Astronomy Archives

March 25, 2009December 24, 2015 by Fraser Cain

How Are Volcanoes Formed?

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Some of the most dramatic mountains in the world are volcanoes. Volcanoes can grow to enormous heights quickly, sometimes just a few years. But have you ever wondered, how are volcanoes formed?

As you probably know, you’re standing on the Earth’s crust; a relatively thin layer of solid Earth. Beneath this is the mantle, an extremely hot region just a few dozen kilometers beneath your feet. Although the mantle is almost entirely solid, it can form small pockets of liquid rock and hot gasses. It’s hard to think of this way, but the molten rock – called magma – is more buoyant than the surrounding solid rock. It slowly forces its way upward through weaknesses in the Earth’s crust. These become volcanoes.

When the magma reaches the surface, it wells out onto the surface forming a volcano. What kind of volcano forms depends on the size of the crack in the crust, and the kind of lava that comes out. Some lava is very fluid, and can flow for long distances. This kind of lava creates shield volcanoes, like in the Hawaiian islands. Other lava is very thick, and doesn’t travel very far, creating the more familiar cinder cone shaped volcanoes.

Some very energetic volcanoes will spew rock, ash and magma high into the air. This material falls back down around the vent, and this is how the volcano builds up. The volcano is like a big debris pile surrounding the volcanic vent.

The largest, most dramatic volcanoes in the world are composite volcanoes, or stratovolcanoes. These can have vast networks of volcanic vents and chambers, with many openings to the surface. They can be made up of lava flows and deposits of ash that build up into huge mountains over millions of years. Some of the most dramatic mountains in the world are composite volcanoes: Mt. Fuji, Mt Kilimanjaro, and Mt. Rainier, for example.

We have written many articles about the volcanoes for Universe Today. Here’s an article about the biggest volcano on Earth, and here’s the tallest volcano.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

March 25, 2009December 24, 2015 by Anne Minard

Calling All Amateur Astronomers: Help Comb Arecibo Data for Gems

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Einstein@Home is one of the world’s largest public computing projects, with more than 200,000 people donating time on their own computers to mine gravitational wave data for the tell-tale signs of pulsars.

Now, Einstein@Home will begin searching Arecibo radio data to find binary systems consisting of the most extreme objects in the universe: a spinning neutron star orbiting another neutron star or a black hole.

And the project needs even more public participation.

Today, Bruce Allen, director of the Einstein@Home project, and Jim Cordes, of Cornell University, announced that the Einstein@Home project is beginning to analyze data taken by the PALFA Consortium at the Arecibo Observatory in Puerto Rico. PALFA is the Pulsar Arecibo L-band Feed Array Consortium, an ongoing search effort.

The Arecibo Observatory is the largest single-aperture radio telescope on the planet and is used for studies of pulsars, galaxies, solar system objects, and the Earth’s atmosphere.

Current searches of radio data lose sensitivity for orbital periods shorter than about 50 minutes. But the enormous computational capabilities of the Einstein@Home project (equivalent to tens of thousands of computers) make it possible to detect pulsars in binary systems with orbital periods as short as 11 minutes. The project is based at the University of Wisconsin in Milwaukee and the Albert Einstein Institute in Germany.

“Discovery of a pulsar orbiting a neutron star or black hole, with a sub-hour orbital period, would provide tremendous opportunities to test General Relativity and to estimate how often such binaries merge,” said Cordes.

The mergers of such systems are among the rarest and most spectacular events in the universe. They emit bursts of gravitational waves that current detectors might be able to detect, and they are also thought to emit bursts of gamma rays just before the merged stars collapse to form a black hole.

“While our long-term goal is to detect gravitational waves, in the shorter term we hope to discover at least a few new radio pulsars per year, which should be a lot of fun for Einstein@Home participants and should also be very interesting for astronomers,” Allen added. “We expect that most of the project’s participants will be eager to do both types of searches.”

Einstein@Home participants will automatically receive work for both the radio and gravitational-wave searches.

The large data sets from the Arecibo survey are archived and processed initially at Cornell and other PALFA institutions. For the Einstein@Home project, data are sent to the Albert Einstein Institute in Hannover via high-bandwidth Internet links, pre-processed and then distributed to computers around the world. The results are returned to AEI, Cornell, and UWM for further investigation.

You can join the Einstein@Home effort here.

LEAD IMAGE: Artist’s rendering of a neutron star. Credit: Space Telescope Science Institute.

Source: LIGO Scientific Collaboration Research Group

March 23, 2009December 24, 2015 by Fraser Cain

What Are Volcanoes?

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Volcanoes are mountains. But unlike most mountains in the world, formed from folding continental plates, uplift and erosion, volcanoes are created when material from inside the Earth escapes to the surface. Let’s answer the question, “what are volcanoes”.

As you probably know, the ground you’re standing on is the Earth’s crust. It varies in depth between 10 km under the oceans and 30 km beneath the continental plates. Beneath the crust is a vast region called the Earth’s mantle. The mantle is made up of molten rock called magma. At the boundaries between continental plates, volcanic vents can open up, where magma and gasses from inside the Earth can escape.

When it’s still underground, the molten rock is called magma. Although most of the Earth’s mantle is solid, it can create pockets of liquid which escape from underneath through weaknesses in the Earth’s crust. After it escapes to the surface, it’s called lava. Lava has different levels of viscosity – how easily it flows downhill. The least viscous (easy flowing) lava creates shield volcanoes. The lava can flow for great distances in huge rivers, and creates wide volcanoes with gently sloping sides. The most viscous (thickest) lava piles up around the volcanic vent created the familiar cone-shaped volcanoes.

The simplest volcanoes where a single vent breaks through a weakness in the crust, releasing lava, ash and rocks. After being blasted out of the vent, it piles up around on the surface, allowing the volcano to grow up quickly. Some of the largest, most familiar volcanoes are composite, or stratovolcanoes. These are built up of multiple layers of ash and lava, and can have vast networks of vents.

The word volcano comes from the island of Vulcano in the Mediterranean Sea off Sicily. Ancient people thought that this island was the chimney of the forge of Vulcan, the Roman god of blacksmithing.

We have written many articles about volcanoes for Universe Today. Here’s an article about the biggest volcano on Earth, and here’s one about the tallest volcano.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

March 23, 2009December 24, 2015 by Fraser Cain

Most Active Volcanoes

Most volcanoes are dormant. They erupted millions of years ago, but then the Earth’s plate tectonics closed the vent or caused it to drift away. But some volcanoes are still active and erupt on a regular basis. Here are a list of the most active volcanoes in the world.

The most active volcano on Earth is Kilauea volcano on Hawaii. It’s the most recent of a series of volcanoes that created the Hawaiian archipelago of islands. They formed as a string of islands because the Pacific plate is slowly moving over the Hawaii hotspot. That’s why the islands of Kauai and Oahu are no longer active, but Kilauea is. This volcano only rises 1,247 meters above sea level, but it’s still growing. 90% of the surface of Kilauea is less than 1,100 years old, and there were 45 eruptions of the volcano in the 20th century alone. Even in 2008, there were explosive eruptions from Kilauea.

The second most active volcano in the world is Mount Etna, a composite volcano on the east coast of Sicily. It’s the largest active volcano in Europe, with an altitude of 3,329 meters. It’s in an almost constant state of eruption, but despite this, its flanks support extensive vineyards and orchards. Over the last few thousand years, it has experienced many eruptions. Ash from its eruptions have been found as far away as Rome, 800 km away. There are more than 300 volcanic vents across Mount Etna, ranging in size from small holes to massive craters, hundreds of meters across.

The third most active volcano is Piton de la Fournaise, which is French for the “Peak of the Furnace”. This is a shield volcano on the eastern side of Renunion island in the Indian Ocean. It has erupted in 2006, 2007 and in 2008 – with more than 150 eruptions since the 17th century. Piton de la Fournaise is referred locally as “le Volcan”, and stands at a height of 2,631 meters tall. It has many craters and cinder cones inside the volcano’s caldera and around its outer flanks.

We have written many articles about volcanoes for Universe Today. Here’s an article about how the dinosaurs might have been killed by both volcanoes and asteroids, and how they helped slow the ocean warming trend.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

References:
USGS Volcanoes Page: Kilauea
NASA Earth Observatory
USGS Volcanoes Page: Piton de la Fournaise

March 23, 2009December 24, 2015 by Anne Minard

Moonshadows on Saturn’s Rings Are Harbingers of Spring

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Moonshadows on Saturn’s rings are foretelling the planet’s equinox, when the sun will be exactly aligned with the planet’s equator and rings — and then will shift north from the southern hemisphere, kickstarting northern spring.

NASA’s Cassini spacecraft has captured, for the first time, the tell-tale moonshadows – sort of like groundhogs on Earth.

moonshadow2 — Click to play the short movie. Credit: NASA/JPL/Space Science Institute

The image above is a still from a movie, from Cassini’s hour-long observation of the shadow of the small moon Epimetheus.

Like Earth and most of the other planets, Saturn’s spin axis is tilted relative to its motion around the sun. So the sun, seen from Saturn, cycles from the southern hemisphere to the north and back again. A full sweep of seasonal changes on Saturn and its rings and moons takes a Saturnian year, equal to 29.5 Earth years. Thus, about every 15 Earth years, or half-Saturn-year, the sun passes through the plane containing the planet’s rings.

During these times, the shadows of the planet’s rings fall in the equatorial region on the planet. And the shadows of Saturn’s moons external to the rings, especially those whose orbits are inclined with respect to the equator, begin to intersect the planet’s rings. When this occurs, the equinox period has essentially begun, and any vertical protuberances within the rings, including small embedded moons and narrow vertical warps in the rings, will also cast shadows on the rings. At exactly the moment of equinox, the shadows of the rings on the planet will be confined to a thin line around Saturn’s equator and the rings themselves will go dark, being illuminated only on their edge. The next equinox on Saturn, when the sun will pass from south to north, is Aug. 11, 2009.

Because of these unique illumination circumstances, Cassini imaging scientists have been eager to observe the planet and its rings around the time of equinox. Cassini’s first extended mission, which began on July 1, 2008, was intended to gather observations during this time. Hence its name: Cassini Equinox Mission.

More than just pretty pictures, the observations could reveal any deviations across the rings from a perfectly flat wafer-like disk. Saturn’s ring system is wide, spanning hundreds of thousands of miles or kilometers. But the main inner rings (called A, B and C) are perhaps only 10 meters (30 feet) thick, and they are sometimes obscured from view inside thicker outer rings.

“We hope that such images will help us measure any vertical warping in the A and B rings,” said John Weiss, an imaging team associate from the Space Science Institute in Boulder, Colorado. “Because we know how big the moons are, and where they are in their orbits around Saturn when they cast these shadows, we have all the information we need to infer any substantial vertical structure that might be present.”

On Jan. 8, Epimetheus, a small moon 113 kilometers (70 miles) across, was the first moon observed casting a shadow onto the outer edge of the A ring. Next Pan, 30 kilometers (20 miles) across and orbiting within the rings, was caught casting a shadow on the A ring on Feb. 12. Eventually, more moons will cast shadows on the rings and all shadows will grow longer as exact equinox approaches.

Source: Cassini Imaging Central Laboratory for Operations (CICLOPS)

March 22, 2009December 24, 2015 by Anne Minard

Star Exploded Too Early, May Blow Apart Supernova Theory

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NASA’s Hubble Space Telescope has identified a star a million times brighter than the sun that exploded as a supernova in 2005 — well before it should have, according to current theories of stellar evolution.

The doomed star, estimated at about 100 times our sun’s mass, was not mature enough, according to theory, to have evolved a massive iron core of nuclear fusion ash. This is the supposed prerequisite for a core implosion that triggers a supernova blast.

“This might mean that we are fundamentally wrong about the evolution of massive stars, and that theories need revising,” says Avishay Gal-Yam of the Weizmann Institute of Science, in Rehovot, Israel. The finding appears in the online version of Nature Magazine.

The explosion, called supernova SN 2005gl, was seen in the barred-spiral galaxy NGC 266 on October 5, 2005. NGC 266 is about 200 million light years away, in the constellation Pisces.

The progenitor was so bright that it probably belonged to a class of stars called Luminous Blue Variables (LBVs), “because no other type of star is as intrinsically brilliant,” says Gal-Yam. But there’s a wrinkle: as an LBV-class star evolves, it sheds much of its mass through a violent stellar wind. Only at that point does it develop a large iron core and ultimately explodes as a core-collapse supernova.

“The progenitor identification shows that, at least in some cases, massive stars explode before losing most of their hydrogen envelope, suggesting that the evolution of the core and the evolution of the envelope are less coupled than previously thought, a finding which may require a revision of stellar evolution theory,” co-author Douglas Leonard, from California’s San Diego State University, said in a press release.

One possibility is that the progenitor to SN 2005gl was really a pair of stars — a binary system — that merged. This would have stoked nuclear reactions to brighten the star enormously, making it look more luminous and less evolved than it really was.

“This also leaves open the question that there may be other mechanisms for triggering supernova explosions,” says Gal-Yam. “We may be missing something very basic in understanding how a superluminous star goes through mass loss.”

Gal-Yam and Leonard located the progenitor in archival images of NGC 266 taken in 1997. They then used the Keck telescope to precisely locate the supernova on the outer arm of the galaxy. A follow-up observation with Hubble in 2007 unequivocally showed that the superluminous star was gone.

Extremely massive and luminous stars topping 100 solar masses, such as Eta Carinae in our own Milky Way Galaxy, are expected to lose their entire hydrogen envelopes prior to their ultimate explosions as supernovae.

“These observations demonstrate that many details in the evolution and fate of LBVs remain a mystery,” said Mario Livio, of the Space Telescope Science Institute in Baltimore. “We should continue to keep an eye on Eta Carinae – it may surprise us yet again.”

MOSAIC CAPTIONS: [Top Center] 2005 ground-based image of the supernova; [Bottom Left] 1997 Hubble archival visible-light image of the region of the galaxy where the supernova exploded, with white circle marking the progenitor star; [Bottom Center] Near-infrared light photo of the supernova explosion taken on Nov. 11, 2005, with the Keck telescope, with the blast centered on the position of the progenitor; [Bottom Right] Visible-light Hubble follow-up image taken on September 26, 2007. The progenitor star is gone. Credit: NASA, ESA, and A. Gal-Yam (Weizmann Institute of Science, Israel)

Source: HubbleSite

March 20, 2009December 24, 2015 by Tammy Plotner

SkyWatcher’s Forecast: March 20-26, 2009 – A Messier Marathon Special Edition!

Greetings, fellow SkyWatchers! That’s right… It’s that time again. Equinox and upcoming New Moon means that many of us are going to try and kill ourselves to capture all 110 Messier Catalog objects in just one night. When I was a much younger lass, I used to think that was fun. Now that I’m considerably older and have to pay a physical price for staying outside all night in the cold? Well… It’s not quite as appealing as it used to be. But, I ain’t ready for the dirt nap just yet. If you think you’ve still got what it takes, then follow me…

Friday, March 20, 2009 – Since the beginning of the year, the Sun has been traveling low in the sky, moving higher each day until reaching northern hemisphere vernal equinox. Today the Sun will rise exactly in the east and set exactly in the west – precisely 12 hours later – making it possible for most observers to see all 110 Messier objects in a single night. The Messier Marathon isn’t easy. This year,why not try your own style of marathoning, as we take a less frenzied pace over the next 11 days, enjoying these splendid objects ‘‘ten at a time.’’

When the sky darkens enough to find guidestar Delta Ceti, the M77 (RA 02 42 40.83 Dec -00 00 48.4) spiral galaxy will be your first and the M74 (RA 01 36 41.84 Dec +15 46 59.6) spiral galaxy east of Eta Pisces will be your second mark. Both are telescopic only, and an extreme challenge due to low position. Next is M33, west of Alpha Triangulum. With ideal skies, the Pinwheel Galaxy can be seen in binoculars, but sky glow makes this huge, low-surface brightness spiral difficult for even telescopes at low power. M31 (RA 00 42 44.31 Dec +41 16 09.4), the Andromeda Galaxy, is a delightful capture for both binoculars and scopes just west of Nu Andromedae. For the telescope, two more on the list are companions to M31: elliptical M32 (RA 00 42 41.87 Dec +40 51 57.2) on its southeastern edge, and M110 (RA 00 40 22.00 Dec +41 41 07.0), to the northwest.

Head northwest for two open clusters visible to both telescopes and binoculars. You’ll find M52 (RA 23 24 48.00 Dec +61 35 -0.0) easiest by identifying Alpha and Beta Cassiopeiae, drawing a mental line between them, and extending it the same distance northwest of Beta. Next, hop north of Delta Cassiopeiae to pick up our eighth object—open cluster M103 (RA 01 33 24.00 Dec +60 39 00.0). Head south toward Perseus to telescopically locate the M76 (RA 01 42 19.95 Dec +51 34 31.1) planetary nebula just north of Phi. Binoculars are all that’s needed to see M34, an open cluster located roughly halfway between Algol and the lovely double Almach. As you can see, such a quick journey takes away some of the beauty of learning the history and science behind the objects… But the race is on!

Saturday, March 21, 2009 – Today, note the 1927 birth on this date of Halton Christian Arp, one of the most noted minds of our time regarding the origin and evolution of galaxies. Through his incredible study of peculiar galaxies and quasars, we are no longer able to assume that redshift is a uniform indicator of distance, or that the two are unrelated.

Tonight our marathon will be more relaxed because the fastest-setting objects are already completed. Take a moment to enjoy M45 (RA 03 47 24.00 Dec +24 07 00.0), the Pleiades. The ‘‘Seven Sisters’’ are easily visible high in the west, and their cool, blue beauty is incomparable in binoculars or telescopes. Head for Lepus and identify Beta and Epsilon. Triangulating south with this pair is 5th-magnitude star ADS3954, and the small globular M79 (RA 05 24 10.59 Dec -24 31 27.3) to its northeast. M42 (RA 05 35 17.30 Dec -05 23 28.0) , the Orion Nebula, is next. M43 (RA 05 35 31.00 Dec -05 16 12.0) is part of M42 to the north northeast. The next two objects are M78 (RA 05 46 46.70 Dec +00 00 50.0), northeast of Zeta Orionis and M1 (RA 05 34 31.97 Dec +22 00 52.1), the Crab Nebula, northwest of Zeta Tauri.

Now take a few minutes to relax. The remaining objects on tonight’s list are all very easy, well positioned, and observable with binoculars. Are you ready? Then let’s go! Open cluster M35 (RA 06 09 06.00 Dec +24 21 00.0) is northwest of the toe of Gemini – Eta. The next stop is Auriga, directly between Theta and southern Beta. Slightly to the east you’ll find open cluster M37 (RA 05 52 19.00 Dec +32 33 12.0). Now use Theta and western Iota. Roughly halfway between them and in the center of Auriga you will find open cluster M38 (RA 05 28 43.00 Dec +35 51 18.0). Hop southeast to capture M36 (RA 05 36 12.00 Dec +34 08 24.0).

Although this pace may seem rather scandalous, take stock of what you’ve accomplished! You’ve visited 20 Messier objects in just two nights. . .with time to spare. Return to your favorite objects and enjoy them. As Halton Arp once said:

“Sometimes I think that Astronomy is not so much a science as a series of scandals.”

Sunday, March 22, 2009 – Born on this date in 1394 was Ulugh Beg, builder of the first observatory. Beg’s chart listed 994 stars and was the first produced since Hipparchus! In 1799, Friedrich Wilhelm August Argelander, who cataloged the positions and magnitudes of 324,188 variable stars, was born!

Now get Sirius, go south, and start our list for tonight with open cluster M41. Return to Sirius and head a fist-width east/northeast for M47 (RA 07 36 36.00 Dec -14 29 -0.0). Dimmer, more compressed M46 (RA 07 41 42.00 Dec -14 49 00.0) is east. Drop slowly south about three fingerwidths and encounter lively M93 (RA 07 44 36.00 Dec -23 52 00.0)! Incredibly colorful open cluster M50 (RA 07 02 40.47 Dec -08 21 50.5) is roughly one-third the distance between Sirius and Procyon. Drop south-southeast of Zeta Monocerotis for dim open cluster M48 (RA 08 13 42.00 Dec -05 45 00.0). The ‘‘Beehive’’ – M44 (RA 08 40 24.00 Dec +19 41 -0.0) – is just north-northwest of Delta Cancri. Continue south to Alpha, and then west for M67 (RA 08 51 18.00 Dec +11 48 00.0). It will appear as a fine haze to binoculars, but telescopes see a spectacular cloud of similar magnitude resolvable stars.

Telescopes, head a fist-width east Regulus for finderscope stars 52 and 53, and head between them. Just about 1.5 degrees south of 52 is elliptical galaxy M105 (RA 10 47 49.60 Dec +12 34 53.9). Larger scopes see two additional faint galaxies, NGC 3384 and NGC 3389, to M105’s west. Continue another degree south toward star 53 for the silver-gray beauty of M96 (RA 10 46 45.78 Dec +11 49 10.2). Enjoy its bright nucleus and wispy arms!

Now relax and enjoy a spring evening with two meteor showers. The northern hemisphere Camelopardalids have no definite peak, and a fall rate of only 1 per hour. They’re the slowest recorded meteors, entering our atmosphere at speeds of only 7 kilometers per second! Far more interesting for both hemispheres is tonight’s peak of the March Geminids. These slower than normal meteors will be fun to watch! When you see a bright streak, trace it back to its point of origin: which did you see, a Camelopardalid, or a March Geminid?

Monday, March 23, 2009 – In 2001 on this date the Mir space station ended 15 years in orbit with a fiery return. This date is also the 1837 birth of Richard Anthony Proctor who showed the stars’ motion, distribution, and relation to nebulae. In 1829, Norman Pogson, creator of the magnitude scale still used today, was born. The year 1749 saw the birth of Pierre-Simon Laplace, who theorized that the Solar System formed from a nebula, formulated mathematical probability, and helped create the metric system!

Return to Leo tonight. Identify 52 Leonis and drop south past M105 for M95 (RA 10 43 57.70 Dec +11 42 13.7), which isn’t as bright or large as neighboring M96 (RA 10 46 45.78 Dec +11 49 10.2). Small scopes see central brightening, and large ones begin resolution of this awesome barred spiral. Look to the southwestern star of the three marking Leo’s hips – Theta Leonis. South is faint star 73, and a degree east-southeast is the pairing of M65 and M66. Western M65 (RA 11 18 55.78 Dec +13 05 32.3) and eastern M66 (RA 11 20 15.07 Dec +12 59 21.6) are both beautiful spirals worthy of far more time and attention. Head north for another same-field pair – M81 and M82 – in Ursa Major. Draw a mental line between Gamma and Alpha. Extend the line beyond Alpha the same distance. Begin an eyepiece sweep to locate them. The southernmost is stunning, bright-cored M81 (RA 09 55 33.17 Dec +69 03 55.1). North is the broken, spindle-shaped peculiar galaxy M82 (RA 09 55 52.19 Dec +69 40 48.8). Southeast of Beta Ursae Majoris (UM) is the edge-on galaxy M108 (RA 11 11 31.29 Dec +55 40 31.0).

Continue another half degree southeast for the Jupiter-sized planetary M97 (RA 11 14 47.73 Dec +55 01 08.5). Continue south to Gamma UM for same-field M109 (RA 11 57 35.90 Dec +53 22 35.0). The last in Ursa Major is an error on Messier’s part. M40 (RA 12 22 24.00 Dec +58 05 -0.0) is actually double star WNC4, located northeast of 70 Ursae Majoris. Now to Canes Venatici and our last object tonight: Alpha and northern Beta are easily recognizable to the east of the last star in the handle of the Big Dipper (Eta). You’ll find the soft-spoken spiral galaxy M106 (RA 12 18 57.54 Dec +47 18 14.3) almost directly midway between Beta CVn and Gamma UM less than 2 degrees south of star 3. Add as much aperture as you can to this gorgeous study!

Tuesday, March 24, 2009 – On this date in 1835 Josef Stefan was born, a physicist whose word was ‘‘law’’ to radiation! In 1941 on this date, Joseph Taylor, Jr, the radio astronomer who jointly discovered the first binary pulsar, was born. Last, let’s celebrate the 1893 birth of Walter Baade, who studied the Andromeda Galaxy’s core with the 100’’ Hooker telescope, resolving it (and two different Cepheids) for the first time.

Tonight, identify Canes Venatici’s two brightest stars, Alpha and Beta. Galaxy M94 (RA 12 50 52.63 Dec +41 07 09.3) forms a triangle with Alpha and Beta CnV, the apex toward Eta Ursae Majoris (UM). M63 (RA 13 15 49.28 Dec +42 01 46.5) is one-third the distance between Beta CnV and Eta UM. M51 (RA 13 29 52.37 Dec +47 11 40.8) resides near visual star 24 CnV. You’ll find M101 (RA 14 03 12.51 Dec +54 20 53.1) to the other side of Alkaid. The accepted designation for M102 (RA 14 03 12.59 Dec +54 20 56.7) is lenticular galaxy NGC 5866, located southeast of Iota Draconis. You’ll find small globular cluster M53 (RA 13 12 55.30 Dec +18 10 09.0) northeast of Alpha Comae. M64 (RA 12 56 43.88 Dec +21 41 00.1) is about one-third the distance from Alpha Comae to Eta UM. M3 (RA 13 42 11.23 Dec +28 22 31.6) is one-third the distance between Arcturus and Cor Caroli.

Now for the incredibly rich galaxy fields near Coma Berenices and Virgo. Identify the easternmost star in Leo – Denebola – and head a fist-width due east. M98 (RA 12 13 48.29 Dec +14 54 01.2) is west of star 6 Comae. Return to 6 Comae and drop 1 degree southeast for M99 (RA 12 18 49.52 Dec +14 25 00.4).

Congratulations! In just 5 days you have logged 50 of the brightest and most beautiful members of the deep sky!

Wednesday, March 25, 2009 – Today celebrates the 1786 birth of Giovanni Amici, inventor of the achromatic lens, and in 1923, the birth of Kenneth Linn Franklin, radio astronomer. Tonight continue our marathon around midnight. It’s time to dance…

Leo’s easternmost bright star Denebola points to 6 Comae, about three finger-widths east. Two degrees northeast of 6 you’ll pass two 5th-magnitude stars leading to M100 (RA 12 22 54.95 Dec +15 49 19.5), the largest-appearing galaxy in the Coma-Virgo cluster. Continue 2 degrees north for bright yellow 11 Comae. One degree northeast is 9th magnitude, round M85 (RA 12 25 24.23 Dec +18 11 26.9). Try a “trick of the trade” to locate two more. Return to 6 Comae, relocate M99, turn off your drive, and take a break for 14 minutes. When you return, the elongated form and near-stellar nucleus of M88 (RA 12 31 59.34 Dec +14 25 13.4) will have ‘‘drifted’’ into view. Wait another 2–3 minutes, and the faint, barred spiral M91 (RA 12 35 26.58 Dec +14 29 45.1) will join the show in a 1-degree field of view.

Now locate bright Vindemiatrix (Epsilon Virginis), a handspan due east of Denebola. Hop 4.5 degrees west and a shade north to locate the largest elliptical galaxy presently known, M60 (RA 12 43 40.19 Dec +11 33 08.9). This magnitude 9 galaxy can be spotted with binoculars, but a telescope will reveal faint NGC4647, which only appears to be interacting with M60. In the field west is our next Messier: bright-cored elliptical M59 (RA 12 42 02.39 Dec +11 38 45.1). (Yes, there’s more, but not tonight. Let’s keep our studies to only the Messiers!) Move a degree west for fainter M58 (RA 12 37 43.48 Dec +11 49 04.4). About a degree north will locate face-on spiral M89 (RA 12 35 39.81 Dec +12 33 22.8). One half degree northeast is delightful 9.5 magnitude M90 (RA 12 36 50.08 Dec +13 09 45.7), whose dark dust lanes show in larger scopes. Continue 1.5 degrees southwest for M87 (RA 12 30 49.42 Dec +12 23 28.0), the first radio source galaxy discovered. M87 contains a black hole, and more than 4,000 globular clusters surround its elliptical form.

Now take a break… Things are about to get a lot hotter!

Thursday, March 26, 2009 – Starting at midnight now. Dawn is only a few hours away and the beginning of a new day. It is also a New Moon and the perfect time to try all 110 Messier objects in just one night! What’s that? You want to keep on going ten at a time? Then let’s do just that…

Slightly more than a degree northwest of M87 is the same-field pair, western M84 (RA 12 25 03.74 Dec +12 53 13.1) and eastern M86 (RA 12 26 12.20 Dec +12 56 44.5). Head to 31 Virginis and identify splendid variable R a degree west. Two degrees northwest is galaxy M49 (RA 12 29 46.76 Dec +07 59 59.9). Shift 3 degrees southwest for the handsome yellow double 17 Virginis. A half degree south is large face-on spiral M61. Now go for Spica, and 11 degrees due west. M104 (RA 12 39 59.43 Dec -11 37 23.0), the Sombrero Galaxy, will be your reward for a job well done. Congratulations! You’ve just seen 15 of the finest galaxies in the Coma–Virgo region in just hours, and our “Marathon” continues.

Five degrees south-southeast of Beta Corvi is your marker star, the double A8612, for the same field globular M68 (RA 12 39 28.01 Dec -26 44 34.9), and the Southern Pinwheel, M83 (RA 13 37 00.78 Dec -29 51 58.6) is 10 degrees southeast of Gamma Hydrae. Now make a wide move and head southeast of Arcturus for Alpha Serpentis. Eight degrees southwest is outstanding globular cluster M5 (RA 15 18 33.75 Dec +02 04 57.7) sharing the field with 5 Serpens. Now locate the ‘‘keystone’’ shape of Hercules, and identify Eta in its northwest corner. One-third the way between it and southern Zeta is the fantastic M13 (RA 16 41 41.44 Dec +36 27 36.9), the “Great Hercules Globular Cluster.” More difficult is M92 (RA 17 17 07.27 Dec +43 08 11.5), because there are no stars to guide you. Try this trick: using the two northernmost stars in the “keystone” asterism and form an equilateral triangle in your mind, with its apex to the north. Point your scope there. Way to go, astronomer! You have now passed the most difficult part of the “mini-thon,” and just think of the rewards! In less than a week, you have conquered over half of the Messier catalog.

While you spend a sleepy day, think about a French amateur astronomer who was watching a round black spot transit the Sun today in 1859. His name was Lescarbault, and he was sure he’d witnessed a new planet, which he christened “Vulcan.” Nathaniel Bowditch was also born this date in 1773. He also devised the “Bowditch Curve,” which applies in both physics and astronomy.

Be sure to join us next Friday as we conclude our Messier Marathon special! Until then? Dreams really do come true when you keep on reaching for the stars….

This week’s awesome images are (in order): M74 and M34 (credit – Palomar Observatory, courtesy of Caltech), Halton Arp (historical image), M38, M96, M106, M99, M87 and M61 (credit – Palomar Observatory, courtesy of Caltech). Thank you so much!!

March 19, 2009December 24, 2015 by Nancy Atkinson

Astronomers Observe Bizarre Blazar with Battery of Telescopes

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Quasars visible at gamma-ray energies are called “blazars.” Blazars are among the most energetic objects in the universe and are fueled by supermassive black holes at the core of certain giant elliptical galaxies. An international team of astrophysicists using a combination of ground- and space-based telescopes have uncovered surprising changes in radiation emitted by an active galaxy. The picture that emerges from these first-ever simultaneous observations with optical, X-ray and new-generation gamma-ray telescopes is much more complex than scientists expected and challenges current theories of how blazars generate the radiation they emit.

The galaxy, called PKS 2155-304, emits oppositely directed jets of particles traveling near the speed of light as matter falls into a central supermassive black hole; this process is not well understood. In the case of blazars, the galaxy is oriented such that we’re looking right down the jet.

PKS 2155-304 is located 1.5 billion light-years away in the southern constellation of Piscis Austrinus and is usually a detectable but faint gamma-ray source. But when its jet undergoes a major outburst, as it did in 2006, the galaxy can become the brightest source in the sky at the highest gamma-ray energies scientists can detect — up to 50 trillion times the energy of visible light. Even from strong sources, only about one gamma ray this energetic strikes a square yard at the top of Earth’s atmosphere each month.

Atmospheric absorption of one of these gamma rays creates a short-lived shower of subatomic particles. As these fast-moving particles rush through the atmosphere, they produce a faint flash of blue light. The High Energy Stereoscopic System (H.E.S.S), an array of telescopes located in Namibia, captured these flashes from PKS 2155-304.

One of the H.E.S.S. telescopes in Namabia. Credit: H.E.S.S.

Gamma rays at lower energies were detected directly by the Large Area Telescope (LAT) aboard NASA’s orbiting Fermi Gamma-ray Space Telescope. “The launch of Fermi gives us the opportunity to measure this powerful galaxy across as many wavelengths as possible for the first time,” says Werner Hofmann, spokesperson for the H.E.S.S. team at the Max-Planck Institute for Nuclear Physics in Heidelberg, Germany.

With the gamma-ray regime fully covered, the team turned to NASA’s Swift and Rossi X-ray Timing Explorer (RXTE) satellites to provide data on the galaxy’s X-ray emissions. Rounding out the wavelength coverage was the H.E.S.S. Automatic Telescope for Optical Monitoring, which recorded the galaxy’s activity in visible light.

Between August 25 and September 6, 2008, the telescopes monitored PKS 2155-304 in its quiet, non-flaring state. The results of the 12-day campaign are surprising. During flaring episodes of this and other blazars, the X- and gamma-ray emission rise and fall together. But it doesn’t happen this way when PKS 2155-304 is in its quiet state — and no one knows why.

What’s even stranger is that the galaxy’s visible light rises and falls with its gamma-ray emission. “It’s like watching a blowtorch where the highest temperatures and the lowest temperatures change in step, but the middle temperatures do not,” says Berrie Giebels, an astrophysicist at France’s École Polytechnique who works with both the H.E.S.S. and Fermi LAT teams.

“Astronomers are learning that the various constituents of the jets in blazars interact in fairly complicated ways to produce the radiation that we observe,” says Fermi team member Jim Chiang at Stanford University, Calif. “These observations may contain the first clues to help us untangle what’s really going on deep in the heart of a blazar.”

Source: NASA

March 19, 2009December 24, 2015 by Anne Minard

Disappearing Stars Confirm Supernova Origins

Artist's rendering of SN 1993J, where a red supergiant supernova progenitor star (left) is exploding after having transferred about 10 solar masses of hydrogen gas to the blue companion star (right). Credit: ESA

Artist’s rendering of SN 1993J, where a red supergiant supernova progenitor star (left) is exploding after having transferred about seven solar masses of hydrogen gas to the blue companion star (right). Credit: ESA

Astronomers have caught two stars in the disappearing acts that link them to type II supernova events.

Type II supernovae are widely believed to result from the internal collapse and explosion of massive stars, about nine times the size of our sun. But precious few observations have actually confirmed the relationship.

Now, researchers have spotted two parent stars that showed up in supernovae “before” images — but not in images taken after the blasts.

“The disappearance of the progenitors confirms that these two supernovae were produced by Red Supergiants,” write co-authors Justyn Maund and Stephen Smartt. Their new paper is out in this week’s issue of Science.

SN 2003gd. Credit: Gemini Observatory

So far only one star has been shown to have disappeared after it exploded — the star that exploded as SN 1987A in the Local Group of galaxies. Seven other stars have been spotted in the neighborhoods of type II supernovae before they went off, but none of them has been shown to have disappeared, Maund and Smartt write.

Maund is affiliated with both the University of Copenhagen in Denmark and the University of California at Santa Cruz, and Smartt is from Queen’s University Belfast in the UK. They used the Hubble Space Telescope and the Gemini Telescope to observe the two supernovae.

The progenitor of SN 2003gd, an M-supergiant star in the galaxy M74, “is no longer observed at the SN location,” they found. They estimated 2003gd is seven times the mass of the sun, which they acknowledge “is at the lower end of the mass range considered theoretically possible to produce core-collapse events.” They said there’s enough uncertainty in the object’s mass that it could be greater than seven solar masses — but even if it’s not, several other stars in the low end of the range are suspected of exploding as supernovae.

The co-authors are also careful to point out that dust from the supernova is still visible, and, “One could argue that the star identified as the progenitor was a neighboring star that is now obscured by dust formation.” But their work indicates that the explosion wasn’t dusty enough to obscure a star as luminous as SN 2003gd’s parent. They believe the progenitor star has truly disappeared — although further confirmation will come as the dust continues to clear.

SN 1993J is a truly exceptional case. The K-supergiant star that exploded in that supernova is also no longer present, the authors report — but its B-supergiant binary companion is still observed.

The model for the binary system was of a progenitor star 15 times the mass of the sun, with a slightly less massive binary companion. The progenitor star evolved faster, and transferred some of its mass onto the binary companion, including a substantial amount of its hydrogen envelope. The binary companion grew to 22 times the mass of the sun. The interaction happened over about 250 years and affected the supernova explosion to such an extent that SN 1993J became known as one of the most peculiar supernovae ever seen.

The site of SN 1993J was imaged several times over the 2 to 13 years after the explosion with Hubble and a handful of other telescopes. By the 2004 observation, the red portion of the SN spectral energy distribution had faded below the level of the red spectral energy of the binary progenitor system, “ruling out the continued presence of the K-supergiant star and, hence, confirming it as the progenitor of SN 1993J,” the authors wrote.

They said soon the blue part of the supernova’s spectrum will fade, opening up a window for observations of the remaining companion star.

The authors conclude that their “simple, but time-consuming” method “leaves no doubt that the two stars were the progenitors of the supernovas, SN 2003gd and SN 1993J, and confirms that type II supernovas are birthed from Red Supergiants, as predicted.”

March 19, 2009January 24, 2021 by Tammy Plotner

Vernal Equinox – Busting the Myth of Balancing Eggs

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Spring officially arrives for everyone, including astronomers on March 20. The word “Equinox” literally means “equal night”. It’s all about the balance of light – not the myth of balancing eggs. On the universal date (UTC) of Friday, March 20, 2009 at 11:44 (am) both the day and night are the same length. But what’s so special about it? It’s a date that most of us recognize as symbolic of changing seasons. North of Earth’s equator we welcome Spring, while people south of the equator are gearing up for the cooler temperatures of Autumn. But what’s all this about balancing eggs?

These all too brief, but monumental moments in Earth-time, owe their significance to the slightly more than 23 degree tilt of the Earth’s axis. Because of our planetary angle, we in the northern hemisphere receive the Sun’s rays most directly during the Summer. In the Winter, when we are tilted away from the Sun, the rays pass through the atmosphere at a greater slant, bringing lower temperatures. If the Earth rotated on an axis perpendicular to the plane of the Earth’s orbit around the Sun, there would be no variation in day lengths or temperatures throughout the year, and we would not have seasons. At Equinox, the midway between these two times in Spring and Autumn, the spin axis of the Earth points 90 degrees away from the Sun.

If your head is spinning from all of this, sit and ponder for a moment. Now is a great time to choose a marker and observe what’s happening for yourself. Trying a real science experiment for equinox is much better than the myth of balancing eggs. Just place a stake of some type into the ground (or use a fencepost or signpost) and periodically over the next few weeks measure the length of the shadow when the Sun is at its highest and write down your measurements. I use my south facing deck railing and mark its shadow on the deck boards in chalk. It won’t take long before your marker’s shadow length changes and you notice how the Sun’s position changes in the sky, and with it the ecliptic plane.

In the language of astronomy, an equinox is either of two points on the celestial sphere where the ecliptic and the celestial equator intersect. The Vernal Equinox is also known as “the first point of Aries” – a the point at which the Sun appears to cross the celestial equator from south to north. This is also the the zero point of longitude – the reference plane at which right ascension is defined as 0. Believe it or not, this was defined in 1950 as the northern vernal equinox, but it has moved to the constellation of Pisces now! Why? The equinoxes are not fixed points on the celestial sphere but move westward along the ecliptic, passing through all the constellations of the zodiac in 26,000 years. This is what’s known as the precession of the equinoxes – a motion first noted by Hipparchus roughly in 120 B.C. But what causes it?

The precession is caused the gravitational attraction of both the Moon and Sun on the equatorial bulge of the Earth. Imagine the Earth’s axis patterning itself in a cone as it moves, like a spinning top. As a result, the celestial equator, which lies in the plane of the Earth’s equator, moves on the celestial sphere, while the ecliptic, which lies in the plane of the Earth’s orbit around the Sun, is not affected by this motion. The equinoxes, which lie at the intersections of the celestial equator and the ecliptic, now move on the celestial sphere. Much the same, the celestial poles move in circles on the celestial sphere, so that there is a continual change in the star at or near one of these poles.

After a period of about 26,000 years the equinoxes and poles lie once again at nearly the same points on the celestial sphere. Because the gravitational effects of the Sun and Moon aren’t always the same, there is some wobble in the motion of the Earth’s axis called nutation. This wobble causes the celestial poles to move, not in perfect circles, but in a series of S-shaped curves with a period of 18.6 years that was first explained by Isaac Newton in 1687.

So where did the urban myth of balance eggs on vernal equinox come from? Probably because at one time Easter was celebrated at this time and eggs play a very big role in the whole Esotere, rebirth, and cultural symbolism of this holiday. It may very well have been the good folks in China who orginally began the myth by patiently practicing standing eggs on end during vernal equinox to symbolize the restoration of balance to the world after a season of darkness. If this symbol of fertility could be balanced on such a day of significance, then surely nature was in harmony!

Go ahead and balance eggs for fun… But believe in science.

P.S. The Bad Astronomer Phil Plait has a tutorial video on his website, teaching you how to stand an egg on end, any time of the year. Click here to watch it.

Many thanks to Vasilij Rumyantsev (Crimean Astrophysical Obsevatory) for the excellent solar analemma as it appeared in the July 9, 2002 APOD.