 Detection of MACS J1149 Lensed Star 1 A galactic cluster (left)magnified a distant star (now namedIcarus) more than 2,000 times, making it visible in 2016 from Earth (lower right), 9.34 billion light-years away—although visible in 2016, the star was not visible in 2011 (upper right). | |
| Observation data EpochJ2000[1] EquinoxJ2000[1] | |
|---|---|
| Constellation | Leo[1][2] |
| Right ascension | 11h 49m 35.59s[1] |
| Declination | 22° 23′ 47.4″[1] |
| Astrometry | |
| Distance | Redshift of 1.49 yieldscomoving distances of 14.4 billion ly |
| Characteristics | |
| Spectral type | B[2] |
| Apparent magnitude (V) | ≈28.4[2] (normally 29.9)[note 1] |
| Apparent magnitude (R) | ≈28.2[2] (normally 29.7) |
| Apparent magnitude (Z) | ≈27.9[2] (normally 29.4) |
| Apparent magnitude (J) | 27.3[2] (normally 28.8) |
| Apparent magnitude (H) | 27.4[2] (normally 28.9) |
| Details | |
| Surface gravity (log g) | 2 - 4[2] cgs |
| Temperature | 11,000 – 14,000[2] K |
| Metallicity | ≈0.006[2] |
| Age | ~8[2] Myr |
| Other designations | |
| Icarus, LS1, MACS J1149 LS1, MACS J1149 Lensed Star 1 (LS1), MACS J1149+2223 Lensed Star 1 | |
MACS J1149 Lensed Star 1, also known asIcarus,[note 2] is ablue supergiantstar observed through agravitational lens. It is the seventhmost distant individual star to have been detected so far (afterEarendel,Godzilla,Mothra,Quyllur,star-1 and star-2), at approximately 14 billionlight-years fromEarth (redshift z=1.49;comoving distance of 14.4 billion light-years;lookback time of 9.34 billion years).[3][2][4][5][6][7][8] Light from thestar was emitted 4.4 billion years after theBig Bang.[7] According to co-discoverer Patrick Kelly, the star is at least a hundred times more distant than the next-farthest non-supernova star observed,SDSS J1229+1122, and is the first magnified individual star seen.[4][7]
In April and May 2018,[2] the star was found in the course of studying the supernovaSN Refsdal with theHubble Space Telescope. Astronomer Patrick Kelly of theUniversity of Minnesota is the lead author of the finding, published in the journalNature Astronomy.[2][8]
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 bygravitational lensing.[2][4][5][6][7][9] The light from LS1 was magnified not only by the huge total mass of thegalaxy clusterMACS J1149.5+2223—located 5 billion light-years away—but also transiently by another compact object of about threesolar masses within the galaxy cluster itself that passed through the line of sight, an effect known asgravitational microlensing.[7][9][10] 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.[2] There was a second peak near the brightness curve maximum, which may indicate the star wasbinary.[2] The microlensing body may have been a star or a black hole in the cluster. Continuous monitoring of the starIcarus may one day rule out the possibility that primordial black holes constitute a sizable fraction ofdark matter.[9] Normally, the only astronomical objects that can be detected at this range would be either whole galaxies,quasars, orsupernovas, but the light from the star was magnified by the lensing effect. They determined the light was from a stable star, not asupernova, as its temperature did not fluctuate; the temperature also allowed them to catalog the star as ablue supergiant.[11] 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.[11]
The formal name MACS J1149 is a reference toMAssive Cluster Survey and the star's coordinates in theJ2000 astronomical epoch.
While Kelly had wanted to name the starWarhol, alluding toAndy Warhol's notion of having15 minutes of fame, the team ended up naming the starIcarus based on theGreek mythological figure.[8]
The discovery shows that astronomers can study the oldest stars in backgroundgalaxies of the earlyuniverse by combining the strong gravitational lensing effect from galaxy clusters with gravitational microlensing events caused by compact objects in these galaxy clusters.[2][12] By using these events, astronomers can study and test some models about dark matter in galaxy clusters and observe high energy events (supernovae,variable stars) in young galaxies.[9][12][13]
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