Studying Binary Stars a Few Photons at a Time

Elliott Horch, CIS

Astronomy

Stars are

very

VERY

VERY

…cool.

What do we want to know about stars?

How do they form? How much matter is needed? Are planets involved?

How do stars work? Do they change? How long do they

live? Why do they appear in groups

sometimes? What can they tell us about how the

Galaxy formed?

What’s going to help us out in answering those questions?

Mass Luminosity (total light output) Size (radius) Surface Temperature Age Heavy Metal Content

(“metallicity”) etc.

What do we think we know about stars?

Energy production mechanisms Basic life cycle features Pulsation Spectral features

What still confuses us? Details, details… (Sigh.)

e.g. how to calibrate luminosities, etc??

Neutrinos Formation Processes “Jumps” in HR diagram etc.

Masses and the “MLR”

Theory: Mass and luminosity are related.

log(M/Msun)

log

(L/L

su

n)

0

0Our favoritestar!

Reality: Large Uncertainties!

Why are masses so hard to measure?

Binary stars. Gravitation --> orbit.

N

N

N

N

N

N

N

N

N

N

N

Okay, well how?Scales? Ha!

BUT: need SIZEof orbit, which meanswe need the distance.

Why are distances so hard to measure? Parallax

Earth

Our Home Galaxy

Our Home Galaxy - The Comic Book Version

Bulge

Disk

Halo

Globular Clusters

Two “Populations”

Population I: Disk dwellers metal rich

Population II: Halo dwellers metal poor

log(M/Msun)

log

(L/L

su

n)

0

0

MLR

Pop I

Pop II

Imaging Binary Stars

That *3$%%^*&$$% Atmosphere!! Blurs out star images, can’t see both stars

distinctly if they’re too close together. Related to twinkling.

Telescopes and camera systems: the rest of the optical system. Big telescopes can resolve closer pairs. Need high-speed cameras to “freeze” the

twinkling.

Why the atmosphere is such a bummer...

Ground

Atmosphere

light

At Big Telescopes, Stars “Speckle”

speckle images integrated image

At Big Telescopes, Stars “Speckle”

speckle images integrated image

Speckling Binary Star

t=0.00s

t=0.05s

t=0.10s

t=0.15s

Speckling Binary Star

t=0.00s

t=0.05s

t=0.10s

t=0.15s

Speckling Binary Star

t=0.00s

t=0.05s

t=0.10s

t=0.15s

Reminds me of...

A “Close Binary”

t=0.00s

t=0.05s

t=0.10s

t=0.15s

A “Close Binary”

t=0.00s

t=0.05s

t=0.10s

t=0.15s

A “Close Binary”

t=0.00s

t=0.05s

t=0.10s

t=0.15s

We can Beat the Atmosphere!!

long exposure speckle analysis

1 arcsec

KPNO

The WIYN Telescope

Kitt Peak,Arizona

Inside the WIYN Dome

Hipparcos (True) Binaries

H91

W97W98

W99

H91

C95

W99.02W99.89

Space Telescope FGSs

single star

double star

x

sig

nal

Koesters Prism

A Real FGS Transfer Function

FGS will help us study Pop II binaries.

Orbits Masses Luminosities

Pop II MLR !!!!!!! Better Ages and

Distances to Glob. Clusters!!!!

Henry et al. (1999)

arcsec-0.8 0.8

Conclusions

Stars are interesting. Star images taken at big

telescopes “speckle.” Interferometric imaging of binary

stars helps us determine their masses and luminosities, which in turn helps us understand how they work. Speckle imaging from the ground. Fine Guidance Sensor data from the Hubble

Space Telescope.