Two New Review Articles in Science Advances About Axion Dark Matter

Summary: As we all know, and is explained in the text, dark matter is “a thing”, but we still don’t know much more about it than that it exists. Lately particle physicists have been getting excited about the possibility that dark matter consists of axions. I found these two recent review articles (February issue of Science Advances) to be very helpful.  They reminded me of particle physics that I had forgotten, caught me up on the arguments that particle physicists are making in favor of axion dark matter, and helped me understand the observational strategy to try to detect axions.  These are not articles for introductory astronomy students to read; they are written at far too high a level.  But they may be useful for busy astronomy teachers, who need a refresher about the issue---just in case this turns out to be the answer!

Articles:

What is it?  

How might we observe it?  


Science And Society: Starlink

For several years now, I have met the “science and society” general education learning goal with a unit on climate change.  This year, SpaceX gave me another option, with the latest installment of the planned 42,000 satellite constellation known as Starlink.  I had strong feelings when 40 satellites were destroyed at launch by a solar storm, and I shared those feelings with students.  We had the opportunity for a free-ranging discussion in class about the tension between technological advances and preserving the resources we hold in common.

There were many articles, but here’s one:

A few other resources that might be useful:

The Starlink Situation   (last update 3/2020)

Starlink and the Astronomers (an update from 4/2020)

How do Starlink Satellites Work?

It also affects radio astronomy 

A web search for “starlink astronomy images” tends to yield images taken shortly after launch, with a large number of satellite tracks from the latest batch.

About the cost of Starlink internet (the article includes both premium and standard rates)

IAU’s stance


Addressing Equity in Astronomy 101, Part 4:

In this four-part series, Dr. Stacy Palen will discuss her own journey toward recognizing and addressing issues of equity in the Astro 101 classroom. We encourage this to be an open communication and discussion through the comment section below.

To read the previous post, follow the link here.

Addressing Equity in Astronomy IV: It’s Different for Everyone

Addressing equity in the classroom is complex, and a moving target. There is a lot of pressure to modify a lot of teaching methods to be more inclusive: have flexible deadlines, creative grading policies, invite informality in the classroom, etc.  But these methods sometimes have unintended consequences for particular faculty members.

Consider this article in the Chronicle of Higher Education: https://www.chronicle.com/article/academe-has-a-lot-to-learn-about-how-inclusive-teaching-affects-instructors?cid2=gen_login_refresh&cid=gen_sign_in

Different faculty need to behave differently in the classroom, in order to be perceived as the “competent”. Of all the faculty in my Department, I am the only one who has been called “obstinate” by a student because I insisted that he learn to write proper lab reports with error bars on his graphs. Other faculty are far worse sticklers than I am, but by nature of their personal attributes, their feedback to students is accepted more readily. I cannot “get away” with being on a first-name basis with my students, or with having an open-door policy, as some of my colleagues can.  How do I know? I tried it. The boundaries fell, and I was swamped by people who were not even my students but wanted help with their coursework assigned by my colleagues.  My colleagues would ask for advice on how to get students to come to their office hours. “Smile more,” I would say, somewhat tongue in cheek.

I believe learning is different for everyone---what motivates any given student, and what works for them is deeply individual. In the same way, teaching is different for everyone---what works for you is deeply individual. Teaching is not a Shakespeare play, with a pre-determined set of lines to say and movements to make across the stage.  Teaching is improv (sometimes comedy) where the action can go in all sorts of directions along the way to telling the story.

All of which to say: be kind to yourself and your colleagues as you figure out how to teach more equitably. What works for you may not work for them; what works for them may not work for you. If you receive advice to try something…but it doesn’t work, abandon it, and try something else. Experiment! Tell your students that you are experimenting, and why, so that they can give you good feedback about how your experiments affect them.  Not only will you find surprising ways to engage students, but this will help you stay engaged in the process of teaching.  I suspect all of us could use a little help with that just now.


Addressing Equity in Astronomy 101, Part 3:

In this four-part series, Dr. Stacy Palen will discuss her own journey toward recognizing and addressing issues of equity in the Astro 101 classroom. We encourage this to be an open communication and discussion through the comment section below.

To read the previous post, follow the link here.

Addressing Equity in Astronomy III: One More Thing…Attitude Matters

Addressing equity in the classroom is complex, and a moving target.  I am often surprised by how the “real world” impacts students; it’s not always in the way I predicted.  During the pandemic, for example, I heard from some students that the low-cost eBook solution was counter-productive for them. Why? Because they had only one computer at home that was shared between two parents going to work and school; each had to limit their time on the computer so that the other could attend Zoom meetings.  Meanwhile, although the children in the household were issued Chromebooks by their schools, there were times when their internet just couldn’t keep up.  These same families were hampered when it came to attending class at a time or watching videos.

This was not what I expected, because I made assumptions about other people’s lives.

For some other students, laying out the price of a print textbook was too expensive, but they had a tablet at home that they could download an eBook to, so that they could curl up on the sofa away from the computer to read it. They had already laid out the capital investment for the tablet, so the incremental cost of the eBook was the best solution.

This WAS what I expected because I made assumptions about other people’s lives.

Many of my students “attended” virtual class from their cars in a McDonald’s parking lot, accessing the internet on their phones.  Some of them shared with me that they were living in their cars.  Others told me they didn’t have internet at home. Others told me they didn’t have QUIET at home. In any event, a car in a McDonald’s parking lot is not an ideal learning environment.

In the end, I let go of the idea that one solution would work for everyone (in retrospect, I must say “duh”.) I gave students multiple options for how to access…everything.  They could use the book, the eBook, the videos, my office hours, whatever tool they could access on whatever day. Because it was the pandemic, I also gave them mix-and-match assignments, flexible due dates, and office hours at non-standard times. And then I listened to them when they told me they needed something else and tried to figure out how to make that happen.

Was I exhausted? Sure. Was I overwhelmed? Yes. I still am. But as I went along, I realized it was just more of the same thing that I had been doing for years---trying to meet students where they are, to figure out the resources and experiences they need to take their next steps. I don’t think that being “equitable” in the classroom is really a new thing.  I just think the diversity is bigger now, so we must do what we’ve always done, but more. We need to be vulnerable enough to admit that we cannot know what students need, in advance. We need to be open to asking, “What do you need, right now?” We need to be willing to listen, and have a lot of tools at our fingertips, so that we can reach for a different one when the first one doesn’t work for a particular student. Fortunately, as we grow as teachers, that gets easier and easier.  Unfortunately, as classes get larger, it gets harder and harder to treat each student as an individual.  But if we keep expanding the “menu” of learning options for students, more and more of them will be able to find what they need.

Next time: It's different for everyone


Addressing Equity in Astronomy 101, Part 2:

In this four-part series, Dr. Stacy Palen will discuss her own journey toward recognizing and addressing issues of equity in the Astro 101 classroom. We encourage this to be an open communication and discussion through the comment section below.

To read the first post, follow the link here.

Addressing Equity in Astronomy II: My Framework:

My approach to course planning is to begin by writing down the content, skills and attitudes that form the goals that I have for the course.  I spend some time thinking about how the goals all fit together in a logical order, and if there are pre-requisite content areas, skills or attitudes that I forgot to include.  This process sets the narrative arc for the course and determines what I will focus on in each week of the semester.  Sometimes, I can find a book that matches my plan…but sometimes I have to write it myself.

Once I have goals and an overall arc, I start addressing the equity issue by thinking hard about multiple ways of approaching each of these goals. For example: Can students learn about ellipses just by looking at a figure? Do they need to watch someone draw one (and simultaneously talk through the process)? Do they need to actually draw an ellipse themselves? If so, is a rough sketch sufficient, or do they need to actually tie a string to two pencils, and make an accurate ellipse?  What is it that I actually NEED them to know about ellipses in order to understand about orbits?

This is a multi-solving problem. While students have preferences for how they learn best (or think they do), it’s simultaneously true that different content areas or skills are best learned in one way or another.  Furthermore, different students arrive in my classroom with different backgrounds or resources that leave them differently prepared. For example: If a student is not absolutely clear on the idea of a circle, or the term “symmetric”, then an ellipse is likely to be a different kind of challenge than for someone who simply lacks precision in their idea of an ellipse---that is, they may mistakenly think an ellipse is an egg-shaped oval, thinner at one end.

Because of this, I will offer many options for learning about each content area or each goal.  I often take a “Learn by Doing” approach, which is successful for many students, partly because it necessarily incorporates several different approaches for each content area or skill. Especially if students are working in groups, they can try seeing, hearing, visualizing, explaining, manipulating, touching, acting…all sorts of approaches all at once. In an ideal world, at least one of those approaches will help them reach a content, skill or attitude goal.

This is a menu-style approach to addressing equity in the classroom.  Instead of trying to predict what students will need (I am well aware of the enormity of all the things I don’t know about them!), I present them with as many kinds of ways to learn as I can think of.  Then I use assessments to try to figure out who I’ve missed.

One advantage of in-classroom assessments (like activities or think-pair-share) is that I can eavesdrop to see how they explain things to each other. That leads to a lot of insights about background concepts they might be missing.  For example, I recently discovered that some of my students don’t know what an “Appendix” is, so when the book says, “See Appendix 4”, they don’t know what that means.  This is a perfectly logical result when someone who grew up with physical books runs into someone who has only ever read eBooks…and not one that I could have predicted, a priori.  I just had to try stuff, and then listen in to find out when confusion happened!  It’s also a problem that can be fixed with a sentence, or even just a phrase, that gives students the information they need to find Appendix 4.  I would never have known that this was an issue if I were not moving around the room, listening in.

Next time: Adjusting my attitude.


Addressing Equity in Astronomy 101, Part 1:

Over the past few years, major events have brought into the spotlight the injustices some face in their everyday lives. Unfortunately, the world of academia offers no exemptions. Every student differs when it comes to factors like race, age, gender and gender expression, socio-economic status, technology access, and food security. In the introductory astronomy classroom, our challenge is to reach every student, regardless of their background.

In this four-part series, Dr. Stacy Palen will discuss her own journey toward recognizing and addressing issues of equity in the Astro 101 classroom. We encourage this to be an open communication and discussion through the comment section below.

 

Before I really dive in, let me first say that the issue of equity is complex, fast-moving and developing. Equity is an issue of fairness and justice in the way people are treated.  But we can’t always identify these issues without help from others.  In the words of Maya Angelou, “Do the best you can until you know better. Then when you know better, do better.”  Be a little kind to yourself as you learn all the ways that we, both individually and as a society, fail to live up to our stated goal of “justice for all”.

There are many axes along which people may lack equity or fair treatment.  An incomplete list might include socio-economic status, sex, race, age, marital status, and disabilities of all kinds. My goal is to make every bit of astronomy as approachable as possible for every student in my classroom.  This is hard to do, frankly. It has meant learning to see the pursuit of equity as a challenge, a puzzle, or a chance to sharpen my problem-solving skills. Like most faculty, I am often overwhelmed by my To-Do list which literally never gets shorter, and it can sometimes be hard to summon enthusiasm for creating yet another way to explain a concept or teach a skill.  Usually, I can find the grit to take a deep breath and then dive in.

I should say a few words about where I teach, to clarify my background.  I am not an expert in educational equity, race or gender relations, or any kind of sociology.  Instead, I am a person who has spent a long time in the trenches of teaching and learning, trying to adapt to the environments in which I work. I have been 20 years now at Weber State University in Ogden, UT. We are a “regional, open-enrollment, dual-mission University”. To translate:

Regional: we primarily draw students from the surrounding area who are non-traditional. Students may be older, married, have children, full-time jobs or be full-time caretakers for parents or other relatives.  A very small fraction of students look like the “typical” college student.  On the plus side, nearly every student lives off campus and commutes, so we don’t have any party-school problems!  On the minus side, that means they don’t really form study groups or stick around on campus to find out what a college education is really all about (I would argue: NOT job-training).

Open-enrollment: we have no admissions standards; we take everyone. I say we are a “second chance” institution, not a “second-rate” institution. I would put my best students at Weber into competition with my best students at the University of Washington (where I used to work) any day of the week.  The proportion of those top students is much smaller, however, because of the competing responsibilities in student’s lives.  Very few of my students can focus the majority of their effort or time on their education, and a very large fraction of them are first generation college students. First-gen students have special challenges simply (sometimes literally) navigating the campus.

Dual-mission: we co-locate a community college onto the university campus.  At registration, no distinction is made among those students.  This means a typical Astro101 course will have students from high school through the end of college and beyond. We have a significant fraction of “community” students; retired aerospace engineers, teachers working professional development, etc.

We also have a significant focus on supporting Hill Air Force Base, which means we have a significant population of current military personnel and veterans. Deployment creates a unique set of problems to solve!

Also in my background is my undergraduate education, which occurred at Rutgers University in Camden, NJ, across the river from Philadelphia. Camden is a famously dangerous place to live, even now. It was there that I really learned what “disadvantaged” and “underserved” meant.  My eyes were opened by that experience, and I try hard to keep them that way.

This practical background has led to a teaching approach that has equity at its heart, because it led me to experiment so widely with approaches that could reach students who were facing enormous challenges in their pursuit of their education.  I’m not always successful, but I’m always learning.  And when I know better, I can do better.

Next time: The framework I have developed for myself for addressing equity in my classroom.


Current Events: Moon Formation around Exoplanets

By Stacy Palen

ALMA continues to delight us with its unsurpassed and exquisite resolution and sensitivity. In this case, we have the first clear detection of a moon-forming disc around a planet orbiting a very, very young star.

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

1). What is extraordinary about this observation?

Answer: For the first time, astronomers clearly identified a disc around a planet and estimated its size.

2). What sort of planet is PDS 70b at the center of this disc?

Answer: A gas giant, like Jupiter.

3). How large (in AU) is the moon-forming disc, and how much mass does it have?

Answer: The disc is about 1 AU in diameter, and it has the mass of about 3 of Earth’s moons.

4). Why is such a disc not detected around PDS 70b?

Answer: That planet did not have enough dust around it, because its dust was “stolen” by PDS 70c.

5). Does this observation support or refute the basic theory of star and planet formation that you learned about in the text?

Answer: This observation supports that theory and is basically exactly what we would predict we should find!


Current Events: Astronomers Discover Record-Breaking Star As Small As the Moon but with More Mass Than the Sun

By Stacy Palen

Astronomers set a new record for the densest known white dwarf.

Below are some questions to ask your students about this article.

1). How is a white dwarf typically formed?

Answer: A star less than about 8 times the mass of the Sun loses its outer layers, leaving behind a dense carbon core. (Note: This is NOT in the article, but they should know it from class.)

2). How might a system of two white dwarfs form?

Answer: If a binary star system consists of two stars less than 8 times the mass of the Sun, and both stars evolve, the system will become a binary white dwarf system.

3). The lead author states, “Smaller white dwarfs are more massive.” Is this how normal matter (like cows and people) behaves? What is the name for matter that behaves this way?

Answer: No; degenerate matter.

4). How massive is the combined star?

Answer: 1.35 times the mass of the Sun.

5). Why did this pair of white dwarfs not become a supernova when they merged?

Answer: Because this combined mass is under the Chandrasekhar limit.

6). What comes next for this white dwarf?

Answer: It may become a neutron star, as it is dense enough for charge destruction to take place.

7). How often does a merger like this happen?

Answer: We don’t know, but they are probably common, if there is one nearby.

8). This white dwarf has an extreme magnetic field. How did it develop such a strong magnetic field?

Answer: Nobody knows!


Current Events: "There May Not Be Conflict After All" in Expanding Universe Debate

By Stacy Palen

The two main ways to measure the expansion of the universe have turned in different answers. For the last several years, astronomers have been arguing about whether this disagreement is unimportant (a result of measurement errors) or important (a result of new, unknown physics). This is a terrific example of the process of science. In June 2021, Wendy Freedman published a new review paper arguing that there is not a conflict after all.

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

1). What is the Hubble constant?

Answer: The Hubble constant measures the rate at which the universe is expanding.

2). What are the two ways to measure the Hubble constant?

Answer: The first way is to look at the cosmic microwave background. The second is to measure the velocities and distances of galaxies to make the Hubble law graph.

3). What are the two values of the Hubble constant derived from these two methods?

Answer: 67.4 km/s/Mpc and 72 km/s/Mpc.

4). Historically, the distance to nearby galaxies was determined using Cepheid variables. What is the problem with these measurements?

Answer: They are noisy and more complicated, and the observations may be contaminated.

5). What other objects are now being used to measure the distance to nearby galaxies?

Answer: Freedman is using red giant stars, which always reach the same peak brightness before fading. These observations are less noisy.

6). What does this new method of measuring distances give for the value of the Hubble constant?

Answer: 69.8 km/s/Mpc.

7). Is this new method in better or worse agreement with the method that uses the cosmic microwave background?

Answer: This new method gives a value that is much closer—it cuts the disagreement in half.

8). Review the Scientific Method flowchart in Chapter 1 of the textbook. What part of the flowchart describes the science that’s described in this article?

Answer: The science in the article is on the loop on the left. Previous tests did not agree, so a new hypothesis was suggested (that Cepheid variables are subject to too much noise), and a new experiment (measuring red giants) was devised and performed. Further tests will be in the loop on the right.


Current Events: The Milky Way's Shredded Companion Provides Clues about Dark Matter

By Stacy Palen

The Milky Way is tearing apart the Sagittarius dwarf galaxy. Gaia observations of the resulting tidal streams permit sufficient accuracy to detect the influence of the Large Magellanic Cloud on the interaction. Simulations show that the Milky Way’s dark matter halo is complex.

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

1). Prior to this study, what was known about the shape of the dark matter halo?

Answer: Not much. Different simulations found various shapes, some more symmetric than others.

2). In this study, what is new that allows astronomers to build a more detailed picture?

Answer: The Gaia satellite pinpoints the location of stars with truly unprecedented accuracy.

3). The following questions cannot be answered directly from the article but can be answered with a Google search. The paper discussed in this article was posted to the preprint server arXiv. What is a preprint?

Answer: It is a full draft that has not been peer reviewed.

4). In the process of scientific publication, what comes after the preprint stage?

Answer: The article undergoes formal peer review, and then it might be published.

5). What is the advantage of preprints?

Answer: They give access to the most up-to-date research.

6). Should you treat the results discussed here with more or less skepticism than the results published in a peer-reviewed journal?

Answer: You should treat them with more skepticism.

7). How could you know if the results held up to peer review?

Answer: You could search for the authors’ names or the topic in a database of journal articles.