- Binary Star § Astrometric binaries (Wikipedia)
Astronomers have discovered some stars that seemingly orbit around an empty space. Astrometric binaries are relatively nearby stars which can be seen to wobble around a point in space, with no visible companion. The same mathematics used for ordinary binaries can be applied to infer the mass of the missing companion. The companion could be very dim, so that it is currently undetectable or masked by the glare of its primary, or it could be an object that emits little or no electromagnetic radiation, for example a neutron star.
- St. Croix River (Wisconsin–Minnesota) (Wikipedia)
The St. Croix River (/ˈseɪnt ˈkrɔɪ/ SAYNT KROY; literally “holy cross” in French) is a tributary of the Mississippi River, approximately 169 miles (272 km) long, in the U.S. states of Wisconsin and Minnesota. The lower 125 miles (201 km) of the river form the border between Wisconsin and Minnesota. The river is a National Scenic Riverway under the protection of the National Park Service. A hydroelectric plant at the Saint Croix Falls Dam supplies power to the Minneapolis–St. Paul metropolitan area.