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This is a list of astronomical objects with the spectral type Y. They are a mix of brown dwarfs and planetary-mass objects. They are the coldest such objects in interstellar space and have a temperature around below 500 Kelvin (227°C; 440°F). Only a few are known due to their faint nature. The list is sorted after distance.
| Name | spectral type[1] | Teff[1]
(Kelvin) |
Mass estimate
(MJ) |
distance[1] | Year of discovery |
|---|---|---|---|---|---|
| Jupiter | Y-class analog[2] | 125 | 1 | solar system | known since ancient times |
| WISE J0855−0714 | Y4 (extrapolated) | 250 ± 50 | 3−10[3] | 7.43 ± 0.04 | 2014[4] |
| Epsilon Indi Ab[5] | Y3[lower-alpha 1] (estimated) | 275 | 6.31+0.60 −0.56 |
11.867±0.004 | 2018 (discovered) 2024 (imaging) |
| WISE J1639−6847 | Y0pec | 412 ± 88 | 5−14[6] or 9−17[7] | 15.45 ± 0.04[8] | 2012[9] |
| WISE J0350−5658 | Y1 | 388 ± 88 | 3−8[6] or 7−13[7] | 18.49 ± 0.24 | 2012[10] |
| WISEPA J1541−2250 | Y1 | 432+11 −18[11] |
8−20[6] | 19.54 ± 0.23 | 2011[12][13] |
| WISE J2209+2711 | Y0[11] | 371+9 −13[11] |
8−19[6] or 5[14] | 20.17 ± 0.25 | 2014[15] |
| WISEPC J1405+5534 | Y0.5 (pec?) | 412+10 −17[11] |
9−21[6] | 20.6 ± 0.3 | 2011[12][13] |
| WISE J0825+2805 | Y0.5 | 406+10 −16[11] |
3−8[6] or 5[14] | 21.4 ± 0.4 | 2015[16] |
| WISEPA J0410+1502 | Y0 | 451 ±88 | 8−20[6] | 21.6 ± 0.3 | 2011[12][13] |
| CWISE J1055+5443[17] | Y0 (pec) | 500 ± 150 | 4−6 | 22+3 −2 |
2023 |
| WISEPC J2056+1459 | Y0 | 510+14 −25[11] |
13−23[7] or 5[14] | 23.2 ± 0.3 | 2011[12][13] |
| WISEPA J1738+2732 | Y0 | 450 ± 88 | 5−14,[6] 3−9[18] or 11−21[7] | 24.9 ± 0.4 | 2011[12][13] |
| WISEA J2354+0240 | Y1 | 362+10 −12[11] |
8−14[7] | 25.0 ± 0.6 | 2015[16] |
| CWISEP J0402−2651 | ≥Y1 (estimated) | 367 ± 79 | 28.0+6.0 −4.2 |
2020[19] | |
| WISENF J1936+0408 | Y0 (estimated) | 460 ± 79 | 28.6+1.0 −0.9 |
2020[19] | |
| WISE J0713−2917 | Y0 | 464 ± 88 | 13−29[6] | 29.8 ± 0.6 | 2012[10] |
| WISEPC J1217+1626 B | Y0 | 460 ± 79 | 8−20[6] | 30.4 ± 1.0 | 2012[20] |
| WISEA J1930−2059 | ≥Y1 (estimated) | 367 ± 79 | 30.7+1.5 −1.4 |
2020[21] | |
| WISEA J1141−3326 | Y0 | 460 ± 79 | 3–8[6] | 31.4 ± 0.9 | 2014[22] |
| CWISEP J1446−2317 | Y1[11] | 366 ± 14[11] | 8.0 or 14.6[23] | 31.4+1.6 −1.4[11] |
2020[19] |
| CWISEP J2256+4002 | ≥Y1 (estimated) | 367 ± 79 | 32.0+4.0 −3.2 |
2020[19] | |
| WISEPA J1828+2650 | ≥Y2 | 406 ± 88 | 3–8[6] | 32.5+0.7 −0.6 |
2011[12][13] |
| WISE J0336−0143 A | Y0:[24] | 460 ± 79 | 8.5–18[25] | 32.7 ± 0.7 | 2012[10] |
| WISE J0336−0143 B[25] | Y2.5[lower-alpha 1] (estimated) | 285–305[26] | 5–11.5 | 32.7 ± 0.7 | 2023 |
| WISE J0647−6232 | Y1 | 393 ± 88 | 5–13[6] | 32.8 ± 0.6 | 2013[27] |
| WISEU J0503−5648 | ≥Y1 (estimated) | 367 ± 79 | 33.2+1.4 −1.3 |
2020[21] | |
| WISE J2220−3628 | Y0 | 452 ± 88 | 8–20[6] | 34.2+0.8 −0.7 |
2012[10] |
| CWISE J0925−4720 | Y0 (estimated) | 460 ± 79 | ~35.0 | 2021[28] | |
| CWISER J0216+4230 | Y0 (estimated) | 460 ± 79 | ~35.2 | 2023[1] | |
| WISEA J0830+2837 | ≥Y1 (estimated) | 367 ± 79 | 4−13[29] | 36+6 −5 |
2020[29] |
| CWISEP J0238−1332 | ≥Y1 (estimated) | 367 ± 79 | 38+13 −8 |
2020[19] | |
| WISE J1206+8401 | Y0 | 499+14 −24[11] |
6−14[6] or 12−22[7] | 38.5+1.0 −0.9 |
2015[16] |
| CWISE J2351−7000 | Y0 (estimated) | 460 ± 79 | ~42.7 | 2020[21] | |
| WISE J0734−7157 | Y0 | 493+14 −24[11] |
9−20[6] | 43.8 ± 1.0 | 2012[10] |
| WISE J0359−5401 | Y0 | 468+13 −23[11] |
12−22[7] or 13[14] | 44.3 ± 1.2 | 2012[10] |
| WISE J0304−2705 | Y0 pec | 465 ± 88 | 44.6+1.6 −1.5 |
2014[30] | |
| CWISEP J2230+2549 | ≥Y1 (estimated) | 367 ± 79 | 46+13 −8 |
2020[19] | |
| CWISEP J2011−4812 | Y0 (estimated) | 460 ± 79 | 46 ± 2 | 2020[19] | |
| CWISE J1811+6658 | early-Y (estimated) | 412 ± 79 | 47+5 −4 |
2023[1] | |
| CWISEP J1935−1546 | ≥Y1 (estimated) | 367 ± 79 | 47+3 −2 |
2019[31] | |
| WISE J0535−7500 | Y1[11] | 526+16 −26[11] |
8−20[6] or 12+18[14] | 47.5+1.4 −1.3 |
2012[10] |
| CWISEP J1047+5457 | Y1[11] | 415+20 −22[11] |
20.6 or 15.9[23] | 47.9+3.7 −3.2[11] |
2020[19] |
| CWISEP J0321+6932 | Y0.5 (estimated) | 412 ± 79 | 48 ± 3 | 2020[19] | |
| WISEA J2243−1458 | Y0 (estimated) | 460 ± 79 | ~47.8 | 2020[21] | |
| CWISEP J0938+0634 | Y0 (estimated) | 460 ± 79 | 48+12 −8 |
2020[19] | |
| CWISEP J0940+5233 | ≥Y1 (estimated) | 367 ± 79 | 49+11 −8 |
2020[19] | |
| CWISEP J0634+5049 | Y0 (estimated) | 460 ± 79 | 53+4 −3 |
2020[19] | |
| WISEA J1534−1043 | esdT/Y (estimated) | 686 ± 79 | 53 ±4 | 2020[19] | |
| WISEA J1257+7153 | ≥Y1 (estimated) | 367 ± 79 | ~54.2 | 2020[21] | |
| WISEA J0302−5817 | Y0: | 460 ± 79 | 55 ± 3 | 2018[32] | |
| CWISE J1531−3306 | Y0 (estimated) | 460 ± 79 | ~55.4 | 2021[28] | |
| CWISEP J2356−4814 | Y0.5 (estimated) | 412 ± 79 | ~56.6 | 2020[19] | |
| Ross 19 B | T/Y (estimated) | 460 ±79 | 15−40[33] | 56.89 ± 0.04 | 2021[33] |
| WISE 0226-0211 B | T9.5 to Y0 (estimated) | 511 ±79 | 57.9+2.7 −2.4 |
2019[34] | |
| L 97-3 B | Y1 (estimated) | 377 ± 88 | 7−9[6] | 62.73 ± 0.02 | 2011[35] |
| WISE J0146+4234 B | Y0 | 460 ± 79 | 8−20[6] | 63 ± 2 | 2015[36] |
| CWISE J2227+2604 | Y0 (estimated) | 460 ± 79 | ~65.2 | 2023[1] | |
| CWISEP J0859+5349 | Y0 (estimated) | 460 ± 79 | 70+13 −14 |
2020[19] | |
| CFBDSIR 1458+10 B[37] | Y0 (estimated) | 370 ± 40 | 6–15 | 75.34 ± 7.83 | 2011 |
- Estimated using the effective temperature. By using Eric Mamajek's table[lower-alpha 2] one can compare Teff with the spectral type. Alternatively one can fit a curve to T5-Y4 dwarfs, which gives the formula , with SpType 19 is T9, 20 is Y0, 21 is Y1, etc. Might be inaccurate for objects with non-solar metallicity.
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