Discovery of a new planetary system

One planet is good, 3 planets is a crowd!

A team of Canadian, American and British researchers photographed for the 1st time a distant planetary system similar to our Solar System. The feat was achieved using observations obtained at the Gemini North and Keck telescopes. The system consists of three planets that are still young enough to radiate in the infrared. The system is older than 60 million years and its planets still releasing a measurable amount of heat.

Figure 1 : vue d’artiste du système planétaire. Source : Gemini Observatory Artwork by Lynette Cook

Figure 1 : Artist view of HR8799’s planetary system. Credit: Gemini Observatory, Artwork by Lynette Cook.

An analysis of the brightness of the 3 objects at several infrared wavelengths and at different epochs, shows that these planets have masses between 7 and 10 times that of Jupiter (fig. 1) and that they revolve around the central star. The outermost planet moves in an orbit just inside a debris disk very similar to the Kuiper1 belt in our solar system, from which comets are coming from. In many ways, this solar system is similar to our own (fig. 2).

The research team includes three Quebecers: René Doyon (Université de Montréal), member of the Centre de recherche en astrophysique du Québec (CRAQ) and Director of the Observatoire du Mont-Mégantic, Christian Marois of the Herzberg Institute of Astrophysics and David Lafrenière (Université de Montréal). These three researchersare  behind the technique of angular differential imaging (IDA2) a sophisticated image processing algorithm which, combined with the technology of adaptive optics has allowed a better detection of three planets around the star HR87993 located in the constellation Pegasus.

Christian Marois, leader of the research team, says that obtaining images of several planets orbiting a star outside our solar system is a first. This discovery is a crucial step towards this ultimate quest of detecting rocky planets like Earth. All the great telescopes of the world will now look at this star to learn more about this fascinating planetary system. “Says René Doyon, co-author of the paper.

A previous study the GPDS4 on the Gemini North telescope, co-directed by René Doyon and David Lafrenière from 2004 to 2007, showed that the giant planets (like Jupiter) are rare around young stars at orbital separations beyond 10 astronomical units (AU), which is the distance between Saturn and the Sun. “We looked very actively using the IDA technique around 85 young stars of masses  less than or equal to that of the sun and none of them showed any planets. The next step was to look around a lot more stars but also to turn to stars more massive than the Sun. This system is a true gift of nature. It is amazing that our first detection include not one, not two but three planets orbiting the same star! “Remarked enthusiastically René Doyon.

The observations of the star HR8799 are part of a large scale study IDPS5 of 80 relatively young massive stars, surrounded by a disk of dust and located in the vicinity of the solar system. The study uses the Keck 10m and Gemini North 8m telescopes (both located in Hawaii) and one of the four ESO-VLT6 8m telescope from to obtain images of planets that look like giant Jupiter.

Christian Marois noted that this 1st detection occurs after only a few stars were probed. It could be that the existence of giant planets around massive stars is more common than we think. The observing campaign (IDPS) currently underway will address this issue.

Details of the discovery are published in online edition of the journal Science Express, November 13, 2008.

Team members :

  • Christian Marois – NRC Herzberg Institute of Astrophysics, Victoria, B.-C., Canada
  • Bruce Macintosh – Lawrence Livermore National Laboratory, Livermore, Calif., US
  • Travis Barman – Lowell Observatory, Flagstaff, Ariz., US
  • Benjamin Zuckerman – Astronomy Dep’t, University of California, Los Angeles, Calif., US
  • Jennifer Patience – School of Physics, University of Exeter, Exeter, U.-K.
  • Inseok Song – University of Georgia, Athens, GA, US
  • David Lafrenière – Institut de planétologie de Montréal, Université de Montréal, CRAQ, Montréal, Qc, Canada
  • René Doyon – Institut de planétologie de Montréal, Université de Montréal, CRAQ, Montréal, Qc, Canada
Figure 2

Figure 2

Figure 2 : Schematic representation of the HR8799 planetary system (left) and our solar system on the same scale (right).

 

 

 

 

Figure 3

Figure 3

Figure 3 : The star HR8799 photographed by the Keck telescope (left). The same star after image processing with the IDA technique (right). The three planets are clearly indicated as red dots at approximately 1 pm, 5 pm and 10 pm. The three planets revolve counter clockwise at orbital distances of 25, 40 and 70 astronomical units (AU). An astronomical unit is the average distance between the Earth and the Sun.

 

 

Movie showing the orbits of the 3 planets around HR8799.

Notes :

  1. The Kuiper Belt
  2. The Gemini Deep Planet Survey (GDPS)
  3. HR8799 is 60 million years old and 1.5 times more massive than the Sun. It is naked-eye star located 130 lightyears from  the Sun.
  4. Gemini Deep Planet Survey
  5. International Deep Planet Survey
  6. VLT = Very Large Telescope – ESO = European Southern Observatory