2 Lacertae

{{Short description|Star in the constellation Lacerta}}

{{Starbox begin|name=2 Lacertae}}

{{Starbox image

| image=

{{Location mark

|image=Lacerta constellation map.svg|alt=|float=center|width=220

|label=|position=right

|mark=Red circle.svg|mark_width=8|mark_link=2 Lac

|x=556|y=698

}}

|caption=Location of 2 Lacertae (circled)

}}

{{Starbox observe

|epoch=J2000

|constell=Lacerta

|ra={{RA|22|21|01.54727}}{{cite journal|title=Validation of the new Hipparcos reduction|author1=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|+46|32|11.6461}}

|appmag_v=4.53{{snd}}4.56

}}

{{Starbox character

|class=B6V{{cite journal|bibcode=1968ApJS...17..371L|title=The Kinematics of the Gould Belt: An Expanding Group?|journal=Astrophysical Journal Supplement|volume=17|pages=371|last1=Lesh|first1=Janet Rountree|year=1968|doi=10.1086/190179|doi-access=free}} {{nowrap|(B6IV + B6V)}}

|b-v=−0.14

|u-b=−0.49

|variable=Ellipsoidal (suspected){{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|author1=Samus, N. N.|author2=Durlevich, O. V.|year=2009}}

}}

{{Starbox astrometry

|radial_v={{val|−9.5|2}}{{cite journal|title=General catalogue of stellar radial velocities|journal=Washington|author=Wilson, Ralph Elmer|date=1953|bibcode=1953GCRV..C......0W}}

|prop_mo_ra=22.35

|prop_mo_dec=1.45

|parallax=5.88

|p_error=0.14

|parallax_footnote=

|absmag_v=−1.19{{cite journal|bibcode=2009PASP..121.1045K|title=Lacerta OB1 Revisited|journal=Publications of the Astronomical Society of the Pacific|volume=121|issue=884|pages=1045–1053|last1=Kaltcheva|first1=Nadia|year=2009|doi=10.1086/606037|s2cid=120329065 |doi-access=free}}

}}

{{Starbox orbit

|reference=

|period={{val|2.616430|0.000003}}

|periastron={{val|2427770|0.18}}

|eccentricity={{val|0.040|0.018}}

|periarg={{val|97.4|25.3}}

|k1=7{{val|9.5|1.8}}

|k2={{val|100.0|1.8}}

}}

{{Starbox detail

| component1 = primary

| mass = 6.99{{cite journal |last1=Kraicheva |first1=Z. |last2=Popova |first2=E. |last3=Tutukov |first3=A. |last4=Yungelson |first4=L. |title=Catalogue of physical parameters of spectroscopic binary stars. |journal=Bulletin d'Information du Centre de Donnees Stellaires |date=July 1980 |volume=19 |pages=71 |issn=1169-8837 |bibcode=1980BICDS..19...71K}}

| temperature = 15,000

| rotational_velocity = 50{{cite journal

| title=Tidal Effects in Binaries of Various Periods

| last1=Abt | first1=Helmut A. | last2=Boonyarak | first2=Chayan

| journal=The Astrophysical Journal

| volume=616 | issue=1 | pages=562–566 | date=November 2004

| doi=10.1086/423795 | bibcode=2004ApJ...616..562A | doi-access=free }}

| gravity = 3.0

|age_myr=

| component2 = secondary

| mass2 = 5.55

| rotational_velocity2 = 35

| temperature2 =

}}

{{Starbox catalog

|names=BD+45°3894, HD 212120, HIP 110351, HR 8523, SAO 51904

}}

{{Starbox reference|Simbad=2+Lac}}

{{Starbox end}}

File:LacertaCC.jpg]]

File:2LacLightCurve.png for 2 Lacertae, plotted from TESS data{{cite web |title=MAST: Barbara A. Mikulski Archive for Space Telescopes |url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html |publisher=Space Telescope Science Institute |access-date=8 December 2021}}]]

2 Lacertae is a binary star in the constellation of Lacerta. With an apparent magnitude of about 4.5, it is faintly visible to the naked eye. Its parallax, measured by the Hipparcos spacecraft, is 5.88 milliarcseconds, corresponding to a distance of about 550 light years (170 parsecs). It is projected against the Lacertae OB1 stellar association to the northeast of the main concentration of stars, but it is likely to be a foreground object.

2 Lacertae is a double-lined spectroscopic binary. Its components are too close to be resolved, however periodic Doppler shifts in its spectrum reveal that there are two stars orbiting each other. Both stars are B-type main-sequence stars, orbiting each other every 2.616 days and with an eccentricity of about 0.04. The primary is estimated to be about one magnitude brighter than the secondary. The primary component is close to moving off the main sequence, and has nearly exhausted its core hydrogen (possibly also its companion).{{cite journal|title=The binary systems 14 Cephei and 2 Lacertae|author=Hilditch, R. W.|date=1974|journal=Monthly Notices of the Royal Astronomical Society|volume=169|issue=2|pages=323–329|bibcode=1974MNRAS.169..323H|doi=10.1093/mnras/169.2.323|doi-access=free}} It is estimated to have completed over 90% of its time on the main sequence.{{cite journal|bibcode=2012A&A...537A.120Z|arxiv=1201.2052|title=Rotational velocities of A-type stars. IV. Evolution of rotational velocities|journal=Astronomy & Astrophysics|volume=537|pages=A120|last1=Zorec|first1=J.|last2=Royer|first2=F.|year=2012|doi=10.1051/0004-6361/201117691|s2cid=55586789}}

2 Lacertae is a rotating ellipsoidal variable, a binary system in which the stars are close enough to each other for one or both stars to be significantly distorted by tidal forces. The stars' orbital plane is not aligned closely enough to our line of sight for the stars to eclipse each other, but the stars' orbital motion does cause us to view different portions of the non-spherical stars' surfaces, leading to brightness changes. 2 Lacertae varies by about 0.03 magnitudes as the stars orbit each other.{{cite web |title=NSV 14130 |url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=52754 |website=The International Variable Star Index |publisher=AAVSO |access-date=12 September 2022}}

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