

The Secrets of Star Birth: A New Podcast Sponsored by EIU Physics September 19, 2010

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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

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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.
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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/

Rare Outburst of the Recurrent Nova U Scorpii Begins January 28, 2010

Posted by jcconwell in Nova, stars, supernova, white dwarf.
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Artists rendition of the recurrent nova RS Oph Credit: David Hardy/PPARC

(From Universe Today): Today, two amateur astronomers from Florida detected a rare outburst of the recurrent nova U Scorpii, which set in motion satellite observations by the Hubble Space Telescope, Swift and Spitzer. The last outburst of U Scorpii occurred in February of 1999. Observers around the planet will now be observing this remarkable system intensely for the next few months trying to unlock the mysteries of white dwarfs, interacting binaries, accretion and the progenitors of Type IA supernovae.

One of the remarkable things about this outburst is it was predicted in advance by Dr. Bradley Schaefer, Louisiana State University, so observers of the American Association of Variable Star Observers (AAVSO) have been closely monitoring the star since last February, waiting to detect the first signs of an eruption. This morning, AAVSO observers, Barbara Harris and Shawn Dvorak sent in notification of the outburst, sending astronomers scrambling to get ‘target of opportunity observations’ from satellites and continuous coverage from ground-based observatories. Time is a critical element, since U Sco is known to reach maximum light and start to fade again in one day.

Movie of Chi Cygni pulsating over 408 days December 21, 2009

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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.

First Spectra of Epsilon Aurigae July 30, 2009

Posted by jcconwell in Astronomy, Epsilon Aurigae, IYA 2009, Observatory, stars.
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I was up last night from 2:30 am to 3:30 am looking at clouds. Fun if you in meteorology, but not astronomy. I was trying to get my second good spectra of Epsilon Aurigae, a mysterious eclipsing binary (see earlier post) . Most of the people looking at this object are doing photometry, measuring the brightness of the star either visually or with a camera (usually a CCD digital camera). Since I have a larger telescope (16″) on a nice permanent equatorial mount, and since the star is bright at 3rd magnitude, I decided to take spectra. Most information about an astronomical object, chemical composition, doppler shifts, temperature, magnetic fields, come from looking at spectra.

Now you may not know that the reason the “arms race” for bigger and bigger scopes began in the early 1900’s  to take spectra. You need telescopes that are big “light buckets”, because the light that the telescope would normally put into one point to make a nice image on a camera has to be spread out. The light is diluted by a prism or diffraction grating into a long strip  of  light to make a spectrum. If it’s a color camera  it would look like smear from a rainbow. Since what use to land on a few pixels of my camera is now landing on several hundred the image is MUCH dimmer. So to take a good spectra you either have to take a much longer exposure, stick to much brighter objects, or get a bigger telescope. Brightness or exposures increase by a factor of 100, or for you astronomy experts about 5 magnitudes in brightness.

Now instruments are stupid (as are theoretical physicists trying to be observational astronomers at 3:00 am in the MORNING), they don’t know how the position of the light in the camera is related to wavelength. So when I take the spectra of a star, I also take a spectra of a Mercury lamp with known spectra lines for calibration. I take both spectra, making sure I don’t change anything with the camera or telescope (like focus). That way I can tell my computer that this pixel means this wavelength (color). As Shown below:

Raw First Spectra of Epsilon Aurigae (9/27/09)

Raw First Spectra of Epsilon Aurigae (9/27/09)

Mercury Spectrum used for calibration

Mercury Spectrum used for calibration

Now you may notice the star’s spectrum has dark lines because it’s an absorption spectra, while the mercury spectrum is a bright line or emission spectra. Once the computer knows what the wavelengths are we can look at a plot of a star’s spectrum, a lot easier to read that the picture. There are other steps, like subtracting out spectral lines from the Earth’s atmosphere, but I thought you’d like to see a preliminary result.

Low resolution preliminary spectra of Epsilon Aurigae

Low resolution preliminary spectra of Epsilon Aurigae

With any luck, clear weather, we’ll be able to take some more spectra in the next few days to see any changes in the spectra as the eclipse stars. That way we hope to learn about the object causing the eclipse.

Formation of the Elements July 20, 2009

Posted by jmegenhardt in 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.

hydrogen

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.

HeliumAtom2

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.

In the Center of Star

More mass in center → More gravity in center

↑                                        ↓

More gravity in center ← More mass in center

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

fusion layers

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:

The Universe Adventure

Questia

Think Space

NASA