In-Between Jovian Exoplanets

[lpetrich]

At Last, Scientists Have Found The Galaxy's Missing Exoplanets: Cold Gas Giants

We search for exoplanets using several techniques, and these techniques are most sensitive to planets with certain ranges of parameters, like very close ones and very far ones.

The main techniques used, radial velocity and transits, are most sensitive to close exoplanets, while direct imaging is most sensitive to very distant ones that are young enough to glow brightly in the infrared. Gravitational microlensing can detect planets across a full range of distances, but it has the problem that its observations are one-off and not repeated.

The first exoplanet discovered to orbit a Sunlike star was 51 Peg b, and it is a "hot Jupiter", orbiting about 0.053 AU away from its star. The most notable of distant exoplanets are likely HR 8799 b, c, d, and e, at distances 14.5, 24, 38, and 68 AU. GRAVITY instrument breaks new ground in exoplanet imaging | ESO United States - the light from four large optical telescopes was combined to observe planet e.

That's where a dedicated, long-period study of stars can come in to fill in that gap. A large team of scientists, led by Emily Rickman, conducted an enormous survey using the CORALIE spectrograph at La Silla observatory. They measured the light coming from a large number of stars within about 170 light-years on a nearly continuous basis, beginning in 1998.

Radial velocity again, but with 20 years of observations to catch planets with long periods. From Kepler's 3rd law, period, distance, and mass are related by P ~ M^(-1/2) * a^(3/2) giving a ~ M^(1/3) * P^(2/3). Velocity v ~ M^(1/2) * a^(-1/2) ~ M^(1/3) * P^(-1/3). So distant planets are somewhat harder to observe with radial-velocity observations, but not by much.

• HD 181234 b (new) a = 7.5, P = 20.4, e = 0.73, M = 8.4
• HD 13724 b (new) a = 12.4, P = 40.4, e = 0.34, M = 26.8
• HD 25015 b (new) a = 6.2, P = 16.5, e = 0.39, M = 4.5
• HD 92987 b (new) a = 9.6, P = 28.4, e = 0.21, M = 16.9
• HD 50499 b (new) a = 3.9, P = 6.8, e = 0.27, M = 1.5
• HD 50499 b (upd) a = 9.0, P = 23.6, e = 0.00, M = 2.9
• HD 92788 b (upd) a = 1.0 P = 0.89, e = 0.35, M = 3.8
• HD 98649 b (upd) a = 6.6, P = 16.5, e = 0.86, M = 6.8
• HD 92788 c (conf) a = 10.5, P = 31.8, e = 0.46, M = 3.7

a in AU, P in yr, M in M(Jupiter)*sin(i). The planet - brown-dwarf boundary is at 13 M(Jup). The sin(i) is an orbit-geometry projection factor.

All more massive than Jupiter, and several of them have rather eccentric orbits, something common among exoplanets. The Extrasolar Planets Encyclopaedia and NASA Exoplanet Archive both have exoplanet-data plotting facilities.

 

[lpetrich]

These results were from [1904.01573v2] The CORALIE survey for southern extrasolar planets XVIII. Three new massive planets and two low mass brown dwarfs at separation larger than 5 AU done at La Silla Observatory | ESO United States

Here are some more results:

Gemini Planet Imager analyzes 300 stars
Jupiter-like exoplanets found in sweet spot in most planetary systems
noting
The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics from 10 to 100 au - IOPscience

Detected: 6 giant planets and 3 brown dwarfs.

Jupiter-like planets are more likely to orbit stars with masses more than about 1.5 solar masses, at least if their masses are between 2 and 13 Jupiter masses. Their occurrence peaks between 3 and 10 AU's, with it dropping farther out.

Brown dwarfs are much rarer, with around 1% of stars having one between 10 and 100 AU.