Sunday, October 7, 2012

Stellar Fingerprinting


As most of you are aware, since the 90's, astronomers have been scouring the galaxy, looking for alien planets that circle distant stars. Some of which, may harbor intelligent species that may or may not be anything like the life we're accustomed to here on Earth. Their efforts haven't been in vain as there are thousands of exoplanets that have been observed and confirmed. Most though are hot-Jupiter exoplanets that are composed primarily of gas, but orbit their parent stars at only a fraction of the distance that separates Mercury from our sun. Due to the difficulty of spotting the smaller, terrestrial planets that could harbor earth-like life -- not many of those discovered have been seriously considered as viable options for extraterrestrial beings to exist on. However, astronomers have developed a new system that could radically alter our terrestrial planet hunting methods.

This new method of discovery, nicknamed 'stellar fingerprinting,' is a technique that was first developed for looking for telltell signs of Earth-like planets that may exist in the Alpha Centauri A system, which is one of the brightest stars in the night sky and it just so happens to be one of the primary contenders for observation in the search for Earth-like exoplanets. In the past through our observations, one thing has became clear. Stars that are host to terrestrial planets appear to be slightly anemic (containing less iron than as per usual) compared to stars that are found to be wandering the galaxy alone.

Our best planet formation hypothesis says that a small fraction of heavy elements are locked up in the terrestrial planets, comets, asteroids, meteoroids and planetesimals in alien solar systems. Most of the rocky objects are born from the dust disk that encircles a star when it's still wrapped in its proto-star cocoon before the star transitions to main-sequence star, capable of fusing hydrogen into helium in its core. In this scenario, the star will lack certain elements for enrichment since most of them will never manage to be captured by the star's gravitational influence, before being engulfed by the star. Even a planet that's only a few times more massive than the Earth will in theory, use up a noticeable amount of the elements present in the planetary system.

When an astronomer from the University of Texas, Ivan Ramirez studied the composition of 11 targeted stars using spectroscopy to separate the starlight from various stars into a prism to see which elements are present in the stars, which corresponds to different wavelengths of light. What he found in his 'spectroscopic survey' was that 15 percent of solar type stars bears circumstantial evidence that the stars harbor terrestrial planets simply by observing the chemical composition of the star's spectral fingerprints. His number came in a bit lower than that of NASA's Kepler Space Observatory, which has detected over 2,300 alien planets to date -- with the numbers of confirmed exoplanets growing exponentially by day.

Ramirez used 16 Cygni, a triple star system that's located approximately 70 light-years from Earth as a test subject of some sorts. One of the stars in the system is host to a confirmed exoplanet, while its companion appears to be planet-less. In this system, the star with the planet was found to have a slight deficiency of heavier elements compared to its companion that doesn't have any.

As I mentioned earlier, by far, the most exciting candidate to use this technique lies only 4.3 light-years from Earth in the constellation of Centaurus, Alpha Centauri A -- the largest star in a triple star system, which are our closest stellar neighbors. Out of 85% of the stars that were studied in Ramirez's spectroscopic survey, Alpha Centauria A is the most similar to our sun in temperature and and iron abundance. To him, this strongly suggests that this is strong circumstantial evidence that one or more terrestrial planet is circling the star. Indeed, it may be MORE surprising if we *didn't* find an orbiting rocky planet since it's far enough away from the other stars in the multiple star system -- Alpha Centauri B, for a planet to remain in stable orbit around its primary parent star.

So far, no evidence by Kepler or Hubble has been presented to suggest any planets exist in Alpha Centauri A's system, but searches remain underway as I type this article. I think I speak for the entire scientific community when I say it would be a truly exhilarating moment to discover a terrestrial Earth-like planet located so closely to home. Not only is the distance pretty small in cosmological distances, but Alpha Centauri is approximately the same age as the sun. Therefore, it wouldn't be a ridiculous assumption to believe that its solar system could have evolved in a similar way and time-span to our own. If a terrestrial planet was discovered to have an atmosphere laced biotracers like methane, oxygen, carbon dioxide and ozone -- it may be that any life present on the planet may have had the time to evolve into multicellular forms of life.. perhaps even life that is semi intelligent? Regardless of whether life has began to thrive on this hypothetical exoplanet or not, there is a lot that could be learned from its discovery.. even moreso, it may aid us in understanding where planets of similar composition with similar stars went wrong in not allowing creatures such as you and I to exist.

- Jaime

Source Material:
"Stellar Fingerprinting Hints Nearest Star Hosts Planets:"
http://news.discovery.com/space/earth-like-planet-might-whirl-around-alpha-centauri-a-121003.html

"Our Galaxy May Have 50 Billion Exoplanets–and It’s Still Making More:"
http://blogs.discovermagazine.com/80beats/2011/02/25/our-galaxy-may-have-50-billion-exoplanets-and-its-still-making-more/

Further Reading:

"How do scientists know what stars are made of?"
http://wiki.answers.com/Q/How_do_scientists_know_what_chemicals_are_in_stars
"Kepler space telescope finds 1,091 new exoplanet candidates
http://www.wired.co.uk/news/archive/2012-02/29/kepler-data-dump

Image Credit: L. Cal├žada/ESO

The Largest Telescopes in the World



For some of us we've looked at getting a telescope, gone down to the street and seen telescopes going for prices between $200 all the way up to the fancy $8,000 mark. You know, the ones you look at dreaming that you could own or that your spouse would let you buy ;)

Well on a documentary entitled "Big, Bigger Biggest: Telescopes" it was mentioned that the 8m mirrors that went into the Large Binocular Telescope cost $10 million a piece and there are two of them!
While looking at telescopes like these I just wish I could afford one myself!

There are currently some very large telescopes scattered around the globe, some larger than others but not by much. Before having a look at some of the proposed telescopes to come it would be good to reflect on what we currently have to give a better appreciation of what is to come. Several of the current largest telescopes include:
Gran Telescopio Canarias
Keck
SALT

Gran Telescopio Canarias is a 10.4 meter telescope in the Canary Islands, Spain. The GTC is based on the design of the Keck telescope in that it's main mirror is made up of 36 smaller segments. It's a US$179 million telescope that began operations in 2007 although not officially opened until 2009. The GTC is at an altitude of 2,400 meters above sea level and it at this stage the largest optical telescope on Earth.

Keck is probably one of the more well known telescopes globally, although it is in fact two telescopes. Keck I and Keck II which are both 10 meter telescopes which can both work either on their own or together effectively one larger mirror. When both of these 10m mirrors work collectively they give the effective aperture of about 14m.

The Keck telescopes are located in Hawaii and have been running since 1993 and 1996 respectively at an altitude of 13,796 feet, 4,204m. Although Keck doesn't have the largest primary mirror in the world, the two of them combined does still make the largest optical telescope in the world.

Southern African Large Telescope (SALT) is the largest single mirror in the southern hemisphere and currently the third largest in the world. SALT is based on the design of Hobby Eberly Telescope but with some modifications to the design that allows it to have a larger field of view and effective collecting area. SALT is made of 91 individual 1.2m hexagonal mirrors which makes a mirror 9.8x11.1m . Unlike most telescopes SALT is designed to only move on one axis and is inclined at an angle of 37° from the horizon, designing the telescope in this way made is considerably cheaper even with the added complexity of the telescopes design. SALT is located at the South African Astronomical Observatory near Sutherland.

These are just a couple of the latest telescopes around the world at the moment but there are more to come, but that is a post for another day. For now though, just close your eyes and imagine being able to view the sky through a pair of binoculars like the Keck telescopes!

§ Colin

For additional reading:

http://astro.nineplanets.org/bigeyes.html

Image source:

https://www.sciencephoto.com/media/322000/enlarge
Credit: MAGRATH PHOTOGRAPHY/NIELSEN/SCIENCE PHOTO LIBRARY
Keck 1 and Keck 2

Inflation


Inflation. We’ve know about it for years, but when you tell a bunch of scientists ‘the universe is expanding’ they are going to ask ‘how fast.’ This is one of the greatest questions in cosmology, exactly how fast is the universe expanding and how fast is this expansion accelerating? Answering these questions will help give us a better understanding of everything, from the age of the universe to its ultimate fate. Once again, the Spitzer Space Telescope comes to the rescue.

Michael Werner from NASA’s Jet Propulsion Laboratory (JPL) says, “Spitzer is yet again doing science beyond what it was designed to do. First, Spitzer surprised us with its pioneering ability to study exoplanet atmospheres and now, in the missions later years, it has become a valuable cosmology tool.”

So, what exactly has Spitzer done? It has provided a more accurate measurement of the Hubble constant. This constant is named after Edwin Hubble who essentially confirmed the universes expansion. Later, it was proved that this expansion is accelerating. The Hubble constant is the value of the expanding universe. While making observations in long-wavelength infrared, Spitzer was able to improve on our past measurements by a factor of three.

The new measurement has determined that space is expanding at 74.3 plus or minus 2.1 kilometers per second per megaparsec. In other words, about 74.3 kilometers per second per 3-million light-years - that is about 46 miles per second.

Spitzer was able to obtain these measurements by observing Cepheids – a type of variable star that pulses at precise times. These pulses are also directly related to the stars brightness, so scientists are able to use them as a measuring stick by recording their brightness, comparing it to their know brightness, and using that to figure out how far that object is from Earth. Spitzer took measurements of 10 cepheids located within the Milky Way, then took measurements of 80 cepheids located in the Large Magellanic Cloud (a satellite galaxy to the Milky Way).

The new measurement decreases our uncertainty from percentages in the double digits to 3%, which is a magnificent improvement. That means we are 97% certain the new value for the Hubble constant is accurate.

That is an astonishing feat.

~Joshua

Sources and further reading: