Transcript Are Earth-like exoplanets common?

Chineseinternational
collaboration
solved the
central
question:
”How common
are planets
like the Earth”
Exoplanet research with SONG:
Jupiter-Saturn like exoplanets are uncommon –
Are Earth-like exoplanets common?
Is our solar system ”normal” or is something
unusual the cause for our existence?
SONG is particular sensitive to
planets as in our solar system
-- are they common or rare?
.
Design driver: 5 years of observation
will tell number of Earths in the Galaxy
Doppler and
transit planets
dominate the
number of known
exoplanets –-This will change
in the future
420/ 70 of 440 known
Primarily oxygen-rich
stars are orbited by
giant exoplanets
16 stars of 250,000
toward the galactic
centre showed
transiting exoplanets
110 expected from
solar neighbourhood
ince 2004 we have searched for exoplanets
sing the Danish 1.54m telescope at ESO La Silla
edicated 4 months/year for microlensing search.
ONG can do Doppler and microlensing, but
ill do microlensing 200 times more efficient
hat traditional telescopes.
Habitable exoplanets:
orbits: 0.4 AU – 4 AU around stars A5 - M0 (0.5-2.5M_sun)
¼ of all stars
¾ of all stars
SONG: first telescope
with main sensitivity to exoplanets as all the planets in our solar system
 E (mas) 
2.85 M L / M sun DLS / DL DS
A(u ) 
u 2
2
u u 4
2
lens
star
u(t )  u 2 (t0 )  [(t  t0 ) / t E ]2
A(u ) 
u2  2
u u2  4
Amax  1  4(E / S )
2
Observed 5.5
Earth-mass planet
OB05390 is on the limit
of what existing
telescopes can observe
Hypothetical
1 Earth-mass
planet
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
imagin
camer
MOA finding chart
(1.8m NewZeeland)
Lucky Imaging
1.54m Danish, Chile
VLT/NACO 8m
Amax 
1  4( E /  S ) 2
SONG is a
follow-up survey
able to find small
planets
mikrolinser
--jordlignende
exo-planeter
To observe smaller mass planets,
requires to be able to resolve smaller
source stars (i.e Lucky Imaging
if fields are crowded), and observe
more events (i.e. faster telescopes,
observing a larger fraction of the
year and night).
Pan-STARRS at Haleakala, Maui, Hawaii: next step in NEOsearch
Aim: 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 size
0.3” resolution. Vlim=24 (intg 29.4)
6000 sqr.deg. pr night = the full
sky scanned every week.
Large Synoptic Survey Telescope
LSST will detect NEOs to 100 m diam.
One 8.4 m mirror, 3 Gpixel CCD, Vlim = 27
full sky cover every 3 nights from 2014; 30 TB/night
10 sqr.deg. in each 15 sec exposure
at 0.2”resolution in 5 bands, 4000Å-1.06mu
2.7km Cerro Pachon in North Chile
Tests with microlensing alerts
in the whole Galactic plane
are now being performed at
VYSOS-5” (right) and
Mauna Loa Observatory
in Hawaii
and
VYSOS-6” (below) at
Cerro Armazones Observatory
in Atacama, Chile.
The SONG telescopes have:
Smaller PSF (factor 9)
Better throughput (factor 1.5)
mikrolinser
Faster slew and pointing (factor
2)
--jordlignende
Broader filters (factor 4) exo-planeter
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 on
Earth-Mars like planets in 5 years
Will we have microlenses
enough to observe?
Difraction limit:
The best seeing at La Silla,
DK1.54m is 0.8”;
typical seeing is 1” to 1.5”
Lucky Imaging tests: 0.35”
For a 1m mirror, the
diffraction limit is
0.15” at 5000 Å
0.25” at 8000 Å
To understand whether we can benefit from
surveys in the general Galactic plane,
I have made a simple Galactic model:
Disk: cylinder of r = 15 kpc, h = 2 kpc
M (disk )  1010 M `  disk  0.1* / pc 3
Bulge:  (r )   b 0 exp((r / rb ) ); rb  1kpc;   1.2
M (bu lg e)  1010 M  bu lg e  10  0.3disk
Extinction: 0.63mag per kpc
s(m)  10
(16.5 m ( source ))/ 
;   1.75
We now integrate the total Einstein areas
2

 E 
s l
ds 10 dl  s
 
 (2.85 M l (d s  dl ) / d s dl ) 2 l dl  s ds
ds  0 dl  0
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 of
an exoplanet from ground:
VB10b May 2009.
GAIA expects to
identify 10,000
giant exoplanets
within 200 pc
First 9 direct imaging detected
exoplanets indicate a huge
future potential for this method
WASP-2
Transit accuracy of 0.5 milli-mag from the
ground (DK1.54m); timing accuracy of 10 s
WASP-6
The Kepler satellite has
5 times better photometric
accuracy (0.1 milli-mag)
Many more transiting exoplanets
will be announced in coming
years.