The Varuna stellar occultation
of 19 February 2010

On 19 February 2010 around 23:00 -- 23:10 UT (night of Friday February 19th to Saturday February 20th, 2010), the Trans-Neptunian-Object Varuna may occult the star UCAC2 410140042, or UCAC3: 3UC 233-085933 with Vmag~ 11.1

Such an event, if observed at various sites, could allow us to:

- pin down Varuna's radius to km-accuracy, while its diameter is presently poorly constrained between ~ 500 and 1000 km.

- provide its shape, if non-spherical

- detect a possible faint atmosphere around that body.

Independent predictions are posted on:
the MIT page.

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Update as of 06 February 2010 by the Rio group, using star position derived from observations made at Pico dos Dias:

α= 07h 29mn 22.4714 sec +/- 26 mas
δ= +26d 07' 23.173" +/- 31 mas (J2000/UCAC2)

and the following offset for Varuna wrt JPL#18 ephemeris:

Δα cos(δ)= -2 +/- 66 mas
Δδ = -74 +/- 26 mas.

click to enhance: Click on images for enhancement

Shadow moves from right to left. Dots are spaced by 1 mn, with larger dot marking geocentric C/A (23:07:24 UT).
Dotted lines are typical errors on global path, roughly +/-1700 km, or about +/-40 mas.
Dark gray: astronomical night.
Light gray: astronomical twilight.

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Charts

Click on images for enhancement

Charts prepared by Felipe Braga Ribas (Rio de Janeiro). Left 30x30 arcmin, right 5x5 arcmin.