02/14/2006
Bent Light - New Planet
Oh, no! As I start to edit this column, the sound of a jackhammer resounds through our 3rd floor condo unit here on Marco Island. Last year in another condo it was the decks that were being torn up to address corroded reinforcing metal rods in the concrete. Now we find that hurricane Wilma is responsible for our current problem. Last week I mentioned that the upper floors of our new building suffered more water damage than the ground floor. So, in the 4th floor unit directly above ours, water got under the parquet floor and the workmen are now digging up the floor in every room of the unit! Things were so quiet for the first half of our stay.
At least there’s the consolation that we missed a humdinger of a snowstorm back home in New Jersey. However, it hasn’t been that warm here in Florida, sections of which were hit with temperatures at or approaching the freezing mark this week. Here on Marco Island, with early morning temperatures in the 40s and “breezy” conditions, I’m sure the wind chill factor was in the 30s. The cold temps and windy conditions have curtailed the number and duration of my predawn walks on the beach. The birds must be cold as well. I have seen a relatively small numbers of gulls and barely a handful of my favorites, the pelicans. Is it the cold weather or have I become jaded after all these years coming to Marco? The only thing that really caught my attention on these walks has been the brightness of the planet Venus in the predawn sky.
Unusual brightness of heavenly objects was the topic of an article that Brian Trumbore called to my attention recently. Last week, I touched on the discovery of the world’s smallest vertebrate, a tiny fish. How about the smallest planet? In the world of astronomy, there are a number of Holy Grails that are being pursued. One is to determine the nature of dark matter, another, to determine the origin and nature of dark energy. As we’ve discussed before, these mysterious dark things make up over 90 percent of our universe. However, for us mortals, the ultimate Holy Grail would be to find life on planets outside our solar system. This means we’ve got to find a planet about the size of Earth that orbits its star at a distance conducive to warmth and liquid water.
We haven’t found such a planet but the article I mentioned, from BBC News by science reporter Rebecca Morelle, tells of the discovery of the smallest, most Earth-like and most distant of the more than 170 planets found to date outside our solar system. The method and the effort behind the discovery is truly impressive and, as with so many important discoveries and inventions, this one traces back to Albert Einstein. Back around 1912, he predicted that a massive star’s gravity would be so great that a beam of light would be bent as it passed the star. It was the confirmation of this prediction that first brought public acclaim and, though hardly anyone understood his theories, everyone knew Einstein’s name.
Well, knowing that a star can bend light rays, what would you expect if a star passes directly between the light from a more distant star and our planet? While this is a rare event it does occur, thanks to the motion of the stars in our galaxy around its center. When it happens, the light from the more distant star is bent as it passes the closer star. The effect is like a lens, gathering light and magnifying the image of the farthest star, making it appear brighter. The magnified image is very small and, according to a press release from Princeton University, it takes a telescope that can produce images a thousand times sharper than does the Hubble Space Telescope. For this reason, the effect we’re talking about is called “microlensing”.
As we said, the chances of finding a case where a star passes directly between Earth and another star are small. However, there are a number of groups that are concentrating their efforts on searching for these rare cases. One of these groups is OGLE, a Polish/American operation led by Andrzej Udalski of Warsaw University and Bohdan Paczynski of Princeton University. Since 1992 OGLE has used the Las Campanas Observatory in Chile and currently employs the so-called Warsaw Telescope to observe more than 150 million stars each night!
It really boggles my feeble brain that they have mastered the handling of such huge amounts of data and can pick out changes in brightness that indicate microlensing. I like to think of it this way. You have a film taken one night with images of the 150 million stars. Take the same picture the next night and see if any of the stars are brighter. Sounds simple but that’s a huge number of stars! I assume they have very sophisticated computer programs for storing and interpreting the data.
It was Paczynski and his student Shude Mao who, in 1991, predicted that microlensing could be used to detect planets. We’ve talked before about two methods that have been used to find planets – the “wobble” in position of a star as its planet(s) orbit around it and also the decrease in light when a planet passes between the star and us. Pacyzynski and Mao’s proposal was that if the closer star has a planet, as the planet orbits it will have its own effect on the light bending depending on its position in its orbit. In 2004, OGLE and another microlensing group known as MOA (a New Zealand/Japan led group) announced the first unequivocal discovery of a planet using microlensing. The planet was the most distant found to that time and orbited a star near the center of our Milky Way galaxy.
Last month, OGLE, MOA and PLANET (another microlensing group) announced the discovery of not only the most distant, but also the smallest earth-like planet, OGLE-2005-BLG-390Lb. The name doesn’t trip off the tongue lightly but, at only about 5 times the mass of Earth, it’s the closest we’ve come to something resembling our own abode. The planet orbits its star in an orbit over twice as far out as our orbit around the Sun. Its sun is only about a fifth the size of our sun and it doesn’t burn as brightly, being what is known as a red dwarf. As a consequence, the planet, thought to have a rocky core, is extremely cold at over 350 degrees F below zero. Not a promising candidate for life as we know it. However, most of the other more than 170 planets discovered to date are vastly bigger or much too hot or both.
How did they detect this planet? I went to Princeton’s OGLE Web site, which shows the plot of the brightness data from various telescopes and pinpoints the star in a photo of hundreds or perhaps thousands of stars in the region nearer to the center of our galaxy. As the closer star crossed the path of the light from the distant star, the brightness of the latter slowly increased to a peak and then fell smoothly as the closer star moved out of the light’s path. As the light intensity was falling close to its normal intensity for the distant star, there was a blip in the curve, an increase in brightness that lasted only for a few hours. That’s how a new planet is discovered. You have to be lucky enough to catch that brief blip.
By modeling the shape and changes in brightness as the closer star and its planet passed in front of the distant star, researchers calculated the mass of the planet and its orbit and the mass of its star. This frigid planet orbits its red dwarf star roughly 25,000 light years away from us and is now the most distant planet we’ve found outside our solar system. That’s some 150,000,000,000,000,000 miles away, if my math is right, and that we can pick up that distant brief blip of light lasting just a couple of hours is truly remarkable.
OK, I’ve had my “fix” of universe-type stuff for this month. Regular readers will know that I’m hooked on such things. Now back to my beach walks and stuff down here on Earth, like dealing with the aftereffects of Wilma in our condo.
Allen F. Bortrum
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