The oblong heart of Comet Tempel 1 has been revealed by NASA鈥檚 fast-approaching Deep Impact spacecraft for the first time. The image will help mission managers pinpoint the location of the spacecraft鈥檚 impact into the comet on 4 July.
Comets have cores, or nuclei, of solid ice and rock which are enshrouded in dust and gas boiled off the nuclei by the heat of the Sun. This hazy atmosphere, or coma, is usually all astronomers can see.
Now, astronomers have used a mathematical model of the comet鈥檚 atmosphere to 鈥渟ubtract鈥� the coma from images taken by Deep Impact at the end of May, from a distance of 32 million kilometres. The images reveal a bright, elongated nucleus about 15 kilometres long and 5 km wide 鈥� in line with previous observations by the Hubble and Spitzer space telescopes.
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鈥淏eing able to distinguish the comet鈥檚 nucleus in these images helps us to better understand its rotational, which is helpful for targeting this elongated body,鈥� says Deep Impact principal investigator Michael A鈥橦earn of the University of Maryland in College Park, US.
Constructive collision
One of the mission鈥檚 two spacecraft, a copper-tipped 鈥渋mpactor鈥� about the size of a washing machine, will be launched in the comet鈥檚 path for an impact on 4 July.
The impact may create a crater more than 100 metres wide, ejecting ice, dust and gas in the process. Astronomers hope to study the crater and ejected material to reveal the comet鈥檚 composition.
The Deep Impact team will continue taking images of the nucleus as the spacecraft nears the comet in order to measure the comet鈥檚 rotation. 鈥淲e need to determine how the comet is rotating in space so we can figure out what part we will hit,鈥� A鈥橦earn says.
