After over just a year in space, NASA’s Transiting Exoplanet Survey Satellite, TESS, has traveled more than 20 million miles at speeds of around 2,200 miles per hour. Hurtling through space, the telescope has discovered 10 new exoplanets outside the Milky Way. Now, TESS has found the first exoplanet close to the size of Earth. It’s the smallest planet identified at the halfway mark of its 2-year mission into space.
The small planet is named HD 21749c and orbits a relatively nearby star that is 52 light years from Earth. As it orbits the star named HD 21749, it travels so fast that it heats up to as much as 800 degrees Fahrenheit and makes a full orbit in just 7.8 days. NASA says the planet is 89% Earth’s diameter and its host star is 70% the size of our own Sun.
“The star that HD 21749c orbits is bright and relatively nearby, and therefore well suited to more detailed follow-up studies, which could provide critical information about the planet’s properties, including potentially the first mass measurement of an Earth-size planet found by TESS,” wrote NASA’s Rob Garner.
A larger previously-described planet, HD 21749b is closer to the size of Neptune, the 4th largest planet in our Solar System. The “sub-Neptune” exoplanet orbits around the same star in 36 days.
The astronomers from MIT have been able to determine that HD 21749c has a rocky uninhabitable surface. Although neither of these worlds seems to be habitable, (or are they?) the new findings may just be the beginning, as the researchers expect to find clusters of as many as two dozen exoplanets orbiting each star that they study with TESS. Some of those worlds may be within the “habitable zone” of the stars they orbit like Earth.
On the other hand, some scientists think there may very well be alien extremophiles capable of living in the harshest of conditions on planets like HD 21749c.
TESS member Diana Dragomir, the lead author of the paper announcing the new find in Astrophysical Journal Letters, says the Earth-size exoplanet marks a major milestone for astronomers.
“For stars that are very close by and very bright, we expected to find up to a couple dozen Earth-sized planets,” said Dragomir. “And here we are — this would be our first one, and it’s a milestone for TESS. It sets the path for finding smaller planets around even smaller stars, and those planets may potentially be habitable.”
MIT Torres Fellow Chelsea Huang introduces the newest @NASA_TESS planet, HD 21749, a small planet with the longest period yet from TESS. (Paper led by Hubble Fellow Diana Dragomir). pic.twitter.com/a4lK8eqqlG
— TESS at MIT (@TESSatMIT) January 7, 2019
According to MIT News, TESS uses four cameras to monitor the light emitted from the nearest and brightest stars in the sky. As an exoplanet passes in front of a star, it blocks the starlight temporarily, giving itself away to the telescope.
Here's an animated gif of FFIs from the first 8 TESS sectors, centered on the ecliptic pole, using swarp. Shows the continuous coverage in camera 4 nicely. pic.twitter.com/bU8WmvQKmV
— Roland Vanderspek (@twitspek) April 22, 2019
TESS can monitor the sky in month-long “sectors” that reveal the intensity of starlight across a huge swath of outer space. Then, software pinpoints patterns in the light intensity, revealing the signature of an orbiting planet. That data is so accurate that the planet’s mass can also be determined.
“Dragomir picked out this newest, Earth-sized planet from the first four sectors of TESS observations. When these data became available, in the form of light curves, or intensities of starlight, she fed them into a software code to look for interesting, periodic signals. The code first identified a possible transit that the team later confirmed as the warm sub-Neptune they announced earlier this year,” wrote Jennifer Chu for MIT News.
Examining the sector data, the astronomers find new exoplanets. So far they have worked with four sectors from TESS, and as the mission continues they expect to identify as many as 50 small, rocky planets and determine their mass.
Although astronomers have previously identified 2,662 planets using the now-retired Kepler Space Telescope, the new data from TESS focusses on the closest stars to Earth.
Kepler revealed that there are more planets than stars in the galaxy, so the sky is the limit for discoveries.
Last month, 18-year-old high school senior, Ana Humphrey, won a prize of $250,000 for calculating the potential for finding more exoplanets outside our solar system using the data collected by Kepler. That data could reveal as many as 560 more exoplanets upon closer examination.
She also won a $250,000 science prize🏆
— NASA Planetquest (@PlanetQuest) March 28, 2019
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Featured image: Screenshot via YouTube