Chinese-internationalcollaboration solved the

central question:

”How common are planets

like the Earth”

Jupiter-Saturn like exoplanets are uncommon –Are Earth-like exoplanets common?

Is our solar system ”normal” or is somethingunusual the cause for our existence?

SONG is particular sensitive toplanets as in our solar system-- are they common or rare?.

Design driver: 5 years of observationwill tell number of Earths in the Galaxy

Exoplanet research with SONG:

Primarily oxygen-richstars are orbited bygiant exoplanets 16 stars of 250,000

toward the galacticcentre showed transiting exoplanets

Doppler andtransit planetsdominate thenumber of known exoplanets –--This will change in the future

420/ 70 of 440 known

110 expected from solar neighbourhood

Since 2004 we have searched for exoplanetsusing the Danish 1.54m telescope at ESO La Silladedicated 4 months/year for microlensing search.SONG can do Doppler and microlensing, butwill do microlensing 200 times more efficient that traditional telescopes.

Habitable exoplanets: orbits: 0.4 AU – 4 AU around stars A5 - M0 (0.5-2.5M_sun)

with main sensitivity to exoplanets as all the planets in our solar system

¾ of all stars

¼ of all stars

SONG: first telescope

200

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M M D D D

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lensstar

Observed 5.5 Earth-mass planet

Hypothetical1 Earth-mass planet

OB05390 is on the limit of what existing telescopes can observe

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microlensning = observations in dense stellar fields

10 microlensing exoplanets are now known; incl a 3 and a 5 Earth-mass,terrestrial planet in an Earth-like orbit. SONG will be able to detect Mars mass planets in terrestrial orbits

”Lucky Imaging” cameras at the SONG telescopes will reach almost as sharp images as a space-telescope.

Normal camera Lucky

imagingcamera

MOA finding chart(1.8m NewZeeland)

Lucky Imaging1.54m Danish, Chile

VLT/NACO 8m

mikrolinser--jordlignendeexo-planeter

To observe smaller mass planets,

requires to be able to resolve smallersource stars (i.e Lucky Imagingif fields are crowded), and observe more events (i.e. faster telescopes,observing a larger fraction of theyear and night).

max

21 4( / )E S

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SONG is afollow-up survey able to find small planets

Pan-STARRS at Haleakala, Maui, Hawaii: next step in NEOsearchAim: to identify ”all” NEOs > 1km, and 99% > 300m.It goes 5 mag (i.e. a factor 100) deeper than previous surveys, and is expected to identify 10 mill new main belt asteroids, and >10.000 new NEOs and TNOs

First of 4 planned telescopes has started

The camera has 1.4 billion pixels and a field of 7 sqr deg pr exposure.Two exposures pr minute of 2Gb size0.3” resolution. Vlim=24 (intg 29.4)6000 sqr.deg. pr night = the fullsky scanned every week.

Large Synoptic Survey TelescopeLSST will detect NEOs to 100 m diam.One 8.4 m mirror, 3 Gpixel CCD, Vlim = 27full sky cover every 3 nights from 2014; 30 TB/night10 sqr.deg. in each 15 sec exposureat 0.2”resolution in 5 bands, 4000Å-1.06mu

2.7km Cerro Pachon in North Chile

VYSOS-5” (right) and Mauna Loa Observatory in Hawaii

and VYSOS-6” (below) at Cerro Armazones Observatory in Atacama, Chile.

Tests with microlensing alerts in the whole Galactic planeare now being performed at

mikrolinser--jordlignendeexo-planeter

The SONG telescopes have: Smaller PSF (factor 9)Better throughput (factor 1.5)Faster slew and pointing (factor 2)Broader filters (factor 4)Better use of the year (factor 2)

Roughly speaking, SONG can reach 3 mag fainter stars (=see smaller planets) with a 10 times higher efficiency => statistics onEarth-Mars like planets in 5 years

Will we have microlenses enough to observe?

Difraction limit:

For a 1m mirror, the diffraction limit is0.15” at 5000 Å0.25” at 8000 Å

The best seeing at La Silla, DK1.54m is 0.8”; typical seeing is 1” to 1.5”Lucky Imaging tests: 0.35”

To understand whether we can benefit from surveys in the general Galactic plane, I have made a simple Galactic model:

Bulge: 0( ) exp( ( / ) ); 1 ; 1.2b b br r r r kpc

Extinction: 0.63mag per kpc

(16.5 ( ))/( ) 10 ; 1.75m sources m

Disk: cylinder of r = 15 kpc, h = 2 kpc

10lg( lg ) 10 10 0.3bu e diskM bu e M

10 3( ) 10 ` 0.1* /diskM disk M pc

We now integrate the total Einstein areas

102 2

0 0

(2.85 ( ) / )ds dl s

E l s l s l l s

s l ds dl

M d d d d dl ds

out through a cone of 1 square degree of the sky

The Einstein-area is the probability of a source star at distance ds being linsed.

When multiplied by the number of source stars at ds, it gives the total number of lensing events at any given time of some baseline magnitude.

The number per year is then approx. 52/3 times this number.

This integration with the simple Galactic model gives good agreement with the number and distribution of OGLE events, and predict that the number of events could be doubled by looking out of center with a modest sized telescope.

A global network of 1m telescopes for long time series observations

High resolution imaging for microlensing at summer time

High resolution spectrograph for low mass RV observations in winter

First astrometric detection ofan exoplanet from ground:VB10b May 2009.

GAIA expects to identify 10,000giant exoplanetswithin 200 pc

First 9 direct imaging detectedexoplanets indicate a hugefuture potential for this method

Transit accuracy of 0.5 milli-mag from the ground (DK1.54m); timing accuracy of 10 s

WASP-2

WASP-6

The Kepler satellite has5 times better photometricaccuracy (0.1 milli-mag)

Many more transiting exoplanetswill be announced in coming years.