Category Archives: Astronomy

Articles related to the general science of Astronomy

715 Newly Verified Planets by the Planet Finder, Kepler

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On February 26, 2014 NASA announced that the Kepler Space Telescope had found 715 new planets. This is 715 verified planets, not planet candidates, as has been released in the past. This brings the total of verified planets to almost 1700, while the number of planetary candidates is over 3800. These planets orbit around 305 stars and are all multi-planet solar systems.

This is significant because the techniques established to verify these planets bypassed the process where other ground/space based observatories would observe the stars associated with planetary candidates to independently verify the presence of orbiting planets. This was done by measuring the transits of the planets or the star’s “wobble” as the planets tug on the star during their orbit. (For more information on these techniques, see the blogs Finding Exoplanets Part 1: The Transit Method and Part 2 – It’s All About the Mass).

So what did the wizards behind the Kepler telescope come up with to speed up the process? Well, they present an amusing and unique analogy that works quite well when you understand the entire picture. Quoting from their press release*:

“This method can be likened to the behavior we know of lions and lionesses. In our imaginary savannah, the lions are the Kepler stars and the lionesses are the planet candidates. The lionesses would sometimes be observed grouped together whereas lions tend to roam on their own. If you see two lions it could be a lion and a lioness or it could be two lions. But if more than two large felines are gathered, then it is very likely to be a lion and his pride. Thus, through multiplicity the lioness can be reliably identified in much the same way multiple planet candidates can be found around the same star.”

So, if you observe a star and you see evidence of transits—multiple transits—you are very sure that you have a multi-planet solar system; its not random noise. This is because the other sources of error: electrical noise in the detectors, eclipsing binary stars (of which 2165 have been discovered at the time of this article), background eclipsing binary stars or optical ghosting tend to lead to single transit-like events, which would cause confusion in identifying a single planet orbiting the star. This ability to filter out the random noise that might obscure the data leads to a confidence rate of better than 99% for these 715 planets. This conclusion was arrived at after careful statistical analysis of 340 planetary systems, taking into consideration false alarms, false positives and noise in the data. (Check out the references below for links to the papers presented on this technique.)

Within this collection of planets we have four that orbit in the habitable zone of their parent star (meaning liquid water could exist on their surfaces) and are less than 2.5 times the size of Earth. An important thing to keep in mind is that these results come from only the first two years of Kepler data. There is over another year’s worth of data yet to be released on Kepler’s discoveries.

Unfortunately, Kepler ended its planet hunting mission last year due to failures of two reaction wheel controllers (out of 4 total, one being a backup) that are used to precisely point the telescope. Kepler served its main mission and was given an extension to keep planet hunting, but that ended in the spring of 2013 with the failure of the second reaction wheel. It’s interesting to note that having only two reaction wheels prevented Kepler from counteracting the force being placed on it by the Sun’s light pressure, causing it to be unable to lock onto the star it was observing. But, Kepler is not down and out yet as there is a proposal—K2—which will allow the spacecraft to continue its planet hunting to a degree as well as observe star clusters, active galaxies and supernovae.

More planets, more possibilities of life elsewhere in the Universe—as we know it or not! Can’t wait for the James Webb Space Telescope to get into space and come online. The better we can see, the more we can see!

I’ll leave you with a new wallpaper—Change of Season. It’s not too hard to imagine an extraterrestrial planet in some distant star system, with the right geological evolution and astronomical orientation, that its inhabitants have built their own version of Stonehenge to mark the change of seasons.

3D Wallpaper: Change of Season

Change of Season

Till next time,

RC Davison

References:

*Kepler Press Release: For more information, images and video about this topic

Science papers – Lissauer et al, 2014; Rowe et al, 2014

The Multidimensional Constellation of Orion

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When we look at the night sky ablaze with stars it is very easy to interpret what we see as a two dimensional image. It’s difficult to associate depth to what we see, because all we see are points of light of varying brightness. We do equate distance with brightness, but overall it’s hard to get a real sense of depth in the night sky, partly because distance can be camouflaged by an object’s brightness.

The Moon and planets give us a little bit more of a visual clue, being bigger and brighter, but that may be more because we know they are closer and not because we perceive a distinct difference in distance. It’s easy to see why the ancient astronomers constructed crystalline shells to transport the stars, planets, Sun and Moon around the sky. The stars were the easiest, as they slowly shifted with the seasons and never changed position, but the planets, Moon and Sun (not to mention comets!) were a different story, and their observed behavior led to very complex solutions to explain their motions.

The constellation of Orion (Wikimedia Commons)

The constellation of Orion, the great hunter, floats across our night sky as the seasons change, just as it did for the ancients. It is a good example of a two dimensional construct that exists in a very three dimensional form—the stars and nebula that we see in Orion are not all at the same distance from Earth. If we could take a ride on a starship and gain a new perspective on this mighty constellation we would see a very different arrangement of stars. Check out the illustration below.

The depth of the Orion constellation. (Click for a larger image.)

This new perspective allows us to see that the star in Orion closest to Earth is Bellatrix, a blue-white supergiant, at 243 light years (ly).  The next closest star is Betelgeuse, the amazingly large red supergiant star at 643 ly. In the not too distant future we will have a ringside seat to a supernova explosion, as Betelgeuse will end its life in one of the most spectacular events in the cosmos.

The next closest star to Earth is Saiph, a blue supergiant that anchors the right leg of Orion. Saiph is followed “closely” by the brightest star in the constellation, Rigel, a blue supergiant about 17 times bigger than our Sun and part of a binary system. Although Saiph and Rigel are both blue supergiants, and Saiph is closer to us, it is dimmer than Rigel. The reason for this is that Saiph is hotter than Rigel and it radiates more light in the ultraviolet end of the spectrum, which we can’t see and therefore appears dimmer in visual part of the spectrum we are sensitive to.

The stars that make up the belt of Orion, Alnitak, Alnilam and Mintaka are all very similar second-magnitude stars, again blue-white supergiants. Alnitak has two smaller companions, making it a triple star system. Alnilam, the most distant of all the stars in the constellation at 1344 ly, makes up for that distance by being the brightest star in the belt. Mintaka is the right-most star in the belt and it is a binary star system with a small companion star.

The stars that make up the constellation of Orion, aside from Betelgeuse, are all hot, young supergiant stars that will end their lives in a supernova. Betelgeuse is just an example of what’s to come, having already entered its red giant stage. They all formed from the same molecular cloud, tens to hundreds of millions of years ago.

There is one more element to Orion that we can easily see with the naked eye, and that is the Orion Nebula, just below Orion’s belt. This nebula is a nest for new stars to form and there are many images on the web that show this in great detail. The nebula is not “within” the constellation as we might imagine it to be but is further from us, with published distances varying from 1300 – 1600 ly. The video below gives a very nice 3D fly through the Orion Nebula.

The Universe is boundless, and we, unfortunately, are at the mercy of our limited senses when we gaze into it. Thankfully we’ve been able to develop the technology that is just beginning to allow us to see the wonders it holds.  Keep looking up and remember, there’s more there than meets the eye…

Till next time,

RC Davison

Reference:

http://stars.astro.illinois.edu/sow/sowlist.html

Water, Water Everywhere?

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Water was once a commodity only thought to exist on our blue planet (once we got past thinking that Mars had a canal system and Venus was a tropical paradise!), but as we have advanced our technology and our observation techniques we’ve found evidence of water on our Moon and Mars and now on exoplanets a 1000 light-years away.  The more we look, the more we see that elements and conditions for life as we know it in the Universe are more common than we thought.

NASA has released a study that has detected water in the atmospheres of five exoplanets: WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b. These planets are very large and orbit very closely to their stars, earning the moniker, “hot Jupiters”. So they may not be havens for life as we see on Earth.  But, it does point to water being present in those solar systems, and there may be other planets around those stars yet to be discovered in the habitable zone that also have water and moderate temperatures more conducive for life.  Not to mention moons about those planets that also may be habitable.

The Hubble Space Telescope was used to observe the starlight as it passed through the atmospheres of these planets and astronomers teased-out the water signatures from the resulting spectra. The video below describes this discovery and the techniques used in finding the water. It moves along pretty quickly, presenting a lot of information, so you might want to pause it or play it again to pick up on the details.


(NASA’s Goddard Space Flight Center.  Additional animations courtesy ESA/Hubble)

What amazes me is that we are able to glean this information about these planets’ atmospheres at the distances of 500 to 1000 light-years. This is only one more example of the ingenuity and inventiveness the astronomical community has applied to pushing the boundaries of our knowledge.

There was a time when the consensus was that we would not be able to detect planets around another star, but in 1992 two planets were discovered around the pulsar PSR 1829-10. This was a surprise in that astronomers didn’t think a pulsar would have planets orbiting them. The first planet found around a Sun-like star was discovered three years later and is labeled as 51 Pegasi b, which is about 50 light-years away.

Many didn’t believe we would be able to directly image a planet around a star, but that was all changed in 2008 when a team of astronomers using the Gemini telescope in Mauna Kea photographed a planet about 8 times the mass of Jupiter around the star 1RXS J160929.1-210524, which is about 500 light-years from Earth.

Exoplanet circled in red around parent star. Image courtesy of Gemini Observatory

There were a number of other planetary images released later in 2008 by Gemini and Hubble.

As one might imagine, detecting elements and compounds in an exoplanet’s atmosphere was also thought to be beyond our reach, but that too has been disproven with this latest discovery. How long before we find oxygen, indicative of biological processes or the compounds of smog, indicating a potential industrialized society, around some other exoplanet?

These are good examples of what the human species can achieve when facing a challenge. We should have more faith in our abilities and realize that there is very little we can not do if we set out minds to it.  Who knows what else is out there to amaze us!

Till next time,

RC Davison

The Majesty of Saturn

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The Cassini spacecraft has been orbiting Saturn since June 30, 2004 and has returned many amazing images of this majestic planet. On July 19, 2013 Cassini took a series of images over a period of more than four hours that resulted in the image you see here. (Click on the picture for a larger image.)

Saturn small

Saturn as taken by Cassini on July 19, 2013

The planet is back-lit by the Sun and shows off its spectacular ring system in great detail. From the finely etched inner rings to the diaphanous outer “E” ring, which is created by the ice geysers on Saturn’s moon Enceladus. Enceladus can be seen as the bright dot embedded in the ring on the left side of the image. This ring system spans 404,880 miles (651,591 kilometers). Consider that the average distance between the Earth and our Moon is about 239,000 miles (384,000 km), one can see how our system would fit nicely within Saturn’s rings.

This image is even more remarkable because of the other celestial objects that are also present. Our home planet lies to the lower right of Saturn, while Mars and Venus are above and to the left. There are also seven Saturnian moons visible in the picture. Follow this link for a larger annotated image that highlights these objects.

This isn’t the first time Earth has been photographed from Saturn or even further from home. Check out the blog post “The Pale Blue Dot” if you would like to read more.

One last spectacular image of Saturn, which can be seen below was taken on October 10, 2013. Here, Cassini is flying over the top of the planet and the amazing hexagonally shaped weather system is in full view. If you zoom in to the image you can see numerous smaller cyclonic storms and circular weather patterns near the pole. (Click on the picture for a larger image.)

Saturn from above. October 2013. Image Courtesy of NASA/JPL

These are only a few representations of this beautiful planet that can be found at NASA’s JPL website. For a more detailed discussion of how the latest image of Saturn was taken and processed, check out CICLOPS (Cassini Imaging Central Laboratory Operations)  “The Day the Earth Smiled”.

Two last comments:

The amazing success of the mission, and the wealth of knowledge that Cassini has brought to us about this planet makes me wish that NASA had the foresight to launch similar probes to Jupiter, Uranus and Neptune. Imagine the wonders we would have discovered!

Lastly, Carl Sagan tried to put our fragile existence into perspective when he lobbied NASA to take the first image of our planet from the distant reaches of our Solar System – the original “Pale Blue Dot” image in 1990. For me, it’s hard to look at our planet as a few pixels in the vast blackness of the cosmos and not be reminded of the stark reality that this is the only home mankind has had—and will have—for many, many generations to come. We can’t afford to waste it.

Till next time.

RC Davison

Death in the Cosmos

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Death, is it the end of existence?

A large star will end its life in a supernova. A spectacular explosion that allows the star to outshine the galaxy it resides in. This explosion will seed the cosmos with elements that were made within the star as it aged, along with elements (like gold and platinum) that were directly produced during the supernova.

Supernova in the galaxy NGC1365. Image courtesy of Martin Pugh (http://www.martinpughastrophotography.id.au/)

Our Sun will not explode; it does not have enough mass to generate a supernova. But, it will eventually become a red giant and engulf the Earth, as it begins to burn helium after exhausting the hydrogen at its core. As the star consumes its helium it will go through a series of oscillations, shrinking and expanding. This process will blow off layers of material from the star that will form a nebula, called a planetary nebula, which will mark the location of our star as it shrinks down to a small white dwarf star and slowly cools over the eons.

The Ring Nebula, a planetary nebula 2000 light-years away. Image courtesy of NASA.

In both cases, material from the star is returned to the cosmos that can become the seed material for a new star and planetary system. So, the death of a star is really the beginning of a new generation.

Humans, every plant, animal, rock and drop of water on this planet were all formed from the elements cast into the Universe by stars that have passed out of existence. When we pass from the world of the living and are interred on this Earth, we will return our borrowed elements to Mother Earth. And, when the Sun goes through its final stages of life and our planet is consumed by the bloated star, everything on it will be returned to the cosmos and become the raw materials for a new solar system and maybe someday, a new form of life. As Carl Sagan said, we are all star stuff.

But, what of that collection of electrical impulses makes each of us unique, that makes us human—the soul, if you will? What happens to that entity?

Those with religious beliefs will say that the soul moves on to heaven or hell or some other after-life, depending on one’s conduct on Earth. Scientists may try to measure the change in electromagnetic energy a person has after death. But, the former provides no proof that we transcend to a higher plane of existence, while the latter only quantifies the energy we possess and doesn’t reveal the unique life-force it contains. The bottom line is that we just don’t know. That spark which makes us – us, is surely contained within the bounds of the cosmos. But, what it is, how it works, where it comes from and where it goes is a mystery.

Just as the star lives on by casting its elements throughout the cosmos, so does a person live on through the people they encounter in day-to-day life, from family to friends to co-workers to strangers. We all can carry some part of the essence of that person into the future, and we will pass it on to our friends, family and acquaintances through the stories we tell and the actions we take.

This cosmos we live in is so vast, with so many unknowns. We have many questions to answer, and many more to ask.

This post is dedicated to the memory of my father, Edwin Allen Davison Sr. (June 30, 1925 – September 21, 2013). His spark has been returned to the cosmos. I will miss our discussions of the wonders of our Universe…

Hubble Extreme Deep Field. Image courtesy of NASA

Till next time,

RC Davison

 

Neutron Stars, General Relativity and Elephants

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The discovery of an unusually massive neutron star with a white dwarf companion was revealed in a paper published by John Antoniadis, a PhD student at the Max Planck Institute for Radio Astronomy and others on the international team this past April. Using radio telescopes from observatories around the planet to identify and study the neutron star, and the European Southern Observatory’s (ESO) Very Large Telescope (VLT) with its FORS2 spectrograph located at the Cerro Paranal observatory in Chili, to study the white dwarf star, the astronomers have discovered the most massive neutron star found to date. Labeled as PSR J0348+0432, the neutron star weighs in at twice the mass of the Sun.

White dwarf star orbiting a pulsar, a neutron star beaming radio frequency energy, generating gravity waves as they revolve about a common center. Image courtesy of ESO

So what? One might ask.

Well, what’s remarkable is that this mass exits in a sphere only 12.4 miles (20 km) in diameter. This means that the density of the material inside this defunct star is on the order of 1 billion tons per cubic centimeter—the size of a sugar cube! The force of gravity on the surface of the star is 300 billion times stronger than what we experience here on Earth.

This super dense ball is rotating 25 times per second and has a white dwarf companion star with a mass 0.17 that of our Sun and a diameter of 56,000 miles (90,000 km) orbiting it every 2.5 hours. This neutron star is also a pulsar. It sends a highly directional beam of radio frequency energy out into the cosmos and provided the pulsating beacon that we detected to locate this unique stellar system.

This super massive star along with it’s companion provides a wonderful natural laboratory for Earth based astronomers to study Albert Einstein’s General Theory of Relativity, which describes how space is curved by mass and energy and we observe in part as gravity. Studying this high intensity gravitational system may help us better understand gravity waves, predicted by Einstein’s theory, and explore the realm where general relativity and quantum mechanics may meet.

The team of astronomers have already measured a reduction in the orbital period of 8 millionths of a second per year due to energy being radiated from the system by gravity waves, as predicted by general relativity. Although gravity waves have been inferred by this and other binary systems, they have yet to be detected by the Laser Interferometer Gravitational Wave Observatories—LIGO—facilities on Earth.

But, wait! A sugar cube size piece of neutron star stuff that weighs 1 billion tons? How do you wrap your head around that piece of information? How do you compare that to everything you touch in your day-to-day routine? Let’s see what a billion tons of stuff might look like.

A good, massive object that most people have a concept of might be the African bull elephant.

Weighing in at about six tons on average, ten feet high by twenty feet long and eight feet wide, we would need only 167 million bull elephants to equal one cubic centimeter of neutron star material. That’s a lot of elephants!

To get a better perspective on how large this number of elephants is, consider if you packed these pachyderms side by side, front to back, you would cover an area of 26.7 billion square feet. (Whoops! We’re back to billions again. Better to convert that to square miles/kilometers.) That’s 956.5 square miles (2477 sq km); equivalent to a square with sides 30.93 miles (49.8 km) long. You could comfortably park them all in the tiny country of Luxemburg, which has an area of 998 square miles (2586 sq km), with a little room to spare.

How about something bigger, even more iconic, like the Empire State Building (ESB). Standing 1,454 ft (443.2 m) high, it has an estimated weight of 365,000 tons. We would need only 2740 ESBs to offset a balance with 1 sugar cube-size piece of neutron star stuff on it. That’s at least a number we can begin to have an intuitive sense for.

So how much area would 2740 ESBs cover? With a foot print of 79,288 ft2 (7240 m2 ) or .003 square miles (.007 square km), our collection of buildings would cover 7.8 square miles (20.3 sq km) – about 1/3 of the island of Manhattan, which has an area of 22.96 square miles (59.5 sq km). It’s a bit hard to imagine a third of Manhattan covered in Empire State Buildings. But, we can reduce the number and get a better handle on a billion tons.

Let’s take our Empire State Building and make it completely out of gold, all 37 million cubic feet (1.04 million cubic meters) of it. With gold weighing 1204 pounds per cubic foot, the solid gold building would weigh 44.5 billion pounds or 22.3 million tons. Now all we would need is 45 of these precious metal buildings to reach 1 billion tons.

This gilded collection would cover about 23 city blocks or an area from where the ESB is now to Times Square, assuming two buildings per block. Try to imagine this the next time you fly to New York City: the core of downtown Manhattan populated with 45 gleaming, solid gold Empire State Buildings and all that is equivalent to 1 cubic centimeter—one sugar cube-size of neutron star stuff.

Hopefully this helped you get a little better feel for what a billion tons might be. It’s helpful to do these simple calculations and comparisons and try to put into perspective or get a better grasp on some of the enormous numbers that come out of the study of this amazing Universe we live in.

When considering the cosmos and all the numbers we produce to describe it, I cannot help but feel that all we hold dear on this tiny blue planet, floating through the vastness of space, is insignificant when compared to what we are immersed in. Yet, we are sentient beings, and curious about the Universe we live in and that makes us very significant, because for all we know now, we are the only creatures in this entire cosmos that are looking up and asking these big questions.

Till next time,

RC Davison

Link to the research paper: “A Massive Pulsar in a Compact Relativistic Orbit”, by John Antoniadis et al.

 

 

Asteroid 2012 DA14, Tunguska Impact, Meteor Crater, and the Russian Meteor of 2013

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(Post updated 2/19/2013 with latest assessment on asteroid from ESA.)

Wow! Two wake up calls for the planet Earth in one day! Maybe it’s about time that the people of planet Earth realize that they are inside the pinball machine that makes up our Solar System. Sooner or later that ball is going to hit us head on. Today we were lucky – twice!

Russian Meteor, February 15, 2013

The spectacular meteor that streaked across Russia’s sky Friday morning has been estimated to be about 56 feet (17 meters) across, weighing in at more than 7000 metric tons and moving at speed around 40,000 mph (64, 373 km/h). It exploded about 9-12 miles (15-20 km) above the surface of the Earth with an equivalent of 500 kilotons of TNT—30 times the energy of the Hiroshima atomic bomb.  The consequent shockwave shattered windows and damage buildings in and around the Russian city, Chelyabinsk, resulting in over 1000 injuries.

This meteor was not related to the flyby later in the day of asteroid 2012 DA14. This asteroid skimmed by the Earth at a distance a little over 17,000 miles (27,400 km). Friday, February 15, 2013 could have turned out a lot different if either of these cosmic messengers had a slight change in course, which in the case of the Russian asteroid, could have detonated lower and over a more populated area or for 2012 DA14, a direct hit instead of a near miss.

We have two good examples of the consequences of an asteroid the size of 2012 DA14 (150 feet, 45 meters, ~130,000 metric tons) hitting the Earth in the Tunguska explosion of 1908 in Siberia (120 feet, 37 meters, ~100,000 metric tons) and the nickel-iron meteor (150 feet, 50 meters, ~270,000 metric tons) responsible for Meteor Crater in Arizona.

Map of Tunguska Impact (Sullivan 1979 and Kridec 1966.)

The Tunguska explosion occurred in the air above Siberia at a height of about 28,000 feet

(8500 meters) and generated the equivalent energy of about 1000 Hiroshima atomic bombs. The result was over 800 square miles of forest destroyed and a shock waves that

were recorded as far as western Europe and registered a magnitude 5 earthquake. As of today, no crater has been found to mark an impact of the remnants of the asteroid, leading some to think it might have been piece of a comet that entered Earth’s atmosphere that day, which is made mostly of ice.

Meteor Crater (AKA Barringer Crater) Arizona – Wikimedia Commons

Contrasting Tunguska is the nickel-iron meteor that did leave a crater in what is now Arizona. About 50,000 years ago this meteor entered the atmosphere at a speed of about 27,000 mph (43,000 km/hr) and fragmented to some degree due to the stresses associated with entry into the atmosphere, but the bulk of it hit the Earth creating a crater that is 4000 feet (1200 meters) in diameter and 570 feet (174 meters) deep. The explosive energy released from the impact has been estimated to be as high as 200 times that of the bomb dropped on Hiroshima.

Impact effects at Meteor Crater – Image courtesy of the Space Imagery Center and/or David A. Kring

We see two very different effects from two similarly sized asteroids.  But, it is the different composition that makes the difference.  The high density nickel-iron meteor survives the descent to the surface, while the less dense, ice-rich meteor fragments due to the high stresses experienced in its passage through thicker layers of the atmosphere. The temperatures experienced by these fragments can reach 45,000 °F (25,000 °C) causing the massive fireball and resulting shockwave and destruction.

We don’t, by any stretch of the imagination have knowledge of every asteroid in the Solar System that poses a potential threat to Earth.  The more we look the more we see, and with regard to near Earth asteroids (NEA), the sooner we find them the better.  It is possibly the only natural disaster we may be able to avert, given enough time.

Till next time,

RC Davison

References:

Russian asteroid impact ESA update and assessment

The Tunguska Impact – 100 Years Later

Damage by Impact — the Case at Meteor Crater, Arizona

Barringer Meteor Crater and Its Environmental Effects

 

Planet Found in the Alpha Centauri System – Could Pandora Be Discovered Soon?

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Artist's illustration of the Alpha Centauri System. Credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)

Reminiscent of the movie AVATAR, a planet has been discovered in the nearest star system to our Sun, Alpha Centauri. This is a trinary system consisting of three stars: Alpha Centauri A, B, and C. Alpha Centauri A is the same type of star as our Sun but slightly larger while its companion, Alpha Centauri B is slightly smaller and cooler. Alpha Centauri C is a red dwarf star also known as Proxima Centauri and is the closest star to our solar system at a distance of 4.22 lightyears. Alpha Centauri A and B orbit each other at a distance of about 23 AU (Astronomical Unit: 93 million miles/150 million kilometers) or about the distance between the Sun and Uranus.

This newly discovered planet is no Polyphemus, the gas giant in the movie that the moon Pandora orbited. The planetary system was in orbit around the star Alpha Centauri A. This planet (designated Alpha Centauri B b) is in orbit about Alpha Centauri B and has an orbital period or year of 3.236 days. It’s mass (minimum mass) is 1.13 times that of Earth and it orbits its star at a distance of about six million kilometers, 3.6 million miles.

The simple facts about this planet belies the huge effort that was put forth to push the envelope of the technology and analysis techniques to find the planet.  This information was gleaned out of data collected from over of four years of observations using the HARPS spectrograph at the ESO LaSilla Observatory (See Finding Exoplanets – Part 2: It’s All About the Mass for more information on the HARPS instrument.) The team of astronomers, lead by Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper were able to improve on the sensitivity of the HARPS instrument by taking into account:

  • The radial motion of the Alpha Centauri star system relative to Earth
  • The stellar oscillation modes for Alpha Centauri B, akin to seismic vibrations
  • The granulation of the star’s surface (the convective zones of rising hot plasma and sinking cooler plasma on the surface, which contribute noise to the measured radial-velocity of the star)

    Image of the granulation of the Sun's surface. Image courtesy of ESA

  • The rotational contribution of the star (as the star rotates, the side moving toward us will be blue shifted while the side rotating away from us will be red shifted)
  • Spots on the surface that are brighter or darker than the mean
  • Magnetic cycle activity
  • Light from Alpha Centauri A contaminating the spectrum of the B star
  • Instrument noise.

After extensive data reduction and analysis, the team determined that the star was wobbling at a velocity of 51 cm/sec (20 inches/sec) due to the planet’s motion. This is about 1.8 km/hr or 1.1 mile per hour!

Although the planet discovered is too close to its parent star to be habitable, at least with life as we know it, the analysis techniques developed to pull the presence of the planet out of the noise can be used to identify planets with a minimum mass of 4 times Earth’s mass in the habitable zone of a star. This opens up a new category of planets that can be searched for.  Note that this is the first planet found in the Alpha Centauri, it may not be the last. It may only be a matter of time before a planet (or moon) like Pandora from AVATAR is found in a star system in the Milky Way.

Till next time,

RC Davison

References:
Planet Found in Nearest Star System to Earth: http://www.eso.org/public/news/eso1241/
Paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1241/eso1241a.pdf

Lithium, Stars and Planets

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On Earth, the element lithium has certain medicinal properties when applied to conditions like depression and bipolar disorder, and it is extensively used in the battery technology powering most of our portable electronics. In stars, the amount of lithium present is an indicator of the age of a star.

The older the star is, the lower the concentration of lithium measured in the photosphere – the part of the star that we can see. Typically as a star ages, lithium is moved through convective motion deeper into the star where the temperatures are higher and the element is consumed. When astronomers find a star that shows a higher than normal lithium content for its age, eyebrows get raised and heads get scratched.

After the big bang, the Universe (by mass) was about 75% hydrogen, 25% helium and extremely small trace amounts of lithium, all the other elements we have today have been synthesized in stars as they move through their normal life cycle.  Elements heavier than iron are produced when the more massive stars explode as supernova.  The first stars that formed after the big bang (called Population III stars) reflected the amounts of hydrogen, helium and lithium originally present.  Second generation stars (Population II) contained higher levels of the elements heavier than lithium thanks to the first generation enriching the cosmos, but these are considered “metal poor” when compared to Population I stars, like our Sun.  (Astronomers consider any elements heavier than helium to be metals.)

The planets that form around a star contain the primordial elements of the big bang, along with whatever new elements have been seeded in the protoplanetary dust cloud from novae and supernovae. Lithium is preserved in the relatively cold planets as they condense and solidify. If a planet containing lithium is pulled into its parent star, it will disintegrate, spreading its contents though out the star’s atmosphere. This mechanism can explain how a star can have a higher than normal lithium content for its age.  But, this process is transitory.  Eventually, the lithium will be processed by the star.

There have been two recent observations of stars that show higher than normal amounts of lithium:

One is associated with a red giant star (BD+48 740) that is suspected to have at least one planet orbiting it in a highly eccentric orbit. Dr. Alex Wolszczan, professor of Astronomy and Astrophysics at Penn State University, has led the team which discovered this youthful red giant. Evidence indicates that the star has a massive planet in a very elliptical orbit, which is unusual but can be attributed to gravitational interactions between planets in the solar system. This interaction may have contributed to another planet moving too close to the parent star and being engulfed as the red giant swells with age, giving rise to the higher than normal lithium content.

Red Giant engulfs one of its planets. (Image courtesy of NASA)

The other observation is of a star (#37934) in the globular cluster NGC 6121, also known as Messier 4 or M4.  The ESO (European Southern Observatory) has released an image of M4 and discusses the surprising discovery.

Globular cluster M4, NGC 6121 (Image courtesy of the European Southern Observatory)

This star peculiar in that it is exhibiting a much higher than normal level of lithium for the ancient stars (Population II) that typically make up globular clusters. In the paper presented on this observation the authors present two scenarios that may explain this star’s unusual concentration of lithium.  The first is that the star formed with a higher than normal amount of the element  – i.e. it was polluted by its environment.  The other thought is that the star, for some unknown reason, hasn’t processed the lithium like the rest of the stars in the cluster.  Both ideas are up for debate as there isn’t enough evidence to prove either one correct.

But, could this star have sacrificed one of its planets for a brief period of youthful lithium enrichment like BD+48 740? (This assumes that it has or had planets orbiting it.)

Star in M4 exhibiting higher than normal lithium levels. (Image courtesy of the European Southern Observatory)

Perhaps the discovery by Dr. Wolszczan and his team shows a stellar process that is more common than thought.  If one considers the high number of planets being discovered by Kepler, which is leading astronomers to predict even greater number of stars with orbiting planets, this idea may be even more plausible.

Another case of the cosmos leading us down a rabbit hole just like Alice in Wonderland – the more we look, the more we see and the more questions we raise.  The Universe just gets curiouser and curiouser!

Link to published papers:

BD+48 740 – Li overabundant giant star with a planet. A case of recent engulfment?

Lithium and sodium in the globular cluster M4. Detection of a Li-rich dwarf star: preservation or pollution?

Till next time,

RC Davison

Galaxies in Collision

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In the vastness of the cosmos it seems amazing that objects run into each other, but they do. The pervasiveness of gravity has dominated and shaped the Universe as we see it today, from simple planets and solar systems to vast galactic clusters containing thousands of galaxies bound together. Galaxies collide, and galactic collisions create some of the most beautiful structures we’ve seen in our search of the cosmos.

Here we have The Mice:

Two galaxies colliding, known as The Mice - NGC 4676. Image Courtesy of NASA/Hubble Space Telescope

The Exclamation Point:

Arp 302 - Two galaxies about to collide - Image courtesy X-ray NASA/CXC/IfA/D.Sanders et al; Optical NASA/STScI/NRAO/A.Evans et al

Sometimes what appears to be a collision about to happen is really a case of one’s perspective, as can be seen in this image from the Hubble Space Telescope of NGC 3314.

Colliding galaxies? Not really. Image courtesy of NASA/Hubble Space Telescope

The galaxy that we see almost face-on – NGC 3314a is in the foreground and is tens of millions of light years from the background galaxy NGC 3314b. These two galaxies will not become another statistic in the annals of galactic collisions. But, the same can not be said for our own Milky Way galaxy and the Andromeda galaxy (M31).

In the next four million years or so, these two galaxies will begin to become one through a graceful pas de deux that will take millions of years and result in what theory predicts will be a large elliptical galaxy. This information, along with some amazing simulations and illustrations can be found at the Hubble Space Telescope’s site.

Here’s a graphic illustrating the collision showing the paths of the two galaxies along with another galaxy in our Local Group, Triangulum (M33):

Illustration of the Milky Way and Andromeda galaxies ultimate demise. - Image courtesy of NASA/Hubble Space Telescope

In this artist’s conception, the collision is seen from the perspective of an observer on Earth.

Illustration of the Andromeda galaxy's approach - Image courtesy of NASA/Hubble Space Telescope

The last few frames shows how Andromeda dominates the night sky and effectively blocks our view of that portion of the Universe. Future astronomers will not be able to appreciate the night sky as we are able to today.  But, who knows if humans will still be observing the Universe by the time this event takes place.

Looking at these images I can’t help but wonder about the alien astronomers living in the Triangulum galaxy. What a spectacular view they have of this doomed pair of galaxies. I wonder if they have mapped out the motions of these island universes (as they were once known) and understand that they will eventually collide. And, even more mind-boggling: Are they looking at us and wondering if someone is looking back?

Till next time,

RC Davison