Posted on by Tammy Plotner

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

Venus & Jupiter above Backyard Observatory - Credit: John Chumack

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Greetings, fellow SkyWatchers! What an awesome display of planets! Please take the time to walk outdoors just after skydark – regardless of where you live – and enjoy the bright display of Venus and Jupiter! However, this isn’t the only planetary action going on this week… Mars and M96 pair up, as well as Uranus and the Moon. There’s even a Southern Hemisphere meteor shower to enjoy! Pretty exciting, huh? Join the party by getting out your binoculars or telescopes and meet me for more in the backyard…

Monday, March 12 – No. That’s not the “headlights” of a UFO on the western horizon tonight… It’s a very cool pairing of Venus and Jupiter! It’s not often you see the two visually brightest planets making a close visual pass at each other and tonight you’ll spot the inner planet to the south and the outer planet to the north. This would make a great photo opportunity! Why not consider adding something interesting to your picture like a scenic building, tree, or even a person? Watch in the days ahead as Jupiter appears to stay in the same spot at the same time, yet Venus will climb higher.

Tonight let’s return again to NGC 2362 and start at the cluster’s north-northeast corner to have a look at a single, unusual star – UW Canis Majoris. At magnitude 4.9, this super-giant spectroscopic binary is one of the most massive and luminous in our galaxy. Its two stars are separated by only 27 million kilometers (17 million miles) and revolve around each other at a frenzied pace – in less than four and a half days. This speed means the stars themselves are flattened and would appear to be almost egg-shaped. The primary itself is shedding material that’s being collected by the secondary star.

Now drop southwest of NGC 2362 for another open cluster – NGC 2354 (Right Ascension: 7 : 14.3 – Declination: -25 : 44). While at best this will appear as a small, hazy patch to binoculars, NGC 2354 is actually a rich galactic cluster containing around 60 metal-poor members. As aperture and magnification increase, the cluster shows two delightful circle-like structures of stars, similar to a figure 8. Be sure to make a note… You’ve captured another Herschel 400 object!

Tuesday, March 13 – On this day in 1781, Uranus was discovered by William Herschel. Also on this day, in 1855, Percival Lowell was born in Boston. Educated at Harvard, Lowell went on to found the observatory which bears his name in Flagstaff, Arizona, and spent a lifetime studying Mars. During the early morning hours, you can honor Lowell by seeing Mars yourself – it’s best viewed when as high a possible on the ecliptic. While there won’t be a great many details, think of how many strides have been made since Lowell’s time and how advanced our knowledge of Mars has become!

Tonight let’s hop about four fingerwidths east-northeast of Sirius. Look for 5th magnitude SAO 152641 to guide you to a faint patch of stars in binoculars and a superb cluster in a telescope – NGC 2360 (Right Ascension: 7 : 17.8 – Declination: -15 : 37). Comprised of around eighty 10th magnitude and fainter stars, this particular cluster will look like a handful of diamond dust scattered on the sky. Discovered by Caroline Herschel in 1783, this intermediate-aged galactic cluster is home to red giants and heavy in metal abundance. Mark your notes, because not only is this a Herschel object, but is known as Caldwell 58 as well!

Wednesday, March 14 – Today is the birthday of Albert Einstein. Born in 1879, Einstein was one of the finest minds of our times. He developed the theory of gravity in terms of spacetime curvature – dependent on the energy density. Winner of the 1921 Physics Nobel prize, Einstein’s work on the photoelectric effect is the basis of modern light detectors.

Tonight let’s hop about a fistwidth north of bright Eta Canis Majoris and have a look at a “double cluster” – NGC 2383 (Right Ascension: 7 : 24.8 – Declination: -20 : 56) and NGC 2384 (Right Ascension: 7 : 25.1 – Declination: -21 : 02). Just showing in binoculars as a faint patch, this pair will begin resolution with larger scopes. Studied photometrically, it would appear these fairly young clusters have contaminated each other by sharing stars – which has also occurred in some clusters located in the Magellanic Clouds. Enjoy this unusual collection of stars…

Thursday, March 15 – Today celebrates the birth of Nicolas Lacaille. Born in 1713, Lacaille’s measurements confirmed the Earth’s equatorial bulge. He also named fourteen southern constellations. To honor Lacaille tonight, let’s begin some explorations in a constellation he named – Puppis!

For SkyWatchers living in high northern latitudes, you’ll never see all of this constellation, but there will be some things for you to explore, as well as a great deal for our friends in the southern hemisphere. The first is a Herschel object that lies directly on the galactic equator around five degrees north-northwest of Xi.

NGC 2421 (Right Ascension: 7 :36.3 – Declination: -20 : 37) is a magnitude 8.3 open cluster that will look like an exquisitely tiny “Brocchi’s Cluster” in binoculars and begin good resolution of its 50 or so members to an intermediate telescope, in an arrowhead-shaped pattern. It’s bright, it’s fairly easy to find, and it’s a great open cluster to add to your challenge study lists!

If you’re looking for a curiosity, then look no further than Leo and Mars. Tonight the happy red planet is situated just to the east of Messier 96 (Right Ascension: 10 : 46.8 – Declination: +11 : 49)! Enjoy celestial mechanics over the next few nights as Mars gently changes its position in relation with this distant galaxy… and gets much closer!

Friday, March 16 – On this day in 1926, Robert Goddard launched the first liquid-fuel rocket. But he was first noticed in 1907 when a cloud of smoke issued from a powder rocket fired in the basement of the physics building in Worcester Polytechnic Institute. Needless to say, the school took an interest in the work of this shy student. Thankfully they did not expel him, and thus began his lifetime of work in rocket science. Goddard was also the first to realize the full implications of rocketry for missiles and space flight, and his lifetime of work was dedicated to bringing this vision to realization. While most of what he did went unrecognized for many years, tonight we celebrate the name of Robert H. Goddard. This first flight may have gone only 12 meters, but forty years later on the date of his birth, Gemini 8 was launched, carrying Neil Armstrong and David Scott into orbit!

Let’s begin our observing evening with Mars. While you may have been keeping track of its position, did you know that it’s less than a degree away from a Messier object tonight? That’s right! You’ll find the dusty red planet just to the north of M96 (Right Ascension: 10 : 46.8 – Declination: +11 : 49).

Tonight we’ll pick up a challenge cluster and a planetary nebula on the Herschel list by returning to NGC 2421 and hopping about a fingerwidth northeast for NGC 2432 (Right Ascension: 7 : 40.9 – Declination: -19 : 05). This small, loose open cluster is rather dim and contains around 20 or so faint members shaped like the letter B. About another degree northeast is NGC 2440 – an elongated, small 11th magnitude planetary nebula. Look for its central star to cause a brightening and up the magnifying power to reveal it.

While out, be on watch for the Corona-Australids meteor shower. While the fall rate is low – 5 to 7 per hour – our friends in the southern hemisphere might stand a chance with this one!

Saturday, March 17 – On this day in 1958, the first solar-powered spacecraft was launched. Named Vanguard 1, it was an engineering test satellite. From its orbital position, the data taken from its transmission helped to redefine the true shape of the Earth.

Tonight let’s return to Xi Puppis and head less than a fingerwidth east-northeast for Herschel study NGC 2482 (Right Ascension: 7 : 54.9 – Declination: -24 : 18). At magnitude 7, this small fuzzy spot in binoculars will resolve into around two dozen stars to the telescope. Look for the diagonal chain of stars along its edge.

Now let’s have a look at an open cluster easily located in northeastern Orion. This 5.9 magnitude scattered group of stars may have been first observed by Giovanni Batista Hodierna in the mid-17th century. While bright enough to have been a Messier object, William Herschel added it to his log of discoveries on October 15, 1784, as H VIII.24. Of the 30 known stars associated with this 3,600 light-year distant group, the brightest is 50 million years old. A half-dozen of the cluster’s very brightest members can be seen in small scopes at mid-range powers. Look for NGC 2169 (Right Ascension: 6 : 08.4 – Declination: +13 : 57) slightly less than a fist width north-northeast of Betelguese and slightly south of Xi and Nu Orionis.

Sunday, March 18 – Although you can’t see it with just your eyes, Uranus is less than a degree from the Moon this morning. For some areas this could be an occultation, so be sure to check IOTA information!

Today in 1965, the first ever spacewalk was performed by Alexei Leonov onboard the Soviet Voskhod spacecraft. The “walk” only lasted around 20 minutes and Alexei had problems in re-entering the spacecraft because his space suit had enlarged slightly. Imagine his fear as he had to let air leak out of his space suit in order to squeeze back inside. When they landed off target in the heavily forested Ural Mountains, the crew of two had to spend the night in the woods surrounded by wolves. It took over twenty-four hours before they were located and workers had to chop their way through the forest and recover them on skis. Brave men!

Tonight let’s honor them by studying a small area which contains not only three Herschel objects – but two Messiers as well – M46 and M47. You’ll find them less than a handspan east of Sirius and about a fistwidth north of Xi Puppis.

The brighter of the two clusters is M47 (Right Ascension: 7 : 36.6 – Declination: -14 : 30) and at 1600 light-years away, it’s a glorious object for binoculars. It is filled with mixed magnitude stars that resolve fully to aperture with the double Struve 1211 near its center. While M47 is in itself a Herschel object, look just slightly north (about a field of view) to pick up another cluster which borders it. At magnitude 6.7, NGC 2423 isn’t as grand, but it contains more than two dozen fairly compressed faint stars with a lovely golden binary at its center.

Now return to M47 and hop east to locate M46 (Right Ascension: 7 : 41.8 – Declination: -14 : 49). While this star cluster will appear to be fainter and more compressed in binoculars, you’ll notice one star seems brighter than the rest. Using a telescope, you’ll soon discover the reason. 300 million year old M47 contains a Herschel planetary nebula known as NGC 2438 in its northern portion. The cluster contains around 150 resolvable stars and may involve as many as 500. The bright planetary nebula was first noted by Sir William Herschel and then again by John. While it would appear to be a member of the cluster, the planetary nebula is just a little closer to us than the cluster. Be sure to mark your notes… There’s a lot there in just a little area!

Until next week? May all of your journeys be at light speed!

Many thanks to John Chumack for the inspiring image!

Posted on by Paul Scott Anderson

‘Stealth Merger’ of Dwarf Galaxies Seen in New Images

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Space may be vast, but accidents can still happen, like when galaxies “collide,” usually resulting in the smaller one having its stars scattered by the larger one. New high-resolution images of two dwarf galaxies merging together have now been obtained by astronomers, providing a more detailed look at something which could only barely be seen before. While the larger galaxy of the two, NGC 4449, is easily visible, its smaller companion was little more than just a faint smudge until now.

The new study comes from an international team of astronomers led by David Martínez-Delgado of the Max Planck Institute for Astronomy in Heidelberg. Their paper will be published in an upcoming issue of Astrophysical Journal Letters.

When the galaxies collide, the smaller one essentially gets torn apart by the larger one. As explained by Aaron Romanowsky, an astronomer at the University of California, Santa Cruz (UCSC), “This is how galaxies grow. You can see the smaller galaxy coming in and getting shredded, eventually leaving its stars scattered through the halo of the host galaxy.”

The remains of the smaller galaxy appear as a dense stream of stars in the outer regions of the larger one. It was initially seen as just a faint smudge in digitized photographic plates from the Digitized Sky Survey project. Because this smaller galaxy, or what’s left of it, is so difficult to see, the merging process has been referred to as a “stealth merger.”

The new images, taken by the Black Bird Observatory and Subaru Telescope, show the merger in such detail that individual stars can be seen. “I don’t think I’d ever seen a picture of a galaxy merger where you can see the individual stars. It’s really an impressive image,” said Romanowsky.

NGC 4449 is about 12.5 million light-years from Earth and is part of a group of galaxies found in the constellation Canes Venatici. It is similar to one of our own Milky Way’s satellite galaxies, the Large Magellanic Cloud.

While larger galaxies merging with other large galaxies are commonly seen, it has been more difficult to find examples of smaller galaxies doing the same thing. Romanowsky continues: “We should see the same things at smaller scales, with small galaxies eating smaller ones and so on. Now we have this beautiful image of a dwarf galaxy consuming a smaller dwarf.”

In addition, the companion galaxy was also independently discovered by astronomers at the University of California, Los Angeles (UCLA). Their own paper will be published in the February 9, 2012  issue of Nature.

The paper is available here. See also the Subaru Telescope press release here.

Posted on by Nancy Atkinson

Hubble Captures a Classic Barred Spiral Galaxy

The barred spiral galaxy NGC 1073, which is found in the constellation of Cetus (The Sea Monster). Credit: NASA & ESA

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Is this what we look like? Astronomers don’t know for sure exactly what the Milky Way looks like, but searching out other barred spiral galaxies like this one is helping scientists to learn more about our home. Galaxy NGC 1073 is located in the constellation of Cetus (The Sea Monster).Most of the known spiral galaxies have a bar structure in their center, and this new image offer a stunning, if not clear view of one of these types of galaxies.

One piece of information that might be available from a central bar is the galaxy’s age. Some astronomers have suggested that the formation of a this structure might signal a spiral galaxy’s passage from intense star-formation into adulthood. Two-thirds of nearby, younger galaxies have the bar, while only a fifth of older, more distant spirals have one.

While Hubble’s image of NGC 1073 is in some respects an archetypal portrait of a barred spiral, the Hubble team have pointed out a couple of quirks.

One, ironically, is almost — but not quite — invisible to optical telescopes like Hubble. In the upper left part of the image, a rough ring-like structure of recent star formation hides a bright source of X-rays. Called IXO 5, this X-ray source is likely to be a binary system featuring a black hole and a star orbiting each other. Comparing X-ray observations from the Chandra spacecraft with this Hubble image, astronomers have narrowed the position of IXO 5 down to one of two faint stars visible here. However, X-ray observations with current instruments are not precise enough to conclusively determine which of the two it is.

Hubble’s image does not only tell us about a galaxy in our own cosmic neighborhood, however. We can also discern glimpses of objects much further away, whose light tells us about earlier eras in cosmic history.

Right across Hubble’s field of view, more distant galaxies are peering through NGC 1073, with several reddish examples appearing clearly in the top left part of the frame.

More intriguing still, three of the bright points of light in this image are neither foreground stars from the Milky Way, nor even distant stars in NGC 1073. In fact they are not stars at all. They are quasars, incredibly bright sources of light caused by matter heating up and falling into supermassive black holes in galaxies literally billions of light-years from us. The chance alignment through NGC 1073, and their incredible brightness, might make them look like they are part of the galaxy, but they are in fact some of the most distant objects observable in the Universe.

Source: ESA Hubble

Posted on by Nancy Atkinson

Distant Invisible Galaxy Could be Made Up Entirely of Dark Matter

The gravitational lens B1938+666 as seen in the infrared when observed with the 10-meter Keck II telescope. Credit: D. Lagattuta / W. M. Keck Observatory

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Astronomers can’t see it but they know it’s out there from the distortions caused by its gravity. That statement describes dark matter, the elusive substance which scientists have estimated makes up about 25% of our universe and doesn’t emit or absorb light. But it also describes a distant, tiny galaxy located about 10 billion light years from Earth. This galaxy can’t be seen in telescopes, but astronomers were able to detect its presence through the small distortions made in light that passes by it. This dark galaxy is the most distant and lowest-mass object ever detected, and astronomers say it could help them find similar objects and confirm or reject current cosmological theories about the structure of the Universe.

“Now we have one dark satellite [galaxy],” said Simona Vegetti, a postdoctoral researcher at the Massachusetts Institute of Technology, who led the discovery. “But suppose that we don’t find enough of them — then we will have to change the properties of dark matter. Or, we might find as many satellites as we see in the simulations, and that will tell us that dark matter has the properties we think it has.”

This dwarf galaxy is a satellite of a distant elliptical galaxy, called JVAS B1938 + 666. The team was looking for faint or dark satellites of distant galaxies using gravitational lensing, and made their observations with the Keck II telescope on Mauna Kea in Hawaii, along with the telescope’s adaptive optics to limit the distortions from our own atmosphere.

They found two galaxies aligned with each other, as viewed from Earth, and the nearer object’s gravitational field deflected the light from the more distant object (JVAS B1938 + 666) as the light passed through the dark galaxy’s gravitational field, creating a distorted image called an “Einstein Ring.”

Using data from this effect, the mass of the dark galaxy was found to be 200 million times the mass of the Sun, which is similar to the masses of the satellite galaxies found around our own Milky Way. The size, shape and brightness of the Einstein ring depends on the distribution of mass throughout the foreground lensing galaxy.

Current models suggest that the Milky Way should have about 10,000 satellite galaxies, but only 30 have been observed. “It could be that many of the satellite galaxies are made of dark matter, making them elusive to detect, or there may be a problem with the way we think galaxies form,” Vegetti said.

The dwarf galaxy is a satellite, meaning that it clings to the edges of a larger galaxy. Because it is small and most of the mass of galaxies is not made up of stars but of dark matter, distant objects such as this galaxy may be very faint or even completely dark.

“For several reasons, it didn’t manage to form many or any stars, and therefore it stayed dark,” said Vegetti.

Vegetti and her team plan to use the same method to look for more satellite galaxies in other regions of the Universe, which they hope will help them discover more information on how dark matter behaves.

Their research was published in this week’s edition of Nature.

The team’s paper can be found here.

Sources: Keck Observatory, UC Davis, MIT

Posted on by Nancy Atkinson

What Color is the Milky Way? White as Snow (not Milk)

An image of one of the Milky Way analogs found by Timothy Licquia and Jeffrey Newman. This galaxy, known to astronomers as SDSS J083909.27+450747.7, has properties which closely match those of the galaxy we live in. Credit: Sloan Digital Sky Survey

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What color would the Milky Way appear to alien civilizations looking at our galaxy through their telescopes? It turns out the Milky Way has approximately the right name – but for all the wrong reasons. “The true color of the Milky Way is as white as fine-grained new spring snow seen in early morning light,” said Dr. Jeffrey Newman, from the University of Pittsburgh, speaking at a press conference from the American Astronomical Society (AAS) Meeting.

Our ancestors gave our galaxy the name “Milky Way” because when they looked up and saw the band of the stars that stretches from one horizon to the other, it appears white to our human eyes. “But that’s only because our low-light vision isn’t sensitive to color,” said Newman. “There are portions of the Milky Way that are more yellow or red versus more blue, but our eyes can’t pick that up. But a sensitive instrument or photograph can.”

When we look at other galaxies, we can see them in their entirety, and can examine them for color and luminosity. Color and luminosity have been great tool for astronomy, helping us to understand stars and galaxies.

“Unfortunately we can’t get a complete picture of the Milky Way from outside, so we have had to resort to other methods,” said Newman. “Not only are we looking at Milky Way from the inside, but it’s even worse than that — our view is blocked by dust, both in clouds and diffuse dust. We can only see about 1,000 -2,000 light years in any direction, even though our galaxy is a 100,000 light years across.”

A digital all-sky mosaic of our view of the Milky Way from Earth, assembled from more than 3,000 individual CCD frames. Credit: Axel Mellinger. Click on image to view a zoomable panorama.

So if you ask, ‘what is the integrated color of the Milky Way,’ we can can’t tell from a picture like the one above, we can only tell what color the local neighborhood is.

“We have had to resort to different techniques, and rather than looking at the Milky Way directly, we look at other galaxies that should be like the Milky Way and we can determine what their color and luminosity are,” Newman said.

Newman, along with Timothy Licquia, a PhD student in physics at Pitt, used images from the Sloan Digital Sky Survey — which contains detailed properties of nearly a million galaxies — and looked for galaxies with similar properties to the Milky Way in regards to total mass and star formation rates. The Milky Way Galaxy should then fall on a plot somewhere within the range of colors of these matching objects.

While the composite color of the Milky Way is snowy-white, our galaxy appears more yellow towards the center and more blue out in the spiral arms.

Newman and Licquia determined the light color temperature of the Milky Way is 4,840 K, which closely matches the light from a standard light bulb with a color temperature of 4,700-5,000K. “It is well within the range our eye can perceive as white—roughly halfway between the light from old-style incandescent light bulbs and the standard spectrum of white on a television,” said Newman. “Our eyes treat both as white.”

The color of new snow is the whitest natural color on Earth. While milk has a more bluish color than snow, the association of our Milky Way to milk has proven to be very appropriate, given the Milky Way’s true color.

Newman even wrote a Haiku about the color:

Look at new spring snow
See the River of Heaven
An hour after dawn

The Milky Way’s color could be on either side of a standard dividing line between red and blue galaxies: relatively red galaxies rarely form new stars and blue galaxies have stars still being born. This adds to the evidence that although the Milky Way is still producing stars, it is “on its way out,” according to Newman. “A few billion years from now, our Galaxy will be a much more boring place, full of middle-aged stars slowly using up their fuel and dying off, but without any new ones to take their place. It will be less interesting for astronomers in other galaxies to look at, too: The Milky Way’s spiral arms will fade into obscurity when there are no more blue stars left.”

Source: Pitt, AAS press briefing

Posted on by Jason Major

Astronomers Witness a Web of Dark Matter

Dark matter in the Universe is distributed as a network of gigantic dense (white) and empty (dark) regions, where the largest white regions are about the size of several Earth moons on the sky. Credit: Van Waerbeke, Heymans, and CFHTLens collaboration.

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We can’t see it, we can’t feel it, we can’t even interact with it… but dark matter may very well be one of the most fundamental physical components of our Universe. The sheer quantity of the stuff – whatever it is – is what physicists have suspected helps gives galaxies their mass, structure, and motion, and provides the “glue” that connects clusters of galaxies together in vast networks of cosmic webs.

Now, for the first time, this dark matter web has been directly observed.

An international team of astronomers, led by Dr. Catherine Heymans of the University of Edinburgh, Scotland, and Associate Professor Ludovic Van Waerbeke of the University of British Columbia, Vancouver, Canada, used data from the Canada-France-Hawaii Telescope Legacy Survey to map images of about 10 million galaxies and study how their light was bent by gravitational lensing caused by intervening dark matter.

Inside the dome of the Canada-France-Hawaii Telescope. (CFHT)

The images were gathered over a period of five years using CFHT’s 1×1-degree-field, 340-megapixel MegaCam. The galaxies observed in the survey are up to 6 billion light-years away… meaning their observed light was emitted when the Universe was only a little over half its present age.

The amount of distortion of the galaxies’ light provided the team with a visual map of a dark matter “web” spanning a billion light-years across.

“It is fascinating to be able to ‘see’ the dark matter using space-time distortion,” said Van Waerbeke. “It gives us privileged access to this mysterious mass in the Universe which cannot be observed otherwise. Knowing how dark matter is distributed is the very first step towards understanding its nature and how it fits within our current knowledge of physics.”

This is one giant leap toward unraveling the mystery of this massive-yet-invisible substance that pervades the Universe.

The densest regions of the dark matter cosmic web host massive clusters of galaxies. Credit: Van Waerbeke, Heymans, and CFHTLens collaboration.

“We hope that by mapping more dark matter than has been studied before, we are a step closer to understanding this material and its relationship with the galaxies in our Universe,” Dr. Heymans said.

The results were presented today at the American Astronomical Society meeting in Austin, Texas. Read the release here.

Posted on by Nancy Atkinson

A Star-Making Blob from the Cosmic Dawn

This image shows one of the most distant galaxies known, called GN-108036, dating back to 750 million years after the Big Bang that created our universe. Credit: NASA, ESA, JPL-Caltech, STScI, and the University of Tokyo

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Looking back in time with some of our best telescopes, astronomers have found one of the most distant and oldest galaxies. The big surprise about this blob-shaped galaxy, named GN-108036, is how exceptionally bright it is, even though its light has taken 12.9 billion years to reach us. This means that back in its heyday – which astronomers estimate at about 750 million years after the Big Bang — it was generating an exceptionally large amount of stars in the “cosmic dawn,” the early days of the Universe.

“The high rate of star formation found for GN-108036 implies that it was rapidly building up its mass some 750 million years after the Big Bang, when the Universe was only about five percent of its present age,” said Bahram Mobasher, from the University of California, Riverside. “This was therefore a likely ancestor of massive and evolved galaxies seen today.”


An international team of astronomers, led by Masami Ouchi of the University of Tokyo, Japan, first identified the remote galaxy after scanning a large patch of sky with the Subaru Telescope atop Mauna Kea in Hawaii. Its great distance was then confirmed with the W.M. Keck Observatory, also on Mauna Kea. Then, infrared observations from the Spitzer and Hubble space telescopes were crucial for measuring the galaxy’s star-formation activity.

“We checked our results on three different occasions over two years, and each time confirmed the previous measurement,” said Yoshiaki Ono, also from the of the University of Tokyo.

Astronomers were surprised to see such a large burst of star formation because the galaxy is so small and from such an early cosmic era. Back when galaxies were first forming, in the first few hundreds of millions of years after the Big Bang, they were much smaller than they are today, having yet to bulk up in mass.

The team says the galaxy’s star production rate is equivalent to about 100 suns per year. For reference, our Milky Way galaxy is about five times larger and 100 times more massive than GN-108036, but makes roughly 30 times fewer stars per year.

Astronomers refer to the object’s distance by a number called its “redshift,” which relates to how much its light has stretched to longer, redder wavelengths due to the expansion of the universe. Objects with larger redshifts are farther away and are seen further back in time. GN-108036 has a redshift of 7.2. Only a handful of galaxies have confirmed redshifts greater than 7, and only two of these have been reported to be more distant than GN-108036.

About 380,000 years after the Big Bang, a decrease in the temperature of the Universe caused hydrogen atoms to permeate the cosmos and form a thick fog that was opaque to ultraviolet light, creating what astronomers call the cosmic dark ages.

“It ended when gas clouds of neutral hydrogen collapsed to generate stars, forming the first galaxies, which probably radiated high-energy photons and reionized the Universe,” Mobasher said. “Vigorous galaxies like GN-108036 may well have contributed to the reionization process, which is responsible for the transparency of the Universe today.”

“The discovery is surprising because previous surveys had not found galaxies this bright so early in the history of the universe,” said Mark Dickinson of the National Optical Astronomy Observatory in Tucson, Ariz. “Perhaps those surveys were just too small to find galaxies like GN-108036. It may be a special, rare object that we just happened to catch during an extreme burst of star formation.”

Sources: Science Paper by: Y. Ono et al., Subaru , Spitzer Hubble

Posted on by Jon Voisey

How Can Growing Galaxies Stay Silent?

Andromeda Galaxy

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Beginning around 2005, astronomers began discovering the presence of very large galaxies at a distance of around 10 billion lightyears. But while these galaxies were large, they didn’t appear to have a similarly large number of formed stars. Given that astronomers expect galaxies to grow through mergers and mergers tend to trigger star formation, the presence of such large, undeveloped galaxies seemed odd. How could galaxies grow so much, yet have so few stars?

One of the leading propositions is that the galaxies have undergone frequent mergers, but each one was very small and didn’t encourage large scale star formation. In other words, instead of mergers between galaxies of similar size, large galaxies developed quickly and early in the universe, and then tended to accumulate through the integration of minor, dwarf galaxies. While this solution is straightforward, testing it is difficult since the galaxies in question are at vast distances and detecting the minor galaxies as they are devoured would require exceptional observations.

Seeking to test this hypothesis, a team of astronomers led by Andrew Newman from the California Institute of Technology combined observations from Hubble and the United Kingdom Infra-Red Telescope (UKIRT), to search for these diminutive companions. The team examined over 400 galaxies that didn’t display signs of active star formation (called “quiet” galaxies) in search of possible companion galaxies from distances of 10 billion light years to a relatively close 2 billion lightyears in order to determine how this minor merger rate has evolved over time.

From their study, they determined that around 15% of quiet galaxies had a nearby counterpart that had at least 10% the mass of the larger galaxy. This took into account the possibility that some galaxies may have been more distant but along the line of sight by ensuring that both galaxies had similar redshifts. Over time, the partner galaxies became rarer suggesting that they were becoming rarer as more were consumed by the larger brethren. Using this as a rate at which mergers must occur, the team was able to answer the question of whether or not these minor mergers could account for the galaxy growth discovered six years earlier.

For galaxies closer than a distance of roughly 8 billion light years, the rate of minor mergers was able to completely explain the overall growth of galaxies. However, for the growth rate of galaxies at times earlier than this, such minor mergers could only account for around half of the apparent growth.

The team proposes several reasons this may be the case. Firstly, many of the basic assumptions could be flawed. Teams may have overestimated the sizes of the massive galaxies, or underestimated the rate of star formation. These key properties were often derived from photometric surveys which are not as reliable as spectroscopic observations. In the future, if better observations can be made, these values may be revised and the problem may resolve itself. The other option is that there are simply additional processes at work that astronomers have yet to understand. Either way, the question of how growing galaxies avoid advertising their growth is unanswered.

Posted on by Amy Shira Teitel

New Submillimetre Camera Sheds Light on the Dark Regions of the Universe

A composite image of the Whirlpool Galaxy (also known as M51). The green image is from the Hubble Space Telescope and shows the optical wavelength. The submillimetre light detected by SCUBA-2 is shown in red (850 microns) and blue (450 microns). The Whirlpool Galaxy lies at an estimated distance of 31 million light years from Earth in the constellation Canes Venatici Credit: JAC / UBC / Nasa

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The stars and faint galaxies you see when you look up at the night sky are all emitting light within the visible light spectrum — the portion of the electromagnetic spectrum we can see with our unaided eyes or through optical telescopes. But our galaxy, and many others, contain huge amounts of cold dust that absorbs visible light. This accounts for the dark regions.

A new camera recently unveiled at the James Clerk Maxwell Telescope (JCMT) in Hawaii promises to figuratively shed light on this dark part of the universe. The SCUBA-2 submillimetre camera (SCUBA in this case is an acronym for Submillimetre Common-User Bolometer Array) can detect light at lower energy levels, allowing astronomers to gather data on these dark areas and ultimately learn more about our universe and its formation. 

Light is measurable; its intensity or brightness is measured by photons while colour is measured by the energy of the photons. Red photons have the least energy and violet photons have the most energy. This can also be thought of in terms of wavelengths. Light at longer wavelengths have less energy and light at shorter wavelengths have more energy. This continues beyond the visible light spectrum. As electromagnetic waves get shorter, we get ultraviolet light, x-rays, and gamma rays. As wavelengths get longer, we get infrared light, submillimetre light, and finally radio waves.

Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. Image credit: Thomas Jarrett, IPAC/Caltech.

On the longer end of the electromagnetic spectrum, infrared and radio telescopes have been around for decades helping astronomers understand more about the universe. But this is only part of the picture. The cold dust that absorbs the visible light to create the dark regions seen through optical telescopes is actually absorbing the light’s energy and reemitting it at longer wavelengths in the submillimetre region.

The first submillimetre camera, SCUBA, was designed and constructed at the Royal Observatory in Edinburgh in collaboration with the University of London. In 1997, it was up and running at the JCMT. Observations of submillimetre wavelengths are typically harder to gather — it takes a long time to image a small portion of the sky in this region. Nevertheless, submillimetre observations have already revealed a previously unknown population of distant, dusty galaxies as well as images of cold debris discs around nearby stars. This latter finding could be an indication of the presence of planetary systems.

A team of astronomers has recently developed the camera SCUBA-2 that can probe the submillimetre region with increased speed and much greater detail. But it’s a touchy instrument. Director of the JCMT Professor Gary Davis explains that for SCUBA-2 to detect extremely low energy radiation in the submillimetre region, “the instrument itself needs to be [extremely cold]. The detectors… have to be cooled to only 0.1 degree above absolute zero [–273.05°C], making the interior of SCUBA-2 colder than anything in the Universe that we know of!”

The infant Universe as imaged in the radio wavelength spectrum. Image Credit: NASA/WMAP Science Team.

The camera is a huge step in observational astronomy. Director of the United Kingdom Astronomy Teaching Centre Professor Ian Robson likened the technological leap between early sub-millimetre cameras and SCUBA-2 to the difference between wind-on film cameras and modern digital technology. “It is thanks to the ingenuity and abilities of our scientists and engineers that this immense leap in progress has been achieved,” he said.

Dr Antonio Chrysostomou, Associate Director of the JCMT, explains that SCUBA-2’s first task will be to carry out a series of surveys throughout the sky, mapping sites of star formation within our Galaxy, as well as planet formation around nearby stars. It will also survey our galactic neighbours and look into deep space to sample the youngest galaxies in the Universe. This latter task will be critical in helping astronomers understand how galaxies have evolved since the Big Bang.

The SCUBA-2 camera is housed on the 15 metre (about 50 foot) diameter JCMT situated close to the summit of Mauna Kea, Hawaii, at an altitude of 4092 metres (about 13,425 feet). It is typically used to study our Solar System, interstellar dust and gas, and distant galaxies.

Source: Revolutionary New Camera Reveals Dark Side of the Universe

 

The James Clerk Maxwell Telescope. Image credit: www.jach.hawaii.edu

 

 

Posted on by Amy Shira Teitel

Astronomers Find the Most Supermassive Black Holes Yet

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For years, astronomer Karl Gebhardt and graduate student Jeremy Murphy at The University of Texas at Austin have been hunting for black holes — the dense concentration of matter at the centre of galaxies. Earlier this year, they made a record-breaking discovery. They found a black hole weighing 6.7 billion times the mass of our Sun in the centre of the galaxy M87.

But now they shattered their own record. Combining new data from multiple observations, they’ve found not one but two supermassive black holes that each weigh as much as 10 billion Suns.

“They just keep getting bigger,” Gebhardt said.

An artist's impression of the black hole at the centre of the M87 galaxy. Image credit: Gemini Observatory/AURA illustration by Lynette Cook

Black holes are made of extremely densely packed matter. They produce such a strong gravitational field that even light cannot escape. Because they can’t be seen directly, astronomers find black holes by plotting the orbits of stars around these giant invisible masses. The shape and size of these stars’ orbits can determine the mass of the black hole.

Exploding stars called supernovae often leave behind black holes, but these only weigh as much as the single star. Black holes billions of times the mass of our Sun have grown to be so big. Most likely, an ordinary black hole consumed another, captured huge numbers of stars and the massive amount of gas that they contain, or be the result of two galaxies colliding. The larger the collision, the more massive the black hole.

The supermassive black holes Gebhardt and Murphy have found are at the centres of two galaxies more than 300 million light years from Earth. One weighing 9.7 billion solar masses is located in the elliptical galaxy NGC 3842, the brightest galaxy in the Leo cluster of galaxies 320 million light years away in the direction of the constellation Leo. The other is as large or larger and sits in the elliptical galaxy NGC 4889, the brightest galaxy in the Coma cluster about 336 million light years from Earth in the direction of the constellation Coma Berenices.

Each of these black holes has an event horizon — the point of no return where nothing, not even light can escape their gravity — 200 times larger than the orbit of Earth (or five times the orbit of Pluto). That’s a mind-boggling 29,929,600,000 kilometres or 18,597,391,235 miles. Beyond the event horizon, each has a gravitational influence that extends over 4,000 light years in every direction.

The illustration shows the relationship between the mass of a galaxy's central black hole and the mass of its central bulge. Recent discoveries of supermassive black holes may mean that the black holes in all nearby massive galaxies are more massive than we think. This could signal a change in our understanding of the relationship between a black hole and its surrounding galaxy. Image credit: Tim Jones/UT-Austin after K. Cordes & S. Brown (STScI)

For comparison, the black hole at the centre of our Milky Way Galaxy has an event horizon only one-fifth the orbit of Mercury — about 11,600,000 kilometres or 7,207,905 miles. These supermassive black holes are 2,500 times more massive than our own.

Gebhardt and Murphy found the supermassive black holes by combining data from multiple sources. Observations from the Gemini and Keck telescopes revealed the smallest, innermost parts of these galaxies while data from the George and Cynthia Mitchell Spectrograph on the 2.7-meter Harlan J. Smith Telescope revealed their largest, outmost regions.

Putting everything together to deduce the black holes’ mass was a challenge. “We needed computer simulations that can accommodate such huge changes in scale,” Gebhardt said. “This can only be done on a supercomputer.”

But the payoff doesn’t end with finding these massive galactic centre. The discovery has much more important implications. It “tells us something fundamental about how galaxies form” Gebhardt said.

These black holes could be the dark remnants of previously bright galaxies called quasars. The early universe was full of quasars, some thought to have been powered by black holes 10 billion Solar masses or more. Astronomers have been wondering where these supermassive galactic centres have since disappeared to.

Gebhardt and Murphy might have found a key piece in solving the mystery. Their two supermassive black holes might shed light on how black holes and their galaxies have interacted since the early universe. They may be a missing link between ancient quasars and modern supermassive black holes.

Source: McDonald Observatory Press Release.

Where Have All the Quasars Gone?