Of this trio of planets, both the mass and radius is only known for GJ 357 b and the global team of scientists led by Rafael Luque, at the Institute of Astrophysics of the Canary Islands (IAC) on Tenerife who discovered the system, have calculated that it has a mean density like Earth.
"With a thick atmosphere, the planet GJ 357 d could maintain liquid water on its surface like Earth, and we could pick out signs of life with telescopes that will soon be online". And with the first TESS science conference taking place at MIT this week, a handful of new discoveries are slowly coming to light, including its discovery of three planets hiding around a nearby star.
TESS began its space operation in July 2018, promising to survey about 85 per cent of the sky.
One of the most intriguing discoveries just announced is GJ 357 d; a super-Earth located about 31 light-years away orbiting a diminutive M-type dwarf star that has been described as relatively inactive.
It may be noted that a super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune.
In February, TESS cameras caught the star dimming slightly every 3.9 days, revealing the presence of a transiting exoplanet - a world beyond the solar system - that passes across the face of its star during every orbit and briefly dims the star's light.
Follow-up observations from the ground led to the discovery of two more exoplanetary siblings: GJ 357 c and GJ 357 d.
"We describe GJ 357 b as a 'hot Earth, '" said Enric Pallé, study co-author and astrophysicist at the Institute of Astrophysics of the Canary Islands.
Dr Diana Kossakowski, from the Max Planck Institute for Astronomy in Heidelberg, said: "GJ 357D is located within the outer edge of its star's habitable zone, where it receives about the same amount of stellar energy from its star as Mars does from the Sun". An atmosphere could make it warmer.
In a nod to her institute's namesake, the late Cornell professor Carl Sagan, Kaltenegger said: "If GJ 357 d were to show signs of life , it would be at the top of everyone's travel list - and we could answer a 1,000-year-old question on whether we are alone in the cosmos".
The middle planet, GJ 357C, has a mass approximately 3.4 times Earth's, and orbits around its star every 9.1 days. That's not so great for life, as we know it, but it does provide researchers an opportunity to study its atmosphere because it's the third-closest exoplanet we've yet found.
The researchers also discovered more signals of exoplanets in the system. "It took TESS to point us to an interesting star where we could uncover them".
"TESS will cast a wider net than ever before for enigmatic worlds whose properties can be probed by NASA's upcoming James Webb Space Telescope and other missions".