XO-4b

{{Infobox planet

| name = XO-4b

Hämarik

| image = Exoplanet Comparison XO-4 b.png

| caption = Size comparison of XO-4b with Jupiter.

| discoverer = McCullough et al.

| discovery_site = Maui, Hawaii

| discovered = May 19, 2008

| discovery_method = Transit

| apsis = astron

| semimajor = {{convert|0.0555|±|0.00011|AU|km|abbr=on}}

| eccentricity = 0.0024

| period = 4.12502 ± 2e-5 d
0.011293 y

| inclination = 88.7 ± 1.1

| star = XO-4

| mean_radius = 1.34 ± 0.048 {{Jupiter radius|link=y}}

| mass = 1.72 ± 0.2 {{Jupiter mass|link=y}}

| density = {{cvt|948|kg/m3|g/cm3|lk=on|disp=out}}{{fact|date=July 2024}}

| surface_grav = {{convert|24.8|m/s2|g0|lk=on|abbr=on}}

| single_temperature = ~1333{{clarify|date=October 2023}}

}}

XO-4b is an extrasolar planet approximately 956 light years away in the constellation of Lynx. This planet was found by the transit method by McCullough in May 2008. The planet has mass {{Jupiter mass|link=y|1.72}} and radius {{Jupiter radius|link=y|1.34}}. This planet orbits very close to the F-type parent star, as it is typical for transiting planets, classing this planet as Hot Jupiter.

Orbit

It takes only 4.125 days (or 99 hours) to orbit at a distance of 8.3 gigameters (0.0555 AU) away from the star.

The study in 2012, utilizing a Rossiter–McLaughlin effect, have determined the planetary orbit is strongly misaligned with the equatorial plane of the star, misalignment equal to -46.7{{±|8.1}}°.{{citation|arxiv=1206.6105|title=Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments|year=2012|doi=10.1088/0004-637X/757/1/18|last1=Albrecht|first1=Simon|last2=Winn|first2=Joshua N.|last3=Johnson|first3=John A.|last4=Howard|first4=Andrew W.|last5=Marcy|first5=Geoffrey W.|last6=Butler|first6=R. Paul|last7=Arriagada|first7=Pamela|last8=Crane|first8=Jeffrey D.|last9=Shectman|first9=Stephen A.|last10=Thompson|first10=Ian B.|last11=Hirano|first11=Teruyuki|last12=Bakos|first12=Gaspar|last13=Hartman|first13=Joel D.|journal=The Astrophysical Journal|volume=757|issue=1|page=18|bibcode=2012ApJ...757...18A|s2cid=17174530}}

Naming

The planet XO-4b is named Hämarik. The name was selected in the NameExoWorlds campaign by Estonia, during the 100th anniversary of the IAU. Hämarik is Estonian for dusk, and was named for a character in a folk tale written by Friedrich Robert Faehlmann.{{Cite web|url=http://www.nameexoworlds.iau.org/final-results|title=Approved names|website=NameExoworlds|language=en|access-date=2020-01-02}}{{Cite web|url=https://www.iau.org/news/pressreleases/detail/iau1912/|title=International Astronomical Union {{!}} IAU|website=www.iau.org|access-date=2020-01-02}}{{Cite web|url=https://estonianworld.com/knowledge/estonia-has-been-assigned-its-own-star-and-planet|title=Estonia has been assigned its own star and planet|website=Estonian World|date=20 January 2020|language=en|access-date=2020-01-20}}

References

{{Reflist|refs=

{{cite arXiv | title=XO-4b: An Extrasolar Planet Transiting an F5V Star | last1=McCullough | first1=P. R. | last2=Burke | first2=Christopher J. | last3=Valenti | first3=Jeff A. | last4=Long | first4=Doug | last5=Johns-Krull | first5=Christopher M. | last6=Machalek | first6=P. | last7=Janes | first7=K. A. | last8=Taylor | first8=B. | last9=Gregorio | first9=J. | display-authors=1 | date=2008 | class=astro-ph | eprint=0805.2921}}

}}