2 Aurigae

---

title: "2 Aurigae" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["k-type-giants", "barium-stars", "binary-stars", "auriga", "durchmusterung-objects", "flamsteed-objects", "henry-draper-catalogue-objects", "hipparcos-objects", "bright-star-catalogue-objects"] description: "Possible binary star system in the constellation Auriga" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/2_Aurigae" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Possible binary star system in the constellation Auriga ::

| image= |image=Auriga constellation map.svg|alt=|float=center|width=240 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=2 Aurigae |x=736|y=524 |caption=Location of 2 Aurigae (circled) | epoch = J2000.0 (ICRS) | constell = Auriga | ra = | dec = | appmag_v = +4.79 | type = | class = K3- III Ba0.4 | b-v = | u-b = | variable = | radial_v = | prop_mo_ra = −25.731 | prop_mo_dec = −3.867 | parallax = 6.3340 | p_error = 0.2695 | parallax_footnote = | absmag_v = –1.84 | source = | mass = 2.86 | radius = | luminosity = | temperature = | metal_fe = | gravity = 1.79 | rotational_velocity = 2.3 | age_gyr = 1.80 | names = | Simbad = 2+Aur

::figure[src="https://upload.wikimedia.org/wikipedia/commons/3/31/2_Aurigae-wiki-01-adj.jpg" caption="2 Aurigae in optical light"] ::

2 Aurigae is a possible binary star system in the northern constellation of Auriga. This object is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of +4.79. It forms an attractive four-star asterism when viewed in a low power eyepiece, together with the nearby HIP 22647 and another very loose visual pair, HIP 22776 and HIP 22744, all above magnitude 8. 2 Aurigae is moving closer to the Earth with a heliocentric radial velocity of −17 km/s.

The visible component is an aging giant star with a stellar classification of K3- III Ba0.4. The suffix notation indicates this is a mild barium star, which means the stellar atmosphere is enriched with s-process elements. It is either a member of a close binary system and has previously acquired these elements from a (now) white dwarf companion or else it is on the asymptotic giant branch and is generating the elements itself. 2 Aurigae is 1.80 billion years old with 2.86 times the mass of the Sun and has expanded to 48 times the Sun's radius. It is radiating 599 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,115 K.

References

| 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 | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | s2cid=119257644 | postscript=. }}

| last1=Jasniewicz | first1=G. | last2=Parthasarathy | first2=M. | last3=de Laverny | first3=P. | last4=Thévenin | first4=F. | title=Late-type giants with infrared excess. I. Lithium abundances | display-authors=1 | journal=Astronomy and Astrophysics | volume=342 | pages=831–838 | date=February 1999 | bibcode=1999A&A...342..831J }}

| 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 | postscript=. | bibcode=1989ApJS...71..245K | doi=10.1086/191373 | s2cid=123149047 }}

| last1=Takeda | first1=Y. | last2=Tajitsu | first2=A. | title=On the observational characteristics of lithium-enhanced giant stars in comparison with normal red giants | journal=Publications of the Astronomical Society of Japan | volume=69 | issue=4 | pages=978–88 | date=August 2017 | doi=10.1093/pasj/psx057 | arxiv=1706.02273 | bibcode=2017PASJ...69...74T | postscript=. }}

| title=Abundances in the Local Region. I. G and K Giants | last1=Luck | first1=R. Earle | journal=Astronomical Journal | postscript=. | volume=150 | issue=3 | at=88 | year=2015 | arxiv=1507.01466 | bibcode=2015AJ....150...88L | doi=10.1088/0004-6256/150/3/88 | s2cid=118505114 }}

| display-authors=1 | last1=Gomez | first1=A. E. | last2=Luri | first2=X. | last3=Grenier | first3=S. | last4=Prevot | first4=L. | last5=Mennessier | first5=M. O. | last6=Figueras | first6=F. | last7=Torra | first7=J. | title=Absolute magnitudes and kinematics of barium stars | journal=Astronomy and Astrophysics | postscript=. | volume=319 | pages=881 | year=1997 | bibcode=1997A&A...319..881G }}

References

1. {{cite DR2. 198271397081746560
2. "2 Aur".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::