B Y

V I K R A M L O N D H E

( F E L L O W O F R O Y A L

A S T R O N O M I C A L S O C I E T Y )

To Discover Exoplanets

Outline of Research

Study existing exoplanets.

To discover new exoplanets with diverse atmospheric conditions.

Analysis of real time data of exo planets

Practice Transit and Doppler spectroscopy for wide range of exoplanets.

To obtain a photometric curve for a star .

Observe a change in magnitude related to the transit of an exoplanet

Brief History

There are currently more than 160 confirmed exoplanets.

First definite exoplanet was found in orbit around 51

Pegasi located near the center of the Pegasus constellation on October 6, 1995.

The first confirmed transiting exoplanet was HD 209458 “b” found in late 1999 this planet’s sun is also located in the Pegasus constellation.

Where as the first exoplanet found using the transit method was OGLE TR 56 “b” in Sagittarius.

Past Experience

The types of exoplanets observed where “Hot Jupiter” type exoplanets. These planets are characterized by:

-Being very close to their parent star (about 0.05 AU)

-Having masses similar to that of Jupiter

-Having very small periods

Observed three stars:

-Stars with known transiting planets

-TrES-1 located in the constellation Lyra HD 189733 located in the summer triangle

Star with a known planet but unknown transit

GL 581 located in the constellation

Methodology

Deciding the are for search:

The area with rich star field.

Its easy to observe transit of Bright Stars.

Transit curve can be easily analyzed.

Easily observable by Ground base Telescope.

Doppler Spectroscopy

The Doppler radial velocity Method This method allows us to detect an exoplanet by observing the red shift and blue shift of a star’s light caused by a slight wobble in the star due to the presence of a planet.

Information gained through Doppler Spectroscopy

From the Doppler Method the planet’s mass, distance from it’s star and the eccentricity of it’s orbit can be determined.

However, to determine any other characteristics of the planet it must transit it’s parent star.

What is Transit?

A transit occurs when a planet passes in front of its sun. What is an exoplanet? An exoplanet, also know as an extra-solar planet, is any planet that does not orbit our sun, sol, rather it orbits another star.

The Transit Method • Using this method an exoplanet is detected when

it transits it’s star. • As the planet transits a portion of the light from

the star is blocked causing a decrease in the magnitude of the star.

Information gained through transit

Using the transit method the planet’s size can be determined, this coupled with the mass of the planet found using the Doppler Method can provide the density of the planet.

Also the composition of a transiting planet’s atmosphere can be determined.

Analysis

• To detect a transit we must create a light curve for the star. • Do this through differential photometry.

-Take images of target star before, during and after a predicted transit window.

-Calibrate images using Bias, Dark and Flat-Field Frames

-Determine raw instrumental magnitudes for the variable star, and comparison stars.

• Plot the Variable star’s magnitude subtracted by the first comparison star’s magnitude.

Image Calibration

•CCD cameras generate

unwanted noise known as dark

current. To remove this noise a

dark frame must be subtracted

from the images.

•Dark current is a small current

that flows through a

photosensitive device even when

no photons are entering the

device

Example of a Master Dark Frame

Image Calibration

• Also Bias Frames

must be taken to

correct for bias

voltage in the CCD.

Bias voltage is

random noise

created by CCD’s

on chip amplifier.

Example of a Master Bias Frame

Image Calibration

• Finally, Flat-Field

Fames must be

subtracted from

the images to

correct for

variations in the

CCD sensitivity.

Example of a Master Flat-Field Frame

Creating a light Curve

Differential photometry is used to create a light curve for the observed star.

Raw instrumental magnitudes of the variable and comparison stars are determined using astronomical image processing software.

Creating a Light Curve

After magnitudes have been determined the variable star’s magnitude, V, is subtracted from the magnitude of the first comparison star C1.

Differential magnitude = (V-C1)

C1 is assumed to be constant. We check that it is a constant by subtracting C1 by the magnitude of the second comparison star.

TrES-1

TrES-1

Comparison star 1

Comparison star 2

Period: 3.0312 Dys Length of Transit: 149.92 mins

Image after callibration

0.83 0.84 0.85 0.86 0.87 0.88 0.89 0.9 0.91

0.2

0.22

0.24

Johnson V filter [2006/02/26]

0.26

Ma

gn

itu

de

0.28

0.3

0.32

0.34

0.36

Time (Julian +2453792)

Johnson V Filter

TrES-1

GL 581

GL 581

Comparison Star 1

Comparison Star 2

Period: 5.366 days Length of Transit: 88.78 min.

Image after Callibration

Conclusions • For TrES-1 successfully obtained a

photometric curve related to the ending of a transit for an exoplanet.

• For GL 581 no change in magnitude

related to an exoplanet transit was shown on the photometric curve.

Current Plan:

To observe

-Transit in Cygnus and analysis of different stars.

-Transit of Alpha Centauri.

Image of Cygnus Constellation

Few Achievements

Elected as Fellow of Royal astronomical Society, London on 12th Oct 2012. Membership No.: 7883.

Presented Exoplanet Simulation model at conference on “Comparative Climatology of Terrestrial Planet” organized by NASA, USRA and hosted by LPI. Abstract No: 8002.

Honored by Excellence award by University of Pune.

Acknowledgements

I’m thankful of my Research supervisor Prof. S. P. Bholane to encourage me to work in astronomy.

I also wants to thank may friends to support me.

And Thanks to Sigma Xi to give me this opportunity to share my research.

Thank You!