Sunday, March 26, 2017

Two Million Free Eclipse Glasses through Libraries (and a Free Booklet)

As you may know, there will be a rare eclipse of the Sun on August 21, 2017, and it will be visible throughout the United States. A spectacular TOTAL eclipse will be seen on a narrow path (about 70 miles wide) from Oregon to South Carolina. The rest of the U.S. and North America will see a PARTIAL eclipse, where only a part (but a substantial part) of the Sun is covered by the Moon. To look at the Sun when part of it is showing, special (but not expensive) glasses are required or you could damage the sensitive tissue in your eyes.
Millions of people will need glasses on August 21, and for the last year I have been grappling with the issue of how to get glasses to as many people as possible. Now, I am delighted to tell you that several astronomy colleagues and I have been able to get funding for glasses to be distributed through public libraries nationwide.
Thanks to the generosity of the Gordon and Betty Moore Foundation near San Francisco and Google, two million safe eclipse glasses will be made available through public libraries. Each library will get a supply of glasses to share free of charge and a booklet all about the eclipse and how to explain it to the public. The booklet, which I wrote with my colleague Dennis Schatz, is now ready and can be downloaded free at:
The first part of the booklet explains all about eclipses, the August eclipse and when and how it will be visible in different parts of the country, and how to observe it safely. It's written for beginners in science, so we hope everyone can benefit from it. The second part consists of information to help librarians plan public programs around the eclipse.
You could do your city or town a big favor by taking the booklet or just its web address in to your local library and encouraging them to participate in the eclipse and the glasses giveaway. Libraries can register for the program (through the STARNet Library Network at the Space Science Institute) at the website:
If, for some reason, your library can't participate in the program, there is information in the booklet on how to get eclipse glasses from the companies that manufacture the certified safe glasses that will protect you and your family's eyes. This spring is the time to make plans for where you will be and what you will do when the eclipse arrives on August 21.

Sunday, March 19, 2017

Bubbly Burp Tracks Giant Black Hole's Last Meal

Observations with a number of telescopes, including the Hubble, have now dated a kind of burp in the eating habits of the giant black hole at the center of our Milky Way Galaxy. It appears that about six million years ago, the central black hole "ate" a large cluster of stars and the neighborhood around it was energized by the process of the meal.

Black holes are regions where material (starting with dead stars) has collapsed so much, that nothing, not even light, can get out. The black hole at the center of our Milky Way now includes enough material to make more than 4 million stars like the Sun! It's what we call a "supermassive black hole" and lurks in the middle of our Galaxy like a giant speed trap for unwary stars or star groups that get too close.
As material is in the process of being "swallowed" by the black hole, it glows with desperate radiation, just before it falls in and disappears from view. A great bubble produced by the black hole as it ate its last serious meal has now been tracked by astronomers with much greater precision.
Just like the sound of the burp your uncle makes (after a heavy Thanksgiving meal) can travel through the dining room, so the bubble from this last meal can be seen traveling through the Galaxy like a giant expanding shell. The shell was probe by the Hubble as the light of distant objects raced through it and astronomers were able to measure the speed of the bubble's motion.
Six million or so years ago, it appears that a large clump of stars or gas (the raw materials of stars) was consumed by the black hole, making two "Fermi bubbles" in the Galaxy. Since then, the black hole has only been "snacking" -- tearing apart and eating an occasional star or random bit of gas. But no serious meal has made a big bubble from the mouth of the black hole since then.
Our diagram shows how in the six million years since that meal, the bubble has expanded at speeds of two million miles per hour and made a giant bubbles north and south of the black holes that extend for tens of thousands of light years. That kind of puts your uncle's last burp into perspective!