Comet Lovejoy Update
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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 324 2012 January 1
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COMET LOVEJOY PLUNGES PAST THE SUN AND SURVIVES
NASA
In mid-December there was an exciting event, when Comet Lovejoy passed
through the Sun's corona and emerged intact. The comet's close
encounter was recorded by at least five spacecraft. In movies made by
the SDO (Solar Dynamics Observatory), the comet's tail was seen to
wriggle wildly, no doubt as a result of electrical or magnetic
interaction in the corona, as the comet plunged through the Sun's
corona only 120,000 km above the photosphere. Comet Lovejoy was
discovered on December 2 by amateur astronomer Terry Lovejoy in
Australia. Researchers quickly realized that the new find was a
member of the Kreutz family of Sun-grazing comets. Named after the
German astronomer Heinrich Kreutz, who first studied them, Sun-grazers
are fragments of a giant comet that broke apart in the 12th century
(probably the Great Comet of 1106). Kreutz Sun-grazers are very
numerous and typically small (~10 metres), although there have been
major examples such as Ikeya-Seki in 1965, which on the day of
perihelion passage was visible to the naked eye in full daylight (the
Sun of course having to be hidden from view behind a chimney or
something!) The Solar and Heliospheric Observatory sees one falling
into the Sun every few days. At the time of discovery, Comet Lovejoy
appeared to be much larger than the usual run of Kreutz Sun-grazers,
perhaps in the 100-200-m range, but researchers are revising those
numbers upward.
ASTRONOMERS FIND EARTH-SIZED PLANETS
NASA
Astronomers think that they have found two Earth-sized planets
orbiting a star similar to the Sun. The discovery follows
confirmation last month of a super-Earth-sized planet, called
Kepler-22b, that circles the right distance from its parent star for
liquid water to exist on its surface. The newly discovered planets,
called Kepler-20e and 20f, have at least three gas-giant siblings, in
one of the larger planetary systems found to date. But the family is
nothing like our Solar System, where rocky planets like Venus, the
Earth and Mars are grouped together relatively near the Sun, while gas
giants like Jupiter and Saturn are segregated in the outer regions.
The two Earth-like and three Neptune-sized planets in the Kepler-20
system are interspersed, and all of them orbit closer to the parent
star than Mercury does to the Sun. The system is located about 1,000
light-years away in the constellation Lyra.
RAPID STAR FORMATION IN A GALAXY ALMOST AT THE DAWN OF TIME
University of California
One of the most distant galaxies known, GN-108036, which is at a
red-shift of 7.2 and a distance of about 12.9 billion light-years, has
been found to be forming stars at a particularly high rate. The
galaxy is the brightest one found to date at such a great distance.
An international team of astronomers using the Japanese Subaru
telescope on Mauna Kea in Hawaii first identified it; then infrared
observations from Spitzer and Hubble were used to estimate that the
galaxy's star-formation rate is equivalent to about 100 Suns per year.
For comparison, our Milky Way galaxy is about five times larger and
100 times more massive than GN-108036, but makes stars at a rate of
about 3 Suns per year. The discovery is surprising, because previous
surveys had not found such bright galaxies so early in the history of
the Universe. According to the researchers, GN-108036 may be a
special, rare object that they happened to observe during an extreme
burst of star formation.
Bulletin compiled by Clive Down
(c) 2012 the Society for Popular Astronomy
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