Delta Doradus

{{Starbox begin

| name = Delta Doradus

}}

{{Starbox observe

| epoch = J2000.0

| equinox = J2000.0 (ICRS)

| constell = Dorado

| ra = {{RA|05|44|46.37811}}

| dec = {{DEC|−65|44|07.9011}}

| appmag_v = +4.34

}}

{{Starbox character

| class = A7 V

| b-v = +0.22

| u-b = +0.11

| r-i =

| variable =

}}

{{Starbox astrometry

| radial_v = {{Val|−8.3|0.8}}

| prop_mo_ra = −28.91

| prop_mo_dec = +5.17

| parallax = 21.80

| p_error = 0.14

| parallax_footnote =

| absmag_v = +1.03

}}

{{Starbox detail

| source =

| mass = 1.85

| radius = 2.1

| luminosity = 29

| temperature = {{Val|7828|266|fmt=commas}}

| gravity = 3.89

| metal_fe = −0.40

| rotational_velocity = 172

| age_myr = 940

}}

{{Starbox catalog

| names = δ Dor, CPD−65° 496, FK5 1154, HD 39014, HIP 27100, HR 2015, SAO 249346

}}

{{Starbox reference

| Simbad = del+Dor

}}

δ Doradus (often Latinised to Delta Doradus, abbreviated to δ Dor or delta Dor) is a star in the southern constellation of Dorado. Based upon an annual parallax shift of 21.80 mas as seen from Earth, it is located around 150 light years from the Sun. The star is visible to the naked eye with an apparent visual magnitude of +4.34.

This is an A-type main sequence star with a stellar classification of A7 V. The star is spinning rapidly with a projected rotational velocity of 172 km/s. This is giving the star an oblate shape with an equatorial bulge that is 12% larger than the polar radius. Although A-type stars are not expected to harbor a magnetic dynamo needed to power X-ray emission, an X-ray flux of {{Val|3.6e27|u=erg/s}} has been detected at these coordinates. This may indicate that the star has an unseen companion. δ Doradus displays an infrared excess suggesting it may be a Vega-like star with an orbiting debris disk.

Currently this star is the Moon's south pole star, which occurs once every 18.6 years.{{citation |title=The Guinness Book of Astronomy Facts & Feats |page=29 |author=Patrick Moore |author-link=Patrick Moore |year=1983 |quote=In 1968 the north pole star of the Moon was Omega Draconis; by 1977 it was 36 Draconis. The south pole star is Delta Doradus.}} The pole star status changes periodically, because of the precession of the Moon's rotational axis. When δ Doradus is the pole star, it is better aligned than Earth's Polaris (α Ursae Minoris), but much fainter. It is also the south pole star of Jupiter.{{citation needed|date=January 2019}}

References

{{Reflist|refs=

{{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=. }}

{{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 | doi=10.1134/S1063773712050015

| arxiv=1108.4971 | s2cid=119257644 | postscript=. }}

{{citation

| display-authors=1

| last1=Pasinetti Fracassini | first1=L. E. | last2=Pastori | first2=L.

| last3=Covino | first3=S. | last4=Pozzi | first4=A.

| title=Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)

| edition=3rd | journal=Astronomy and Astrophysics

| volume=367 | pages=521–524 | date=February 2001

| doi=10.1051/0004-6361:20000451 | bibcode=2001A&A...367..521P

| arxiv=astro-ph/0012289 | s2cid=425754 | postscript=. }}

{{citation

| title=X-ray emission from A-type stars

| last1=Schröder | first1=C. | last2=Schmitt | first2=J. H. M. M.

| journal=Astronomy and Astrophysics | postscript=.

| volume=475 | issue=2 | pages=677–684 | date=November 2007

| doi=10.1051/0004-6361:20077429 | bibcode=2007A&A...475..677S | doi-access=free }}

{{citation

| title=Spectroscopic metallicities of Vega-like stars

| last1=Saffe | first1=C. | last2=Gómez | first2=M.

| last3=Pintado | first3=O. | last4=González | first4=E.

| journal=Astronomy and Astrophysics | postscript=.

| volume=490 | issue=1 | pages=297–305 | date=October 2008

| doi=10.1051/0004-6361:200810260 | bibcode=2008A&A...490..297S |arxiv = 0805.3936 | s2cid=15059920 }}

{{citation

| display-authors=1 | last1=McDonald | first1=I.

| last2=Zijlstra | first2=A. A. | last3=Boyer | first3=M. L.

| title=Fundamental Parameters and Infrared Excesses of Hipparcos Stars

| journal=Monthly Notices of the Royal Astronomical Society

| volume=427 | issue=1 | pages=343–57 | date=2012

| bibcode=2012MNRAS.427..343M | arxiv=1208.2037

| doi=10.1111/j.1365-2966.2012.21873.x | doi-access=free | s2cid=118665352 | postscript=. }}

{{citation

| last1=van Belle, Gerard T.

| title=Interferometric observations of rapidly rotating stars

| journal=The Astronomy and Astrophysics Review

| volume=20 | issue=1 | page=51 | date=March 2012

| doi=10.1007/s00159-012-0051-2 | bibcode=2012A&ARv..20...51V

| postscript=. | arxiv=1204.2572

| s2cid=119273474

}}

{{citation

| last1=de Bruijne | first1=J. H. J. | last2=Eilers | first2=A.-C.

| title=Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project

| journal=Astronomy & Astrophysics

| volume=546 | id=A61 | pages=14 | date=October 2012

| doi=10.1051/0004-6361/201219219 | bibcode=2012A&A...546A..61D

| arxiv=1208.3048 | s2cid=59451347 | postscript=. }}

{{citation

| last1=David | first1=Trevor J. | last2=Hillenbrand | first2=Lynne A.

| title=The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets

| journal=The Astrophysical Journal

| volume=804 | issue=2 | pages=146 | year=2015

| bibcode=2015ApJ...804..146D | doi=10.1088/0004-637X/804/2/146

| arxiv=1501.03154 | s2cid=33401607 | postscript=. }}

{{citation

| display-authors=1 | last1=Royer | first1=F.

| last2=Zorec | first2=J. | last3=Gómez | first3=A. E.

| title=Rotational velocities of A-type stars. III. Velocity distributions

| journal=Astronomy and Astrophysics

| volume=463 | issue=2 | pages=671–682 | date=February 2007

| doi=10.1051/0004-6361:20065224 | bibcode=2007A&A...463..671R

| arxiv=astro-ph/0610785 | s2cid=18475298 | postscript=. }}