Researchers from Denmark help to discover distant planets using an old telescope from 1975

Tech Science 13. sep 2021 3 min Professor Uffe Gråe Jørgensen Written by Kristian Sjøgren

An international research team with participation from Denmark used a series of small telescopes to identify a low-mass planet orbiting a low-mass dwarf star halfway across our galaxy. However, finding life on other planets looks increasingly unlikely.

It might be assumed that discovering distant planets requires gigantic and very expensive advanced telescopes. However, scientists can find planets with them – but surprisingly only nearby in our galaxy.

By contrast, a small Danish telescope from 1975 and a technology especially suited to this type of observatory can discover planets on the far side of the galaxy.

This is precisely what researchers from Denmark achieved using a telescope in Chile with a mirror measuring only 1.5 metres in diameter.

They found a planet orbiting a dwarf star 20,000 light-years away. The planet is within the zone where life could be present, but the discovery is interesting for another reason.

“The interesting thing is that we can find planets that are so far away with such a simple telescope. Moreover, the method of finding the planets is extremely suitable for identifying the planets that are similar to those in our solar system. Other methods are also really good, but they often find planets that are so close to the star that life cannot exist there,” explains a researcher involved in discovering the new planet, Uffe Gråe Jørgensen, Professor In Astrophysics, Centre for ExoLife Sciences, Niels Bohr Institute, University of Copenhagen.

The discovery has been published in The Astronomical Journal.

Several methods for discovering planets orbiting distant stars

Space researchers, such as Uffe Gråe Jørgensen, use three methods to find distant planets.

  • Researchers measure the light from distant stars using the true eclipse method. If the light becomes dimmer, this indicates that a planet is passing in front of the star. By measuring the reduction in light intensity, researchers can calculate how big the planet is and how far from the star it is orbiting.
  • Another method analyses the light spectrum from the distant star. When a planet passes around a star, gravity pulls the planet towards and away from us, and this changes the light spectrum. This enables researchers to determine whether a planet is rotating around the star and how large it is.
  • The third method that Uffe Gråe Jørgensen and colleagues used to find the new planet (OGLE-2018-BLG-1185b) uses the effect of relativity on light from distant stars. Researchers look at two stars that are aligned. The light from the star behind will be deflected around the closer star, and researchers can analyse this deflected light to determine whether planets are rotating around it.

“This last method is good for finding planets similar to those in our solar system. They may also be the most likely places for finding life,” says Uffe Gråe Jørgensen.

New low-mass planet is 20,000 light-years away

OGLE-2018-BLG-1185b offers little hope for finding life.

It is hard to imagine life being possible on a planet that is 10 times larger than Earth with enormous gravitational force. In addition, it probably comprises a solid core and a huge amount of gas.

OGLE-2018-BLG-1185b is 20,000 light-years away, and the researchers discovered it by examining the deflection of light from a star 30,000 light-years away.

“Our whole fascination with finding other planets is based on the question of whether we are alone in the universe or not. Mapping the planets orbiting around other stars are part of understanding the possibilities. However, as we discover more and more planets, we find that not many solar systems are like ours,” explains Uffe Gråe Jørgensen.

Life on other planets increasingly unlikely

According to Uffe Gråe Jørgensen, researchers are trying to determine whether a solar system like ours is the norm and what enabled life to emerge here.

For the Earth, water is one prerequisite.

A theory in this field claims that the past movements of Jupiter and Saturn helped to send many icy comets to Earth and thus created the oceans.

If this theory is correct, researchers not only have to find Earth-like planets around distant stars but also have to find them in solar systems that also have some large planets like Jupiter and Saturn.

This inevitably narrows the field of candidates.

“Our measurements indicate that this is not very common. Our best guess right now is that only about one in a hundred stars have Earth-like planets and also have other large planets similar to our solar system. This limits the possibility for life, not to mention the possibility of finding intelligent life and civilisations,” says Uffe Gråe Jørgensen.

Uffe Gråe Jørgensen also points to another fact that suggests that we may be alone – at least in our own galaxy.

“If other intelligent civilisations are out there and have been looking at other planets and may have been engaged in space flight and exploration of space much longer than we have, then it is only natural to ask why no one has been here and said hello,” concludes Uffe Gråe Jørgensen.

OGLE-2018-BLG-1185b: a low-mass microlensing planet orbiting a low-mass dwarf” has been published in The Astronomical Journal. In 2019, the Novo Nordisk Foundation awarded a grant to Uffe Gråe Jørgensen for the project Effects of Bacteria on Atmospheres of Earth, Mars, and Exoplanets – Adapting and Identifying Life in Extraterrestrial Environments.

The first exoplanets, i.e. planets outside our own solar system, were discovered only a few decades ago. Today we know of thousands of them, and they...

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