Posted on by Nancy Atkinson

New Hubble Images Show Pluto is Changing

New images of Pluto from the Hubble Space Telescope. Credit: NASA, ESA, and M. Buie (Southwest Research Institute).

Pluto-philes (and astronomers, too) have always bemoaned the fact that the best image of the principal dwarf planet wase just a fuzzy, pixelized haze. Bemoan no more. The most detailed look to date of the entire surface of Pluto has been constructed from hundreds of images taken by the Hubble Space Telescope. The images were taken during 2002 to 2003, and it took four years of computer crunching and software tweaking to create the global images. Surprisingly, the images show Pluto changed noticeably during the two-year photo shoot; the dwarf planet’s color became “redder,” and astronomers could see Pluto’s ice sheets were shifting.

“These Hubble pictures represent a true-color appearance of what you would see if you were near Pluto, comparable to looking at our own Moon with the naked eye,” said principal investigator Marc Buie of the Southwest Research Institute. “We now know we’re looking at something that has the biggest surface changes of any object in our solar system.”

The pictures show nitrogen ice growing and shrinking, getting brighter in the north and darker in the south.

Buie and planet hunter Mike Brown from Caltech introduced the Hubble images during a teleconference with reporters today, and emphasized how surprised they were with the changes seen on Pluto in just a relatively short period of time. Even accounting for seasonal changes, seasons can last 120 years in some regions of Pluto.

The top picture was taken in 1994 by the European Space Agency’s Faint Object Camera. The bottom image was taken in 2002-2003 by the Advanced Camera for Surveys. The dark band at the bottom of each map is the region that was hidden from view at the time the data were taken. Credit: NASA, ESA, and M. Buie (Southwest Research Institute)

They said the images underscore that Pluto is not simply a ball of ice and rock but a dynamic world that undergoes dramatic atmospheric changes. While they believe the changes are driven by the seasons, it may mostly come from how quickly things can change on Pluto. The seasons are propelled as much by the planet’s 248-year elliptical orbit as its axial tilt — unlike Earth where the tilt alone drives seasons. On Pluto spring transitions to polar summer quickly in the northern hemisphere because Pluto is moving faster along its orbit when it is closer to the Sun.

“If Earth had such an extreme orbit, and we were experiencing a nice springtime day with 60-70 degree F temperatures, as the orbit changed it could suddenly drop to -90 degrees F,” said Brown.

There is also a mysterious bright spot on the center of Pluto, which has been observed in earlier images. But the spot is unusually rich in carbon monoxide frost.

Click here to see a video of Pluto rotating.

The astronomers said Pluto is so small and distant that the task of resolving the surface is as challenging as trying to see the markings on a soccer ball 40 miles away. Buie said we won’t have a better look at Pluto until the New Horizon’s spacecraft is six months away from the dwarf planet in 2015.

The images were taken with the Advanced Camera for Surveys on HST, and the 348 images taken in 2002 and 2003 were the last ones taken of Pluto with high enough resolution to be useful. “I had time allocated two years ago to look at Pluto, which came just three or four weeks after the high resolution camera failed,” Buie. “That was very disappointing.”

But the images do show Pluto is significantly redder than it had been for the past several decades. Astronomers use the word “red” to mean it reflects more red light than blue or green light. To the human eye, Pluto has a yellowish-orange color, and is about 20% redder than it used to be. “It’s not as red as the surface of Mars, but more red than Io,” Buie said.

Red is usually associated with carbon. The astronomers said there is also methane, which is not usually stable in an environment like Pluto’s.

“This business about the color change had me scared for awhile,” Buie confessed. “I got the result years ago, but it was so hard to understand and believe. I’m still nervous about it. It could be that I completely screwed this up, but I can tell you Charon is on the same images, and Charon has the same color throughout but Pluto changed. I don’t’ know how the camera system on HST could have given me the wrong colors on Pluto.”

This was previously the best image of Pluto, taken in 2000 by HST. Credit: Eliot Young (SwRI) et al., NASA

Someone suggested that Pluto is reddening because of its recent demotion from full planethood. “Yes, people have said that Pluto is mad at me,” said Brown, who has the nickname of the “Pluto killer” because he discovered other Kuiper Belt objects which led to the new class of dwarf planets.

“For a long time Pluto was this lonely oddball that we didn’t have anything else to compare it with,” said Brown. “Understanding this all as a new class of objects is a much more interesting way of looking at the solar system and it is quite a bit of fun, too.”

More information from Buie’s webpage on the Pluto images.

The paper about the images isn’t posted online yet, but it will be up on this webpage soon.

Source: Conference call.
Additional images and info from NASA

Posted on by Nancy Atkinson

Double Hubble Sequence Shows Galaxies Go Spiral

This image created from data taken from both the NASA/ESA Hubble Space Telescope and the Sloan Digital Sky Survey demonstrates that the Hubble sequence six billion years ago was very different from the one that astronomers see today. Credit: NASA, ESA, Sloan Digital Sky Survey, R. Delgado-Serrano and F. Hammer (Observatoire de Paris)

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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.

Papers:
Hammer, et al.
Delgado-Serrano et al.

Source: Space Telescope Institute

Posted on by Nancy Atkinson

Hubble Takes A Look at Possible Asteroid Collision

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

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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

Posted on by Nancy Atkinson

Latest from Hubble: Star Formation Fizzling Out in Nearby Galaxy

NGC 2976.. NASA, ESA, and J. Dalcanton and B. Williams (University of Washington, Seattle)

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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

Posted on by Nancy Atkinson

Hubble Repairman to Lead Space Telescope Science Institute

John Grunsfeld. Credit: NASA

Self proclaimed “Hubble Hugger” and telescope repairman Dr. John Grunsfeld has been appointed Deputy Director of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, the organization that coordinates all the science done with HST. Grunsfeld’s new job starts today, January 4, 2010. “This is an incredibly exciting opportunity for me to work at a focal point of top astronomers at the leading edge of scientific inquiry. The team at STScI has a demonstrated record of meeting the high performance challenges of operating the Hubble Space Telescope, and preparing for the James Webb Space Telescope. I look forward to working with this excellent team as we continue to explore the mysteries of the universe.”

Grunsfeld is a veteran of five space flights, including three missions to service HST: STS-103 in Dec. 1999, STS-109 in March 2002, and STS-125 in May 2009. He has logged over 835 hours in space, including nearly 60 hours of Extravehicular Activity during eight space walks.

He succeeds Dr. Michael Hauser, who stepped down in October. STScI is the science operations center for NASA’s orbiting Hubble Space Telescope and the James Webb Space Telescope planned to be launched in 2014.

Grunsfeld’s research has covered X-ray and gamma-ray astronomy, high-energy cosmic ray studies, and development of new detectors and instrumentation. Grunsfeld has conducted observations of the far-ultraviolet spectra of faint astronomical objects and the polarization of ultraviolet light coming from stars and distant galaxies.

“We are absolutely delighted that he has accepted the position,” said STScI Director, Dr. Matt Mountain. “John brings to us a wealth of expertise in the areas of space exploration concepts and technologies for use beyond low-earth orbit. He will be invaluable in our continued efforts to conduct world-class science with state-of-the-art observatories and instrumentation.

Source: HubbleSite, STSci

Posted on by Nancy Atkinson

Blue Stragglers Can Be Either Vampires or Stellar Bad-Boys

Messier 30, from HST’s Advanced Camera for Surveys. Credit: NASA, ESA and Francesco Ferraro (University of Bologna

Blue stragglers are stars that stay on the main sequence longer than expected. They even appear to regress from “old age” back to a hotter and brighter “youth,” gaining a new lease on life in the process. Astronomers have thought blue stragglers were “vampires” that suck fresh hydrogen from companion stars to heat up and maintain their youthfulness. But now there appears to be two kinds of blue stragglers. In addition to the vampires, there are also the bad-boys: these blue stragglers steal mass from companion stars by crashing into their neighbors, as if they were in a stellar mosh pit. A team of astronomers used data from the Hubble Space Telescope to study the blue straggler star content in Messier 30, a swarm of several hundred thousand stars located about 28,000 light-years from Earth.

This wide-field image of the sky around the globular cluster Messier 30 was created from photographs forming part of the Digitized Sky Survey 2. Located about 28 000 light-years away from Earth, this cluster -- a swarm of several hundred thousand stars -- is about 90 light-years across. The field of view is approximately 2.9 degrees across. Credit: ESO and Digitized Sky Survey 2 Acknowledgment: Davide De Martin
This wide-field image of the sky around the globular cluster Messier 30 was created from photographs forming part of the Digitized Sky Survey 2. Located about 28 000 light-years away from Earth, this cluster -- a swarm of several hundred thousand stars -- is about 90 light-years across. The field of view is approximately 2.9 degrees across. Credit: ESO and Digitized Sky Survey 2 Acknowledgment: Davide De Martin

Blue stragglers have been known since the early 1950s, but how they formed remains an astrophysical puzzle. Of all the stars in Messier 30, which formed about 13 billion years ago, a small fraction of them appeared to be significantly younger.

“It’s like seeing a few kids in a group photo of residents of a retirement home, and ask, ‘How did they get there?'” said Alison Sills, assistant professor at McMaster University. “In short, we seem to have found that there are two fountains of youth for stars.”

Previously, it was thought that that the less massive star in a binary system acts as a “vampire”, siphoning fresh hydrogen from its more massive companion star that allows the smaller star to heat up, growing bluer and hotter. However, the new study shows that some of the blue stragglers have instead been rejuvenated by a sort of “cosmic facelift”, courtesy of cosmic collisions. These stellar encounters are nearly head-on collisions in which the stars actually merge, mixing their nuclear fuel and re-stoking the fires of nuclear fusion. Merged stars and binary systems would both be about twice the typical mass of individual stars in the cluster.
This illustration demonstrates the two ways that blue stragglers — or "rejuvenated" stars — in globular clusters form. Credit: NASA/ESA
“The observations, which agree with our models, demonstrate that blue stragglers formed by collisions have slightly different properties from those formed by vampirism. This provides a direct demonstration that the two formation scenarios are valid and that they are both operating simultaneously in this cluster,” said Sills, who was part of an international steam that made the findings.

Using data from the now-retired Wide Field Planetary Camera 2 (WFPC2) aboard Hubble, astronomers found that these “straggling” stars are much more concentrated towards the center of the cluster than the average star.

The central regions of high density globular clusters are crowded neighborhoods where interactions between stars are nearly inevitable. Researchers conjecture that one or two billion years ago, Messier 30 underwent a major “core collapse” that started to throw stars towards the centre of the cluster, leading to a rapid increase in the density of stars. This event significantly increased the number of collisions among stars, and favored the formation of one of the families of blue stragglers. On the other hand, the increase of stellar crowding due to the collapse of the core also perturbed the twin systems, encouraging the vampirism phenomenon and thus forming the other family of blue stragglers.

The study will be published in the Dec. 24 issue of Nature.

Sources: ESA Hubble Information, Center, McMaster University University of Wisconsin/Madison

Posted on by Nancy Atkinson

Hubble Finds Smallest Kuiper Belt Object Ever Seen

Artists impression of a small KBO detected by Hubble as it transited a star. Credit: NASA, ESA, and G. Bacon (STScI)

Like finding a needle in a haystack, the Hubble Space Telescope has discovered the smallest object ever seen in visible light in the Kuiper Belt. While Hubble didn’t image this KBO directly, its detection is still quite impressive. The object is only 975 meters (3,200 feet) across and a whopping 6.7 billion kilometers (4.2 billion miles) away. The smallest Kuiper Belt Object (KBO) seen previously in reflected light is roughly 48 km (30 miles) across, or 50 times larger. This provides the first observational evidence for a population of comet-sized bodies in the Kuiper Belt.

The object detected by Hubble is so faint — at 35th magnitude — it is 100 times dimmer than what Hubble can see directly.

So then how did the space telescope uncover such a small body? The telltale signature of the small vagabond was extracted from Hubble’s pointing data, not by direct imaging. When the object passed in front a of star, Hubble’s instruments picked up the occulation.

Hubble has three optical instruments called Fine Guidance Sensors (FGS). The FGSs provide high-precision navigational information to the space observatory’s attitude control systems by looking at select guide stars for pointing. The sensors exploit the wavelike nature of light to make precise measurement of the location of stars.

Illustration of how Hubble found a tiny KBO. Credit: NASA, ESA, and A. Feild (STScI)
Illustration of how Hubble found a tiny KBO. Credit: NASA, ESA, and A. Feild (STScI)

In details of a paper published in the December 17th issue of the journal Nature, Hilke Schlichting of the California Institute of Technology in Pasadena, Calif., and her collaborators determined that the FGS instruments are so good that they can see the effects of a small object passing in front of a star. This would cause a brief occultation and diffraction signature in the FGS data as the light from the background guide star was bent around the intervening foreground KBO.

They selected 4.5 years of FGS observations for analysis. Hubble spent a total of 12,000 hours during this period looking along a strip of sky within 20 degrees of the solar system’s ecliptic plane, where the majority of KBOs should dwell. The team analyzed the FGS observations of 50,000 guide stars in total.

Scouring the huge database, Schlichting and her team found a single 0.3-second-long occultation event. This was only possible because the FGS instruments sample changes in starlight 40 times a second. The duration of the occultation was short largely because of the Earth’s orbital motion around the Sun.

They assumed the KBO was in a circular orbit and inclined 14 degrees to the ecliptic. The KBO’s distance was estimated from the duration of the occultation, and the amount of dimming was used to calculate the size of the object. “I was very thrilled to find this in the data,” says Schlichting.

Hubble observations of nearby stars show that a number of them have Kuiper Belt–like disks of icy debris encircling them. These disks are the remnants of planetary formation. The prediction is that over billions of years the debris should collide, grinding the KBO-type objects down to ever smaller pieces that were not part of the original Kuiper Belt population. The Kuiper Belt is therefore collisionally evolving, meaning that the region’s icy content has been modified over the past 4.5 billion years.

The finding is a powerful illustration of the capability of archived Hubble data to produce important new discoveries. In an effort to uncover additional small KBOs, the team plans to analyze the remaining FGS data for nearly the full duration of Hubble operations since its launch in 1990.

Source: HubbleSite

Posted on by Nancy Atkinson

Incredible New Hubble Image is Full of Stars!

This is a Hubble image of the star cluster R136 at the heart of the Tarantula Nebula. It's a starburst region that's home to several extremely massive stars, including R136a1, which is almost 200 times more massive than the Sun. Image Credit: By NASA, ESA, F. Paresce (INAF-IASF, Bologna, Italy), R. O'Connell (University of Virginia, Charlottesville), and the Wide Field Camera 3 Science Oversight Committee

A brand new Hubble image from Wide Field Camera 3 shows the most detailed view of the largest stellar nursery in our local galactic neighborhood. The massive, young stellar grouping, called R136, is only a few million years old and resides in the 30 Doradus Nebula, a turbulent star-birth region in the Large Magellanic Cloud (LMC), a satellite galaxy of our Milky Way. There is no known star-forming region in our galaxy as large or as prolific as 30 Doradus. Many of the diamond-like icy blue stars are among the most massive stars known. Several of them are over 100 times more massive than our Sun. In a few million years, this region should provide an incredible show: that’s when these hefty stars are destined to pop off like a string of firecrackers, as supernovas.

The image, taken in ultraviolet, visible, and red light by Hubble’s Wide Field Camera 3, spans about 100 light-years. The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the birth and evolution of stars in the universe. The Hubble observations were taken Oct. 20-27, 2009. The blue color is light from the hottest, most massive stars; the green from the glow of oxygen; and the red from fluorescing hydrogen.

Ground-based version of the Doradus Constellation. Credit: A. Fujii
Ground-based version of the Doradus Constellation. Credit: A. Fujii

The LMC is located 170,000 light-years away and is a member of the Local Group of Galaxies, which also includes the Milky Way.

Click here for larger (and eye-popping!) versions of this image.

You can also “zoom” in and out of this image here on the “Starry Critters” website.
Source: HubbleSite

Posted on by Nancy Atkinson

Hubble Captures Birth, Annihilation of Young Solar Systems in Orion Nebula

Young stellar objects with circumstellar disk, as seen in the Orion Nebula by Hubble Space Telescope. These newly forming stars may one day also have planetary systems around them.
Young stellar objects with circumstellar disk, as seen in the Orion Nebula by Hubble Space Telescope. These newly forming stars may one day also have planetary systems around them.

Looking deep inside the Orion Nebula, the Hubble Space Telescope has captured a stunning collection of protoplanetary disks – or proplyds – which are embryonic solar systems in the making. Using Hubble’s Advanced Camera for Surveys (ACS), researchers have discovered 42 protoplanetary blobs, which are being illuminated by a bright star cluster. These disks, which sometimes appear like boomerangs, arrows, or space jellyfish, surround baby stars and are shedding light on the mechanism behind planet formation.

One of 42 new proplyds discovered in the Orion Nebula, 181-825 is one of the bright proplyds that lies relatively close to the nebula’s brightest star, Theta 1 Orionis C. Resembling a tiny jellyfish, this proplyd is surrounded by a shock wave that is caused by stellar wind from the massive Theta 1 Orionis C interacting with gas in the nebula. Credit: NASA/ESA and L. Ricci (ESO)
One of 42 new proplyds discovered in the Orion Nebula, 181-825 is one of the bright proplyds that lies relatively close to the nebula’s brightest star, Theta 1 Orionis C. It resembles a tiny jellyfish. Credit: NASA/ESA and L. Ricci (ESO)

As newborn stars emerge from the nebula’s mixture of gas and dust, proplyds form around them. The center of the spinning disc heats up and becomes a new star, but remnants around the outskirts of the disc attract other bits of dust and clump together. This is the beginning of a solar system.

But not all proplyds face a bright and happy future, even in these beautiful images.

Bright star that illuminates some of the proplyds is both a blessing and a curse. The disks that lie close to the brightest star in the cluster (Theta 1 Orionis C) are being zapped by the star’s powerful emissions. The radiation that lights them up and makes them visible also threatens their very existence. As the disk material begins to heat, it is very likely to dissipate and dissolve, destroying the potential for planets to form. Some of these proplyds will be torn apart; however others will survive and perhaps evolve into planetary systems.

One of 42 new proplyds discovered in the Orion Nebula, 321-602 is one of the dark proplyds that lies relatively far from the nebula’s brightest star, Theta 1 Orionis C. Credit: NASA/ESA and L. Ricci (ESO)
One of 42 new proplyds discovered in the Orion Nebula, 321-602 is one of the dark proplyds that lies relatively far from the nebula’s brightest star, Theta 1 Orionis C. Credit: NASA/ESA and L. Ricci (ESO)

Discs that are farther away do not receive enough energetic radiation from the star to heat up the gas and so they can only be detected as dark silhouettes against the background of the bright nebula, as the dust that surrounds these discs absorbs background visible light. By studying these silhouetted discs, astronomers are better able to characterize the properties of the dust grains that are thought to bind together and possibly form planets like our own.

A montage of 30 proplyds in the Orion Nebula. Credit: NASA/ESA and L. Ricci (ESO
A montage of 30 proplyds in the Orion Nebula. Credit: NASA/ESA and L. Ricci (ESO

The brighter discs are indicated by a glowing cusp in the excited material and facing the bright star, but which we see at a random orientation within the nebula, so some appear edge on, and others face on, for instance. Other interesting features enhance the look of these captivating objects, such as emerging jets of matter and shock waves.

It is rare to see proplyds in visible light, but the astronomers were able to use Hubble for this ambitious survey of the familiar and photogenic Orion Nebula.

Source: ESA