Reporting from Down Under: It’s a solar eclipse shark attack in Australia

Published by Carolyn S on November 15, 2012 at 2:27 pm in Astronomy

I had never realized before that a photograph of a partial solar eclipse behind lots of colorful clouds at sunrise looks so much like a shark attack. Especially if you’re watching it over the Pacific Ocean with about 40,000 other people in Cairns, Australia.

See the fin?

In my nine eclipse expeditions, I have never seen these unique atmospheric conditions before. Traditional knowledge suggests it’s best if your solar eclipse view is cloudless, with the sun’s corona surrounding the moon’s black disk at totality. But if clouds spoil that view, I discovered that dramatic images can hide in the cloud decks, especially if the clouds are thick enough to filter the sun’s light (effective neutral density of four or greater) and allow a camera to capture images without a solar filter. (Safety note: We kept solar filters ready at a moment’s notice if conditions improved. We also viewed only through the LED display of the digital camera, not through the viewfinder.)

The museum’s solar eclipse travelers had a front row seat from the balcony of their rooms on the 11th floor of our Australia hotel. Boats had anchored in the harbor below us, and eclipse watchers camped on the boardwalk by the water. The event became a dynamic interplay of clouds and the partially eclipsed sun. Sunrise began with decks of clouds drifting between the sun and us. We aimed cameras mounted on telescopes to the place where we knew the sun would appear when the clouds parted.

The view from out hotel balcony at 6 a.m., when the sun was just clearing the peninsula’s tallest peaks. The Takahashi FCT-76 is on the left and the FS-60 is on the right, riding on a Sky Patrol equatorial mount.

Rays of sunlight through cloud decks also showed the sun’s location. As the beams moved across the land, we knew it would soon be our turn to see through a tiny thinning of the clouds just before totality. As totality approached, the sky gradually darkened and the temperature dropped. The city lights below us had just turned off at sunrise and now flickered back to life. Flash bulbs blinked over the city as photographers hoped in vain to light a path through the clouds. For the two minutes of totality, the rays of sunlight vanished, the clouds became black shadows and a sunrise glow illuminated the horizon. Then daylight returned, and we looked to see if our cameras had captured anything our eyes had missed. That’s when we discovered the shark fin shapes of the partially eclipsed sun appearing to sail behind a fantastic display of pale hued clouds. Did we have the best view of totality? Maybe not. But in the interplay of thick colorful cloud decks, we were treated to a very rare unfiltered solar eclipse at sunrise.

Photographs tell the story better:

Here I’m focusing the Celestron 5 telescope. Next to me is the Takahashi FCT-76 and the Takahashi FS-60 is closest to the camera.

At about 6:20 a.m., the partially eclipsed sun peeks through the clouds. Photography through a Celestron 5 with focal reducer (focal length 800mm).

The shark’s fin is the sun’s disk, partially covered by the moon and by several banks of Earth clouds. Photography through a Celestron 5 with focal reducer (focal length 800mm).

At about 6:25 a.m., totality is just over 10 minutes away. The colors become more dramatic as the sunlight level drops. Photography through a Celestron 5 with focal reducer (focal length 800mm).

The camera cuts off most of this shark fin, but notice the sunrise colors lingering in the clouds. Photography through a Takahashi FCT-76.

At about 6:30 a.m., the clouds and colors become dramatic as totality nears.
Photography through the Takahashi FS-60 at 600 mm focal length.

Four and a half minutes later, as totality approaches, the clouds darken, with only the closest illuminated by the last rays of the sun’s photosphere and perhaps the first faint glows of the corona. Photography through the Takahashi FS-60 at 600 mm focal length

At 6:38 a.m., totality began and the clouds obscured the fainter corona. The sky became as dark as a full moon night with sunrise colors streamed across the horizon.

The Sun burps and the Earth reaches for the Lysol: Learn why in our Nov. 15 lecture, Our Explosive Sun

Published by Caroline on November 7, 2012 at 11:46 am in Education

Welcome guest blogger Dr. David Alexander, Director of the Rice Space Institute.

If there’s one star in the sky that everyone can name — and point to, if needed — it’s the Sun. Kisosen, Wuriupranili, Huitzilopochtli, Bel, Ra, Sol, Apollo — the Sun has many names and has served many purposes for humanity over the ages. As a banisher of night, celestial timekeeper, or navigational aid, the Sun has been a constant presence over the history of humankind, bringing the hope of a new day and the renewal of returning spring.

Even today, in the early years of the 21st century, the Sun is no less important, although perhaps in a very different way. As we increasingly rely on technology in our daily lives, the Sun’s impact on the Earth can be both beautiful and alarming. The Earth is not only bathed in the light from the Sun but is embedded in its atmosphere, and as such is subject to the vagaries of the Sun’s dynamic activity. You might say that when the Sun burps, the Earth reaches for the Lysol.

Spectacular aurora over the city of Tromsø, Norway. Courtesy of Pål Brekke.

The Sun exhibits a wide range of energetic activity over a wide variety of timescales. The most dramatic of these are the so-called solar storms that drive clouds of ionized gas (plasma) outward from the Sun at speeds of millions of miles an hour. When these clouds reach the Earth some one to three days later, the effects can be catastrophic. The immediate effect is energizing the Earth’s magnetic environment in space, leading to a wide array of effects from enhanced atmospheric phenomena such as aurora, with the biggest storms generating aurora as far south as Houston, to increased particle energies and densities in low earth orbit, causing severe hazard for spacecraft and astronauts. In addition, the geomagnetic enhancements caused by these storms can also lead to noticeable effects on the ground, including the disruption of regional electrical grids with power outages being a not uncommon occurrence.

Today, a flotilla of spacecraft and a battalion of ground-based observatories are constantly monitoring the Sun across the electromagnetic spectrum and measuring the changing properties of the solar atmosphere, its magnetic field, and flow speed. Solar scientists use this huge wealth of information to generate an understanding of the physical processes that govern the solar variability and how the effects of this variability propagate through space and ultimately interact with the Earth.

Dr. Pål Brekke

On Thursday, Nov. 15, the Houston Museum of Natural Science, the Rice Space Institute and the Royal Norwegian Consulate host solar physicist and author Dr. Pål Brekke of the Norwegian Space Centre for a lecture in the Museum’s Wortham Giant Screen Theatre as part of Transatlantic Science Week 2012. Dr. Brekke will present a visually spectacular tour of the solar atmosphere and the geomagnetic phenomena that it generates. So please, join us as we celebrate Apollo, the Sun, in all his celestial glory as he burps his way through the 21st century. Tickets are $18 and may be purchased in advance here.

About our guest blogger:
Dr. David Alexander is a Professor of Physics and Astronomy and Director of the Rice Space Institute. He is Chair of the Solar Physics Division of the American Astronomical Society and the Solar Heliospheric and Interplanetary Environment (SHINE) program. He received the Presidential Early Career Award for Scientists and Engineers in 2004 and was appointed a Kavli Frontiers Fellow in 2006 by the National Academy of Sciences. He is author of The Sun, part of the Greenwood Press Guides to the Universe series.

Seeing Stars with James Wooten: Join us for a once-in-a-lifetime viewing of Venus in transit June 5

Published by James on June 1, 2012 at 2:00 pm in Astronomy

Mark your calendars for Tuesday, June 5, people.

The Houston Museum of Natural Science invites the public to observe a rare and special event on the afternoon of Tuesday, June 5. On that date, the planet Venus will transit the Sun, appearing as a black dot against the Sun’s disk. Weather permitting, the Museum will provide telescopes with filters to safely observe the Sun near the sundial just outside the Museum’s main entrance, as well as at the George Observatory and at our museum in Sugar Land.

A photograph taken of the 2004 transit of Venus at 3:39 p.m. Hong Kong time from Tuen Mun, New Territories, Hong Kong.

What’s the big deal?

On June 5, Venus passes the Earth on its faster orbit around the Sun. Venus’s orbit is between ours and the Sun, so it passes between Earth and Sun about once every 584 days. However, since Venus’s orbit is tilted by about five degrees to our own, it usually “misses” the Sun by a wide margin as seen from Earth. But on June 5, Venus lines up almost exactly with the Earth and the Sun. This causes Venus to appear as a black dot silhouetted on the Sun’s disk, an event called a “transit.” Only Mercury and Venus can transit the Sun because they are the only planets that pass between the Earth and Sun.

How often does this happen?

Transits of Venus occur in pairs eight years apart — and then not again for more than a century. Because of the way Venus’s orbit is aligned, transits occur only in June or December. This is the second of this pair of transits (the other, not visible in Houston, occurred in June 2004). The next transit visible here in Houston will occur the morning of December 8, 2125.

So how do I see Venus on the Sun’s disk?

Venus remains in front of the Sun for about six hours. Its disk will be over 30 times smaller than the Sun’s — roughly the size of a sunspot. To view the transit, we will provide solar telescopes and solar projection devices at the Museum, at the George Observatory, and at our Museum in Sugar Land. We will also have special solar glasses (the same kind used to watch eclipses) for purchase at all three locations.

As the transit begins, Venus will appear as a small dot on the right side of the Sun low in the western sky. Unlike any sunspots present, Venus will move quite noticeably across the Sun’s disk. Also, sunspots can be irregular in shape, while the disk of Venus is round. The transit begins in the afternoon at 5:09 p.m. and will still be in progress at sunset at 8:19 p.m.

If the Sun was still up, we would see Venus exit the Sun’s disk at 11:31 pm. Due to the trees surrounding Hermann Park and the deck at George Observatory, we will observe at these sites until 7:00 pm. At Sugar Land, however, the clear horizon means we can observe the Sun until 8:00 p.m.

At all three Museum locations, we will have free planetarium previews of the Venus transit, illustrating why it happens and why it is so rare. We’ll also take a virtual voyage to the planet. These special shows will be offered at 4:00, 4:15, 4:30, and 4:45 p.m. in preparation for the event beginning at 5:09 p.m.

This is the last transit of Venus that anyone alive today will ever be able to see, so don’t miss it!

Do not attempt to observe the Sun with the naked eye or through an unfiltered telescope. Failure to use appropriate filtration may result in permanent eye damage or blindness.

Ride on a Shooting Star: Space Fuel

Published by Daniel B on September 30, 2011 at 9:12 am in Energy

After the decimation suffered during World War II, mankind took a look at all the new technologies he had created to fight the war and turned his gaze towards the stars. From the late 1940’s this onward and upward reach has helped to fuel the engines of our ingenuity, but what has fueled those stellar ambassadors that now dot our solar system and beyond.

photo credit: Patrick Hoesly

To move from the surface of the earth to this new ocean a rocket must be moving about 7 miles per second. That takes a lot of energy. Many different propellants have been used. The very first rocket fuels were a mix of kerosene and liquid oxygen. Alcohol, hydrogen peroxide, and liquid hydrogen have also been used, in addition to solid fuels. They can provide thrust without the need for all the refrigeration and containment equipment that some of the liquid fuels, such as liquid hydrogen and oxygen, require.

Once the probe is beyond the reach of the atmosphere there is no way to change what’s on board.

The probe cannot drop by the local Radio Shack and pick up a fresh pair of AA batteries. While the probe is being built on Earth, the engineers must make sure that they provide a source of power that will give the probe the right amount of power.

Too little power and the scientific instrumentation won’t work; too much power could over heat the probe. On board chemical batteries can be used, but they take space that could be used for scientific instruments. Solar panels can be used, but only up to a certain distance from the sun. Beyond the orbit of Jupiter, probes need an internal power supply that will last for years.

They use the heat from radioactive decay of fissionable isotope.

photo credit: FlyingSinger

Early probes like Sputnik and Explorer 1 used chemical batteries to power their systems. In March of 1958 Vanguard 1, the 4th artificial satellite and the 1st powered by solar power, was launched. Probes with solar panels have more space on board for scientific instruments than probes that use only chemical batteries. Probes sent into the inner solar system (sun to Mars) are almost all powered using solar arrays.

Mariner 2, the first USA probe to Venus, suffered the loss of one of its solar arrays, but because it was closer to the sun, it was able to operate using only one solar array. No American manned space craft have made use of solar arrays yet (the new Multi-Purpose Crew Vehicle may), the Russian Soyuz spacecraft have used them since 1967.

The International Space Station (ISS) is the largest man-made structure outside our atmosphere.

Larger than a football field (but smaller than a football pitch), this outpost orbits the earth every hour and a half. It is also powered completely by solar power. Past the atmosphere, solar power becomes more practical and more consistent (there is no night in space). Because of the orbital path of the ISS, it is eclipsed by the earth for 30 minutes out of every hour and a half. The station makes use of rechargeable batteries to make sure it is never without power.

photo credit: Undertow851

As the probes go farther and farther away from the sun, the light that can reach them is less and less.

Until August of 2011, no probe to Jupiter had ever been powered just by solar panels. Juno, the latest probe to Jupiter, has the largest solar arrays given to a deep space probe and the first probe to Jupiter to use solar arrays.

Jupiter receives only 4% of the sunlight we enjoy on Earth. Advances in solar technology have now made it practical to use solar panels out 5 Astronomical Units (AUs) from the sun. All other deep space probes have used a radioisotope thermoelectric generator (RTG).

A RTG works by converting the heat from the decay of a radioactive fuel into electricity. American probes have been using Plutonium 238 (an isotope of Plutonium) since the late 1960’s. It has a half life of about 88 years. RTGs have powered all our interplanetary probes (the Voyagers and Pioneers and soon to be New Horizons). However, NASA has begun to run out of fuel for the RTGs and the creation of more is full of political and safety considerations.

There he goes, after an all day long work.

photo credit: giumaiolini

The technology that we’ve made to go out to the ‘verse with will also help us here on the cool, green hills of earth. RGTs have been used, mainly by Russia, to provide power for off the grid light houses. Advances in solar panels for space are used down here on Terre Firma. With the reliably of solar power in space, there are even attempts to construct orbital solar collectors to beam down electricity. There will be from heaven to Earth more than is dreamt of.

BEYONDbones

Houston Museum of Natural Science

Tag Archives: sun

Reporting from Down Under: It’s a solar eclipse shark attack in Australia

The Sun burps and the Earth reaches for the Lysol: Learn why in our Nov. 15 lecture, Our Explosive Sun

Seeing Stars with James Wooten: Join us for a once-in-a-lifetime viewing of Venus in transit June 5

Ride on a Shooting Star: Space Fuel

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