Starship Asterisk*

zloq wrote:On the "Fast Facts" page for the image at the HST site, fortunately they have info on the filters and exposures. The image is very much false color, based on five different filters in the IR and vis - including OIII and Ha. The main information is in the raw data and this picture may have had colors combined for maximum visual impact - to punch up the yellow region, etc. Apparently the gas is very hot and has many emission lines, plus continuum, but the corresponding visual color mapping would be basically greenish, though not pure OIII. The yellow in the image is just from the chosen false color mapping and how the channels were mixed.

zloq

Fast Facts wrote:This image is a composite of separate exposures acquired by the WFC3 and ACS instruments on HST. Several filters were used to sample broad and narrow wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are:

Code: Select all

WFC3/IR     F160W (H)                     dark green
WFC3/UVIS   F814W (I)                     dark red
ACS/WFC     FR716N (Redshifted H-alpha)   red
ACS/WFC     FR505N ([O III])              green
WIYN        (B)                           blue

Click to view full size image

One of the strangest space objects ever seen is being scrutinized by the penetrating vision of NASA's Hubble Space Telescope. A mysterious, glowing green blob of gas is floating in space near a spiral galaxy. Hubble uncovered delicate filaments of gas and a pocket of young star clusters in the giant object, which is the size of our Milky Way galaxy.

The Hubble revelations are the latest finds in an ongoing probe of Hanny's Voorwerp (Hanny's Object in Dutch), named for Hanny van Arkel, the Dutch teacher who discovered the ghostly structure in 2007 while participating in the online Galaxy Zoo project. Galaxy Zoo enlists the public to help classify more than a million galaxies catalogued in the Sloan Digital Sky Survey. The project has expanded to include the Hubble Zoo, in which the public is asked to assess tens of thousands of galaxies in deep imagery from the Hubble Space Telescope.

In the sharpest view yet of Hanny's Voorwerp, Hubble's Wide Field Camera 3 and Advanced Camera for Surveys have uncovered star birth in a region of the green object that faces the spiral galaxy IC 2497, located about 650 million light-years from Earth. Radio observations have shown an outflow of gas arising from the galaxy's core. The new Hubble images reveal that the galaxy's gas is interacting with a small region of Hanny's Voorwerp, which is collapsing and forming stars. The youngest stars are a couple of million years old.

"The star clusters are localized, confined to an area that is over a few thousand light-years wide," explains astronomer William Keel of the University of Alabama in Tuscaloosa, leader of the Hubble study. "The region may have been churning out stars for several million years. They are so dim that they have previously been lost in the brilliant light of the surrounding gas."

Recent X-ray observations have revealed why Hanny's Voorwerp caught the eye of astronomers. The galaxy's rambunctious core produced a quasar, a powerful light beacon powered by a black hole. The quasar shot a broad beam of light in Hanny's Voorwerp's direction, illuminating the gas cloud and making it a space oddity. Its bright green color is from glowing oxygen.

"We just missed catching the quasar, because it turned off no more than 200,000 years ago, so what we're seeing is the afterglow from the quasar," Keel says. "This implies that it might flicker on and off, which is typical of quasars, but we've never seen such a dramatic change happen so rapidly."

The quasar's outburst also may have cast a shadow on the blob. This feature gives the illusion of a gaping hole about 20,000 light-years wide in Hanny's Voorwerp. Hubble reveals sharp edges around the apparent opening, suggesting that an object close to the quasar may have blocked some of the light and projected a shadow on Hanny's Voorwerp. This phenomenon is similar to a fly on a movie projector lens casting a shadow on a movie screen.

Radio studies have revealed that Hanny's Voorwerp is not just an island gas cloud floating in space. The glowing blob is part of a long, twisting rope of gas, or tidal tail, about 300,000 light-years long that wraps around the galaxy. The only optically visible part of the rope is Hanny's Voorwerp. The illuminated object is so huge that it stretches from 44,000 light-years to 136,000 light-years from the galaxy's core.

The quasar, the outflow of gas that instigated the star birth, and the long, gaseous tidal tail point to a rough life for IC 2497.

"The evidence suggests that IC 2497 may have merged with another galaxy about a billion years ago," Keel explains. "The Hubble images show in exquisite detail that the spiral arms are twisted, so the galaxy hasn't completely settled down."

In Keel's scenario, the merger expelled the long streamer of gas from the galaxy and funneled gas and stars into the center, which fed the black hole. The engorged black hole then powered the quasar, which launched two cones of light. One light beam illuminated part of the tidal tail, now called Hanny's Voorwerp.

About a million years ago, shock waves produced glowing gas near the galaxy's core and blasted it outward. The glowing gas is seen only in Hubble images and spectra, Keel says. The outburst may have triggered star formation in Hanny's Voorwerp. Less than 200,000 years ago, the quasar dropped in brightness by 100 times or more, leaving an ordinary-looking core.

New images of the galaxy's dusty core from Hubble's Space Telescope Imaging Spectrograph show an expanding bubble of gas blown out of one side of the core, perhaps evidence of the sputtering quasar's final gasps. The expanding ring of gas is still too small for ground-based telescopes to detect.

"This quasar may have been active for a few million years, which perhaps indicates that quasars blink on and off on timescales of millions of years, not the 100 million years that theory had suggested," Keel says. He added that the quasar could light up again if more material is dumped around the black hole.

[size=85]This diagram explains the formation of the strange green object known as Hanny’s Voorwerp. Astronomers believe that it is part of the long streamer of gas that extends from galaxy IC 2497, lit up brightly by the beam of a recently extinguished quasar.[/size]

---

Almost four years ago a group of astronomers known as the Galaxy Zoo made a very exciting discovery – one they named “Hanny’s Voorwerp”. Although the action occurred a hundred thousand years ago and somewhere in the neighborhood of 700 million light years away, a once upon a time quasar burned brighter than its neighboring galaxy. While the tidal pull of massive spiral IC 2497 shredded a gas rich dwarf galaxy, the incredible outpouring of ultraviolet and X-ray radiation combined with the quasar ignited the gases to light… but what exactly is it? The Hubble Space Telescope turned its eye in the direction of Leo Minor to find out…

According to the American Astronomical Society press release: “One of the strangest space objects ever seen is being scrutinized by the penetrating vision of the NASA/ESA Hubble Space Telescope. A mysterious, glowing green blob of gas is floating in space near a spiral galaxy. Hubble uncovered delicate filaments of gas and a pocket of young star clusters in the giant object, which is the size of the Milky Way. The Hubble revelations are the latest finds in an ongoing probe of Hanny\rquote s Voorwerp (Hanny’s Object in Dutch). It is named after Hanny van Arkel, the Dutch schoolteacher who discovered the ghostly structure in 2007 while participating in the online Galaxy Zoo project. Galaxy Zoo enlists the public to help classify more than a million galaxies catalogued in the Sloan Digital Sky Survey. The project has expanded to include Galaxy Zoo: Hubble, in which the public is asked to assess tens of thousands of galaxies in deep imagery from the Hubble Space Telescope.” In the sharpest view yet of Hanny’s Voorwerp, Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys have uncovered star birth in a region of the green object that faces the spiral galaxy IC 2497 — a bright, energetic object that is powered by a black hole.

This Hubble view reveals new details in colorful clarity – such as a area of star clusters whose members are only a couple of million years old… and the chemically charged yellowish-orange area at the tip of Milky Way sized Hanny’s Voorwerp. The image was made by combining data from the Advanced Camera for Surveys (ACS) and the Wide Field Camera 3 (WFC3) onboard Hubble, with data from the WIYN telescope at Kitt Peak, Arizona, USA. The ACS exposures were taken 12 April 2010; the WFC3 data, 4 April 2010.

“The star clusters are localized, confined to an area that is over a few thousand light-years wide,” explains astronomer William Keel of the University of Alabama in Tuscaloosa, leader of the Hubble study. “The region may have been churning out stars for several million years. They are so dim that they have previously been lost in the brilliant light of the surrounding gas.”

The press release goes on to state that recent X-ray observations have revealed why Hanny’s Voorwerp caught the proverbial eye of astronomers. The galaxy’s rambunctious core produced a quasar, a powerful light beacon powered by a black hole. The quasar shot a broad beam of light in Hanny’s Voorwerp’s direction, illuminating the gas cloud and making it a space oddity. Its bright green color is from glowing oxygen. “We just missed catching the quasar, because it turned off no more than 200,000 years ago, so what we’re seeing is the afterglow from the quasar,” Keel says. “This implies that it might flicker on and off, which is typical of quasars, but we’ve never seen such a dramatic change happen so rapidly.”

The quasar’s outburst also may have cast a shadow on the blob. This feature gives the illusion of a gaping hole about 20,000 light-years wide in Hanny’s Voorwerp. Hubble reveals sharp edges around the apparent opening, suggesting that an object close to the quasar may have blocked some of the light and projected a shadow on Hanny’s Voorwerp. This phenomenon is similar to a fly on a movie projector lens casting a shadow on a movie screen. (Or your little brother Tom making a duck face with his hand while your Mom isn’t looking.) Radio studies have revealed that Hanny’s Voorwerp is not just an island gas cloud floating in space awaiting a three-hour tour. The glowing blob is part of a long, twisting rope of gas, or tidal tail, about 300,000 light-years long that wraps around the galaxy. The only optically visible part of the rope is Hanny’s Voorwerp. The illuminated object is so huge that it stretches from 44,000 light-years to 136,000 light-years from the galaxy’s core. The quasar, the outflow of gas that instigated the star birth, and the long, gaseous tidal tail point to a rough life for IC 2497.

“The evidence suggests that IC 2497 may have merged with another galaxy about a billion years ago,” Keel explains. “The Hubble images show in exquisite detail that the spiral arms are twisted, so the galaxy hasn’t completely settled down.” In Keel’s scenario, the merger expelled the long streamer of gas from the galaxy and funneled gas and stars into the center, which fed the black hole. The engorged black hole then powered the quasar, which launched two cones of light. One light beam illuminated part of the tidal tail, now called Hanny’s Voorwerp.” says Keel. “About a million years ago, shock waves produced glowing gas near the galaxy’s core and blasted it outward. The glowing gas is seen only in Hubble images and spectra. The outburst may have triggered star formation in Hanny’s Voorwerp. Less than 200,000 years ago, the quasar dropped in brightness by 100 times or more, leaving an ordinary-looking core.

New images of the galaxy’s dusty core from Hubble’s Space Telescope Imaging Spectrograph show an expanding bubble of gas blown out of one side of the core, perhaps evidence of the sputtering quasar’s final gasps. The expanding ring of gas is still too small for ground-based telescopes to detect. “This quasar may have been active for a few million years, which perhaps indicates that quasars blink on and off on timescales of millions of years, not the 100 million years that theory had suggested,” Keel says. He added that the quasar could light up again if more material is dumped around the black hole.

Fascinating evidence which confirms the team’s original explanation… Go Zoo!

Credits: NASA, ESA, William Keel -University of Alabama, Tuscaloosa, the Galaxy Zoo team and STScI Press releases.

IC 2497 & Hanny's Voorwerp [i](Credit: WIYN/William Keel/Anna Manning)[/i]

---

While sorting through hundreds of galaxy images as part of the Galaxy Zoo citizen science project two years ago, Dutch schoolteacher and volunteer astronomer Hanny van Arkel stumbled upon a strange-looking object that baffled professional astronomers. Two years later, a team led by Yale University researchers has discovered that the unique object represents a snapshot in time that reveals surprising clues about the life cycle of black holes.

In a new study, the team has confirmed that the unusual object, known as Hanny’s Voorwerp (Hanny’s “object” in Dutch), is a large cloud of glowing gas illuminated by the light from a quasar—an extremely energetic galaxy with a supermassive black hole at its center. The twist, described online in the Astrophysical Journal Letters, is that the quasar lighting up the gas has since burned out almost entirely, even though the light it emitted in the past continues to travel through space, illuminating the gas cloud and producing a sort of “light echo” of the dead quasar.

“This system really is like the Rosetta Stone of quasars,” said Yale astronomer Kevin Schawinski, a co-founder of Galaxy Zoo and lead author of the study. “The amazing thing is that if it wasn’t for the Voorwerp being illuminated nearby, the galaxy never would have piqued anyone’s interest.”

The team calculated that the light from the dead quasar, which is the nearest known galaxy to have hosted a quasar, took up to 70,000 years to travel through space and illuminate the Voorwerp—meaning the quasar must have shut down sometime within the past 70,000 years.

• Astrophysical Journal Letters 724(1) L30 (20 Nov 2010) DOI: 10.1088/2041-8205/724/1/L30
  arXiv.org > astro-ph > arXiv:1011.0427 > 01 Nov 2010

http://www.symmetrymagazine.org/breaking/2008/11/26/hannys-voorwerp-explained/ wrote:

25-year old Hanny Van Arkel, pictured above, got turned onto astronomy by Brian May, the Queen guitarist, after reading his book “Bang! The Complete History of the Universe”.

---

Westerbork Synthesis Radio Telescope observations reveal a radio jet (white contours) emanating from the centre of the nearby galaxy IC2497, headed straight in the direction of [color=#00BF00][b]Hanny's Voorwerp[/b][/color]. The observations also reveal [color=#FF8000][b]a huge reservoir of hydrogen gas[/b][/color] that probably arose from a previous encounter between IC2497 and another galaxy. The presence of strong neutral hydrogen absorption (top right plot) argues that the central regions of IC2497 are highly obscured. Credit: ASTRON & Dan Herbert, Isaac Newton Telescope.

---

<<Hanny’s voorwerp, a mysterious giant green astronomical object found over a year ago now has a partial explanation, according to a press release from Astron, the Netherlands Institute for Radio Astronomy. It seems that a jet of energetic particles from a nearby black hole has cleared a path in the interstellar medium so that visible and ultraviolet light associated with the black hole can heat the cloud, ionizing the particles, and causing it to glow green. The black hole resides at the center of the galaxy IC 2497, which is about 60,000 light years away from Hanny’s voorwerp.

In the press release, Dr. Tom Oosterloo says he thinks he has seen such a phenomenon before: “It has all the hallmarks of an interacting system–the gas probably arises from a tidal interaction between IC 2497 and another galaxy, several hundred million years ago”. Oosterloo also thinks he can identify the culprits, “the stream of gas ends three hundred thousand light years westwards of IC2497–all the evidence points towards a group of galaxies at the tip of the stream being responsible for this freak cosmic accident”.>>

Click to view full size image

Swing on this news, Spider-Man. Dick Tracy, your wristwatch has a message for you. Superman, return to your phone booth at once.

The world’s best known comic book characters should take note. There’s a crop of new faces coming soon to colorized panels and speech bubbles near you. A cast of real-life astronomers and a Dutch schoolteacher who collaborated in the discovery and analysis of an unusual object in space are featured in a comic book to be unveiled Sept. 3 in Atlanta.

The unveiling at DragonCon, an annual event dubbed as the world’s largest fantasy/science fiction convention, will showcase, in comic book form, the winding, unlikely tale of an object that came to be known as Hanny’s Voorwerp.
...
Edited by Kelly McCullough and Gay and written by Mike Beatini, Keel, Mike Schoenberg and Jason and Jodi Thibeault, the comic book’s line art is by Elea Braasch, and its colorist and letterer is Chris Spangler.

About 500 copies of the comic book are being printed with others available for order. Anyone interested will be able to read the comic book online at http://hannysvoorwerp.zooniverse.org beginning at 10 p.m. Sept. 3.

What an inventive article title.

Click to view full size image

Everyone loves this story because a young schoolteacher got to make a significant discovery -- something that is much harder to accomplish in the 21st century than it was in William Herschel's time. Projects like Galaxy Zoo are a great way of bringing amateurs back into the astronomy fold. In fact, there may be lots of other galaxies with active black holes, giving rise to numerous "voorwerpje's" (junior voorwerps).

And now it seems as if Hanny's wonderful tale is going to become the stuff of Web comics. I spent last weekend at CONvergence in Minneapolis, where I finally had the chance to meet astronomy educator/blogger Pamela Gay (StarStryder) in person. And she told me about a nifty new project underway to create a digitized Webcomic telling Hanny's amazing story -- except rather than just one person writing it, the comic is a collective effort.

Gay and sci-fi author Kelly McCullough ran a two-part workshop at CONvergence -- dubbed "the writer's sandbox" -- to map out the narrative and illustrations, and collaborate in the writing, with oversight provided by the kind folks at Galaxy Zoo (because scientific accuracy is as important as the creative storytelling). The full comic will be released at Dragon-Con in Atlanta, Georgia, this fall, no doubt to great fanfare among astronomy buffs.

"By telling Hanny's story we are showing how everyday people can sometimes rewrite science," proclaims the new Zooniverse blog tied to the project. And all because one young woman dared to ask, "Hey -- what's that stuff?"

aunt maggie wrote:It surely dies look like Kermit! That was my first thought when I first glanced at today's picture!! Yup! Kirmit dancing in space - how cool is that?!

APOD: What is Hanny's Voorwerp? (2008 June 25)

Credit: Galaxy Zoo Project, ING

---

In 2007, a Dutch school teacher called Hanny van Arkel discovered an extraordinary object while combing though images for the Galaxy Zoo project to classify galaxies. The object appears as a bright green blob close to a spiral galaxy in the constellation of Leo Minor and soon became known as Hanny's Voorwerp (meaning Hanny's object in Dutch).

Hanny's Voorwerp is astounding because astronomers have never seen anything like it. Although galactic in scale, it is clearly not a galaxy because it does not contain any stars. Detailed spectrographic observations since its discovery suggest that it is a giant cloud of gas that is glowing an unusual green colour.

That raises an obvious question: what is causing the gas to glow?

Today, Hayden Rampadarath at the Joint Institute for VLBI in Europe, based in the the Netherlands and a multitude of friends, provide an answer. Their data comes from a new study of the nearby spiral galaxy IC 2497 using a couple of very long baseline interferometers to study the region at various wavelengths.

Their conclusion is that, like many galaxies, IC 2497 contains a massive black hole at its centre. The infall of matter into the black hole generates a cone of radiation emitted in a specific direction. The great cloud of gas that is Hanny's Voorwerp just happens to be in the firing line. The black hole radiation is ionising the gas, causing it to glow green.

What has confused the issue is that another cloud of dust and gas sits between us on Earth and IC 2497 and this prevents us from directly seeing the black hole (or the active galactic nucleus as astronomers call it).

That seems a sensible interpretation. And certainly more likely than another idea put forward last year. This proposed that some 10,000 years ago, IC 2497 suddenly underwent a dramatic outburst of quasar-like radiation and then became quiet. What we see today from this cloud of gas some 10,000 light years from IC 2497, is simply a reflection of this outburst. In other words, Hanny's Voorwerp is a quasar light echo.

That was unsatisfactory because it resolved one mystery merely by posing another: what could cause an entire galaxy to flare up briefly and suddenly?

The evidence that IC 2497 is still active today puts to rest this idea. It also explains why Voorwerps are so rare: the radiation cones from active galactic nuclei are highly directional so only occasionally do unlucky gas clouds get caught in the cross fire.

• arXiv.org > astro-ph > arXiv:1006.4096 > 21 Jun 2010

Radio observations of IC 2497: The European VLBI Network (EVN) and the UK's Multi-Element Radio Linked Interferometer Network (MERLIN). Background: an optical image of Hanny's Voorwerp and IC 2497. (Credit: William Keel, Anna Manning, 3.5-m WIYN Telescope). Foreground: the associated high-resolution radio observations. (Copyright: ASTRON).

---

A group of researchers, led by Professor Michael Garrett, General Director of the Netherlands Institute for Radio Astronomy, ASTRON, have made new, high resolution radio observations of the region of space around Hanny's Voorwerp, the mysterious, greenish gas cloud discovered by Dutch school teacher Hanny van Arkel.

The astronomers undertook an observational campaign at radio wavelengths using the European Very Long Baseline Interferometry Network (EVN) and the UK's Multi-Element Radio Linked Interferometer Network (MERLIN), pointing their telescopes at the centre of the neighbouring galaxy IC 2497. In these measurements, several radio telescopes across Europe and the UK were linked together in real-time, in order to gain a detailed picture of the very central region of the galaxy. They observed a field a few arcseconds (the 3600th part of a degree) across, with a spatial resolution of about 70 milliarcseconds (0.07 arcseconds).

According to Garrett: "the observations show two bright and very compact sources with broadband spectra that argue strongly for the existence of an active galactic nucleus (AGN) at the centre of the galaxy, IC2497. One of the sources appears to be identified with the base of the super-massive blackhole at the centre of the AGN itself, while the other one is likely to be the result of an energetic jet expelled by the black-hole and now interacting with the dense gas that surrounds IC2497". The radiation output from the AGN is believed to heat Hanny's Voorwerp to a temperature above 10000 degrees.

But this is only part of the story. It also appears that surrounding the AGN, a lot of extended radio emission is also observed. The researchers argue that this is radio emission associated with a nuclear starburst. "We knew that IC 2497 is forming stars, but we were susprised to find that the star formation seems to be concentrated in a very small central region, only 3000 light years across", Hayden Rampadarath (University of Machester) explains. Garrett: "It is fairly unusual to find both vigorous star formation and AGN radio activity in the same system and on similar scales. It seems that IC2497 swings both ways".

The radio observations show that in this small region, IC 2497 is producing stars with a total mass of 70 suns every year. This star formation rate is pretty large, especially in the local Universe - it is about 6 times higher than in the nearby 'Starburst-Galaxy' poster-child, M82." "We know of only a few hundred of these types of galaxy, Luminous Infrared Galaxies, LIRGs, in the local universe", Gyula Józsa, support scientist at ASTRON, adds, "but they must have been much more frequent in the past". At half the universe's age, most stars have been formed in LIRGs. It is also typical that for this kind of galaxy large amounts of dust obscure optical and ultraviolet light towards the observer.

The observations support the group's earlier hypothesis that a hidden AGN in the centre of IC2497 is ionising a distinct region of gas that surrounds the giant galaxy. That distinct region is what we know as Hanny's Voorwerp. Such phenomenae must be rare in the local Universe, as they depend on a specific geometry of the observer, galaxy and gas, plus the interaction of several galaxies in the field in order to fuel the AGN and the starburst, and to create the gas reservoir that forms part of the Voorwerp.

dcrosby wrote:I got to thinking - the green in the picture on APOD reminds me of the "green flash" I saw a picture of some years back. It gave me the idea that it might be the product of a gravitational distortion of light somehow. I guess if it's because of a black hole, I wasn't too far off, but if it's really blue then I guess I was further off than I thought.

• An eerie green cloud lurking around a nearby galaxy has puzzled scientists since it was discovered last year. New observations reveal that the cloud's ghoulish appearance may have to do with radiation streaming from a black hole inside the galaxy. The cloud was first discovered by Dutch schoolteacher Hanny van Arkel, who volunteered to sift through astronomical data as part of the Galaxy Zoo project. Van Arkel came across an image of a huge, irregular-shaped greenish-yellowish cloud near the spiral galaxy IC2497. The unusual object became known as "Hanny's Voorwerp," Dutch for "Hanny's thing."

JohnD wrote:Earlier reports showed it as blue, now its seen as green.
This site: http://www.astr.ua.edu/keel/research/voorwerp.html discusses frequencies in the emission spectrum, and comes down on the side of it being "more green [than blue] if seen with the eye's sensitivity." That equivocal statement doesn't match the intense green shown in the pics.

But we're shown lots of pics with 'synthetic colours' to represent wavelengths that are totally invisible the eye. These are usually wavelengths of extreme specificity, when the eye sees a wide range of frequencies as "green" or "blue".

Anthraquinone wrote:I am now wondering if ... there is an equivalent to 1st April ...

JohnD wrote:henk, how is the 'W' of VoorWerp pronounced? An Anglophone on BAUT suggest the whole word as "four-vairp". How close is that? J.