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-Elizabeth Landau
Comets are notoriously difficult to study, and they need
more than 200 years to make one revolution around the Sun because they spend
most of their time far from our area of the solar system. Many
"long-period comets" will never approach the Sun in a person's
lifetime. NASA's WISE spacecraft shared new insights about these distant
wanderers. Scientists found that there are about seven times more long-period
comets measuring at least 0.6 miles (1 kilometer) across than had been
predicted previously. They also found that long-period comets are on average up
to twice as large as "Jupiter family comets," whose orbits are shaped
by Jupiter’s gravity and have periods of less than 20 years. Moreover,
researchers also observed that in eight months, three to five times as many
long-period comets passed by the Sun than had been predicted.
Astronomers did not have a good way of measuring the sizes
of how long-periods the comets are, yet they already had broader estimates of
long-periods the comets. It was caused the comet has a "coma" (a
cloud of gas and dust). However, now scientists were able to
"subtract" the coma from the overall comet and estimate the nucleus
sizes of these comets by using the WISE data showing the infrared glow of this
coma. The data came from 2010 WISE observations of 95 Jupiter family comets and
56 long-period comets.
The results reinforce the idea that comets pass by the Sun
more often tend to be smaller than those spending much more time away from the
Sun because Jupiter family comets get more heat exposure where it causes
volatile substances like water to sublimate and drag away other material from
the comet’s surface as well.
"Our results mean there's an evolutionary difference
between Jupiter family and long-period comets," Bauer said.
by Dini Dwintika Karuniati
16611042
Article Science
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