Category Archives: lectures

Celestial Pig Pens and new tricks for old scopes

It takes a lot of detective work to figure out the nature of a type Ia supernova. Celestial Pig Pens and new tricks from old telescopes are contributing to the effort. That’s what we learned at the most recent meeting of Astronomy on Tap Seattle.

Messy Siblings: Supernovae in Binary Systems

Dr. Melissa Graham is a project science analyst for the Large Synoptic Survey Telescope, working out of the Astronomy Department at the University of Washington. Her main research focus is supernovae. In particular, she’s doing a lot of work on type Ia supernovae, which occur in binary star systems. One of the stars involved will be a carbon-oxygen white dwarf star.

“It’s a star that wasn’t massive enough to fuse anything else inside the carbon layers,” Graham explained. Outer layers of hydrogen and helium are thrown off in a planetary nebula phase, so the carbon and oxygen are what’s left.

Melissa Graham
Melissa Graham. UW photo.

“Carbon-oxygen white dwarf stars are very compact, very dense, about the size of the Earth but they can be up to about 1.4 times the mass of the Sun,” Graham said. These stars are pretty stable as stars go, so they don’t blow up under normal circumstances.

“When we do see these kind of supernovae that are clearly the explosion of carbon-oxygen white dwarf stars we have to wonder why,” she said. It turns out there are two possible scenarios. The binary can be a pair of carbon-oxygen white dwarf stars that spiral in on each other, merge, and then explode. Or the binary can include one white dwarf and a more typical hydrogen-rich companion star.

“In this case the companion star can feed material onto this carbon-oxygen white dwarf star, might make it go over 1.4 solar masses, become unstable, and then explode,” Graham said.

Which is which?

The key to figuring out which of these scenarios actually occurred is to take a look at the area around the supernova. If the companion is a more hydrogen-rich companion star, the neighborhood can get a little messy.

“It’s sort of like a celestial Pig Pen star that leaves a lot of material lying around,” Graham said. A blast from a supernova can interact with this material and cause it to brighten. The trouble is that astronomers typically only observe type Ia supernovae for a couple of months; they fade quickly. So if this extra material is far away from the event, they might not see the interaction. The answer is patience, to look at the supernova sites for up to 2-3 years after.

Graham did exactly that, using the Hubble Space Telescope to keep an eye on the locations of 65 type Ia supernovae.

“Out of these 65, I very luckily found one” in which there was brightening much later. They checked the spectrum of the light and found hydrogen, a sure sign that the companion in this particular type Ia supernova was a Pig Pen. Graham suspects that up to five percent of such explosions involve messy sibling stars.

Graham looks forward to having the Large Synoptic Survey Telescope (LSST) come on line. She expects it will find some 10 million supernovae in a decade.

“This marks a massive increase in our ability to both find and characterize supernovae,” she said.

Old scope, new tricks

While we wait for LSST an old workhorse telescope is doing interesting work in a similar vein. Professor Eric Bellm of the UW works with the Zwicky Transient Facility (ZTF), which uses the 48-inch telescope at Palomar observatory in California. The scope is a Schmidt, completed in 1948, and for years it was the largest Schmidt telescope in the world. It’s main function at first was to use its wide-field view of the sky to create maps that helped astronomers point Palomar Mountain’s 200-inch Hale Telescope.

Eric Bellm
Eric Bellm. UW photo.

The 48-inch was used to do numerous sky surveys over the years. It discovered many asteroids, and Mike Brown used it to find the dwarf planets he used to kill Pluto. The old photographic plates gave way to modern CCDs, and Bellm became the project scientist for the Zwicky Transient Facility—named for astronomer Fritz Zwicky, a prolific discoverer of supernovae—in 2011.

They outfitted the scope with a new camera with 16 CCDs that are four inches per side. They got some big filters for it and put in a robotic arm that could change the filters without getting in the way of the camera. They started surveying in March of last year and can photograph much of the sky on any given night.

“That’s letting us look for things that are rare, things that are changing quickly, things that are unusual,” Bellm said.

Examples of what the ZTF has found include a pair of white dwarfs that are spinning rapidly around each other, with a period of just seven minutes. They can see the orbits decay because of gravitational wave radiation. It has discovered more than 100 young type 1a supernovae. And it found an asteroid with the shortest “year” of any yet discovered; its orbit is entirely within that of Venus.

It’s doing the same sort of work that the LSST will do when it comes online.

“It’s super cool that we’ve got this more than 70 year old telescope that we’re doing cutting-edge science with thanks to the advances of technology,” Bellm said.

Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington, and typically meets on the fourth Wednesday of each month at Peddler Brewing Company in Ballard. The next event is set for September 25.

A surprise discovery from Apollo 11 lunar samples

As we look back at the 50th anniversary of the Apollo 11 Moon landing, Toby Smith notes that the most interesting science that came out of the mission was a bit of a surprise. Smith, a senior lecturer in astronomy at the University of Washington, gave a talk at the most recent meeting of Astronomy on Tap Seattle.

“There’s only one reason Apollo existed—to beat the Soviet Union to the surface of the Moon,” Smith noted. Few considered the mission to be scientific. “It wasn’t fully embraced by the scientific community even in its day, even among planetary scientists.”

But they figured as long as they were there, they should do some sort of science.

“This little bit of science they did fundamentally changed how we view not only the Moon, but the Earth-Moon system and our solar system,” Smith said.

The Apollo 11 landing site, the Sea of Tranquility on the Moon, is essentially an ancient lava flow, a featureless plain of cooled volcanic rock, Smith said. Think of it like Big Island of Hawaii, except you don’t really see the solidified lava on the Moon. The surface is soft, ground down and rounded off into a soft powder by billions of years of impacts. As Neil Armstrong observed just after his first step, it has the consistency of flour. That consistency almost accidentally led to the mission’s best science.

Moon rock box
An Apollo Lunar Sample Return container on display at the Destination: Moon exhibit at the St. Louis Science Center in 2018. (Photo: Greg Scheiderer)

Armstrong spent about 15 minutes of the two-and-a-half hour Moon walk picking up rocks and putting them into a box. At the end he collected nine scoops of lunar regolith and dumped it into the Apollo Lunar Sample Return Container (a fancy NASA term for the case for rocks) as sort of a packing material so the larger rocks wouldn’t clatter around. If they’d taken any styrofoam peanuts he might have used those instead.

Naturally, when this material was brought back to Earth, the scientists looked at it, and Smith said it just might be the most studied geological sample ever.

Smith noted that the regolith is highly angular; lunar dust is sharp.

“This is not material that was broken up by being tumbled,” he said. “This is material that was broken up by being fractured by impacts.”

It’s a diverse sample. It contains basalt, breccia (material created by impacts that shatters and sometimes melts back together), and impact spheres. There was also one unusual, bright white material in the collection. It turned out to be anorthosite, which makes up about four percent of the sample.

“It represents a piece of the original crust of the Moon long since destroyed by four and a half billion years of impacts,” Smith explained. Anorthosite is an igneous rock, like basalt, that comes from the cooling of melted rock. Basalt is created when lava moves across the ground, but Smith noted that anorthosite doesn’t work that way.

“Anorthosite forms in big pools of lava, huge pools of lava, huge chambers of lava,” he said. “As these chambers of lava slowly cool over time, the anorthosite floats to the top.”

“If this was found on the Moon it must mean that at some point early in the Moon’s history it must have been almost completely molten,” Smith added. This information made scientists re-think their notions about the origins of the Moon.

“Before Apollo there was no indication that the whole, entire Moon was almost completely melted,” he said.

The leading theory about the formation of the Moon these days is that something pretty big, about the size of Mars, smacked into the early Earth, and that material flung into space by the impact eventually coalesced into the Moon. The catch is that computer simulations of this event don’t often result in a completely molten Moon. So more study is needed. The lunar samples have been under constant scrutiny for the last 50 years, and Smith says he’s interested to see what new information can be gleaned from those samples as new analytical technology is developed.

Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington. The next gathering is set for Wednesday, August 28, 2019 at Peddler Brewing Company in Ballard.

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Seattle Astronomy talks Apollo anniversary at Tacoma libraries

Moonwalk talks

Greg gave the first of his series of talks about Apollo 11 June 29 at the Kobetich Branch of Tacoma Public Library.

Seattle Astronomy is doing our small part in celebrating  the 50th anniversary of Apollo 11 and the first human landing on the Moon. Greg Scheiderer will give six talks as part of the Tacoma Public Library system’s summer reading program.

The talks, titled “Moon Walk: Apollo 11 and a Man on the Moon,” will explore the extraordinary shared experiences of the Apollo missions, look at the history that got us step-by-step up to the giant leap, share some of the iconic photography of Apollo, and, since it’s the summer reading program, offer a list of Apollo readings for adults and kids alike.

The first talk was given on Saturday, June 29, 2019 at the library’s Kobetich Branch. The rest of the schedule is as follows:

You can also find schedule information on our calendar, in our Facebook events section, and on the library’s summer reading club events calendar. Come out and join us for a fun look back at Apollo 11!

Here’s our Apollo reading list!

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Apollo 11 50th anniversary reading list

I’m giving a series of six talks this summer at various branches of Tacoma Public Library about the 50th anniversary of the Apollo 11 mission and the first humans to walk on the Moon. It’s part of the library’s summer reading club. My talk includes some suggested reading about Apollo. Here’s what I recommend:

A lot of the material for my talk came from James Donovan‘s excellent book Shoot for the Moon: The Space Race and the extraordinary Voyage of Apollo 11 (Little, Brown and Company, 2019). Apollo 11 command module pilot Michael Collins calls the book “The best book on Apollo that I have read.”

Shoot for the Moon takes us on a tour of the space race from Sputnik up through the Apollo missions. Marvelously detailed and highly accessible, I could hardly put it down. It’s a marvelous chronicle of this great adventure.

Amazon

Tacoma Public Library

Seattle Public Library


Rod Pyle‘s First on the Moon: The Apollo 11 50th Anniversary Experience (Sterling, 2019) includes a forward by the mission’s Buzz Aldrin, second man to walk on the Moon. It’s a beautifully illustrated volume that is a fitting commemoration of Apollo 11.

Amazon

Tacoma Public Library (N/A)

Seattle Public Library


Charles Fishman‘s One Giant Leap: The Impossible Mission That Flew Us to the Moon (somebody, 2019) focuses on many of the people behind the scenes—technicians, engineers, scientists—who made the Moon landing possible. About 400,000 people in all worked on some aspect of the Apollo missions.

Fishman gave a talk about the book June 28 at Town Hall Seattle but unfortunately I wasn’t able to attend. The book is next on my nightstand, though.

Amazon

Tacoma Public Library

Seattle Public Library


David Whitehouse‘s Apollo 11: The Inside Story (Icon Books, 2019) is based on the author’s interviews with a host of astronauts, NASA personnel, politicians, and other insiders to tell the tale about how Apollo came about.

Amazon

Tacoma Public Library (N/A)

Seattle Public Library (N/A)

 


Richard Maurer‘s Destination Moon: The Remarkable and Improbable Voyage of Apollo 11 (Roaring Book Press, 2019) goes back in time. While most tales about the space race start with Sputnik, Maurer begins with fighter pilots in World War II. He traces the origins of the Apollo program to a few exceptional soldiers, a Nazi engineer, and a young eager man who would become president.

Amazon

Tacoma Public Library

Seattle Public Library


The Space Race: The Journey to the Moon and Beyond (DK Children, 2019) by Sarah Cruddas is targeted for kids from ages 6–9 and takes them from the race to the Moon to the future and the possibility of perhaps one day living on Mars.

The Space Race includes a forward by Eileen Collins, the first women to be commander of a space shuttle mission.

Amazon

Tacoma Public Library

Seattle Public Library


Two books by John M. Logsdon, founder and long-time director of the Space Policy Institute at George Washington University, wrap up our list. They’re not new, but both offer interesting discussions of the public policy debates behind the Space Race and how the decisions changed the future of U.S. space exploration.

John F. Kennedy and the Race to the Moon (Palgrave Studies in the History of Science and Technology, 2010) and After Apollo?: Richard Nixon and the American Space Program (Palgrave Studies in the History of Science and Technology, 2015) are great reads for those interested in public policy and how challenging decisions are made. The books are relevant now as we observe the anniversary of Apollo, and as we consider the pros and cons of a return to the Moon and possible future missions to Mars.

Check out our 2015 article about Logsdon’s discussion of the future of space exploration given at that winter’s meeting of the American Astronomical Society.


Books marked at N/A at the library branches were not listed in their catalogs as of June 30, 2019. They may be on the way, as most of the titles are fresh off the presses. If you purchase from Amazon through the links above, a small percentage of the sale comes to Seattle Astronomy at no cost to you. This helps support our work on astronomy journalism.

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Jacobsen Observatory resumes open houses this week

TJO

Theodor Jacobsen Observatory at the UW. Photo: Greg Scheiderer.

Spring has sprung, and one of the many wonderful manifestations of that is the resumption of bi-monthly open houses at the University of Washington’s Theodor Jacobsen Observatory. The first of the year will be held beginning at 8 p.m. Tuesday, April 2. Future open houses will be held on the first and third Tuesday of each month through September.

The day of the week is a change. The open houses have been held on Wednesday evenings ever since we can remember.

The open houses typically include a couple of astronomy talks by UW students. This week Aislynn Wallach will talk about The Future of Telescopes and Aleezah Ali will discuss Binary Stars. Unfortunately, reservations for these free events are usually snapped up pretty early, and the April 2 event is already listed as full. The observatory classroom in which the talks are held only holds 45 people. You can check out future topics and make reservations on the TJO website.

Volunteers from the Seattle Astronomical Society staff the observatory dome on open house evenings and, weather permitting, give visitors a look through the vintage 1892 telescope, which has a 6-inch Brashear objective lens on a Warner & Swasey equatorial mount.

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Seattle is just like Mars, and other lessons from a 3-D trip

Attendees at the most recent gathering of the Seattle Astronomical Society went on an entertaining and informative 3-D trip to Mars, and learned that Seattle is just like the Red Planet.

Antonio Paris

Antonio Paris

Our tour guide was Dr. Antonio Paris, chief scientist at the Center for Planetary Science, assistant professor of astronomy and astrophysics at St. Petersburg College in Florida, and author of Mars: Your Personal 3D Journey to the Red Planet (Center for Planetary Science, 2018).

Paris said he loves Mars and expects that humans will be going there sooner than later.

“I suspect that, the way things are going, probably in about 10 to 15 years we’re going to be on Mars,” he said, adding that he doesn’t think anyone is going to go it alone.

“Mars, in my personal opinion, is going to be an international effort, both with corporations as well as the government,” Paris said.

The book was something of a spinoff of an exhibit about Mars that Paris helped put together at the Museum of Science and Industry in Tampa. The exhibit proved pretty popular, and the book seemed the next natural step. Proceeds from book sales support the work of the Center for Planetary Science.

Paris featured fantastic 3-D images of a great many Martian geological features in his presentation. While his Ph.D. is in astronomy, he’s really morphed into something of a rock hound.

“We are primarily geologists that are studying all of the geological features here on Earth,” he said, “and we’re trying to compare and contrast them with what we see on the lunar surface, what we see on Mercury, Venus, and all of the terrestrial planets.”

Paris called the process comparative planetology.

Ripples

Ripple marks such as those shown in this photo from the rover Opportunity were deposited by water moving back and forth. Image: NASA/JPL

“If I look at something here on Earth and I can determine how that thing happened,” he said, “and I see the same thing on Mars, I can deduce that the same processes have occurred, most likely.”

That caveat was included on most of his deductions, but the comparisons are pretty compelling. For example, Paris passed around a flat piece of rock with ripple marks on it that he collected in the Canyonlands in Utah. Such ripple marks are created by water moving back and forth over the rock, and the Canyonlands piece looks exactly like stuff the rovers have seen on Mars.

Paris also showed photos of rock formations made when moving or freezing water breaks up bedrock, and wears it down into small pebbles. At least, that’s how it happens on Earth.

Potholes on Mars

This set of images compares the Link outcrop of rocks on Mars with similar rocks seen on Earth. Image: NASA/JPL-Caltech/MSSS and PSI

“We call that either fragmented sidewalk or conglomerate terrain,” he said. Here in Seattle, especially after our recent cold and snowy weather, we just call it a pothole, and that’s how the Emerald City is like the Red Planet! Potholes all over the place!

Paris does a lot of rock hunting in the American southwest, which has a lot of Mars analog sites that scientists and NASA use in their Mars work. These include Moenkopi in Arizona, Canyonlands, the Mojave Desert, Death Valley, and the Flagstaff area.

The website for the Center for Planetary Science notes that Paris will make a presentation in Portland in September at a time and place not yet published. Dollars to Voodoo Doughnuts it will be with Rose City Astronomers. Stay tuned.

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Black holes and LIGO on Bainbridge Island

The Laser Interferometer Gravitational-wave Observatory—LIGO—is leading scientists to discoveries at an impressive clip. Just two years ago we wrote about UW Bothell physics professor Joey Shapiro Key’s talk to the Seattle Astronomical Society about the detection of gravitational waves from the merger of two stellar-mass black holes—a discovery that won the Nobel Prize. Last week at Bainbridge Island Open Mic Science Key talked about LIGO, its latest detections, and plans for even bigger science in the future.

Joey Key

Joey Shapiro Key

Interferometers are a simple idea. They have two perpendicular arms of equal length. Laser light is split into the two arms, hits mirrors at the far ends, and returns to the source. If something changes the length of an arm, the light waves interfere with each other. LIGO in Hanford and a twin observatory in Louisiana are huge observatories with arms four kilometers long, and they are making amazing measurements.

“When we detect the gravitational waves they are quite pristine, even from billions of light years away,” Key explained. “But it was a challenge because gravitational waves interact so weakly with matter—that’s why they’re so pristine when they reach us—they’re very hard to detect.”

How hard? Einstein, who thought up the notion of gravitational waves and did the math to explain how they would work, thought the effect was too small to ever detect. It took a century to develop the technology to do it. LIGO can detect unbelievably minute changes in the length of its arms when a wave passes through.

“This is the most sensitive measuring device in the world,” Key said of LIGO. “For those four-kilometer arms, the change in the length in the arms we measure is a thousand times smaller than the width of a proton in the center of an atom.”


Simulation by SXS

The big discovery by LIGO since Key’s previous talk came in August of 2017.

“We detected a gravitational-wave signal from two neutron stars colliding, followed immediately by a detection of a gamma-ray burst by NASA’s Fermi satellite, and this set off a worldwide search for the source of that gravitational wave signal,” Key said. More than half a dozen observatories were involved in the work, observing the event in many wavelengths across the electromagnetic spectrum and pinning down the galaxy in which the collision occurred.

“This is the first ever multi-messenger detection with gravitational waves where we’re doing observations using gravitational waves and light,” Key said. Being able to see light from the event taught us a lot.

“We really learned from this one in particular that most of the heavy elements in our universe, including what solar systems are made of, what planets are made of, and what we are made of, comes from neutron stars colliding and kilonova events,” Key noted.

Just as light has a wide range of wavelengths, so do gravitational waves. Key said LIGO can only detect a limited slice of those wavelengths. It would be not able to find gravitational waves from the collisions of supermassive black holes or from the early universe. That will take a different tool.

“The future of gravitational wave astronomy lies in experiments such as LISA, the Laser Interferometer Space Antenna, that will do laser interferometry in space,” Key said. LISA is a joint venture between NASA and the European Space Agency, but there will be a bit of a wait for it. LISA’s planned launch isn’t until 2034. In the meantime, LIGO has plenty to do, with planned upgrades that will make the detector even more sensitive.

“We really are in a brand new era of gravitational wave astronomy, and there’s a lot to be discovered,” Key said.

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