Astronomers capture first images of multi-planet system around another star

A team of researchers from Canada, the US, and the UK has become the first to capture images of a multi-planet system around a normal star, much like our own solar system. Their findings are published online today (Thursday 13 November) by the leading journal Science.

The images show three planets, each several times larger than Jupiter, orbiting a star known as HR 8799. The star is 130 light years from the Earth in the constellation of Pegasus. It is faintly visible to the naked eye and is encircled by a ring of dust. With a mass of 1.5 times that of the Sun, it is intrinsically brighter than the Sun and, at around 60 million years old, significantly younger.

More than 200 planets orbiting stars other than the Sun have been detected indirectly in the past decade. However, this is the first time that astronomers have been able to capture an image of a system of planets outside our solar system, which are known as extrasolar planets.

The team was led by Dr Christian Marois of the National Research Council of Canada's Herzberg Institute of Astrophysics (Victoria, BC, Canada). According Dr Marois, this discovery is the first time we have directly imaged a family of planets around a normal star outside of our solar system.

"Dr Jennifer Patience of the Astrophysics Group at the University of Exeter (Exeter, UK) and co-author on the paper, said: "We've been trying to capture images of extrasolar planets around stars for many years and now we have pictures of three at once. This is an incredibly exciting moment for astronomy and a key step in the journey towards understanding what is out there, beyond our own solar system."

The team used the giant Gemini-N and Keck and telescopes on Mauna Kea, Hawaii, to capture their infrared images. Gemini-N and Keck are among the largest ground-based telescopes in the world. The telescopes use 'adaptive optics' to minimise the blurring effects of the Earth's atmosphere, producing images with exceptional detail and resolution, exceeding that of the Hubble Space Telescope at these wavelengths.

"We finally have an actual image of an entire system," said Dr Bruce Macintosh of Lawrence Livermore National Laboratory (California, USA), co-author on the paper. "This is a milestone in the search and characterisation of planetary systems around stars."

Through its ongoing work, the team now hopes to discover other extrasolar planetary systems. It also aims to carry out a more detailed study of the properties of this system and to characterise the planets in more detail. Dr Patience is leading the UK's efforts in the next phase of the project, which includes using the European Southern Observatory's Very Large Telescope in Chile.

Professor John Womersley, Director of Science Programmes at the Science and Technology Facilities Council which funds the UK subscription to Gemini, ESO, and some of Dr Patience's work said "The study of planets outside our solar system has made huge progress in just a few years: we have gone from the first discoveries of exoplanets to having ways of finding those that resemble our own planetary system. This image represents another leap forwards, because for the very first time we have been able to directly image a system with three planets in orbit around another star. As our knowledge of exoplanets improves, we will be able to determine how planets form, what chemistry exists on them and one day, we hope, we may even be able to tell whether planets around other stars support life."

The research was carried out by scientists from the NRC Herzberg Institute of Astrophysics, Victoria, BC, Canada; Lawrence Livermore National Laboratory, CA, USA; Lowell Observatory, AZ, USA; University of Georgia, GA, USA; University of Exeter, UK; University of Toronto, ON, Canada; and Université de Montréal, QC, Canada.

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