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The New Worlds Mission is a proposed project comprising a large occulter flying in formation with a
space telescope A space telescope or space observatory is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launch ...
designed to block the light of nearby stars in order to observe their orbiting
exoplanets An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
. The observations could be taken with an existing space telescope or a dedicated visible light
optical telescope An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through elect ...
optimally designed for the task of finding exoplanets. A preliminary research project was funded from 2005 through 2008 by
NASA Institute for Advanced Concepts The NASA Institute for Advanced Concepts (NIAC) is a NASA program for development of far reaching, long term advanced concepts by "creating breakthroughs, radically better or entirely new aerospace concepts". The program operated under the name ...
(NIAC) and headed by Webster Cash of the
University of Colorado at Boulder The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a public research university in Boulder, Colorado. Founded in 1876, five months before Colorado became a state, it is the flagship university of the University of Colorado sy ...
in conjunction with Ball Aerospace & Technologies Corp.,
Northrop Grumman Northrop Grumman Corporation is an American multinational aerospace and defense technology company. With 90,000 employees and an annual revenue in excess of $30 billion, it is one of the world's largest weapons manufacturers and military techn ...
, Southwest Research Institute and others. Since 2010 the project has been looking for additional financing from NASA and other sources in the amount of roughly US$3 billion including its own four-meter telescope.
- arcseconds. Angles this small are impossible to resolve from the ground due to
astronomical seeing In astronomy, seeing is the degradation of the image of an astronomical object due to turbulence in the atmosphere of Earth that may become visible as blurring, twinkling or variable distortion. The origin of this effect are rapidly changing var ...
. *Exoplanets being extremely dim compared to their host stars. Typically, the star will be approximately a billion times brighter than the orbiting planet. This makes it nearly impossible to see planets against the star's glare. The difficulty of observing such a dim planet so close to a bright star is the obstacle that has prevented astronomers from directly photographing exoplanets. To date, only a handful of exoplanets have been photographed. The first exoplanet to be photographed, 2M1207b, is in orbit around a star called
2M1207 2M1207, 2M1207A or 2MASSW J12073346–3932539 is a brown dwarf located in the constellation Centaurus; a companion object, 2M1207b, may be the first exoplanet, extrasolar planetary-mass object, planetary-mass companion to be directly image ...
. Astronomers were only able to photograph this planet because it is a very unusual planet that is very far from its host star, approximately 55
astronomical units The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits ...
(about twice the distance of Neptune). Furthermore, the planet is orbiting a very dim star, known as a
brown dwarf Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...
. To overcome the difficulty of distinguishing more Earth-like planets in the vicinity of a bright star, the New Worlds Mission would block the star's light with an occulter. The occulter would block all of the starlight from reaching the observer, while allowing the planet's light to pass undisturbed. The starshade would be tens of meters across and probably made out of Kapton, a lightweight material similar to
Mylar BoPET (biaxially-oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and a ...
.


Methods

Traditional methods of exoplanet detection rely on indirect means of inferring the existence of orbiting bodies. These methods include: * Astrometry – watching a star move slightly due to the gravitational influence of a nearby planet *Observing Doppler shifts of the star's spectrum due to the star's movement *Observing the amount of light from a star change as an extrasolar planet transits the star, preventing a portion of the light from reaching the observer * Pulsar timing *
Gravitational microlensing Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects that range from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers ...
*Observing radiation from circumstellar disks in the
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
All of these methods provide convincing evidence for the existence of extrasolar planets, but none of them provide actual images of the planets. The goal of the New Worlds Mission is to block the light coming from nearby stars with an occulter. This would allow the direct observation of orbiting planets. The occulter would be a large sheet disc flown thousands of kilometers along the line of sight. The disc would likely be several tens of meters in diameter and would fit inside existing expendable launch vehicles and be deployed after launch. One difficulty with this concept is that light incoming from the target star would
diffract Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a s ...
around the disc and constructively interfere along the central axis. Thus the starlight would still be easily visible, making planet detection impossible. This concept was first famously theorized by Siméon Poisson in order to disprove the wave theory of light, as he thought the existence of a bright spot at the center of the shadow to be nonsensical. However Dominique Arago experimentally verified the existence of the spot of Arago. This effect can be negated by specifically shaping the occulter. By adding specially shaped petals to the outer edge of the disc, the spot of Arago will disappear, allowing the suppression of the star's light. This technique would make planetary detection possible for stars within approximately 10 parsecs (about 32
light years A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
) of Earth. It is estimated that there could be several thousand
exoplanets An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
within that distance. The starshade is similar to but should not be confused with the
Aragoscope An Aragoscope is a telescope design based on diffraction around the edge of an occluding disc, named after French scientist François Arago. Concept The light diffracted around the edge of a perfectly circular occluder interferes constructively at ...
, which is a proposed imaging device designed to use the diffraction of light around a perfectly-circular light-shield to produce an image. The starshade is a proposed sunflower-shaped
coronagraph A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved. Most coronagraphs are intended to view t ...
disc that was designed to block starlight that interferes with telescopic
observations Observation is the active acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the perception and recording of data via the use of scientific instrument ...
of other worlds. The "petals" of the "sunflower" shape of the starshade are designed to eliminate the diffraction that is the central feature of an
Aragoscope An Aragoscope is a telescope design based on diffraction around the edge of an occluding disc, named after French scientist François Arago. Concept The light diffracted around the edge of a perfectly circular occluder interferes constructively at ...
. The starshade is a
spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...
designed by Webster Cash, an astrophysicist at the
University of Colorado at Boulder The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a public research university in Boulder, Colorado. Founded in 1876, five months before Colorado became a state, it is the flagship university of the University of Colorado sy ...
's Center for Astrophysics and Space Astronomy. The proposed spacecraft was designed to work in tandem with
space telescope A space telescope or space observatory is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launch ...
s like the James Webb Space Telescope, which did not use it, or a new 4-meter telescope. It would fly in front of a space telescope (between the telescope and a target star) and approximately away from Earth, outside of Earth's heliocentric orbit. When unfurled, the starshade resembles a sunflower, with pointed protrusions around its circumference. The starshade acts as a very large
coronagraph A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved. Most coronagraphs are intended to view t ...
: it blocks light of a distant star, making it easier to observe associated planets. The unfurled starshade could reduce collected light from bright stars by as much as 10 billion-fold. Light that "leaks" around the edges would be used by the telescope as it scans the target system for planets. With the reduction of the harsh light, astronomers will be able to check exoplanet atmospheres tens of trillions of miles away for the potential chemical signatures of
life Life is a quality that distinguishes matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes, from that which does not, and is defined by the capacity for Cell growth, growth, reaction to Stimu ...
.CU Proposal To Image Distant Planets Is Funded For Second Round Of Study


Objectives

The New Worlds Mission aims to discover and analyze terrestrial extrasolar planets: #Detection: First, using the space telescope and 'starshade', or occulter, exoplanetary systems will be directly detected. #System mapping: Following detection, system mapping would involve the direct mapping of planetary systems through the detection of the planetary light separate from the parent star. In a sufficiently high-quality image, planets would appear as individual star-like objects. A series of images of the planetary system would allow measurements of planetary orbits, and the brightness and broadband colors of the planets would provide information about their basic nature. #Planet studies: At this stage, detailed study of individual planets would take place. With a low noise level and a modest signal, spectroscopy and photometry can be performed. Spectroscopy allows scientists to perform chemical analysis of atmospheres and
surfaces A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. Surface or surfaces may also refer to: Mathematics *Surface (mathematics), a generalization of a plane which needs not be flat * Sur ...
, which might hold clues to the existence of
life Life is a quality that distinguishes matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes, from that which does not, and is defined by the capacity for Cell growth, growth, reaction to Stimu ...
elsewhere in the
universe The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. ...
. Photometry will show variation in color and intensity as surface features rotate in and out of the field of view, allowing for the detection of oceans, continents, polar caps and clouds. #Planet imaging: A large increase in capability is needed to achieve true planet imaging. However, techniques of interferometry show that, in principle, this is possible to achieve. Fifty to one hundred percent of a planet's surface could theoretically be mapped, depending on the planet's
inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...
. #Planetary assessment: The final step in extrasolar planet studies would be the ability to study these distant worlds in the same way that Earth-observing systems study the Earth's surface. Such a telescope would need to be extremely large, to collect enough light to resolve and analyze small details on the planet's surface. However, these kinds of studies do not lie in the foreseeable future, for it takes square kilometers of collecting area to capture the needed signal. In addition to finding and analyzing terrestrial planets, it can also discover and analyze
gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...
s. The New Worlds Mission will also find
moons A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'' ...
and
rings Ring may refer to: * Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry * To make a sound with a bell, and the sound made by a bell :(hence) to initiate a telephone connection Arts, entertainment and media Film and ...
orbiting extrasolar planets. This technique will involve direct imaging of planets by blocking the starlight with a starshade. It will study the moons and rings in detail and find whether moons can also support life if gas giant planets orbit in the
habitable zone In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.J. F. Kast ...
s of parent stars.


Architecture

There are many possibilities for various New Worlds Missions, three of which are: #New Worlds Discoverer proposed to use an existing space telescope (like the James Webb telescope), to find exoplanets. The size of the starshade could be optimized for the observing telescope. #New Worlds Observer would use two spacecraft, one that has a dedicated telescope and one with a starshade to find exoplanets. The possibility of two starshades is also a consideration. One starshade to point towards the desired target while the other moves into position for the next target. This would eliminate some of the time delay in observing different systems and allow for many more targets to be observed in the same timespan. #New Worlds Imager would use many spacecraft/starshades. This would allow observers to resolve the planet and obtain true planetary imaging.


See also

*
Coronagraph A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved. Most coronagraphs are intended to view t ...
, a telescopic attachment to block out the light from a star so that nearby objects can be resolved *
Space sunshade A space sunshade or sunshield is a parasol that diverts or otherwise reduces some of the Sun's radiation, preventing it from hitting a spacecraft or planet and thereby reducing its insolation, which results in reduced heating. Light can be di ...
*
Aragoscope An Aragoscope is a telescope design based on diffraction around the edge of an occluding disc, named after French scientist François Arago. Concept The light diffracted around the edge of a perfectly circular occluder interferes constructively at ...


References


External links


New World's official website at University of Colorado, BoulderFinding planets through a pinhole
{{Exoplanet search projects Diffraction Exoplanet search projects Proposed spacecraft Space telescopes Articles containing video clips NASA programs