A solar gravitational lens or solar gravity lens (SGL) is a theoretical method of using the Sun as a large lens with a physical effect called gravitational lensing. [1] It is considered one of the best methods to directly image habitable exoplanets.
The solar gravitational lens is characterized by remarkable properties: it offers brightness amplification of up to a factor of ~1011 (at 1 μm ) and extreme angular resolution (~10−10 arcsec). [2]
Albert Einstein predicted in 1936 that rays of light from the same direction that skirt the edges of the Sun would converge to a focal point approximately 542 AUs from the Sun. [3] A probe positioned at this distance from the Sun could use it as a gravitational lens for magnifying distant objects on the opposite side of the Sun. The probe's location could shift around as needed to select different targets relative to the Sun. In 1979, Von Eshleman was the first author proposing to use the Sun as a large lens. [4]
The Sun's gravitational field bends light more prominently the closer it gets to the Sun. Light rays passing on opposite sides of the Sun meet at a focal point, forming a series of points along a line that extends from the star through the Sun's center. With the solar corona having an active and dynamic atmosphere, the beams of light passing close to the Sun are affected by the particles of the atmosphere. [5]
A probe called SETIsail and later FOCAL was proposed to the ESA in 1993, but is expected to be a difficult task. If a probe does pass 542 AU, magnification capabilities of the lens will continue to act at farther distances, as the rays that come to a focus at larger distances pass further away from the distortions of the Sun's corona.
In 2020, NASA physicist Slava Turyshev presented his idea of direct multi-pixel imaging and spectroscopy of an exoplanet with a solar gravitational lens mission. The lens could reconstruct the exoplanet image with ~25 km-scale surface resolution in 6 months of integration time, enough to see surface features and signs of habitability. [2] His proposal was selected for the Phase III of the NIAC 2020 (NASA Institute for Advanced Concepts). [6] Turyshev proposes to use realistic-sized solar sails (~16 vanes of 103 m2) to achieve the needed high velocity at perihelion (~150 km/sec), reaching 547 AU in 17 years. [7]
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 then recognized as such. The first confirmation of the detection occurred in 1992. A different planet, first detected in 1988, was confirmed in 2003. According to statistics from the NASA Exoplanet Archive, As of 19 September 2024, there are 5,759 confirmed exoplanets in 4,300 planetary systems, with 963 systems having more than one planet. The James Webb Space Telescope (JWST) is expected to discover more exoplanets, and to give more insight into their traits, such as their composition, environmental conditions, and potential for life.
A gravitational lens is matter, such as a cluster of galaxies or a point particle, that bends light from a distant source as it travels toward an observer. The amount of gravitational lensing is described by Albert Einstein's general theory of relativity. If light is treated as corpuscles travelling at the speed of light, Newtonian physics also predicts the bending of light, but only half of that predicted by general relativity.
A galaxy cluster, or a cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity, with typical masses ranging from 1014 to 1015 solar masses. They are the second-largest known gravitationally bound structures in the universe after some superclusters (of which only one, the Shapley Supercluster, is known to be bound). They were believed to be the largest known structures in the universe until the 1980s, when superclusters were discovered. One of the key features of clusters is the intracluster medium (ICM). The ICM consists of heated gas between the galaxies and has a peak temperature between 2–15 keV that is dependent on the total mass of the cluster. Galaxy clusters should not be confused with galactic clusters (also known as open clusters), which are star clusters within galaxies, or with globular clusters, which typically orbit galaxies. Small aggregates of galaxies are referred to as galaxy groups rather than clusters of galaxies. The galaxy groups and clusters can themselves cluster together to form superclusters.
An Einstein ring, also known as an Einstein–Chwolson ring or Chwolson ring, is created when light from a galaxy or star passes by a massive object en route to the Earth. Due to gravitational lensing, the light is diverted, making it seem to come from different places. If source, lens, and observer are all in perfect alignment (syzygy), the light appears as a ring.
The Kepler space telescope is a defunct space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orbit. The principal investigator was William J. Borucki. After nine and a half years of operation, the telescope's reaction control system fuel was depleted, and NASA announced its retirement on October 30, 2018.
Gravitational microlensing is an astronomical phenomenon caused by 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 can only detect bright objects that emit much light (stars) or large objects that block background light. These objects make up only a minor portion of the mass of a galaxy. Microlensing allows the study of objects that emit little or no light.
An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body.
The NASA Innovative 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 NASA Institute for Advanced Concepts from 1998 until 2007, and was reestablished in 2011 under the name NASA Innovative Advanced Concepts and continues to the present. The NIAC program funds work on revolutionary aeronautics and space concepts that can dramatically impact how NASA develops and conducts its missions.
OGLE-2005-BLG-390Lb is a super-Earth exoplanet orbiting OGLE-2005-BLG-390L, a star 21,500 ± 3,300 light-years from Earth near the center of the Milky Way, making it one of the most distant planets known. On January 25, 2006, Probing Lensing Anomalies NETwork/Robotic Telescope Network (PLANET/Robonet), Optical Gravitational Lensing Experiment (OGLE), and Microlensing Observations in Astrophysics (MOA) made a joint announcement of the discovery. The planet does not appear to meet conditions presumed necessary to support life.
The Einstein radius is the radius of an Einstein ring, and is a characteristic angle for gravitational lensing in general, as typical distances between images in gravitational lensing are of the order of the Einstein radius.
Vyacheslav Gennadievich Turyshev is a Russian physicist now working in the US at the NASA Jet Propulsion Laboratory (JPL). He is known for his investigations of the Pioneer anomaly, affecting Pioneer 10 and Pioneer 11 spacecraft, and for his attempt to recover early data of the Pioneer spacecraft to shed light on such a phenomenon.
An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016; no planet discovery has yet come from that evidence. What turned out to be the first detection of an exoplanet was published among a list of possible candidates in 1988, though not confirmed until 2003. The first confirmed detection came in 1992, with the discovery of terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 24 July 2024, there are 7,026 confirmed exoplanets in 4,949 planetary systems, with 1007 systems having more than one planet. This is a list of the most notable discoveries.
FOCAL is a proposed space telescope that would use the Sun as a gravity lens. The gravitational lens effect was first derived by Albert Einstein, and the concept of a mission to the solar gravitational lens was first suggested by professor Von Eshleman, and analyzed further by Italian astronomer Claudio Maccone and others.
Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail interstellar probes named Starchip, to be capable of making the journey to the Alpha Centauri star system 4.34 light-years away. It was founded in 2016 by Yuri Milner, Stephen Hawking, and Mark Zuckerberg.
The Large Ultraviolet Optical Infrared Surveyor, commonly known as LUVOIR, is a multi-wavelength space telescope concept being developed by NASA under the leadership of a Science and Technology Definition Team. It is one of four large astrophysics space mission concepts studied in preparation for the National Academy of Sciences 2020 Astronomy and Astrophysics Decadal Survey.
The Habitable Exoplanet Observatory (HabEx) is a space telescope concept that would be optimized to search for and image Earth-size habitable exoplanets in the habitable zones of their stars, where liquid water can exist. HabEx would aim to understand how common terrestrial worlds beyond the Solar System may be and determine the range of their characteristics. It would be an optical, UV and infrared telescope that would also use spectrographs to study planetary atmospheres and eclipse starlight with either an internal coronagraph or an external starshade.
Kepler-1649c is an Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf star Kepler-1649, the outermost planet of the planetary system discovered by Kepler’s space telescope. It is located about 301 light-years (92 pc) away from Earth, in the constellation of Cygnus.
A Terrestrial Atmospheric Lens is a theoretical method of using the Earth as a large lens with a physical effect called atmospheric refraction.