Posted on by Tammy Plotner

Planetary Pinball – Uranus Gets The “Tilt”

Between 3 to 4 billion years ago, a body twice the size of Earth impacted Uranus, knocking the ice giant onto its side. Image Credit: Jacob A. Kegerreis/Durham University
Near-infrared views of Uranus reveal its otherwise faint ring system, highlighting the extent to which it is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory.

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Popular theory on how Uranus ended up with a highly eccentric axis has always been pretty standard – one giant blow. However, at today’s (October 6) EPSC-DPS Joint Meeting in Nantes, astronomers are thinking things may have occurred slightly differently. Instead of a singular impact, the glowing blue-green gas giant may have been the victim of a series of smaller punches.

At a 98 degree inclination, Uranus and its satellites have always been somewhat of a mystery to planetary scientists. While many of the Solar Systems planets have an inclined axis, none can compare with nearly being on its side. It has always been popular conjecture that Uranus was plastered that way at some point in its evolution by a body a few times larger than Earth. While this seems plausible, only one hole remains in the theory. Why did its moons take on the same inclination instead of staying in their original position?

This long-standing puzzle may have been solved by an international team of scientists led by Alessandro Morbidelli (Observatoire de la Cote d’Azur in Nice, France). Their theory relies on computer modeling – and the thought the impact might have occurred while Uranus was still forming. If the simulations are correct and the strike happened when the planet was still surrounded by a protoplanetary disk, ” the disk would have reformed into a fat doughnut shape around the new, highly-tilted equatorial plane. Collisions within the disk would have flattened the doughnut, which would then go onto form the moons in the positions we see today.”

But that’s not a neat answer. Just like throwing a tilt into pinball, the game changes. In this new scheme, the moons displayed retrograde motion – precisely the opposite of the way things are now. So what’s a player to do? Change the game again by re-arranging the parameters. By adding multiple strikes to Uranus – instead of just one large – the satellites now behave as we observe them.

Of course, when you “tilt” the game is over, and the new research doesn’t jive with current theories of planetary formation. This may mean re-writing the rules again. Morbidelli elaborates: “The standard planet formation theory assumes that Uranus, Neptune and the cores of Jupiter and Saturn formed by accreting only small objects in the protoplanetary disk. They should have suffered no giant collisions. The fact that Uranus was hit at least twice suggests that significant impacts were typical in the formation of giant planets. So, the standard theory has to be revised.”

That deaf, dumb and blind kid… Sure plays a mean pinball!

Original Story Source: Europlanet News Release.

Posted on by Nancy Atkinson

New Horizons Flies by Uranus

An 'overhead' view of New Horizons' location. Credit: NASA

The Pluto-bound New Horizons spacecraft will fly by another planet today (March 18, 2011). However, the robotic craft won’t be taking any images as it zooms past Uranus’ orbit at about 6 p.m. EDT, 3.8 billion kilometers (2.4 billion miles) away from the gas giant (and 2.0 billion km (1.8 billion miles) from Earth). New Horizons is currently in hibernation mode, and the great distance from Uranus means any observations wouldn’t provide much as far as data and images. But, even so, this event is a ‘landmark’ so to speak in New Horizon’s gauntlet across the solar system.

“New Horizons is all about delayed gratification, and our 9 1/2-year cruise to the Pluto system illustrates that,” said Principal Investigator Alan Stern, of the Southwest Research Institute. “Crossing the orbit of Uranus is another milepost along our long journey to the very frontier of exploration.”

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New Horizons is now well over halfway through its journey to Pluto. Motoring along at 57,900 km/hr (36,000 mph), it will travel more than 4.8 billion km (3 billion miles) to fly past Pluto and its moons Nix, Hydra and Charon in July 2015.

But the journey doesn’t end there. After that, New Horizons will head off to a post-Pluto encounter with other objects within the Kuiper Belt, some event(s) which might take place even into the 2020’s. The planetary science community is working on the selection of potential targets.

The mission still has more than 4 years to go to get to Pluto; it will take 9 nine months to send all the data back to Earth.

The next planetary milestone for New Horizons will be the orbit of Neptune, which it crosses on Aug. 25, 2014, exactly 25 years after Voyager 2 made its historic exploration of that giant planet.

“This mission is a marathon,” says Project Manager Glen Fountain, of the Johns Hopkins University Applied Physics Laboratory. “The New Horizons team has been focused on keeping the spacecraft on course and preparing for Pluto. So far, so good, and we are working to keep it that way.”

Source: New Horizons

Posted on by Anne Minard

First-Time Solar System Mosaic From the Inside Out

MESSENGER's new solar system portrait, from the inside out

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Say cheese! The MESSENGER spacecraft has captured the first portrait of our Solar System from the inside looking out. The images, captured Nov. 3 and 16, 2010, were snapped with the Wide Angle Camera (WAC) and Narrow Angle Camera (NAC) of MESSENGER’s Mercury Dual Imaging System (MDIS).

All of the planets are visible except for Uranus and Neptune, which at distances of 3.0 and 4.4 billion kilometers were too faint to detect with even the longest camera exposure time of 10 seconds. Their positions are indicated. The dwarf-planet Pluto, smaller and farther away, would have been even more difficult to observe.

Earth’s Moon and Jupiter’s Galilean satellites (Callisto, Ganymede, Europa, and Io) can be seen in the NAC image insets. Our Solar System’s perch on a spiral arm provided a beautiful view of part of the Milky Way galaxy, bottom center.

The following is a graphic showing the positions of the planets when the graphic was acquired:

The new mosaic provides a complement to the Solar System portrait – that one from the outside looking in – taken by Voyager 1 in 1990.

These six narrow-angle color images were made from the first ever 'portrait' of the solar system taken by Voyager 1, which was more than 4 billion miles from Earth and about 32 degrees above the ecliptic. The spacecraft acquired a total of 60 frames for a mosaic of the solar system which shows six of the planets. Mercury is too close to the sun to be seen. Mars was not detectable by the Voyager cameras due to scattered sunlight in the optics, and Pluto was not included in the mosaic because of its small size and distance from the sun. These blown-up images, left to right and top to bottom are Venus, Earth, Jupiter, and Saturn, Uranus, Neptune. The background features in the images are artifacts resulting from the magnification. The images were taken through three color filters -- violet, blue and green -- and recombined to produce the color images. Jupiter and Saturn were resolved by the camera but Uranus and Neptune appear larger than they really are because of image smear due to spacecraft motion during the long (15 second) exposure times. Earth appears to be in a band of light because it coincidentally lies right in the center of the scattered light rays resulting from taking the image so close to the sun. Earth was a crescent only 0.12 pixels in size. Venus was 0.11 pixel in diameter. The planetary images were taken with the narrow-angle camera (1500 mm focal length). Credit: NASA/JPL

“Obtaining this portrait was a terrific feat by the MESSENGER team,” says Sean Solomon, MESSENGER principal investigator and a researcher at the Carnegie Institution. “This snapshot of our neighborhood also reminds us that Earth is a member of a planetary family that was formed by common processes four and a half billion years ago. Our spacecraft is soon to orbit the innermost member of the family, one that holds many new answers to how Earth-like planets are assembled and evolve.”

Source: MESSENGER

Posted on by Nancy Atkinson

Voyager 2 at Uranus, 25 Years Ago Today

These two pictures of Uranus -- one in true color (left) and the other in false color -- were compiled from images returned Jan. 17, 1986, by the narrow-angle camera of Voyager 2. Credit: NASA/JPL

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Voyager 2 is the only spacecraft that has flown close by one of the more enigmatic planets in our solar system (and the butt of many one-liners): Uranus. It was 25 years ago today (Jan. 24) that Voyager made the close pass, and scientists from JPL have been reminiscing about how they pored over the data being returned by the Grand-Touring Voyagers.

“Voyager 2’s visit to Uranus expanded our knowledge of the unexpected diversity of bodies that share the solar system with Earth,” said Project Scientist Ed Stone, who is now based at the California Institute of Technology in Pasadena. “Even though similar in many ways, the worlds we encounter can still surprise us.”

Voyager 2 has discovered two "shepherd" satellites associated with the rings of Uranus. Image Credit: NASA/JPL

From the flyby, we saw for the first time Uranus’ small group of tenuous rings, and the tiny shepherding moons that sculpted them. Unlike Saturn’s icy rings, they found Uranus’ rings to be dark gray, reflecting only a few percent of the incident sunlight.

Miranda, innermost of Uranus' large satellites, is seen at close range in this Voyager 2 image, taken Jan. 24, 1986, as part of a high-resolution mosaicing sequence. Image credit: NASA/JPL

The images also showed the small, icy Uranus moon Miranda that had a grooved terrain with linear valleys and ridges cutting through the older terrain and sometimes coming together in chevron shapes. They also saw dramatic fault scarps, or cliffs. All of this indicated that periods of tectonic and thermal activity had rocked Miranda’s surface in the past.

The scientists were also shocked by data showing that Uranus’ magnetic north and south poles were not closely aligned with the north-south axis of the planet’s rotation. Instead, the planet’s magnetic field poles were closer to the Uranian equator. This suggested that the material flows in the planet’s interior that are generating the magnetic field are closer to the surface of Uranus than the flows inside Earth, Jupiter and Saturn are to their respective surfaces.

Voyager 2 was launched on Aug. 20, 1977, 16 days before its twin, Voyager 1. After completing its prime mission of flying by Jupiter and Saturn, Voyager 2 was sent on the right flight path to visit Uranus, which is about 3 billion kilometers (2 billion miles) away from the sun. Voyager 2 made its closest approach – within 81,500 kilometers (50,600 miles) of the Uranian cloud tops – on Jan. 24, 1986.

By the end of the Uranus encounter and science analysis, data from Voyager 2 enabled the discovery of 11 new moons and two new rings, and generated dozens of science papers about the quirky seventh planet.

Voyager 2 moved on to explore Neptune, the last planetary target, in August 1989. It is now hurtling toward interstellar space, which is the space between stars. It is about 14 billion kilometers (9 billion miles) away from the sun. Voyager 1, which explored only Jupiter and Saturn before heading on a faster track toward interstellar space, is about 17 billion kilometers (11 billion miles) away from the sun.

“The Uranus encounter was one of a kind,” said Suzanne Dodd, Voyager project manager, based at JPL. “Voyager 2 was healthy and durable enough to make it to Uranus and then to Neptune. Currently both Voyager spacecraft are on the cusp of leaving the sun’s sphere of influence and once again blazing a trail of scientific discovery.”

Click on the images above to see higher resolution versions on JPL’s Photojournal website. Or see this link on the Photojournal to see all images of Uranus.

Posted on by Nancy Atkinson

Pluto Spacecraft Gets Brain Transplant

Artist rendition of New Horizons in the Kuiper Belt. Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

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Still seven years away from its rendezvous with Pluto, the New Horizons spacecraft was awoken from hibernation for the second annual checkout of all systems. The spacecraft and its team back on Earth will also undergo three months of operations as the New Horizons will make observations of Uranus, Neptune, and Pluto. But the first order of business was uploading an upgraded version of the software that runs the spacecraft’s Command and Data Handling system. “Our ‘brain transplant’ was a success,” says New Horizons Principal Investigator Alan Stern. “The new software – which guides how New Horizons carries out commands and collects and stores data – is now on the spacecraft’s main computer and operating, over a billion miles from home!”

The mission ops team at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, radioed the software load and the commands to start it earlier this week through NASA’s Deep Space Network of antennas to the spacecraft, now just more than 1.01 billion miles (1.62 billion kilometers) from Earth. In the next 10 days the team will beam up additional new software for both the spacecraft’s Autonomy and Guidance and Control systems.

Space Science Mission Operations Center at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
Space Science Mission Operations Center at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

Alice Bowman, New Horizons mission operations manager at APL, says the spacecraft and its computers are healthy. “The new software fixes a few bugs and enhances the way these systems operate, based on what we’ve learned in running the spacecraft in the nearly three years since launch,” she says. “They also configure the onboard systems to be ready to support the Pluto-Charon encounter rehearsals scheduled for next summer.”

New Horizons is more than 200 million miles beyond Saturn’s orbit and more than 11 astronomical units (1.02 billion miles) from the Sun, flying about a million miles per day toward Pluto. Annual Checkout 2 (ACO-2) continues through mid-December; follow its progress through frequent updates on the New Horizons Twitter page.

Source: New Horizons Press Release

Posted on by Astronomy Cast

Podcast: Uranus

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This week, we’re on to the next planet in the solar system. Having only visited it up close once with Voyager 1, we don’t know much about this sideways-spinning ice giant. But today we’ll cover what we do know, including its faint rings, sideways axis of rotation and rocky core – a first in the gas planets we’ve encountered so far in our tour.
Click here to download the episode

Uranus – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Posted on by Fraser Cain

Uranus’ Rings Seen Edge On

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Once every 42 years, the angle between Uranus and the Earth is perfectly lined up so that the planet’s rings are seen edge on. Since the rings were only discovered back in 1977, this is the first opportunity astronomers will have to view the planet without the glare and dust from the rings. It doesn’t happen on a specific date, though, it’s a little more complicated than that.

Because the Earth goes around the Sun much more quickly than Uranus, there are actually three separate times that Uranus and the Earth line up perfectly: May 3 and August 16 in 2007, and then February 20 in 2008. Unfortunately, during that last point, the Sun will be directly in between our two planets, so we won’t be able to see Uranus.

The first to image Uranus during this special occasion was a team of astronomers from UC Berkeley. They imaged Uranus on May 28th with the near infrared camera and adaptive optics on the W.M. Keck II telescope atop Hawaii’s Mauna Kea. Their images revealed the nearly edge on ring appearing as a bright line passing right through Uranus.

The next images come from Hubble, taken on August 14th. Hubble captured its images on nearly the precise moment when the rings were aligned with the Earth, showing similar features to the Keck image, and also seeing some recently discovered outer rings. The outermost ring, seen by Hubble, is difficult to view in infrared.

Astronomers are hoping these images will reveal more details about the moons that help tend the ring, called Cordelia and Ophelia, keeping it in place. But it’s also thought that there are additional moons in the region, helping to tend all 9 rings. This precise geometry might allow the telescopes to reveal moons that would normally be lost in the glare of the rings.

One other important date:

“December 7 is the Uranian equinox, when the rings are perfectly edge-on to the sun, and after that, there is a brief period again when we will view the dark side of the rings, before they become illuminated again for another 42 years,” said Heidi B. Hammel of the Space Science Institute in Boulder, Colorado.

Original Source: UC Berkeley News Release

Posted on by Fraser Cain

Dark Spot in Uranus’ Clouds

The Hubble Space Telescope has discovered a giant cloud vortex in the upper atmosphere of Uranus. This cloudy feature measures 1,700 kilometers by 3,000 kilometers (1,100 miles by 1,900 miles) – large enough to engulf 2/3rd of the US. Although rare on Uranus, these cloud spots are actually quite common on Neptune, since the ice planet has a much more active atmosphere. Since this region of Uranus’ atmosphere was previously in shadow, astronomers theorize that heat from the sun created the vortex.
Continue reading “Dark Spot in Uranus’ Clouds”

Posted on by Fraser Cain

Hubble Sees a Rare Transit on Uranus

The Hubble Space Telescope recently captured a very rare event: the transit of its moon Ariel across the surface of Uranus. On Earth we call this an eclipse, when the Moon’s shadow falls upon the surface of our planet. This situation is rare on Uranus; however, because the blue-green planet is tilted over on its side. The Sun, the moons and Uranus only line up once every 42 years. The last time a transit like this could have been seen was 1965, but Earth-based telescopes weren’t powerful enough to image the event at the time.
Continue reading “Hubble Sees a Rare Transit on Uranus”