HD 85512 b

HD 85512 b is a currently-disputed exoplanet orbiting HD 85512, a K-type main-sequence star approximately 37 light-years from Earth in the constellation of Vela.^[3][1]

Due to its mass of at least 3.6 times the mass of Earth, HD 85512 b is classified as a

The planet has a minimum Earth mass of 3.6 ± 0.5, minimum surface gravity of about 1.4 g and assuming an atmosphere like Earth's despite its far greater mass, an estimated temperature of 298 K (24.85 °C or 76.73 °F) at the top of its atmosphere. The estimated temperature is noted to be similar to temperatures in Southern France,^[2][5] but various atmospheric conditions prevalent in the planet have to be analyzed to estimate the temperature of the surface.^[2] An estimated radius of 1.3 R_🜨 is possible based on its mass.

Host star

The planet orbits a (K-type) star named HD 85512. The star has a mass of 0.69 M_☉ and a radius of around 0.53 R_☉. It has a surface temperature of 4715 K and is 5.61 billion years old. In comparison, the Sun is about 4.6 billion years old^[6] and has a surface temperature of 5778 K.^[7]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 7.43 Therefore, HD 85512 is too dim to be seen with the naked eye, but can be viewed using good binoculars.

Orbit

The planet orbits the parent star (which has about 11% of the Sun's luminosity) at a distance of about 0.26 AU,^[4] with an orbital period of about 54 days,^[4] and is possibly tidally locked.

Habitability and climate

Models generated by Pepe et al (2011) suggest that for the temperature to be below 270 K (-3.15 °C), for a circular orbit, the planetary albedo should be 0.48 ± 0.05 and for an eccentricity of 0.11, the planetary albedo should be 0.52.^[1] If the planet has 50% cloud cover, water may exist in liquid form on the planet^[8] provided its atmosphere is similar to our own, thus increasing the planet's habitability potential.^[9][10][11] Also, if the albedo of the planet is increased due to cloud cover, water could be present in its liquid form on the planet, which would mean that the planet is on the edge of the habitability zone.^[1][11]

However, PHL's new definition of the circumstellar habitable zone classifies this planet in the "too hot" zone, and it considers the planet "not habitable".^[12]

The planet would likely be inhospitable because of a

On August 17, 2011, researchers released a study of the planet. The study makes assumptions about the planet actually having the minimum mass allowed by existing observations, not being tidally locked, and having one specific composition out of the wide parameter set available to conclude that HD 85512 b is the most habitable exoplanet discovered up to that point[1] and one of the most stable exoplanets discovered by the High Accuracy Radial Velocity Planet Searcher.^[2]

In 2023, a study reassessed the radial velocity data of HD 85512. A signal was detected with a period of 51 days, inconsistent with the previously published 58-day orbital period of HD 85512 b, but consistent with previous estimates of the stellar rotation period. This indicates that the signal is very likely to be caused by the stellar rotation, rather than an orbiting planet.^{[14]: 25–27 [14]: 44}

Possibility as target for interstellar probe

Reaching this planet at the current record spacecraft speed, the Helios Probes' 247,517 kilometres per hour (153,800 mph), would take 156,971 years.^[15]

See also

• Carbon planet
• Circumstellar habitable zone
• Earth analog
• Gliese 581 d
• Gliese 581 g
• Gliese 667 Cc
• Habitable zone
• Kepler 22 b
• Planetary habitability
• Super-Earth

Wikimedia Commons has media related to HD 85512 b.

References