St Albans astronomer researches two new planets

Two new planets orbiting a very old star in a nearby galaxy have been reported in a new study by an international team of astronomers, including a St Albans researcher.

Local astronomer Dr Mikko Tuomi, based at the University of Hertfordshire’s centre for astrophysics research, said that one of these planets, circling Kapteyn’s star, could be ripe for life as it orbits at the right distance to allow liquid water on its surface.

Discovered at the end of the 19th century by the Dutch astronomer Jacobus Kapteyn, the star is the second fastest moving one in our sky and belongs to the galactic halo.

This “halo” is an extended cloud of ancient stars orbiting our Galaxy with very elliptic orbits.

With one-third of the mass of our Sun, this red dwarf can be seen in the southern constellation of Pictor with an amateur telescope.

Dr Tuomi said: “The planet known as Kapteyn b has a mass at least five times that of Earth and orbits the star every 48 days - this is an orbit where it might have liquid water.

“The second planet, Kapteyn c, is a massive super-Earth in comparison. Its year lasts for 121 days and we think it’s too cold to support liquid water.”

He added: “At the moment only a few properties are known for these planets, but by measuring their atmospheres with next-generation instruments which are under construction, we will try to establish whether these planets are water-bearing worlds.”

Guillem Anglada-Escude, the study’s lead author, from Queen Mary University of London, said experts had not expected to find such a level of variability in an old star, so they were on the lookout for planets.

He added that astronomers had used new data from an observatory in Chile to measure tiny periodic changes in the motion of the star.

Then, by using the Doppler Effect, which shifts the star’s light spectrum depending on its velocity, the scientists worked out some properties of these planets, such as their masses and orbital periods.

The study also combined data from two other high-precision spectrometers to secure the detection, including an observatory in Hawaii.

Kapteyn’s star is the 25th nearest star to the Sun and it is only 13 light years away from Earth.