1. Oumuamua: discovered by PANSTARRS 19th Oct. 2017
Meech et al 2017

2. Perihelion = 0.25 AU; v_∞ = 25 km/s
Q: why couldn’t it have originated within the solar system and been scattered?
First interstellar object (ISO) – its detection suggests there are ~ 10^4 present at any
time within orbit of Neptune or ~ 10^15 /pc^3

3. What do we know about its properties?
Elongated
Tumbling
No coma
Red
From light curve
Subject to impulse after solidified
No ice near surface: arguments about whether icy inside
Suggests organic compounds

4. Where did it come from?
Velocity consistent with typical relative velocity of local young stars
Could have been ejected from circumstellar environment of another star
Don’t know which one
Or white dwarf?
Do the numbers work out?

5. What are the prospects for finding more?
How much would discovering another one (or ten) help our understanding?
What about exotic theories?
e.g. `lithospermia’