HD 1

{{starbox begin

| name = HD 1

}}

{{starbox image

|image = 230px

|caption = HD 1 is the bright star in the middle

}}

{{starbox observe

| epoch = J2000.0

| constell = Cepheus

| ra = {{RA|00|05|08.84054}}

| dec = {{DEC|+67|50|23.9805}}

| appmag_v = 7.42{{±|0.01}}

}}

{{starbox character

| type = Red-giant branch

| class = G9-K0 IIIa

}}

{{starbox astrometry

| radial_v = {{val|-30.177|0.007}}

| prop_mo_ra = +7.480

| prop_mo_dec = −5.045

| pm_footnote =

| parallax = 2.668

| p_error = 0.0485

| parallax_footnote =

| absmag_v = {{val|-0.73|0.03}}

}}

{{Starbox orbit

| reference =

| period = {{val|{{convert|2318.70|day|year|disp=number}}|{{convert|1.1|day|year|disp=number}}|fmt=none}}

| axis_unitless = {{val |p=≥| {{convert|122.2|e6km|AU|disp=number}} | {{convert|0.4|e6km|AU|disp=number}} | fmt=none | ul=AU }}

| eccentricity = {{val|0.503|0.002}}

| inclination =

| periastron = 2,450,000 + {{val|2317.8|1.1|ul=JD|fmt=commas}}

| periarg = {{val|221.0|0.4}}

| k1 = {{val|4.435|0.013}}

}}

{{starbox detail

| source =

| mass = {{val|3.5|0.1}}

| radius = {{val|20.7|0.3}}

| luminosity = {{val|217|6}}

| gravity = {{val|2.18|0.13}}

| temperature = {{val|4882|36|fmt=commas}}

| metal = {{M/H|{{val|-0.16|0.04}}}}

| rotational_velocity = {{val|9.11|0.02}}

| age_myr = 300

}}

{{starbox catalog

| names = {{odlist|HD = 1|BD = +67°1599|GSC = 04294-00080|HIP = 422|SAO = 10963|AG = +67°4}}

}}

{{starbox reference

| Simbad = HD+1

}}

HD 1, also known as HIP 422, is the first star catalogued in the Henry Draper Catalogue. It is located in the northern circumpolar constellation Cepheus and has an apparent magnitude of 7.42, making it readily visible in binoculars, but not to the naked eye. The object is located relatively far away at a distance of 1,220 light years but is approaching the Solar System with a spectroscopic radial velocity of {{val|-27.3|ul=km/s}}.

Characteristics

Originally thought to be a single object, observations from Griffin & McClure (2009) reveal it to be a single-lined spectroscopic binary. The components take {{convert|2318.70|day|year}} years to fully orbit each other in a mildly-eccentric orbit. The visible component is an evolved red-giant branch (RGB) star with a stellar classification of G9-K0 IIIa, a spectral class intermediate between a G9 and K0 giant star. It has 3.5 times the mass of the Sun, but at the age of 300 million years it has expanded to 20.7 times its radius. It radiates 217 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of {{val|4882|ul=K|fmt=commas}}, giving it a yellowish-orange hue. HD 1A is metal-poor, with a metal-to-hydrogen abudance ratio 70% of the Sun's level. The object spins modestly with a projected rotational velocity of {{val|9.11|0.02|ul=km/s}}.

There is evidence for a third object in the system on a much wider orbit.

References

{{Reflist|refs=

{{cite journal | last1 = Høg | first1 = E. | last2 = Fabricius | first2 = C. | last3 = Makarov | first3 = V. V. | last4 = Urban | first4 = S. | last5 = Corbin | first5 = T. | last6 = Wycoff | first6 = G. | last7 = Bastian | first7 = U. | last8 = Schwekendiek | first8 = P. | last9 = Wicenec | first9 = A. | title = The Tycho-2 catalogue of the 2.5 million brightest stars |journal=Astronomy and Astrophysics | date = March 2000 | volume = 355 | pages = L27–L30 | bibcode = 2000A&A...355L..27H | issn = 0004-6361}}

{{cite journal |last1=Griffin |first1=R. F. |last2=McClure |first2=R. D. |title=Spectroscopic binary orbits for the Henry Draper Catalogue stars |journal=The Observatory |date=February 2009 |volume=129 |pages=28–32 |issn=0029-7704 |bibcode=2009Obs...129...28G}}

{{Cite journal |last=Strassmeier |first=Klaus G. |last2=Weber |first2=Michael |date=December 2020 |title=On the binary orbit of Henry Draper one (HD 1) |journal=Astronomische Nachrichten |language=en |volume=341 |issue=10 |pages=983–988 |doi=10.1002/asna.202013855 |arxiv=2011.13330 |issn=0004-6337}}

{{cite journal | last1 = Strassmeier | first1 = K.G. | last2 = Weber | first2 = M. | last3 = Granzer | first3 = T. | last4 = Dall | first4 = T.H. | title = HD 1: The number-one star in the sky | journal = Astronomische Nachrichten | date = 20 April 2010 | volume = 331 | issue = 4 | pages = 368–377 | issn = 0004-6337 | eissn = 1521-3994 | doi = 10.1002/asna.201011356 | bibcode = 2010AN....331..368S}}

{{cite journal | last1 = Anderson | first1 = E. | last2 = Francis | first2 = Ch. | title = XHIP: An extended hipparcos compilation | journal = Astronomy Letters | date = May 2012 | volume = 38 | issue = 5 | pages = 331–346 | issn = 1063-7737 | eissn = 1562-6873 | doi = 10.1134/S1063773712050015 | bibcode = 2012AstL...38..331A | arxiv = 1108.4971| s2cid = 119257644 }}

}}

Category:Spectroscopic binaries

000422

Category:K-type giants

Category:G-type giants

Category:Cepheus (constellation)

BD+67 01599