Alpha Centauri at a Crossroads by Tom Ayres Contents

Chandra News Chandra News Issue 24 Spring 2017 Alpha Centauri at a Crossroads by Tom Ayres Contents Alpha Centauri at a Crossroads �� 1 Director’s Log � � � � � � � � � � � � � � � � � 8 Project Scientist’s Report � � � � � � � � � � � � � � 10 Program Manager’s Report �� 11 Chandra Source Catalog �� 12 Authentic Data Inquiry a Focus in STEM Programs � � � � � � � 12 HiPS: the Future of Chandra Data Visualization � � � � � � � � 14 Recent Updates to Chandra Calibration � � � � � � � � � � 15 Michael Juda (1959–2016) � � � � � � � � � � � � � 16 ACIS Update � � � � � � � � � � � � � � � � � 18 Martin Zombeck (1936–2016) � � � � � � � � � � � � 19 HRC Update � � � � � � � � � � � � � � � � � 20 HETG Update � � � � � � � � � � � � � � � � � 21 LETG Update �� 26 CIAO 4.9 and Beyond � � � � � � � � � � � � � � � 29 The Results of the Cycle 18 Peer Review � � � � � � � � � � 32 Einstein Fellowship Program � � � � � � � � � � � � � 36 2016 Press Releases � � � � � � � � � � � � � � � 37 An August Week: Chandra Science for the Next Decade � � � � � � 38 The Chandra Newsletter appears once a year and is edited by Rodolfo Montez Jr., with editorial assistance and layout by Tara Gokas. We welcome contributions from readers. Comments on the newsletter, or corrections and additions to the hardcopy mailing list should be sent to: [email protected]. Follow the Chandra Director's Office on Facebook, Google+ and Twitter (@ChandraCDO). Spring 2017 1 Alpha Centauri at a Crossroads The two larger stars, Alpha Cen A and B, are in a relative- ly tight 80-year orbit, about the size of the outer Solar Sys- Tom Ayres tem. Tiny C, not much bigger than Jupiter, revolves around Center for Astrophysics and Space Astronomy the central pair at a great distance, a few hundred times that University of Colorado of Pluto from the Sun, taking perhaps half a million years Boulder, Colorado to make a full circuit. C just happens to be on the sunward At the Dillon Dam Brewery side of AB at the moment, temporarily claiming the honor “Proxima.” iz and I were celebrating New Year’s Eve up in the Alpha Cen A is an early-G-type dwarf, almost identi- Lmountains, at the Dillon Dam Brewery, with our friend cal to our Sun, although slightly more massive, larger, and Sally. During the lull after the band’s first set, Sally turned more luminous. Its companion, Alpha Cen B, is an ear- to me and asked, slyly, “So, Mr. Astronomer, what’s up with ly-K star, slightly less massive, smaller, and dimmer than the nearest star?” I hesitated, wary of an ASTRO-101 trick the Sun. Stellar structure studies suggest that the system is question from the mischievous Sally, an education spe- metal-rich, about twice solar, with an age of perhaps 6 bil- cialist. Accordingly, I launched into a discussion of all the lion years, somewhat older than the Sun (Flannery & Ayres amazing new things we astronomers were learning about 1978; Eggenberger et al. 2004). our Sun, especially why this cool star (if you consider 6000 In fact, the nearby hierarchical triple contains exam- Kelvin “cool”) has a super-hot, million degree outer atmo- ples of all the most common types of the Milky Way’s cool sphere, the corona. (Mention of the solar “coronal heating stars: those that sustain outer convective envelopes. These problem” caused Liz, of the biotech world, to glaze over “late-type” stars often are afflicted by surface magnetic a bit: she had heard all this before. To be sure, I often get “starspots” (whose intense fields suppress vertical kinetic the same response from colleagues on the “Dark Side,” al- transport of energy, leading to local darkening); the heart of though to be fair, AGN also have hot coronae and their own stellar activity. This is what powers the Sun’s Space Weather, coronal heating problem.) I continued with an impassioned mentioned earlier, with its numerous potentially bad con- description of all the good that the Sun does for our Earth, sequences for our technological civilization (GPS and cell glossing over the bad stuff coming up in the far distant fu- phones at risk, need I say more?). ture (as the Sun inexorably brightens), except to mention Breakthrough Starshot: Voyage to Alpha Centauri the impact of solar “Space Weather” on our planet, reason As I drifted into the discussion of magnetic activity, I enough to keep a watchful eye on our nearby star. sensed I was in danger of losing my—albeit small, though “Very cute, Tommy,” Liz interrupted, “but you know Sal- so far politely attentive—audience, so I decided to amp up ly really was asking about the next nearest star.” “Well, nice the Alpha Centauri narrative. “Hey Sals,” I asked, “have you try,” I thought. So, I shifted gears into a new mini-lecture heard about the crazy new project called Starshot, to send a about “Proxima b,” an Earth-sized, probably rocky, planet swarm of nanobots to Alpha Centauri sometime this centu- in the Habitable Zone of Proxima Centauri, a diminutive ry?” Liz knew about this already, and rolled her eyes brief- red dwarf that still holds the title of the Sun’s nearest stellar ly. I went on to describe the out-of-the-box idea from the neighbor. But I didn’t stop there. I went on to opine that Cover image: 2MASS near-IR field around Alpha Centauri A Proxima was pretty wimpy, as stars go, but, remarkably, has and B (center black dots) with superimposed montage of Chan- a couple of bigger, more sunlike siblings close-by. Together, dra X-ray imaging (blue) of the pair over the past 15 years (see expanded view in inset image). Full map is about 0.5° on a side. these three stars comprise the Alpha Centauri system. Figure 1: Rogues gallery: Sun, the Alpha Centauri stars, and Jupiter to scale. 2 CXC Newsletter Breakthrough Initiatives Foundation to launch credit-card The Solar-Stellar Connection sized “starchips,” carried by laser-propelled light sails, for a Thankfully—for Liz and Sally—the band returned from decades-long trip to nearby stars, ultimately to photograph, its break, and the dancers re-took the floor, in anticipation up close and personal, any habitable planets around them. of the New Year only an hour or so away. With my compan- I explained that the nearest stars are in fact unimaginably ions otherwise diverted, my thoughts wandered back to my far away. For example, our most advanced rocket-propelled first encounters with Alpha Centauri, culminating in my spacecraft—New Horizons, which recently flew past Plu- more recent high-energy adventures with Chandra. to—would need about a thousand centuries to reach Alpha I, and my colleagues, have long been interested in Al- Centauri, even at its record speed. pha Cen AB because they are so similar to the Sun; perfect To break the “Tyranny of the Rocket Equation,” Starshot subjects for what we call the “Solar-Stellar Connection.” envisions a one-way trip, traveling fast and light, relying on We know a lot about the Sun for the simple reason that it external propulsion. A giant Earth-based laser “beamer”— is only light minutes away, whereas the nearest stars are effectively a square-kilometer optical telescope—boosts the several light years, or more. However, the Sun is just one starchips to a stunning 20% of lightspeed. Even so, the jour- example of a G-type star at a particular stage of evolution, ney to Alpha Centauri would take more than twenty years formed with a specific set of initial chemical abundances, (with an another 4.3 years for any transmissions from the seed magnetic fields, rotation rate and other properties that nanobots back to Earth). might, or might not, be representative of G-type stars in The beamer blasts the photon-sails on their way, staged general. It’s like choosing a person from the crowd at the from a mother ship in high Earth orbit; but also receives, decades later, the faint laser downlinks from the starchips Dam Brewery, and examining her carefully to deduce what as they race through their brief, hours-long encounter with human beings are all about. Sure, you would learn a lot, Alpha Cen. Because the journey has multiple hazards— but then again there would be a lot you would miss. It’s the mainly interstellar dust and gas along the way—you have to same idea with the Solar-Stellar Connection: build a ba- send many, perhaps thousands, of the nanobots to hope for sic framework anchored in the Sun, then extend outward a few to survive. through—necessarily more superficial—consideration of Alpha Cen is an obvious first target of Starshot, because the more remote stars. second closest—“Barnard’s Star,” an unremarkable old red Back in the 1970’s, when I was a grad student at Colora- dwarf—is a couple of light years further on. Also, there are do, then postdoc at the Harvard-Smithsonian CfA, we were three possible hosts for habitable planets in the Alpha Cen pretty much stuck analyzing optical activity indicators of system, and we already know there’s at least one, Proxima b. the stars, like the faint “chromospheric” cores at the bot- Wacky as it might seem, Starshot is the only way, with toms of the strong K and H resonance absorption lines of foreseeable technology, to explore the nearest stars. Thus, singly ionized calcium (at 3933 Å and 3968 Å). The more it’s worth, well, a shot. dependable X-rays (symptomatic of million-degree coronal gas) were mostly beyond reach. Aside from the Sun, only very intense emissions from compact binaries with neutron stars or black holes were known at the time. The chromosphere, itself, is a temperature inversion layer in the solar atmosphere about 500 kilometers above the Sun’s visible surface, something like the Earth’s Ther- mosphere.

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