Posts Tagged ‘Spitzer space telescope’

A Mirror of Our Creation

Friday, October 31st, 2008 by Evan Finnes

In a planetary system only 10 light years away, Spitzer has discovered that there is much more to Epsilon Eridani besides a great setting for an Asimov novel. Epsilon Eridani is the star at the center of the planetary system closest to home. This Star is relatively young, perhaps less than a billion years old, and has a mass which is about .85 times the mass of the sun. As far as atomic creation goes, this sun is relatively inactive, producing not much more than Helium.

This system has been a source of great discovery; in the past it has been found to host two planets, an asteroid belt which orbits the star at a similar distance to which our asteroid belt orbits the Sun, and distant ring of dust and ice which is very similar to our Kuiper Belt. Recently, Spitzer observed that there is not just one, but two asteroid belts orbiting the not so distant star. What makes this discovery so exciting is the idea that by observing this system, we are basically looking back in history to observe our own creation.

According to the Nebular Hypothesis, solar systems are formed because massive clouds of dust and helium condense to form stars. This condensing occurs because these clouds are gravitationally unstable, so they collapse inwards into smaller clumps which accumulate to form a star, such as our Sun or Epsilon Eridani. As this star forms it sheds a disk of matter which over time begins to accumulate and form protoplanets. Although planetary formation is not well understood, it is thought by some that because of the gravitational pull of the forming star, the dense accumulating rock stays closer to and orbits the star, while the less dense gasses are able to stay further from the star in their orbit. This could be why the terrestrial planets such as Earth are closer to the Sun, while the gas giants such as Jupiter form much further out (of course there have been recent discoveries of gas giants closer to the sun than even Mercury).

Some theorize that the asteroid belts in our solar system are the result of the tidal forces produced by the gravitational pulls of the Sun and the gas giants. These tidal forces keep the rocks in the asteroid belt from coalescing to form protoplanets. The gas giants might also have another roll in solar system formation. It is possible that that the gas giants sweep out asteroids as they rotate the star, protecting the terrestrial planets from catastrophic impacts. However, some scientists also believe that the gas giants could act has a gravitational sling shot which could attract and hurl asteroids into the inner solar system.

One of the planets discovered to orbit Epsilon Eridani is located about 3.5 Au’s from the star, just outside of the range of the newly discovered asteroid belt. This is the first time a planetary system has been discovered to have an arrangement which is comparable to Jupiter and our asteroid belt.

Does this discovery prove that our solar system was formed with agreement to the Nebular Hypotheses? No, but it is defiantly worth observing this relatively young star system to see if its evolution correlates at all with any of our ideas. Who knows, maybe we could even watch as the formation of an Earthlike planet unfolds before our very eyes.

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Bigger, Brighter, and More Numerous

Friday, August 29th, 2008 by Bellatrix

Edmond Halley first discovered the star Eta Carinae in 1677. At first it wasn’t that special, it was a magnitude 4 star located in the Carina constellation in the Southern Hemisphere. However, people started to take notice when it kept changing its brightness. First, getting dimmer but then brightening and it has continued to brighten for several hundred years. Nowadays it is known as the brightest star in our galaxy. It has a mass more than 100 times the mass of the sun and is more than three million times brighter. Eta Carinae was thought to be at the limit of how large and how luminous a star can be; well there’s a new star giving Eta Carinae a run for its money.

A star nicknamed the “Peony Nebula Star” may be the new reigning champ for the title of brightest star in the galaxy. It has so far been estimated at 3.7 million times as bright as the sun, or 3.7 million solar luminosities. However, the mass seems to beat Eta Carinae, weighing in at 150 to 200 solar masses. Now this isn’t a newly discovered star, we’ve known that this star existed for some time, but had no idea about its astounding qualities. Peony is buried deep in the galaxy center where it was obscured from our telescopic eyes by gas, dust, and other types of interstellar medium. It was only recently with the help of the NASA Spitzer space telescope that we were able to peer through all of that and see the true star that lied beyond it all.

Spitzer was able to accomplish this because it is an infrared telescope and because it is a space telescope. Peony’s optical light is absorbed in all the interstellar gas and dust so we are not able to see it well on earth, but we would be able to see it’s infrared light. However, Earth’s atmosphere absorbs a very large majority of infrared radiation that comes to us, thus ground based telescopes are not able to see the infrared light from Peony. Spitzer solves these problems by being both above the atmosphere and an infrared telescope.

People first thought that stars like Eta Carinae were rare. This is because of something called the Eddington Limit. The Eddington Limit is a theoretical limit on the size and luminosity of a star, saying that if a star is much larger than about 100 solar masses the outward pressure of the radiation literally blows the star apart. And we now know that Eta Carinae is actually blowing itself apart. But now we may have to question how rare these stars really are and what the size limit really might be. As Spitzer continues to probe the center of the galaxy, where more of these monsters are thought to be hiding, we may have to change what we thought we knew about these massive fireballs.

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