Habitable planet found
Astronomers have discovered the most Earth-
The star is called Gliese 581. It is among the closest of stars to us, just 20.5 light years away in the constellation Libra. It is a red dwarf.
These are small and faint, but they are the most common stars in our galaxy. Among the hundred closest stars to us, eighty are red dwarfs.
A team of Swiss, French and Portuguese scientists discovered the new planet using the European Southern Observatory 3.6-
This new exoplanet, which is what astronomers call planets in orbit around stars other than the sun, is the smallest yet found. It completes a full orbit in 13 days. It is 14 times as close to its star as the Earth is to the sun.
But Gliese 581 is much smaller and colder than the Sun. This makes it far less bright. So although the planet is so close it does lie in the habitable zone. This is the region around a star in which water on a planet would be liquid, rather than steam or ice.
"Liquid water is critical to life as we know it," says Xavier Delfosse. He is a member of the team from Grenoble University (France).
Because of its temperature and nearness to Earth, this planet will be an important target for future space missions looking for extraterrestrial life, he added. "On the treasure map of the Universe, one would be tempted to mark this planet with an X.
Red dwarfs are ideal targets for the search for planets like Earth, says Xavier Bonfils, of Lisbon University. "Because such dwarfs emit less light, the habitable zone is much closer to them than it is around the Sun."
Planets close to their suns are much more easily detected with the radial velocities method, the most successful method for detecting exoplanets. This looks for wobbles in the motion of the star caused by the planet, by studying small changes in the star’s light.
"We have estimated that the mean temperature of this super-
Its radius should be only 1.5 times the Earth’s radius, he added. "And models predict that the planet should be either rocky, like our Earth, or covered with oceans."
The same team of astronomers found a planet around Gliese 581 two years ago. It is 15 times as massive as the Earth. It is similar to Neptune, and has a year that is just 5.4 days long. At the time, the astronomers had hints of another planet. So they obtained a new set of measurements.
With these they found the new super-
HARPS can measure velocities with a precision better than one metre per second. It is one of the most successful instruments for detecting exoplanets, and holds several recent records. These include the discovery of a ‘trio of Neptunes’.
The new planet was detected through small changes it caused in the speed of motion of its star. These were only about 2 to 3 metres per second. This is the speed of a person walking fast. Such tiny signals could not have been detected with most spectrographs.
"HARPS is a unique planet-
"We are confident that, given the results obtained so far, finding a planet with the mass of the Earth around a red dwarf is within reach."
This research is reported in a paper submitted as a Letter to the Editor of Astronomy and Astrophysics.
What’s it all about?
What kind of story is this?
Learning to do science is about learning to think. Experiments, direct teaching, group activities and discussions all have a part to play. So do science news stories.
Like other non-fiction texts, science stories contain different kinds of statements. To get at the science behind the words -
We've met some of these in the later questions of the previous activity. Science news stories usually include the aims of the research or reasons for doing it. They often contain a hypothesis. Sometimes evidence for a hypothesis is given, or a hypothesis is used to make a prediction. Towards the end of a story the direction of future research the scientists are planning is often discussed, as well as outstanding questions the research will be designed to answer.
All these types of statement occur in some science stories. Virtually all science stories, however, will contain statements of the following four types:
- new findings or developments;
- the technology and methods the scientists used;
- previous or accepted knowledge, which may or may not be supported by the new findings;
- issues, implications and applications of the research.
So the next activity is designed to engage students with the latest science news by exploring the meaning and structure of a story as revealed by the content and balance of these four statement types:
Pulling it apart
In groups students should read through the story looking for new findings or developments. Once they have reached agreement, or at least consensus, and have underlined all the statements about what the scientists have just discovered or achieved, they can compare their thoughts with ours
In groups they should go through the story again looking for the technology and methods the scientists used in their research. Once they have reached agreement or consensus, and have underlined the statements that talk about the methods and equipment the scientists used, they can compare their thoughts with ours.
They should repeat the activity for existing knowledge and compare their thoughts with ours.
Any areas of disagreement in these activities - whether among the students, between teacher and students, or between the class and our own ideas - should be regarded as opportunities for discussion rather than errors to be corrected.
Having fully engaged with the latest science news through the above activities, students will be far better able to talk and think about the science and its implications than someone who has simply read about it in a newspaper or watched a brief item on television.
Now it's time for them to get to grips with the issues raised by the research.
Young people have opinions. But school science traditionally allowed little scope for forming and expressing these - which is why it turned many of them off the subject for life.
Putting it together again
In groups, students should read through the latest story looking for issues, implications and applications. Once they have reached agreement, or at least consensus, and have underlined all the relevant statements in the story, they can compare their thoughts with ours.
Having done all this the students are well armed to explore the issues raised by the story. A suggested discussion topic specific to this new story is provided below.
Topic for group discussions, web research or pupil presentations on the new exoplanet discovery
1. Discuss what effect the discovery of life on other planets would have on how people think about science. Would the subject become more popular? Would religions with their teaching that Earth humans are special fade away or be drastically modified? Would the answers to these two questions be different if the extraterrestrial life we discovered were intelligent beings like us or "just" micro-organisms?
2. There are now scientists called astrobiologists who aim to discover if there is life on other planets, by analysing the light that comes from them. Amazingly they are preparing to do this for exoplanets such as this latest discovery. Separating the light from these planets from the light from their stars has been compared to spotting a candle placed beside a lighthouse that is 1000 kilometres away. Students should read an interview with astrobiologist Giovanna Tinetti then in groups prepare a short presentation on what an astrobiologist actually does. Tips for science class discussions and groupwork
...there is a distinct trend to make better use of practical activity through class and group discussions both on the evidence for particular points of view and on the social issues concerned with the application of science. This technique of encouraging reasoned discussion amongst pupils is borrowed from successful practice in social studies and recognises the constructivist principle that learning is not just a matter of absorbing information, nor even of discovering information, but involves a paradigm shift in belief by learners which is most likely to be brought about by open discussion.
Adey, P. and Shayer, M. (1994) Really Raising Standards. London and New York: Routledge.