Another gorgeous image from Hubble! This close-up of NGC 7023, or the Iris Nebula, shows an area filled with cosmic dust. Illuminated from above by the nearby star HD 200775, the dust resembles pink cotton candy, accentuated with diamond-like stars. The “cotton candy” is actually made up of tiny particles of solid matter, with sizes from ten to a hundred times smaller than those of the dust grains we find on Earth, and the “diamonds” are both background and foreground stars.
The image was taken previous to Hubble’s recent servicing mission, using the Advanced Camera for Surveys. Astronomers also used Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) instrument to try to determine which chemical elements are present in the nebula.
NGC 7023 is a reflection nebula, which means it scatters light from the massive nearby star. Reflection nebulae are different from emission nebulae, which are clouds of gas that are hot enough to emit light themselves. Reflection nebulae tend to appear blue because of the way light scatters, but parts of the Iris Nebula appear unusually red-ish or pink.
Particulates from pollution mixing with clouds above the US (NASA)
[/caption]I bet some of you are fascinated with certain cloud formations. My eldest son once pointed to the sky, excited upon seeing a bunch of clouds taking shape of a menacing dragon. He was however disappointed after a few minutes when the dragon cloud slowly began to deform and fuse with the rest. So how are clouds formed?
First, water evaporates, rises, and fills up the atmosphere. The evaporated water, a.k.a. water vapor then clings to other numerous particles or dust found in the atmosphere. This dust comes from automobiles, fires, volcanoes, bacteria, and sea spray.
As water vapor rises, it cools. Now, the lower the temperature of air, its capacity to hold water vapor (also known as the saturation point of air) also drops.
Eventually, the rising water vapor condenses and forms the structure of the cloud. You can’t however see this structure unless it has its own color. Well, we know that clouds are either white or dark, and that’s why we’re able to see them.
Most clouds are white. That’s because water and ice particles that make up a cloud have just the right amount and sizes to scatter light in all possible wavelengths. When light of practically all wavelengths combine, the result is white light.
However, when too many water and ice particles build up, just like in a storm cloud, much of the scattered light is simply re-scattered into the cloud. In other words, too much particles prevent some of the light from escaping. Hence is the reason why storm clouds are dark.
Try slowly adding milk in water and notice how its color slowly shifts from white to dark as more milk is added.
I’m sure you’ve noticed that clouds easily form on mountains. How are clouds formed on mountains? When a wall of air and water vapor encounters a mountain side, it has nowhere else to go but up the slopes. Well, if you recall, rising water vapor cools and eventually condenses to form clouds.
Thus, mountains don’t have special particles that enhance cloud formation. Rather, it is the barriers that they so form that forces the water vapor to rise and hence develop into cloud structures. A cloud formed due to topographical features is called an orographic cloud.
We’ve got lots of articles about clouds here in Universe Today. For starters, here are two:
Cloud Types
Cirrus Clouds
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The Helix Nebula is one of the most familiar nebulae in astronomy, and it’s been nicknamed the “Eye of God”. Its official designation is NGC 7293, the Helix Nebula is located inside the constellation of Aquarius. The Helix Nebula is one of the closest examples of a planetary nebula. Astronomers have estimated its distance to only be 700 light-years away.
The central star of the Helix Nebula was once a star very similar to our own Sun. As the star neared the end of its life, it expanded into a red giant and puffed away its outer layers. The central star is destined to become a white dwarf star, as it slowly cools down. It’s no longer actively fusing hydrogen, and only shines with the remaining heat from when it was once a star.
The Helix Nebula that we see today is actually just a momentary phase in the death of the star. The inner layers of gas and dust expanding away from the central star were probably released about 6,500 years ago, with the outer layer released about 12,000 years ago. We can see them because they’re illuminated by the central star. But eventually they’ll get far enough away that they’re no longer bright enough to see. From that point on we’ll just see the central white dwarf star.
Because the Helix Nebula is so close, images from the Hubble Space Telescope revealed knots of material in the expanding shells of gas and dust. There are more than 20,000 of these knots in the nebula, and they have cometlike tails stretching away from the central star.
One of the most successful mission ever sent to Mars is the Mars Exploration Rover program, with the two rovers Spirit and Opportunity. They were launched separately to Mars in 2003 and landed safely several months later. They were supposed to last about 3 months on the surface of Mars, but have now survived more than 5 years.
Spirit and Opportunity used technology developed with the Mars Pathfinder mission. They used an airbag system to land on the surface of Mars without using retrorockets to touch down gently. They also use the rover technology first used with the Sojourner rover, but instead of operating from a base, Spirit and Opportunity were designed to be completely independent, able to communicate directly back to Earth.
The purpose of the Mars Exploration Rover mission (MER) was to search the surface of Mars for evidence of past water on the surface of Mars. Spirit landed in the huge Gusev Crater on Mars, a region that could have been an ancient lake on Mars. Opportunity touched down on the other side of the planet in a region called Meridiani Planum.
Both Spirit and Opportunity are equipped with solar panels that supply electricity to let them crawl around the surface of Mars, as well as their scientific instruments that let them study the surface of Mars and its rocks. They’re also equipped with a grinding tool that lets them scrape away the outer layer of rocks and see the material underneath.
Within just a few months of arriving on Mars, both Spirit and Opportunity fulfilled their mission objectives, and discovered evidence that large quantities of water used to be on the surface of Mars. Spirit discovered hints that water had acted on a rock called Humphrey, while Opportunity found layers of sedimentary rock that would have been formed by deposits in water. Both rovers continued to find additional evidence for the presence of water.
Over the course of their mission on the surface of Mars, both rover traveled several kilometers. Spirit climbed a small mountain, and Opportunity crawled into a large crater to sample the walls for evidence of past water. And both rovers continued to perform quite well, for many years beyond their original estimate life spans.
We have written many articles about the Mars Exploration Rovers for Universe Today. Here’s an article about the troubles for the Spirit rover, and here’s an article about Martian weather.
Mars and Venus are the two terrestrial planets most similar to Earth. One orbits closer to the Sun, and one orbits more distant to the Sun. But both are visible with the unaided eye, and two of the brightest objects in the night sky.
Venus orbits at an average distance of only 108 million km from the Sun, while Mars is an average of 228 million km. Venus gets as close to Earth as 38 million km, and Mars gets as close as 55.7 million km.
In terms of size, Venus is almost a twin planet of Earth. Its diameter is 12,104 km, which is 95% the diameter of Earth. Mars is much smaller, with a diameter of only 6,792 km. And again, in terms of mass, Venus is almost Earth’s twin. It has 81% the mass of Earth, while Mars only has 10% the mass of Earth.
The climates of Mars and Venus are very different, and very different from Earth as well. Temperatures on the surface of Venus average 461 °C across the entire planet. That’s hot enough to melt lead. While the average temperature on Mars is a chilly -46 °C. This temperature difference comes from the fact that Venus is closer to the Sun, but also because it has a thick atmosphere of heat trapping carbon dioxide. The atmosphere on Venus is nearly 100 times thicker than Earth’s atmosphere at sea level, while the atmosphere on Mars is 1% the thickness of Earth.
Mars is the most studied planet in the Solar System (after the Earth). There have been dozens of missions sent to Mars, including orbiters and rovers. Although many missions have been lost, there have been several that have successfully orbited the planet and several that have landed on the surface. Missions have also been sent to Venus, and you might be surprised to know that the Soviets sent a series of landers called Venera that actually reached the surface of Venus and survived long enough to send back a few photographs.
Mars has two moons, Phobos and Deimos, while Venus has no moons. And neither planet has rings.
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Mars Pathfinder was NASA mission to Mars, which launched on December 4th, 1996 and landed on the surface of Mars on July 4, 1997. Unlike the missions that went before it, the Pathfinder lander was also equipped with a tiny rover called Sojourner, which could venture away from the lander, crawl around the surface of Mars and study rocks up close. It was a relatively inexpensive mission that tested out many of the technologies build into later missions, like the Mars Exploration rovers Spirit and Opportunity.
The purpose of Pathfinder was to prove that the concept of “faster, better and cheaper” missions would work. Pathfinder only cost $150 million and was developed in under 3 years. It was also sent to study the surface of Mars, including the geochemistry of the rocks, the magnetic properties of the surface and the structure of the planet’s atmosphere.
When the Pathfinder mission arrived at Mars, it entered the atmosphere and deployed a parachute. Instead of using retrorockets to land gently on the surface, however, Pathfinder used an airbag system. This allowed it to save fuel; instead of landing gently, it was dropped from an altitude of about 100 meters onto the Martian surface. It bounced several times and came to a rest before opening up like the petals of a flower. Once everything checked out, the tiny Sojourner Rover was deployed onto the surface of Mars.
The area around the Pathfinder site had many rocks, large and small, and the NASA scientists gave them unique names like “Barnacle Bill” and “Yogi”. Sojourner was able to crawl around and study these rocks up close. It was able to study the chemical makeup of the rocks, and confirmed that they formed from past volcanic activity. Over the course of the entire mission, Pathfinder and Sojourner returned 16,500 images and made millions of measurements of the Martian atmosphere.
Pathfinder stopped communicating with Earth after 83 days on the surface of Mars. Its battery was only designed to be recharged 40 times, and once its battery stopped working, the spacecraft was unable to keep its electronics heated in the cold Martian night. After it stopped communicating, NASA decided to name the lander after Carl Sagan. It became The Carl Sagan Memorial Station.
An artist's impression of how quasars may be able to construct their own galaxies. Image Credit: ESO/L. Calcada
The birth of galaxies is quite a complicated affair, and little is known about whether the supermassive black holes at the center of most galaxies formed first, or if the matter in the galaxy accreted first, and formed the black hole later. Observations of the quasar HE0450-2958, which is situated outside of a galaxy, show the quasar aiding a nearby galaxy in the formation of stars. This provides evidence for the idea that supermassive black holes can ‘build’ their own galaxies.
The quasar HE0450-2958 is an odd entity: normally, supermassive black holes – also known as quasars – form at the center of galaxies. But HE0450-2958 doesn’t appear to have any host galaxy out of which it formed. This was a novel discovery in its own right when it was made back in 2005. Here’s our original story on the quasar, Rogue Supermassive Black Hole Has No Galaxy.
The formation of the quasar still remains a mystery, but current theories suggest that it formed out of cold interstellar gas filaments that accreted over time, or was somehow ejected from its host galaxy by a strong gravitational interaction with another galaxy.
The other oddity about the object is its proximity to a companion galaxy, which it may be aiding to form stars. The companion galaxy lies directly in the sights of one of the quasar’s jets, and is forming stars at a frantic rate. A team of astronomers from France, Germany and Belgium studied the quasar and companion galaxy using the Very Large Telescope at the European Southern Observatory. The astronomers were initially looking to find an elusive host galaxy for the quasar.
The phenomenon of ‘naked quasars’ has been reported before, but each time further observations are made, a host galaxy is found for the object. Energy streaming from the quasars can obscure a faint galaxy that is hidden behind dust, so the astronomers used the VLT spectrometer and imager for the mid-infrared (VISIR). Mid-infrared observations readily detect dust clouds. They combined these observations with new images obtained from the Hubble Space Telescope in the near-infrared.
Observations of HE0450-2958, which lies 5 billion light years from Earth, confirmed that the quasar is indeed without a host galaxy, and that the energy and matter streaming out of the jets is pointed right at the companion galaxy. This scenario is ramping up star formation in that galaxy: 340 solar masses of stars a year are formed in the galaxy, one-hundred times more than for a typical galaxy in the Universe. The quasar and the galaxy are close enough that they will eventually merge, finally giving the quasar a home.
David Elbaz of the Service d’Astrophysique, who is the lead author of the paper which appeared in Astronomy & Astrophysics, said “The ‘chicken and egg’ question of whether a galaxy or its black hole comes first is one of the most debated subjects in astrophysics today. Our study suggests that supermassive black holes can trigger the formation of stars, thus ‘building’ their own host galaxies. This link could also explain why galaxies hosting larger black holes have more stars.”
‘Quasar feedback’ could be a potential explanation for how some galaxies form, and naturally the study of other systems is needed to confirm whether this scenario is unique, or a common feature in the Universe.
What accretes quietly in the night and can be a blast to observe? Try a FUor… These high accretion, high luminosity phase pre-main sequence stars may only last a few decades – but display an extreme change in magnitude and spectral type in a very short period of time. While FU Orionis may be the prototype you know about, there’s a lot more to learn and even more to observe! Step outside in the dark with me and let’s take a look…
What we know so far about FU Orionis-type stars is they flare with abrupt mass transfer from an accretion disc onto a young, low mass T Tauri-type star. In itself, this is very exciting because nearly half of T Tauri stars have circumstellar disks or protoplanetary discs. These could very well be the forerunners of planetary systems similar to our own solar system! How do we know there is a disc there? Try variablility. “Variable circumstellar extinction is pointed out as responsible for the conspicuous variations observed in the stellar continuum flux and for concomitant changes in the emission features by contrast effect. Clumpy structures, incorporating large dust grains and orbiting the star within a few tenths of AU, obscure episodically the star and, eventually, part of the inner circumstellar zone, while the bulk of the hydrogen lines emitting zone and outer low-density wind region traced by the [OI] remain unaffected.” says E. Schisano (et al), “Coherently with this scenario, the detected radial velocity changes are also explainable in terms of clumpy materials transiting and partially obscuring the star.”
While accretion rates for a FUor could range anywhere from 4 to 10 solar masses annually and its eruptions last up to a year or longer, astronomers believe their entire lifetimes only last a few decades. The proto-star itself may also be limited to undergoing an average of one to two eruptions each year. “The brightness of FUors increases by several magnitudes within one to several years. The currently favored explanation for this brightness boost is that of dramatically rising accretion from the disc material around a young star. The mechanism leading to this accretion increase is a point of debate.” says S. Pfalzner, “The induced accretion rates, the overall temporal accretion profile, the decay time, and possibly the binarity rate we obtain for encounter-induced accretion agree very well with observations of FUors. However, the rise time of one year observed in some FUors is difficult to achieve in our simulations unless the matter is stored somewhere close to the star and then released after a certain mass limit is transgressed. The severest argument against the FUors phenomenon being caused by encounters is that most FUors are found in environments of low stellar density.”
Surprisingly enough, even given the short period of time in which a FUor exists, no one has ever seen one phase out. “A cross-correlation analysis shows that FUor and FUor-like spectra are not consistent with late-type dwarfs, giants, nor embedded protostars. The cross-correlations also show that the observed FUor-like HH energy sources have spectra that are substantively similar to those of FUors.” says Thomas P. Greene (et al), “Both object groups also have similar near-infrared colors. The large line widths and double-peaked nature of the spectra of the FUor-like stars are consistent with the established accretion disk model for FUors, also consistent with their near-infrared colors. It appears that young stars with FUor-like characteristics may be more common than projected from the relatively few known classical FUors.”
Just how common and observable are these unusual characters? A lot more than you might think. According to Bo Reipurth (et al); “The original FUor class was defined by a small number (5-6) of pre-main sequence stars that had been observed to brighten up by 3-6 magnitudes on time scales of 1-10 years. The class has since been augmented by a comparable number of stars that have similar spectra or SEDs to the classical FUors, but that have not been observed to behave photometrically in that way. It is likely that the FUor phenomenon is recurrent, but it is not at all clear whether it is a property shared by ordinary T Tauri stars, or whether it is confined to a special minority among them. It is important that more examples be found, and found promptly, and as the result of systematic search rather than by accident as has been the case in the past. The goal would be to examine, on a regular monthly basis, all the molecular clouds within about 2 kpc that lie along the galactic plane and Gould’ s Belt for faint (or previously invisible) stars that had brightened up by a magnitude or more. It is essential that any such detections be followed up spectroscopically as soon as possible, to weed out interlopers: flare stars, cataclysmic variables, Miras, and EXors (the latter also being pre-main sequence but which unlike FUors soon return to their original brightness level, usually in a year or less). All of these objects are readily distinguishable from one another even at modest spectroscopic resolution. Such an on-going survey would serve also to follow the development of FUors.”
So let’s do the FUor dance!
IRAS 09068 641 FU Ori type object - Joe Brimacombe
According to CBET 2033 released on November 21, 2009 from the International Astronomical Union: “The discovery of a possible FU-Ori-type eruption (see Hartmann and Kenyon 1996, ARAA 34, 207) is located at R.A. = 6h09m19s.32, Decl. = -6o41’55”.4 (equinox 2000.0), and coincident with the infrared source IRAS 06068-0641. Discovered by the CRTS on Nov. 10, it has been continuously brightening from at least early 2005 (when it was mag 14.8 on unfiltered CCD images) to the present magnitude of 12.6, and may possibly brighten further. On recent images, a faint cometary reflection nebula is visible to the east. A spectrum (range 350-900 nm), taken with the SMARTS 1.5-m telescope at Cerro Tololo, on November 17, shows H-alpha in emission, all other Balmer lines and He I (at 501.5 nm) in absorption, and a very strong Ca II infrared triplet in emission, confirming it to be a young stellar object. The object lies inside a dark nebula to the south of the Mon R2 association, and is likely related to it. In addition, also inside this dark nebula, a second object at R.A. = 6h09m13s.70, Decl. = -6o43’55”.6, coincident with IRAS 06068-0643, has been varying between mag 15 and 20 over the past few years, reminiscent of UX-Ori-type objects with very deep fades. Also, this second object supports a variable cometary reflection nebula, extending to the north. The spectrum of this object also shows H-alpha and the strong Ca II infrared triplet in emission.”
Visible? Yeah. You know it. And here are the wide field results as taken by Joe Brimacombe…
IRAS 06068 641 FU Ori type widefield - Joe Brimacombe
“A smaller site of ongoing star formation in the Mon R2 molecular cloud are the objects associated with GGD 16 and 17. To the south of GGD 17, the T Tauri star Bretz 4 is probably associated with the GGD object. This star has been studied spectroscopically and was classified by as a K4 spectral type with a class 5 emission spectrum.” says Carpenter and Hodapp, “The infrared source IRS 2 is positionally coincident with Bretz 4, while the more deeply embedded IRS 1 has no optical counterpart and lies between the GGD objects. A detailed optical study showed that GGD 17 is part of a curved jet extending north of the star Bretz 4 and consisting of HH 271, and possibly also HH 273. Nebulosity close to the star shows the typical morphology of scattered light from an outflow cavity wall. The embedded infrared objects and optical reflection nebulosity in the general GGD 16-17 region is associated with 850 um emission.”
Capture a FUor… It may be the most unusual thing you’ve ever done!
Many thanks to Joe Brimacombe for the awesome images and awakening my ‘FUor’ curiousity!
Following today’s departure of the three man crew of Expedition 21 aboard the Soyuz TMA 15 capsule, staffing on the International Space Station (ISS) is now temporarily reduced to a skeleton crew of just 2 men for the first time since July 2006. The ISS had hosted a complete 6 person and truly international crew complement for the first time ever since its inception, starting in May of this year.
Soyuz Commander Roman Romanenko (Russia), European Space Agency Flight Engineer Frank De Winne (Belgium) and Canadian Space Agency Flight Engineer Bob Thirsk floated into their three segment Soyuz return capsule on Monday evening, Nov 30. After powering up systems and a farewell ceremony the hatches were closed at 7:43 PM EST. They disengaged hooks and latches and then physically undocked from the Zarya module at 10:56 PM over Mongolia after spending 188 days in space. De Winne was the first European commander of the ISS. All prior commanders have been either Russian or American. Romanenko is a second generation cosmonaut. His father Yuri, flew his first mission in 1980. Thirsk is the first long duration Canadian astronaut. Soyuz TMA 15 landing track. Credit: NASA TV
Retro rockets were fired for 4 min 19 sec at 1:26 AM Tuesday morning to initiate the de-orbit braking maneuver for the fiery plunge of atmospheric reentry. 19 minutes later the three Soyuz segments pyrotechnically separated at an altitude of 87 miles. The Soyuz barreled backwards as it hit the earth’s atmosphere at 400,000 ft above Africa and the crew experienced maximum G forces. The three parachuted to a safe touchdown strapped inside their Soyuz descent module onto the snowy steppes of Kazakhstan at 2:15 AM Tuesday Dec 1 (1:15 PM Kazakhstan local time) thereby concluding a mission that began with a May 27 blast off. Russian search and recovery forces drove to the ice cold landing zone at Arkalyk to greet and assist the trio in opening the hatch, exiting the craft, readapting to earth’s gravity and returning to Star City. This was the first December landing of a Soyuz since 1990.
Poor icy weather and low clouds grounded the normal recovery force of 8 helicopters. The capsule landed right on target and in an upright configuration. Recovery forces sped quickly into place. Romanenko was first to depart out the top hatch of the capsule, followed by Thirsk and De Winne. They were carefully extracted by the ground based recovery team and immediately assisted into stretchers while smiling broadly and waving to the crowd. Then they were swiftly slid into all terrain vehicles larger than their capsule for the initial leg of the ride back to Russia. Flight surgeons confirmed the health of the crew who are eager to re-unite with family and friends and earthly comforts.
The Expedition 22 core crew of NASA Commander Jeff Williams and Russian Flight Engineer Max Suraev remain as the sole two occupants for about three weeks until the Dec 23 arrival of the next international crew comprising Russian cosmonaut Oleg Kotov, NASA’s T.J. Creamer, and Soichi Noguchi of the Japan Aerospace Exploration Agency who head to the station Dec. 20 on the Soyuz TMA-17 craft from the Baikonur Cosmodrome. Williams and Suraev arrived by Soyuz capsule TMA -16 in October.
US astronaut Nicolle Stott rounded out the six person ISS crew until her departure just days ago on Nov 25 aboard shuttle Atlantis (link) left just five people on board. She spent 91 days aloft conducting science experiments and has the distinction of being the last ISS resident to hitch a ride up and down on a shuttle. Future crew rotations are planned via Russian Soyuz rockets since the shuttle will be retired by late 2010 and NASA’s Ares / Orion launch system won’t debut until 2015 or later.
During 7 days of joint operations in late November, the ISS boasted an ethnically diverse population of 12 humans from the combined crews of STS 129 Atlantis and the resident ISS members from two docked Soyuz capsules, just shy of the record 13 occupants. With all the comings and goings of assorted manned and robotic spaceships lately it’s been an exceptionally busy time that required careful planning and traffic coordination among the world’s space agencies.
The 800,000 pound station is now 86% complete and thus far larger and more complex compared to the last instance of a two person contingent. Since the 2005 Return to Flight of the shuttle following the Columbia accident, several habitable modules (Harmony, Columbus, Kibo, Poisk), truss segments, radiators, stowage platforms and giant solar arrays have been attached. All this has vastly expanded the astronauts and cosmonauts daily responsibilities of both maintaining station systems and carrying out a much expanded scientific research program.
Bill Gerstenmaier, NASA’s chief of space operations, said the ISS partners have carefully looked at the operational challenges of this three week interlude to make sure “there is not a lot of activity going on then, other than some software uploads. We moved all the major activities that were occurring to other periods when there will be more crew. We are prepared and ready to cut back a little on operations but still be able to do a little bit of science research with just two crew members on orbit.”
Atlantis delivered two large pallets loaded with 15 tons of critical spare parts that will help extend the working lifetime of the ISS and serve as a hedge against on orbit equipment failures ahead of the fast approaching deadline when the space shuttle is no longer available to loft such bulky gear.
Only 5 flights remain until the shuttle era ends late in 2010. The Orion capsule will not debut for at least five years and perhaps longer, dependent on funding decisions in Washington, DC. The station will then be completely dependent for supplies and equipment on Russian, European and Japanese cargo vehicles. Test flights of US commercial ISS transport vessels begin next year.
Not until another three person Soyuz blasts off next April 2010, will the station return to a full team of six. But science research will be full speed ahead.
