Archive for November 15, 2018

11/15/2018 – Ephemeris – Last year’s interstellar visitor was acting funny

November 15, 2018 Comments off

Ephemeris for Thursday, November 15th. The Sun will rise at 7:39. It’ll be up for 9 hours and 34 minutes, setting at 5:14. The Moon, at first quarter today, will set at 12:18 tomorrow morning.

Last year about this time a fast moving asteroid with an odd cigar shape passed through the inner solar system. It’s velocity was such that it didn’t come from around here, meaning our solar system. It was named ‘Oumuamua by its discoverers in Hawai’i. It was spotted as it was heading out, away from the Sun. As it does so, it decelerates as the Sun’s gravitational pull tries to pull it back in. After studying its motion, astronomers noticed that it wasn’t decelerating as fast as it should if it was on a simple ballistic trajectory. Something about it was accelerating it, or causing it to not decelerate as fast as it should. Despite rampant speculation that it’s an interstellar craft on social media ‘Omuamua’s acceleration is well within that possible for comets.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


Artist visualization of ‘Oumuamua. Credit: European Southern Observatory / M. Kornmesser
Orbit of 'Oumuamua
Orbit of ‘Oumuamua 1I/2017 U1. Uncredited image from Ars Technica.