{{Short description|Star in the constellation Lupus}} {{Starbox begin}} {{Starbox image | image = {{Location mark |image=Lupus constellation map.svg|alt=|float=center|width=250 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=2 Lupi |x=500|y=245 }} | caption = Location of 2 Lupi (circled in red) }} {{Starbox observe | epoch = J2000 | constell = [[Lupus (constellation)|Lupus]] | ra = {{RA|15|17|49.83809}}<ref name=vanLeeuwen2007/> | dec = {{DEC|−30|08|55.2165}}<ref name=vanLeeuwen2007/> | appmag_v = 4.33<ref name=McWilliam1990/> }} {{Starbox character | type = giant | class = {{nowrap|K0 IIIa CH-1}}<ref name=perkins1989/> | b-v = {{Val|1.100|0.004}}<ref name=Anderson2012/> | u-b = | variable = none<ref name=Samus2017/> }} {{Starbox astrometry | radial_v = {{Val|−2.91|0.15}}<ref name=GaiaDR2/> | prop_mo_ra = −10.16<ref name=vanLeeuwen2007/> | prop_mo_dec = −3.66<ref name=vanLeeuwen2007/> | parallax = 10.01 | p_error = 0.21 | parallax_footnote = <ref name=vanLeeuwen2007/> | absmag_v = −0.65<ref name=Anderson2012/> }} {{Starbox detail | source = | mass = | radius = {{Val|11.0|0.7|0.8}}<ref name=GaiaDR2/> | luminosity = {{Val|65.6|0.8}}<ref name=GaiaDR2/> | temperature = {{Val|4953|197|148|fmt=commas}}<ref name=GaiaDR2/> | metal_fe = 0.11<ref name=McWilliam1990/> | gravity = 2.84<ref name=McWilliam1990/> | rotational_velocity = | age_gyr = }} {{Starbox catalog | names = {{odlist | B=f Lupi | F=2 Lup | CD=−29°11630 | FK5=3207 | HD=135758 | HIP=74857 | HR=5686 | NSV=7012 | SAO=183346 }}<ref name=Simbad/> }} {{Starbox reference | Simbad = f+Lup }} {{Starbox end}}

'''2 Lupi,''' also known by its Bayer designation ''f Lupi'', is a solitary<ref name=Eggleton2008/>[[star]] in the [[Southern celestial hemisphere|southern]] [[constellation]] of [[Lupus (constellation)|Lupus]],<ref name=Simbad/> situated approximately 326&nbsp;[[light-year]]s away from the [[Sun]].<ref name=vanLeeuwen2007/> It has the [[Bayer designation]] '''f Lupi'''; ''2 Lupi'' is the [[Flamsteed designation]]. It is visible to the naked eye as a faint, orange-hued star with an [[apparent visual magnitude]] of 4.33.<ref name=McWilliam1990/> It is moving closer to the Earth with a heliocentric [[radial velocity]] of −3&nbsp;km/s.<ref name=GaiaDR2/>

This is an aging [[giant star]] with a [[stellar classification]] of {{nowrap|K0 IIIa CH-1}}.<ref name=perkins1989/> The suffix notation indicates abnormally [[absorption line|weak lines]] of [[carbyne]]. Having exhausted the hydrogen at its [[stellar core|core]], the star [[stellar evolution|evolved]] away from the [[main sequence]] by expanding to 11<ref name=GaiaDR2/> times the [[Sun's radius]]. The star is radiating 65.6<ref name=GaiaDR2/> times the [[luminosity of the Sun]] from its enlarged [[photosphere]] at an [[effective temperature]] of {{val|4953|fmt=commas|ul=K}}.<ref name=GaiaDR2/>

2 Lupi is also moving steadily toward our solar system at a rate of roughly –3 km/s. This slow approach is observable through its measured radial velocity.<ref>{{Cite web |title=2 Lupi - Star in Lupus {{!}} TheSkyLive |url=https://theskylive.com/sky/stars/2-lupi-star |access-date=2025-08-19 |website=theskylive.com}}</ref>

==References== <references>

<ref name=GaiaDR2>{{cite DR2|1443435089669339648}}</ref>

<ref name=Simbad>{{cite simbad | title=2 Boo | access-date=2019-04-06 }}</ref>

<ref name=Samus2017>{{citation | display-authors=1 | last1=Samus | first1=N. N. | last2=Kazarovets | first2=E. V. | last3=Durlevich | first3=O. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | title=General Catalogue of Variable Stars | version=5.1 | journal=Astronomy Reports | year=2017 | volume=61 | issue=1 | pages=80–88 | doi=10.1134/S1063772917010085 | bibcode=2017ARep...61...80S | s2cid=125853869 | postscript=. }}</ref>

<ref name=perkins1989>{{citation | last1=Keenan | first1=Philip C. | last2=McNeil | first2=Raymond C. | title=The Perkins catalog of revised MK types for the cooler stars | journal=Astrophysical Journal Supplement Series | volume=71 | pages=245 | year=1989 | bibcode=1989ApJS...71..245K | doi=10.1086/191373 }}</ref>

<ref name=Anderson2012>{{citation | title=XHIP: An extended hipparcos compilation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | arxiv=1108.4971 | doi=10.1134/S1063773712050015 | s2cid=119257644 | postscript=. }}</ref>

<ref name=vanLeeuwen2007>{{citation | title=Validation of the new Hipparcos reduction | last1=van Leeuwen | first1=F. | 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 | postscript=. }}</ref>

<ref name=Eggleton2008>{{citation | last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A. | title=A catalogue of multiplicity among bright stellar systems | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=389 | issue=2 | pages=869–879 | date=September 2008 | doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | bibcode=2008MNRAS.389..869E | arxiv=0806.2878 | s2cid=14878976 | postscript=. }}</ref>

<ref name=McWilliam1990>{{citation | last1=McWilliam | first1=Andrew | title=High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances | journal=Astrophysical Journal Supplement Series | volume=74 | pages=1075–1128 | date=December 1990 | doi=10.1086/191527 | bibcode=1990ApJS...74.1075M | doi-access=free }}</ref>

</references>

{{Stars of Lupus}}

[[Category:K-type giants]] [[Category:Lupus (constellation)]] [[Category:Bayer objects|Lupi, f]] [[Category:Durchmusterung objects|CD-29 11630]] [[Category:Flamsteed objects|Lupi, 2]] [[Category:Henry Draper Catalogue objects|135758]] [[Category:Hipparcos objects|074857]] [[Category:Bright Star Catalogue objects|5686]] [[Category:Population I stars]]