11. August 2011 by RC Davison.

    The Hubble Space Telescope has taken a fascinating image of a planetary nebula known as the Necklace Nebula.

    Planetary nebula are the remains of a star like our Sun as it goes through the final stages of its life expanding and blowing off its outer layers.  The bright blobs embedded in the nebula are areas of gas that are energized by ultraviolet light from the star at the center.  The blue-green color of the nebula reflects the hydrogen and oxygen present, with red indicating nitrogen.  The Necklace Nebula lies about 15,000 light years from us and is located in the constellation Sagitta.

It’s interesting to compare this planetary nebula with the remains of the supernova 1987a:

     Another piece of cosmic jewelry, but one made from a very different process and from a star that was much larger than our Sun. The supernova is the foundry that produces all the heavy metals we have today, from the iron in the hemoglobin of your red blood cells to the gold and silver in the jewelry you may be wearing right now.

     Both of these nebulae are still evolving, and as time passes they will continue to evolve into new shapes, and eventually (10s to 100s of thousands of years) they will fade from view.  But, their remains will fuel the next generation of stars and planets in the cosmos.

Till next time,

RC Davison

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28. May 2011 by RC Davison.

     Kepler has opened up the Universe for us with evidence that there are many more planets orbiting stars than we previously thought.  The consequences of this is that the potential for life beyond Earth has grown exponentially.  Recent news from a team of astronomers lead by Takahiro Sumi from Osaka University in Japan and published in the journal Nature has revealed that there may be as many as 400 billion planets roaming the Milky Way Galaxy, free from their parent stars.

This discovery was made by using a technique called gravitational lensing or microlensing in this particular case.  According to Einstein’s General Theory of Relativity, the gravitational field of a massive object will bend light that passes through it.  This technique has been used to view distant galaxies that are behind an intervening large cluster of galaxies, which magnify and distort the image of the more distant objects.

In the case of gravitational microlensing, the intervening objects are these rogue planets and the distant objects are stars.  The alignment of the star, planet and Earth is almost perfect, such that when the planet passes in front of the star its gravitational field causes the star to brighten and dim in a predictable fashion.  This is a brief event and will not repeat itself.

These objects are similar in mass to Jupiter.  And, if they are truly planets or possibly brown dwarf stars (small stars that generate heat but are too small to trigger the fusion process to burn brightly), they may have been ejected from their solar system of birth through the normal dynamics that force a solar system into a stable state.  Interestingly, this challenges the definition of planet, which was decided upon by the International Astronomical Union (IAU) and led to Pluto’s demotion to dwarf planet, but that is a a discussion for another blog.

The objects detected are fairly massive, which begs the question: What about smaller Earth-like planets?  Can we see them and how many of them are there out there?  As usually happens in the world of astronomy, discoveries bring more questions than they answer.

The discovery of these objects challenges the current theories of planetary evolution and possibilities for life in the Universe.  More research in this area will be conducted when NASA’s Wide-Field Infrared Survey Telescope (WFIRST) is launched, allowing for the faster blips of light to be detected, indicative of Earth-mass type objects.

Till next time,

RC Davison

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24. February 2011 by RC Davison.

     Kepler’s been in the news lately, revealing some of its latest discoveries. At the time I’m writing this, Kepler has logged 1235 potential planets and 1879 eclipsing binary stars. Of the 1235 planetary candidates, 15 have been confirmed to be real planets. That may seem like a very small number, but it takes time to confirm these candidates with ground/space based telescopes. The number is sure to rise.

     As I was looking at the Kepler site, it struck me as to how small Kepler’s view is of the entire sky. It covers an area of about 105 square degrees. Now that’s a pretty large area when you consider that our full Moon spans about a half a degree, and has an area of about .2 square degrees. But, if you think about it from the point of view of the entire visible sky, which covers 41,253 square degrees (encompassing both the northern and southern hemispheres), Kepler is only sampling 0.25% of the sky! If Kepler’s sample of our galaxy is typical of the entire galaxy, then we could expect a minimum of about 500,000 planets in the galaxy with equivalent short period orbits.

      Remember that these planets pass between their stars and Kepler, so any star systems in which the planets rotate in a plane almost perpendicular to Kepler’s view would not be recorded. So, this rough number is even a smaller percentage of the potential total number of planets out there. Oh, and don’t forget about the moons that may orbit these planets (and others yet discovered) and could have atmospheres and environments conducive for life to form.

      Out of these potential candidates, 68 are known to be Earth-sized and 288 fit the category of “super-earth”-size ­-­ 2-5 times the size of the Earth. These are all rocky-type planets, verses the gas giants like Jupiter. Some of these are also in or near the habitable zones of the stars they orbit. This is a region where temperatures on the planets would allow water to exist in a liquid state, essential for most life as we know it on Earth.

      Almost two years of Kepler’s 3.5 year mission has passed, and it has documented 1235 planetary candidates. This means that these potential planets have passed in front of their parent stars at least 4 times in this two year period to provide reliable data to confirm that it’s a planet. In the next one-and-a-half years, more planets will be documented as they pass in front of their stars causing the star’s light to dim and allowing Kepler to record another transit. The longer Kepler looks at a star, the more planets it will see, because they are further from the star and have longer orbital periods.

      If Kepler were looking at our Sun, it would have already documented Mercury, because Mercury orbits the Sun every 88 days. (Actually it would have to be a much larger version of Mercury to be seen by Kepler.) Venus would also have been identified, with its orbital period of 224 days, three transits could have been recorded in two years. Earth could also be a likely candidate, but unconfirmed with two possible transits in the two year observation period. But, Kepler wouldn’t have anything more than possibly one transit for Mars and/or the other planets beyond it during this time period. With Jupiter’s orbital period of almost12 years, it would take 48 years for Kepler to gather enough data to confirm its existence.

      The cosmos is teaming with planets, I have no doubt. I also think that the cosmos is teaming with life, in some shape or form. Our own experience with extremophiles here on Earth should be a good indication that life will find a way. How advanced that life is, is open to debate. Time will tell.

     If you would like to participate in identifying potential planets from the data that Kepler has produced, take a look at the site: Planet Hunters. At the site you will go through some training and then will be able to identify transits that may indicate a planet passing in front of a star. A nice way to be able to participate in a profession astronomy project.

     As always, comments and discussions are welcome.

Till next time,

RC Davison

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28. December 2010 by RC Davison.

     In the last post (It’s Full of Galaxies) we saw an infrared image from the Herschel space telescope looking at a tiny piece of the cosmos revealing thousands of galaxies 10 - 12 billion light-years from us.  The image below is also an infrared image, but it is a view of millions of galaxies as taken by the 2MASS (Two Micron All Sky Survey) looking across the night sky.

      The blue band in the image comes from the stars in our own galaxy.  Note that the distribution of galaxies is not uniform, as one might expect but there are clusters, strings and webs of galaxies.  These structures are remnants of the big bang and the gravitational attraction between matter and the mysterious dark matter.  Think about this:  All of the matter we can see and account for in the Universe only adds up to about 4-5% of the total mass of the Universe!

     The  2MASS survey was conducted using two 1.3 meter telescopes, one in Arizona and the other in Chile, imaging the sky at 3 separate frequencies in the near infrared.  Imagine what this would look like if we were able to use telescopes in space that are above the filtering effects of our atmosphere in the infrared.

      Check these links for more information and a larger image.

Till next time,

RC Davison

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24. December 2010 by RC Davison.

      These are not stars but galaxies, thousands and thousands of them and each one containing billions of stars.  This snapshot from the Herschel infrared space telescope shows galaxies that are 10-12 billion years old with the red ones being the most distant.  The white  ones indicate galaxies with the greatest star formation.  Looking closely at the image one does not see an even distribution of dots/galaxies, which indicates that some of these galaxies were forming in clusters at that time.

     This image was one taken as part of the Herschel Multi-tiered Extragalactic Survey (HerMES) Key Project.  The purpose of the project is to study the evolution of galaxies in the distant cosmos.  This particular image lies in a region of space called the Lockman Hole, which is in the constellation of Ursa Major and provides a relatively unobstructed view into a far corner of the Universe.

     The next night you are out, take a look up into the night sky and think about the fact that all you can see is in the optical region of the spectrum.  Consider what lies beyond our narrow view of the vast cosmos.

Till next time,

RC Davison

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