Posts Tagged ‘star’

A Younger Version of Our Solar System

Wednesday, November 12th, 2008 by Bellatrix

New information about a neighboring star has shed some light on our theories of solar system formation and given hope to terrestrial planet hunters. The near by star Epsilon Eridani has features very similar to our own solar system, it is however much younger than our own system, perhaps giving us a glimpse to how our solar system might have looked in its very early stages.

The star itself is about 10.5 light years away. It is the third brightest star seen with the naked eye. The star is a K2 spectral type star; it is slightly smaller and less massive than the sun. It is thought to be less than a billion years old, where our sun is close to 5 billion years old. Because of it’s young age it has a much higher level of magnetic activity than the sun and a stellar wind about 30 times as strong.

Recently, using the Spitzer Space Telescope, astronomers have identified two areas of rocky rings, or asteroid belts, just like our solar system. It has an inner asteroid belt at an equivalent distance from its star as our asteroid belt to the sun. An outer asteroid belt is also present at about the position where our Uranus is. This outer belt contains about 20 times more material than the inner belt. A third ring of icy materials is set out about 35 to 100 AU from the star, very similar to our Kuiper Belt but with about 100 times more material. This extra material makes sense, given the systems age. Our solar system is much older and thus has had more time for collisions to take place and either destroy material or send it out of orbit.

Spitzer also noticed large gaps in these rings. The most logical explanation for these gaps is the presence of planets. Astronomers predict at least three planets with masses between that of Neptune and Jupiter, and another possible smaller planet may lie near the innermost ring. These gaps and the closeness of this star, plus evidence from other planet hunting techniques such as observing radial velocities, makes this star high on the list of planet hunters trying to find earth like planets, and even possibly life. With all the similarities noticed thus far between the two systems, one might think it surprising not to find smaller rocky planets in the inner part of the system.

Studying this system is exciting ad enlightening for astronomers. Seeing that our solar system is not totally unique means that our theories about how solar systems for may not be completely off base. Also, studying this solar system more intensely may show us things about our early solar system we wouldn’t have otherwise known. As the resolving power of our telescopes improve new discoveries from this system should be something to watch out for.

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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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