Another episode of Astronomy on Tap Seattle is on the calendar for this week, and astronomer, artist, and author Tyler Nordgren will visit the Museum of Flight to talk about his latest book about total solar eclipses.
The whole premise of Astronomy on Tap is that astronomy is even better with beer. This month we go even one step further, learning how beer isn’t possible without science as we go “From Stars to Beer.” The gathering will be at 8 p.m. Wednesday, July 26 at Peddler Brewing Company in Ballard.
AoT co-host Trevor Dorn-Wallenstein will give a talk titled, “An Unbeerlievable Tale: How atoms come together in stars to make the most glorious structure in the low-redshift universe: beer.” That may be the longest subtitle ever, too! Dr. Meredith Rawls will discuss her research about “Weighing Stars with Starquakes” with a fantastic technique called asteroseismology.
Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington. It’s free, but buy beer. Bring your own chair to create premium front-row seating in Peddler’s outdoor beer garden.
Nordgren on Eclipses
We’ve covered a number of talks by Tyler Nordgren over the last several years. Nordgren, astronomy professor at the University of Redlands, is also an author, artist, dark-sky advocate, and entertaining presenter. He’ll be at the Museum of Flight at 2 p.m. Saturday, July 29 to talk about his latest book, Sun Moon Earth: The History of Solar Eclipses (Basic Books, 2016).
The book is part travelogue covering some of Nordgren’s recent eclipse-chasing adventures, part history of eclipses and the myths and science surrounding them, and part primer for the total solar eclipse that will be visible from the United States next month. It’s a marvelous volume and we recommend it highly.
Nordgren spoke about the book at Town Hall Seattle back in January. You can read our re-cap of that talk and our review of the book. Nordgren will sign copies of Sun Moon Earth following his talk Saturday. Grab the book by clicking the book cover or link above; it helps Seattle Astronomy exist!
SAS will hold its free monthly public star parties at 9 p.m. Saturday, July 29 at two locations: Green Lake in Seattle and Paramount Park in Shoreline. Bad weather cancels these star parties, so watch the SAS website or social media for updates. But hey, we’re on a good-weather roll!
Jazz Under the Stars
The Tacoma Astronomical Society and Pacific Lutheran University physics department will lead stargazing at PLU’s Keck Observatory on Thursday, July 27 following the PLU Jazz Under the Stars concert. The artist for the free concert, which begins at 7 p.m. in the outdoor amphitheater of the Mary Baker Russell Music Center at PLU, is Anjali Natarajan, a Brazilian jazz vocalist out of Olympia. If the weather is bad the stargazing may be off, but the concert will just move indoors.
Jazz Under the Stars concerts will also be held on the next two Thursdays, August 3 and 10.
The universe is full of mysteries; that’s one of the reasons that astronomy is so interesting! We dug into a couple of puzzling phenomena at the most recent gathering of Astronomy on Tap Seattle at Peddler Brewing Company in Ballard. The session was dubbed “CSI: Universe,” and Brett Morris, one of the co-hosts of Astronomy on Tap Seattle and a Ph.D. candidate at the University of Washington, gave a talk about the star KIC 8462852, more commonly called Tabetha Boyajian’s star, thank goodness. His talk was titled, “The Weirdest Star Gets Weirder.”
Citizen scientists were the first to notice that there was something odd about Tabby’s Star. The Kepler Space Telescope was searching for exoplanets by watching for slight but regular dips in a stars brightness, a possible indication of a planet in orbit around a distant star. Morris noted that it can be difficult to write a computer algorithm to filter out noise in the data, so they enlisted the help of the public through the website PlanetHunters.org.
Brett Morris (Photo: Greg Scheiderer)
“What you can do on this website is help scientists look for things that are weird,” Morris said. People identify objects that don’t look right, then professional astronomers check them out. “Through this process they found a whole bunch of stars that misbehave.”
One of them was Boyajian’s.
“If we look at its colors, if we look at its spectrum, it behaves like all the other F-stars,” Morris said, “and so we were a little bit puzzled when we started looking at data.”
There were dips in light from Tabby’s Star, all right. There were smaller dips early in the mission that never really matched up. Then in March 2011 there was a huge dip of 15 percent of the star’s light, and it lasted for days, not hours as most transits do. Then in February 2013 there was an even bigger reduction in brightness of 20 percent. Nobody has come up with a plausible explanation for this.
“Whatever this is, this thing’s big,” Morris said.
No easy answer
An astounding array of possible explanations have been thrown out there. Examples include an object like Saturn with rings that could cause variations in the light curve, a passing comet, debris from a huge planetary impact like the one thought to have formed our Moon, and Tabby’s Star’s indigestion from having just swallowed a whole planet. The one in vogue at present is that a family of 10 to 20 comets, all giving off material, are creating these odd light curves. Morris doesn’t quite buy this one, either.
“The more bodies that you imagine being there, the easier it is to fit a light curve,” he said. “If you just keep adding new parameters into your model, eventually it will fit.”
“If you invoke wierdly shaped objects, you can fit it perfectly,” Morris added. “If you invoke the kinds of objects that we expect are most likely, it’s a lot harder. We really don’t know what this star is doing.”
Some have wondered if something between us and Tabby’s Star, maybe interstellar gas or dust, caused the strange light curves. Morris himself investigated this one. Back in May he got a Tweet—he said this is mostly how astronomers communicate these days!—noting that Tabby’s Star’s brightness was changing. He used the Apache Point Observatory to look for signs of absorption from interstellar gas or dust. But the spectra didn’t change even though the star was changing.
“We’re slowly ruling things out,” Morris said. “It’s not something in our solar system, it’s not something between us and the star; it’s got to be something near the star, but we don’t know what near the star could be doing this.”
As for wild speculation that the strange light curves could be caused by a Dyson Sphere or other “alien megastructure”:
“Extraordinary claims require extraordinary evidence, and I do not have any evidence to suggest that we can make a claim as extraordinary as that,” Morris said. He and a team of undergraduates at the University of Washington continue to work on the puzzle.
Coroner for the Stars
The second talk of CSI: Universe came from Prof. Melissa Graham of the UW, who does work on supernovae. These mark the death of a star, and Graham’s job is to figure out whodunnit.
Melissa Graham (Photo: Greg Scheiderer)
Graham pointed out that a star is considered alive if it’s in hydrostatic equilibrium; that is, when atomic fusion in the star’s core supports the star by counteracting gravity. Sometimes the death of a star is from natural causes. A typical star will fuse hydrogen and helium into carbon, then gradually fuses neon, oxygen, and heavier elements until eventually a core of iron forms. Graham said this means trouble, because fusing iron into something heavier is not exothermic; it doesn’t release energy.
“If you end up with a core of iron, your hydrostatic equilibrium suffers because you are losing out on that fusion in the core,” she said. “The core collapses because it can’t support itself anymore, the outer layers fall onto the inner layers, and you end up with a supernova explosion.”
Material blows away and leaves neutron star behind.
“That’s death by natural causes,” Graham said.
Type 1a supernovae are more interesting to stellar criminologists. These involve a white dwarf star, which is the remnant of a smaller star that doesn’t have enough mass to fuse carbon and oxygen into anything heavier.
“The carbon and oxygen core shrinks under its own self-gravity, and the outer layers are lost, which causes a really pretty planetary nebula,” Graham said. “The star is now supported by electron degeneracy pressure.”
This means the star isn’t alive because it’s not fusing elements.
“It’s more of a zombie star,” Graham said. “It’s died once and continues to live.”
The usual suspects
It’s a suspicious death when you see one of these explode. Graham rounded up the usual suspects: It could be a binary companion, such as a red giant or a sun-like star or another white dwarf. Sometimes it could be a pair of white dwarfs with a third companion star. A type 1a supernova also might from from a white dwarf’s impact with a primordial black hole or comet.
One way to figure this out is to simply look at the scene of the crime.
“Once this white dwarf star explodes, the other companion star would still be there,” Graham said. A companion would heat up and get brighter, so it might be detectable. Interstellar dust and gas may also light up from the energy of a supernova. Looking back at the scene later might detect such material that is at significant distance from the event. Graham is using the Hubble Space Telescope to check to find out if this is happening. She’s also looking forward to the completion of the Large Synoptic Survey Telescope, which is expected to find some ten million supernovae over its 10-year mission. With so many new examples we will, “really start to understand how these carbon-oxygen white dwarfs die,” Graham said.
Two astronomers recently came independently to the conclusion that the way to figure out the fate of the universe is to build bigger and better telescopes. Prof. Sarah Tuttle of the University of Washington and Dr. Ethan Siegel of the Starts With a Bang blog and podcast both made informative and entertaining presentations about the dark universe at the most recent gathering of Astronomy on Tap Seattle at Peddler Brewing Company in Ballard.
UW astronomy Prof. Sarah Tuttle spoke at Astronomy on Tap Seattle May 24, 2017 at Peddler Brewing in Ballard. (Photo: Greg Scheiderer)
In her talk titled, “Dark Matter, Dark Energy, and Otters,” Tuttle joked that astronomers are “the universal accountants,” and that right now these bean counters are thinking that 68 percent of the universal energy budget consists of dark energy.
“If I were you, I would be concerned, because I both just told you that most of the universal energy budget is dark energy, and we don’t know what it is,” Tuttle said. “Dark matter we can measure and observe, but we don’t know what that is, either.”
There are a lot of theorized particles that could be in the dark-matter mix, but Tuttle said we don’t really understand them yet.
“We are in the process of measuring them and trying to figure out what it could actually be that is dark matter, how it is interacting with everything around it, because it is the dominant form of matter in our universe,” she said. We’re even more in the dark about dark energy.
“We are able to pin down that dark energy exists, that the universe is expanding and accelerating, and we’re not yet quite sure how to explain that,” Tuttle said.
How do we know?
Three experiments have helped reveal dark energy. Observations of the cosmic microwave background and type 1a supernovae have shown us that the universe is expanding. Tuttle is involved with a project called HETDEX—the Hobby Eberly Telescope Dark Energy Experiment—using a 10-meter telescope in West Texas. HETDEX is taking spectra of faint, young galaxies that are Lyman-alpha emitters to try to detect baryon acoustic oscillations. Huh?
“We’re using the clustering of a particular kind of galaxy to measure the distortion of spacetime,” Tuttle explained. She said it’s like throwing a grid of lights over a three-dimensional object—the lights will reveal the shape of the object.
“We use these galaxies to show us the shape of spacetime underneath to expose how dark energy changes with time,” Tuttle said. Other efforts like EBOSS and the South Pole Telescope are working on the same problem.
“We use a lot of different techniques to try to figure out what we’re doing to expose what dark energy is,” Tuttle said. “It turns out it’s going to take more beer and more time before we can answer that question.”
Our fate is in dark energy’s hands
Dr. Ethan Siegel of the Starts with a Bang blog and podcast spoke at Astronomy on Tap Seattle May 24. (Photo: Greg Scheiderer)
Siegel’s talk was titled “The Fate of the Universe: After 13.8 billion years, where is everything headed?” He noted that it astronomers once saw three possible scenarios for the future of our universe. It could keep on expanding forever, it could eventually collapse back onto itself, or expansion and gravity could balance out just right for a universe that remains about the way it is.
“That’s what we thought for years and years and decades and decades: the fate of the universe is going to be one of these three,” Siegel said. “The whole field of cosmology, which is my field, was the quest to measure what’s it going to be.”
“They’re all wrong,” he said. Dark energy is the wild card. Siegel pointed out that matter dilutes with the expansion of the universe, and radiation gets weaker; it redshifts. Dark energy? We’re not so sure.
“If there’s any type of energy that’s inherent to the fabric of space, then as space grows this energy is just growing,” Siegel explained. “As your universe grows, it’s like you’re just making more and more of this new type of energy if there’s any non-zero energy to space itself.”
A big assumption
Siegel gave a lengthy description of the fate of the universe, from the boiling oceans of Earth to the last black hole standing. It was all based on the assumption that dark energy is constant. But what if it gets stronger over time? Siegel said that would mean that galaxies and solar systems and the Earth would all get torn apart.
“In the fiery final moments, everything, even the atoms that made you up, even the nuclei that made you up, would be ripped apart as well,” he said. “That fate is known as the Big Rip, and it’s possible. I don’t think it’s right, but you can’t be sure unless you measure it.”
Dark energy could get weaker, too, and that could lead to the opposite outcome, a big crunch.
“That’s something we could also measure,” Siegel said. “We haven’t constrained it well enough to know that it won’t rip or that it won’t turn around and crunch again. The way we’re going to find out is through bigger and better telescopes and observatories.”
HETDEX is a big part of that, Siegel noted, and said that the ESA’s Euclid telescope will measure dark energy to better precision than ever before. NASA’s WFIRST (Wide Field Infrared Survey Telescope), scheduled to launch in mid-2020, and the Large Synoptic Survey Telescope, under construction in Chile with hopes of being fully operational by 2022, will also make key contributions to this work.
“If you think that this stuff is fun, I’m telling you it’s going to get even better in the 2020s,” Siegel concluded. Stay tuned.
If you couldn’t attend AOT Seattle, you can watch online! In May they live-streamed the event for the first time.
It’s possible that some extraterrestrials were at the most recent Astronomy on Tap Seattle gathering, at which we explored the possibility of life on Mars and looked at exciting new techniques for capturing images of exoplanets.
We have met the Martians and they are us—maybe
“Are we all Martian-Americans? We still don’t know,” said Bob Abel, a professor of applied physics at Olympic College and collaborator with the University of Washington’s Large Synoptic Survey Telescope Group. Abel gave a talk titled, “Where Are the Martians?” at Astronomy on Tap Seattle April 26.
Giving a quick geological and topographical history of Mars, Abel said that the Red Planet is just one-half the diameter of Earth, and thus has just one-eighth the volume of Earth, so Mars cooled off pretty quickly.
Curiosity shot this image in Gale Crater on Mars. The mudstones indicate a long history of standing water in that location. Photo: NASA.
“During the early formation of the solar system, it would have cooled to the point where liquid water could exist on its surface before the Earth got to that point,” Abel said, adding that it’s clear that water was once abundant on Mars. The rovers Spirit and Curiosity both landed in craters that used to be lakes, and Opportunity set down on the edge of what scientists think was once a salty sea.
In addition, Abel said that Spirit found opaline silica in Gusev Crater on Mars.
“The place where you find this on Earth is near geysers and hydrothermal vents,” Abel said. You’ll find heat, water, and minerals around these vents. “You’ve got all the stuff for life, and you find the most primitive life clustered around these on Earth.”
Prof. Bob Abel of Olympic College gave a talk about Mars and Martians at Astronomy on Tap Seattle April 26, 2017. Photo: Greg Scheiderer.
The surface of Mars is awfully barren now, but life could have conceivably existed there in the distant past. Scientists have found meteorites from Mars on Earth, and inside some of those meteorites they’ve found structures that look like nanobacteria. The debate continues over whether these are biological or not.
“It’s still somewhat up in the air, but it’s tantalizing evidence,” Abel said. “The question still remains, did life start earlier on Mars, since it was capable of being inhabited? And by the time Earth was habitable, did meteorites come to Earth and start life on Earth?”
The investigation continues.
As for present-day Mars, while the surface appears devoid of life, we may find something if we dig a little deeper. Abel said that Curiosity detects occasional outbursts of methane on Mars. He pointed out that most methane on Earth is created by biology.
“I’m personally rooting for flatulence, but we don’t know yet what’s causing it,” he laughed. But, through measurements made by many different Mars orbiters, we’ve learned that the planet’s outer core is molten. So beneath the surface there is heat, water, hydrocarbons, and soil: everything life wants. Abel recalled a talk last year by Penelope Boston, head of the NASA Astrobiology Institute.
“She can’t see how life doesn’t exist below the surface of Mars,” Abel said.
Snapshots of exoplanets
Getting photographs of exoplanets—planets orbiting far-away stars—is a relatively new field within astronomy. The first such images were captured just eight years ago or so. Benjamin Gerard said the technology and capabilities within the field are advancing rapidly. Gerard, a doctoral student in physics and astronomy at the University of Victoria in British Columbia, uses the Gemini Planet Imager to trick out pictures of planets near stars that are many light years away. These photos can be useful for figuring out the components of a planet’s atmosphere and whether it has oceans and continents.
Doctoral student Benjamin Gerard gave a talk about his work imaging exoplanets at Astronomy on Tap Seattle April 28. Photo: Greg Scheiderer.
Gerard said the main challenges in exoplanet imaging are resolution and contrast. He explained that the key to good resolution is adaptive optics. If you’ve looked through a telescope you have likely had nights when the objects you observe appear to be wiggling around because of atmospheric turbulence. Gemini corrects for this with adaptive optics.
Light from the object hits a deformable mirror as well as a component called a wave-front sensor. The sensor measures the amount of turbulence, sends the information to the mirror’s actuators, which can correct for the aberration.
“The mirror deforms once every millisecond,” Gerard said. “This aberration gets corrected and is constantly re-focused onto the camera. Once it reaches that point this image that is very turbulent suddenly becomes much more stable and we can get much better resolution.”
Gerard said this is a plus for ground-based telescopes.
“With this technique, we can basically take a ten-meter telescope and make it like we were in space,” he said. “With adaptive optics we actually do better than any space telescope in resolution.”
The problem of contrast is apparent to anyone who has visited social media, which is full of bad-contrast photos. Especially common are pics of people posed in front of windows. Often the people appear as silhouettes because the light from the window is way brighter. While exoplanets don’t pose in front of cosmic windows, contrast is a huge problem when it comes to getting the images.
“A planet like Earth is about ten billion times dimmer than it’s host star,” Gerard pointed out. Using a coronagraph helps block out the light of the star and remove its glare from the image. They also use a technique called angular differential imaging to overcome aberrations within the instruments. This is a little bit counter-intuitive to the amateur astrophotographer who typically uses an instrument rotator during long exposures to compensate for the apparent motion of objects caused by the rotation of the Earth.
“For exoplanet imaging this is actually helpful, so we turn off the instrument rotator and the planet appears to rotate with respect to the view of the fixed telescope instrumental aberrations,” Gerard said. “We can distinguish one from the other.” Computer algorithms can later put images made in this way back together to create even greater contrast.
Gerard hopes they’ll be able to do even better in the near future. The Wide Field Infrared Survey Telescope (WFIRST) is scheduled to launch in the mid-2020s. It will have a deformable mirror that should have the capability to image smaller planets like Earth.
“This is many orders of magnitude better than we can do on ground-based telescopes, because on a space telescope you’re much more stable,” Gerard said. “On the Hubble Space Telescope now we can’t reach this sort of contrast because there is no deformable mirror.”
If there’s any anti-science sentiment around these parts it wasn’t evident last Friday at Peddler Brewing Company in Ballard, where some 500 space enthusiasts packed the brewer’s beer garden—yes, we were sitting outside, in Seattle, in January—to hear from employees of Kent-based Blue Origin about the company’s latest testing and the prospects for an affordable ride to space any time soon. The event was the latest installment of Astronomy on Tap Seattle, organized by graduate students in astronomy at the University of Washington.
L-R Nicholas Patrick, Dan Kuchan, and Sarah Knights of Blue Origin after their presentation at Peddler Brewing Company. Astronomy on Tap photo: Brett Morris and Nicole Sanchez.
“Our ultimate mission is to have millions of people living and working in space,” said Sarah Knights, outreach coordinator at Blue Origin. “The way that we’re focused on that is to lower the cost of human spaceflight, and one of the ways to do that is to make vehicles reusable, so that’s our primary focus right now.”
Blue Origin’s current test vehicle is the New Shepard, a capsule and vertical takeoff/vertical landing rocket. It’s powered by the BE-3, for Blue Engine 3, which is fueled by liquid oxygen and liquid hydrogen and can deliver 110,000 pounds at full thrust. As suggested, the rocket blasts off, and then lands softly back on Earth.
“As it’s coming back down we can throttle it back to about twenty percent of its full throttle, so that means that as the propulsion module is coming down we can have an equal thrust-to-weight ratio, find the landing pad, and very gently set it down,” Knights explained.
Blue Origin safety test
Dan Kuchan, Product Development Team lead engineer on the New Glenn program at Blue Origin, said the most recent test of New Shepard, conducted in October, was of the vehicle’s full-envelope crew escape system.
“That means that if the rocket at some point decides that we can’t go to space today, the crew capsule can jettison itself and get out of Dodge,” Kuchan explained. It was the first such in-flight escape test for a space vehicle since 1965, during the Apollo program. Kuchan showed this video of the flight test during the presentation.
“That was an awesome test and it capped off the fifth flight and landing for that booster,” Kuchan said. “The system worked flawlessly.”
So far New Shepard has only flown without a crew, but they hope to have astronauts on board soon. That’s where Nicholas Patrick comes in. Patrick, a former NASA astronaut who flew on space shuttle missions for construction of the International Space Station, is now Blue Origin’s human integration architect.
“I’m responsible for worrying constantly about every aspect of flying on our spacecraft,” Patrick said. That includes everything from meeting rules and regulations, testing to make everything right, and every imaginable human factor.
They chose a capsule rather than a winged vehicle like the space shuttle partly for safety. The smaller capsule can get away from the booster quickly, as demonstrated in the video above. Patrick said it’s also a better way to travel.
“For those who are paying to ride aboard a New Shepard in the coming years this is a more authentic rocket flight experience than most other ways you could get to space,” he said.
The New Shepard capsule has big windows, the largest ever flown in space, and all passengers will have one of their own; there are no middle seats on New Shepard. Suborbital flights will last about eleven minutes, and passengers will be weightless for several minutes.
“We want to give them the best imaginable experience,” Patrick said. He showed this video animation of what a New Shepard flight will be like.
“That’s a New Shepard flight that we hope will be available to anybody who can get in and out of the capsule, who can tolerate the three Gs on ascent, and a little higher on descent,” Patrick said. “So start saving.”
At what cost?
How much to save is a question that Patrick said hasn’t yet been answered.
“Obviously everybody’s goal is to get this price down a long way,” he said. “We’re not going to get millions of people living and working in space by charging a quarter of a million or a hundred thousand dollars just for a suborbital flight.”
The question of when people will fly on New Shepard also hasn’t been answered.
“We’re not driven by that kind of schedule,” Patrick said. “We’re driven by our flight test program and the success or challenges we face in each of those tests.”
“What I can tell you is that I expect we’ll be flying people in the next year or two,” he added.
Kuchan noted that, in a way, New Shepard astronauts will be human guinea pigs.
“New Shepard and everything we’re doing, sending tourists into space, is all a way for us to practice and master landing a reusable rocket, and using it in a commercially viable way, so that over the next 50, 100, 200 years we can move civilization deeper into space,” Kuchan said.
Next steps: a bigger rocket
Blue Origin’s motto is gradatim ferociter—step by step, ferociously. The next step for the company is on the drawing board now: the New Glenn, which will get payloads into Earth orbit. The New Glenn will dwarf the New Shepard. While the latter is powered by one BE-3 engine that delivers 110,000 pounds of thrust, the New Glenn will have seven BE-4 engines that deliver 550,000 pounds of thrust each. That’s a lot of oomph. Again, there’s no totally firm timeline, but Kuchan said they’ve been asked to deliver the rocket by the end of the decade, and added that they plan to do so. It’s another step on the way to having millions of people living and working in space.
“Every single decision that gets made at Blue Origin is weighed against that ultimate goal,” Knights said.
The book is the story of the contributions of women at the observatory who made major advancements in the science, often without getting proper credit or recognition. From Williamina Fleming, originally hired as a maid, who identified ten novae and more than three hundred variable stars to Dr. Cecilia Helena Payne-Gaposchkin, appointed as the first woman professor of astronomy at Harvard in 1956, this group of remarkable women disproved the notion that “the gentler sex” had little to contribute to human knowledge.
December’s edition of Astronomoy on Tap Seattle will consist of three shows at the University of Washington Planetarium on Wednesday, December 14. The program will be a guided tour of the universe. Unfortunately, all of the seats for the three shows were snapped up quickly, but you might watch the AoT Facebook event page to see if any openings occur.
Public night in Pierce County
The Tacoma Astronomical Society plans one of its public nights for 7:30 p.m. Saturday, December 17 at the Fort Steilacoom campus of Pierce College. The indoor program will be a viewing of a movie about the Christmas star. If the weather is clear they’ll break out the telescopes for some observing, too.
You can scout out future astronomy events on our calendar. The page also features a full schedule of planetarium and stage science shows at Pacific Science Center. Recently added events include:
The Geminid meteor shower peaks this week, but will have to compete with the full Moon. The Sky This Week from Astronomy magazine and This Week’s Sky at a Glance from Sky & Telescope offer more observing highlights for the week.