How was Trappist-1 discovered?
I was going through all the questions in this community related to TRAPPIST-1 in order to know how planets TRAPPIST-1b to TRAPPIST-1h were discovered, but there aren't any.
How were they discovered?
Your question asks how Trappist-1 (the star) was discovered, but the answer that you've accepted states how Trappist-1b thru Trappist-1h (the planets) were discovered. Assuming that the accepted answer is what you were looking for, can. you update the question so it accurately reflects what you wanted to know?
Please also don't edit the question to include an answer -- you can post your own answer below. Please also summarize the video rather than just linking it (links are great for reference and further detail, but we want answers to be standalone -- a link-only answer becomes useless if the link goes down / video is removed / etc.).
The star at the center of TRAPPIST-1 is called 2MASS J23062928-0502285. It was discovered by the Two Micron All-Sky Survey (2MASS), which imaged the whole sky in the infrared between 1997 and 2001. This resulted in a catalog of over 300 million objects. TRAPPIST-1 itself was cataloged in 1999. The name is actually its coordinates in right ascension and declination.
The planets of the TRAPPIST-1 were discovered by the method of transit photometry. The way this works is a telescope watches a star for a period of time and records the amount of light coming from the star. They chart how much light is coming from the star as a function of time, creating a light curve. If they see periodic dips in the intensity from the star, there is a high likelihood that that star has a planet in orbit around it. The planet blocks the light from the star every time it passes between us and the star. This causes the dips in the light curve. One advantage to this method is that you can scan multiple stars in the same field of view, analyzing them all for planets.
By measuring how long it takes planets to pass in front of the star, how much light it blocks, and how often they orbit, scientists can calculate the masses of these planets and how far away from the star they are by using Kepler's laws of motion.
TRAPPIST-1 was initially determined to have planets orbiting it by the Transiting Planets and Planetesimals Small Telescope - South team. From their data they determined that it had at least 3 planets. One of these planets was in the habitable zone of the star. They published their results in the journal Nature in May 2016.
Once TRAPPIST had determined that the system had planets around it, NASA trained the Spitzer Space Telescope on it. Ground-based observations of Trappist-1 are difficult because it is so dim. Spitzer, an infrared telescope, made more precise measurements of the light curves and determined that there were at least 7 planets in orbit around it, 3 of which were in the habitable zone. Additional observations were made by numerous other telescopes including the Very Large Telescope, UKIRT, the Liverpool Telescope, and the William Herschel Telescope. The results were also published in Nature.
Here's an image showing the light curve of the TRAPPIST-1 system as measured by Spitzer.
the light takes 39 years to travel from there to here.. does it means that the state of that star system we know today is 39 years old? It may have been destroyed or anything by now and we don't know?
Yes, since the system is 39 light years away, it takes the light 39 years to reach us. Therefore what we're seeing is what the system looked like 39 years ago. However, on cosmic timescales, 39 years is a tiny, tiny amount. The odds that the system has changed significantly in that amount of time are incredibly low.
okay, well, what if the system has been destroyed and we kept on searching for life on it or even send a manned spacecraft (maybe 20 years from now) only to find out that it doesn't exists anymore? HAHA!
Again, the odds of that are pretty low. But even if it was destroyed, this system is a very important discovery, since it has so many earth-like exoplanets. Studying the system, even for just 20 years, could reveal a great deal of information about the formation of solar systems - a subject which we still don't know too much about.
yes, I agree with the fact that it is a very important discovery and am also very excited.
You don't need a transit photometric method to discover a star, you've got something wrong here in your understanding. See the correct answer below from @GBowman
@RobJeffries I assumed that Hammad was asking specifically about how the system and planets were discovered, rather than the star itself, as that is what all the hullabaloo is about.
Yes, of course. But if that *is* the question, it is a poor one, since the information is available in every news item that I have seen about the discovery.
@RobJeffries And yet, as far as I could tell, there hasn't ever been a question on here about how transit photometry works.
Do you happen to know how long between the dips of light are(and how long they last for)? Thanks
@Cruncher the length and period of the dips depend on the period of the planets and size of the star. Since Trappist-1 is so small and the planets are all orbiting very close to it, the dips for the innermost planet occur about every 1.5 days, while the outermost planet probably circles every 20 days. In each case, the dip only lasts for a few hours. I'll add a picture showing the light curve to the answer.
@HammadNasir If solar systems are getting destroyed in such a short time frame (Earth is 4 500 000 000 years old), we definitely want to know because chances are someone built a death star...
@RobJeffries I think the easiest way to resolve this is to modify the question to include the discovery of the star and the discovery of the planetary system. Then, both answers remain valid and the question is useful.