1 Geminorum

{{short description|Triple star system in the constellation Gemini}}

{{Starbox begin}}

{{Starbox image

| image=

{{Location mark

|image=Gemini constellation map.svg|alt=|float=center|width=280

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=1 Gem

|x=855|y=337

}}

|caption=Location of 1 Geminorum (circled)

}}

{{Starbox observe

|epoch=J2000

|constell=Gemini

|ra={{RA|06|04|07.21544}}{{cite journal|title=Validation of the new Hipparcos reduction|url=http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2007A%2526A...474..653VFUL|author=van Leeuwen, F.|display-authors=etal|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|date=2007|arxiv=0708.1752|bibcode=2007A&A...474..653V|doi=10.1051/0004-6361:20078357|s2cid = 18759600}}

|dec={{DEC|+23|15|48.0401}}

|appmag_v=4.15{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|author1=Ducati, J. R.|year=2002}} (4.77 / 5.50){{cite web|url=http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6|title=Sixth Catalog of Orbits of Visual Binary Stars|publisher=United States Naval Observatory|accessdate=15 May 2017|archive-date=1 August 2017|archive-url=https://web.archive.org/web/20170801102553/http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6|url-status=dead}}

}}

{{Starbox character

|type=red clump

|class=K0III + (F6IV + G2V){{cite journal|bibcode=2014ApJ...783....3L|doi=10.1088/0004-637X/783/1/3|title=The Orbits of the Triple-Star System 1 Geminorum from Phases Differential Astrometry and Spectroscopy|journal=The Astrophysical Journal|volume=783|pages=3|year=2014|last1=Lane|first1=Benjamin F.|last2=Muterspaugh|first2=Matthew W.|last3=Griffin|first3=R. F.|last4=Scarfe|first4=C. D.|last5=Fekel|first5=Francis C.|last6=Williamson|first6=Michael H.|last7=Eaton|first7=Joel A.|last8=Shao|first8=M.|last9=Colavita|first9=M. M.|last10=Konacki|first10=Maciej|issue=1|doi-access=free}}

|b-v=+0.83{{cite journal|author1=Mermilliod, J.-C.|title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)|journal=Catalogue of Eggen's UBV Data|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1986EgUBV........0M&db_key=AST&nosetcookie=1|date=1986|bibcode= 1986EgUBV........0M}}

|u-b=+0.53

|variable=suspected

}}

{{Starbox astrometry

|radial_v=22.39 ± 0.28{{cite journal|bibcode=2008AJ....135..209M|doi=10.1088/0004-6256/135/1/209|title=Rotational and Radial Velocities for a Sample of 761 Hipparcos Giants and the Role of Binarity|journal=The Astronomical Journal|volume=135|pages=209–231|year=2008|last1=Massarotti|first1=Alessandro|last2=Latham|first2=David W.|last3=Stefanik|first3=Robert P.|last4=Fogel|first4=Jeffrey|issue=1|s2cid=121883397 |doi-access=free}}

|prop_mo_ra=-1.61

|prop_mo_dec=-118.33

|parallax=21.39

|p_error=0.03

|parallax_footnote=

|absmag_v=0.84{{cite journal|title=Fundamental parameters of nearby stars from the comparison with evolutionary calculations: masses, radii and effective temperatures|author1=Allende Prieto, C.|author2=Lambert, D. L.|journal=Astronomy and Astrophysics|volume=352|pages=555–562|date=1999|bibcode=1999A&A...352..555A|arxiv=astro-ph/9911002}}

}}

{{Starbox orbit

|reference=

|primary=1 Gem A

|name=1 Gem B

|period_unitless={{val|4,877.6|1.0|fmt=commas|ul=d}}

|axis={{val|0.2010|0.0004}}

|axis_unitless={{val|9.399|0.010|ul=au}}

|inclination={{val|59.33|0.04}}

|node={{val|353.67|0.04}}

|periastron={{val|2445119|2.3}}

|eccentricity={{val|0.3709|0.0004}}

|periarg={{val|21.29|0.09}}

|k1={{val|11.34|0.03}}

|k2={{val|8.07|0.04}}

}}

{{Starbox orbit

|reference=

|primary=1 Gem Ba

|name=1 Gem Bb

|period_unitless={{val|9.60|ul=d}}

|axis={{val|0.002638|0.000005}}

|axis_unitless={{val|0.1234|0.0001|ul=au}}

|eccentricity={{val|0.0024|0.0005}}

|inclination={{val|93.2|1.1}}

|node={{val|137.5|1.9}}

|periastron-{{val|53220.5|0.3}}

|periarg={{val|154.3|11.8}}

|k1={{val|52.0|0.1}}

|k2={{val|87.7|0.2}}

}}

{{Starbox detail

|component1=1 Gem A

|mass=1.94 ± 0.01

|gravity=3.1

|metal_fe=-0.01

|component2=1 Gem Ba

|mass2=1.707 ± 0.005

}}

{{Starbox detail|no_heading=y

|component1=1 Gem Bb

|mass=1.012 ± 0.003

}}

{{Starbox catalog

|names={{odlist|BD=+23°1170|FK5=1163|HD=41116|HIP=28734|HR=2134|SAO=77915|NSV=16765}}

}}

{{Starbox reference

|Simbad=1+Gem|sn=1 Gem

}}

{{Starbox end}}

1 Geminorum (1 Gem) is a star in the constellation Gemini. Its apparent magnitude is 4.15.

In the 19th century, John Flamsteed numbered the brighter stars, by constellation, from west to east, and 1 Geminorum was the first star listed in Gemini. It is also listed in the Bright Star Catalogue as star 2134, usually designated HR 2134 with the HR standing for the Harvard Revised catalog, the precursor to the Bright Star Catalogue.

In 1948, 1 Geminorum was discovered to be a close double star whilst using it to focus a telescope for observations of the planet Uranus. From initial observations of the spectrum, it was estimated that both components were giants and that the secondary was itself double.{{cite journal|doi=10.1086/145095|title=A New Bright Double Star|journal=The Astrophysical Journal|volume=108|pages=542|year=1948|last1=Kuiper|first1=Gerard P.|bibcode=1948ApJ...108..542K|s2cid=121068264 }} Radial velocity variations had been found in 1906, but only one set of absorption lines could be detected in the spectrum and it was not possible to calculate a reliable orbit until 1976.{{cite journal|bibcode=1976Obs....96..188G|title=Spectroscopic binary orbits from photoelectric radial velocities. Paper 10: 1 Geminorum B|journal=The Observatory|volume=96|pages=188|last1=Griffin|first1=R. F.|last2=Radford|first2=G. A.|year=1976}}

1 Geminorum is a triple star system 0.17 degree south of the ecliptic. The primary component of the system, 1 Geminorum A, is a K-type red clump giant star around twice the mass of the Sun.{{cite journal|bibcode=2001ApJ...551L..85Z|title=High-Resolution Spectroscopic Observations of Hipparcos Red Clump Giants: Metallicity and Mass Determinations|journal=The Astrophysical Journal|volume=551|issue=1|pages=L85|last1=Zhao|first1=G.|last2=Qiu|first2=H. M.|last3=Mao|first3=Shude|year=2001|doi=10.1086/319832|s2cid=119700315 }} Component A is orbited by a spectroscopic binary pair of stars at a separation of about 9.4 astronomical units every 4877.6 days. The two secondary components, 1 Geminorum Ba and Bb, have not been resolved, but regular periodic Doppler shifts in the spectrum indicate orbital motion of a binary pairing consisting of an F-type subgiant and a solar-mass star that may be G-type, separated by approximately 0.1234 astronomical units.

In 1893, a 14th magnitude companion was reported by Sherburne Wesley Burnham {{val|94|ul="}} from the naked-eye star,{{cite journal | bibcode=2001AJ....122.3466M | doi=10.1086/323920 | title=The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog | journal=The Astronomical Journal | volume=122 | issue=6 | pages=3466 | year=2001 | last1=Mason | first1=Brian D. | last2=Wycoff | first2=Gary L. | last3=Hartkopf | first3=William I. | last4=Douglass | first4=Geoffrey G. | last5=Worley | first5=Charles E. | doi-access=free }} but it is a distant background object.{{cite DR2|3424609220194081280}}

1 Geminorum is listed as a suspected variable star with an amplitude of 0.05 magnitudes.{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}