Download No. 35 - Institute for Astronomy

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THE ONES WHO LOOK TO THE STARS
No. 35 • 2010
A Newsletter from the
Institute for Astronomy
University of Hawai‘i
Imaging Other Worlds: NICI Planet-Finding Campaign
by Michael C. Liu
One of the most exciting developments in astronomy
has been the discovery and characterization of
exoplanets—planets orbiting stars other than our Sun.
Our understanding of these objects has advanced by
leaps and bounds over the past 15 years, since the
discovery of the first exoplanet around the Sun-like
star 51 Pegasi in 1995.
Gemini NICI Planet-Finding Campaign
What’s Inside
Humboldt Awards
pg 3
Mānoa Open House
& Hilo AstroDay
pg 4
Galaxy Collisions Create
Large Black Holes, Quasars
Sun’s Constant Size pg 6
When, How Did Earth
Become Friendly to Life?
Upcoming Events
pg 7
From the Director
pg 8
The University of Hawai‘i
is an Equal Opportunity/
Affirmative Action Institution.
NICI image of a young star near Earth with a candidate
low-mass companion. The bright star in the center of the
image is heavily dimmed by a barely transparent
circular mask. The companion is at the 4 o'clock
position. It would be undetectable by ordinary imagers,
but is easily detected by NICI.
We now are entering a rich and special time for
such studies. The current exoplanet census now
exceeds 400 objects, most of them with masses
comparable to the gas-giant planet Jupiter, which has a
mass of one-thousandth that of the Sun, or 300 times
that of Earth. Most exoplanets have been identified by
the very subtle gravitational tug they exert on their
host stars. While these discoveries have been
groundbreaking, such planets are studied only
indirectly. Other planets have been found as they
transit across the face of their host stars, thereby
diminishing the amount of light we detect from them.
Such planets can be studied in great detail, but they
orbit very close to their stars, making them unlike any
planets in our solar system.
The next major advance is direct imaging, that is,
taking actual digital images of planets around other
stars. Directly detecting light from exoplanets opens
the door to a host of new information about their
properties (temperature, composition, etc.) and their
formation. Direct detection is Please see NICI, pg 2
Planet Detected in Habitable Zone of Nearby Star
by Louise Good
A team led by IfA astronomer Nader Haghighipour has
discovered a planet with about the same mass as
Saturn in the habitable zone of a star 36 light-years
from Earth. Its detection is important because it
“indicates that observational techniques are on the
right track for finding habitable low-mass rocky
planets similar to Earth,” according to Haghighipour.
A planet is considered to be in the habitable zone if
its temperature is just right for having liquid water.
The approximate surface temperature of the abovementioned newly discovered planet is about minus 42
degrees F, which was calculated by considering the
surface temperature of the star, the planet’s size, the
proportion of the star’s light that the planet may
reflect, and the time that it spends in close proximity
to the star. This temperature is colder than the value
one gets for Earth for the same kind of calculation.
However, if the planet’s atmosphere holds in heat
sufficiently, then the surface temperature will
certainly be warmer than minus 42 degrees.
The planet (HIP 57050b) circles its central star (HIP
57050) every 41 days. The star, which is classified as
an M dwarf, has a radius approximately 0.4 times that
of the Sun, and has a mass about one-third of the
Sun’s. “Because HIP 57050b is a giant planet, it is
unlikely that it is habitable,” Haghighipour notes.
In the quest for potentially habitable planets, the
nearest stars are of special importance. We know their
precise distances, as well as their masses, sizes, and
temperatures, and they are the only stars for which
follow-up by Please see Planet Detected, pg 2
NICI from pg 1
incredibly challenging. We see the planets in our own
solar system because they reflect light from the Sun.
Imaging the reflected light of exoplanets is currently
impossible because the light reflected by the planets
is swamped by the glare of their host stars, which are
about a billion times brighter. However, when gasgiant planets are young, they also emit their own light
at infrared wavelengths, by releasing the heat stored
in their interiors at the time of formation. This makes
young planets much easier to detect, since they are
only(!) about one million times fainter than their
parent star. In 2008, astronomers took the first direct
images of young gas-giant exoplanets, thereby opening
the door to this new way of learning about them.
My research group is leading an international effort
known as the Gemini NICI Planet-Finding Campaign
to expand the census of exoplanets detected by direct
imaging. NICI (the Near-Infrared Coronagraphic
Imager) is a powerful new instrument installed on the
Gemini South 8.1-meter telescope in Chile, the twin
of the Gemini North telescope on Mauna Kea. Most
astronomical instruments can do multiple kinds of
observations, but NICI was designed to do only one
thing very well, namely, image exoplanets directly.
NICI was built by Doug Toomey of Mauna Kea
Infrared in Hilo, with heavy involvement by IfA
faculty members Christ Ftaclas and Mark Chun, and
funding from NASA. NICI is designed as a complete
end-to-end system for exoplanet imaging. It is based
on an advanced adaptive optics system that corrects
for the blurring of astronomical images caused by
Earth’s turbulent atmosphere.
Since December 2008, we have been using NICI to
obtain very sensitive images of 300 nearby young
stars (within about 200 light-years) to search for
gas-giant planets in emitted light. The campaign will
take about three years and obtain a total of 50 nights
of observations. This makes it the largest single
program ever carried out at the Gemini telescopes. By
having a major campaign, it is possible to assemble a
large-scale coherent science program with a unified
set of goals, observing methods, and data analysis
techniques. While the observations are carried out in
Chile, the planning and analysis are done here at the
IfA, with postdoctoral fellow Zahed Wahhaj and
Hubble Fellow Beth Biller being key contributors.
The campaign is about halfway finished. We have
imaged about 180 stars so far, already making NICI
the largest direct imaging search to date. However, in
some sense, we are just getting started. Many of the
stars we have imaged have very faint companions
next to them, but we do not yet know what these are.
They could be gas-giant planets in orbit around these
stars, or they could be ordinary background stars that
are much farther away but by chance are projected on
the sky nearby. The way to check is to make a second
set of observations about one year later to see if the
faint candidates move with the target star, thereby
proving that they are gravitationally bound together.
We are in the process of doing that right now. Once
candidates are confirmed, we can learn a great deal
about the properties of young planets through
dedicated follow-up observations to measure their
brightnesses, colors, atmospheres, and orbits.
Planet Detected from pg 1
astrometry and direct imaging is possible. While the
majority of the currently known extrasolar planets
have been detected around larger nearby stars, more
than 70 percent of the nearest stars are M dwarfs. As
such, these stars have the special properties (distances
and masses) that drive exoplanetary science, astrobiology, and the next generation of interferometry and
direct imaging missions.
The low surface temperatures of M dwarfs place
their habitable zones at distances that are approximately 10 to 20 percent of Earth’s distance from the
Sun. These distances correspond to orbital periods of
20–50 days, another advantage of M dwarfs as potential targets for detecting habitable planets—because of
their small masses, these stars respond more noticeably to the gravitational forces of close-in planets.
2
Orbit of the planet HIP 57050b superimposed on our solar system. The orbits are to scale, but the
size of the Sun and the planets are not. The star HIP 57050 is much smaller than our Sun.
Haghighipour adds that it is interesting to speculate about the possible presence of a moon around HIP
57050b. While it is not out of the question that HIP
57050b could harbor a moon, and that moon would
thus be in the habitable zone of the parent star, an
object with only one-fifth the mass of Mars is
probably not a particularly good prospect for habitability from various standpoints. Furthermore, direct
detection of such a moon would be extremely
challenging.
IfA Astronomers Win 2010 Humboldt Awards
Two IfA astronomers are the recipients of senior
research awards from the Alexander von Humboldt
Foundation in Germany. These research awards are
intended to recognize the lifelong academic
achievements of the awardees, are granted on the basis
of nominations by eminent German scholars, and
enable awardees to come to Germany to work on a
research project with a German host.
IfA Director Rolf-Peter Kudritzki, who will relinquish the IfA directorship at the end of 2010, plans to
use his Humboldt award during a 2011 sabbatical in
Germany to investigate the physics of galaxies.
Kudritzki will use the brightest stars in the
Universe as tools to dissect galaxies. He will analyze
spectra of hundreds of supergiant stars (stars with radii
as large as 300 times the Sun and a hundred thousand
times brighter) in distant galaxies. By applying
completely new methods developed with his
collaborators, who include IfA astronomers Fabio
Bresolin and Miguel Urbaneja, Kudritzki will be able
to use the spectra to determine the chemical
compositions of galaxies and their distances from us.
For instance, in spiral galaxies like our own Milky
Way, the stars in the center have a higher percentage of
elements heavier than hydrogen and helium than the
stars at the edges of the rotating spiral arms.
Data about the chemical composition of galaxies
can be used to test the present theory about how
galaxies have formed in an expanding Universe that is
dominated by cold dark matter (matter that does not
interact with any form of light and whose constituent
particles move more slowly than light) and dark
energy (the mysterious force that is accelerating the
expansion of the Universe). In fact, chemical analysis
is one of the very few ways to test this scenario quantitatively. So far, the present knowledge of the chemical
composition of spiral galaxies is very uncertain.
Kudritzki’s new method will be the first to provide
accurate numbers.
“This project is entirely new. Nobody has ever
done anything like this, except Fabio, Miguel, and me.
Thus, I am truly excited and look forward to spending
all my energy and time on it. I will use all the largest
telescopes in the world for this project, including those
on Mauna Kea and in Chile, and also the Hubble Space
Telescope,” Kudritzki said.
Jeff Kuhn received his award on the strength of his
cumulative research studying the Sun. This is the first
time that a solar scientist from the United States has
been granted the prize. Kuhn’s research has often
focused on finding new ways to understand the solar
interior by using observations of its surface made by
instruments on the ground and in space. His group
recently found that, unlike almost everything else that
we measure about the Sun, it is constant in diameter
Rolf-Peter Kudritzki (right) working with collaborator Fabio
Bresolin. They have worked together for more than 10 years.
to better than a few parts in a million (see article on
page 6). Kuhn said, “I plan to use this award to
develop new models of how and why the solar cycle is
so dependent on the death cycle of sunspots.” He
added that the physics is not known but critical to
understanding how all stars evolve and change, and
that “this understanding may ultimately help us
predict how and when a changing Sun affects Earth's
climate.”
IfA astronomer J. Patrick Henry spent the spring in
Germany on a Humboldt award that is a follow-up to
the one he received in 2003. Henry is one of the
world’s experts on the cosmological evolution of
clusters of galaxies. He pioneered the use of X-ray
observations of clusters to understand how the entire
Universe grows. His work provided some of the
earliest evidence for what has become the standard
description of that growth, including the idea that
most matter in the Universe is dark matter. While in
Germany, Henry finished a paper describing the
properties of one of the most distant clusters of
galaxies yet found. These very distant objects let
astronomers actually see how clusters of galaxies are
formed rather than deducing how they formed from
studying the properties of fully grown examples.
IfA astronomer David Sanders is also a previous
winner of a Humboldt research award.
Jeff Kuhn
Pat Henry
3
Making Comets
Open House, Astroday Events
Hundreds of visitors attended the Mānoa Open House,
on April 18. Some came to see a fresnel lens melt a penny
and fry an egg. Others came to hear the talks, such as
Robert Jedicke explaining the connection between the
origin of the Universe and the Large Hadron Collider.
Children enjoyed making comets and sundials, seeing a
show in the StarLab planetarium, packaging an egg so that
it would survive a drop from the second floor (the Mars
Drop), and launching a bottle rocket. While the weather
cooperated, visitors viewed sunspots and Venus.
Lego Enthusiasts Association of Hawaii
IfA Mānoa Open House
The Mars Drop
4
Sunspot
Observing
Magnetic Fields of the Sun
AstroDay at Prince Kūhiō Plaza
Making Sundials
NASA IRTF demonstration
with infrared camera
The ninth annual AstroDay Festival, which
celebrates astronomy and Hawaiian culture, took place
on May 1 at Prince Kūhiō Plaza in Hilo. More than 30
scientific and cultural booths provided attendees with
the opportunity to play games, see planetarium shows
and demonstrations, and win Celestron telescopes. As
always, there was good entertainment, too. At the
beginning of the festivities, members of the Mauna Kea
Observatories Outreach Committee honored AstroDay
organizer (and IfA Science Education and Public
Outreach Officer) Gary Fujihara for his efforts to bring
astronomy to the people.
UH NAI Astrobiology
Ask an
Astronomer
Mānoa Open House photos by Karen Teramura.
The Fresnel Lens
“The Big Bang and Back Again”
talk by Robert Jedicke
5
Merging galaxies
Artistic representation of
the quasar stages after a
major galaxy merger.
Initially, the growing black
hole is completely
enshrouded by large
amounts of gas and dust.
After about 100 million
years, the strong pressure
provided by the quasar
emission is enough to blow
out most of the surrounding
gas, thus unveiling a
“naked” quasar, which is
clearly detectable at optical
and ultraviolet wavelengths.
Obscured quasar
Unobscured quasar
Merging galaxies: NASA, STScI/AURA, ESA
Art by Karen Teramura
Galaxy Collisions Create Large Black Holes and Quasars
Giant black holes at the centers of galaxies grow mainly
as a result of intergalactic collisions, according to IfA
astronomer Ezequiel Treister, leader of a study published
in March. As gas clouds in galaxies are sucked into the
central black hole, they emit vast amounts of radiation,
giving rise to quasars, which are very luminous active
galactic nuclei. “We find that these growing black holes
are originally hidden by large amounts of dust, but after
10–100 million years this dust is blown out by the strong
radiation pressure, leaving a naked quasar that is visible
at optical wavelengths and keeps shining for another 100
million years,” Treister said.
For this study, Treister and his colleagues combined
data obtained with the Hubble, Chandra, and Spitzer
space observatories to identify a large number of
obscured, dust-enshrouded quasars at very large
distances, up 11 billion light-years away, seen as they
were when the Universe was still in its infancy. “For
many years, astronomers believed that these sources
were very rare. Now we are seeing them everywhere!”
Treister said. Because most of the emission from these
obscured quasars is hidden, astronomers looked at
infrared wavelengths for signs of very hot dust, and in
X-rays, which are less affected by obscuration. The
investigators discovered that the number of obscured
quasars relative to the unobscured ones was
significantly larger in the early Universe than it is now.
Other team members are Priyamvada Natarajan,
Meg Urry, and Kevin Schawinski (Yale), IfA astronomer
David Sanders, and former IfA graduate student Jeyhan
Kartaltepe, who is now with the National Optical
Astronomy Observatories in Arizona.
Sun’s Constant Size Surprises Scientists
A group of astronomers led by the IfA’s Jeff Kuhn has found that in recent times the
Sun’s size has been remarkably constant. Its diameter has changed by less than one part
in a million over the last 12 years.
“This constancy is baffling, given the violence of the changes we see every day on
the Sun’s surface and the fluctuations that take place over an 11-year solar cycle,”
commented Kuhn, the IfA associate director who is responsible for Haleakalā
Observatories.
Kuhn’s work is part of worldwide efforts to understand the influence of the Sun on
Earth’s climate. “We can’t predict the climate on Earth until we understand these
changes on the Sun,” he said.
6
The Sun’s disk showing active region 10486, which
became the largest sunspot seen by SOHO, the
satellite Kuhn and collaborators used to monitor
the Sun’s diameter. Courtesy of SOHO/MDI
consortium. SOHO is a project of international
cooperation between ESA and NASA.
Kuhn and his colleagues (Rock Bush from Stanford, Marcelo Emilio from Brazil, and
Isabelle Scholl at IfA) used NASA’s long-lived Solar and Heliospheric Observatory
(SOHO) satellite to monitor the Sun’s diameter, and they will soon repeat the
experiment with much greater accuracy using NASA’s new Solar Dynamics
Observatory (SDO), which was launched on February 11. According to Kuhn, the
ultimate solution to this puzzle will depend on probing the smallest observable scales
of the solar surface using the Advanced Technology Solar Telescope (ATST), which is
scheduled for completion on Haleakalā in 2017.
“To be able to predict what the Sun will do, we need both the big picture and the
details. Just as powerful hurricanes on Earth start as a gentle breeze, the analogs of terrestrial storms on the Sun start as small kinks in the Sun’s magnetic field,” said Kuhn.
Upcoming Events
Please check with the sponsoring
organization for specific times and
locations for all events.
O‘ahu Events: call (808) 956-8566
www.ifa.hawaii.edu/specialevents/
September (TBA), Frontiers of Astronomy
Community Lecture.
Astrobiology Laboratory Institute for
Instructors (ALI‘I) National Summer
Teacher Workshop, June 27–July 2,
2010.
Art by Karen Teramura
When, How Did Earth Become Life Friendly?
www.ifa.hawaii.edu/UHNAI/epo/alii.htm
On March 31, a Frontiers of Astronomy Community Lecture presented by the IfA and the UH
NASA Astrobiology Institute (NAI) attempted to answer the question, “When and how did our
planet become conducive to life?”
Friends of the IfA Events:
Call (808) 956-6665 for more
information.
A panel consisting of Jeff Taylor, a geologist from the Hawai‘i Institute of Geophysics and
Planetology and a member of the UH NAI team; Karen Meech, IfA astronomer and principal
investigator for UH NAI; and Steve Mojzsis from the Department of Geological Sciences at the
University of Colorado explained what we know so far about this process. Steve Freeland, an
evolutionary biologist who is now the project manager of UH NAI, served as moderator.
www.ifa.hawaii.edu/friends/
Maui Events: call (808) 573-9516
Maui Maikalani Community Lectures
usually occur on the second Friday of
the month at the Maikalani Advanced
Technology Research Center, 34 ‘Ōhia
Kū Street, Pukalani, 6:30 p.m. Free.
Freeland explained that NASA organized the NASA Astrobiology Institute (NAI) in 1998 to
study the origins, evolution, distribution, and future of life in the Universe and that UH NAI is
one of 14 NAI centers located throughout the United States. Life on Earth, he said, is amazingly
diverse, with only a small fraction of it visible to the unaided eye.
Hawai‘i Island Events:
(808) 932-2328 or [email protected]
So how did Earth, at first a ball of molten rock, evolve into a planet with a surface of blue
oceans and green lands filled with life? First, it was necessary to build a planet. Taylor spoke
about what he termed the “haphazard” construction of our planet. In the solar nebula, dust grains
collided and stuck together. Collisions led to larger and larger bodies. Less volatile elements and
compounds, such as ferrous oxide (FeO), condensed out of the solar nebula at the higher
temperatures prevalent in the inner solar system, so early Earth was mostly metallic and rocky.
The AstroTalk lecture series is a monthly
free presentation at ‘Imiloa Astronomy
Center with the intent of bringing
together students, scientists, and
members of the community. For
information, www.imiloahawaii.org
But what about water, which condenses at a much lower temperature? Liquid water is
required for life as we know it, so next Meech discussed the origin of Earth’s water. There is
evidence of some water in many locations in the solar system—on Saturn’s moon Enceladus, on
Mars, and on the Moon—but generally speaking, the inner planets are dry. Even on Earth, the
oceans account for only 0.023 percent of the planet’s mass, and the total amount of water is
estimated at no more than a tenth of a percent of Earth’s mass. The exact amount of water on our
planet is undetermined, because scientists can only estimate how much water is deep beneath
Earth’s surface.
VISITING MAUNA KEA
The Onizuka Center for International
Astronomy Visitor Information Station
(VIS) at Hale Pohakū (9,300-foot level of
Mauna Kea) is open daily, 9:00 a.m. to
10:00 p.m.
"The Universe Tonight" features recent
discoveries, 6:00 p.m., first Saturday of
every month.
So where did Earth’s water come from? Was it captured from the solar nebula because water
molecules stuck to the dust that eventually formed the planet? Did a major impact cause Earth’s
surface to melt into a magma ocean, after which hydrogen in the atmosphere reacted with oxygen
to form water? Or did it arrive when asteroids or comets collided with Earth? Scientists are trying
to match the ratio of deuterium (D) to hydrogen (H) in the water from these sources with that on
Earth, but such attempts may not be accurate because we do not know the D/H ratio for water
inside Earth. Meech concluded by saying Earth’s water probably came from many sources.
"Malalo I Ka Lani Pō," cultural aspects of
Mauna Kea, 6:00 p.m., third Saturday of
every month.
Public stargazing nightly from 6:00 to
10:00 p.m. Summit tours begin at the
VIS at 1:00 p.m. on Saturday and
Sunday. For essential information, see
Mojzsis spoke about how Earth became habitable, and how it is a laboratory in the search for
life elsewhere. Evidence shows that about 4.53 billion years ago (about 40 million years after the
solar system formed), a large body collided with the proto-Earth, causing the formation of the
Moon and vaporizing magma on both bodies. After the collision, Earth cooled rapidly. Two
million years later, it had an atmosphere of rock vapor and water vapor. Forty million to 600
million years after the solar system formed, Earth had water and a crust, and was ready for life.
We know this because geologists have found rocks that are 4.3 billion years old and include
minerals that required abundant water to form.
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It appears, then, that the answer to the question, “When and how did our planet become
conducive to life?” is “very early, and we still have much to learn.”
www.ifa.hawaii.edu/info/vis/summittour.html
Dear Friends of the Institute for Astronomy,
Summer on a university campus is often a relatively quiet time, but so far, this summer has not been quiet
at IfA Mānoa. While some of our faculty and staff are on out-of-town trips, they have more than been
replaced by visitors from afar. First, undergraduates from throughout the United States (and one from France)
arrived for the tenth annual Research Experiences for Undergraduate program. Each student will work with a
faculty mentor on a research project throughout the summer. Eight of them are at IfA Mānoa, four are at IfA
Hilo, and two are on Maui.
Photo by Rainer Arlt/AIP,
Astronomischen Gesellschaft 2009, Potsdam
On June 4, a group of Hawai‘i students entering grades 7–11 and their teachers came to Mānoa to
participate in the Hawai‘i Student/Teacher Astronomy (HI STAR) program. Sponsored by the UH NASA
Astrobiology Institute, with additional support from private donors, HI STAR is a weeklong “astronomy
boot camp” for students and teachers who are passionate about astronomy and want to learn more about it.
At this very hands-on workshop, they learned how to make observations, do image processing, and use
software to measure the position and brightness of the observed objects.
From June 7 to 10, 65 people attended the 2010 COSMOS Team Meeting here. COSMOS—the Cosmic
Evolution Survey—has used the Hubble Space Telescope and other space- and ground-based observatories to
survey a two-square-degree region of the sky in unprecedented detail. Team members came from 10
countries to share information and plan future research.
Our solar scientists on Maui have also been busy. They hosted the Sixth Solar Polarization Workshop
May 30 through June 4 at the Sheraton Maui Resort and Spa. One hundred scientists from throughout the
world gathered to talk about using the technique called “polarimetry” to study the Sun and other stars.
Have a safe and enjoyable summer.
Aloha!
Rolf-Peter Kudritzki
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UH Institute for Astronomy
2680 Woodlawn Drive
Honolulu, HI 96822-1897
Nā Kilo Hōkū
“The Ones Who Look to the Stars”
No. 35 • 2010
Published by
The University of Hawai‘i
Institute for Astronomy
Rolf-Peter Kudritzki IfA Director
Louise H. Good Editor
Karen Teramura Design/Production
Education & Outreach
Gary Fujihara, Island of Hawai‘i
Mary Kadooka, O‘ahu, all islands
J. D. Armstrong, Maui
2680 Woodlawn Drive
Honolulu, Hawai‘i 96822
telephone (808) 956-8566
http://www.ifa.hawaii.edu/
Nā Kilo Hōkū is also online:
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