Current Events

Current Events: The Tides of the Moon and the Suez Canal

By Stacy Palen

How delightful! The phases of the Moon were in the news in late March, giving all of us an opportunity to teach students about the practical applications of astronomy in the modern world. You will likely recall the giant container ship that was stuck in the Suez Canal for almost a week, disrupting supply chains around the world. The arrival of spring tide helped float the ship off the bank where it was wedged, setting it free.

CNN reported about this news, although there are other outlets as well. 

I have included some snippets about this news with some questions on my final exam, asking students to sketch the relative positions of the Earth, Moon, and Sun during spring tide, and to make a sketch that demonstrates why so-called “supermoons” result in extra-high spring tides. Sketches like these are very quick to grade, so I like to use them during any times of the semester when I have a large grading load.

I can also code these questions as addressing the “Science and Society” general-education learning outcome, so that the crowd that does our general-education assessment will be able to check the box on their report.

I have in mind that I could build an entire assignment around this event, for future semesters, but I haven’t done it yet. Like you, I am just trying to put one foot in front of the other to get to the end of this semester!


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.


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!


Current Events: Formal Education, The Fun They Had, and Plan B

By Adam Johnston

This week, we have a guest post from a colleague at Weber State University. In addition to teaching at Weber State, Adam Johnston is also the author of the blog First Drafts in which he writes about education, science, and personal experiences. In the post below, Adam discusses the shift in our methods of teaching brought about by COVID-19, stresses the importance of managing our personal expectations, and suggests using this moment to think about what our overarching educational goals should be. Click here to access the original post.

 

In the face of pandemic and social upheaval, what teachers and families and students are doing right now is nothing short of heroic. They’ve been sent away from their buildings and communities yet are told to still conduct school, and a steady stream of accolades are being appropriately shouted from our socially distant social media streams. Teachers I work with in the K-12 settings and my colleagues in university programs are building new vehicles and plans and schedules and methods on the fly, while they’re flying, and it’s all quite extraordinary. And our students — the two in my house are navigating all of this newness in the face of trauma as they try to finish a senior year of high school and a second year of college, respectively — are wading through completely new arrangements, unfamiliar structures, and major tectonic shifts. Daughter 1 still has belongings and a made bed in a dorm room hundreds of miles away that she essentially evacuated at the start of spring break; Daughter 2 is facing the reality of graduating from our K-12 system without a formal graduation ceremony with the people she’s essentially shared her entire lifetime with. These are just the two student stories right here before me, in our privileged home. There are literally millions of others, each with their own story.1

These are difficult times; I admire all that everyone, everywhere is doing.

And yet, I am quite certain that we’re going at it all wrong, for understandable reasons.

To be clear, I don’t think this education roller coaster was avoidable and I don’t have an immediate solution. School is in a massive mode of triage, and we’re doing the best we can in the moment with what we have in front of us. Let’s finish the year with that in mind, no judgements. And please, let’s not beat ourselves up when our teaching and our learning isn’t the same in these formats. In fact, let’s not even pretend that they could be.2

Schools are sacred spaces, places we’ve designed specifically to bring people together to learn, for their current selves and for our future citizenship and society. Sitting among the very greatest human inventions like poetry, science, democracy, beer, libraries, and music, I think that education should top the list. The problem is that we don’t realize that it is, in fact, invented — it didn’t come from out of the blue, after all, not handed to us on stone tablets — and that this means that we also have the ability to change it. At the same time, I think that schools are incredibly beautiful and beneficial and egalitarian and, overall, good, even as there’s always room for improvement and reform.

The latest model of education, a century old at least, is a vision of all children in America all walking up concrete steps and into congregating classrooms and spending roughly 180 days in these spaces among friends and caring teachers and chalkboards and frog dissections and readers and math manipulatives and recesses and maybe a unit on square dancing that doubles for both PE and music.3 Teachers love their students, and I don’t say this as a throw-away, trite line. I see this firsthand in classrooms. And, I know firsthand that students love their teachers. For all of the pains that we might associate with school and schooling, kids are walking up those steps into rooms where they are loved for who they are, where they collaborate and work with peers, and where they have a system that, for the most part, is designed to focus on the needs of each human. This may sound as if there should be rainbows and butterflies and fairy dust sprinkled about this fantasy scene, but I’ve worked with enough teachers, students, and classrooms that I can verify this is as true as my love for my own children.

In that genuinely caring context, schools and teachers create and cultivate community. There are reading circles and discussions; teachers know how to pair students together, and they know how to separate them; students share with teachers, in one way or another, that they’re excited or scared or having a tough go of things. I’m confident that every teacher worth their salt has a story of when a student, Kindergartener, 4th grader, high school senior, or pre-med major came to them crying. And I’m confident that each of those teachers knows about the celebrations in their students’ lives. And even when they don’t know the details they know when the kids walking through the door carry excess burdens or are lifted by extra joys in their lives. And in the mix of all this, teachers adapt to their students. Like I said, these are acts of love, hosted in brick buildings paid for with taxpayer dollars all over the country.

                                        

A couple years ago I reviewed the finalists for our university’s major teaching award. In the process, the other committee members and I pored over nominations and piles of supporting material, but the real joy of the task was in visiting these teachers’ natural classroom habitats.4 They were all expert in their fields and engaging in the classroom, well organized and clear. They were centered on students’ ideas and guided them not just through the details, but the big picture and purpose of a given teaching episode. I saw this in chemistry as well as in social work, in economics and education as well as in journalism. Yet, the teaching expertise and classroom seemed secondary to something else. The subtle but clear commonality in each of these extraordinary instructors was how they related to their students on a personal level. They revealed details about themselves and they knew their students, the personal stories, affects, efficacies, and histories. The connections and interactions were vibrant and joyful, simultaneously gluing and stimulating the class. In all this, it wasn’t merely a dissemination of information, but the building of relationships.

In contrast, I recently remembered and re-read Isaac Asmiov’s classic kid’s story, The Fun They Had. This was a futuristic vision when it was written in the 1950s, and still was when I read it as part of my reading packet around 1980. Set in the year 2157, the premise is that two kids are contrasting their version of a “teacher,” essentially a computer as envisioned before computers (or even microprocessors) were commonplace, with our human version. The children had to have their teachers tuned and occasionally repaired to deliver lessons in their own homes; and students turned in handwritten work that these machines evaluated. The plot twist here is that Tommy has found “a real book” in an attic and they talk about how ridiculous these pages are and how it comes from a time when schools were places children would gather and teachers were real people. As Margie considers the arithmetic lesson for the day at the close of the story:

 

She was thinking about the old schools they had when her grandfather’s grandfather was a little boy. All the kids from the whole neighborhood came, laughing and shouting in the schoolyard, sitting together in the schoolroom, going home together at the end of the day. They learned the same things so they could help one another on the homework and talk about it.

And the teachers were people . . .

The mechanical teacher was flashing on the screen: “When we add the fractions 1/2 and 1/4 —”

Margie was thinking about how the kids must have loved it in the old days. She was thinking about the fun they had.

 

I suspect there are students, now, thinking about the fun they had only weeks ago. And they have real people as teachers, on the other end of an internet connection that even Asimov hadn’t imagined two centuries of technology could create. These are the same loving teachers, dedicated instructors, who host students in the learning environments in our neighborhoods schools when the doors are open. And surely, I know, they do all they can to sustain these relationships in more meaningful ways than Margie and Tommy’s “teachers.” But I also know teachers who, daily, break down in tears because they cannot possibly connect with their students in the ways they can when they’re all sharing the same physical space.

Besides interpersonal connections, there are clear advantages to working with students face-to-face. These are interwoven with the way that we’ve deliberately crafted our school system. We have lab benches and sinks, performance spaces and whiteboards, recess spaces and reading circles. The simple act of walking down a hallway as a class is an act of collaboration; singing together in the music room is a community celebration. Walk by an old elementary school on a warm spring day and listen for the joy that seeps out of open windows.5 If all that there was to learn could be had by reading, then we’d simply teach the kids to read and then send them home with a collection of books. When you’ve finished those, come back and get more; and when you’ve finished all the books then we’ll give you a piece of paper that you can put on your wall and gain yourself admission to a new school with new books.

This is, at its face, absurd. We know that there’s more to learning than just reading books, or at least that the reading of the books or the listening to the lectures or the watching of the presentation doesn’t itself turn into learning. There’s a working with and among one another that creates new meaning. Application and practice create new levels of understanding. Gaining a sense of self and making connection to something greater are important, if not critical, pieces of what we aim for in our schooling. Students talk about this in their graduation speeches, that there’s greater meaning and application and synthesis, and that schools aren’t really about the delivery of information into students’ cognitive processors. We’ve all had the privilege of experiencing this in our schools, and our students talk about these learningful outcomes and how they result from being on a debate team, a basketball team, a historical debate, a physics lab. They talk about what they’ve learned through all of the connections they’ve built and interactions they’ve had, with teachers and students and others.

The community, relationships, direct interconnections with one another—these are all the things we can’t expect from online education, now or ever, simply because this isn’t what online education has to offer. Rather than wring our hands and lament this, we should celebrate it. Let’s look at all that our in-school education does for us and herald this as one of society’s great accomplishments; and then let’s not expect online to do the same.

                                        

But maybe we can do something fundamentally different with online education in the future. It can’t be the same as the schools we now have, but it could be something else, something additional, not a replacement but an altogether different system with an altogether different goal.

As an analogy, let’s take trains.

I love to ride the train, big or small, near or far, and in so many ways it’s the ideal form of transportation for me to get from my town to another that could be 30 minutes, an hour, or two hours away. I have to plan ahead and be conscious of the schedule and a few various regulations. The infrastructure for the train, right-of-way and tracks, employment of the operators, and all that background operation have to be engineered and arranged, but once it’s there I have an ideal way to get myself from point A to point B. The arrangement is so ingrained into a community that I could easily take it for granted.6

So I imagine the painful scenario that follows if, one day, trains are suddenly closed. After a brief pivot, everyone scrambles and looks for the alternative transportation mode, and while I am really upset about the lack of my smooth and fast transport, I have faith that I’ll be given an alternative, a “plan B.”7 I imagine being handed a backpack and some walking sticks, and perhaps someone checks to see if I have the right shoes on my feet and they offer an alternative pair of sneakers in case mine aren’t quite up to the task. Am I then setup to succeed?

I have all the tools of transit, albeit substitutions. But it should be obvious that I’m not going to walk the entire length of the tracks. And no one could expect me to go at the same pace as the train. With this new mode, I have limitations. I need to change my destination and expectations. And, I’d change my perspective and gaze.

This would be a completely new experience. I like walking. I love putting stuff into backpacks. I might even appreciate the new shoes to try. I won’t cover the same distance, and it won’t be as fast, but with each step I’m going to see different things than I would on the train. Everything goes by slower but the concentration on specific features would be more intense. I won’t get as far, but I’ll get somewhere. Details will be crisper, the pace will be my own, and there will be choices about how I make my way.

These walks won’t replace the train; they’ll make me appreciate it all the more. But they’ll also help me see what the alternatives will bring if, if, I’m so willing to use the new mode in a way that matches what it’s good for. At-home learning could be self-paced and introspective, the chance to break away from the regular commute. There are opportunities to take notice of what might be in my backyard or where the sun sets at night8; my writing could take on a different form, focus, and structure9; I’m going to make a lunch from scratch instead of brown-bagging it or waiting in the cafeteria line. These things are all small, but they still provide opportunities to know my world and build experiences in a different way.

All the while, I’ll miss school and appreciate that community, the collaboration, the love inherent in that space. I’m confident we’ll get the train running again — a faith I have simply because I can’t imagine our society or my own personal world without it. So, this introspective, self-contained time away from the formality and congregation of our school buildings might be a good chance for us to appreciate what traditional schools do for us as people, individually and collectively. We might have a better perspective on what we value and prioritize for schooling in the future — the things we can’t otherwise replicate.

For now, and for any other moment in the future when we don’t have our schools operating normally, let’s not try to replace the system. We can value alternatives for what they are, use them for what they are, even draw from them for additional resources and learning opportunities. But let’s not expect ourselves, even with fancy shoes, to walk at the pace or with the inherent community of a train. Let’s not expect new tools, unlearned and mostly untested and most certainly un-utilized until now, to attempt to be all that we really value about education. Let’s forgive ourselves. Let’s expect less of ourselves, our families, our teachers, and our students right now. Let’s appreciate the walk, and, next time, in the future, let’s think about how any “plan B” is not just a different tool, but something that has an altogether different purpose.

Much later, when there’s room to breathe, let’s think again about what we want from education in the first place, “the fun they had,” and if we’re using all our tools and modes in meaningful ways to reach those goals. But right now, in this moment, in these times and with these conditions, let’s breathe, give ourselves a break, share some compassion and empathy, and just get through the school year as best we can.

                                        

 

 

1 The other human member of our home, my wife, Karyn, teaches knitting classes. As I’m writing, she just walked by exclaiming how much more work she is putting into new formats for her students who are dialing in online. They’re appreciative, but replicating what she can do face-to-face is arduous, and actually impossible.

2 Watching the various classroom practices whirling around me as though I’m in an educational tornado, I asked a colleague if they’d let me into their now-online class, just to observe and understand various strategies. They were initially open, but then thought twice and said they weren’t happy enough about what they were doing to want anyone else to peek inside. I can’t blame them. 

3 The meaning of “all” and our dedication to it continues to have some inconsistencies. In spite of court rulings and legislation, schools are still segregated and unequal, and we can’t ignore this. I’m envisioning a shared ideal here, that we want all children to get a K-12 education and graduate. That traces back to the early 20th century, though the legacy of our schools goes back much further, still.

4 My favorite professional task is teaching, but my second favorite is observing others teach.

5 I know that “modern” schools are often sealed up and air conditioned, but I’ve been happy to get to live next to some older buildings with no such amenities.

6 Here in Ogden, Utah, while we don’t have the same rail infrastructure as people back East or in other countries, we do have a smooth commuter rail that extends up and down the Wasatch Front and connects to light rail systems in the Salt Lake metro area. More interesting, maybe, is the fact that Ogden is a traditional hub of railroad history, being the junction near the joining of the transcontinental line 150 years ago. This brought prosperity and interesting characters (and oh so many stories and legends) to Ogden, and we’re still built on that foundation even as the rail system has been supplanted by the interstate system.

7 A dear friend and backpacking companion tells me, “Plan B is the same as Plan A, but with rain gear.” This seems simultaneously so wise and dumb. And it feels universally familiar, in backpacking or otherwise.

8 It changes position every day, and as the seasons change the amount and direction it moves changes as well. Standing on an east-west running street as the sun goes down can give you some orientation, and watching this from the same place (though different times!) on different days will provide a good comparison.

9 Let’s admit that writing in the midst of a pandemic isn’t easy, though. There have been a lot of blank screens staring back at me these days. Giving myself the diversion to write in footnotes has been a good lubricant.


Current Events: Milky Way’s Warp Caused by Galactic Collision

By Stacy Palen

According to this article published by the European Space Agency, the extremely precise mapping being done by the Gaia satellite shows that the warp in the Milky Way Galaxy is moving far faster than expected. This implies that it is caused by interactions with another galaxy rather than by magnetic fields or the dark matter halo.

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

1) What is unprecedented about the data that Gaia is taking now?

Answer: Gaia is taking more precise position and velocity data on a very large number of objects.

2) What do astronomers mean when they talk about a “warp” in the disk of the Milky Way?

Answer: They mean that one side of the disk is twisted up, while the other side is twisted down.

3) Where else in your study of astronomy have you run into the term precession? How does that use of the term compare to the one used here?

Answer: Precession was also used to talk about how Earth’s pole points in different directions over a 26,000-year period. It’s similar to this usage because if you imagine an axis perpendicular to the warped disk, that axis would likewise point in different directions over time. The time scale here, however, is much longer.

4) What is it about the warp that makes it possible for astronomers to rule out all causes but one?

Answer: The speed of the warp matters. It moves too fast for anything but an intergalactic collision to be causing it.

5) Consider what you have learned about galaxy formation and interactions. If you were an astronomer, what might you look for in other spiral galaxies in order to confirm this result?

Answer: If warps are caused by interactions, then every time I see one, I should also see small companion galaxies that are very close—with orbits close enough to pass through the disk of the larger spiral galaxy.

6) The Sagittarius dwarf galaxy may be the cause of the Milky Way’s warped disk. What is the ultimate fate of the Sagittarius dwarf galaxy?

Answer: The Sagittarius dwarf galaxy will ultimately be absorbed by the Milky Way.

7) Speculate: after the Sagittarius dwarf galaxy meets its ultimate fate, what do you expect to happen to the warp in the Milky Way’s disk?

Answer: The warp should slowly disappear, once there is no longer a galaxy tugging the disk around.


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.