By Matt Hill and Alison Hammond. Orbiting a star other than the Sun A planetary-mass object (No deuterium burning) Artist’s Impression.

By Matt Hill and Alison Hammond

• Orbiting a

star other than the

Sun

• A planetary-mass

object (No deuterium

burning)

Artist’s Impression

• 313 currently confirmed exoplanets• A significant astrophysics research

area.• Understand planet formation

• New Technology enables direct imaging

• Find locations for extra-terrestrial life.

Previously Used Indirect Methods

New

Direct MethodsStar’s gravitational wobble.

Variations in radial velocity.

Transit of Planets

Gravitational micro-lensing.

Imaging -using adaptive optics

-using aperture

masking

-enables

spectroscopy

Requires Special Circumstances

-Faint star

-High mass companion

-Large star-exoplanet separation

-Young, infrared radiating companion

• Originally with NIRC2 at Keck (2007)

• Further images in 2008 with NIRC2 and PHARO at Palomer.

Note

• NIRC2 is astrometrically calibrated to a high specification

• PHARO is less sufficiently calibrated

• Some stars in upper Scorpius seemed likely possibilities.

Upper Scorpius

Credit: M. Bessell

De Zeeuw (1999)

aka GSC 06214-00210

Visual Companion

• aka1RXS J160929.1-210524 or GSC 06213-01358

Visual Companion

» aka RXJ1607.0-2036

Visual Companion

Visual Companionship doesn’t imply physical companionship!

EarthEarth

Relative motion of stars and their companions

1. Image to usable image

2. Usable image to relative x and y coordinates

3. Converting data to relative positions (separation and angle) for a series of dates

4. Converting this into real positioning ready to be graphed

• Dark Subtraction• Flat Fielding• Distortion solution• Bad Pixel Removal

Using image examination device of ATV in IDL

Locations of Centroid: K99-98

Date Image# Star(x) Star(y) Comp(x) Comp(y) Star(f) Comp(f)

080617 244 597.1 425.4 773.8 308.1 5.3081e+7 27107

080617 249 579.7 570.8 755.9 453.7 5.4126e+7 32632

080617 251 370.2 799.0 546.8 682.1 5.3532e+7 24881

Relative positions: K99-98

Distance (pixels) Angle (degrees) Flux ratio (s/c)

212.09 -123.58 1985

211.79 -123.50 2130

211.56 -123.61 1655

Relatively simply algebra enables the following data manipulation.

• Calibration inconsistencies– Using NIRC2 to assist PHARO calibration

• Conversion to miliarcseconds

• Finding real relative angle

Ghez (2008)

• So we obtained the actual position data.

1676-123.632110.29

2152-123.372110.02

1958-123.452113.05

Flux ratio (s/c)Angle (degrees) Distance (milliarcseconds)

Relative positions: K99-98

Imperfectly calibrated Pharo data

BACKGROUND STAR

31/5/07

17/6/08

23/6/08

Unlikely

PHYSICAL COMPANION

But unusual for

BACKGROUND STAR

29/8/07 30/5/07

17/6/08

Physical companion!

6/6/07

17/6/08

K99-98 P98-50 P98-70

-Appears to follow proper motion line-PHARO data only varied by small amount

-Does not remain in same position

-Deviates sideways from expected motion

-The two positions after one year are arguably exactly the same

Background Star

Star in Galaxy Bulge

Extra-solar planet

• P98-50 – Conflicting measurements can be reconciled with images in march 2009

• K99-98 – useful having a background star close by for studying K99-98’s motion.

• P98-70 –Alison and I are moving there after completing uni

• P98-50 – Conflicting measurements can be reconciled with images in march 2009

• K99-98 – useful having a background star close by for studying K99-98’s motion.

• P98-70 – Astronomers will now continue to study and monitor the planet.

• Supervisors: Michael Ireland and Peter Tuthill

• Dick Hunstead

• Sydney University school of physics