Posted on by Fraser Cain

Redesigning Universe Today… Again

In case you haven’t noticed yet, I’ve redesigned Universe Today… again. I know I do this almost every year, but I just get itchy feet. Anyway, I’m taking an HTML/CSS design course as part of my computer science degree, so I figured I’d put it to good use. Right now on the homepage and the article pages have been redesigned, but I thought I’d get your feedback. Here are some of the changes I made:
– pushed stuff to the sides so you don’t have go so far down before reading articles
– spaced out the text on articles a little bit to make them easier to read
– implemented printer templates for everything. Now every page is “printable”. Check it out, just click “Print Preview” in your brower and you’ll see what it’ll look like.

I’m still fine tuning stuff, so please feel free to give me any feedback, suggestions, or complaints. Email me at [email protected]. Once the website’s done, I’ll update the newsletter, etc.

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Pluto Was Born With Its Moons

Artist’s illustration showing a giant collision similar to Pluto’s newly discovered moons scenario. Image credit: Don Davis Click to enlarge
In a paper published today in Nature, a team of U.S. scientists led by Dr. S. Alan Stern of Southwest Research Institute (SwRI), concludes that two newly discovered small moons of Pluto were very likely born in the same giant impact that gave birth to Pluto’s much larger moon, Charon. The team also argues that other, large binary Kuiper Belt Objects (KBOs) may also frequently harbor small moons, and that the small moons orbiting Pluto may generate debris rings around Pluto.

The team making these findings included Drs. Bill Merline, John Spencer, Andrew Steffl, Eliot Young and Leslie Young of SwRI; Dr. Hal Weaver of the Johns Hopkins University Applied Physics Laboratory; Max Mutchler of the Space Telescope Science Institute; and Dr. Marc Buie of the Lowell Observatory. This team discovered Pluto’s two small moons in 2005 using sensitive images obtained by the Hubble Space Telescope, as reported by Weaver et al. in an accompanying paper in the February 23 issue of Nature.

“The evidence for the small satellites being born in the Charon-forming collision is strong; it is based around the facts that the small moons are in circular orbits in the same orbital plane as Charon, and that they are also in, or very near, orbital resonance with Charon,” says lead author Stern, executive director of the SwRI Space Science and Engineering Division.

“Tests of this scenario will come from refined orbital data, from measuring the rotational periods of these moons, and from determinations of their densities and surface compositions,” says co-author Weaver.

Collisions, both large and small, are major processes that shaped many aspects of our solar system. Scientists use computer simulations to study the origin of planetary systems formed by impact events of a scale much larger than could be simulated in a laboratory. Another large collision, like the one thought to have created Charon and Pluto’s small moons, is believed responsible for the formation of the Earth-moon pair.

“The idea that Pluto’s small moons and Charon resulted from a giant impact now seems compelling. Future simulations to determine the characteristics of the impact required to produce all three satellites should provide improved constraints on the early dynamical history of the Kuiper Belt,” adds Dr. Robin Canup, director of SwRI’s Space Studies Department, who in 2005 produced the most comprehensive models to date of the Charon-forming impact.

Based on the growing realization that binary “ice dwarf” pairs like Pluto-Charon are common in the Kuiper Belt, the Pluto satellite discovery team concludes that numerous triple, quadruple and even higher-order systems may be discovered across the Kuiper Belt in years to come.

“Finding small satellites around KBOs is difficult because their large distance from the Sun makes them appear very faint. As a result, we don’t really know how common it is for KBOs to have multiple satellites,” adds co-author Steffl. “One good way to test this is to search around objects that have been ejected from the Kuiper Belt into orbits that bring them much closer to the Sun. So far, about 160 of these objects, called Centaurs, have been discovered. We hope to use Hubble to search for faint moons around some of them.”

Co-author Merline adds, “If Pluto’s small moons generate debris rings from impacts on their surfaces, as we predict, it would open up a whole new class of study because it would constitute the first ring system seen around a solid body rather than a gas giant planet.”

“The Pluto system never fails to reward us when we look at it in new ways,” concludes Stern. “What a bonanza and an illustration of the richness of nature Pluto has consistently proved to be. Our discovery of its two new moons reinforces that lesson yet again.”

The paper, “A Giant Impact Origin for Pluto’s Small Moons and Satellite Multiplicity in the Kuiper Belt,” by Stern et al. is available in the February 23 issue of Nature. NASA funded this work.

Original Source: SwRI News Release

Update: Pluto is no longer a planet.

Posted on by Fraser Cain

Dark Lava Floor of Crater Billy

Lunar crater Billy as seen by SMART-1. Ima ge credit: ESA/SPACE-X Click to enlarge
This composite image, taken by the Advanced Moon Imaging Experiment (AMIE) on board ESA’s SMART-1 spacecraft, shows crater Billy at the edge of a large lava plain on the Moon.

The AMIE camera obtained two images in consecutive orbits, from a distance of about 1260 kilometres with a ground resolution of approximately 114 metres per pixel. Each image has a field of view of 56 kilometres.

Crater Billy is located on the southern fringes of the Oceanus Procellarum, on the western half of the Moon’s Earth-facing side (50??bf? West, 13.5??bf? South). It lies to the south-east of the similar-sized crater Hansteen and west-south-west of the lava-flooded crater Letronne.

The Oceanus Procellarum’s southern area is low on spectacle but high in terms of geological interest. An irregular bay, the Mare Humorum on the edge of the ‘ocean’ can be seen below and to the east of the craters Billy and Hansteen.

Billy is an old impact crater, 46 kilometres in diameter, with a rim rising to 1300 metres above its flat floor. The floor of Billy has been flooded by basaltic lava with a low albedo, meaning it leaves a dark surface.

Billy’s floor is one of the darkest spots on the Moon’s face, and can easily be seen any time when it is illuminated, even at full Moon. Billy contrasts with Hansteen, which is light-coloured with a hummocky floor.

Billy is named after the French Jesuit astronomer Jacques de Billy (1602-79), who was one of the first to reject the role of astrology in science, along with superstitious notions about the malevolent influence of comets.

Original Source: ESA Portal

Posted on by Fraser Cain

Nearby Exoplanet is Scorching Hot

Artist’s concept of planet orbiting a star. Image credit: NASA Click to enlarge
A NASA-led team of astronomers have used NASA’s Spitzer Space Telescope to detect a strong flow of heat radiation from a toasty planet orbiting a nearby star. The findings allowed the team to “take the temperature” of the planet.

“This is the closest extrasolar planet to Earth that has ever been detected directly, and it presents the strongest heat emission ever seen from an exoplanet,” said Drake Deming of NASA’s Goddard Space Flight Center, Greenbelt, Md. Deming is the lead author of a paper on this observation to be published in the Astrophysical Journal on June 10. An advance copy of the paper will be posted on the astro-ph website on Feb. 22.

The planet “HD 189733b” orbits a star that is a near cosmic neighbor to our sun, at a distance of 63 light years in the direction of the Dumbbell Nebula. It orbits the star very closely, just slightly more than three percent of the distance between Earth and the sun. Such close proximity keeps the planet roasting at about 844 Celsius (about 1,551 Fahrenheit), according to the team’s measurement.

The planet was discovered last year by Francois Bouchy of the Marseille Astrophysics Laboratory, France, and his team. The discovery observations allowed Bouchy’s team to determine the planet’s size (about 1.26 times Jupiter’s diameter), mass (1.15 times Jupiter), and density (about 0.75 grams per cubic centimeter). The low density indicates the planet is a gas giant like Jupiter.

The observations also revealed the orbital period (2.219 days) and the distance from the parent star. From this distance and the temperature of the parent star, Bouchy’s team estimated the planet’s temperature was at least several hundred degrees Celsius, but they were not able to measure heat or light emitted directly from the planet.

“Our direct measurement confirms this estimate,” said Deming. This temperature is too high for liquid water to exist on the planet or any moons it might have. Since known forms of life require liquid water, it is unlikely to have emerged there.

Last year, Deming’s team and another group based at the Harvard-Smithsonian Center for Astrophysics used Spitzer to make the first direct detection of light from alien worlds, by observing the warm infrared glows of two other previously detected “Hot Jupiter” planets, designated HD 209458b and TrES-1.

Infrared light is invisible to the human eye, but detectable by special instruments. Some infrared light is perceived as heat. Hot Jupiter planets are alien gas giants that zip closely around their parent stars, like HD 189733b. From their close orbits, they soak up ample starlight and shine brightly in infrared wavelengths.

Deming’s team used the same method to observe HD 189733b. To distinguish the planet’s glow from its hot parent star, the astronomers used an elegant method. First, they used Spitzer to collect the total infrared light from both the star and its planet. Then, when the planet dipped behind the star as part of its regular orbit, the astronomers measured the infrared light coming from just the star. This pinpointed exactly how much infrared light belonged to the planet. Under optimal circumstances this same method can be used to make a crude temperature map of the planet itself.

“The heat signal from this planet is so strong that Spitzer was able to resolve its disk, in the sense that our team could tell we were seeing a round object in the data, not a mere point of light,” said Deming. “The current Spitzer observations cannot yet make a temperature map of this world, but more observations by Spitzer or future infrared telescopes in space may be able to do that.”

Deming’s team includes Joseph Harrington, Cornell University, Ithaca, N.Y.; Sara Seager, Carnegie Institution of Washington; and Jeremy Richardson, NASA Postdoctoral Fellow at Goddard, in the Exoplanets and Stellar Astrophysics Laboratory.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for the agency’s Science Mission Directorate. Science operations are conducted at the Spitzer Science Center at Caltech. JPL is a division of Caltech.

Original Source: NASA News Release

Posted on by Fraser Cain

New Type of Star Discovered

An artist’s impression of a neutron star with its magnetic field lines showing. Image credit: Russell Kightly Media. Click to enlarge
Astronomers of the University of Manchester’s Jodrell Bank Observatory (UK) have led an international team which used the Parkes radio telescope in Australia to find a new kind of cosmic object which sends out radio flashes. These flashes are very short and very rare: one hundredth of a second long, the total time the objects are visible amounts to only about one tenth of a second per day.

The discovery will be published in this week’s issue of the journal Nature.

Eleven sources of flashes have been found in different parts of the plane of the Milky Way in a survey for radio pulsars, which are small, compressed, highly-magnetised, neutron stars that produce regular pulses as they rotate, like cosmic light-houses. While that survey found over 800 pulsars and is the most successful in history, it also uncovered this new type of star. Rather than searching only for the periodic trains of pulses, the astronomers developed new techniques for detecting single short bursts of radiation.

Dr Maura McLaughlin explained: “It was difficult to believe that the flashes we saw came from outer space, because they looked very much like man-made interference”. The isolated flashes last for between 2 and 30 milliseconds. In between, for times ranging from 4 minutes to 3 hours, the new stars are silent.

After confirmation of their celestial nature, studies over the next 3 years revealed that 10 of the 11 sources have underlying periods of between 0.4 seconds and seven seconds.

“The periodicities found suggest that these new sources are also rotating neutron stars, but different from radio pulsars”, says Professor Andrew Lyne. “It is for this reason that we call them Rotating Radio Transients or RRATs. It’s as if, following a flash, a RRAT has to gather its strength during perhaps a thousand rotations before it can do it again !”.

RRATs are a new flavour of neutron stars in addition to the conventional radio pulsars and to the magnetars, which are also believed to be rotating neutron stars and are known to give off powerful X-ray and gamma-ray bursts. It is possible that RRATs represent a different evolutionary phase of neutron stars to or from magnetars.

The new objects probably far outnumber both their cousins. “Because of their ephemeral nature, RRATs are extremely difficult to find and so we believe that there are about 4 RRATs for every pulsar” says Dr Richard Manchester of the Australia Telescope National Facility. He is part of the team which also includes astronomers from the US, Canada and Italy.

Original Source: Jodrell Bank Observatory

Posted on by Fraser Cain

Southern Enceladus Covered in Fresh Snow

Saturn’s moon Enceladus. Image credit: NASA/JPL/SSI Click to enlarge
A false color look reveals subtle details on Enceladus that are not visible in natural color views.

The now-familiar bluish appearance (in false color views) of the southern “tiger stripe” features and other relatively youthful fractures is almost certainly attributable to larger grain sizes of relatively pure ice, compared to most surface materials.

On the “tiger stripes,” this coarse-grained ice is seen in the colored deposits flanking the fractures as well as inside the fractures. On older fractures on other areas of Enceladus, the blue ice mostly occurs on the exposed wall scarps.

The color difference across the moon’s surface (a subtle gradation from upper left to lower right) could indicate broad-scale compositional differences across the moon’s surface. It is also possible that the gradation in color is due to differences in the way the brightness of Enceladus changes toward the limb, a characteristic which is highly dependent on wavelength and viewing geometry.

See PIA07709 for a monochrome version of this view.

Terrain on the trailing hemisphere of Enceladus (505 kilometers, or 314 miles across) is seen here. North is up.

The view was created by combining images taken using ultraviolet, green and infrared spectral filters, and then was processed to accentuate subtle color differences. The images were taken with the Cassini spacecraft narrow-angle camera on Jan. 17, 2006 at a distance of approximately 153,000 kilometers (95,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 29 degrees. Image scale is 912 meters (2,994 feet) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Gemini Counts Up the Dark Matter in NGC 3379

NGC 3379. Image credit: NASA/University of Michigan. Click to enlarge
Using Gemini observations of globular clusters in NGC 3379 (M105), a team led by PhD student Michael Pierce and Prof. Duncan Forbes of Swinburne University in Australia, have found evidence for normal quantities of dark matter in the galaxy??bf?s dark halo. This is contrary to previous observations of planetary nebulae that indicated a paucity of dark matter in the galaxy.

The observations of 22 globular clusters in the Leo Group elliptical galaxy were made using the Gemini Multi-Object Spectrograph (GMOS) on Gemini North in early 2003. The data were obtained in the GMOS multi-slit mode with exposures of 10 hours on-source at a spectral resolution of FWHM ~4Aa over an effective wavelength range of 3800A-6660A. The final spectra have a signal-to-noise ratio of 18-58/A at 5000 A. The spectroscopic data allowed the team to derive ages, metallicities and α-element abundance ratios for the sample of globular clusters. All of the globular clusters were found to be >~ 10 Gyr, with a wide range of metallicities. A trend of decreasing α-element abundance ratio with increasing metallicity is also identified.

Most significantly, including 14 extra globular clusters from Puzia, et al. (2004), the projected velocity dispersion of the globular cluster system was found to be constant with radius from the galaxy center, indicating significant dark matter at large radii in its halo. This result is in stark contrast to the ??bf?No/Low Dark Matter??bf? interpretation by Romanowsky, et al. (2003) in the journal Science using observations of planetary nebula that indicated a decrease in the velocity dispersion profile with radius.

Reconciling the two velocity dispersion profiles is possible. Dekel, et al. (2005) recently showed that stellar orbits in the outer regions of merger-remnant elliptical galaxies are elongated and that declining planetary nebula velocity dispersions do not necessarily imply a dearth of dark matter.

Another possibility the authors suggest is that NGC 3379 could be a face-on S0 galaxy (as originally suggested by Capaccioli, et al. 1991). If a significant fraction of the planetary nebulae belong to the disk, this could suppress the line-of-sight velocity dispersion of the planetary nebulae relative to that of the globular clusters that lie in a more spherical halo.

Original Source: Gemini Observatory

Posted on by Fraser Cain

NASA Builds a Stardust Factory

The Cat’s Eye nebula taken by the Hubble Space Telescope. Image credit: NASA./ESA Click to enlarge
Researchers using a “stardust factory” at NASA’s Goddard Space Flight Center, Greenbelt, Md., have solved a mystery of how dying stars make silicate dust at high temperatures. Understanding this process helps us understand our origin, because this dust will become part of another generation of stars and planets, just as previous generations of stars contributed dust grains into our solar system that at least on one planet led to life.

Dying stars heat up internally while expelling their outer layers of gas into space. The gas expands and cools, allowing some matter in it to condense into dust grains. Observations over the last quarter century show dust grains made of silicon and oxygen (SiO or amorphous silicate grains) condensing at 1,300 degrees Fahrenheit (more than 700 degrees Celsius) in the billowing clouds of gas (nebulae) surrounding old stars. The prevailing theory said that this temperature was too high to condense solid silicate grains – the silicon and oxygen should have remained in the gas.

“Even though theory said it was impossible, stars made dust grains at high temperatures anyway — it was happening right before our eyes,” said Dr. Joseph Nuth of Goddard, lead author of a paper on this research recently submitted to the Astrophysical Journal. “So we went to our laboratory at Goddard where we vaporize material in a vacuum and observe how it condenses to see what we were missing.”

The experiment revealed that the “vapor pressure” at which the dust grains condense was too high in the theory. Just as fog (water vapor) condenses out of the air when the temperature drops or the humidity rises, SiO will condense out of nebular gas at certain temperatures and pressures. Warm air holds more water as gas than cold air, which is why 100 percent humidity — the amount of water gas required to completely saturate the air — feels so much more uncomfortable on a hot summer day. Similarly, at high temperatures, it takes more SiO gas in the circumstellar outflow before it will become completely saturated and condense into dust grains.

The pressure at which the SiO gas starts to condense is called its saturated vapor pressure — 100 percent humidity for SiO gas. The experiment revealed that the actual value at 1,300 degrees F was about 100,000 times lower than what was predicted by the theory. The lower actual value means that SiO gas can form dust grains in a 1,300 degree-nebula at concentrations about 100,000 times lower than previously believed. “If weather forecasters had made a similar prediction about the vapor pressure for water, they would say rain was impossible — they would think there was never enough water in the air to make it rain,” said Nuth.

“We plugged the actual, lower saturated vapor pressure values from our experiment into the theory, and it was almost good enough. The modified theory predicted that the SiO gas was very close to condensing into dust grains, but there was still some factor missing,” said Dr. Frank Ferguson of the Catholic University of America, Washington, Co-author of the paper.

According to the researchers, the missing factor was that the SiO molecules can lose energy by radiating it out into space. Molecules can vibrate at different levels, each with more energy than the one below, until, at the highest vibrational levels, they have so much energy that they just break apart. If nothing excites a molecule, giving it energy by hitting it for example, the molecule will spontaneously lose energy by dropping to a lower-energy vibrational level, and will continue to do this until it reaches the ??bf?ground state??bf? or lowest level possible. Since the pressure is low in the outflowing nebular gas, a SiO molecule there does not often collide with another gas molecule. It is also unlikely to be excited by light from the dying star, since the nebula is expanding into the darkness of deep space and only part of its field of view includes the star itself. Under these circumstances a large population of ground-state SiO molecules develops that contain minimal vibrational energy.

To begin forming a silicate dust grain, two SiO molecules have to stick together (condense). This releases energy. That energy has to go somewhere ??bf? likely into more energetic vibrational levels. Two molecules already in high-energy states are more likely to gain too much energy from the condensation reaction, so they would simply split apart again. On the other hand, two low-energy SiO molecules are more likely to remain stuck together with the reaction energy going temporarily into higher-level vibrational states until the larger molecule can radiate this energy into space. Therefore when many of the SiO molecules in the nebula are in low-energy vibrational states, they can condense at a slightly higher temperature than their vapor pressure alone indicates because these molecules are cooler than the surrounding gas.

“When we use the new vapor pressure and account for the vibrational levels of the SiO molecules in the expanding gas, silicate dust condenses easily,” said Nuth. “This result shows how experiment, observation, and theory all complement each other in the search to understand what really happens in nature.” The research was funded by NASA??bf?s Cosmochemistry Research and Analysis Program, NASA Headquarters.

Original Source: NASA News Release

Posted on by Fraser Cain

So, Is Pluto a Planet or Not?

Hubble photograph of Pluto and its three moons. Image credit: Hubble. Click to enlarge.
Unfortunately, the Solar System isn’t so simple. The case for Pluto’s planethood status has gotten a little eroded since its discovery, and there are further challenges facing it into the future.

The four gas giants are clearly planets. They dominate their respective orbits, and have clusters of moons, rings and all sorts of features that separate them from the rock and rubble of asteroids, comets, and other icy objects. Pluto, on the other hand, is nestled inside the Kuiper Belt; a vast population of ice bodies extending beyond the orbit of Neptune. There are an estimated 70,000 objects in the belt larger than 100 km (62 miles) across, and Pluto appears to just be a particularly large example.

As powerful observatories and space-based telescopes push out our understanding of the Kuiper Belt, many new objects have been discovered; several are close in size to Pluto. For every scientific measurement you can give Pluto: size, mass, moons, orbit, it ends up being a large Kuiper Belt Object. The brave members of the Bad Astronomy/Universe Today forum are giving this challenge their best attempt to define a planet.

And this controversy has been expanded with the discovery of 2003UB313 by the team of Michael Brown, Chad Trujillo, and David Rabinowitz. Also part of the Kuiper Belt, this object – code named Xena for now – is about 3000 km across. That makes it 700 km (430 miles) larger than Pluto! Its 557-year orbit is highly eccentric, varying between 38 and 98 astronomical units (the distance of the Earth to the Sun). Pluto, on the other hand, has an orbit that varies between 29 and 49 AU, and Neptune is 30 AU.

So there are times when Xena gets closer to the Sun than Pluto… and it’s bigger. Oh, and it probably has a moon too (code named Gabrielle). Is Xena a planet? If not, why does Pluto get to remain a planet, since it’s smaller, and sometimes orbits further from the Sun.

Objects have been unplaneted already. Before astronomers realized there were thousands of asteroids in the main asteroid belt, the first 4 discovered were considered planets for several decades: Ceres, Pallas, Juno and Vesta.

What’s a planet then? The International Astronomical Union has developed some definitions in 2001 for extrasolar planets, and modified them as recently as 2003, so we can start there.

Under their definition, planets are any objects orbiting stars or stellar remnants (like pulsars) which are below the limiting mass for thermonuclear fusion of deuterium. This sets an upper limit at about 13 times the mass of Jupiter.

What about a lower limit? Well, the IAU goes on to state that the minimum size/mass for an extrasolar planet should be under the same criteria for what’s used to define planets in the Solar System. This brings us right back to the beginning. When super powerful telescopes are developed that can detect objects as small as Pluto around other stars, whether or not they’re planets depends on Pluto’s planetary status.

Back to the beginning, then.

Mike Brown, one of the astronomers who original discovered Xena, has heard rumours that the International Astronomical Union is going to be discussing this dilemma at their upcoming meeting in Prague in August 2006. We could wind up with 8 planets (sorry Pluto), 9 planets (nothing changes), or 10 planets (welcome Xena and all future super-Plutos). And if the IAU extends this to 10 planets, will 11 be around the corner? Are you ready to memorize the 30 planets?

Brown states on his website:

  • A special committee of the International Astronomical Union (IAU) was charged with determining “what is a planet.”
  • Sometime around the end of 2005, this committee voted by a narrow margin for the “pluto and everything bigger” definition, or something close to it.
  • The executive committee of the IAU then decided to ask the Division of Planetary Sciences (DPS) of the American Astronomical Society to make a recommendation.
  • The DPS asked their committee to look in to it.
  • The DPS committee decided to form a special committee.
  • Rumor has emerged that when the IAU general assembly meets in August in Prauge they will make a decision on how to make a final decision!

Whatever they decide, NASA is going to see Pluto up close. New Horizons just launched earlier this year, and it will take 9 years to reach Pluto in 2015. Its Pluto/Charon encounter will begin in July, and last for more than 100 days, giving us our first close up look at this planet/big Kuiper Belt Object. By the time it arrives, we can only hope the IAU has made up their minds.

If the decision were up to me, I’d say Pluto is a planet. For starters we wouldn’t have to go back and edit all those astronomy textbooks, websites, sculptures, museum exhibits and PBS documentaries. Our Solar System just isn’t so simple; objects scale from the tiny to the huge, with all sizes in between. Any decision on Pluto’s planethood will be an arbitrary one, and the arbitrary decision I like is… Pluto’s a planet.

Written by Fraser Cain

Posted on by Fraser Cain

What’s Up This Week – February 20 – February 26, 2006

What's Up 2006

Download our free “What’s Up 2006” ebook, with entries like this for every day of the year.

M41. Image credit: NOAO/AURA/NSF. Click to enlarge.
Monday, February 20 – Today in 1962, John Glenn was onboard Friendship 7 and became the first American to orbit the Earth. As Colonel Glenn looked out the window, he reported seeing “fireflies” glittering outside his Mercury space capsule. Let’s see if we can find some…

The open cluster M41 in Canis Major is just a quick drift south of the brightest star in the northern sky – Sirius. Even the smallest scopes and binoculars will reveal this rich group of mixed magnitude stars and fill the imagination with strange notions of reality. Through larger scopes, many faint groupings emerge as the star count rises to well over 100 members. Several stars of color – orange in particular – are also seen along with a number of doubles.

First noted telescopically by Giovanni Batista Hodierna in the mid-1500s, ancient texts indicate that Aristotle saw this naked-eye cluster some 1800 years earlier. Like other Hodierna discoveries, M41 was included on Messier’s list – along with even brighter clusters of antiquity such as Praesepe in Cancer and the Pleiades in Taurus.
Open cluster M41 is located 2300 light years away and recedes from us at 34km/sec – about the speed Venus moves around the Sun. M41 is a mature cluster, around 200 million years old and 25 light years in diameter. Remember M41…Fireflies in night skies.

Tuesday, February 21 – Be sure to have a look at the Moon this morning before dawn, because Jupiter will be joining it!

Tonight Luna will rise well after midnight, so let’s return to look at two of the few globular clusters of the season. Starting with M79 in Lepus, head due south around 15 degrees into Columba – the Dove. There you’ll find a second winter cluster almost a full magnitude brighter than M79 – NGC 1851. Give it a try!

Want another challenge? Head for bright Alnitak – the easternmost star in Orion’s belt. Using medium to low power, carefully shift bright Alnitak out from the center of the field about a full moon’s width to the west. With dark skies, you will see a large, faint, tulip-shaped nebulosity broken by one or more dark lanes. This is the “Flame Nebula”
– NGC 2024. Congratulations. This one isn’t easy, but on the darkest of nights it may surprise you!

Wednesday, February 22 – If skies are clear this evening, all you need do is step outside as the last glow of the long-set Sun pales to the southwest. Prepare your eyes – and heart – to follow the great expanse of the many brilliant stars of the winter Milky Way. Arching from Puppis to Cassiopeia, you might also see a fading Deneb – crown star of the Northern Cross – descending west. If you live towards the southern hemisphere, you should see brilliant Canopus – second brightest star in the night sky high to the south. In honor of the many splendid lights of the winter Milky Way, take out your binoculars and explore the marvels that await you!

Did you find something in the binoculars that caught your eye? Why not get the scope out and see if you can track it down. Navigating with a scope can be a challenge. Things look differently by eye, binoculars, finderscope, and telescope, but that’s what learning the night sky is all about.

Thursday, February 23 – On this date in 1987, Ian Shelton made an astonishing discovery – a supernova. At 160,000 light years away, distant SN1987a was the brightest novae display seen in almost 400 years. More importantly, before it occurred, a blue star of roughly 20 solar masses was already known to exist in that same location within the Large Magellanic Cloud. Catalogued as Sanduleak -69?202, that star is now gone. With available data on the star, astronomers were able to get a “before and after” look at one of the most extraordinary events in the universe! Tonight, let’s have a look at a similar event known as “Tycho’s Supernova.”

Located northwest of Kappa Cassiopeia, SN1572 appeared so bright in that year that it could be seen with the unaided eye for six months. Since its appearance was contrary to Ptolemaic theory, this change in the night sky now supported Copernicus’ views and heliocentric theory gained credence. We now recognize it as a strong radio source, but can it still be seen? There is a remnant left of this supernova, and it is challenging even with a large telescope. Look for thin, faint filaments that form an incomplete ring around 8 arc minutes across.

Friday, February 24 – In 1968, during a radio-telescope search for quasars, Susan Jocelyn Bell discovered the first pulsar. At first the regularity of the pulses was so precise that Bell and her college advisor, D. A. Hewish, thought they might be receiving a signal from a distant civilization. It soon became clear as the number of these objects multiplied that all were natural – rather than artificial – phenomena. Two co-directors of the project, Hewish and Ryle, later matched Bell’s observations to the notion of a rotating neutron star. This won them the 1974 Physics Nobel Prize and proved a theory brought forward thirty years earlier by J. Robert Oppenheimer.
Tonight let’s take a journey just a breath above Zeta Tauri and spend some quality time with a pulsar embedded in the most famous supernova remnant of all. Factually, we know the Crab Nebula to be the remains of an exploded star recorded by the Chinese in 1054. We know it to be a rapid expanding cloud of gas moving outward at a rate of 1,000 km per second, just as we understand there is a pulsar in the center. We also know it as first recorded by John Bevis in 1758, and then later cataloged as the beginning Messier object – penned by Charles himself some 27 years later to avoid confusion while searching for comets. We see it revealed beautifully in timed exposure photographs, its glory captured forever through the eye of the camera — but have you ever really taken the time to truly study M1?

Then you just may surprise yourself…

In a small telescope, M1 might seem to be a disappointment – but do not just glance at it and move on. There is a very strange quality to the light which reaches your eye, even though initially it may just appear as a vague, misty patch. Allow your eyes to adjust and M1 will appear to have “living” qualities – a sense of movement in something that should be motionless. The “Crab” holds true to many other spectroscopic studies. The concept of differing light waves crossing over one another and canceling each other out – with each trough and crest revealing differing details to the eye – is never more apparent than during study. To observe M1 is to at one moment see a “cloud” of nebulosity, the next a broad ribbon or filament, and at another a dark patch. When skies are stable you may see an embedded star, and it is possible to see six such stars.

Many observers have the ability to see spectral qualities, but they need to be developed. From ionization to polarization – our eye and brain are capable of seeing to the edge of infra-red and ultra-violet. Even a novice can see the effects of magnetism in the solar “Wilson Effect.” But what of the spinning neutron star at M1’s heart? We’ve known since 1969 that M1 produces a “visual” pulsar effect. About once every five minutes, changes occurring in the neutron star’s pulsation affect the amount of polarization, causing the light waves to sweep around like a giant “cosmic lighthouse” and flash across our eyes. M1 is much more than just another Messier. Capture it tonight!!

Saturday, February 25 – Since we’ve studied the “death” of a star, why not take the time tonight to discover the “birth” of one? Our journey will start by identifying Aldeberan (Alpha Tauri) and move northwest to bright Epsilon. Hop 1.8 degrees west and slightly to the north for an incredibly unusual variable star – T Tauri.
Discovered by J.R. Hind in October 1852, T Tauri and its accompanying nebula, NGC 1555, set the stage for discovery with a pre-main sequence variable star. Hind reported the nebula, but also noted that no catalog listed such an object in that position. His observations also included a 10th magnitude uncharted star and he surmised that the star in question was a variable. On each count Hind was right, and both were followed by astronomers for several years until they began to fade in 1861. By 1868, neither could be seen and it wasn’t until 1890 that the pair was re-discovered by E.E. Barnard and S.W. Burnham. Five years later? They vanished again.

T Tauri is the prototype of this particular class of variable stars and is itself totally unpredictable. In a period as short as a few weeks, it might move from magnitude 9 to 13 and other times remain constant for months on end. It is about equal to our own Sun in temperature and mass
– and its spectral signature is very similar to Sol’s chromosphere – but the resemblance ends there. T Tauri is a star in the initial stages of birth!

T Tauri are all pre-main sequence and are considered “proto-stars”. In other words, they continuously contract and expand, shedding some of their mantle of gas and dust. This gas and dust is caught by the star’s rotation and spun into an accretion disc – which might be more properly referred to as a proto-planetary disc. By the time the jets have finished spewing and the material is pulled back to the star by gravity, the proto-star will have cooled enough to have reached main sequence and the pressure may have allowed planetoids to form from the accreted material.

Sunday, February 26 – Today is the birth date of Camille Flammarion. Born in 1842, he became a widely read author of astronomy and originated the idea that we were not alone – the notion of extraterrestrial intelligence. Yet, Flammarion was more than the great grandfather of SETI. In 1877, Flammarion found Charles Messier’s personal notes and catalog in an antiquarian book store. Based on those notes, he was able to identify M102 as Dreyer’s NGC 5866 and associate NGC 4594 with M104. Because of Flammarion’s hard work of scholarship and astronomical observation, two previously obscure references to faint studies in the Messier Catalogue were properly identified.

To locate these two studies, you’ll be waiting until around local midnight. Start at Iota Draconis and head about half a fistwidth in the direction of bright Arcturus to a solitary 5.2 magnitude star. Small, 10th magnitude M102 is about one degree due north toward Polaris. M104 – the “Sombrero Galaxy” – is just a bit more than a fistwidth west of Spica. At magnitude 8.3, it can be easily seen as a small faint glow in binoculars or finderscope. But it requires a telescope and a dark sky to hint at its namesake.

While you’re waiting for them to rise, relax and enjoy the Delta Leonid meteor shower. Entering our atmosphere at speeds of up to 24 kilometers per second, these slow travelers will seem to radiate from a point around the middle of Leo’s “back.” The fall rate is rather slow at 5 per hour, but any meteor trail is a delight to catch!

May all your journeys be at light speed… ~Tammy Plotner. With Jeff Barbour @astro.geekjoy.com