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March 2019

April 2019

Reading Astronomy News: The Lyrids are Coming!

Meteor Shower

Image Credit: NASA/Bill Ingalls

By Stacy Palen

Don’t forget to remind your students to watch for the Lyrid Meteor Shower this month. The peak occurs around April 21-22.

This meteor shower comes as Earth passes through the debris left behind by Comet Thatcher. Particles lost from the comet continue to drift in the Solar System, gradually changing their position.

As Earth moves through space, it passes near the trajectory of the comet and runs into collections of these particles. This will happen repeatedly at particular times of the year as Earth returns to the same point in its orbit. The particles burn up, creating meteors as they fall through the atmosphere.

Comet Thatcher has a 415 year orbit, so it is a long-period comet. It will not be back in the inner Solar System until 2276.

To watch a meteor shower, go to a clear dark site where the horizon is not obstructed. Spend about half an hour in the dark, without your cell phone or other bright light in view. This will allow your eyes to adapt to the dark. Then just watch for meteors! They are best seen with the naked eye.

If you are careful and methodical, your observations can contribute to the study of meteors and meteor streams! To learn more, visit the Astronomical League’s Meteor Observing Program website.

Resources: First Ever Image of a Black Hole

By Stacy Palen

My students came in talking about this, and so I thought I’d pass on a couple of resources that I used while answering questions in class! 

I felt I needed to put the new image in context, with respect to M87 and all its fascinating parts.  This photo has the angular sizes labeled, as well as the wavelengths of the observations. It’s a quick place to get all those numbers right away.


ESO has an image of the global array:

Veritasium has a nice short explainer video about the light paths:

Which then matches beautifully onto the actual image and has some fun information about the technical difficulties with data transfer etc.:

I made a point of taking them to the summary research paper:

Both so that they could just see it, but also because I wanted to show the author list and acknowledgements. This is an important thing that science does: model how to have international collaboration. The paper summarizes the achievement nicely: “In conclusion, we have shown that direct studies of the event horizon shadow of supermassive black hole candidates are now possible via electromagnetic waves, thus transforming this elusive boundary from a mathematical concept to a physical entity that can be studied and tested via repeated astronomical observations.”

We happen to have just done two of the Learning Astronomy by Doing Astronomy activities about black holes: Bent Space and Black Holes, and Light Travel Time and the Size of a Quasar. So, this was a lucky moment when we were all thinking about these concepts anyway!

Book Recommendation: Present at the Beginning: Galileo’s Sidereus Nuncius


By Dr. Bradley W. Carroll

We live at a unique point in history. For the first time, we humans know the entire story of our species, at least in broad outline. We know how the universe expanded from the initial Big Bang, how generations of stars manufactured a periodic-table’s worth of elements and then dispersed them throughout space as those stars exploded, and how clouds seeded with those elements gravitationally collapsed to form planets. We understand the evolution of the life that arose on this particular planet, and how an astronomical impact led to the dominance of the hairless apes that eventually became our friends and neighbors.

But what was it like to be alive four centuries ago when almost everything was a mystery? What was it like to discover, for the very first time, that the Moon has mountains, that there is a universe filled with stars we cannot see with the naked eye, and that other moons orbit Jupiter? Fortunately, we know exactly what it was like because the man who made these discoveries has told us: Galileo Galilei.

Sidereus Nuncius (The Starry Messenger) is not filled with the dry dialectics of Galileo’s other tomes. In this book you can sense Galileo’s exuberance, his sense of wonder at what he has seen for the very first time through the crude telescope he made with his own hands. He tells you how he labored over its construction until he could see objects “over sixty times larger.”

Galileo writes that “having dismissed Earthly things, I applied myself to explorations of the heavens.” He grabs your sleeve to pull you toward his eyepiece so you can see these wonders for yourself.

And what wonders they were to his eyes! Galileo sees the tops of mountains on the Moon lit by the Sun, and asks us, “On Earth, before sunrise, aren’t the peaks of the highest mountains illuminated by the Sun’s rays while shadows still cover the plains?” Galileo alone now knows that the Moon is not a perfect sphere. Using shadows, he calculates that one lunar mountain is “higher than 4 Italian miles.”

Galileo swings his telescope toward the constellation of Orion, and breathlessly tells us that “to the three [stars] in Orion’s belt and six in his sword that were discovered long ago, I have added eighty others.”

Then, on January 7, 1610, Galileo trains his telescope on Jupiter to see “three little stars” near Jupiter that are “arranged exactly along a straight line and parallel to the ecliptic.” Night after night Galileo keeps track of these stars, now grown to four, as they stalk Jupiter, passing back and forth across its disk.

Finally, on March 2, Galileo calls them “planets,” and later, the “Medicean planets.” (In the opening passages of Sidereus Nuncius, Galileo, in his never-ending quest for patronage, proposes naming these four moons of Jupiter for Cosimo II de’ Medici, the Fourth Grand Duke of Tuscany.)

Thirty years ago, I attended a meeting of the American Astronomical Society in Ann Arbor. There on display was a draft of a short letter Galileo sent to the Doge of Venice on August 24, 1609 that described his telescope. But at the bottom of the letter are Galileo’s first recordings of the moons of Jupiter, made on this paper he happened to have nearby.

I felt overwhelmed knowing that when Galileo’s hand made these marks upon this sheet of paper, the world changed. Galileo now knew with certainty that Earth was not the center of the all things, because here were four moons orbiting Jupiter. Galileo went on to make more astronomical discoveries. He discovered spots on the Sun and the phases of Venus, but his Sidereus Nuncius announced his first discoveries to the world.

Reading the Sidereus Nuncius, I am struck by encountering a fully modern mind, so different from the mysticism of Johannes Kepler. It marked a revolution. After Sidereus Nuncius, astronomy no longer had to rely on the word of ancient authority for its conclusions. Astronomy became an observational science, and anyone with a telescope could see what Galileo saw. Sidereus Nuncius is a short book, just 62 pages. My version, translated by Albert Van Helden, has useful notes along with an introduction and conclusion. Read it for yourself and be present with Galileo at the beginning of modern astronomy.