Universe Today

December 4, 2008December 24, 2015 by Nancy Atkinson

Iran to Launch Animals to Space

Kavoshgar rocket. Credit: Satnews Daily

Iran is planning to launch animals into space. According to Mohammed Ebrahimi from Iran’s Aerospace Research Institute, in the near future, the Kavoshgar-3 and -4 rockets will use animals as test passengers before they attempt a human mission. On November 26, Iran successfully launched its second space rocket, the Kavoshgar-2, which contained a space lab and a data-monitoring and processing unit. This Iranian rocket is fully capable of packing a small payload and then re-entering Earth’s atmosphere with a high degree of accuracy, according to reports. They will attempt two more test flights before trying to launch a working satellite into orbit with a larger rocket, the Safir-e Omid (or Ambassador of Peace) rocket. In August, Iran claimed they successfully launched a dummy satellite into space, which was refuted by the US. Officials from Iran insist the country’s space program is non-military in nature.

No information was released about what kinds of animals would be launched. On Nov. 26 Iranian state television reported that the Kavoshgar-2 completed its mission and returned to Earth via parachute after 40 minutes, and that the rocket had been designed and built by Iranian aerospace experts.

Much of Iran’s technological equipment derives from modified Chinese and North Korean technology. Earlier in November, Iran said it had also test-fired a new medium-range missile. Its 2,000-km (1,240-mile) range would be capable of reaching Western Europe. However, Iran denies that its long-range ballistic technology is linked to its atomic program.

The country is already under international pressure to give up its nuclear work, which it says is purely civilian.

Sources: Satnews Daily, BBC

December 4, 2008December 24, 2015 by Nancy Atkinson

Mars Science Laboratory Mission Delayed Two Years

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NASA’s Mars Science Laboratory has been delayed for two years and will now launch in the fall of 2011. The decision to delay is based on various technical problems the MSL team has encountered and having enough time to work through the problems, as well as provide adequate time for testing all the systems on the car-sized rover. The main problems are the actuators, the gear boxes for all the moving parts. Mars program manager Doug McCuistion said the team is actually only a few months behind schedule, but in going to Mars, that doesn’t matter since a launch window to the Red Planet only comes once every 26 months. “We know these actuator motors must work on Mars and we’ve got anomalies on some of them we don’t understand,” said McCuistion. “It’s the right thing to delay the mission to take the appropriate time to understand the technical issues and test everything thoroughly.”

“Failure is not an option for this mission,” said Ed Weiler, NASA’s associate administrator for science.

The MSL mission will send a next-generation rover with unprecedented research tools to study the early environmental history of Mar, with the fundamental purpose to explore if the conditions for microbial life on Mars ever existed, or if they exist now.

The slip to 2011 will cost $400 million, making the total cost the mission about 2.2-2.3 billion in life cycle costs.

Weiler said there will some “pain” in planetary science and other Mars missions, but there will be paybacks, and no cancelations of any missions or programs are expected. There could be subsequent delays in other missions, however.

“There’s nobody who would like to launch in 2009 more than this team,” said JPL Director Charles Elachi. “These are the same people who put the face of NASA on the front page of newspapers the past few years with our other Mars missions. Unfortunately despite full support by NASA headquarters and the contractors, we just came a little short on time. The plan is to understand these technical issues, look for solution and do a very comprehensive test program. You can’t rely on luck to be successful on Mars.”

The vast majority of the hardware for the rover has been completed, but not everything is working well, particularly the actuators. NASA officials at today’s press conference all said they can’t send MSL to Mars without knowing everything they can about the issues with the actuators.

“The actuators are basically motors in a gear box,” said McCuistion. “All our landers have robotic actuators, and they enable the rover to do what they do: to drive and stop, they run the elbow and wrist join for the robotic arm and drills in sample handling devices. That’s why they are absolutely crucial to these missions. If the actuators can’t move, we essentially have junk on the surface of Mars.”

There are 31 different actuators on MSL, and 60 flight actuators and 45 engineering actuators are being built. Some of the problems have come from the manufacturing side with workmanship, and the most recent issue is drag torque issues within the devices. “The criticality and the number of these actuators is key,” said Elachi. “These actuators are much more massive than for MER mission since the MSL rover is about 8 times bigger, and they are very sophisticated.”

When asked if NASA had considered canceling the MSL mission, Griffin said absolutely not. “Before canceling I’d have to believe the project is going badly in a technical sense, but it’s not. When you’re doing things that have never been done before, you’re likely to encounter unforeseen difficulties. But just having difficulties is no cause to cancel. We had problems with Hubble, and we had problems with COBE, but I don’t think today anyone regrets having Nobel prize winning science from these missions. Unless you’re interested in building cookie cutter copies of previous spacecraft, and nobody is interested in doing that, you’ll encounter problems with hardware that’s never been built before.”

Source: NASA TV

December 3, 2008December 24, 2015 by Ian O'Neill

Swift Detects X-Ray Emissions from Comets

Swift's Ultraviolet/Optical Telescope (UVOT) captured Comet 73P/Schwassmann-Wachmann 3's fragment C as it passed the famous Ring Nebula (oval, bottom) on May 7, 2006 (NASA)

[/caption]Things appeared to get a little strange in the field of X-ray astronomy when the NASA/ESA ROSAT observatory started seeing emissions from a series of comets. This discovery in 1996 was a conundrum; how could X-rays, more commonly associated with hot plasmas, be produced by some of the coldest bodies in the Solar System? In 2005, NASA’s Swift observatory was launched to look out for some of the most energetic events in the observable Universe: gamma-ray bursts (GRBs) and supernovae. But in the last three years, Swift has also proven itself to be an expert comet hunter.

If X-rays are usually emitted by multi-million Kelvin plasmas, how can X-rays possibly be generated by comets composed of ice and dust? It turns out there is an interesting quirk as comets interact with the solar wind within 3AU from the solar surface, allowing instrumentation designed to observe the most violent explosions in the Universe to also study the most elegant objects closer to home…

“It was a big surprise in 1996 when the NASA-European ROSAT mission showed that comet Hyakutake was emitting X-rays,” said Dennis Bodewits, NASA Postdoctural Fellow at the Goddard Space Flight Centre. “After that discovery, astronomers searched through ROSAT archives. It turns out that most comets emit X-rays when they come within about three times Earth’s distance from the sun.” And it must have been a very big surprise for researchers who assumed ROSAT could only be used to glimpse the transient flash of a GRB or supernova, possibly spawning the birth of black holes. Comets simply did not feature in the design of this mission.

However, since the launch of another GRB hunter in 2005, NASA’s Swift Gamma-ray Explorer has spotted 380 GRBs, 80 supernovae and… 6 comets. So how can a comet possibly be studied by equipment intended for something so radically different?

As comets begin their death-defying sunward orbit, they heat up. Their frozen surfaces begin to blast gas and dust into space. Solar wind pressure causes the coma (the comet’s temporary atmosphere) to eject gas and dust behind the comet, away from the Sun. Neutral particles will be carried away by solar wind pressure, whereas charged particles will follow the interplanetary magnetic field (IMF) as an “ion tail”. Comets therefore can often be seen with two tails, a neutral tail and an ion tail.

This interaction between the solar wind and comet has another effect: charge exchange.

Energetic solar wind ions impact the coma, capturing electrons from neutral atoms. As the electrons become attached to their new parent nuclei (the solar wind ion), energy is released in the form of X-rays. As the coma can measure several thousand miles in diameter, the comet atmosphere has a huge cross section, allowing a vast number of these charge exchange events to occur. Comets suddenly become significant X-ray generators as they get blasted by solar wind ions. The total power output from the coma can top a billion Watts.

Charge exchange can occur in any system where a hot stream of ions interact with a cooler neutral gas. Using missions such as Swift to study the interaction of comets with the solar wind can provide a valuable laboratory for scientists to understand otherwise confusing X-ray emissions from other systems.

Source: Physorg.com

December 3, 2008December 24, 2015 by Nancy Atkinson

Seeing Venus in a New Light

Venus in ultraviolet. Credits: ESA/MPS/DLR/IDA

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New images taken by instruments on board ESA’s Venus Express are providing insight into the turbulent atmosphere of our neighboring planet. When viewed in beyond visible light, the ultraviolet reveals the structure of the clouds and the dynamic conditions in the atmosphere of Venus, where the infrared provides information on the temperature and altitude of the cloud tops. Most intriguing are the puzzling dark and bright zones seen on Venus in ultraviolet.

Scientists have seen equatorial areas on Venus that appear dark in ultraviolet light, and have been mystified by them. The new views with Venus Express show the cause of these different colored areas is the uneven distribution of a mysterious chemical in the atmosphere that absorbs ultraviolet light, creating the bright and dark zones. While the scientists haven’t been able to identify the chemical, they have figured out the process that causes the changes in cloud types across Venus.

Professor Fred Taylor, one of the Venus Express scientists, from Oxford University said, “The features seen on Venus in ultraviolet light have been a puzzle to astronomers for nearly a century. These new images have revealed the structure in the clouds that produces them and shows how they result from complex meteorological behaviour. We can now study in much greater detail and try to understand the origin of features such as the large hurricane-like vortex over the north and south poles. Like many things on Venus, including global warming, this feature has similarities to atmospheric and environmental process on Earth, but the Venus version is much more extreme.”

With data from Venus Express, scientists have learned that the equatorial areas on Venus that appear dark in ultraviolet light are regions of relatively high temperature, where intense convection brings up dark material from below. In contrast, the bright regions at mid-latitudes are areas where the temperature in the atmosphere decreases with depth.

Venus in infrared and ultraviolet. Credits: VMC ultraviolet image: ESA/MPS/DLR/IDA VIRTIS infrared image: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

Observations in the infrared have been used to map the altitude of the cloud tops. Researchers were surprised to find the clouds in both the dark tropics and the bright mid-latitudes are located at about the same height of about 72 km.

Sources: ESA, Science & Technology Facilities Council

December 3, 2008December 24, 2015 by Nancy Atkinson

Head-sized Meteorite Found From Canadian Fireball

The 13 kg meteorite is roughly the size of a human head. Bruce McCurdy, Edmonton Space & Science Foundation / Royal Astronomical Society of Canada)

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Several more fragments have been found from the 10-ton asteroid that exploded over western Canada on November 20, including a head-sized piece weighing 13-kilograms (28 lbs). Imagine that landing on your house or car (or head!). University of Calgary professor Alan Hildebrand, who is leading the search estimates there could be 2,000 fragments per hectare (about 2.5 acres) in the area near where fragments were initially found. The asteroid is becoming known as the Buzzard Coulee fireball, named after the picturesque, but luckily uninhabited valley where the first pieces were located. Check out the website of Bruce McCurdy of Edmonton Space & Science Foundation and the Royal Astronomical Society of Canada, who has joined in the search for more meteorite images.

More than two dozen pieces of the asteroid have been found by researchers or members of the public. The search is focused on a 24-square-kilometer section of agricultural land along the Battle River where the scientists calculated the debris would be located. Hildebrand was appreciative all the eyewitness reports and help from the public in obtaining as much information as possible about the fireball that lit up the sky. “I was gratified that my first prediction was close,” he said of his estimate of where the fragments could be found. “We couldn’t have done this so quickly without the eyewitnesses and security camera records, and we still need the security camera records to determine the pre-fall orbit of this asteroid.”

Searchers from the University of Calgary have been joined by other members of the Canadian Space Agency-funded Small Bodies Discipline Working Group, as well as members of the public who wanted to join the search and find a chunk of history. A father and son team found the big 13 kg piece, which was given to the rancher that owned the land on which it was found.

Sources: Bruce McCurdy’s website, University of Calgary

December 3, 2008December 24, 2015 by Tammy Plotner

Microscopium

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The small constellation of Microscopium resides just south of the ecliptic plane and was created by Nicolas Louis de Lacaille. It was adopted by the International Astronomical Union and accepted as one of the permanent 88 modern constellations. Microscopium covers approximately 210 square degrees of sky and contains 5 very dim stars in its asterism. It has 13 Bayer/Flamsteed designated stars within its confines and is bordered by the constellations of Capricornus, Sagittarius, Telescopium, Indus, Grus and Piscis Austrinus. It can be seen by observers located at latitudes between +45° and ?90° and is best seen at culmination during the month of September.

Because Microscopium is considered a “new” constellation, it has no mythology associated with it – but Nicolas Louis de Lacaille was a man of science and the constellation names he chose to add to his southern star catalog – Coelum Australe Stelliferum – favored this love of technological advances. During Lacaille’s time, the microscope wasn’t a particular new invention, having been created by Hans Lippershey (who also developed the first real telescope) over 100 years earlier, but it was making some serious optical advances when Anton van Leeuwenhoek’s work popularized it in Lacaille’s world. Although the dim stars bear no real resemblance to an actual microscope – who can fault him for his love of science and optics? After all… He was exploring the southern hemisphere with a half inch diameter spyglass and discovering all kinds of deep sky wonders!

Let’s begin our binocular tour of Microscopium with barely visible Alpha Microscopii – the “a” symbol on our map. At a distance of 380 light years from Earth, this G-class giant star shines with the candlepower of 163 Suns. It’s a helium fusing customer – busy working on developing its carbon-oxygen core and just minding its own business. Alpha ignited some 420 million years ago as a class B8 hydrogen-fusing dwarf and has been quiet ever since… But take a closer look in a telescope. Do you see a 10th magnitude companion star? Say hello to Alpha B. While many folks might argue that Alpha B isn’t a true binary star companion, research has shown that it has it has moved seven arc seconds closer to the primary since 1834. A pretty good indication or orbital motion, don’t you think?

Now turn your binoculars toward Theta 1 Microscopii – the curved “U1″ on our map. Here we have a variable star – but not by much. Theta1 Microscopii is an Alpha CV type star with a very small magnitude range of 4.77 to 4.87 every 2 days, 2 hours and 55 minutes. Not revealed on our map (because the symbols would be too close) is Theta 2 just to the southeast (21h 24.4m, -41 00′). Theta 2 is a very nice binary star, but it will require the use of a telescope at high magnification to split this 6.4 and 7th magnitude pair. Theta 1 and 2 will be a great optical double star for binoculars!

Get out the big telescope and let’s take a look at NGC 6925 (RA 20h 34.3m, Dec. -31 59′). At slightly fainter than magnitude 11, this inclined spiral galaxy is going to require dark skies to get a view, but it’s worth it. NGC 6925 is home to a mega-maser – water vapor being collected in the black hole of an active galactic nuclei! Look for a very stellar nucleus and just a wisp of extension.

More? Then try your luck with NGC 7057 (RA 21h 24m 58.5s Dec -42° 27′ 38.0”). This little elliptical galaxy runs around magnitude 12 and it isn’t going to be easy, either. What challenge is? Since it is a very isolated elliptical, it was used in studies to compare star formation rates between interacting and merging galaxies as opposed to those with no close companions. Believe it or not, according to Bergvall (et al) “from the global star formation aspect, generally (they) do not differ dramatically from scaled up versions of normal, isolated galaxies.”

How about IC 5105 (21h 24m 22.0s Dec -40° 32′ 14.0″)? Let us know if you see anything there! Supposedly there is an elliptical galaxy in this position and it has been studied for its stellar population and infrared emissions. Maybe we need infrared just to see it! Kinda’ like Microscopium, huh?

Sources:
http://www.ianridpath.com/startales/microscopium.htm
http://www.astro.wisc.edu/~dolan/constellations/constellations/Microscopium.html

Chart courtesy of Your Sky.

December 3, 2008December 24, 2015 by Nancy Atkinson

Astronomers ‘Time Travel’ to 16th Century Supernova

Tycho's Supernova Remnant. Credit: Spitzer, Chandra and Calar Alto Telescopes.

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On November 11, 1572 Danish astronomer Tycho Brahe and other skywatchers observed what they thought was a new star. A bright object appeared in the constellation Cassiopeia, outshining even Venus, and it stayed there for several months until it faded from view. What Brahe actually saw was a supernova, a rare event where the violent death of a star sends out an extremely bright outburst of light and energy. The remains of this event can still be seen today as Tycho’s supernova remnant. Recently, a group of astronomers used the Subaru Telescope to attempt a type of time travel by observing the same light that Brahe saw back in the 16th century. They looked at ‘light echoes’ from the event in an effort to learn more about the ancient supernova.

A ‘light echo’ is light from the original supernova event that bounces off dust particles in surrounding interstellar clouds and reaches Earth many years after the direct light passes by; in this case, 436 years ago. This same team used similar methods to uncover the origin of supernova remnant Cassiopeia A in 2007. Lead project astronomer at Subaru, Dr. Tomonori Usuda, said “using light echoes in supernova remnants is time-traveling in a way, in that it allows us to go back hundreds of years to observe the first light from a supernova event. We got to relive a significant historical moment and see it as famed astronomer Tycho Brahe did hundreds of years ago. More importantly, we get to see how a supernova in our own galaxy behaves from its origin.”

The view of the light echoes from Tycho’s supernova. Credit: Subaru Telescope

On September 24, 2008, using the Faint Object Camera and Spectrograph (FOCAS) instrument at Subaru, astronomers looked at the signatures of the light echoes to see the spectra that were present when Supernova 1572 exploded. They were able to obtain information about the nature of the original blast, and determine its origin and exact type, and relate that information to what we see from its remnant today. They also studied the explosion mechanism.

What they discovered is that Supernova 1572 was very typical of a Type Ia supernova. In comparing this supernova with other Type Ia supernovae outside our galaxy, they were able to show that Tycho’s supernova belongs to the majority class of Normal Type Ia, and, therefore, is now the first confirmed and precisely classified supernova in our galaxy.

This finding is significant because Type Ia supernovae are the primary source of heavy elements in the Universe, and play an important role as cosmological distance indicators, serving as ‘standard candles’ because the level of the luminosity is always the same for this type of supernova.

For Type Ia supernovae, a white dwarf star in a close binary system is the typical source, and as the gas of the companion star accumulates onto the white dwarf, the white dwarf is progressively compressed, and eventually sets off a runaway nuclear reaction inside that eventually leads to a cataclysmic supernova outburst. However, as Type Ia supernovae with luminosity brighter/fainter than standard ones have been reported recently, the understanding of the supernova outburst mechanism has come under debate. In order to explain the diversity of the Type Ia supernovae, the Subaru team studied the outburst mechanisms in detail.

This observational study at Subaru established how light echoes can be used in a spectroscopic manner to study supernovae outburst that occurred hundreds of years ago. The light echoes, when observed at different position angles from the source, enabled the team to look at the supernova in a three dimensional view. This study indicated Tycho’s supernova was an aspherical/nonsymmetrical explostion. For the future, this 3D aspect will accelerate the study of the outburst mechanism of supernova based on their spatial structure, which, to date, has been impossible with distant supernovae in galaxies outside the Milky Way.

The results of this study appear in the 4 December 2008 issue of the science journal Nature.

Source: Subaru Telescope

December 3, 2008December 24, 2015 by Tammy Plotner

Mensa

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The southern circumpolar constellation of Mensa was created by Nicolas Louis de Lacaille and was originally named Mons Mensae. It was later changed and adopted by the International Astronomical Union and accepted as one of the permanent 88 modern constellations. Mensa encompasses only 153 square degrees of sky – ranking 75th in size. It possesses no bright stars and only 4 stars form its cup-shaped asterism. There are, however, 16 Bayer/Flamsteed designated stars within its confines. Mensa is bordered by the constellations of Chamaeleon, Dorado, Hydrus, Octans and Volans. It is visible to observers positioned at latitudes between +18° and ?90° and is best seen at culmination during the month of January.

There is an annual meteor shower connected with this constellation is called the Delta Mensids – so named because the meteors appear to radiate from a point in the sky close to the star Delta Mensae. The meteor shower begins on or about March 14 and lasts until about March 21. Studies have shown there may be two seperate meteoriod streams responsible for this shower – one which causes a maximum on or about March 18 and another on or about March 19 with the debris suspected to have originated from Comet Pons, which was visible in 1804. Just as Mensa isn’t much of a constellation, the Delta Mensids aren’t much a meteor shower, either… The maximum fall rate only averages about 1 to 2 per hour at most.

Since Mensa is considered a relatively “new” constellation, there is no mythology associated with it, but there are several legends about how it came to be so named. It is believed that Nicolas Louis de Lacaille called in “Mons Mensae” in honor of Table Mountain, which overlooked his home observatory in Cape Town, South Africa. Since the top of the flat mountain was often covered by clouds, and the stellar formation is topped by the Large Magellanic Cloud, the name seems to fit perfectly! There is also a tall tale of a man who loved to smoke his pipe – but his wife forbid him to in the house. As a result, he would climb to the table mountain to enjoy the view while he smoked and one fine day he met the devil. Of course, he bragged how much he could smoke, so they engaged in a contest. The result left the mountain in a fog and the Magellanic Cloud in the stars! Other legendary tales suggest that our neighboring galaxy is either a god or a monster left on the high hill to guard the cape from unwary travelers… But no matter how Mensa came about its name, it is still a very faint constellation and will require patience and practice to see.

When you are ready, let’s start with a binocular tour of Mensa and its brightest star, Alpha – the “a” symbol on our map. Just barely visible to the unaided eye at magnitude 5.09 Alpha Mensae is a main sequence dwarf star located about 33 light years away from Earth. Shining away at about 80% the luminosity of our own Sun, Alpha is very similar. It is also a slow stellar rotator, taking about 32 days to complete a full rotation on its axis. At around 10 million years old, it comes within 7% of being about the same size as Sol, too… But we better enjoy it while we can. Even as we speak, Alpha Mensae is heading away from us at a speed of 35 kilometers per second!

Now aim your binoculars towards Beta Mensae – the “B” symbol on our map. Beta has the distinction of being a foreground star on the southern edge of the Large Magellanic Cloud! It’s a G-type giant star – again similar to our own Sun. What’s that? Try a main sequence star that’s happy in the “Yellow Evolutionary Void”. Unlike Alpha, it’s a lot further away… About 640 light years from our solar system.

Next stop? Pi Mensae – the “TT” symbol on our map. Pi is a yellow subgiant star with a high proper motion. Located approximately 60 light years away, Pi simply dwarfs our Sun in terms of mass, size, luminosity, temperature, and metallicity, yet it’s 730 million years younger! What makes it special? Pi ranks 100th on the list of top 100 target stars for the planned Terrestrial Planet Finder mission. On October 15, 2001, that search became successful when one of the most massive superjovian planets (HD 39091 b) ever found was discovered orbiting Pi Mensae. While it currently has a very eccentric orbit and takes approximately 2064 days (5.65 years) to revolve around its parent star, it does pass through a habitable zone – which means it probably would have disrupted the orbits of Earth-like planets long ago, either sending them into the parent star, or off into interstellar space.

While touring Mensa in binoculars, be sure to take in the full depth and breadth of the Large Magellanic Cloud which also crosses into Dorado. For a telescope challenge, try locating an open cluster in another galaxy! NGC 1711 (RA 04:50:36.0 Dec -69:59:06.0) is a very rich, 10th magnitude galactic star cluster which borders on the edge of being globular. It is actually a very young object whose data serves as a base for the study of mass functions and for the comparison with theoretical cosmological models.

For even more telescope challenges, try globular cluster NGC 2019 (RA 05:31:56:0). Also at home in the LMG, this small, bright-cored globular is a worthy target for mid-sized telescopes. Other globular clusters include NGC 2134, NGC 2065, NGC 2107, NGC 2058, NGC 1943, NGC 1987 and NGC 2121 in descending order of magnitude. These were all discovered by Sir William Herschel and are all located in the Mensa portion of the LMG.

Mensa is also home to quasar PKS 0637-752 (RA 06:35:46 Dec -75:16:12) – the first study of the Chandra X-Ray Observatory. When gathering first light on August 15, 1999, Chandra presented the world with a pair of images which revealed the quasar PKS0637-752 – a bright distant galaxy. Quasars like this are fairly “normal” galaxies which contain an active and massive black hole at its center. The brightness of the quasar is a result of material falling into the black hole. As well as the bright core of emission around the black hole, these images revealed a jet of material ejected from the black hole undergoing a remarkably sharp turn. With overlaying radio contours and optical images provided by Chandra, the newly revealed x-ray jet displayed the power far great than any radio jet ever recorded. It produces as much energy as 10 trillion Suns, all from a volume smaller than our own solar system!

Sources: Wikipedia, Chandra Observatory
Chart courtesy of Your Sky.

December 3, 2008December 24, 2015 by Nancy Atkinson

Brown Dwarfs Form Like Stars

This artist's conception shows the brown dwarf ISO-Oph 102.Credit: ASIAA

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Brown dwarfs are an interesting sort, and can only be classified in a kind of cosmic periphery between stars and planets: they are too small to be called stars and too large to be called planets. And astronomers haven’t been sure whether they form like stars, from the gravitational collapse of gas clouds, or if they form like planets, where rocky material comes together until it grows massive enough to draw in nearby gas. But now strong evidence has been found that brown dwarfs form more like stars. Using the Smithsonian’s Submillimeter Array (SMA), astronomers detected molecules of carbon monoxide shooting outward from a brown dwarf ISO-Oph 102. This type of molecular outflows typically is seen coming from young stars or protostars. However, this object has an estimated mass of 60 Jupiters, meaning it is too small to be a star, and has therefore been classified as a brown dwarf. But this new finding means brown dwarfs are more like stars than planets.

Typically, brown dwarfs have masses between 15 and 75 Jupiters, and the theoretical minimum mass for a star to sustain nuclear fusion is 75 times Jupiter. As a result, brown dwarfs are sometimes called failed stars. A star forms when a cloud of interstellar gas draws itself together through gravity, growing denser and hotter until fusion ignites. If the initial gas cloud is rotating, that rotation will speed up as it collapses inward, much like an ice skater drawing her arms in. In order to gather mass, the young protostar must somehow shed that angular momentum. It does so by spewing material in opposite directions as a bipolar outflow.

ISO-Oph 102 offers the first strong evidence in favor of brown dwarf formation through gravitational collapse. Credit: David A. Aguilar (CfA)

A brown dwarf is less massive than a star, so there is less gravity available to pull it together. As a result, astronomers debated whether a brown dwarf could form the same way as a star. Previous observations provided hints that they could. The serendipitous discovery of a bipolar molecular outflow at ISO-Oph 102 offers the first strong evidence in favor of brown dwarf formation through gravitational collapse.

As might be expected, the outflow contains much less mass than the outflow from a typical star: about 1000 times less, in fact. The outflow rate is also smaller by a factor of 100. In all respects, the molecular outflow of ISO-Oph 102 is a scaled-down version of the outflow process seen in young stars.

“These findings suggest that brown dwarfs and stars aren’t different because they formed in different ways,” said Paul Ho, an astronomer at the Harvard-Smithsonian Center for Astrophysics and director of ASIAA. “They share the same formation mechanism. Whether an object ends up as a brown dwarf or star apparently depends only on the amount of available material.”

The paper on ISO-Oph 102 will be published in the December 20 issue of the Astrophysical Journal Letters.

Source: CfA

December 3, 2008December 24, 2015 by Nancy Atkinson

This Week’s Where In The Universe Challenge

Are you ready for another Where In The Universe Challenge? Take a look at the image above and see if you can name where in the Universe this image is from. Give yourself extra points if you can name the spacecraft responsible for the image. We’ll provide the image today, but won’t reveal the answer until tomorrow. This gives you a chance to mull over the image and provide your answer/guess in the comment section — if you dare! Check back tomorrow on this same post to see how you did. Good luck!

UPDATE (12/4): The answer has now been posted below. If you haven’t made your guess yet, no peeking before you do!!

A variety of guesses this week, but many answers were correct: Saturn’s moon Iapetus. The Cassini spacraft zoomed in on the cratered moon to provide this stunning close-up. And did you know you can golf the moons of Saturn? The Cassini scientists created a Flash-based game based on some of the best images from the spacecraft’s tour of Saturn and its moons. It’s called Golf Sector 6, and its pretty fun. As many of you mentioned, this image shows the equatorial bulge of Iapetus, with mountainous terrain reaching about 10 km in height. Above the middle of the image can be seen a place where an impact has exposed the bright ice beneath the dark overlying material.

The image was taken on 10 September 2007 with the Cassini’s narrow-angle camera at a distance of approximately 3870 km from Iapetus. Image scale is 23 m per pixel. Credits: NASA/ JPL/ Space Science Institute.

And you know-it-alls out there don’t have to provide links to images or videos in your guesses! Give everyone the equal chance to play, please!

Tune in again next week for another WITU challenge!