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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.

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School Teachers Aid in the Search for Killer Asteroids July 29, 2009

Posted by jcconwell in Asteroids, Astronomy.
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My graduate class in astronomy for science teachers just completed its summer course.

Teachers learning the ins and outs of asteroid hunting

Teachers learning the ins and outs of asteroid hunting

One of the last thing we do is to have some outside speakers come in. On Monday, Bob Holmes head of the Astronomical Research Institute based here in Charleston, Illinois, spoke to the students about one of his NASA projects that he involved with. Searching for NEO’s (Near Earth Objects)

bd81 asteroid discovered

bd81 asteroid discovered

ARI’s telescopes can take more than 1000 photos a night, while hunting for objects that can cross Earth’s orbit, like the movie above. So high school teachers and their students are needed to to go through and hunt for objects that may hit us. The software is free, and if a new object is found,  the student get credit and published in the minor planet circular at Harvard University. For more information, if you, and your students might be interested in this search contact ARI: http://ari.home.mchsi.com/contact_astro_research.htm

or

INTERNATIONAL ASTRONOMICAL SEARCH COLLABORATION

http://iasc.hsutx.edu/index.htm

And for information about the software used Astrometrica:

http://iasc.hsutx.edu/index_files/Page389.htm

Hubble back just in time for Jupiter July 26, 2009

Posted by jcconwell in Astronomy, planets.
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The Hubble space telescope took time out from calibration to snap the clearest photo of the recent impact on Jupiter.

Hubble Photo of Impact on Jupiter

Hubble Photo of Impact on Jupiter

Scientists used the telescope Thursday to capture what they call the “sharpest visible-light picture” so far of the expanding gash. An amateur stargazer in Australia spotted the impression last Sunday. If you are interested in viewing the dark spot yourself, look to the article at “Universe Today”, which gives the times of viewing for the next few days: http://www.universetoday.com/2009/07/24/viewing-the-jupiter-impact-with-your-telescope/

Are we still looking for other worlds? July 25, 2009

Posted by schsscience in Astronomy, planets.
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What ever happened to extrasolar planets?  They used to make the news.  The search for these distant worlds, however, is as fervent as ever.  As better technology and new techniques have been developed, finding them has become commonplace.  To date, the known number of exoplanets, as they are commonly known, has increased to over 350.  But what are exoplanets, exactly?  How are they detected? And why are we looking for them?

The term extrasolar planet refers to any planet orbiting a star other than our sun.  Though their presence had been predicted for hundreds of years, the first one wasn’t found until 1992.  We didn’t have the technology to detect them.  After all, compared to its parent star, even a Jupiter-sized planet is very small and dim.  Furthermore, most of these planets orbit close to their parent star, making it even harder to distinguish them.  Thus far most exoplanets found have been very large, multiple times larger than Jupiter.

Astronomers use several methods to search for and identify exoplanets.  Each method has its advantages and disadvantages.  Depending on the distance, the size, or the orientation of a planet’s orbital plane one method may be more effective than another.  Sometimes more that one method can be used on the same planet giving a more complete picture of what the planet may be like.

The most successful method for detecting exoplanets is the radial-velocity or Doppler shift method.  In this method, the presence of a planet is detected by measuring tiny changes in the frequency of the star’s light.  As a planet orbits a star it causes it to wobble very slightly about the system’s center of mass (see image below).  As the star is pulled away from us its spectrum is shifted towards the red end, and as it is pulled towards us it is shifted to the blue end.  This method only works if the planet’s orbital plane is aligned parallel to the Earth’s orbit.  It is not possible to determine the size of these planets using this method.

Red/Blue Shift Caused by Star's Wobble

Click here to see an animation of the wobble.

The first planets were detected using pulsar timing.  Pulsars are neutron stars that rotate very quickly.  As they rotate, they emit flashes of radio waves at very regular intervals like a light-house.  These flashes can be detected and timed.  A planet orbiting a pulsar will cause very slight variations in the timing of these flashes which can be used to detect it.

When a planet’s orbital plane is perpendicular to Earth’s, another method known as astrometry works well to detect the star’s tiny wobble.   In this method the star’s position is precisely measured against the background stars.  Tiny shifts in its position indicate the tug of a planet orbiting it.  Astronomers are hopeful that this method will lead to the detection of smaller Earth-sized planets.

In transit photometry the dimming of a star is detected as a planet crosses in front of it.  Using this method, astronomers can measure the size of a planet.  Even more intriguing is that astronomers can sometimes determine the absorption spectrum of a planet’s atmosphere as the star’s light passes through it.  This allows them to determine the composition of the planet’s atmosphere.

As the planet passes in front of the star, it's dims slightly.

For the average person the most exciting method of observation is direct imaging. Unfortunately this requires a rare set of conditions.  The method works best when the planet’s orbital plane is perpendicular to Earth’s, the planet is bright and its star dim, and the star is relatively close to Earth.  So far only a few planets have been found using this method.

In November of 2008 the Hubble telescope imaged a planet orbiting the star Fomalhaut.  The planet is estimated to be about 2 times the size of Jupiter and is extraordinarily bright.  Since then several others have been seen.

A trio of planets (faint dots indicated with arrows) orbits the young, massive star HR 8799, some 130 light-years from Earth. Discovered using the Hawaii Keck telescope. Credit: Marois, National Research Council/Canada, Keck

In recent months, astronomers have been able to identify planets thought to be more Earth-like than the gas giants they have been finding so far.  These large “super-Earths” lack the dense atmosphere of the gas giants and have a dense rocky composition.  So far around 30 such planets have been found, but scientists believe that they probably far outnumber the gas giants.

There are some exciting implications of these recent finds.  If a rocky planet orbits a main sequence star like our sun in the so-called “Goldilocks zone, it is possible that it could support life. In the near future, Astronomers hope to analyze the atmospheres of these super-Earths using new telescopes such as the James Webb Telescope, scheduled for launch in 2013.  If they can find signs of carbon dioxide and water, it could mean that the planet may support life.  On the other hand, if they find oxygen and methane, it may indicate that life already exists there!

Top 10 Ways the Universe Could Kill Us! July 24, 2009

Posted by kfarley in Asteroid, Astronomy, Cosmology.
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Asteroid Impact

Asteroids and other near-Earth objects (NEOs) come near the Earth more frequently than one would guess. Question: Why don’t we ever hear of these objects hitting the Earth? Answer: Because they don’t. More often than not our atmosphere causes great friction on these solar bodies causing them to burn up. This happens before the asteroids can go through our atmosphere and hit the Earth. Our atmosphere can be a good friend to us – protecting us from solar debris that could potentially hit Earth and end civilization as we know it. If an asteroid were to make it through our atmosphere it becomes classified as a meteor. It is theorized that a large meteor hit the Earth about 65 million years ago wiping out the dinosaurs. According to NASA, a meteor about 1/5 that size will hit the Earth about once or twice every million years. If Earth did get hit by an asteroid of that caliber we would most likely not survive. I haven’t heard of an asteroid that size hitting the Earth in quite some time, maybe we’re overdue. With ≈6.7 billion people in the world your chance of seeing the Earth hit by that size meteor is…well, you do the math. To learn more information on NEOs check out NASA’s FAQs.

Illustration of an asteroid that could have wiped out the dinosaurs.

Illustration of an asteroid that could have wiped out the dinosaurs.

Solar Flare

A solar flare is a huge explosion of energy in the Sun’s atmosphere. Think of it like a giant spike of light and heat that suddenly rises off the surface of the Sun. The rays emitted (mainly X-rays and UV rays) from this explosion are strong enough to disrupt radio communication on Earth! The flares can influence the surface of Earth by having an effect on our weather. Just outside our atmosphere, the flares can present radiation hazards to spacecraft and astronauts. The solar flares can also produce streams of highly energetic particles in our atmosphere. These highly energetic particles help in the production of the beautiful aurora borealis! On the other hand, the radiation from solar flares also pose incredible complications that could arise during manned missions to Mars, the Moon, or other space travel. Satellites’ orbital paths can also be disrupted by the solar flares. Kind of a catch-22, amazing Northern lights produced but also possible space travel limit. Hmm…

Aurora borealis co-created by solar flares.

Aurora borealis co-created by solar flares.

Supernova

Ever had someone shine a flashlight in your eyes? Not very nice, huh? Think of shining a light in your eyes a billion times brighter! A supernova is just that – an exploding star billions of times brighter that our Sun. After the core of a star collapses it emits great energy as a flash of growing intensity before fading back out of sight. If a supernova was close enough and aimed toward our solar system, it could wipe out our atmosphere. Our planet would overheat from UV rays causing mass extinction. It’s messy too. The supernova will throw large clouds of dust and gas into space that could exceed 10 times the mass of our Sun. We should be thankful for supernovae in a way. It is hypothesized supernovae created the heavier elements such as gold, iron, and uranium found here on Earth.

Supernova.

Supernova.

Gamma Ray Burst

Gamma ray bursts (GRBs) are flashes of gamma rays that last from fractions of a second to almost an hour. They normally last a few seconds and usually come from outside our galaxy. They are the most luminous (electromagnetic) events that occur in the universe. GRBs often have an afterglow affect as longer wavelengths travel from the blast. The blast from a GRB in our galaxy would definitely cause mass extinction from the intense rays that would encompass our planet. It is hypothesized such an event caused the mass planetary extinction on Earth about 444 million years ago. A GRB depleted the ozone layer leaving our planet helpless to direct UV rays that heated and kill organisms until food chains were depleted.

P.S. Gamma rays gave the Hulk his powers (I think that is fictional though).

Illustration of a gamma ray burst hitting a planet like Earth.

Illustration of a gamma ray burst hitting a planet like Earth.

Black hole

Black holes are areas in space in which the gravitational field is so incredible that nothing can escape its pull. Not even light can be reflected from this object, hence its name. It is virtually impossible to escape a black hole once its immense gravitational pull has a hold of you. The point of no return at a black hole is called the horizon. It is an area just outside a black hole where the gravitational pull begins. Once you hit the horizon of a black hole your fate is sealed and escape from the black hole is futile. Knowing not even light can escape the pull of the black hole, you would have to travel faster than the speed of light to escape. If you were to see an object being pulled into a black hole (assuming the object can still reflect light), it would become extremely distorted. The gravitational pull is so intense, the part of the object entering the black hole first would stretch out of normal proportions. For example, if you were floating through space with your arms in front of you (Superman-style) and began to be sucked into a black hole, your arms would stretch out incredibly long before the rest of your body. Black holes are also very massive. They can range anywhere from 10 times to a million times the mass of our Sun. Currently, there are no known black holes in our galaxy. This known with the fact our space travel is limited to our Moon, you are probably safe from a black hole fate.

Illustration of what a black hole over the Milky Way might look like.

Illustration of what a black hole over the Milky Way might look like.

Death of Sun

The Sun goes through different stages during its life cycle. It’s about halfway through the “main sequence” before it goes into a different star phase. The Sun will most likely turn into a Red Giant star peaking at its highest luminosity. The Sun will then start to burn out as it turns into a small dwarf star. The Sun won’t turn into a Red Giant for another 5 billion years or so. A more immediate problem, as the Sun moves toward the next stage it becomes gradually warmer. It will get really hot. Life on Earth most likely won’t make it to the Red Giant stage. The Earth will warm up to the point where life will not be sustainable. The Sun has slowly been warming up ever since its birth. The Sun used to not be as hot, one of the reasons life didn’t always exist on the Earth. Just as the warmth of the Sun allowed life on Earth, it will also take it away.

The life cycle of our Sun.

The life cycle of our Sun.

Heat Death of Universe

The heat death of the universe occurs as all the stars and other universal matter continues to expand and uses up its energy or “burns out.” It’s like letting a candle burn and not blowing it out. Eventually it’s going to use up the wax and wick until it can’t burn anymore. The universe runs on “free” energy that is not endless. At some point the fuel for the universe will run out cutting of the energy for the cosmic bodies that give us life (namely our Sun). This probably won’t be happening anytime soon. It’s estimated the energy will run out after black holes vanish in about 10100 years (according to Hawking’s radiation). That’s one big candle!

The flame of life.

The flame of life.

The Big Rip

Just like how it sounds, all matter of the universe will be ripped apart.  We’ve all heard that the universe is expanding.  What would happen if the expansion increased at an accelerated rate?  If the universe expanded much faster than it is now, all the galaxies, stars, planets, dust, etc. would be ripped apart!  Think of it like a twizzlers.  If you pull slowly you can stretch out the twizzlers pretty far.  If you stretch too fast the twizzlers will just snap in half.  This is a possibility for our universe.  The hands pulling on our universe is something called dark energy.  Dark energy is a hypothetical energy that saturates all our universe.  It is theorized it helps our universe expand – at an accelerating pace.  This means the expansion is moving at a faster and faster rate as time goes by.  Eventually the universe will reach that point where it is pulling to fast, ripping apart everything.  What happens when everything is ripped apart and away from each other?  No one knows.

The Big Rip.

The Big Rip.

Cannibal Galaxies

Cannibal galaxies occur when a smaller galaxy is eaten by a larger galaxy! Natural selection at its best. Galaxies are gravitationally bound collections of stars, stellar bodies such as planets, space dust, and other objects. You are probably most familiar with the Milky Way galaxy (you should know this one, we live in it). Scientists can now detect our Milky Way galaxy is currently tearing apart and engulfing the Sagittarius galaxy as you read this! Closer to home than you might have expected. I guess we are saved this time but poor little Sagittarius galaxy…

Larger galaxy engulfing a smaller galaxy. (Swinburne)

Larger galaxy engulfing a smaller galaxy. (Swinburne)

Pulsar

When a star collapses on itself a neutron star is left behind. If we were to survive this giant explosion, we would have a new problem of pulsars to deal with. A pulsar is a neutron star that emits rays of electromagnetic radiation. Electromagnetic radiation is rays that vary depending on their frequency and wavelength. Some rays provide us with the visible light we use every day. Other rays below or above the spectra can be very harmful to us. For instance, radio waves (beyond red in the visible spectra) can vibrate the cells in your body heating them up to a deadly temperature while gamma rays (beyond blue in the visible spectra) can stop the function of the cells in your body. Oddly enough, both radio waves and gamma rays are used to treat different ailments.

The Vela Pulsar. NASA pic.

The Vela Pulsar. NASA pic.

Earth’s Deadliest Nemesis: The Gamma Ray Burst? July 24, 2009

Posted by heisman50 in Astronomy, Gamma Ray Bursts.
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Maybe not right now, nor maybe not even tomorrow, but it could happen. Life on Earth could be in serious jeopardy. And the enemy is not anyone or anything on this planet, but rather the workings of an enemy 5000 to 8000 light years away. The sad thing is, there may be no way to see it coming, and most certainly nothing we can do about it. There are over 300,000 gamma ray bursts a year so there is a chance that one could be directed straight towards Earth.

When an enormous star detonates into a supernova, radioactive nuclei are shot out into interstellar space releasing countless photons. This radiation tends to be very low wavelength, high frequency in the gamma ray portion of the electromagnetic spectrum.

To quantify the amount of energy we can use Plank’s Law. According to Plank’s law the energy of a photon can be expressed by the following equation:

plank's law
E = energy of a photon
h = Plank’s constant = 6.625 x 10-34 J*s or 4.135 x 10-15 eV*s
λ = wavelength of light

Using this equation, the photons of gamma rays will have the highest energy of all as their wavelength is exceptionally small. Thus, a gamma ray photon would produce the largest amount of energy of any type of electromagnetic radiation in the electromagnetic spectrum. While the release of one photon may seem small, the radiation from a supernova directed towards Earth may carry the energy of seemingly countless photons. The result is a tremendously high amount of energy bound for the Earth. To put the amount of energy into perspective, Dr. Edo Berger, an astrophysicist at Harvard University, the energy released by a gamma ray burst is equivalent to powering the world for 1027 years.[1]

The effects could be substantial. One scenario popularized by the History Channel’s series Mega Disasters depicts the gamma radiation attacking and destroying the ozone layer of the Earth while releasing a smog of nitrogen oxide, nitrogen dioxide, and dinitrogen trioxide compounds that effectively block the Sun, break down ozone and cause acid rain. Without the Sun’s rays, a global cooling would exist and plant life could not continue, abruptly disrupting the food chain for all on Earth. According to Dr. Derek Fox, an astrophysicist at Penn State University, a gamma ray burst could irradiate the Earth to the equivalence of 100,000 atom bombs exploding just outside of the Earth’s atmosphere.[2]

So how likely is the threat? The biggest possibility comes from WR104 that sits about 8000 light-years away. If directed perfectly at Earth, the effect on life could be devastating and the fate of the planet may be in jeopardy. But don’t get all worked up just yet. According to David Thompson, a NASA astrophysicist and deputy project director on the Fermi Gamma-ray Space Telescope, the likelihood of a gamma ray burst from WR104 is equivalent to, “the danger I might face if I found a polar bear in my closet in Bowie, Maryland. It could happen, but it is so unlikely that it is not worth worrying about.”[3]

1.http://www.astro.caltech.edu/~ejb/faq.html
2. History Channel. MEGA DISASTERS: GAMMA RAY BURST ©2007
3. http://blogs.discovermagazine.com/badastronomy/2008/03/03/wr-104-a-nearby-gamma-ray-burst/

Orion July 23, 2009

Posted by heritageag in Astronomy.
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Orion as depicted in Urania's Mirrow, a set of constellation cards published in London in 1825.

Orion as depicted in Urania's Mirrow, a set of constellation cards published in London in 1825.

Lauren Hopper has her blog at:   http://heritageag.wordpress.com/

This great hunter in the sky has been my favorite constellation for as long as I can remember.  Any clear dark night available I try to find those three diamonds in his belt.

The constellation Orion is one of the largest, most obvious and most recognizable constellations in the sky.  Orion includes a group of stars known as the ‘belt’ of Orion. These three bright stars in a row (aka. The Three Kings) make up the line of his belt. Surrounding the belt are four bright stars, which are considered to represent the outline of Orion’s body. Descending from the belt is a smaller line of stars that make up the hunter’s sword.  One of these stars is not exactly a star but the Orion Nebula.

The surrounding constellations are often shown to be related to Orion.  He is shown standing next to the river Eridanus.  He is accompanied by his two hunting dogs Canis Major and Canis Minor.  Orion is also shown fighting Taurus the bull. He is also often times illustrated hunting

Orion has often times been a useful tool to find other stars and constellations.  If you extend the line of Orion’s belt out southeastward you can find the star Sirius. If you extend his belt out northwestward you will find the star Aldebaran. If you extend a line eastward across his two shoulders you will find the star Procyon.  You can also extend a line through Rigel and Betelgeuse and find the stars Castor and Pollux.

Illustration showing how to use Orion to find neighbor stars.

Illustration showing how to use Orion to find neighbor stars.

Some other interesting facts about the constellation Orion are: there is a meteor shower that reaches its peak around Oct. 21 each year. It’s named the Orionid Meteor Shower.  It has been know that you can see at least 20 meteors per hour at times.

Orionids Meteor Shower

Orionids Meteor Shower

The constellation Orion is over 1,000 light-years deep.  It’s nearest star Rigel being 900 light-years away and its farthest Kappa which is around 2,100 light years away. The constellation is over 700 light-years wide.  You can look for Orion high in the SE in the January early evenings or just after twilight on the meridian in February.  In March it will still be noticeable in the early evenings in the SW.

Information from:

http://en.wikipedia.org/wiki/Orion_(constellation)

Craig Crossen & Wil Tirion “Binocular” Astronomy 2nd Edition”

www.nightskyhunter.com

Total Solar Eclipse on July 22, 2009 July 22, 2009

Posted by misskblog in Astronomy.
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TOTAL SOLAR ECLIPSE COMING UP ON JULY 22, 2009

On Wednesday, July 22nd, a total solar eclipse will take place.  The thought of this eclipse takes me back to my years in junior high when our teacher prepared us for an upcoming solar eclipse.  It was to take place during a school day in either around 1993   and everyone was excited about this fantastic astronomical event.  We made pinhole eclipse viewers using shoe boxes and black paper and every student got a pair of solar glasses to wear so that we could lie on our backs and stare up at the sky waiting for just the right moment.  I will never forget the hush that came over the area as the moon crossed in front of the Sun.  Everything on the playground and school yard went very dim and things got very quiet.  Birds even stopped chirping, confused by the lack of daylight.  What an amazing and teachable moment!

The upcoming solar eclipse will not, however, be able to be seen from North America.  It will take place in a narrow swath that goes across half the Earth.  At sunrise on July 22, 2009, the moon’s umbra—the cone-shaped part of the moon’s shadow—will fall on India’s Gulf of Khambhat.  The path of the moon’s umbral shadow will then cross through Nepal, Bangladesh, Bhutan, Myanmar and China. The cities in China that will see the total eclipse of the Sun are as follows: Beijing, Wulumuqi, Changchun, Xining, Xi’an, Shanghai, Wuhan, Chongqing, Hong Kong, and Kunming.  In Nepal the sun will be totally eclipsed in Biratnagar.  In Taiwan, there will be a partial eclipse of the Sun in Taipei. And in Mongolia, it will be seen from Ulaanbaatar.  Japan has partially eclipsed sun in Sapporo, Tokyo and Fukuoka.  After leaving mainland Asia, the path crosses Japan’s Ryukyu Islands and curves southeast through the Pacific Ocean.  A partial eclipse will also be seen within the much broader path of the Moon’s penumbral shadow, which includes most of eastern Asia, Indonesia, and the Pacific Ocean.

eclipse2

This solar eclipse is the longest total solar eclipse that will occur in the twenty-first century, and will not be surpassed in duration until June 13, 2132.  Totality will last for up to 6 minutes and 39 seconds, with the maximum eclipse occurring in the ocean at 02:35:21 UTC about 100 km south of the Bonin Islands, southeast of Japan. The umbra travels along a track that is about 15,150km (about 9414 miles) long and covers 0.71 percent of the earth’s surface area over a course of three hours and 25 minutes.  The North Iwo Jima island is the landmass with totality time closest to maximum.

The Times of India publication was urging its readers to get out and enjoy the eclipse, as it will be the last one visible for quite some time.  The next total solar eclipse that can be viewed from India will occur on June 3, 2114.  As a teacher now myself I would love the opportunity to share this awe-inspiring display with my students.  That will be some time from now, as the next total eclipse that can be seen from North America is predicted to be on August 21, 2017.  I guess that will give me plenty of time to prepare my students!

Aurora Borealis – Best Light Show on Earth July 21, 2009

Posted by chemfan in Astronomy, Solar and Space weather.
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Sergey Zinovichik has his blog at:       http://chemfan.wordpress.com/

Red and Green Aurora

Aurora Borealis or commonly named The Northern Lights is a natural display of lights in the North Pole regions of our globe.  The lights appear as flowing streams of color in the sky taking different shapes and contours and often look like a multicolored curtain coming down from outer space.

The light show comes to us courtesy of our Sun.  Electrically charged particles produced on the Sun are ejected in all directions and a great amount of them head toward Earth.  As these particles (called solar wind) encounter the Earth’s outer regions, the magnetic field of the Earth begins to interact with the particles.

What results is a change in energy and direction of the particles: they head along magnetic field lines toward the poles of Earth.  Just like a bar magnet has its field lines returning at the opposite ends so the Earth’s magnetic lines come together around the poles.  This is why the aurora borealis is brightest and most easily seen in the northern regions of our planet.

Image taken from Wikipedia.org

Image taken from Wikipedia.org

The colors that we see in the aurora get produced from the collision of solar wind with atoms and molecules of our atmosphere.  Every atom and molecule has around them orbiting electrons.  The electrons sit in different energy levels with the highest energy electrons being furthest from the nucleus.

Although the orbits of electrons around the atom are complicated we can represent  their arrangement with a simple picture:

Electron orbits

We can see the first important aspect of orbiting electrons: They can only have certain energies analogous to planets orbiting at certain distances from the Sun.

When a fast moving solar wind particle collides with an atom the electrons in the atom “jump up” to a higher energy level.  The electrons in this excited state are usually unstable and will eventually fall back down releasing the energy they absorbed.  The way electrons release energy is in the form of electromagnetic radiation or what we would call light.

Image taken from HowStuffWorks.com

Image taken from HowStuffWorks.com

The type of light emitted depends on the type of atom that was excited.  This is because an oxygen atom’s energy levels differ somewhat from a nitrogen or helium atom.  The energy released corresponds to a certain visible color and the color corresponds to the energy that was lost as the electron returned to its previous state.  The colors we see in aurorae are regular because the energy levels in an atom are the same and because electrons can assume only certain quantized energies.

In some aurora red and green colors are prevalent.  This is characteristic of oxygen atoms being excited and releasing energy.   Molecular nitrogen can produce blue or violet colors.  Helium in rare occasions can produce orange light.  Compounds of oxygen and nitrogen can produce their own characteristic light.

When a mixture of different colors comes together the aurora we see is colored white just like the visible light from the sun put together from all the colors of the rainbow appears white.

Image Taken from APOD

Image Taken from APOD

The beauty of the Northern Lights can sometimes come down from the polar region and become visible at lower latitudes.  This is due to periods of high solar wind corresponding to unusual activity on the Sun.  In August and September of 1859 The Northern Lights were seen from the Midwestern region of the United State and were very bright.   Worldwide reports of unusual aurora intensity and frequency  that year were confirmed by magnetographs recording high levels of magnetic activity from the Kew observatory in England.

The southern pole of the planet experiences a similar phenomenon called Aurora Australis or Southern Polar lights and this light show is visible only in the southern hemisphere.

If you are fortunate enough to live in a part of the globe that has auroral displays you will probably agree that the light show that nature displays cannot be rivaled by anything humans can create.

Image taken from APOD

Image taken from APOD

New Impact on Jupiter July 21, 2009

Posted by jcconwell in Asteroid, Astronomy, planets.
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Jupiter-impact

Taken from the article by Nancy Atkinson at Universe Today

Amateur astronomer Anthony Wesley from Canberra, Australia captured an image of Jupiter on July 19 showing a possible new impact site. Anthony’s image shows a new dark spot in the South Polar Region of Jupiter, at approximately 216° longitude in System 2. It looks very similar to the impact marks made on Jupiter when comet Shoemaker-Levy 9 crashed into the gas giant in 1994. (But read the Bad Astronomer’s post that the black spot could also be weather.)
UPDATE (7/20): It has been confirmed this is an impact on Jupiter. Mike Salway shared the news Glenn Orton from JPL has imaged the Jupiter black spot with the NASA Infrared Telescope and he has confirmed it’s an impact.