Artist concept of how a galaxy might accrete mass from rapid, narrow streams of cold gas. These filaments provide the galaxy with continuous flows of raw material to feed its star-forming at a rather leisurely pace. Credit: ESA–AOES Medialab
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Was the universe a kinder, gentler place in the past that we have thought? The Herschel space observatory has looked back across time with its infrared eyes and has seen that galaxy collisions played only a minor role in triggering star births in the past, even though today the birth of stars always seem to be generated by galaxies crashing into each other. So what was the fuel for star formation in the past?
Simple. Gas.
The more gas a galaxy contained, the more stars were born.
Scientists say this finding overturns a long-held assumption and paints a nobler picture of how galaxies evolve.
Astronomers have known that the rate of star formation peaked in the early Universe, about 10 billion years ago. Back then, some galaxies were forming stars ten or even a hundred times more vigorously than is happening in our Galaxy today.
In the nearby, present-day Universe, such high birth rates are very rare and always seem to be triggered by galaxies colliding with each other. So, astronomers had assumed that this was true throughout history.
GOODS-North is a patch of sky in the northern hemisphere that covers an area of about a third the size of the Full Moon. Credit: ESA/GOODS-Herschel consortium/David Elbaz
But Herschel’s observations of two patches of sky show a different story.
Looking at these regions of the sky, each about a third of the size of the full Moon, Herschel has seen more than a thousand galaxies at a variety of distances from the Earth, spanning 80% of the age of the cosmos.
In analyzing the Herschel data, David Elbaz, from CEA Saclay in France, and his team found that even though some galaxies in the past were creating stars at incredible rates, galaxy collisions played only a minor role in triggering star births. The astronomers were able to compare the amount of infrared light released at different wavelengths by these galaxies, the team has shown that the star birth rate depends on the quantity of gas they contain, not whether they are colliding.
They say these observations are unique because Herschel can study a wide range of infrared light and reveal a more complete picture of star birth than ever seen before.
“It’s only in those galaxies that do not already have a lot of gas that collisions are needed to provide the gas and trigger high rates of star formation,” said Elbaz.
Today’s galaxies have used up most of their gaseous raw material after forming stars for more than 10 billion years, so they do rely on collisions to jump-start star formation, but in the past galaxies grew slowly and gently from the gas that they attracted from their surroundings.
Blastoff of Delta II Heavy rocket and twin GRAIL Lunar Mappers on Sept 10 blast off unveiled at night at Launch Pad 17B. GRAIL liftoff was postponed to Sept. 10 at 8:29 a.m EDT after high levels winds scrubbed the Sept 8 launch attempt. Credit: Ken Kremer
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NASA renewed its focus on ground breaking science today with the thunderous blastoff of a pair of lunar bound spacecraft that will map the moons interior with unparalled precision and which will fundamentally alter our understanding of how the moon and other rocky bodies in our solar system – including Earth – formed and evolved over 4.5 Billion years.
Today’s (Sept. 10) launch of the twin lunar Gravity Recovery and Interior Laboratory (GRAIL) spacecraft atop the mightiest Delta II rocket from Cape Canaveral Air Force Station in Florida at 9:08 a.m. EDT was a nail biter to the end, coming after a two day weather delay due to excessively high upper level winds that scrubbed the first launch attempt on Sept. 8, and nearly forced a repeat cancellation this morning.
Liftoff of the nearly identical GRAIL A and B lunar gravity mappers from Space Launch Complex 17B took place on the second of two possible launch attempts after the first attempt was again waived off because the winds again violated the launch constraints.
GRAIL A and B gravity mappers rocket to the moon atop a Delta II Heavy booster on Sept. 10 from Cape Canaveral, Florida. View to Space Launch Complex 17 gantry from Press Site 1.
Credit: Ken Kremer (kenkremer.com)
After the final “GO” was given, the Delta II Heavy booster suddenly roared to life and put on a spectacular show spewing smoke, flames and ash as it pushed off the pad and shot skywards atop a rapidly growing plume of exhaust and rumbling thunder into a nearly cloudless sky.
The solar powered dynamic duo were propelled to space by the last ever Delta II rocket slated to depart Earth from Cape Canaveral, Florida. After more than 50 years of highly reliable service starting in 1960, the venerable Delta II family will be retired after one final launch in October from Vandenberg Air Force Base in California.
GRAIL and Delta II rocket soar to space.
View to Space Launch Complex 17 Pad A & Pad B (right) from Press Site 1. Credit: Ken Kremer
On this special occasion the media were allowed to a witness the launch from Press Site 1 – a location just 1.5 miles away from the pad with a gorgeous and unobstructed view to the base of the pad which magnified the tremendous roar of the rocket engines.
“Since the earliest humans looked skyward, they have been fascinated by the moon,” said GRAIL principal investigator Maria Zuber from the Massachusetts Institute of Technology in Cambridge. “GRAIL will take lunar exploration to a new level, providing an unprecedented characterization of the moon’s interior that will advance understanding of how the moon formed and evolved.”
Delta II arcs over atop long exhaust plume casting shadow for long lunar journey. Credit: Ken Kremer
The spacecraft separation and deployment of the solar arrays worked exactly as planned, the mission team reported at a post launch briefing for reporters. Both probes are power positive and healthy.
GRAIL A and B are now speeding towards the moon on a low energy path that will take about 3.5 months compared to just three days for the Apollo astronauts. The slower and longer path covering more than 2.5 million miles (4 million kilometers) enables the spacecraft to use a smaller engine and carry less fuel for the braking maneuver required to place the probes into a polar elliptical orbit when they arrive at the moon about 25 hours apart on New Year’s Eve and New Year’s Day 2012.
“Our GRAIL twins have Earth in their rearview mirrors and the moon in their sights,” said David Lehman, GRAIL project manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. “The mission team is ready to test, analyze and fine-tune our spacecraft over the next three-and-a-half months on our journey to lunar orbit.”
During the 82 day science phase, the primary objective of is to study the moons interior from crust to core and map its gravity field by 100 to 1000 times better than ever before. GRAIL A and GRAIL B will fly in tandem formation in near circular polar orbit at an altitude of some 50 km above the lunar surface as the moon rotates beneath three times.
GRAIL lunar twins depart Earth for the Moon
All 3 Air-lit solids have ignited after all 6 ground lit solids have been jettisoned.Credit: Ken Kremer
The mission will provide unprecedented insight into the structure and composition of moon from crust to core, unlock the mysteries of the lunar interior and advance our understanding of the thermal evolution of the moon that can be applied to the other terrestrial planets in our solar system, including Mercury, Venus, Earth and Mars.
Three people enjoy the summer sky over the Delaware river, NJ, USA in August 2006. Image Credit: Wikimedia
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It’s a great time to be an amateur astronomer! Nowadays, “backyard” astronomers armed with affordable CCD imagers, high-quality tracking mounts, inexpensive PC’s and the internet at their fingertips are making real contributions to Astronomy science.
How are people in their backyards contributing to real science these days?
Consider that in 1991, the Hubble Space Telescope launched with a main camera of less than 1 megapixel. (HST’s array was 800×800 pixels – just over half a megapixel). Currently, “off-the-shelf” imaging equipment available for a few hundred dollars or less easily provides 1 megapixel or more. Even with a “modest” investment, amateurs can easily reach the ten megapixel mark. Basically, the more pixels you have in your imaging array, the better resolution your image will have and the more detail you’ll capture (sky conditions notwithstanding).
With access to fairly high resolution cameras and equipment, many amateurs have taken breathtaking images of the night sky. Using similar equipment other hobbyists have imaged comets, supernovae, and sunspots. With easy access to super-precise tracking mounts and high-quality optics, it’s no wonder that amateur astronomers are making greater contributions to science these days.
One spectacular example of amateur discoveries was covered by Universe Todayearlier this year. Kathryn Aurora Gray, a ten year old girl from Canada, discovered a supernova with the assistance of her father and another amateur astronomer, David Lane. The discovery of Supernova 2010lt (located in galaxy UGC 3378 in the constellation of Camelopardalis) was Kathryn’s first, her father’s seventh and Lane’s fourth supernova discovery. You can read the announcement regarding Ms. Gray’s discovery courtesy of The Royal Astronomical Society of Canada at: http://www.rasc.ca/artman/uploads/sn2010lt-pressrelease.pdf
Often times when a supernova is detected, scientists must act quickly to gather data before the supernova fades. In the image below, look for the blinking “dot. The image is a before and after image of the area surrounding Supernova 2010lt.
A before and after animation of Supernova 2010lt. Credit: Dave Lane
Before Kathyrn Gray, astronomer David Levy made headlines with his discovery of comet Shoemaker-Levy 9. In 1994, comet Shoemaker-Levy 9 broke apart and collided with Jupiter’s atmosphere. Levy has gone on to discover over twenty comets and dozens of asteroids. Levy has also published several books and regularly contributes articles to various astronomy publications. If you’d like to learn more about David Levy, check out his internet radio show at http://www.letstalkstars.com/, or visit his site at http://www.jarnac.org/
Hubble image of comet P/Shoemaker-Levy 9, taken on May 17, 1994. Image Credit: H.A. Weaver, T. E. Smith (Space Telescope Science Institute), and NASAThe International Space Station and Space Shuttle Atlantis transiting the sun. Image Credit: Thierry Legault
Rounding out news-worthy astronomers, astrophotographer Thierry Legault has produced many breathtaking images that have been featured here on Universe Today on numerous occasions. Over the past year, Thierry has taken many incredible photos of the International Space Station and numerous images of the last few shuttle flights. Thierry’s astrophotography isn’t limited to just the sun, or objects orbiting Earth. You can read more about the objects Thierry captures images of at: http://www.astrophoto.fr/ You can also read more about Thierry and the equipment he uses at: http://legault.perso.sfr.fr/info.html
Performing science as an amateur isn’t limited to those with telescopes. There are many other research projects that ask for public assistance. Consider the Planet Hunters site at: http://www.planethunters.org/. What Planet Hunters aims to achieve is a more “hands-on” approach to interpreting the light curves from the publicly available data from the Kepler planet finding mission. Planet Hunters is part of the Zooniverse, which is a collection of citizen science projects. You can learn more about the complete collection of Zooniverse projects at: http://www.zooniverse.org
Another citizen science effort recently announced is the Pro-Am White Dwarf Monitoring (PAWM) project. Led by Bruce Gary, the goal of the project is to explore the possibility of using amateur and professional observers to estimate the percentage of white dwarfs exhibiting transits by Earth-size planets in the habitable zone. The results from such a survey are thought to be useful in planning a comprehensive professional search for white dwarf transits. You can read more about the PAWM project at: http://www.brucegary.net/WDE/
Transit simulation. Image Credit: Manuel Mendez/PAWM
One very long standing citizen project is the American Association of Variable Star Observers (AAVSO). Founded in 1911, the AAVSO coordinates, evaluates, compiles, processes, publishes, and disseminates variable star observations to the astronomical community throughout the world. Currently celebrating their 100th year, the AAVSO not only provides raw data, but also publishes The Journal of the AAVSO, a peer-reviewed collection of scientific papers focused on variable stars. In addition to data and peer reviewed journals, the AAVSO is active in education and outreach, with many programs, including their mentor program designed to assist with disseminating information to educators and the public.
If you’d like to learn more about the AAVSO, including membership information, visit their site at: http://www.aavso.org/
For over a decade, space enthusiasts across the internet have been taking part in SETI@Home. The official description of SETI@home is “a scientific experiment that uses Internet-connected computers in the Search for Extraterrestrial Intelligence (SETI)”. By downloading special client software from the SETI@Home website at http://setiathome.berkeley.edu/, volunteers from around the world can help analyze radio signals and assist with SETI’s efforts to find “candidate” radio signals. You can learn more about SETI@Home by visiting http://setiathome.berkeley.edu/sah_about.php
The projects and efforts featured above are just a small sample of the many projects that non-scientists can participate in. There are many other projects involving radio astronomy, galaxy classification, exoplanets, and even projects involving our own solar system. Volunteers of all ages and educational backgrounds can easily find a project to help support.
Ray Sanders is a Sci-Fi geek, astronomer and space/science blogger. Visit his website Dear Astronomer and follow on Twitter (@DearAstronomer) or Google+ for more space musings.
For many exoplanet systems that have been discovered by the radial velocity method, astronomers have found excess emission in the infrared portion of the spectrum. This has generally been interpreted as remnants of a disk or collection of objects similar to our own Kupier belt, a ring of icy bodies beyond the orbit of Pluto. But as Kepler and other exoplanet finding missions rake in the candidates though transits of the parent star, astronomers began noticing something unusual: None of the exoplanet systems discovered through this method were known to have debris disks. Was this an odd selection effect, perhaps induced by the fact that transiting planets often orbit close to their parent stars, making them more likely to pass along the line of sight which could in turn, betray different formation scenarios? Or were astronomers simply not looking hard enough? A recent paper by astronomers at the Astrophysikalisches Institut in Germany attempts to answer that question.
In order to do so, the team compared the (at the time) 93 known transiting exoplanets to stars for which archival data was available through infrared missions such has IRAS, ISO, AKARI, and WISE. The team then searched the data looking for a previously unrecognized bump in the emission in the infrared. Many of the stars they searched were faint, due to distance, so most of the IR telescopes did not have images with sufficient depth to draw much in the way of conclusions. Between IRAS, ISO, Spitzer, and AKARI, the team was only able to examine three stars, and all of those came from Spitzer observations.
The most plentiful return came from the WISE telescope which had 53 entries that overlapped with known transiting systems, one of which was excluded due to image defects. From these 52 candidates, the team found four that may have contained excess emission. To follow up, the team added observations from other observatories that lied in the near infrared (the 2MASS survey) and the visual portion of the spectrum. This allowed them to build a more complete picture of the brightness of the stars at various wavelengths which would make the excess stand out even more. While all four systems deviated from an ideal blackbody in the portion of the spectrum expected for a debris disk, only two of them, TrES-2, and XO-5, did so in a manner that did so in a statistically significant manner.
While this study shows that debris disks are possible around transiting stars, it was only able to confirm their presence in two stars out of 52, or just under 4% of their sample. But how does that compare to systems discovered by other methods? One of the studies cited in the paper used a similar method of comparing archival data from IR observatories to known exoplanet system discovered by other methods in 2009. In this study, the team found debris disks around 10 of the 150 planet-bearing stars, which is roughly 7%. Due to the low return rate on both of these studies, the inherent uncertainty puts these two figures within a plausible range of one another, but certainly, more studies will be in order in the future. They will help astronomers determine just what difference exists, if any, as well as giving more insight into how planetary system form and evolve.
Artist Concept of Extra-Solar Planet Courtesy of NASA
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Using the High Accuracy Radial velocity Planet Searcher (HARPS), a team of scientists at University of Geneva, Switzerland, led by the Swiss astronomer Stephane Udry made a sound discovery… an Earth-like planet orbiting star HD 85512. Located about 36 light years away in the constellation of Vela, this extrasolar planet is one of the smallest to be documented in the “habitable zone” and could very well be a potential home to living organisms.
Circling its parent star every 54 days at about the quarter of the distance which Earth orbits the Sun, the newly discovered planet shows every sign of a temperate climate and a possibility of water. However, the rocky little world would need to exhibit some very cloudy skies to make the grade.
“We model rocky planets with H2O/CO2/N2 atmospheres, representative of geological active planets like Earth, to calculate the maximum Bond albedo as a function of irradiation and atmosphere composition and the edges of the HZ for HD 85512 b. These models represent rocky geological active planets and produce a dense CO2 atmosphere at the outer edge, an Earth-like atmosphere in the middle, and a dense H2O atmospheres at the inner edge of the HZ.” says the team. “The inner limit for the 50% cloud case corresponds to the “Venus water loss limit”, a limit that was empirically derived from Venus position in our Solar System (0.72 AU).”
But there’s always from one extreme to another when it comes to a planet being in just the right place. “The inner edge of the (Habitable zone) denotes the location where the entire water reservoir can be vaporized by runaway greenhouse conditions, followed by the photo-dissociation of water vapor and subsequent escape of free hydrogen into space. The outer boundary denotes the distance from the star where the maximum greenhouse effect fails to keep CO2 from condensing permanently, leading to runaway glaciation,” says the Kaltenegger/Udry/Pepe study.
While the whole scenario might not be exciting to some, the study is helping to lay a very solid foundation for evaluating current and future planet candidates for life supporting conditions. “A larger sample will improve our understanding of this field and promises to explore a very interesting parameter space that indicates the potential coexistence of extended H/He and H2O dominated atmospheres as well as rocky planet atmospheres in the same mass and temperature range.” says Kaltenegger. “HD 85512 b is, with Gl 581 d, the best candidate for exploring habitability to date, a planet on the edge of habitability.”
And one step closer to better understanding what’s out there…
The timing couldn’t be better. A new supernova, named PTF11kly, which was discovered on August. 24, 2011 is continuing to brighten and should be visible to backyard astronomers this weekend using just a pair of binoculars. It’s not quite naked-eye material but this is an exciting opportunity for amateurs (as well as the pros!) to view a supernova first-hand. Of course, if your backyard is full of light, the best option is to go to an area with darker skies, and you’ll be able to see it much better. Astronomers say PTF11kly will likely continue to shine for some time, and be at its brightest on about Sept. 9, 2011.
In this video Peter Nugent, an astrophysicist from Lawrence Berkeley National Labs explains just how to find this star that exploded about 21 million light years away.
The James Webb Space Telescope.
Image Credit: NASA/JPL
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The James Webb Space Telescope or JWST has long been touted as the replacement for the Hubble Space Telescope. The telescope is considered to be the one of the most ambitious space science projects ever undertaken – this complexity may be its downfall. Cost overruns now threaten the project with cancellation. Despite these challenges, the telescope is getting closer to completion. As it stands now, the telescope has served as a technical classroom on the intricacies involved with such a complex project. It has also served to develop new technologies that are used by average citizens in their daily lives.
Although compared to Hubble, the two telescopes are dissimilar in a number of ways. The JWST is three times as powerful as Hubble in its infrared capabilities. JWST’s primary mirror is 21.3 feet across (this provides about seven times the amount of collecting power that Hubble currently employs).
The JWST’s mirrors were polished using computer modeling guides that allowed engineers to predict that they will enter into the proper alignment when in space. Each of the mirrors on the JWST has been smoothed down to within 1/1000th the thickness of a human hair. The JWST traveled to points across the country to assemble and test the JWST’s various components.
Eventually the mirrors were then sent to NASA’s Marshall Space Flight Center in Huntsville, Alabama. Once there they measured how the mirrors reacted at extremely cold temperatures. With these tests complete, the mirrors were given a thin layer of gold. Gold is very efficient when it comes to reflecting light in the infrared spectrum toward the JWST’s sensors.
A comparison of the primary mirror used by Hubble and the primary mirror array used by the James Webb Space Telescope. Photo Credit: NASA
The telescope’s array of mirrors is comprised of beryllium, which produces a lightweight and more stable form of glass. The JWST requires lightweight yet strong mirrors so that they can retain their shape in the extreme environment of space. These mirrors have to be able to function perfectly in temperatures reaching minus 370 degrees Fahrenheit.
After all of this is done, still more tests await the telescope. It will be placed into the same vacuum chamber that tested the Apollo spacecraft before they were sent on their historic mission’s to the moon. This will ensure that the telescopes optics will function properly in a vacuum.
A life-sized model of the JWST was placed on display in Seattle, Washington - it was several stories tall and weighed several tons. Photo Credit: Rob Gutro/ NASA
With all of the effort placed into the JWST – a lot of spinoff technology was developed that saw its way into the lives of the general populace. Several of these – had to be invented prior to the start of the JWST program.
“Ten technologies that are required for JWST to function did not exist when the project was first planned, and all have been successfully achieved. These include both near and mid-infrared detectors with unprecedented sensitivity, the sunshield material, the primary mirror segment assembly, the NIRSpec microshutter array, the MIRI cryo-cooler, and several more,” said the James Webb Space Telescope’s Deputy Project Scientist Jason Kalirai. Kalirai holds a PhD in astrophysics and carries out research for the Space Telescope Science Institute. “The new technologies in JWST have led to many spinoffs, including the production of new electric motors that outperform common gear boxes, design for high precision optical elements for cameras and cell phones, and more accurate measurements of human vision for people about to undergo Laser Refractive Surgery.”
The James Webb Space Telescope encapsulated atop the Ariane V rocket tapped launch it, next to an early image of the telescope. Image Credit: NASA
If all goes according to plan, the James Webb Space Telescope will be launched from French Guiana atop the European Space Agency’s Arianne V Rocket. The rationale behind the Ariane V’s selection was based on capabilities – and economics.
“The Ariane V was chosen as the launch vehicle for JWST at the time because there was no U.S. rocket with the required lift capacity,” Kalirai said. “Even today, the Ariane V is a better tested vehicle. Moreover, the Ariane is provided at no cost by the Europeans while we would have had to pay for a U.S. rocket.”
It still remains to be seen as to whether or not the JWST will even fly. As of July 6 of this year the project is slated to be cancelled by the United States Congress. The James Webb Space Telescope was initially estimated at costing $1.6 billion. As of this writing an estimated $3 billion has been spent on the project and it is has been estimated that the telescope is about three-quarters complete.
Astronomers have combined two decades of Hubble observations to make unprecedented movies revealing never-before-seen details of the birth pangs of new stars. This sheds new light on how stars like the Sun form. Credit: Hubble/ESA
[/caption]Don’t you know that you are a shooting star… Thanks to the NASA/ESA Hubble Space Telescope, an international team of scientists led by astronomer Patrick Hartigan of Rice University in Houston, USA, has done something pretty incredible. Using photos and information gathered from the last 14 years of observations, they’ve sewn together an unprecedented look at young jets ejected from three stars. Be prepared to be “blown” away…
The time-lapse sequence of “moving pictures” offers us an opportunity to witness activity that takes place over several years in just a few seconds. Active jets can remain volatile for periods of up to 100,000 years and these movies reveal details never seen – like knots of gas brightening and dimming – and collisions between fast-moving and slow-moving material. These insights allow scientists to form a clearer picture of stellar birth.
“For the first time we can actually observe how these jets interact with their surroundings by watching these time-lapse movies,” said Hartigan. “Those interactions tell us how young stars influence the environments out of which they form. With movies like these, we can now compare observations of jets with those produced by computer simulations and laboratory experiments to see which aspects of the interactions we understand and which we don’t understand.”
As a star forms in its collapsing cloud of cold gas, it gushes out streams of material in short bursts, pushing out from its poles at speeds of up to about 600,000 miles an hour. As the star ages, it spins material and its gravity attracts even more, creating a disc which may eventually become protoplanetary. The fast moving jets may be restricted by the neophyte star’s magnetic fields and could cease when the material runs out. However, by looking at this supposition in action, new questions arise. It would appear that the dust and gas move at different speeds.
“The bulk motion of the jet is about 300 kilometers per second,” Hartigan said. “That’s really fast, but it’s kind of like watching a stock car race; if all the cars are going the same speed, it’s fairly boring. The interesting stuff happens when things are jumbling around, blowing past one another or slamming into slower moving parts and causing shockwaves.”
But the “action” doesn’t stop there. In viewing these sequential shockwaves, the team was at a loss to understand the dynamics behind the collisions. By enlisting the aid of colleagues familiar with the physics of nuclear explosions, they quickly discovered a recognizable pattern.
“The fluid dynamicists immediately picked up on an aspect of the physics that astronomers typically overlook, and that led to a different interpretation for some of the features we were seeing,” Hartigan explained. “The scientists from each discipline bring their own unique perspectives to the project, and having that range of expertise has proved invaluable for learning about this critical phase of stellar evolution.”
Hartigan began using Hubble to collect still frames of stellar jets in 1994 and his findings are so complex he has employed the aid of experts in fluid dynamics from Los Alamos National Laboratory in New Mexico, the UK Atomic Weapons Establishment, and General Atomics in San Diego, California, as well as computer specialists from the University of Rochester in New York. The Hubble sequence movies have been such a scientific success that Hartigan’s team is now conducting laboratory experiments at the Omega Laser facility in New York to understand how supersonic jets interact with their environment.
“Our collaboration has exploited not just large laser facilities such as Omega, but also computer simulations that were developed for research into nuclear fusion,” explains Paula Rosen of the UK Atomic Weapons Establishment, a co-author of the research. “Using these experimental methods has enabled us to identify aspects of the physics that the astronomers overlooked — it is exciting to know that what we do in the laboratory here on Earth can shed light on complex phenomena in stellar jets over a thousand light-years away. In future, even larger lasers, like the National Ignition Facility at the Lawrence Livermore National Laboratory in California, will be able explore the nuclear processes that take place within stars.”
And all the world will love you just as long… as long as you are… a shooting star!
Supernova PTF11kly in M101 on August 24, 2011. Credit: BJ Fulton, LCOGT.
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Literally an event of stellar proportions, a new Type Ia supernova has been identified in a spiral galaxy 25 million light-years away! Spotted by Caltech’s Palomar Transit Factory project, this supernova, categorized as PTF11kly, is located 58″.6 west and 270″.7 south of the center of M101. It was first seen yesterday, August 24, 2011.
According to AAVSO Special Notice #250 P. Nugent et al. reported in Astronomical Telegram #3581 that a possible Type-Ia supernova has been discovered by the Palomar Transient Factory shortly after eruption in the galaxy M101 and has been designated “PTF11kly”. The object is currently at a magnitude of 17.2, but may well rise by several magnitudes. The object is well placed within M101 for good photometry, and observations of this potential bright SNIa are strongly encouraged.
There are currently no comparison stars available in VSP for this field; please indicate clearly the comparison stars that you use for photometry when reporting observations to AAVSO. Please retain your images and/or photometry for recalibration when comparison star magnitudes are available.
Need coordinates? The (J2000) coordinates reported for the object are RA: 14:03:05.81 , Dec: +54:16:25.4. Messier 101 is located in the constellation of Ursa Major at RA: 14h 03m 12.6s Dec: +54 20′ 57″
Charts for PTF11kly may be plotted with AAVSO VSP. You should select the DSS option when plotting, as the galaxy will not appear on standard charts. This object has been assigned the name “PTF11kly” for use with AAVSO VSP and WebObs; please use this name when reporting observations until it is conclusively classified as a supernova and a proper SN name is assigned.
Image of M101 and PTF11kly by Joseph Brimacombe.
Type Ia supernovae are the result of a binary pair of mismatched stars, the smaller, denser one feeding on material drawn off its larger companion until it can no longer take in any more material. It then explodes in a catastrophic event that outshines the brightness of its entire galaxy! Astronomers believe that Type Ia supernovae occur in pretty much the same fashion every time and thus, being visible across vast distances, have become invaluable benchmarks for measuring distance in the Universe and gauging its rate of expansion.
The fact that this supernova was spotted literally within a day of its occurrence – visibly speaking, of course, since M101 is 25 million light-years away and thus 25 million years in our past – will be extremely handy for astronomers who will have the opportunity to study the event from beginning to end and learn more about some of the less-understood processes involved in Type Ia events.
“We caught this supernova earlier than we’ve ever discovered a supernova of this type. On Tuesday, it wasn’t there. Then, on Wednesday, boom! There it was – caught within hours of the explosion. As soon as I saw the discovery image I knew we were onto something big.”
– Andy Howell, staff scientist at Las Cumbres Observatory Global Telescope
It’s a big Universe and there are a lot of stars and therefore a lot of supernovae, but getting a chance to study one occurring so recently in a galaxy so relatively close to our own is something that is getting many astronomers very excited.
So, get those CCD camera out and best of luck!
Keep up with the latest news on PTF11kly on the rochesterastronomy.org site, and check out Phil Plait’s informative article on his BadAstronomy blog. Also read the press release from the University of California here.
Tammy Plotner also contributed to this article.
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Jason Major is a graphic designer, photo enthusiast and space blogger. Visit his website Lights in the Dark and follow him on Twitter @JPMajor and on Facebook for more astronomy news and images!
The variations in brightness can be interpreted as vibrations, or oscillations within the stars, using a technique called asteroseismology. The oscillations reveal information about the internal structure of the stars, in much the same way that seismologists use earthquakes to probe the Earth's interior. Credit: Kepler Astroseismology team.
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Asteroseismology is a relatively new field in astronomy. This branch uses sound waves in stars to explore their nature in the same way seismologists on Earth have used waves induced by tectonic activity to probe the interior of our planet. These waves aren’t heard directly, but as they strike the surface they can cause it to undulate, shifting the spectral lines this way and that, or compress the outer layers causing them to brighten and fade which can be detected with photometry. By studying these variations, astronomers have begun peering into stars. This much is generally known, but some of the specific tricks aren’t often brought up when discussing the topic. So here’s five things you can do with asteroseismology you may not have known about!
1. Determine the Age of a Star
From high school science you should know sound will travel through a medium at a characteristic speed for a given temperature and pressure. This information tells you something about the chemical composition of the star. This is a fantastic thing since astronomers can then check that against predictions made by stellar models. But astronomers can also take that one step further. Since the core of a star slowly converts hydrogen to helium over its lifetime, that composition will change. How much it has changed from its original composition towards the point where there’s no longer enough hydrogen to support fusion, tells you how far through the main sequence lifetime a star is. Since we know the age of the solar system very well from meteorites, astronomers have calibrated this technique and begun using it on other stars like α Centauri. Spectroscopically, this star is expected to be nearly identical to the Sun; it has very similar spectral type and chemical composition. Yet a 2005 study using this technique pinned α Cen as 6.7 ± 0.5 billion years which is about one and a half billion years older than the Sun. Obviously, this still has a rather large uncertainty to it (nearly 10%), but the technique is still new and will certainly be refined in the future.
And if that wasn’t cool enough by itself, astronomers are now beginning to use this technique on stars with known planets to get a better understanding of the planets! This can be important in many cases since planets will initially glow more brightly in younger systems since they still retain heat from their formation and this amount of extra light could confuse astronomers on just how might light is being reflected leading to inaccurate estimates of other properties like size or reflectivity.
2. Determine Internal Rotation
Cover of a Book on the Solar Tachocline showing abrupt transition discovered by helioseismology
We already know that stars rotation is a bit funny. They rotate faster at their equator than at their poles, a phenomenon known as differential rotation. But stars are also expected to have differences in rotation as you get deeper. For stars like the Sun, this effect is related to a difference in energy transport mechanisms: radiative, where energy is conducted by a flow of photons in the deep interior, to convective, where energy is carried by bulk flow of matter, creating the boiling motion we see on the surface. At this boundary, the physical parameters of the system change and the material will flow differentially. This boundary is known as the tachocline. Within the Sun, we’ve known it’s there, but using asteroseismology (which, when used on the Sun is known as helioseismology), astronomers actually pinned it down. It’s 72% the way out from the core.
3. Find Planets
Until very recently, the most reliable way to find planets has been to look for the spectroscopic wiggle as the planets tug the star around. This technique sounds very straightforward, and it can be, unless the star has a lot of wiggle of its own due to the effects that make asteroseismology possible. Those effects can easily be much larger than those created by planets. So if you want to find planets lost in the forest of noise, you’d best understand the effects caused by the pulsating stellar surface. After astronomers cancelled out those effects on V391 Pegasi, they discovered a planet. And what a weird one it was. This planet is orbiting a sub-dwarf star, which is the helium core of a post-main sequence star which has ejected its hydrogen envelope. Of course, this occurs during the red giant phase when the star should have swollen up to engulf the gas giant planet in orbit. But apparently the planet survived, or somehow came along later.
4. Find Buried Sunspots
Turning to recent news, helioseismology recently found some sunspots. This wouldn’t be a big deal. Anyone with a properly filtered telescope can find them. Except these ones were buried some 60,000 km beneath the Sun’s surface. By using the seismic data, astronomers found an overdense region beneath the surface. This region was caused, just as sunspots are, by a tangle in the magnetic field keeping the material in place. As it rose to the surface, it became a sunspot. Here’s the vid:
5. Make “Music”
Because many of the events that create the soundwaves in stars are periodic, they are rhythmic in nature. This has prompted many explorations into using these naturally created beats to make music. A direct example is this one which simply assigns tones to the modes of pulsation. The site also notes that the beat created by one of the stars, has been used as a base for club music in Belgium. This has also been done for longer “symphonies” by Zoltan Kollath.
