Tag Archives: Rodrigo Luger

Celebrating three years of Astronomy on Tap Seattle

Astronomy on Tap Seattle observed its third anniversary last month, and celebrated by breaking format, with updates on talks from the past year and some new tidbits of information.

One of the fun new items was a story by Dr. James Davenport about how he helped convince NASA to use the Kepler space telescope to take a selfie of Earth.

“This is a personal story,” Davenport explained. “This is a story about an image that we asked NASA to take, and they were kind enough to take it.”

It took more than a year of cajoling, using the usual bureaucratic channels and also social media campaigns to get the shot.

Selfie from space

Selfie from space: Earth as observed by Kepler in December. (Image: NASA)

“We guilted them into taking this picture that we wanted for no other value than just to have this amazing image,” Davenport said. He noted that NASA has a long tradition of taking photos of the home planet, starting with the “Earthrise” photo from Apollo 8 and going through the “Pale Blue Dot” image from Voyager and the more recent pic of Earth from Cassini at Saturn.

The Kepler telescope usually points away from Earth, but sometimes NASA moves the aim to look at a different part of the sky, and that’s when Earth can move through the scope’s field of view. This happened on December 10, 2017, and that’s when Kepler got this shot. Now, Kepler usually looks a dim objects that are far away—a typical exposure is about 30 minutes. This isn’t the best setup for taking a photo of Earth from about 94 million miles.

“We expected it to look like a bright mess,” Davenport said. “We were not disappointed.”

It’s a personal story for Davenport because he was doing an entirely different thesis project for his Ph.D. program when Kepler came on line. He was so excited about the hunt for exoplanets that he ditched his other thesis and started working with Kepler.

“It represented a huge turning point in my career,” he said.

Polarimetry

Back in September Kim Bott gave a talk about how she and other astronomers are using polarimetry to try to figure out if exoplanets are habitable or inhabited. Since then she’s done some actual modeling of Venus at various phases to see if polarimetry can tell us what we need to know.

The short answer appears to be no, at least for right now. The instruments simply aren’t senstive enough to detect the changes in light wiggle that might reveal a variety of indicators.

“It’s just a couple orders of magnitude,” Bott explained, “so something that we might be able to obtain within the next decade” as the technology improves.

Trappist 1

The planets around the star Trappist 1 have attracted a lot of interest since they were discovered beginning in 2015. There are seven planets in all orbiting this red dwarf star; they’re all roughly the size of Earth, and three of them orbit within the star’s habitable zone.

Trappist-1 system“These are planets that could be a lot like Earth, that could potentially support life,” said Dr. Rodrigo Luger, adding that this is an active area of research. Luger said it’s interesting that all seven planets are in orbital resonance.

“There’s a very distinct pattern linking the orbital periods of all seven planets,” he said. Interestingly enough, this resonance and the gravitational influence the planets have on each other makes the transit times of the planets change from orbit to orbit.

“It’s just like when you’re at the bus stop here in Seattle,” he explained. “Sometimes the bus comes early, sometimes it’s on time, sometimes it’s late. Transits are the same way.”

This gives astronomers a lot of information about the system.

“By studying the transit time variations you can actually get the mass of the planets because you know how strong their gravity is,” Luger said. “Because of the geometry of the system we can get the radius of the planets—the size when it transits the star—and by doing some clever numerology and math we can figure out their mass. If you have the radius and the mass you actually have the density, so you have an idea what these planets are made of.”

It turns out that the Trappist planets mostly appear to be of lower density than Earth and Venus. This could mean that the planets have large amounts of water or large hydrogen atmospheres.

“These planets are going to be studied a ton in the next decade to figure out if in fact they are habitable,” Luger said.

Astronomy on Tap Seattle co-founder Brett Morris noted that much future study of exoplanets was to have been done by the James Webb Space Telescope, but the recent decision to delay the launch of that instrument has been disappointing to many.

“That affected some people a lot,” Morris said. “Some of those people were me!”

When the announcement that the launch would be pushed out to 2020 was made last month, Morris and others were coming up on what was an April 6 deadline to propose observing targets for the Webb.

“We were all working really hard because this telescope is super cool and it’s going to be the one that’s going to tell us if these planets are actually habitable and what’s going on in their atmospheres,” Morris noted. “Then the rug got pulled out from under us.”

R-process is better than your process

Back in July Trevor Dorn-Wallenstein told the AoT crowd how the universe makes beer for us. Last month he explained how heavier elements are made, and how we now know that theory to be true.

Dorn-Wallenstein explained how elements are made within stars. Typically, when neutrons collide with protons, they are captured. Nature stabilizes this through a process known as beta decay; the neutron just turns into a proton. This causes the release of an electron and a neutrino, or maybe an anti-neutrino.

“The jury is still out on whether neutrinos are the same as anti-neutrinos,” Dorn-Wallenstein observed. In any case these particles just go away.

“What we’ve really done here is we’ve converted one of those neutrons into a proton, and in doing so we’ve made a whole new element,” Dorn-Wallenstein said. “We’ve gone from hydrogen to helium, though both are unstable and have oddball numbers of neutrons.”

This happens slowly—that’s why it’s called the s-process. It occurs in low-mass stars, which can make strontium, barium, and lead.

Then there’s the r-process, which is rapid. In this process neutrons get bombarded onto atomic nuclei so quickly that beta decay can’t happen, and you get ridiculously unstable nuclei. Eventually neutron capture either slows, or it becomes so unstable that beta decay happens all at once, and BAM, you’re making silver, gold, platinum, and other heavier elements.

Essentially to do this you need three big explosions. First you need two supernovae to leave behind a pair of neutron stars. Then the neutron stars need to merge. Their collision is called a kilonova.

“There’s a lot of free neutrons around, and maybe those free neutrons are created rapidly enough that the r-process occurs,” Dorn-Wallenstein said. To confirm this you’d need to see evidence of a neutron star collision, a gamma-ray burst from the event, and follow up to make sure r-process elements were actually being formed. That’s exactly what happened when LIGO detected gravitational waves from a neutron star merger back in August.

“We found evidence that r-process elements were being formed and it confirmed that neutron star mergers were the dominant sites of the r-process,” Dorn-Wallenstein concluded.

Exoplanet instruments

Back in August Lupita Tovar did a talk about LUVOIR and SAMURAI and how they will help us map exoplanets. Her latest interest is the Transiting Exoplanet Survey Satellite—TESS—which launched April 18. Its primary mission is to search for Earths and super-Earths. While Kepler looked at a relatively small swath of sky, TESS will scan about 80 percent of the sky and observe some 200,000 stars.

“You can imagine how many more things we’re going to be finding,” Tovar marveled. TESS will look at brighter stars than Kepler was able to observe, and will be a constant source of data. It will send back full-frame images every half hour or so, and about 200,000 smaller “postage stamp” images every two minutes.

“What that translates to is a whole lot of data that’s going to be coming down from this telescope,” Tovar said. “You’re going to get a lot of planets—planets everywhere!”

There could be as many as 20,000 new ones; Tovar said many will likely be gas giants, which are easier to spot.

SPAMS a lot

UW student Aislynn Wallach is involved in a project called The Search for Planets Around post-Main Sequence Stars—SPAMSS.

The question is what becomes of planets like Earth when their host stars become red giants.

“They blow up to a larger size, much like a marshmallow in a microwave,” Wallach said. After that the stars become white dwarfs. The prospects for the close-in planets aren’t good.

“Anything inside (the expanded red giant) will probably be disintegrated,” Wallach noted. “That’s what we’re looking for we’re trying to find—these broken up planets around stars like the Sun.”

The approach is to look at the spectra of white dwarf stars. If we spot heavier elements in those spectra, the elements will have come from ripped-up planets. If those materials were part of the star, they would sink quickly from its surface.

For her search Wallach has been using the ARCSAT (Astrophysical Research Consortium Small Aperture Telescope) at the Apache Point observatory in New Mexico. Results of her search so far: nothing.

“Nothing is still a result!” She laughs. The search continues.

The beautiful music of the universe

An interesting new approach to data is to turn it into sound. Locke Patton is doing this with the brightness of supernovae. Brighter data points are assigned higher musical pitches. The process is called sonification.

“We don’t just look at it, we listen to it,” said Patton of the data.

Sadly, his recording of a supernova sound didn’t play—a rare technical glitch at Astronomy on Tap Seattle. He sang it. Sort of! You can hear a recording here.

###

Please support Seattle Astronomy with a subscription through Patreon.

Become a Patron!

 

Share

Exoplanets, killer stars, and beer

Astronomers are busy trying to figure out if and when an enormous flare from the Sun might fry us—or at least zap our mobile phones—and also are looking for planets like Earth in orbit around other stars. Those were the subjects of the talks at Astronomy on Tap Seattle last week at Bad Jimmy’s Brewing Company in Ballard. The Kepler Space Telescope figured in both talks.

DSC_0008

Rodrigo Luger spoke about the hunt for other Earths in a presentation at Astronomy on Tap 5 last week. Photo: Greg Scheiderer.

University of Washington astronomy graduate student Rodrigo Luger led off the evening’s festivities with a talk titled, “Syzygies in Silhouette: The Search for Alien Earths.” A syzygy is simply an alignment of three astronomical bodies, and when that happens we can detect a planet orbiting a distant star; the planet essentially casts its shadow on Earth, and we can measure the slight drop in brightness of the star.

Luger called Kepler “by far the most successful planet-detection mission.”

“We currently know of more than five thousand potential planetary objects around other stars, which is amazing,” Luger said, noting that, twenty years ago, we knew of maybe a couple. “It’s a fascinating time for exoplanet science.”

Luger pointed out that the number of discoveries is especially incredible when you consider that Kepler is staring at such a tiny patch of the sky.

“If there are thousands of planets (in that field), imagine how many there are in the entire Milky Way,” he marveled.

Where is Earth 2.0?

One frustration is that Kepler has yet to find an exoplanet that is a close match for Earth. Luger said planets our size are a bit tougher to tease out of the background noise that Kepler collects. That may change, he said, when NASA launches the Transiting Exoplanet Survey Satellite (TESS) in 2017.

“TESS is different; rather than looking at a tiny patch of the sky, it’s going to look at the entire sky,” Luger said.

“It’s going to focus primarily on smaller stars,” he added, noting that looking at these makes it “much easier when you want to detect Earth-like planets.”

By coincidence, the day after Luger’s talk the Kepler team announced the discovery of planet Kepler 452b, the closest match yet to Earth.

The Sun takes aim

James Davenport makes a point during his talk about solar activity. Photo: Greg Scheiderer.

James Davenport makes a point during his talk about solar activity. Photo: Greg Scheiderer.

James Davenport, who just earned his Ph.D. in astronomy at the UW, uses Kepler in his work as well. His main purpose is to better understand our own nearby star, the Sun, and figure out when it might aim a solar flare or coronal mass ejection at us.

Davenport’s talk, “How Stars Keep Active as They Age,” started with a history lesson. Back in 1859 English astronomer Richard Carrington was making daily sketches of his observations of the Sun. He was tracking a huge sunspot and, as he watched it, a couple of enormous bright patches appeared. It turns out that this was the first observation of a solar flare. About twelve hours later, people on Earth saw the most stunning aurorae in centuries.

“The sky lit up red and green, and you could see it as far south as Cuba,” Davenport said. “It was this magnificent, incredible event.” The penny dropped and scientists recognized that the solar flare was the cause of the aurora. The flare created such an electric surge that some telegraph operators suffered burns.

Don’t mess with that

“If a giant solar flare like the one that Carrington observed impacted the Earth today, it would cause trillions if not hundreds of trillions of dollars of damage,” Davenport observed, noting that TV, the Internet, and your mobile phone could get fried. “It could ruin the global economy. It would be a disaster of untold proportions, and there’s noting we can do about it. The sun is just going to hurtle these flares at us whenever it decides to.”

Davenport noted that this isn’t just an academic discussion; a flare of that magnitude barely missed Earth in July 2012.

“If it had been launched a few days earlier and it hit the Earth, we’d still be recovering,” he said.

The Sun is pretty unpredictable, Davenport said. Huge sunspots turn up about every 25 years, but there aren’t always giant flares that go with them. The good news is we’re learning more about the Sun all the time. Data from the Solar Dynamics Observatory is like an HD movie of the Sun that plays 24/7. There is always someone watching. Astronomers also are doing computer models of the Sun to try to figure out more about its processes. Kepler comes in to play by helping us look at thousands of stars of all ages. The younger ones tend to be more active, while older stars like the Sun are relatively serene. It wasn’t always that way for old Sol.

“The young Sun had bigger flares and more of them, and probably dumped out a hundred times more x-rays with every single flare,” Davenport said. “You don’t want to stand in the way of that.”

Cupcakes and beer

Mmmm. Cupcakes.

Mmmm. Cupcakes.

A lifetime of soaking up astronomical minutiae finally paid off for Seattle Astronomy at Astronomy on Tap 5 as our team, the Wild Guessers, took home top honors in both Pluto trivia contests of the evening. The prize: treats from Trophy Cupcakes decorated with images of the highly active Sun. We learned that Bad Jimmy’s strawberry mango hefeweizen goes well with cupcakes. Just watch out for the CMEs: cupcake mass ejections.

Astronomy on Tap Seattle hosts events at Bad Jimmy’s monthly. The next one is scheduled for August 26.

Share