Posted on by Nancy Atkinson

Star Endured Unique Explosion That Didn’t Destroy

Eta Carinae Credit: Gemini Observatory artwork by Lynette Cook

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There’s ‘smoked but didn’t inhale,’ ‘promised but didn’t deliver,’ and now there’s ‘exploded but didn’t destroy.’ Eta Carinae, the galaxy’s biggest, brightest and perhaps most studied star after the sun, appears to be driven by an entirely new type of stellar explosion that is fainter than a typical supernova and does not destroy the star. Astronomer Nathan Smith proposes that Eta Carinae’s historic 1843 explosion was, in fact, an outburst that produced a fast blast wave similar to, but less energetic than, a real supernova. This well-documented event in our own Milky Way Galaxy is probably related to a class of faint stellar explosions in other galaxies recognized in recent years by telescopes searching for extragalactic supernovae.

“There is a class of stellar explosions going off in other galaxies for which we still don’t know the cause, but Eta Carinae is the prototype,” said Smith, a UC Berkeley postdoctoral fellow.

Eta Carinae (η Car) is a massive, hot, variable star visible only from the Southern Hemisphere, and is located about 7,500 light years from Earth in a young region of star birth called the Carina Nebula. In 1843, observers saw Eta Car brighten immensely. Visible now is the resulting cloud of gas and dust, known as the Homunculus nebula, wafting away from the star. A faint shell of debris from an earlier explosion is also visible, probably dating from around 1,000 years ago.

But these shells of gas and dust are moving relatively slowly at 650 kilometers per second (1.5 million miles per hour) compared to the blast shell of a regular supernova.

Presumably blown off by the star’s fierce wind, the shells of gas and dust are moving slowly – at speeds of 650 kilometers per second (1.5 million miles per hour) or less – compared to the blast shell of a supernova. But new observations by Smith show filaments of gas moving five times faster than the debris from the Homonuculus, which would equal speeds of materials accelerated fast blast wave of a supernova explosion.

The fast speeds in this blast wave could roughly double earlier estimates of the energy released in the 1843 eruption of Eta Carinae, an event that Smith argues was not just a gentle surface eruption driven by the stellar wind, but an actual explosion deep in the star that sent debris hurtling into interstellar space. In fact, the fast-moving blast wave is now colliding with the slow-moving cloud from the 1,000-year-old eruption and generating X-rays that have been observed by the orbiting Chandra Observatory.

“These observations force us to modify our interpretation of what happened in the 1843 eruption,” he said. “Rather than a steady wind blowing off the outer layers, it seems to have been an explosion that started deep inside the star and blasted off its outer layers. It takes a new mechanism to cause explosions like this.”

If Smith’s interpretation is correct, supermassive stars like Eta Carinae may blow off large amounts of mass in periodic explosions as they approach the end of their lives before a final, cataclysmic supernova blows the star to smithereens and leaves behind a black hole.

“Looking at other galaxies, astronomers have seen stars like Eta Carinae that get brighter, but not quite as bright as a real supernova,” he said. “We don’t know what they are. It’s an enduring mystery as to what can brighten a star that much without destroying it completely.”

Source: EurekAlert

Posted on by Astronomy Cast

Podcast: The Strong and Weak Nuclear Forces

Nuclear reactor
Nuclear reactor

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After a quick Dragon*Con break, we’re back to our tour through the fundamental forces of the Universe. We’ve covered gravity and electromagnetism, and now we’re moving onto the strong and weak nuclear forces. We didn’t think they’d really need to be separate episodes, so we’re putting them together. And then we’ll cap the whole series with the quest for the theory of everything.

Click here to download the episode.

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

The Strong and Weak Nuclear Forces show notes.

Posted on by Fraser Cain

Large Hadron Collider Worst Case Scenario

The Large Hadron Collider (LHC). Credit: CERN

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I apologize that Universe Today has been a little slow over the last couple of days. That’s because my webserver is completely bogged down with Google searchers worried that the world is going to end thanks to the Large Hadron Collider.

Don’t worry, it’s not. In fact, the twin proton beams fired for the first time today. Since you’re reading this, the Universe wasn’t torn apart.

But let’s just say that the Large Hadron Collider does create a microscopic black hole? What then… are we doomed? Nope. Ethan Seigel over at Starts With a Bang has done the calculations to figure out how massive a black hole would be created, and how much of the Earth it would consume if it fell down into the planet. He also calculates how long it should last before evaporating away. There you go, you can use these calculations to help your panicked friends realize there’s no need to worry about microscopic black holes.

Check out Ethan’s post, I won’t give away his final numbers.

And in a strange twist of irony, Google has changed today’s logo to celebrate the Large Hadron Collider. At least, that’s what I’m seeing here in Canada.

Google's LHC logo
Google's LHC logo

Posted on by Nancy Atkinson

Blinding Gamma Ray Burst Was Directed at Earth

Artists depiction of GRB 080319B Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones

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On March 19, 2008 at 2:13 am EDT, NASA’s Swift satellite detected an explosion from the constellation Bootes, and sent an alert to ground-based telescopes. At the same moment, the Russian KONUS instrument on NASA’s Wind satellite and a robotic wide-field optical camera called “Pi of the Sky” in Chile captured the first visible light from this incredibly bright and powerful gamma ray burst. Within the next 15 seconds, the burst brightened enough to be visible in a dark sky to human eyes. For a few moments, the GRB had a million times the luminosity of the entire Milky Way Galaxy. It briefly crested at a magnitude of 5.3 on the astronomical brightness scale. Incredibly, the dying star was 7.5 billion light-years away. Astronomers say the reason this gamma ray burst was so bright was that it was aimed almost directly at Earth.

Observations of the event, formally named GRB 080319B, are giving astronomers the most detailed portrait of a GRB ever recorded. “You have to have the satellites in orbit and the rapid response telescopes on Earth in order take complete advantage this rare kind of event,” said David Burrows, head of the Swift X-ray telescope team, at today’s press conference detailing the GRB.

Judith Racusin of Penn State University and a team of 92 coauthors report on observations across the spectrum that began 30 minutes before the explosion and followed its afterglow for months. The team concludes the burst’s extraordinary brightness arose from an unusual two component jet that shot material directly toward Earth at 99.99995 percent the speed of light.

Telescopes around the world already were studying the afterglow of another burst when GRB 080319B exploded just 10 degrees away.

Immediately after the blast, Swift’s UltraViolet and Optical Telescope and X-Ray Telescope indicated they were effectively blinded. Racusin initially thought something was wrong. Within minutes, however, as reports from other observers arrived, it was clear this was a special event. A head-on burst directed towards Earth only occurs by chance only about once a decade, so GRB 080319B is a rare catch.

Gamma-ray bursts are the universe’s most luminous explosions. Most occur when massive stars run out of nuclear fuel. As a star’s core collapses, it creates a black hole or neutron star that, through processes not fully understood, drive powerful gas jets outward. These jets punch through the collapsing star. As the jets shoot into space, they strike gas previously shed by the star and heat it. That generates bright afterglows.


The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 of a degree across. This core resided within a slightly less energetic jet about 20 times wider. “A normal signature is different from what we saw in this burst,” said Racusin . “In this object, we see two signatures of jets with two different properties.”

“Perhaps every gamma-ray burst has a narrow jet, but astronomers miss it most of the time,” says team member Stefano Covino. “We happened to view this monster down the barrel of the very narrow and energetic jet.”

These unique beacons of light were observed only 8 minutes after the trigger, and are the brightest bursts ever detected. Additional study of this event can also help provide more information on relativity and cosmology.

Burrows said if a similar event happened at our own galaxy, we would be in considerable trouble. “It’s been postulated that a nearby gamma ray burst directed at earth could affect our atmosphere, causing something like a nuclear winter. We are fortunate in that we don’t believe there are any stars in our galas that will produce a gamma ray burst.”

NASA, NASA News Audio

Posted on by Tammy Plotner

The Dragon Slayer – NGC 5985, NGC 5982, NGC 5981 by Ken Crawford

Draco Trio - By Ken Crawford

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There are wonderful tales which surround the circumpolar Draco constellation. According to Greek legend, Draco represents the dragon killed by Cadmus before founding the city of Thebes – or perhaps it represented the dragon which guarded the golden fleece and was eventually killed by Jason and his famous Argonauts. To the Romans, it was simply a creature killed by Minerva and tossed into the sky as stars to be remembered. The Egyptians called it Tawaret. But the most famous of all representations of Draco was one of the twelve labors that Hercules had to overcome. Many of us will never see the jewels that hide within the boundaries of this sprawling constellation, but thanks to the Herculean efforts of Ken Crawford – we can share in its mysteries…

To deep sky observers, the group of NGC 5985, NGC 5982 and NGC 5981 is commonly known as the “Draco Trio”. Two barred spirals at different angles and a face on elliptical all in the same field of view is a rare sight and makes for a beautiful celestial portrait. The beautiful spiral is NGC 5985. The proper designation for the elliptical galaxy is NGC 5982. The catalog number for the edge-on is NGC 5981. While these galaxies span huge amounts of light years apart, they share telescopic space at RA: 15h 38m 40s Dec: +59°21’22” as a center and share photons in the eyepiece at around 25 arc minutes. While the Draco group is far too small to be considered its own galaxy cluster and has never been classified as a compact group, oddly enough all three are around 100 million light years away from the Sol System.

I did mention there were mysteries here, didn’t I? Then let’s explore them…

Take a closer look at the grand spiral, NGC 5985. It’s a Seyfert. According to research done by Simões Lopes (et al) it may also harbor a wonderful black hole right in there with its active galactic nucleus. “This result demonstrates a strong correlation between the presence of circumnuclear dust and accretion onto the central, supermassive black hole in elliptical and lenticular galaxies. Current estimates suggest the dust settling or destruction time is on order of 108 yr, and therefore the presence of dust in ~50% of early-type galaxies requires frequent replenishment and similarly frequent fueling of their central supermassive black holes. The observed dust could be internally produced (via stellar winds) or externally accreted, although there are observational challenges for both of these scenarios. Our analysis also reveals that approximately one-third of the early-type galaxies without circumnuclear dust have nuclear stellar disks. These nuclear stellar disks may provide a preferred kinematic axis to externally accreted material, and this material may in turn form new stars in these disks. The observed incidence of nuclear stellar disks and circumnuclear dust suggests that episodic replenishment of nuclear stellar disks occurs and is approximately concurrent with the fueling of the central AGN.”

But that’s not all, because there’s a quasar there, too. According to a 2001 study done by one of my heroes – Halton Arp and David Russell; “The distribution on the sky of clusters of galaxies shows significant association with relatively nearby, large, active galaxies. The pattern is that of clusters paired equidistant across a central galaxy with the apparent magnitudes and redshifts of their constituent galaxies being closely matched. The clusters and the galaxies in them tend to be strong X-ray and radio emitters, and their redshifts occur at preferred redshift values. The central, low-redshift galaxies often show evidence of ejection in the direction of these higher redshift clusters. In all these respects the clusters resemble closely quasars which have been increasingly shown for the last 34 years to be similarly associated with active parent galaxies. New, especially significant pairings of quasars are presented here, which are, at the same time, associated with Abell clusters of galaxies. It is argued here that, empirically, the quasars are ejected from active galaxies. They evolve to lower redshift with time, forming stars, and fragmenting at the end of their development into clusters of low-luminosity galaxies. The cluster galaxies can be at the same distance as their lower redshift parents because they still retain a component of their earlier, quasar intrinsic redshift.”

Now, let’s take a look at the quiet little elliptical – NGC 5982. Just this year it was studied by Del Burgo (et al) for its dust shell. According to the report: “Shells in Ellipticals are peculiar faint sharp edged features that are thought to be formed by galaxy mergers. We use Spitzer data in the wavelength range from 3.6 to 160 μm and HST/ACS optical data. After subtracting the galaxy models, residual images are used to identify the shells. We detect for the first time shells from mid-infrared data. The very different distributions of dust, warm gas and HI gas together with the presence of shells and a kinematically decoupled core suggest a minor merger in NGC 5982.”

Ah, ha! So, it’s always the quiet ones that get ya’, huh? Then it might interest you to know that NGC 5982 may also contain its own black hole, a peculiar population of stars, a low luminosity active galactic nucleus and may have even been a product of a black hole merger! What more, new globular clusters may have formed during these interactions without the benefits of gaseous materials. Simply too cool…

Now… How about the wild looking edge-on, NGC 5981? Science loves to examine what it just can’t quite see and in the case of this highly inclined spiral, we’ve found out that the stellar disc just might be cut off – or foreshortened. According to a 2007 work done by Florido (et al); “This is the first work reporting observations of the truncation of a stellar disc, in both the optical and the NIR spectral ranges. No galaxy has been observed at both wavelengths with the required depth. The optical radial profiles of spiral galaxy discs seem to suggest a double exponential behaviour, whilst NIR profiles seem to show a real truncation. NGC 6504 has a real truncation in both the optical and the NIR radial profiles. A double exponential does not fit the observed optical profile. The truncation radius is larger in the V band than in the NIR by ~10 arcsec, about 3 kpc (equivalent to about 10%).”

But, just because its equipment is a little shorter than most, does that mean it doesn’t produce as many stars? Not hardly. It just means its peanut-shaped central bulge may be embedded in a dark halo. Thanks to the work of Joop Schaye who also took a look at NGC 5981, we know a little more about these properties. “We study global star formation thresholds in the outer parts of galaxies by investigating the stability of disk galaxies embedded in dark halos. The disks are self-gravitating, contain metals and dust, and are exposed to UV radiation. We find that the critical surface density for the existence of a cold interstellar phase depends only weakly on the parameters of the model and coincides with the empirically derived surface density threshold for star formation. Furthermore, it is shown that the drop in the thermal velocity dispersion associated with the transition from the warm to the cold gas phase triggers gravitational instability on a wide range of scales. The presence of strong turbulence does not undermine this conclusion if the disk is self-gravitating. Models based on the hypothesis that the onset of thermal instability determines the star formation threshold in the outer parts of galaxies can reproduce many observations, including the threshold radii, the column densities, and the sizes of stellar disks as a function of disk scale length and mass.”

While we’ll never see the Draco Trio in the telescope eyepiece as well as what this incredible image by Ken Crawford presents, we welcome the Dragon Slayer for the opportunity it gives us to take a closer look at another cosmic mystery. Is the Draco Group really a galaxy group? Perhaps. According to independent research papers done by both Giuricin and Garcia, this small group of friends collectively known as the NGC 5866 Group (because it’s the brightest) is located to the northwest of both the M101 Group and its companion galaxies which makes it proximity. Also nearby is the M51 Group, home to the Whirlpool Galaxy, the Sunflower Galaxy, and several others. The distances to these three groups was gathered by studying their individual members and science has found they are similar – and perhaps part of a much larger, more loose association than we’ve yet discovered.

But we’re learning…

Many thanks to AORAIA member Ken Crawford for the use of the spectacular image and the awesome research challenge it posed! My gratitude for the inspiration and the learning challenge…

Posted on by Nancy Atkinson

Oops, TW Hydrae b Isn’t a Planet; Just a Sunspot

Artists depiction of what the TW Hydrae system might have looked like. Credit: Max Planck Institute

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You gotta love this about science; someone is always checking your work. Early this year a new exoplanet discovery was announced: TW Hydrae b, a huge planet about ten times as massive as Jupiter. Astronomers thought the planet was in a super-tight orbit around its host star (TW Hydrae), circling in only 3.56 days at a distance of about 6 million kilometers, which is about 4 percent of the distance from the Sun to the Earth. However, another group of astronomers decided to analyze some new optical and infrared data to confirm the radial velocity signal of the planet. Something didn’t seem right, so they ran a few more tests and computer models and determined what they were seeing wasn’t a planet. It was a big sunspot. “Our model shows that a cold spot covering 7% of the stellar surface and located at a latitude of 54 deg can reproduce the reported RV variations,” the astronomers reported in their paper. The rest of the astronomical world must agree with the new determination, as TW Hydrae b has now been dropped from the Planet Quest New Worlds Atlas (a fun site to peruse.) But nature doesn’t like a void, — and astronomers have been working hard in the planet-search department, — so, three new extra solar planets have been discovered and added to the atlas, for a current planet count of 309.

GJ 832 b is about half the size mass of Jupiter and orbits 3.4 AU from its tiny host star. The star is a yellow, sun-like G star, about 16 light years from Earth. It was found with the Anglo-Australian Telescope. Astronomers say it has the largest angular distance from its star among radial velocity detected exoplanets, which makes it a potentially interesting target for future direct detection.

HD 205739 b was also just announced:. This exoplanet is 1.37 times the size mass of Jupiter, and orbits about .9 AU from its star, a blue to white star, which is 1.22x the size of the sun, and 294 light years from Earth. It has an eccentric orbit, and astronomers believe there may be an additional planet in this system, because of how the planet orbits.

Another planet found by the same astronomical team is HD 154672 b. This is a biggie, at about five times the size mass of Jupiter, but only about .6 AU distant from its star, which is just about sun-size, and about 213 light years from Earth. The planet has an orbital period of 163.9 days.

These last two planets were found using the N2K Doppler planet search program with the Magellan telescopes.

Sources: arXiv (here, here and here) and Twitter, PlanetQuest

Posted on by Nancy Atkinson

China To Launch Manned Mission This Month

China's Long March rocket. Credit: Xinhua

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China will launch its third manned space mission in late September, sending three astronauts into Earth orbit. The mission will feature China’s first-ever space walk, according to the Xinhua News Agency, the official news agency of China. The Shenzhou 7 launch will take place sometime between Sept. 25 and 30, from the Jiuquan Satellite Launch Center in northwestern Gansu province. The space walk will be broadcast live using cameras mounted on the inside and outside of the spacecraft.

The Long March rocket was loaded with fuel on Sunday. “All the major systems involved in the launching are now in the final preparation. The main tests for the spacecraft, the Long-March II-F rocket, suits for the space walk and a satellite accompanying the fly have also been finished,” said the spokesman.

On April 12, China launched a new space tracking satellite to assist with the Shenzhou-7 spacewalk mission. The new space tracking ship is the sister ship of the Yuanwang-5, which was put into use a year ago. Xinhua said the two vessels will play a key role in the Shenzhou-7 mission.

In 2003, China became the third country in the world — along with the United States and Russia — to send a human into orbit. It followed with a two-man mission in 2005.

China also launched the Chang’e 1 moon orbiter in October of 2007.

Source: Xinhua

Posted on by Tammy Plotner

UT Reader Promotes IYA in “Canoe Africa”

Canoe Africa Team

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If you haven’t heard of UT reader, Brian Sheen, you will over the next few months. Brian is not only a reader here, but he’s also a member of the Roseland Observatory in Cornwall and he’s about to embark on an adventure that most of us only dream about. Four men, one canoe, one river, 2,500 miles, in six months…

Brian Sheen
Brian Sheen
Canoe Africa is a unique project ready to launch by the UK astronomer just as soon as the proverbial waters reach safe levels. Brian and a small team of scout leaders will begin their journey on foot in the mountains of Guinea, at the source of one of the longest rivers in the world – the Niger. Then it’s into a dugout canoe to travel almost 2,500 miles passing through the countries of Guinea, Mali, Niger, Benin and Nigeria, with their epic journey stopping about 100 miles away from wilds of the Niger Delta. Along the way they will meet with local scout troops for support and company in their journey, but there’s much more to the story than just a deliverance.

Brian is no stranger to long distance canoeing, nor is this his first time in West Africa. Forty years ago he was there providing relief with the Red Cross during the Niger Crisis, and returned again in 1981 to canoe 150 miles through the Delta from Onitsha to Port Harcourt. While the team will be promoting the UK Scouting Movement, astronomer Sheen also sees this as a unique opportunity to promote the International Year of Astronomy. “The vision of the International Year of Astronomy (IYA2009) is to help the citizens of the world rediscover their place in the Universe through the day- and night time sky, and thereby engage a personal sense of wonder and discovery. All humans should realize the impact of astronomy and basic sciences on our daily lives, and understand better how scientific knowledge can contribute to a more equitable and peaceful society.”

How does Universe Today tie into this? Thanks to being a constant reader, Brian discovered the Celestron Sky Scout and the Coronado PST. When he wrote me telling me what he was going to do and asking for help locating a French version of the Celestron SkyScout, not only did I find him the correct update, but I found more support for his project as well. Thanks to Michelle Meskill from Celestron International, Celestron Life: IYA has donated speakers for the journey as well! Now, not only will the Celestron SkyScout speak in French when needed – but is now able to reach large groups of people at once!

Map Provided by BBC
Map Provided by BBC

Brian will soon be on his way down the River Niger with binoculars, solar scope, Celestron SkyScout and more. We wish him the best of luck on his IYA Journey and look forward to bringing you further updates on our fearless UT reader and his African Astronomy Adventures during the coming months. Brille sur…

Posted on by Nancy Atkinson

Clumps Growing on Phoenix Lander Legs

Clumps of material have adhered to the legs of the Phoenix Mars Lander, and the clumps continue to change and grow. The science team has discussed various possible explanations for these clumps. One suggestion is that they may have started from a splash of mud if Phoenix’s descent engines melted icy soil during the landing. Another is that specks of salt may have landed on the strut and began attracting atmospheric moisture that freezes and accumulates. The clumps are concentrated on the north side of the strut, usually in the shade, so their accumulation could be a consequence of the fact that condensation favors colder surfaces. Below, compare images taken on September 1, 2008, or the 97th Martian Day or sol, since landing with another image taken about three months earlier, on Sol 8.

Sol 97 image under the lander. Credit: NASA/JPL/Caltech/U of AZ

Sol 8 image from under the lander. Credit: NASA/JPL/Caltech/U of AZ

Phoenix’s Robotic Arm Camera took both images. The top image from Sol 97 was taken at about 4 a.m. local solar time. The view in this Sol 97 image is southward. Illumination is from the early morning sun above the northeastern horizon. This is quite different from the illumination in the Sol 8 image, bottom which was taken in mid-afternoon.

The two images also show a contrast in the flat, smooth patch of exposed ice underneath the lander. Phoenix team members believe the ice was exposed from the spacecraft’s thrusters as it landed. In the latest image, the patches of ice exposed underneath the lander seem to be partly covered by darker material left behind as ice vaporizes away. The flat patch in the center of the image has the informal name “Holy Cow,” based on researchers’ reaction when they saw the initial image of it.

Source: Phoenix Gallery

Posted on by Nancy Atkinson

‘Laser Comb’ To Measure the Accelerating Universe

Back in April, UT published an article about using a device called a ‘laser comb’ to search for Earth-like planets. But astronomers also hope to use the device to search for dark energy in an ambitious project that would measure the velocities of distant galaxies and quasars over a 20-year period. This would let astronomers test Einstein’s theory of general relativity and the nature of the mysterious dark energy. The device uses femto-second (one millionth of one billionth of a second) pulses of laser light coupled with an atomic clock to provide a precise standard for measuring wavelengths of light. Also known as an “astro-comb,” these devices should give astronomers the ability to use the Doppler shift method with incredible precision to measure spectral lines of starlight up to 60 times greater than any current high-tech method. Astronomers have been testing the device, and hope to use one in conjunction with the new Extremely Large Telescope which is being designed by ESO, the European Southern Observatory.

Astronomers use instruments called spectrographs to spread the light from celestial objects into its component colors, or frequencies, in the same way water droplets create a rainbow from sunlight. They can then measure the velocities of stars, galaxies and quasars, search for planets around other stars, or study the expansion of the Universe. A spectrograph must be accurately calibrated so that the frequencies of light can be correctly measured. This is similar to how we need accurate rulers to measure lengths correctly. In the present case, a laser provides a sort of ruler, for measuring colors rather than distances, with an extremely accurate and fine grid.

New, extremely precise spectrographs will be needed in experiments planned for the future Extremely Large Telescope.

“We’ll need something beyond what current technology can offer, and that’s where the laser frequency comb comes in. It is worth recalling that the kind of precision required, 1 cm/s, corresponds, on the focal plane of a typical high-resolution spectrograph, to a shift of a few tenths of a nanometre, that is, the size of some molecules,” explains PhD student and team member Constanza Araujo-Hauck from ESO.

The new calibration technique comes from the combination of astronomy and quantum optics, in a collaboration between researchers at ESO and the Max Planck Institute for Quantum Optics. It uses ultra-short pulses of laser light to create a ‘frequency comb’ – light at many frequencies separated by a constant interval – to create just the kind of precise ‘ruler’ needed to calibrate a spectrograph.

The device has been tested on a solar telescope, a new version of the system is now being built for the HARPS planet-finder instrument on ESO’s 3.6-metre telescope at La Silla in Chile, before being considered for future generations of instruments.

More information on laser combs.

Source: ESO