Posted on by Tammy Plotner

Perseid Radio Astronomy from the Fourth Plinth With Chris Lintott

Perseid Radio Fireball by Andy Smith

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Within hours, the peak of the annual Perseid meteor shower will begin. If you’re worried you’ll be clouded out, then let’s take a look at a different way that you can observe the activity… without your eyes!

Did you know that you can “listen” to meteor showers? If you’re a ham radio operator, then you prize the ionized trails that meteors leave in our atmosphere to allow further signals to “bounce” to more distant receivers. However, you don’t really need complicated equipment to listen to a meteor shower – just an FM receiver and an external antenna. Even your car radio will work!

Place your radio setting on the lowest frequency that doesn’t receive a clear signal and simply listen to the static. When a meteor passes overhead you’ll hear snatches of radio signals from distant stations, pops, buzzes, pings, shrieks, howls, and simple changes in the white noise. Sometimes it’s subtle – and sometimes it’s striking. One thing is for sure, the noises you hear are definitely out of this world! Your equipment can run the gambit from connecting a genuine outdoor FM antenna to an indoor receiver and recording with a tape deck for later playback, to a portable radio. I’ve even used an old television set connected to an outdoor television antenna tuned to channel 3. It’s all fun – and the results are amazing. Here are the dates for the 2009 Perseids.

chrislintottTo open the public’s eyes to just how easy radio meteor listening can be, astrophysicist Chris Lintott will be doing a presentation live in Trafalgar Square on August 14th, 19-20h BST. Chris is a co-presenter of the BBC’s “The Sky at Night” astronomy programme, and is a lecturer at University College London and the project he’s about to take part in is very unique… The Fourth Plinth.

This summer, sculptor Antony Gormley has invited the world to help create an astonishing living monument. He is asking the people of the UK to occupy the empty Fourth Plinth in Trafalgar Square in London, a space normally reserved for statues of Kings and Generals. They will become an image of themselves, and a representation of the whole of humanity. Every hour, 24 hours a day, for 100 days without a break, a different person will make the Plinth their own.

Because of the appalling levels of light pollution in London, Lintott remembered a radio-meteor demonstration given by Andy Smith of G7IZU Radio Reflection Detection and his friend David Entwistle for “The Sky at Night” a couple of years ago, and wanted to do something along those lines. Since no power or wiring are allowed on the Plinth, Chris will be utilizing a recording done by Andy beginning tonight… a talent he’s quite good at! For every hour from midnight on, G7IZU Radio Reflection Detection will be recording the Perseid event and sending Chris the most active hours as MP3 files. He’ll then play these
to the masses over an amplified speaker while holding up photos of how it all works.

If you’re interested in the live radio-meteor/astronomy demonstration, you can access a live video of the Fourth Plinth – and be sure to join them on August 14th, 19-20h BST for Chris Lintott’s presentation!

Posted on by John Carl Villanueva

Fate of the Universe

Images of three galaxies from the Galaxy Zoo (top) and STAGES surveys (bottom) show examples of how the newly discovered population of red spiral galaxies on the outskirts of crowded regions in the Universe may be a missing link in our understanding of galaxy evolution.

[/caption]What is the ultimate fate of our universe? A Big Crunch? A Big Freeze? A Big Rip? or a Big Bounce? Measurements made by WMAP or the Wilkinson Microwave Anisotropy Probe favor a Big Freeze. But until a deeper understanding of dark energy is established, the other three still cannot be totally ignored.

Ever since scientists proved the Big Bang to be the most plausible cosmological theory, and since it only focused more on how it might have all began, their attention started to shift to how the Universe would end. Thus, all 4 theories mentioned above (Big Crunch, Big Freeze, etc.) are actually offshoots of the Big Bang.

The Big Crunch predicts that, after having expanded to its maximum size, the Universe will finally collapse into itself to form the greatest black hole ever.

On the opposite side of the coin, the Big Freeze foretells of a universe that will continue to stretch forever, distributing heat evenly in the process until none is left to be usable enough. Hence, it is also known as the Heat Death.

A more dramatic version of the Big Freeze is the Big Rip. In this scenario, the Universe’s rate of expansion will increase substantially so that everything in it, down to the smallest atom, will be ripped apart.

In a cyclic or oscillatory model of the Universe, there will be no end … for matter and energy, that is. But for us and the Universe that we know of, there will definitely be a conclusion. In an oscillatory model, the Big Bang and Big Crunch form a pair known as the Big Bounce. Essentially, such a universe would simply expand and contract (or bounce) forever.

For astronomers to determine what the ultimate fate of the Universe should be, they would need to know certain information. Its density is supposedly one of the most telling.

You see, if its density is found to be less than the critical density, then only a Big Freeze or a Big Rip would be possible. On the other hand, if it is greater than the said critical value, then a Big Crunch or Big Bounce would most likely ensue.

The most accurate measurements on the cosmic microwave background radiation (CMBR), which is also the most persuasive evidence of the Big Bang, shows a universe having a density virtually equal to the critical density. The measurements also exhibit the characteristics of a flat universe. Right now, it looks like all gathered data indicate that a Big Crunch or a Big Bounce is highly unlikely to occur.

To render finality to these findings however, scientists will need to know the exact behavior of dark energy. Is its strength increasing? Is it diminishing? Is it constant? Only by answering these will they know the ultimate fate of the Universe.

We’ve got a few articles that touch on the fate the universe here in Universe Today. Here are two of them:

NASA also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Sources: NASA, Hubblesite

Posted on by Nancy Atkinson

Spitzer Finds Evidence of Violent Planetary Collision

Artists impression of the planetary smash-up. Image credit: NASA/JPL-Caltech


One of the main theories of how our Moon formed involves a violent cosmic collision between two planets. Astronomers have only been able to hypothesize what this collision was like, but now they have a better idea of what would ensue after such an event. With its infrared eyes the Spitzer Space Telescope has found the aftermath a collision between two planets, and what it shows is brutal. “This collision had to be huge and incredibly high-speed for rock to have been vaporized and melted,” said Carey M. Lisse of the Johns Hopkins University Applied Physics Laboratory, “This is a really rare and short-lived event, critical in the formation of Earth-like planets and moons. We’re lucky to have witnessed one not long after it happened.”

Watch the animation/recreation of the event in the video above.

LIsse and his team say that two rocky bodies, one as least as big as our moon and the other at least as big as Mercury, slammed into each other within the last few thousand years or so — not long ago by cosmic standards. The impact destroyed the smaller body, vaporizing huge amounts of rock and flinging massive plumes of hot lava into space.

Spitzer’s infrared detectors were able to pick up the signatures of the vaporized rock and amorphous silica — essentially melted glass — along with pieces of refrozen lava, called tektites.
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Spitzer observed a star called HD 172555, which is about 12 million years old and located about 100 light-years away in the far southern constellation Pavo, or the Peacock (for comparison, our solar system is 4.5 billion years old).

The astronomers used an instrument on Spitzer, called a spectrograph, to break apart the star’s light and look for fingerprints of chemicals, in what is called a spectrum. What they found was very strange. “I had never seen anything like this before,” said Lisse. “The spectrum was very unusual.”

What they were seeing was the amorphous silica. Silica can be found on Earth in obsidian rocks and tektites. Obsidian is black, shiny volcanic glass. Tektites are hardened chunks of lava that are thought to form when meteorites hit Earth.

Large quantities of orbiting silicon monoxide gas were also detected, created when much of the rock was vaporized. In addition, the astronomers found rocky rubble that was probably flung out from the planetary wreck.

The mass of the dust and gas observed suggests the combined mass of the two charging bodies was more than twice that of our moon.

Their speed must have been tremendous as well — the two bodies would have to have been traveling at a velocity relative to each other of at least 10 kilometers per second (about 22,400 miles per hour) before the collision.

“The collision that formed our moon would have been tremendous, enough to melt the surface of Earth,” said co-author Geoff Bryden of NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Debris from the collision most likely settled into a disk around Earth that eventually coalesced to make the moon. This is about the same scale of impact we’re seeing with Spitzer — we don’t know if a moon will form or not, but we know a large rocky body’s surface was red hot, warped and melted.”

We know that collisions such as this must happen frequently. Giant impacts are thought to have stripped Mercury of its outer crust, tipped Uranus on its side and spun Venus backward, to name a few examples. Such violence is a routine aspect of planet building. Rocky planets form and grow in size by colliding and sticking together, merging their cores and shedding some of their surfaces. Though things have settled down in our solar system today, impacts still occur, as was observed last month after a small space object crashed into Jupiter.

“Almost all large impacts are like stately, slow-moving Titanic-versus-the-iceberg collisions, whereas this one must have been a huge fiery blast, over in the blink of an eye and full of fury,” said Lisse.

The team’s paper will appear in the Aug. 20 issue of the Astrophysical Journal.

Source: NASA

Posted on by Anne Minard

Sun, Earth Are Unlikely Pair to Support Life

The violent youth of solar proxies. Courtesy of IAU.

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We don’t know how lucky we are — really.

We know the interaction between Earth and Sun is a rarity in that it allowed life to form. But scientists working to understand the possibility that it could have happened elsewhere in the Universe are still far from drawing conclusions.

What is becoming clearer is that life probably shouldn’t have formed here; the Earth and Sun are unlikely hosts.
A series of presentations at this year’s meeting of the International Astronomical Union meeting, in Brazil last week, focused on the role of the Sun and Sun-like stars in the formation of life on planets like Earth.

Edward Guinan, a professor of astronomy and astrophysics at Villanova University in Pennsylvania, and his collaegues have been studying Sun-like stars as windows into the origin of life on Earth, and as indicators of how likely life is elsewhere in the cosmos. The work has revealed that the Sun rotated more than ten times faster in its youth (over four billion years ago) than today. The faster a star rotates, the harder the magnetic dynamo at its core works, generating a stronger magnetic field, so the young Sun emitted X-rays and ultraviolet radiation up to several hundred times stronger than it does today.

A team led by Jean-Mathias Grießmeier from ASTRON in the Netherlands looked at another type of magnetic fields — that around planets. They found that the presence of planetary magnetic fields plays a major role in determining the potential for life on other planets as they can protect against the effects of both stellar particle onslaughts.

“Planetary magnetic fields are important for two reasons: they protect the planet against the incoming charged particles, thus preventing the planetary atmosphere from being blown away, and also act as a shield against high energy cosmic rays,” Grießmeier said. “The lack of an intrinsic magnetic field may be the reason why today Mars does not have an atmosphere.”

All things considered, the Sun does not seem like the perfect star for a system where life might arise, added Guinan.

“Although it is hard to argue with the Sun’s ‘success’ as it so far is the only star known to host a planet with life, our studies indicate that the ideal stars to support planets suitable for life for tens of billions of years may be a smaller slower burning ‘orange dwarf’ with a longer lifetime than the Sun — about 20-40 billion years,” he said.

Such stars, also called K stars, “are stable stars with a habitable zone that remains in the same place for tens of billions of years,” he added. “They are 10 times more numerous than the Sun, and may provide the best potential habitat for life in the long run.”

Not are planets like Earth the best places to harbor life, he said. Planets double or triple the size of Earth would do a better job of hanging onto an atmosphere and maintaining a magnetic field: “Furthermore, a larger planet cools more slowly and maintains its magnetic protection.”

Manfred Cuntz, an associate professor of physics at the University of Texas at Arlington, and his collaborators have examined both the damaging and the favorable effects of ultraviolet radiation from stars on DNA molecules. This allows them to study the effect on other potential carbon-based extraterrestrial life forms in the habitable zones around other stars. Cuntz says: “The most significant damage associated with ultraviolet light occurs from UV-C, which is produced in enormous quantities in the photosphere of hotter F-type stars and further out, in the chromospheres, of cooler orange K-type and red M-type stars. Our Sun is an intermediate, yellow G-type star. The ultraviolet and cosmic ray environment around a star may very well have ‘chosen’ what type of life could arise around it.”

Rocco Mancinelli, an astrobiologist with the Search for Extraterrestrial Life (SETI) Institute in California, observes that as life arose on Earth at least 3.5 billion years ago, it must have withstood a barrage of intense solar ultraviolet radiation for a billion years before the oxygen released by these life forms formed the protective ozone layer. Mancinelli studies DNA to delve into some of the ultraviolet protection strategies that evolved in early life forms and still persist in a recognizable form today. As any life in other planetary systems must also contend with radiation from their host stars, these methods for repairing and protecting organisms from ultraviolet damage serve as models for life beyond Earth. Mancinelli says “We also see ultraviolet radiation as a kind of selection mechanism. All three domains of life that exist today have common ultraviolet protection strategies such as a DNA repair mechanism and sheltering in water or in rocks. Those that did not were likely wiped out early on.”

The scientists agree that we do yet know how ubiquitous or how fragile life is, but as Guinan concludes: “The Earth’s period of habitability is nearly over — on a cosmological timescale. In a half to one billion years the Sun will start to be too luminous and warm for water to exist in liquid form on Earth, leading to a runaway greenhouse effect in less than 2 billion years.”

Why is the Sun yellow?

Source: International Astronomical Union (IAU). A link to the meeting is here.

Posted on by Anne Minard

Early Black Holes Are Starving, Not Feasting

Credit: KIPAC/SLAC/M. Alvarez, T. Abel and J. Wise

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A new black hole may not voraciously devour nearby gas — because it may kick out most of the gas in its neighborhood, a new study shows.

Marcelo Alvarez, of Stanford University, and his colleagues performed a new supercomputer simulation designed to track the fate of the universe’s first black holes. They found that, counter to expectations, young black holes couldn’t efficiently gorge themselves on nearby gas.

“The first stars were much more massive than most stars we see today, upwards of 100 times the mass of our sun,” said John Wise, a post-doctoral fellow at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and one of the study’s authors. “For the first time, we were able to simulate in detail what happens to the gas around those stars before and after they form black holes.”

The intense radiation and strong outflows from these massive stars caused nearby gas to dissipate. “These stars essentially cleared out most of the gas in their vicinity,” Wise said. A fraction of these first stars didn’t end their lives in grand supernovae explosions. Instead, they collapsed directly into black holes.

But the black holes were born into a gas-depleted cavity and, with little gas to feed on, they grew very slowly. “During the 200 million years of our simulation, a 100 solar-mass black hole grew by less than one percent of its mass,” Alvarez said.

Movie, credit KIPAC/SLAC/M. Alvarez, T. Abel and J. Wise
Movie, credit KIPAC/SLAC/M. Alvarez, T. Abel and J. Wise

Starting with data taken from observations of the cosmic background radiation — a flash of light that occurred 380,000 years after the big bang that presents the earliest view of cosmic structure — the researchers applied the basic laws that govern the interaction of matter and allowed their model of the early universe to evolve. The complex simulation included hydrodynamics, chemical reactions, the absorption and emission of radiation, and star formation.

In the simulation, cosmic gas slowly coalesced under the force of gravity and eventually formed the first stars. These massive, hot stars burned bright for a short time, emitting so much energy in the form of starlight that they pushed away nearby gas clouds.

These stars could not sustain such a fiery existence for long, and they soon exhausted their internal fuel. One of the stars in the simulation collapsed under its own weight to form a black hole. With only wisps of gas nearby, the black hole was essentially “starved” of matter on which to grow.

Yet, despite its strict diet, the black hole had a dramatic effect on its surroundings. This was revealed through a key aspect of the simulation called radiative feedback, which accounted for the way X-rays emitted by the black hole affected distant gas.

Even on a diet, a black hole produces copious X-rays. This radiation not only kept nearby gas from falling in, but it heated gas a hundred light-years away to several thousand degrees. Hot gas cannot come together to form new stars. “Even though the black holes aren’t growing significantly, their radiation is intense enough to shut off star formation nearby for tens and maybe even hundreds of millions of years,” said Alvarez.

Source: NASA. The study appears in The Astrophysical Journal Letters.

Posted on by Anne Minard

Planet Precursors May be Sized Like Trucks, Not Towns

Credit: NASA/JPL-Caltech/T. Pyle (SSC-Caltech)

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A typical model has planets forming from collisions of material swirling around stars. But new laboratory experiments indicate the colliding bodies may be much smaller than most people have thought.

Lead author Oliver Tschauner, of the University of Nevada in Las Vegas, and his colleagues have synthesized a mineral called wadsleyite that naturally exists only in meteorites and deep below the Earth’s crust. It’s believed to be the most abundant mineral in the Earth between the depths of 410 and 520 km (254 to 323 miles).

The conditions where wadsleyite forms are known from long-duration, high-pressure experiments, but the only confirmed natural occurrence is in shocked meteorites, which are remnants of the early solar system. The researchers found small quantities of wadsleyite after a high-pressure laboratory collision between thin layers of magnesium oxide and fused quartz. They suggest the mineral formed in approximately one one-millionth of a second.

On the basis of their experiments, the group inferred that the wadsleyite in ancient meteorites could be generated by collisions between bodies one to five meters (three to 16 feet) in diameter, rather than one to five kilometers (.6 to three miles).

“Based on the present results we suggest that the interpretation of the high-grade shock-metamorphic record in meteorites needs a re-evaluation,” the authors write.

Source: PNAS

Posted on by Nancy Atkinson

Astro Art of the Week

Earth, Moon and Stars by Aaron Nako

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Here’s the fifth edition of our new feature, showcasing our readers’ prowess with image editing software. This week’s Astro Art of the Week is a conglomeration of several images created by Aaron Nako. “The blue background with vertical lines is actually a distorted and colour-adjusted picture of the Carina nebula,” Aaron wrote, “and the stars in the electricity/waves are from a picture of NGC 6384 taken from the Rancho Del Sol Observatory. The grunge darker blueish bit coming from the top right-hand corner is actually our sun. The stars were Photoshop brushes that I changed a little bit.”

Thanks for sharing your photo-editing wizardry Aaron! If you’ve got a space or astronomy image you’ve created and would like to share it, submit it to Nancy . We’re also still mulling over what to call this new feature — so if you have any suggestions, post your idea in the comments.

Posted on by Nancy Atkinson

Carnival of Space #115

This week’s Carnival of Space is hosted by New Frontier News.

Click here to read the Carnival of Space #115.

And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let Fraser know if you can be a host, and he’ll schedule you into the calendar.

Finally, if you run a space-related blog, please post a link to the Carnival of Space. Help us get the word out.

Posted on by Nancy Atkinson

Have You Ever Seen a Moonbow?

Photo of a Lunar Rainbow taken from the Zambia side of Victoria Falls. The constellation Orion is visible behind the top of the moonbow. Credit: Calvin Bradshaw

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They are elusive, but powerful to see. “Moonbows” are rainbows created by light from the Moon. Conditions have to be just right, and there are only a small number of places in the world where they regularly materialize, such as Victoria Falls on the border between Zambia and Zimbabwe as seen above, Cumberland Falls in Kentucky, Yosemite Falls in California, and Waimea on Hawaii. Because they are so faint, moonbows are difficult to see with the naked eye (they usually appear just white). But with long-exposure photography, all the colors of moonbows can be seen. Below, check out a gorgeous video of stars, a moonbow and rainbow over Torres del Paine in Patagonia, Chile, and more moonbow images at Environmental Graffiti.

Posted on by Abby Cessna

Radius of the Planets

Size of the planets compared.

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One way to measure the size of the planets is by radius. Radius is the measurement from the center of an object to the edge of it.

Mercury is the smallest planet with a radius of only 2,440 km at its equator. Mercury is not that much larger than the Moon, and it is actually smaller than some of our Solar System’s larger satellites, such as Titan. Despite Mercury’s small size, it is actually dense with higher gravity than you would expect for its size.

Venus has a radius of 6,052 kilometers, which is only a few hundred kilometers smaller than Earth’s radius. Most planets have a radius that is different at the equator than it is at the poles because the planets spin so fast that they flatten out at the poles. Venus has the same diameter at the poles and at the equator though because it spins so slowly.

Earth is the largest of the four inner planets with a radius of 6,378 kilometers at the equator. This is over two times larger than the radius of Mercury. The radius between the poles is 21.3 km less than the radius at the equator because the planet has flattened slightly since it only takes 24 hours to rotate.

Mars is a surprisingly small planet with a radius of 3,396 kilometers at the equator and 3,376 kilometers at the poles. This means that Mars’ radius is only about half of Earth’s radius.

Jupiter is the largest of all the planets. It has a radius of 71,492 kilometers at the equator and a radius of 66,854 kilometers at the poles. This is a difference of 4,638 kilometers, which is almost twice Mercury’s radius. Jupiter has a radius at the equator 11.2 times Earth’s equatorial radius.

Saturn has an equatorial radius of 60,268 kilometers and a radius of 54,364 kilometers at the poles making it the second largest planet in our Solar System. The difference between its two radiuses is a little more than twice the radius of Mercury.

Uranus has an equatorial radius of 25,559 kilometers and a radius of 24,973 kilometers at the poles. Although this is much smaller than Jupiter’s radius, it is around four times the size of Earth’s radius.

Neptune’s equatorial radius of 24,764 kilometers makes it the smallest of the four outer planets. The planet has a radius of 24,341 kilometers at the poles. Neptune’s radius is almost four times the size of Earth’s radius, but it is only about a third of Jupiter’s radius.

Universe Today has articles on the radius of Neptune and the size of the planets.

If you are looking for more information, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.

Astronomy Cast has an episode on Venus and more on all the planets.