APOD: Ultraviolet Earth from an on the... (2018 Oct 28)

[APOD Robot]

Ultraviolet Earth from an Observatory on the Moon

Explanation: Which planet is this? Earth. The featured false color picture shows how the Earth shines in ultraviolet (UV) light. The image is historic because it was taken from the surface of the Moon by humanity's only lunar observatory. Although very little UV light is transmitted through the Earth's atmosphere, what sunlight does make it through might cause a sunburn. The part of the Earth facing the Sun reflects much UV light, but perhaps more interesting is the side facing away from the Sun. Here bands of UV emission are the result of auroras and are caused by charged particles expelled by the Sun. Other planets showing auroras in the UV include Mars, Saturn, Jupiter, and Uranus.

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[Ann]

Looks like the Earth has ultraviolet "sunspots", including a large one near the upper part of the terminator.

Ann

[Boomer12k]

Interesting...

:---[===] *

[amirazad]

What is the green lump on the right side of the disk?

[heehaw]

The ultraviolet pictures of the Earth taken from the surface of the Moon were taken with a camera invented by https://en.wikipedia.org/wiki/George_Robert_Carruthers

[De58te]

Looks like the Earth has ultraviolet "sunspots", including a large one near the upper part of the terminator.

Ann

Just a guess, but the description from NASA reads that this is artificial colors not of hydrogen but of ultraviolet atomic oxygen and molecular nitrogen. Not knowing which color is which but if the yellow color was oxygen, the sunspot could be a large forest fire which reduces the oxygen level thereby resulting in a darker yellow color. Anybody know whether there was a forest fire when the picture was tken?

[Ben Deacon]

Do I see stars in the “dark” half of the earth? How is that possible?

[Tragic Astronomy]

Working the fugitive dust
Under the conquering sun
Nature, please be good to us
Under the conquering sun

[RJN]

It turns out that there is another UV lunar observatory! This one is part of China's Chang'e 3 lander. Information about it is here:
http://english.nao.cas.cn/Research2015/ ... 73602.html

Therefore, the main APOD text has been updated to account for this. We apologize for the oversight.

- RJN

(ht to James Davenport via Twitter: https://twitter.com/jradavenport/status ... 2157840384)

[neufer]

Do I see stars in the “dark” half of the earth? How is that possible?

One can see "stars" all over the earth This is no doubt noise due to cosmic rays.

“The most immediately obvious and spectacular results were really for the Earth observations, because this was the first time that the Earth had been photographed from a distance in ultraviolet light, so that you could see the full extent of the hydrogen atmosphere, the polar auroris and what we call the tropical airglow belt.” — Dr. George Carruthers

The Far-UV Camera in position with Charlie Duke and the LRV in the background.

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The Moon Show Lots and Lots of Stars
Posted by Jason Major on April 4, 2017

It was a gold-plated, 3-inch telescope and camera with a cesium iodide cathode and film cartridge, developed by African-American physicist Dr. George Carruthers while working at the U.S. Naval Research Laboratory. The camera was sensitive to light “at wavelengths between 500 and 1600 Angstroms…Emission at these wavelengths comes primarily from very hot stars of spectral classes O, B, and A, with surface temperatures of 10,000° to 50,000° K. For comparison, the temperature at the visible surface of the Sun is about 5800° K or 11,000°F. Stars as faint as magnitude 11, or 100 times fainter than can be seen with the human eye, were recorded.”

<<One of the favorite allegations by those who continue to be skeptical of the Apollo moon landings is that there are no stars visible in the photographs taken by the astronauts while they were “supposedly” on the Moon. Now while there’s a rather short but succinct list of why that’s the casethe truth is that there ARE stars visible in photographs taken from the Moon—photographs taken in ultraviolet light during the penultimate Apollo 16 mission in April of 1972. So as we can clearly see, stars were captured on camera from the Moon. It just required a long exposure and a steady, tripod-mounted camera aimed upward from a dark location—not one strapped to the chest of an astronaut’s space suit aimed toward the bright surface of the Moon.

The Far Ultraviolet Camera was set up at the start of the first Apollo 16 EVA in the shade of the LM and aimed at planned points of astronomical interest during the course of the mission, and allowed to expose the film at various lengths as needed. At the end of the mission the film was retrieved and brought back to Earth; the camera itself remains on the surface in Descartes Highlands next to the LM descent stage.

“Specific planned targets were the geocorona, the Earth’s atmosphere, the solar wind, various nebulae, the Milky Way, galactic clusters and other galactic objects, intergalactic hydrogen, solar bow cloud, the lunar atmosphere, and lunar volcanic gases (if any).”

The Earth’s atmosphere blocks much of the UV light that comes in from distant stars; having an observatory on the Moon, even for a brief few days, was worth it for astronomers—especially in the days before orbiting space telescopes like Hubble.>>

George Carruthers, center, principal investigator for the Lunar Surface Ultraviolet Camera, discusses the instrument with Apollo 16 Commander John Young, right. Carruthers is employed by the Naval Research Lab in Washington, D.C. From left are Lunar Module Pilot Charles Duke and Rocco Petrone, Apollo Program Director.

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<<George Robert Carruthers (born October 1, 1939) is an award-winning African-American inventor, physicist, and space scientist. Carruthers invented the ultraviolet camera/spectograph for NASA to use when it launched Apollo 16 in 1972. His work also demonstrated that molecular hydrogen exists in the interstellar medium. In 2003, Carruthers was inducted into the National Inventor's Hall of Fame. He received an honorary doctorate for Engineering from Michigan Technological University.

Carruthers was born October 1, 1939, in Cincinnati, Ohio to George and Sophia Carruthers. At an early age George developed an interest in physics, science and astronomy, which his father encouraged. At the age of 10 he built his first telescope out of cardboard tubing and lenses purchased using money he earned as a delivery boy.

His father died when Carruthers was 12, and at that time his family moved to the South Side of Chicago where he stayed until he went to college. He did not perform well in school at a young age, earning poor grades in math and physics. However, he won three separate science fair awards during this time. Also as a child, he enjoyed visiting Chicago museums, libraries and the Adler Planetarium that caused him to be an avid science-fiction reader and enjoyed constructing model rockets. Later he became a member of the Chicago Rocket Society and various science clubs.

After graduating from Englewood High School, he entered the College of Engineering at the University of Illinois, and received a Bachelor of Science degree in aeronautical engineering in 1961. Carruthers did his graduate work at the University of Illinois and earned Master's degree in nuclear engineering in 1962. Carruthers received a Ph.D. in aeronautical and astronomical engineering in 1964. While conducting his graduate studies, Carruthers worked as researcher and teaching assistant studying plasma and gases.

During the 1980s, Carruthers helped create a program called the Science & Engineers Apprentice Program, which allows high school students to spend a summer working with scientists at the Naval Research Laboratory. Carruthers now works with NRL’s community outreach organization, and as such helps support several educational activities in the sciences in the Washington D.C. area. During the summers of 1996 and 1997 he taught a course in Earth and Space Science for D.C. Public Schools Science teachers. He also helped develop a series of videotapes on Earth and Space science for high-school students.>>

[Chris Peterson]

Looks like the Earth has ultraviolet "sunspots", including a large one near the upper part of the terminator.

Ann

Just a guess, but the description from NASA reads that this is artificial colors not of hydrogen but of ultraviolet atomic oxygen and molecular nitrogen. Not knowing which color is which but if the yellow color was oxygen, the sunspot could be a large forest fire which reduces the oxygen level thereby resulting in a darker yellow color. Anybody know whether there was a forest fire when the picture was tken?

This is essentially a broadband UV image with the light from atomic hydrogen blocked. There is no spectral information- it's just intensity over the sensitivity range of the camera (less the blocking filter). The raw image is a single frame on B&W film. So the color here doesn't map anything except intensity of the UV signal, which includes both reflected and emitted light.

[Fred the Cat]

Is the entirety of stuff we’ve landed on the visible side because of logistics or because we suspect the difficulties exploring the far side too expensive versus new knowledge?

Sounds like China is going to try to find out.