Posted on by Nancy Atkinson

Graphic Shows Biggest and Closest Near Earth Objects (and it’s not scary)

Near Earth Objects graphic, created by Zachary Vabolis. Used by permission.

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Just for fun, graphic design student Zachary Vabolis created this fantastic graphic showing the closest and biggest Near Earth Objects. However, Vabolis wants to make clear that the information represented here is not meant to portray that the end of the world is nigh. His image has appeared on several websites recently, and some of the headlines have included words such as “doomsday,” etc. But, that’s not what he intended.

“I’m not sure if anyone who has seen my graphic is reading more into it than I intended,” Vabolis told Universe Today, “but I wanted to state that I did not create this graphic to scare people. In fact if you look at the information it contains, Earth has almost no chance of being hit by any of the asteroids listed and NASA even mentions that as well on their website.”

Vabolis said he created the graphic because he really enjoys creating projects outside of his curriculum to help hone his skills, plus it is just a fun pastime for him. “I’ve always been fascinated by outer space so I wanted to do a graphic within that subject,” Vabolis said in an email. “I came up with the Near Earth Objects topic because it’s a fairly current subject and after doing a little research I found that no one else had created such a graphic yet.”

The graphic was created using the information on NASA’s Near Earth Object Fact Sheet website, which states, “There are no known NEO’s on a collision course with the Earth. There is a possibility that an as yet undiscovered large NEO may hit the Earth, but the probability of this happening over the next 100 years is extremely small.”

So breathe easy and enjoy learning more about NEO’s from Vabolis’ graphic. You can see more of his work at his page on Behance.

Posted on by Nancy Atkinson

Watch Kepler Press Conference Today Live On Universe Today

Get the news of the latest findings regarding stars and their structures during a press conference that will be streamed live from Aarhus University in Denmark today at 11 am EDT (1500 GMT). Using data from NASA’s Kepler spacecraft, an international research team has examined and characterized thousands of stars by using the natural pulse of stellar light waves, thereby gaining new insights into stellar structure and
evolution.

Posted on by Nicholos Wethington

Another X-ray Nova Detected by ISS, Swift

The X-ray nova MAXI J1409-619, as observed by the MAXI instrument aboard the ISS. Image Credit: JAXA/RIKEN/MAXI team

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A new X-ray emitting object in the Milky Way has been recently announced by the Monitor of All-sky X-ray Image (MAXI) team and the Swift satellite astronomers. MAXI, a Japan Aerospace Exploration Agency supported instrument, monitors the entire sky in the X-ray portion of the spectrum from its perch on the International Space Station module “Kibo”. On October 12th, MAXI noticed nothing out of the ordinary in a portion of the sky in the constellation Centaurus.

On October 17th, however, things started to brighten up in the region but were still dark enough that the team wanted to analyze their observations before announcing it to the world. By the 20th, they were able to confirm the X-ray source as something more unusual, and sent out an Astronomer’s Telegram (ATel No.2959) at 2:00 a.m. EDT alerting other astronomers to the object.

The Swift satellite – in keeping with its name – began taking observations a mere nine hours later. Swift is equipped with an X-ray telescope, as well as an optical/ultraviolet telescope, and is designed to maneuver quickly to home in on gamma-ray bursts (GRBs)

David Burrows, professor of astronomy and astrophysics at Penn State and the lead scientist for Swift’s X-ray Telescope said in a press release, “The Swift observation suggests that this source is probably a neutron star or a black hole with a massive companion star located at a distance of a few tens of thousands of light years from Earth in the Milky Way…The contribution of Swift’s X-ray Telescope to this discovery is that it can swing into position rapidly to focus on a particular point in the sky and it can image the sky with high sensitivity and high spatial resolution.”

The object has been named MAXI J1409-619. The area of the sky that it was discovered in is not a known source of bright X-rays, though there were two dimmer objects located in the same area detected by the BeppoSAX X-ray survey on January 29th, 2000. One of the objects is consistent with the Swift observation, though this most recent flare-up made it almost 52 times brighter in the X-ray than previously observed.

The X-ray nova as seen by the Swift satellite. The bright portion is 0.2 degrees in radius. Image Credit: MAXI/Swift team

X-ray novae are short-lived events, with an initial bright burst that falls off over a period of weeks or months. Their source is generally understood to be material falling into a black hole or accreting onto a neutron star.

This is not the first discovery made by the MAXI instrument. It detected another X-ray source on the 25th of September in the constellation Ophiuchus – named MAXI J1659-152 – which we wrote about here.

Further observations of the new object are likely in the works, so we’ll keep you posted.

Sources: Eurekalert, JAXA, ATel 2965, Penn State Press Release

Posted on by Nicholos Wethington

Watch a Mars Rover Under Construction – LIVE!

If you are tired of the drama of your favorite reality TV show, it might be time to switch things up a bit. The most recent reality show, available ad free on the internet, features a spunky robot and a huge cast of characters. The spunky robot is Curiosity, the name of the Mars Science Laboratory rover. The characters are all wearing white clean room “bunny suits,” so it will be difficult to tell them apart. Surely, if you spend enough time watching you’ll be able to discern who’s who.

In all seriousness, you can watch the construction of Curiosity live via Ustream. The NASA/JPL team that is constructing the rover will be at work between 8 a.m. to 11:00 p.m. PDT Monday through Friday. Otherwise, things will be a little quiet. The camera looks out onto a pretty active part of the clean room, but they may move the rover outside of the view of the camera. Some of the busy periods will be archived at the bottom of the Ustream feed, so if you end up watching during a quiet period, take a look at those while you’re waiting for the next work period to start up.

For more on the rover and its mission, visit the mission page or see our story on Universe Today from September, “5 Things about the Next Mars Rover“.

Source: JPL

Posted on by Jon Voisey

Interstellar Scintilation

Barnard 68 (Credit: ESO)
Barnard 68 (Credit: ESO)

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Anyone who has looked at stars in the night sky (especially ones low on the horizon) has undoubtedly seen the common effect of twinkling. This effect is caused by turbulence in the atmosphere as small over densities cause the path of the light to bend ever so slightly. Often, vivid color shifts occur since the effects are wavelength dependent. All of this happens in the short distance between the edge of the atmosphere and our eyes. Yet often times, giant molecular clouds lie between our detectors and a star. Could these clouds of gas and dust cause a twinkling effect as well?


In theory, there’s no reason they shouldn’t. As the giant molecular clouds intercepting the incoming starlight move and distort, so too should the path of the light. The difference is that, due to the extremely low density and extremely large size, the timescales over which this distortion would take place would be far longer. Should it be discovered, it would provide astronomers another method by which to discover previously hidden gas.

Doing this is precisely the goals of a team of astronomers working from the Paris University and Sharif University in Iran. To get and understanding of what to expect, the team first simulated the effect, taking into account the properties of the cloud (distribution, velocity, etc…) as well as refraction and reflection. They estimated that, for a star in the Large Magellanic Cloud with light passing through typical galactic H2 gas, this would produce twinkles with changes taking around 24 minutes.

Yet there are many other effects which can produce modulations on the same timescale such as variable stars. Additional constraints would be necessary to claim that a change would be due to a twinkling effect and not a product of the star itself. As stated before, the effect is different for different wavelengths which would produce a “variation of the characteristic time scale … between the red side of the optical spectrum and the blue side.”

With expectations in hand, the team began searching for this effect in areas of the sky in which they knew especially high densities of gas to exist. Thus, they pointed their telescopes towards dense nebulae known as Bok globules like Barnard 68 (pictured above). Observations were taken using the 3.6 meter ESO NTT-SOFI telescope since it had the capabilities to also take infrared images and better explore the potential effects on the red side of the spectrum.

From their observations over two nights, the team discovered one instance in which the modulation of brightness in the different wavelengths followed the predicted effects. However, they note that from a single observation of their effects, it does not conclusively demonstrate the principle. The team also observed stars in the direction of the Small Magellanic Cloud to attempt to observe this twinkling effect in that direction due to previously undetected clouds along the line of sight. In this attempt, they were unsuccessful. Further similar observations along these lines in the future could help to constrain the amount of cold gas within the galaxy.

Posted on by Jon Voisey

The Hunt for Young Exoplanets

While there is a great deal of excitement and effort in the hopes of finding small, terrestrial sized exoplanets, another realm of exoplanet discovery that is often overlooked is that of ones of differing ages to explore how planetary systems can evolve. The first discovered exoplanet orbited a pulsar, showing that planets can be hardy enough to survive the potential violent deaths of their parent stars. On the other end, young planets can help astronomers constrain how planets form and a potential new discovery may help in those regards.


Historically, astronomers have often avoided looking at stars younger than about 100 million years. Their young nature tends to make them unruly. They are prone to flares and other eccentric behaviors that often make observations messy. Additionally, many young stars often retain debris disks or are still embedded in the nebula in which they formed which also obscures observations.

Despite this, some astronomers have begun developing targeted searches for young exoplanets. The age of the exoplanet is not independently derived, but instead, taken from the age of the host star. This too can be difficult to determine. For isolated stars, there are precious few methods (such as gyrochronology) and they generally have large errors associated with them. Thus, instead of looking for isolated stars, astronomers searching for young exoplanets have tended to focus on clusters which can be dated more easily using the main sequence turn off method.

Through this methodology, astronomers have searched clusters and other groups, such as Beta Pictoris which turned up a planet earlier this year. The Beta Pic moving group boasts an age of ~12 million years making it one of the youngest associations currently known.

Trumpler 37 (also known as IC 1396 and the Elephant Trunk Nebula) is one of the few clusters with an even younger age of 1-5 million years. This was one of several young clusters observed by a team of German astronomers led by Gracjan Maciejewski of Jena University. The group utilized an array of telescopes across the world to continuously monitor Trumpler 37 for several weeks. During that time, they discovered numerous flares and variable stars, as well as a star with a dip in its brightness that could be a planet.

The team cautions that the detection may not be a planet. Several objects can mimic planetary transit lightcurves such as “the central transit of a low-mass star in front of a large main-sequence star or red giant, grazing eclipses in systems consisting of two main-sequence stars and a contamination of a fainter eclipsing binary along the same line of sight.” Due to the physics of small objects, the size of brown dwarfs and many Jovian type planets are similar leading difficulty in distinguishing from the light curve alone. Spectroscopic results will have to be undertaken to confirm the object truly is a planet.

However, assuming it is, based on the size of the dip in brightness, the team predicts the planet is about twice the radius of Jupiter, and about 15 times the mass. If so, this would be in good agreement with models of planetary formation for the expected age. Ultimately, planets of such age will help test our understanding of how planets form, whether it be from a single gravitational collapse early on, or slow accretion over time.

Posted on by Matt Williams

Last Day of Summer

Winter Solstice
Earth as viewed from the cabin of the Apollo 11 spacecraft. Credit: NASA

Summertime is a joyous time for so many reasons. There’s the sense of vacation, that feeling of freedom we remember so fondly from our childhoods. There’s the warmth weather, the sunshine, the early mornings and cool, late evenings. Seriously, there’s nothing wrong with summer, except the unfortunate fact that sooner or later, it has to end.

But when exactly is the very last day of summer? Well, it differs from place to place, depending on your location, whether you are north or south of the equator and by how much. But in the Northern Hemisphere, the change in seasons occurred on September 22nd for the year of 2010. In the Southern Hemisphere, it took place on February 28th.

In order to understand why this date was pegged as the end of the season, we need to understand exactly how the season itself is measured. These have to do with the equinoxes and solstices, seasonal markers that occur twice a year respectively. From an astronomical point of view, the equinoxes and solstices are in the middle of the respective seasons, but a variable seasonal lag means that the meteorological start of the season, which is based on average temperature patterns, occurs several weeks later than the start of the astronomical season.

According to meteorologists, summer extends for the whole months of June, July and August in the northern hemisphere and the whole months of December, January and February in the southern hemisphere. Interestingly enough, in this hemisphere, the end of the summer season is also dependent on whether or not it is a leap year (during leap years, an extra day is added).

In North America, summer is often fixed as the period from the summer solstice (June 20 or 21, depending on the year) to the fall equinox (September 22 or 23, again depending on the year). Therefore, Sept. 22 was the last day of summer and the beginning of the 2010 autumnal equinox, which officially began at 11:09 p.m. EST., the full moon having peaked the following morning at 5:17 a.m. EST which marked it as the first day of fall in the Northern Hemisphere.

The moon closest to the September equinox is considered the “Harvest Moon.” Its name stems from when farmers would rely on the light to work in the fields as the days grew shorter. For the first time since 1991, the full moon fell on the equinox, creating a “Super Harvest Moon.” In the Southern Hemisphere, the last day of summer was February 28th since 2010 was not a leap year.

We have written many articles about Summer for Universe Today. Here’s an article about the summer solstice, and here’s an article about the Earth seasons.

If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Sources:
http://en.wikipedia.org/wiki/Summer
http://www.tonic.com/article/last-day-of-summer-first-night-of-fall-super-harvest-moon/
http://en.wikipedia.org/wiki/Equinox
http://en.wikipedia.org/wiki/Solstice
http://wiki.answers.com/Q/What_is_the_last_day_of_summer_in_Southern_Hemisphere

Posted on by Matt Williams

What is Interstellar Space?

Glittering Metropolis of Stars
Glittering Metropolis of Stars

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The boundary of what is known, that place known as the great frontier, has always intrigued and enticed us. The mystery of the unknown, the potential for discovery, the fear, the uncertainty; that place that exists just beyond the edge has got it all! At one time, planet Earth contained many such places for explorers, vagabonds and conquerors. But unfortunately, we’ve run out of spaces to label “here be dragons” here at home. Now, humanity must look to the stars to find such places again. These areas, the vast stretches of space that fall between the illuminated regions where stars sit, is what is known as Interstellar Space. It can be the space between stars but also can refer to the space between galaxies.

On the whole, this area of space is defined by its emptiness. That is, there are no stars or planetary bodies in these regions that we know of. That does not mean, however, that there is absolutely nothing there. In fact, interstellar areas do contain quantities of gas, dust, and radiation. In the first two cases, this is what is known as interstellar medium (or ISM), the matter that fills interstellar space and blends smoothly into the surrounding intergalactic space. The energy that occupies the same volume, in the form of electromagnetic radiation, is known as the interstellar radiation field. On the whole, the ISM is thought to be made up primarily of plasma (aka. ionized hydrogen gas) because its temperature appears to be high by terrestrial standards.

The nature of the interstellar medium has received the attention of astronomers and scientists over the centuries. The term first appeared in print in the 17th century in the works of Sir Francis Bacon and Robert Boyle, both of whom were referring to the spaces that fell between stars. Before the development of electromagnetic theory, early physicists believed that space must be filled with an invisible “aether” in order for light to pass through it. It was not until the 20th century though that deep photographic imaging and spectroscopy that scientists were able to postulate that matter and gas existed in these regions. The discovery of cosmic waves in 1912 was a further boon, leading to the theory that interstellar space was pervaded by them. With the advent of ultraviolet, x-ray, microwave, and gamma ray detectors, scientists have been able to “see” these kinds of energy at work in interstellar space and confirm their existence.

Many satellites have been launched with the intention of sending back information from interstellar space. These include the Voyager 1 and 2 spacecraft which have cleared the known boundaries of the Solar System and passed into the heliopause. They are expected to continue to operate for the next 25 to 30 years, sending back data on magnetic fields and interstellar particles.

We have written many articles about interstellar space for Universe Today. Here’s an article about deep space, and here’s an article about interstellar space travel.

If you’d like more information on the Interstellar Space, here’s a link to Voyager’s Interstellar Mission Page, and here’s the homepage for Interstellar Science.

We’ve recorded an episode of Astronomy Cast all about Interstellar Travel. Listen here, Episode 145: Interstellar Travel.

Sources:
http://en.wikipedia.org/wiki/Interstellar_space#Interstellar
http://en.wikipedia.org/wiki/Interstellar_medium
http://www.seasky.org/solar-system/interstellar-space.html
http://en.wikipedia.org/wiki/Electromagnetic_radiation
http://en.wikipedia.org/wiki/Heliopause#Heliopause

Posted on by Matt Williams

Cosmology

Planck Time
The Universe. So far, no duplicates found@

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Ever wonder why we are here, how and why the universe that we inhabit came to be, and what our place is in it? If so, than in addition to philosophy, religion, and esotericism, you might be interested in the field of Cosmology. This is, in the strictest sense, the study of the universe in its totality, as it is today, and what humanity’s place is in it. Although a relatively recent invention from a purely scientific point of view, it has a long history which embraces several fields over the course of many thousand years and countless cultures.

In western science, the earliest recorded examples of cosmology are to be found in ancient Babylon (circa 1900 – 1200 BCE), and India (1500 -1200 BCE). In the former case, the creation myth recovered in the EnûmaEliš held that the world existed in a “plurality of heavens and earths” that were round in shape and revolved around the “cult place of the deity”. This account bears a strong resemblance to the Biblical account of creation as found in Genesis. In the latter case, Brahman priests espoused a theory in which the universe was timeless, cycling between expansion and total collapse, and coexisted with an infinite number of other universes, mirroring modern cosmology.

The next great contribution came from the Greeks and Arabs. The Greeks were the first to stumble onto the concept of a universe that was made up of two elements: tiny seeds (known as atoms) and void. They also suggested, and gravitated between, both a geocentric and heliocentric model. The Arabs further elaborated on this while in Europe, scholars stuck with a model that was a combination of classical theory and Biblical canon, reflecting the state of knowledge in medieval Europe. This remained in effect until Copernicus and Galileo came onto the scene, reintroducing the west to a heliocentric universe while scientists like Kepler and Sir Isaac Newton refined it with their discovery of elliptical orbits and gravity.

The 20th century was a boon for cosmology. Beginning with Einstein, scientists now believed in an infinitely expanding universe based on the rules of relativity. Edwin Hubble then demonstrated the scale of the universe by proving that “spiral nebulae” observed in the night sky were actually other galaxies. By showing how they were red-shifted, he also demonstrated that they were moving away, proving that the universe really was expanding. This in turn, led to the Big Bang theory which put a starting point to the universe and a possible end (echoes of the Braham expansion/collapse model).

Today, the field of cosmology is thriving thanks to ongoing research, debate and continuous discovery, thanks in no small part to ongoing efforts to explore the known universe.

We have written many articles about cosmology for Universe Today. Here’s an article about the galaxy, and here are some interesting facts about stars.

If you’d like more info on cosmology, the best place to look is NASA’s Official Website. I also recommend you check out the website for the Hubble Space Telescope.

We’ve recorded many episodes of Astronomy Cast, including one about Hubble. Check it out, Episode 88: The Hubble Space Telescope.

Sources:
http://en.wikipedia.org/wiki/Cosmology#cite_note-5
http://en.wikipedia.org/wiki/En%C3%BBma_Eli%C5%A1
http://en.wikipedia.org/wiki/Timeline_of_cosmology
http://www.newscientist.com/article/dn9988-instant-expert-cosmology.html
http://en.wikipedia.org/wiki/Geocentric_model
http://en.wikipedia.org/wiki/Heliocentrism
http://en.wikipedia.org/wiki/Red_shift

Posted on by Steve Nerlich

Astronomy Without A Telescope – Blazar Jets

A 5000 light year long jet observable in optical light from the giant elliptical galaxy M87 - which is not technically a blazar, but only because it's jet isn't more closely aligned with Earth. Credit: ESA/Hubble.

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Polar jets are often found around objects with spinning accretion disks – anything from newly forming stars to ageing neutron stars. And some of the most powerful polar jets arise from accretion disks around black holes, be they of stellar or supermassive size. In the latter case, jets emerging from active galaxies such as quasars, with their jets roughly orientated towards Earth, are called blazars.

The physics underlying the production of polar jets at any scale is not completely understood. It is likely that twisting magnetic lines of force, generated within a spinning accretion disk, channel plasma from the compressed centre of the accretion disk into the narrow jets we observe. But exactly what energy transfer process gives the jet material the escape velocity required to be thrown clear is still subject to debate.

In the extreme cases of black hole accretion disks, jet material acquires escape velocities close to the speed of light – which is needed if the material is to escape from the vicinity of a black hole. Polar jets thrown out at such speeds are usually called relativistic jets.

Relativistic jets from blazars broadcast energetically across the electromagnetic spectrum – where ground based radio telescopes can pick up their low frequency radiation, while space-based telescopes, like Fermi or Chandra, can pick up high frequency radiation. As you can see from the lead image of this story, Hubble can pick up optical light from one of M87‘s jets – although ground-based optical observations of a ‘curious straight ray’ from M87 were recorded as early as 1918.

Polar jets are thought to be shaped (collimated) by twisting magnetic lines of force. The driving force that pushes the jets out may be magnetic and/or intense radiation pressure, but no-one is really sure at this stage. Credit: NASA.

A recent review of high resolution data obtained from Very Long Baseline Interferometry (VLBI) – involving integrating data inputs from geographically distant radio telescope dishes into a giant virtual telescope array – is providing a bit more insight (although only a bit) into the structure and dynamics of jets from active galaxies.

The radiation from such jets is largely non-thermal (i.e. not a direct result of the temperature of the jet material). Radio emission probably results from synchrotron effects – where electrons spun rapidly within a magnetic field emit radiation across the whole electromagnetic spectrum, but generally with a peak in radio wavelengths. The inverse Compton effect, where a photon collision with a rapidly moving particle imparts more energy and hence a higher frequency to that photon, may also contribute to the higher frequency radiation.

Anyhow, VLBI observations suggest that blazar jets form within a distance of between 10 or 100 times the radius of the supermassive black hole – and whatever forces work to accelerate them to relativistic velocities may only operate over the distance of 1000 times that radius. The jets may then beam out over light year distances, as a result of that initial momentum push.

Shock fronts can be found near the base of the jets, which may represent points at which magnetically driven flow (Poynting flux) fades to kinetic mass flow – although magnetohydrodynamic forces continue operating to keep the jet collimated (i.e. contained within a narrow beam) over light year distances.

Left: A Xray/radio/optical composite photo of Centaurus A - also not technically a blazar because its jets don't align with the Earth. Credit: X-ray: NASA/CXC/CfA/R.Kraft et al.; Submillimeter: MPIfR/ESO/APEX/A.Weiss et al.; Optical: ESO/WFI. Right: A composite image showing the radio glow from Centaurus A compared with that of the full Moon. The foreground antennas are CSIRO's Australia Telescope Compact Array, which gathered the data for this image.

That was about as much as I managed to glean from this interesting, though at times jargon-dense, paper.

Further reading: Lobanov, A. Physical properties of blazar jets from VLBI observations.