Astronomy. How do I figure out what star is at a certain point?

Question

Does anyone know what star is at 3h 8m 17.8s; DEC=40 degrees, 57' 52.4"? Supposedly this is a well known star and is eclipsed sometimes. Can anyone help with this? Thanks.

Thank you for responding everyone.

Answer 1

It is Algol in Perseus, also known as Beta persei. I took some time with this thinking it was a trick question. You didn't give the + or - for the Declination so I checked the southern hemisphere too. Nothing there.

Your coordinates match up pretty closely, within a few seconds, of the J2000 coordinates below. Note that the J2000 coordinates do NOT correspond to TODAY's coordinates which we call "epoch of date" (meaning in this case July 7 2007). But ya know, it's close enough, you bring up the star chart, there's Algol.

As previously noted by the first man up with the answer, Algol is an eclipsing binary. It is about 22.5 degrees off the ecliptic which is way too far to be "eclipsed" (occulted) by planets, the moon, sun, etc. So the "eclipsing" reference you got had to be about the binary aspect.

This is an easy star to find with a planisphere. You start with Cassiopeia "the W" then move "down" to Perseus. The double cluster should appear as a faint patch (in a good sky) and is a wonderful binocular and small telescope object. Perseus has an *intense* galaxy cluster that is spectacular in a small telescope and surprisingly often overlooked by amateur astronomers.

I have given you below all the data from Sky Map Pro v. 11 on Algol which is more than almost anyone wants to know about Algol.

The Wiki link is a good stick-figure of the constellation. You can see the double cluster in the upper right and still further you see the bottom of one part of the constellation Cassiopeia, near the object M103.

Hope that helps,

GN


Sky Map Pro summary
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Information about beta Persei
Summary
Maximum magnitude: 2.12
Minimum magnitude: 3.39
Type of variability: EA/SD
Spectral type: B8V
Distance: 92.8 +/- 2.3 light years

Position information for 07 Jul 2007 11:03:21 PM
JD: 2454289.62733
Apparent RA: 03h 08m 38.84s
Apparent Dec: +40° 59' 01.1"
Constellation: Perseus
Altitude: -1° 55' 2"
Azimuth: 22° 37' 41"
Hour angle: 14h 2m 29s
Rise: 23h 21m 14s
Transit: 9h 3m 9s
Set: 18h 41m 9s

Names and Catalog Numbers
Proper name: Algol
Bayer letter: b Persei
Flamsteed number: 26 Persei
GCVS designation: beta Persei
Tycho catalog number: TYC 2851-2168-1
Hipparcos catalog number: HIP 14576
PPM catalog number: PPM 45864
SAO catalog number: SAO 38592
HD catalog number: HD 19356
Bright star number: HR 936
BD number: BD +40 0673
WDS designation: BU 526

Star atlas chart numbers
Herald-Bobroff Astroatlas: Chart C-37
Millennium Star Atlas: Charts 99-100 (Vol I)
Sky Atlas 2000.0: Chart 4
Uranometria 2000: Chart 63, Vol 1

Display Yale Bright Star Catalog record
Display Hipparcos record
Display Tycho 2 Catalog record
Display WDS Catalog record
Display binary star orbit record
Display GCVS Catalog record


Yale Bright Star Catalog Data
Preliminary Version of the Bright Star Catalogue, 5th Revised Edition. Dorrit Hoffleit, Department of Astronomy, Yale University, Wayne H. Warren Jr., ST Systems Corporation, National Space Science Data Center, NASA Goddard Space Flight Center (1991)
Identification
Bright star catalog number: HR 936

Position
RA (J2000.0): 03h 08m 10.1s
Dec (J2000.0): +40° 57' 20"
RA (B1900.0): 03h 01m 39.5s
Dec (B1900.0): +40° 34' 14"

Galactic coordinates (system II)
Longitude: 148.98°
Latitude: -14.90°

Magnitude and spectral information
Magnitude: 2.12 [V on UBV (Johnson) system]
B-V on Johnson system: -0.05
U-B on Johnson system: -0.37
R-I: -0.03 (on Johnson system)
Spectral type: B8V

Annual proper motion for J2000.0 on FK5 system
RA: +0.004"
Dec: -0.001"

Parallax and radial velocity
Trigonometricparallax: +.045"
Heliocentric radial velocity: +004 km/sec
Radial velocity comments: Spectroscopic binary; Orbital data available
Projected rotational velocity (v sin i): 65 km/sec

Double/Multiple star information
ADS catalog number (Aitken 1934): ADS 2362

Component data
Identification: AD
Magnitude difference: 8.3
Separation: 81.9"
Total number known: 6

Cross references to other catalogs
Variable star designation: Bet Per
Durchmusterung: BD+40 673
Henry Draper catalog: HD 19356
SAO catalog: SAO 38592
FK5 catalog: 111
Infrared source: NASA Merged Infrared Catalogue, Schmitz et al. 1978.

Remarks
Colours: Color excess E(B-V) = +0.03.
Double/multiple stars: A* var. B8V, 1.858y, a = 0.011" or 1.862y, a = 0.104". Apparent apsidal period 28.4y or 32y. Resolved by speckle interferometry: sep. 0.086", 2-3v fainter than primary. This may be Algol C. Four visual companions all optical: B, 12.7v at 59"; C, 12.5 at 67"; D, 10.5 at 82"; BC sep. 15"; E, 12.5v at 11" from D.
Miscellaneous: One of the few known galactic radio sources in which the dominant star is normal. 21cm radio source.
Names: ALGOL; Gorgona; Gorgonea Prima; Demon Star; El Ghoul.
Spectra: B8V+G.
Spectroscopic binary: Algol ABxC: 1.8613y, K 12.0k/s, V0 +3.7k/s, msin3i 3.91, asini 109. Spectra B8V, G5IV, Am. Mass Algol AB, 5.3 Suns; C, 1.8 Suns. Circumstellar gas fills Roche lobe of hot component. ADS 19356A: 2.8673d, K 44.0k/s, V0 var., asini 1.73. Resolved by speckle interferometry 1982.17, sep. 0.052", 1983.94, sep. 0.08".
Variability: ADS 2362A is the prototype Algol star, first discovered as variable by Montanari in 1669. The first period determined by Goodricke in 1783, who also interpreted the variations as due to eclipses. The prototype star proves to be a more a complicated system than most of the Algol-type stars, i.e., compact triple system with separation of the components well under 0.1". The components usually designated Algol A, B, C, sometimes A, a, P. Two formerly additionally desig- nated components D and E, inferred on the basis of an apparent 32 year apsidal motion, are now considered spurious. The various Algol components must not be confused with the visual components ADS 2362 B-E, optical companions at much greater distances from A. ADS 2362A, EA 2.12 - 3.40V, 2.86732442d, abrupt period changes. Orbital and rotation periods synchronized. Rotational velocity 65k/s. Radio flares extending to about 1 A.U., not associated with X-ray activity. Radio flare activity appears correlated with period discontinuities, attributed to "starquakes." Mass flow from K to B8 component at rate of 1.8x10E-08 solar masses/year. Possible circumstellar material associated with radio or H alpha emission.

Answer 2

The only bright star near that location that I see is Algol (RA=3h, 8m, 40s; Dec=40°, 59', 10s). It is a well-known eclipsing binary.

Answer 3

Stars do not eclipse, except when they are BINARY with a companion, such as ALGOL

ALL stars are charted and found in books like the Handbook of the Royal Astronomical Society of Canada.

Answer 4

Get a copy of 'Red Shift,' you will have all the information you will ever need.

Answer 5

man try nasa.gov web site