Glossary

Ep. 14 Dark Matter Part 1 - HD and the Void

In preparation for a future interview with someone who knows much more about astroparticle physics and dark matter than I do, tune in this week for a quick-and-dirty breakdown of a theoretical particle that, if it exists, would clarify a couple of...

We’re getting theoretical here, and not just astronomy theory but particle theory. That’s right, it’s a dark matter podcast! Learn what some astronomers think it is and why other astronomers think there are better explanations for certain nutty galactic phenomena. Hear about MACHOs and WIMPs! Also learn what dark matter is too hot, too cold, too medium, or just right! 

Below the cut are my sources, music credits, a vocab list, a timeline of the scientists I mention, and the transcript of this episode. Tell me 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 and maybe review it, and tell friends if you think they’d like to listen!

(There’s a lot of ever-evolving info about dark matter and I was not able to cover all of it in just one episode, so get excited to hear about dark matter’s friend, dark energy, on November 6th. My thoughts on the episode after that are still the Voyager golden records, space race history, the transit of Venus, the Moon landing, or Edmond Halley. Let me know what you think!)

Glossary

astroparticle physics - the interface between astrophysics and particle physics.

baryons - heaviest particles. Ex. Protons, neutrons. In astroparticle physics, electrons are included in baryonic matter.

bosons - particles that can exist in the same state at the same location at the same time. Ex. Photons, Higgs boson.

cosmic microwave background radiation - the electromagnetic radiation left over from the time of recombination in Big Bang cosmology.

dark matter - a theoretical mass made up of unknown particles that have not been created on Earth. It is used to explain why galaxy clusters have 10x the mass that their light output suggests they would have; why distant stars on the edges of spiral galaxies orbit at the same speed as stars near the center of the galaxy; and the accretion of gases that created galaxies at the beginning of the universe.

fermions - particles that cannot exist in the same state at the same location at the same time. Ex. Protons, neutrons, electrons, leptons.

gravitational lensing - when light from more distant sources passes near a massive star, galaxy, or galaxy cluster and the object’s gravity bends the light like a lens to provide a warped angle view of space.

leptons - lightest particles. Ex. Electrons, neutrinos, tau particles, muons.

MACHO - acronym for MAssive Compact Halo Object. Made of baryonic matter, these objects are a theoretical explanation that takes the place of dark matter and include neutron stars, black holes, or brown dwarfs.

mesons - medium-weight particles. Ex. Pions, kaons.

Planck satellite - a spacecraft that operated from 2009 to 2012. It measured the dark matter content of the universe by looking at the cosmic microwave background radiation and seeing how dark matter clumped and drew the regular matter together to form galaxies.

WIMP - acronym for Weakly Interacting Massive Particle. Theoretical particles that can pass through ordinary matter without affecting it.

Wilkinson Microwave Anisotropy Probe - a spacecraft operating from 2001 to 2010 which measured temperature differences in the cosmic microwave background radiation leftover from the Big Bang.

Transcript

Sources

Fritz Zwicky via the Swedish Morphological Society

Fritz Zwicky via the American Museum of Natural History

Zwicky: “Astronomers are spherical bastards. No matter how you look at them they are just bastards“

Vera Rubin via the American Museum of Natural History

Vera Rubin via Astronomy Magazine

Morton Roberts’ 2007 article on dark matter via Harvard

Particle classifications via PhysicsNet.co.uk

Leptons via Georgia State University, copyright 2001 and all written by Carl “Rod” Nave, who has a teaching award named after him at GSU. Go Rod!

Fermions and bosons via The Particle Adventure

MOND theory by Mordehai Milgrom, published in Scientific American Aug. 2002

Newton’s Second Law of Motion via NASA

MACHOs and WIMPs via NASA

MACHOs and WIMPs via the Encyclopedia of Astronomy and Astrophysics

Bertone, Gianfranco. Behind the Scenes of the Universe: From the Higgs to Dark Matter. Oxford U P: Oxford, 2013.

Tucker, Wallace H. Chandra’s Cosmos: Dark Matter, Black Holes, and Other Wonders Revealed by NASA’s Premier X-Ray Observatory. Smithsonian Books: Washington, D.C, 2017.

“a mysterious force that causes the observed accelerating expansion of the universe” (3).

“sterile neutrinos, axions, asymmetric dark matter, mirror dark matters, and extradimensional dark matter” (23).

“the concentration of dark matter is leveling off, rather than peaking sharply, in the central regions of this cluster” (31).

Timeline

Albert Einstein, German/Austrian (1879-1955)

Edwin Hubble, American (1889-1953)

Walter Baade, German (1893-1960)

Fritz Zwicky, Swiss (1898-1974)

Enrico Fermi, Italian (1901-1954)

Morton S. Roberts, American (1926- )

Vera Rubin, American (1928-2016)

Peter Higgs, English (1929- )

Kent Ford, American (1931- )

Mordehai Milgrom, Israeli (1946- )

Romeel Dave

Rachel Somerville

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

Filler Music: ‘Darkmatter’ by Andrew Bird off his album Fingerlings 3

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

Cassini Just Sent Back Closest Ever Images of Saturn, And They're Incredible

NASA's Cassini probe is plunging to its death. The nuclear-powered spacecraft has orbited Saturn for 13 years, and sent back hundreds of thousands of images. The photos include close-ups of the gaseous giant, its famous rings, and its enigmatic moons - including Titan, which has its own atmosphere, and icy Enceladus, which has a subsurface ocean that could conceivably harbour microbial life.

YO THAT SHIT BALLER AS FUCK HOLY SHIT

Ep. 7 Measuring Mechanisms - HD and the Void

Learn about four ancient (and contemporary, if you work on a ship) devices that utilize very specific areas of astronomy to help you figure out where you are and what time it is, and also predict where celestial bodies will be on other dates and a...

Observing stars is all well and good, but how can I use stars to make my life easier? With a few handy tools and a lot of complicated math and careful table scouting, of course! Okay, it’s not actually any easier to tell where you are, predict when the Sun will rise or where the star Rigel will be at 11:36pm EST, or guess when the next eclipse will be using these tools, but if you don’t have a computer handy maybe it will help.

I did my best to describe all these odd devices in the clearest terms I could but you can hit me up with questions if you have them! Definitely check out some of the video links if you can’t quite picture what I said. I’m also on Twitter at @HDandtheVoid if you’d rather ask me there. And please check out the podcast on iTunes, rate it or review it if you’d like, and subscribe! I’ll always post all the extras here on Tumblr but iTunes is probably more convenient for downloading.

Below the cut are my sources, music credits, vocab list, and the transcript. I mention a play and a story/book and quote an astronomy book in this episode so if you want to see that written down, those sources are there as well. Let me know what you think of this episode, let me know what you think I should research next*, tell me a fun space fact… anything’s helpful!

*(My thoughts were planets, spectroscopy, or Edmond Halley. Let me know by the 6th and I’ll have the next podcast up by July 17th!)

Glossary:

armillary sphere - a device showing the apparent daily motion of the Sun depending on the season, the date, and the latitude of observation. See example video in the link.

Antikythera Mechanism - a device used to establish a calendar based on the Metonic Cycle; eclipse prediction; the location of planets, the Sun, and the Moon on a particular day; and determine the phase of the Moon on a particular day. See example video in the link.

astrolabe - a device for measuring the altitudes of certain celestial objects and for calculating latitude before the development of the sextant. One side is indented, the space called the mater, and can hold a plate depicting the local latitude. Over this plate is a rete, which points out different fixed stars as well as the Sun’s ecliptic, divided into 30 degree sections representing the zodiac signs. On top of the rete was a clock-like hand that stretched the diameter of the astrolabe, called the rule. The rule and rete could be rotated over the face of the plate. See example in the link.

azimuth -  a section of the horizon measured between a fixed point and the vertical circle passing through the center of an object. See example in the link.

declination - the angle of the Sun relative to the equator. The Sun’s angle changes with the seasons.

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

exeligmos cycle - a cycle that is 3 times the saros cycle, or 669 months. It is more accurate means of predicting eclipses and additionally predicts eclipses that will be visible from a location close to the initial eclipse.

kamal - an Arabic navigation tool consisting of a knotted string and a piece of wood. A navigator would tie a knot in the string and, by holding it in their teeth, sight the North Star along the top of the wooden piece and the horizon along the bottom. To return home, the navigator would sail north or south to bring Polaris to the altitude they had observed in their home port, then turn left or right and sail down the latitude, keeping Polaris at a constant angle. Over time, Arab navigators started tying knots at regular intervals of a fingerwidth, called an issbah, that’s about 1 degree and 36 minutes.

metonic cycle - a 19-year cycle developed by the Babylonians to sync their lunar months with the solar year. In the Metonic cycle, there would be 12 years that lasted 12 lunar months and 7 years that lasted 13 months.

saros cycle - a cycle of 223 months that is used to predict eclipses.

sextant - a device used to determine an observer’s location based on the observation of a known celestial object and a lot of calculation. It is still in use by sailors.

stereographic projection - a process for depicting a spherical, 3-dimensional object on a flat surface. An imaginary line is drawn from one point on the object to a point on the flat surface, following an angle to achieve the same relationship between each point on the object. See example in the link

Script/Transcript

Sources:

Video of how to use an armillary sphere

History of the armillary sphere via University of Cambridge

Video lecture on using an armillary sphere. It sounds like he’s trying to sell it.

Video of how to use an astrolabe

Make your own astrolabe suggestions via In the Sky.org

An old guy kept up a website on astrolabes but he died in April 2016, it’s very sad. Excellent info though.

Explanation of unequal hours

Pullman Car Hiawatha summary, just to prove it’s a real play

Chaucer’s Canterbury Tales with its brief astrolabe mention

Video on how to use a sextant

The many uses of a sextant via Classic Sailing

Why a sextant works via Trailnotes

The history of the sextant

The definition of azimuth

The definition of declination

Video of Antikythera Mechanism’s virtual model based on a theoretical and mechanical model. Just a theoretical model!

Antikythera Mechanism via Smithsonian Magazine

The Antikythera Mechanism Research Project website

Antikythera Mechanism via The New Yorker

Saros cycle via NASA

Saros and Exeligmos cycles

Crouper, Heather and Nigel Henbest. The History of Astronomy. Firefly Books: Buffalo, NY, 2007.

“The circular gear wheels of the Antikythera Mechanism reflect the ancient Greeks’ preoccupation with circles—and with the idea that everything in the sky moves around in circular paths, because the heavens are the home of perfection, and a circle is the ideal shape.” (59)

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

Filler Music: ‘Brooklyn Nights Guitar’ loop from Garageband

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

The Orion Nebula

via reddit

Does all capsules drops in Kazakhstan on return after every mission?

Since the US Space Shuttle retired in 2011, we launch to and return from the Space Station with the Russian Space Agency.  So yes, these capsules (the Soyuz) land in Kazakhstan (or surrounding regions).  However, different spacecrafts have different reentry trajectories, depending on where they aim to land.  As you might recall, the Apollo mission capsules landed in the ocean.  Since Space-X and Boeing are currently building new vehicles so that we will also launch from the US again to get to the International Space Station, these spacecraft will return to the US. For example, you may have seen footage of Space-X cargo vehicles splashing down into the Pacific over the last few years. The Boeing Starliner plans to land on land instead of water. NASA is also currently building the Orion spacecraft, which will take us to destinations beyond low earth orbit (where the Space Station is), whether that be the Moon or Mars or another target.  Orion will also splash down in the ocean.  

When the sun sets on Stonehenge on the shortest day of the year, it’s rays align with several important stones.  Twice a year, the streets of Manhattan also line up with the setting sun, a phenomenon dubbed “Manhattanhenge”. Really, most cities with grid systems will see a similar effect (though it’s most dramatic in cities with tall buildings and a view of the true horizon).  You can use a great tool called The Photographer’s Ephemeris to find out the “henge” dates for your city grid - or even individual streets.

Yesterday, (Friday, January 24th) the sun lined up with New York Avenue, a street in DC that runs diagonally up to the White House. (The orange line indicates alignment with the setting sun).

I went out with our multimedia intern Meg Vogel, and captured some images of the sun setting in line with a rather Stonehenge-y sculpture that sits in the middle of that street.

Here are dates for sunset “henge” events in some cities this year:

Manhattan May 25th, July 17th

Philadelphia April 5th, September 6th

Washington DC March 18th, September 24th

Chicago March 16th, September 26th

Phoenix March 20th, September 22nd

Portland, OR March 18th, September 24th

Is your city/town a grid? When’s your henge?

why is there star

gas cloud get squished (gravitational collapse) then sometimes smaller elements can squish together to make bigger elements (nuclear fusion) and this continues as long as the smolest elements (hydrogen and helium) are in the core

NASA's Swift Mission Maps a Star's 'Death Spiral' into a Black Hole

NASA - Swift Mission patch. March 20, 2017 Some 290 million years ago, a star much like the sun wandered too close to the central black hole of its galaxy. Intense tides tore the star apart, which produced an eruption of optical, ultraviolet and X-ray light that first reached Earth in 2014. Now, a team of scientists using observations from NASA’s Swift satellite have mapped out how and where these different wavelengths were produced in the event, named ASASSN-14li, as the shattered star’s debris circled the black hole. “We discovered brightness changes in X-rays that occurred about a month after similar changes were observed in visible and UV light,” said Dheeraj Pasham, an astrophysicist at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts, and the lead researcher of the study. “We think this means the optical and UV emission arose far from the black hole, where elliptical streams of orbiting matter crashed into each other.”

Swift Charts a Star’s ‘Death Spiral’ into Black Hole

Video above: This animation illustrates how debris from a tidally disrupted star collides with itself, creating shock waves that emit ultraviolet and optical light far from the black hole. According to Swift observations of ASASSN-14li, these clumps took about a month to fall back to the black hole, where they produced changes in the X-ray emission that correlated with the earlier UV and optical changes. Video Credits: NASA’s Goddard Space Flight Center. Astronomers think ASASSN-14li was produced when a sun-like star wandered too close to a 3-million-solar-mass black hole similar to the one at the center of our own galaxy. For comparison, the event horizon of a black hole like this is about 13 times bigger than the sun, and the accretion disk formed by the disrupted star could extend to more than twice Earth’s distance from the sun. When a star passes too close to a black hole with 10,000 or more times the sun’s mass, tidal forces outstrip the star’s own gravity, converting the star into a stream of debris. Astronomers call this a tidal disruption event. Matter falling toward a black hole collects into a spinning accretion disk, where it becomes compressed and heated before eventually spilling over the black hole’s event horizon, the point beyond which nothing can escape and astronomers cannot observe. Tidal disruption flares carry important information about how this debris initially settles into an accretion disk. Astronomers know the X-ray emission in these flares arises very close to the black hole. But the location of optical and UV light was unclear, even puzzling. In some of the best-studied events, this emission seems to be located much farther than where the black hole’s tides could shatter the star. Additionally, the gas emitting the light seemed to remain at steady temperatures for much longer than expected. ASASSN-14li was discovered Nov. 22, 2014, in images obtained by the All Sky Automated Survey for SuperNovae (ASASSN), which includes robotic telescopes in Hawaii and Chile. Follow-up observations with Swift’s X-ray and Ultraviolet/Optical telescopes began eight days later and continued every few days for the next nine months. The researchers supplemented later Swift observations with optical data from the Las Cumbres Observatory headquartered in Goleta, California.

Image above: This artist’s rendering shows the tidal disruption event named ASASSN-14li, where a star wandering too close to a 3-million-solar-mass black hole was torn apart. The debris gathered into an accretion disk around the black hole. New data from NASA’s Swift satellite show that the initial formation of the disk was shaped by interactions among incoming and outgoing streams of tidal debris. Image Credit: NASA’s Goddard Space Flight Center.  In a paper describing the results published March 15 in The Astrophysical Journal Letters, Pasham, Cenko and their colleagues show how interactions among the infalling debris could create the observed optical and UV emission. Tidal debris initially falls toward the black hole but overshoots, arcing back out along elliptical orbits and eventually colliding with the incoming stream. “Returning clumps of debris strike the incoming stream, which results in shock waves that emit visible and ultraviolet light,” said Goddard’s Bradley Cenko, the acting Swift principal investigator and a member of the science team. “As these clumps fall down to the black hole, they also modulate the X-ray emission there.”

Swift spacecraft. Image Credit: NASA

Future observations of other tidal disruption events will be needed to further clarify the origin of optical and ultraviolet light. Goddard manages the Swift mission in collaboration with Pennsylvania State University in University Park, the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Virginia. Other partners include the University of Leicester and Mullard Space Science Laboratory in the United Kingdom, Brera Observatory and the Italian Space Agency in Italy, with additional collaborators in Germany and Japan. Related: Scientists Identify a Black Hole Choking on Stardust (MIT): http://news.mit.edu/2017/black-hole-choking-stardust-0315 ASASSN-14li: Destroyed Star Rains onto Black Hole, Winds Blow it Back: http://chandra.harvard.edu/photo/2015/tidal/ 'Cry’ of a Shredded Star Heralds a New Era for Testing Relativity: https://www.nasa.gov/mission_pages/swift/bursts/shredded-star.html Researchers Detail How a Distant Black Hole Devoured a Star: https://www.nasa.gov/mission_pages/swift/bursts/devoured-star.html All Sky Automated Survey for SuperNovae (ASASSN): http://www.astronomy.ohio-state.edu/~assassin/index.shtml Las Cumbres Observatory: https://lco.global/ NASA’s Swift: http://www.nasa.gov/mission_pages/swift/main/index.html Images (mentioned), Video (mentioned), Text, Credits: NASA’s Goddard Space Flight Center, by Francis Reddy/Karl Hille. Greetings, Orbiter.ch Full article

Binary star systems have come up a lot in the past 18 podcasts, and here is a perfect example of them!

As promised, here is a comic about the brightest star in the northern Hemisphere: Sirius! Sirius B will be shown in future comics as 2018 is year of the dog and since Sirius is the dog star, it is year of the Sirius!

Enjoy!

https://www.space.com/21702-sirius-brightest-star.html