MACS J1149 Lensed Star 1, also known as Icarus,Other names include ''LS1'', ''MACS J1149 LS1'', ''MACS J1149 Lensed Star 1 (LS1)'' and ''MACS J1149+2223 Lensed Star 1'' is a

blue supergiant A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blu ...

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

observed through a

gravitational lens 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 ...

. It is the seventh most distant individual star to have been detected so far (after Earendel,

Godzilla is a fictional monster, or ''kaiju'', that debuted in the eponymous 1954 film, directed and co-written by Ishirō Honda. The character has since become an international pop culture icon, appearing in various media: 33 Japanese films p ...

Mothra is a fictional monster, or '' kaiju'', which first appeared as the title character in Ishirō Honda's '' 1961 film of the same name'', produced and distributed by Toho. Mothra has appeared in several Toho ''tokusatsu'' films, often as a recur ...

, Quyllur, star-1 and star-2), at approximately 14 billion

light-year 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 Astr ...

s from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

(

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 ...

z=1.49;

comoving distance In standard cosmology, comoving distance and proper distance (or physical distance) are two closely related distance measures used by cosmologists to define distances between objects. ''Comoving distance'' factors out the expansion of the univ ...

of 14.4 billion light-years; lookback time of 9.34 billion years). Light from the

was emitted 4.4 billion years after the

Big Bang The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including th ...

. According to co-discoverer Patrick Kelly, the star is at least a hundred times more distant than the next-farthest non-

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

star observed,

SDSS J1229+1122 SDSS J1229+1122 (SDSS J122952.66+112227.8) is a blue supergiant O-type star in the tail of dwarf irregular galaxy IC 3418. It illuminates a nebula clump of gas, and was discovered from the spectrum of the illumination source. The clump o ...

, and is the first magnified individual star seen.

History

NASA-Icarus-BlueSuperGiantSpectrum-Hubble-20180402

In April and May 2018, the star was found in the course of studying the supernova

SN Refsdal SN Refsdal is the first detected multiply-lensed supernova, visible within the field of the galaxy cluster MACS J1149+2223. It was named after Norwegian astrophysicist Sjur Refsdal, who, in 1964, first proposed using time-delayed images from a ...

with the

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 ...

. Astronomer Patrick Kelly of the

University of Minnesota The University of Minnesota Twin Cities (historically known as University of Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Twin Cities of Minneapolis and Saint ...

is the lead author of the finding, published in the journal ''

Nature Astronomy ''Nature Astronomy'' is a peer reviewed scientific journal published by Nature Portfolio. It was first published in January 2017 (volume 1, issue 1), although the first content appeared online in December 2016. The editor-in-chief is Paul Woods, w ...

''. While astronomers had been collecting images of this supernova from 2004 onward, they recently discovered a point source that had appeared in their 2013 images, and become much brighter by 2016. They determined that the point source was a solitary star being magnified more than 2,000 times by

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 ...

. The light from LS1 was magnified not only by the huge total mass of the

galaxy cluster 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. Clusters consist of galax ...

MACS J1149.5+2223 —located 5 billion light-years away—but also transiently by another compact object of about three

solar mass The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxie ...

es within the galaxy cluster itself that passed through the line of sight, an effect known as

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, astronom ...

. The galaxy cluster magnification is probably a factor of 600, while the microlensing event, which peaked in May 2016, brightened the image by an additional factor of ~4. There was a second peak near the brightness curve maximum, which may indicate the star was

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two values (0 and 1) for each digit * Binary function, a function that takes two arguments * Binary operation, a mathematical op ...

. The microlensing body may have been a star or a black hole in the cluster. Continuous monitoring of the star ''Icarus'' may one day rule out the possibility that primordial black holes constitute a sizable fraction of

dark matter In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...

. Normally, the only astronomical objects that can be detected at this range would be either whole galaxies,

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 ...

s, or

s, but the light from the star was magnified by the lensing effect. They determined the light was from a stable star, not a

, as its temperature did not fluctuate; the temperature also allowed them to catalog the star as a

. Because the visible light is the redshifted ultraviolet tail, the star does not appear blue to us but reddish or pink. The light observed from the star was emitted when the universe was about 30% of its current age of 13.8 billion years. Kelly suggested that similar microlensing discoveries could help them identify the earliest stars in the universe.

Name

The formal name MACS J1149 is a reference to

MAssive Cluster Survey The MAssive Cluster Survey (MACS) compiled and characterized a sample of very X-ray luminous (and thus, by inference, massive), distant clusters of galaxies. The sample comprises 124 spectroscopically confirmed clusters at 0.3 < z < 0.7. Candidate ...

and the star's coordinates in the

J2000 In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to ...

astronomical epoch. While Kelly had wanted to name the star ''Warhol'', alluding to

Andy Warhol Andy Warhol (;''Random House Webster's Unabridged Dictionary''"Warhol" born Andrew Warhola Jr.; August 6, 1928 – February 22, 1987) was an American visual artist, film director and producer. A leading figure in the pop art movement, Warhol ...

's notion of having

15 minutes of fame 15 minutes of fame is short-lived media publicity or celebrity of an individual or phenomenon. The expression was inspired by a quotation misattributed to Andy Warhol: "In the future, everyone will be world-famous for 15 minutes." Attributed to ...

, the team ended up naming the star ''Icarus'' based on the Greek mythological figure.

Astrophysical implications

The discovery shows that astronomers can study the oldest stars in background

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar Sys ...

of the early

universe The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...

by combining the strong gravitational lensing effect from galaxy clusters with gravitational microlensing events caused by compact objects in these galaxy clusters. By using these events, astronomers can study and test some models about dark matter in galaxy clusters and observe high energy events (supernovae,

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

s) in young galaxies.

Notes

References

External links

Hubble Discovers Supernova Split by Cosmic Lens
–

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

(2017)
View of SN Refsdal
–

National Geographic Society The National Geographic Society, headquartered in Washington, D.C., United States, is one of the largest nonprofit scientific and educational organizations in the world. Founded in 1888, its interests include geography, archaeology, natural sc ...

(2015)
Images of SN Refsdal
–

HubbleSite The Space Telescope Science Institute (STScI) is the science operations center for the Hubble Space Telescope (HST), science operations and mission operations center for the James Webb Space Telescope (JWST), and science operations center for the ...