Computer simulation showing the development and evolution of the disk of a galaxy such as the Milky Way. Credit: Rok Roškar
The Milky Way has been around a long, long time. The age of our galaxy is approximately 13.6 billion years, give or take 800 million years. But how did the galaxy get here? What did baby photos of the Milky Way look like?
First off, there weren’t always stars in the Universe, and the Milky Way hasn’t been around forever. After the big bang happened, and the Universe cooled for a bit, all there was was gas uniformly spread throughout. Small irregularities allowed the gas to coalesce into larger and larger enough clumps, heating up and eventually starting the nuclear fusion that powers stars. The stars started to gravitationally attract each other into larger groups. The oldest of these groups of stars are called globular clusters, and some of these clusters in the Milky Way galaxy date back to the very, very early Universe.
Not all of the stars in the Milky Way date back to the primordial Universe, though. The Milky Way produces more than 7 stars per year, but it acquired much of its mass in another fashion. The Milky Way is often referred to as a “cannibal” galaxy, because during formation it swallowed up smaller galaxies. Astronomers think that this is how many larger galaxies have come to be the size they are today.
In fact, the Milky Way is currently gobbling up another galaxy, (and a stellar cluster) at this very moment. Called the Canis Major Dwarf Galaxy, the remnant stars are 45,000 light years from the galactic center, and a mere 25,000 light years from our Sun.
Older stars in the Milky Way are to be found distributed spherically in the galactic halo, meaning that it’s likely the galaxy had a spherical shape to start out. Younger stars in the galaxy are located in the disk, evidence that as it started to get heavier, the mutual orbit of material started the galaxy spinning, which resulted in the spiral one sees in representations of the Milky Way.
To get you started on how the formation of our galaxy looked, here’s an animated simulation of what a galaxy much like the Milky Way looks like as it goes from the gas cloud at the beginning of the Universe to a beautiful barred spiral, a few billion years condensed into a couple of short minutes. And to get a handle on the formation of a spiral arms in a galaxy, check out this spiral galaxy simulator.
M82. The VLA image (top left) clearly shows the supernova (SN 2008iz). Credit: MPIfR
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Supernovae are extremely luminous explosions of stars and cause bursts of radiation that often outshine an entire galaxy. So, when a supernova exploded last year in a nearby galaxy, why didn’t we see it? Was this an undercover supernova; a top-secret, covert event? Well, kind of. The secret is in the dust.
M82 is an irregular galaxy in a nearby galaxy group located 12 million lightyears from Earth. Despite being smaller than the Milky Way, it harbors a vigorous central starburst in the inner few hundred lightyears. In this stellar factory more stars are presently born than in the entire Milky Way. M82 is often called an ‘exploding galaxy’, because it looks as if being torn apart in optical and infrared images as the result of numerous supernova explosions from massive stars. Many remnants from previous supernovae are seen on radio images of M82 and a new supernova explosion was long overdue. For a quarter of century astronomers kept an eye on M82, hoping to catch a supernova in the act, but with no luck. Astronomers were starting to wonder why the galaxy has been so silent in recent years.
However, a recent explosion actually did occur in M82, and it was the closest supernova in the last five years. But the explosion was shrouded by gas and dust, leaving it invisible to our human eyes, and visible only in radio wavelengths. Astronomers say without the obscuration, this explosion would have been visible even with medium-sized amateur telescopes.
On April 9, 2009, Dr. Andreas Brunthaler from the Max Planck Institute for Radio Astronomy noticed something unusual in the data of M82 taken just the previous day with the Very Large Array (VLA) of the National Radio Astronomy Observatory in New Mexico, USA. “I then looked back into older data we had from March and May last year, and there it was as well, outshining the entire galaxy!” he said. Observations taken before 2008 showed neither pronounced radio nor X-ray emission at the position of this supernova. The Very Large Array. Credit: MPIfR
On the other hand, observations of M82 taken last year with optical telescopes to search for new supernovae showed no signs of this explosion. Furthermore, the supernova is hidden on ultraviolet and X-ray images. The supernova exploded close to the center of the galaxy in a very dense interstellar environment.
Astronomers began to realize they had perhaps found the clue to the mystery about the long silence of M82. Actually, it hasn’t been silent and perhaps many supernova events have occurred, and are something like “underground explosions”, where the bright flash of light is covered under huge clouds of gas and dust and only radio waves can penetrate this dense material. “This cosmic catastrophe shows that using our radio telescopes we have a front-row seat to observe the otherwise hidden universe”, said Prof. Heino Falcke from Radboud University.
Radio emission can be detected only from core collapse supernovae, where the core of a massive star collapses and produces a black hole or a neutron star. It is produced when the shock wave of the explosion propagates into dense material surrounding the star, usually material that was shed from the massive progenitor star before it exploded.
By combining data from the ten telescopes of the Very Long Baseline Array (VLBA), the VLA, the Green Bank Telescope in the USA, and the Effelsberg 100m telescope in Germany, using the technique of Very Long Baseline Interferometry (VLBI), the team was able to produce images that show a ring-like structure expanding at more than 40 million km/h or 4% of the speed of light, typical for supernovae. “By extrapolating this expansion back in time, we can estimate the explosion date. Our current data indicate that the star exploded in late January or early February 2008,” said Brunthaler.
Only three months after the explosion, the ring was already 650 times larger than Earth’s orbit around the Sun. It takes the extremely sharp view of VLBI observations to resolve this structure which is as large as a 1 Euro coin seen from a distance of 13.000 km.
The asymmetric appearance of the supernova on the VLBI images indicates also that either the explosion was highly asymmetric or the surrounding material unevenly distributed. “Using the super sharp vision of VLBI we can follow the supernova expanding into the dense interstellar medium of M82 over the coming years and gain more insight on it and the explosion itself,” said Prof. Karl Menten, director at the MPIfR.
Discoveries like this supernova will be routine with the next generation of radio telescopes, such as the Low Frequency Array (LOFAR) which is currently under construction in Europe, the Allen Telescope Array (ATA) in the USA, or the planned Square Kilometer Array (SKA). These will have the capability to observe large parts of the sky continuously.
Lead image description: Zooming into the center of the galaxy M82, one of the nearest starburst galaxies at a distance of only 12 Million light years. The left image, taken with the Hubble Space Telescope (HST), shows the body of the galaxy in blue and hydrogen gas breaking out from the central starburst in red. The VLA image (top left) clearly shows the supernova (SN 2008iz), taken in May 2008. The high-resolution VLBI images (lower right) shows an expanding shell at the scale of a few light days and proves the transient source as the result of a supernova explosion in M82.
Graphics: Milde Science Communication, HST Image: /NASA, ESA, and The Hubble Heritage Team (STScI/AURA); Radio Images: A. Brunthaler, MPIfR. (Click image for higher resolution).
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I came across a new website, and it has an interesting purpose: the website proposes to create a Space Exploration Day national holiday in the US, and fittingly, suggests July 20 as the date. July 20, of course, is the date that the Apollo 11 mission landed on the Moon, and this year we celebrate the 40th anniversary of that historic mission.
The official website for the Space Exploration Day invites US citizens to sign a petition to create this new holiday, which they suggest could be on the order of Flag Day. Additionally, the website advocates July 16 – 24 be designated as a period of U.S. Space Observance, in commemoration of the nine day Apollo 11 Mission.
From the website:
“Whereas on July 20, 1969, the people of the world were brought closer together by the first manned exploration of the Moon; …”
“Whereas in this same spirit of greatness that made possible, the placing of astronauts on the Moon can be applied to all noble pursuits, including peace, brotherhood, advancement of the human spirit, and the exploration of new frontiers for the benefit of all mankind… ”
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Classify this under news of the weird. A Russian scientist claims that aliens downed the Tunguska meteorite 101 years ago to protect our planet from devastation. Yuri Lavbin says he found unusual quartz crystals at the site of the massive Siberian explosion. Ten crystals have holes in them, placed so the stones can be united in a chain, and other have drawings on them. “We don’t have any technologies that can print such kind of drawings on crystals,” said Lavbin. “We also found ferrum silicate that can not be produced anywhere, except in space.”
OK, just a few holes in this story, too.
Photograph from the Soviet Academy of Science 1927 expedition led by Leonid Kulik
The Tunguska Event was a powerful explosion that occurred in an uninhabited and desolate area near the Tunguska River in Russia, on June 30, 1908. Although the cause of the explosion is the subject of debate, it is commonly believed to have been caused by the explosion of a large meteoroid or comet fragment, occurring the in Earth’s atmosphere about 5–10 kilometers (3–6 miles) high. The blast flattened an estimated 60 million trees over 2,150 square kilometers, but no crater or “smoking gun” meteorite has ever been found. Different studies have yielded varying estimates of the object’s size, but there is general agreement that it was a few tens of meters across.
A couple of expeditions have gone to the remote site of the crash. Lavbin says that one expedition located the unusual crystals.
While I’m not a chemist, I couldn’t find any information on “ferrum silicate.” Seemingly, it doesn’t exist.
This isn’t the first time a UFO has been claimed to associated with the Tunguska event. Another report from 2004 said a scientific expedition to the site found blocks of an extraterrestrial technical device, and one 50-kilogram piece of the stone was brought to the city of Krasnoyarsk to be studied and analyzed. No subsequent reports or analysis could be located during an internet search.
Other claims of exploding alien spaceships or alien weapons detonating to “save the Earth from an imminent threat” appear to originate from a science fiction story “A Visitor From Outer Space” written by Soviet engineer Alexander Kazantsev in 1946, in which a nuclear-powered Martian spaceship, seeking fresh water from a lake blew up in mid-air. This story was was said to be inspired by Kazantsev’s visit to Hiroshima in late 1945.
Many events in Kazantsev’s tale were subsequently confused with the actual occurrences at Tunguska. A “reveal-all” book was published in 1976 (The Fire Came By) but was written by two television drama critics — so much for a scientific background. In 1998 the television series The Secret KGB UFO Files was broadcast on Turner Network Television, and referred to the Tunguska event as “the Russian Roswell” and claimed that crashed UFO debris had been recovered from the site.
However, not one proponent of the Tunguska/UFO hypothesis have ever been able to provide any significant evidence for their claims.
Lavbin says the stones, when put together form a map, and might be part of a navigational system of a spaceship.
But Lavbin says what proves his hypothesis is a strange portrait of a strange person on one of the stones.
I just got an email out of the blue from former CNN anchor Miles O’Brien letting me know about a recent blog post at True/Slant about the recent repair of the Hubble Space Telescope. It’s a great article, go read it and then dig back through the archives. I think the first article is here.
When I first got the email, I was a little puzzled about why it was coming from regular Miles O’Brien, and not CNN anchor O’Brien, so I did a little digging and it turns out CNN started dismantling their science and technology division earlier this year. Yes, I’m completely out of touch with current events, and possibly even reality.
Are they insane? Universe Today has been growing in leaps and bounds, to the point that I’ve got several writers working with me to feed your voracious appetite for space news. And as science progresses at an exponentially faster rate, people will need better and better coverage to comprehend the complicated implications of scientific discovery. I can guarantee that the demand is there, we just need people who can explain it better, and stand up for the science.
Science and technology is doing just fine thank you very much. Feel free to leave the field CNN, I’m happy to fill the void.
Anyway, if you want to catch up with Miles O’Brien, he’s got his blogging gig over at True/Slant and he’s doing a weekly video cast for Boing Boing called This Week in Space.
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Three astronauts set to launch on a Soyuz rocket will bring a new era to the International Space Station by doubling the permanent crew size. Also, for the first time all the ISS partners will be represented on board the station at once as astronauts from NASA, CSA, ESA, JAXA and Russia will be part of the first six-person permanent crew. Liftoff is scheduled for 4:34 p.m. local time (1034 GMT; 0634 EDT) Wednesday from Russia’s Baikonur cosmodrome in Kazakhstan. The Soyuz TMA-15 capsule is expected to dock with the space station about two days later.
On board the Soyuz will be a truly international contingent, with Canadian astronaut Bob Thirsk, Russian cosmonaut Roman Romanenko, and Belgium’s Frank De Winne. They will join the current crew of the orbiting laboratory: Russia’s Gennady Padalka, U.S. astronaut Michael Barratt and Japan’s Koichi Wakata.
Thirsk called the expansion from a three-person to a six-person crew a “milestone” and said one of their goals was “to prove the station can support six people for a long duration.” Bob Thirsk of the Canadian Space Agency, Russian Cosmonaut Roman Romanenko and Flight Engineer Frank De Winne of the European Space Agency. Credit: NASA
“This is the most international crew we’ve ever had” said Courtenay McMillan, Expedition 20 lead flight director. “It opens up a lot more possibilities and lets us schedule more science. We also have a lot more maintenance activities that can be done. Having six people on board does present a bit of challenge in communications with the ground, as we have twice as many people but no more ‘phone lines’, but folks are getting creative. We’ve learned a lot from the handover periods.”
A current crew of three typically has only about 20 hours a week to devote to science, but with six crew members, ISS officials hope to nearly triple the amount of time spent on science experiments. “This is a big transition from where we have been short on time. Now we have time,” said McMillan. “The crew has been very active in working with science community, ground control teams and to take advantage of the time we have.” McMillan added that the crew will have the ability to do not just new science, but doing additional runs on science that is up on board the station now.”
The last few shuttle missions to the ISS and Progress re-supply ships have been bringing up enough supplies to accommodate the increase in crew size. Now that the urine recycling system is working well, food is the biggest consumable the crews have had to stockpile.
“We have good margins on consumables,” said McMillan. ” We’ve piled up more margin than we usually do, to protect against flight slips. NASA said there is enough supplies on board that the crew could have enough to eat though October, even if no shuttles or Russian ships made it to the station. However two shuttle missions and two Soyuz capsules are scheduled to arrive at the station before the end of October.
Blobs of something "growing" on the Phoenix lander's legs.
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Finding perchlorates on Mars was not only surprising for the Phoenix lander science team, it also has created a bit of a rift among the researchers. In March, Ian reported on one scientist who used strictly photographic evidence to say that blobs appearing on the lander’s legs were actually water. Other scientists, however, including principal investigator Peter Smith were dubious about the “water on Mars now” claims. But now, a group of researchers at the University of Arkansas say they have now demonstrated a potential stable liquid on present-day Mars in the immediate environment of the lander.
The salts formed from perchlorates discovered at the Phoenix landing site act as “anti-freeze” and have the potential to be found in a liquid solution under the temperature and pressure conditions on present-day Mars, say professor Vincent F. Chevrier and graduate students Jennifer Hanley and Travis S. Altheide. Their research is published in the current issue of Geophysical Research Letters.
“Under real, observed Martian conditions, you can have a stable liquid,” said Chevrier.
The researchers studied the properties of sodium and magnesium perchlorates, salts detected by the Phoenix lander, under the temperature, pressure and humidity conditions found at the landing site. The discovery of perchlorates on Mars by the Phoenix mission surprised scientists – the compounds are rare on Earth, found mostly in extremely arid environments such as the Atacama Desert in Chile. This image was taken by the Phoenix land on the 97th day of the mission. Credit: NASA/JPL
The scientists studied the properties of these salts at varying temperatures using the Andromeda Chamber in the W.M. Keck Laboratory for Space Simulation – a chamber that can imitate the pressure and atmospheric conditions found on Mars. They also performed thermodynamic calculations to determine the state of salt and water combinations on the Martian surface and to see if there was any potential for liquid to be found.
The extreme temperatures found on Mars typically lead to either crystallization or evaporation of water, making it difficult to imagine that water could be found in liquid form. However, salts have been shown to lower the freezing point of water – which is why street crews use salt on the roads to melt ice, Hanley said. Some salts, like perchlorates, lower the freezing point substantially. It turns out that the temperature for the liquid phase of magnesium perchlorate – 206 degrees Kelvin – is a temperature found on Mars at the Phoenix landing site. Based on temperature findings from the Phoenix lander, conditions would allow this perchlorate solution to be present in liquid form for a few hours each day during the summer.
“The window for liquid is very small,” Hanley said. Nevertheless, this finding further supports the possibility of finding life on Mars.
“You don’t necessarily need to have a lot of water to have life,” Chevrier said. “But you need liquid water at some point.”
EPOXI image of the Moon transiting Earth from 31 million miles. Credit: NASA/JPL
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By looking back at Earth from alien’s point of view, scientists have developed a new technique to look for other worlds that might harbor oceans, and therefore life. Using the old Deep Impact spacecraft, which is now being used for the EPOXI mission, scientists are able to look at the spectrum of an extrasolar planet’s light which would reveal the presence of water. “We used the High Resolution Imager telescope on Deep Impact to look at Earth from tens of millions of miles away,” said Nicolas B. Cowan, of the University of Washington, ” and developed a method to indicate the presence of oceans by analyzing how Earth’s light changes as the planet rotates. This method can be used to identify extrasolar ocean-bearing Earths.”
Last year, the EPOXI science team was able to take videos of the Moon transiting Earth, (see our article from July 2008). The team has now practiced the technique by looking back at Earth, and have determined that they should be able to detect oceans on other worlds by looking at the changing spectrum of light the planet gives off as it rotates.
Cowan is lead author of a paper on this research appearing in the August 2009 issue of the Astrophysical Journal. Our planet looks blue all the time because of Rayleigh scattering of sunlight by the atmosphere, the same reason that the sky appears blue to us down on the surface, points out Cowan. “What we studied in this paper was how that blue color changes in time: oceans are bluer than continents, which appear red or orange because land is most reflective at red and near-infrared wavelengths of light. Oceans only reflect much at blue (short) wavelengths,” said Cowan.
“A ‘pale blue dot‘ is the best picture we will get of an Earth-like extrasolar world using even the most advanced telescopes planned for the next couple decades,” Cowan continued. “So how do we find out if it is capable of supporting life? If we can determine that the planet has oceans of liquid water, it greatly increases the likelihood that it supports life.”
This narrow-angle color image of the Earth, dubbed ‘Pale Blue Dot‘, is a part of the first ever ‘portrait’ of the solar system taken by Voyager 1, and made famous by astronomer Carl Sagan. The spacecraft acquired a total of 60 frames for a mosaic of the solar system from a distance of more than 4 billion miles from Earth and about 32 degrees above the ecliptic. From Voyager’s great distance Earth is a mere point of light, less than the size of a picture element even in the narrow-angle camera. Earth was a crescent only 0.12 pixel in size. Coincidentally, Earth lies right in the center of one of the scattered light rays resulting from taking the image so close to the sun. This blown-up image of the Earth was taken through three color filters — violet, blue and green — and recombined to produce the color image. The background features in the image are artifacts resulting from the magnification. Credit: NASA JPL
The maps that the team created are only sensitive to the longitudinal (East – West) positions of oceans and continents. Furthermore, the observations only pick out what is going on near the equator of Earth: the equator gets more sunlight than higher latitudes, and the EPOXI spacecraft was above the equator when the observations were taken. These limitations of viewing geometry could plague observations of extrasolar planets as well: “We could erroneously see the planet as a desert world if it had a nearly solid band of continents around its equator and oceans at its poles,” said Cowan.
Other things besides water can make a planet appear blue; for example, in our solar system the planet Neptune is blue due in part to the presence of methane in its upper atmosphere. “However, a Neptune-like world would appear as an unchanging blue using this technique, and again it’s the changes in the blue color that reveal oceans to us,” said Cowan. “There are some weird scenarios you can dream up that don’t involve oceans but would lead to varying patches of blue on a planet, but these are not very plausible.”
“A spectrum of the planet’s light that reveals the presence of water is necessary to confirm the existence of oceans,” said Drake Deming, a co-author of the paper at NASA’s Goddard Space Flight Center in Greenbelt, Md. Instruments that produce a spectrum are attached to telescopes and spread out light into its component colors, like a prism separates white light into a rainbow. Every element and molecule emits and absorbs light at specific colors. These colors can be used like a fingerprint to identify them.
“Finding the water molecule in the spectrum of an extrasolar planet would indicate that there is water vapor in its atmosphere, making it likely that the blue patches we were seeing as it rotates were indeed oceans of liquid water. However, it will take future large space telescopes to get a precise spectrum of such distant planets, while our technique can be used now as an indication that they could have oceans,” said Deming. The technique only requires relatively crude spectra to get the intensity of light over broad color ranges, according to the team.
EPOXI is a combination of the names for the two extended mission components: a search for extrasolar planets during the cruise to Hartley 2, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact eXtended Investigation (DIXI).
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You might have heard through the celestial grape vine that Universe Today correspondent Ian O’Neill has been tagged to lead the space news team over at the Discovery Channel’s space blog network. So if you’re wondering why there aren’t many O’Neill articles over here, or at his own website Astroengine.com, that’s because he writing (and editing) his big heart over at Discovery.com: Space Disco. The previous producer, Dave Mosher has moved on to manage the web development for a non-profit foundation.
A big thanks to Ian for all his dedicated work on Universe Today and I really hope everything goes well with his work over at the Discovery Channel.
Ian has promised he’ll still be contributing the occasional article for Universe Today. And if he’s too busy for that, we’ll still be linking to his coverage when we can.
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When it comes to liquids, viscosity is a measurement of how thick or syrupy it is. Water has low viscosity, while corn syrup, for example, is highly viscous. You can measure lava in terms of viscosity as well. And the lava viscosity defines the size and shape of a volcano. Even though lava is 100,000 times more viscous than water, it can still flow great distances.
When lava has low viscosity, it can flow very easily over long distances. This creates the classic rivers of lava, with channels, puddles and fountains. You can also get bubbles of lava filled with volcanic gasses that burble and pop on the surface of the lava. And over time, volcanoes made from low lava viscosity are wide and have a shallow slope; these are known as shield volcanoes. Classic examples of shield volcanoes are Mauna Kea and Mauna Loa in Hawaii, as well as Olympus Mons on Mars.
When lava has a high viscosity, it’s very thick and doesn’t flow very well at all. Instead of rivers of lava, you can get crumbling piles of rock flowing down hill. It can also clog up the volcanic vent and form blocks that resist the flow of lava. Viscous lava will trap pockets of gas within the rock, and not let them pop as bubbles on the surface. But most importantly, highly viscous lava is associated with explosive eruptions and dangerous pyroclastic flows.
An example of a low viscosity (fast flowing) lava is basaltic lava. This flows quickly out of a volcano at a temperature of about 950 degrees Celsius. This flows out for great distances creating shield volcanoes or flood basalt fields. An example of high viscosity lava is felsic lava, like rhyolite or dacite. It erupts at lower temperatures, and can flow for tens of kilometers.
We have written many articles about lava for Universe Today. Here’s an article about lava flows, and here’s an article about the temperature of lava.
