Posted on 08/26/2004 3:46:32 AM PDT by alnitak
Fifteen years ago, the largest telescopes in the world had yet to locate a planet orbiting another star. Today telescopes no larger than those available in department stores are proving capable of spotting previously unknown worlds.
A newfound planet detected by a small, 4-inch-diameter telescope demonstrates that we are at the cusp of a new age of planet discovery. Soon, new worlds may be located at an accelerating pace, bringing the detection of the first Earth-sized world one step closer.
"This discovery demonstrates that even humble telescopes can make huge contributions to planet searches," says Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics (CfA), a co-author on the study.
This is the first extrasolar planet discovery made by a dedicated survey of many thousands of relatively bright stars in large regions of the sky.
It was made using the Trans-Atlantic Exoplanet Survey (TrES), a network of small, relatively inexpensive telescopes designed to look specifically for planets orbiting bright stars.
A team of scientists co-led by Edward Dunham of Lowell Observatory, Timothy Brown of NCAR, and David Charbonneau (CfA), developed the TrES network.
The network's telescopes are located in Palomar Observatory (California, USA), Lowell Observatory (Arizona, USA), and the Canary Islands (Spain).
"The advantage of working as a network is that we can 'stretch the night' and monitor our fields for a longer time, increasing our chance of discovering a planet," says Georgi Mandushev (Lowell Observatory), a co-author of the paper.
This research study is posted online and will appear in an upcoming issue of The Astrophysical Journal Letters.
"It took several Ph.D. scientists working full-time to develop the data analysis methods for this search program, but the equipment itself uses simple, off-the-shelf components," says co-author David Charbonneau (CfA/Caltech).
Although the small telescopes of the TrES network made the initial discovery, follow-up observations at other facilities were required.
Observations at the W. M. Keck Observatory which operates the world's two largest telescopes in Hawaii for the University of California, Caltech, and NASA, were particularly crucial in confirming the planet's existence.
Planet Shadows The newfound planet is a Jupiter-sized gas giant orbiting a star located about 500 light years from the Earth in the constellation Lyra. This world circles its star every 3.03 days at a distance of only 4 million miles (6 million kilometers), much closer and faster than the planet Mercury in our solar system.
Although such planets are relatively common, astronomers used an uncommon technique to discover it.
This world was found by the "transit method," which looks for a dip in a star's brightness when a planet crosses directly in front of the star and casts a shadow. A Jupiter-sized planet blocks only about 1/100th of the light from a Sun-like star, but that is enough to make it detectable.
"This Jupiter-sized planet was observed doing the same thing that happened in June when Venus moved across (or transited) the face of our Sun," says Mandushev. The difference is that this planet is outside of our solar system, roughly 500 light years away."
To be successful, transit searches must examine many stars because we only see a transit if a planetary system is located nearly edge-on to our line of sight. A number of different transit searches currently are underway.
Most examine limited areas of the sky and focus on fainter stars because they are more common, thereby increasing the chances of finding a transiting system.
However the TrES network concentrates on searching brighter stars in larger swaths of the sky because planets orbiting bright stars are easier to study directly.
"All that we have to work with is the light that comes from the star," says Tim Brown (NCAR), a study co-author. "It's much harder to learn anything when the stars are faint."
Most known extrasolar planets were found using the "Doppler method," which detects a planet's gravitational effect on its star by looking for motions in the star's spectrum, or rainbow of colors.
However, the information that can be gleaned about a planet using the Doppler method is limited.
For example, only a lower limit to the mass can be determined because the angle at which we view the system is unknown. A high-mass brown dwarf whose orbit is highly inclined to our line of sight produces the same signal as a low-mass planet that is nearly edge-on.
"When astronomers find a transiting planet, we know that its orbit is essentially edge-on, so we can calculate its exact mass. From the amount of light it blocks, we learn its physical size. In one instance, we've even been able to detect and study a giant planet's atmosphere," says Charbonneau.
Sorting Suspects The TrES survey examined approximately 12,000 stars in 36 square degrees of the sky (about half of the size of the bowl of the Big Dipper) in the constellation Lyra. Roi Alonso (IAC), a graduate student of Brown's, identified 16 possible candidates for planet transits. "The TrES survey gave us our initial line-up of suspects.
Then, we had to make a lot of follow-up observations to eliminate the imposters," says co-author Alessandro Sozzetti (University of Pittsburgh/CfA).
After compiling the list of candidates in late April, the researchers used telescopes at CfA's Whipple Observatory in Arizona, Oak Ridge Observatory in Massachusetts, and Lowell Observatory in Arizona to obtain additional photometric (brightness) observations, as well as spectroscopic observations that eliminated eclipsing binary stars.
In a matter of two month's time, the team had zeroed in on the most promising candidate. High-resolution spectroscopic observations by Torres and Sozzetti using time provided by NASA on the 10-meter-diameter Keck I telescope in Hawaii clinched the case.
"Without this follow-up work the photometric surveys can't tell which of their candidates are actually planets. The proof of the pudding is a spectroscopic orbit for the parent star. That's why the Keck observations of this star were so important in proving that we had found a true planetary system," says co-author David Latham (CfA).
Remarkably Normal The planet, called TrES-1, is much like Jupiter in mass and size. It is likely to be a gas giant composed primarily of hydrogen and helium, the most common elements in the Universe. But unlike Jupiter, it orbits very close to its star, giving it a temperature of around 1500 degrees F.
Astronomers are particularly interested in TrES-1 because its structure agrees so well with theory, in contrast to the first discovered transiting planet, HD 209458b. The latter world contains about the same mass as TrES-1, yet is around 30% larger in size.
Even its proximity to its star and the accompanying heat don't explain such a large size.
"Finding TrES-1 and seeing how normal it is makes us suspect that HD 209458b is an 'oddball' planet," says Charbonneau.
TrES-1 orbits its star every 72 hours, placing it among a group of similar planets known as "hot Jupiters." Such worlds likely formed much further away from their stars and then migrated inward, sweeping away any other planets in the process.
The many planetary systems found to contain hot Jupiters indicate that our solar system may be unusual for its relatively quiet history.
Both the close orbit of TrES-1 and its migration history make it unlikely to possess any moons or rings. Nevertheless, astronomers will continue to examine this system closely because precise photometric observations may detect moons or rings if they exist.
In addition, detailed spectroscopic observations may give clues to the presence and composition of the planet's atmosphere.
More articles here http://www.scienceblog.com/community/article3786.html and here http://www.lowell.edu/press_room/releases/recent_releases/TrES-1_rls.html.
The paper should be here http://arxiv.org/abs/astro-ph/0408421
We live WAY OUT in the boonies on a lake where there are no lights. Perfect gazing spot is off our back deck. We have a clear 360 degree view. Guess we lucked out, huh? Picnic is no problem, obviously.
Thanks much for the answer!
There are a bunch of good amateur astronomers on FR- Joe is one of them.
I have an ETX-90, I just moved cross country and haven't had a place to really play with it yet. Maybe very soon though.
I see that the DS-90AT has Autostar. The scope, generally speaking needs two things: polar alignment (Meade's documentation is usually pretty good at explaining this), and it needs to know where a couple of easy to find objects are. Also, it'll ask you the time, date, and latitude/longitude. Then the onboard computer will be able to find and track pretty much everything else.
Thanks!! And y'all keep the lessons coming. We want all the info we can get.
This'll keep you busy for a while! :-)
http://www.weasner.com/etx/links.html
Do you know your way around the sky? If you don't have one, a planisphere is a great help. You can buy one for a few dollars or make your own (try google). You need to get one for your latitude.
Oh and wrap up warm :-)
Since I live in Houston, I make mine as portable as possible. Unless the planets are up, there isn't much point to taking it out.
Pretty much the only bright, obvious thing in astronomy is the moon. The planets, mainly Jupiter and Saturn are good targets. Every few years Mars is a good target.
Everything else (nebulae,clusters) requires a big telescope to be any more than a faint fuzzy patch.
Pick up the book Nightwatch by Dickinson. I teach observational astronomy and use it in the class. Start by learning the night sky stars and constellations and you can find plenty of stuff without the fancy software.
Pick up the book Nightwatch by Dickinson. I teach observational astronomy and use it in the class. Start by learning the night sky stars and constellations and you can find plenty of stuff without the fancy software.
OH! OH! OH! Thanks for reminding me!
http://www.shatters.net/celestia/
Celestia- FREE planetarium software/visualization. Needs a little bit of computing horesepower to do it justice, but it's fun stuff.
One thing - get a flashlight with a red filter. It makes setting up the telescope so much easier and it won't spoil your night vision.
You probably have a local astronomy club too. They'll be happy to show you how to use your scope.
I wrote a high school paper on lens grinding (40 years ago) and am still at awe with amateurs that grind their own. I could probably make one that could be use as privacy screens in leaded glass art.
When I belonged to the Chabot Observatory, they had classes for it, and mirror-grinding. It was pretty straightforward- just required a lot of elbow grease. They had all of the necessary instruments for checking your work as you went along, and lots of helpful people to get you on the right track. Great bunch of people.
I recently got plans for a (mirror) grinding machine. I am almost scared to put the thing together, for fear of what I might do with it and how much money I might end up spending on building telescopes.
Several years ago I took a piece of glass with me on a business trip to San Diego and worked on it in their workshop. I got to look at Saturn through the scope (20" Clark refractor). Then I went to a star party on Mt. Hamilton and saw it through a 7" Astro-Physics refractor.
"Backyard Telescopes For New Planets"
Is this a new 527 group? :)
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