text:   gravitational-wave astronomy",8,"['New on the arXiv today: an #Astro2020 white paper on the awesomeness of extreme-mass-ratio inspirals, a unique #GravitationalWave source for @LISACommunity <LINK> <LINK>', 'Extreme-mass-ratio inspirals are when one smaller stellar-mass black hole orbits a supermassive one. The resulting orbits are extremely complicated (as illustrated in this rather lovely figure). It is this structure which encodes lots of information into the #GravitationalWaves https://t.co/T39r9yPVij', ""We're not sure how many inspirals we'll see—measuring the number would teach us lots about galactic cores. We estimated ~1–2000 per year, so they're a bankable source across a 4 year @LISACommunity mission! I describe more in my blog https://t.co/N0XOHYqXId #Astro2020"", ""Since the orbits are so complicated, we'll be able to measure the properties of the source *really* well. Black hole spins are hard to measure with @LIGO, but here we'll get them to 1 part in 10,000–1,000,000! The spins encode lots of information about how black holes grow"", ""Because we'll get such ridiculously detailed measurements of the properties, we can really test the structure of the massive black hole. If there's a missing piece to @AlbertEinstein's theory of general relativity, here is an excellent place to look! #Astro2020"", ""Putting together a few extreme-mass-ratio inspirals, we can start to reconstruct the mass distribution of massive black holes. @LISACommunity is sensitive to black holes with masses 10^4–10^7 times the mass of our Sun. We don't know what the distribution is like at the lower end!"", 'If we can cross-correlate the location of the source we work out from the #GravitaitonalWave signal with galaxy catalogues, we can also measure the Hubble constant, perhaps to 1% after 20 detections! This is a great check of other methods #Astro2020', 'Extreme-mass-ratio inspirals are a wonder opportunity for #GravitationalWave astronomy. There is only one currently scheduled mission that can detect them: @LISACommunity https://t.co/wJEjE7ORi6  💞💓❤️ #Astro2020']",19,03,1968