The 232nd Meeting of the American Astronomical Society: Day 3

Posted by Jake Parks
on Thursday, June 7, 2018

Hello! I’m back again, checking in on the third and final full day of activities at the 232rd Meeting of the American Astronomical Society. It’s been an amazing week so far, with plenty to do and plenty to see, and today was certainly no exception. I’ve been shotgunned by astronomical science this week, so we’ll be diving into plenty of intriguing research and news in the days and weeks that follow. But for now, let’s explore some of the highlights from today, which range from our own Sun to erupting and escaping stars in other galaxies.

By utilizing iPosters, attendees are able to browse numerous studies with the flick of a finger. Credit: Jake Parks
Studying the Sun

As per usual, the meeting’s third day kicked off with a stroll through the early morning poster session before everyone took their seats for the first lecture of the day – The George Ellery Hale Prize Lecture: Amazing Journeys to the Hearts of Stars. The talk, given (unsurprisingly) by this year’s Hale Prize winner, Sarbani Basu, explored the wonderful world of asteroseismology. In this relatively young branch of astronomy, researchers probe the internal structures of stars by measuring the oscillations within them.

According to Basu, the Sun oscillates in millions of different modes simultaneously. (This is similar to how the overall sound of a guitar strum is due to multiple strings vibrating with unique modes.) By isolating the Sun’s different modes and studying how the waves propagate, researchers are able to investigate which physical processes play the most important roles in stellar interiors. Specifically, Basu is very interested in determining the overall metallicity, or fraction of a star that is not hydrogen or helium, of the Sun, which is surprisingly uncertain.

Although Basu is still working toward constraining the Sun’s metallicity, predicting the solar dynamo, and understanding the Sun’s meridional flow – a current of material streaming from the Sun’s equator to its poles – a later lecture focused on something a bit more tangible: the Daniel K Inouye Solar Telescope (DKIST).

DKIST, a powerful solar telescope that is under construction on the highest peak of the Hawaiian island of Maui, will be complete in just two short years. Credit: NSO
In a talk given by Valentin Martinez Pillet of the National Solar Observatory, we were filled in on the latest status of what will be the highest-resolution solar telescope in the world. The 4-meter DKIST telescope, which has been under construction for over eight years, will soon investigate how energy is transferred from the surface of the Sun to the corona. Furthermore, DKIST is planning to carry out coordinated missions with the Parker Solar Probe, the Solar Orbiter, and ALMA, as well as search the Sun for a possible second, turbulence-driven dynamo.

From eruptions to escapes

Although DKIST will surely teach us a great deal about the Sun (and stars in general) in due time, some research presented today already has results on a few intriguing stellar objects found outside our solar system. During the first press conference of the day, we were filled in on multiple new studies related to both erupting and escaping stars. In a presentation by Thomas Ayres, from the University of Colorado, Boulder, we learned about the potential hazards of the star system that may be our first destination for interstellar travel – Alpha Centauri. In the Alpha Centauri system, there are three stars: Alpha Centauri A, Alpha Centauri B, and Alpha Centauri C (also known as Proxima Centauri). Both A and B are semi-Sun-like stars, however, C is a low-mass red dwarf.

To investigate the true habitability around these stars, Ayres took into account each star’s X-ray emissions, particularly during high-energy events. According to Ayres (and backed up by Chandra X-ray observations), Alpha Centauri A seems to be a relatively pleasant host star to be stationed around, with relatively low X-ray emissions and few large flares. Alpha Centauri B may still have a habitable zone, but it emits five to six times more X-rays than the Sun. And then there’s the puny Alpha Centauri C, which, according to Ayres, “is star weather hell.” Despite this tiny red dwarf’s size, it emits nearly 500 times more X-rays than the Sun, and occasionally experiences flares that emit 50,000 times more.

In another presentation, Andrea Kunder of Saint Martin’s University discussed her research investigating a population of stars that seemingly have escaped the clutches of their original globular cluster, NGC 6441. Globular clusters, says Kunder, are extremely old and are like the fossils of the Milky Way – they contain relics from the past that can provide details of the most ancient stars.

To investigate NGC 6441, Kunder looked at RR Lyrae stars, which are periodic variable stars known for being great distance indicators. “If you can find these stars,” said Kunder, “and if you know what their brightness is, you can immediately tell what their distance is.” However, since this particular cluster is somewhat obscured by gas and dust, it is difficult to determine the true brightness of these stars. So instead, Kunder and her colleagues looked at the Gaia-collected proper motions for these RR Lyrae stars. They found that almost half of them have proper motions consistent with being cluster members, but are located outside of NGC 6441. According to Kunder, this means that NGC 6441 may have once been a dwarf spheroidal galaxy that merged with another galaxy, and, as a result, it is losing its original population of stars.

Stay tuned

The Sun and other stars are far from the only topics that were discussed today. We also were treated to multiple talks concerning the incredibly luminous cores of galaxies, but this will have to wait for another day, as there is much to share about this subject. To learn more about all the exciting research that was presented this week at the 232rd Meeting of the American Astronomical Society, stay tuned over the next few weeks as we dive deeper into many individual studies.



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