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Saturday, 21 June 2008

The Science Behind the Summer Solstice - Science News | Science & Technology | Technology News

With 8 inches of hail falling in parts of Nebraska this week and Arizona reaching triple digit temperatures last week, it may seem rather arbitrary to call June 20 the first day of the summer this year, aka the summer solstice. But scientists really do have a reason.
It's all about Earth's cockeyed leanings and some celestial configurations that even the ancients understood.
Our planet is tilted 23.5 degrees on its spin axis. On June 20 this year (some years it's June 21), the North Pole is pointing toward the sun as much as is possible.
Imagine Earth as an apple sitting on one side of a table, with the stem being the North Pole. Tilt the apple 23.5 degrees so the stem points toward a candle (the sun) at the center of the table. That's summer for the top half of the apple.
Now keep the stem pointing in the same direction but move the apple to the other side of the table: Now the stem points away from the candle, and it's winter on the top half of the fruit.
The setup at June solstice puts the sun as high in our sky as it can go, yielding the longest day of the year in the Northern Hemisphere.
Scientists put the exact moment of the solstice this year at 7:59 p.m. EDT on June 20 (keep in mind that the sun is always up somewhere, and the gods don't favor the Eastern time zone) 23.50 Hours UT or 00.50 BST (June 20-21st).
As long ago as the fourth century B.C., ancient peoples in the Americas understood enough of this that they could create giant calendars driven by sunlight.
They built observatories of stone to mark the solstices and other times important for planting or harvesting crops. Shrines and even tombs were also designed with the sun in mind.
The sun comes up each day (except at or very near the poles) because our planet rotates once on its axis every 24 hours or so. It is Earth's tilt, and our 365-day orbit around the sun, that explain much about how our world changes during the year.
Seasons: As Earth orbits the sun, the orientation of the planet's axis, in relation to the sun, changes constantly. A quarter of the way around in the orbit, fall sets in.
By winter, we'll be on the other side of the sun, with the North Pole pointing away from the sun. That winter solstice, around Dec. 21 each year, will be the Northern Hemisphere's shortest day, and researchers in Antarctica will be basking in 24-hour sunlight.
Shifting stars: As we orbit the sun, the part of the night sky that's in our view changes. A given star sets about 4 minutes earlier each night. Over a month, this amounts to two hours.
In winter, this all means that we're looking at stars that during the summer were in our daytime sky, overwhelmed of course by the glare of the sun. Since we complete a circle every year, the stars of summer, such as the Big Dipper, are always the stars of summer.
Endless summer: At the North Pole, the sun rises once a year, around March 19. It rises until the summer solstice, then sinks but does not truly set until around Sept. 24.
During summer on the top half of Earth, our planet is actually farther from the sun than during winter, a fact owing to our non-circular orbit around the sun.
The difference is about 3 million miles (5 million kilometers), and it makes a difference in radiant heat received by the entire Earth of nearly 7 percent.
But the difference is more than made up for by the longer days in the Northern Hemisphere summer with the sun higher in the sky.
Which brings up a common question: If the June solstice is the longest day of the year, why are the dog days of August typically hotter?
It takes a while for the oceans to warm up, and a lot of weather on land is driven by the heat of the oceans.

Wednesday, 11 June 2008


Not much change from last month although I have updated and added a few more things that maybe of interest.....

Comet 17P/Holmes: has now faded to beyond magnitude 6 and has expanded into the dark background of the sky now in the Constellation Of Auriga on the border with Gemini-it is now very diffuse and difficult if not impossible to pick out against the North Western Evening Twilight.
C/2007 Comet Boattini which attained a reasonable Magnitude 9 by the beginning of May this year is now lost to the South Western Evening Twilight and on June 20th it should reach its best brightness of 5.5 although it will be in a daylight sky and won't be able to be Observed in the Constellation of Lepus underneath Orion and too close to the Sun to be seen around this time of the year, when it returns in the very early morning Twilight during mid July at Magnitude 6.9 to 7 it may be a good small Telescope or Binocular object to be observed and picked out, from then on it will fade and be beyond magnitude 10 by the end of the Summer around late August so not a very good viewing window for this one either side of the Summer Solistice but its one I will be looking out for during the Summer months-I didn't get to see this in the early part of this Month though.
Another Comet that may become Binocular Bright in 2009 of next year is C/2007 N3 Lulin which will become Observable after the new year 2009 in January in the early morning skies around magnitude 8 becoming Binocular bright in the Winter skies of Feburary whilst entering the Evening skies around the 12th of that month and becoming a good viewing Object around magnitude 5.9 on the 20th moving from Virgo into Leo and not starting to fade much before mid March when it will be Magnitude 8.5.
There are around 16 other Comets worldwide to be observed by amature astronomers at the moment but with Magnitude ranges of 11.5 to 14 are a little too faint to be seen in the Summer twilight skies for us Northern Observers.
As I have reported once before if I do see and Observe any of these Comets I will send out text and Email alerts to notify Observers in where best to look for these Phenomena.
7th June: Mercury at Inferior Conjuction
8th June: Mars is 1.1 Degrees North of the Moon and a daylight Occultation from New Zealand
9th June: Venus is in Superior Conjuction Saturn is 3 Degrees North of the Moon
16th June: Possible June Lyrids although maybe very unfavourable due to azure twilight as well as a Gibbous Moon in the way
17th June: Antares is 0.2 Degrees North of the Moon
19th June: Mercury is Stationary
20th June: Midsummers day and the Summer Solstice at 23.50 hours U.T an Interesting and noting point this year about the Mid Summer Solstice is that it occurs just before midnight in G.M.A.T so therefore in affect the Solstice happens on 2 days one for 20th (23.50 Hours G.M.A.T) and one for the 21st (00.50 Hours B.S.T) Jupiter is 2 Degrees North of the Moon, Pluto is Stationary
23rd June:Neptune will be 0.8 Degrees South of the Moon
25th June: Uranus is 4 Degrees South of the Moon
26th to 27th June: Possible June Bootids maybe several per hour around the Early morning at 02.30 U.T for U.K Observers-worth checking out for.
27th June: Uranus Stationary
SKYLIGHT: The lighter Evenings will not give way much to deep sky viewing this Month but there is still the Moon and Planets such as Saturn and Mars in the Evening sky and Jupiter now becoming very prominent in the South East around Midnight
Mercury: passes through Inferior Conjuction this month and is not Observable.
Venus: Passes through Superior Conjuction on June 9th and also will not be Observable.
Mars: Still reatains a reasonable Evening Observing window amongst the stars of Leo but as the Month proceed the viewing window will be reduced in the Evening Twilight and setting before Midnight at the end of June.
Jupiter: Is in the South Eastern sky and is unmistakeably very bright heading for the evening skies and an oppisition in July.
Saturn: Still in Leo and Mars will close in on this but only in the the low evening Twilight at the end of this month.
Uranus and Neptune: Uranus: now moving away from the South Eastern Morning Twilight and may be visible with Binoculars before Nautical Twilight, Neptune is now reasonably placed in the Morning skies in the Constellation of Capricornus and can be seen with a good Telescope.
Dwarf Planet Pluto: At opposition on 20th June low in sagittarius and Observable all night

THE MOON: First quarter was on the 10th June, full Moon will occur on the 18th June, last quarter occurs on the 26th June and new Moon is on 3rd of July.
Perigee: 3rd June at 13.25 U.T, Distance: 357.254 km, Diameter: 33' 27"
Apogee: 16th June at 17.30 U.T, Distance 406,225 km, Diameter 29' 25"
Space Shuttle Mission: Blasted off from Kennedy space center at 21.02 Hours G.M.T 5.02 pm EDT on May 31st to return to the ISS for 3 space walks to assemble various parts and has already delivered Japans Science logistics Laboratory Kibo which is quite large and weighs several Tons.

15th June Will be 21.49 Hours
30th June will be 21.51 Hours
16th July will be 21.40 Hours
31st July will be 21.19 Hours
Good Clear skies.....

Monday, 2 June 2008

Spaceflight Now | Delta Launch Report | Phoenix science investigations

Phoenix science investigations

The Phoenix Mars Lander will investigate a site in the far north of Mars to answer questions about that part of Mars, and to help resolve broader questions about the planet. The main questions concern water and conditions that could support life.

The landing region has water ice in soil close to the surface, which NASA's Mars Odyssey orbiter found to be the case for much of the high-latitude terrain in both the north and south hemispheres of Mars.

Phoenix will dig down to the icy layer. It will examine soil in place at the surface, at the icy layer and in between, and it will scoop up samples for analysis by its onboard instruments. One key instrument will check for water and carbon-containing compounds by heating soil samples in tiny ovens and examining the vapors that are given off. Another will test soil samples by adding water and analyzing the dissolution products. Cameras and microscopes will provide information on scales spanning 10 powers of 10, from features that could fit by the hundreds into the period at the end of this sentence to an aerial view taken during descent. A weather station will provide information about atmospheric processes in an arctic region where a coating of carbon- dioxide ice comes and goes with the seasons.

Mars is a vast desert where water is not found in liquid form on the surface, even in places where mid-day temperatures exceed the melting point of ice. One exception may be fleeting outbreaks that have been proposed to explain modern-day flows down some Martian gullies. Today's arid surface is not the whole story, though. Previous Mars missions have found that liquid water has persisted at times in Mars' past and that water ice near the surface remains plentiful today.

Water is a key to four of the most critical questions about Mars: Has Mars ever had life? How should humans prepare for exploring Mars? What can Mars teach us about climate change? How do geological processes differ on Mars and on Earth? Water is a prerequisite for life, a potential resource for human explorers and a major agent of climate and geology. That's why NASA has pursued a strategy of "follow the water" for investigating Mars. Orbiters and surface missions in recent years have provided many discoveries about the history and distribution of water on Mars -- such as minerals that formed in wet environments long ago and liquid flows that are still active today in hillside gullies.

The landing site and onboard toolkit of Phoenix position this mission to follow the water further. The mission's three main science objectives are:

1. Study the history of water in all its phases.

On a time scale of billions of years, ice near the surface where Phoenix will land might be the remnant of an ancient northern sea. Several types of evidence point to plentiful liquid water on ancient Mars, and the northern hemisphere is low and smooth compared to the southern hemisphere. Much of the water that could have remained liquid when ancient Mars had a thicker atmosphere may now be underground ice.

On a time scale of tens of thousands to a few million years, ice near the surface where Phoenix lands might periodically thaw during warmer periods of climate cycles. The tilt of Mars' axis wobbles more than Earth's, and the shape of Mars' orbit also cycles over time, from rounder to more elongated. Currently, Mars is about 20 percent farther from the sun during northern summer than during northern winter, so the summers are relatively cool in the north. As the orbit varies, the northern ice cap will enjoy warm winters on a 50,000-year cycle. The wobble of Mars' axis may also cause the climate to change on a time scale of 100,000 to millions of years.

On much shorter time scales, the arctic ground "breathes" every day and every season, converting tiny amounts of ice into water vapor on summer days and condensing tiny amounts of frost from the atmosphere at night or in winter. In this way, the ice table slowly rises and recedes as the climate changes.

Phoenix will collect information relevant for understanding processes affecting water at all these time scales, from the planet's distant past to its daily weather.

2. Determine if the Martian arctic soil could support life.

Life as we know it requires liquid water, but not necessarily its continuous presence. Phoenix will investigate a hypothesis that some ice in the soil of the landing site may become unfrozen and biologically available at times during the warmer parts of long-period climate cycles. Life might persist in some type of dormant microbial form for millions of years between thaws, if other conditions were right.

The spacecraft is not equipped to detect past or present life. However, in addition to studying the status and history of water at the site, Phoenix will look for other conditions favorable to life.

One condition considered essential for life as we know it is the presence of molecules that include carbon and hydrogen. These are known as organic compounds, whether they come from biological sources or not. They include the chemical building blocks of life, as well as substances that can serve as an energy source, or food, for life. Phoenix would be able to detect even very small amounts and identify them. Two Viking spacecraft that NASA landed on Mars in 1976 made the only previous tests for organic compounds in Martian soil, and they found none. Conditions at the surface may be harsh enough to break organic molecules apart and oxidize any carbon into carbon dioxide. Phoenix will assess some factors in those oxidizing conditions, and it will check for organic chemicals below the surface, as well as in the top layer. Organic chemicals would persist better in icy material sheltered from sunshine than in surface soil exposed to harsh ultraviolet radiation from the sun.

Phoenix will also be checking for other possible raw ingredients for life. It will examine how salty and how acidic or alkaline the environment is in samples from different layers. It will assess other types of chemicals, such as sulfates, that could be an energy source for microbes.

3. Study Martian weather from a polar perspective.

In Mars' polar regions, the amount of water vapor in the thin atmosphere -- the humidity -- varies significantly from season to season. Winds carrying water vapor can move water from place to place on the planet. The current understanding of these processes is based on observations from orbit and limited meteorological observations from earlier Mars landers closer to the equator. Phoenix will use an assortment of tools to directly monitor several weather variables in the lower atmosphere at an arctic site.

Phoenix will measure temperatures at ground level and three other heights to about 2 meters (7 feet) above ground. It will check the pressure, humidity and composition of the atmosphere at the surface. And it will identify the amounts, altitudes and movements of clouds and dust in the sky above.

Over the course of the mission, this unprecedented combination of Martian meteorological measurements will help researchers evaluate correlations such as whether southbound winds carry more humidity than northbound winds; whether drops in air pressure are associated with increased dust; and how the amount of water vapor at the bottom of the atmosphere changes from late spring to mid-summer or later.