Category Archives: astronomy

Astro Biz: Star Ice & Fuel

Star Ice & FuelMany businesses, products, and places have names rooted in space and astronomy. We’re featuring one every Tuesday on Seattle Astronomy.

This week’s Astro Biz is Star Ice & Fuel. The company has been in operation since 1888, the year before Washington became a state. They were located in downtown Tacoma for 122 years, and moved into a new facility between Fife and Federal Way in 2010.

Star Ice & Fuel makes ice: crushed, shaved, block, and dry. They also do heating oil, propane, kerosene, firewood, and wood pellets.

More info:

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A lighthearted look at the dark universe

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.

Sarah Tuttle

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

Ethan Siegel

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.

More reading:

  • Article about BOSS from a 2016 Astronomy on Tap
  • Article about the LSST from a 2016 Astronomy on Tap
  • Siegel’s talk about the expanding universe given to Rose City Astronomers in February
  • Siegel’s talk about the discovery of gravitational waves given to RCA in 2015
  • Siegel’s book, Beyond the Galaxy
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Seeking life beyond Earth

The 21st Century is an exciting time for those who study exoplanets. As the number of confirmed worlds in orbit around far-away stars grows almost daily—as of this writing the NASA Exoplanet Archive lists 3,489 of them—Lucianne Walkowicz says it’s becoming more than just a tally.

Lucianne Walkowicz

Adler Planetarium astronomer Lucianne Walkowicz gave a talk titled “Seeking Life Beyond Earth” May 23, 2017 at the Pacific Science Center. (Photo: Greg Scheiderer)

“We are starting to get to know these planets not just as a new marble in the bin, but something that you can understand what its environment might be like,” Walkowicz said. “We’re right around the corner from being able to really understand these places as worlds, and not just compare their size or their orbit to the planets in our solar system.”

Walkowicz is an astronomer at the Adler Planetarium in Chicago who earned her master’s and doctoral degrees at the University of Washington. She was back in Seattle recently to give a talk at the Pacific Science Center about the latest in exoplanet research and the prospects for figuring out if life exists on any of them. The talk complemented the Mission: Find Life! astrobiology exhibit that is presently running in the center’s Portal to Current Research space. (Check our previous post and podcast for more about the exhibit.)

While a majority of the early exoplanet finds by the Kepler mission were of gas giants on the order of Jupiter, Walkowicz said that was because bigger planets are easier to find because they block more light when they pass in front of, or transit, their host stars.

“The smaller planets that are more like Earth that might be out taking a full year to go around their star are even harder (to find) because you have a very small signal that takes years and years to repeat,” she said. As time went on, more and more smaller exoplanets were detected.

It turns out that, “The things that are a little bit bigger than Earth and little bit smaller than Neptune are super common,” Walkowicz noted. This threw planetary formation theorists for a loop. They’d spent careers constructing formation models that did not result in planets of that size because we don’t have any in our solar system. While journalists tend to rush toward a declaration of some of these planets as “Earth-like,” Walkowicz said that’s typically premature.

“It’s not the discovery of life around other stars,” she said of the finding exoplanets in this size range, “but it does mean that there is a lot of real estate for us to look.”

Goldilocks lives in the habitable zone

Walkowicz discussed the concept of the so-called habitable zone around stars—an area that could be at the right temperature for liquid water to exist on a planet’s surface. This is a ballpark figure; she noted that distant astronomers looking at our solar system would declare Venus, Earth, and Mars all to be within our Sun’s habitable zone. Yet these are very different worlds and two of them are not particularly hospitable at present. The type and kind of starlight, a planet’s orbit, tidal heating, radiation protection, and the actual existence of water, ice, haze, or clouds all can make big differences for a planet’s potential habitability.

As we move forward, astronomers will look not just at exoplanets’ location, but also at their biosignatures, which Walkowicz explained are the, “signatures of the chemical species that make up a planet’s atmosphere and whether they mean that life can be there.” Finding oxygen, ozone, water, carbon dioxide, and methane all could be positive indicators for life. On the other hand, finding carbon monoxide in a planet’s atmosphere would mean life is less likely. But even the right ingredients don’t necessarily mean life exists.

Local help from VPL

VPL logoThe Virtual Planetary Laboratory (VPL) at the University of Washington is leading the way in looking at such biosignatures and interpreting what they could mean for varying planets around different types of stars. Having so many possible combinations can be on the confusing side.

“Planets are complicated,” Walkowicz said. “They’re not just spheres orbiting around a star that’s getting some illumination at some distance.”

“It’s usually just not one thing, its the balance of things overall. You have to be able to look at the complete picture in order to interpret what you find,” she added.

That is difficult to do at present, but a couple of future space telescopes will be able to help. The Transiting Exoplanet Survey Satellite (TESS) is scheduled to launch next March, and the James Webb Space Telescope is targeted for launch in October 2018. TESS will look for more exoplanets by watching for their transits in front of some 200,000 nearby stars. The Webb, according to Walkowicz, will look into the infrared and explore the plentiful small, red stars in the galaxy and try to take the spectra of the atmospheres of planets in orbit around them.

“In some cases, we’ll be able to get this chemical fingerprint of what the planet’s atmosphere is made up of,” Walkowicz enthused. She added that the VPL’s work will help astronomers decide which planets to study with the new space telescopes—it will be important to winnow the field down to the most promising candidates, as competing demands for time on these scopes will limit the observing opportunities for any one project.

We might well have a better idea if there’s life elsewhere in the not-too-distant future.


 

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Herschel’s observation of comets

To say that Woody Sullivan is interested in William Herschel would be quite an understatement.

“I have dressed up as Herschel for Astronomy 101 half a dozen times,” said Sullivan, a professor emeritus of astronomy at the University of Washington. He started a file on Herschel, the 18th and 19th Century astronomer, some 30 years ago, but can’t exactly pin down why he was so drawn to him.

“I have eclectic interests,” Sullivan said. “I’m always looking for what I call astronomy on the edges: astronomy and music, astronomy and astrology, history, literature, sundials.”

“Herschel was that way to some degree,” Sullivan added. “Perhaps that was it; I saw a fellow traveler there.”

Woody Sullivan

Prof. Woody Sullivan at the May meeting of the Seattle Astronomical Society. (Photo: Greg Scheiderer)

Sullivan noted that it was nine years ago that he started doing more serious research into Herschel with the intent to write a biography. While there have been many penned, including a couple in the last decade or so, Sullivan noted that none have been particularly scholarly, and so that’s a void he’s aiming to fill. After all of that research, the actual writing has begun.

“I do need to get on because I’m getting on,” Sullivan quipped. He spoke about his work at the most recent meeting of the Seattle Astronomical Society, discussing Herschel’s work on comets, about which few biographers have gone into much detail.

While his sister Caroline Herschel discovered eight comets, six of which bear her name, William never found one, though he came close a couple of times. He once reported a comet discovery, but the French astronomer Jean-Louis Pons had already found it a month before. Then in 1781 Herschel reported another comet discovery. But after six or eight months of observation, astronomers more skilled in the calculation of orbits found this new object to be in a nearly circular one well beyond Saturn’s. It was a new planet: Uranus.

First to “discover” a planet

“It’s hard to think about what a new planet means. What planets did we have before? We had the same planets that we had had since Ogg the caveman,” Sullivan noted. “Herschel was the first one to find a planet telescopically, and this made him instantly famous.”

William Herschel

William Herschel. (Photo: Public domain)

Herschel parlayed that into a gig as the court astronomer for King George III. It was actually a pay cut from Herschel’s work as a professional musician in Bath, but he supplemented his income by building and selling telescopes, and by marrying a rich widow. Herschel was mostly interested in deep-sky objects, but comets came to his attention on occasion, in part because he was interested in change.

“A comet is change par excellence,” Sullivan said. “It just appears in the sky, it’s different every day, you never know what’s going to happen.”

While Caroline wanted to discover them, William aimed to understand what they were. Sullivan noted that this wasn’t what most astronomers were doing then.

A different sort of astronomer

“Astronomy at that time was measuring accurate positions of things; planets and their moons and comets and stars for catalogs,” he said. “That’s why you had the Greenwich Observatory. The government was paying for that, not because they loved astronomy but they loved the navy, and you needed that for navigation.”

Herschel’s observations of the great comets of 1807 and 1811 were interesting. Sullivan pointed out that astronomers at the time thought there might be a planet or other object at the nucleus of a comet. Herschel was the first to claim he’d spotted one. When others couldn’t find it, Herschel chalked it up to the superior optics of his telescope. By the 1811 comet, he was trying to figure out if the nucleus reflected light from the Sun, or generated its own light. Herschel declared that the nucleus of this comet was perfectly round, and thus self-illuminated, because if it reflected light it would show phases. Sullivan, after poring through Herschel’s logs, concluded that he had fallen into a trap that scientists need to avoid.

“There’s just no doubt that he was picking and choosing the observations that fit into his concept,” Sullivan said. It was a bit of a reach to claim to be able to determine the roundness of an object of perhaps an arcsecond in width within the fuzzy coma of a comet.

“He’s getting all of his theory and observations mixed up,” Sullivan said. “This can get you in trouble.”

Though Herschel missed on this particular analysis, Sullivan noted that Herschel made some interesting conclusions, particularly in describing the tail of a comet as its atmosphere being pushed away by pressure from the Sun. Though it’s not the atmosphere, but dust and gasses, nobody to that point had really postulated that the Sun might be pushing on things. Other descriptions Herschel made of the mechanics of comets are not so far off from what is held true today.

Sullivan’s presentations are always interesting, and we look forward to the completion of the book and to learning about William Herschel, a fascinating character in the history of science.


 

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AstronoMay and more at PacSci

It’s been a month filled with astronomy at Pacific Science Center, and they’ll wrap it up big this weekend with their celebration of AstronoMay Saturday, Sunday, and Monday. According to Dave Cuomo, supervisor for science interpretation programs and the Willard Smith Planetarium at the center, there will be a lot going on.

“We will have expanded planetarium shows,” Cuomo said. “We will have lectures about astronomy featured on our Science on a Sphere exhibit. We will talk about astrobiology in some of those. We will have space scientists that visitors can speak with and talk about their study and research about astronomy. And, weather permitting, we will have some solar telescopes out so you can safely observe the Sun.”

Planetarium-palooza

Willard Smith PlanetariumThere’s a great variety of selections for shows in the planetarium. One that will run this weekend is called “The Search for Life.”

“It will be an exploration of the different ways that astrobiologists are looking for life, both in the solar system and outside of the solar system,” Cuomo said. That show is a great complement to the “Mission: Find Life!” exhibit about astrobiology that is presently in the center’s Portal to Current Research space. (See our post from last month for more about that.) Another show, titled “Let’s Explore Light,” is about the basic physics of light.

A third planetarium show called “The Skies of Ancient China,” created to complement the popular Terracotta Warriors exhibit at the center, looks at more than 4,000 years of Chinese astronomy. Cuomo noted that Chinese astronomers in the day had a pretty high-stakes job.

“They were hired by the emperor because the emperor ruled the Earth because he had the mandate from the heavens,” Cuomo explained, “so he needed to be able to know what was going to happen in the sky.”

The astronomers predicted planetary conjunctions and eclipses of the Sun and the Moon. Conjunctions in particular were considered omens of pending regime change, and, say what you will about whether the heavens influence lives on Earth, a couple of empires actually did flip at around the time of a conjunction. More amazing is the accuracy of both the Chinese astronomical observations and their record keeping.

“Modern astronomers have associated at least nine supernova remnants with ‘guest stars’ that the Chinese observed and recorded the location of,” Cuomo marveled. “There is also almost two thousand years of history of a returning star every 76 years, which we now know was Halley’s Comet.”

Cuomo found it interesting that there wasn’t much mythology around the heavens with the Chinese astronomers as compared to that in many other cultures. He and three of the center’s planetarians created the show with research help from the British Library, the Hong Kong Space Museum, and many others across the country and the world.

The daily schedule for planetarium shows is on the PacSci website and also on our Seattle Astronomy calendar page. We saw “The Skies of Ancient China” last week and found it to be exceptionally well done.

Solar eclipse

The astronomy doesn’t stop once May ends. The Pacific Science Center is gearing up for the total solar eclipse that will happen on August 21. The entire month of August will be PacSci “Up in the Sky.”

“We will talk about solar astronomy, observational astronomy, weather; anything that you look up to see, we’ll want to talk about,” Cuomo said. They’ll also have eclipse glasses on hand for safe viewing of the Sun, and probably some solar projectors for watching the eclipse.

Although the eclipse will only be partial in Seattle, the center plans to open early, at 8:30, that morning.

“We will have solar telescopes available and educators talking about the eclipse and the science of the eclipse,” Cuomo said. First contact—when the Moon starts moving across the face of the Sun—will happen at 9:08 a.m. at PacSci, and it will be over by 11:30. But they’ll have live feeds from other eclipse events from all across the country so you can keep watching.

Cuomo will be in Madras, Oregon for the total eclipse, along with other educators from the Pacific Science Center in partnership with Lowell Observatory. They’re leading a four-day trip to view the total eclipse. Space is limited; if you’re interested in going along, you can find out more online.


Podcast of our interview with Dave Cuomo

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Lots of great choices for astronomy events this week

There are tons of great astronomy events on the calendar this week, topped by the opening of the Museum of Flight’s Apollo exhibit and a visit from the Night Sky Guy.

Apollo

ApolloA couple of years in the making, the new Apollo exhibit opens Saturday, May 20 at the Museum of Flight, though museum members can get an early sneak-peek Wednesday evening. The exhibit includes the F-1 engine parts fished out of the Atlantic Ocean by Bezos Expeditions, an intact F-1, and many more great space exploration artifacts. Check out our recent article and podcast previewing the exhibit.

The Museum will also hold its annual Space Fest over the weekend with a variety of presentations, exhibits, and discussions focused on Apollo and the Moon.

The Night Sky Guy and Mars

Andrew Fazekas, aka The Night Sky Guy, is in Seattle for three talks at Benaroya Hall. Titled “Mankind to Mars,” the event will be an exploration of what it will take to get humans to the Red Planet. It’s produced in conjunction with the Mars miniseries created by the National Geographic channel. One show was Sunday afternoon, and Fazekas also appears on Monday, May 15 and Tuesday, May 16, both at 7:30 p.m.

Fazekas is the author of Star Trek: The Official Guide to Our Universe: The True Science Behind the Starship Voyages (National Geographic, 2016).

AstronoMay at PacSci

Pacific Science CenterAstronoMay is under way at the Pacific Science Center, and a couple of interesting events are on the calendar for this week. Astronaut Nicholas Patrick will host a viewing and discussion of the film A Beautiful Planet 3-D at 7 p.m. Tuesday, May 16. The film is a portrait of Earth from space captured by the astronauts aboard the International Space Station. Patrick will introduce the show and lead a Q&A session after. He’s now with Blue Origin; see our article about Patrick’s recent talk at Astronomy on Tap Seattle. Admission is $10, or $5 for science center members.

Then learn the ABCs of total solar eclipses, and get ready for the one that will be visible in parts of the United States in August, with Dennis Schatz, nationally recognized astronomy educator and Pacific Science Center senior advisor. Total Solar Eclipse 101 happens at 7 p.m. Wednesday, May 17. Cost is $5, free for members.

JWST

RiekeNASA’s next great space observatory, the James Webb Space Telescope (JWST), is scheduled for launch in October 2018. George Rieke, a professor of astronomy at the University of Arizona and science team lead for the Mid-Infrared Instrument (MIRI) that will fly onboard the scope, will speak at the University of Washington astronomy colloquium at 4 p.m. Thursday, May 18. The talk will focus on the capabilities of JWST, emphasizing the advances over present (and even some future) facilities, with examples of the science it will enable.

Club events

Rose City Astronomers will hold their monthly meeting at 7:30 p.m. Monday, May 15 in the OMSI auditorium in Portland. It will be their annual swap meet and astronomy information fair. The club, along with OMSI and the Vancouver Sidewalk Astronomers, will host public star parties at 8 p.m. Saturday, May 20 at both Rooster Rock State Park and L.L. “Stub” Stewart State Park.

The Island County Astronomical Society will hold its monthly meeting at 6:30 p.m. Monday, May 15 at the Oak Harbor Library.

The Seattle Astronomical Society monthly meeting will be at 7:30 p.m. Wednesday, May 17 in room A102 of the Physics/Astronomy building on the University of Washington campus in Seattle. Guest speaker Woody Sullivan, professor emeritus of astronomy, will talk about the contributions of William and Caroline Herschel to our understanding of comets. Sullivan is working on a biography of William Herschel.

The Tacoma Astronomical Society plans one of its free public nights for 9 p.m. Saturday, May 20. The topic for the indoor presentation will be black holes. If the weather cooperates they’ll break out the telescopes for some observing.

TJO

Theodor Jacobsen ObservatoryThe bi-monthly open house at the UW’s Theodor Jacobsen Observatory is set for 9 p.m. Wednesday, May 17. The topic for the evening’s astronomy talk has not been published. It’s a good idea to make reservations early, as these typically are filled up. Volunteers from the Seattle Astronomical Society will conduct tours of the observatory dome and, weather permitting, offer a look through its vintage telescope.

Planetarium shows

The Bellevue College Planetarium will run a public show about black holes at 6 p.m. and again at 7 p.m. on Saturday, May 20. The show will include animations of the formation of the early universe, star birth and death, the collision of giant galaxies, and a simulated flight to a super-massive black hole lurking at the center of our own Milky Way Galaxy. It’s free, but reservations are suggested. See the website for registration info and other details.

The Willard Smith Planetarium at the Pacific Science Center offers a variety of shows every day. Their full schedule is posted on our calendar page, where you can also scout out more future astronomy events.

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Meeting the Martians and getting snapshots of far-away planets

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.

Mars Mudstones

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.”

Bob Abel

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.

Gerard

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.”

Since Gerard gave the talk NASA announced an independent review of WFIRST that could change its timeline and instrumentation.


The next Astronomy on Tap Seattle gathering is set for May 24 at Peddler Brewing Company.

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