Posted on by Ken Kremer

A Continent Ablaze in Auroral and Manmade Light

Aurora Borealis over Western Canada from the ISS Expedition 30 crew. Credit: NASA


Video Caption: Up the East Coast of North America. Credit: NASA

The North American continent is literally set ablaze in a confluence of Auroral and Manmade light captured in spectacular new videos snapped by the astronauts serving aboard the International Space Station (ISS).

The Expedition 30 crew has recently filmed lengthy sequences of images that are among the most stunning ever taken by astronauts flying in orbit some 240 miles (385 kilometers) over the United States and Canada.

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Teams working at the Crew Earth Observations center at NASA’s Johnson Space Center in Houston, Texas have assembled hundreds of individual still images taken onboard the ISS into a series of amazing videos.

Two videos collected here focus on the East and West coasts of North America and show the path traveled by the station from the crew’s perspective as they photographed the light emitted by hundreds of millions of humans living below and the brilliant light of the Aurora Borealis shining above them.

Recently we highlighted a single night time snapshot of the East Coast and tens of millions of humans.

Night time Panorama of US East Coast from the ISS
Astronauts captured this stunning nighttime panorama of the major cities along the East Coast of the United States on Jan. 29. Credit: NASA

Now the NASA team has assembled the entire sequence of images taken on January 29, 2012 from 05:33:11 to 05:48:10 GMT into a video -see above.

The orbital pass runs from Central America just southwest of Mexico and continues to the North Atlantic Ocean, northeast of Newfoundland. It begins by looking over Central America towards the Gulf of Mexico and the southeastern United States. As the ISS travels northeast over the gulf, some southeastern United States cities can be distinguished, like New Orleans, Mobile, Jacksonville, and Atlanta. Continuing up the east coast, some northeastern states, like Washington, D.C., Baltimore, Philadelphia, and New York City stand out brightly along the coastline. The Aurora Borealis shines in the background as the pass finishes near Newfoundland

The 2nd video is titled “Across Southwest Canada at Night”

This sequence of shots was taken January 25, 2012 from 12:34:11 to 12:36:28 GMT, on a pass from near the border of British Columbia, Canada and Washington state, near Vancouver Island, to southern Alberta, near Calgary.

The main focus of this video is the Aurora Borealis over Canada, which appears very near the ISS during this short and exciting video.

And don’t forget the fabulous ISS shots of Comet Lovejoy taken in December 2011 by Expedition 30 Commander Dan Burbank.

Comet Lovejoy on 22 Dec. 2011 from the International Space Station. Comet Lovejoy is visible near Earth’s horizon in this nighttime image photographed by NASA astronaut Dan Burbank, Expedition 30 commander, onboard the International Space Station on Dec. 22, 2011. Credit: NASA/Dan Burbank

For an otherworldly and eerie perspective, click here to see what a Manmade artifact on the surface of Mars looks like as seen from Mars Orbit – also taken just a few days ago on Jan. 29, 2012, but this time by a robot in place of a human !

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast – February 12-18, 2012

Spirograph Nebula Courtesy of the Hubble Space Telescope

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Greetings, fellow SkyWatchers! As the Moon fades away, dark sky studies return and so do we as we take a look at a great collection of nebulae this week and expand your Herschel studies. Get out your binoculars and telescopes, because here’s what’s up!

Sunday, February 12 – Today is the anniversary (2001) of NEAR landing on asteroid Eros. The Near Earth Asteroid Rendezvous (NEAR) mission was the first to ever orbit an asteroid, successfully sending back thousands of images. Although it was not designed to land on Eros, it survived the low speed impact and continued to send back data. Would you like to view Eros for yourself? It will be visible a few hours after sky dark. At somewhere between magnitude 11 and 12, Eros will require at least a mid-sized telescope, but is very viewable to both hemispheres along the Hydra/Crater border… and about a handspan southwest of Mars! Be sure to check resources for a planetarium program or on-line service which will give you a precise location for your time and area.

Tonight we’ll continue onward with our studies of Lepus as we head for two more of the coveted Herschel 400 objects. Our hop starts with beautiful Gamma and NGC 2073. Located less than a fingerwidth northeast of Gamma (RA 05 45 53.90 Dec -21 59 59.0), NGC 2073 might be magnitude 12.4, but its small size makes it anything but easy. Even if it does have some highly studied molecular cloud structure, be prepared to see nothing but a tiny, egg-shaped contrast change in the elliptical Herschel 241.

Continue northeast a little more than 2 degrees (RA 05 54 52.30 Dec -20 05 03.0) to encounter Herschel 225 – NGC 2124. Although it is slightly fainter, we are at least picking up something with more recognizable structure. Oriented north/south, Herschel 225 is an inclined spiral with a bright nucleus. Set in a wonderfully rich star field, it’s difficult to spot at first with low power, but its slim structure holds up well to magnification. This one is really a pleasure.

Monday, February 13 – Today is the birthday of J.L.E. Dreyer. Born in 1852, the Danish-Irish Dreyer came to fame as the astronomer who compiled the New General Catalogue (NGC) published in 1878. Even with a wealth of astronomical catalogs to chose from, the NGC objects and Dreyer’s abbreviated list of descriptions still remain the most widely used today.

Tonight let’s make Dreyer proud as we finish up our Herschel 400 studies for Herschel 267. At magnitude 13, NGC 2076 (Right Ascension: 5 : 46.8 – Declination: -16 : 46 ) is a lot less forgiving of scope size and sky conditions than some galaxies, but if aperture and sky cooperate, you are in for a real treat! Although it is fairly small and somewhat faint, NGC 2076 is an edge-on that will show indications of a dark dustlane across its brighter nucleus, when using aversion. The lane itself has been highly studied for dust extinction and star forming properties and as recently as 2003 a supernova event was reported just south of the nucleus.

Now let’s drop south about one degree and pick up Herschel 270! Far brighter at magnitude 11.9, don’t let the ordinary elliptical NGC 2089 (Right Ascension: 5 : 47.8 – Declination: -17 : 36) fool you. What would appear to be a stellar nucleus is indeed stellar. Studies done by AAVSO have shown that the bright point of light is actually a line of sight star. Congratulations on your studies and be sure to write down your Herschel “homework!”

Tuesday, February 14 – Happy Valentine’s Day! Today is the birthday of Fritz Zwicky. Born in 1898, Zwicky was the first astronomer to identify supernovae as a separate class of objects. His insights also proposed the possibility of neutron stars. Among his many achievements, Zwicky also catalogued galaxy clusters and designed jet engines.

In mythology, Lepus the Hare is hiding in the grass at Orion’s feet. As we have seen, there are many objects of beauty hidden within what seems to be a very ordinary constellation. Before we leave the “Rabbit” for this year, there is one last object that is worthy of attention. If you look to the feet of Orion and the brightest star of Lepus, you will see that they make a triangle in the sky. Tonight we are headed towards the center of that triangle for a singular object – the Spirograph Nebula.

Shown in all its glory through the eye of the Hubble Telescope, the light you see tonight from the IC 408 (Right Ascension: 5 : 17.9 – Declination: -25 : 05) planetary nebula left in the year 7 AD. Its central star, much like our own Sol, was in the final stages of its life at that time, and but a few thousand years earlier was a red giant. As it shed its layers off into about a tenth of a light-year of space, only its superheated core remained – its ultraviolet radiation lighting up the expelled gas. Perhaps in several thousand years the nebula will have faded away, and in several billion years more the central star will have become a white dwarf – a fate that also awaits our own Sun.

At magnitude 11, it is well within reach of a small to mid-size telescope. Like all planetary nebulae, the more magnification – the better the view. The central star is easily seen against a slightly elongated shell and larger telescopes bring an “edge” to this nebula that makes it very worthwhile studying. Spend some quality time with this object. With larger scopes, there is no doubt a texture to this planetary that will delight the eye…and touch the heart!

Wednesday, February 15 – Born on this day in 1564 was the man who fathered modern astronomy – Galileo Galilei. Two and a half centuries ago, he became first scientist to use a telescope for astronomical observation and his first target was the Moon. Just before dawn this morning you will have the opportunity to observe the waning crescent and the tiny crater named for Galileo. Almost central along the terminator and caught near the edge of Oceanus Procellarum, you will see a small, bright ring. This is Reiner Gamma and you will find Galileo just a short hop to the northwest as a tiny, circular crater. What a shame the cartographers did not pick a more vivid feature to name after the great Galileo!

With absence of the Moon in our favor tonight, it’s time to learn the constellation of Monoceros as the skies darken and Orion begins to head west. By using the red giant Betelgeuse, diamond-bright Sirius and the beacon of Procyon, we can see these three stars form a triangle in the sky with Sirius pointing towards the south. The “Unicorn” is not a bright constellation, and most of its stars fall inside this area with its Alpha star almost a handspan south of Procyon.

Using the belt of Orion as a guide, look a handspan east, this is Delta. A fistwidth away to the southeast is Gamma; with Beta about two fingerwidths further along. About a palmwidth southeast of Betelguese is Epsilon. Although this might seem simplistic, knowing these stars will help you find many wonderful objects. Let’s start our journey tonight two fingerwidths northwest of Epsilon… NGC 2186 (Right Ascension: 6 : 12.2 – Declination: +05 : 2) is a triangular open cluster of stars set in a rich field that can be spotted with binoculars and reveals as many as 30 or more stars to even a small telescope. Not only is this a Herschel 400 object that can be spotted with simple equipment, but a highly studied galactic cluster that contains circumstellar discs!

Thursday, February 16 – On this day in 1948, Gerard Kuiper was celebrating his discovery of Miranda – one of Uranus’ moons. Just 42 years earlier on this day, both Kopff and Metcalf were also busy – discovering asteroids! Today is the birthday of Francois Arago. Born in 1786, Arago became the pioneer scientist in the wave nature of light. His achievements were many and he is also credited as the inventor of the polarimeter and other optical devices.

Tonight let’s celebrate Arago’s achievements in polarization as we return again to Epsilon Monocerotis. Our destination is around a fingerwidth east as we seek out another star cluster that has an interesting companion – a nebula!

NGC 2244 (Right Ascension: 6 : 32.4 – Declination: +04 : 52) is a star cluster embroiled in a reflection nebula spanning 55 light-years and most commonly called “The Rosette.” Located about 2500 light-years away, the cluster heats the gas within the nebula to nearly 18,000 degrees Fahrenheit, causing it to emit light in a process similar to that of a fluorescent tube. A huge percentage of this light is hydrogen-alpha, which is scattered back from its dusty shell and becomes polarized.

While you won’t see any red hues in visible light, a large pair of binoculars from a dark sky site can make out a vague nebulosity associated with this open cluster. Even if you can’t, it is still a wonderful cluster of stars crowned by the yellow jewel of 12 Monocerotis. With good seeing, small telescopes can easily spot the broken, patchy wreath of nebulosity around a well-resolved symmetrical concentration of stars. Larger scopes, and those with filters, will make out separate areas of the nebula which also bear their own distinctive NGC labels. No matter how you view it, the entire region is one of the best for winter skies.

Friday, February 17 – Tonight is a good time for us to go hunting some obscure objects that will require the darkest of skies. Once again, we’ll use our guide star Epsilon and tonight we’ll be heading about three fingerwidths northeast for a vast complex of nebulae and star clusters.

To the unaided eye, 4th magnitude S Monocerotis is easily visible and to small binoculars so are the beginnings of a rich cluster surrounding it. This is NGC 2264 (Right Ascension: 6 : 41.1 – Declination: +09 : 53). Larger binoculars and small telescopes will easily pick out a distinct wedge of stars. This is most commonly known as the “Christmas Tree Cluster,” its name given by Lowell Observatory astronomer Carl Lampland. With its peak pointing due south, this triangular group is believed to be around 2600 light-years away and spans about 20 light-years. Look closely at its brightest star – S Monocerotis is not only a variable, but also has an 8th magnitude companion. The group itself is believed to be almost 2 million years old.

The nebulosity is beyond the reach of a small telescope, but the brightest portion illuminated by one of its stars is the home of the Cone Nebula. Larger telescopes can see a visible V-like thread of nebulosity in this area which completes the outer edge of the dark cone. To the north is a photographic only region known as the Foxfur Nebula, part of a vast complex of nebulae that extends from Gemini to Orion.

Northwest of the complex are several regions of bright nebulae, such as NGC 2247, NGC 2245, IC 446 and IC 2169. Of these regions, the one most suited to the average scope is NGC 2245 (Right Ascension: 6 : 32.7 – Declination: +10 : 10), which is fairly large, but faint, and accompanies an 11th magnitude star. NGC 2247 (Right Ascension: 6 : 33.2 – Declination: +10 : 20) is a circular patch of nebulosity around an 8th magnitude star, and it will appear much like a slight fog. IC 446 is indeed a smile to larger aperture, for it will appear much like a small comet with the nebulosity fanning away to the southwest. IC 2169 is the most difficult of all. Even with a large scope a “hint” is all!

Enjoy your nebula quest…

Saturday, February 18 – On this day in 1930, a young man named Clyde Tombaugh was very busy checking out some photographic search plates taken with the Lowell Observatory’s 13″ telescope. His reward? The discovery of Pluto! And just where is the planet that isn’t a planet any more? You can find it before dawn! The little rascal is hiding out in a very stellar field just east of M25 and a couple of degrees northwest of the slender crescent Moon. How do you know which faint “star” is Pluto? Well, if you set a computerized telescope to RA 18h 24m 59s – Dec 19°18’44”, it will be precisely in the center of the field if you are perfectly polar aligned. If you are using a manual telescope, you will need to sketch the field and return over a period of several days to see which “star” moves. It would be a great lesson – since early astronomers did it that way!

This evening let us return to the realm of binoculars and small telescopes as we head now for Beta Monocerotis and a little more than a fingerwidth north for NGC 2232 (Right Ascension: 6 : 26.6 – Declination: -04 : 45). This wonderful collection of stars sparkles with chains and various magnitudes – the brightest of which is 5th magnitude 10 Monocerotis. Well resolved with a small telescope, its apparent size of about a full moon-width makes it a true delight and it can even be spotted unaided from a dark sky site. Be sure to note it, because it is on many open cluster study lists.

Now head back to Beta and about the same distance west for Class D cluster NGC 2215 (Right Ascension: 6 : 21.0 – Declination: -07 : 17). At magnitude 8, it is still within the realm of binoculars, but will look like a small fuzzy patch beyond resolution. Try this one with a telescope! Set in a rich field, the compressed area of near equal magnitude stars isn’t the most colorful in the sky, but you can add another to your Herschel hits!

Until next week, may all your journeys be at light speed!

Posted on by Mike Simonsen

Hubble’s 1923 Nova in Andromeda Erupts Again!

M31N 1923-12c in Andromeda, position plotted by the AAVSO Chart Plotter

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On December 11, 1923, Edwin Hubble discovered a nova in the Andromeda galaxy. Novae occurring in our Milky Way’s sister galaxy have proven to be not that uncommon, as there have been over 800 novae detected in M31 in the last 100 years. Hubble’s 1923 discovery became known as M31N 1923-12c, the third nova discovered in December of 1923.

Fast forward to January 21, 2012, and another nova has been discovered in M31, already the second novae seen in January 2012. K. Nishiyama and F. Kabashima reported the discovery and it has been given the designation, PNV J00423804+4108417. A day later, a spectrum was taken with the 9.2m Hobby-Eberly Telescope using the Marcario Low-Resolution Spectrograph, confirming the new nova in M31, and that it is a member of the He/N spectroscopic class.

What’s even more interesting, however, is that the new nova likely comes from the same progenitor as Hubble’s 1923 nova!

Artist's rendition of the recurrent nova RS Oph Credit: David Hardy/PPARC

Classical novae are a subclass of cataclysmic variable stars. They are semi-detached binary systems where an evolved, late-type star fills its Roche lobe and transfers mass to its white dwarf companion. If the mass accretion rate onto the white dwarf is sufficiently low, it allows this gas to pile up and become degenerate. Eventually, after thousands to tens of thousands of years, a thermonuclear runaway ensues in this highly pressurized layer of gas, leading to a nova eruption. These eruptions can reach an absolute magnitude as bright as about MV -10, making them among the most luminous explosions in the Universe. Their high luminosities and rates, about 50 per year in a galaxy like M31, make novae very useful to astronomers exploring the properties of close binaries in extragalactic stellar populations.

Comparing its position with the approximately 900 novae in W. Pietsch’s M31 nova catalog revealed that PNV J00423804+4108417 was located about six arc seconds from the cataloged position of M31N 1923-12c, the nova discovered by Edwin Hubble on December 11, 1923. Given that the positions of M31 novae from early photographic surveys were typically reported to a precision of only ten arc seconds, and that He/N spectra are often associated with recurrent novae, astronomers considered the possibility that M31N 1923-12c and PNV J00423804+4108417 represented two outbursts arising from the same nova progenitor. To explore this possibility further, F. Schweizer (Carnegie Observatories) located Hubble’s original plate in the Carnegie Observatories archives and performed an eyeball comparison of the position of Hubble’s nova with that of PNV J00423804+4108417, finding them to match within ~1.5″. You can see the images for yourself here.

Edwin Hubble

After digitally scanning the Hubble plate and comparing the position of the nova relative to those of three nearby USNO reference stars, analysis revealed that M31N 1923-12c was located
at R.A. = 00 42 38.06; Decl. = 41 08 41.0 (J2000). Hubble’s M31N 1923-12c and this year’s PNV J00423804+4108417 are the same object!

88 years and a handful of days later, PNV J00423804+4108417 represents the second recorded outburst of the recurrent nova M31N 1923-12c. Like the telescope named for him, Hubble’s legacy to astronomy and astrophysics continues to grow to this very day. Way to go, Edwin.

This blog post adapted from Astronomer’s Telegram #3914
M31N 1923-12c is a recurrent nova in M31
Authors: A. W. Shafter (SDSU), M. J. Darnley, M. F. Bode (Liverpool JMU, UK), R. Ciardullo (PSU), F. Schweizer (Carnegie Observatories)

Posted on by Nancy Atkinson

GALEX Mission Comes to an End

The GALEX spacecraft before its launch in 2003. Credit: JPL

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A mission which helped map the ultraviolet sky and worked to confirm the nature of dark energy is coming to an end. Galaxy Evolution Explorer, or GALEX, was placed in standby mode today after nearly nine years of service and will be decommissioned later this year. With data from the mission, scientists were able to catalog millions of galaxies spanning 10 billion years of cosmic time.

The Galaxy Evolution Explorer launched in April of 2003 on board a Pegasus XL rocket. It completed its prime mission in the fall of 2007, but the mission was extended to continue its census of stars and galaxies.

The variable star Mira. Image credit: Galex

Other mission highlights include the discovery of a gigantic comet-like tail behind a speeding star, finding rings of new stars around old galaxies, exploring “teenager” galaxies, which help to explain how galaxies evolve, and catching a black hole devouring a star.
The mission was part of NASA’s Explorer’s program and was built and managed by the Jet Propulsion Laboratory. Scientists from around the world participated in GALEX studies.

For a complete list of discoveries by GALEX, see this JPL webpage.

Posted on by Tammy Plotner

The Milky Way Galactic Disk – Forever Blowing Bubbles

Ten Milky Way Project images most-favourited by volunteers, in no particular order. Coordinates are image centres, image sizes are indicated by the zoom level (zoom).

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Score another one for citizen science! In a study released just days ago, a new catalog containing over five thousand infrared bubble entries was added through the “Milky Way Project” website. The work was done independently by at least five participants who measured parameters for position, radius, thickness, eccentricity and position angle. Not only did their work focus on these areas, but the non-professionals were responsible for recovering the locations of at least 86% of additional bubble and HII catalogs. Cool stuff? You bet. Almost one third of the Milky Way Project’s studied bubbles are located at the edge of an even larger bubble – or have more lodged inside. This opens the door to further understanding the dynamics of triggered star formation!

Just what is the Milky Way Project? Thanks to the Galaxy Zoo and Zooniverse, scientists have been able to enlist the help of an extensive community of volunteers able to tackle and analyze huge amounts of data – data that contains information which computer algorithms might miss. In this case it’s visually searching through the Galactic plane for whole or broken ring-shaped structures in images done by Spitzer’s Galactic Legacy Infrared Survey Extraordinaire (GLIMPSE) project. Here the bubbles overlap and the structures are so complex that only humans can sort them out for now.

Screenshot of the Milky Way Project user interface.
Screenshot of the Milky Way Project user interface.
“The MWP is the ninth online citizen science project created using the Zooniverse Application Programming Interface
(API) tool set. The Zooniverse API is the core software supporting the activities of all Zooniverse citizen science projects.” says R. J. Simpson (et al). “Built originally for Galaxy Zoo 2, the software is now being used by 11 different projects. The Zooniverse API is designed primarily as a tool for serving up a large collection of `assets’ (for example, images or video) to an interface, and collecting back user-generated interactions with these assets.”

Through the interface, users mark the location of bubbles and other areas of significance such as small bubbles, green knots, dark nebulae, star clusters, galaxies, fuzzy red objects or simply unknowns. During this phase, the citizen scientist can make as many annotations as he or she wants before they submit their findings and receive a new assignment. Each annotated image is then stored in a database as a classification and the user can access their image again in an area of the website known as “My Galaxy”. However, images may only be classified once.

Example of raw user drawings and reduced, cleaned result using a sample MWP image. A GLIMPSE-only colour sam- ple is included to illustrate the dierences in the appearance of images inspected by CP06 and the MWP users.
When identifying galactic bubbles, the user creates a circle around the area which can be scaled to size and stretched into an elliptical configuration. Initially as the object is identified and marked, the user can control the position and size of the bubble. Once annotated the parameters can be edited, such as the ellipticity, annular thickness and rotation. The program even allows for regions where no obvious emission is present, such as a broken or partial bubble. This allows the user to match the bubbles they find in individual images to achieve an accurate representation You can even mark a favorite or interesting configuration as well!

“In order to assist in the data-reduction process, users are given scores according to how experienced they are at drawing bubbles. We treat the first 10 bubbles a user draws as practice drawings and these are not included in the final reduction. Users begin with a score of 0 and are given scores according to the number of precision bubbles they have drawn.” explains the team. “Precision bubbles are those drawn using the full tool set, meaning they have to have adjusted the ellipticity, the thickness and the rotation. This is done to ensure that users’ scores reflect their ability to draw bubbles well. While only precision bubbles are used to score volunteers, all bubbles drawn as included in the data reduction. The scores are used as weights when averaging the bubble drawings to produce the catalogue.”

Now it’s time to combine all that data. As of October of last year, the program has created a database of 520,120 user-drawn bubbles. The information is then sorted out and processed – with many inclusions left for further investigation. However, not all bubbles make the cut. When it comes to this project, only bubbles that have been identified fifty times or more are included into the catalog. What remains is a “clean bubble” – one that has been verified by at least five users and picked out at least 10% of the time by the volunteers when displayed.

“It is not known how many bubbles exist in the Galaxy, hence it is impossible to quantify the completeness of the MWP catalogue. There will be bubbles that are either not visible in the data used on the MWP, or that are not seen as bubbles.” says the team. “Distant bubbles may be obscured by foreground extinction. Faint bubbles may be masked by bright Galactic background emission or confused with brighter nebular structures. Fragmented or highly distorted bubbles present at high inclination angles may not appear as bubbles to the observer.”

Error measurements for MWP bubble MWP1G309059+01661. This bubble has a hit rate of 0.437, and a dispersion of 1.61'. Top gures show reduced and raw bubble drawings. Bottom figures show dispersions in measurements of position and size.
But don’t let it burst your bubble. This citizen science approach is an excellent idea from the the standpoint of observer objectivity and the final, reduced catalogue contains 5,106 visually identified bubbles. Of these, they are divided into a catalogue of 3,744 large bubbles identified by users as ellipses, and a catalogue of 1,362 small bubbles annotated by users at the highest zoom level images in the MWP.

And that’s not all… “In addition to the reduced bubble catalogue, a crowd sourced `heat map’ of bubble drawings has also been produced. The MWP `heat maps’ allow the bubble drawings to be explored without them needing to be reduced to elliptical annuli. Rather, the `heat maps’ allow contours of overlapping classifications to be drawn over regions of the Galactic plane reflecting levels of agreement between independent classifiers. In most cases the structures outlined in these maps are photo-dissociation regions traced by 8 um emission, but more fundamentally they are regions that multiple volunteers agree reflect the rims of bubbles.”

Yep. They are bubbles alright. Bubble produced around huge stars when an HII region is hollowed out by thermal overpressure, stellar winds, radiation pressure or a combination of them all. This impacts the surrounding, cold interstellar medium and creates a visible shell – or bubble. These regions serve as perfect observation points “to test theories of sequential, massive star formation triggered by massive star winds and radiation pressure” and to keep us forever fascinated…

And forever studying bubbles.

Original Story Source: The Milky Way Project First Data Release: A Bubblier Galactic Disk. For Further Reading: The Milky Way Project Zooniverse Blog.

Posted on by Tammy Plotner

The Milky Way’s Magnetic Personality

The sky map of the Faraday effect caused by the magnetic fields of the Milky Way. Red and blue colors indicate regions of the sky where the magnetic field points toward and away from the observer, respectively. The band of the Milky Way (the plane of the Galactic disk) extends horizontally in this panoramic view. The center of the Milky Way lies in the middle of the image. The North celestial pole is at the top left and the South Pole is at the bottom right. (Image Credit: Max Planck Institute for Astrophysics)

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Recently we took a look at a very unusual type of map – the Faraday Sky. Now an international team of scientists, including those at the Naval Research Laboratory, have pooled their information and created one of the most high precision maps to date of the Milky Way’s magnetic fields. Like all galaxies, ours has a magnetic “personality”, but just where these fields come from and how they are created is a genuine mystery. Researchers have always simply assumed they were created by mechanical processes like those which occur in Earth’s interior and the Sun. Now a new study will give scientists an even better understanding about the structure of galactic magnetic fields as seen throughout our galaxy.

The team, led by the Max Planck Institute for Astrophysics (MPA), gathered their information and compiled it with theoretical simulations to create yet another detailed map of the magnetic sky. As NRL’s Dr. Tracy Clarke, a member of the research team explains, “The key to applying these new techniques is that this project brings together over 30 researchers with 26 different projects and more than 41,000 measurements across the sky. The resulting database is equivalent to peppering the entire sky with sources separated by an angular distance of two full moons.” This huge amount of data provides a new “all-sky” look which will enable scientists to measure the magnetic structure of the Milky Way in minute detail.

In this map of the sky, a correction for the effect of the Galactic disk has been made in order to emphasize weaker magnetic field structures. The magnetic field directions above and below the disk seem to be diametrically opposed, as indicated by the positive (red) and negative (blue) values. An analogous change of direction takes place across the vertical center line, which runs through the center of the Milky Way. (Image Credit: Max Planck Institute for Astrophysics)
Just what’s so “new” about this map? This time we’re looking at a quantity called Faraday depth – an idea dependent on a line-of-sight information set on the magnetic fields. It was created by combining more than 41,000 singular measurements which were then combined using a new image reconstruction method. In this case, all the researchers at MPA are specialists in the new discipline of information field theory. Dr. Tracy Clarke, working in NRL’s Remote Sensing Division, is part of the team of international radio astronomers who provided the radio observations for the database. It’s magnetism on a grand scale… and imparts even the smallest of magnetic features which will enable scientists to further understand the nature of galactic gas turbulence.

The concept of the Faraday effect isn’t new. Scientists have been observing and measuring these fields for the last century and a half. Just how is it done? When polarized light passes through a magnetized medium, the plane of the polarization flips… a process known as Faraday rotation. The amount of rotation shows the direction and strength of the field and thereby its properties. Polarized light is also generated from radio sources. By using different frequencies, the Faraday rotation can also be measured in this alternative way. By combining all of these unique measurements, researchers can acquire information about a single path through the Milky Way. To further enhance the “big picture”, information must be gathered from a variety of sources – a need filled by 26 different observing projects that netted a total of 41,330 individual measurements. To give you a clue of the size, that ends up being about one radio source per square degree of sky!

The uncertainty in the Faraday map. Note that the range of values is significantly smaller than in the Faraday map (Fig. 1). In the area of the celestial south pole, the measurement uncertainties are particularly high because of the low density of data points. (Image Credit: Max Planck Institute for Astrophysics)
Even with depth like this, there are still areas in the southern sky where only a few measurements have been cataloged. To fill in the gaps and give a more realistic view, researchers “have to interpolate between the existing data points that they have recorded.” However, this type of data causes some problems with accuracy. While you might think the more exact measurements would have the greatest impact on the map, scientists aren’t quite sure how reliable any single measurement could be – especially when they could be influenced by the environment around them. In this case, the most accurate measurements don’t always rank the highest in mapping points. Like Heisenberg, there’s an uncertainty associated with the process of obtaining measurements because the process is so complex. Just one small mistake could lead to a huge distortion in the map’s contents.

Thanks to an algorithm crafted by the MPA, scientists are able to face these types of difficulties with confidence as they put together the images. The algorithm, called the “extended critical filter,” employs tools from new disciplines known as information field theory – a logical and statistical method applied to fields. So far it has proven to be an effective method of weeding out errors and has even proven itself to be an asset to other scientific fields such as medicine or geography for a range of image and signal-processing applications.

Even though this new map is a great assistant for studying our own galaxy, it will help pave the way for researchers studying extragalactic magnetic fields as well. As the future provides new types of radio telescopes such as LOFAR, eVLA, ASKAP, MeerKAT and the SKA , the map will be a major resource of measurements of the Faraday effect – allowing scientists to update the image and further our understanding of the origin of galactic magnetic fields.

Original Story Source: Naval Research Laboratory News.

Posted on by Tammy Plotner

Recycling Pulsars – The Millisecond Matters…

An artist's impression of an accreting X-ray millisecond pulsar. The flowing material from the companion star forms a disk around the neutron star which is truncated at the edge of the pulsar magnetosphere. Credit: NASA / Goddard Space Flight Center / Dana Berry

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It’s a millisecond pulsar… a rapidly rotating neutron star and it’s about to reach the end of its mass gathering phase. For ages the vampire of this binary system has been sucking matter from a donor star. It has been busy, spinning at incredibly high rotational speeds of about 1 to 10 milliseconds and shooting off X-rays. Now, something is about to happen. It is going to lose a whole lot of energy and age very quickly.

Astrophysicist Thomas Tauris of Argelander-Institut für Astronomie and Max-Planck-Institut für Radioastronomie has published a paper in the February 3 issue of Science where he has shown through numerical equations the root of stellar evolution and accretion torques. In this model, millisecond pulsars are shown to dissipate approximately half of their rotational energy during the last phase of the mass-transfer process and just before it turns into a radio source. Dr. Tauris’ findings are consistent with current observations and his conclusions also explain why a radio millisecond pulsar appears age-advanced over their companion stars. This may be the answer as to why sub-millisecond pulsars don’t exist at all!

“Millisecond pulsars are old neutron stars that have been spun up to high rotational frequencies via accretion of mass from a binary companion star.” says Dr. Tauris. “An important issue for understanding the physics of the early spin evolution of millisecond pulsars is the impact of the expanding magnetosphere during the terminal stages of the mass-transfer process.”

By drawing mass and angular momentum from a host star in a binary system, a millisecond pulsar lives its life as a highly magnetized, old neutron star with an extreme rotational frequency. While we might assume they are common, there are only about 200 of these pulsar types known to exist in galactic disk and globular clusters. The first of these millisecond pulsars was discovered in 1982. What counts are those that have spin rates between 1.4 to 10 milliseconds, but the mystery lay in why they have such rapid spin rates, their strong magnetic fields and their strangely appearing ages. For example, when do they switch off? What happens to the spin rate when the donor star quits donating?

“We have now, for the first time, combined detailed numerical stellar evolution models with calculations of the braking torque acting on the spinning pulsar”, says Thomas Tauris, the author of the present study. “The result is that the millisecond pulsars lose about half of their rotational energy in the so-called Roche-lobe decoupling phase. This phase is describing the termination of the mass transfer in the binary system. Hence, radio-emitting millisecond pulsars should spin slightly slower than their progenitors, X-ray emitting millisecond pulsars which are still accreting material from their donor star. This is exactly what the observational data seem to suggest. Furthermore, these new findings can help explain why some millisecond pulsars appear to have characteristic ages exceeding the age of the Universe and perhaps why no sub-millisecond radio pulsars exist.”

Thanks to this new study we’re now able to see how a spinning pulsar could possibly brake out of an equilibrium spin. At this age, the mass-transfer rate slows down and affects the magnetospheric radius of the pulsar. This in turn expands and forces the incoming matter to act as a propeller. The action then causes the pulsar to slow down its rotation and – in turn – slow its spin rate.

“Actually, without a solution to the “turn-off” problem we would expect the pulsars to even slow down to spin periods of 50-100 milliseconds during the Roche-lobe decoupling phase”, concludes Thomas Tauris. “That would be in clear contradiction with observational evidence for the existence of millisecond pulsars.”

Original Story Source: Max-Planck-Institut für Radioastronomie News Release>. For Further Reading: Spin-Down of Radio Millisecond Pulsars at Genesis.

Posted on by Nancy Atkinson

Are You Listening to Astronomy.FM?

Are you listening to Astronomy.FM? If not, you should join the audience of over 25,000 listeners in 85 countries who are enjoying this amazing free service. Astronomy.FM is billed as “The only all-Astronomy radio station in the Known Universe.” You can listen to this one-of-a-kind radio station on-line anytime, as it is streaming 24 hours a day and it includes both wonderful original astronomy programming and replays of many great astronomy shows and podcasts including Astronomy Cast, 365 Days of Astronomy, Planetary Radio, 60-Second Science and Slacker Astronomy, and also they have just recently added the Weekly Space Hangouts to their lineup. They also have science and astronomy news – the kind of stuff you really want to hear! (As Astronomy.FM announcer Rob Berthiaume said, “Who cares about Snooki? Give me more supernovae!”

What is really awesome about Astronomy.FM (besides their great programming) is that it is an all-volunteer organization. Everyone who you hear on-air does it for their love of astronomy.

Right now, Astronomy.FM is having their annual funding drive. They are trying to raise $6,000 for their annual budget. Can you imagine – running a 24-hour radio station for just $6,000 USD?? All revenue is spent on hardware, software, radio programming, and broadcast bandwidth. And 100% of their operational costs are funded solely by listener donations. They receive no government or commercial support, and none of their team members are paid. But, as you can imagine, the streaming fees alone are significant. In addition, with their growing listenership, they also are in need of a back-up server and advanced digital broadcast technology.

Astronomy.FM has some wonderful talent. On-air personality and Program Director Michael Foerster has an amazing voice that I could listen to all day, as well as having a wealth of knowledge about space and astronomy. Rob Keown, Tavi Greiner, and Marleen Bryan are also just some of the other wonderful voices you’ll hear on Astronomy.FM.

If you are already a listener, please consider donating to make sure this great service can remain online. If you aren’t familiar with Astronomy.FM, check it out, and enjoy all their great programming. And then consider supporting it. If you are interested in sharing your talents, here’s the “Contact” page for Astronomy.FM

Anything you can contribute will make a big difference, as they need to make their goal of $6,000 soon. I just donated and I hope you will too.

Posted on by Nancy Atkinson

Hitchcock Haunts a Nebula

The star-forming region NGC 3324. The intense radiation from several of NGC 3324's massive, blue-white stars has carved out a cavity in the surrounding gas and dust. The ultraviolet radiation from these young hot stars also cause the gas cloud to glow in rich colors. Credit: ESO

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First impression after seeing this new image of NGC 3324? It’s Alfred Hitchcock, bulbous nose and all (see image below for comparison). The right edge of the wall of gas and dust in this star-forming region really bears a strong resemblance to the famous profile of the British film director and producer, notorious for his thriller movies from the 1940’s through the 1970’s.

NGC 3324 is located in the southern constellation of Carina, roughly 7500 light-years from Earth. It is on the northern outskirts of the chaotic environment of the Carina Nebula. All the gas and dust here fueled a burst of star birth several millions of years ago and led to the creation of several hefty and very hot stars that are prominent in the new picture.

Alfred Hitchcock. Via iwatchstuff.com

A nickname for the NGC 3324 region is the ‘Gabriela Mistral Nebula,’ after the Nobel Prize-winning Chilean poet but I think I’ll start a petition to call it the Hitchcock Nebula. Hitchcock liked to make cameo appearances in his own movies, and perhaps he is making a pareidoliaic guest appearance here.

The new image of NGC 3324 was taken with the Wide Field Imager on the the European Southern Observatory’s 2.2-metre telescope at the La Silla Observatory in Chile. Read more about it on the ESO website.

Posted on by VirtualAstro

Night Sky Guide: February 2012

Special thanks to Ninian Boyle astronomyknowhow.com for information in parts of this guide

This month, the Solar System gives us a lot to observe and we’ll even start to see the ‘spring’ constellations appear later in the evenings. But February still has the grand constellations of winter, with mighty Orion as a centrepiece to long winter nights.

The Sun has finally started to perform as it should as it approaches “Solar Maximum.” This means we get a chance to see the northern lights (Aurora), especially if you live in such places as Scotland, Canada, Scandinavia, or Alaska or the southern light (Aurora Australis) if you live in the southern latitudes of South America, New Zealand and Australia. Over the past few weeks we have seen some fine aurora displays and will we hope to seesome in February!

We have a bit of a treat in store with a comet being this month’s favourite object with binoculars as well, so please read on to find out more about February’s night sky wonders.

You will only need your eyes to see most of the things in this simple guide, but some objects are best seen through binoculars or a small telescope.

So what sights are there in the February night sky and when and where can we see them?

Aurora

Looking north from the science operations center at Poker Fla,Alaska. Credit: Jason Ahrns.

The Aurora or Northern Lights (Aurora Borealis) have been seen from parts of Northern Europe and North America these last few weeks. This is because the Sun has been sending out huge flares of material, some of which have travelled towards us slamming into our magnetic field. The energetic particles then follow the Earth’s magnetic field lines towards the poles and meet the atoms of our atmosphere causing them to fluoresce, similar to what happens in a neon tube or strip light.

The colours of the aurora depend on the type of atom the charged particles strike. Oxygen atoms for example usually glow with a green colour, with some reds, pinks and blues. So the more active the Sun gets, the more likely we are to see the Northern (or Southern) Lights.

All you need to see aurora is your eyes, with no other equipment is needed. Many people image the aurora with exposures of just a few seconds and get fantastic results. Unfortunately auroras are “space weather” and are almost as difficult to predict as normal terrestrial weather, but thankfully we can be given the heads up of potential geomagnetic storms by satellites monitoring the Sun such as “STEREO” (Solar TErrestrial RElations Observatory).

Spaceweather.com is a great resource for aurora and other space weather phenomenon and the site has real-time information on current aurora conditions and other phenomenon.

Planets

Mercury is too close to the Sun to be seen at the beginning of the month, but will be visible very low in the south west from the 17th onwards. At the end of February Mercury will be quite bright at around mag -0.8 and will be quite a challenge. It can be seen for about 30 minutes after sunset.

Venus will improve throughout the month in the south west and will pass within half a degree of Uranus on the 9th of February. You can see this through binoculars or a small telescope. On the 25th Venus and the slender crescent Moon can be seen together a fabulous sight. At the end of month Venus closes in on Jupiter for a spectacular encounter in March.

Venus

Mars can easily be spotted with the naked eye as a salmon pink coloured “star” and starts off the month in the constellation of Virgo and moves into Leo on the 4th. Mars is at opposition on March 3rd but is also at its furthest from the Sun on the 15th February making this opposition a poor one with respect to observing due to its small apparent size. The planet will still be visually stunning throughout the month.

Mars

Jupiter starts off the month high in the south as darkness falls and is still an incredibly bright star-like object. Through good binoculars or a small telescope you can see its four Galilean moons – a fantastic sight. On the 8th at around 19:50 UT, Europa will transit Jupiter and through a telescope you will see the tiny moons shadow move across its surface. Throughout February, Jupiter moves further west for its close encounter with Venus in March.

Jupiter

Saturn rises around midnight in the constellation of Virgo and appears to be a bright yellowish star. Through a small telescope you will see the moon Titan and Saturn’s rings as well.

Saturn

Uranus is now a binocular or telescope object in the constellation of Pisces. On the 9th Uranus and the planet Venus will be within half a degree of each other.

Uranus

Neptune is not visible this month.

Comets

Comet Garradd Credit: astronomy.com

Comet Garradd is still on show early in the month — if you have binoculars — and as the month progresses the viewing should improve. You can find the comet in the constellation of Hercules not far from the globular cluster M92. It is about a half a degree away or around the same width as the full Moon. The comet is around magnitude 7 or a little fainter than the more famous globular cluster M13 also to be found in Hercules, so you will definitely need binoculars to see it. The comet is heading north over the course of the month which should mean that it will become a little easier to see. At the beginning of the month you will have to get up early to see it, the best time being around 5:30 to 6:30 GMT. By the end of the month though, it should be visible all night long.

Moon phases

  • Full Moon – 7th February
  • Last Quarter – 14th February
  • New Moon – 21st February

Constellations

In February, Orion still dominates the sky but has many interesting constellations surrounding it.

Above and to the left of Orion you will find the constellation of Gemini, dominated by the stars Castor and Pollux, representing the heads of the twins with their bodies moving down in parallel lines of stars with each other.

Legend has it that Castor and Pollux were twins conceived on the same night by the princess Leda. On the night she married the king of Sparta, wicked Zeus (disguised as a swan) invaded the bridal suite, fathering Pollux who was immortal and twin of Castor who was fathered by the king so was mortal.

Castor and Pollux were devoted to each other and Zeus decided to grant Castor immortality and placed Castor with his brother Pollux in the stars.

Gemini has a few deep sky objects such as the famous Eskimo nebula and some are a challenge to see. Get yourself a good map, Planisphere or star atlas and see what other objects you can track down.

Credit: Adrian West