Credit: ESO, Colin Snodgrass
(Max Planck Institute for Solar System Research, Germany)
ESA's Rosetta spacecraft will wake up today, 20 January, after 31
months in deep space hibernation, to finally close in on comet
67P/Churyumov-Gerasimenko (67P/CG).
This image shows the most recent observations of the 4-kilometre diameter comet, taken on 5 October 2013 by ESO's Very Large Telescope
(VLT) when the comet was around 500 million kilometres away — before it
passed behind the Sun and out of view from Earth's perspective.
For this image, a long series of observations was processed to reveal
both the comet without the background stars (on the left panel), and
the star field with the track of the comet marked (on the right). Viewed
against a crowded star field towards the centre of the Milky Way, the
comet was still so far from the Sun that the icy nucleus was not
releasing any gas or dust, and appears as a simple spot. As it
approaches the Sun, its surface will heat up and its ices will
sublimate, dragging dust out to form a tail.
The observation marks the start of a close collaboration between ESA
and ESO to monitor the comet from the ground during Rosetta's encounter
with 67P/CG later this year. Rosetta was launched in 2004 and aims to
explore the surface of the comet, deploying a lander down onto 67P/CG to
see what its surface is like [1].
The comet is on a 6.5-year orbit around the Sun and is currently out
towards the orbit of Jupiter. It will be closest to the Sun — roughly
between the orbits of Earth and Mars — in August 2015. This image
suggests that the comet is not yet active, so scientists will be keen to
check in on the comet again in February, when it is next observable by
the VLT, and much closer to the Sun.
In the meantime, the observations carried out in October have been
used to confirm the comet's orbit ahead of the major rendezvous
manoeuvre planned for Rosetta in May, to line it up for orbiting 67P/CG
in August. Further calculations will be made once Rosetta sights the
comet in its own imaging system.
Notes
[1] Since its launch, Rosetta has travelled around
the Sun five times, picking up speed and aligning itself with its final
destination. For the coldest leg of the mission, as Rosetta ventured out
beyond the orbit of Jupiter, the spacecraft was put into deep-space
hibernation. 67P/CG is on a reasonably stable and well-known orbit,
meaning that calculations for Rosetta's trajectory could be made far in
advance of the spacecraft's launch, and it is far enough away from the
Sun to make it a safe target.
Links
- VLT snap of comet 67P/Churyumov-Gerasimenko in October 2013
- The path of comet 67P/Churyumov-Gerasimenko in October 2013
- ESA Space Science Image of the Week
- ESA information on Rosetta
- ESA Call for Media: Rosetta Wake Up Event
- ESO's Very Large Telescope
Source: ESO (imagens)
