Current Events: NASA Releases Stunning Hi-Res Photos of Jupiter's Swirling Atmosphere

By Stacy Palen

Sometimes, you just want to look at a lot of pretty pictures. Juno’s got ‘em. This is a nice intersection of science and society because there are issues of intellectual property rights here that can prompt students to think a little more deeply about who owns science and scientific data.

Below are some questions to ask your students based on this article.

1). What is a “citizen scientist?”

Answer: A citizen scientist helps scientists analyze raw data or produce images from raw data.

2). The images shown in the article have been processed to create “visually pleasing work for the public.” Click through to the dedicated Juno website to look at a few raw images. How do these processed images differ from the raw images?

Answer: The processed images have much greater contrast and are more colorful. The colors are often changed.

3). What information is lost when the images are processed in this way, and what information is made more available? 

Answer: Information about composition is lost, especially if the color is changed, but information about wind patterns is enhanced and made more visible.

4). Is it “honest” to process images in this way and present them as images of Jupiter?

Answer: Answers vary.

5). Are these images art, science, or something in between? Support your answer with an argument about the purpose of art and/or science.

Answer: Answers vary, but something in between is most likely.

6). What is the benefit of making “visually pleasing work for the public?”

Answer: Answers vary, but I expect to see something about public support for science.

7). You may have heard the term “intellectual property”; this is the concept that gives rise to copyright law, for example, where artists and writers own their work. Historically, images from NASA spacecraft have been part of the public domain—because the public paid for the spacecraft, they own its products, and anyone could use them to make posters or T-shirts. These images, though, have a more complicated origin. The raw data comes from the spacecraft, but the processing has been done by an unpaid graphic artist who has done something absolutely unique with each image. Who do YOU think “owns” these images: the public or the artist?  Explain and support your viewpoint.

Answer: Answers vary, but I’m looking for something “well-reasoned and insightful.”


Current Events: Hubble Uncovers Concentration of Small Black Holes

By Stacy Palen

Astronomers have long been on the hunt for “intermediate-mass” black holes. These are black holes with masses between a few hundred and a few ten-thousands of solar masses. It was thought that these should exist in globular clusters. While looking for these, astronomers have instead found a swarm of smaller black holes, forming a mini-cluster in the center of a globular cluster!

Below are some questions to ask your students based on this article.

1). What is the approximate range of masses for an intermediate-mass black hole?

Answer: Tens to hundreds of thousands of solar masses.

2). How old is this globular cluster? 

Answer: This globular cluster is almost as old as the universe itself, so nearly 13.7 billion years old.

3). How do astronomers find the age of a globular cluster?

Answer: They make an H-R diagram and find the main-sequence turnoff.

4). How does the team of astronomers from the IAP know that there is not one single black hole at the center, but rather a swarm of black holes?

Answer: The shape of the orbits of nearby stars shows that the mass at the center is extended in size, rather than point-like.

5). How do they know that those masses in the core are black holes and not stars?

Answer: They used the theory of stellar evolution, combined with the fact that the mass is invisible.

6). Why are all the black holes in the cluster found near the core?

Answer: Because of dynamical friction, where they lose momentum to other less-massive stars.

7). How might astronomers further test this idea about the core of this globular cluster?

Answer: Mergers of these black holes might be detected by LIGO/VIRGO.


Current Events: Best Map of Milky Way Reveals a Billion Stars in Motion

By Stacy Palen

Gaia’s latest data haul, from December 2020, includes the proper motions of more than 1 billion stars. So the Gaia astronomers did the fun thing and mapped their future positions as they move against the background of the Milky Way.

Below are some questions to ask your students based on this article.

1). There are two motions that are discussed in this article. One of them, “proper motion,” is the “nearly imperceptible motions across the Galaxy year after year.” The other is parallax. How could astronomers tell these two motions apart?

Answer: Parallax is a back-and-forth motion. The star returns to its starting point after a year. The proper motion adds every year, with the star moving farther and farther from its starting point.

2). Why is it important to know the distance to stars?

Answer: Because the distance measurement is connected to the luminosity measurement, and the luminosity is necessary to find out about stars' size, age, structure, and evolution.

3). Study the image in the article that shows the star trails. Are there any trends in the motions of the stars shown here?

Answer: Yes. As you look toward the galactic center, they seem more random, whereas the farther out, toward the corners of the image, the trails are more parallel to one another.

4). How many years will it take each of these stars to travel along one of those trails?

Answer: 400,000 years.

5). Do you expect that you will see any of these stars move a significant distance in your lifetime?

Answer: Absolutely not.

6). Working backwards from the trails that you see here, have the visible constellations changed significantly since the pyramids were built…a bit more than 4,000 years ago?

Answer: No. The stars will have moved about 1/100th of the way along a track in that time, which is not very far.


Current Events: The First Black Hole Ever Photographed Now Appears to Be "Wobbling"

By Stacy Palen

In 2019, astronomers released the first image of the shadow of a black hole’s event horizon. Further processing of earlier data shows that the accretion disk has rotated.

Below are some questions to ask your students based on this article.

1). What is the black circle in the middle of the image?

Answer: This is the shadow of the event horizon. It is larger than the event horizon and shows where the light has been bent away from the line of sight and into the black hole.

2). What is the bright ring around the outside?

Answer: This is light coming from the accretion disk around the black hole. This light has been bent by the black hole’s gravity into our line of sight.

3). A series of models of the black hole are shown in the figure titled "M87* black hole appearance in 2009-2017." If the bright spot were on a clock face in 2009, it would have been at about 5:00 p.m. Where was it in 2017?

Answer: Nearly all the way around to 5:00 p.m. again, so about 6:00 p.m.

4). If this motion is periodic (that is, it repeats over and over, taking the same amount of time each time), what is the period?

Answer: 8 years.

5). How long will astronomers have to wait to find out if this motion is periodic?

Answer: At least one more period, so 8-16 years.

6). In the video and written text, the black hole is described as "sucking up light." Many astronomers object to this terminology, insisting that black holes don’t "suck in light" but that "light falls in." What distinction are astronomers trying to make?

Answer: Black holes have gravity rather than some super-strong supernatural force.


Classroom Stories: Teaching Parallax—A Map

By Stacy Palen

You may have noticed that, by now, we have acquired quite an enormous catalog of materials for teaching astronomy. There are so many different pieces, in fact, that even I sometimes find them overwhelming or forget that I did something! I find it useful, then, to pick a couple of topics to focus on each semester. For each one, I put together a series of materials that aims to touch on all the bases for students as they approach the topic. These materials must be intentional, transparent, flexible, coherent, and equitable. In other words, they have to meet the needs of students where they arenot where I wish they wereand help bring students towards mastery, no matter what background they may have.

This semester, I was thinking about parallax. When I meet with students in the classroom environment, I often revisit this concept several times during the semester, giving them a nudge to remember how we measure distance, so that when we arrive at the distance ladder later, they haven’t forgotten this fundamental rung. But in the online environment, I find this sort of “callback” to be much more difficult to arrange. So from the very large catalog of items relating to parallax, I have pulled together six pieces that introduce and teach the concept, assess and refine student understanding, and then ask students to take their knowledge further.

First, in my introductory video for the chapter about stellar properties (Chapter 10 in Understanding Our Universe), I ask students to do the same classroom demo that I ordinarily do: sticking their thumb in front of their face, moving it forward and back, and blinking one eye and then the other. This gives them an intuition for how parallax works and also gives them a way to test their comprehension later; if their answers imply that the object will appear to move more when it is farther away, I can ask them to remember “the thing with your thumb.” My kinesthetic learners really appreciate this.

Next, I ask students to read the chapter, paying close attention to the parallax figure. I do this in my introductory video, and then I have SmartWork questions attached to this concept in their homework to give them a further nudge to do the necessary work of reading the chapter. Some students learn really well in the traditional format of reading and answering questions.

The “Astronomy in Action” video is also in SmartWorkwith questionsand shows this concept from a different perspective. Students who learn best by watching demonstrations find this video really helpful. It also helps them with a course-long project of learning how to switch perspectives from the “inside looking out” to the “outside looking in.”

At the end of the week, students do the Learning Astronomy by Doing Astronomy exercise about parallax (Activity 19 in the Second Edition). I have a very short (3 minute) video for each activity, which some students watch. In this video, I recall the thumb exercise and remind them to think about whether more distant objects move more or less. The activity itself also ties back to the demonstration that asks students to use their thumbs and also reminds them of the figure from either Understanding Our Universe or 21st Century Astronomy.

The following week, I have a follow-up question about the image of Alpha Centauri in Chapter 10. I ask students whether this distance could be measured by parallax and how they would know. There are a couple of ways to answer this question, depending on how well they understand the concept. I’m always impressed by the students who explain that since this is the closest star, and we can measure the parallax for many stars, then of course we can measure the parallax for Alpha Centauri. Other students calculate the parallax angle and compare it to the smallest measurable parallax, while others look it up on the Internet. In any case, I get a sense of how they are thinking about the topic.

Finally, each week, we have a discussion question in Canvas, which is open-ended and speculative. I call them “What If?” questions. The parallax-related discussion question is about measuring the distance to stars that appear to be associated with one another in the sky. I’m asking students to take the concept just a little further by having them think about how knowing the distance helps us figure out how stars are distributed in three dimensions. For some students, this speculative discussion is the best thing that happens to them all week, and they get super into it. Others, naturally, post a sort-of-related answer that they didn’t think hard about. That’s fine, because one of the other things that I’ve asked them to do might be more their “thing.”

Surprisingly, even though there are already six different pieces to this instructional map, I have left out some other things that I could have done—for example, I have a news article about parallax that I could have asked students to read. But I don’t feel compelled to have them do every single thing they could do. Instead, I try to pull together a set of materials that gives them different ways to attack the concept, test their understanding, and then further refine and extend their knowledge.

Do I think this hard about how I assemble the teaching materials for every topic? Not yet...but I’m getting there. I find it really fun to think about how to put different pieces together to build a module that has maximum impact; it’s kind of like playing with Legos, but for teachers!


Current Events: Mars and Perseverance

By Stacy Palen

Heads up, everyone! NASA is making another extraordinary rover landing on Mars.

Mars is an easy target for students to view this month and is easily visible between sunset and midnight. It’s the only bright planet visible just now and is typically easy for students to identify because of its distinctive red color.

But in other news, the Perseverance rover is landing on Mars on February 18. This is another one of these amazing multi-method landings, involving parachutes and space cranes. A delightfully real-looking CGI “trailer” for the event can be found here.

The landing will be broadcast live on NASA TV, and there are a number of broadcasts leading up to the landing. You can find those listed (in EST) here.

The rover is looking for signs of ancient life and will collect rock and soil samples for their possible return to Earth. It’s also carrying along several prototypes, such as a helicopter and “Moxie,” which produces O2 from Martian CO2. These prototypes test concepts for equipment for future exploration, including astronaut missions to Mars.

Full mission details can be found at Nasa.gov

This entire episode dovetails nicely with Activity 12 (Planning a Manned Mission to Mars) in Learning Astronomy by Doing Astronomy, Second Edition. I’ve got my students watching the landing and doing the activity in the same week. If we’re lucky, we might even get a break in the clouds one evening between now and then so they can see Mars with their own eyes!


Classroom Stories: Endings...and Planning for Beginnings!

By Stacy Palen

I love the moment when my attention turns from the current semester to the next one. I love the feeling that I’ve turned the page and that the new course will start fresh, with no mistakes in it. And I love looking back at the semester, as though it were a research project, as I ponder future work.

One of the most important practices in my teaching is to take a few minutes at the end of the semester to actually reflect and then write down what I think worked and what I think didn’t work. I compare this to what I had written down in previous semesters and see how the course has either improved or gone off the rails. Then I take a few more minutes to think about what experiment I would like to try in the next semester to improve the course in some way. And then I build that in when I plan out the next semester.

I do this before the student evaluations come in, because it’s useful for me to have my own thoughts first. It’s sort of the professor’s equivalent of “think” in “think-pair-share.” Sometimes I remember to compare my thoughts to the students’ thoughts and then write them down. More often, I just add their thoughts to my own. The students’ view tends to be very prescriptive; “more homework,” “less homework,” “make homework due on Saturday, not Friday,” or “I couldn’t ever find the Zoom link.”

My own thoughts tend more to, “This time around, they understood the expanding universe but confounded it with inflation and are still not specifically understanding that the two things have very different time scales,” or “The discussions did not accomplish what I wanted them to; next time, I need to make the grading out of more points so it can be more clear and fine-grained that I expect thoughtful responses.”

This entire exercise has a selfish purpose, as well as a selfless one; it gives me a powerful narrative for my tenure and promotion portfolios. I never had to worry if one of my experiments didn’t work out, because I always had a narrative that something wasn’t working, so I tried this experiment, and then this one, and then a third one, which was the most successful. That made me bold about trying new things.

This semester has been extraordinary, and I imagine that a lot of junior faculty, in particular, are feeling vulnerable and uncertain about how to handle their successes and failures this semester. I encourage everyone to take a few minutes to reflect on what worked and what didn’t, and on what you might try next semester to hold on to the successes and improve upon the failures. I’ll be doing it, too.


Classroom Stories: Missing the "Aha!" Moments during Online Teaching

By Stacy Palen

I’ve been talking to a lot of people about the transition to online instruction. Most of these conversations have been with people who are not academics and who seem to have the idea that I sit around eating bonbons and drinking bourbon in the afternoon now that I don’t have to “actually” work. Once I take a deep breath, I find myself saying, “I hate it,” which gives me the opportunity to reflect about why I hate it.

I had not taught an all-online course before, so there was an enormous learning curve. This problem was magnified because I was moving five distinct courses online between the spring and the fall. So I didn’t have a whole lot of time to think hard about what I was doing in any one of them. Just keeping track of what I had finished and what I had just thought about took multiple “to-do” spreadsheets. So that’s part of it: feeling like it’s the first time I’ve ever taught, and it’s all too much.

But there’s something else, too, something more fundamental. I’m missing the “Aha!” moments. When I teach in person, much of the time is spent moving around the room, listening to conversations, and nudging students to think differently or ask different questions. Most of the “lecture” time is spent answering questions and having wide-ranging discussions sparked by the material. At least once in every class period, some student would say, “Ooooohhhh!” or “Aha! I get it now!” as we finally figured out where they had gone off track, or what misconception they held without knowing it.

I miss that. It turns out that those “Aha!” moments were a primary motivator for me, as a teacher. That’s where I found joy. More than once, I’ve told friends, “If this is what teaching was when I started, I never would have done it at all. I would’ve been an engineer, instead.”

Well, so...enough complaining. Nobody would have asked for a giant global pandemic. What can I do about it? I’ve poked around a little bit, looking at “best practices” for student engagement in online courses and haven’t found my own “Aha!” yet about how to find what I’m seeking. I’ve had a couple of thoughts, but Im still mulling over the direction I want to go.

I have discussions open in Canvas every week and have managed to mostly respond to comments posted in those discussions, but students generally don’t respond to my responses. These are “graded,” but I set them up to be, fundamentally, a participation grade. In Astro101, I’m using open-ended “What If?” questions to spark discussion, and students do occasionally talk to one another there. In other classes, I’ve made them prompts about their struggles with assignments; however, students rarely comment on those. Going forward, I can modify these discussion prompts and grading practices for the upcoming semester to see if I can make them more useful but not onerous.

I’ve been available for students in my Zoom-room 15 hours a week, and I often have students drop in for a minute or two to ask a specific question (or I have students from the Physics with Calculus lab who stay signed in for three hours while they work through the lab and occasionally ask me questions). But much of the time, I’m doing other things—like grading, or chasing down why my Kaltura links are broken—while the box in the corner of my computer screen stays empty. I could make some of those times into synchronous instruction, or make it required for students to drop in and talk to me. But I hesitate because some of my students are already so stretched…so I’m not sure about it.

I’m still thinking about this problem, and I welcome ideas from professors who’ve taught online before. What practices are you using to help stay connected to the things that bring you joy in your teaching? I’d love to hear about them in the “Comments” section below!


Reading Astronomy News: Betelgeuse Might Be 25% Closer Than Previously Believed

By Stacy Palen

This week, I draw your attention to this piece of news that neatly encapsulates many of the concepts that you might be teaching at this point in the semester! Betelgeuse’s recent variability may be caused by dust and pulsation—so no nearby supernova in the works for us this year. That’s typical 2020 for you right there. Disappointing, all around.

Below are some questions to ask your students based on this article.

1) Why were astronomers, earlier in the year, talking about Betelgeuse exploding as a supernova sometime soon?

Answer: Because it had abruptly become dimmer, and evolution to supernova was one possible explanation.

2. What key conclusion in this most recent study definitively rules out the supernova-soon scenario?

Answer: Betelgeuse is still fusing helium in its core, which means that it has a significant amount of time left before it makes the full, onion-like set of fusion shells that precede a supernova.

3) Typically, astronomers first determine the distance to a star and then infer its size from knowing something about its evolutionary state and where it sits on the H-R Diagram. What did astronomers do differently in this study?

Answer: In this study, astronomers used stellar seismology to find the size of the star first and then worked backwards to determine the distance. This distance agrees (it is within the error bars) with previously determined distances to Betelgeuse.

4) Will Betelgeuse eventually explode as a supernova (even if we don’t get to see it this year)?

Answer: Yes, because it is a red supergiant.

5) Will that affect life on Earth?

Answer: Probably not. It is too far away to have an impact on life on Earth, although it would become incredibly bright for a short time.


Classroom Resources: Zombies and Aliens

By Stacy Palen

Apropos of the last few posts by Ana Larson about online classes and cheating (Thanks, Ana!), this week, I’m working on my Astro101 midterm.

It’s important to state up front that I think the purpose of exams varies from course to course. In Astro101, I think the purpose of exams is to make students look back over the last several weeks and connect different concepts across the material. For Astro101, the review is the goal, as far as I’m concerned. Therefore, I design my exams to guide them to do that review in a fun and engaging new context. In contrast, in a different course, such as Physics with Calculus, I have other goals, and they really need that material to be quickly accessible and at their fingertips for the next course. I design those exams differently, and I ask them to do the review on their own and then take the exam.

Historically, my Astro101 exams are story exams. I plunk students down on desert islands or in zombie apocalypses or some other contrived (and not entirely realistic) situation, and ask them to solve astronomy puzzles in order to survive. They might need to be able to tell time by the phase of the Moon, or find out whether it’s before or after the vernal equinox by judging the position of the rising Sun against the (formerly determined) position of Orion’s belt. I’m always bemused that students tell me that they think these exams are fun and practical.

I give students several days to do them, because they really do need to read the question and then think about it for a while—in this particular class, I’m not interested in whether they can do things quickly. And they can use any resources they have except other people.

But the things that I really like about these exams is that they are:

  1. Motivating: Students want to figure them out for themselves…because how could they ever know if they could survive the zombie apocalypse otherwise?!
  2. Fun: Students like to take them. Truly. They talk about them to their friends, and I usually get questions on the first day of class about whether I’m going to do this kind of exam again. Sometimes, even in other courses, if a student took Astro101 with me, they’ll ask if we are going to have fun exams or normal exams.”
  3. Fast to Grade: I have students draw pictures to answer a lot of the questions, which I can then grade out of a scale of three in less than a few seconds. For example, if the answer is first quarter, the Moon, Earth, and Sun are present and in the right orientation (3); they are all there, but drawn for third quarter (2); they are not all there or are in a completely different orientation, but they still drew something (1); or they did not answer the question at all (0). It typically takes me a full day (8-10 hours) to grade 120 exam papers because these picture questions take virtually no time to grade.
  4. Easy to Change, from One Semester to the Next: For example, I give them some data about the altitude of Polaris and ask whether they need to go north or south to reach a certain point. I can change that altitude, and people who are looking up answers online will not notice. So if I get last semester’s answer, I know to separate that exam to a different pile for…careful study. Or maybe they notice that this year it’s different. But to know why that difference matters, and give the correct answer, requires processing the material. And that meets my goal.
  5. Difficult to Cheat, Given My Goals: If I make them draw pictures in their own hand, then at some point, the information went through their brain, so some of it will stick. I’m satisfied because it meets my goal that they need to review the material and apply it in a new context. Because that’s my goal, I’m not bothered about how they go about it.

This semester, I hesitated all weekend about whether to send them the zombie apocalypse midterm. It seemed…insensitive, maybe…or just too stressfully close to reality. But then I made a joke of it, instead: It’s 2020of course there will be zombie apocalypse! I bet they LOL and dive right in.