YOU ARE HERE: Home > News & Press > News archive > News 2014 > One small star, one small planet... at least!

I want information on:

Information for:


One small star, one small planet... at least!

Last Updated on Tuesday, 04 March 2014 13:57
Published on Tuesday, 04 March 2014 03:00

A group of astronomers from the UK and Chile report the discovery of eight new small planets orbiting nearby red dwarf stars, three of which may be habitable.  From this result the scientists, led by Mikko Tuomi of the University of Hertfordshire, estimate that a large fraction of red dwarfs, which make up at least three quarters of the stars in the universe, has associated low-mass planets. The new work appears in the journal Monthly Notices of the Royal Astronomical Society.

Herts exoplanet smallArtist's impression of one of the newly discovered planets, in orbit around a red dwarf star at top left. Credit: Neil Cook, University of Hertfordshire. Click for a full-resolution imageThe researchers found the planets by analysing archival data from two high-precision planet surveys made with the Ultraviolet and Visual Echelle Spectrograph (UVES) and High Accuracy Radial velocity Planet Searcher (HARPS), both operated by the European Southern Observatory in Chile. The two instruments are used to measure how much a star is affected by the gravity of a planet in orbit around it.

As an unseen planet orbits a distant star, the gravitational pull between the two causes the star to move back and forth in space. This periodic wobble is detected in the star's light. By combining the data from UVES and HARPS, the team was able to detect signals that were not strong enough to be seen in the data from either instrument alone.

With this more sensitive technique, the astronomers discovered the eight worlds, three of which are in the so-called ‘habitable zone’ of their stars and only a little more massive than the Earth. Planets in this region, where the temperature is just right for water to be present as a liquid, are more likely to be able to support life.

All the newly discovered planets orbit red dwarf stars between 15 and 80 light years from the Sun, making them relatively close to the Solar system. The eight planets take between two weeks and nine years to complete each orbit, placing them at a distance from their stars of between 6 and 600 million km (equivalent to between 0.04 and 4 times the distance from the Earth to the Sun).

“We were looking at the data from UVES alone, and noticed some variability that could not be explained by random noise. By combining those observations with data from HARPS, we managed to spot this spectacular haul of planet candidates”, said Mikko Tuomi. “We are clearly probing a highly abundant population of low-mass planets, and can readily expect to find many more in the near future – even around the very closest stars to the Sun.”

The team used novel analysis techniques to squeeze the planetary signals out of the data. In particular, they applied Bayes' rule of conditional probabilities that enables us to answer the question “What is the probability that a given star has planets orbiting it based on the available data?” This approach, together with a technique enabling the researchers to filter out excess noise in the measurements, made the detections possible.

Hugh Jones, also from the University of Hertfordshire, says, “This result is somewhat expected in the sense that studies of distant red dwarfs with the Kepler mission indicate a significant population of small radius planets. So it is pleasing to be able to confirm it with a sample of stars that are among the brightest in their class.”

These discoveries add eight new exoplanet signals to the previous total of 17 already known around such low-mass stars. The team also plan to follow up a further ten weaker signals.


Media contact

Julie Cooper
University of Hertfordshire Press Office
Tel: +44 (0)1707 284095
This email address is being protected from spambots. You need JavaScript enabled to view it.

Science contacts

Mikko Tuomi
University of Hertfordshire
United Kingdom
This email address is being protected from spambots. You need JavaScript enabled to view it.

Hugh Jones
University of Hertfordshire
This email address is being protected from spambots. You need JavaScript enabled to view it.

John Barnes
University of Hertfordshire
This email address is being protected from spambots. You need JavaScript enabled to view it.

Guillem Anglada-Escudé
Astronomy Unit, School of Mathematical Sciences
Queen Mary, University of London
United Kingdom
This email address is being protected from spambots. You need JavaScript enabled to view it.

James S. Jenkins
Departamento de Astronomĩa
Universidad de Chile
This email address is being protected from spambots. You need JavaScript enabled to view it.


Other images

A number of other images are available from the Planetary Habitability Laboratory
Credit: Abel Méndez, University of Puerto Rico at Arecibo


Further information

The new work appears in “Bayesian search for low-mass planets around nearby M dwarfs – Estimates for occurrence rate based on global detectability statistics”, Mikko Tuomi, Hugh R. A. Jones, John R. Barnes, Guillem Anglada-Escudé and James S. Jenkins, Monthly Notices of the Royal Astronomical Society, Oxford University Press, in press.


Notes for editors

  • The University of Hertfordshire is the UK’s leading business-facing university and an exemplar in the sector.  It is innovative and enterprising and challenges individuals and organisations to excel.
  • The University is one of the region’s largest employers with over 2,650 staff and a turnover of almost £233 million. With a student community of over 27,200 including more than 2,800 students from eighty-five different countries, the University has a global network of over 175,000 alumni.
  • It is also one of the top 100 universities in the world under 50 years old, according to the new Times Higher Education 100 under 50 rankings 2012.
  • Research is at the core of the University’s strategy to facilitate far-reaching engagement with business, community and national and international partners. The University’s research is world-leading and has been recognised by the 2008 Research Assessment Exercise (RAE).

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

Follow the RAS on Twitter via @royalastrosoc