Hubble Captures Double Aurorae Light Show on Saturn

In January and March 2009, researchers using Hubble took advantage of a rare opportunity to record Saturn when its rings are edge-on, resulting in a unique look featuring both of the giant planet’s poles. And Saturn cooperated by providing an incredible double light show with Saturn’s own northern and southern lights. Since Saturn is only in this position every 15 years or so, this favorable orientation has allowed a sustained study of the two beautiful and dynamic aurorae.

Since it takes Saturn almost thirty years to orbit the Sun, the opportunity to image both of its poles occurs only twice in that period. Hubble has been snapping pictures of the planet at different angles since the beginning of the mission in 1990, but 2009 brought a unique chance for Hubble to image Saturn with the rings edge-on and both poles in view. At the same time Saturn was approaching its equinox so both poles were equally illuminated by the Sun’s rays.


These recent observations go well beyond just a still image and have allowed researchers to monitor the behavior of both Saturn’s poles in the same shot over a sustained period of time. The movie they created from the data, collected over several days during January and March 2009, has aided astronomers studying both Saturn’s northern and southern aurorae. Given the rarity of such an event, this new footage will likely be the last and best equinox movie that Hubble captures of our planetary neighbor.

Despite its remoteness, the Sun’s influence is still felt by Saturn. The Sun constantly emits particles that reach all the planets of the Solar System as the solar wind. When this electrically charged stream gets close to a planet with a magnetic field, like Saturn or the Earth, the field traps the particles, bouncing them back and forth between its two poles. A natural consequence of the shape of the planet’s magnetic field, a series of invisible “traffic lanes” exist between the two poles along which the electrically charged particles are confined as they oscillate between the poles. The magnetic field is stronger at the poles and the particles tend to concentrate there, where they interact with atoms in the upper layers of the atmosphere, creating aurorae, the familiar glow that the inhabitants of the Earth’s polar regions know as the northern and southern lights.

At first glance the light show of Saturn’s aurorae appears symmetric at the two poles. However, analysing the new data in greater detail, astronomers have discovered some subtle differences between the northern and southern aurorae, which reveal important information about Saturn’s magnetic field. The northern auroral oval is slightly smaller and more intense than the southern one, implying that Saturn’s magnetic field is not equally distributed across the planet; it is slightly uneven and stronger in the north than the south. As a result, the electrically charged particles in the north are accelerated to higher energies as they are fired toward the atmosphere than those in the south. This confirms a previous result obtained by the space probe Cassini, in orbit around the ringed planet since 2004.


Double Hubble Sequence Shows Galaxies Go Spiral


Galaxies come in all sorts of shapes. But in the past, the various galaxy shapes used to be more diverse and “peculiar” than they are now. Over time, according to a new study, galaxies tend to become spirals. “Six billion years ago, there were many more peculiar galaxies than now — a very surprising result,” said Rodney Delgado-Serrano, lead author of a new paper. “This means that in the last six billion years, these peculiar galaxies must have become normal spirals, giving us a more dramatic picture of the recent Universe than we had before.”

Using data from the Hubble Space Telescope and the Sloan Digital Sky Survey, a team of astronomers created the first demographic census of galaxy types at two different points in the Universe’s history, putting together two Hubble sequences from different eras that help explain how galaxies form. The results showed that the Hubble sequence six billion years ago was very different from the one that astronomers see today.

The top image represents the current — or local — universe, and the bottom image represents the make up of the distant galaxies (six billion years ago), showing a much larger fraction of peculiar galaxies. In sampling 116 local galaxies and 148 distant galaxies, the researchers found that more than half of the present-day spiral galaxies had so-called peculiar shapes only 6 billion years ago.

Edwin Hubble invented the Hubble Sequence, sometimes called the Hubble tuning-fork diagram. The diagram divides galaxies into three 3 broad classes based on their basic shapes: spiral, barred spiral, and elliptical.

“Our aim was to find a scenario that would connect the current picture of the Universe with the morphologies of distant, older galaxies — to find the right fit for this puzzling view of galaxy evolution,” said François Hammer of the Observatoire de Paris who led the team of astronomers.

The astronomers think that these peculiar galaxies did indeed become spirals through collisions and merging. This is contrary to the widely held opinion that galaxy mergers result in the formation of elliptical galaxies, but Hammer and his team propose a “spiral rebuilding” hypothesis, which suggests that peculiar galaxies affected by gas-rich mergers are slowly reborn as giant spirals with discs and central bulges.

Crashes between galaxies give rise to enormous new galaxies and, although it was commonly believed that galaxy mergers decreased significantly eight billion years ago, the new result implies that mergers were still occurring frequently after that time — up to as recently as four billion years ago.

Link to higher resolution version of the top image.

Hammer, et al.
Delgado-Serrano et al.

Source: Space Telescope Institute

Hubble Takes A Look at Possible Asteroid Collision


We reported earlier that on January 6, 2010, ground-based observatories may have spotted evidence of an asteroid collision in the asteroid belt. Now, the Hubble Space Telescope has taken a look at the mysterious X-shaped debris pattern and trailing streamers of dust. With Hubble’s sharp vision, astronomers believe a head-on collision between two asteroids has actually occured. Astronomers have long thought the asteroid belt is being ground down through collisions, but such a smashup has never been seen before.

“This is quite different from the smooth dust envelopes of normal comets,” said principal investigator David Jewitt of the University of California at Los Angeles. “The filaments are made of dust and gravel, presumably recently thrown out of the nucleus. Some are swept back by radiation pressure from sunlight to create straight dust streaks. Embedded in the filaments are co-moving blobs of dust that likely originated from tiny unseen parent bodies.”

Asteroid collisions would likely have an average impact speed of more than 11,000 miles per hour, or five times faster than a rifle bullet. The comet-like object imaged by Hubble, called P/2010 A2, was first discovered by the Lincoln Near-Earth Asteroid Research, or LINEAR, program sky survey on Jan. 6. New Hubble images taken on Jan. 25 and 29 show a complex X-pattern of filamentary structures near the nucleus.
Hubble shows the main nucleus of P/2010 A2 lies outside its own halo of dust. This has never been seen before in a comet-like object. The nucleus is estimated to be 460 feet in diameter.

Close-up of Comet-like Asteroid P/2010 A2. Credit: NASA, ESA, and D. Jewitt (UCLA)

Normal comets fall into the inner regions of the solar system from icy reservoirs in the Kuiper Belt and Oort Cloud. As a comet nears the sun and warms up, ice near the surface vaporizes and ejects material from the solid comet nucleus via jets. But P/2010 A2 may have a different origin. It orbits in the warm, inner regions of the asteroid belt where its nearest neighbors are dry rocky bodies lacking volatile materials.

This leaves open the possibility that the complex debris tail is the result of an impact between two bodies, rather than ice simply melting from a parent body.

“If this interpretation is correct, two small and previously unknown asteroids recently collided, creating a shower of debris that is being swept back into a tail from the collision site by the pressure of sunlight,” Jewitt said.

The main nucleus of P/2010 A2 would be the surviving remnant of this so-called hypervelocity collision.

“The filamentary appearance of P/2010 A2 is different from anything seen in Hubble images of normal comets, consistent with the action of a different process,” Jewitt said. An impact origin also would be consistent with the absence of gas in spectra recorded using ground-based telescopes.

The asteroid belt contains abundant evidence of ancient collisions that have shattered precursor bodies into fragments. The orbit of P/2010 A2 is consistent with membership in the Flora asteroid family, produced by collisional shattering more than 100 million years ago. One fragment of that ancient smashup may have struck Earth 65 million years ago, triggering a mass extinction that wiped out the dinosaurs. But, until now, no such asteroid-asteroid collision has been caught “in the act.”

At the time of the Hubble observations, the object was approximately 180 million miles from the sun and 90 million miles from Earth. The Hubble images were recorded with the new Wide Field Camera 3 (WFC3).

Source: HubbleSite

Latest from Hubble: Star Formation Fizzling Out in Nearby Galaxy

Most galaxies are throughout the universe are happenin’ places, with all sorts of raucous star formation going on. But for a nearby, small spiral galaxy, the star-making party is almost over. In this latest Hubble release, astronomers were surprised to find that star-formation activities in the outer regions of NGC 2976 are fizzling out, and any celebrating is confined to a few die-hard partygoers huddled in the galaxy’s inner region.

The reason? Well, the star birth began when another party-crashing galaxy interacted with NGC 2976. But that happened long ago, and now star formation in the galaxy is fizzling out in the outer parts as some of the gas was stripped away and the rest collapsed toward the center. With no gas left to fuel the party, more and more regions of the galaxy are going to sleep.

“Astronomers thought that grazing encounters between galaxies can cause the funneling of gas into a galaxy’s core, but these Hubble observations provide the clearest view of this phenomenon,” explains astronomer Benjamin Williams of the University of Washington in Seattle, who directed the Hubble study, which is part of the ACS Nearby Galaxy Survey Treasury (ANGST) program. “We are catching this galaxy at a very interesting time. Another 500 million years and the party will be over.”

NGC 2976 does not look like a typical spiral galaxy. It has a star-forming disk, but no obvious spiral pattern. Its gas is centrally concentrated, but it does not have a central bulge of stars. The galaxy resides on the fringe of the M81 group of galaxies, located about 12 million light-years away in the constellation Ursa Major.

“The galaxy looks weird because an interaction with the M81 group about a billion years ago stripped some gas from the outer parts of the galaxy, forcing the rest of the gas to rush toward the galaxy’s center, where it is has little organized spiral structure,” Williams says.

The galaxy’s relatively close distance to Earth allowed Hubble’s Advanced Camera for Surveys (ACS) to resolve hundreds of thousands of individual stars. What look like grains of sand in the image are actually individual stars. Studying the individual stars allowed astronomers to determine their color and brightness, which provided information about when they formed.

The image was taken over a period in late 2006 and early 2007.

“This type of observation is unique to Hubble,” Williams says. “If we had not been able to pick out individual stars, we would have known that the galaxy is weird, but we would not have dug up evidence for a significant gas rearrangement in the galaxy, which caused the stellar birth zone to shrink toward the galaxy’s center.”

Simulations predict that the same “gas-funneling” mechanism may trigger starbursts in the central regions of other dwarf galaxies that interact with larger neighbors. The trick to studying the effects of this process in detail, Williams says, is being able to resolve many individual stars in galaxies to create an accurate picture of their evolution.

Williams’ results will appear in the January 20, 2010 issue of The Astrophysical Journal.

Source: HubbleSite

Hubble Unveils Stunning Star Birth in M83

It appears Hubble’s new Wide Field Camera 3 (WFC3) is working. And how! The new camera installed during Servicing Mission 4 in May has delivered the most detailed view of star birth in the graceful, curving arms of the nearby spiral galaxy M83. Nicknamed the Southern Pinwheel, M83 is undergoing more rapid star formation than our own Milky Way galaxy, especially in its nucleus. The sharp “eye” of WFC3 has captured hundreds of young star clusters, ancient swarms of globular star clusters, and hundreds of thousands of individual stars, mostly blue supergiants and red supergiants.

M83 from ESO and Hubble. Credit for Hubble Image: NASA, ESA, R. O'Connell (University of Virginia), B. Whitmore (Space Telescope Science Institute), M. Dopita (Australian National University), and the Wide Field Camera 3 Science Oversight Committee
M83 from ESO and Hubble. Credit for Hubble Image: NASA, ESA, R. O'Connell (University of Virginia), B. Whitmore (Space Telescope Science Institute), M. Dopita (Australian National University), and the Wide Field Camera 3 Science Oversight Committee

The image at right is Hubble’s close-up view of the myriad stars near the galaxy’s core, the bright whitish region at far right. An image of the entire galaxy, taken by the European Southern Observatory’s Wide Field Imager on the ESO/MPG 2.2-meter telescope at La Silla, Chile, is shown at left. The white box outlines Hubble’s view.

WFC3’s broad wavelength range, from ultraviolet to near-infrared, reveals stars at different stages of evolution, allowing astronomers to dissect the galaxy’s star-formation history.

Now that’s the birth of a star!

See more views of M83 and a video at the HubbleSite

New Hubble Release: Dramatic Galaxy Collision

At first glance, this latest image release from Hubble appears to be one really bizarre-looking galaxy. But actually, this is a pair of spiral galaxies that resemble our own Milky Way smashing together at breakneck speeds. The centers have already merged into one nucleus, and the two tidal tails stretching out from the center are sparkling with active star formation, prompted by the exchange of mass and gases from the dramatic collision. This object, NGC 2623, or Arp 243, is about 250 million light-years away in the constellation of Cancer (the Crab), and is in the late stages of the merging process.

The prominent lower tail is richly populated with bright star clusters — 100 of them have been found in these observations. The large star clusters that the team has observed in the merged galaxy are brighter than the brightest clusters we see in our own vicinity. These star clusters may have formed as part of a loop of stretched material associated with the northern tail, or they may have formed from debris falling back onto the nucleus. In addition to this active star-forming region, both galactic arms harbor very young stars in the early stages of their evolutionary journey.

Watch this video for more information on NGC 2623:

Some mergers (including NGC 2623) can result in an active galactic nucleus, where one of the supermassive black holes found at the centers of the two original galaxies is stirred into action. Matter is pulled toward the black hole, forming an accretion disc. The energy released by the frenzied motion heats up the disc, causing it to emit across a wide swath of the electromagnetic spectrum.

NGC 2623 is so bright in the infrared that it belongs to the group of very luminous infrared galaxies (LIRG) and has been extensively studied as the part of the Great Observatories All-sky LIRG Survey (GOALS) project that combines data from Hubble, the Spitzer Space Telescope, Chandra X-ray Observatory and the Galaxy Evolution Explorer (GALEX). The combination of resources is helping astronomers characterize objects like active galactic nuclei and nuclear star formation by revealing what is unseen at visible wavelengths.

The data used for this color composite were actually taken in 2007 by the Advanced Camera for Surveys (ACS) aboard Hubble, but is just being released now, as a team of over 30 astronomers, led by Aaron S. Evans, recently published an overview paper, detailing the first results of the GOALS project. Observations from ESA’s X-ray Multi-Mirror Mission (XMM-Newton) telescope contributed to the astronomers’ understanding of NGC 2623.

NGC 2623 paper
GOALS Overview paper
GOALS website

Source: European Hubble website

Hubble’s Amazing Rescue on NOVA

In a world where you have just one chance to save a dying explorer, the only hope is a space shuttle mission …(said in my deepest, most dramatic voice….) Enjoy this movie-like trailer for the upcoming NOVA special on PBS stations in the US, “Hubble’s Amazing Rescue.” It looks like a great show, providing the chance to re-live the exciting 12-day Hubble Servicing Mission 4 and its five pressure-filled spacewalks. Hubble’s Amazing Rescue premieres Tuesday, October 16th at 8PM ET/PT on PBS. Find out more about the show and check local listings for your area here.

Hubble Sees Galaxies Stripped by Ram Pressure


Strange forces of nature are stripping away gas from galaxies in the Virgo cluster. An extremely hot X-ray emitting gas known as the intra-cluster medium permeates the regions between galaxies inside clusters and, as fast moving galaxies whip through this medium, strong winds tear through galaxies distorting their shape and even halting star formation with a process known as “ram pressure stripping.” Hubble spied two galaxies “losing it” to these forces.

Ram pressure is the drag force that results when something moves through a fluid — much like the wind you feel in your face when bicycling, even on a still day — and occurs in this context as galaxies orbiting about the centre of the cluster move through the intra-cluster medium, which then sweeps out gas from within the galaxies.

The two galaxies — NGC 4522 and NGC 4402 – were imaged by the old Advanced Camera for Surveys on Hubble before it suffered from a power failure in 2007. Astronauts on Servicing Mission 4 in May 2009 were able to restore ACS during their 13-day mission.

This image shows NGC 4522 within the context of the Virgo Cluster.   Credit: NASA, ESA and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble)
This image shows NGC 4522 within the context of the Virgo Cluster. Credit: NASA, ESA and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble)

The spiral galaxy NGC 4522 is located some 60 million light-years away from Earth and it is a spectacular example of a spiral galaxy currently being stripped of its gas content. Astronomers estimate the galaxy is moving at more than 10 million kilometers per hour, and its rapid motion within the cluster results in strong winds across the galaxy as the gas within is left behind. A number of newly formed star clusters that developed in the stripped gas can be seen in the Hubble image.

The image provides a vivid view of the ghostly gas being forced out of it. Bright blue pockets of new star formation can be seen to the right and left of centre. The image is sufficiently deep to show distant background galaxies.

The image of NGC 4402 also highlights some telltale signs of ram pressure stripping such as the curved, or convex, appearance of the disc of gas and dust, a result of the forces exerted by the heated gas. Light being emitted by the disc backlights the swirling dust that is being swept out by the gas. Studying ram pressure stripping helps astronomers better understand the mechanisms that drive the evolution of galaxies, and how the rate of star formation is suppressed in very dense regions of the Universe like clusters.

Source: Hubble Science Center

Hubble Ultra Deep Field in 3-D

Here’s a new way to appreciate the Hubble Ultra Deep Field image, by flying through the 10,000 galaxies in this deepest of all Hubble images. Watch the whole video if you need the background on the Hubble Deep Field and subsequent Ultra Deep Field. Start at about 3:00 if you just want to see the distances between the galaxies in this image. Nice.

Via Gizmodo

Hubble Powers Up to Capture Jupiter Impact Site


The Hubble Space Telescope was undergoing a thorough checkout of all its systems following the recent servicing mission, but scientists decided to drop everything and interrupt the observatory’s checkout and calibration to take an image of what every other telescope has by trying to view: the impact site on Jupiter. But Hubble does it better than anyone. This image, taken just yesterday (July 23) shows the black spot on the giant planet — created a small comet or asteroid — is expanding.

“Because we believe this magnitude of impact is rare, we are very fortunate to see it with Hubble,” said Amy Simon-Miller of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Details seen in the Hubble view shows a lumpiness to the debris plume caused by turbulence in Jupiter’s atmosphere.”

The new Hubble images also confirm that the May servicing visit by space shuttle astronauts was a big success.

The Jupiter impact has been a sensation ever since Australian amateur astronomer Anthony Wesley imaged a black spot on the planet on July 19. , The only other time such a feature has been seen on Jupiter was 15 years ago after the collision of fragments from comet Shoemaker-Levy 9.

For the past several days, Earth-based telescopes have been trained on Jupiter. To capture the unfolding drama 360 million miles away, Matt Mountain, director of the Space Telescope Science Institute in Baltimore, gave observation time to a team of astronomers led by Heidi Hammel of the Space Science Institute in Boulder, Colo.

“Hubble’s truly exquisite imaging capability has revealed an astonishing wealth of detail in the impact site,” Hammel said. “By combining these images with our ground-based data at other wavelengths, our Hubble data will allow a comprehensive understanding of exactly what is happening to the impact debris.”

Simon-Miller estimated the diameter of the impacting object was the size of several football fields. The force of the explosion on Jupiter was thousands of times more powerful than the suspected comet or asteroid that exploded over the Siberian Tunguska River Valley in June 1908.

The image was taken with the Wide Field Camera 3. The new camera, installed by the astronauts aboard space shuttle Atlantis in May, is not yet fully calibrated. While it is possible to obtain celestial images, the camera’s full power has yet to be seen.

“This is just one example of what Hubble’s new, state-of-the-art camera can do, thanks to the STS-125 astronauts and the entire Hubble team,” said Ed Weiler, associate administrator of NASA’s Science Mission Directorate in Washington. “However, the best is yet to come.”

Source: NASA