The Cloverleaf quasar (H1413+117, QSO J1415+1129) is a bright, gravitationally lensed

quasar A quasar ( ) is an extremely Luminosity, luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by accretion onto a supermassive black hole with a mass rangi ...

discovered by Hazard, Morton, Terlevich and McMahon in 1984 . It receives its name because of

gravitational lensing A gravitational lens is matter, such as a galaxy cluster, 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 Ge ...

spitting the single quasar into four images.. Gravitational lensing of the quasat H1413+1011 was discovered in Magain et al. in 1988 discovered that the quasars was split by gravitational lensing by a foreground galaxy into four images gave it the name "Cloverleaf quasar".

Quasar

Molecular gas (notably CO) detected in the host galaxy associated with the quasar is the oldest molecular material known and provides evidence of large-scale star formation in the early universe. Thanks to the strong magnification provided by the foreground

lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...

, the Cloverleaf is the brightest known source of CO emission at high redshift and was also the first source at a

redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and e ...

to be detected with HCN or HCO⁺ emission. This suggests the quasar is currently undergoing an intense wave of star formations thus increasing its

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

. A radio jet has also been found on the side of quasar according to a study published in 2023. The 4 quasar images were originally discovered in 1984; in 1988, they were determined to be a single quasar split into four images, instead of 4 separate quasars. The

X-rays An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

from iron atoms were also enhanced relative to X-rays at lower energies. Since the amount of brightening due to gravitational lensing doesn't vary with the wavelength, this means that an additional object has magnified the X-rays. The increased

magnification Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a size ratio called optical magnification. When this number is less than one, it refers to a reduction in size, so ...

of the X-ray light can be explained by gravitational

microlensing 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, astronome ...

, an effect which has been used to search for compact

stars A star is a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of ...

and

planets A planet is a large, rounded astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets by the most restrictive definition of the te ...

in our galaxy. Microlensing occurs when a star or a multiple star system passes in front of light from a background object. If a single star or a multiple star system in one of the foreground galaxies passed in front of the light path for the brightest image, then that image would be selectively magnified.

Black hole

The X-rays would be magnified much more than the

visible light Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm ...

if they came from a region around the central

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (). Black holes are a class of astronomical ...

of the lensing galaxy that was smaller than the origin region of the visible light. The enhancement of the

from

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

ions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

would be due to this same effect. The analysis indicates that the X-rays are coming from a very small region, about the size of the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

, around the central black hole. The visible light is coming from a region ten or more times larger. The angular size of these regions at a distance of 11 billion

light years A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astro ...

is tens of thousands times smaller than the smallest region that can be resolved by the Hubble Space

Telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

. This provides a way to test models for the flow of gas around a supermassive black hole. Additionally, inner regions of the quasar's

accretion disk An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is most frequently a star. Friction, uneven irradiance, magnetohydrodynamic effects, and ...

around the black hole has been detected suggesting outflow wind.

Lensing galaxy and partial Einstein ring

Data from NICMOS and a special

algorithm In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...

resolved the lensing galaxy and a partial Einstein ring. The Einstein ring represents the host galaxy of the lensed quasar.

History

The Cloverleaf quasar was discovered in 1988. Data on the Cloverleaf collected by the

Chandra X-ray Observatory The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources ...

in 2004 were compared with that gathered by optical telescopes. One of the X-ray components (A) in the Cloverleaf is brighter than the others in both optical and X-ray light but was found to be relatively brighter in X-ray than in optical light. The X-rays from iron atoms were also enhanced relative to X-rays at lower energies.

Gallery

File:Coverleaf Quasar HST ACS+HRC.png, Quadruple image of the quasar taken with

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

. File:Gravitational Lensing Graphic - PIA23641.tiff, Graphic illustration of four images of the quasar caused by gravitational lensing.

References

External links

* Chandra at Havard CfA
"Cloverleaf Quasar: Chandra Looks Over a Cosmic Four-Leaf Clover"
20 February 2009 {{DEFAULTSORT:Cloverleaf Quasar Gravitationally lensed quasars Boötes