What does the **first** known active **comet from another star** looks like? **2I/Borisov**, the comet, visited us in late 2019, and telescopes around the world observed it ~~to see if it an alien's spacecraft~~ to explore its properties. Our teams successfully used UVOT/Swift to measure its water, and COS/HST to measure its carbon monoxide. The interesting conclusions can be learned from the following buttons.
How can we measure solar wind in high ecliptic latitudes? It is very hard to send a satellite there, and speculation is also difficult because solar wind changes rapidly during propagation. Here come comets! Comets can reach there! The interaction SWCX between comets and solar wind can tell us a lot about solar wind, comets' coma, and even atomic physics. HKU has a great opportunity to launch a satellite to observe SWCX in EUV band. I analysed SWCX for 5 comets in X-ray band and predicted EUV spectra for the satellite design.