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A Space Discovery Milestone, as Kepler Confirms 1000th Exoplanet

Kepler Mission Logo

Kepler Mission logo

It was just a few years ago, and I was excitedly reporting to you the first few exoplanets that the NASA Kepler space instrument was detecting and verifying. In fact, it was almost exactly 4 years ago today that I was telling you about confirmed exoplanet find number 9. That exoplanet, Kepler-10b, was the first confirmed find of a rocky world outside of our own solar system, and at the time was the smallest exoplanet ever discovered, at 1.4 times the diameter of Earth. Then, at the end of that year, I was telling you about the first exoplanet located by Kepler in the “habitable zone”. And in a short period of time, I was telling you about dozens of more exoplanets being confirmed, and mini-planetary systems, and exoplanets that orbit two different stars.

Well since then, Kepler’s been hard at work confirming exoplanet after exoplanet. Today, that count has reached a milestone:

NASA’s Kepler Marks 1,000th Exoplanet Discovery, Uncovers More Small Worlds in Habitable Zones

1,000 confirmed other worlds, orbiting other stars. Let me put that significance into perspective: if you were born in 1988 or earlier, you are the exoplanet generation, for 1988 was the year the first exoplanet was confirmed. I don’t know about you, but that fact really resonates with me. It proclaims to me that I live in a fantastic moment of human history. I was alive when Earthlings first knew for certain that there were planets outside of our own Solar system. And in less than three decades, we’ve found over 1,000 more. There are worlds out there, and we’re alive precisely at the time to first know it. And what’s even cooler, at least eight of those are roughly the same size as our own world and orbit their host star in what’s referred to as the habitable zone.

Artist's depiction of the 8 Earthlike planets confirmed by Kepler.

 

The Kepler mission will always be one of the most exciting for me personally, and is expected to confirm thousands more exoplanets over the coming years. What a time to be alive!

If this is as interesting to you as it is to me, here are a couple of other articles posted about Kepler discoveries that I think you’ll particularly appreciate:

Exciting Kepler News – Part 1: Mini-Planetary System

Exciting Kepler News – Part 2: New Circumbinary Planets

Kepler Finds First Earth-Sized Planets


Exciting Kepler News – Part 2: New Circumbinary Planets

 There were two exciting Kepler (the NASA mission tasked with discovering planets outside of our solar system) news released yesterday. I’m covering them in two separate posts. This is Part 2; read Part 1.

The second exciting Kepler news release is one of the most interesting yet; in fact, this discovery confirmed the existence of an entirely new class of planetary system! Today, astronomers announced the discovery of two new “circumbinary” planet systems; these follow the first circumbinary planet system announced in September of last year, the planet Kepler-16b.

So what does circumbinary mean anyway, and why is it so interesting? Let me answer the first question, which should preclude the need to answer the second.

Scene from Star Wars Episode IV: A New Hope, showing binary stars from Tatooine.
Classic scene from Star Wars Episode IV: A New Hope, showing a dual sunset from the circumbinary planet, Tatooine.

A circumbinary planet is one that orbits not one, but two stars. When Kepler-16b was confirmed last Fall, it wasn’t clear whether we should expect many more circumbinary planets or if that system was just a fluke. With the discovery of these two new systems, it is becoming apparent that circumbinary planets are abundant.

What makes this interesting is that binary-star systems are abundant in our galaxy. From the report published in Nature:

The observed rate of circumbinary planets in our sample implies that more than ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.

At least several million!

As for the planets themselves, they are both gas giants about the size of Saturn.  Kepler-34b orbits its binary-pair of Sun-like stars every 289 days, while the stars themselves orbit and eclipse each other every 28 days. Kepler-35b orbits its smaller pair of stars every 131 days, with the stars orbiting and eclipsing one another every 21 days.  The Kepler-34 and Kepler-35 systems lie in the constellation Cygnus, 4,900 and 5,400 light-years from Earth, respectively.


For more information, check out these links:

NASA Kepler News Release

The paper, published in Nature

The news release for Kepler-16b, the first circumbinary planet discovered


Exciting Kepler News – Part 1: Mini-Planetary System

 

There were two exciting Kepler (the NASA mission tasked with discovering planets outside of our solar system) news releases today. I’ll cover them in two separate posts. This is Part 1; stay tuned for Part 2.

KOI-961 Artist Concept

(Click to englarge / Image credit: NASA/JPL-Caltech)

Announced today was the discovery of the three smallest exoplanets (planets orbiting a star other than the Sun) ever discovered. These planets are orbiting a red dwarf star, currently1 named KOI-961 (KOI = Kepler Object of Interest). These planets are all smaller than our home planet, having a radius of .78, .73, and .57 that of Earth’s. (The smallest is about the size of Mars.) Though the planets are thought to be rocky, they orbit KOI-961 very closely, making them too hot to have any likelihood of being habitable.

The planets, currently 2 named KOI-961.01, KOI-961.02, and KOI-961.03, circle their host star at a fair clip, completing an orbit in less than two Earth-days. The star, KOI-961, has much less mass than our Sun. Its diameter is 1/6 the size of the Sun (which is only about 70% larger than Jupiter).

The discovery announced today came from a team of scientists, led by astronomers from the California Institute of Technology (Caltech). They made their discovery by analyzing publicly-released data from the Kepler mission. Studying KOI-961, they were able to greatly refine the preliminary estimated size of the red dwarf, and subsequently verify the presence of the three small exoplanets.

KOI-961 exoplanet comparisons

(Click to enlarge / Image Credit: NASA/JPL-Caltech)

If you’re interested in further details about how Caltech made the discovery, I highly recommend you read their press release.

So let’s take a step back and ponder about what this latest discovery means. Coupled with the many frequent previous Kepler discoveries, we’re starting to create a big picture in which planets are ubiquitous throughout the Universe. Red dwarfs are the most common type of star in at least our own galaxy, and if one red dwarf has a planetary system, it’s likely more do… maybe even most do. We’re discovering planets around different types of stars; those similar to the Sun and those considerably different. Planets of different sizes and compositions as well. Not just large gas giants with little hope for containing life, but smaller, rocky worlds. Other Earth-sized worlds. Other Earth-like orbits. Other… Earths.

The speed at which we’re making these otherworldly discoveries is astounding and encouraging. It wasn’t long ago, I sat wondering if there were other planets out there, beyond our solar system, and if they might be discovered in my life. Today, I’m overwhelmed trying to keep up with all of the new exoplanet discoveries!

This is an exciting era to live in.


  1. I say currently, because once Kepler exoplanets are confirmed, the star generally gets the designation Kepler followed by a number, and the exoplanets are named after the star, followed by a letter designation. For example, Kepler-22b orbits the star Kepler-22. The designation “b” indicates it was the second expolanet discovered in that system.
  2. See the first footnote!

Kepler Finds First Earth-Sized Planets

NASA just announced that the Kepler mission has discovered the first Earth-sized planets outside of our solar system.

The planets, Kepler-20e and Kepler-20f,  while Earth-sized and thought to be rocky, are not believed to be habitable. They are much too close to their Type G star, Kepler-20, and too hot to retain liquid water.  Kepler-20e has a radius about 13% smaller than the Earth, making it just slightly smaller than Venus, and whips around Kepler-20 in a mere 6.1 days. Kepler-20f has a radius 3% larger than that of the Earth, with its year being a still fast 19.6 days.  The Kepler-20 system is approximately 1,000 light years from Earth.

Read the NASA release for even more details.

The Kepler mission is playing out like the fairy-tale, Goldilocks and the Three Bears. By that, I mean that we’re closing in on those planets that are “just right” for harboring life. We’ve discovered large planets inside the habitable zone that lacked a rocky surface (Kepler-22b) and gas giants not unlike Jupiter. Today, we’re finding Earth-sized planets with a rocky terrain. We’re getting ever so close to discovering those “Goldilocks” planets, with the size, composition, and being within the habitable zone, that allow them to be habitable.  And with more than 2300 candidates out there still waiting to be verified by Kepler, and Kepler’s current rate of discovery, I believe the announcement of a goldilocks planet is just around the corner.

Earth-class Planets Line Up

ANOTHER Kepler Announcement Tuesday

Kepler Mission Logo

Kepler Mission logo

Kepler keeps on Kepler-ing on.

Earlier this year, I mentioned that the Kepler mission team was about to make an announcement the following day about a new discovery. The following day, the Kepler team announced the confirmation of a 9th exoplanet. Then, just earlier this week, I posted about Kepler’s 28th confirmed discovery, Kepler-22b. Kepler-22b was exciting, as the data reveals that it exists within the habitable zone of its host star.

Well, Kepler is set to make another announcement tomorrow!:

NASA’s Kepler Announcing Newly Confirmed Planets

MOFFETT FIELD, Calif. — NASA will host a news teleconference at 1 p.m. EST, Tuesday, Dec. 20, announcing new discoveries by the Kepler mission.

Kepler is the first NASA mission capable of finding Earth-size planets in or near the “habitable zone,” the region in a planetary system where liquid water can exist on the surface of an orbiting planet. Although additional observations will be needed to reach that milestone, Kepler is detecting planets and possible candidates with a wide range of sizes and orbital distances to help scientists better understand our place in the galaxy.

We’ll check back in tomorrow to learn what new and exciting discovery Kepler has for us.

*UPDATE: The press conference starts in 1pm (EST); you can listen to it live at this link: http://www.nasa.gov/news/media/newsaudio/index.html

Kepler-22b: Things Are Beginning to Look Familiar

At the beginning of this year, we were excited to help break the news of the 9th planet confirmed by the Kepler spacecraft. Not even an entire year later, Kepler is up to 28 confirmed planets and more than 2000 more candidates waiting to be studied and potentially verified!

Last week, the Kepler mission had a very exciting announcement: Kepler-22b became the first exoplanet to be located within the habitable zone.

So let’s take a look at this exoplanet. Kepler-22b has a radius around 2.4 times that of the Earth. It is located 587 light-years from Earth, orbiting a star not so much different than our own. Though Kepler-22b’s host star — Kepler-22 — is slightly smaller and cooler than the Sun, Kepler-22b orbits closer than the Earth does to the Sun, compensating for the difference. Kepler-22b’s mass and surface composition is still unknown.
Kepler Diagram
(Diagram showing a comparison between our solar system’s habitable zone with Kepler-22’s. / Credit: NASA/Ames/JPL-Caltech)
So, we have a planet not too much larger than the Earth (though we don’t know its composition or mass), orbiting a star not too much smaller/cooler than our Sun, in the so-called habitable zone. What are the chances of life? First, we have to remember that while the Earth sits in our solar system’s habitable zone, so does Mars, Ceres, and sometimes Venus, and those are hardly bodies that appear to be very conducive for life (though, I think the book on Mars still has many pages to be read). But, then there’s the Earth, that Goldilocks planet within Sol’s habitable zone; life flourishing.

So. Not only is Kepler looking in the right places but it is finding what it is looking for, and proving quite able to find out just how rare planets like our own might be. At 587 light years from Earth we won’t be sending a probe to Kepler-22b to do reconnaissance anytime soon, but this discovery does fuel our imaginations, fill our minds with knowledge, and inspire us to carry on looking. At the very least, it proves just how capable the Kepler spacecraft is and just how amazing the mission truly is.

Follow-Up To Kepler Announcement

Kepler Mission Logo

Kepler Mission logo

As mentioned in the last post, NASA’s Kepler mission made an announcement today, about the confirmation of another exoplanet.

This was a fascinating find, as the planet discovered — Kepler-10b — is only 1.4 times the size of Earth, and probably terrestrial (rocks and metal; not a gas giant) in nature. This discovery marks the smallest exoplanet yet discovered! Not bad, for something 560 light years away.

Remember, Kepler’s goal is to discover “Earth-like” planets, and then determine how many of them might be in a habitable zone. Is Kepler-10b habitable? It would be highly unlikely. The planet orbits its host star, Kepler 10 (see how they do that?), in an orbit that brings it much closer than Mercury is to the Sun; more than 20 times closer. This means Kepler-10b is hot… several thousand degrees hot! On top of that, it has more than 4-and-half times the mass of the Earth. Standing on Kepler-10b would give new meaning to the phrase, “hot and heavy”.

Planet Kepler-10b Transiting Its Host Star (Artist's Depiction)

Planet Kepler-10b Transiting Its Host Star (Artist's Depiction) / Credit: NASA/Kepler Mission/Dana Berry

Another interesting bit of information, is that it’s expected to be tidally locked to Kepler 10. Just as the Moon only shows its one face to Earth, Kepler-10b only shows one face to its star. My imagination quickly conjures up an imagination of a planet habitable on one side, and a scorched realm of hellfire on the other — but the facts probably indicate the entire thing is closer to the latter; a big dense glob of molten material.

So, let’s quickly recap some of the highlights of Kepler’s 9th confirmed exoplanet discovery.

Diameter: 1.4 Earths
Mass: 4.6 Earth mass
Smallest exoplanet ever discovered
Orbital period: .84 days (that thing is screaming around the Kepler 10)
Harbors Life?: Highly improbably (no, not even arsenic-based life!)

Following the announcement, NASA/Kepler held a chat with Kepler Mission expert, Natalie Batalha. It was open to anyone who wanted to join in, and I noticed about 250 participants during the event. There were some great questions and answers, and a full transcript should be up within a couple of days.

I collected a few questions and answers to keep you interested while we wait:

Q: Can Kepler determine anything about the chemical content of a candidate planet’s atmosphere to determine if it would be suitable for life as we know it?

Natalie: Kepler can not probe the atmosphere of the planet, no. However, I fully expect other telescopes and missions to do transmission spectroscopy to see if it has an atmosphere. With transmission spectroscopy, you observe the planet when it is right in front of the star (allowing starlight to stream through its atmosphere) and then you observe it when it is not in front of the star. Then, you compare the two to see what the atmosphere might have done to the starlight.

Q: How do you measure the planet mass, size and the distance to the star? And the planet composition?

Natalie: Mass comes from the Doppler measurements of the wobble of the star as the planet/star orit about their commone center of mass. Radius comes from the amount of dimming of starlight that occurs during transit. The distance can be derived if you know the surface temperature and radius of the star. Together they give the intrinsic brightness. We know how bright the star appears to us. Knowing how right it SHOULD be instrinsically allows us to determine how far away it is — 560 light-years for Kepler-10.

Q: What are the prospects for additional planets in the Kepler 10 star system? Any hints?

Natalie: There is actually already a very compelling signature of another potential planet in this system. There is a transit event that recurs once every 45 days and is suggestive of a planet a bit larger than 2 times the radius of the Earth.

The Kepler Mission is a wonderful tool to unlocking our understanding of planets outside our own solar system. It’s an exciting time to be on the one known planet (so far!) that allows us to enjoy it.

Kepler Planet Discovery Announcement On Monday

Kepler Mission Logo

Kepler Mission logo

NASA’s Kepler mission will be holding a press conference tomorrow, to make an announcement about a “new planet discovery”.

From the Kepler website:

A new planet discovery will be announced Monday Jan. 10 during the ‘Exoplanets & Their Host Stars’ presentation at the American Astronomical Society (AAS) conference in Seattle, Washington.

Natalie Batalha of the NASA Kepler Mission Team will be online answering your questions about this new planet finding on Monday, Jan. 10 from 3:30 p.m. to 4:30 p.m. EST / 12:30 p.m. to 1:30 p.m. PST. Natalie will be chatting with you live from the conference in Seattle.

The chat can be found at this website.

Painting of the Milky Way, with details of Kepler Mission added - Credit: NASA Kepler and Jon Lomberg


To summarize the mission, Kepler is a space-observatory –launched in 2009 — designed to discover Earth-like planets orbiting other stars. It has a planned mission lifetime of 3.5 years. Kepler measures light from stars, and watches for dimming which could indicate a planet transiting in front of the star. Many of the stars Kepler has observed have been variable stars — stars whose brightness changes naturally, as opposed to anything blocking some of its light. These variable stars are dropped from the target database, and replaced with new candidates.

What types of exoplanets is Kepler looking for specifically? According to the Kepler mission page:

The challenge now is to find terrestrial planets (i.e., those one half to twice the size of the Earth), especially those in the habitable zone of their stars where liquid water and possibly life might exist.

The Kepler Mission, NASA Discovery mission #10, is specifically designed to survey a portion of our region of the Milky Way galaxy to discover dozens of Earth-size planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets.

So far, Kepler has found more than 700 planet candidates, which require further data-analysis and ground-based observations to rule out any “false signatures”. Kepler has 8 confirmed planets. These have ranged in mass from 7.7% to more than double the mass of Jupiter. For comparison, Jupiter is 317 times more massive than the Earth — or, Earth is .3% the mass of Jupiter.

So, we wait until tomorrow (or today for many of you) to find out the details of our newly discovered exoplanet friend.

7 Earth-Sized Worlds Discovered Orbiting Nearby Star

Artist's concept of the surface of TRAPPIST1-f.

Artist’s concept of the surface of TRAPPIST1-f. – Credit: NASA/JPL-Caltech

NASA held a press conference today, announcing an exciting new discovery: A record-breaking seven Earth-sized planets have been discovered orbiting a star located about 40 light years from Earth. Three of these planets are firmly located within what’s called the habitable zone–the area around a star that is likely to have rocky planets with liquid water.

The star is named TRAPPIST-1 (also known as 2MASS J23062928-0502285). It’s an ‘ultra-cool dwarf’ star, with approximately 8% of the mass and 11% of the radius of our Sun. Size-wise, this is approximately the difference between a basketball and a golfball.

The seven plants surrounding TRAPPIST-1 orbit much closer to their star than Earth does to the Sun. As well, these exoplanets are much closer to each other than the planets in our own system. You could stand on one of these planets and see the next closest one with a similar type of view that we have with the Moon here on Earth, and you could clearly make out the disc-shape of many of the other planets rather than mere points of light.

The discoveries were made using data from the Spitzer Space Telescope, which was launched in 2003. Although Spitzer wasn’t specifically designed to observe exoplanets, the suite of instruments it carries allows it to discover exoplanets in the same manner that the Kepler spacecraft uses. These observatories can discover exoplanets by precisely measuring dips in the light emitted from a star that coincides with a planet orbiting in-between that star and our vantage point and blocking a portion of the light that we can measure. Continued observations can determine orbital periods, distance from the star, and the number of exoplanets in a system. This data can be used to plot habitable zones.

During the press conference, the team stated that they had preliminary mass measurements for six of the planets, and they believe that one is likely to have a water-rich composition.

Artist's concept shows what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances.

Artist’s concept shows what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances. – Credit: NASA/JPL-Caltech

There currently isn’t a system for naming exoplanets in the way that bodies like asteroids are named, so they’re simply provided with alphabetic designations appended to their host stars’ name, with the designation ‘b’ being the closest to the star.

These planets orbit so close to their star that they’re likely tidally-locked in the same manner that the Moon is to the Earth. These planets would have permanent day and night sides.

One of the planets, Trappist-1c, is very similar in size to Earth and receives about the same amount of light as Earth receives from the Sun. It could very well have temperatures similar to those we have on Earth. Trappist-1f has a 9-day orbit and receives about as much light as Mars does. Trappist-1g is the largest planet in the system with an estimated radius 13% larger than Earth.

All of the planets are within a few times the distance between the Earth and the Moon of each other, and being so close to their star their orbits (their years) are about 1.5 Earth days for the closest planet and 20 days for the furthest.

Concept art for TRAPPIST-1 and its seven Earth-sized exoplanets.

Concept art for TRAPPIST-1 and its seven Earth-sized exoplanets. – Credit: NASA/JPL-Caltech

The next step, which is already ongoing, is to study their atmospheres and to look for water. This can be accomplished using a technique called transmission spectroscopy. We have observatories that can do this now, such as the Hubble Space Telescope, and the future James Webb Space Telescope (JWST) will be able to push these capabilities even further. JWST will be able to look for greenhouse gas content and determine the surface temperatures of these planets, as well as detect gases that are produced by life. It’s expected that the first cycle of observations of the JWST will include the TRAPPIST-1 system.

Thomas Zurbuchen, associate administrator of the agency’s Science Mission Directorate in Washington, referred to our moment in time as “the gold rush phase of exoplanet discovery.”  It was just in 1995 that the first exoplanet was discovered, he explained, and that thousands have been discovered since.

Following the announcement, the panel held a Q&A session. During the course of their answers, they explained that there was no indication of these planets having moons, but that if water was present there would be tidal activity resulting from the other planets. They said they expect substantial progress in determining the atmospheric composition of these exoplanets within the next 5 years, utilizing the Hubble Space Telescope and the James Webb Space Telescope after it begins operations in 2018. JWST’s transmission spectroscopy will cover the range needed to determine the potential for life.

One member asked if any attempts have been made to listen to the system with SETI-style instruments, to which there was a reply that SETI itself had listened to the system but hadn’t picked-up any signals.

One of the most interesting answers came from Zurbuchen, when he was asked when we could expect to construct a craft that could journey to this system. Rather than give an estimate in the number of years in the future we could expect such capabilities, he answered with the estimated “number of miracles” that are required before we get there. He explained that the JWST required 10 miracles to become possible. He likened the construction of a craft that could explore TRAPPIST-1 as requiring “100 miracles”, but that we shouldn’t be dissuaded, that to get there you have to “start inventing your way forward.” Some of the “miracles” require advancements in propulsion systems and radiation-protection, and that the good news was that substantial work is already being accomplished towards about 5-10 of these miracles. He said it’s about “leaning forward” and “not backing up”.

Discoveries like these are constant reminders of just how big and amazing our Universe is. We’re reminded that the night sky isn’t just full of points of light, but worlds, perhaps some of which might be very similar to our own.

A poster advertising a hypothetical planet-hopping trip in the Trappist-1 system

A poster advertising a hypothetical planet-hopping trip in the Trappist-1 system – Credit: NASA-JPL/Caltech