News and commentary about the Great Frontiers

ISS007-E-10807 (21 July 2003) --- This view of Earth's horizon as the sunsets over the Pacific Ocean was taken by an Expedition 7 crewmember onboard the International Space Station (ISS). Anvil tops of thunderclouds are also visible. Credit: Earth Science and Remote Sensing Unit, NASA Johnson Space Center

Image Credit: ISS007-E-10807 (21 July 2003) – Earth Science and Remote Sensing Unit, NASA Johnson Space Center

Five Planets Make Record System



This artist's concept shows four of the five planets that orbit 55 Cancri, a star much like our own.

Image Credit: NASA – “Plentiful Planetary System” – “This artist’s concept shows four of the five planets that orbit 55 Cancri, a star much like our own.”

NASA announced during a press telecon this morning the discovery of a fifth planet in the 55 Cancri system. This sets a new record for exoplanets in a single system and might indicate that multi-planet systems like our own are common in the Milky Way.

The discovery brings to five the number of planets detected in this system since the first was discovered over a decade ago. The technique used was the “wobble” method, also known as the radial velocity technique. Planets tug on their parent stars, and this tug will show up as a doppler shift of the star as viewed from the Earth. Plotting these shifts over a period of 18 years and taking advantage of technological progress for both hardware and software, scientists collected the necessary data to indicate the presence of this planet. The newly detected planet orbits 55 Cancri, located approximately 41 light years away in the constellation Cancer, near Orion. The planet is located 0.78 AU away from 55 Cancri, about the distance of Venus from the Sun in our own system.

This location appears to be within the star’s habitable zone, a theoretical location around stars where temperate temperatures may allow liquid water to puddle on planetary surfaces. The new planet is 45 times the mass of the Earth, suggesting it is an ice or gas giant, but any moon located around the planet could be interesting places to search for liquid water, and life. Debra Fischer, astronomer from San Francisco State University, stated that the 55 Cancri system is packed with planets, like our own system. Technology trends along with steady funding support from NASA and the NSF allowed Earth-based telescopes to increase in capability enough to pull about the separate tugs of the five planets in the 55 Cancri system. New imaging technologies could lead to the discovery of the first Earth-sized planet within 15 to 20 years, according to Jonathan Lunine, a planetary scientist at the University of Arizona.

Geoff Marcy, an astronomer at the University of California, Berkeley, said the discovery “has me jumping out of my socks.” To date, most exoplanets discovered have been single members of their parent stars. The 55 Cancri system might indicate that the Milky Way is full of billions of planetary systems and increases the possibility of Earth-like planets. Marcy highlighted the structure of the new system, reminiscent of our own system. Four of the planets, including the newly discovered planet, occupy the inner system while there is a large gap between .78 AU and 5.9 AU in the 55 Cancri system. A planet many times more massive than Jupiter exists at the other end of this gap. It is currently not known whether other planets might be located within this gap, or if the larger planet is sufficiently massive to prevent planet formation in the gap.

Lunine waxed philosophically about the discovery. He quoted St. Albertus Magnus who asked approximately 760 years ago: “Do there exist many worlds, or is there but a single world? This is one of the most noble and exalted questions in the study of Nature.” It took over 7.5 centuries to answer his question, with the first detection of a planet outside of our own solar system, but only now are systems of planets similar to our own being discovered. Rapid improvements in science and technology are closing in on a more definitive answer to Magnus’ question.

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