OGLE-2005-BLG-390Lb
Although the title may look like gibberish it is actually the catalogue name of the smallest mass extrasolar planet found to date; it is just 5.5 times the mass of the Earth and orbits its star at a distance 2.6AU. Each orbit lasts roughly 3800 days - much longer than it would be in our solar system - because its parent star is only about a fifth the mass of the Sun.
There are several techniques used for finding planets around other stars. The most obvious is to take an image of one. That is incredibly difficult firstly because the system is likely to be too far away to distinguish the planet and parent star and secondly because the parent star is so much brighter. It can be like looking for a glow worm next to a sport stadium's floodlight. A second technique finds planets by looking for the tiny wobble they impart on their star as the planet completes its orbit. This doppler method is easier to detect if the planet is larger and close to its star. A third method requires the plane of the planet's orbit to be lined up with the Earth; every time the planet passes between us and the star the overall amount of light is reduced. This is called the transit method and should be familiar to you if you saw the transit of Venus back in 2004.
OGLE-2005-BLG-390Lb was found using a totally different method; gravitational microlensing. This method relies on the star and planet passing directly infront of a distant bright object. As the closer star passes in front of a distant star it acts as a gravitational lens and magnifies the light of the further object. If you are monitoring the distant object you can plot a light curve - how the brightness varies with time - and you see a shape that looks a bit like a child's drawing of a mountain (see below). When the lensing star has a planet orbiting it, the planet can also add to this effect as it passes by. The light curve below shows the planet as the little 'blip' on the right-hand side of the 'mountain'. Measuring the size of the blip tells you about the mass of the planet that caused it.
The light curve of a planet 5.5 times the mass of the Earth CREDIT: PLANET, OGLE
This is exciting because it allows us to detect much smaller planets than is currently possible with the other techniques. The only trouble is that microlensing events are rare as they rely on a planetary system passing in front of another star. They are also one off events, so follow-up may have to wait for future space-based missions. Still, gravitational microlensing events such as this may find the first Earth-mass planet.
Comments: OGLE-2005-BLG-390Lb
This exo-planet got quite a bit of coverage here in New Zealand because several of the scientists involved are New Zealanders. However, there was some sloppy reporting as The Dominion newspaper and Channel One both said this was the most Earth-like planet yet discovered. They should have said the most Earth-like outside of our solar system; Venus is more similar to the Earth than OGLE-2005-BLG-390Lb.
Posted by Stuart on Friday 27th Jan 2006 (20:37 UTC)
I believe that the speculations on the existence of life in places like this new planet", they don't stop to be imaginative and until the moment we count or we doesn't want to have the necessary thing to find civilizations or already at least to find life outside of the earth. This new planet could be, from my point of view, one of those but next to our solar system.
Posted by FRANCISCO C.R on Monday 30th Jan 2006 (14:11 UTC)
I want to go there.
Posted by Darkmaster on Thursday 02nd Feb 2006 (13:42 UTC)
Could you please tell me what the name means? What is OGLE, BLG and Lb in the context of Astronomy? I'm just really really curious about it.. Thanks if you can help..
Posted by Megan F. on Wednesday 15th Mar 2006 (07:35 UTC)
OGLE is the name of one of the collaborations involved in the search for extrasolar planets. I suspect the rest of the designation is just a boring catalogue number, astronomers can often be found making lists of things, just like Charles Messier did.
Posted by Megan on Thursday 16th Mar 2006 (19:13 UTC)
As Megan says, OGLE is the name of the collaboration that discovered it. OGLE stands for Optical Gravitational Lensing Experiment. The BLG indicates that the observation was in the bulge of our galaxy rather than the Large or Small Magellanic clouds (LMC/SMC). These three areas are where the lensing folks tend to look the most as there are more stars. The 2005 is the year of discovery as you probably guessed anyway.
The Lb is a tricky one to work out. I'm not entirely sure, but it may be a designation of the type of variability that was detected in the foreground star - the one with the planet - that passed infront of the background star. Variable stars are given designations such as Mira, semi-regular (SRb) and cool irregular (Lb). I may be wrong about this though as it isn't my area.
Posted by Stuart on Friday 17th Mar 2006 (02:25 UTC)
Nice site!
Posted by Ian on Wednesday 16th Aug 2006 (23:16 UTC)
i wnt a similarities and differenciation chart between earth and ogle-2005-blg-390lb
Posted by ha ha ha ha on Saturday 30th Jun 2007 (12:08 UTC)