Caltech’s Planet Hunter: A Conversation with Dimitri Mawet

first_img faithfernandez More » ShareTweetShare on Google+Pin on PinterestSend with WhatsApp,Virtual Schools PasadenaHomes Solve Community/Gov/Pub SafetyCitizen Service CenterPASADENA EVENTS & ACTIVITIES CALENDARClick here for Movie Showtimes Associate Professor of Astronomy Dimitri Mawet Credit: Lance Hayashida/CaltechThe star HR 8799 has three planets (b, c, and d) that can be seen with the vortex coronagraph. The ‘X’ marks the nulled-out star’s position. Credit: E. Serabyn, D. Mawet, and R. Burrus/Caltech/JPLAssociate Professor of Astronomy Dimitri Mawet has joined Caltech from the Paranal Observatory in Chile, where he was a staff astronomer for the Very Large Telescope. After earning his PhD at the University of Liège, Belgium, in 2006, he was at JPL from 2007 to 2011—first as a NASA postdoctoral scholar and then as a research scientist.Q: What do you do?A: I study exoplanets, which are planets orbiting other stars. In particular, I’m developing technologies to view exoplanets directly and analyze their atmospheres. We’re hunting for small, Earth-like planets where life might exist—in other words, planets that get just the right amount of heat to maintain water in its liquid state—but we’re not there yet. For an exoplanet to be imaged right now, it has to be really big and really bright, which means it’s very hot.In order to be seen in the glare of its star, the planet has to be beyond a minimum angular separation called the inner working angle. Separations can also be expressed in astronomical units, or AUs, where one AU is the mean distance between the sun and Earth. Right now we can get down to about two AU—but only for giant planets. For example, we recently imaged Beta Pictoris and HR 8799. We didn’t find anything at two AU in either star system, but we found that Beta Pictoris harbors a planet about eight times more massive than Jupiter orbiting at 9 AU. And we see a family of four planets in the five- to seven-Jupiters range that orbit from 14 to 68 AU around HR 8799. For comparison, Saturn is 9.5 AU from the sun, and Neptune is 30 AU.Q: How can we narrow the working angle?A: You either build an interferometer, which blends the light from two or more telescopes and “nulls out” the star, or you build a coronagraph, which blots out the star’s light. Most coronagraphs block the star’s image by putting a physical mask in the optical path. The laws of physics say their inner working angles can’t be less than the so-called diffraction limit, and most coronagraphs work at three to five times that. However, when I was a grad student, I invented a coronagraph that works at the diffraction limit.The key is that we don’t use a physical mask. Instead, we create an “optical vortex” that expels the star’s light from the instrument. Some of our vortex masks are made from liquid-crystal polymers, similar to your smartphone’s display, except that the molecules are “frozen” into orientations that force light waves passing through the center of the mask to emerge in different phase states simultaneously. This is not something nature allows, so the light’s energy is nulled out, creating a “dark hole.”If we point the telescope so the star’s image lands exactly on the vortex, its light will be filtered out, but any light that’s not perfectly centered on the vortex—such as light from the planets, or from a dust disk around the star—will be slightly off-axis and will go on through to the detector.We’re also pushing to overcome the enormous contrast ratio between the very bright star and the much dimmer planet. Getting down to the Earth-like regime requires a contrast ratio of 10 billion to 1, which is really huge. The best contrast ratios achieved on ground-based telescopes today are more like 1,000,000 to 1. So we need to pump it up by another factor of 10,000.Even so, we can do a lot of comparative exoplanetology, studying any and all kinds of planets in as many star systems as we can. The variety of objects around other stars—and within our own solar system—is mind-boggling. We are discovering totally unexpected things.Q: Such as?A: Twenty years ago, people were surprised to discover hot Jupiters, which are huge, gaseous planets that orbit extremely close to their stars—as close as 0.04 AU, or one-tenth the distance between the sun and Mercury. We have nothing like them in our solar system. They were discovered indirectly, by the wobble they imparted to their star or the dimming of their star’s light as the planet passed across the line of sight. But now, with high-contrast imaging, we can actually see—directly—systems of equally massive planets that orbit tens or even hundreds of AU’s away from their stars, which is baffling.Planets form within circumstellar disks of dust and gas, but these disks get very tenuous as you go farther from the star. So how did these planets form? One hypothesis is that they formed where we see them, and thus represent failed attempts to become multiple star systems. Another hypothesis is that they formed close to the star, where the disk is more massive, and eventually expelled one another by gravitational interactions.We’re trying to answer that question by starting at the outskirts of these planetary systems, looking for massive, hot planets in the early stages of formation, and then grind our way into the inner reaches of older planetary systems as we learn to reduce the working angle and deal with ever more daunting contrast ratios. Eventually, we will be able to trace the complete history of planetary formation.Q: How can you figure out the history?Once we see the planet, once we have its signal in our hands, so to speak, we can do all kinds of very cool measurements. We can measure its position, that’s called astrometry; we can measure its brightness, which is photometry; and, if we have enough signal, we can sort the light into its wavelengths and do spectroscopy.As you repeat the astrometry measurements over time, you resolve the planet’s orbit by following its motion around its star. You can work out masses, calculate the system’s stability. If you add the time axis to spectrophotometry, you can begin to track atmospheric features and measure the planet’s rotation, which is even more amazing.Soon we’ll be able to do what we call Doppler imaging, which will allow us to actually map the surface of the planet. We’ll be able to resolve planetary weather phenomena. That’s already been done for brown dwarfs, which are easier to observe than exoplanets. The next generation of adaptive optics on really big telescopes like the Thirty Meter Telescope should get us down to planetary-mass objects.That’s why I’m so excited about high-contrast imaging, even though it’s so very, very hard to do. Most of what we know about exoplanets has been inferred. Direct imaging will tell us so much more about exoplanets—what they are made out of and how they form, evolve, and interact with their surroundings.Q: Growing up, did you always want to be an astronomer?A: No. I wanted to get into space sciences—rockets, satellite testing, things like that. I grew up in Belgium and studied engineering at the University of Liège, which runs the European Space Agency’s biggest testing facility, the Space Center of Liège. I had planned to do my master’s thesis there, but there were no openings the year I got my diploma.I was not considering a thesis in astronomy, but I nevertheless went back to campus, to the astrophysics department. I knew some of the professors because I had taken courses with them. One of them, Jean Surdej, suggested that I work on a concept called the Four-Quadrant Phase-Mask (FQPM) coronagraph, which had been invented by French astronomer Daniel Rouan. I had been a bit hopeless, thinking I would not find a project I would like, but Surdej changed my life that day.The FQPM was one of the first coronagraphs designed for very-small-working-angle imaging of extrasolar planets. These devices performed well in the lab, but had not yet been adapted for use on telescopes. Jean, and later on Daniel, asked me to help build two FQPMs—one for the “planet finder” on the European Southern Observatory’s Very Large Telescope, or VLT, in Chile; and one for the Mid-Infrared Instrument that will fly on the James Webb Space Telescope, which is being built to replace the Hubble Space Telescope.I spent many hours in Liège’s Hololab, their holographic laboratory, playing with photoresists and lasers. It really forged my sense of what the technology could do. And along the way, I came up with the idea for the optical vortex.Then I went to JPL as a NASA postdoc with Eugene Serabyn. I still spent my time in the lab, but now I was testing things in the High Contrast Imaging Testbed, which is the ultimate facility anywhere in the world for testing coronagraphs. It has a vacuum tank, six feet in diameter and eight feet long, and inside the tank is an optical table with a state-of-the-art deformable mirror. I got a few bruises crawling around in the tank setting up the vortex masks and installing and aligning the optics.The first vortex coronagraph actually used on the night sky was the one we installed on the 200-inch Hale Telescope down at Palomar Observatory. The Hale’s adaptive optics enabled us to image the planets around HR 8799, as well as brown dwarfs, circumstellar disks, and binary star systems. That was a fantastic and fun learning experience.So I developed my physics and manufacturing intuition in Liège, my experimental and observational skills at JPL, and then I went to Paranal where I actually applied my research. I spent about 400 nights observing at the VLT; I installed two new vortex coronagraphs with my Liège collaborators; and I became the instrument scientist for SPHERE, to which I had contributed 10 years before when it was called the planet finder. And I learned how a major observatory operates—the ins and outs of scheduling, and all the vital jobs that are performed by huge teams of engineers. They far outnumber the astronomers, and nothing would function without them.And now I am super excited to be here. Caltech and JPL have so many divisions and departments and satellites—like Caltech’s Division of Physics, Mathematics and Astronomy and JPL’s Science Division, both my new professional homes, but also Caltech’s Division of Geology and Planetary Sciences, the NASA Exoplanet Science Institute, the Infrared Processing and Analysis Center, etc. We are well-connected to the University of California. There are so many bridges to build between all these places, and synergies to benefit from. This is really a central place for innovation. I think, for me, that this is definitely the center of the world. 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Required fields are marked *center_img Top of the News Get our daily Pasadena newspaper in your email box. Free.Get all the latest Pasadena news, more than 10 fresh stories daily, 7 days a week at 7 a.m. First Heatwave Expected Next Week Subscribe Business News Science and Technology Caltech’s Planet Hunter: A Conversation with Dimitri Mawet By DOUGLAS SMITH Published on Monday, May 18, 2015 | 11:08 am Pasadena’s ‘626 Day’ Aims to Celebrate City, Boost Local Economy Community News More Cool Stufflast_img read more

Didn’t see that coming: Five biggest surprises of the 2019 MLB season

first_imgChristian Yelich is doing amazing things this year for the Brewers, following up on his MVP season with a year that — if he continues to produce at a similar pace all year — will be incredibly great. But it wasn’t impossible to see that coming. After all, we just witnessed what he did in the second half of the 2018 season.What we’re doing today is looking at five people — well, four people and one team — doing things that would have seemed pretty damn impossible to believe just a couple of months ago. Four of them are very good surprises, but one is decidedly bad.  Why that’s, um, surprising: Despite his positional versatility — he’s started at least 50 big league games at second base, third base, left field and first base — and 16 homers in 149 games with a 112 OPS+ in 2018, the Marlins designated Dietrich for assignment last November. He remained in the world of free agency until late February, when he signed a minor league deal with the Reds. Dietrich had spent his entire big league career with the Marlins; a second-round pick by the Rays in 2010, he was traded to the Marlins after the 2012 season and made his MLB debut in May 2013. Kyle Freeland, RockiesWhat he’s doing: We’ll finish this piece with a downer. Sorry about that. Freeland is currently in Triple-A Albuquerque, a stunning development that was necessary after the lefty posted a 7.13 ERA in 12 starts for the Rockies. In those dozen games, Freeland allowed 16 homers, 47 earned runs and 68 hits in 59 1/3 innings. In his final three starts before the demotion, the lefty lasted a total of 8 2/3 innings, allowing 21 hits, 15 earned runs and almost as many homers (four) as strikeouts (five). And this wasn’t just a Coors Field thing; in six road starts, Freeland’s ERA was 5.04, too. In his first Triple-A start, Freeland allowed nine hits and four runs in five innings, striking out only two hitters.  Why that’s, um, surprising: I had an NL Cy Young vote last year, and I spent hours evaluating Freeland’s season before casting my ballot with his name in the fifth spot. His season wasn’t in the class of Jacob deGrom or Max Scherzer, or even Aaron Nola, my third choice. But Freeland was damn good at limiting damage. Last year he held opposing hitters to a .546 OPS with runners in scoring position; in 2019 that number is 1.051. Yeah. Expecting him to improve on 2018 might have been unrealistic, but not nearly as unrealistic as what has actually happened this year. Let’s jump in. MORE: Watch ‘ChangeUp,’ a new MLB live whiparound show on DAZNTommy La Stella, AngelsWhat he’s doing: La Stella has been the best Angels’ hitter not named Mike Trout this year. In his first 62 games in his new uniform, the lefty who spent the first five years of his career primarily as a utility/pinch-hitter type has become a stalwart in manager Brad Ausmus’ lineup. He’s popped 15 home runs to go with a .307 average and .900 OPS. Only one other AL hitter equals/beats La Stella’s numbers in those three categories: George Springer (though Trout is close, with a .295 average).Why that’s, um, surprising: In his 396 games in the major leagues heading into 2019, covering parts of five seasons, La Stella hit exactly 10 home runs. Last year for the Cubs, La Stella played in 123 games but only started 24 of those in the field. He was a reliable pinch hitter for manager Joe Maddon, posting a .402 on-base percentage in 90 pinch-hit plate appearances, but he only had six extra-base hits (five doubles and one homer) in that role. In the offseason, La Stella was traded to the Angels because he didn’t fit into Chicago’s plans, and he wasn’t a lock to make his new team’s roster this spring, either. Lucas Giolito, White SoxWhat he’s doing: Giolito leads the AL with his 2.46 FIP, is third in the league with his 2.28 ERA and is one of only 14 pitchers in the bigs to throw a shutout so far this season. In 75 innings, he’s allowed only 47 hits, 22 walks and four homers, while striking out 89. In his past seven starts, Giolito has a 0.88 ERA and he’s working on a scoreless streak of 22 innings. Yeah. Super impressive. Why that’s, um, surprising: Look, we’ve long wanted to believe in Giolito. He has the talent and the raw stuff to be successful in the big leagues. That’s why he was a first-round pick in the 2012 MLB Draft and why he was a centerpiece in the trade that sent Adam Eaton from the White Sox to the Nationals. But, yikes, 2018 was ugly. Giolito made 32 starts and posted a 6.13 ERA. To put that in perspective: In all of baseball history, only 10 pitchers have ever made at least 32 starts with an ERA worse than 6.13. Yeah. Any realistic hopes for the big right-hander in 2019 involved him staying in the rotation and being serviceable, at best. Minnesota TwinsWhat they’re doing: The Twins are tied with the Astros and Dodgers for best winning percentage in baseball (.672); Houston and Los Angeles have more wins (45 each to Minnesota’s 43), but they’ve both played three more games. With a 10.5-game lead over second-place Cleveland, the Twins own the largest division advantage in baseball. Their starters have the fourth-best ERA in the sport (3.59) and the fourth-best BB/9 (2.31). The offense has produced 14 more runs than any other team in baseball and 125 homers (Seattle tops MLB at 126). The team batting average (.274), OPS (.856), wOBA (.357) and wRC+ (124) all easily lead baseball. Why that’s, um, surprising: The Twins were pretty disappointing last year, so much so that manager Paul Molitor was fired after the season, a year after he was named the AL Manager of the Year for 2017. Those stats mentioned in the previous graph? Here’s where the Twins ranked in those categories in 2018: starter’s ERA (22nd, 4.54) and BB/9 (29th, 3.79), and on offense: runs (13th, 738) homers (23rd, 166), average (15th, .250), OPS (18th, .723), wOBA (18th, .313) and wRC+ (19th, 95).Derek Dietrich, RedsWhat he’s doing: In his first at-bat for the Reds, Dietrich slugged a three-run pinch-hit home run in the seventh inning of a game Cincinnati won 5-3. He hit two home runs against the Pirates in just his third start of the year, on April 7, then hit a solo homer and a two-run triple against the Cardinals on April 12 — and a folk hero was born. Dietrich had another two-homer game against the Giants on May 3 and a three-homer game against the Pirates on May 28. So far this year, Dietrich has 17 homers and a .984 OPS in just 169 plate appearances. last_img read more