Planet-hunting astronomy student discovers 17 new worlds

Planet-hunting astronomy student discovers 17 new worlds including one that is Earth-sized, rocky and potentially habitable using data from the Kepler Space Telescope

  • The new worlds range from two thirds the size of Earth to eight times its size 
  • KIC-7340288 b is a potentially habitable world about 1,000 light years away
  • The planets were discovered by searching through data from the Kepler mission 

A planet hunting astronomy student has discovered 17 new worlds including a potentially habitable Earth-sized rocky body that may have liquid water.

University of British Columbia student Michelle Kunimoto searched through data captured by NASAs Kepler Space Telescope to make her discoveries.

The most exciting find from within the 17 planets is one called KIC-7340288 b that is one and a half times the size of Earth and in the habitable zone of its star. 

Kunimoto says it’s one of only 15 small habitable zone planets found in the Kepler data so far – but ‘it’s 1,000 light-years away, so we’re not getting there anytime soon’.

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This graphic shows the sizes of the 17 new planet candidates – compared to Mars, Earth, and Neptune. The planet in green is KIC-7340288 b, a rare rocky planet in the Habitable Zone

The rocky Earth-like planet found by Kunimoto has a year that is 142 and a half days long and orbits 41 million miles from its parent star.

That is just slightly further out than Mercury is from the Sun in our Solar System but the planet only gets a third of the light Earth gets from the Sun as the star is smaller.

Of the other 16 new planets discovered, the smallest is only two-thirds the size of Earth – one of the smallest planets to be found with Kepler so far. 

The rest range in size with the largest about eight times the size of Earth.

Kunimoto is no stranger to discovering planets: she previously discovered four during her undergraduate degree at UBC. 

Now working on her PhD at UBC, she used what is known as the ‘transit method’ to look for the planets among the roughly 200,000 stars observed by Kepler.

‘Every time a planet passes in front of a star, it blocks a portion of that star’s light and causes a temporary decrease in the star’s brightness,’ Kunimoto said. 

‘By finding these dips, known as transits, you can start to piece together information about the planet, such as its size and how long it takes to orbit.’ 

Kunimoto also collaborated with UBC alumnus Henry Ngo to obtain razor-sharp follow-up images of some of her planet-hosting stars.

They used the the Near InfraRed Imager and Spectrometer (NIRI) on the Gemini North 8-metre Telescope in Hawaii.

WHAT IS THE HABITABLE ZONE? 

The habitable zone is the range of orbits around a star in which a planet can support liquid water. 

The temperature from the star needs to be ‘just right’ so that liquid water can exist on the surface. 

The boundaries of the habitable zone are critical. 

If a planet is too close to its star, it will experience a runaway greenhouse gas effect, like Venus.

But if it’s too far, any water will freeze, as is seen on Mars. 

This is a technology that uses the near infrared region of the electromagnetic spectrum to study the atmosphere of cool stars.

It can also be used to look at the Doppler shift of stars as a planet moves around them to get more information on the planet.

‘I took images of the stars as if from space, using adaptive optics,’ she said. 

‘I was able to tell if there was a star nearby that could have affected Kepler’s measurements, such as being the cause of the dip itself.’ 

In addition to the new planets, Kunimoto was able to observe thousands of known Kepler planets using the transit-method.

Using the new findings she will be working to completely reanalyse the exoplanet census.

This is the guide to all planets outside the Solar System that have been discovered using a range of methods and technologies.

‘We’ll be estimating how many planets are expected for stars with different temperatures,’ said Kunimoto’s PhD supervisor and UBC professor Jaymie Matthews.

‘A particularly important result will be finding a terrestrial Habitable Zone planet occurrence rate. How many Earth-like planets are there? Stay tuned.’ 

UBC astronomy student Michelle Kunimoto (pictured) is no stranger to planet discovery – for her masters degree she found four exoplanets in Kepler data

Kunimoto, an astronomy PhD student, was named in the Forbes magazine 30 under 30 list in 2017 after discovering four planet candidates from Kepler data.

She also worked on tracking data needed by astronomers to get a better understanding of a type of quasar known as a dusty hyperluminous quasar. 

The latest discovery brings her total to 21 but the student also plans to examine previously suspected ‘planetary candidates’ in more detail using the Kepler data. 

The Kepler space telescope was launched by NASA in March 2009 with the aim of searching for planets outside of the solar system.

Data from the satellite has helped astronomers find thousands of exoplanets until it took its last image of space in September 2018.

During its over nine and a half years of service, Kepler observed 530,506 stars and detected 2,662 planets.

The green object in the top of this image depicts the rocky world found in the habitable zone by Kepler – it is larger than Earth but could potentially support life. The orange objects are other worlds found by Kunimoto

A number of planets have been discovered by human scientists – including amateur volunteers since 2010 when Kepler data was made public.

The Kepler team say this allows people to look for transit events in the light curves of Kepler images to identify planets that computer algorithms might miss.

The next stage of research will see Kunimoto and others study the full catalogue of known exoplanets to determine the rate they are likely to be discovered.

They also want to try and calculate how common rocky habitable zone planets are around stars studied by Kepler. 

She thanked NASA for making Kepler data available to the public, adding ‘without which this paper would not be possible.’

As well as Kepler data they used information from the European Space Agency Gaia mission and the NASA Exoplanet Archive run by MIT.

The findings have been published in the Astronomical Journal. 

WHAT IS THE KEPLER TELESCOPE?

The Kepler mission has spotted thousands of exoplanets since 2014, with 30 planets less than twice the size of Earth now known to orbit within the habitable zones of their stars.

Launched from Cape Canaveral on March 7th 2009, the Kepler telescope has helped in the search for planets outside of the solar system. 

It captured its last ever image on September 25 2018 and ran out of fuel five days later.

When it was launched it weighed 2,320 lbs (1,052 kg) and is 15.4 feet long by 8.9 feet wide (4.7 m × 2.7 m).

The satellite typically looks for ‘Earth-like’ planets, meaning they are rocky and orbit within the that orbit within the habitable or ‘Goldilocks’ zone of a star.

In total, Kepler has found around 5,000 unconfirmed ‘candidate’ exoplanets, with a further 2,500 ‘confirmed’ exoplanets that scientists have since shown to be real. 

Kepler is currently on the ‘K2’ mission to discover more exoplanets. 

K2 is the second mission for the spacecraft and was implemented by necessity over desire as two reaction wheels on the spacecraft failed. 

These wheels control direction and altitude of the spacecraft and help point it in the right direction.

The modified mission looks at exoplanets around dim red dwarf stars.  

While the planet has found thousands of exoplanets during its eight-year mission, five in particular have stuck out.

Kepler-452b, dubbed ‘Earth 2.0’, shares many characteristics with our planet despite sitting 1,400 light years away. It was found by Nasa’s Kepler telescope in 2014

1) ‘Earth 2.0’

In 2014 the telescope made one of its biggest discoveries when it spotted exoplanet Kepler-452b, dubbed ‘Earth 2.0’.

The object shares many characteristics with our planet despite sitting 1,400 light years away.

It has a similar size orbit to Earth, receives roughly the same amount of sun light and has same length of year.

Experts still aren’t sure whether the planet hosts life, but say if plants were transferred there, they would likely survive.

2) The first planet found to orbit two stars

Kepler found a planet that orbits two stars, known as a binary star system, in 2011.

The system, known as Kepler-16b, is roughly 200 light years from Earth. 

Experts compared the system to the famous ‘double-sunset’ pictured on Luke Skywalker’s home planet Tatooine in ‘Star Wars: A New Hope’.

3) Finding the first habitable planet outside of the solar system

Scientists found Kepler-22b in 2011, the first habitable planet found by astronomers outside of the solar system.

The habitable super-Earth appears to be a large, rocky planet with a surface temperature of about 72°F (22°C), similar to a spring day on Earth.

4) Discovering a ‘super-Earth’

The telescope found its first ‘super-Earth’ in April 2017, a huge planet called LHS 1140b.

It orbits a red dwarf star around 40 million light years away, and scientists think it holds giant oceans of magma.

5) Finding the ‘Trappist-1’ star system

The Trappist-1 star system, which hosts a record seven Earth-like planets, was one of the biggest discoveries of 2017. 

Each of the planets, which orbit a dwarf star just 39 million light years, likely holds water at its surface.

Three of the planets have such good conditions that scientists say life may have already evolved on them.

Kepler spotted the system in 2016, but scientists revealed the discovery in a series of papers released in February this year. 

Kepler is a telescope that has an incredibly sensitive instrument known as a photometer that detects the slightest changes in light emitted from stars

How does Kepler discover planets?

The telescope has an incredibly sensitive instrument known as a photometer that detects the slightest changes in light emitted from stars.

It tracks 100,000 stars simultaneously, looking for telltale drops in light intensity that indicate an orbiting planet passing between the satellite and its distant target.

When a planet passes in front of a star as viewed from Earth, the event is called a ‘transit’.

Tiny dips in the brightness of a star during a transit can help scientists determine the orbit and size of the planet, as well as the size of the star.

Based on these calculations, scientists can determine whether the planet sits in the star’s ‘habitable zone’, and therefore whether it might host the conditions for alien life to grow. 

Kepler was the first spacecraft to survey the planets in our own galaxy, and over the years its observations confirmed the existence of more than 2,600 exoplanets – many of which could be key targets in the search for alien life

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