New Horizons and Ultima Thule

Just after midnight on January 1st, the New Horizons spacecraft will have its close encounter with the Kuiper Belt object Ultima Thule, also known as (486958) 2014 MU69. Since New Horizons flew by Pluto in July 2015 it has been preparing for this moment. Ultima Thule wasn’t even targeted until after the Pluto encounter was over, and it was only discovered in 2014. 

New Horizons spacecraft

Of course, the next thing is simulating the encounter in Starry Night. The first problem here is that the mission path provided for New Horizons in Starry Night doesn’t extend to the present day. However, the JPL HORIZONS service can provide updated state vectors, which I have put into the attached file New Horizons.xyz.

To get the updated mission path of New Horizons into your SciDome, download this zip, open it, and copy “New Horizons.xyz” into this folder on your Preflight computer running SciDome Version 7:

C:\ProgramData\Simulation Curriculum\Starry Night Prefs\Sky Data\Space Missions

This is a networked folder that exists on both Preflight and Renderbox computers, so the file only needs to be in one place in order to be accessible in both computers. If there is no “Space Missions” subfolder of this SkyData folder, you may have to create it. Although there will then be more than one version of the New Horizons file on your system, this one will take precedence.

Ultima Thule imagery captured by New Horizons

Next, we have to add Ultima Thule to Starry Night. I find the best way to do this is to right-click on the Sun and in the details window that pops up, select ‘New Asteroid…’ In the ‘Asteroid: Untitled’ window that pops up, enter the following data, which comes from the Minor Planet Center at Harvard:

Name: Ultima Thule
Mean Distance: 44.581400  
Eccentricity: 0.041725   
Inclination: 2.4512  
Ascending Node: 158.9977  
Arg of Pericentre: 174.4177  
Mean Anomaly: 316.5508  
Epoch: 2458600.5

Exit this window and answer the prompt, ‘Do you want to save changes…?’ with yes. The next time you quit Starry Night, this new object will be saved into a file called “User Planets.ssd” that lives on your Preflight computer, but is not automatically networked to the Renderbox. In order to get it to live on the Renderbox, you have to find “User Planets.ssd” and copy it into part of the Sky Data folder we looked at above.

Locate ‘User Planets.ssd’ in the following folder:

C:\Users\SPITZ\AppData\Local\Simulation Curriculum\Starry Night Prefs\Preflight\

Verify that this file was last modified on the date you are doing this work. 

The destination the file should be copied to is:

C:\ProgramData\Simulation Curriculum\Starry Night Prefs\Sky Data\

If there is an older version of ‘User Planets.ssd’ in the destination, better save it to a safe location, just in case.

The Ultima Thule encounter could be a strange one. Pluto is about as big as the United States, from the 49th parallel to the Rio Grande, but Ultima Thule is only about as big as Nantucket Sound. Its shape has been worked out from occultations, and it looks elongated, not round. You can get more data about the mission to share from this blog entry from Emily Lakdawalla at the Planetary Society.

You can run a simulation of the encounter on your phone with the free Pluto Safari app from Simulation Curriculum, our partners in developing Starry Night Dome and The Layered Earth Dome for SciDome planetariums.

Simulating Apollo 8 on SciDome

Tomorrow, Friday, will be the 50th anniversary of the launch of Apollo 8, the first crewed space flight to orbit the Moon. You can simulate Apollo 8, and the other eight Apollo missions that went to the Moon, on your SciDome.

Apollo 8 mission patch, showing the “figure 8” path the spacecraft travelled from the Earth to the Moon

First, make sure that ‘Space Missions’ are checked to be visible in your View Options pane. If you type in ‘Apollo’ in the Starry Night search engine pane, each mission will come up, and you can break each one down by “Mission Path segments” that each describe a phase of flight, and look at the Command Module and Lunar Module separately at relevant points.

These missions can only be seen when Starry Night is displaying the right time between 1968 and 1972, which you can get by right-clicking on the mission you want and selecting “Set Time to Mission Event…” and picking “Launch”, for example. The best way to see the mission path of Apollo is to be looking at it from well above the Earth’s surface, with ‘Hover as Earth Rotates’ set so that the Earth’s surface can rotate underneath you and the fixed stars stay fixed on the dome.

Apollo 8 follows a curving path out from the Earth to the Moon, orbits around the Moon ten times, and then returns to the Earth. The different mission path segments are different colors. 

You can see that the spacecraft orbits around the Moon from lunar west to lunar east. However, when we look up at Apollo’s path around the Moon it appears to be opposite the path that spacecraft orbit the Earth, even though everything launched from Cape Canaveral also goes towards the east. The Apollo spacecraft were launched into a figure-eight trajectory, so the “patching of conics” that reverses the frame of reference is like when two people shake hands on their right side. From one person’s point of view the other person is shaking their left hand, even though both participants are using their right.

The Apollo spacecraft and the Saturn V rocket are rendered in 3D in Starry Night if you go to them and look at them up close. The Apollo 8 spacecraft is pointed at the Earth by default.

Apollo 8 “Earthrise” photo

The famous “Earthrise” photo was taken at the beginning of the fourth orbit, on December 24th, 1968, at about 16:25 Universal Time, as shown in SciDome. There is some question of which of the three astronauts – Commander Frank Borman, Command Module Pilot Jim Lovell, or “Lunar Module” Pilot Bill Anders – took the photo, and the question was resolved by Apollo historian Andrew Chaikin, who recounts his investigations in Smithsonian Magazine.

In Starry Night Preflight’s ‘SkyGuide’ pane there is a section on the Apollo missions, and Apollo 8 has 13 sub-headings that go into phases of flight like the Earthrise photo in some detail. Each subheading calls up a Starry Night application favourite scene that describes that phase of flight, with some text and images that appear in the SkyGuide pane.

Solar System Scale: Copernicus’ Method

Nicolaus Copernicus’ (1473 – 1543) paradigm-changing work de Revolutionibus Orbium Coelestium (On the Revolutions of the Celestial Spheres) famously laid the groundwork for the overthrow of the geocentric universe that had held sway for millennia. But what many people are not aware of is that Copernicus’ heliocentric system allowed for the first scale model of the entire known solar system in terms of the size of the Earth’s orbital radius.

What I find most incredible is that the values he determined, despite assuming incorrectly that the planets’ orbits must be circular with the planets traveling at constant orbital speed, are very close to the modern-day measurements (shown in Table 1).

In my never-ending quest to create meaningful and engaging planetarium curriculum, Clint Weisbrod and I have developed the ability to reproduce Copernicus’ method using SciDome and new features in Starry Night which allow us to do solar system geometry.

Table 1 – Results of Copernicus’ model versus modern values.

We begin by looking at the planets closer to the Sun than the Earth, the inferior planets Mercury and Venus (first denoted as such by Copernicus). Figure 1 shows the configuration for greatest elongation of Venus. By definition, this will occur when Venus appears to be the farthest away from the Sun as seen from Earth.

Via Euclid’s geometry we can prove that when Venus is at greatest elongation the angle at the position of Venus has to be exactly 90°. The line of sight from Earth to Venus must be tangent to Venus’ orbit, otherwise the line of sight would intersect the orbit in two places, both of which would display smaller angular separations from the Sun. The elongation angle θ is measured from the Earth as the angle between Venus and the Sun.

Knowing θ and that the angle at Venus is 90°, we can solve all sides of the triangle if we know one side of the triangle. Alas, we do not know any of the lengths, but if we define the distance from the Earth to the Sun (the hypotenuse) as 1 astronomical unit (1 AU), then we can immediately calculate the side of the triangle opposite the elongation angle θ as

Venus distance from Sun = (1 AU) sin θ

Figure 1 – The geometry (greatest elongation) of inferior planet distances from the Sun.

Figure 2 shows this configuration as seen from a top-down view of the Solar System in Starry Night using the new Copernican Method lines.

The value of the radius of the orbit of Venus (again assuming a circular orbit) is

Venus distance from Sun = (1 AU)sin(45.9°) = 0.72 AU

This is a remarkably accurate result, mostly due to Venus’ nearly circular orbit! The results for Mercury are not as accurate, but of course Mercury’s orbit is far from a circle. However, if enough measurements are made of multiple greatest elongations, the average will come out to be a fairly close estimate to the modern-day value.

Figure 2 – The Copernican Method lines for Venus in SciDome.

 

What’s awesome about the new feature in SciDome is that we can actually display the Copernican Method lines as seen from Earth as well as from space, as shown in Figure 3.

The line drawn between Venus and the Sun (just below the horizon) also displays the angular separation of the two bodies (45.9°) and the angle at Venus is the angle made between that line and the Earth’s line of sight (89.9° – close enough to 90° for government work).

The greatest elongation angle (45.9°) can be measured (in modern times) using a sextant (invented in 1715), so this new Copernican Method lines feature allows us to draw “sextant measurement lines” between the Sun and the planets.

Figure 3 – Venus’ greatest eastern elongation as seen from Philadelphia on August, 15, 2018.

Determining the sizes of the orbits of the planets further from the Sun than the Earth—the superior planets—is not quite so straightforward. The method is explained below, remembering again that we’re assuming the orbits are all circular and the planets are moving at constant orbital speeds.

Figure 4 shows the geometry of the situation for superior planets. We begin by noting the date (Julian Date) of an opposition of the planet, when the planet and the Sun are on opposite sides of the Earth—the superior planet would rise when the Sun sets, and be highest in the sky (on your local meridian) at midnight. We then wait and observe the planet until it is 90° from the Sun, a position Copernicus defined as quadrature.

We calculate the number of days that have passed since opposition, and this will allow us to calculate how many degrees each planet has traversed in their respective orbits. For example, the Earth takes 365.2422 days to cover 360° (again, we’re assuming circular orbits and constant orbital velocity) so it will move

 

Figure 4 – The geometry of measuring the size of the orbits of the superior planets.

A similar calculation can be done for all the planets since Copernicus had calculated the sidereal periods of all the visible planets (see the Synodic Periods minilessons in Volume 3 of the Fulldome Curriculum). For example, Jupiter’s sidereal period is 4332.59 days yielding an angular rate of travel in its orbit of 0.0831 deg/day.

Since we know how many days it took for the planets to reach quadrature from opposition, we can immediately calculate how many degrees each planet traveled in their respective orbits. The Earth will travel a greater angle in its orbit in this time, and the difference between these two angles is the angle θ shown in Figure 5.

Assuming that the distance from Earth to the Sun is 1 AU, we can calculate the distance from the Sun to Jupiter (the hypotenuse of the triangle in Figure 5) as 

So, what Earth observers would need to do is to measure the number of days from the opposition of a planet to the next quadrature, calculate the difference in degrees traveled between the two planets, and then take the reciprocal of the cosine of that angle to calculate the superior planet’s distance from the Sun.

Figure 5 – The quadrature triangle to solve for Jupiter’s distance from the Sun.

In the case of Jupiter, one set of measurements placed opposition on May 9, 2018 (JD 2458247.75) and the following quadrature on August 6, 2018 (JD 2458337.492), for a difference in days of 89.74. This value, multiplied by the difference in angular velocities between Earth and Jupiter, yielded a θ = 81.0°. This resulted in an orbital radius for Jupiter of 6.41 AU, whereas the modern value is 5.20 AU (a 23% difference). The view from Earth of this quadrature is shown in Figure 6.

At first glance, this value seems to be significantly off from the modern value…and it is! Have we made a mistake, or is this yet another opportunity to encourage our students to think? What assumptions have we made that are probably not accurate? We (as did Copernicus) assumed circular orbits and constant orbital velocities, and neither of these assumptions is correct for any of the planets!

So how can we use this method and the (wrong) assumption of circular orbits and constant orbital velocities to arrive at relatively accurate values for the sizes of the superior planets’ orbits?

The answer is to take multiple measurements over at least one orbital cycle of the planet in order for the answers to average out to some median value which indeed will approach the modern-day value. I did this for Jupiter taking 11 successive opposition-quadrature pairs over one 11-year cycle of its orbit from 2007 to 2018. When I averaged these 11 determinations I obtained a value of 5.46 AU, an error of only 5% from the modern value.

Don’t see this as a problem but rather as a very teachable moment for your students. You might challenge them as a class to take multiple measurements of successive opposition and quadrature pairs and they can watch for themselves how the values average out to close to the modern-day value. They can see for themselves how the errors introduced by our assumptions of circular orbit and constant orbital velocities can be minimized (but not eliminated) by multiple observations.

It’s appropriately mind-blowing to see the genius of Copernicus through these observations that your students can now undertake for themselves in the SciDome planetarium! They will gain a much greater understanding of how Copernicus created his solar system scale model, as well as see how these measurements could actually be made from the ground.

Figure 6 – The quadrature of Jupiter as seen from Philadelphia on August 6, 2018.

Sulawesi Earthquake in The Layered Earth

When we’ve been discussing applications of Starry Night in the dome, there was usually little need to worry about the human element, but with The Layered Earth (TLE) this is different. Most of the layers we use and stories we’re going to tell are about consequences that profoundly affect humanity.

2018 Sulawesi earthquake and aftershocks

Earlier today a large earthquake struck Sulawesi, an island in Indonesia. There’s a cluster of shallow (red) tremor marks on TLE’s 7-day USGS Earthquake Data layer, but if your SciTouch can’t identify the main M 7.5 event, please check the layer’s “settings”. 7.5 is actually the maximum strength of quakes that can be shown with this layer, and the layer settings may specify and earthquake like this is “offscale high” unless you widen the scale.

In TLE, shallow earthquakes are displayed as red, intermediate ones as yellow, and deep quakes are green (and earthquakes above sea level are white.) These colors conceptually indicate that shallow earthquakes are more dangerous.

A tsunami caused by this earthquake appears to have devastated the city of Palu, which is very close to the epicenter of the quake. Palu is located at the far end of a long bay that opens out onto the Makassar Strait. The effect of the tsunami may have been magnified by the shape of the bay. Social media is already carrying video of the tsunami that’s comparable to the 2004 Indian Ocean and 2011 Tohoku events.

The Makassar Strait is not a tectonic plate boundary that can be seen in TLE, but Indonesia is located at the convergence of several plates and there are lots of tectonic fault lines that are not located on plate boundaries. The Palu-Koro Trandform Fault can be seen in TLE in the indent under “Fault Types” layers, and the “Global Strain Rate” layer is red in that area.

The earthquake was detected at Greenville, DE even though the range to the earthquake (15323 km, or 138°) puts it inside the “shadow zone” created by refraction of primary vibrations off of the outer edge of the Earth’s liquid outer core. Weaker earthquakes that are between 104° and 140° away from the detector generally aren’t picked up because of the “shadow zone”, but stronger ones generate enough primary and secondary vibrations that the shaking is picked up worldwide. But it takes longer for these waves to be picked up. If you’ve experienced an earthquake you may have felt the gap between the arrival of primary and then secondary vibrations.

Mission Impossible: Ghost Particle

Earlier this month, another “multi-messenger” announcement was made of the discovery of a new astronomical outburst by different instruments that study different parts of the universe. The first major multi-messenger astronomy discovery was announced last year after the collision of two neutron stars was observed in the nearby galaxy NGC 4993. The neutron star collision was observed first with the LIGO and Virgo gravitational wave detectors, coincident with a gamma ray burst detected by the Fermi space telescope, pinpointed with an optical telescope in South America, and followed up with different kinds of detectors.

IceCube Neutrino Observatory diagram
from IceCube Science Team

This new announcement is based on the detection of a very unusual neutrino or “ghost particle” at the IceCube Neutrino Observatory at the South Pole. This event is worth pointing out in SciDome because we have a horizon panorama that matches the horizon at the South Pole, and one or two other points that may help students understand how the sky works and what neutrinos are.

Neutrinos have been observed with detectors in both the northern and southern hemispheres of Earth, and they are created as a byproduct of various nuclear reactions. Neutrinos hardly interact with normal matter at all, and they tend to radiate outwards from their point of creation at the speed of light.

Neutrinos at rest were assumed to be massless until evidence to the otherwise shown by Art McDonald and Raymond Davis, Jr., led to them being awarded the Nobel Prize in Physics in 2015.

The interaction of neutrinos with normal matter is so weak that most neutrinos that encounter the Earth fly straight through it without hitting anything. In February 1987 when a nearby supernova popped off in the Large Magellanic Cloud, 25 neutrinos were detected at neutrino observatories in the northern hemisphere, where the Large Magellanic Cloud never rises above the horizon.

The new neutrino detection from IceCube at the South Pole was detailed enough to provide a vector back to its point of origin, somewhere within a 1.3-degree-wide circle on the sky.

The Spitz Fulldome Curriculum, included with every SciDome system, includes dozens of lessons prepared by noted astronomy educator Dr. David Bradstreet

The circle enclosed a radio source discovered in 1983, a galaxy 3.7 billion light years away with an active supermassive black hole at its core. This is one of the quasars like Dr. Bradstreet uses in his “Quasars Fulldome” show from the Fulldome Curriculum Vol. 3. Because this quasar’s jet is pointed at us, it is called a “blazar”; this term originated because the first of its type happened to be named “BL Lacertae”, and because blazars can appear brighter than normal quasars and their brightness can vary more quickly than normal quasars.

Like before, this neutrino detected from the South Pole had flown through the Earth to get to the detector. The blazar TXS 0506+056 is located at about 5 hours right ascension and +5° north of the celestial equator. Only objects south of the celestial equator are above the horizon as seen from the South Pole.

TXS 0506+056 is conveniently located in the Shield of Orion, part of the most easily recognized equatorial constellation on the sky. The blazar is labeled “MG 0509 +0541” in SciDome and is one of the quasars in Dr. Bradstreet’s “Galactocentric Distributions” minilesson.

In the part of the Fulldome Curriculum “Seasons” class that visits the South Pole, the audience may have a hard time recognizing Orion because it is upside down and its northern half, including TXS 0506+056 is below the horizon. The horizon needs to be switched off and then tilted up to bring the rest of the constellation into view to simulate a “neutrino filter”.

The prefix TXS stands for ‘Texas’, where UT-Austin astronomers set up a radio telescope array outside of Marfa for several years in the 1980s – now removed. MG stands for ‘MIT-Green Bank Observatory’.

The mass of neutrinos and other particles is calculated in electron volts, but because they are so small, only particles that have a large amount of kinetic energy are comparable to things that we can comprehend. 1 trillion electron volts (1 TeV using the prefix tera-) is comparable to the kinetic energy of a mosquito in flight. The most powerful cosmic ray ever detected had a mass of 300 quintillion electron volts, comparable to a pitched baseball.

The single neutrino detected by IceCube from TXS 0506+056 had a mass of 290 TeV. After crossing 3.7 billion light years in space, this is by far the most distant neutrino emission ever detected: the only other objects in the sky that have produced detected neutrinos have been the Sun (8 light-minutes away) and Supernova 1987A (168,000 light-years.)

(In 2012, the IceCube Collaboration detected three other high-energy neutrinos, which they named Bert, Ernie and Big Bird, but where Bert and Ernie came from is not known, and Big Bird was probably generated by the blazar PKS B1424-418 with a certainty of 95%. That’s only two sigma, which does not hold water with particle physicists who have much stricter statistical significance limits. TXS 0506+56 was much more narrowly confined.)

Because matter and energy are relative, an electron volt is equivalent to the energy exchanged by the charge of a single electron moving across an electric potential difference of one volt. The only way a neutrino can be detected is on the rare occasion when it enters a neutrino detector (like a large underground tank of heavy water or tetrachloroethylene or linear alkylbenzene or another chemical) and collides with an atomic nucleus or an electron inside the detector, emitting light that can be detected with photomultiplier tubes. IceCube is unusual because its detectors have been drilled into the Antarctic ice pack and are not suspended in water or another fluid.

Spitz Fulldome Curriculum Volume 3 Overview

I’m excited to announce that Volume 3 of the Spitz Fulldome Curriculum is being released to all SciDome users, and will of course be automatically incorporated into all future SciDome installations.  We thought that this would be an opportune time to give a very brief overview of what’s contained in this volume.  There are several revisions to previous minilessons as well as several all new offerings:


 

Galilean Moons

This minilesson gives 26 examples (in order of date) of Galileo’s first observations of the four major moons of Jupiter during the winter of 1610.  The actual configuration of each night is beautifully displayed on the dome by Starry Night and then Galileo’s sketch is presented directly underneath it so that your audience can compare the sketch to reality.  You will be astonished at Galileo’s accuracy, as well as the restrictions of his poor optics and resolution that confined his work.  My students enjoy these comparisons even more than I do!

 


 

North Celestial Pole (NCP) Altitude

My students always scratch their heads when presented with the idea that the North Celestial Pole is always the same number of degrees above your horizon as your latitude.  This series of overlaying diagrams attempts to clearly lay out exactly why this is the case.

 

 


 

Planetary Tilts

Steve Sanders, Observatory Administrator at Eastern University and my right hand man, came up with this idea to beautifully illustrate the various planetary axis tilts side by side as well as their rotation periods.  This animation is so impactful that the folks at ViewSpace used it in one of their presentations last year!


 

Quasars Fulldome

This is one of my all time favorite mind-blowing demonstrations!  In a series of overlaying fulldome illustrations (again created by Steve Sanders), the second cosmological principle of the universe looking the same everywhere is demonstrated by using the appearance of quasars as seen from any galaxy, starting from the Milky Way.  Your audience will be left awestruck when they discover that the Milky Way is a quasar as seen by a distant galaxy which to us looks like a quasar!


 

Roemer’s Method Revised

One of my favorite minilessons from Volume 1, we’ve revised this presentation with a new animation by Steve Sanders which very clearly shows the concept behind the light time effect and how Roemer was the first to demonstrate that the speed of light was finite and approximate its value.  You can not only show this effect to your audience but make an incredibly precise and straightforward measurement from it of the speed of light!


 

Solar System Scale Revised

I still use this minilesson in nearly every one of my presentations and for all ages.  We have greatly improved the graphics used in this minilesson and I know you will like the results!

 

 


 

Stellar Sizes Revised

Like Solar System Scale, I use this minilesson frequently in most of my presentations, and we’ve revised it by adding a final graphic at the end which shows VY Canis Majoris in its entirety on the dome in one final scale shift.

 

 


 

Synodic Periods of Mercury, Venus, Mars and Jupiter

These are my favorite new additions in Volume 3! Each is a separate minilesson and carefully steps the audience through how Copernicus disentangled synodic periods of the planets into their sidereal periods around the Sun! Although very few people have ever been taught this concept, it’s very straightforward and illuminating when you see it on the dome. Test one out for yourself and you’ll be hooked!

 


 

Titius-Bode Rule

We often mention this infamous “Law” in our astronomy classes, so I wanted to present it in a historical fashion to demonstrate what effect it had on astronomer’s thinking when the Solar System was being explored and new planets being discovered.  It’s the perfect example of a mathematical oddity that may or may not be scientifically meaningful.  I think you will find it a fascinating subject as presented on the dome in this minilesson!


 

Watery Constellations

This little minilesson playfully depicts the fact that the region of the sky known as “The Sea” by the ancients has water-related constellations residing in it for a specific reason, namely that the Sun traversed this part of the sky during the rainy season in the Mediterranean. You will also be able to show your audience in a natural way that the position of the winter solstice used to be in Capricorn around 1000 BC, and hence that latitude parallel is called the Tropic of Capricorn.

 


Perhaps the greatest contribution to the official contents of Volume 3 is the availability of three unique fulldome interactive programs: Epicycles, Newton’s Mountain, and Tides.  These three programs allow you to clearly demonstrate subjects which I have found extremely challenging for my students:

  • Epicycles shows many of the intricacies and systematics of the simplified Ptolemaic geocentric system and will alert your audiences to the vagaries of “saving the model at any cost.”
  • Newton’s Mountain is a 21st century interactive version of Newton’s attempt to explain exactly what an orbit is allowing you to show your audience in real time different orbits as a cannonball literally falls around the Earth.
  • Tides shows exactly why the Moon causes the water to bulge on either side of the Earth via differential gravitational forces as well as demonstrating that the bulge is not the same on both sides!

REQUIRES WINDOWS 7 ON THE RENDERBOX COMPUTER. Multi-projector systems must be based on Scaleable – not compatible with EasyBlend.

These three programs require purchase because of the many years of work which went into their development and implementation. They are now available for online purchase and immediate download:

Purchase Astrophyics Apps

I hope that you and your audiences thoroughly enjoy this latest addition to the Fulldome Curriculum, and that they will be helpful as you continue to strive to educate people in the subjects that we all love.