An exoplanet smaller than Earth

With the infrared Spitzer space telescope, a planet, which is one-third smaller than ours in diameter, has been detected. Registered as UCF-1.01, it spins close to a star situated 33 light-years away and may be covered in lava.

 

UCF-1.01: a world slightly smaller than the Earth and that spins around a star situated 33 light-years away from us. Due to the intense heat, it would be covered in magma (artist’s impression). Credit: NASA/JPL-Caltech/R. Hurt (SSC)

 

The vast majority of exoplanets, planets that orbit around other suns, discovered to date are larger than Earth. Is that to say that our world is an exception? Actually, no, due to technological limitations, telescopes used (on the ground or in space) detect larger planets more easily! Fortunately, the instruments and methods used are progressing and now astronomers are more often finding distant worlds that are no longer the size of Jupiter or Neptune, to make a comparison in our solar system.

A world of lava?
UCF-1.01 is an example. The GF 436 red-dwarf star, situated 36 light-years away from Earth, is also known to have a planet the size of Neptune (GF 436b). But by carefully analysing the infrared data from NASA’s Spitzer space telescope, the astronomer Joseph Harrington and his team from the University of Central Florida have noticed slight dips in the light streaming from the star which doesn’t explain the presence of the imposing GF 436b (when passing in front of its sun, the planet blocks part of the light, a detection method known as transit).

The Spitzer space telescope (illustration). Credit: NASA/JPL-Caltech/R. Hurt (SSC)

By quantifying the dips in luminosity and when they occur, the scientists have deducted that this UCF-1.01 presents a diameter of only 8,400km (12,756km for Earth) with a year lasting only 1.4 Earth days! This obviously implies that this world turns around its sun at a very close distance. A proximity that explains why it is estimated that the surface temperature must be 600°C. With such conditions, it is most probably a dead world and without any atmosphere, similarly to Mercury in our solar system. However, Joseph Harrington puts forward his hypothesis based on the fact that a temperature as high as this would be capable of melting the surface, “the planet could also be covered with magma” he said. A world of lava that could be just as well from a science-fiction novel!
The animated video below will take you from the Earth to UCF-1.01.



Published 20th July 2012