Posted on by Jason Major

How To Measure the Universe

The Royal Observatory Greenwich is giving free presentations of "Measuring the Universe: from the Transit of Venus to the Edge of the Cosmos" from now until September 1.


Measuring distance doesn’t sound like a very challenging thing to do — just pick your standard unit of choice and corresponding tool calibrated to it, and see how the numbers add up. Use a meter stick, a tape measure, or perhaps take a drive, and you can get a fairly accurate answer. But in astronomy, where the distances are vast and there’s no way to take measurements in person, how do scientists know how far this is from that and what’s going where?

Luckily there are ways to figure such things out, and the methods that astronomers use are surprisingly familiar to things we experience every day.

[/caption]The video above is shared by the Royal Observatory Greenwich and shows how geometry, physics and things called “standard candles” (brilliant!) allow scientists to measure distances on cosmic scales.

Just in time for the upcoming transit of Venus, an event which also allows for some important measurements to be made of distances in our solar system, the video is part of a series of free presentations the Observatory is currently giving regarding our place in the Universe and how astronomers over the centuries have measured how oh-so-far it really is from here to there.

Video credits:
Design and direction: Richard Hogg
Animation: Robert Milne, Ross Philips, Kwok Fung Lam
Music and sound effects: George Demure
Narration and Astro-smarts: Dr. Olivia Johnson
Producer: Henry Holland

Posted on by Nancy Atkinson

SKA, the World’s Largest Telescope Will Be Built at Two Sites

SKA dishes by night. Credit: SPDO/TDP/DRAO/Swinburne Astronomy Productions.

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In an anticipated great compromise, South Africa and Australia will share their sites for the Square Kilometre Array telescope, the world’s largest and most sensitive radio telescope. Both sites were competing to win the $2 billion contract for the SKA, which is hoped shed light on how the Universe began, why it is expanding and whether there is any other life beyond our planet.

“We have decided on a dual site approach,” said SKA board chairman John Womersley, following a meeting of the SKA organisation’s members. “This position was reached after very careful consideration of information gathered from extensive investigations at both candidate sites.”

An SKA press release said the majority of the members were in favor of a dual-site implementation model for SKA. The members noted the report from the SKA Site Advisory Committee that both sites were well suited to hosting the SKA and that the report provided justification for the relative advantages and disadvantages of both locations, but that they identified Southern Africa as the preferred site. The members also received advice from the working group set up to look at dual site options.

Therefore, the majority of SKA dishes in Phase 1 will be built in South Africa, combined with MeerKAT, a seven-dish prototype interferometer array built by South Africa, where 190 dishes will be added. 60 dishes will be added to the Australian Square Kilometre Array Pathfinder (ASKAP) array in Australia, as well as a large number of omni-directional dipole antennas. This will give the Australian site a wide-field survey capability, whereas South Africa will be able to look deeply into a narrow part of the sky.

Three antenna types, high frequency dishes and mid and low frequency aperture arrays, will be used by the SKA to provide continuous frequency coverage from 70 MHz to 10 GHz. Combining the signals from all the antennas will create a telescope with a collecting area equivalent to a dish with an area of about one square kilometer.

All the dishes and the mid frequency aperture arrays for Phase II of the SKA will be built in Southern Africa while the low frequency aperture array antennas for Phase I and II will be built in Australia.

“It’s a distinct possibility that we’ll discover a new type of astronomical object,” CSIRO SKA Director Brian Boyle told Universe Today in interview earlier this year. “History has shown that every time we’ve gone to a new astronomical wavelength domain, we pick up new objects.” An example of that is the discovery of pulsars in radio

At the lowest frequencies, the SKA will be looking for red-shifted hydrogen, looking at the very earliest events of our Universe. At highest frequencies will look for things like pulsars or even pre-biotic molecules in space. The array will also be very effective in looking for transient events like supernovae or gamma ray bursts.

“The placement of the array will give it a phenomenally wide field of view, between 30 and 100 square degrees,” Boyle said. “It is hoped to provide the first all-sky survey at phenomenal depths at these wavelengths, which can then be compared with other all-sky surveys done at optical wavelengths.”

One downside of splitting the frequencies between the two sites is that some of the science may suffer. One of the original science requirements of the SKA was to look at the same piece of the sky at the same time in different frequencies. Boyle said there is not much common sky between the two locations.

Another is cost for having redundant computing and networking capabilities, not cheap for the remote areas where both sites are located.

But the dual-site approach solves political issues, and the SKA press release says the arrangement “will deliver more science and will maximize on investments already made by both Australia and South Africa.”

Womersley said that in this approach “Science is the winner,” and by building on existing pilot projects in both countries, the SKA will be made even more powerful.

Additionally, technology is sure to get a boost, as the SKA project will drive technology development in antennas, data transport, software and computing, and power.

Additionally, the SKA members say the influence of the SKA project extends beyond radio astronomy.

“The design, construction and operation of the SKA have the potential to impact skills development, employment and economic growth in science, engineering and associated industries, not only in the host countries but in all partner countries,” said their press release.

Posted on by Jenny Winder

Ecological Concerns in Losing Our Starry Night

Earth at Night. Courtesy DMSP and NASA
Earth at Night. Courtesy DMSP and NASA

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Images of the Earth at night, taken from space are always a stunning sight, with cities, countries and whole continents glittering like jewels. But this beauty comes at a price. It used to be that anyone looking up on a clear night could see the Milky Way. As more and more of us are drawn to live in urban areas, our view of the sky is blotted out by the glare of our lights. Astronomers have known about the growing problem of light pollution for a long time. Now ecologists are becoming concerned that our artificial lights are affecting more than our view of the stars.

Researchers at the University of Exeter studying the ecological impact of artificial lighting have noted changes in distribution of invertebrate communities around artificial lighting which could affect the broader wildlife that depend on them. Simply put, it is easier for predators to find their prey, and harder for the prey to hide, in brightly lit areas. Streetlights may also be disrupting the natural rhythms of both fauna and flora, changing hibernation patterns and flowering times. It may also be affecting our own circadian rhythms as well as being a colossal waste of energy, an estimated $2.2 billion per year in the U.S. alone! On average, 30% of the light from a streetlight shines up and out.

Light pollution is a growing problem. Artificial lighting is increasing at the rate of 6% each year globally and is only going to get worse, as developing nations use more and more electric light. Since 1988 The International Dark-Sky Association has campaigned to protect and preserve the night environment and promote energy efficient options. Light what you need, when you need it, they say.

One of their projects is the International Dark Sky Places program which certify locations with exceptional nightscapes, either as communities, parks or reserves. The Kielder Forest and adjacent Northumberland national park covering 400 square miles in the UK is the latest area hoping to join the 12 dark sky reserves already recognised by the IDA worldwide. Such status can bring economic advantages too, astronomy is rapidly growing in popularity and with it astronomy based tourism, offering dark skies, observing opportunities and star parties and star camps.

Losing the stars can have a lasting impact on our culture too. Think of all the art, literature and music that have been inspired by the night sky. As we become increasingly disconnected from nature the stars are one of our most important links. There are many people today who have never been able to look up and see the Milky Way arching over their heads. Looking up at the stars allows us a vital opportunity to engage with the larger questions posed by the universe.

Find out more at The International Dark-Sky Association
and The British Astronomical Association’s Campaign for Dark Skies

Posted on by Jon Voisey

A Planetary System That Never Was Teaches About Those That May Be

While Kepler and similar missions are turning up planets by the fist full, there’s long been many places that astronomers haven’t expected to find planetary systems. The main places include regions where gravitational forces conspire to make the region around potential host stars too unstable to form into planets. And there’s no place in the galaxy with a larger gravitational force than the galactic center where a black hole four and a half million times more massive than the Sun, lurks. But a new study shows evidence that a disk, potentially far enough along to begin forming planets, is in the process of being disrupted.

The new study investigates an ionized cloud of gas discovered earlier this year, plummeting in towards the black hole. The cloud has been formed into an elliptical ring with a maximum distance of 0.04 parsecs (1 parsec 3.24 light years) which is coincident with a ring of young stars that orbit the black hole. At such distances from us, astronomers have been unable to learn much about the population of stars that may exist since only the brightest, most massive stars are visible.

However, such massive stars are able to determine an age limit for the group, which has been set somewhere between 4-8 million years. This age is crucial since most low-mass stars retain gas disks and are held to form planets at an age around 3 million years young. But by an age of 5 million years, the stars have begun clearing out that disk system halting planetary formation and only one fifth of stars less than 1 solar mass retain their disks.

This entire process is even more precarious because the gravitational perturbations from the nearby black hole would begin eating away at the edge of a potential disk. Astronomers predict that this should limit the size to 12 AU in radius. For even less massive stars, this could be as small as 8 AU. Still, theory predicts that these truncated disks could form in the vicinity of the Milky Way’s black hole. But such small disks would be impossible to observe directly with present technology.

The new research suggests that one of these stars was knocked from its stable orbit in the ring in much the same way that comets in the Oort cloud are occasionally jostled into falling towards the inner solar system. There, the tidal forces from the black hole as well as heavily ionizing UV radiation created by the black hole’s accretion disk would strip the gas and dust from the parent star, which is too faint to see directly, leaving it in an elliptical orbit.

If this theory is correct, it would provide the first indirect evidence of the presence of planet forming disks near the galactic center. This comes on top of evidence from earlier this year suggesting stars may be able to form in situ near the galactic center making this region a far more dynamic place than previously expected.

Yet, even if planets do form, living near a supermassive black hole is still not a hospitable place for life. The extreme amounts of UV radiation emitted as the black hole devours gas and dust is likely to sterilize the region.

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: May 21-27, 2012

NGC 4038/39 - Palomar Observatory Courtesy of Caltech

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Greetings, fellow SkyWatchers! Here’s hoping you had an opportunity to witness yesterday’s eclipse! Even the partial phase here in Ohio was exciting… and to be able to watch virtually via live feeds was equally impressive! The week begins with dark skies and deep studies. Get up early to enjoy the apparition of Jupiter and Mercury just ahead of the rising Sun and check out Venus as it dances near the Earthshine Moon. When you’re ready to observe, meet me in the back yard!

Monday, May 21 – In 1961, United States President John F. Kennedy launches the country on a journey to the Moon as he makes one of his most famous speeches to Congress: “I believe this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth. No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space…”

Tonight we’ll take an exploration of space as we study an interacting pair of galaxies. All that is required is that you find 31 Corvii, an unaided eye star west of Gamma and Epsilon Corvii. Now we’re ready to nudge the scope about one degree north. The 11th magnitude NGC 4038/39 (Right Ascension: 12 : 01.9 – Declination: -18 : 52) is a tight, but superior pair of interacting galaxies. Often referred to as either the “Ringtail” or the “Antenna”, this pair deeply captured the public’s imagination when photographed by the Hubble. (Unfortunately, we don’t have the Hubble – that’s why I used a more “natural image”, but what we have is set of optics and the patience to find them.) At low power the pair presents two very stellar core regions surrounded by a curiously shaped nebulosity. Now, drop the power on it and practice patience – because it’s worth it! When that perfect moment of clarity arrives, we have crackling structure. Unusual, clumpy, odd arms appear at strong aversion. Behind all this is a galactic “sheen” that hints at all the beauty seen in the Hubble photographs. It’s a tight little fellow, but worth every moment it takes to find it.

Tuesday, May 22 – Celestial scenery alert! If you’re up before dawn this morning, look for the very close pairing of Jupiter and Mercury racing together just ahead of sunrise. The disparate pair will be less than half a degree apart. It’s worth getting up early for!

Tonight the slender crescent Moon will make a very brief appearance at dusk along the western skyline. If your atmosphere is very steady, why not set the telescope down on it and look for some very unusual features that will soon wash out as the Sun overtakes the moonscape. Almost central along the eastern lunar limb, look for Mare Smythii and Mare Marginis to its north. Between them you will see the long oval crater Neper bordered by Jansky at the very limb. And speaking of the limb, did you notice bright Venus accompanying the Moon? It’s a splendid conjunction and well worth alerting friends, family and neighbors to watch for! But don’t delay… The pair will set quickly!

Now let’s visit a galaxy very similar to our own Milky Way – NGC 2903 (Right Ascension: 9 : 32.2 – Declination: +21 : 30). Located less than two degrees south of Lambda Leonis, this magnificent 9.0 magnitude barred spiral can be spotted with binoculars from a dark location, and is easily seen in a small scope.

While NGC 2903’s size and central bar closely resemble our own galaxy’s structure, the Hubble Space Telescope crossed the 25 million light-year gap and found evidence of young globular clusters in its galactic halo – unlike our own old structures. This widespread star forming region is believed to be attributed to the gravity of the central bar. Small telescopes will show the bar as a lateral concentration across the central structure, while larger apertures will reveal spiral arms and condensed regions of innumerable stars.

Wednesday, May 23 – Tonight the Moon is a little bit older and brilliantly lit with earthshine. Power up and let’s go look for crater named for historian and theologian Denis Petau – Petavius!

Located almost centrally along the terminator in the southeast quadrant, a lot will depend tonight on your viewing time and the age the moon itself. Perhaps when you look, you’ll see 177 kilometer diameter Petavius cut in half by the terminator. If so, this is a great time to take a close look at the small range of mountain peaks contained in its center as well as a deep rima which runs for 80 kilometers across its otherwise fairly smooth surface. To the east lies a long furrow in the landscape. This deep runnel is Palitzsch and its Valles. While the primary crater that forms this deep gash is only 41 kilometers wide, the valley itself stretches for 110 kilometers. Look for crater Haas on Petavius’ southern edge with Snellius to the southwest and Wrottesley along its northwest wall.

Now let’s have a look at Iota Virginis. While there is nothing particularly special about this spectral F type star, it does reside in a very interesting field for low power. Enjoy the colors!

Thursday, May 24 – If you chose to scope tonight, we’re going in search of another lunar club challenge that will prove difficult because you’ll be working without a map. Relax! This will be much easier than you think. Starting at Mare Crisium, move along the terminator to the north following the chain of craters until you identify a featureless oval that looks similar to Plato seen on a curve. This is Endymion…and if you can’t spot it tonight don’t worry. We’ll take a look in the days ahead at some features that will point you to it!

While the Moon is still west, let’s have a look at telescopic star W Virginis located about three and a half degrees southwest of Zeta (RA 13 26 01.99 Dec -03 22 43.4). This 11,000 light-year distant Cepheid type variable is oddly enough a Population II star that lies outside the galactic plane. This expanding and contracting star goes through its changes in a little over 17 days and will vary between 8th and 9th magnitude. Although it is undeniably a Cepheid, it breaks the rules by being both out of place in the cosmic scheme and displaying abnormal spectral qualities!

Friday, May 25 – Tonight let’s take our own journey to the Moon as we look at a beautiful series of craters – Fabricius, Metius and Rheita.

Bordered on the south by shallow Jannsen, lunar club challenge Fabricius is a 78 kilometer diameter crater highlighted by two small interior mountain ranges. To its northeast is Metius, which is slightly larger with a diameter of 88 kilometers. Look carefully at the two. Metius has much steeper walls, while Fabricius shows differing levels and heights. Metius’ smooth floor also contains a very prominent B crater on the inside of its southeast crater wall. Further northeast is the lovely Rheita Valley which stretches almost 500 kilometers and appears more like a series of confluent craters than a fault line. 70 kilometer diameter crater Rheita is far younger than this formation because it intrudes upon it. Look for a bright point inside the crater which is its central peak.

Now let’s go revisit Omega Centauri. At magnitude 3.7, NGC 5139 (Right Ascension: 13 : 26.8 – Declination: -47 : 29) is one of the few studies in the night sky receiving a Greek letter despite being decidedly “unstarlike!”

Recorded by Ptolemy as a star, given the designation “Omega” by Bayer, and first noted as non-stellar by Edmond Halley in 1677, J.L.E. Dreyer went on to add three exclamation marks (!!!) to his abbreviated description after including it as entry 5139 in the 1888 New General Catalogue. As the largest globular cluster in our own galaxy, this 5 million solar mass “star of stars” contains more matter than Sagittarius A – the supermassive black hole on which the Milky Way pivots. Omega’s mass is greater than some dwarf galaxies. Of the more than thirty galaxies associated with our Local Group, only the Great Andromeda possesses a globular (G1) brighter than Omega!

Saturday, May 26 – Tonight the Moon will be our companion. Now well risen above atmospheric disturbance, this would be a great time to have a look for several lunar club challenges that you might have missed.

Most prominent of all will be two craters to the north named Atlas and Hercules. The eastern-most Atlas was named for the mythical figure which bore the weight of the world on his shoulders, and the crater spans 87 kilometers and contains a vivid Y-shaped rima in the interior basin. Western Hercules is considerably smaller at 69 kilometers in diameter and shows a deep interior crater called G. Power up and look for the tiny E crater which marks the southern crater rim. North of both is another unusual feature which many observers miss. It is a much more eroded and far older crater which only shows a basic outline and is only known as Atlas E.

If you want to continue with tests of resolution, why not visit Theta Virginis? It might look as close as the Moon, but it’s only 415 light-years away from Earth! The primary star is a white A-type subgiant, but it’s also a spectroscopic binary of two companions which orbit each other about every 14 years. In turn, this is orbited by a 9th magnitude F-type star which is a close 7.1 arc-seconds away from the primary. Look for the fourth member of the Theta Virginis system well away at 70 arc-seconds, but shining at a feeble magnitude 10.4.

Sunday, May 27 – Tonight no two lunar features in the north will be more prominent than Aristoteles and Eudoxus. Why not revisit them? Viewable even in small binoculars, let’s take a closer look at larger Aristoteles to the north.

As a Class 1 crater, this ancient old beauty has some of the most massive walls of all lunar features. Named for the great philosopher, it stretches across 87 kilometers of lunar landscape and drops below the average surface to a depth of 366 meters – a height which is similar to Earth’s tallest waterfall, the Silver Cord Cascade. While it has a few scattered interior peaks, the crater floor remains almost unscarred. As a telescopic lunar club challenge, be sure to look for a much older crater that sits on Aristoteles eastern edge. Tiny Mitchell is extremely shallow by comparison and only spans 30 kilometers. Look carefully at the formation, for although Aristoteles overlaps Mitchell, the smaller crater is actually part of the vast system of ridges which supports the larger.

When you’re done, let’s have a look at another delightful pair that’s joined together – Gamma Virginis…

Better known as Porrima, this is one cool binary with almost equal spectral types and brightnesses. Discovered by Bradley and Pound in 1718, John Herschel was the first to predict this pair’s orbit in 1833 and state that one day they would become inseparable to all but the very largest of telescopes – and he was right. In 1920 the A and B stars had reached their maximum separation, and during 2007 they will be as close together as they will ever be. Observed as a single star in 1836 by William Herschel, its 171 year periastron will put Porrima in the exact position now as it was when Sir William saw it!

Until next week? Ask for the Moon… But keep on reaching for the stars!

Posted on by Jason Major

How Do The Biggest Telescopes Work?

The VLT's laser beam creates a "false star" for adaptive optics calibration. (ESO/Y. Beletsky)

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Located high in the mountains of Chile’s Atacama Desert, the enormous telescopes of the European Southern Observatory have been providing astronomers with unprecedented views of the night sky for 50 years. ESO’s suite of telescopes take advantage of the cold, clear air over the Atacama, which is one of the driest places on Earth. But as clear as it is, there is still some turbulence and variations to contend with — especially when peering billions of light-years out into the Universe.

So how do they do it?

Thanks to adaptive optics and advanced laser calibration, ESO can negate the effects of atmospheric turbulence, bringing the distant Universe into focus. It’s an impressive orchestration of innovation and engineering and the ESO team has put together a video to show us how it’s done.

We all love the images (and the science) so here’s a look behind the scenes!

Video: ESO

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: May 14-20, 2012

NGC 4565 - Credit: Palomar Observatory, courtesy of Caltech

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Greetings, fellow SkyWatchers! Dark skies mean galactic studies and this is going to be a terrific week for sacrificing Viginis. But, hang on to your socks… Because it’s solar eclipse time! We’re talking about an annular event that occurs over a 240 to 300 kilometre-wide track which crosses eastern Asia, the northern Pacific Ocean and the western United States. It’s a generous event where a partial eclipse also occurs that includes much of Asia, the Pacific and the western 2/3 of North America. Whenever you’re ready, just meet me outside…

Monday, May 14 – No galactic tour through Coma Berenices would be complete without visiting one of the most incredible “things that Messier missed.” You’ll find NGC 4565 (Right Ascension: 12 : 36.3 – Declination: +25 : 59) located less than two degrees east of 17 Comae…

Residing at a distance of around 30 million light-years, this large 10th magnitude galaxy is probably one of the finest edge-on structures you will ever see. Perfectly suited for smaller scopes, this ultra-slender galaxy with the bright core has earned its nickname of “The Needle.” Although photographs sometimes show more than what can be observed visually, mid-to-large aperture can easily trace out NGC 4565’s full photographic diameter.

Although Lord Rosse in 1855 saw the nucleus of the “Needle” as stellar, most telescopes will resolve a bulging core region with a much sharper point in the center and a dark dust lane upon aversion. The core itself has been extensively studied for its cold gas and emission lines, pointing to the fact that it has a barred structure. This is much how the Milky Way would look if viewed from the same angle! It, too, shines with the light of 30 billion stars…

Chances are NGC 4565 is an outlying member of the Virgo Cluster, but its sheer size points to the fact that it is probably closer than any of the others. If we were to gauge it at a distance of 30 million years as is accepted, its diameter would be larger than any galaxy yet known! Get acquainted with it tonight…

Tuesday, May 15 – Tonight we’ll take a closer look at the work of Abbe Nicholas Louis de la Caille (or de Lacaille). Born in 1731, the French astronomer and mapmaker was the first to demonstrate Earth’s bulge at its equator. From 1751 to 1753, he had the great fortune to observe southern skies and, putting his cartography skills to use, he mapped the southern skies and established the 14 constellations that remain in use to this day – including Musca. Even though Lacaille was best known for the constellation names, he and his productive half-inch telescope (that’s no type!) also cataloged 9766 stars in his two year observing period. Of these, one stands out for good reason – Lacaille 8760.

Its designation is also AX Microscopii, and it is a dwarf red flare star which resides only 12.9 light-years from us. While it might not seem that important, it is the target of interferometer studies in search of planets that may have formed in a “habitable zone” around life-giving stars similar to our own. Even though AX is slightly smaller than Sol, this cool main sequence star might be inhospitable due to its daily flare activity.

Since it will be awhile before the constellation of Microscopium rises high enough for southern observers to capture this star, let’s have a look at an object from Lacaille’s catalog known as I.5.

Located less than two handspans south of Spica, most of us know this globular cluster best as NGC 5139 (Right Ascension: 13 : 26.8 – Declination: -47 : 29) – or Omega Centauri. As the most luminous of all globular clusters, Lacaille reported it as a “nebula in Centaurus; with simple view, it looks like a star of 3rd magnitude viewed through light mist, and through the telescope like a big comet badly bounded.” Yet, through even the most modest of today’s telescopes, Omega Centauri will explode into a fury of stars. Located about 17,000 light-years away, it took around 2 million years to form and it is believed that it may be the remnant of another galaxy’s core captured by our own. With more than one million members, it’s the size of a small galaxy in itself!

While this object is very low to northern observers, it is not impossible for those who live lower than 40 degrees north. Our atmosphere will rob this giant of a galaxy of some of its beauty, but I encourage you to try! It’s a sight you’ll never forget…

Wednesday, May 16 – Tonight let’s take a look about five degrees north of Eta Virginis for M61 (Right Ascension: 12 : 21.9 – Declination: +04 : 28).

This 9.7 magnitude galaxy was discovered on May 5, 1779 by man named Barnabus Oriani while following the same comet as Charles Messier, who also observed it on the same night and mistook it for the comet itself for two additional nights. (Nice shootin’, Chuck!) Happily enough, Mr. Herschel also assigned it his own designation of H I.139 seven years later.

It is one of the largest galaxies of the Virgo Cluster and small telescopes will make out a faint, round glow with a brighter nucleus, while larger aperture will see the core as more stellar with notable spiral structure. Four supernova events have been observed in M61, as recently as 1999, and surprisingly two of them were exactly 35 years apart… But don’t confuse an event with foreground stars!

Thursday, May 17 – Today in 1835, J. Norman Lockyer was born. While that name might not stand out, Lockyer was the first to note previously unknown absorption lines while making visual spectroscopic studies of the Sun in 1868. Little did he know at the time, he had correctly identified the second most abundant element in our universe – helium – an element not discovered on Earth until 1891! Also known as the “Father of Archeoastronomy,” Sir Lockyer was one of the first to make the connection with ancient astronomical structures such as Stonehenge and the Egyptian pyramids. (As a curious note, 14 years after Lockyer’s notation of helium, a sun-grazing comet made its appearance in photographs of the solar corona taken during a total eclipse in 1882… It hasn’t been seen since.)

If you would like to see a helium rich star, look no further tonight than Alpha Virginis – Spica. As the sixteenth brightest star in the sky, this brilliant blue/white “youngster” appears to be about 275 light-years away and is about 2300 times brighter than our own Sun. Although we cannot see it visually, Spica is a double star. Its spectroscopic companion is roughly half its size and is also helium rich.

Now, shake your fist at Spica – because that’s all it takes to find the awesome M104 (Right Ascension: 12 : 40.0 – Declination: -11 : 37), eleven degrees due west. (If you still have trouble finding M104 even after practicing earlier this year, don’t worry. Try this trick! Look for the upper left hand star in the rectangle of Corvus – Delta. Between Spica and Delta is a diamond-shaped pattern of 5th magnitude stars. Aim your scope or binoculars just above the one furthest south.)

Also known as the “Sombrero,” this gorgeous 8th magnitude galaxy was discovered by Pierre Mechain in 1781, added by hand to Messier’s catalog and observed independently by Herschel as H I.43 – who was probably the first to note its dark inclusion. The Sombrero’s rich central bulge is comprised of several hundred globular clusters and can be hinted at in just large binoculars and small telescopes. Large aperture will revel in this galaxy’s “see through” qualities and bold, dark dustlane – making it a seasonal favorite!

Friday, May 18 – On this day in 1910, Comet Halley transited the Sun, but could not be detected visually. Since the beginning of astronomical observation, transits, eclipses and occultations have provided science with some very accurate determinations of size. Since Comet Halley could not be spotted against the solar surface, we knew almost a century ago that the nucleus had to be smaller than about 100 km.

Once the sky has become fully dark, it is time to get serious. For the large telescope and seasoned observer, your challenge for this evening will be five and a half degrees south of Beta Virginis and one half degree west. Classified as Arp 248 (Right Ascension: 11h 46m 36s – Declination -3º 52′ 00”) and more commonly known as “Wild’s Triplet,” these three very small interacting galaxies are a real treat! Best with around a 9mm eyepiece, use wide aversion and try to keep the star just north of the trio at the edge of the field to cut glare. Be sure to mark your Arp Galaxy challenge list!

Saturday, May 19 – Tonight we’re heading for the galaxy fields of Virgo about four fingerwidths east-southeast of Beta Leonis. As part of Markarian’s Chain, this set of galaxies can all be fitted within the same field of view with a 32mm eyepiece and a 12.5″ scope, but not everyone has the same equipment. Set your sights toward M84 and M86 and let’s discover!

Good binoculars and small telescopes reveal this pair with ease as a matched set of ellipticals. Mid-sized telescopes will note the western member of the pair – M84 (Right Ascension: 12 : 25.1 – Declination: +12 : 53) – is seen as slightly brighter and visibly smaller. To the east and slightly north is larger M86 (Right Ascension: 12 : 26.2 – Declination: +12 : 57) – whose nucleus is broader, and less intensely brilliant. In a larger scope, we see the galaxies literally “leap” out of the eyepiece at even the most modest magnifications. Strangely though, additional structure fails to be seen.

As aperture increases, one of the most fascinating features of this area becomes apparent. While studying the bright galactic forms of M84/86 with direct vision, aversion begins to welcome many other mysterious strangers into view. Forming an easy triangle with the two Messiers and located about 20 arc-minutes south is NGC 4388 (Right Ascension: 12 : 25.8 – Declination: +12 : 40). At magnitude 11.0, this edge-on spiral has a dim star-like core to mid-sized scopes, but a classic edge-on structure in larger ones.

At magnitude 12, NGC 4387 (Right Ascension: 12 : 25.7 – Declination: +12 : 49) is located in the center of a triangle formed by the two Messiers and NGC 4388 (Right Ascension: 12 : 25.8 – Declination: +12 : 40). NGC 4387 is a dim galaxy – hinting at a stellar nucleus to smaller scopes, while the larger ones will see a very small face-on spiral with a brighter nucleus. Just a breath north of M86 is an even dimmer patch of nebulosity – NGC 4402 (Right Ascension: 12 : 26.1 – Declination: +13 : 07) – which needs higher magnifications to be detected in smaller scopes. Large apertures at high power reveal a noticeable dust lane. The central structure forms a curved “bar” of light. Luminosity appears evenly distributed end to end, while the dust lane cleanly separates the central bulge of the core.

East of M86 is two brighter NGC galaxies – 4435 and 4438. Through average scopes, NGC 4435 (Right Ascension: 12 : 27.7 – Declination: +13 : 05) is easily picked out at low power with a simple star-like core and wispy round body structure. NGC 4438 (Right Ascension: 12 : 27.8 – Declination: +13 : 01) is dim, but even large apertures make elliptical galaxies a bit boring. The beauty of NGC 4435 and NGC 4438 is simply their proximity to each other. 4435 shows true elliptical structure, evenly illuminated, with a sense of fading toward the edges… But 4438 is quite a different story! This elliptical is much more elongated. A highly conspicuous wisp of galactic material can be seen stretching back toward the brighter, nearby galaxy pair M84/86. Happy hunting!

Sunday, May 20 – Heads up! It’s eclipse time… According to NASA’s Fred Espenak, an annular solar eclipse will be visible from a 240 to 300 kilometre-wide track that traverses eastern Asia, the northern Pacific Ocean and the western United States. A partial eclipse is seen within the much broader path of the Moon’s penumbral shadow which includes much of Asia, the Pacific and the western 2/3 of North America. Partial phases of the eclipse are visible primarily from the USA, Canada, the Pacific and East Asia. Be sure to visit the resources pages for a visibility map and link to pages for precise times and locations!

New Moon! Since tonight will be our last chance to galaxy hunt for awhile, let’s take a look at one of the brightest members of the Virgo Cluster – M49 (Right Ascension: 12 : 29.8 – Declination: +08 : 00).

Located about 8 degrees northwest of Delta Virginis almost directly between a pair of 6th magnitude stars, giant elliptical M49 holds the distinction of being the first galaxy in the Virgo cluster to be discovered – and the second beyond our local group. At magnitude 8.5, this type E4 galaxy will appear as an evenly illuminated egg shape in almost all scopes, and as a faint patch in binoculars. While a possible supernova event occurred in 1969, don’t confuse the foreground star noted by Herschel with something new!

Although most telescopes won’t be able to pick this region apart – there are also many fainter companions near M49, including NGC 4470 (Right Ascension: 12 : 29.6 – Declination: +07 : 49). But a sharp-eyed observer named Halton Arp noticed them and listed them as “Peculiar Galaxy 134” – one with “fragments!”

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

Posted on by Jenny Winder

Asterisms: Signposts in the Sky

Sagittarius Teapot Asterism Author Eoghanacht via wikimedia commons

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Humans have been grouping stars into patterns since the beginning of time, each culture placing its own myths and folklore in the sky, but it wasn’t until 1930 that the International Astronomical Union (IAU) divided the sky into 88 constellations each with its own strict boundary. Though many of these are well known, and the stories they depict are well documented, few look like the figures they are supposed to represent. Asterisms are more user friendly guides and the starting point for most astronomers. These bright, simple, more prosaic shapes, stand out among the constellations and often serve as useful landmarks, pointing the way to celestial delights!

The best known and most instantly recognisable asterism is probably the Plough or Big Dipper in Ursa Major. Two of its stars, Merak and Dubhe, (The Pointers) pointing the way to the North Star Polaris in Ursa Minor. NASA’s Juno spacecraft stopped on its 5 year journey to Jupiter on March 21 to capture this image of our best known asterism:

The Big Dipper by Juno Credit: NASA/JPL-Caltech/SWRI/MSSS

In the Northern hemisphere, each season is heralded by its own asterism: The Autumn sky is dominated by the great Square of Pegasus, formed by stars from both Pegasus and Andromeda and its top left corner points the way to the Andromeda Galaxy, just a hop, skip and jump away. Most people recognise the three stars Alnitak, Alnilam and Mintaka, making up the Belt of Orion, which shines bright in the Winter sky indicating one of the richest regions in the sky, the Orion Molecular Cloud Complex. The Diamond of Virgo marking the Spring, consists of Arcturus (Boötes), Spica (Virgo), Denebola (Leo) and Cor Caroli (Canes Venatici). These encompass the constellation Coma Berenices and many of the galaxies within the Virgo Cluster. The Summer Triangle of Deneb (Cygnus), Altair (Aquila), and Vega (Lyra) currently sails over us guiding the way to the Ring Nebula in its top right corner.

Searching for Leo? Look for the Sickle, a backwards question mark that represents the lion’s head. Hunting for Hercules? The Keystone is the key and you will also find the Hercules Cluster (M13) on its right hand side. Boötes is easier to spot if you look for the Kite or Ice Cream Cone, than try to make out an ox driver! Not many people can see poor Queen Cassiopia, punished for her vanity to circle the heavens, but the W that marks the constellation is instantly recognisable. The Circlet is a lovely signpost to one of the fish of Pisces. You’d be hard pressed to recognise Sagittarius as the centaur it depicts, but there is the Teapot (Bertrand Russell was right, there is a celestial teapot!) showing the way to this rich patch of sky.

The Southern hemisphere has no shortage of asterisms either, most notably Argo Navis which represents the entire ship Argo sailed by Jason and the Argonauts and would be the largest constellation in the sky if it hadn’t been broken up in 1752 by French astronomer Nicolas Louis de Lacaille into the constellations we know today as Carina (the keel), Puppis (the poop deck) and Vela (the sails). Also in the Southern hemisphere are found The Three Patriachs in Triangulum Australe and the Fish Hook in Scorpius among others.

There are many more obscure asterisms too. Job’s Coffin graces the constellation of Delphinus, Asses and the Manger are in Cancer, Poniatowski’s bull (named for the King of Poland) is part of Ophiuchus and Aquila. There are the Lozenge, Saxophone, Coathanger, and many more.

The sky can seem a bewildering place, filled with gods, kings and mythical creatures. Asterisms like the Teapot make a more welcoming and friendly introduction, allowing a novice stargazer to easily pick their way around the sky and gain confidence and as many stars get swallowed by increasing light pollution, asterisms still shine out to show the way.

Find out more about asterisms here.

Posted on by Fraser Cain

M55 — Or a Swarm of Angry Bees?

M55. Image credit: ESO
M55. Image credit: ESO

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Globular clusters are my absolute favorite telescope targets. Okay, Saturn, and then globular clusters. And that’s why I’ve absolutely fallen in love with this amazing picture from the European Southern Observatory of the globular cluster M55, located in the constellation Sagittarius. In fact, it’s my new desktop wallpaper (it should be yours too, click here and download the screensize that fits your monitor)

Globular clusters contain vast numbers of stars clumped together in a tight area. In the case of M55, there are about 100,000 stars grouped up within a sphere only 100 light-years across. Astronomers know that globular clusters are old, almost as old as the Universe itself. In fact, for the longest time, astronomers calculated the age of globular clusters to be older than the estimated age of the Universe. Of course, there was an incorrect measurement there, and astronomers eventually aligned the age of globular clusters and the Universe.

M55 is thought to have formed 12.3 billion years ago, when the Universe was less than 3 billion years old. The most ancient stars in the cluster burned out a long time ago, detonating as supernovae. We’re now left with the cooler, lower mass stars, which slowly wink out one-by-one becoming white dwarfs as they proceed through the full stellar life cycle. Our own Sun is only halfway through its own lifespan, before it runs out of hydrogen fuel and becomes a white dwarf.

There are at least 160 globular clusters scattered across the Milky Way, grouped up more towards our galaxy’s core. We can only see some of the clusters because the bright core of the Milky Way obscures our view to objects on the other side. But other galaxies, with their own globular clusters show us what our own galaxy probably looks like from afar.

M55 is part of the Messier catalog; a collection of objects that looked comet-like to the eyes of Charles Messier, a French astronomer working in the 18th century. Messier recorded a list of more than 100 objects which could be confused as comets: galaxies, clusters, and nebulae.

Want to see M55 on your own? You’ll need at least a pair of 50 mm binoculars or a small telescope, some nice dark skies, and a clear view to the constellation Sagittarius. Sagittarius looks exactly like a teapot in the sky, hovering above the southern horizon in summer. The further south you go, the higher Sagittarius will be in the sky.

But you’ll never see a view or take an image as detailed as this photo. That’s because it was captured with the ESO’s 4.1-metre (13.4 foot) Visible and Infrared Survey Telescope for Astronomy (VISTA) at ESO’s Paranal Observatory in northern Chile.

Original Source: ESO News Release