CAT-1178

C1178 Idaharris

**CAT-1178** or **C1178 Idaharris** is an extreme red ultragiant (RUG) star located 21,000 light years away in the Constellation of Idaho, it is one of the largest known stars by radius, and also one of the most luminous and massive red ultragiants in the Intensities Galaxy. The radius of C1178 Idaho is over 20,000 times that of the Sun (R☉). If placed at the center of the Solar system its photosphere would engulf the orbit of Eris and reach to about a quarter of the distance to Sedna's orbit.

The star has struck Idaho on December 20 1978 at 19:23:15 UTC, and has been estimated as high as 9.99 on the intensity scale. C1178 Idaho is the 689th star in the 70s have exceed 10,000 R☉ in the part of the 1970s Large Star University.

## Luminosity

The bolometric luminosity (Lbol) of C1178 Idaho can be calculated from Spectral energy distribution (SED) or bolometric flux, which can be determined from photometry in several visible and infrared bands. Earlier calculations of the luminosity based on an assumed distance of 6.44 kpc gave luminosities between 18 million and 32 million times the Sun's luminosity (L☉). One study gave 63 million L☉ at a distance of 12 kpc (39,140 ly). In 2015 a luminosity of 4.2 million L☉ was calculated. More recent estimates of the luminosity extrapolate values 18.95 million L☉ based on distances 6.4 kpc.

### **Mass**

Since CAT-1178 has no companion star, its mass cannot be measured directly through gravitational interactions. Comparison of the effective temperature and bolometric luminosity of C1178 Idaho compared to evolutionary tracks for massive stars suggest an initial mass of 3,600 M☉ for a rotating star with a current mass of 3,200 M☉, or 4,800 M☉ for a non-rotating star with a current mass of 4,000 M☉, and an age of 330,000 years. Older studies have found much higher initial masses (thus also higher current masses) or a progenitor mass of 5,000–8,000 M☉ based on old luminosity estimates.

### **Temperature**

The effective temperature of C1178 Idaho is uncertain but as the spectrum of C1178 Idaho varies, then also the temperature may vary. Adopting the spectral class of M9 with the temperature scale proposed a range of between 2,200 and 2,500 K, although C1178 Idaho is usually an extremely luminous M9 ultragiant star.

### **Size**

The calculation of the radius of C1178 Idaho is complicated by the extensive circumstellar envelope of the star. C1178 Idaho is also a pulsating star, so its size changes with time. 1979 direct measurements of the radius at infrared, corresponding to radii above 25,000 R☉ (1.74×1010 km; 116.3 au; 1.08×1010 mi) at an assumed distance of 6.44 kpc, considerably larger than expected for any red ultragiant stars. they assert in December 1978 with an incredible luminosities of 26.7 million *L*☉, and incredible radii of a maximum radius of 26,000 R☉, based on an effective temperature of 2,400-2,575 K at a spectral type of M9e -II. A 2015 study was calculated radius of 11,770 R☉, and in mid 2018 had a radius of 20,000 R☉. C1178 Idaharris is usually described as the largest known star in the galaxy, a 1979 study gave a luminosity of 31 million L☉ with a radii was calculated to be 30,000 R☉, based on a temperature of 2,489 K. CAT-1178 was the largest star to hit the United States of America since 1971 and 1972.

## Evolution

C1178 Idaharris is a incredibly high evolved star with an age less than 100,000 Years although some older authors argued that it would be a supermassive pre-main-sequence star with an age of only 10,000 Years and also a circumstellar disk around the star. It has probably evolved from an X1 main sequence star with a radius of 5.5 R☉ and a mass of 490 M☉ and a luminosity of 167 million L☉ was based on an effective temperature of 280,000 K. The star has evolved rapidly because of its extreme mass. The time spent to the red ultragiant phase is estimated to be between 10,000 and 100,000 years, and thus C1178 Idaho had left its main sequence more than 5,000 years ago. When an ultragiant star has converted elements in its core to iron, the core collapses to produce a hypernova and the star is destroyed. For a star as massive as C1178 Idaharris, the remnant is probably to be an intermediate-mass black hole. Just like all red ultragiants will evolve back to an extreme yellow ultragiant, then a Luminous blue variable, and finally a Wolf-Rayet before their cores collapse, and C1178 Idaho appears to be massive enough for this to happen. A massive red ultragiant will produce a luminous hypernova, while a Wolf Rayet star will produce a hypernova or supernova.