Hubble Succeeds Where TESS Couldn’t: It Measured the Nearest Transiting Earth-Sized Planet. Twenty-two light-years away, a rocky world orbits a red dwarf. It’s called LTT 1445Ac, and NASA’s Transiting Exoplanet Survey Satellite (TESS) found it in 2022. However, TESS was unable to gauge the small planet’s size.
NASA’s Hubble Space Telescope measured the size of the nearest Earth-sized exoplanet, LTT 1445Ac. This planet is 22 light-years away from Earth in the constellation Eridanus. It orbits a red dwarf star and has a surface temperature of about 500 degrees Fahrenheit.
The Hubble Space Telescope found that LTT 1445Ac is 1.07 times Earth’s diameter. It’s a rocky world with similar surface gravity to Earth.
NASA’s Transiting Exoplanet Survey Satellite (TESS) found LTT 1445Ac in 2022. However, TESS couldn’t measure the planet’s size. TESS couldn’t tell if the planet was fully transiting its star or if it was just grazing the edge of the star.
The Transiting Exoplanet Survey Satellite (TESS) searches for Earth-like planets by looking for dips in the brightness of stars. These dips are caused by planets passing in front of the stars, blocking some of their light. The larger the planet, the larger the dip in brightness.
TESS scans the night sky using 26 sectors, each scanned for 27 days. The satellite focuses on M dwarfs, which are the most common type of star in the Milky Way. TESS also looks at younger and hotter stars than those in the Kepler mission.
TESS’s four cameras each have seven lenses, detectors, and electronics to detect exoplanets. Astronomers can use the data from TESS to calculate the size, density, and orbital period of the exoplanets
The Transiting Exoplanet Survey Satellite (TESS) has found over 4,000 candidate exoplanets. In 2021, TESS found 2,200 candidates, and by the end of the year, it had discovered over 5,000.
TESS’s observational program could identify as many as 20,000 new exoplanets. The satellite’s data could have an impact far beyond the search for life.
NASA’s Kepler/K2 mission is similar to TESS. The Kepler space telescope was launched in 2009 to find Earth-sized planets orbiting other stars
To find a transiting exoplanet with a telescope, you can use the transit method:
- Attach a camera to a telescope
- Continuously record the brightness of a star before an exoplanet passes in front of it
- Analyze the data to reveal a reduction in the star’s light curve
The brightness of the star will decrease slightly as the transit begins. The star will appear to be at its lowest brightness in the middle of the transit, when the planet is between the star and the telescope. As the planet completes its transit, the star’s brightness will increase.
Other methods for detecting exoplanets include:
- Microlensing: Measuring the gravitational lensing effect caused by the exoplanet
- Transit photometry: Subtracting the star’s light spectrum when the planet is hidden from the spectrum when it is visible
- Astrometry: Tracking the motion of a star using precise measurements
Telescopes can also detect planets orbiting other stars using these methods:
- Radial-velocity This method uses a prism to split a star’s light into a spectrum. The star’s slight movement in response to the planet’s gravitational pull can be detected.
- Astrometry This method measures the star’s position on the sky to detect its motion. The star’s wobble can indicate the presence of a planet.
- Spectroscopy This method samples the infrared light from a planet. The Hubble Space Telescope uses spectroscopy to map an exoplanet’s temperature and water.
Other methods include: Gravitational lensing, Doppler, Direct imaging
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