Reading Astronomy News: This Interstellar Asteroid is Accelerating


By Stacy Palen

As I was working on the first draft of Chapter 3 for the fourth edition of Understanding Our Universe, I ran across this wonderful summary article about ‘Oumuamua by Steven Spence of GotScience Magazine. You probably remember that ‘Oumuamua is the first interstellar object that we’ve observed in our Solar System. This article compactly lays out the case for how we know it comes from another star, how fast it’s moving, and why its acceleration as it leaves the Solar System is “weird." It’s practically chapter 3 in a nutshell! 

To read This Interstellar Asteroid, by Steven Spence, click here.

  1. In the discussion of where ‘Oumuamua came from, the author states that it is “moving on an open hyperbolic trajectory.” Make a sketch of what such a trajectory would look like. How is it different than a path followed by an orbiting object?

    Answer: They should draw a hyperbola; many will have to look this up. A hyperbola is not closed, like an ellipse is closed.

  2.  ‘Oumuamua’s trajectory is described as having an eccentricity of 1.23. But the maximum eccentricity for an ellipse is 1.00. What is the resolution of this apparent contradiction?

    Answer: Only objects that are orbiting, and bound to the system by gravity, travel on ellipses. Objects that are unbound can travel on trajectories that don’t meet the requirements for an ellipse.

  3. In the article, ‘Oumuamua’s speed is described as fast enough to cover the distance from Earth to the Moon in 73 minutes. The New Horizons space craft covered the same distance in 8 hours. Approximately how many times faster is ‘Oumuamua traveling than New Horizons?

    Answer: In “cowboy” math, 73 minutes is about an hour. So ‘Oumuamua must be traveling about 8 times faster than New Horizons, to cover the same distance in an 8th of the time.

  4. ‘Oumuamua reached the orbit of Jupiter about an hour earlier than expected. Why does this imply that the object has accelerated?

    Answer: In order to cover the distance in less time than expected, the object must be traveling faster than expected. This means there must be an unexpected increase, or less-than-expected decrease, in the speed of the object.

  5. The best idea, currently, for how ‘Oumuamua is accelerating is that it is “comet-like outgassing.” Outgassing occurs when a jet of gas shoots out from the object. Use Newton’s third law to explain how an object “outgassing” can cause an object like ‘Oumuamua to accelerate.

    Answer: This is exactly how a rocket accelerates! Because it is a closed system, if some of the mass accelerates in one direction, there must have been a force that pushed that mass. By Newton’s third law, there must be an equal and opposite force pushing the rest of the mass in the opposite direction.




Reading Astronomy News: Earth’s Magnetic Field On The Move

Earth's Magnetic field
Image Credit: Emmanuel Masongsong/UCLA EPSS/NASA

By Stacy Palen

In January, geologists updated the model of Earth’s magnetic field, a year ahead of schedule.


1. Study the map titled “Magnetic Motion.” How much time separates each pair of red dots between 1900 and 2010?

Answer: The dots indicate 10-year time intervals until 2010. There is an extra dot placed for 2015.


2. In general, how does the movement of the magnetic pole since 1990 compare to the movement of the pole prior to that time?

Answer: Because the red dots are much farther apart after 1990, we can conclude that the pole is moving a lot faster in the last few decades than it did prior to that.


3. Why do we care about what happens to the magnetic pole of Earth?

Answer: The position of the magnetic pole underlies all navigation. If we don’t know where the pole is, we don’t know where we are.


4. Why did geologists decide to update the model a year earlier than expected?

Answer: Because the position of the pole was changing so fast that navigation was becoming inaccurate.


5. What is the working hypothesis for why the position of the magnetic pole is changing so rapidly right now?

Answer: A jet of liquid iron is weakening the magnetic field in Canada. This means that a second patch of magnetic field in Siberia is relatively stronger, so the pole is moving in that direction.


6. How does this news article relate to what you have learned about Earth’s magnetic field?

Answer: We have learned that Earth’s magnetic field changes over time, and that the history of those changes are recorded in rocks. We have also learned that the magnetic field affects the aurorae in Earth’s atmosphere. As the magnetic field changes, this should affect the aurorae as well.

Current Event: The Eta Aquariids are Coming!


By Stacy Palen

Don’t forget to remind your students about the Eta Aquariid Meteor Shower, coming in the beginning of May.  The peak occurs around May 4-5.  This is the last chance for most of us to remind Spring semester students to go out and watch a meteor shower!

This meteor shower occurs when Earth passes through the debris left behind by Halley’s Comet.  Particles lost from the comet continue to drift in the Solar System, gradually changing their position. As Earth moves through space, it passes near the trajectory of the comet and runs into collections of these particles.  The particles burn up, creating meteors as they fall through the atmosphere. This will happen repeatedly at particular times of year, as Earth returns to the same point in its orbit. 

Halley’s comet has a 76-year orbit, so it is a short-period comet. It will not be back in the inner Solar System until 2061.

To watch a meteor shower, go to a clear dark sight where the horizon is not obstructed.  Spend about half an hour in the dark, without your cell phone or other bright light in view.  This will allow your eyes to adapt to the dark. Then just watch for meteors!  They are best seen with the naked eye.

If you are careful and methodical, your observations can contribute to the study of meteors and meteor streams!  To learn more, visit the Astronomical League’s Meteor Observing Program website.

Reading Astronomy News: The Lyrids are Coming!

Meteor Shower

Image Credit: NASA/Bill Ingalls

By Stacy Palen

Don’t forget to remind your students to watch for the Lyrid Meteor Shower this month. The peak occurs around April 21-22.

This meteor shower comes as Earth passes through the debris left behind by Comet Thatcher. Particles lost from the comet continue to drift in the Solar System, gradually changing their position.

As Earth moves through space, it passes near the trajectory of the comet and runs into collections of these particles. This will happen repeatedly at particular times of the year as Earth returns to the same point in its orbit. The particles burn up, creating meteors as they fall through the atmosphere.

Comet Thatcher has a 415 year orbit, so it is a long-period comet. It will not be back in the inner Solar System until 2276.

To watch a meteor shower, go to a clear dark site where the horizon is not obstructed. Spend about half an hour in the dark, without your cell phone or other bright light in view. This will allow your eyes to adapt to the dark. Then just watch for meteors! They are best seen with the naked eye.

If you are careful and methodical, your observations can contribute to the study of meteors and meteor streams! To learn more, visit the Astronomical League’s Meteor Observing Program website.

Resources: First Ever Image of a Black Hole

By Stacy Palen

My students came in talking about this, and so I thought I’d pass on a couple of resources that I used while answering questions in class! 

I felt I needed to put the new image in context, with respect to M87 and all its fascinating parts.  This photo has the angular sizes labeled, as well as the wavelengths of the observations. It’s a quick place to get all those numbers right away.


ESO has an image of the global array:

Veritasium has a nice short explainer video about the light paths:

Which then matches beautifully onto the actual image and has some fun information about the technical difficulties with data transfer etc.:

I made a point of taking them to the summary research paper:

Both so that they could just see it, but also because I wanted to show the author list and acknowledgements. This is an important thing that science does: model how to have international collaboration. The paper summarizes the achievement nicely: “In conclusion, we have shown that direct studies of the event horizon shadow of supermassive black hole candidates are now possible via electromagnetic waves, thus transforming this elusive boundary from a mathematical concept to a physical entity that can be studied and tested via repeated astronomical observations.”

We happen to have just done two of the Learning Astronomy by Doing Astronomy activities about black holes: Bent Space and Black Holes, and Light Travel Time and the Size of a Quasar. So, this was a lucky moment when we were all thinking about these concepts anyway!

Book Recommendation: Present at the Beginning: Galileo’s Sidereus Nuncius


By Dr. Bradley W. Carroll

We live at a unique point in history. For the first time, we humans know the entire story of our species, at least in broad outline. We know how the universe expanded from the initial Big Bang, how generations of stars manufactured a periodic-table’s worth of elements and then dispersed them throughout space as those stars exploded, and how clouds seeded with those elements gravitationally collapsed to form planets. We understand the evolution of the life that arose on this particular planet, and how an astronomical impact led to the dominance of the hairless apes that eventually became our friends and neighbors.

But what was it like to be alive four centuries ago when almost everything was a mystery? What was it like to discover, for the very first time, that the Moon has mountains, that there is a universe filled with stars we cannot see with the naked eye, and that other moons orbit Jupiter? Fortunately, we know exactly what it was like because the man who made these discoveries has told us: Galileo Galilei.

Sidereus Nuncius (The Starry Messenger) is not filled with the dry dialectics of Galileo’s other tomes. In this book you can sense Galileo’s exuberance, his sense of wonder at what he has seen for the very first time through the crude telescope he made with his own hands. He tells you how he labored over its construction until he could see objects “over sixty times larger.”

Galileo writes that “having dismissed Earthly things, I applied myself to explorations of the heavens.” He grabs your sleeve to pull you toward his eyepiece so you can see these wonders for yourself.

And what wonders they were to his eyes! Galileo sees the tops of mountains on the Moon lit by the Sun, and asks us, “On Earth, before sunrise, aren’t the peaks of the highest mountains illuminated by the Sun’s rays while shadows still cover the plains?” Galileo alone now knows that the Moon is not a perfect sphere. Using shadows, he calculates that one lunar mountain is “higher than 4 Italian miles.”

Galileo swings his telescope toward the constellation of Orion, and breathlessly tells us that “to the three [stars] in Orion’s belt and six in his sword that were discovered long ago, I have added eighty others.”

Then, on January 7, 1610, Galileo trains his telescope on Jupiter to see “three little stars” near Jupiter that are “arranged exactly along a straight line and parallel to the ecliptic.” Night after night Galileo keeps track of these stars, now grown to four, as they stalk Jupiter, passing back and forth across its disk.

Finally, on March 2, Galileo calls them “planets,” and later, the “Medicean planets.” (In the opening passages of Sidereus Nuncius, Galileo, in his never-ending quest for patronage, proposes naming these four moons of Jupiter for Cosimo II de’ Medici, the Fourth Grand Duke of Tuscany.)

Thirty years ago, I attended a meeting of the American Astronomical Society in Ann Arbor. There on display was a draft of a short letter Galileo sent to the Doge of Venice on August 24, 1609 that described his telescope. But at the bottom of the letter are Galileo’s first recordings of the moons of Jupiter, made on this paper he happened to have nearby.

I felt overwhelmed knowing that when Galileo’s hand made these marks upon this sheet of paper, the world changed. Galileo now knew with certainty that Earth was not the center of the all things, because here were four moons orbiting Jupiter. Galileo went on to make more astronomical discoveries. He discovered spots on the Sun and the phases of Venus, but his Sidereus Nuncius announced his first discoveries to the world.

Reading the Sidereus Nuncius, I am struck by encountering a fully modern mind, so different from the mysticism of Johannes Kepler. It marked a revolution. After Sidereus Nuncius, astronomy no longer had to rely on the word of ancient authority for its conclusions. Astronomy became an observational science, and anyone with a telescope could see what Galileo saw. Sidereus Nuncius is a short book, just 62 pages. My version, translated by Albert Van Helden, has useful notes along with an introduction and conclusion. Read it for yourself and be present with Galileo at the beginning of modern astronomy.


How-To: Orchestrating Active Learning in a Less-Than-Ideal Environment


By Stacy Palen

Somehow or other, classroom architects in the 1960s, 1970s, and as far along as the 2010s did not get the memo that instructors would sometimes want students to work together on projects. It’s a mystery. Even in our two-year-old science building, the lecture halls are set up for presenting to large groups. This is fine, but presents a challenge when I want to have students collaborate.

Often, I’ll put students in groups of two for brief discussion on things such as clicker questions or to work through a worksheet. “Groups” of two are easy to accomplish. But sometimes, we just need more room, either to work in groups of three or four, or to work with “manipulables” like paper moons or large maps.

When this happens, I need an advance plan. Typically, I will need about twice as much space as I have in the seating area of the lecture hall. I’ll look for space in the front or back of the lecture hall, and down the stairs on either side of banks of chairs, and estimate how many groups of 3–4 I can fit in those areas. I will scout out nearby alternative locations for students to work, like a stairwell, outdoor retaining wall, or atrium. Sometimes there are groups of chairs at the end of a hallway, or benches outside the classroom.

At the beginning of class, I’ll spend a few minutes on the typical introduction to the activity and the material, and then I’ll invite the students to spread themselves out to work in the spaces I’ve designated. About a third of them stay in the seating area of the lecture hall, turning backwards and kneeling in their chairs to work with the people behind them. The rest move out into the larger spaces and form into small groups.

I spend the rest of the time walking through those spaces: interrupting groups who’ve gone off track, or who aren’t making progress, gently nudging students to ask better questions and suggesting that student X take a turn holding the paper “Moon.”

It sounds like chaos, but it actually works out very well. One unexpected benefit is that I am harder to find. This means that students must struggle on their own a bit longer before they can ask me for help. Often, that little bit of “extra” time lets them solve their own problem.

I’ve never had a student complain about this, nor have I heard from the professors teaching in neighboring classrooms that it has been in any way disruptive. Sometimes, they just shut their door.

I have, on occasion, had students who are wheelchair users or whose mobility is restricted in some other way, and so I make certain to keep an eye out for any obstacles to group inclusion, physical or otherwise. Most always find a group without issue, but I do keep an eye on the situation, just in case.

Possibly the most common question I get asked about active learning is, “How can I do this in a lecture hall?” Depending on the individual situation, it may be difficult. But take a look around—often you might find you can “rent” a little space outside the confines of the lecture hall for the fun activities you want to do!

How-to: Learning is a Social Phenomenon

Books-classroom-close-up-289737 (1)

By Stacy Palen

As I mentioned in the last post, David Brooks recently collated several different studies of teaching and learning into an Op-Ed for the New York Times titled “Students Learn From People They Love.” Two paragraphs of this article particularly caught my attention; one about brain activity in a group, which I discussed in my last post, and the subject of this week’s post about in-person vs video teaching.

Brooks states in his article:

Patricia Kuhl of the University of Washington has shown that the social brain pervades every learning process. She gave infants Chinese lessons. Some infants took face-to-face lessons with a tutor. Their social brain was activated through direct eye contact and such, and they learned Chinese sounds at an amazing clip. Others watched the same lessons through a video screen. They paid rapt attention, but learned nothing.

This study reminded me of a welding course I took last year, in which the welding instructors were testing two different ways to teach welding.

The first method used real-time feedback from a computer/robot setup, which had lights and sounds to let you know when you moved the welding tip too fast or too slow. The second used a more traditional combination of videos and live instruction. I was in the second group.

I found that I could watch the instructor do something once, and then feel competent to try it myself. While my hand-eye coordination needed development, and I couldn’t necessarily make the weld as smoothly as I wanted, I easily remembered the series of steps required.

But if I was learning by video, I had to watch the video multiple times, and once I even had to stop in the middle of a weld to remember how to do what came next (turn a corner, as I recall).

I did not get to participate with the “robot teacher” but heard later that it was not as effective as the live instruction.

Students came to rely on the robot feedback rather than actually training their own eye. They made great welds as long as the robot was there to continuously correct them. But the students did not make the next step to being able to determine on their own that a correction was needed.

That’s interesting, it implies that correction alone will not help a student to identify their mistakes, even in real time; something more is required.

In another recent experience at a “meet the candidate” event for people running for local school board, a member of the public asked me why public education has not taken greater advantage of internet-based learning to keep costs down. His premise was, in my opinion, faulty in two ways.

First, education has taken advantage of the internet more than most fields.

Second, as I stated at the time, if the internet was going to replace teachers, then books would have done so, or television, or DVDs.

But we’ve all had the experience of watching the TV show or the video, and then being completely unable to repeat the task on our own. In fact, there’s a whole new series of “nailed it” shows that poke fun at this very human experience.

Clearly, some things can be learned from watching, and some by reading. But other things need to be learned by doing, and they are learned faster and more effectively with a person who can show you how. Research into learning and neuroscience is beginning to figure out why, and it’s fascinating!

How-to: Learning Relies on Soft Skills


By Stacy Palen

David Brooks recently collated several different studies of teaching and learning into an Op-Ed for the New York Times titled “Students Learn From People They Love.” Two paragraphs of this article particularly caught my attention, one about in-person vs video teaching, and one about brain activity in a group. I’ll talk about each one separately, in this and the next post.

In the article, Brooks writes, “Suzanne Dikker of New York University has shown that when classes are going well, the student brain activity synchronizes with the teacher’s brain activity. In good times and bad, good teachers and good students co-regulate each other.”

This one caught my attention because I’m not at all sure what “synchronized brain activity” means. It sounds a little…unscientific.

But when I think about it more, I’m pretty sure I have a guess about what it feels like. I bet you do too.

We’ve all been in a classroom where the professor and the students were all working toward a common purpose, and we felt like the professor knew our questions before we could articulate them. Even hard things seemed approachable, because the professor was keyed in to our confusions. We would work extra-hard to please those teachers, and it paid off with faster and deeper learning.

On the other side of the desk, we’ve all had those students who helped clarify for us the confusion in the classroom. For better or worse, there’s sometimes that one kid who seems to respond to what we are saying just a little bit quicker. And when her eyebrows furrow, we pause and back up and try to explain again.

This sometimes extends to an entire classroom of students. I’ve had back-to-back classes in which the classroom vibe was completely different. In one hour, the group was chatty and involved and asked questions and was prepared each day. And the next hour, it felt like pulling teeth just to get them to actually push a button to answer clicker questions.

But all of this is very “fuzzy,” and that makes us uncomfortable. We would love to have a concrete set of steps to take so that if we want to improve student outcomes by 7.3%, we can simply invoke 20% more clicker questions in the classroom, and the student outcomes would improve accordingly. But if that were true, we would all be teaching perfectly already. It cannot possibly be so formulaic or teaching astronomy would be done by reading the cookbook.

Be reassured by the burgeoning research that learning is a social experience. It’s an interaction and therefore, each teacher-student pair does it differently. What works for me won’t necessarily work for you. And what works for you with student X won’t necessarily work with student Y. And even what works with student X for topic A won’t necessarily work for topic B!

This can be frustrating, but it also makes teaching fun and exciting. Teaching is a giant research experiment, where you are always trying something new, to see how it works. Not because there is one right answer, but because there are a hundred right answers, and matching up the method to the topic and the interaction is a subtle art.

The elephant in the room, of course, is evaluation. Brooks points out:

The bottom line is this, a defining question for any school or company is: What is the quality of the emotional relationships here?

And yet think about your own school or organization. Do you have a metric for measuring relationship quality? Do you have teams reviewing relationship quality? Do you know where relationships are good and where they are bad? How many recent ed reform trends have been about relationship-building?

In my experience, the answer to all of these questions is no because it’s really hard to measure these “soft skills,” like relationship building and communication. It’s much easier to measure changes in learning that are made by a change of specific instructional techniques than those that rely on interpersonal relationships between a teacher and their students.

So then the very best answer is to try things, all the time, to find the set of techniques that work best for you in your classroom with your students. And then sit down at the end of term and write down your thoughts for your evaluation file.

Explain what you tried, and why you think it worked or didn’t work, whether you’d try it again, and what you’d change. Your teaching will only benefit from the moment of reflection, and I suspect the committee that evaluates your work will too.

Classroom Resources: Astronomy in Action- Angular Momentum

Stacy Palen has created 23 videos on key topics to accompany her textbooks, Understanding Our Universe and 21st Century Astronomy, that instructors can assign as pre-class activities or show in class. A mixture of live demos and mini lectures, these videos explain key concepts in an understandable and compelling way. In the angular momentum video, Stacy stands on the “rotating platform of doom” and is given a small shove with outstretched arms, and then brings those arms in close to her body to demonstrate the conservation of angular momentum. Watch the video below and let us know what types of live demos you do in class!