Video News Release 18: Trio of Neptunes and their Belt (eso0618a)

HARPS Instrument Finds Unusual Planetary System

Using the ultra-precise HARPS spectrograph on ESO''''s 3.6-m telescope at La Silla (Chile), a team of European astronomers have discovered that a nearby star is host to three Neptune-mass planets. The innermost planet is most probably rocky, while the outermost is the first known Neptune-mass planet to reside in the habitable zone. This unique system is likely further enriched by an asteroid belt.

During more than two years, the astronomers carefully studied HD 69830, a rather inconspicuous nearby star slightly less massive than the Sun. Located 41 light-years away towards the constellation of Puppis (the Stern), it is, with a visual magnitude of 5.95, just visible with the unaided eye. The astronomers' precise radial-velocity measurements allowed them to discover the presence of three tiny companions orbiting their parent star in 8.67, 31.6 and 197 days.

The video shows the La Silla Observatory, the ESO 3.6-m telescope and the HARPS instrument and three computer animations.

The first two ones are an artist impression of how the planetary system surrounding the nearby star HD 69830 may look like. The HARPS measurement indeed reveal the presence of three planets with masses between 10 and 18 Earth masses. The planets’ mean distance are 0.08, 0.19, and 0.63 the mean distance between the Earth and the Sun.

From previous observations, it seems that there exists also an asteroid belt, whose location is unknown. It could either lie between the two outermost planets, or farther from its parent star than 0.8 the mean Earth-Sun distance. The second animation illustrates the system, seen from inside the asteroid belt, which is assumed here to lie between the two outermost planets. The third animation illustrates the method used to detect the planets. A planet in orbit around a star will manifest its presence by pulling the star in different directions, thereby changing by rather small amounts its measured velocity. Here, the observer is assumed to be sitting at the right of the image. Using highly accurate spectrographs, like HARPS on the 3.6-m ESO telescope, astronomers therefore measure with the velocity of a star to detect the signature of one or more planets. The amplitude of the shifts provide astronomers with information on the mass of the planets.

The video was recorded on the occasion of the discovery of an unsual planetary Neptune -like system using the HARPS instrument on the ESO 3.6-m telescope.

Read more about it on eso0618.

This Video News Release is targeted especially at broadcasters for further editing. In order to keep the audio tracks editable, different sound information has been recorded on two separate tracks at optimal volumes as is common standard in professional post production. This video is not meant for on screen viewing — on ESOcasts are better suited for that.