Newfound Planetary System Has "Hometown" LookThe star, 55 Cancri in the constellation Cancer, was already known to have one planet, announced by Butler and Marcy in 1996. That planet is a gas giant slightly smaller than the mass of Jupiter and whips around the star in 14.6 days at a distance only one-tenth that from Earth to the Sun. Using as a yardstick the 93-million mile Earth-Sun distance, called an astronomical unit or AU, the newfound planet orbits at 5.5 AU, comparable to Jupiter's distance from our Sun of 5.2 AU (or about 512 million miles). Its slightly elongated orbit takes it around the star in about 13 years, comparable to Jupiter's orbital period of 11.86 years. It is 3.5 to 5 times the mass of Jupiter... The star 55 Cancri is 41 light years from Earth and is about 5-billion years old. Further data are needed to determine whether yet another planet is orbiting it, because the two known planets do not explain all the observed Doppler wobbling. One possible explanation is a Saturn-mass planet orbiting about .24 AU from the star.
Jet Propulsion Laboratory
University of California, Berkeley
June 13, 2002
Astronomers Discover Two More Neptune-Sized Planets[T]he planet recently discovered around the sun-like 55 Cancri completes a full orbit in less than three days, compared to the 365-day year of planet Earth. This Neptune-sized planet circles its star much more closely than the Earth orbits the Sun. In fact, it circles 55 Cancri at a distance of 3.5 million miles less than 4% the distance between the Earth and the Sun. The other planet just announced which circles Gliese 436 at a distance of 2.6 million miles also orbits at relatively short range, at least when compared to Earths 93 million mile distance from the Sun... As the only four-planet system known thus far, in McArthurs view the 55 Cancri system is the closest analog we have to our own solar system. In fact, the earlier detection of planets around 55 Cancri was sufficient reason to put it toward the top of the list of stars to be observed by the SETI Institutes Project Phoenix, which looked at the star several years ago. Using a custom-made supercomputer and the National Radio Astronomy Observatory at Green Bank, West Virginia, 55 Cancri was examined as part of as part of the worlds most sensitive search for extraterrestrial intelligence. No signs of intelligence were found.
by Doug Vakoch
September 2, 2004
55 (Rho1) Cancri 2The star may be roughly twice (186 percent) as enriched as Sol with elements heavier than hydrogen ("metallicity"), based on its abundance of iron (Marcy et al, 2002, in pdf; and exoplanets.org). It appears to be either a super metal-rich dwarf or a slightly metal-poor K0 subgiant (Baliunas et al, 1997), but a recent study suggests that the metals enrichment may have been primordial (Santos et al, 2001). According to the Yale Bright Star Catalogue, 1991 5th Revised Edition notes entry for HR 3522, enhanced CN and C2 and perhaps CH has been detected in its spectrum. The star may be between two to eight billion years old (e.g., five billion years old, see: Marcy et al, 2002, in pdf; and Baliunas et al, 1997) -- appearing to be middle aged and chromospherically inactive. 55 Cancri A has a widely separated, dim companion Star ("B") located about 1,100 AUs (85" at 40.9 ly) away that seems to be gravitationally bound to it.
Sun and planets:55 Cancri b is a massive planet, orbiting very close to its parent star. In this respect it is similar to 51 Pegasi b, though these two worlds are different in some important aspects. Both planets are sufficiently massive to retain an atmosphere, but for 51 Pegasi b, it will be blown into space by the nearby star. 55 Cancri b has more than twice the orbital radius than 51 Pegasi b and a higher mass, so it would retain most of its gases. If it actually formed at its current position, an issue highly disputed among scientists, it would have a large, rocky core. With its high mass and dense atmosphere, 55 Cancri b may look like a hybrid between Venus and Jupiter.
55 Cancri system:
Extrasolar Planets: 55 Cancri
There are strong sources of heat on 55 Cancri b. One of them is the intense radiation from the nearby star, but another source is tidal friction caused by the star's gravity. The planet's surface may even be completely molten. Enormous volcanic eruptions would fill the atmosphere with carbondioxide and sulphur compounds, producing a thick yellowish cloud cover. Any daring explorer would be crushed by the immense pressure at ground level, and vaporized by the heat - and he could not even see the disk of dust recently discovered around 55 Cancri.
No known form of life could exist on 55 Cancri b. A volcanically hyperactive world, where pure sulphuric acid rains on oceans of molten rock, and titanic strikes of lightning from earth-sized thunderclouds give an eerie illumination, 55 Cancri b would be among the best places to call Hell.
California & Carnegie Planet Search Team
Latest Orbital Parameters Planet Period Tperi (JD-2450000) ecc omega (deg) Vel Amp, K (m/s) M sin i (Mjup) a (AU) b 14.653 d 1.479 .02 99 72.2 0.84 0.115 c 44.28 d 31.4 .34 61 13.0 0.21 0.24 d 5360 d 2785 .16 201 49.3 4.05 5.9
The inner planet was announced by Butler et al. in January 1997. Analysis of extended velocity measurements reveals additional velocity variations.
A Star Like Our OwnAn asteroid belt may have been found surrounding a star much like our own Sun, according to Dr. Charles Beichman of CIT. His team used NASA's Spitzer Space Telescope to make the discovery. If confirmed, this would be the first asteroid belt detected around a star that is about the same age and size as our Sun. If true, it could offer a rare look at a star system that closely resembles our own... According to the astronomers, it is possible that a giant comet, as big as the planet Pluto, got knocked into the inner solar system and is slowly boiling away, shedding dust in the process. "The 'super comet' theory is more of a long shot," Beichman said, "but we'll know soon enough." Future observations of the star using Spitzer and ground-based telescopes are expected to conclude whether asteroids or comets are the source of the dust.
by Bill Christensen
29 April 2005
Artist's conception of the system shows the view from a planet that might exist in the system. Note the asteroid collision in the foreground - this replenishes the dust detected by the Spitzer telescope.
Planets Found in Potentially Habitable SetupThree medium-sized planets of roughly the same mass as Neptune have been discovered around... HD 69830, a star slightly less massive than the Sun located 41 light-years away in the constellation Puppis (the Stern)... previously discovered multi-planet solar systems besides our own contain at least one giant, Jupiter-sized planet... The outermost planets is located just within the star's habitable zone, where temperatures are moderate enough for liquid water to form, and the system also contains an asteroid belt. The newly discovered planets have masses of about 10, 12 and 18 times that of Earth and they zip around the star in rapid orbits of about 9, 32 and 197 days, respectively... Recent observations by NASA's Spitzer Space Telescope last year revealed that HD 69830 also hosts an asteroid belt, making it the only other Sun-like star known to have one.
by Ker Than
17 May 2006
An artist's impression of the newly discovered planetary system. The planets are each about the mass of Neptune and orbit around the Sun-like star HD 69830. Credit: ESO
for the "That Makes One" dep't.Small Rocky Planet Found Orbiting Normal StarIts orbit is farther from its host star than Earth is from the Sun. Most known extrasolar planets reside inside the equivalent of Mercurys orbit. The planet is estimated to be about 5.5 times as massive as Earth and thought to be rocky. It orbits a red dwarf star about 28,000 light-years away. Red dwarfs are about one-fifth as massive as the Sun and up to 50 times fainter... Prior to this discovery, the smallest extrasolar planet found around a normal star was about 7.5 Earth masses. Earth-sized planets have been detected, but only around dying neutron stars... The planet and star are separated by about 2.5 astronomical units (AU). One AU is equal to the distance between the Earth and the Sun. Until now, no small planet had been found farther than 0.15 au from its parent star... "Microlensing should have discovered dozens of Jupiters by now if they were as common as these five-Earth-mass planets," said study co-author David Bennett. That suggests most of our galaxys planets are small and rocky. This prediction agrees with the standard model for solar system formation, known as the "core accretion" model.
by Ker Than
25 January 2006