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Volcanism on Icy Io July 20, 2012

Posted by epscienceblog in Astronomy, moon, Solar and Space weather.
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Io, the closest moon to Jupiter, has an orange-brown
surface containing sulfur, the light areas are an icy
mix of sulfur and the dark areas highlight volcanic areas. Composite picture from NASA

As we have studied the Universe, one of the main ways that we have learned in the past is by using the Earth as a comparison, using all that we know about our planet as a reference for the other galactic bodies that we explore.  What is amazing now is the shift that is taking place, where we are beginning to use what we learn about other celestial bodies and apply that information to our own planet.  We learn even more about Earth as advances are being made in the exploration of our universe.  One example of how we are applying our knowledge of other bodies is Io.  The new information that is being gained from Io gives clues to the processes that occurred on Earth when it was young.

Io is an icy satellite of Jupiter 628,866,000 km from Earth, far enough from the sun that its surface temperature is 175 K (-143°C or -230°F) and is covered in sulfur dioxide frost.  Io’s yellow tinged crust is not fractured, therefore, it is not thought to have tectonic activity.  Despite these two factors, Io has the most volcanic activity in our solar system, spewing out over 100 times as much lava as all Earth’s volcanoes combined and may have as many as 300 active volcanoes.

Image from New Horizons, highlighting the Tvashtar volcanic plume reaching 300 km above the horizon.
Credit: NASA

The surface of Io is much different than previous expectations had dictated, and contains potential clues to the history of Earth.  When the Voyager spacecraft missions took images of Io in1979, NASA was surprised to see that Io was not full of craters, as had previously been thought.  It was assumed that Io would be cratered much like our moon.  Yet Io hardly had any craters at all, instead it had irregular pits and blotches of color.  When the images were carefully examined, volcanic plumes and lava flows were discovered.  Infrared spectrometry also detected abundant sulfur and sulfur dioxide in the volcanic plumes.

The sulfur on Io’s cold crust is solid, though when heated inside the crust, it explodes much like steam in a geyser on Earth.  The sulfur cools as it is ejected and may fall back down as “snow” on Io’s surface.  The lava flows on Io can range in color from orange to red to black and are found around the active vents.  The Galileo spacecraft monitored volcanic areas in the late 90s and found that the active lava flows of Io were between 1700 to 2000 K (around 1450 to 1750°C, or 2600 to 3150°F).  Earth’s lava temperatures are around 1300 to 1450 K.  The lava on Io is probably ultramafic, containing magnesium and iron that have higher melting points.  Ultramafic lava is found on Earth, but was formed when the Earth was young and the interior was much hotter than today.

A blue-tinged volcanic eruption forcing out rock and sulfurous gas,
taken from the NASA Galileo spacecraft.

The volcanoes on Io are mostly caldera-like, containing  large pools of lava, though some are fissures or cracks where the molten material can flow over the surface.  Loki Patera is a caldera with a diameter of 200 km, which makes it the largest in the solar system.  Some of the volcanoes form fountains, umbrella-shaped flows that spread up and out over large distances.  The Prometheus plume is a volcanic region that has been seen in almost every image taken of Io from 1979 to 1997, suggesting that it has been continually erupting for years.

Jupiter’s four largest moons (from left to right: Io, Europa, Ganymede, Callisto)
with sizes to scale. Credit: NASA

Aside from the similarities, we can also learn from the stark differences between Earth and Io.  While the heat in Earth’s core is mainly due to the radioactive decay of uranium, thorium and potassium, Io’s extreme internal temperature is caused by gravity.  Io is the closest natural satellite to Jupiter and is one of Jupiter’s four largest moons.  Due to the close proximity to Jupiter and the slightly elliptical orbit of Io, the gravitational pull on Io ebbs and flows, creating contraction and expansion on Io’s crust.  The next two moons closest to Io, Europa and Ganymede, also interact gravitationally with Io and increase the forces on Io as they routinely pass by.  The speed of the moon’s orbits are not the same; during the same period of time Ganymede orbits once, Europa orbits twice and Io orbits four times around Jupiter.  The differences in the orbits cause the moons to line up often.  This increases the gravitational pull on Io from both Europa and Ganymede as well as from Jupiter.  This continual pull creates tidal heating causing temperatures that melt the rock within Io and fuels the intense volcanic activity.  The process of squeezing and flexing is similar to how a ball of clay will soften and warm as a person kneads it.  However, the heating of Io is unlike what we have ever experienced on Earth.  The tidal heating on Io adds as much energy as 24 tons of TNT exploding every second.  Io’s surface receives 2.5 watts of power to each square meter, compared to 0.06 watts per square meter on the Earth’s crust from global heating.  The only areas on Earth that are comparable to Io’s average are in Earth’s volcanic areas.


Posted by jcconwell in Astronomy, planets, Solar and Space weather, Sun.
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Come to the Charleston public library to view the transit of Venus. From 4:30pm to 6:00PM TODAY!!


NEW PODCAST UP: Encore, The Magnetosphere August 31, 2011

Posted by jcconwell in Podcast, Solar and Space weather.
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Sponsored by the EIU Physics department.

Description: This is a short non mathematical introduction to some important elements of space plasma physics. Stephen plays the role of a confused student to allow a pedagogical dialog to progress.

Bio: Terry did graduate research in space physics at the University of Iowa

2011 SUMMER SOLSTICE June 21, 2011

Posted by jcconwell in Astronomers, Solar and Space weather.
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Today, June 21, 2001, at 17:16 UTC (12:16 p.m. Central US time), the Earth’s axis will point toward the center of the Sun. Or from an Earth-boundpoint of view old Sol will reach its peak in its northward travels this year. This moment is the summer solstice. Known as “Midsummer” the Summer Solstice in the Northern Hemisphere, Winter in the Southern hemisphere. The origin from  the Latin for sol (sun) and sistere (to stand still). The Sun reaches its most Northerly point, or it is the highest in the sky from the northern hemisphere, creating around this date the longest day and shortest night.  Momentarily standing still before starting its journey South until it reaches its most Southerly point “Winter Solstice”, before repeating the cycle. This is basically how we get our seasons.


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.

Geminid Meteor Shower December 12, 2010

Posted by jcconwell in Astronomy, meteor, Solar and Space weather.
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The Geminid meteor shower, which peaks this year on Dec. 13th and 14th, is the most intense meteor shower of the year. It lasts for days, is rich in fireballs, and can be seen from almost any point on Earth.

The Geminids is the final major meteor shower of the year; it’s also one of the most eye-catching! To observe the Geminids look anywhere from 50 degrees to 60 degrees above the horizon and about 20 degrees away from the constellation Gemini. The Geminids meteor shower can be seen all over the world, but the best viewing opportunities are for those in the Northern Hemisphere (above the equator). Those in the Southern Hemisphere will still have a worthwhile viewing experience.

For the best viewing experience, find an area unobstructed by structures and that is far away from city lights. Using binoculars or telescores is not recommended – you’ll be more likely to miss a hooting star whizzing by. Just gaze the skies with your eyes.

credit: Wally-Pacholka

A Geminid fireball explodes over the Mojave Desert in 2009. Credit: Wally Pacholka / AstroPics.com / TWAN.

Most meteor showers come from comets, which spew ample meteoroids for a night of ‘shooting stars.’ The Geminids are different. The parent is not a comet but a weird rocky object named 3200 Phaethon that sheds very little dusty debris—not nearly enough to explain the Geminids.”Of all the debris streams Earth passes through every year, the Geminids’ is by far the most massive,” says Cooke. “When we add up the amount of dust in the Geminid stream, it outweighs other streams by factors of 5 to 500.”

This makes the Geminids the 900-lb gorilla of meteor showers. Yet 3200 Phaethon is more of a 98-lb weakling.

3200 Phaethon was discovered in 1983 by NASA’s IRAS satellite and promptly classified as an asteroid. What else could it be? It did not have a tail; its orbit intersected the main asteroid belt; and its colors strongly resembled that of other asteroids. Indeed, 3200 Phaethon resembles main belt asteroid Pallas so much, it might be a 5-kilometer chip off that 544 km block.

“If 3200 Phaethon broke apart from asteroid Pallas, as some researchers believe, then Geminid meteoroids might be debris from the breakup,” speculates Cooke. “But that doesn’t agree with other things we know.”

Researchers have looked carefully at the orbits of Geminid meteoroids and concluded that they were ejected from 3200 Phaethon when Phaethon was close to the sun—not when it was out in the asteroid belt breaking up with Pallas. The eccentric orbit of 3200 Phaethon brings it well inside the orbit of Mercury every 1.4 years. The rocky body thus receives a regular blast of solar heating that might boil jets of dust into the Geminid stream.

“We just don’t know,” says Cooke. “Every new thing we learn about the Geminids seems to deepen the mystery.”

This month Earth will pass through the Geminid debris stream, producing as many as 120 meteors per hour over dark-sky sites. The best time to look is probably between local midnight and sunrise on Tuesday, Dec. 14th, when the Moon is low and the constellation Gemini is high overhead, spitting bright Geminids across a sparkling starry sky.

Bundle up, go outside, and savor the mystery.

Credit: NASA Science, Dr. T. Phillips

Sunspot Group 1123 Erupts November 13, 2010

Posted by jcconwell in Astronomy, Solar and Space weather.
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Sunspot 1123 eruption; Credit NASA/SDO Click for animation

Coronagraph images on the morning of November 12 from the Solar and Heliospheric Observatory (SOHO) and NASA’s twin STEREO spacecraft show a weak mass ejection emerging from the sunspots 1123 heading off in a direction just south of the sun-Earth line. The coronal mass ejection is expected to graze the Earth’s magnetic field sometime on Nov. 14th or 15th. High altitude observers may expect a nice aurora show those days.

As the solar cycle matures, we may expect an increase of this type of activity over the next few years

First Sunspot Photo! March 16, 2010

Posted by jcconwell in Observatory, Solar and Space weather.
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It’s spring break at EIU and today I finally  installed the full aperture solar filter, which cuts down the light by a factor of 100,000 on the 16″ telescope. Until 2010 there were no sunspots to see;  then there were no clear skies, and no time with the semester beginning. But with spring break I had some fun. Good news… I get to do this at noon, NOT at 3:00 in the morning. Bad news… focusing can take a while since I did not have some nice bright pinpoint stars. You have to use a blue filter and .12 second exposure (the fastest the ST-8 camera will do), or else you overexpose the picture. Picture taken at F-10 (4000mm focal length)

First sunspot photo through the 16" scope

NASA Launches Solar Dynamics Observatory February 11, 2010

Posted by jcconwell in satellites, Solar and Space weather.
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NASA has launched the most advanced solar observatory ever built.

Credit: NASA

An unmanned rocket lifted off Thursday with the Solar Dynamics Observatory. The  mission goal is to shed light on Earth’s star. Scientists want to better understand the violent solar activity that influences life on Earth. This space weather can disrupt communications, knock out power and disable satellites.

The Atlas V rocket carrying the Solar Dynamics Observatory lifted off from Cape Canaveral, Florida, at 10:23 a.m. ET Thursday. NASA had delayed the launch three times Wednesday because of windy conditions.

SDO: The Solar Dynamics Observatory is the first mission to be launched for NASA’s Living With a Star (LWS) Program, a program designed to understand the causes of solar variability and its impacts on Earth. SDO is designed to help us understand the Sun’s influence on Earth and Near-Earth space by studying the solar atmosphere on small scales of space and time and in many wavelengths simultaneously.

SDO’s goal is to understand, in order to predict, the solar variations that influence life and technological systems (like satellites and power grids)on Earth. Measurements hope to determine:

  • how the Sun’s magnetic field is generated and structured
  • how this stored magnetic energy is converted and released into the heliosphere and geospace in the form of solar wind, energetic particles, and variations in the solar irradiance.

Sunspots at last & Astronomy Club tonight! September 23, 2009

Posted by jcconwell in Astronomy, IYA 2009, Solar and Space weather.
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After many months of a dry season the first major group of sunspots for this solar cycle 24 have appeared around the bend. Now we can try our new solar filter for the 16 ” telescope….if only it would stop raining. To see more live pictures go to SOHO’s web site.

SUNSPOTs from SOHO 9/23/2009

SUNSPOTs from SOHO 9/23/2009

Also telescope training tonight at teh Astronomy club. Room 2153 physical science building at 8:00 PM.