Astronomers Discover More Than 100 New Exoplanets

The finding increases the chances of habitability on TRAPPIST-1b and TRAPPIST-1c.

The researchers hope to use Hubble to conduct follow-up observations to search for thinner atmospheres, composed of elements heavier than hydrogen, like those of Earth and VENUS.

“These are the first planets that combine a few key properties”, lead author Julien de Wit, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences, told me.

To further investigate the promising planets, the researchers pointed NASA’s Hubble Space Telescope at TRAPPIST-1 just in time to catch a double transit, which is when two planets pass in front of the same star at nearly the same time. Were you to stand on one of TRAPPIST-1’s planets, the star would appear to have a low, dark-red glow.

“The data turned out to be pristine, absolutely flawless, and the observations were the best that we could have expected”, de Wit said.

However it is this kind of light that allows astronomers to make the observations that allowed them to discover the planets were rocky ones that could have an atmosphere like Earth, Venus or Mars.

Then, shortly before announcing the triple-find, the researchers realized that two of the planets would be transiting the star almost simultaneously, allowing the scientists a rare opportunity to study the planets’ atmospheres in one go.

“The data turned out to be pristine, absolutely ideal, and the observations were the best that we could have expected”, de Wit says. “The force was certainly with us”.

The dips in starlight that occurred when the planets crossed in front of the star indicated that the planets have compact atmospheres, which are more suitable to life. A big change would indicate the planets had light and large atmospheres such as with Jupiter, while little to no change would suggest a denser atmosphere on a rocky planet.

But that’s not the case.

“Now we can say that these planets are rocky”.

With the telescope trained on the star system, the researchers watched closely as the starlight dipped and flickered on its way through the atmosphere of each planet.

Now, scientists have said their atmospheres are likely to be similar to those of Earth, Venus or Mars, rather than being large and diffuse, as is the case with Jupiter. “The next step is to try to disentangle all these possible scenarios that exist for these terrestrial planets”. All were Earth-sized and may have regions with the right temperatures to support liquid water, and even life.

The system’s star, TRAPPIST-1, is an ultra-cool dwarf star – one just one-eighth the mass of our sun, and much cooler.

De Wit’s colleagues from the University of Liège came up with the idea to look for planets around such stars, as they are much fainter than typical stars and their starlight would not overpower the signal from planets themselves.

Using data gathered from the Hubble Space Telescope, researchers at MIT witnessed two occultation events from the innermost planets, TRAPPIST-1b and 1c.

Four larger versions of the Trappist telescope are now being built in Chile to focus on other ultracool dwarf stars in the southern sky.

This artist’s illustration shows two Earth-sized planets, TRAPPIST-1b and TRAPPIST-1c, passing in front of their parent red dwarf star, which is much smaller and cooler than our sun. They’re also raising money for similar telescopes set up to survey the Northern sky.

“Each telescope is about $400,000 – about the price of an apartment in Cambridge”, de Wit says.

“That was really, really, really last minute”, De Wit said, “but fortunately it worked out”.

De Wit added: “With more observations using Hubble, and further down the road with James Webb, we can know not only what kind of atmosphere planets like Trappist-1 have, but also what is within these atmospheres”. The launch of the James Webb Space Telescope in 2018 will also allow scientists to carry out detailed observations of the system.