--------- #1430 - SOFIA is a flying telescope aboard a 747.
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- Attachments : Boeing 747
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- Why not put a telescope on an airplane and fly it far above the dense atmosphere that disturbs the images that reach the telescope on the ground. Also, the atmosphere attenuates many of the light wavelengths that never reach the surface of Earth. The light above the atmosphere is much richer.
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- Well, NASA has done it. The plane is a Boeing 747 and the telescope is called SOFIA, Stratospheric Observatory for Infrared Astronomy. The telescope is 2.5 meter reflector. The 747 flies at 45,000 feet which is above 99% of the water vapor that soaks our atmosphere and distorts telescope images. It is an infrared telescope used to detect those wavelengths in the light spectrum that do not normally penetrate the denser atmosphere.
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- SOFIA operates like a space telescope but it comes home for dinner every night. The astronomers have 8 cameras and spectrographs attached to the telescope. Each mission lasts 7 to 12 hours in the air. It is planned to fly at least 200 missions per year for the next 20 years. Over that entire time constant upgrades will be made on equipment to continually improve performance of the telescope.
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- Last June 23,2011, SOFIA flew in the shadow of Pluto. That’s right. We normally think of an eclipse as the Moon passing in front of the Sun and casting a shadow on the Earth. In this case the planet, or dwarf planet if you insist, Pluto will pass in front of the star Sagittarius. Sagittarius is a Magnitude 15 star. ( see footnote below). The star’s light will disappear behind Pluto as Pluto passes in front of it..
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- The shadow of Pluto will trace a path over the surface of Earth. Unfortunately, as luck would have it, this time the shadow was over the Pacific Ocean. A perfect mission for an airplane that could fly there to reach the shadow. Why is that such a good idea?
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- The result will determine if Pluto has an atmosphere or not. The background star is a point and if its light passes behind Pluto and switches off then on like a light switch it did not pass through an atmosphere. If that background light fades and brightens gradually that means the light is passing through Pluto’s atmosphere.
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- SOFIA’s telescope is in the back half of the 747 sealed off so the front half is under cabin pressure for the astronomers. It is a 17- ton telescope. The door alone weighs 1.5 tons. The door opens up to the outside atmosphere when the telescope is operating. The giant hole in the back of the airplane is a unique design that does not disrupt the control of the aircraft as it is opened and closed. And, in an emergency the 747 might have to land with the door open. So, the design is well tested to work under all conditions.
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- The telescope is mounted on a giant bearing so it can rotate to get in position. Everything in the design is to have counter weights to stabilize movements in flight. When the telescope is in operation it is held in rock steady position and the aircraft moves for stabilization.
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- SOFIA flew through Pluto’s shadow on June 22 and yes Pluto has an atmosphere.
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- A space craft was launched January 9,2006 with a mission to visit Pluto inn 2015. It is a 1,054 pound spacecraft that will fly past Pluto examining the planet in unprecedented detail. Now they know they can expect to be viewing through Pluto’s atmosphere
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- Check out SOFIA on the Internet to learn about its many missions in high flying astronomy. An announcement will be made shortly, stay tuned.
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The naked eye can see a star that is 6 Magnitude. The larger the Magnitude number the dimmer the star. Stars can be dim because they are small or because they are further away.
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The Greek astronomer Hipparchus created this Magnitude scale in 135 B.C. and we have been stuck with it ever since. He had divided 850 stars into 6 ranges of dimness. The brightest stars got a 1 and the dimmest stars got a 6 Magnitude. 1,500 years later Galileo discovered the moons of Jupiter that were invisible to the naked eye. He called the next dimmest star a 7 Magnitude in 1610. In order to assign Magnitudes to the brightness of the Moon, the planets, astronomers had to use negative numbers. The star Sirius has an apparent Magnitude of -1.46.
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- In 1856 an English astronomer put math behind it at decided a difference of 5 magnitudes corresponded to a brightness difference of 100 times. Apparent Magnitude is what you see with your eye. Absolute Magnitude defines apparent brightness if all stars were exactly 32.6 lightyears away. Our Sun has an Absolute Brightness of 4.8 Magnitude.
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707-536-3272, Wednesday, March 14, 2012
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