Tag Archives: Astronomy on Tap Seattle

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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Waffles and big data in the universe

Waffles and big data were on the menu at the most recent gathering of Astronomy on Tap Seattle at Peddler Brewing Company in Ballard.

Leah Fulmer

Fulmer at work. Photo: Astronomy on Tap Seattle

Leah Fulmer, who is working at the University of Washington on her Ph.D. in astronomical data science, gave a talk titled, “Data-Driven Astronomy in the 2020s and Beyond.” Fulmer explained that we’re in the midst of a “data tsunami” that’s been growing over the last three decades of astronomical surveys.

Back in the 1990s the Palomar Digital Sky Survey and the Two Micron All-Sky Survey each collected about a terabyte of data. That’s a trillion bytes; 1012 bytes. Enough to fill a thousand one-gigabyte smartphones.

The 2000s brought the Sloan Digital Sky Survey (SDSS) and the Galaxy Evolution Explorer. These collected in the tens of terabytes of data. In the 2010s Pan-STARRS collected a petabyte of data; a quadrillion bytes.

In the future this astronomical growth in data collection will continue. The Large Synoptic Survey Telescope (LSST) under construction in Chile will survey the entire night sky every few nights for ten years. It will ultimately collect an astounding 500 petabytes of data—that’s 20 terabytes every single night.

“SDSS had a total data collection of 40 terabytes,” Fulmer pointed out. “We’re going to have one SDSS every two nights in the 2020s. This is a big freaking deal.”

On top of the data, Fulmer noted that the LSST will alert its network when it finds something interesting. Given the amount of data, Fulmer said there will be ten million alerts every night, or about 232 every second.

“This is overwhelming; this is a data tsunami,” she said. “With this sort of data collection astronomers cannot do our science in the way we have up until this point.”

A new way to look at data

Up until recently astronomers would apply for telescope time, make their observations, take the data home, and analyze it. That won’t work in the era of big data for a couple of reasons. First, you can’t jam that much data onto your laptop. Second, there just aren’t enough astronomers to sort through data on objects one by one. As you might guess, we need the help of computers.

“Specifically, we need the help of machine learning,” Fulmer said. This can be both “supervised” and “unsupervised” learning. Astronomers can identify objects by their light curves, and the computers can be taught what those are. That’s supervised. In unsupervised learning, the computers can go out on their own and sort various observations into categories with similar characteristics, and we can figure out what’s in each category.

Once you figure that out, a data broker like ANTARES (the Arizona-NOAO Temporal Analysis and Response to Events System, and yes, astronomers still rule at acronyms) can let the right people know about discoveries in a timely manner.

Fulmer said it’s interesting that ANTARES will never look at the sky, just at data, and that many future astronomers may never visit a telescope, just analyze the data. Different fields can learn from each other about how to process all of this information.

Fulmer finds the era of big data exciting.

“It’s not just data-driven astronomy, it’s data-driven everything,” she said.

Astronomy with your breakfast

N. Nicole Sanchez is working on her Ph.D. in astronomy at the UW, and her research interest is in spiral galaxies like our own Milky Way and how they evolve. This, naturally, led her to think of galaxies as waffles. Thus the title of her talk, “Black Holes, Gas, and Waffles.”

Spiral galaxies form into disks, she explained, and a waffle is a disk. The galaxies have a central bulge, represented on the waffle by a big pat of butter. Marshmallows, suspended by toothpicks, represent globular clusters of stars. Red and blue sprinkles represent old red stars and young blue ones. You just have to imagine the supermassive black hole at the center of the waffle. It may be massive, but it’s super small compared to the size of the waffle.

Sanchez came up with the idea for this model while teaching at the UW in the “Protostars” summer science camp for middle school girls the last couple of years. In the waffle model, syrup represents the gas in the galaxy.

“That’s what you’re making your stars out of, so there’s going to be a lot in your disk,” Sanchez said.

In fact, her faculty advisors got wind of the waffle model and said it would need A LOT of syrup, which led to the hilarious twitter thread below. Click on it to see the academic discussion.

Sanchez admitted that her waffle galaxy may be “a bit too simplified” as a model. But the syrup is important.

“There’s actually tons of gas around really all galaxies, in what’s called the circumgalactic medium,” Sanchez said. The gas is important to the evolution of a galaxy. It feeds the black hole and helps  form stars.

Sanchez studies galaxies by using cosmological hydrodynamic simulations.

“I put a bunch of particles in a box, turn on gravity, and let time happen,” she laughed. After running a simulation she looks for a galaxy similar to the Milky Way, and examines interactions between the galaxy’s supermassive black hole and the circumgalactic medium.

“The supermassive black hole is actually really vital to the evolution of the CGM because it’s moving all of this metal that’s being created in the hearts of stars in the disk of the galaxy and it’s propagating them out into the CGM,” Sanchez explained. Without a supermassive black hole, the circumgalactic medium would not look like what astronomers have observed.

Pass the syrup.

LSST to the rescue

We hope the Large Synoptic Survey Telescope (LSST), under construction in Chile on a timeline that would have it begin science work in 2022, works. There are a bunch of astronomers banking on it to make their lives a lot easier. A group of them—the LSST Solar System Science Collaboration—met earlier this month in Seattle, and four of them gave talks at a special edition of Astronomy on Tap Seattle at Peddler Brewing Company in Ballard.

David Trilling of Northern Arizona University noted that the LSST will have an 8.4-meter mirror and a camera the size of a small car.

“In terms of telescopes, this is a really, really, really big machine,” he understated. That car-sized camera will boast 3.2 billion pixels.

“You’d need 1,500 HDTV screens to look at a single LSST image,” Trilling said. LSST will scan the entire night sky every three to four nights for ten years.

“That’s about ten terabytes of data every night, which is a huge computational challenge,” he noted.

It’s an asteroid. It’s a comet. It’s complicated…

Michael Mommert of Lowell Observatory studies asteroids and comets. He said that sometimes it’s difficult to tell one from another. An asteroid can look like a comet if the asteroid is “active.” This could be because it collided with something else, or it is spinning rapidly, or it was warmed by its proximity to the Sun.

“If we can understand those active asteroids we can better understand the average asteroid,” Mommert said. “We can learn a lot about the mechanisms that are going on in asteroids from those active asteroids.”

Similarly comets can go dormant, with no tail, and look more like asteroids. As they often share similar properties, Mommert said comets and asteroids are on something of a continuum rather than being two distinct types of objects.

In his research Mommert is tracking about 20 active asteroids and 50 dormant comets. He figures he spends 30 nights per year using a telescope. He’ll be able to cut down that time tremendously with LSST; he’ll be able to find his targets and pull data collected by the telescope.

“LSST will improve our understanding of small body populations,” Mommert said. “Asteroids, comets, active asteroids, everything that is out there.”

Tales from the Outer Solar System

Kat Volk of the University of Arizona focuses her research on objects in the outer solar system. Pluto, Eris, and other far-out objects have been discovered by comparing photos of an area of sky and looking for something that moved. In fact, Pluto was the first object discovered in this way.

There are about 2,000 known objects in the Kuiper Belt. That’s about how many asteroids we knew of a century ago.

“Kuiper Belt science is a hundred years behind Asteroid Belt science because these things are just so much more difficult to find,” Volk said, because they’re far away, faint, and move slowly. “We had to wait until we had digital cameras and computers to process those images.”

Volk said we probably have discovered all of the 10-kilometer asteroids and most of the 1-kilometer ones. They’re easier to spot because they’re brighter, and there’s money for the hunt because of the potential threat asteroids pose to Earth.

“For comparison, the smallest ever observed Kuiper Belt object is 30 kilometers across, very roughly,” Volk said, adding that we only found that one because the Hubble Space Telescope was used to look for another target for the New Horizons mission after it passed Pluto.

“We’re pretty incomplete in terms of our object inventory in the outer solar system,” Volk said. She said LSST will change that.

“They expect 40,000 new Kuiper Belt ojects,” Volk said. “It’s going to be an entirely new era for the Kuiper Belt with a huge playground of new objects to look at.”

“I am realy excited to see what we’re going to find with LSST, and it’s going to completely revamp our idea of the outer solar system.”

A Crash Course in Asteroid Defense

Andy Rivkin of the Johns Hopkins University Applied Physics Laboratory said that even a 20-meter asteroid packs a wallop when it smashes into Earth. That was roughly the size of the Chelyabinsk meteor in 2013.

Doing the math tells us that there should be about 10 million objects of that size zipping around the solar system, but so far we’ve found only around 10 thousand of them. Back in 2005 Congress told NASA to find 90 percent of objects 140 meters or larger.

“LSST is going to be a critical piece in reaching this goal,” Rivkin said, “and we expect that by 2034 about 86 percent of hazardous asteroids will be found.”

So, what do we do when we spot one headed our way? Rivkin said that for really small ones, like Chelyabinsk, and really large ones, the best idea might be duck and cover. There’s not much to be done about something very large, and small ones don’t pose much of a threat. For those in between, a few options are viable. For one, we could try to deflect the asteroid with a nuclear bomb.

“A lot of people are uncomfortable with nuclear explosions in space, for good reason, and so there’s been a lot of interest in having something else that could work,” Rivkin said.

That something else is a kinetic impactor, which is a fancy way of saying we’ll just smash something into the asteroid to change its speed, and therefore its orbit. It’s a fine idea in theory, but we have no idea if it would actually work. Rivkin is involved in a project that will give it a try.

It’s called DART, which is for Double Asteroid Redirection Test. DART is on schedule to launch for the asteroid Didymos in June of 2021, and then crash into its satellite, nicknamed “Didymoon,” in October 2022. Astronomers will watch through ground-based telescopes and see what happens. Rivkin called it a dress rehearsal for the day we might have to do something about an incoming asteroid.

“A dress rehearsal for, needless to say, a performance we hope never to actually stage,” he said, “demonstrating that we could do this, allowing us to pin these computer simulations to something real, allowing us to better understand asteroidal properties, and giving us a lot of science as an ancillary benefit.”

Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington.

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The search for Earth 2.0

Astronomers have to date discovered more than 3,700 exoplanets—planets in orbit around stars other than our Sun. With each discovery, someone wants to know if the newly discovered planet is like Earth.

Elizabeth Tasker

Elizabeth Tasker at Astronomy on Tap Seattle.

Elizabeth Tasker thinks that’s not a very good question. Tasker, associate professor at the Japan Aerospace Exploration Agency, Institute of Space and Aeronautical Science and author of The Planet Factory: Exoplanets and the Search for a Second Earth (Bloomsbury Sigma, 2017) gave a talk at the most recent edition of Astronomy on Tap Seattle. She said that some of the exoplanets confirmed so far have at least a little resemblance to Earth.

“Roughly one third of those are approximately Earth-sized, by which I mean their physical radius is less than twice ours,” Tasker said. News media often wish to leap from that to describing a planet as Earth-LIKE, but Tasker said we don’t have nearly enough information to make that sort of call. Our current methods of detecting an exoplanet can give us either its radius or its minimum mass, and a pretty good read of its distance from its host star.

“The problem is neither of those directly relates to what’s going on on the surface,” Tasker noted. Part of the challenge is what Tasker feels is the somewhat oversimplified notion of the “habitable zone” around a star, a band of distance in which liquid water—a key to life as we know it—could exist on a planet’s surface.

“Like all real-estate contracts, there is small print,” Tasker said. “Just because you’re inside the habitable zone doesn’t mean you’re an Earth-like planet. Indeed, of all the planets we’ve found in the habitable zone around their stars, there are five times as many planets that are very likely to be gas giants like Jupiter than have any kind of solid surface.”

Another misleading metric that has been used is something called the “Earth similarity index.” This method compared exoplanets to Earth on the basis of properties such as density, radius, escape velocity, and surface temperature.

“None of these four conditions actually measure surface conditions at all,” Tasker said, pointing out that the index didn’t take into account such features as plate tectonics, a planet’s seasons, it’s magnetic fields, greenhouse gases, or existence of water. We can’t observe any of those things about exoplanets yet. As an example of the flaws of the index, Venus came out at 0.9, pretty similar to Earth, which is at 1.0 on the zero-to-one scale. While Venus is about the size of Earth and is around the inner edge of the Sun’s habitable zone, its surface temperature could melt lead. Not very Earth-like, or habitable. It’s one of the reasons that the index is seldom used these days. So we don’t have much of a clue about conditions on any of the known exoplanets.

“Our next generation of telescopes is going to change that,” Tasker said. She noted that NASA’s James Webb Space Telescope is scheduled to launch next year, the ESA’s Ariel in 2026, and the UK’s Twinkle in the next year or so.

“All of these are aiming at looking at atmospheres, and these may be able to tell us what is going on on the surface, and may even give us the first sniff of life on another planet,” Tasker said. “Maybe then we’ll be able to talk seriously about Earth 2.0.”

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Astronomy on Tap and a blue moon this week

It’s a light calendar of astronomy events for Easter week, but you can celebrate Astronomy on Tap Seattle’s third birthday and enjoy our second blue moon of the year!

Happy three to AOT

AOT March 28It’s hard to believe it’s been three years since a group of graduate students in astronomy started up the Astronomy on Tap Seattle lecture series, but this week’s edition will mark the 36th consecutive month that they’ve offered interesting talks, astronomy trivia, fun prizes, and great beer. Head to Peddler Brewing Company in Ballard at 7 p.m. Wednesday, March 28 for updates on the astronomy AOT has covered in the last year, and a look at the exciting new science that has come out recently—neutron star mergers, new planets, and more!

It’s free, but buy some beer. Bring your own chair to create premium, front-row seating.

Blue moon

It turns out “once in a blue moon” isn’t all that rare! Saturday’s full moon will already be the second one this year, at least by the definition that a blue moon is the second full moon in a calendar month. We had a blue moon in January, too; see the video below of Seattle Astronomy’s Greg Scheiderer talking on KING-TV’s New Day Northwest about the super blue blood moon.

The next blue moon after this week will be on Halloween in 2020.

Exploring alien moons

The search for extraterrestrial life keeps getting smaller in scale. It’s difficult to discover planets around other stars, but now scientists are looking for exomoons and alien bacteria. Two University of Washington graduate students shared their work at an Astronomy on Tap Seattle gathering at Peddler Brewing Company in Ballard last week.

To date more than 3,500 exoplanets have been discovered in orbit around stars other than our Sun, but we haven’t seen an exomoon orbiting any of those planets. Tyler Gordon, a second year grad student in astronomy and astrobiology at UW, thinks it’s only a matter of time before we do.

“We have every reason to expect that there are a lot of moons out there in the universe, probably many more than there are exoplanets,” Gordon said. Thinking about our own solar system, he pointed out that there are 19 moons that are big enough to be rounded by their own gravity, which is more than twice as many such moons as there are planets.

Despite the fact that no exomoons have yet been found, Gordon said there are three good reasons to look for them:

  • They might be habitable
  • The presence or absence of a moon can give a clue about how a planet formed
  • A moon can be a factor in a planet’s habitability

There are two reasons for that third point. Moons can raise tides, and some scientists think that tides battering the shore on early Earth delivered nutrients and created places for life to develop. In addition, moons can influence a planet’s orbital characteristics, especially obliquity, and help stabilize oscillations of its rotational axis.

“An exomoon can keep a planet from tumbling back and forth onto its side and can insulate it from having really extreme changes in seasons, which is something that we think could be very bad for life,” Gordon said.

Where are they?

It’s been hard enough to identify exoplanets, and there’s an obvious challenge in hunting for exomoons.

“Exomoons are probably really small, and small is a problem because small things are really hard to see,” Gordon noted.

Just how small are moons? Gordon explained that observation and modeling have found that the mass of a planet’s satellites generally scales with the mass of the planet itself. For any given planet, “We expect that the total mass of its satellites adds up to between one ten-thousandth and two ten-thousandths of the mass of their host,” Gordon said.

Thus to find an exomoon as big as Earth—someting we could actually see—its host planet would have to be about 30 times the mass of Jupiter. Something that big probably wouldn’t be a planet; it would more likely be a brown dwarf.

Finding an exomoon

Most of the exoplanets discovered to date have been spotted because they cause a dip in the light we see coming from their star when they transit in front of it. An exomoon would do the same thing, but Gordon said there are a couple of challenges. Since the exomoon would be far smaller than the planet, so would the dip it would cause. Plus, sometimes the exomoon will be ahead of, behind, or blocked by the planet, making patterns more difficult to tease out of the data.

Gordon noted that a team from Columbia University recently tried to do that by looking at a ton of Kepler data and searching for scattering called the “orbital sampling effect.” In all of the data they found exactly one potential signal for an exomoon; it’s in orbit around the planet Kepler-1625b. This is a big planet, about ten times the mass of Jupiter, and the moon—Kepler-1625bi—is about the size of Neptune, which is way bigger than would be expected according to the scaling rule. Gordon said that raised a lot of questions.

“Is Kepler-1625b even a planet if it’s that’s big? Is the moon actually even there at all?” he asked. “And if it is there, how can such a large moon form?”

The Columbia team used the Hubble Space Telescope to look at the system back in October, but analysis of the data and any answers to those questions have yet to be published.

Gordon said that the James Webb Space Telescope will be a big help to exomoon hunters. While Kepler looked in the visual, JWST is equipped for other wavelengths.

“By using JWST’s ability to see in different parts of the electromagnetic spectrum we may be able to disentangle the transit of an exomoon from stellar variability that could obscure that transit,” Gordon said.

Space bacteria

Max Showalter is looking for stuff way smaller than exomoons. He’d like to spot interplanetary bacteria.

Showalter, a Ph.D. student in oceanography at the UW, gave a talk titled, “Looking for Life When the Trail Goes Cold.” He noted that the hunt for biosignatures is at the heart of the search for life. Biosignatures can be chemical, say oxygen in an atmosphere. They can be structures, such as fossils. They could be biological molecues like amino acids or nucleotides.

“They tell us that either life has been there in the past, or life is there now, or life could be there in the future,” Showalter said. “We want lots of biosignatures all telling us the same thing in order for us to decide that there’s life.”

Showalter would add another biosignature to the list: movement. After all, there’s no better sign of life than if something comes up and waves at you. Still, when you’re looking for microbial life, the tough questions are whether bacteria swim in space, and how we’ll see them if they do.

“It’s hard enough to see microbes on Earth, let alone millions of miles away,” Showalter noted. His research specialty is studying things that live in sea ice. When salt water freezes, the salt can either fall out or get stuck inside the ice. If it’s inside, the salt gets concentrated and melts pockets of ice, creating what are called brine pores.

“These brine pores are great because they make a really good habitat for a lot of things to live inside the ice,” Showalter said.

Ice-beings on Earth

Showalter has looked at bacteria from Arctic sea-ice on site with a microscope called SHAMU, which stands for “Submersible Holographic Astrobiology Microscope with Ultra-resolution.” SHAMU works on principles of holography. A laser in a box is split into two beams. One beam goes through the brine sample, the other goes straight to a camera. The waves of light interfere with each other, and computer analysis can create a hologram: “A 3-D image of a tube of liquid where you can see bacteria swimming,” Showalter said. (Read a longer article about SHAMU from a talk Showalter gave at Town Hall Seattle in 2016.)

The application for SHAMU in the search for life is at places like Saturn’s moon Enceladus and Jupiter’s moon Europa, both of which have salt water oceans under thick crusts of ice. Some of this salt water shoots out of geysers on the moons and into space.

“Which presents a really incredible opportunity for us as astrobiologists—or astronomers if you’re one of those people—to be able to sample that ocean without having to drill through eight kilometers of ice!” Showalter said.

An upcoming NASA mission called Europa Clipper will take a shot at that. The spacecraft is presently scheduled for launch some time between 2022 and 2025. SHAMU isn’t going, and none of the instruments selected for the mission will be looking for bacterial motility, but Showalter holds out hope that motility will prove to be a useful biosignature in the future.

He said he doubts that Europa Clipper will find life, but expects it will come across some tantalizing clues.

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