See Jupiter and Moon Pair Up on St. Patrick's Day

On Sunday evening, revelers can cap their St. Patrick’s Day by enjoying a view of a rendezvous involving two of the brightest objects in the night sky: the moon and the planet Jupiter. 

About 45 minutes after sunset on Sunday (March 17), the eye-catching celestial duo will be visible in the southwest sky, roughly two-thirds up from the horizon to the point directly overhead (called the zenith).  

The moon will be a wide crescent at the time, 34 percent illuminated by the sun, and will sit below Jupiter. At its closest pass — which will occur at around 10:30 p.m. local daylight time along the U.S. East Coast, and around 7:00 p.m. local time for the West Coast — Earth's natural satellite will be just 2 degrees from the giant planet. (For reference, your clenched fist held at arm's length measures about 10 degrees.)

After its closest approach, the moon, moving at its own apparent diameter per hour, will appear to slowly move away from Jupiter to the east (left). [Amazing Night Sky Photos by Stargazers (March 2013)]

Even without the moon, Jupiter readily attracts attention. It’s the brightest "star" of the night, coming into view high in the southwest during the early stages of twilight. The first-magnitude star Aldebaran flickers into view next, about 5 degrees to the lower left of Jupiter, its orange color helping it to stand out from the deepening dark-blue sky.

Last to appear are the famous Pleiades and Hyades star clusters as the sky darkens from purple to black.  The entire array of the moon, planet, bright star and star clusters sits within the constellation of Taurus (The Bull).

Binoculars are perfect for observing the whole Taurus get-together. Even the most ordinary pair will show dozens of Pleiades and Hyades stars, and at least one, two, or three of Jupiter’s four bright Galilean moons (Ganymede, Callisto, Io and Europa).

Be sure to check out Jupiter on the evening of March 24, when any small telescope will show it closely flanked above and below by two seventh-magnitude background stars in Taurus, masquerading as an extra pair of renegade Galilean satellites.   

In a telescope, Jupiter is best observed during early evening when it’s still high and its image reasonably calm. Viewing at such times shows the king of planets as a great big belted ball with tantalizing glimpses of detail. 

As the evening grows late, the whole assemblage wheels lower in the west and sets soon after midnight.

Editor's note: If you snap an amazing photo of Jupiter and the moon in the night sky, or any other celestial object, and you'd like to share for a possible story or image gallery, please send images and comments, including location information, to managing editor Tariq Malik at spacephotos@space.com

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York. Follow us @Spacedotcom, Facebook or Google+. Originally published on SPACE.com. Copyright 2013 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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Moon & Jupiter to Shine Close Together Tonight (SPACE.com)

Joe Rao, SPACE.com Contributor
Space.com Joe Rao, Space.com Contributor
space.com – Thu Oct 13, 6:30 pm ET

The two most brilliant objects in our current night sky will make for an eye-catching duo tonight (Oct. 13), weather permitting. 

Looking low to the east-northeast around 7:30 p.m. local daylight time, you’ll see a nearly full waning gibbous moon. Sitting just to the right of the moon will be the lordly light belonging to the largest planet in our solar system: Jupiter.  

Jupiter will hover about 5 degrees from the moon's right. Your clenched fist held at arm's length covers about 10 degrees, so moon and Jupiter will be separated by about half a fist. 

The sky map of the moon and Jupiter here shows how they will appear together tonight.

Cosmic dance of Jupiter and moon

If you stay up through the night, you may notice the moon slowly pulling away from Jupiter at a rate of one lunar diameter per hour, and the orientation between the two bright objects will change as well. [Photos of Jupiter: Solar System's Largest Planet]

By around 1 a.m. local daylight time (early Friday morning), the moon will seem to hover high above and to Jupiter's left. By 6:30 a.m. — with morning twilight rapidly brightening the sky in the east — the moon will seem to hang high and almost directly above Jupiter.

In the days that follow, the moon will pull away to the east and diminish in illumination, leaving glorious Jupiter to rule the October night.

On Oct. 28, Jupiter will arrive at opposition against the sparse background stars of the constellation Aries, the Ram. Since it is then opposite to the sun, the planet rises at sunset, crosses the sky from east to west during the night and sets at sunrise. 

Beginning in November, Jupiter will already be up in the eastern sky when the sun goes down. This will continue for the rest of the fall season in the Northern Hemisphere.

Jupiter shining bright

Opposition generally brings a "superior" planet (an outer planet as compared with Earth) closest to the Earth, and this is why Jupiter now shines more brilliantly than it has all year.

Astronomers use a reverse number scale to measure the brightness of objects in the sky, with smaller numbers corresponding to brighter objects. A negative number, for example, represents an extremely bright object. At an eye-popping magnitude of - 2.9 — fully four times brighter than Sirius, the brightest star — Jupiter is far brighterthan any nighttime star.

But this year's apparition of Jupiter is an exceptionally good one. Although "Big Jupe" comes to opposition every 13 months (every time the Earth sweeps between it and the sun), 2011 is also Jupiter's year of perihelion. This is when it is closest to the sun in its 12-year orbit, so it's also particularly close to the Earth. 

Jupiter is 33 light-minutes away this month, compared to its most distant opposition of the last decade in 2005. 

Actually, last October's opposition placed Jupiter about 1.5 million miles (2.4 million kilometers) closer than this year, but that makes no difference in how bright Jupiter is now compared to a year ago, and in a telescope, its apparent disk size measures only 0.4 percent smaller. Truth be told, for the next month or so, Jupiter's disk is the most generous that a planet can be: large and fully illuminated, and — when observed with a good telescope — decorated with numerous bands and other intricate features. 

In fact, there are now more features and surface area visible on this one disk than on all the other planets combined. And after this year, Jupiter will not attain such a pinnacle of extreme brilliance again until the year 2022.

Jupiter's moons visible in telescopes

On Thursday evening, good binoculars or a telescopewill reveal three of the famous Galilean satellites during the early evening hours: Ganymede and Europa on one side of Jupiter, with Callisto on the other.  Io and its shadow will be passing in front of Jupiter, an event that can be seen in moderate-sized telescopes. 

Io's shadow will be evident as a tiny black dot and is called a shadow transit. Io itself may be invisible from insufficient contrast with the background disk of Jupiter, but it can be readily seen for a short while as a white dot just as it is about to move off of Jupiter's west limb (at 10:03 p.m. EDT, 0230 GMT).

Io's shadow will move off Jupiter's disk 23 minutes earlier at 9:40 p.m. EDT (0140 GMT).  

If you snap an amazing photo of Jupiter, the moon or the moon and Jupiter together, and would like to share the image with SPACE.com for a possible gallery or story please contact managing editor Tariq Malik at Harvest Moon of 2011: Amazing Skywatcher Photos Video: Top 10 Amateur Telescopes10 Coolest New Moon Discoveries

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NASA's Juno probe sets sail for Jupiter

An Atlas V rocket with NASA's Juno spacecraft payload is seen the evening before its planned launch at Space Launch Complex 41 of the Cape Canaveral Air Force Station in Florida, August 4, 2011.

Credit: Reuters/Bill Ingalls/NASA

By Irene Klotz

CAPE CANAVERAL, Florida | Fri Aug 5, 2011 4:55pm EDT

CAPE CANAVERAL, Florida (Reuters) - An unmanned rocket blasted off from Cape Canaveral Air Force Station on Friday, sending a robotic scout on its way to Jupiter to gather details about how the solar system formed.

The Atlas 5 rocket carrying NASA's Juno spacecraft lifted off at 12:25 p.m. (1625 GMT), the first step in a five-year, 445-million mile (716-million km) odyssey to the largest planet in the solar system.

Launch was delayed almost an hour while United Launch Alliance fixed a technical problem with ground support equipment. The Boeing-Lockheed Martin joint venture builds and flies Atlas and Delta rockets for NASA, as well as the military and commercial customers.

"Next stop is Jupiter," an elated Scott Bolton, head of the Juno science team, told reporters after launch. "I couldn't be happier. This is sort of like a dream come true."

Upon arrival in July 2016, Juno is to spend a year in an unprecedented polar orbit around the giant planet, measuring its water content, mapping its magnetic fields and searching for signs of a solid core.

With more than twice the mass than all its sibling planets combined, Jupiter is believed to hold a key piece to the puzzle of how the planets formed some 4.65 billion years ago from the gas and dust left over after the birth of the sun.

"We're really looking for the recipe for planet formation," said Bolton, who is with the Southwest Research Institute in San Antonio, Texas.

"We're going after the ingredients of Jupiter by getting the water abundance as well as very precise measurements of the gravity field that will help us understand whether there's a core of heavy elements or a core of rocks in the middle of Jupiter."

INSIDE RADIATION BELTS

The measurements will help scientists sort through theories about what the early solar system looked like and how Jupiter, believed to be the first planet to form, was created.

To make its observations, Juno will soar as close as 3,100 miles above Jupiter's cloud tops, the first spacecraft to fly inside the planet's radiation belts.

With its sensitive electronics housed in a vault of titanium, Juno should last through 33 orbits around Jupiter, which is about a year on Earth.

Its last maneuver will be a plunge into the planet's thick atmosphere, which will incinerate the probe to avoid possible contamination of Jupiter's water-bearing moons.

Now that NASA has retired its shuttle fleet, the U.S. space spotlight is shifting toward the robotic probes and observatories that have brought the biggest leaps in understanding the cosmos.

More than 10,000 people flocked to the Cape Canaveral area to watch the Atlas launch, the first rocket to fly from Florida since the shuttle's retirement last month. That was part of an outreach effort by NASA, which typically invites around 300 guests for an unmanned rocket launch.

"We're extremely excited about coupling the energy that the nation has for human spaceflight into understanding what we're doing in science because right now science is really the positive face of this agency," said Jim Adams, NASA's deputy director for planetary science.

The Juno mission is the second in NASA's lower-cost, scientist-led New Frontiers program, and it was accomplished on schedule and within its $1.1 billion budget.

The spacecraft was built by Lockheed Martin Astronautics of Denver, Colorado.

In addition to launching science probes and other satellites, United Launch Alliance is in the process of certifying its Atlas 5 rockets to fly astronauts to the International Space Station, one of several possible commercial rockets contending to replace NASA's space shuttle fleet.

(Editing by Jane Sutton and Xavier Briand)

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Did a Wandering Jupiter Stunt Growth of Mars? (SPACE.com)

The migration of the planet Jupiter as the solar system formed may have kept Mars the planetary runt, smaller than its rocky neighbors Earth and Venus, that it is today, a new study suggests.

Mars is only about half the size of Earth and one-tenth the mass of our planet — a fact that has so far perplexed scientists. But in the new study, researchers calculated that Jupiter's movement might have been responsible for the odd setup.

"This work not only solves a difficult problem in solar system formation, it shows that the solution lies in the giant planets of our solar system undergoing significant early migration, which was generally thought to only have occurred in extrasolar planetary systems," said David P. O'Brien, a researcher at the Planetary Science Institute in Tucson, Ariz. [The Solar System To Scale (Infographic)]

Mysterious mass

Previous simulations of the formation process of the four inner planets in the solar system — Mercury, Venus, Earth and Mars — generally produced a version of Mars far more massive than the real planet.

 "We tried a large variety of simulation parameters to solve this problem, but nothing seemed to work," O'Brien said in a statement.

A 2009 study by Brad Hansen from UCLA offered a new clue: Hansen showed that if the initial distribution of solid material in the solar system was assumed to have an outer boundary at 1 astronomical unit (the distance from the sun to Earth, about 93 million miles or 150 million kilometers), a smaller Mars could form.

But the presence of a sharp outer boundary at 1 AU required in Hansen's work was difficult to explain, given the existence of the asteroid belt between 2 and 4 AU, the giant planets between 5 and 30 AU and the Kuiper Belt beyond that.

Jupiter's shifting migrations

However, previous simulations over the past decade have shown that Jupiter and Saturn could drift around in the early solar system when gas was still present, and in some cases could move inward and then back outward to roughly their current locations.

"Rapidly the pieces of the story came together," said Kevin J. Walsh, leader of the new study, who began work on the project at the Observatoire de la Cote d'Azur in Nice, France and is now at the Southwest Research Institute in Boulder, Colo. "If Jupiter had moved inwards from its birth place down to 1.5 AU from the sun and then had turned around because of the formation of Saturn, eventually migrating outward toward its current location, it would have truncated the distribution of solids in the inner solar system at about 1 AU, as required to explain the small mass of Mars."

Jupiter now orbits the sun at 5.2 AU — about 483.7 million miles (778.4 million km).

 "The problem was to understand whether the inward and outward migration of Jupiter through the 2 to 4 AU region could be compatible with the existence of the asteroid belt today," Walsh said. "So we started to do a huge number of simulations."

"The result was fantastic," Walsh said. "The simulations showed that the migration of Jupiter was consistent with the existence of the asteroid belt, but it also explained properties of the belt never understood before."

A Jovian 'Grand Tack Scenario'

The passage of Jupiter depleted then re-populated the asteroid belt region, with inner-belt bodies originating between 1 and 3 AU and outer belt bodies originating in a very distinct region between and beyond the giant planets, naturally producing the significant compositional differences existing today across the belt.

The collaborators call their simulation the "Grand Tack Scenario," from the abrupt change in the motion of Jupiter at 1.5 AU, like that of a sailboat tacking around a buoy.

The migration of the gas giants is also supported by observations of many extrasolar planets found in widely varying ranges from their parent stars, implying migrations of planets elsewhere in universe.

Walsh and his colleagues detail their findings this week in the journal Nature.

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