Barnard's Star has planets after all

I remember reading old popular books claiming that Barnard's Star has planets - way back before the modern exoplanet era. Turns out it does, but probably not the ones it was supposed to.

The planet's mass is thought to be 3.2 times that of our own, placing it in a category of world known as a "super-Earth". It orbits Barnard's star, which sits "just" six light-years away. The star is an extremely faint "red dwarf" that's about 3% as bright as the Sun.

Co-author Guillem Anglada Escudé said the newly discovered world was "possibly a mostly rocky planet with a massive atmosphere. It's probably very rich in volatiles like water, hydrogen, carbon dioxide - things like this. Many of them are frozen on the surface".

Dr Anglada Escudé, from Queen Mary University of London, added: "The closest analogue we may have in the Solar System might be the moon of Saturn called Titan, which also has a very thick atmosphere and is made of hydrocarbons. It has rain and lakes made of methane."

The planet, Barnard's Star b, is about as far away from its star as Mercury is from the Sun. On distance alone, it's estimated that temperatures would be about -150C on the planet's surface. However, a massive atmosphere could potentially warm the planet, making conditions more hospitable to life.

When the next generation of telescopes come online, scientists will be able to characterise the planet's properties. This will likely include a search for gases like oxygen and methane in the planet's atmosphere, which might be markers for biology. "The James Webb Space Telescope might not help in this case, because it was not designed for what's called high contrast imaging. But in the US, they are also developing WFirst - a small telescope that's also used for cosmology," said Dr Anglada Escudé.

WFIRST will have a mirror the same size as Hubble's (2.4 m diameter), designed for big cosmological projects, with a budget of $3.2 billion. Calling it a "small telescope that's also used for cosmology" is a bit like saying that coffee is a minor drink popular in some parts of the world and also used to keep people awake.

"If you take the specs of how it should perform, it should easily image this planet. When we have the image we can then start to do spectroscopy - looking at different wavelengths, in the optical, in the infrared, looking at whether light is absorbed at different colours, meaning there are different things in the atmosphere."

https://www.bbc.com/news/science-environment-46196279