Glossary

The Crab Nebula

via reddit

Ep. 21 Radio Astronomy and RQZs - HD and the Void

Be brave in the face of an extremely technical episode where I tackle radio astronomy! Astronomers collect radio waves to map distant objects. To do their work they need a level of quiet that's hard to find without some help from Radio Frequency I...

I’ve gotten some feedback that episodes can be too technical. Unfortunately, that feedback came too late to save you from this week’s episode, which requires me to summarize the electromagnetic spectrum, radio astronomy, a concept called interferometry, and government regulations to talk about the topic that originally started me on this path: radio quiet zones. Please, bear with me! Pardon my mess! It was all very interesting stuff, I couldn’t resist digging into it.

Below the cut are my sources, music credits, a vocab list, a timeline of the astronomers I mention, and the transcript of this episode. I’ve bolded those sources I mention in the podcast, including the podcast that started me on this topic: The Adventure Zone! Please 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. I’d love it if you would subscribe on iTunes, rate my humble little podcast and maybe review it, and tell friends if you think they’d like to hear it!

(My thoughts on the next episode are SOFIA, which you need to listen to find out what it stands for, or the pilot Chuck Yaeger. The next episode will go up February 26th.)

Glossary

aperture synthesis - the process of collecting electromagnetic radiation from a variety of separate, small telescopes and then combining this data to recreate the image at a higher resolution than would be possible with a single telescope.

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

hertz - the number of times an electromagnetic wave cycles per second. One cycle per second is 1 hertz.

interferometry - a group of techniques to extract information from superimposing electromagnetic waves to create interference. In radio astronomy, this is done by using a wide spread of receivers to look at the same distant object, then bringing that data together with a correlator that can create a larger, clearer picture than an individual radio telescope alone could.

radiation - energy that travels and spreads out as it goes.

Script/Transcript

Timeline

Joseph-Louis Lagrange, French (1736-1813)

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

Edward W. Morley, American (1838-1923)

Albert A. Michelson, American (1852-1931)

Sir Martin Ryle, British (1918-1984)

Bernard Yarnton Mills, Australian (1920-2011)

Derek Vonberg, British (1922-2015)

Antony Hewish, British (1924- )

Sources

Electromagnetic spectrum via NASA

Observatories across the EM spectrum via NASA

Fermi satellite via NASA

The Neil Gehrels Swift Observatory via NASA

NuSTAR via Caltech

NuSTAR via NASA

Chandra X-Ray Observatory via Harvard

The Galaxy Evolution Explorer (GALEX) via Caltech

Kepler satellite via NASA

Hubble Space Telescope via NASA

Spitzer satellite via Caltech

Stratospheric Observatory for Infrared Astronomy (SOFIA)

Planck satellite via ESA

Spekt-R Radioastron from Russia

High Energy Stereoscopic System (HESS)

W. M. Keck Observatory on Mauna Kea

South Africa Large Telescope (SALT) in Namibia

The Combined Array for Research in Millimeter-Wave Astronomy (CARMA) via Caltech

CARMA public page (decommissioned)

Very Large Array (VLA) via NRAO

Space radio telescope (1997) via NRAO

Highly Advanced Laboratory for Communications and Astronomy (HALCA) via NASA

A timeline of the history of radio interferometry via University of Groningen (Netherlands)

Interferometers via the LIGO Laboratory

Michelson-Morley Experiment via University of Virginia

Astronomical Interferometry via Magdalena Ridge Observatory

Interferometry via XKCD

How Radio Works via How Stuff Works

Radio Spectrum Allocation via the Federal Communications Commission

Interferometry via the European Space Observatory

National Radio Quiet Zone via National Radio Astronomy Observatory

“minimize possible harmful interference to the National Radio Astronomy Observatory (NRAO) in Green Bank, WV and the radio receiving facilities for the United States Navy in Sugar Grove, WV.”

National Radio Quiet Zone via CNN

“Tucked in the Allegheny Mountains, researchers are listening to exploding galaxies at the edge of the universe – a signal that is so faint, it’s about a billionth of a billionth of a millionth of a watt.”

The Quiet Zone: Where mobile phones are banned via BBC News (May 2015)

Enter The Quiet Zone: Where Cell Service, Wi-Fi Are Banned via NPR (Oct 2013)

Green Bank Observatory in West Virginia, USA

Karen O’Neil: “The types of energies we look at are less than the energy of a single snowflake falling on the Earth.”

Characteristics of radio quiet zones via International Telecommunication Union (Sept 2012)

“transmissions below 15 GHz are restricted within a certain radius around the Arecibo Observatory, located in Puerto Rico. Since no observations are carried out, nor are any expected to be carried out above that frequency in the future, no restrictions are needed on higher frequency transmissions. The reverse is not necessarily true, however. For example, some restrictions may be imposed on transmissions below 30 GHz in the neighbourhood of the large international ALMA observatory even though it is not expected to ever observe below that frequency, due to its susceptibility to interference at these lower frequencies in the signal path.”

“It is important to emphasize that a RQZ does not imply a complete absence of radio transmissions. The existence of, and coexistence with, a range of man-made devices will always be necessary. A RQZ may include options for notification of other users and for negotiation in mitigating interference. On the other hand, a RQZ does not consist entirely of mitigating techniques implemented by the radio astronomy facility; some level of control on externally-generated interference is intrinsic to a RQZ.

A RQZ is therefore a buffer zone that allows for the implementation of mechanisms to protect radio astronomy observations at a facility within the zone from detrimental radio frequency interference, through effective mitigation strategies and regulation of radio frequency transmitters.”

ALMA Observatory website

The Scientific Committee on Frequency Allocations for Radio Astronomy (IUCAF) website

Google Map of worldwide radio quiet zones (Aug 2016)

ITU-R Recommendations of Particular Importance to Radio Astronomy by A. Richard Thompson

“the necessity of maintaining the shielded zone of the Moon as an area of great potential for observations by the radio astronomy service and by passive space research, and consequently of maintaining it as free as possible from transmissions.”

The Adventure Zone: Amnesty setup episode via Maximum Fun

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

Filler Music: ‘Junkyard Chandelier’ by Radical Face aka Ben Cooper, who primarily releases music as Radical Face but also has at least three other bands or band names he’s working with/has released music as.

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

NASA Parachute Device Could Return Small Spacecraft from Deep Space Missions

ISS - International Space Station patch. March 7, 2017

After a two-month stay aboard the International Space Station, NASA’s Technology Educational Satellite (TechEdSat-5) that launched Dec. 9, 2016, was deployed on March 6, 2017 from the NanoRacks platform and into low-Earth orbit to demonstrate a critical technology that may allow safe return of science payloads to Earth from space. Orbiting about 250 miles above Earth, the Exo-Brake, a tension-based, flexible braking device resembling a cross-shaped parachute, opens from the rear of the small satellite to increase the drag. This de-orbit device tests a hybrid system of mechanical struts and flexible cord with a control system that warps the Exo-Brake. This allows engineers to guide the spacecraft to a desired entry point without the use of fuel, enabling accurate landing for future payload return missions.

Small Satellite With Exo-Brake Technology Launches From International Space Station

Two additional technologies will be demonstrated on TechEdSat-5. These include the ‘Cricket’ Wireless Sensor Module, which provides a unique wireless network for multiple wireless sensors, providing real time data for TechEdSat-5. The project team seeks to develop building blocks for larger scale systems that might enable future small or nanosatellite missions to reach the surface of Mars and other planetary bodies in the solar system. For more information on NASA’s small spacecraft technology missions, visit: http://www.nasa.gov/cubesats Image, Video, Text, Credits: NASA/Ames Research Center/Kimberly Williams. Greetings, Orbiter.ch Full article

Does Mars Have Rings? Not Right Now, But Maybe One Day

NASA - Mars Science Laboratory (MSL) patch. March 20, 2017 As children, we learned about our solar system’s planets by certain characteristics – Jupiter is the largest, Saturn has rings, Mercury is closest to the sun. Mars is red, but it’s possible that one of our closest neighbors also had rings at one point and may have them again someday. That’s the theory put forth by NASA-funded scientists at Purdue University, Lafayette, Indiana, whose findings were published in the journal Nature Geoscience. David Minton and Andrew Hesselbrock developed a model that suggests that debris that was pushed into space from an asteroid or other body slamming into Mars around 4.3 billion years ago alternates between becoming a planetary ring and clumping together to form a moon. One theory suggests that Mars’ large North Polar Basin or Borealis Basin – which covers about 40 percent of the planet in its northern hemisphere – was created by that impact, sending debris into space. “That large impact would have blasted enough material off the surface of Mars to form a ring,” Hesselbrock said. Hesselbrock and Minton’s model suggests that as the ring formed, and the debris slowly moved away from the Red Planet and spread out, it began to clump and eventually formed a moon. Over time, Mars’ gravitational pull would have pulled that moon toward the planet until it reached the Roche limit, the distance within which a planet’s tidal forces will break apart a celestial body that is held together only by gravity.

Image above: The image from NASA’s Curiosity Mars rover shows one of Mars’ two moons, Phobos, passing directly in front of the other, Deimos, in 2013. New research suggests the moons consolidated long ago from dust rings around the planet and, in the distant future, may disintegrate into new rings. Image Credits: NASA/JPL-Caltech/Malin Space Science Systems/Texas A&M Univ. Phobos, one of Mars’ moons, is getting closer to the planet. According to the model, Phobos will break apart upon reaching the Roche limit, and become a set of rings in roughly 70 million years. Depending on where the Roche limit is, Minton and Hesselbrock believe this cycle may have repeated between three and seven times over billions of years. Each time a moon broke apart and reformed from the resulting ring, its successor moon would be five times smaller than the last, according to the model, and debris would have rained down on the planet, possibly explaining enigmatic sedimentary deposits found near Mars’ equator. “You could have had kilometer-thick piles of moon sediment raining down on Mars in the early parts of the planet’s history, and there are enigmatic sedimentary deposits on Mars with no explanation as to how they got there,” Minton said. “And now it’s possible to study that material.” Other theories suggest that the impact with Mars that created the North Polar Basin led to the formation of Phobos 4.3 billion years ago, but Minton said it’s unlikely the moon could have lasted all that time. Also, Phobos would have had to form far from Mars and would have had to cross through the resonance of Deimos, the outer of Mars’ two moons. Resonance occurs when two moons exert gravitational influence on each other in a repeated periodic basis, as major moons of Jupiter do. By passing through its resonance, Phobos would have altered Deimos’ orbit. But Deimos’ orbit is within one degree of Mars’ equator, suggesting Phobos has had no effect on Deimos. “Not much has happened to Deimos’ orbit since it formed,” Minton said. “Phobos passing through these resonances would have changed that.” “This research highlights even more ways that major impacts can affect a planetary body,” said Richard Zurek of NASA’s Jet Propulsion Laboratory, Pasadena, California. He is the project scientist for NASA’s Mars Reconnaissance Orbiter, whose gravity mapping provided support for the hypothesis that the northern lowlands were formed by a massive impact. Minton and Hesselbrock will now focus their work on either the dynamics of the first set of rings that formed or the materials that have rained down on Mars from disintegration of moons. Curiosity is part of NASA’s ongoing Mars research and preparation for a human mission to Mars in the 2030s. Caltech manages JPL, and JPL manages the Curiosity mission for NASA’s Science Mission Directorate in Washington. For more about Curiosity, visit: http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/ For more information about NASA missions investigating Mars, visit: https://mars.nasa.gov/ Image (mentioned), Text, Credits: NASA/Laurie Cantillo/Dwayne Brown/JPL/Guy Webster/Purdue University/Steve Tally/Emil Venere/Writer: Brian Wallheimer. Best regards, Orbiter.ch Full article

General Relativity in 8 gifs

The Moon of Lakes and Rivers - Saturn’s moon Titan

Saturn’s moon Titan is the only world - other than earth - that we know has liquid’s pooled on its surface. Unlike Earth, Titan has lakes of liquid methane - you wouldn’t want to swim in these lakes.

Titan’s “methane cycle” is analogy to Earth’s water cycle. In the 3rd and 4th images above we can see clouds of methane in Titan’s atmosphere. Ever since NASA’s Voyager 1 spacecraft, we have known that the gases that make up Titan’s brown colored haze were hydrocarbons. The atmosphere of Titan is largely nitrogen; minor components lead to the formation of methane–ethane clouds and nitrogen-rich organic smog.

It is thanks to the Cassini spacecraft that we now understand more about the climate of Titan - though we still understand very little!

The Cassini Space craft has mapped most of the Northern polar region of Titan, this is the region that contains almost all of Titan’s lakes. Cassini is systematically sweeping across Titan and mapping the surface of this strange alien world. The image below is an example of Cassini’s mapping process:

Credit: NASA/JPL/Cassini

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

Spaceprob.es

Ep. 13 Lunar and Solar Orbits - HD and the Void

This is a short one but I do explain concepts you can see and track yourself over the months with very little effort. The shapes of the Moon and how long it takes different planets to orbit the Sun! Time is a human construct! Tidal forces and the ...

Why do the Sun and Moon move the way they do? What’s up with that? Orbits? What? It’s a short but snug little episode here about the Sun and the Moon and how they look from Earth as they zoom across the sky.

Below the cut are my sources, music credits, a vocab list, the transcript of this episode, a composite image of the different phases of the Moon, and a list of the different names for the full moons through the course of a year. 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 subscribe to  the podcast on iTunes, rate it or review it, and maybe tell your friends about it if you think they’d like to listen!

(My thoughts on the next episode, because I still haven’t found the time to cover them, are the Voyager golden records, space race history, the transit of Venus, the Moon landing, or Edmond Halley. Let me know by the 6th and I’ll hopefully have the next podcast up on October 16th.)

Glossary

blue moon - when you get two full moons in one calendar month. An older definition is when you get 4 full moons in a season, the third moon is called the ‘blue moon.’

ecliptic - the path of the Sun over the course of a year.

prograde - when a planet spins from east to west. 

retrograde - when a planet spins from west to east.

spaghettification - when extreme tidal forces pull an object apart in space.

Script/Transcript

Sources

Rising and setting times of the Sun on Earth via Cornell University

Seasons on Earth via Cornell University

Lunar phases and the Moon’s relationship to the Sun via Harvard

Tides via Hyperphysics

Tidal forces equation via AstronomyOnline.org

Tidal forces and spaghettification via NASA handout

Lunar phases composite via Fred Espenak

Names of the different full moons throughout the year via EarthSky.org

Blue moons via EarthSky.org

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

Filler Music: ‘See The Constellation’ by They Might Be Giants off their album Apollo 18

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