Glossary

Views of Pluto Through the Years.

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Ep. 10 Spectroscopy - HD and the Void

Double digits for the podcast! To celebrate, I'm talking about something I've mentioned a lot in past episodes; spectroscopy! Hear about the history of this area of astronomical science, how it opened up new understanding about the Sun and stars a...

I’ve been dropping the word ‘spectroscopy’ with only minimal explanation for quite a few episodes now and it’s high time I expanded on this topic. Join me for the double-digit episode of this podcast to learn about the history of spectroscopes and spectroscopy, how it taught us about the Sun and stars, and what advancements were made to take spectroscopes into the 20th century.

Below the cut are sources, music credits, a vocabulary list, a timeline of all the astronomers and chemist and physicists I mention, and the transcript of this episode. Let me know what you think I should research next by messaging me here, tweeting at me at @HDandtheVoid, or asking me to my face if you know me in real life. And please check out the podcast on iTunes, rate it or review it if you’d like, subscribe, and maybe tell your friends about it if you think they’d like to listen!

(My thoughts on the next episode were probes through the ages or the transit of Venus. I could also talk about more modern spectroscopy, and I’m planning to interview a friend after the eclipse next week about her graduate-level research into the history of the universe. Let me know by the 17th and I’ll have the next podcast up on August 28th, barring any new-job-related delays.)

Glossary

absorption lines - dark spectral lines that appear in a spectroscope when a gaseous or burned-up element has light shone through it.

angstrom - a unit of length—one hundred-millionth of a centimeter—that is usually used to express wavelengths and the distances in atoms.

emission lines - bright spectral lines that appear in a spectroscope when you burn an element up.

Fraunhofer lines - a standard set of spectral absorption lines observed by Joseph von Fraunhofer. He mapped 574 lines and designated them alphabetically from red to violet in the spectrum with the letters A through K, with weaker lines assigned other, lowercase letters.

incandescent - luminous or glowing due to intense heat.

spectroscopy - the study of light from an incandescent source (or, more recently, electromagnetic radiation and other radiative energy) that has its wavelength dispersed by a prism or other spectroscopic device that can disperse an object’s wavelength. The spectra of distant astronomical objects like the Sun, stars, or nebulae are patterns of absorption lines that correspond to elements that these objects are made up of. This area of study is the major source of the study of astrophysics as well as advancements in chemistry, astronomy, and quantum mechanics.

Script/Transcript

Sources 

Prisms vs. diffraction gratings via CSIRO

Definition of ‘angstrom’ via Encyclopedia Brittanica

Definition of ‘incandescent’ via Merriam-Webster

Current uses of spectroscopy in astronomy

Some past and current satellites with spectroscopic capabilities via a John Hopkin’s professor’s old webpage

Spectral classification of stars via University of Nebraska-Lincoln

Common, A. A. “Astronomy.” In Popular Astronomy 8 (1900), 417-24. Located on Google Books preview.

Hirshfeld, Alan. Starlight Detectives. Bellevue Library Press: NY, 2014.

“the Fraunhofer lines, as they were soon to be called, originate in the sun itself, and are neither optical artifacts of the spectroscope nor the result of selective absorption of sunlight within earth’s atmosphere” (168-9).

“the flame’s radiance did not ‘fill in’ the dark D [sodium] lines , as [Kirchhoff] had expected, but reinforced the absorption of these wavelengths of light” (178).

Kirchhoff: “the dark lines of the solar spectrum … exist in the consequence of the presence, in the incandescent atmosphere of the sun, of those substances which in the spectrum of a flame produce bright lines in the same plane” (178).

“a body with a propensity to emit light at a given wavelength must have an equal propensity to absorb light at that wavelength” (178).

“expresses the wavelength of a spectral line, depending on its derivation angle and the density of grooves in the grating” (187).

“mosaic of the solar spectrum assembled from prints of twenty-eight negatives” (187).

“visual confirmation of the chemical unity of the Sun and stars” (203).

Doppler “claimed in 1842 that the perceived frequency of a wave is altered by one’s state of motion” (209).

“In Doppler’s schema, waves from a steadily approaching source are compressed: as their frequency is increased, their wavelength is shortened. Waves from a steadily receding source are stretched: as their frequency is reduced, their wavelength is elongated” (210).

“Yet history has shown that credit for an evolving theory or field, such as stellar spectrum photography, often goes not to individuals who are first to publish, but to those who most convincingly establish the validity and worth of their results” (223).

“Vogel confirmed that the Sun does not rotate as a solid body; Its rotation rate varies with solar latitude, fastest at the equator, progressively slower towards the poles” (231). 

“The deviation of the star’s G line from its solar position revealed the star’s Doppler shift and, via a mathematical formula, its line-of-sight motion” (232).

“What Pickering had accomplished for stellar spectral classification with the Henry Draper project, Campbell had accomplished for stellar radial velocities with the Lick catalog” (233).

Johnson, George. Miss Leavitt’s Stars. Atlas Books: NY, 2005.

“When Kirchhoff and Bunsen made the discovery, the existence of atoms was still controversial. Once they were discovered, the effect could be simply understood: when an atom is energized, its electrons jump into higher orbits. When they fall back down they emit various frequencies of light. Every kind of atom is built a little differently, its electrons arrayed in a specific way, resulting in a characteristic pattern. For similar reasons, if you shine a light through a gaseous substance, like hydrogen or helium, certain colors will be filtered out. The result in this case is a characteristic pattern of black ‘absorption’ lines interrupting the spectrum—another unique chemical fingerprint. (The same colors marked by the absorption lines would appear as bright emission lines if the element was burned.)” (102-103).

Rhodes, Richard. The Making of the Atomic Bomb. 2nd ed. Simon & Schuster: NY, 2012.

Timeline

William Herschel, German/English (1738-1822)

Thomas Melvill, American (1751-1832)

William Hyde Wollaston, English (1766-1828)

David Brewster, Scottish (1781-1868)

Françoise Arago, French (1786-1853)

Joseph von Fraunhofer, Bavarian (1787-1826)

William Henry Fox Talbot, English (1800–1877)

George Airy, English (1801-1892)

Christian Doppler, Austrian (1803-1853)

Robert Wilhelm Bunsen, German (1811-1899)

Anders Ångström, Swedish (1814-1874)

Lewis Morris Rutherfurd, American (1816-1892)

William Allen Miller, English (1817-1870)

Pietro Angelo Secchi, Italian (1818-1878)

Armand-Hippolyte-Louis Fizeau, French (1819-1896)

William Huggins, English (1824-1910)

Gustav Kirchhoff, German (1824-1887)

Giovanni Battista Donati, Italian (1826-1873)

James Clerk Maxwell, Scottish (1831-1879)

Henry Draper, American (1837–1882)

Mary Anna Palmer Draper, American (1839–1914)

Hermann Carl Vogel, German (1841-1907)

Edward Charles Pickering, American (1846–1919)

Margaret Lindsay Huggins, Irish/English (1848-1915)

Henry Augustus Rowland, American (1848-1901)

Williamina “Mina” Fleming, Scottish (1857–1911)

William Wallace Campbell, American (1862-1938)

Annie Jump Cannon, American (1863-1941)

Antonia Maury, American (1866-1952)

Vesto Melvin Slipher, American (1875-1969)

Edwin Hubble, American (1889-1953)

Intro Music: ‘Better Times Will Come’ by No Luck Club off their album Prosperity

Outro Music: ‘Fields of Russia’ by Mutefish off their album On Draught

Take a moment, look outside your window. 🌷🌼

Today is the #FirstDayOfSpring in the Northern Hemisphere, also known as the vernal equinox.

#DYK Earth’s tilted axis causes the season? Throughout the year, different parts of Earth receive the Sun’s most direct rays. So, when the North Pole tilts toward the Sun, it’s summer in the Northern Hemisphere. And when the South Pole tilts toward the Sun, it’s winter in the Northern Hemisphere.

These images are of Zinnias. They are part of the flowering crop experiment that began aboard the International Space Station on Nov. 16, 2015, when NASA astronaut Kjell Lindgren activated the Veggie system and its rooting “pillows” containing zinnia seeds.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

I mention New Horizons in today’s podcast but here’s some more up-to-date info!

Solar System: Things to Know This Week

Time for a little reconnaissance. 

Our New Horizons spacecraft won’t arrive at its next destination in the distant Kuiper Belt—an object known as 2014 MU69—until New Year’s Day 2019, but researchers are already starting to study its environment thanks to a few rare observational opportunities this summer, including one on July 17. This week, we’re sharing 10 things to know about this exciting mission to a vast region of ancient mini-worlds billions of miles away.

1. First, Some Background 

New Horizons launched on Jan. 19, 2006. It swung past Jupiter for a gravity boost and scientific studies in February 2007, and conducted a six-month reconnaissance flyby study of Pluto and its moons in summer 2015. The mission culminated with the closest approach to Pluto on July 14, 2015. Now, as part of an extended mission, the New Horizons spacecraft is heading farther into the Kuiper Belt.

2. A Kuiper Belt refresher

The Kuiper Belt is a region full of objects presumed to be remnants from the formation of our solar system some 4.6 billion years ago. It includes dwarf planets such as Pluto and is populated with hundreds of thousands of icy bodies larger than 62 miles (100 km) across and an estimated trillion or more comets. The first Kuiper Belt object was discovered in 1992.

3. That’s Pretty Far

When New Horizons flies by MU69 in 2019, it will be the most distant object ever explored by a spacecraft. This ancient Kuiper Belt object is not well understood because it is faint, small, and very far away, located approximately 4.1 billion miles (6.6 billion km) from Earth.

4. Shadow Play 

To study this distant object from Earth, the New Horizons team have used data from the Hubble Space Telescope and the European Space Agency’s Gaia satellite to calculate where MU69 would cast a shadow on Earth’s surface as it passes in front of a star, an event known as an occultation.

5. An International Effort 

One occultation occurred on June 3, 2017. More than 50 mission team members and collaborators set up telescopes across South Africa and Argentina, aiming to catch a two-second glimpse of the object’s shadow as it raced across the Earth. Joining in on the occultation observations were NASA’s Hubble Space Telescope and Gaia, a space observatory of the European Space Agency (ESA).

6. Piecing Together the Puzzle 

Combined, the pre-positioned mobile telescopes captured more than 100,000 images of the occultation star that can be used to assess the Kuiper Belt object’s environment. While MU69 itself eluded direct detection, the June 3 data provided valuable and surprising insights. “These data show that MU69 might not be as dark or as large as some expected,” said occultation team leader Marc Buie, a New Horizons science team member from Southwest Research Institute in Boulder, Colorado.

7. One Major Missing Piece 

Clear detection of MU69 remains elusive. “These [June 3 occultation] results are telling us something really interesting,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute. “The fact that we accomplished the occultation observations from every planned observing site but didn’t detect the object itself likely means that either MU69 is highly reflective and smaller than some expected, or it may be a binary or even a swarm of smaller bodies left from the time when the planets in our solar system formed.”

8. Another Opportunity 

On July 10, the SOFIA team positioned its aircraft in the center of the shadow, pointing its powerful 100-inch (2.5-meter) telescope at MU69 when the object passed in front of the background star. The mission team will now analyze that data over the next few weeks, looking in particular for rings or debris around MU69 that might present problems for New Horizons when the spacecraft flies by in 2019. “This was the most challenging occultation observation because MU69 is so small and so distant,” said Kimberly Ennico Smith, SOFIA project scientist.

9. The Latest 

On July 17, the Hubble Space Telescope will check for debris around MU69 while team members set up another “fence line” of small mobile telescopes along the predicted ground track of the occultation shadow in southern Argentina.

10. Past to Present 

New Horizons has had quite the journey. Check out some of these mission videos for a quick tour of its major accomplishments and what’s next for this impressive spacecraft.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com

Solar System by Jian Guo

Great detail of the famous crawler that transported the mighty Saturn V and all the space shuttles to the launch pads.  An engineering feat in its own right.

People can’t anticipate how much they’ll miss the natural world until they are deprived of it. I have read about submarine crewmen who haunt the sonar room, listening to whale songs and colonies of snapping shrimp. Submarine captains dispense “periscope liberty” - a chance to gaze at clouds and birds and coastlines - and remind themselves that the natural world still exists. I once met a man who told me that after landing in Christchurch, New Zealand, after a winter at the South Pole research station, he and his companions spent a couple of days just wandering around staring in awe at flowers and trees. At one point, one of them spotted a woman pushing a stroller. “A baby!” he shouted, and they all rushed across the street to see. The woman turned the stroller and ran. Nothing tops space as a barren, unnatural environment. Astronauts who had no prior interest in gardening spend hours tending experimental greenhouses. “They are our love,” said cosmonaut Vladislav Volkov of the tiny flax plants - with which they shared the confines of Salyut 1, the first Soviet space station. At least in orbit, you can look out the window and see the natural world below. On a Mars mission, once astronauts lose sight of Earth, they’ll be nothing to see outside the window. “You’ll be bathed in permanent sunlight, so you won’t eve see any stars,” astronaut Andy Thomas explained to me. “All you’ll see is black.”

Mary Roach. Packing for Mars: The Curious Science of Life in the Void (via coneyislands)

No matter where you hang your stockings, I wish you a very Merry Christmas!

Ep. 24 Airborne Infrared Astronomy - HD and the Void

I have spoken about radio astronomy, so it makes sense to move on to infrared astronomy. The method for gathering infrared data involves telescopes mounted in planes that can fly above Earth's atmosphere, and there is a rich history of airborne as...

Did you know that some observatories are not on the ground and not orbiting Earth, but are mounted on airplanes? I finally researched SOFIA, an infrared observatory in a repurposed plane, and discovered there’s a rich history of airborne astronomy. And by airborne astronomy, I mean a lot of people took pictures of astronomical phenomena from planes!

Below the cut, I have the glossary, transcript, sources, and music credits. If you have suggestions for topics I could cover, please send me a Tumblr message or tweet at me on Twitter at @HDandtheVoid, or you can ask me to my face if you know me. Please subscribe on iTunes, rate my podcast and maybe review it, and tell friends if you think they’d like to hear it!

(My thoughts on the next episode are Chuck Yeager, Stephen Hawking and his theories, the opposition of Mars, famous comets, recent developments and discoveries in the astronomer community, or an atmospheric phenomenon called ‘Steve.’ The next episode will go up April 30th, lord willing and the creek don’t rise!)

Glossary

absorption bands - the areas of the electromagnetic spectrum that are absorbed by atmospheric gases.

atmospheric windows - the areas of the electromagnetic spectrum where the atmosphere is transparent, or does not absorb the radiation of specific wavelengths. 

corona - the hot outer atmosphere of the Sun.

electromagnetic spectrum - the range of wavelengths or frequencies over which electromagnetic radiation extends. A photon transmits electromagnetic radiation at different frequencies, which are in a range that includes (from highest frequency to lowest) gamma rays, X-rays, ultraviolet light, visible light, infrared, microwaves, and radio waves

frequency - the number of times a wave oscillates up and down per second.

hypoxia - insufficient oxygen in the blood. Symptoms include vertigo, nausea, weakness, hyperventilation, slowed thinking, poor coordination, dimmed vision, and increased heart rate.

photon - a type of elementary particle that moves in a wave. It transmits electromagnetic radition such as light. The more energy a photon has, the higher its frequency.

Script/Transcript

Sources

A map of every active satellite orbiting Earth via Quartz

Infrared radiation via Gemini Observatory (Feb 1999)

Absorption Bands and Atmospheric Windows via NASA

Gladys Ingle of the 13 BLACK CATS changes planes in mid-air via YouTube

Milestones in Airborne Astronomy: From the 1920's to the Present by Wendy Whiting Dolci (1997)

Limits to human performance: elevated risks on high mountains, by Huey, Raymond B. and Xavier Eguskitza. Journal of Experimental Biology (2001)

When Humans Fly High by Linda Pendleton (Nov 1999)

Dalton's Law tells us that the total pressure of any mixture of gases (with constant temperature and volume) is the sum of the individual pressures (also called partial pressure) of each gas in the mixture. Also, partial pressure of each gas is proportional to that gas's percentage of the total mixture. Because the percentage of oxygen in the atmosphere remains constant at 21%, Dalton's Law lets us calculate the partial pressure of the oxygen in the atmosphere at any altitude. As we'll see shortly, the human body is affected by the pressure of the gases in the atmosphere. The partial pressure of oxygen (and to a lesser extent other gases) available in the surrounding air is important in determining the onset and severity of hypoxia.

Henry's Law states that the amount of gas dissolved in a solution is proportional to the partial pressure of the gas over the solution. A bottle of carbonated liquid demonstrates Henry's Law. When the bottle is uncapped, the carbon dioxide (CO2) in the mixture will slowly diffuse to the atmosphere until the pressure of CO2 in the liquid equals the pressure of CO2 in the surrounding air. The soda will then be "flat." A bottle of soda opened in an unpressurized aircraft at 10,000 feet will foam and overflow. The opposite will happen with soda opened at pressures greater than one atmosphere. A champagne cork won't pop in a diving bathysphere pressurized for deep ocean exploration.

Boyle's Law states that the volume of a gas is inversely proportional to the pressure on the gas as long as the temperature remains constant. A gas will expand when the pressure on it is decreased. This law holds true for all gases, even those trapped in body cavities. A volume of gas at sea level pressure will expand to approximately twice its original volume at 18,000 feet, nearly nine times its original volume at 50,000 feet.

Graham's Law tells us that a gas at higher pressure exerts a force toward a region of lower pressure. There's a permeable or semi-permeable membrane separating the gases, and gas will diffuse across the membrane from the higher pressure to the lower pressure. This will continue until the pressure of the gas is equal, or nearly equal, on both sides of the membrane. Graham's Law is true for all gases and each gas in a mixture behaves independently. It's possible to have two or more gases in a solution diffusing in opposite directions across the same membrane and, in fact, this is what happens to make oxygen transfer possible in the cells and tissues of the human body.

High-Altitude Hypoxia via Harvard (July 2012)

Kuiper Airborne Observatory via NASA (May 2005)

NASA's Kuiper Airborne Observatory via YouTube

SOFIA Science Center

Up all Night with SOFIA, NASA's Flying Observatory via YouTube

Intro Music: ‘Better Times Will Come’ by No Luck Club off their album Prosperity

Filler Music: ‘A Bite Out of My Bed’ by The New Pornographers off their album Together.

Outro Music: ‘Fields of Russia’ by Mutefish off their album On Draught

Talking to a real cosmonaut

I met cosmonaut Sergei Volkov the other day as well as astronaut Andreas Mogensen (yeah I was geeking out hard) and I asked Sergei, after a total of 1½ year in space, what came as the biggest surprise and I expected this grand answer..

but he was like “in space, your t-shirt is floating too. It’s not hanging on you. It’s a weird sensation. There’s not really anything in space that stresses your body which is why we exercise.. like Andreas said, first time in space, you forget that you can just leave your fork floating while you’re opening your food. you try and put it down on a surface or hold everything in your hand like you’re afraid to drop it. And the fact that you can work 10 hours and concentrate really hard and not be sore in your neck.. Because there’s no gravity pulling at you. Dreams change as well after a while. I would dream about doing stuff on the space station but in my dreams there was gravity. It’s such a basic human thing, gravity.”

on the subject of returning back to earth: “Once you get back to earth, the first few days are tough. I took a shower instead of a bath, and it felt like the water was crushing me, I had to step out of the shower, it was just too overwhelming. Holding up your cell phone to your ear, It’s like holding a brick.”