Thursday, June 29, 2017

The Sun, a Primer

The Sun is a huge, glowing ball at the center of our solar system. The sun provides light, heat, and other energy to Earth. The sun is made up entirely of gas. Most of it is a type of gas that is sensitive to magnetism. This sensitivity makes this type of gas so special that scientists sometimes give it a special name: plasma. The planets and their moons, dwarf planets, tens of thousands of asteroids, and trillions of comets revolve around the sun. The sun and all these objects are in the solar system. Earth travels around the sun at an average distance of about 92,960,000 miles (149,600,000 kilometers) from it.

An Extreme Ultraviolet Imaging Telescope (EIT) image of the Sun and a huge, handle-shaped prominence, taken on September 14,1999, in the 304 angstrom wavelength. Prominences are huge clouds of relatively cool dense plasma suspended in the Sun's hot, thin corona. At times, they can erupt, escaping the Sun's atmosphere. Image credit: NASA/European Space Agency

The sun's radius (distance from its center to its surface) is about 432,000 miles (695,500 kilometers), approximately 109 times Earth's radius. The following example may help you picture the relative sizes of the sun and Earth and the distance between them: Suppose the radius of Earth were the width of an ordinary paper clip. The radius of the sun would be roughly the height of a desk, and the sun would be about 100 paces from Earth.

The part of the sun that we see has a temperature of about 5500 degrees C (10,000 degrees F). Astronomers measure star temperatures in a metric unit called the Kelvin (abbreviated K). One Kelvin equals exactly 1 Celsius degree (1.8 Fahrenheit degree), but the Kelvin and Celsius scales begin at different points. The Kelvin scale stars at absolute zero, which is -273.15 degrees C (-459.67 degrees F). Thus, the temperature of the solar surface is about 5800 K. Temperatures in the Sun's core reach over 15,000,000 K (27,000,000 degrees F).

The energy of the sun comes from nuclear fusion reactions that occur deep inside the sun's core. In a fusion reaction, two atomic nuclei join together, creating a new nucleus. Fusion produces energy by converting nuclear matter into energy.

The sun, like Earth, is magnetic. Scientists describe the magnetism of an object in terms of a magnetic field. This is a region that includes all the space occupied by the object and much of the surrounding space. Physicists define a magnetic field as the region in which a magnetic force could be detected—as with a compass. Physicists describe how magnetic an object is in terms of field strength. This is a measure of the force that the field would exert on a magnetic object, such as a compass needle. The typical strength of the sun's field is only about twice that of Earth's field.

But the sun's magnetic field becomes highly concentrated in small regions, with strengths up to 3,000 times as great as the typical strength. These regions shape solar matter to create a variety of features on the sun's surface and in its atmosphere, the part that we can see. These features range from relatively cool, dark structures known as sunspots to spectacular eruptions called flares and coronal mass ejections.

Flares are the most violent eruptions in the solar system. Coronal mass ejections, though less violent than flares, involve a tremendous mass (amount of matter). A single ejection can spew approximately 20 billion tons (18 billion metric tons) of matter into space. A cube of lead 3/4 mile (1.2 kilometers) on a side would have about the same mass.

The sun was born about 4.6 billion years ago. It has enough nuclear fuel to remain much as it is for another 5 billion years. Then it will grow to become a type of star called a red giant. Later in the sun's life, it will cast off its outer layers. The remaining core will collapse to become an object called a white dwarf, and will slowly fade. The sun will enter its final phase as a faint, cool object sometimes called a black dwarf.

To be continued...


Wednesday, June 28, 2017

Are You an Umbraphile? You May Be After August 21!

um-bra-phile (ˈəm-brə-ˌfī(-ə)l) noun. 1. an avid observer of, or a person with a great interest in, eclipses. [from Latin umbra ‘shade’ and Greek philos ‘loving’]

An umbraphile is, literally, a "shadow lover." He or she is addicted to total solar eclipses. Those who have not stood in the moon’s shadow may not understand. But those who have, do. For many umbraphiles, it is way of life. These are the “solar eclipse chasers.” Once every 16 months, on average, umbraphiles drop what they are doing and travel, by whatever means necessary, to gather along a narrow strip in some remote corner of the globe defined by the laws of celestial mechanics.

The next total solar eclipse will occur August 21, crossing the continental United States from coast to coast. Are you an umbraphile? If you aren't, you may be very soon!


Tuesday, June 27, 2017

Have You Made Your Reservations for the August 21 Total Solar Eclipse?

There are less than two months until the August 21 total solar eclipse. The path of totality will pass from coast to coast across the entire continental United States. The path of totality is about 70 miles wide. So, there are lots of great places in the U.S. you can see the event.

The Path of Totality for the August 21, 2017 Total Solar Eclipse. Image Credit: NASA

If you are coming from outside the path of totality and hope to stay overnight within the path August 20, before the August 21 event, you should make your plans now if you have not done so already. Hotels are filing up fast, and are already filled up in some locations.

Please do not wing this! The Department of Transportation is asking that people DO NOT pull off to the side of the interstate. Visit the DoT website where you can see how traffic may be affected by the eclipse. Visit the Fact Sheet link below.

2017 Solar Eclipse Transportation Fact Sheet for State and Local Departments of Transportation

Here are the states through which the center line of the path of totality will pass.

  • Oregon
  • Idaho
  • Wyoming
  • Nebraska
  • Kansas
  • Missouri
  • Kentucky
  • Tennessee
  • Georgia
  • South Carolina

To get more of an idea of the location of the path of totality, check out this list of major cities that will be in the path.

  • Corvallis, Albany and Lebanon, Oregon
  • Idaho Falls, Idaho
  • Casper, Wyoming
  • Grand Island, Lincoln Nebraska
  • St Joseph, Missouri
  • Kansas City, Kansas
  • St Louis, Missouri
  • Bowling Green, Kentucky
  • Nashville, Tennessee
  • Greenville, South Carolina
  • Columbia, South Carolina

The website has a great page to see what cities will be in the path and how long totality will last at those locations. Follow the link below.

Cities that lie in the Path of Totality


Sunday, June 25, 2017

Make a Pinhole Camera to View the Solar Eclipse

Pinhole Camera

You don't need a lot of money to observe a solar eclipse in complete safety. With just a few simple supplies, you can make a pinhole camera that lets you watch a solar eclipse safely and easily from anywhere. 

A pinhole camera is a simple camera without a lens. Instead of a lens, it has a tiny aperture, a pinhole. Light from a scene passes through the aperture and projects an inverted image, which is known as the camera obscura effect.

Remember: You should never look at the sun directly without equipment that's specifically designed for looking at the sun. Even using binoculars or a telescope, you could severely damage your eyes or even go blind! The totality portion of a solar eclipse is safe. But looking at anything as bright as the sun is NOT safe without proper protection. And no, sunglasses do NOT count. 

Now, let's make a pinhole camera! You will need the following materials.
  • 2 pieces of white card stock
  • 1 piece of unused, smooth, aluminum foil
  • 1 pair of scissors
  • 1 roll of tape
  • 1 pin or paper clip

Image Credit: NASA/JPL-Caltech

1. Cut a square hole into the middle of one of your pieces of card stock.
Image Credit: NASA/JPL-Caltech

2. Tape a piece of aluminum foil over the hole.
Image Credit: NASA/JPL-Caltech

3. Use your pin or paper clip to poke a small hole in the aluminum foil.
Image Credit: NASA/JPL-Caltech

4. Place your second piece of card stock on the ground and hold the piece with aluminum foil above it (foil facing up). Stand with the sun behind you and view the projected image on the card stock below! The farther away you hold your camera, the bigger your projected image will be.

To make your projection a bit more defined, try putting the bottom piece of card stock in a shadowed area while you hold the other piece in the sunlight.
Image Credit: NASA/JPL-Caltech

5. For extra fun, try poking multiple holes in your foil, making shapes, patterns and other designs. Each hole you create will turn into its own projection of the eclipse, making for some neat effects. Grab a helper to take photos of your designs for a stellar art project you can enjoy even after the eclipse has ended. 
Image Credit: NASA/JPL-Caltech


Saturday, June 24, 2017

Ugarit Total Solar Eclipse

Trivia: The Ugarit Total Solar Eclipse

In 1948, a clay tablet was discovered in the port city of Ugarit in Northern Syria. In the text of the tablet, a Mesopotamian historian noted, "On the day of the new moon, in the month of Hiyar, the sun was put to shame, and went down in the daytime, with Mars in attendance." Scientists realized the text described a total solar eclipse in which the planet Mars was visible during totality.

Researchers originally dated the eclipse event as May 3, 1375 B.C. But further study suggested a different eclipse. Researchers considered the dating of the tablet, combined with the text's statement of the month in which the eclipse occurred and the fact that Mars was seen during totality. This evidence pointed to the total eclipse of March 5, 1223 B.C. The revised findings were first published in 1989 in the journal Nature.

The Ugarit eclipse is one of the earliest solar eclipses recorded. The path of totality began in the Atlantic Ocean, crossed north-western Afrca, Turkey, and central Asia.

The Accelerating Moon, the Decelerating Earth

The dating of ancient solar eclipses provides astronomers with reference points to determine long-term evolution of angular momentum in the Earth-Moon system--that is, it helps astronomers understand how the moon's orbit and Earth's rotation have changed over time. The revised date--March 5, 1223 B.C.--implies that the secular deceleration of Earth's rotation has changed very little during the past 3,000 years.

Secular What?

Ocean tides are caused by the gravitational pull of the moon (and, to a lesser extent, the Sun). The resulting tidal bulge in Earth's oceans is dragged ahead of the moon in its orbit due to the daily rotation of Earth. As a consequence, the ocean mass offset from the Earth-Moon line exerts a pull on the moon and accelerates it in its orbit. Conversely, the moon's gravitational tug on this mass exerts a torque that decelerates the rotation of Earth. The length of the day gradually increases as energy is transferred from Earth to the moon, causing the lunar orbit and period of revolution about Earth to increase.

You can learn more about secular acceleration from the following NASA article.


Thursday, June 22, 2017

Total Solar Eclipse of January 1, 1889

Trivia: The Total Solar Eclipse of January 1, 1889, also known as the New Year’s Day Eclipse of 1889.

The path of totality began in the Bering Sea, crossed the North Pacific Ocean, passed through California to the north of San Francisco, through northern Nevada, Idaho, northwestern Wyoming, Montana, the northwestern part of North Dakota, and into central Canada, passing through southern Manitoba, and finishing on the western edge of Ontario.

The first photograph of a solar eclipse was taken during solar eclipse of July 28, 1851. But even with this technological advancement, most of the recorded observations of a total solar eclipse remained in the form of the written word and drawings. For the January 1, 1889 eclipse, a group of amateur and professional astronomers joined forces with a new photography society in San Francisco. They agreed to combine their resources to observe and record the eclipse. One example of the efforts was a photographic plate on which multiple exposures were made, showing many partial eclipse phases leading to totality.

On February 7, the group reunited in downtown San Francisco and presented their observations. The group enjoyed the experience so much that they agreed to form their own astronomical society, called the Astronomical Society of the Pacific (ASP). Originally a society of forty members, the ASP has grown to a national society dedicated to astronomy education and outreach. The ASP helps people of all ages learn astronomy and helps those people share their knowledge with others.

You can learn more about the ASP at the society’s official website:


Wednesday, June 21, 2017

Two NASA Briefings on the Total Solar Eclipse of August 21, 2017

On June 21, representatives from NASA, other federal agencies, and science organizations, provided important viewing safety, travel and science information on the August 21, 2017 total solar eclipse. This eclipse will be the first in 99 years that will cross the entire continental United States.
Two briefings were held at the Newseum in Washington. The briefings aired live on NASA Television and streamed on the agency’s website.

Over the course of 100 minutes, 14 states across the United States will experience more than two minutes of darkness in the middle of the day. Additionally, a partial eclipse will be viewable across all of North America. The eclipse will provide a unique opportunity to study the sun, Earth, moon and their interaction because of the eclipse’s long path over land coast to coast. Scientists will be able to take ground-based and airborne observations over a period of an hour and a half to complement the wealth of data and images provided by space assets.

The June 21 briefings were:

Logistics Briefing
  • Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate at the agency’s headquarters in Washington
  • Vanessa Griffin, director of the National Oceanic and Atmospheric Administration’s Office of Satellite and Product Operations in Suitland, Maryland
  • Brian Carlstrom, deputy associate director of Natural Resource Stewardship and Science at the National Park Service in Washington
  • Martin Knopp, associate administrator of the Office of Operations in the Federal Highway Administration at the U.S. Department of Transportation in Washington

Science Briefing
  • Thomas Zurbuchen
  • Angela Des Jardins, principal investigator of the Eclipse Ballooning Project at Montana State University, Bozeman
  • Angela Speck, professor of astrophysics and director of astronomy at the University of Missouri, Columbia
  • Dave Boboltz, program director of solar physics in the Division of Astronomical Sciences at the National Science Foundation in Arlington, Virginia
  • Linda Shore, executive director of the Astronomical Society of the Pacific in San Francisco
  • Matt Penn, astronomer at the National Solar Observatory in Tucson, Arizona

For more information on the eclipse, and how to safely view it, visit: