Reading Astronomy News: Lost Cities and Climate Change

By Stacy Palen

Remnants of the lost city of Cahokia. Credit: Steve Moses/Flickr (CC BY 2.0)


In this article from Scientific American, a climate scientist talks about why she is not reassured by the idea that “the climate has changed before.” This is an opinion piece, but it is worth a read if you have students who raise this argument.


1) The author points out that climate has changed many times in the past. Does that imply that Earth’s climate is sensitive to small changes or insensitive to small changes?

It implies that Earth’s climate is very sensitive to small changes.


2) This scientist is making the case that historical climate change has had dramatic and long-lasting effects on human communities. Do they provide evidence to support this argument?

Yes. The author mentions many examples, from both prehistoric and historic times.


3) The author also makes the case that many factors contributed to these effects. Identify an example of a pre-existing condition that was made worse by natural climate change.

Answers vary, but the overextended Roman empire or inequality in France might be mentioned.


4) Do you see any evidence for a similar pre-existing condition in the country today? Explain.

Answers will obviously vary depending on where you live. This is a small test of how well-informed students are about what’s happening in the larger society.


5) Describe how climate change might impact the condition you noted in (4).

Answers will vary, but should be consistent with their answer to 4. So, for example, if they mention immigration, they might include here a mention of how drought drives migratory patterns.


6) In your own words, explain the argument this scientist proposes that historical climate change should be seen as concerning rather than reassuring.

Answers will vary based on the students’ comprehension of the post.


Posters Celebrating Women in STEM


By Stacy Palen

This set of nifty (free!) posters came through my inbox over the summer. We printed some of them to hang around the Physics Department, and the College of Science more generally.

In addition to raising awareness of the contribution of women, they raise awareness of the contribution of other marginalized groups as well.

Take a look!

Classroom Stories: A Useful Reminder About Names at the Start of the School Year

Credit:Tony Tallec / Alamy Stock Photo

By Stacy Palen

Here in August, just as we are getting ready to go back to school, this Teen Vogue article that came across my desk was a useful reminder that people care deeply about their names.

I have a name that is not very hard to pronounce, but it is apparently easily confused with other names. For the longest time people would randomly call me “Tracy.” Then, in 2008, I started to get “Sarah” ALL. THE. TIME.

So I sympathize with my students and their genuine desire to be called by their actual names!

Before class begins every semester, I scroll through the list of students registered for the class and sound out any names that I’ve not seen before. Utah is particularly famous for unique spellings that take a moment to sound out like “Aunistee,” which is pronounced “Honesty.”

It has served me well to take a moment to look through these names ahead of time. In fact, I believe this is one of those “top ten” teaching tips on some website somewhere.

I am completely up front on the first day with my 120 introductory astronomy students that I will not know their names until about week three. After that, I will only know their name if they come to class all the time. They are generally surprised that I think that learning their names is an important thing to do at all.

In order to learn their names, every Friday, while they are working on their in-class activities, I hand back the past week’s activity by calling out their name and then handing the activity directly to the student. (This is arguably required by laws protecting student privacy. Students should not be able to see the scores of other students. There are other ways to handle that problem, but that’s a different blog post).

If I don’t know how to pronounce a student’s name, I will ask them to help me practice saying it. Then, I will make sure to practice it again after class. When I’m inputting grades on their written work, I’ll practice saying their name once more, alone in my office, until I’m pretty sure I’ve got it right.

Knowing your students’ names is a surprisingly simple and effective way to make your students feel like you see them and value their contribution to the class. It’s important to realize that you don’t have to be perfect. I find that if I know about a quarter of the names in the class, the students think I know them all. Then, when I call on a student whose name I know, I use their name every time.

Some names I never learn. At this point in my career it’s usually because I can’t remember if this guy is “Joe,” “John,” or “Jim.” I’ve seen those names attached to so many different people that it’s hard to keep track. I simply call on them with “Yes?” and a nod or tilt of my head.

I often get a comment in my evaluations like “I can’t believe she knew all of our names.” I was surprised the first time I saw that, but in retrospect, it makes sense to me. Students can feel lost in a large lecture classroom. Hearing their name out loud helps them find their place.

Reading Astronomy News: Japan (Very Carefully) Drops Plastic Explosives Onto An Asteroid

By Stacy Palen

Summary: Hayabusa2 has been investigating the asteroid Ryugu. This is a sample-return mission, which has implications for Solar System formation and may cast light on the origins of life on Earth.

Article: Japan (Very Carefully) Drops Elastic Explosives Onto an Asteroid

1. Consider what you know about the origin of the Solar System. What are astronomers hoping to learn from Hayabusa2’s mission to Ryugu?

Answer: They are hoping to learn about the composition of matter in the Solar System when it formed. This could confirm or refute our ideas about Solar System formation and the formation of the asteroid belt. The precursor molecules for life are also present on the asteroid, which may give us clues about the origins of life on Earth.

2. The article states that Hayabusa2 “physically touched down” on Ryugu in February 2019, and took a sample of dust kicked up. Go online and read more about it. Describe this event in more detail. Do you consider “physically touched down” to be an accurate characterization of what happened?

Answer: The spacecraft approached the surface and shot a small projectile into the asteroid. A sampler horn collected the kicked up dust and the spacecraft moved on. This is not quite what’s implied by the summary sentence in the news article.

3. Ryugu is less than a mile across, in an orbit between Earth and Mars. Using an average orbital radius between those two planets (1.25 AU), find the orbital period of Ryugu. Convert this orbital period to seconds.

Answer: This is a review of Kepler’s third law. The period is 1.16 years, which equals 3.7 X 107 seconds.

4. The circumference of Ryugu’s orbit is 1.2 X 1012 Divide this distance traveled by the period to find the speed of the asteroid in its orbit. This is the speed that Hyabusu2 must be traveling in order to rendezvous with the asteroid.

Answer: This is a reminder of the definition of the properties of an orbit (what is the circumference, and what is the period). The speed is 32,000 m/s.

5. When was the spacecraft launched, and when is the sample return mission expected to arrive back here on Earth?

Answer: The spacecraft launched in December 2014, and will return a capsule to Earth in December 2020.


Image Contributor: Mark Garlick/Science Photo Library, 1 March 2013

Classroom Stories: Sky Maps and Apps

JMGR70 (1)
Credit: Vadym Drobot / Alamy Stock Photo

By Stacy Palen

Everyone has their favorite sky maps, planispheres, and apps. I am no exception! Here are two resources that I go back to again and again as I prepare for class or for observing sessions.

Sky Maps is my favorite source for star charts. The star charts are free, have the right amount of detail for introductory students, and they photocopy well. The back page has a list of objects that can be seen with the naked eye, with binoculars, and with a telescope.

At the beginning of each semester, I bring a stack of these star charts to hand out. I explain how to use them (pointing out, for example, that East and West are switched and asking the students why this might be), and then explain that during the semester, we’ll be figuring out all of the object types on the back.

I then tell them to go observing. I suspect that few of them actually do, but for some reason, they do not thereafter complain that I didn’t teach them the constellations! Go figure…

At various times and in various classes, I’ve used different planetarium programs on the computer. At the moment I teach in the planetarium, so this is not as critical a question as it has been in the past.

When students ask me for a recommendation, I recommend that they look at Celestia, which is open source and runs on Windows, Mac, and Linux. Celestia is a 3-D program so students can use it both as an Earth-bound sky simulator and as a space simulator.

It’s not the easiest planetarium software to use, but the price tag more than makes up for getting lost in the universe once in a while!

I’m not particularly fond of using phone apps for looking at the sky because I find that they are too sensitive to the tilt of the phone. This makes sharing them difficult, even with someone standing next to you. As well, I’ve always been disappointed at what I can find out about the objects in view.

Perhaps I’m just grumpy, but if I can click on something, I really want to be able to click on something and find out all about it. I don’t miss that functionality with a paper star chart, but I do miss it when such a vast informational repository is already available in my phone!

What maps and apps have you found useful for your students? Feel free to comment with your own favorites!

Reading Astronomy News: Galactic Superbubbles

By Stacy Palen

It’s that time of the semester when we are talking about galaxies, galactic structure, and supermassive black holes. Fortunately, Chandra has our back and has released a new image of a superbubble in NGC3079. The picture is sufficiently spectacular that I want to let you know about it right now!

Article: NGC: Galactic Bubbles Play Cosmic Pinball with Energetic Particles

1. Along the bottom of the composite image on the website, there are tabs that allow you to switch back and forth between the composite image, the X-ray image and the optical image.  Compare the X-ray image and the optical image. 

Answer: The X-ray image contains mostly just point sources, as well as two larger fuzzy patches. One of these fuzzy patches is shaped like a ring. The optical image, however, shows the entire galaxy, including dark lanes of dust and gas and bright light from stars and emission nebulae.

2. How big are the superbubbles, compared to the diameter of the disk of the Milky Way Galaxy?

Answer: The superbubbles have diameters of a few thousand light years. The disk of the Milky Way has a diameter of a few hundred thousand light years. So, these bubbles are about 1/100 (0.01 or 1%) the size of the Milky Way’s disk.

3. What is a cosmic ray? 

Answer: A high energy positively charged particle traveling through space. Note: they will have to click through to find this answer, if they don’t already know it! Let’s encourage that behavior!

4. Humans also accelerate particles, in particle accelerators, funny enough. How much more energy do the particles in these bubbles have than those accelerated by humans?

Answer: These particles have 100 times more energy than those in particle accelerators.

5. Run your mouse over the composite image to see it with labels on it. Why do astronomers think these superbubbles are associated with a supermassive black hole?

Answer: Because they are located together in space. 


 Photo credit:

 X-ray: NASA/CXC/University of Michigan/J-T Li et al.; Optical: NASA/STScI


Reading Astronomy News: Chasing Down the Mystery

Credit: Sloan Digital Sky Survey,


Once in a while something new happens. In the case of an article published in The Atlantic, astronomers observed an object that had properties like those of a supernova explosion, but much too fast. That led to some detective work across the electromagnetic spectrum to try to figure out what was happening!


1. What event triggered astronomers to pay attention to this particular location in space?

Answer: A bright spot appeared where none had been before.


2. How did astronomers communicate with each other that something interesting was happening?

Answer: They used The Astronomer’s Telegram, a global astronomy alert system.


3. Where did the event happen?

Answer: This event occurred in a nearby galaxy. It was detected at a telescope in Hawaii. (Note: I would use answers to this question to find out if students have sorted out what an “event” is, and the difference between an “event” and the detection of it.)


4. What about this event made it clear that this was not a “normal” supernova?

Answer: It was too bright, and also faded away too quickly. This is weird because brighter supernovae should fade away more slowly, not more quickly.


5. What is the current working hypothesis about what happened in the event?

Answer: Astronomers think this may have been the formation of a black hole or a neutron star.


6. How will astronomers test this hypothesis?

Answer: This event is over, so astronomers will have to wait for another one to occur to test their ideas against observations of that future event.

Book Recommendation: Hawaiki Rising

Hawaiki Rising

By Stacy Palen

On May 18, 2014, Hokule’a left Oahu for a 3-year voyage that would take her and her sister vessel, Hikianalia, around the globe. The journey covered 47,000 nautical miles with stops in 26 countries, and ended in Hawaii on June 17, 2017. The vast majority of the navigation on this journey was celestial navigation. Specifically, the celestial navigation of pre-contact Pacific Islanders. The voyage was a celebration of the revitalization of an art and a science that were nearly lost to the world.

In his book, Hawaiki Rising, Sam Low tells the story of the rediscovery of this lost art. The book reads like a mystery story with adventure chapters. Along the way, it covers the principles of the celestial sphere in a fair amount of detail.

The story begins with a very brief history of Captain Cook’s discovery of Hawai’i and the aftermath. This sets the stage for the shift in culture that caused the art of navigation to be lost and simultaneously hints at the trail of breadcrumbs that would be followed in order to rediscover this ancient art. After a brief nod to Thor Heyerdahl, whose famous voyage forms the basis of the movie Kon Tiki, the story shifts to following the “detectives” in 1968 who asked the question, “How did they do it?” By the seventh page of the main text, we are already on the trail of the answer to that question.

Two of the most interesting characters along the way are Mau Piailug, known simply as Mau, and Nainoa Thompson. Mau learned to navigate “the old way”; from oral tradition stretching back generations, and Nainoa Thompson learned from him as a young adult. Nainoa Thompson is now the President of the Polynesian Voyaging Society, and knows more about this method of navigation than anyone else, at this point. Not long ago, he gave a talk on the experience at Stanford, which I highly recommend. 

The astronomical content is spread throughout the book and is all related to the celestial sphere and the appearance of the sky from various locations. As such, it does not provide content that is broadly applicable across the whole course, but it does provide a fascinating motivation for learning the content in those initial few chapters. We often mention “people used to navigate this way,” but beyond talking about finding the North Star, we tend to gloss over the details.

For myself, this book gave me new ideas for how to motivate that section of the course. Many students are already somewhat familiar with these ideas from the Disney movie “Moana,” in which a young Pacific Islander girl sets out to rediscover how to navigate the oceans. The movie gets it right, which is encouraging. Students are interested to learn that a movie they loved has an application to what they are studying in class.

Students in a book group will undoubtedly stumble across the PBS documentary The Navigators: Pathfinders of the Pacific, directed by Sam Low and Boyd Estus. The film centers on Mau Piailug, the last known navigator from the Micronesian islands, who was so instrumental to the revival of this type of navigation. In 57 minutes, the film cannot possibly cover the story, and especially the astronomy, at the level of detail of the book.

It would be interesting to try combining all these resources in one semester: First, assign students to watch Moana, or at least watch the clip of the song “We Know the Way.” Read the book throughout parts of the semester, then watch Nainoa Thompson’s talk. Finish by watching the PBS documentary. Comparing and contrasting the three different treatments of the material would allow for interesting discussions that draw on students’ competencies beyond the astronomy classroom.


Book Recommendation: Unstoppable

Screen Shot 2019-06-06 at 1.07.30 PM

By Stacy Palen

Perhaps I should not have been surprised to find out that many of my students see Bill Nye (the Science Guy) as a personal hero, but I was. It’s probably got something to do with the bow ties…or the lab coat…or something.

I was too early for Bill Nye, but I was young enough for Carl Sagan’s original Cosmos, and still remember the impact it had on my young brain. So I was delighted to find that my current students have someone who inspires them in the same way. I suspect that in a decade or so I will see students for whom Neil deGrasse Tyson is the person who inspired them when they were very, very young.

At any rate, Bill Nye has several books out which are broad in scope and only peripherally related to astronomy concepts. Still, if my students love Bill Nye, I’m perfectly willing to harness that in the interest of getting them to read about science, even if it’s slightly off-topic!

Of all his books, the one most closely related to the coursework is Unstoppable: Harnessing Science to Change the World. This book lays out the scientific case on climate change before looking at the solutions required on both the national and global scales. Bill then dives in for a look at his own home through a friendly competition that he has going with Ed Begley Jr. for the greenest home in town. He finishes with an optimistic call to action.

Students will find here an antidote to the despair that sometimes overtakes them at the end of the chapter on atmospheres; when they have started to internalize the science of climate change but haven’t yet started to figure out what solutions look like and how to achieve them.

Students often ask me for this material, but there is little time to cover it during the astronomy course (we have an entire course in our Department about solutions that I recommend to them).

The material is at a completely accessible level for students and the public. Also included are a handful of experiments that students can do on their own, like heating up water in the microwave (not to the boiling point) to see that hot water takes up more space than cold water.

Reading and discussing or writing about this book would, I feel, satisfy general education learning objectives based around “Science and Society;” particularly if students are asked to tie the material back to the information about atmospheres that they learn when comparing Venus, Earth and Mars.

It’s an optimistic take on the subject from someone that students already admire and trust. If you decide to assign it in your class, I’ll be interested to hear about how the experiment goes!

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.