Posts Tagged ‘planet’

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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Update on Extrasolar Planet Hunting

Wednesday, September 17th, 2008 by Bellatrix

So as fate would have it two days after writing my most recent blog entry, an article was published with the title “First Picture of Planet around Sun-Like Star”. In my previous blog post I mentioned how we had only indirectly observed planets around other stars and had yet to photograph one directly. Well first I must say that even before this new discovery, my statement was not entirely correct. Some people within the last year have claimed that they had photographed planets around stars. I did not mention it because the jury is still out on these pictures as to whether or not what is seen is actually an orbiting planet or perhaps just a background object.

However, even with those couple of photos floating around, this new one is slightly more interesting. Those few photos we have so far of possible planets have all been around very dim stars called red dwarfs or even dimmer brown dwarfs. This new picture is of a star that is very much like our sun. The planet observed is giant (about eight times the mass of Jupiter) and lies far out from its star (about 330 times the Earth-Sun distance). It’s large mass, or size, is one the key factors in being able to view it directly. This planet is extremely far out from its host star; for frame of reference, Neptune is our farthest planet and lies only 30 times the earth-sun distance.

The discovery was made by the Gemini North Telescope on top of Mauna Kea, which is associated with the previously mentioned Subaru Telescope. However, more studies will have to be done to prove this object is in fact orbiting the observed star, but evidence from the indirect method of detection supports the idea that this is not just a background object in the picture.

Given the distance to its star and other strange qualities such as its large mass and hot temperature (about 1500C compared to Jupiter at 110C), we may have to really start looking at our models of planet formation. Currently our theories would not predict, or allow for, such a planet to be where it is and how it is. For those who want to see the pretty picture of the planet, Google the star name 1RXS J160929.1-210524 (nice name huh?) or should be available from the Gemini observatory’s website.

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Extrasolar Planet Finding

Monday, September 15th, 2008 by Bellatrix

As of September 2008 a total of 309 extrasolar planets have been discovered. So far only massive gas giants, like Jupiter, have been detected, although some as small as Neptune. No terrestrial, or earth like planets, have been discovered yet. This is because of the current limitations on the technology, or the method, used to detect planets. However, this will hopefully be changing soon.

Currently it is difficult to locate earth-sized planets because they are very small, and do not give off much reflected light from their stars. So far no planet has been bright enough on its own to be detected by our telescopes. We can only detect planets by the small gravitational effects these planets have on their host stars. Planets do not have much mass compared to stars but the little mass they have exerts a pull on their stars; it makes them wobble slightly. We can use the Doppler effect to measure this wobble. The Doppler effect makes it so that the light from the star is bluer when moving toward us, and redder when moving away from us. So when watching a star with a planet around it, the pull from the planet as it orbits the star causes this shift in the observed light from the star, thus we know the planet is there. However, the mass of earth-sized planets is too small to create any noticeable wobble.

However, progress is definitely being made. The Subaru Telescope, located atop mount Mauna Kea in Hawaii, has an 8.2-meter mirror and has recently started scanning nearby stars looking for planets. There are eight innovative cameras and spectrographs at Subaru optimized for various astronomical investigations in optical and near-infrared wavelengths. One of these cameras is called HiCIAO, or High Contrast Instrument for the Subaru Next Generation Adaptive Optics. It is designed to block out the harsh direct light from a star, so that nearby faint objects such as planets can be viewed. The new adaptive optics system uses 188 actuators behind a deformable mirror to remove the atmospheric distortion from its view, allowing Subaru Telescope to observe close to its theoretical performance limits. The Subaru Telescope hopes to be the first to directly observe a planet outside our solar system.

Now even though Subaru hopes to be the first to direct image a planet, it still cannot detect an earth-sized planet. NASA was planning on launching a space telescope for this purpose called the terrestrial planet finder. This would consist of two observatories planned to not only detect these types of planets but also even study their characteristics such as size, distance from star, and even atmospheric components. However, due to budget cuts at NASA the project has been postponed indefinitely. I think until this project, or a similar one is funded and launched, we will continue to be limited by our current earth-based telescopes, and earth-like planets will remain outside our view.

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