HD 69830 b

{{Short description|Neptunian-sized exoplanet orbiting HD 69830}}

{{Infobox planet

| name = HD 69830 b

| discoverer = C. Lovis et al.

| discovered = May 18, 2006

| discovery_method = Radial velocity

| apsis = astron

| semimajor = {{convert|0.0764|±|0.0017|AU|km|abbr=on}}

| eccentricity = {{val|0.128|0.028}}

| period = {{val|8.66897|0.00028|ul=d}}

| time_periastron = 2,453,496.8 ± 0.06

| arg_peri = 340 ± 26

| semi-amplitude = {{val|3.4|0.1|ul=m/s}}

| star = HD 69830

| mass = {{val|10.1|0.38|0.37|p=≥|ul=Earth mass}}

| single_temperature = ~804 K

|image=HD_69830_b_(Celestia).jpg}}

HD 69830 b is a Neptune-mass or super-Earth-mass exoplanet orbiting the star HD 69830. It is at least 10 times more massive than Earth. It also orbits very close to its parent star and takes 8²/₃ days to complete an orbit.

Based on theoretical modeling in the 2006 discovery paper, this is likely to be a rocky planet, not a gas giant. However, other work has found that if it had formed as a gas giant, it would have stayed that way,{{cite journal | journal=Geophysical Research Abstracts | volume=9| issue=7850 |date=2007 | url=http://www.cosis.net/abstracts/EGU2007/07850/EGU2007-J-07850.pdf?PHPSESSID=1eb3a7a98603083dda25d18001ea2a33 | title=The impact of nonthermal loss processes on planet masses from Neptunes to Jupiters |author=H. Lammer|display-authors=etal}} and it is now understood that planets this massive are rarely rocky.{{cite journal |arxiv=1603.08614|doi=10.3847/1538-4357/834/1/17 |title=Probabilistic Forecasting of the Masses and Radii of Other Worlds |year=2017 |last1=Chen |first1=Jingjing |last2=Kipping |first2=David |journal=The Astrophysical Journal |volume=834 |issue=1 |page=17 |s2cid=119114880 |bibcode=2017ApJ...834...17C |doi-access=free }}

If HD 69830 b is a terrestrial planet, models predict that tidal heating would produce a heat flux at the surface of about 55 W/m². This is 20 times that of Io.{{cite journal|title=Tidal Heating of Extra-Solar Planets| first= Brian| last= Jackson|author2=Richard Greenberg |author3=Rory Barnes | journal=Astrophysical Journal | date=2008|doi=10.1086/587641|volume=681|pages=1631|arxiv=0803.0026|issue=2| bibcode=2008ApJ...681.1631J| s2cid= 42315630}}