Glossary:

Geocentric map of the Solar System.

LUCIDA 

[noun] 

the brightest star in a constellation.

Etymology: from the full phrase in Latin stella lūcida meaning “bright star”. Lucida can be traced to the Latin verb lūcēre, "to shine,“ from lux, "light.”

[Tim Barton - Amber of the Void]

NASA asks Twitter to name the new planets.

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

People think they know darkness, and that they experience darkness everyday, but they don’t, really.

Across the United States, natural darkness is an endangered resource. East of the Mississippi, it is already extinct; even in the West, night sky connoisseurs admit that it’s quicker to find true darkness by flying to Alice Springs, Australia, than traveling to anywhere in the lower forty-eight.

Ever since the nation’s first electric streetlight made its debut in Cleveland, on April 29, 1879, the American night has become steadily brighter. In his new book, The End of Night: Searching for Natural Darkness in an Age of Artificial Light, Paul Bogard aims to draw attention to the naturally dark night as a landscape in its own right — a separate, incredibly valuable environmental condition that we overlook and destroy at our own peril.

Read More.

The Orion Nebula

via reddit

Ep. 4 Henges and Archaeoastronomy - HD and the Void

Henges are only one type of astronomical tracking and observation monument. Other kinds include using big rocks that already exist and then building something close enough to observe its interaction with the Sun; building an observatory or a big p...

Henges! What the heck are they? And why is the word for studying them (and various monuments around the world that serve a similar purpose) so friggin long? Archaeoastronomy? What even is that? I got quite a few requests for this one so hopefully I did it justice... in my own special, somewhat contrary way.

Below the cut is some elaboration on the episode itself, including my sources, music credits, a glossary, some Google Maps images of the locations I talk about, and a transcript (not an exact record of this episode, but it’s the loose, fairly conversational script I was working with). I mention a couple of books and quote a couple people in this episode so if you want to see that written down, those sources are there too. I’m also on Twitter at @HDandtheVoid.

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 at this point!

*(My thoughts were planets or star classifications. Give me some feedback by May 25th so I can start working on it! The next episode will be on June 5th.)

Glossary:

archaeoastronomy - the study of the astronomical practices, celestial lore, mythologies, religions, and world-views of all ancient cultures. The anthropology of astronomy.

equinox - twice a year, in the spring (vernal equinox) and fall (autumnal equinox), the 23.5-degree tilt of the Earth’s axis and Earth’s orbit around the sun combine in such a way that the axis is inclined neither away from nor toward the sun. The day and night are of equal length.

henge - a prehistoric monument consisting of a circle of stone or wooden uprights.

kiva - a room used for rituals and political meetings for many Southwest American Indian tribes.

petroglyph - rock carvings made by pecking directly on the rock surface using a stone chisel and a hammerstone. The desert varnish on the surface of the rock is chipped off, exposing the lighter rock underneath.

solstice - twice a year, in the summer (Midsummer) and winter (Midwinter), the 23.5-degree tilt of the Earth’s axis and Earth’s orbit around the sun mean that the axis is inclined away from or toward the sun. In Midsummer, the day is longest; in Midwinter, the day is shortest.

Script/Transcript (I do tend to embellish in the moment of recording so it’s not exact, but all the facts are there and I can’t know a fact and not talk about it so trust me, all you’re missing is probably another swear word or two)

Chaco Canyon, New Mexico, United States of America

Chichen Itza, Yucutan, Mexico

Stonehenge, Salisbury, England

Newgrange, County Meath, Republic of Ireland

Sources:

The definition of ‘henge’

A slightly more exciting definition of ‘henge,’ with pictures

Classifications of henges in the British Isles

The definition of a petroglyph, with pictures

A 3-minute video about solstices and equinoxes that has images of Chichen Itza and Stonehenge as well as Macchu Picchu, via National Geographic

Another explanation of the equinoxes and solstices; no video, though

The great Stonehenge Purchase!

More on the great Stonehenge Purchase!

Neil deGrasse Tyson writes about Manhattanhenge

Find your own city’s henge!

Burl, Aubrey. The Stone Circles of Britain, Ireland, and Brittany. Yale UP: New Haven, CT, 2000. Located on Google Books.

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

Clive Ruggles quote: “Generally people in indigenous cultures in the past tried to make sense of the cosmos—of the world around them—by drawing links between things; things in the sky, things around them in the landscape, and social things too—all mixed in” (14).

G.B. Cornucopia quote: “One of the Chacoan people’s tools was certainly astronomy, and they were interested in astronomy because anyone living in this harsh environment who does not understand their environment will not survive” (11).

Ed Krupp quote: “Usually monumental architecture isn’t dedicated to observing the sky. It’s a way that people express how they feel at home in the universe; but also how they control the universe” (21).

Glowacki, Donna M. Living and Leaving: A Social History of Regional Depopulation in Thirteenth-Century Mesa Verde. U of AZ P: Tucson, AZ, 2015. Located on Google Books.

McCluskey, S. C.  “Historical Archaeoastronomy: The Hopi Example.”  Archaeoastronomy in the New World.  Ed. A. F. Aveni.  London: Cambridge UP, 1982 (31-58).

McCluskey quote: “began watching when the sun ‘went in’ near the cultural center and motel on Second Mesa” (38).

Williamson, R. A. et al.  “Anasazi Solar Observatories.”  Native American Astronomy.  Ed. A. F. Aveni.  Austin: U Texas P, 1977 (203-218).

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

Filler Music: ‘Leaves’ by Patients 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

Escape velocities for every planet in the solar system

Jupiter’s moon, Callisto.

Check out the makeshift pinhole-camera results from 99% totality! Leaves and my own hands work quite nicely to get an image of the little sliver of sunlight that was left. I had eclipse glasses but don't have any pictures from them: 99% is still not enough to reduce the sun's light very much. It got a little gloomier and I talked about it on Twitter but otherwise it was pretty uneventful! I'm glad I'm not on the road home from eclipsing. It would be cool to see totality one day, though.