Hubble Space Telescope
Cycle 11 General Observer Proposal
Searching for Possible Earth-like Exoplanets around
Red Dwarf Stars
Principal Investigator: Mr. Taylor Esformes
Institution: Stony Brook University
USA/NY
Electronic mail: boomboxer@gmail.com
Scientific category: COOL STARS
Scientific keywords: EXTRA-SOLAR PLANETS, LOW-MASS AND COOL
STARS, PROTO-PLANETARY DISKS
Instruments: ACS, NICMOS, STIS Proprietary period: 12
Cycle 11 primary orbits: 100
Cycle 11 parallel orbits: 0
Special Proposal Types: Innovative
Abstract
The search for exoplanets has met with considerable success lately, mostly thanks to the
efforts of ground-based projects such as the SuperWASP in the UK, the Very Large Telescope
in Chile, and the California-based Lick-Carnegie survey, which discovered exoplanets in the
habitable zone of star Gliese 581g. What many of these discoveries have in common is that
they occur around dimmer main sequence and red dwarf stars. Larger stars with brighter
coronas tend to obscure their planets and exhibit nearly undetectable drops in luminosity
due to transits, when compared to their smaller counterparts. This project aims to conduct
a systematic survey of 10 known red dwarf systems and measure transits with the aim of
identifying possible expolanets. Using known information about the stars luminosity and
the period of the transits, planets possibly inhabiting the habitable zone of their star will be
identified, and marked for further, more detailed study. The HSTs resolution wide field of
view, along with the light-occluding capabilities of the Advanced Camera for Surveys, will
allow for a very efficient wide-angle survey and highly detailed images of possible exoplanets
once the survey data is processed. 100 orbits was deemed necessary due to the possible
uncertainties that can result from possibly measuring transits with periods shorter than the
interval between measurements.
Mr. Taylor Esformes
Searching for Possible Earth-like Exoplanets around Red Dwarf Stars
Investigator
Mr. Taylor Esformes
PI:
CoI:
Total number of investigators:
Institution
Stony Brook University
Country
USA/NY
2
Configuration,mode,aperture
DEC
V
spectral elements
16 34.6
8.5
ACS/HRC IMAGING
F270W
BD-18 359
02 05
-17 36
2.5
ACS/HRC IMAGING
F125N
G 160-28
03 50
-06 05.7
12.89
ACS/HRC IMAGING
F125N
CD-31 9113
11 35
32 23
12.5
ACS/HRC IMAGING
F125N
HIP 82724
16 54.5
-62 24
11.85
ACS/HRC IMAGING
F125N
LHS 2037
08 40
-23 27
3.5
ACS/HRC IMAGING
F125N
LHS 495
20 40
15 29
4.5
ACS/HRC IMAGING
F125N
LHS 1761
05 28
09 38
3.5
ACS/HRC IMAGING
F125N
LTT 7072
17 46
-32 06
2
ACS/HRC IMAGING
F125N
LHS 508
12 29
17 38
4
ACS/HRC IMAGING
F125N
Grand total orbit request
NOTE: This grand total (30) does not equal the sum of cycle 11 primary (100)
orbits plus cycle 12 primary (0) and parallel (0) orbits plus cycle 13 primary (0)
orbits on page 1
Observing Summary:
Target
RA
BD+15 4733 A
22 56
2
Total
orbits
3
Flags
3
3
3
3
3
3
3
3
3
30
and parallel (0)
and parallel (0)
Mr. Taylor Esformes
Searching for Possible Earth-like Exoplanets around Red Dwarf Stars
Scientific Justification
There are several compelling justifications for this survey, hopefully the first of many that
will be conducted using the HST to look for exoplanets.
First of all, the search for exoplanets has been mostly conducted from ground-based
telescopes that suffer from resolution problems that space-based telescopes do not deal with.
The confirmation of the discovery of Gliese 581g, for example, was complicated by uncertainties and inconsistencies in the combined ground-based data sets used to determine if a
planetary signal could be detected. Although mostly settled now, the controversy could have
been quickly solved by high resolution data taken by the HST. All of the targets are within
ten parsecs of Earth in order to make resolving subtle features caused by planetary motion
easier.
In addition to its high resolution, the HST is equipped with a device called the Advanced
Camera for Surveys, which in addition to having a wide field of view excellent for a survey of
this kind, also has light suppressing filters which allow for the star itself to be occluded and
the planets effect on the stars luminosity, especially around the corona, to be much more
visible. Having these devices on the same instrument allows researchers to quickly follow up
on data that looks promising, something it is difficult to do when more than one data set is
needed to get reliable results.
The other two devices on board that will be used by the project. These are the Space
Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object
Spectrometer(NICMOS). The NICOMOS device on board specializes in capturing infrared
radiation, which will be useful for imaging some of the dimmer targets, especially as red
dwarf stars emit more of their spectrum in these frequencies than main sequence stars. 4
exoplanets within the 10 parsec search radius have already been discovered in archival data
from NICOMOS, demonstrating its utility in detecting planetary phenomena that might not
be detectable at visible frequencies. STIS also focuses on infrared imaging, and features a
video mode that may prove useful in measuring rapid transits. The STIS recently detected
and made the first measurement of the spectrum of an exoplanet’s atmosphere, that of HD
209458b.
10 orbits per target was considered reasonable, since the exoplanets we’re focused on
are ones in the star’s habitable zone, and are therefore closer to their parent star and have
higher angular velocity. Statistical analysis will be necessary to determine the period of
transits shorter than the interval between measurements, so a large data set is desirable.
It is vital for the future of exoplanet research to be able to identify planets orbiting
around low-luminosity stars. Despite the relative ease of detecting large gas giants in orbit
around brighter main sequence stars, the likelihood is much higher that possibly habitable
planets will be found orbiting closely around a cooler main sequence or red dwarf star.
This search can be made far more efficient by making use of infrared astronomy and spacebased telescopy. The HST and its specialized instruments will do an excellent job producing
data with the resolution and clarity necessary to observe the extremely subtle variations in
luminosity that characterize exoplanet systems.
3
Mr. Taylor Esformes
Searching for Possible Earth-like Exoplanets around Red Dwarf Stars
Description of the Observations
Each star will be observed for 3 orbits, in an attempt to capture at least two planetary transits. Upon identifying which stars exhibited periodic drops in luminosity, further observation
will be decided based on probability that the exoplanet lies within its star’s habitable zone.
The time used is necessary, because of the difficulties involved in determining transit periods
using measurements that are farther apart than the period itself.
Special Requirements
N/A
Coordinated Observations
N/A
Justify Duplications
N/A
Previous HST Programs
None (and for good reason, too).
4