List of Y-dwarfs

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.

List of Y-dwarfs

Name	spectral type[1]	Teff[1] (Kelvin)	Mass estimate (MJ)	distance[1] (light years)	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[a] (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]	18.9 ± 0.2[12]	2011[13][14]
WISE J2209+2711	Y0[11]	371+9 −13[11]	8−19[6] or 5[15]	20.17 ± 0.25	2014[16]
WISEPC J1405+5534	Y0.5 (pec?)	412+10 −17[11]	9−21[6]	20.6 ± 0.3	2011[13][14]
WISEPA J0410+1502	Y0	451 ±88	8−20[6]	21.32 ± 0.10[12]	2011[13][14]
WISE J0825+2805	Y0.5	406+10 −16[11]	3−8[6] or 5[15]	21.4 ± 0.4	2015[17]
CWISE J1055+5443[18]	Y0 (pec)	500 ± 150	4−6	22+3 −2	2023
WISEPC J2056+1459	Y0	510+14 −25[11]	13−23[7] or 5[15]	22.27 ± 0.07[12]	2011[13][14]
WISEPA J1738+2732	Y0	450 ± 88	5−14,[6] 3−9[19] or 11−21[7]	24.4 ± 0.2[12]	2011[13][14]
WISEA J2354+0240	Y1	362+10 −12[11]	8−14[7]	25.0 ± 0.6	2015[17]
CWISEP J0402−2651	≥Y1 (estimated)	367 ± 79		28.0+6.0 −4.2	2020[20]
WISENF J1936+0408	Y0 (estimated)	460 ± 79		28.6+1.0 −0.9	2020[20]
WISE J0647−6232	Y1	393 ± 88	5–13[6]	29.6 ± 0.6[12]	2013[21]
WISE J0713−2917	Y0	464 ± 88	13−29[6]	29.6 ± 0.2[12]	2012[10]
WISEPC J1217+1626 B	Y0	460 ± 79	8−20[6]	30.4 ± 1.0	2012[22]
WISEA J1930−2059	≥Y1 (estimated)	367 ± 79		30.7+1.5 −1.4	2020[23]
WISEA J1141−3326	Y0	460 ± 79	3–8[6]	31.4 ± 0.9	2014[24]
CWISEP J1446−2317	Y1[11]	366 ± 14[11]	8.0 or 14.6[25]	31.4+1.6 −1.4[11]	2020[20]
CWISEP J2256+4002	≥Y1 (estimated)	367 ± 79		32.0+4.0 −3.2	2020[20]
WISEPA J1828+2650	≥Y2	406 ± 88	3–8[6]	32.5+0.7 −0.6	2011[13][14]
WISE J0336−0143 A	Y0:[26]	460 ± 79	8.5–18[27]	32.7 ± 0.7	2012[10]
WISE J0336−0143 B[27]	Y2.5[a] (estimated)	285–305[28]	5–11.5	32.7 ± 0.7	2023
WISEA J0830+2837	≥Y1 (estimated)	367 ± 79	4−13[29]	32.9+2.3 −2.0[30]	2020[29]
WISEU J0503−5648	≥Y1 (estimated)	367 ± 79		33.2+1.4 −1.3	2020[23]
WISE J2220−3628	Y0	452 ± 88	8–20[6]	34.9 ± 0.4[12]	2012[10]
CWISE J0925−4720	Y0 (estimated)	460 ± 79		~35.0	2021[31]
CWISER J0216+4230	Y0 (estimated)	460 ± 79		~35.2	2023[1]
CWISEP J0238−1332	≥Y1 (estimated)	367 ± 79		38+13 −8	2020[20]
WISE J1206+8401	Y0	499+14 −24[11]	6−14[6] or 12−22[7]	38.5+1.0 −0.9	2015[17]
CWISE J2351−7000	Y0 (estimated)	460 ± 79		~42.7	2020[23]
WISE J0359−5401	Y0	468+13 −23[11]	12−22[7] or 13[15]	44.3 ± 1.2	2012[10]
WISE J0734−7157	Y0	493+14 −24[11]	9−20[6]	44.5 ± 0.4[12]	2012[10]
WISE J0304−2705	Y0 pec	465 ± 88		44.6+1.6 −1.5	2014[32]
CWISEP J2230+2549	≥Y1 (estimated)	367 ± 79		46+13 −8	2020[20]
CWISEP J2011−4812	Y0 (estimated)	460 ± 79		46 ± 2	2020[20]
CWISE J1811+6658	early-Y (estimated)	412 ± 79		47+5 −4	2023[1]
CWISEP J1935−1546	≥Y1 (estimated)	367 ± 79		47+3 −2	2019[33]
WISE J0535−7500	Y1[11]	526+16 −26[11]	8−20[6] or 12+18[15]	47.5+1.4 −1.3	2012[10]
CWISEP J1047+5457	Y1[11]	415+20 −22[11]	20.6 or 15.9[25] or 1–3[30]	47.9+3.7 −3.2[11]	2020[20]
CWISEP J0321+6932	Y0.5 (estimated)	412 ± 79		48 ± 3	2020[20]
WISEA J2243−1458	Y0 (estimated)	460 ± 79		~47.8	2020[23]
CWISEP J0938+0634	Y0 (estimated)	460 ± 79		48+12 −8	2020[20]
CWISEP J0940+5233	≥Y1 (estimated)	367 ± 79		49+11 −8	2020[20]
CWISEP J0634+5049	Y0 (estimated)	460 ± 79		53+4 −3	2020[20]
WISEA J1534−1043	esdY0–esdY2 (estimated)[34]	447 ± 45[35]		53 ±4	2020[20]
WISEA J1257+7153	≥Y1 (estimated)	367 ± 79		~54.2	2020[23]
WISEA J0302−5817	Y0:	460 ± 79		55 ± 3	2018[36]
CWISE J1531−3306	Y0 (estimated)	460 ± 79		~55.4	2021[31]
CWISEP J2356−4814	Y0.5 (estimated)	412 ± 79		~56.6	2020[20]
Ross 19 B	sdY (estimated)[34]	460 ±79	15−40[37]	56.89 ± 0.04	2021[37]
WISE 0226-0211 B	T9.5 to Y0 (estimated)	511 ±79		57.9+2.7 −2.4	2019[38]
L 97-3 B	Y0[39]	377 ± 88	7−9[6]	62.73 ± 0.02	2011[40]
WISE J0146+4234 B	Y0	460 ± 79	8−20[6]	63 ± 2	2015[41]
CWISE J2227+2604	Y0 (estimated)	460 ± 79		~65.2	2023[1]
CWISEP J0859+5349	Y0 (estimated)	460 ± 79		70+13 −14	2020[20]
CFBDSIR 1458+10 B[42]	Y0 (estimated)	370 ± 40	6–15	75.34 ± 7.83	2011
CWISEP J0156+3255	sdY (estimated)			125+19 −17	2020/2024[20][34]

Notes

1. Estimated using the effective temperature. By using Eric Mamajek's table^[43] one can compare T_eff with the spectral type. Alternatively one can fit a curve to T5-Y4 dwarfs, which gives the formula ${\displaystyle T_{eff}=1.35\times 10^{7}\times SpType^{-3.441}}$, with SpType 19 is T9, 20 is Y0, 21 is Y1, etc. Might be inaccurate for objects with non-solar metallicity.