Published on July 15, 2015, an international group of astronomers has used the ESO 3.6-metre telescope to detect a twin of Jupiter orbiting at the same mean distance to a twin of the Sun. HIP 11915, a G-class star some 175 light-years away in Cetus shining at 8.58 magnitudes (visible in binoculars). The sun as seen from HIP 11915 has a similar apparent magnitude located in the opposite constellation of Boötes near Arcturus. The existence of a Jovian-mass planet in a Jupiter-like orbit around a Sun-like star opens the possibility that the system of planets around this star may be very similar to our own Solar System. HIP 11915 is about the same age as the Sun, only 500 million years younger while its Sun-like composition suggests that there may also be rocky planets orbiting closer to the star. With a 0.99 jovian mass, HIP 11915 b orbits its host star in 10.486 years at a mean distance of 4.8AU close to that of Jupiter in our solar system. Based on models, it is expected to have a temperature of around -155°C, again, nearly the same as the planet Jupiter though its eccentricity is 0.1, slightly higher than its Jupiter analog.
Image credit: RWD
Planet Designation | Title | Constellation | Distance | SMA | Period | Mass | Radius | Year | |
---|---|---|---|---|---|---|---|---|---|
1 | Proxima b | Nearest Known Exoplanet | Centaurus | 4.24ly | 0.04856AU | 11.1868d | 1.27⊕ | 2016 | |
2 | Barnard b | Second Closest Known Exoplanet | Ophiuchus | 5.9ly | AU | d | 3.23⊕ | ||
3 | Epsilon Eridani b | Asteroid Belts and Controversal Planets | Eridanus | 10.48ly | 3.53AU | 2671d | 245⊕ | 2000 | |
4 | Ross 128 b | Third Closest Known Exoplanet | Virgo | 11.03ly | 0.0496AU | 9.8658d | 1.35⊕ | 2017 | |
5 | Tau Ceti e | Planets Needing Confirmation | Cetus | 11.91ly | 0.538AU | 162.87d | 3.29⊕ | 2017 | |
6 | Luyten's Star b | Only 1.2 Light-Years Away from Procyon | Canis Minor | 12.2ly | 0.091101AU | 18.6498d | 2.89⊕ | 2017 | |
7 | Kapteyn's Star c | Oldest-known Cold Exoplanet | Pictor | 12.76ly | 0.311AU | 121.54d | 4.8⊕ | 2014 | |
8 | Wolf 1061 c | Temperate Super-Earth or Super-Mars | Ophiuchus | 14.04ly | 0.089AU | 17.8719d | 3.41⊕ | 2015 | |
9 | Gliese 832 c | Large Planet as Temperate as Earth | Grus | 16.1ly | AU | d | 5.4⊕ | ||
10 | 40 Eridani b | Hot Super-Earth in Triple Star System | Eridanus | 16.26ly | 0AU | 42.378d | 8.47⊕ | 2018 | |
11 | Gliese 3323 b | Little Known in Habitable Zone | Eridanus | 17.54ly | 0.03282AU | 5.3636d | 2.02⊕ | 2017 | |
12 | LTT 1445A b | Planet in Triple Red Dwarf System | Eridanus | 22.5ly | 0.022AU | 5.35876d | 2.2⊕ | 1.18⊕ | 2019 |
13 | Gliese 667C c | Earth-like Planet in Triple Star System | Scorpius | 23.6ly | 0.125AU | 28.14d | 3.71⊕ | 2013 | |
14 | HD 85512 b | Bordering the Habitable Zone | Vela | 36.4ly | 0.26AU | 58.43d | 3.6⊕ | 2011 | |
15 | Gliese 1132 b | Heat Planet with Atmosphere | Vela | 39.3ly | 0.0153AU | 1.62893d | 1.66⊕ | 1.13⊕ | 2015 |
16 | Trappist-1 d | Small but Most Earth-like Known Planet | Aquarius | 39.5ly | 0.02227AU | 4.04922d | 0.297⊕ | 0.78⊕ | 2016 |
17 | LHS 1140 b | A Massive Super-Earth Inside Habitable Zone | Cetus | 40.67ly | 0.0946AU | 24.7372d | 6.64⊕ | 1.72⊕ | 2017 |
18 | Gliese 143 b | A Huge Neptunian Around a K-Star | Reticulum | 53.2ly | 0.1915AU | 35.6125d | 30.63⊕ | 2.61⊕ | 2019 |
19 | TOI-270 b | Nearby M-Dwarf Planets | Dorado | 73.23ly | AU | d | 1.9⊕ | ||
20 | Gliese 3470 b | Evaporating Planet | Cancer | 95.5ly | 0.0355AU | 3.33665d | 13.4⊕ | 4.57⊕ | 2012 |
21 | K2-3 b | Super-Earths Trio in Leo | Leo | 143.9ly | 0.0747AU | 10.0547d | 2.7⊕ | 2.07⊕ | 2015 |
22 | HIP 11915 b | A Twin of Jupiter | Cetus | 175ly | AU | d | 0.99⊕ | ||
23 | K2-288B b | Detected by Citizen Scientists | Taurus | 226ly | 0.164AU | 31.3935d | 4⊕ | 1.90⊕ | 2018 |
24 | Kepler-186 f | Earth-sized Cold Kepler Planet | Cygnus | 582ly | 0.432AU | 129.944d | 1.4⊕ | 1.16⊕ | 2014 |
Most of the stars introduced on this page are 'Red Dwarfs'. Actually they represent the most common type of stars. About 73% of all stars in the Milky Way galaxy are dim red dwarfs, featuring less than half the solar surface temperature and low luminosity, but in turn high stellar activity, such as flares and hazardous radiation that can hit red dwarf planets hard potentially prohibiting formation of known lifeforms.
Given its minute energy emission, the habitable zone (HBZ, an imaginary ring where temperatures support liquid water) of a red dwarf is situated near the star, as are planets orbiting inside this zone. The gravitational pull of the star can tidally lock a nearby planet which then faces one hemisphere to the star while the other is enshrouded in darkness - like the Earth moon - the axial rotation period equals the orbital period.
Some densely populated systems, such as TRAPPIST-1, have several planets orbiting in close proximity in that an observer on a planet could see other planets larger than our moon in the sky. Also, the planet may have one or multiple moons themselves. In any case a truly impressive spectacle with fast changes.
Due to their low visual luminosity no known red dwarf is visible by the naked eye, not even the nearest such as Proxima Centauri or the solitary Barnard's Star. Others, such as Gliese 667, are triple star systems but anywhere near visual magnitude
Image Credit: NASA/ESA/STScl