How to find the planets

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Fun Facts for Spica

All Planets are on the same Arc in the Sky

During a year, the Sun appears to move on a path called the “Ecliptic” which leads through 12 constellations. These constellations are: Aquarius, Capricornus, Sagittarius, Scorpius, Libra, Virgo, Leo, Cancer, Gemini, Taurus, Aries, and Pisces.

Now, the ecliptic is the plane of Earth’s orbit around the Sun, while the other seven planets are moving near the ecliptic which passes through the above 12 constellations.

So, you will find any planet somewhere in either constellation. A planisphere for your location will show you which constellations are currently up over the horizon.

Above an example to show why you see a certain planet in a certain constellation. Viewing from Earth, you see Saturn in the constellation of Aquarius and Jupiter in the constellation of Leo. The inner red circle is the ecliptic (Earth-Sun orbit), the outer is its imaginary extention towards the stars. For better understanding, the drawing is not to real scale.

Wandering Stars

‘Planet’ means “wandering star”, rightfully, because planets are moving around the Sun as Earth does, but in other distances and at different speeds. Planets orbiting between Earth and the Sun, also called “inner planets”, are moving faster than planets beyond Earth, also called “outer planets”. The closer a planet to the attracting force of the Sun the faster it moves and the quicker it changes its position in the sky.

If you see a bright “star” in a constellation which is not marked on your planisphere, then, you are obviously seeing a planet. Far away stars twinkle because they send their own light to us. Planets do not twinkle because they are illuminated by the Sun. Aim a torch at a ball in the dark and you will see that the ball is illuminated. Your torch is the Sun. In the same way planets receive sunlight thanks to which we can see them. With Spica, you can easily see the planets Venus, Mars, Jupiter and Saturn. The other planets are too faint or too far away for Spica.

Planets within Spica’s Reach

How to find the planetsTo recognize a planet that Spica can see is fairly easy:

Venus is the second planet from the Sun. It does not show any surface details because it is enveloped by thick poisonous clouds of gas. Venus shows phases as our Moon and can be seen shortly after sunset in the west (“evening star”) or before sunrise in the east (“morning star”).

Mars is the fourth planet, smaller than Earth, and therefore very tiny to watch in Spica, but its reddish-orange color is prominent. That’s why Mars is also called ‘The Red Planet’. Mars has a solid surface which has been examined by Mars rovers.

Jupiter is the fifth and largest planet in our Solar System — ‘The King of Planets’. It is like a huge ball of gas and clouds without solid surface. Its four brightest moons named Io, Europa, Ganymede and Callisto have been discovered by Galileo Galilei as he first pointed his self-made telescope towards Jupiter — just like you.

Well, and Saturn is the sixth planet and famous for its ring, most likely your favorite target for Spica. Like Jupiter there is no solid surface. Because of its beautiful, majestic ring, Saturn is also called ‘The Lord of the Rings’. The ring consists of loose rocks up to house sizes.

How Big is our Solar System?

Sizes, diameters and distances in space are often hard to imagine. Earth measures 12,756 km in diameter and the Sun is 150 million kilometers on average away from Earth. Well, these are big numbers and no fun to deal with. Let’s shrink Earth to the size of a big ball of 1 meter in diameter and look again at our Solar System.

If Earth were just one meter in diameter, the Moon would be 30 meters away and 27cm large. The Sun would be 12 kilometers away and 109 meters in diameter. Now that’s much easier. The sizes of the major planets: Mercury = 38cm, Venus = 95cm, Earth = 1 meter (of course), Mars = 53cm, Jupiter 11.2m and Saturn = 9.5m.

Observing Jupiter with Spica it is like seeing an 11.2 meters big ball in a distance of 60 kilometers. Or, a smaller ball of 9.5 meters in a distance of 112 kilometers, namely Saturn. That’s quite impressive, isn’t it?

You are Galileo!

Already 400 years ago, Galileo Galilei has observed all these bright planets with his small telescope and scribbled what he saw. Your Spica is almost of the same structure, but of much better optical quality and you can see a six times wider sky in your eyepiece than Galileo did in his. Nevertheless, Galileo Galilei set the landmark of the beginning of modern astronomy with telescopes, as Spica will ignite your fascination with the Moon, the planets and the stars above.

Mercury, Venus, Mars, Jupiter and Saturn will put on a show.

Gael Fashingbauer Cooper

CNET freelancer Gael Fashingbauer Cooper, a journalist and pop-culture junkie, is co-author of “Whatever Happened to Pudding Pops? The Lost Toys, Tastes and Trends of the ’70s and ’80s,” as well as “The Totally Sweet ’90s.” If Marathon candy bars ever come back, she’ll be first in line.

Set your alarm and wake up early this Sunday, July 19. About 45 minutes before sunrise, you’ll be able to see five planets and the crescent moon without using a telescope. Mercury, Venus, Mars, Jupiter and Saturn, and the moon, all will be visible.

Jeffrey Hunt, an astronomy educator and former planetarium director who has written about the event in a post on his site, When the Curves Line Up, talked me through how best to get a glimpse.

How to find the planets

“Step outside early in the morning, at least an hour before sunrise,” Hunt said. “Find the four bright planets — Venus, Mars, Saturn and Jupiter. They look like overly bright stars. Brilliant Venus is low in the east-northeast. Mars is the lone ‘star’ in the southeast, and Jupiter and Saturn are the stars in the southwest. To your eyes, they won’t look like the photos made by spacecraft, just overly bright stars.”

Mercury might be the toughest to spot. Hunt advises trying for Mercury about 45 minutes before sunrise, using binoculars.

On his website, Hunt offers tips for finding each planet. Venus, he says, will “blaze in the eastern sky.” The thin crescent moon will be very low in the east-northeast part of the sky, and will only be about 1 percent illuminated. Mercury will be to the right of the moon, Mars will be about halfway up in the sky in the south-southeast, Jupiter will be just above the horizon in the southwest, and Saturn will be to the upper left of Jupiter.

More celestial events

Newbie stargazers may want to seek out some technological help. “Google Sky, Night Sky, and Star Walk are apps that may help early risers locate the planets in the sky,” Hunt says.

The sight will be visible in both the northern and southern hemisphere. From south of the equator, Hunt notes, Mars is in the northwest rather than the southeast.

If you miss out, you’ll still be able to see the five planets in the sky for a few additional mornings after July 19, but you won’t also see the moon.

“On successive mornings, look 3-4 minutes earlier each day,” Hunt advises. “You may catch (the five planets) in the sky until about July 25.”

Miss this five-planets-and-the-moon gathering, and you’ll have a bit of a wait. We’ll next get to see this gathering in late June 2022, Hunt told me.

Before we get into the subject of gravity and how it acts, it’s important to understand the difference between weight and mass.

We often use the terms “mass” and “weight” interchangeably in our daily speech, but to an astronomer or a physicist they are completely different things. The mass of a body is a measure of how much matter it contains. An object with mass has a quality called inertia. If you shake an object like a stone in your hand, you would notice that it takes a push to get it moving, and another push to stop it again. If the stone is at rest, it wants to remain at rest. Once you’ve got it moving, it wants to stay moving. This quality or “sluggishness” of matter is its inertia. Mass is a measure of how much inertia an object displays.

Weight is an entirely different thing. Every object in the universe with mass attracts every other object with mass. The amount of attraction depends on the size of the masses and how far apart they are. For everyday-sized objects, this gravitational pull is vanishingly small, but the pull between a very large object, like the Earth, and another object, like you, can be easily measured. How? All you have to do is stand on a scale! Scales measure the force of attraction between you and the Earth. This force of attraction between you and the Earth (or any other planet) is called your weight.

If you are in a spaceship far between the stars and you put a scale underneath you, the scale would read zero. Your weight is zero. You are weightless. There is an anvil floating next to you. It’s also weightless. Are you or the anvil mass-less? Absolutely not. If you grabbed the anvil and tried to shake it, you would have to push it to get it going and pull it to get it to stop. It still has inertia, and hence mass, yet it has no weight. See the difference?

The Relationship Between Gravity and Mass and Distance

As stated above, your weight is a measure of the pull of gravity between you and the body you are standing on. This force of gravity depends on a few things. First, it depends on your mass and the mass of the planet you are standing on. If you double your mass, gravity pulls on you twice as hard. If the planet you are standing on is twice as massive, gravity also pulls on you twice as hard. On the other hand, the farther you are from the center of the planet, the weaker the pull between the planet and your body. The force gets weaker quite rapidly. If you double your distance from the planet, the force is one-fourth. If you triple your separation, the force drops to one-ninth. Ten times the distance, one-hundredth the force. See the pattern? The force drops off with the square of the distance. If we put this into an equation it would look like this:

The two “M’s” on top are your mass and the planet’s mass. The “r” below is the distance from the center of the planet. The masses are in the numerator because the force gets bigger if they get bigger. The distance is in the denominator because the force gets smaller when the distance gets bigger. Note that the force never becomes zero no matter how far you travel. Perhaps this was the inspiration for the poem by Francis Thompson:

This equation, first derived by Sir Isaac Newton, tells us a lot. For instance, you may suspect that because Jupiter is 318 times as massive as the Earth, you should weigh 318 times what you weigh at home. This would be true if Jupiter was the same size as the Earth. But, Jupiter is 11 times the radius of the Earth, so you are 11 times further from the center. This reduces the pull by a factor of 11 2 resulting in about 2.53 times the pull of Earth on you. Standing on a neutron star makes you unimaginably weighty. Not only is the star very massive to start with (about the same as the Sun), but it is also incredibly small (about the size of San Francisco), so you are very close to the center and r is a very small number. Small numbers in the denominator of a fraction lead to very large results!

Have you ever really seen the Solar System with your own eyes? We’re all used to seeing pictures in textbooks of the eight planets all lined up in a row, starting with Mercury and ending with Neptune (or Pluto, which was de-throned as a planet in 2009), but very rarely do we actually get to see a line of planets in the night sky at the same time.

That’s what’s happening this week as all five planets visible to the naked eye — Mercury, Venus, Mars, Jupiter, and Saturn —appear simultaneously.

Although you’ve probably glimpsed Venus or Jupiter before, this is a great chance to see a few planets at the same time.

When and How to See Five Planets in the Night Sky

It’s going to take a bit of effort because only those willing to rise early — really early — on Sunday, July 19, 2020 will get to see the planets. You won’t need a telescope unless you want a close-up of each.

How to Find Jupiter, Saturn, and Mars

About two hours before sunrise, you’ll be able to see Jupiter sinking in the southwestern sky with Saturn, the ringed planet, just above to the right. Trace a curved line going through both planets and into the southern sky, and you’ll hit Mars, the red planet, high above the southeastern horizon.

How to Find Venus and Mercury

Mars is at the peak of the ecliptic — the line we always see planets orbiting along — so trace its curve down to the horizon in the northeast. Before you get there, you’ll easily spot the super-bright planet Venus. It’s one of the brightest objects in the night sky. Mercury is always tricky to see, and you have to get your timing right; it will rise in the northeast 45 minutes before sunrise as seen from New York City. You’re looking for a small, red dot, and it will help if you have a pair of binoculars. With any luck, you may even see it accompanied by a very slender crescent moon just to its left.

We'll be back with new data soon! In the mean time, you can search for planets in a totally different data set over on Planet Hunters NGTS.

How to find the planets

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Chat with the research team and other volunteers!

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Every click counts! Join Planet Hunters TESS's community to complete this project and help researchers produce important results. Click "View more stats" to see even more stats.

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The data is finally here! Together we can find the most complex, the most unusual and the most exciting planetary systems in our Galaxy!

About Planet Hunters TESS

The Transiting Exoplanet Survey Satellite (TESS) is providing us with a huge amount of data that lets us look for planets outside of our own Solar System, including planets that could support life. With your help, we are going to find planets that will help us understand how these extrasolar systems form and evolve over time. The results may even bring us closer to answering the question that we all want to answer: Are we alone in the Universe?

Connect with Planet Hunters TESS

We'll be back with new data soon! In the mean time, you can search for planets in a totally different data set over on Planet Hunters NGTS.

How to find the planets

Join the Search for Undiscovered Worlds

You can do real research by clicking to get started here!

Chat with the research team and other volunteers!

Planet Hunters TESS Statistics

Keep track of the progress you and your fellow volunteers have made on this project.

Every click counts! Join Planet Hunters TESS's community to complete this project and help researchers produce important results. Click "View more stats" to see even more stats.

By the numbers

Message from the researcher

The data is finally here! Together we can find the most complex, the most unusual and the most exciting planetary systems in our Galaxy!

About Planet Hunters TESS

The Transiting Exoplanet Survey Satellite (TESS) is providing us with a huge amount of data that lets us look for planets outside of our own Solar System, including planets that could support life. With your help, we are going to find planets that will help us understand how these extrasolar systems form and evolve over time. The results may even bring us closer to answering the question that we all want to answer: Are we alone in the Universe?

Planets are massive celestial objects, so physically weighing them is practically impossible. It’s not like we have a humongous planet-sized weighing scale just lying around! Therefore, the only way to do this is through a theoretical approach. Sounds a bit tough… how many of you, the knowledge-seekers, would volunteer to undertake such a cosmic mission?

How to find the planets

Mesmerizing universe Credits:NikoNomad/Shutterstock

The theoretical approach to determining the weight of the planet involves the laws of physics, and as it turns out, the approach isn’t really that complicated. The secret to the calculation, as you may expect, mostly lies in mathematics.

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The Science of Weighing

When you stand on a scale, the scale measures how strongly the Earth’s gravity is pulling you. Now, when it comes to measuring the weight of the planet, scale not only relies on the gravitational pull that the planet exerts, but also the mass of the planet itself. The heavier the planet, the greater its gravitational pull. So, scientists can weigh planets by measuring how hard they pull on other celestial objects. Let’s see how the planet’s weight is calculated using different approaches.

Before we begin, there needs to be one clarification. What astrophysicists often calculate is the ‘mass’ of the planet and not the ‘weight’. Yes, many of us use these terms interchangeably, but scientifically they are quite different. The mass measures how much matter is present in an object under consideration. On the other hand, weight measures how heavy the object is in a given gravitational context. To better understand this, you need to think about astronauts on a moon. Out there, he would feel much lighter, but his mass would remain the same. It’s simply that the pull of gravity on the moon is much less than what is experienced on Earth. So yes, mass is what they usually endeavor to measure.

Using Newton’s Law

To evaluate the mass of a planet, such as Earth, we can use Newton’s Law of Universal Gravitation. Using this, we know that the force of attraction between two objects is proportional to the product of their masses divided by the square of the distance between their centers of mass. In order to simplify the calculation part, we assume that their geographical centers are their centers of mass (the point where the body’s center of gravity is located).

Since we know the radius of Earth, we can use Newton’s Law of Universal Gravitation to calculate the mass of Earth in terms of the gravitational force it has on an object, i.e., its weight on the Earth’s surface, using the radius of Earth as our distance variable.

Using Kepler’s Law

In the sixteenth century, Kepler extended Newton’s work and derived an equation that we now know as Kepler’s Law. This equation finds the relation between a planet and its moon using the period of the moon’s orbit and the mass of the planet. Thus, if the distance to the moon from the planet is known, along with the time taken for that moon to orbit around the planet, then using Kepler’s third law, the mass of the planet can be calculated.

How to find the planets

Johannes Kepler a renowned German astronomer and mathematician (Photo Credit : public domain/Wikimedia Commons)

To calculate the mass of a particular planet using Kepler’s third law, we first need to know how far the planet is from Earth. This is generally done by bouncing signals off that planet and calculating the time it takes for the radar to return. Doppler radio is used for this purpose.

Thus, to calculate the mass of the planet, we need the distance of that planet from Earth, represented by R. Next, we need to know the orbital period of the moon, denoted by T. Finally, we need to know the largest angular separation of the planet and the moon, denoted by θ.

Kepler’s third law is given by the formula:

How to find the planets

The radius of the earth, r, given in the formula above, can be calculated using the formula: r=Rθ

Rearranging the equation with Kepler’s equation:

How to find the planets

If the moon is very small compared to the planet, we assume the moon’s mass to be nil and substitute a value of m=0 and directly get the mass of the planet. This method works for most of the moons in the solar system.

However, if the moon is relatively large, such as Charon, then we need to calculate the center of mass of the planet. The distance between the center of the planet to the center of mass of the planet and moon, denoted by d, can be subsequently used to calculate the mass of the planet using the equation: Md=m(r-d)

How to find the planets

Calculation of mass using Kepler’s third law of planetary motion

This gives the mass of the planet as:

How to find the planets

Using geometry

Another way to guess the mass of the planet is by applying principles of geometry. However, this involves more calculative guessing than the actual measurement. If you can calculate the volume of the planet and make a rough estimate about the density of the planet based on its composition, you can get a rough value of its mass. Remember, mathematically we know that the volume of the planet (sphere) can be calculated using the formula: Volume=(4/3)*π*(radius) 3

By rearranging the density formula, we can calculate the mass of the planet from this equation: mass= density*volume.

How to find the planets

Who knew that the seemingly herculean task of measuring our planet’s weight could be done quite easily by applying the basic laws of physics and mathematics!

"Can you explain the transit method that astronomers use to find exo-planets?"

Today, we pick a question out of Pandora’s Jar.* The query relates to how astronomers find exo-planets, those worlds in orbit around other stars.

We’ll begin with defining “transit.” A transit occurs when a planet moves directly in front of a star. We sometimes see transits of Mercury and Venus** from Earth. Astronomers can use transits of planets around other stars to detect them. As these stars are so far away, they can’t actually observe the transit. Instead, astronomers can measure the slight brightness decrease which a star experiences when a planet passes in front of it from our perspective.

Unlike the radial velocity (“wobble”) method which can only detect planets sufficiently massive to induce detectable gravitational tugs, the transit method can be employed to discover smaller, Earth-sized planets. As it requires very sensitive equipment, the transit method has only been in use for slightly more than ten years. In 2002, astronomers found OGLE-TR-56b***, the first exo-planet discovered through use of the transit method. Since this first discovery, hundreds of exo-planets have been found through this technique, principally by the Kepler Probe, a spacecraft that has been in service since 2009. This craft is monitoring more than 145,000 stars within the Cygnus region for evidence of periodic dimming related to transiting planets.

As some planets require years to complete a single orbit, the transit method requires prolonged observation times to establish that the brightness diminishment is periodic. Brilliantly, some planets can be indirectly discovered through the transit method as astronomers can measure the slight perturbations that other planets exert on those whose transits they are observing.

Through the transit method, terrestrial planets have been found within the habitable zones of their parent stars. These zones are neither excessively hot nor cold and could therefore allow for the formation and evolution of life forms. (Less than fifty such worlds have so far been identified.) While astronomers have not gathered conclusive evidence that life actually exists elsewhere in the Universe, the discovery that such planets are not uncommon lends hope, Pandora, to those of us who hope that life proliferates in the Universe.

I hope this response is helpful.

*Pandora, the first human woman created by the Greek Gods, was the personification of curiosity and so we wanted to name the question vessel after her. She was said to have opened a jar, not a box, which released all of humanity’s dread and despair. By the time she managed to close the jar, only hope remained enclosed within it.

**Transits of Mercury and Venus are not common events. The last transit of Venus occurred in June 2012. The next Venus transit won’t occur until December 2117. The last transit of Mercury was in November 2006. The next occurs in May 2016. Transits are visible from other planets, as well. For instance, someone on Mars would have seen a transit of Earth in 1984. The next transit of Earth from Mars happens in November 2084.

***That strange name relates to the Optical Gravitational Lensing experiment. Though its focus is on the discovery of dark matter through gravitational lensing, it has also been utilized to discover exo-planets.

This artist’s impression shows an example of a rogue planet detected in the Rho Ophiuchi region . [+] where ESO observations have recently helped uncover at least 70 of these objects. Rogue planets have masses comparable to those of the planets in our Solar System but do not orbit a star, instead roaming freely on their own.

A team of astronomers have discovered at least 70 new “rogue” planets in our Milky Way galaxy. It’s the largest group of these “galactic nomads” found so far and could teach astronomers how these mysterious cosmic oddities came to be.

Rogue planets are planets that move through space without orbiting a star. Often described as free-floating, they’re isolated bodies that are planet-like, having possibly been ejected from a star system. Another theory is that rogue planets can form from the collapse of a gas cloud that is too small to lead to the formation of a star.

“We did not know how many to expect and are excited to have found so many,” said Núria Miret-Roig, an astronomer at the Laboratoire d’Astrophysique de Bordeaux, France and the University of Vienna, Austria, and the first author of the new study published today in Nature Astronomy.

This image shows a small region of the sky in the direction of the Upper Scorpius constellation. It . [+] zooms in on a recently discovered rogue planet, meaning a planet that does not orbit a star but instead roams freely on its own. The rogue planet is the tiny, bright red dot at the very centre of the image. The image was created by combining data from the OmegaCam instrument on VLT Survey Telescope (VST) and from the VIRCAM instrument on the Visible and Infrared Survey Telescope for Astronomy (VISTA), both located at ESO’s Paranal Observatory in Chile. Observations with these and other instruments helped the scientists tell the planets apart from stars, brown dwarfs and other objects in this region of the sky. Lurking far away from any star illuminating them, rogue planets would normally be impossible to image, but shortly after formation they emit a faint glow that can be detected by sensitive cameras on powerful telescopes.

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So how did they find them? Though dark and cold—and therefore impossible to find—Miret-Roig and her team used the fact that rogue planets are still hot enough to glow in the few million years after their formation. So they can be detected by sensitive cameras on large telescopes. “We measured the tiny motions, the colours and luminosities of tens of millions of sources in a large area of the sky,” said Miret-Roig. “These measurements allowed us to securely identify the faintest objects in this region, the rogue planets.”

All 70 new rogue planets have masses comparable to Jupiter’s in a star-forming region in the Upper Scorpius and Ophiuchus constellations. Ophiuchus is known as the 13th constellation because despite being a large constellation on the ecliptic—so therefore hosting the Sun just like Leo, Taurus and all the others—it was the victim of ancient Babylonians hatred of the number 13.

To find the rogue planets the team used data from 20 years and from a range of telescopes, including the European Southern Observatory’s Very Large Telescope (VLT), the Visible and Infrared Survey Telescope for Astronomy (VISTA), the VLT Survey Telescope (VST) and the MPG/ESO 2.2-metre telescope in Chile.

This image shows the locations of 115 potential rogue planets recently discovered by a team of . [+] astronomers in the direction of the Upper Scorpius and Ophiuchus constellations, highlighted with red circles. Rogue planets have masses comparable to those of the planets in our Solar System, but do not orbit a star and instead roam freely on their own. The exact number of rogue planets found by the team is between 70 and 170, depending on the age assumed for the study region. This image was created assuming an intermediate age, resulting in a number of planet candidates in between the two extremes of the study.

ESO/N. Risinger (

“We used tens of thousands of wide-field images from ESO facilities, corresponding to hundreds of hours of observations, and literally tens of terabytes of data,” said Hervé Bouy, an astronomer at the Laboratoire d’Astrophysique de Bordeaux, France, and project leader of the new research. The team also used data from the European Space Agency’s Gaia satellite.

Could there be more rogue planets? “There could be several billions of these free-floating giant planets roaming freely in the Milky Way without a host star,” said Bouy. However, to find more scientists will require a bigger, even more sensitive telescope. Cue the ESO’s forthcoming Extremely Large Telescope (ELT), which is currently under construction in Chile. “These objects are extremely faint and little can be done to study them with current facilities,” said Bouy. “The ELT will be absolutely crucial to gathering more information about most of the rogue planets we have found.”

Astronomers have discovered that stars, even when near death, can possibly still birth planets

Though planets are not usually much older than the stars around which they revolve – as seen in the case of the Sun: which was born 4.6 billion years ago, with the Earth’s formation being not long after.

KU Leuven astronomers have learnt that an entirely different scenario is also possible, that even if stars are near death, some types of stars can possibly still form planets.

Planets such as Earth and other planets were formed not long after the Sun. As the sun began burning around 4.6 billion years ago, matter around it eventually clumped into protoplanets, forming our solar system

The birth of the planets in that protoplanetary disc – a ‘gigantic pancake’ made of dust and gas (as described by authors), with the Sun in its centre – explains why they all orbit in the same plane.

Signs pointing to planetary formation

The aforementioned discs of dust and gas do not specifically only surround newborn stars, however. They can also develop independently from star formation, as seen with binary stars, when one of which is dying (binary stars are two stars that orbit each other, also called a binary system).

When a medium-sized star, like the Sun, comes to die, it catapults the outer part of its atmosphere into space, after which it slowly dies out as a so-called white dwarf.

However, in the case of binary stars, the gravitational pull of the second star causes the matter ejected by the dying star to form a flat, rotating disc. Furthermore, this disc strongly resembles the protoplanetary discs that astronomers observe around young stars elsewhere in the Milky Way.

The new information which KU Leuven researchers introduce in this study however, is that the discs surrounding evolved binary stars demonstrate signs which could point to planet formation, highlighting that this is the case for one in ten of these binary stars.

KU Leuven astronomer Jacques Kluska, first author of the article in the journal Astronomy & Astrophysics in which the discovery is described, said: “In 10% of the evolved binary stars with discs we studied, we see a large cavity (a void/opening, ed.) in the disc. This is an indication that something is floating around there that has collected all matter in the area of the cavity.”

Planets may not form at the beginning of one of a stars’ life, but at the end

The researchers uncovered this information when drawing up an inventory of evolved binary stars in our Milky Way, based on existing, publicly available observations.

Counting 85 of such binary star pairs, in ten pairs, the researchers came across a disc with a large cavity on the infrared images.

The researchers additionally suggest that the ‘clean-up’ of the matter could be the work of a planet – that planet might not have formed at the very beginning of one of the binary stars’ life, but rather, at the very end.

Finding further strong indications for the presence of such planets, the researchers do not rule out the possibility several planets could be formed around these binary stars.

Kluska said: “In the evolved binary stars with a large cavity in the disc, we saw that heavy elements such as iron were very scarce on the surface of the dying star. This observation leads one to suspect that dust particles rich in these elements were trapped by a planet.”

Professor Hans Van Winckel, head of the KU Leuven Institute of Astronomy, said: “The confirmation or refutation of this extraordinary way of planet formation will be an unprecedented test for the current theories.”

The KU Leuven astronomers plan to verify their hypothesis themselves by using the big telescopes of the European Southern Observatory in Chile to take a closer look at the ten pairs of binary stars whose discs show a large cavity. They suggest that if this is confirmed, theories on planet formation will need to be adjusted.