For the past week, over three thousand astronomers from all over the world (including yours truly) met in Seattle, Washington for the American Astronomical Society Winter Meeting, the largest astronomy conference in the world. Much science was announced and discussed, and I took notes to give you some highlights.
This year’s meeting was a little bit disrupted because of the U.S. government shutdown, which prevented most NASA employees from attending—10%-15% of the total attendees. Nonetheless, the AAS did an admirable job of keeping most of the events running and finding replacement speakers when they were needed.
By tradition, the first talk of the conference is always about some important new development in astronomy from the past six months, and this year, it was ‘Oumuamua, the interstellar (probably-)comet that was seen zipping through the Solar System last October. Greg Laughlin from Yale and Ka’iu Kimura from the ‘Imiloa Astronomy Center in Hawai’i spoke together to describe not only the scientific findings about this object, but also how its discoverers made efforts to involve the native Hawai’ian culture of the lands on which the observatory that discovered it sits. After the discovery, ‘Imiloa scrambled to produce a name in keeping with Hawai’ian naming traditions and decided on ‘Oumuamua, which has roughly the sense of “first distant messenger.”
Other notable properties of ‘Oumuamua are that it is reddish (which is common in comet-like objects), rotates in 7.2 hours (also common), is splinter-shaped (very unusual), and has no visible dust around it (which we aren’t sure is unusual, but is definitely not what we expected). Most interestingly, the detection of ‘Oumuamua suggests that such interstellar comets are very common. Each star could very well eject many trillions of comets when it forms, adding up to about the mass of the Earth. It also means that distant giant planets like Neptune should also be common to actually do the scattering. If true, Neptune would be one of the few ways in which our own Solar System is actually normal.
Other highlights from the conference include:
Gravitational waves from colliding black holes are helping us narrow down not only the number of black holes in the universe, but also their properties and the properties of other stars as well. We now have a pretty good estimate of the number of black hole mergers: between 26 and 109 per cubic gigaparsec (35 cubic gigalightyears) per year. Also, the mass range of black holes is narrower than we expected, which provides more evidence for something called a pulsational pair-instability supernova, by which very massive stars can explode without leaving anything behind.
The Atacama Large Millimeter Array (ALMA) is teaching us a whole lot of stuff, including finding the most distant confirmed galaxy ever found at a redshift of 9.1. (The Hubble Space Telescope might have found farther ones, but it can’t measure them very accuratly.) It is also doing a lot of work to tease out the mysteries of planet formation.
Finding habitable planets is incredibly difficult, and it also works differently around red dwarf stars. For example, on Earth, we have ice-albedo feedback: more ice reflects light from our yellow sun and cools the planet. But on a planet orbiting a red dwarf, ice absorbs infrared light from the red sun, warming the planet. This could mean that planets orbiting red dwarfs are more protected from freezing over as Earth did a couple times.
And…we still haven’t found dark matter. And physicists are getting kind of worried (or excited depending on which theories you believe). A lot of people think we should have seen it by now, and if we don’t in the next few years, it’ll be a sign that dark matter is even weirder than we thought.