Glossary
Stargazing is a difficult task, especially under adverse weather conditions, but human beings have also made it much harder for ourselves with all these pesky electrical lights and such. Light pollution affects vast swathes of inhabited land, but the introduction of Dark Sky Reserves helps to improve observational conditions for amateur and professional astronomers. Today, you get to hear more about Dark Sky Reserves as well as the Bortle Scale, which is used to judge the amount of light pollution affecting stargazing within an area.
Below the cut are my sources, music credits, a vocab list, and the transcript of this episode. Suggest 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. Please subscribe on iTunes, rate it and maybe review it, and tell friends if you think they’d like to hear it!
(My thoughts on the next episode are space race history, the transit of Venus, Shen Kuo, or Walter Baade. The next episode will be up on December 18th.)
Glossary
airglow - a very faint, bluish, naturally occurring glow that hangs around the horizon on Earth, usually within about 15 degrees of the horizon line.
Bortle Scale - an objective scale to measure the clarity and effect of light pollution on a night’s stargazing. Black and grey zones are the best for stargazing, blue is for rural skies, green and yellow are the rural/suburban transition zone, orange is the suburban sky, red is bright suburbia, and white is for cities and inner cities.
deep-sky object - any cosmological object that isn’t individual stars or something from our Solar System. It’s a classification that includes nebulae, galaxies, and star clusters, and it has its roots in amateur astronomy.
ecliptic - the path of the Sun across the sky over the course of a year.
gegenschein - a faint brightening in the night sky directly opposite the Sun. Astronomers think it’s caused by the reflection of sunlight off of dust ejected by comets or resulting from asteroid destruction.
light pollution - the excessive, misdirected, or intrusive use of artificial, human-made lighting. There are several major types of light pollution:
glare - when too-bright and poorly directed lights blind people.
light trespass - when neighboring lights are so bright that their light spills over and illuminates others’ property.
overillumination - when excessive lights are used in a small area.
skyglow - the visible glow caused by light scattering and reflecting off of the droplets of atmospheric molecules.
lumen - a measurement of a light’s brightness.
magnitude - the measurement of a star’s brightness as seen from Earth. The brighter it is, the lower its magnitude value. Ex. the Sun has an apparent magnitude of -27.
Messier object - a deep-sky object included on a list of 103-110 deep-sky objects made by Charles Messier and his colleagues in the 18th century in an attempt to prevent fuzzy, bright objects from being confused with comets.
zodiacal light - a faint brightening in the night sky along the ecliptic that results from sunlight scattered forward off dust in the direction of the Sun.
Transcript
Sources
Sodium lamp light pollution reduction effects via Flagstaff Dark Skies Coalition
Types of light pollution via the British Astronomical Association’s Campaign for Dark Skies, 2009
Light pollution via Sky and Telescope, Dec 2008
The World Atlas of Artificial Night Sky Brightness via the Light Pollution Science and Technology Institute
Lumens and watts via Lowes
UNESCO World Heritage Site list
Invention of the light bulb via SPS Industrial
Lightbulb components via CIO
Walter Baade bio via the Royal Astronomy Society of Canada
International Dark-Sky Association
“An IDA International Dark Sky Reserve is a public or private land possessing an exceptional or distinguished quality of starry nights and nocturnal environment that is specifically protected for its scientific, natural, educational, cultural, heritage and/or public enjoyment. Reserves consist of a core area meeting minimum criteria for sky quality and natural darkness, and a peripheral area that supports dark sky preservation in the core. Reserves are formed through a partnership of multiple land managers who have recognized the value of the natural nighttime environment through regulations and long-term planning.”
“The core area must provide an exceptional dark sky resource, relative to the communities and cities that surround it, where the night sky brightness is routinely equal to or darker than 20 magnitudes per square arc second.”
John Bortle’s article on his magnitude scale via Sky and Telescope, July 2006
“I have created a nine-level scale. It is based on nearly 50 years of observing experience. I hope it will prove both enlightening and useful to observers — though it may stun or even horrify some! Should it come into wide use, it would provide a consistent standard for comparing observations with light pollution.”
John E. Bortle receives the Leslie C. Peltier Award in 2013 via the Astronomical Society
Bortle dark sky scale via Big Sky Astronomy Club
Bortle dark sky scale via LSU
Gegenschein via Sky and Telescope, Oct 2015
Messier List via Fred Espenak’s website, Astropixels
Caldwell List via Students for the Exploration and Development of Space (SEDS)
Intro Music: ‘Better Times Will Come’ by No Luck Club off their album Prosperity
Filler Music: ‘New Son/Burnt Iron’ by Trampled by Turtles off their album Palomino
Outro Music: ‘Fields of Russia’ by Mutefish off their album On Draught
More Posts from Fillthevoid-with-space and Others
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.”
Voyager is so happy, because it’s the bravest satellite of all. It has gone the furthest. And it’s not lonely, because it’s talking to us. It phones home. And it tells us all about the wonderful things that it’s seeing. …There’s a whole universe to explore, and it’s just leaving our Solar System right now. It’s very brave and very lucky to be doing what it’s doing, so it’s not going to get lost. It’s traveled further than anything we’ve ever built has traveled before. It’s actually showing us the way. … It might have been safer for it to just stay home, and stay inside a building, but then it would have been sad forever, because it never would have done its purpose. It never would have discovered things. It’s all a wonderful story of great discovery and success, and it couldn’t have happened if Voyager hadn’t been brave… It’s not really the fact that everything always has a start and an end, it’s what happens in the middle that counts. What do you while you’re alive? What do you do while you’re laughing? And I think we’re doing exactly what makes Voyager joyful and as happy as it could be. Think about the fact that you’re a little bit like Voyager. In that you’re going to go see the world, and you’re going to call your mom on the phone and tell her about the wonderful things that you see. … You wouldn’t want to spend your whole life hiding under your bed and never seeing anything in your whole life, you want to be able to do what makes you happy and joyful and learn about things to discover. You might be the person that discovers something really important for everybody else on the world, but you can never discover that if you just hide and only do things that are safe. So think about yourself a little bit like Voyager. What makes you laugh? It’s not just staying, hiding underneath your bed safely at home.
Cmdr. Chris Hadfield, reassuring a five-year-old who was worried about the Voyager satellite (source)
oh no I’m having feelings about a satellite
tagging Doctor Who, because.
(via reconditarmonia)
Happy long weekend to folks in the US who are lucky enough to HAVE a long weekend! I finally fulfilled my promise to bring you an episode on comets—I didn’t last month but I had a good reason, and that reason was black holes. Now you can learn about comets! I’ve likewise talked about comets before, but now I go in-depth on what they are, some great comets throughout human history, and some of the missions we’ve sent out to collect info on comets.
Below the cut are the glossary, transcript, a timeline of all the people I mention, sources, and music credits. Send me any topic suggestions via Tumblr message (you don’t need an account to do this, just submit as anonymous). You can also tweet at me on Twitter at @HDandtheVoid, or you can ask me to my face if you know me in real life. Subscribe on iTunes to get the new episodes of my semi-monthly podcast, and please please please rate and review it. Go ahead and tell friends if you think they’d like to hear it, too!
(The next episode is... not decided, or even thought about much. It’ll go up at the end of June if I come up with a topic, though!)
Glossary
coma - the cloud of dust and gas particles that is burned off of a comet and trails behind it, helping to form the comet’s tail.
comet - a small, icy body that orbits the Sun. When its orbit takes it close to the Sun, the comet warms up and releases gases and debris that produce a visible atmosphere, sometimes called the comet’s tail. (ep. 8, 9, 33)
hyperbolic comets - comets which will only ever enter our solar system once.
long period comets - comets come near our Sun for brief times every few thousand years, following egg-shaped elliptical orbits that often send them beyond Pluto before they return to the Sun.
short-period comets - comets that orbit the Sun closely and show up at regular intervals.
sungrazing comets - comets which come within about 850,000 miles from the Sun at their perihelion, though many of these kinds of comets come even closer, to within a few thousand miles at perihelion.
perihelion - a comet’s closest approach to the Sun in its orbit.
Transcript
Timeline
Ephorus of Cyme (c. 400-330 BCE), Greek
Taqi ad-Din (1526–1585), Turkish
Tycho Brahe (1546-1601), Danish
Gottfried Kirch (1639-1710), German
Isaac Newton (1643-1727), English
Eusebio Kino (1645-1711), Spanish
Edmund Halley (1656-1742), English
Battista Donati (1826-1873), Italian
Jérôme Eugène Coggia (1849-1919), French
Heinrich Kreutz (1854-1907), German
Frank Skjellerup (1875-1952), Australian
Edmundo Maristany (1895-1983), Argentinian
Sylvain Arend (1902-1992), Belgian
Georges Roland (1922-1991), Belgian
Eugene Shoemaker (1928-1997), American
Carolyn Shoemaker (1929- ), American
Tsutomu Seki (1930- ), Japanese
Richard Martin West (1941- ), Danish
Kaoru Ikeya (1943- ), Japanese
David H. Levy (1948- ), Canadian
Thomas Bopp (1949-2018), American
Yuji Hyakutake (1950- ), Japanese
Robert McNaught (1956- ), Scottish-Australian
Alan Hale (1958- ), American
Terry Lovejoy (1966- ), Australian
Sources
Comets via Cool Cosmos (August 2013)
Comet Introduction via Views of the Solar System
On Hyperbolic Comets by David W. Hughes (1991)
What is a Sungrazing Comet? via NASA (July 2013)
Missions to Comets via NASA
Galileo via NASA
Shoemaker-Levy 9 via NASA
Rosetta Images via ESA (video)
Rosetta spacecraft image archive complete via EarthSky (June 2018)
Intro Music: ‘Better Times Will Come’ by No Luck Club off their album Prosperity
Filler Music: ‘Stories We Build/Stories We Tell’ by José González off his album Vestiges & Claws
Outro Music: ‘Fields of Russia’ by Mutefish off their album On Draught
Five Famous Pulsars from the Past 50 Years
Early astronomers faced an obstacle: their technology. These great minds only had access to telescopes that revealed celestial bodies shining in visible light. Later, with the development of new detectors, scientists opened their eyes to other types of light like radio waves and X-rays. They realized cosmic objects look very different when viewed in these additional wavelengths. Pulsars — rapidly spinning stellar corpses that appear to pulse at us — are a perfect example.
The first pulsar was observed 50 years ago on August 6, 1967, using radio waves, but since then we have studied them in nearly all wavelengths of light, including X-rays and gamma rays.
Typical Pulsar
Most pulsars form when a star — between 8 and 20 times the mass of our sun — runs out of fuel and its core collapses into a super dense and compact object: a neutron star.
These neutron stars are about the size of a city and can rotate slowly or quite quickly, spinning anywhere from once every few hours to hundreds of times per second. As they whirl, they emit beams of light that appear to blink at us from space.
First Pulsar
One day five decades ago, a graduate student at the University of Cambridge, England, named Jocelyn Bell was poring over the data from her radio telescope - 120 meters of paper recordings.
Image Credit: Sumit Sijher
She noticed some unusual markings, which she called “scruff,” indicating a mysterious object (simulated above) that flashed without fail every 1.33730 seconds. This was the very first pulsar discovered, known today as PSR B1919+21.
Best Known Pulsar
Before long, we realized pulsars were far more complicated than first meets the eye — they produce many kinds of light, not only radio waves. Take our galaxy’s Crab Nebula, just 6,500 light years away and somewhat of a local celebrity. It formed after a supernova explosion, which crushed the parent star’s core into a neutron star.
The resulting pulsar, nestled inside the nebula that resulted from the supernova explosion, is among the most well-studied objects in our cosmos. It’s pictured above in X-ray light, but it shines across almost the entire electromagnetic spectrum, from radio waves to gamma rays.
Brightest Gamma-ray Pulsar
Speaking of gamma rays, in 2015 our Fermi Gamma-ray Space Telescope discovered the first pulsar beyond our own galaxy capable of producing such high-energy emissions.
Located in the Tarantula Nebula 163,000 light-years away, PSR J0540-6919 gleams nearly 20 times brighter in gamma-rays than the pulsar embedded in the Crab Nebula.
Dual Personality Pulsar
No two pulsars are exactly alike, and in 2013 an especially fast-spinning one had an identity crisis. A fleet of orbiting X-ray telescopes, including our Swift and Chandra observatories, caught IGR J18245-2452 as it alternated between generating X-rays and radio waves.
Scientists suspect these radical changes could be due to the rise and fall of gas streaming onto the pulsar from its companion star.
Transformer Pulsar
This just goes to show that pulsars are easily influenced by their surroundings. That same year, our Fermi Gamma Ray Space Telescope uncovered another pulsar, PSR J1023+0038, in the act of a major transformation — also under the influence of its nearby companion star.
The radio beacon disappeared and the pulsar brightened fivefold in gamma rays, as if someone had flipped a switch to increase the energy of the system.
NICER Mission
Our Neutron star Interior Composition Explorer (NICER) mission, launched this past June, will study pulsars like those above using X-ray measurements.
With NICER’s help, scientists will be able to gaze even deeper into the cores of these dense and mysterious entities.
For more information about NICER, visit https://www.nasa.gov/nicer
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
Merging Galaxies Have Enshrouded Black Holes
NASA - NuStar Mission patch. May 9, 2017 Black holes get a bad rap in popular culture for swallowing everything in their environments. In reality, stars, gas and dust can orbit black holes for long periods of time, until a major disruption pushes the material in. A merger of two galaxies is one such disruption. As the galaxies combine and their central black holes approach each other, gas and dust in the vicinity are pushed onto their respective black holes. An enormous amount of high-energy radiation is released as material spirals rapidly toward the hungry black hole, which becomes what astronomers call an active galactic nucleus (AGN). A study using NASA’s NuSTAR telescope shows that in the late stages of galaxy mergers, so much gas and dust falls toward a black hole that the extremely bright AGN is enshrouded. The combined effect of the gravity of the two galaxies slows the rotational speeds of gas and dust that would otherwise be orbiting freely. This loss of energy makes the material fall onto the black hole.
Image above: This illustration compares growing supermassive black holes in two different kinds of galaxies. A growing supermassive black hole in a normal galaxy would have a donut-shaped structure of gas and dust around it (left). In a merging galaxy, a sphere of material obscures the black hole (right). Image Credits: National Astronomical Observatory of Japan. “The further along the merger is, the more enshrouded the AGN will be,” said Claudio Ricci, lead author of the study published in the Monthly Notices Royal Astronomical Society. “Galaxies that are far along in the merging process are completely covered in a cocoon of gas and dust.” Ricci and colleagues observed the penetrating high-energy X-ray emission from 52 galaxies. About half of them were in the later stages of merging. Because NuSTAR is very sensitive to detecting the highest-energy X-rays, it was critical in establishing how much light escapes the sphere of gas and dust covering an AGN. The study was published in the Monthly Notices of the Royal Astronomical Society. Researchers compared NuSTAR observations of the galaxies with data from NASA’s Swift and Chandra and ESA’s XMM-Newton observatories, which look at lower energy components of the X-ray spectrum. If high-energy X-rays are detected from a galaxy, but low-energy X-rays are not, that is a sign that an AGN is heavily obscured.
NASA’s NuSTAR telescope. Image Credit: NASA
The study helps confirm the longstanding idea that an AGN’s black hole does most of its eating while enshrouded during the late stages of a merger. “A supermassive black hole grows rapidly during these mergers,” Ricci said. “The results further our understanding of the mysterious origins of the relationship between a black hole and its host galaxy.” NuSTAR is a Small Explorer mission led by Caltech and managed by NASA’s Jet Propulsion Laboratory for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. JPL is managed by Caltech for NASA. Related link: Monthly Notices of the Royal Astronomical Society: https://academic.oup.com/mnras/article/468/2/1273/2939810/Growing-supermassive-black-holes-in-the-late For more information on NuSTAR, visit: http://www.nasa.gov/nustar http://www.nustar.caltech.edu Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau. Greetings, Orbiter.ch Full article
Hubble Showcases a Remarkable Galactic Hybrid : UGC 12591s classification straddles somewhere between a lenticular and a spiral galaxy. It lies just under 400 million light-years from us in the PiscesPerseus Supercluster.
js
This is an article from last year, but still very exciting news! I wonder how far it’s progressed since?
The venerable Voyager 1 spacecraft. Still impressing after all these years.
-
lifeofaliceai liked this · 7 years ago -
fillthevoid-with-space reblogged this · 7 years ago
A podcast project to fill the space in my heart and my time that used to be filled with academic research. In 2018, that space gets filled with... MORE SPACE! Cheerfully researched, painstakingly edited, informal as hell, definitely worth everyone's time.
243 posts