- Andromeda
galaxy larger than it was believed?
- ëMuch bigger, three
times its currently accepted size, due to some new observations and
analysis at the Keck Observatory and presented at the American Astronomical
Society meeting being held currently in Minneapolis.
They now believe a thin sprinkling of stars once thought
to be a halo is in fact part of Andromeda's main disk. That makes the spiral
galaxy, so close to Earth that it appeared as a fuzzy blob to the ancients, more
than 220,000 light-years across -- triple the previous estimate of 70,000 to
80,000 light-years. û
- The former rural
outskirts are now considered the city border, which raises the mass
estimate as well.
- homepage and AAS,
via Reuters
and Technocrat
-
Einstein Year 2005: Measuring the shape of distant stars using
gravitational microlensing
- ë An international team
of astronomers has used a phenomenon first predicted by Einstein in 1936,
called gravitational lensing, to determine the shape of stars. This
phenomenon, due to the effect of gravity on light rays, led to the development
of gravitational optics techniques, among them gravitational microlensing. It
is the first time that this well-known technique has been used to determine
the shape of a star. û
- What is surpising to me is
how
Oblate the local reference stars
can be. Measuring oblateness of stars at all
is amazing, to do so at greater distances is moreso.
- Jodrell Bank Observatory DETAILS, the MOA
collaboration , Astronomy &
Astrophysics of EDP Sciences via
EurekAlert
- NASA
sees orbiting stars flooding space with gravitational waves
- ëA scientist using NASA's Chandra X-ray Observatory
has found evidence that two white dwarf stars are orbiting each other in a
death grip, destined to merge. The data indicate gravitational waves are
carrying energy away from the star system at a prodigious rate, making it a
prime candidate for future missions designed to directly detect these ripples
in space-time. û
- ëThe short orbital period implies that the stars are only about 50,000
miles apart, a fifth of the distance from the Earth to the Moon, and are
moving in excess of a million miles per hour. According to Einstein's General Theory of
Relativity, such a system should produce gravitational waves -
ripples in space-time - that carry energy
away from the system at the speed of light.û
- Now we've got a specific testable prediction -- we've got an object that theory says should be washing us with gravity waves,
and the frequency those waves should be modulated. Can we detect them? Are our current
instruments sensitive enough to do so?
- Chandra X-ray
Center DETAILS , via Jouirnal reference at
EurekAlert
- Shift
of weather patterns necessitates rethinking of reforestation methods
- ëForest landowners can greatly increase the survival rate of pine tree
seedlings by changing when and how they plant, according to research conducted
at the Texas A&M University Research and Extension Center . "There's been
too many (reforestation) failures over the last decade or so," said Dr. Eric
Taylor, Texas Cooperative Extension forestry specialist. "Some landowners have
had to replant two, three or even four years in a row because of poor seedling
survival." û
- This could be significant to
even small foresters; fall plantings could be much more cost-effective as well as restoring the habitat quicker.
- Texas A&M University - Agricultural
Communications ,
via EurekAlert
- Mind the
(Prime) Gap
- ëDespite early hiccups, number theorists say they have finally proved a key
conjecture about prime numbers:
that the smallest possible gap between two large
prime numbers continues to shrink, relative to the natural logarithm of the
smaller number, as the numbers increase. û
- This is related to the Prime Number Theorem,
which counts primes less than N, but sheds more detail on the distribution of those primes.
Intuitively, this is saying that the gaps between primes do not grow as fast as the nubmers,
and pairs of primes can be found pretty much as close as one desires,
which gives new hope for the
Twin Prime Conjecture.
- arXiv
and homepage,
via AAAS Science magazine
- Imaging an earthquate
- Nature has two similar letters, using dense grids of seismic stations in
Japan and Germany to compute detailed images of the seismic events of December
26.
-
Nature
- Deep Roots
of Solar Wind Help Predict Space Weather
- ëA layer deep in the solar atmosphere can be used to estimate the speed of
the solar wind, a stream of electrified gas that constantly blows from the
Sun. Estimating the speed of the solar wind will improve space weather
forecasts.û
- That would be real space weather forecasting!
- NASA Press Release,
via Physlink
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