Current Events: "Not Just A Space Potato": NASA Unveils "Astonishing" Details of Most Distant Object Ever Visited

By Stacy Palen

According to this article on The Guardian, when the New Horizons spacecraft arrived at Arrokoth, it revealed a surprising world. Now, planetary scientists are beginning to reconsider their conclusions about the formation of the Solar System. This new discovery appears to favor a gentler model of planet formation than the hierarchical model.

Here are some questions, inspired by the arrival of the New Horizons probe at Arrokoth, that you can ask your students:

1) Where is Arrokoth located?

Answer: In the Kuiper Belt.

2) Why can observations of Arrokoth yield information about the early Solar System?

Answer: Objects in the Kuiper Belt remain essentially unchanged since the Solar System formed. They do not have the same history of impacts and geologic processes as objects in the inner Solar System.

3) In your own words, state the hierarchical model of planet formation.

Answer: Small bodies smash together to form progressively larger bodies.

4) In your own words, state the cloud collapse theory of planet formation.

Answer: Slightly denser regions of dust and gas clump together and then, all at once, collapse under gravity.

5) What would astronomers expect Arrokoth to look like if the hierarchical model is correct?

Answer: They would expect to see evidence of collisions, like fractures and varied composition across the body.

6) What would astronomers expect Arrokoth to look like if the cloud collapse theory is correct?

Answer: They would expect to see uniform composition and no evidence of smashing.

7) Which model of planetary formation is supported by the actual appearance of Arrokoth?

Answer: Because Arrokoth is relatively smooth and uniform, it supports the cloud collapse theory of planet formation.

Current Events: 7 billion-year-old stardust is the oldest stuff on Earth

By Stacy Palen

I recently stumbled upon this article from The Washington Post about stardust on Earth. Mineral dust in the Murchison meteorite shows traces of neon produced by cosmic rays as the dust traveled through space. The abundance of neon atoms indicates that the dust was formed 7 billion years ago—before the Sun formed.

Here are some questions to ask your students based on the article:

1) What produces neon atoms in grains of interstellar dust?

Answer: Cosmic rays smash into the grain and convert silicon into neon.


2) How does the rate of cosmic rays striking the dust change with time?

Answer: It doesn’t. This rate is constant.


3) Suppose that one grain of dust has twice as much neon as another grain. What can you conclude about the relative time each grain spent in space?

Answer: The one with twice as much neon was out there twice as long.


4) In your own words, describe how astronomers determine the age of a grain of interstellar dust.

Answer: Astronomers count the number of neon atoms and compare that number to the number of neon atoms in a grain of known age. If there are more neon atoms, the dust grain was roaming the galaxy longer.


5) How old is the Sun, and how do we know?

Answer: The Sun is about 4.5 billion years old. We know this from measuring isotope abundances in moon rocks.


6) Are these dust grains older or younger than the Solar System?

Answer: These dust grains are 2.5 billion years older than the Solar System.


7) Is this result consistent with the idea that stars recycle material from the interstellar medium when they form? Explain.

Answer: Yes! Because the Sun and planets formed from material lost from earlier stars (we know this because of the abundance of other materials. Some of that material is still floating in the Solar System, and some of it was lost from stars that died long before the Solar System formed.

Classroom Stories: Another Way to Do the Phases of the Moon

By Stacy Palen

The phases of the Moon are one of those topics that has been extensively studied by the astronomy education research community and is well-known to be more complex than most people think. There’s the change of perspective from Earth-view to space-view. There are multiple motions at once (the rotation of Earth and the Moon, and the revolution of the Moon around Earth). There’s the issue about light rays always traveling in straight lines and not bending. It’s complicated.

Last week, I pulled an old phases-of-the-Moon activity out of the archives, which can be accessed by clicking here, for my students to complete in addition to the activity, “Studying the Phases of the Moon” from the Learning Astronomy by Doing Astronomy workbook. This is not an appropriate activity for Learning Astronomy by Doing Astronomy because it requires students to have Styrofoam balls that have been colored black on one half. (I can’t make the classroom dark, so I can’t use the traditional “balls-on-sticks” approach.) But one thing that I like very much about this activity is that it leads them to figure out how to (approximately) tell time by the Moon, which means that I can ask them a question about it on my zombie-apocalypse midterm—insert evil laugh here!

The activity also asks them to consider the phases of other objects, such as the phases of Earth as seen from the Moon, or the phases of Deimos as seen from Mars or Phobos. Carrying the concept of phases away from Earth seems to help cement the idea that this is a phenomenon that is all about the relative location of the light source and the observer.

I followed this activity the next week with the “Studying the Phases of the Moon” activity from the workbook. I was interested to notice that students finished the activity in record time and were much better prepared for it. The two activities worked well together to really build their picture of how the phases of the Moon actually occur.

Classroom Stories: Energy and Kepler’s Laws: A Surprise for Me about Where the Difficulty Lies

By Stacy Palen

Recently, my students worked on the “Working with Kepler’s Laws” activity from the Learning Astronomy by Doing Astronomy workbook. In this activity, students learn about ellipses, consider the “simple” version of Kepler’s second law (a planet travels faster when nearer to the Sun and slower when farther away), and run some numbers for Kepler’s third law: P2=a3. To my surprise, Kepler 1 and Kepler 3 brought almost no questions from the students (aside from “Am I doing this right?”). It was Kepler’s Second law that brought the most substantive questions.

Over and over they asked “Yes, but WHY does it go faster when it’s closer?”

I used this question as the basis for a whole new activity.

Approaching this question as an energy problem, I had the students throw a ball straight up in the air and make pie charts representing how much kinetic energy, gravitational potential energy, or thermal energy the ball had at various points in its trajectory. Then they threw the ball to a friend and made similar pie charts (in this case the velocity is never zero, so the kinetic energy is also never zero). Then I had them consider a planet in orbit around the Sun and make a third set of pie charts.

Wow! This was so much harder for them than I expected!

First, it turned out that pie charts are a concept that most (but not all) of my students have in common. Who knew?

Second, we ran into the issue about where to put the “zero” of gravitational potential energy. This information was in the Background section, so it was invisible.

Third, we faced our biggest issue: Convincing students that when they threw the ball straight up into the air, the ball had zero speed at the apex of the trajectory. That alone was a 20-minute conversation!

Finally, even though I told them to describe what happens to the ball between the moment after it left their hand to the moment before they caught it, many students turned all the energy into thermal energy. I’ve edited the activity to try to correct these problems and will use it again in the fall in search of perfection.

Despite these problems, I was very happy about the conversations that I overheard as I moved around the room. Some students were completely unfamiliar with the conservation of energy. They made progress simply by learning how the energy transformations occur for a ball thrown in the air!

Other students rocked that part but were stuck when the questions about orbits showed up; this was often because they drew the Sun at the center of the orbit instead of at a focus. What a great opportunity to correct this problem!

Finally, some students spent a very long time arguing about whether they needed to account for energy lost to thermal energy in our current Solar System.

Overall, I was pleased by what I learned about how they think about energy as well as how well they grappled with this material. And I’ve now set them up to have a spark of recognition when they learn about planet migration later in the semester. This activity is a work in progress, but I will definitely try it again!

You can access the activity by clicking here!

Classroom Stories: Classroom Calculators

By Stacy Palen

Here’s the thing: all students have a calculator in their phone. And for a long time, I've thought, “They should use the calculator in their phone so they know how to use the calculator in their phone!” But here’s the other thing: a lot of those calculators are terrible. They don’t all do the order of operations the same way. They don’t all have the same “buttons” on them. They don’t all use the same notation. Therefore, any time I have students do any math at all in the classroom, I spend most of the time running around and helping them figure out how to put the “times ten to the” into their calculator. iPhone calculators are pretty good, but Samsung calculators don’t have the same functionality. Students must painstakingly type “(3 X 10 ^ 8)” rather than “3EE8.” That may not seem so bad, but if they forget the parentheses, the calculator doesn’t see their input as one number. So, if the problem includes division, the student is stymied. In addition, students' having their phone in their hand is distracting to the point of incompetence.

This semester, I had the idea to invest in a classroom set of calculators. I found a fairly simple solar-powered calculator that I could buy for less than $7, and I begged the chair of my department to use some of our lab fees to buy 60 of them.

When we have an activity involving a math problem, I invite students to borrow one, and I use the document camera to show them exactly how to punch things into the calculator. For Kepler’s Third Law, I show them how to square a number and how to take a cube root. For multiplying powers of 10, I show them how to put in “3 X 108” so the calculator interprets it as a single number (3EE8 or 3EXP8).

So far, this has been revolutionary. I spend far less time helping students with their calculators and far more time helping them think about their answers. Students can now help each other with the calculators, too, and they don’t need to wait for me to come around to them. Generally, this seems to be helping them be more patient.

Even for the many students who have their own favorite calculator, they sometimes don’t know how to use it for our specific purpose—it’s set up for stats, for example. While they have the option to borrow a calculator or use their own, I still spend some time helping these students find the “EE” or “EXP” key for scientific notation, but if they otherwise know how to use the calculator, they seem to remember this new function more easily. Looking back, I estimate that I could have bought only half as many calculators for the 70 students in the room, and even fewer if they work in pairs.

As I go along, I’m compiling a list of calculator instructions that I can print and tape to the cover. I may make a large poster of this information, instead, which might work better once we are back in our usual teaching space.

I have been pleasantly surprised by how much easier it is to manage the classroom when all my students have the same tool. In retrospect, it seems obvious that this method would be easier, but it took me nearly 20 years to think of it…

Classroom Stories: Teaching the Seasons in Inadequate Classroom Space

By Stacy Palen

Last week, we continued our struggle with the lack of AV equipment in our temporary teaching space. In order to teach the seasons in this space, I rewrote an old activity that used an overhead projector and a piece of cardboard with a hole cut out to help students understand why the angle of incidence matters.

Not having an overhead projector or cardboard handy, it occurred to me to have the students use their cell phone flashlights and the hole punched in their Learning Astronomy by Doing Astronomy workbook pages to accomplish the same purpose.

I always feel chuffed when I think of some new way to solve the problem!  

I very much liked the way students interacted with this activity.

In Part A, they have to assemble some of their own real-life knowledge about seasons on Earth. In Part B, they have to hold the WRONG idea in their head as if it were true, which is especially challenging! In Part C, they identify and explain the correct explanation. In the final part, they apply their understanding to seasons on Uranus and test their ability to extend their knowledge to a new situation.

It took most students about 25 minutes to do this activity.

When I teach it again, I’ll probably modify some of the language in Part B to make it even more clear that I expect them to write down things that they know are wrong.

This activity may eventually make its way into Learning Astronomy by Doing Astronomy because I’ve now figured out how to do it with no extra equipment!

You can access the activity by clicking here!

Classroom Stories: Teaching in the Trailer, or "This Will Have Been a Good Time"

By Stacy Palen

In my family, we have a saying, “This will have been a good time.” We use it to refer to upcoming events that will be stressful and potentially awful, but that we will remember fondly once they have passed. For example, when my snake-phobic husband and I went to the Amazon: he didn’t enjoy the trip while it was happening, but afterwards, he was glad to have experienced it. The whole time we were planning the trip, we kept repeating, “This will have been a good time.”

For years, I have taught Introductory Astronomy in the planetarium. This is a difficult space to work in because the chairs are comfy, the light levels are low, the board and projector space is limited, and working in groups of three or more is really difficult. The chairs don’t turn; the students have those little desks that lift out of the chair arm for them to write on; and it is almost impossible to get in and out of a row in the middle of class. If I want to access the computer, I have to go to the back of the room. It’s awkward, but I got used to it, and I figured out how to do both active learning and lecturing, even in this difficult space.

This semester, the planetarium building is being renovated so that we will have heating and cooling that actually work. That’s the plan, anyway. Don’t ask me why they couldn’t do this renovation over the summer. Figuring out the decisions of Facilities Management is above my pay grade!

My astronomy class has been moved into a “portable”—a double-wide trailer in the parking lot, which was furnished the day before classes started. The layout of the classroom is awkward, with students facing perpendicular to the long axis, and the computer being stationed in one corner. It’s like teaching in a hallway. The first week of class, none of the A/V equipment was working, so there were no projectors. During the second week of class, some of the A/V equipment worked, but intermittently—something about the HDMI cables, aspect ratios, and temporary equipment being incompatible with the University standards. I don’t expect this system to be stable for at least another week or two. I could complain about this (more!), or I could see it as an “opportunity” to try something new.

So now, I have jettisoned my long-time methods and materials, and I’m experimenting. I’ve reorganized the whole class to involve lots of mini-activities that can be done quickly in larger-than-usual groups, with lots and lots of peer instruction. For my students, there is really no choice but to read the textbook before they come to class, because it’s really not possible for me to lecture at all.

Today, we’ll negotiate the “points” restructuring, and my students will get to have a say in how much weight each component will have in their final grade. Now that we’ve done a few of the longer activities from Learning Astronomy by Doing Astronomy, a few homework assignments, and a few of the mini-activities, my students have a better sense of how much value each component should have. I’ve explained the experimental nature of what we are doing, and they are mostly cheerful about it.

This entire situation has got me going back and resurrecting things that I did a long time ago, such as using parts of Understanding Our Universe and Learning Astronomy by Doing Astronomy in ways that I haven’t before (it never occurred to me to tear the activities apart and do them over multiple days), seeking out new ideas and activities, and oh … let’s call it “innovating” … at breakneck speed. I expect a lot of this to be a mess, some of it to be useful in the long haul, and some of it to appear in future textbooks. It’s definitely a situation that “will have been a good time.”

Current Events: Image Release: Giant Magnetic Ropes in a Galaxy’s Halo

By Stacy Palen

A new composite image released by the National Radio Astronomy Observatory superimposes radio data on a visual image of a galaxy. Magnetic fields here are shown in blue and green, indicating alternate directions.

Here are some questions that you can ask your students based on this image:

1) What is the Hubble type of this galaxy?

Answer: A spiral.

2) How do you know?

Answer: Because there is a disk, viewed edge on.

3) What is the Hubble type of the large galaxy directly above the primary galaxy in this image?

Answer: Elliptical.

4) How do you know?

Answer: There is no disk.

5) The blue and green false color “hair” represents the magnetic fields of the galaxy. Blue indicates that the magnetic field points roughly away from us, while green points roughly toward us. These magnetic fields are described as “spiraling” and as “ropes.” Make a sketch of the magnetic field lines of the galaxy that fits these descriptions and observations.

Answer: This is a genuine question, not a test of their understanding. I am picturing a spiral for each blue/green pair that is roughly perpendicular to the disk. I wonder what students “get” from these descriptions?

6) Are the magnetic fields above the disk of the galaxy symmetric with those below the disk? What might cause this?

Answer: They are not. It could be because the magnetic field is being generated differently, or it could be because the observations are more resolved above the disk than below. That could happen if the galaxy disk was tilted so that the top of the disk is tilted toward us.

Current Events: Probe Gets Close to the Sun—Finds Rogue Plasma Waves and Flipping Magnetic Fields

Sun nasa pic_12_20_2019
Credit: NASA/SDO


By Stacy Palen

Just in time for the close of the semester, we get a present from NASA! According to this article on NPR, the Parker Solar Probe has arrived at the Sun, and it’s sending us back some big surprises.

Here are some questions, inspired by the Parker Solar Probe’s recent discoveries, that you can ask your students:

1) In 2025, the Parker Solar Probe will come within 4 million miles of the Sun, which is 1/10 the orbital distance of Mercury. To date, it has passed within about 15 million miles from the Sun (almost 4/10 the orbital distance of Mercury). Make a sketch of the Sun and the orbit of Mercury, and then draw circles that show the closest distance of the Parker Solar Probe so far, and its distance in 2025.

Answer: A sketch.

2) The Parker Solar Probe has observed unexpected spikes in the flow of solar wind, where its speed suddenly increases by 300,000 miles an hour, which is nearly double its normal, steady speed. These spikes last for varying amounts of time, from a few seconds to hundreds of seconds. Convert this information into a graph of the speed versus time for an outflow over five minutes of observation. Assume that two spikes occur, one of 5 seconds and one of 100 seconds.

Answer: A graph.

3) The Parker Solar Probe may answer a question that’s been around for decades called the “solar corona problem.” From the context of the article, or from some general research on Google, describe this problem in your own words.

Answer: Why is the corona so hot?

4) The article repeatedly mentions that the magnetic field “flips” without thoroughly explaining this process. What exactly does this flipping of the Sun’s magnetic fields mean?

Answer: This means that the north end of the magnetic field switches locations with the south end.

5) Why did astronomers think that their equipment might be malfunctioning?

Answer: Because the changes in the speed and direction of the magnetic field were happening much faster than expected.

Current Events: A Missing Neutron Star May Have Been Found after 30-year Hunt

Credits: NASA/STScI

By Stacy Palen

Supernova 1987a may be the most well-studied supernova in history. But the “corpse” had not been found! However, this may have changed according to this article from Scientific American.

Here are some questions you can ask based on this article:

1) How long ago was this supernova first observed on Earth?

Answer: 30 years.


2) How long ago did the supernova actually occur?

Answer: 163,000 years


3) Why do astronomers typically not worry about the discrepancy between the times in question 1 and question 2?

Answer: We can’t know about anything that happens until the light gets here. As far as we are concerned, the moment we observe it IS the moment when it happened.


4) What is special about supernova 1987a?

Answer: Supernova 1987a is so unusually close that we can see it in detail, and watch it evolve in real time. It is also the first supernova observed for which we had seen the progenitor star.


5) Why had astronomers argued that a neutron star (as opposed to, say, a black hole) should result from this supernova?

Answer: The progenitor star was about 20 solar masses. This is in the range between 8 and 25 solar masses, which is expected to result in a neutron star.


6) What is the evidence that has been presented for the detection of a neutron star?

Answer: A bright blob within a dense dust blob.


7) What will astronomers do to strengthen their conclusions from this evidence?

Answer: Get more data, of course!