This is the distribution on the sky plane of the Lyman-alpha
intensity of Comet Hale-Bopp, recorded by the SWAN instrument
on-board SOHO. It is directly proportionnal to the Hydrogen column
along the line of sight.Since Hydrogen comes from the
photodissociation of water molecules by solar UV radiation, one can
derive easily from such a map the water production of this comet in
tons per second. It is already 3 times more than Comet Halley at
its best with more than 200 tons of water per second.The size of
the Hydrogen cloud is more than 70 millions of km, which makes it
the biggest object in the solar system now. SWAN instrument was
built by Service d'Aeronomie du CNRS in France and by FMI in
Finland.
This is the distribution on the sky plane of the Lyman-alpha intensity of Comet Wirtanen, recorded by the SWAN instrument on-board SOHO. The comet is identified as a small bump on the sky background. The prodiction rate is estimated at 214 kg of water per second. This comet is of special interest since it is the target of space mission ROSETTA of the European Space Agency, with a launch in year 2003 and a rendez-vous in year 2011.