CURIOUS ASTEROID NEARBY
Spaceweather.com
Newly-discovered asteroid 2009 BD passed slowly by the Earth on
January 25 at a distance of only 400,000 miles. It is approximately
10 metres across and poses no significant threat, but it merits
attention because its orbit appears to be almost identical to that
of the Earth. 2009 BD may be a rare 'co-orbital asteroid', circling
the Sun in near-tandem with our planet. If current determinations of
its orbit are correct, 2009 BD will remain in our neighbourhood for
many months and possibly years to come.
METHANE DETECTED ON MARS
NASA
Scientists who used the infrared and Keck telescopes in Hawaii have
belatedly reported the detection of methane in the atmosphere of Mars
in 2003. Methane could be expected to be destroyed in the Martian
atmosphere in a variety of ways, so the apparent existence of plumes
of methane on Mars indicated that some recently operating process was
releasing the gas. The reported plumes were seen over areas that show
evidence of ancient ground ice or flowing water, including a part of
Syrtis Major, an ancient volcano about 1200 km across. Of course
'astrobiologists' are seizing on the detection, because much of the
methane formed on the Earth comes from flatulent cows. Even the most
optimistic enthusiasts for extra-terrestrial life, however, hardly
expect an immediately analogous source to operate on Mars, and in fact
there are purely geological processes that create methane, such as the
conversion of iron oxide into the serpentine group of minerals, a
process that could proceed on Mars. Although no evidence has been
seen of active vulcanism on Mars today, ancient methane that has been
combined with ice in a crystalline structure called methane clathrate
might be released now. One method that might distinguish whether life
produced the methane is measurement of isotope ratios: isotopes of an
element have slightly different chemical properties, and life prefers
to use the lighter isotopes. Methane and water released on Mars
should show distinctive ratios for isotopes of hydrogen and carbon if
life were responsible for methane production. It remains for future
in-situ measurements to try to determine the origin of the Martian
methane.
TRANSIT SEARCH FINDS SUPER-NEPTUNE
Harvard-Smithsonian Center for Astrophysics
Astronomers have discovered a planet somewhat larger and more massive
than Neptune orbiting a star 120 light-years from Earth. While
Neptune has a diameter 3.8 times that of Earth and a mass 17 times the
Earth's, the new-found object, named HAT-P-11b, is 4.7 times the size
of Earth and has 25 Earth masses. HAT-P-11b was discovered because it
transits in front of its parent star, thereby blocking about 0.4% of
the star's light. A network of small automated telescopes known as
HATNet detected the slight periodic dimming. The object is in the
constellation Cygnus; it is the 11th extra-solar planet found by
HATNet, and the smallest yet discovered by any of the several transit
search projects that are currently in operation. The amount of
dimming during a transit tells the astronomers how big the planet must
be, and accurate measurements of the star's radial velocity allow an
estimate to be made of the mass of a transiting planet.
A number of Neptune-like planets has been found recently by radial-
velocity searches, but HAT-P-11b is only the second Neptune-like
planet that has been found to transit its star and thus to permit the
determination of its mass and radius. It orbits very close to its
star, revolving once every 4.88 days. The star itself is about 75%
the size of our Sun and somewhat cooler. There are signs of a second
planet in the HAT-P-11 system, but more radial-velocity data are
needed to confirm that. Another team has located one other transiting
super-Neptune, known as GJ436b, around a different star. It was
discovered by a radial-velocity search and later found to show
transits.
R CORONAE BOREALIS
IAU
The yellow supergiant star R Coronae Borealis is the prototype of a
class of variable stars, which fade by several magnitudes at irregular
intervals. It normally shines at approximately magnitude 6, just
about visible to the naked eye in non-polluted skies, but at random
intervals ranging from several months to many years fades to as faint
as magnitude 14. Over successive months it gradually regains its
normal brightness. The cause of that behaviour is the emission of a
great cloud of carbon dust, in fact soot, from the star's atmosphere.
If the cloud is ejected on our side of the star it can block some or
all of the visible light from our sight. The star never disappears
altogether, but its light can be reduced more than a thousandfold, and
what little is left does not have the normal spectrum; it probably
does not come from the hot surface of the star but from some outer
regions, in rather the same way as the Sun does not disappear
completely during a total solar eclipse but is left with its corona
still visible.
In recent months the star has been fainter than magnitude 14.0, near
or at its historic minimum. It began its current fading episode
around 2007 July 6 it had faded to 12.0 by 2007 August 12, reached
14th magnitude about the end of that year and has continued gently to
fade further ever since. The duration of the current episode and its
depth are similar to that observed during the previous extreme fading
episode that began around 1963 June and continued (with only one brief
interruption) until about 1965 December, when it faded to about
magnitude 14.5.
PLANET WITH WILD TEMPERATURE SWINGS
NASA/JPL
The Spitzer space telescope has observed a planet that heats up to
red-hot temperatures in a matter of hours before quickly cooling
again. The planet is a gas giant that was discovered in 2001;
it is in a 111-day orbit around the star HD 80606, an otherwise
undistinguished star in the constellation Ursa Major, 190 light-years
away. The orbit is very eccentric, taking the planet nearly as
far out as the Earth is from our Sun, and much closer in than Mercury.
HD 80606b spends most of its time relatively far from its star, and
traverses the closest part of its orbit in less than a day. Spitzer
observed HD 80606b before, during and just after its close passage
past the star in 2007 November, as the planet baked in the star's
heat. In just six hours, its temperature rose from 800 to 1,500
Kelvin. Astronomers did not know whether the planet would disappear
completely behind the star, an event called a secondary eclipse, or
whether it would remain in view. Luckily for the observing team, it
did temporarily disappear from view, enabling its initial and final
temperatures to be estimated (had it had not been eclipsed, the team
would have known only the temperature change without knowing the
starting point).
The extreme temperature swing observed by Spitzer indicates that the
'air' near the planet's gaseous surface must quickly absorb and lose
heat. Such atmospheric information about how a planet responds to
sudden changes in heating -- an extreme version of seasonal change --
had not previously been obtained for a planet orbiting another star.
A key factor in being able to make the observations is the planet's
eccentric orbit. Unlike so-called 'hot Jupiter' planets that are in
tight orbits around their stars, HD 80606b rotates on its axis
roughly every 34 hours. Hot Jupiters, on the other hand, are
thought to be tidally locked like our Moon, so one side always faces
their stars. Because HD 80606b spins on its axis many times per
orbit, the astronomers were able to measure how its atmosphere
responds to being baked by the star.
ESA EXPECTS BUSY YEAR IN SPACE
BBC News
Last year the European space agency delivered the 'Columbus' module
to the international space station, and flew its space freighter, the
ATV, there for the first time; the cargo ship will become the main
way of re-supplying the ISS when the US shuttle fleet is retired.
ESA activity this year will include the recruitment of new astronauts
and the first launches by the Russian Soyuz rockets from the European
space-port at Kourou in French Guiana. At least half of all ESA
missions will be launched on Soyuz. The anticipated events include
the launching in the spring, both together on an Ariane 5, of the
'Herschel' infrared telescope and 'Planck', which will study the
cosmic microwave background radiation; there will also be
Earth-observation satellites concerned with ice, soil, and gravity,
and 'Vega', the newest European rocket, which will be used for smaller
payloads.
THOMAS HARRIOT: A TELESCOPIC ASTRONOMER BEFORE GALILEO
RAS
This year the world celebrates the International Year of Astronomy
(IYA2009), marking the 400th anniversary of the first drawings of
celestial objects through a telescope. They have long been attributed
to Galileo Galilei, but astronomers and historians in the UK are keen
to promote a lesser-known figure, English polymath Thomas Harriot, who
made the first drawing of the Moon through a telescope several months
earlier, in 1609 July. Harriot not only preceded Galileo but went on
to make lunar maps that would not be bettered for decades. Harriot
lived from 1560 to 1621. By 1609, he had acquired his first 'Dutch
trunke' (telescope). He turned it towards the Moon on July 26,
becoming the first astronomer to draw an astronomical object as seen
through a telescope. His crude sketch shows a rough outline of the
lunar terminator (the line marking the division between night and day
on the Moon) and includes a handful of features like the dark areas
Mare Crisium, Mare Tranquillitatis and Mare Foecunditatis.
Harriot went on to produce further maps from 1610 to 1613. Not all of
them are dated, but they show an increasing level of detail. By 1613
he had created two maps of the whole Moon, with many identifiable
features such as lunar craters depicted in their correct relative
positions. His work seems all the more impressive when one realises
that the earliest telescopes, of the kind used by Harriot (and
Galileo), had narrow fields of view, so only a small portion of the
Moon could be seen at any one time. Despite his innovative work,
Harriot remains relatively unknown because, unlike Galileo, he did not
publish his drawings.
Topic: Early February Astronomy News (Read 1233 times)