Cassini spacecraft obtains best views of Saturn hexagon
NASA’s Cassini spacecraft has obtained the highest-resolution movie yet of a unique six-sided jet stream, known as the hexagon, around Saturn’s north pole.
This is the first hexagon movie of its kind, using color filters, and the first to show a complete view of the top of Saturn down to about 70 degrees latitude. Spanning about 20,000 miles (30,000 kilometers) across, the hexagon is a wavy jet stream of 200-mile-per-hour winds (about 322 kilometers per hour) with a massive, rotating storm at the center. There is no weather feature exactly, consistently like this anywhere else in the solar system.
"The hexagon is just a current of air, and weather features out there that share similarities to this are notoriously turbulent and unstable," said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. "A hurricane on Earth typically lasts a week, but this has been here for decades—and who knows—maybe centuries."…
From scientist’s understanding of fluid dynamics, Jupiter’s famous Great Red Spot should have disappeared many centuries ago. It has been losing energy by radiating heat and experiences much turbulence which drains the energy of the spot’s winds. So why has it survived for so long?
Pedram Hassanzadeh who is a postdoctoral fellow at Harvard University and Philip Marcus, a professor of fluid dynamics at the University of California have built their own model to try and explain why, and according to their research, the secret lies in the vertical motion of the Red Spot: ”As the vortex loses energy, the vertical flow transports hot gases from above and cold gases from below the vortex toward its center, restoring part of its lost energy.” (phys.org, 13th Nov 2013)
Both scientists are aware that their model is not complete and cannot completely explain the life of the spot however "they believe the occasional absorption of smaller vortices, consistent with observation, may provide the extra energy needed for hundreds of years of life. They have begun modifying their computer model to test this thesis.” (phys.org, 13th Nov 2013)
Read the full article here on the phys.org website
Comet ISON is now inside the orbit of Earth as it plunges headlong toward the Sun for a fiery close encounter on Nov. 28th. The comet is putting on a good show for observatories around the solar system, especially after an outburst on November 13-14 that boosted the comet’s brightness 10-fold. NASA spacecraft and amateur astronomers alike are snapping crisp pictures of the comet’s gossamer green atmosphere and suddenly riotous tail.
Because ISON has never passed through the inner solar system before (it is a first-time visitor from the distant Oort cloud), experts aren’t sure what will happen next. Can the comet survive its Thanksgiving Day brush with the Sun? Will it emerge as a bright naked-eye object?
Lowell Observatory astronomer Matthew Knight, a member of NASA’s Comet ISON Observing Campaign, lays out some of the possibilities.
“I’ve grouped the possible outcomes into three scenarios, discussed in chronological order,” says Knight. “It is important to note that no matter what happens, now that ISON has made it inside Earth’s orbit, any or all of these scenarios are scientifically exciting. We’re going to learn a lot no matter what.”
(PhysOrg) - Astronomers using the combined power of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope and NASA’s Hubble Space Telescope have discovered a far-flung trio of primitive galaxies nestled inside an enormous blob of primordial gas nearly 13 billion light-years from Earth.
"This exceedingly rare triple system, seen when the Universe was only 800 million years old, provides important insights into the earliest stages of galaxy formation during a period known as ‘Cosmic Dawn,’ when the Universe was first bathed in starlight," said Richard Ellis, the Steele Professor of Astronomy at the California Institute of Technology and member of the research team. "Even more interesting, these galaxies appear poised to merge into a single massive galaxy, which could eventually evolve into something akin to the Milky Way."…
(Image: NASA/Hubble. The image in the upper right is a close-up of Himiko with Hubble. The three infant galaxies are clearly resolved where only one was known to exist before. These objects are extremely energetic, suggesting they are undergoing a period of intense star formation.
CREDIT: NASA/Hubble. The image in the lower right is the same object with additional data from the Spitzer Space Telescope and Subaru Telescope on Mauna Kea in Hawaii. The halo of ionized hydrogen gas is clearly seen surrounding Himiko. Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope did not detect any telltale signature from carbon, suggesting that these three objects may be very primitive and have not had enough time to seed the intergalactic medium with heavy elements. Credit: NASA/Hubble; NASA/Spitzer; NAOJ/Subaru)
Chandra helps confirm evidence of jet in Milky Way’s black hole
(Phys.org) — Astronomers have long sought strong evidence that Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is producing a jet of high-energy particles. Finally they have found it, in new results from NASA’s Chandra X-ray Observatory and the National Science Foundation’s Very Large Array (VLA) radio telescope.
Jets of high-energy particles are found throughout the universe, on large and small scales. They are produced by young stars and by black holes a thousand times larger than the Milky Way’s black hole. They play important roles in transporting energy away from the central object and, on a galactic scale, in regulating the rate of formation of new stars…
The galaxy’s ancient brown dwarf population revealed
by Robert Massey
(Phys.org) — A team of astronomers led by Dr David Pinfield at the University of Hertfordshire have discovered two of the oldest brown dwarfs in the Galaxy. These ancient objects are moving at speeds of 100-200 kilometres per second, much faster than normal stars and other brown dwarfs and are thought to have formed when the Galaxy was very young, more than 10 billion years ago. Intriguingly the scientists believe they could be part of a vast and previously unseen population of objects. The researchers publish their results in the Oxford University Press journal Monthly Notices of the Royal Astronomical Society.
Brown dwarfs are star-like objects but are much less massive (with less than 7% of the Sun’s mass), and do not generate internal heat through nuclear fusion like stars. Because of this brown dwarfs simply cool and fade with time and very old brown dwarfs become very cool indeed - the new discoveries have temperatures of 250-600 degrees Celsius, much cooler than stars (in comparison the Sun has a surface temperature of 5600 degrees Celsius)…
One of the most famous objects in the sky - the Cassiopeia A supernova remnant - will be on display like never before, thanks to NASA’s Chandra X-ray Observatory and a new project from the Smithsonian Institution. A new three-dimensional (3D) viewer, being unveiled this week, will allow users to interact with many one-of-a-kind objects from the Smithsonian as part of a large-scale effort to digitize many of the Institutions objects and artifacts.
Scientists have combined data from Chandra, NASA’s Spitzer Space Telescope, and ground-based facilities to construct a unique 3D model of the 300-year old remains of a stellar explosion that blew a massive star apart, sending the stellar debris rushing into space at millions of miles per hour. The collaboration with this new Smithsonian 3D project will allow the astronomical data collected on Cassiopeia A, or Cas A for short, to be featured and highlighted in an open-access program — a major innovation in digital technologies with public, education, and research-based impacts…
Nature Pulls a Fast One - 2 Galaxies Masquerade As 1
by Whitney Clavin
What might look like a colossal jet shooting away from a galaxy turns out to be an illusion. New data from the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) reveal that two galaxies, one lying behind the other, have been masquerading as one.
In a new image highlighting the chance alignment, radio data from the VLA are blue and infrared observations from NASA’s Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) are yellow and orange, respectively. Visible data are also shown, with starlight in purplish blue and heated gas in rose.
The closer galaxy, called UGC 10288, is located 100 million light-years away. It is spiral in shape, but from our viewpoint on Earth, we are seeing its thin edge. The farther galaxy, seen in blue, is nearly 7 billion light-years away. Two giant jets shoot away from this galaxy, one of which is seen above the plane of the closer galaxy’s disk…
Over the next week, early risers will have the chance to view Comet ISON as it begins to grow bright enough to be easily seen. This will be its first and last pass.
Only discovered just last year, the comet appears to be very young, fresh from the Oort Cloud at the edge of the Solar System a mere million years ago. Its path looks to carry it very close to the sun, where it may burn up or disintigrate; but even if it survives that, it is believed to be on an “escape trajectory” - that is, it isn’t captured in the sun’s orbit and will leave the system once it’s made its pass. The comet, approximately 3 miles (5km) wide, is currently visible through binoculars near the constellation Virgo in the pre-dawn sky.
Over the next couple of weeks it will increase in brightness as it approaches the sun, such that eventually it will be visible to the naked eye. Its unusual green tint (as shown in this photo) is likely caused by cyanogen and diatomic carbon. It will reach perihelion - closest approach to the sun - on November 28; if it survives this encounter, it may be very bright in the sky and continue to be visible as late as mid-January.
For more information on when and where to look to see the comet, visit: EarthSky.org
Photo: Adam Block of Mount Lemmon SkyCenter at Univ. of Arizona
This cluster of stars is known as Messier 15, and is located some 35 000 light-years away in the constellation of Pegasus (The Winged Horse). It is one of the oldest globular clusters known, with an age of around 12 billion years.
Both very hot blue stars and cooler golden stars can be seen swarming together in the image, becoming more concentrated towards the cluster’s bright centre. Messier 15 is one of the densest globular clusters known, with most of its mass concentrated at its core. As well as stars, Messier 15 was the first cluster known to host a planetary nebula, and it has been found to have a rare type of black hole at its centre.
This new image is made up of observations from Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys in the ultraviolet, infrared, and optical parts of the spectrum.
Galactic Cirrus clouds billow and obscure the background Universe in this direction. NGC 7497 is seen through partly cloudy skies. These galactic clouds of dust are sculpted by the winds of nearby stars. They are relatively close to us (only hundreds of light years away) and there are few stars in the foreground to hinder of view of them. The color of the clouds is odd due to the fact they are illuminated mostly by diffuse galactic star light.
Image: Adam Block/Mount Lemmon SkyCenter/University of Arizona [high-resolution]
This scene shows a section of Ismeniae Fossae that straddles the southern highlands–northern lowlands of Mars. The 2 km-wide curvilinear trough that runs through this image contains numerous parallel grooves and ridges comprising material from the trough walls and material that has been dragged along the floor by ancient glaciers and ice-rich flows.
In the left portion of the scene the channel truncates a roughly 25 km-wide crater. Material in the crater walls has slumped down into the channel, smoothing over the grooved floor. Around this crater, and elsewhere in Ismeniae Fossae, clusters of circular to elliptical, partially interconnected depressions are observed. These may be either secondary impact craters from debris flung out by larger impact craters, or collapse pits caused by the sublimation of subsurface ice…
Combined observations from NASA’s Spitzer Space Telescope and the newly completed Atacama Large Millimeter/submillimeter Array (ALMA) in Chile have revealed the throes of stellar birth, as never before, in the well-studied object known as HH 46/47. Herbig-Haro (HH) objects form when jets shot out by newborn stars collide with surrounding material, producing small, bright, nebulous regions.
To our eyes, the dynamics within many HH objects are obscured by enveloping gas and dust. But the infrared and submillimeter light seen by Spitzer and ALMA, respectively, pierces the dark cosmic cloud around HH 46/47 to let us in on the action. (Infrared light has longer wavelengths than what we see with our eyes, and submillimeter light has even longer wavelengths.)
In this image, the shorter-wavelength light appears blue and longer-wavelength light, red. Blue shows gas energized by the outflowing jets. The green colors trace a combination of hydrogen gas molecules and dust that follows the boundary of the gas cloud cocooning the young star…