04 - Earth
at aphelion (farthest from Sun) at
8h UT. The Sun - Earth distance
0000is
1.01675 a.u. or about 152.1 million km.
06 - Moon
near Mars at 16h UT (evening sky).
Mag. +1.7.
16 - Moon
near Saturn at 20h UT (evening sky).
Mag. +0.8.
19 - Jupiter
at opposition at 8h UT (mag. -2.7).
Bes time to observe the largest
0000planet
in in the solar system.
10 - Mars 0.64 from Saturn
at 16h UT (47° from Sun, evening sky) Mag.+1.7
& +0.8.
17 - Moon near Jupiter at 14h
UT (midnight sky). Mag. -2.7.
18 - Full Moon at 7:59 UT.
The full moon of July is called the "Thunder
Moon"
0000or
"Hay Moon" .
29 - Mercury at superior conjunction
at 20h UT (not visible). Passes into
the evening sky.
00 0 0
0 0 0//
Get the complete calendar version
at skymaps.com
7 -
The
Outrageous Tales of a Space Shuttle Astronaut
- On February 1, 1978, the first group of space shuttle
astronauts, twenty-nine men and six women, were introduced
to the world. Among them would be history makers, including
the first American woman and the first African American
in space. This assembly of astronauts would carry NASA
through the most tumultuous years of the space shuttle
program. Four would die on Challenger. Mullane vividly
portrays every aspect of the astronaut experience --
from telling a female technician which urine-collection
condom size is a fit; to walking along a Florida beach
in a last, tearful goodbye with a spouse; to a wild,
intoxicating, terrifying ride into space; to hearing
"Taps" played over a friend's grave. Mullane is brutally
honest in his criticism of a NASA leadership whose bungling
would precipitate the Challenger disaster.
Friday, March 30, 2007
NASA Telescope Finds Planets Thrive Around Stellar Twins
The double sunset that Luke Skywalker gazed upon in the film "Star Wars" might not be a fantasy. Astronomers using NASA's Spitzer Space Telescope have observed that planetary systems – dusty disks of asteroids, comets and possibly planets – are at least as abundant in twin-star systems as they are in those, like our own, with only one star. Since more than half of all stars are twins, or binaries, the finding suggests the universe is packed with planets that have two suns. Sunsets on some of those worlds would resemble the ones on Luke Skywalker's planet, Tatooine, where two fiery balls dip below the horizon one by one.
Previously, astronomers knew that planets could form in exceptionally wide binary systems, in which stars are 1,000 times farther apart than the distance between Earth and the sun, or 1,000 astronomical units. Of the approximately 200 planets discovered so far outside our solar system, about 50 orbit one member of a wide stellar duo.
The new Spitzer study focuses on binary stars that are a bit more snug, with separation distances between zero and 500 astronomical units. Until now, not much was known about whether the close proximity of stars like these might affect the growth of planets. Standard planet-hunting techniques generally don't work well with these stars, but, in 2005, a NASA-funded astronomer found evidence for a planet candidate in one such multiple-star system (http://www.jpl.nasa.gov/news/news.cfm?release=2005-115).
Trilling and his colleagues used Spitzer's infrared, heat-seeking eyes to look not for planets, but for dusty disks in double-star systems. These so-called debris disks are made up of asteroid-like bits of leftover rock that never made it into rocky planets. Their presence indicates that the process of building planets has occurred around a star, or stars, possibly resulting in intact, mature planets.
In the most comprehensive survey of its kind, the team looked for disks in 69 binary systems between about 50 and 200 light-years away from Earth. All of the stars are somewhat younger and more massive than our middle-aged sun. The data show that about 40 percent of the systems had disks, which is a bit higher than the frequency for a comparable sample of single stars. This means that planetary systems are at least as common around binary stars as they are around single stars.
In addition, the astronomers were shocked to find that disks were even more frequent (about 60 percent) around the tightest binaries in the study. These coziest of stellar companions are between zero and three astronomical units apart. Spitzer detected disks orbiting both members of the star pairs, rather than just one. Extra-tight star systems like these are where planets, if they are present, would experience Tatooine-like sunsets.
The
Oort cloud, is a postulated spherical cloud
of comets situated about 50,000 to 100,000 AU from
the Sun. This is approximately 1000 times the distance
from the Sun to Pluto or roughly one light year, almost
a quarter of the distance from the Sun to Proxima
Centauri, the star nearest the Sun. The Oort cloud
would have its inner disk at the ecliptic from the
Kuiper belt. Although no direct observations have
been made of such a cloud, it is believed to be the
source of most or all comets entering the inner solar
system (some short-period comets may come from the
Kuiper belt), based on observations of the orbits
of comets. Source: Wikipedia
