TRAPPIST-1 is an M8 dwarf star which is one of the coldest stars on the Hertzsprung-Russell Diagram. It has a surface temperature of about 2550 K (the Sun, by comparison has a surface temperature of 5800 K) and a mass of approximately 0.08 Solar masses.
Recently, astronomers led by Michael Gillon of the University of Liege announced that they discovered three planets orbiting TRAPPIST-1 using the transit method. The two closest are tidally locked to their parent star, much like the Moon is tidally locked to Earth. However, the third planet lies just at the outer edge or beyond the habitable zone of the star.
Theoretically, this planet could harbor life, but in all likelihood, it would nothing like Earth life. By being in the habitable zone, this means that water would be in liquid form, which astronomers believe would be necessary for life to exist.
Showing posts with label extra-solar planets. Show all posts
Showing posts with label extra-solar planets. Show all posts
03 May 2016
16 January 2015
Planets as Dark Matter
We know planets exist. We see the evidence right here in our own solar system. We have also found over 1000 exoplanets outside our solar system. So could planets also be a component of dark matter?
Yes and no. Yes, in that planets do not emit radiation in visible light (they can emit infrared if they are warmed by a parent star. They also reflect light that is incident on them if they have a large enough albedo. But if the planet is a rogue planet, i.e. does not orbit a star, could it be an answer to our dark matter question?
No, in that planets cannot make up a significant amount of dark matter. Just look at our solar system. Yes, Jupiter is a large planet, but even so, it is 1047 times less massive than the Sun. In our solar system, the Sun accounts for over 99.8% of all the mass including all the planets, dwarf planets, asteroid, comets, satellites, everything. Now imagine that all planetary systems are similar in this nature. Even if all planetary system had 10 planets, remember that those planets would only account for 0.2% of the mass of that system. That is not a lot of mass, especially considering what the curve looks like.
Yes and no. Yes, in that planets do not emit radiation in visible light (they can emit infrared if they are warmed by a parent star. They also reflect light that is incident on them if they have a large enough albedo. But if the planet is a rogue planet, i.e. does not orbit a star, could it be an answer to our dark matter question?
No, in that planets cannot make up a significant amount of dark matter. Just look at our solar system. Yes, Jupiter is a large planet, but even so, it is 1047 times less massive than the Sun. In our solar system, the Sun accounts for over 99.8% of all the mass including all the planets, dwarf planets, asteroid, comets, satellites, everything. Now imagine that all planetary systems are similar in this nature. Even if all planetary system had 10 planets, remember that those planets would only account for 0.2% of the mass of that system. That is not a lot of mass, especially considering what the curve looks like.
Could rogue planets then be the answer? Rogue planets had to form around a star. That is the definition of a planet - it formed from the stellar cloud that a star formed in. It become rogue only when the star supernovae or possibly a passing body (star, brown dwarf) pulled on the planet to eject it from the system. Rogue planets are out there, however the total mass they contain is not enough to give a significant dent to the dark matter issue.
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