the brightest stars do not live alone Background Design E. Buunk / S.E. de Mink, HST image: NASA Paresce Selma E. de Mink Hubble Science Briefing , February 7, 2013 Hubble Fellow at Space Telescope Science Institute / Johns Hopkins University

the brightest stars are up to a million times brighter than the Sun are rare Background Design E. Buunk / S.E. de Mink, HST image: NASA Paresce live fast and die young are embedded in clouds of gas & dust are very hard to study 2

This is what we thought … Massive Stars* BOOM Low-mass Stars *8-150 times more massive than the sun …. but it turns out that it is not that simple 3

Some stars are Single 4

The Sun is a single star If the Sun were the size of a baseball … … in Yankee stadium… … the nearest star would be in Houston, TX (1,400 mi. away) Credit: sdowww.lmsal.com, maps.google.com 5

many stars are quite unlike the Sun Artist impression: (ESO/L. Calçada/Nick Risinger) Photo: S. Brunier/ESO. Two stars, each nearly as bright as the other, circle around it, every eighty years. They come within 1.7 billion kilometres of each other, and are 5.3 billion kilometres from each other at their maximum distance apart. Alpha Centauri A and B are practically twin sisters of the Sun. Alpha Centauri, our nearest neighbor, is a multiple system: Star A & B orbit each other every 80 years 6

another famous multiple Alcor & Mizar Credit: J. Benson et al., NPOI Group, USNO, NRL Image Credit: ESO Online Digitized Sky Survey 7

3 binaries forming a sextuple system Alcor A & B Mizar A: a & b Mizar B: a & b A Spectroscopic binary Zimmerman et al. 2009 Credit: J. Benson et al., NPOI Group, USNO, NRL Image Credit: ESO Online Digitized Sky Survey Mizar A & B 8

Classic definition Binary System = a system of two objects in space (usually stars), which are so close that their gravitational interaction causes them to orbit around their common center of mass. According to this definition, almost all stars are binaries (or multiples). The Sun is one of the exceptions. 9

Not every binary is equal Close Binary System Closer than the distance from the Sun to Mars. One orbit takes between a day and few years. Wide Binary System Wider than the distance from the Sun to Jupiter. One orbit takes a few years up to centuries or more. 10

Close binary stars 11

A typical star becomes about 100-1000 times bigger during its life … 12

= Therefore, stars in close binary systems will interact 13

Artist Illustration of a “vampire star system”: ESO: Calçada/Kornmesser/de Mink 14

Questions so far? 15

How many stars are in such close binaries? 16

Six young star clusters 17

Using the Doppler effect to find binaries 18

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How many stars are in such close binaries? 21

What % of massive stars will interact 22 Sana & de Mink et al. Science, Cartoons: de Mink / Buunk

It is not this simple … Massive Stars* Low-mass Stars BOOM See video: http://hubblesite.org/newscenter/archive/releases/2012/33/video/b/ 23

Bonus: cool things that binaries do 24

make fast rotating runaway stars 25

Conclusion 26

the brightest stars do not live alone Background Design E. Buunk / S.E. de Mink, HST image: NASA Paresce Science 27 July 2012: Vol. 337 no. 6093 pp. 444-446 Selma E. de Mink More information: http://hubblesite.org/newscenter/archive/releases/2012/33/full/