Saturday, October 29, 2011

Moon and planets offer triple treat on Friday

Look toward the southwestern horizon just after sunset on Friday night and you’ll see a triple feature of Venus, Mercury, and the two-day old moon. And there's another planet treat in time for the pre-Halloween weekend, too.

You'll need a good low horizon and a clear sky to see the first three objects since they will be very low in the sky, less than 10 degrees up. Binoculars may help. For reference, a closed first held out at arm's length covers about 10 degrees of the night sky.

The accompanying sky map of the moon and planets here shows their locations on Friday evening.

The moon will be a razor-thin crescent, and the so-called "dark" side of the moon — actually its far side facing away from Earth, which is not always dark — should be well lit by sunlight reflecting off the Earth.

Venus should appear very bright, weather permitting. This may be the first glimpse you get of it this season, but it will soon be blazing bright every evening. Mercury will be directly under Venus.

All three objects will be very low because of the shallow angle the ecliptic — the path the sun takes across the sky — makes with the horizon on Friday. Notice that the sun is setting well to the south of the west point on the horizon, now that we're more than a month past the fall equinox.

The only days the sun sets due west is right on the equinoxes, which were March 20 and Sept. 23 this year.

A few minutes after sunset, turn around and look at the eastern horizon. You will see Jupiter rising there slightly north of due east, the brightest object in that part of the sky.

At 10 p.m. EDT on Friday, Jupiter will be opposition, exactly opposite the sun in the sky. On this night, Jupiter rises at sunset and sets at sunrise, so is visible all night long.

Binoculars or a small telescope can reveal Jupiter's four bright moons, allowing you to follow them as they constantly shift position, orbiting around the giant planet.

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Thursday, October 27, 2011

Dwarf planet Eris surprises astronomers

Eris, the dwarf planet whose 2005 discovery led to Pluto losing its status as a planet, has passed in front of a star, providing astronomers with the clearest view of it since it was identified.

It is about the same size as Pluto and is one of the brightest objects in the solar system, according to the new analysis, released Wednesday by the journal Nature.

Scientists' picture of Eris had remained fuzzy because its distance from Earth is so vast: It is about three times farther out from the sun than Pluto. Some estimates pegged Eris as about 25% larger than Pluto, but it was too far away to tell for sure.

"It's very difficult, because it's so small in the sky," said lead author Bruno Sicardy, a planetary scientist at Pierre and Marie Curie University and Observatory in Paris.

With such small, far-off objects, astronomers wait for what's known as a stellar occultation, in which the object will cross over a star, essentially casting a shadow over the Earth. The amount of starlight blocked by the object allows scientists to calculate the object's size.

Witnessing this stellar occultation last year required being in the right place at exactly the right moment during the brief time window that Eris was scheduled to block the star.

To spot the star-crossing, Sicardy's team asked telescope operators at 26 different sites around the world to make observations. Just three telescopes at two of those sites, both in Chile, managed to catch the event.

From the data, the researchers were able to calculate that the dwarf planet's diameter is about 1,445 miles — on a par with Pluto, which is somewhere between 1,429 and 1,491 miles across.

The fact that Eris is smaller than previously estimated means that the amount of light scientists had detected coming from it originated from a smaller-than-anticipated surface area — and therefore its surface is brighter than anyone had thought.

In fact, the new calculations make Eris one of the brightest objects in the solar system, even though its surface should have been darkened from bombardment by cosmic rays and micrometeorites.

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Monday, October 17, 2011

Doomsday comet makes closest approach to Earth

ANTICIPATED by doomsayers as a potentially catastrophic event, Comet Elenin traversed the closest point in its trajectory around Earth (35,000km) early Sunday morning just before sunrise. But save for a few keen observers and astronomers, this went largely unnoticed.

When discovered by astronomer Leonid Elenin in December 2010, the passing of the 3-5 km wide chunk of space ice was predicted to be the astronomical event of the year, which in turn inspired an overkill of apocalyptic theories.

Amateur astronomers and conspiracy theorists put forth the idea that Comet Elenin was responsible for a variety of anomalous events seen throughout 2011; from the scattered outbursts of political uprisings to the earthquake in Japan.

Others extrapolated these prophecies to Comet Elenin representing the end of the world.
However, sometime during the middle of August, Comet Elenin began disintegrating as it crossed the solar system and traveled through the sun’s solar flares. And so at around 4 am Sunday morning, the comet passed within view of ground telescopes in an event that astronomers described as “largely uneventful.”

“I could see a hazy group of dim chunks of rock sitting in the sky, moving very slowly,” said Samir Nawar, a professor at the National Research Institute of Astronomy and Geophysics (NRIAG) in Helwan.

“But it was far less interesting than looking at the sun or the moon on any other day of the year, and a lot less noticeable,” he joked, referring to the Earth’s temperate climate and tides.
On the issue of conspiracy theories, Nawar went on to say that there is an obsession with space phenomena, which are far away and little understood; and that even if Comet Elenin had not disintegrated, the event would have still passed largely unnoticed. –AA

“People like to play on the fact that there are a lot of ‘maybes’ with these ‘unknown’ phenomena,” he continued. “But the truth is there are few maybes; there is a lot of accuracy with understanding space science, more than there is an understanding of what’s at the bottom of the oceans. If there was any issue of concern, NASA or any professional astronomer would be the first to raise the issue.”

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Thursday, October 13, 2011

New Proof That Comets Watered the Earth

By rights, the earth should not be the cosmic garden it is. In a solar system of planets and moons that are solid rock or mostly gas, shrouded in clouds or atmosphere-free, scorchingly hot or bitterly cold, there's only one that's dripping wet. Earthlings like to refer to our home planet as the solar system's water world, and it's a jolly good thing it's as wet as it is, because without plenty of water, life (at least as we know it) would be impossible.

All the same, it's likely our planet was once a far drier, dustier place. You need only look at two of our nearby rocky neighbors — Mercury and Venus — for a reminder of what living so close to the blast furnace of the sun can do to you. Our atmosphere helps us retain the abundant water we do have, but how did it get to us in the first place?

One popular theory has long been comets. The solar system swarms with these little rogue bodies — perhaps a trillion of them, according to astronomers' back-of-the-envelope estimates — and shortly after the sun and planets formed, they were everywhere, flying randomly and free to collide with anything in their way. Since comets are essentially dirty snowballs made of rock, gas and water ice, a few crash landings on earth could have provided all the water we needed quite nicely.

But there was a problem with that theory. All of the comets astronomers observed were indeed packed with water ice, but a lot of it was what's known as heavy water, in which the hydrogen in the H2O mix is an isotope known as deuterium, with one proton and one neutron in its nucleus. The hydrogen found in ordinary water has no neutron. Since the overwhelming share of the water in earth's oceans is made with the light hydrogen atom, astronomers calculated that comets could have accounted for only about 10% of what's there. Now, according to a new paper published in the journal Nature, it appears that those scientists may have been wrong — and the reason for their error is that they were simply looking at the wrong comets.

The paper, co-authored by researchers at the California Institute of Technology, is based on observations conducted by the Herschel Space Observatory, a spacecraft launched by the European Space Agency in 2009. Herschel looked specifically at comet Hartley 2, a small comet discovered in 1986 with an estimated diameter of .75 to .99 mi. (1.2 to 1.6 km). Analyzing the chemical composition of Hartley 2's corona — or the gassy veil surrounding the main comet body — Herschel discovered that its concentration of heavy water was only about half that of any comets observed before. While that wouldn't entirely explain earth's particular heavy- and light-water mix, it does bring the chemistry a lot more into line — and gives the cometary explanation for earthly water a big boost.

"Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early earth," says physicist Dariusz Lis of Caltech, a co-author of the paper.

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Sunday, October 09, 2011

2 Small Asteroids Zoom Between Earth and Moon's Orbit

A small asteroid zipped by Earth well inside the orbit of the moon today (Sept. 30), the second space rock encounter for our planet this week. Both asteroids posed no threat to Earth, scientists say.

"Small asteroid 2011 SM173 just passed Earth at a safe distance of 180,000 miles (290,000 km or .8 lunar distance)," scientists with NASA's Asteroid Watch program announced in a Twitter post today.

Asteroid 2011 SM173 was discovered yesterday by astronomers and is about 56 feet (17 meters) wide, making it about the size of a house. Its flyby came just four days after the pass of another space rock — the asteroid 2011 SE58 —which actually came even closer to Earth.

The 33-foot (10-m) wide asteroid 2011 SE58 slipped within 147,000 miles (236,573 km) of Earth during an evening flyby on Monday (Sept. 26), according to Asteroid Watch scientists.

The average distance between Earth and the moon is about 238,900 miles (384,402 km).

No threat to Earth
Both asteroids were too small to threaten Earth with a serious impact. If they had barreled into Earth, they likely would have burned up completely in Earth's atmosphere, the researchers said.

"Rocky asteroids the size of 2011 SE58 are not considered hazardous as they break up in the atmosphere & cause no ground damage," Asteroid Watch scientists wrote.

Asteroid 2011 SE58 was discovered by skywatchers on Sept. 21, according to database maintained by NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

By coincidence, the asteroid flybys this week occurred just as NASA announced the latest results from its efforts to find the largest near-Earth asteroids, objects that could potentially endanger Earth.

NASA's asteroid census has discovered about 90 percent of the largest near-Earth asteroids and revealed that the population of mid-size space rocks (asteroids about 3,300 feet, or 1,006 m, wide) is far lower than previously thought.

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Wednesday, October 05, 2011

NASA Space Telescope Finds Fewer Asteroids Near Earth

PASADENA, Calif. -- New observations by NASA's Wide-field Infrared Survey Explorer, or WISE, show there are significantly fewer near-Earth asteroids in the mid-size range than previously thought. The findings also indicate NASA has found more than 90 percent of the largest near-Earth asteroids, meeting a goal agreed to with Congress in 1998.

Astronomers now estimate there are roughly 19,500 -- not 35,000 -- mid-size near-Earth asteroids. Scientists say this improved understanding of the population may indicate the hazard to Earth could be somewhat less than previously thought. However, the majority of these mid-size asteroids remain to be discovered. More research also is needed to determine if fewer mid-size objects (between 330 and 3,300-feet wide) also mean fewer potentially hazardous asteroids, those that come closest to Earth.

The results come from the most accurate census to date of near-Earth asteroids, the space rocks that orbit within 120 million miles (195 million kilometers) of the sun into Earth's orbital vicinity. WISE observed infrared light from those in the middle to large-size category. The survey project, called NEOWISE, is the asteroid-hunting portion of the WISE mission. Study results appear in the Astrophysical Journal.

"NEOWISE allowed us to take a look at a more representative slice of the near-Earth asteroid numbers and make better estimates about the whole population," said Amy Mainzer, lead author of the new study and principal investigator for the NEOWISE project at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It's like a population census, where you poll a small group of people to draw conclusions about the entire country."

WISE scanned the entire celestial sky twice in infrared light between January 2010 and February 2011, continuously snapping pictures of everything from distant galaxies to near-Earth asteroids and comets. NEOWISE observed more than 100 thousand asteroids in the main belt between Mars and Jupiter, in addition to at least 585 near Earth.

WISE captured a more accurate sample of the asteroid population than previous visible-light surveys because its infrared detectors could see both dark and light objects. It is difficult for visible-light telescopes to see the dim amounts of visible-light reflected by dark asteroids. Infrared-sensing telescopes detect an object's heat, which is dependent on size and not reflective properties.

Though the WISE data reveal only a small decline in the estimated numbers for the largest near-Earth asteroids, which are 3,300 feet (1 kilometer) and larger, they show 93 percent of the estimated population have been found. This fulfills the initial "Spaceguard" goal agreed to with Congress. These large asteroids are about the size of a small mountain and would have global consequences if they were to strike Earth. The new data revise their total numbers from about 1,000 down to 981, of which 911 already have been found. None of them represents a threat to Earth in the next few centuries. It is believed that all near-Earth asteroids approximately 6 miles (10 kilometers) across, as big as the one thought to have wiped out the dinosaurs, have been found.

"The risk of a really large asteroid impacting the Earth before we could find and warn of it has been substantially reduced," said Tim Spahr, the director of the Minor Planet Center at the Harvard Smithsonian Center for Astrophysics in Cambridge, Mass.

The situation is different for the mid-size asteroids, which could destroy a metropolitan area if they were to impact in the wrong place. The NEOWISE results find a larger decline in the estimated population for these bodies than what was observed for the largest asteroids. So far, the Spaceguard effort has found and is tracking more than 5,200 near-Earth asteroids 330 feet or larger, leaving more than an estimated 15,000 still to discover. In addition, scientists estimate there are more than a million unknown smaller near-Earth asteroids that could cause damage if they were to impact Earth.

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Monday, October 03, 2011

Obscure Full Moon Names of 2011

Jan. 19, 4:21 p.m. EST – Full Wolf Moon: Amid the zero cold and deep snows of midwinter, the wolf packs howled hungrily outside Indian villages. The Full Wolf Moon was also known as the Old Moon or the Moon After Yule. In some tribes, this was also known as the Full Snow Moon; most applied that name to the next moon.

Feb. 18, 3:36 a.m. EST – Full Snow Moon: Usually the heaviest snows fall in this month. Hunting becomes very difficult, and hence to some tribes this was known as the Full Hunger Moon.

Mar. 19, 2:10 p.m. EDT – Full Worm Moon: In this month, the ground softens and the earthworm casts reappear, inviting the return of the robins.

The more northern tribes knew this as the Full Crow Moon, when the cawing of crows signals the end of winter, or the Full Crust Moon because the snow cover becomes crusted from thawing by day and freezing at night. TheFull Sap Moon, marking the time of tapping maple trees, is another variation.

The moon will also arrive at perigee only 50 minutes later at 3:00 p.m. EDT at a distance of 221,565 miles (356,575 kilometers) from Earth. So this is the biggest full moon of 2011. Very high ocean tides can be expected during the next two or three days, thanks to the coincidence of perigee with full moon.

Apr. 17, 10:44 p.m. EDT – Full Pink Moon
: The grass pink or wild ground phlox is one of the earliest widespread flowers of the spring. Other names were the Full Sprouting Grass Moon, the Egg Moon and – among coastal tribes – the Full Fish Moon, when the shad come upstream to spawn.

In 2011, this is also the Paschal Full Moon; the first full moon of the spring season. The first Sunday following the Paschal Moon is Easter Sunday, which indeed will be observed one week later on Sunday, April 24. This, incidentally, is just one day shy of the latest date that Easter can fall.

May 17, 7:09 a.m. EDT – Full Flower Moon: Flowers are now abundant everywhere. This moon was also known as the Full Corn Planting Moon or the Milk Moon.

Jun. 15, 4:14 p.m. EDT – Full Strawberry Moon: Strawberry picking season peaks during this month. Europeans called this the Rose Moon. There will be also be a total lunar eclipse that will be visible across much of South America, Europe, Africa and Asia. Totality will last an unusually long length of time: 1 hour 40 minutes.

Jul. 15, 2:40 a.m. EDT – Full Buck Moon
: when the new antlers of buck deer push out from their foreheads in coatings of velvety fur. It was also often called the Full Thunder Moon, thunderstorms being now most frequent. Sometimes it's also called the Full Hay Moon.

Aug. 13, 2:57 p.m. EDT – Full Sturgeon Moon: When this large fish of the Great Lakes and other major bodies of water like Lake Champlain is most readily caught. A few tribes knew it as the Full Red Moon because when the moon rises it looks reddish through sultry haze, or the Green Corn Moon or Grain Moon.

The occurrence of this full moon on this particular date is rather poor timing for those who enjoy the annual performance of the Perseid meteor shower; this display will peak on this very same day and the brilliant light of the moon will likely wash out all but the very brightest of these swift streaks of light.

Sep. 12, 5:27 a.m. EDT – Full Harvest Moon
: Traditionally, this designation goes to the full moon that occurs closest to the autumnal (fall) equinox. The Harvest Moon usually comes in September in the Northern Hemisphere, but (on average) once or twice a decade it will fall in early October.

At the peak of the harvest, farmers can work into the night by the light of this moon. Usually the moon rises an average of 50 minutes later each night, but for the few nights around the Harvest Moon, the moon seems to rise at nearly the same time each night – just 25 to 30 minutes later across the U.S., and only 10 to 20 minutes later for much of Canada and Europe. Corn, pumpkins, squash, beans and wild rice – the chief Indian staples – are now ready for gathering.

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