Gravity Assist Podcast: Exoplanet Hunting with Jon Jenkins

Gravity Assist Podcast: Exoplanet Hunting with Jon Jenkins

The Gravity Assist Podcast is hosted by NASA’s Chief Scientist, Jim Green, who talks to among the best planetary scientists on the planet, giving a guided tour by way of the Solar System and past within the course of. This weekhe’s joined by Jon Jenkins, who’s a co-investigator for information processing on the Kepler and TESS missions at NASA’s Ames Research Center, to debate exoplanet searching and the wonderful discoveries that Kepler has made, and TESS will quickly make.

Here’s a brief teaser of this week’s podcast:

You can hearken to the complete podcast here, or learn the abridged transcript beneath.

Jon Jenkins presenting discoveries made by Kepler. Image credit score: NASA Ames Research Center.

Jim Green: So, Jon, what do you actually do as a co-investigator for information processing?

Jon Jenkins: What I do primarily is to design, develop, implement after which function the science pipelines for each the Kepler mission and now for the TESS mission. By science pipeline, I imply the power and the software program that permits us to take the uncooked measurements coming down from the spacecraft and course of it to show it into planet candidates

Jim Green: What’s the fundamental precept behind how Kepler works?

Jon Jenkins: Kepler works by observing a area of stars and measuring the brightness of these stars over time, in search of situations when a planet crosses in entrance of the face of the star from our perspective. When that occurs, the star winks at us, and that repeats. We see a dimming of the starlight as soon as each orbital interval of the planet. And the depth, or the quantity by which the star’s mild drops, tells us what the dimensions of the planet is relative to its star. The interval between what we name transits, or crossings of the star by the planet, inform us what the 12 months, or orbital interval, is for that planet.

Jim Green:  Kepler has been a very profitable mission as a result of it checked out so many stars all of sudden through the authentic a part of its mission. How many stars did it take a look at concurrently, and how briskly did it take a look at every star?

Jon Jenkins: We may observe as many as 170,000 stars at any given time, however usually the biggest variety of stars that we noticed concurrently was 165,000 stars.We measured the brightness of every of these stars each half-an-hour. But, we had a small pattern, 512 stars, for which we may make measurements each minute. That was truly crucial as a result of we wanted to know concerning the stars in an effort to know concerning the planets. I mentioned earlier than that we may inform what the dimensions of the planet is by what the fractional drop in brightness is when a planet crosses a star. But that’s a relative measurement, so we have to know the way large the star is in an effort to infer with precision what the dimensions of the planet is. So, for the brightest stars that have been no less than 12th magnitude or brighter, we monitored these stars each minute and measuredacoustic oscillations and pulsations of the celebs attributable to star quakes.

An artist’s impression of the Kepler spacecraft. Image credit score: NASA.

One of the unsung tales of Kepler is the truth that we have been capable of conduct these asteroseismological investigations of those stars. That’s the research of the songs that the celebs sing as they ring like bells. And, like bells, the bigger and extra huge a star is, the decrease the tone. Stars just like the Sun ring with a typical periodicity of about 5 minutes, in order that’s why we wanted the one-minute samples.

By learning the tones the celebs are ringing at, we will measure the dimensions and the mass of a star to a few p.c. That’s phenomenal as a result of we will’t resolve the dimensions of the star by wanting on the photographs, however from a whole lot or hundreds of sunshine years away we will truly measure the mass and the dimensions to a few p.c.

Jim Green: When Kepler seems out and sees this massive inhabitants of stars, is it virtually each sort of star, from what we classify as A all the way in which to M and others?

Jon Jenkins: That is true. For Kepler we had goal stars that we noticed, and over the lifetime of the mission we noticed over 200,000 stars, starting from large, scorching A-type stars all the way in which all the way down to small, cool M-type stars.

Jim Green:What are among the improbable issues that get you enthusiastic about in search of planets?

Jon Jenkins:  Well, I feel some of the thrilling issues that got here out of Kepler by way of exoplanets that we didn’t anticipate was the truth that we noticed properly over 400 programs with a number oftransitingplanets. These are instances the place we don’t simply see one planet crossing the face of its star periodically, however manyplanets.You may see two, three, or as many as eight planets transiting a star. Now, Kepler solely noticed for 4 years, and in order that signifies that all of those programs are very compact. The orbital intervals are a lot smaller on the whole than the orbital intervals of the planets in our Solar System as a result of we weren’t observing lengthy sufficient to see the Jupiter-like planets in 11-year orbital intervals. Kepler-11 was the primary actually good instance of this sort of system, the place there are six planets orbiting and the interior 5 would match inside the orbit of Mercury, whereas the outer planet could be between the orbit of Venus and Earth, in the event that they have been positioned in our Solar System. So, these are small, compact planetary programs in comparison with our personal. That signifies that nature actually likes to make such planetary programs as a result of we noticed so lots of them.

How the transit of a planet throughout the disk of its star causes a dip within the star’s mild that Kepler can detect. Image credit score: NASA Ames Research Center.

Jim Green: Kepler noticed a selected space of sky for about 4 years. Then, in its prolonged mission, it modified that method. What occurred?

Jon Jenkins: Well, the very best, worst factor occurred to Kepler, and that’s that we misplaced the second of our 4 response wheels. These response wheels are sort of like gyroscopes to regulate the pointing of the spacecraft. They accomplish that in a really environment friendly method, however you want no less than three working response wheels to do this. But in May 2013 the second failed, which meant the top of the Kepler mission as we all know it, as a result of we may now not level our spacecraft on the authentic area of view. However, a intelligent engineer at Ball Aerospace, Doug Weimer, had the concept of working with two response wheels by utilizing the  strain of photons of daylight bouncing off the spacecraft to steadiness the spacecraft, in order that we may management the roll angle. With the 2 response wheels we had left, we may management the place we pointed on the sky, however we couldn’t management the roll angle, and we wanted to regulate that.  So, we developed and initiated the prolonged mission, which is known as the K2 Mission, the place we’re capable of observe a area of view within the ecliptic aircraft,  which is the orbital aircraft of the planets round our personal Sun. We can level at a kind of fields for as much as 85 days. K2 has been a phenomenally profitable mission, permitting us to significantly broaden the science affect of the Kepler spacecraft. 

Jim Green: What is one other improbable discovery Kepler has made, out of your perspective?

Jon Jenkins:One of probably the most fascinating discoveries that Kepler has made is that planets don’t type simply round single stars, however they type round binary star systems, like Luke Skywalker’s dwelling planet of Tatooine in Star Wars. Indeed, a part of what introduced me to the mission was that I used to be a part of a really small staff of scientists who have been looking for planets within the CM Draconissystem which is a pair of small M-class stars. We believed that if there have been stars transiting the system, that an Earth-like planet within the liveable zone would have a 17-day orbitalinterval.We noticed it from the bottom for six years and we have been capable of place actually sturdy higher limits on the presence of any planets in that system, however we by no means found any.It took till Kepler to seek out the primary circumbinary planetary system, which was Kepler-16. Since then we’ve discovered a handful of different such programs, however what’s fascinating is that inside the first discoveries we discovered a planet within the liveable zone of a circumbinary star system.

An artist’s impression of the Kepler-11 system, which accommodates six carefully orbiting planets. Image credit score: NASA/Tim Pyle.

Jim Green:  What is the dimensions distribution of the planets that Kepler is discovering?

Jon Jenkins: We uncover extra smaller planets than we do bigger planets. That’s very fascinating as a result of it’s truly more durable to seek out the smaller planets. As beautiful as the information are from Kepler, it’s nonetheless very troublesome for us to seek out Earth-sized planets and Earth-sized orbits. We have only some examples of planets like that. In reality, Kepler’s most important mission was to find out the frequency and distribution of Earth-sized planets and Earth-like orbits round Sun-like stars.We now have a solution to that query, however it’s not very exact. Our presentdatais that about 10 p.c of solar-like stars have a planet concerning the measurement of the Earth with a one-year orbitalinterval. But the error bars on which can be very giant. So that’s a giant hole in our information.

Jim Green:  When we take a look at our personal Solar System, we’ve a set of terrestrial planets and gasoline giants. Then in between them there are Uranus and Neptune, which aren’t as large as Jupiter or Saturn. You would suppose that the Solar System would comprise all of the forms of planets that have to be, however that’s not the case is it?

Jon Jenkins: It seems that super-earths – planets which can be between the dimensions of Earth and Neptune, which is 4 occasions the dimensions of Earth by radius – are the most typical planets we discover. Yet, we’ve no examples of those beasts in our personal zoo right here in orbit round our Sun, so we don’t actually know what they may very well be like. The query is, are these planets extra like giant Earths, or are they extra like mini-neptunes?

We do have some hints. As I mentioned earlier, we solely know the planets in addition to we all know the celebs. It seems that it is rather laborious attempting to know what’s occurring in all 200,000 stars seen by Kepler. It’s actually troublesome to be taught as a lot as you’ll be able to about every a kind of. But, individuals are doing follow-up observations to refine the stellar parameters. They are discovering that there’s a break level between planets of a sure measurement. Those which can be 1.6 Earth radii, which is 60 p.c larger than the Earth, or smaller, seem almost definitely to be rocky, and planets which can be bigger than 1.6 Earth radii look like extra like mini-Neptunes, so small gasoline or ice giants.

Kepler-16b, seen on this artist’s impression, orbits two stars and has double sunsets, similar to Tatooine in Star Wars. Image credit score: NASA/JPL–Caltech/Tim Pyle.

Jim Green: Recently astronomers found the TRAPPIST-1 system of seven planets, and what’s actually thrilling is that star and its planets are solely 39 mild years away.  That’s excellent across the block. That signifies that once we go searching us in our space of the Milky Way Galaxy, there have to be an unlimited variety of planets, and so we wish to begin in search of them, which brings us to TESS. Can you inform us slightly bit about TESS?

Jon Jenkins: The TESS mission is a follow-up to Kepler. It’s an all-sky survey for transiting planets. It observes a area of view that’s a lot, a lot larger than Kepler’s area of view. It’s 24 levels by 96 levels, and so we’re observing a big swath of the sky at any given time. And we re-point the spacecraft to level at a brand new area of view each month. After one 12 months we may have coated one hemisphere, so weflipthe spacecraft the other way up after which cowl the opposite hemisphere. The concept is to watch stars which can be a lot nearer, usually 10 occasions nearer and 100 occasions brighter, than the celebs that Kepler noticed. We wish to ultimately be taught what the atmospheres of the planets orbiting these stars are fabricated from, search for biosignatures, and research their local weather and climate, so discover exoplanets which can be shut by makes that sort of detailed follow-up work a lot simpler.

Jim Green:I actually wish to ask every of my visitors on this program, what was their Gravity Assist that basically received them into the sector and propelled them ahead to turn out to be the scientists they’re at the moment. So, Jon, what was your Gravity Assist?

Jon Jenkins: Well, I had a number of Gravity Assists. I used to be lucky to develop up within the shadow of the VAB constructing.  Both of my dad and mom have been working at Kennedy Space Center.  The VAB constructing is the Vehicle Assembly Building at Kennedy Space Center on Merritt Island, Florida.It’s large. In reality, once they first constructed it, earlier than they received the air-con going, clouds would type, and it will rain contained in the constructing, my dad tells me. He was an engineer at Kennedy Space Center.  He labored on the Mercury, the Gemini and the Apollo applications after which on the shuttle program. I received to observe the launches. I bear in mind being in my pj’s, being introduced out to observe the Moon touchdown. So I’ve had a lifelong fascination with house.

When I did my Ph.D. dissertation on the ambiance of Venus, I used information from the Pioneer Venus Orbiter and the Magellan spacecraft. It was throughout that time frame that I met Bill Borucki, a co-investigator on Pioneer Venus who was learning lightning in Venus’ ambiance. He had this actually wild concept that we may discover Earth-sized planets round Sun-like stars, and 25 years in the past that was actually pie within the sky, and that grew to become the Kepler mission, and he invited me to affix it.He advised me, “Jon, you’re going to figure out how we’re going to be able to find planets like the Earth, even though the stars are highly variable and have star spots.”

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