HYDRA

HYDRA

(Abbreviation: Hya).

The largest constellation in the sky, representing the hundred-headed monster which lived in the Lernæan marshes until it was killed by Hercules. It extends for over 6 hours of R.A. a (Alphard is often known as ‘the Solitary One’, because there are no other bright stars anywhere in the neighbourhood. Hydra contains 10 stars above the fourth magnitude:

BRIGHTEST STARS

STAR	R.A.			DEC			MAG.	ABS.MAG.	SPEC	DIST.PC
STAR	H	M	S	o	‘	“	MAG.	ABS.MAG.	SPEC	DIST.PC
4 d	08	37	39.3	+05	42	13	4.16	0.6	AO	43
5 s	08	38	45.5	+03	20	29	4.44	-0.1	K2	75
7 h	08	43	13.4	+03	23	55	4.30	-1.7	B3	160
12 D	08	46	22.4	+13	32	52	4.32	0.3	G8	64
11 Î	08	46	46.5	+06	25	07	3.38	0.6	GO	34
13 r	08	48	25.9	+05	50	16	4.36	0.6	AO	57
16 z	08	55	23.6	+05	56	44	3.11	0.2	KO	38
22 q	09	14	21.8	+02	18	51	3.88	0.6	AO	45
30 a	09	27	35.2	-08	39	31	1.98	-0.2	K3	26 ALPHARD LY/ 94
31 t¹	09	29	08.8	-02	46	08	4.60	3.7	F6	15
32 t²	09	31	58.9	-01	11	06	4.57	0.0	A3	82
35 i	09	39	51.3	-01	08	34	3.91	-0.2	K3	63
39 n¹	09	51	28.6	-14	50	48	4.12	0.3	G8	58
40 n²	10	05	07.4	-13	03	53	4.60	-1.2	B8	140
41 l	10	10	35.2	-12	21	15	3.61	0.2	K0	46
42 m	10	26	05.3	-16	50	11	3.81	-0.3	K4	59
n	10	49	37.4	-16	11	37	3.11	-0.1	K2	39
x	11	33	00.1	-31	51	27	3.54	0.3	G7	44
o	11	40	12.9	-34	44	40	4.70	0.3	B9	?
b	11	52	54.4	-33	54	28	4.28	-0.3	B9	82
46 g	13	18	55.2	-23	10	17	3.00	0.3	G5	32
R	13	29	42.7	-23	16	52	var	var	Md	100 VERY RED
49 p	14	06	22.2	-26	40	56	3.27	-0.1	K2	47
58 E	14	50	17.2	-27	57	37	4.41	0.3	gK4	88

DOUBLES

STAR	R.A.			DEC			MAGS.	P.A.	DIST.”
STAR	H	M	S	o	‘	“	MAGS.	P.A.	DIST.”
11	08	46	46.5	+06	25	07	3.5,6.9	269	A IS A CLOSE BINARY (15 YEARS)
22	09	14	21.8	+02	18	51	3.9,10.0	197	OPTICAL
b	11	52	54.5	-33	54	28	4.8,5.6	001	P.A. INCREASING
R	13	29	42.7	-23	16	52	var,12.5	324

VARIABLES

STAR	R.A.		DEC		RANGE	PERIOD,D	SPEC	TYPE
STAR	H	M	o	‘	RANGE	PERIOD,D	SPEC	TYPE
RT	08	27.2	-06	09	7.1---10.2	253	M	SEMI-REGULAR
S	08	51.0	+03	16	7.4---13.3	257	M	MIRA
T	08	53.2	-08	57	7.2---13.2	289	M	MIRA
X	09	33.4	-14	28	8.0---13.6	302	M	MIRA
U	10	35.1	-13	07	4.8---5.8	-	N	IRREGULAR
FF	10	35.4	-11	14	7.0---9.0	±20?	M	SEMI-REGULAR?
V	10	49.2	-20	59	6.0---12.5	533	N	MIRA. VERY RED
RU	14	08.5	-28	39	7.2---14.3	334	M	MIRA
W	13	46.2	-28	07	7.5---11.4	382	M	MIRA
R	13	29.7	-23	17	4.0---10.0	386	M	MIRA. VERY RED-
-MIRA PERIOD IS DECREASING FROM OVER 450d IN THE 18^th CENTURY

STARS AND NEBULÆ

OBJECT	R.A.		DEC		TYPE	NOTES
OBJECT	H	M	o	‘	TYPE	NOTES
NGC 2548 M.48	08	11.2	-05	38	OPEN CLUSTER	MAG. 5.5
NGC 2610	08	31.2	-15	38	PLANETARY	MAG. 13.6. CENTER STAR MAG.15.7
NGC 2784	09	10.1	-23	58	GALAXY	MAG. 11.8. ELLIPTICAL (TYPE E8)
NGC 3109	10	00.8	-25	55	GALAXY	MAG. 11.2. IRREGULAR
NGC 3242 H.IV.27	10	22.3	-18	23	PLANETARY	MAG. 9. CENTER STAR MAG. 11.4
NGC 3585	11	10.9	-26	29	GALAXY	MAG. 11. ELLIPTICAL (TYPE E5)
NGC 3904	11	46.7	-29	02	GALAXY	MAG. 12. ELLIPTICAL
NGC 3923	11	48.5	-28	33	GALAXY	MAG. 11. ELLIPTICAL
NGC 4590 M.68	12	36.8	-26	29	GLOBULA	MAG. 8.2
NGC 5061	13	15.3	-26	36	GALAXY	MAG. 12. ELLIPTICAL (TYPE E2)
NGC 5236 M.83	13	34.3	-29	37	GALAXY	MAG. 10. TYPE Sc