07 - Mercury
at inferior conjunction with the Sun
at 15h UT.
0000Mercury
passes into the morning sky (not visible).
08 - Moon
near Mars at 1h UT (evening sky). Mag.
+1.5.
19 - Venus
at superior conjunction with the Sun
at 4h UT.
0000Passes
into the evening sky (not visible).
19 - Moon
near Saturn at 7h UT (evening sky).
Mag. +0.7.
18 - Full Moon at 17:30 UT.
20 - Moon near Jupiter at 14h
UT (morning sky). Mag. -2.7. Jupiter displays
the
0000largest
and most detailed planetary disk of all the
planets. Even a small telescope
0000will
reveal Jupiter's cloud bands and its four largest
moons known as the Galilean
0000moons
(discovered by Galileo in 1610). Jupiter has
a total of 63 moons.
20 - Pluto at opposition at
16h UT. Mag. 14. Requires at least a 10-inch
telescope and
0000a
very dark sky to view.
20 - June solstice at 23:59
UT. The time when the Sun reaches the point
farthest north
0000of
the celestial equator marking the start of summer
in the Northern Hemisphere
000
and winter in the Southern Hemisphere.
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.
Wednesday, June 29, 2005
Cassini Probe Spies Lake-Like Feature on Titan
You might have thought Saturn's moon Titan was a somewhat dead issue after the Cassini spacecraft did not find convincing evidence for methane seas that scientists had predicted would exist. But the smoggy moon is back in the news today as a new Cassini image reveals a dark feature that scientists speculate might be a lake. The feature is "remarkably lake-like," according to a NASA statement that noted the appearance of smooth, shore-like boundaries unlike any seen previously on Titan.
The feature lies in Titan's cloudiest region, which is presumably the most likely site of recent methane rainfall. This, coupled with the shore-like smoothness of the feature's perimeter makes it hard for scientists to resist speculation about what might be filling the lake, if it indeed is one.
Thirty-nine more Titan flybys are planned for Cassini's prime mission. In future flybys the science teams will search for opportunities to observe the lake feature again and to look for mirror-like reflections from smooth surfaces elsewhere on Titan. Such reflections would strongly support the presence of liquids.
Here are some of the projects NASA may undertake in the next 30 years:
- The James Webb Space Telescope, successor to the Hubble Space Telescope.
- The Terrestrial Planet Finder would locate Earth-like planets around other stars that might harbor life.
- The Big Bang Observer would study the first micro-seconds of the universe, when a sudden burst of "inflation" started the expansion that continues today.
- The Interstellar Probe would study the gas and dust filling space between the stars.
- The Black Hole Finder Probe would study the creation and evolution of black holes, objects so dense that not even light can escape them.
- The Black Hole Imager would observe material as it falls into a black hole, never to reappear.
- JDEM (Joint Dark Energy Mission) would study the mysterious force that's driving the universe to expand.
- LISA (Laser Interferometer Space Antenna): Three spacecraft separated by 3 million miles would catch "gravity waves," ripples in space left over from the big bang at the birth of the universe.
- Sun-Solar System Great Observatory: Multiple satellites stationed between the Earth and the sun would study our home star's effect on our planet.
- The JUNO spacecraft would orbit Jupiter and observe what goes on inside our largest planet.
- The Europa Lander would study the ice-covered moon of Jupiter for evidence of possible life.
- Titan Explorer would land on Saturn's biggest moon and see what it's made of.
- Venus Surface Explorer would study the makeup of Earth's nearest neighbor.
- The Mars Science Lab would conduct studies preparatory to a human landing.
- The Mars Sample Return would bring Martian soil and rocks back to Earth for scientific analysis.
A recent flyby of Saturn's hazy moon Titan by the Cassini spacecraft has revealed evidence of a possible volcano, which could be a source of methane in Titan's atmosphere.
Images taken in infrared light show a circular feature roughly 30 kilometers (19 miles) in diameter that does not resemble any features seen on Saturn's other icy moons. Scientists interpret the feature as an "ice volcano," a dome formed by upwelling icy plumes that release methane into Titan's atmosphere. The findings appear in the June 9 issue of Nature.
Titan, Saturn's largest moon, is the only known moon to have a significant atmosphere, composed primarily of nitrogen, with 2 to 3 percent methane. One goal of the Cassini mission is to find an explanation for what is replenishing and maintaining this atmosphere. This dense atmosphere makes the surface very difficult to study with visible-light cameras, but infrared instruments like the visual and infrared mapping spectrometer can peer through the haze. Infrared images provide information about both the composition and the shape of the area studied.
The highest resolution image obtained by the visual and infrared mapping spectrometer instrument covers an area 150 kilometers square (90 miles) that includes a bright circular feature about 30 kilometers (19 miles) in diameter, with two elongated wings extending westward. This structure resembles volcanoes on Earth and Venus, with overlapping layers of material from a series of flows.
In the center of the area, scientists clearly see a dark feature that resembles a caldera, a bowl-shaped structure formed above chambers of molten material. The material erupting from the volcano might be a methane-water ice mixture combined with other ices and hydrocarbons. Energy from an internal heat source may cause these materials to upwell and vaporize as they reach the surface. Future Titan flybys will help determine whether tidal forces can generate enough heat to drive the volcano, or whether some other energy source must be present. Black channels seen by the European Space Agency's Huygens probe, which piggybacked on Cassini and landed on Titan's surface in January 2005, could have been formed by erosion from liquid methane rains following the eruptions.
Scientists have considered other explanations. They say the feature cannot be a cloud because it does not appear to move and it is the wrong composition. Another alternative is that an accumulation of solid particles was transported by gas or liquid, similar to sand dunes on Earth. But the shape and wind patterns don't match those normally seen in sand dunes.
The data for these findings are from Cassini's first targeted flyby of Titan on Oct. 26, 2004, at a distance of 1,200 kilometers (750 miles) from the moon's surface.
The visual and infrared mapping spectrometer instrument can detect 352 wavelengths of light from 0.35 to 5.1 micrometers. It measures the intensities of individual wavelengths and uses the data to infer the composition and other properties of the object that emitted the light; each chemical has a unique spectral signature that can be identified.
Forty-five flybys of Titan are planned during Cassini's four-year prime mission. The next one is Aug. 22, 2005. Radar data of the same sites observed by the visual and infrared mapping spectrometer may provide additional information.
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
