Universe Today

November 27, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – November 27-29, 2009

Greetings, fellow SkyWatchers! Are you ready for what’s hot and what’s not this weekend? Then start by taking a look at Anders Celsius and then journey to some challenging lunar features! Evolve your selenographic knowledge by locating Darwin and double your vision with binary stars. Monkey around? You bet! But only if it’s with a star with unusual spectral qualities that you can see! Whenever you’re ready, I’ll see you in the dark…

Friday, November 27, 2009 – Today is the birthday of Anders Celsius, born in 1701. Although you might easily recognize the name Celsius in connection with temperature, you might not know about the contributions Anders made to astronomy some three centuries ago. Born to a Swedish family of mathematicians and astronomers, one of his first achievements came when he participated in an effort to determine the true shape of Earth. He was also the very first scientist to recognize the connection between magnetism and the aurora. And, by age 39, he had become the director of an observatory. Celsius also developed the first instrument for measuring the brightness of starlight. Ever resourceful, he already possessed tools to measure position and motion but had nothing with which to gauge magnitude. His idea was so simple it was downright elegant: he simply blocked the light with identical glass plates until the star disappeared. The brighter the star, the more plates it took!

Tonight let us go from one extreme to another as we begin on the northernmost limb of the lunar surface. From the northernmost Sinus Roris, look for lens-shaped crater Markov. To Markov’s northeast is a large, flat crater with very few distinguishing characteristics. Its name is Oenopides.

If conditions are stable, look for a gray slash known as Cleostratus on the lunar limb further north of Oenopides. On the southern limb, look for familiar craters Wargentin, Nasmyth, and Phocylides. Even farther south, note the long oval Pingre.

Saturday, November 28, 2009 – On this date in 1659, Christian Huygens was busy at the eyepiece, but he wasn’t studying Saturn. This was the first time any astronomer had seen dark markings on Mars! Why don’t you try your luck at Mars tonight, too? Wait for it to rise well above atmospheric disturbance and power up! It’s too bad it isn’t – or as big (!) as close as the Moon. . .

Tonight the great Grimaldi will again capture the eye, but let’s head southeast for another featureless dark gray oval, Crueger.

Continuing south, the next crater—Darwin—is hard to see because of its rather un-craterlike appearance. Darwin is best caught by focusing on the rima that includes its eastern wall. Look for a Y formation pointing toward Crueger.

Although skies are bright, we can still see double. Locate 5-magnitude Lambda Arietis (RA 01 57 55 Dec +23 35 45) and its companion. This wide pair is an excellent challenge for binoculars. Both stars are F-spectral types and should appear ivory in color to most observers. Having trouble in binoculars? Try a finderscope of equal power and aperture. To locate Lambda, look a finger-width west-southwest of Hamal, at Alpha Arietis.

Sunday, November 29, 2009 – On this date in 1961 Enos the Chimp was launched into fame! His story is a long and colorful one, but Enos was a true astronaut. Selected to make the first American orbital animal flight only 3 days before the launch, he flew into space on board a Mercury-Atlas 5 and completed his first orbit in just under 90 minutes. Although Enos was scheduled to complete three orbits, he was brought back due to ‘‘attitude difficulties.’’ But whose? Malfunctions caused the chimp to be repeatedly shocked when performing the correct maneuvers, but Enos continued to perform flawlessly and was said to run and jump enthusiastically on board the recovery ship. Although he died a year later from an unrelated disease, Enos the chimp remains one of our most enduring space heroes.

Tonight, launch your way toward the Moon and see if you can spot crater Riccioli. . . You’ll find it centermost and almost on the limb!

Now that you’ve viewed a challenging crater, would you like to have a look at a challenging double star? All you have to do is locate Theta Aurigae (RA 05 59 43 Dec +37 12 45) on the east side of the pentagonal shape of this constellation. Located about 110 light-years away, 2.7-magnitude Theta is a four star system, whose members range in magnitude from 2.7 to 10.7. Suited even to a small telescope, the brightest member—Theta B—is itself a binary at magnitude 7.2; it was first recorded by Otto Struve in 1871. The pair moves quite slowly and may take as long as 800 years to orbit at their separation of about 110 Astronomical Units (AU). The furthest member of this system was also noted by Struve as far back as 1852, but it is not a true member, with the separation only occurring thanks to Theta’s own proper motion. While you are there, be sure to note Theta’s unusual color. Although it will appear ‘‘white,’’ look closely at the diffraction caused by our own atmosphere, which acts much like a prism. You’ll notice a lot more purple and blue around this star than many others of the same spectral type. Why? Theta is a silicon star!

Until next week? Ask for the Moon, but keep on reaching for the stars!

This week’s awesome images are (in order of apppearance): Anders Celsius (widely used image), Northwest Limb Mosaic (credit—Alan Chu), Crueger (credit—Alan Chu), Lambda Arietis (credit –Palomar Observatory, courtesy of Caltech), Enos the Chimp (credit–NASA), Riccioli (credit—Alan Chu) and Theta Aurigae (credit—Palomar Observatory, courtesy of Caltech). We thank you so much!

November 27, 2009March 2, 2013 by Nancy Atkinson

Shuttle Atlantis Returns Home (Video)

Space shuttle Atlantis and its crew of seven astronauts landed safely at Kennedy Space Center Friday morning at 9:44 a.m. EST, ending an 11-day journey to the ISS. The Atlantis shuttle flew 171 orbits around Earth and traveled 7,226,176 kilometers (4,490,138 miles) since its Nov. 16 launch. STS-129 was the 129th space shuttle mission, the 31st for Atlantis and the 31st shuttle mission to the International Space Station. It was the fifth and final flight of 2009. Enjoy the landing video!

November 26, 2009December 24, 2015 by Nancy Atkinson

Fermi Finds Gamma-Ray Microquasar

Fermi’s Large Area Telescope has detected bursts of gamma-rays in the binary system Cygnus X-3, which astronomers say are coming from a microquasar. While microquasars have strong emissions across is a broad range of wavelengths, this is the first time this type of object has been detected in gamma rays. “Cygnus X-3 is a genuine microquasar and it’s the first for which we can prove high-energy gamma-ray emission,” said Stéphane Corbel at Paris Diderot University in France.

n Cygnus X-3, an accretion disk surrounding a black hole or neutron star orbits close to a hot, massive star. Gamma rays (purple, in this illustration) likely arise when fast-moving electrons above and below the disk collide with the star's ultraviolet light. Fermi sees more of this emission when the disk is on the far side of its orbit. Credit: NASA's Goddard Space Flight Center

Microquasars are stellar mass object that displays in miniature some of the properties of quasars: a normal star begins shedding its matter onto either a neutron star or a black hole. This phenomenon produces large amounts of radiation and “jets” of material moving at relativistic speeds—more than 10% the speed of light—away from the star. These “relativistic jets” are a great mystery that astronomers are still trying to understand, but this new gamma-ray microquasar could provide new ways to study them.

At the center of Cygnus X-3 lies a massive Wolf-Rayet star. With a surface temperature of 100,255.372 Kelvin (180,000 degrees F,) or about 17 times hotter than the sun, the star is so hot that its mass bleeds into space in the form of a powerful outflow called a stellar wind. “In just 100,000 years, this fast, dense wind removes as much mass from the Wolf-Rayet star as our sun contains,” said Robin Corbet at the University of Maryland, Baltimore County.

The researchers matched the gamma-rays to the known orbital period of the Cygnus X-3 microquasar in order to confirm that the strong pulses of radiation were, in fact, originating from the object. They also matched the gamma-rays with radio emission from the relativistic jets of Cygnus X-3.

Brighter colors indicate greater numbers of gamma rays detected in this Fermi LAT view of a region centered on the position of Cygnus X-3 (circled). The brightest sources are pulsars. Credit: NASA/DOE/Fermi LAT Collaboration

Every 4.8 hours, a compact companion embedded in a disk of hot gas wheels around the star. “This object is most likely a black hole, but we can’t yet rule out a neutron star,” Corbet said.

Between Oct. 11 and Dec. 20, 2008, and again between June 8 and Aug. 2, 2009, Cygnus X-3 was unusually active. The team found that outbursts in the system’s gamma-ray emission preceded flaring in the radio jet by roughly five days, strongly suggesting a relationship between the two.

These new findings should provide more information about the formation of such mysterious and fast-moving relativistic jets. This research appears in the 26 November issue of Science Express.

Read the team’s abstract

Sources: Science, Goddard Spaceflight Center

November 26, 2009December 24, 2015 by Jon Voisey

Comets Posing as Asteroids (or is the the other way around?)

Images of known MBCs from UH 2.2-meter telescope data. Credit: Henry Hsieh

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Asteroids are rocky bodies which belong between Mars and Jupiter. Comets are icy bodies that belong way out beyond Pluto. So what are comet-like objects doing in the asteroid belt?

On the night of August 7, 1996, astronomers Eric Elst and Guido Pizarro were observing what was previously thought to be an ordinary asteroid. To their surprise, the object revealed a faint but distinct tail similar to that of a comet. Initially, this was written off as a minor impact kicking up a debris cloud, but when the tail returned in 2002, when the supposed asteroid again returned to perihelion (the closest approach to the Sun), it once again displayed a tenuous tail. The “asteroid” was then given the designation of 133P/Elst-Pizarro. In 2005, two new asteroids were discovered to sport tails: P/2005 U1 and 118401. In 2008, yet another one of these odd objects was found (P/2008 R1). This new class of objects has been dubbed “Main Belt Comets (MBCs)”.

So where are these objects coming from?

A previous article here on Universe Today explored the possibility that these objects formed like other asteroids in the main belt. After all, each of the objects has an orbit consistent with other apparently normal asteroids. They have a similar distance at with they orbit the Sun, as well as similar eccentricities and inclinations of their orbit. So trying to explain these objects as having origins in the outer solar system that migrated just right into the asteroid belt seemed like little more than special pleading.

Furthermore, a 2008 study by Schorghofer at the University of Hawaii predicted that, if such an icy body were to form, it would be able to avoid sublimation for several billion years if only it were covered with a few meters of dust and dirt thus negating the problems of these objects suffering an early death. (Keep in mind that, much like a melting snowball, the water will evaporate but the dirt won’t, so the dirt will pile up quickly on the surface making this entirely plausible!) However, if the ice were covered by such an amount of dust, it would take a collision to remove the dust and trigger the cometary appearance.

In a recent paper, Nader Haghighipour also at the University of Hawaii explores the viability of collisions to trigger this activation as well as the stability of the orbits of these objects to assess the expectation that they were formed at the same time as other asteroids in the main belt.

For the orbital range in which three of the MBCs lie, it was predicted that “on average, one m[eter]-sized object collides … every 40,000 years.” They stress this is an upper limit since their simulation did not include other, nearby asteroids which would likely deplete the number of available impactors.

When they explored the orbital stability of these objects, the discovered at least two of them were dynamically unstable and would eventually be ejected from their orbits on a timescale of 20 million years. As such, it would be unreasonable to expect such objects to have lasted for the nearly 5 billion year history of the solar system. Thus, an in-situ formation was ruled out. However, due to a similarity in orbital characteristics to a family of asteroids known as the Themis family, suggesting they may have resulted from the same break up of a larger body that created this group. This begs the question of whether or not more of these asteroids are secretly hiding water ice reservoirs and are just waiting for an impact to expose them.

Distinctly separate from this orbital family was P/2008 R1 which exists in an especially unstable orbit near one of the resonances from Jupiter. This suggests that this MBC was likely scattered to its present location, but from where remains to be determined.

So while such Main Belt Comets may not have formed simply as they are now, they are likely to be in orbits not far removed from their original formation. Also, this work supported the earlier notion that minor impacts could reliably expected to expose ice allowing for the cometary tails. Whether or not more asteroids have tails tucked between their legs will be the target of future exploration.

Haghighipour’s Paper

November 26, 2009November 28, 2009 by Nancy Atkinson

Absolutely Amazing Shuttle Ascent Video

This video compilation of the STS-129 ascent is incredible! (and is it now available again after a short hiatus.) It includes video highlights from ground, air, SRB and external tank cameras during the launch of Atlantis on Nov. 16, 2009. It will give you a new appreciation for the space shuttle. The music is great, as well. Not to be missed!
Continue reading “Absolutely Amazing Shuttle Ascent Video”

November 26, 2009December 24, 2015 by Nancy Atkinson

Where In The Universe Challenge, Thanksgiving Edition

Here’s this week’s image for the WITU Challenge, to test your visual knowledge of the cosmos. You know what to do: take a look at this image and see if you can determine where in the universe this image is from; give yourself extra points if you can name the instrument 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. Please, no links or extensive explanations of what you think this is — give everyone the chance to guess. Best wishes to everyone celebrating Thanksgiving, no matter where you are!

UPDATE: The answer is now posted below.

This is the Trifid Nebula, as seen by the Gemini Telescope. This observation was done as a result of an essay contest for elementary school children, and the winner, Ingrid Braul from British Columbia, Canada, wrote: “I think the Trifid Nebula is the most beautiful thing in the whole universe. It’s really pretty with all the colours in it. When I look at it closely, I think of it as a majestic cloud of creation. It makes me think of the beginning of time, and how our solar system started.”

She sure got that right! Read more about the essay contest and see Ingrid’s entire essay here.

November 25, 2009April 26, 2016 by Abby Cessna

Yellowstone National Park Volcano

Artist's impression of a what lies beneath the Yellowstone volcano. Credit: Hernán Cañellas/National Geographic

Yellowstone National Park is known for its geysers, but did you know that it is also the site of one of the world’s largest volcanoes? The same geologic activity that causes the multitude of geysers in the park is also responsible for the huge volcano located there. Scientists estimate that it is one of the largest volcanoes in the world, and so far it is the largest volcano in North America.

The volcano is 55 km by 72 km in size. Yellowstone’s volcano is in the class of super volcanoes due to its size. There is no exact definition for what qualifies as a super volcano; however, some scientists have defined it as a volcano with an eruption greater than 240 cubic miles.

Additionally, the Yellowstone Volcano does not look like the popular image of a volcano. Instead of being a conical mountain, it is a large depression in the ground like a cauldron. This type of volcanic feature is known as a caldera. It is very difficult to see the actual shape because it is covered with trees and has eroded over thousands of years.

*Yellowstone National Park sits on top of a giant volcanic caldera, or an earthen cap that covers a huge reservoir of superhot liquid rock and poison gasses. Credit: IO9*

The cause of the volcano is the hotspot on which Yellowstone is located. At a hotspot, molten mantle rock tends to rise toward the surface causing different geological activity. Volcanic eruptions from the hotspot also helped form the Snake River Plain.

Not only do volcanic eruptions occur around the Yellowstone region, but the area also experiences many earthquakes. The region experiences around 1000 to 2000 earthquakes each year, although most of them are usually quite small.

Despite the fact that the volcano has not erupted in hundreds of years, it is still active. This is a concern to scientists who have placed sensors around Yellowstone, so the volcano is continually monitored. The possible eruption of the Yellowstone Super volcano is of concern because of the enormous destruction it would cause. The last eruption was believed to be approximately 640,000 years ago.

Geologists estimate that 2 million years ago a cataclysmic series of volcanic eruptions in the Yellowsone Caldera was 2,500 times more powerful than the Mt. St. Helens eruption and perhaps was the largest, most violent volcanic eruption in the history of earth. Credit: Extreme Science — Geologists estimate that 2 million years ago a cataclysmic series of volcanic eruptions in the Yellowstone Caldera was perhaps the most violent volcanic eruption in the history of earth. Credit: Extreme Science

The eruption was on such a scale that it made the 1980 Mount St. Helen’s eruption look like nothing and result in damage and destruction many miles around. Scientists estimate that the other two eruptions from the Yellowstone Super volcano came over one and two million years ago. Since the volcano is still active, there is always a possibility it will once again erupt.

However, scientists do not anticipate that there will be another eruption in the near future, at least one on such a massive scale.

Universe Today has articles on Yellowstone eruption and Yellowstone Super Volcano.

For more information, try Yellowstone Volcano and Supervolcano.

Astronomy Cast has an episode on volcanoes hot and cold.

Sources:
http://en.wikipedia.org/wiki/Yellowstone_Caldera
http://volcanoes.usgs.gov/yvo/

November 25, 2009December 24, 2015 by Ryan Anderson

Kaguya Discovers a Lava Tube on the Moon

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Future lunar astronauts may want to brush up on their spelunking skills: the first lava tube has been discovered on the moon.

In a recent paper published in Geophysical Research Letters, Junichi Haruyama and colleagues report that they have discovered a mysterious hole in the lunar surface in high resolution images from the Kaguya spacecraft. The hole is 65 meters in diameter and is located in the volcanic Marius Hills region on the near side of the moon, right in the middle of a long sinuous rille. Sinuous rilles are thought to be formed by flowing lava, either on the surface or in enclosed lava tubes.

Of course, there are a lot of ways to form a hole in the surface of the moon. The most obvious is with an impact: the moon has literally been battered to pieces over the years by rocks from space. Couldn’t this hole be a fresh impact crater? Nope. Haruyama’s team observed the hole nine separate times, at various illumination angles, and even when the sun was almost directly overhead it looked mostly black, suggesting that it is very deep. They calculate a depth of around 88 meters, so the hole is deeper than it is wide. No impact crater is like that.

Four different views of the lava tube skylight at varying sun angles. Arrows indicate the direction of incident sunlight (I) and the viewing direction (V). Image credit: JAXA/SELENE

Another possibility is that the hole is due to some sort of volcanic eruption, but there is no sign of volcanic deposits like lava flows or ash emanating from the hole. The hole is isolated, so it isn’t likely to be due to a fracture in the lunar crust either – you would expect such a fracture to form a chain of holes.

Haruyama’s team concluded that the most likely explanation is that the hole that they discovered is a “skylight” – a location where the roof of a lava tube collapsed, either when the lava filling the tube flowed away, or later in the moon’s history due to an impact, moonquake, or tidal forces from the Earth. If it is a lava tube, their calculations based on the multiple images of the hole show that the tube could be 370 meters across.

Lava tubes are important in understanding how lava was transported on the early moon, but they are not just a scientific curiosity: they may also provide valuable refuges for future human explorers. The surface of the moon is not protected from the harsh radiation of space by a magnetic field or a thick atmosphere, so a long term human presence would be most feasible if astronauts could spend most of their time shielded underground. Digging a hole large enough to fit an entire moon colony in it would be a huge engineering challenge, but lava tubes could provide ready-made locations for a well-shielded base, making future astronauts the most technologically advanced cave-dwellers in history.

November 25, 2009December 24, 2015 by Jon Voisey

Jupiter – Our Silent Guardian?

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We live in a cosmic shooting gallery. In Phil Plait’s Death From the Skies, he lays out the dangers of a massive impact: destructive shockwaves, tsunamis, flash fires, atmospheric darkening…. The scenario isn’t pretty should a big one come our way. Fortunately, we may have a silent guardian: Jupiter.

Although many astronomers have assumed that Jupiter would likely sweep out dangerous interlopers (an important feat if we want life to gain a toehold), little work has been done to actually test the idea. To explore the hypothesis, a recent series of papers by J. Horner and B. W. Jones explores the effects of Jupiter’s gravitational pull on three different types of objects: main belt asteroids (which orbit between Mars and Jupiter), short period comets, and in their newest publication, submitted to the International Journal of Astrobiology, the Oort cloud comets (long period comets with the most distant part of their orbits far out in the solar system). In each paper, they simulated the primitive solar systems with the bodies in question with an Earth like planet, and gas giants of varying masses to determine the effect on the impact rate.

Somewhat surprisingly, for main belt asteroids, they determined, “that the notion that any ‘Jupiter’ would provide more shielding than no ‘Jupiter’ at all is incorrect.” Even without the simulation, the astronomers say that this should be expected and explain it by noting that, although Jupiter may shepherd some asteroids, it is also the main gravitational force perturbing their orbits and causing them to move into the inner solar system, where they may collide with Earth.

Contrary to the popular wisdom (which expected that the more massive the planet, the better it would shield us), there were notably fewer asteroids pushed into our line of sight for lower masses of the test Jupiter. Also surprisingly, they found that the most dangerous scenario was an instance in which the test Jupiter had 20% in which the planet “is massive enough to efficiently inject objects to Earth-crossing orbits.” However, they note that this 20% mass is dependent on how they chose to model the primordial asteroid belt and would likely change had they chosen a different model.

When the simulation was redone for for short period comets, they again found that, although Jupiter (and the other gas giants) may be effective at removing these dangerous objects, quite often they did so by sending them our way. As such, they again concluded that, as with asteroids, Jupiter’s gravitational jiggling was more dangerous than it was helpful.

Their most recent treatise explored Oort cloud objects. These objects are generally considered the largest potential threat since they normally reside so far out in the solar system’s gravitational well and thus, will have a greater distance to fall in and pick up momentum. From this situation, the researchers determined that the more massive the planet in Jupiter’s orbit, the better it does protect us from Oort cloud comets. The attribute this to the fact that these objects are initially so far from the Sun, that they are scarcely bound to the solar system. Even a little bit of extra momentum gained if they swing by Jupiter will likely be sufficient to eject them from the solar system all together, preventing them from settling into a closed orbit that would endanger the Earth every time it passed.

So whether or not Jupiter truly defends us or surreptitiously nudges danger our way depends on the type of object. For asteroids and short period comets, Jupiter’s gravitational agitation shoves more our direction, but for the ones that would potentially hurt is the most, the long period comets, Jupiter does provide some relief.

November 25, 2009December 24, 2015 by Nancy Atkinson

Astronomers Dig Up Relic of the Milky Way’s Central Bulge

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Like archaeologists who dig through the layers of dirt to unearth crucial pieces of the history of mankind, astronomers have been gazing through the thick layers of interstellar dust obscuring the central bulge of the Milky Way and have unveiled an extraordinary cosmic relic. Within the bulge is an unusual mix of stars in the stellar grouping known as Terzan 5, and such a mix has never been observed anywhere in the bulge before. This peculiar conglomeration of stars suggests that Terzan 5 is one of the bulge’s primordial building blocks, most likely the relic of a dwarf galaxy that merged with the Milky Way during its very early days.

The new observations of Terzan 5 show that this object, unlike all but a few exceptional globular clusters, does not harbor stars which are all born at the same time — what astronomers call a “single population” of stars. Instead, the multitude of glowing stars in Terzan 5 formed in at least two different epochs, the earliest probably some 12 billion years ago and then again 6 billion years ago.

“Only one globular cluster with such a complex history of star formation has been observed in the halo of the Milky Way: Omega Centauri,” says team member Emanuele Dalessandro. “This is the first time we see this in the bulge.”

Using ESO’s Very Large Telescope, equipped with the Multi-conjugate Adaptive Optics Demonstrator (MAD), the astronomers were able to “disperse the fog” of the dust clouds in the central bulge to reveal the myriad of stars.

Through the sharp eye of the VLT, the astronomers also found that Terzan 5 is more massive than previously thought: along with the complex composition and troubled star formation history of the system, this suggests that it might be the surviving remnant of a disrupted dwarf galaxy, which merged with the Milky Way during its very early stages and thus contributed to form the galactic bulge.

The team hopes this is only the first in a series of discoveries on the origin of bulges in galaxies.

“The history of the Milky Way is encoded in its oldest fragments, globular clusters and other systems of stars that have witnessed the entire evolution of our galaxy,” says Francesco Ferraro, lead author of a paper appearing in this week’s issue of the journal Nature. “Our new study opens a new window on yet another piece of our galactic past.”

Source: ESO