NASA discovery: ‘most important planet ever found outside the solar system’.

This artist’s conception shows GJ 1132b (foreground) a rocky planet similar to the Earth in size and mass. Picture: Dana Berry of SkyWorks and provided by NASA

THERE’S a new rocky Earth-size planet on our galactic block, and it’s a sizzler.

Astrophysicists on Wednesday revealed the new-found world, GJ 1132b, named after the small nearby star that it orbits.

Even though the mercury can hit 450 degrees at this planet, it’s cool enough to have a thick Venus-like atmosphere. Lucky for scientists, it’s close enough to find out.

Planet GJ 1132b is just 39 light-years away, within the atmospheric study range of the Hubble Space Telescope. Given that a single light-year represents 5.87 trillion miles — the distance light can travel in a year — this planet is about 230 trillion miles away.

A team led by Massachusetts Institute of Technology’s Zachory Berta-Thompson discovered the planet in May, using telescopes in Chile. He and his colleagues reported their findings in the journal Nature on Wednesday.

While scientists said the planet is too hot for life, it’s still much cooler than the rocky fireballs known to orbit stars beyond our solar system. The official term for a planet outside our solar system is exoplanet.

“If we find this pretty hot planet has managed to hang onto its atmosphere over the billions of years it’s been around, that bodes well for the long-term goal of studying cooler planets that could have life,” Berta-Thompson said in a statement.

Berta-Thompson and the others estimate that GJ 1132b has a diameter of about 9,200 miles, slightly bigger than Earth. Its mass, however, is thought to be 60 per cent greater than Earth’s.

Its home star — GJ 1132 — is a red dwarf one-fifth the size of our sun. The planet circles every 1.6 days from just 1.4 million miles out, thus the heatwave.

A slight dip in the starlight every 1.6 days was the giveaway for the observing team.

Astronomer and journal author David Charbonneau, of the Harvard-Smithsonian Center for Astrophysics, said the team’s “ultimate goal is to find a twin Earth but along the way we’ve found a twin Venus”.

“We suspect it will have a Venus-like atmosphere, too, and if it does, we can’t wait to get a whiff,” he said.

The astronomers are seeking follow-up observations from Hubble and the Spitzer Space Telescope.

The James Webb Space Telescope, due to launch in 2018, and other future craft could provide even more details.

In a companion article in Nature, the University of Maryland’s Drake Deming revealed astronomers will be able to study GJ 1132b with “unprecedented fidelity” given its proximity and also the small size of its star, which should minimise light interference with the measurements. That, in large part, makes it “arguably the most important planet ever found outside the solar system.” He was not involved with the study.

It’s unknown, for now, whether this star system harbours other planets.