The 230th Meeting of the American Astronomical Society: Tuesday

Posted by Alison Klesman
on Wednesday, June 07, 2017

These galaxies are just a few of a a larger sample of bright, star-forming galaxies -- and they're all gravitationally lensed. // NASA, ESA, and J. Lowenthal (Smith College)

Tuesday at the AAS was a trip through a number of different astronomical fields, from stars to galaxies and back to the solar system we call home.

The day kicked off with a press conference on “inconstant stars.” Rodolfo Montez from the Smithsonian Astrophysical Observatory spoke about work charting R Aquarii’s X-ray jets. The R Aquarii system contains a white dwarf and a red giant star, whose “volatile stellar relationship” has resulted in a breathtaking nebula that’s been shaped by outbursts from the white dwarf. Now, thanks to the Chandra X-ray observatory, astronomers can watch hot material moving through the nebula and wind back the clock to determine when these blobs were first generated.

The next presentation, by Thomas Kirkman of St. John’s University, outlined the pulse acceleration of a Cepheid variable star in a binary system with a smaller, cooler star. Rather than behaving as expected, the period of this variable star is changing by minutes per decade – much more quickly than other systems. Then, Lorne Nelson of Bishop’s University described the discovery of the shortest-period pre-cataclysmic variable. What does all that mean? Basically, Nelson’s team has found two stars circling each over every 71.22 minutes. One is a white dwarf, while the other is a brown dwarf about 67 times the mass of Jupiter. The white dwarf’s radiation is responsible for heating one side of the brown dwarf, but the cooler side of the companion falls below current detection limits. The system is pre-cataclysmic because no mass transfer is taking place yet – but because the two objects are spiraling inward, eventually (in about 250 million years) they’ll be close enough that the white dwarf will suck matter from its companion, causing it to flare.

The final presentation covered a new database of flaring m dwarfs created with gPhoton, a project led by Chase Million of Million concepts. Million explained that finding these flares has immense implications for planets that might be circling these stars, as flares might hinder – or help – a planet’s habitability for Earth-like life.

The day’s second press conference moved us from galactic stars to intergalactic astronomy, covering a plethora of discoveries that have far-reaching implications for our universe and our understanding of it. Jason Chu from the University of Hawaii’s Institute for Astronomy highlighted the importance of the European Space Agency’s Herschel mission. Although now deactivated, data from the orbiting observatory has played a key role in providing astronomers with a previously unattainable look at galaxies in crucial infrared wavelengths. James Lowenthal of Smith College spoke about how gravitational lensing has brought us the brightest infrared galaxies in the universe, allowing astronomers to peer closely at these objects to determine just why they’re forming so many stars – a currently unanswered question, if you recall Caitlin Casey’s Monday plenary talk. Jack Burns of the University of Colorado, Boulder, explained how the kinetic energy released as galaxy clusters form is “the biggest bang since the Big Bang.” Looking for “shocks” that occur in the gas surrounding smaller protoclusters as they fall together to create larger galaxy clusters helps astronomers learn more about this vital process, which has built the universe into the one we see today. And yet, he said, his current work characterizing the gas in these clusters has raised more questions than answers, showing just how much we still have to learn.

Benjamin Hoscheit of the University of Wisconsin, Madison, rounded out the press conference speaking about the large local void that appears to surround the Milky Way (and, indeed, our Local Group). Galaxies throughout the universe tend to fall into either clumps or voids; while this information is well known, what’s not well known is how living in a void might affect our view of the universe. Hoscheit explained that the “tension” we currently observe in the Hubble constant, which tells us how fast the universe is expanding, could be explained if we’re observing from inside a large void. The effects of this void, and of the mass beyond it, might contribute to the reason astronomers get different values when they measure the Hubble constant using nearby and faraway indicators. 

Konstantin Batygin's talk on Planet Nine was entertaining and informative. // Astronomy: Alison Klesman

I ended my Tuesday at the meeting by attending two plenary talks. The first, “Planet Nine from Outer Space,” was a fantastic overview by Konstantin Batygin of Caltech on our theorized-but-not-yet-found ninth planet. He opened by taking the audience through the history of discovering planets by means other than the naked eye – which, admittedly, has happened only twice. Then he went on to describe the discoveries of Sedna, 2012 VP113 (nicknamed “Biden”), and several other Kuiper Belt Objects whose orbits are suggestive of the presence of a ninth planet in the solar system with a mass equal to or greater than 10 Earth masses. This planet – Planet Nine – remains speculative, but evidence is mounting for its existence as more and more objects are found with orbits that indicate, at least through modeling, that they’ve been affected by not only Neptune, but by a large body much farther out in the solar system as well. I’m definitely glossing over lots of the details, here, but the talk was both well executed and, I admit, extremely convincing. 

As an aside, if you live within driving distance of Chicago, I highly recommend the Planet Nine show at the Adler Planetarium, which I was lucky enough to catch during my last trip there. The show includes much of the data and animations Batygin included in his talk, as well as commentary from his fellow planetary scientist, Mike Brown, who led the team that discovered Sedna.

The last plenary talk I attended was “Flows and Flares Around the Nearest Supermassive Black Hole – Sgr A*” by Daniel Wang from the University of Massachusetts. My most recent work had focused on supermassive black holes, albeit ones much more active than the one in the center of our Milky Way. Nonetheless, Wang’s talk on the behavior, past and present, of Sgr A* (the shortened version of Sagittarius A*, by the way, the name of the Milky Way’s 4 billion-solar mass supermassive black hole), discussed how our observations of the closest supermassive black hole to Earth can help us understand the evolution of our galaxy and the behavior of both active and quiescent black holes in other galaxies. He discussed the X-ray and infrared flares seen from Sgr A*, as well as astronomers’ best guesses for their cause: magnetic events like the ones that cause flares on the Sun, or possibly even asteroids or planets around those stars that are unlucky enough to fall within the black hole’s sphere of influence and disrupt its accretion disk in the process.

In addition to the talks and press conferences, I even managed to catch up with some people you'll know from the pages of the magazine: Martin Ratcliffe and Liz Kruesi. All in all, it was a successful day filled with amazing announcements and fascinating science!

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