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A second planet has been discovered orbiting Proxima Centauri - the closest star to the Sun

Our study, published in Science Advances, estimates that this planet could have a mass of about half that of the planet Neptune. Known as Proxima Centauri c (abbreviated to Proxima c), it has an orbit 1.5 times larger than Earth's orbit around the Sun

The discovered planet (right), next to Proxima Centauri (red), the smaller planet and the dust ring. Illustration: Lorenzo Santinelli
The discovered planet (right), next to Proxima Centauri (red), the smaller planet and the dust ring | Illustration: Lorenzo Santinelli

By: Hugh Jones Professor of Astrophysics, University of Hertfordshire
Translated by: Avi Blizovsky, editor of the knowledge site

Most of the planets outside the solar system are too far away for us to study them directly. It is therefore no wonder that the discovery of a possible planet around the Sun's closest neighbor, Proxima Centauri, a few years ago caused great excitement. Now astronomers have spotted what we think is a second planet around this star.
Our study, published in Science Advances, estimates that this planet could have a mass of about half that of the planet Neptune. Called Proxima Centauri c (abbreviated to Proxima c), it has an orbit 1.5 times larger than Earth's orbit around the Sun.

The star Proxima Centauri is the smallest star in the triple system in the Centaurus group. Because it is the closest star to our sun, it is commonly referred to as Proxima. This star was only discovered in 1915 by the Scottish astronomer Robert Innes because it is too faint to be seen with the naked eye. Like most stars, Proxima Centauri is a cool, small object known as a red dwarf. Their mass is about one eighth of the mass of the Sun and the apparent temperature is about half that of the Sun.

The previously discovered planet Proxima b is (most likely) a rocky planet orbiting the star in the habitable zone. However, Proxima b orbits relatively far from its cool star and is therefore unlikely to be habitable. If it has no atmosphere, it is likely that the temperature on its surface drops to minus 200 degrees Celsius.

Proxima b was discovered by analyzing the star's spectrum - light broken down into its wavelengths that provides a "fingerprint" that shows what the planet is made of. Small variations in the system's parent star can be observed to account for tiny movements of the star in response to the planet's gravitational pull. This method is called the radial velocity technique. The first signal was weak. However additional observations were made and those given a second time to verify the existence of the planet.

The history of discovering and understanding planets has progressed through a wide variety of techniques. The first planets were first discovered in 1992, from radio observations of a pulsar, the collapsing core of a giant star.

Efforts increased significantly in 1995 after the announcement of a planet in an orbit similar to the sun 51 Pegasi in the radial velocity technique. This discovery subsequently won a share of the 2019 Nobel Prize in Physics. However, there have always been concerns that apparent planetary signals could be caused by the activity of the star. Only after the year 2000 and the discovery of the planets using a variety of techniques, the existence of the planets outside the solar system became accepted.

A new discovery

We detected the new planet, Proxima c, using the same radial velocity technique as used in the Nobel Prize-winning study, but the signal is 40 times weaker and the planet's orbital period is 400 times longer. This made it a very challenging discovery. Just like our Sun, Proxima has spots caused by regions of intense magnetic activity that move in and out, varying in intensity over a variety of timescales. These qualities should be taken into account when searching for planetary signals.

This image combines a view of the southern sky from the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower right) and the binary star Alpha Centauri AB (lower left). J. Blatsky (LCO) / ESO / ESA / NASA / M. Zamani
This image combines a view of the southern sky from the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower right) and the binary star Alpha Centauri AB (lower left). J. Blatsky (LCO) / ESO / ESA / NASA / M. Zamani

The sunspots are apparently created by the accumulation of plasma, which causes leaks in the sun's magnetic field in a cycle of about 11 years. For the sun this time range is fairly constant, but the number of sunspots remains difficult to predict. Unlike the Sun, whose observations last for hundreds of years, we know much less about Proxima Centauri, and so it is possible that the cycle of the star's activity can mimic signs of planets. However, further observations could strengthen the evidence for the planet's existence.

The ideal way to verify its existence would be through direct photography. direct. However, for a planet this task would be difficult because they are usually too close to their stars to be seen from Earth with current technology – they are simply drowned in starlight. But Proxima is a cool, dim star, which makes the contrast between the star and its planets significantly easier. The distance and orbit of Proxima c allows us to see both in the sky using large telescopes on Earth.

The reported signal from Proxima c was detected using the La Silla Observatory in Chile, with a 3.6m optical telescope. The Extra Large Telescope, currently under construction on a nearby mountain, will be 39 meters in diameter and may discover Proxima c with the help of several instruments.

can we fly there
Proxima c is an ideal planet for follow-up studies compared to other planets discovered around more distant stars. In order to confirm its existence and characterize its properties, the development of modern technology will be required. However, Proxima C should provide an example of how exoplanets are really similar or different from planets in our own solar system.

Since Proxima is the closest star to our sun, you'd think it would be easier to travel there. However, at 4.2 light years it is still far too far for humans. If the distance between the Earth and the Sun was 1 cm, Proxima is 11 km away. However, an exciting project called Breakthrough Starshot plans to send chip-based spacecraft to the triple system that includes Proxima. Such a starship might be powered by lasers and arrive in the system in a few decades.

Ultimately, the detection of several signals from the nearest star shows that planets are more common than stars. Proxima is an excellent place for understanding the nearest planets and developing new technologies to better understand the universe we live in.

For an article in The Conversation

More on the subject on the science website

4 תגובות

  1. The lowest temperature is 173- absolute zero. And in the article a temperature of -200 is specified. is it possible
    .

  2. Every time a new star is discovered and it's like a world discovery. In fact there is nothing to it. It is known that the universe has billions upon billions of stars. Maybe when you find the means of existence you will publish. The chances of that happening are nil. Like a bacteria that floated in the test of my urine. He sure is the legendary pasta monster……
    Like the smallest fish in the sea that meets the leviathan and is sure that he is God...they will never understand and we are zeros like them and we will never understand anything.
    Then another star was discovered. Really nice...

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