The Times Australia
The Times World News

.
The Times Real Estate

.

Astronomers puzzled by 'planet that shouldn't exist'

  • Written by Daniel Huber, Astronomer, University of Sydney
Astronomers puzzled by 'planet that shouldn't exist'

The search for planets outside our Solar System – exoplanets – is one of the most rapidly growing fields in astronomy. Over the past few decades, more than 5,000 exoplanets have been detected and astronomers now estimate that on average there is at least one planet per star in our galaxy.

Many current research efforts aim at detecting Earth-like planets suitable for life. These endeavours focus on so-called “main sequence” stars like our Sun – stars which are powered by fusing hydrogen atoms into helium in their cores, and remain stable for billions of years. More than 90% of all known exoplanets so far have been detected around main-sequence stars.

As part of an international team of astronomers, we studied a star that looks much like our Sun will in billions of years’ time, and found it has a planet which by all rights it should have devoured. In research[1] published today in Nature, we lay out the puzzle of this planet’s existence – and propose some possible solutions.

A glimpse into our future: red giant stars

Just like humans, stars undergo changes as they age. Once a star has used up all its hydrogen in the core, the core of the star shrinks and the outer envelope expands as the star cools.

In this “red giant” phase of evolution, stars can grow to more than 100 times their original size. When this happens to our Sun, in about 5 billion years, we expect it will grow so large it will engulf Mercury, Venus, and possibly Earth.

Eventually, the core becomes hot enough for the star to begin fusing helium. At this stage the star shrinks back to about 10 times its original size, and continues stable burning for tens of millions of years.

Read more: Explainer: how do you find exoplanets?[2]

We know of hundreds of planets orbiting red giant stars. One of these is called 8 Ursae Minoris b[3], a planet with around the mass of Jupiter in an orbit that keeps it only about half as far from its star as Earth is from the Sun.

The planet was discovered in 2015 by a team of Korean astronomers using the “Doppler wobble” technique, which measures the gravitational pull of the planet on the star. In 2019, the International Astronomical Union dubbed[4] the star Baekdu and the planet Halla, after the tallest mountains on the Korean peninsula.

A planet that should not be there

Analysis of new data about Baekdu collected by NASA’s Transiting Exoplanet Survey Satellite (TESS[5]) space telescope has yielded a surprising discovery. Unlike other red giants we have found hosting exoplanets on close-in orbits, Baekdu has already started fusing helium in its core.

Read more: NASA's planet-hunting spacecraft TESS is now on its mission to search for new worlds[6]

Using the techniques of asteroseismology, which studies waves inside stars[7], we can determine what material a star is burning. For Baekdu, the frequencies of the waves unambiguously showed it has commenced burning helium in its core.

Sound waves inside a star can be used to determine whether it is burning helium. Gabriel Perez Diaz / Instituto de Astrofisica de Canarias

The discovery was puzzling: if Baekdu is burning helium, it should have been much bigger in the past – so big it should have engulfed the planet Halla. How is it possible Halla survived?

As is often the case in scientific research, the first course of action was to rule out the most trivial explanation: that Halla never really existed.

Indeed, some apparent discoveries of planets orbiting red giants using the Doppler wobble technique have later been shown to be illusions created by long-term variations in the behaviour of the star itself[8].

However, follow-up observations ruled out such a false-positive scenario for Halla. The Doppler signal from Baekdu has remained stable over the last 13 years, and close study of other indicators showed no other possible explanation for the signal. Halla is real – which returns us to the question of how it survived engulfment.

Two stars become one: a possible survival scenario

Having confirmed the existence of the planet, we arrived at two scenarios which could explain the situation we see with Baekdu and Halla.

At least half of all stars in our galaxy did not form in isolation like our Sun, but are part of binary systems. If Baekdu once was a binary star, Halla may have never faced the danger of engulfment.

If the star Baekdu used to be a binary, there are two scenarios which can explain the survival of the planet Halla. Brooks G. Bays, Jr, SOEST/University of Hawai'i

A merger of these two stars may have prevented the expansion of either star to a size large enough to engulf planet Halla. If one star became a red giant on its own, it would have engulfed Halla – however, if it merged with a companion star it would jump straight to the helium-burning phase without getting big enough to reach the planet.

Alternatively, Halla may be a relatively newborn planet. The violent collision between the two stars may have produced a cloud of gas and dust from which the planet could have formed. In other words, the planet Halla may be a recently born “second generation” planet.

Whichever explanation is correct, the discovery of a close-in planet orbiting a helium-burning red giant star demonstrates that nature finds ways for exoplanets to appear in places where we might least expect them.

An illustration of a planet in a ring of dust and debris around a star. The planet Halla may have formed from debris created by the merger of two stars. W. M. Keck Observatory / Adam Makarenko

References

  1. ^ research (www.nature.com)
  2. ^ Explainer: how do you find exoplanets? (theconversation.com)
  3. ^ 8 Ursae Minoris b (exoplanets.nasa.gov)
  4. ^ dubbed (www.nameexoworlds.iau.org)
  5. ^ TESS (www.nasa.gov)
  6. ^ NASA's planet-hunting spacecraft TESS is now on its mission to search for new worlds (theconversation.com)
  7. ^ asteroseismology, which studies waves inside stars (exoplanets.nasa.gov)
  8. ^ created by long-term variations in the behaviour of the star itself (ui.adsabs.harvard.edu)

Read more https://theconversation.com/astronomers-puzzled-by-planet-that-shouldnt-exist-208649

The Times Features

Best Deals on Home Furniture Online

Key Highlights Discover the best deals on high-quality outdoor furniture online. Transform your outdoor space into a stylish and comfortable oasis. Explore a wide range of d...

Discover the Best Women's Jumpers for Every Season

Key Highlights Explore lightweight jumpers for spring and summer, ensuring breathability and ease. Wrap up warm with cozy wool jumpers for the chilly autumn and winter season...

Uncover the Elegance of Gorgeous Diamond Tennis Necklaces

Key Highlights Diamond tennis necklaces are a timeless piece of jewelry that exudes elegance and sophistication. They feature a continuous line of brilliant-cut diamonds, cre...

Dental Implants vs. Dentures: Which Is Better for You?

When it comes to replacing missing teeth, two of the most common options are dental implants and dentures. Both have their advantages and disadvantages, so choosing between them ...

What Neck Pain Really Means (And Why It’s More Than Just Poor Posture)

Neck pain is often brushed off as something temporary — a tight spot after a long day at the desk or a poor night’s sleep. But when the discomfort keeps returning, it could be a ...

The Work of Gosha Rubchinskiy: Fashion, Culture, and Youth

From Designer to Cultural Architect Gosha Rubchinskiy is not just a fashion designer—he's a cultural force. Born in Moscow in 1984, Rubchinskiy began his career in fashion in t...

Times Magazine

The Essential Guide to Transforming Office Spaces for Maximum Efficiency

Why Office Fitouts MatterA well-designed office can make all the difference in productivity, employee satisfaction, and client impressions. Businesses of all sizes are investing in updated office spaces to create environments that foster collaborat...

The A/B Testing Revolution: How AI Optimized Landing Pages Without Human Input

A/B testing was always integral to the web-based marketing world. Was there a button that converted better? Marketing could pit one against the other and see which option worked better. This was always through human observation, and over time, as d...

Using Countdown Timers in Email: Do They Really Increase Conversions?

In a world that's always on, where marketers are attempting to entice a subscriber and get them to convert on the same screen with one email, the power of urgency is sometimes the essential element needed. One of the most popular ways to create urg...

Types of Software Consultants

In today's technology-driven world, businesses often seek the expertise of software consultants to navigate complex software needs. There are several types of software consultants, including solution architects, project managers, and user experienc...

CWU Assistive Tech Hub is Changing Lives: Win a Free Rollator Walker This Easter!

🌟 Mobility. Independence. Community. All in One. This Easter, the CWU Assistive Tech Hub is pleased to support the Banyule community by giving away a rollator walker. The giveaway will take place during the Macleod Village Easter Egg Hunt & Ma...

"Eternal Nurture" by Cara Barilla: A Timeless Collection of Wisdom and Healing

Renowned Sydney-born author and educator Cara Barilla has released her latest book, Eternal Nurture, a profound collection of inspirational quotes designed to support mindfulness, emotional healing, and personal growth. With a deep commitment to ...

LayBy Shopping