Kepler mission Archives

January 5, 2017 by Matt Williams

Could Garnet Planets be Habitable?

A new study based on data from Sloan Digital Sky Survey (SDSS) shows how certain exoplanets are dominated by minerals like olivine and garnet. Credit: NASA

The hunt for exoplanet has revealed some very interesting things about our Universe. In addition to the many gas giants and “Super-Jupiters” discovered by mission like Kepler, there have also been the many exoplanet candidate that comparable in size and structure to Earth. But while these bodies may be terrestrial (i.e. composed of minerals and rocky material) this does not mean that they are “Earth-like”.

For example, what kind of minerals go into a rocky planet? And what could these particular compositions mean for the planet’s geological activity, which is intrinsic to planetary evolution? According to new study produced by a team of astronomers and geophysicists, the composition of an exoplanet depends on the chemical composition of its star – which can have serious implications for its habitability.

The findings of this study were presented at the 229th Meeting of the American Astronomical Society (AAS), which will be taking place from Jan. 3rd to Jan. 7th. During an afternoon presentation – titled “Between a Rock and a Hard Place: Can Garnet Planets Be Habitable?” – Johanna Teske (an astronomer from the Carnegie Institute of Science) showed how different types of stars can produce vastly different types of planets.

*The Apache Point Observatory Galactic Evolution Experiment (APOGEE), which collects spectrographic information on distant stars. Credit: astronomy.as.virginia.edu*

Using the Apache Point Observatory Galactic Evolution Experiment (APOGEE), which is part of the Sloan Digital Sky Survey (SDSS) Telescope at Apache Point Observatory, they examined spectrographic information obtained from 90 star systems – which were also observed by the Kepler Mission. These systems are of particular interest to exoplanet hunters because they have been shown to contain rocky planets.

As Teske explained during the course of the presentation, this information could help scientists to place further constraints on what it takes for a planet to be habitable. “[O]ur study combines new observations of stars with new models of planetary interiors,” she said. “We want to better understand the diversity of small, rocky exoplanet composition and structure — how likely are they to have plate tectonics or magnetic fields?”

Focusing on two star systems in particular – Kepler 102 and Kepler 407 – Teske demonstrated how the composition of a planet has a great deal to do with the composition of its star. Whereas Kepler 102 has five known planets, Kepler 407, has two different planets – one gaseous and the other terrestrial. And while Kepler 102 is quite similar to our Sun (slightly less luminous), Kepler 407 has close to the same mass (but a lot more silicon).

In order to understand what consequences these differences could have for planetary formation, the SDSS team turned to a team of geophysicists. Led by Cayman Unterborn from Arizona State University, this team ran computer models to see what kinds of planets each system would have. As Unterborn explained:

“We took the star compositions found by APOGEE and modeled how the elements condensed into planets in our models. We found that the planet around Kepler 407, which we called ‘Janet,” would likely be rich in the mineral garnet. The planet around Kepler 102, which we called ‘Olive,’ is probably rich in olivine, like Earth.”

*Artist rendition of interior compositions of planets around the stars Kepler 102 and Kepler 407. Credit: Robin Dienel/Carnegie DTM*

This difference would have considerable impact on planetary tectonics. For one, garnet is lot more rigid than olivine, which would mean “Janet” would experience less in the way of long-term plate tectonics. This in turn would mean that processes that are believed to be essential to life on Earth – like volcanic activity, atmospheric recycling, and mineral exchanges between the crust and mantle – would be less common.

This raises additional questions about the habitability of “Earth-like” planets in other star systems. In addition to being rocky and having strong magnetic fields and viable atmospheres, it seems that exoplanets also need to have the right mix of minerals in order to support life – life as we know it, at any rate. What’s more, this kind of research also helps us to understand how life came to emerge on Earth in the first place.

Looking forward, the research team hopes to extend their study to include all the 200,000 stars surveyed by APOGEE to see which could host terrestrial planets. This will allow astronomers to determine the mineral composition of more rocky worlds, thus helping them to determine which rocky exoplanets are “Earth-like”, and which are just “Earth-sized”.

Further Reading: SDSS

November 19, 2016November 26, 2016 by Matt Williams

This Star Is The Roundest Natural Object Ever Seen

The star Kepler 11145123 is the roundest natural object ever measured in the universe, with a difference of just 3 km between the radius at the equator and the poles. Credit and ©: Mark A. Garlick

At one time, scientists believed that the Earth, the Moon, and all the other planets in our Solar System were perfect spheres. The same held true for the Sun, which they considered to be the heavenly orb that was the source of all our warmth and energy. But as time and research showed, the Sun is far from perfect. In addition to sunspots and solar flares, the Sun is not completely spherical.

For some time, astronomers believed this was the case with other stars as well. Owing to a number of factors, all stars previously studied by astronomers appeared to experience some bulging at the equator (i.e. oblateness). However, in a study published by a team of international astronomers, it now appears that a slowly rotating star located 5000 light years away is as close to spherical as we’ve ever seen!

Until now, observation of stars has been confined to only a few of the fastest-rotating nearby stars, and was only possible through interferometry. This technique, which is typically used by astronomers to obtain stellar size estimates, relies on multiple small telescopes obtaining electromagnetic readings on a star. This information is then combined to create a higher-resolution image that would be obtained by a large telescope.

Artist's impression of a white dwarf star in orbit around Sirius (a white supergiant). Credit: NASA, ESA and G. Bacon (STScI) — *Artist’s impression of a Sirius, an A-type Main Sequence White star. Credit: NASA, ESA and G. Bacon (STScI)*

However, by conducting asteroseismic measurements of a nearby star, a team of astronomers – from the Max Planck Institute, the University of Tokyo, and New York University Abu Dhabi (NYUAD) – were able to get a much more precise idea of its shape. Their results were published in a study titled “Shape of a Slowly Rotating Star Measured by Asteroseismology“, which recently appeared in the American Association for the Advancement of Science.

Laurent Gizon, a researcher with the Max Planck Institute, was the lead authjor on the paper. As he explained their research methodology to Universe Today via email:

“The new method that we propose in this paper to measure stellar shapes, asteroseismology, can be several orders of magnitude more precise than optical interferometry. It applies only to stars that oscillate in long-lived non-radial modes. The ultimate precision of the method is given by the precision on the measurement of the frequencies of the modes of oscillation. The longer the observation duration (four years in the case of Kepler), the better the precision on the mode frequencies. In the case of KIC 11145123 the most precise mode frequencies can be determined to one part in 10,000,000. Hence the astonishing precision of asteroseismology.”

Located 5000 light years away from Earth, KIC 11145123 was considered a perfect candidate for this method. For one, Kepler 11145123 is a hot and luminous, over twice the size of our Sun, and rotates with a period of 100 days. Its oscillations are also long-lived, and correspond directly to fluctuations in its brightness. Using data obtained by NASA’s Kepler mission over a more than four year period, the team was able to get very accurate shape estimates.

The variations in brightness can be interpreted as vibrations, or oscillations within the stars, using a technique called asteroseismology. The oscillations reveal information about the internal structure of the stars, in much the same way that seismologists use earthquakes to probe the Earth's interior. Credit: Kepler Astroseismology team. — *The variations in brightness can be interpreted as vibrations, or oscillations within the stars, using a technique called asteroseismology. Credit: Kepler Astroseismology team.*

“We compared the frequencies of the modes of oscillation that are more sensitive to the low-latitude regions of the star to the frequencies of the modes that are more sensitive to higher latitudes,” said Gizon. “This comparison showed that the difference in radius between the equator and the poles is only 3 km with a precision of 1 km. This makes Kepler 11145123 the roundest natural object ever measured, it is even more round than the Sun.”

For comparison, our Sun has a rotational period of about 25 days, and the difference between its polar and equatorial radii is about 10 km. And on Earth, which has a rotational period of less than a day (23 hours 56 minutes and 4.1 seconds), there is a difference of over 23 km (14.3 miles) between its polar and equator. The reason for this considerable difference is something of a mystery.

In the past, astronomers have found that the shape of a star can come down to multiple factors – such as their rotational velocity, magnetic fields, thermal asphericities, large-scale flows, strong stellar winds, or the gravitational influence of stellar companions or giant planets. Ergo, measuring the “asphericity” (i.e. the degree to which a star is NOT a sphere) can tell astronomers much about the star structures and its system of planets.

Ordinarily, rotational velocity has been seen to have a direct bearing on the stars asphericity – i.e. the faster it rotates, the more oblate it is. However, when looking at data obtained by the Kepler probe over a period of four years, they noticed that its oblateness was only a third of what they expected, given its rotational velocity.

Laurent Gizon, the lead researcher of the study, pictured comparing images of our Sun and Kepler 11145123. Credit: Max Planck Institute for Solar System Research, Germany. — *Laurent Gizon, the lead researcher of the study, pictured with asteroseismic readings of Kepler 11145123. Credit: Max Planck Institute for Solar System Research, Germany.*

As such, they were forced to conclude that something else was responsible for the star’s highly spherical shape. “”We propose that the presence of a magnetic field at low latitudes could make the star look more spherical to the stellar oscillations,” said Gizon. “It is known in solar physics that acoustic waves propagate faster in magnetic regions.”

Looking to the future, Gizon and his colleagues hope to examine other stars like Kepler 11145123. In our Galaxy alone, there are many stars who’s oscillations can be accurately measured by observing changes in their brightness. As such, the international team hopes to apply their asteroseismology method to other stars observed by Kepler, as well as upcoming missions like TESS and PLATO.

“Just like helioseismology can be used to study the Sun’s magnetic field, asteroseismology can be used to study magnetism on distant stars,” Gizon added. “This is the main message of this study.”

Further Reading: ScienceMag, Max Planck Institute

August 9, 2016September 26, 2016 by Matt Williams

Tabby’s Star Megastructure Mystery Continues To Intrigue

Artist's concept of KIC 8462852, which has experienced unusual changes in luminosity over the past few years. Credit: NASA, JPL-Caltech

Last fall, astronomers were surprised when the Kepler mission reported some anomalous readings from KIC 8462852 (aka. Tabby’s Star). After noticing a strange and sudden drop in brightness, speculation began as to what could be causing it – with some going so far as to suggest that it was an alien megastructure. Naturally, the speculation didn’t last long, as further observations revealed no signs of intelligent life or artificial structures.

But the mystery of the strange dimming has not gone away. What’s more, in a paper posted this past Friday to arXiv, Benjamin T. Montet and Joshua D. Simon (astronomers from the Cahill Center for Astronomy and Astrophysics at Caltech and the Carnegie Institute of Science, respectively) have shown how an analysis of the star’s long-term behavior has only deepened the mystery further.

To recap, dips in brightness are quite common when observing distant stars. In fact, this is one of the primary techniques employed by the Kepler mission and other telescopes to determine if planets are orbiting a star (known as Transit Method). However, the “light curve” of Tabby’s Star – named after the lead author of the study that first detailed the phenomena (Tabetha S. Boyajian) – was particularly pronounced and unusual.

*Freeman Dyson theorized that eventually, a civilization would be able to build a megastructure around its star to capture all its energy. Credit: SentientDevelopments.com*

According to the study, the star would experience a ~20% dip in brightness, which would last for between 5 and 80 days. This was not consistent with a transitting planet, and Boyajian and her colleagues hypothesized that it was due to a swarm of cold, dusty comet fragments in a highly eccentric orbit accounted for the dimming.

However, others speculated that it could be the result of an alien megastructure known as Dyson Sphere (or Swarm), a series of structures that encompass a star in whole or in part. However, the SETI Institute quickly weighed in and indicated that radio reconnaissance of KIC 8462852 found no evidence of technology-related radio signals from the star.

Other suggestions were made as well, but as Dr. Simon of the Carnegie Institute of Science explained via email, they fell short. “Because the brief dimming events identified by Boyajian et al. were unprecedented, they sparked a wide range of ideas to explain them,” he said. “So far, none of the proposals have been very compelling – in general, they can explain some of the behavior of KIC 8462852, but not all of it.”

To put the observations made last Fall into a larger context, Montet and Simon decided to examine the full-frame photometeric images of KIC 8462852 obtained by Kepler over the last four years. What they found was that the total brightness of the star had been diminishing quite astonishingly during that time, a fact which only deepens the mystery of the star’s light curve.

Photometry of KIC8462852 as measured by Kepler data. The analysis reveals a slow but steady decrease in the star’s luminosity for about 1000 days, followed by a period of more rapid decline. Credit: Montet & Simon 2016 — *Photometry of KIC8462852 obtained by the Kepler mission, showing a period of more rapid decline during the later period of observation. Credit: Montet & Simon 2016*

As Dr. Montet told Universe Today via email:

“Every 30 minutes, Kepler measures the brightness of 160,000 stars in its field of view (100 square degrees, or approximately as big as your hand at arm’s length). The Kepler data processing pipeline intentionally removes long-term trends, because they are hard to separate from instrumental effects and they make the search for planets harder. Once a month though, they download the full frame, so the brightness of every object in the field can be measured. From this data, we can separate the instrumental effects from astrophysical effects by seeing how the brightness of any particular star changes relative to all its neighboring stars.”

Specifically, they found that over the course of the first 1000 days of observation, the star experienced a relatively consistent drop in brightness of 0.341% ± 0.041%, which worked out to a total dimming of 0.9%. However, during the next 200 days, the star dimmed much more rapidly, with its total stellar flux dropping by more than 2%.

For the final 200 days, the star’s magnitude once again consistent and similar to what it was during the first 1000 – roughly equivalent to 0.341%. What is impressive about this is the highly anomalous nature of it, and how it only makes the star seem stranger. As Simon put it:

“Our results show that over the four years KIC 8462852 was observed by Kepler, it steadily dimmed. For the first 2.7 years of the Kepler mission the star faded by about 0.9%. Its brightness then decreased much faster for the next six months, declining by almost 2.5% more, for a total brightness change of around 3%. We haven’t yet found any other Kepler stars that faded by that much over the four-year mission, or that decreased by 2.5% in six months.”

Artist's conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech — *Artist’s conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech*

Of the over 150,000 stars monitored by the Kepler mission, Tabby’s Starr is the only one known to exhibit this type of behavior. In addition, Monetet and Cahill compared the results they obtained to data from 193 nearby stars that had been observed by Kepler, as well as data obtained on 355 stars with similar stellar parameters.

From this rather large sampling, they found that a 0.6% change in luminosity over a four year period – which worked out to about 0.341% per year – was quite common. But none ever experienced the rapid decline of more than 2% that KIC 8462852 experienced during that 200 days interval, or the cumulative fading of 3% that it experienced overall.

Montet and Cahill looked for possible explanations, considering whether the rapid decline could be caused by a cloud of transiting circumstellar material. But whereas some phenomena can explain the long-term trend, and other the short-term trend, no one explanation can account for it all. As Montet explained:

“We propose in our paper that a cloud of gas and dust from the remnants of a planetesimal after a collision in the outer solar system of this star could explain the 2.5% dip of the star (as it passes along our line of sight). Additionally, if some clumps of matter from this collision were collided into high-eccentricity comet-like orbits, they could explain the flickering from Boyajian et al., but this model doesn’t do a nice job of explaining the long-term dimming. Other researchers are working to develop different models to explain what we see, but they’re still working on these models and haven’t submitted them for publication yet. Broadly speaking, all three effects we observe cannot be explained by any known stellar phenomenon, so it’s almost certainly the result of some material along our line of sight passing between us and the star. We just have to figure out what!”

So the question remains, what accounts for this strange dimming effect around this star? Is there yet some singular stellar phenomena that could account for it all? Or is this just the result of good timing, with astronomers being fortunate enough to see a combination of a things at work in the same period? Hard to say, and the only way we will know for sure is to keep our eye on this strangely dimming star.

And in the meantime, will the alien enthusiasts not see this as a possible resolution to the Fermi Paradox? Most likely!

Further Reading: arXiv

June 1, 2016June 13, 2016 by Evan Gough

Student Discovers Four New Planets

The four new, but as yet unconfirmed, exoplanets. Image: University of British Columbia

A student at the University of British Columbia (UBC), Canada, has discovered four new exoplanets hidden in data from the Kepler spacecraft.

Michelle Kunimoto recently graduated from UBC with a Bachelor’s degree in physics and astronomy. As part of her coursework, she spent a few months looking closely at Kepler data, trying to find planets that others had overlooked.

In the end, she discovered four planets, (or planet candidates until they are independently confirmed.) The first planet is the size of Mercury, two are roughly Earth-sized, and one is slightly larger than Neptune. According to Kunimoto, the largest of the four, called KOI (Kepler Object of Interest) 408.05, is the most interesting. That one is 3,200 light years away from Earth and occupies the habitable zone of its star.

“Like our own Neptune, it’s unlikely to have a rocky surface or oceans,” said Kunimoto, who graduates today from UBC. “The exciting part is that like the large planets in our solar system, it could have large moons and these moons could have liquid water oceans.”

Her astronomy professor, Jaymie Matthews, shares her enthusiasm. “Pandora in the movie Avatar was not a planet, but a moon of a giant planet,” he said. And we all know what lived there.

On its initial mission, Kepler looked at 150,000 stars in the Milky Way. Kepler looks for dips in the brightness of these stars, which can be caused by planets passing between us and the star. These dips are called light curves, and they can tell us quite a bit about an exoplanet.

“A star is just a pinpoint of light so I’m looking for subtle dips in a star’s brightness every time a planet passes in front of it,” said Kunimoto. “These dips are known as transits, and they’re the only way we can know the diameter of a planet outside the solar system.”

Michelle Kunimoto and her prof., Jaymie Matthews, at the University of British Columbia in Vancouver, Canada. Image: Martin Dee/UBC

One of the limitations of the Kepler mission is that it’s biased against planets that take a long time to orbit their star. That’s because the longer the orbit is, the fewer transits can be witnessed in a given amount of time. The “warm Neptune” KOI 408.05 found by Kunimoto takes 637 days to orbit its sun.

This long orbit explains why the planet was not found initially, and also why Kunimoto is receiving recognition for her discovery. It took a substantial commitment and effort to uncover it. Kepler has discovered almost 5,000 planet and planet candidates, and of those, only 20 have longer orbits than KOI 408.05.

Kunimoto and Matthews have submitted the findings to the Astronomical Journal. They may be the first of many submissions for Kunimoto, as she is returning to UBC next year to earn a Master’s Degree in physics and astronomy, when she will hunt for more planets and investigate their habitability.

The fun didn’t end with her exoplanet discovery, however. As a Star Trek fan (who isn’t one?) she was lucky enough to meet William Shatner at an event at the University, and to share her discovery with Captain James Tiberius Kirk.

It makes you wonder what other surprises might lie hidden in the Kepler data, and what else might be uncovered. Might a life-bearing planet or moon, maybe the only one, be found in Kepler’s data at some future time?

You can read Kunimoto’s paper here.

May 12, 2016May 15, 2016 by Evan Gough

2007 OR10 Needs A Name. We Suggest Dwarfplanet McDwarfplanetyface

Results of a study combining Kepler observations with Herschel data show that 2007 OR10 is the largest unnamed dwarf planet in our Solar System, and the third largest overall. Illustration: Konkoly Observatory/András Pál, Hungarian Astronomical Association/Iván Éder, NASA/JHUAPL/SwRI

Depending on shifting definitions of what exactly is or isn’t a dwarf planet, our Solar System has about half a dozen dwarf planets. They are: Pluto, Eris, Haumea, Makemake, Ceres, and 2007 OR10.

Even though 2007 OR10’s name makes it stand out from the rest, dwarf planets as a group are an odd bunch. They spend their time in the cold, outer reaches of the Solar System, with Ceres being the only exception. Ceres resides in the asteroid belt between Mars and Jupiter.

Their distance from Earth makes them difficult targets for observation, even with the largest telescopes we have. Even the keen eye of the Hubble Telescope, orbiting above Earth’s view-inhibiting atmosphere, struggles to get a good look at the dwarf planets. But astronomers using the Kepler spacecraft discovered that its extreme light sensitivity have made it a useful tool to study the dwarves.

In a paper published in The Astronomical Journal, a team led by Andras Pal, at Konkoly Observatory in Budapest, Hungary, have refined the measurement of 2007 OR10. Using the Kepler’s observational prowess, and combining it with archival data from the Herschel Space Observatory, the team has come up with a much more detailed understanding of 2007 OR10.

Previously, 2007 OR10 was thought to be about 1280 km (795 miles) in diameter. But the problem is the dwarf planet was only a faint, tiny, and distant point of light. Astronomers knew it was there, but didn’t know much else. Objects as far away as 2007 OR10, which is currently twice as far away from the Sun as Pluto is, can either be small, bright objects, or much larger, dimmer objects that reflect less light.

This is where the Kepler came in. It has exquisite sensitivity to tiny changes in light. Its whole mission is built around that sensitivity. It’s what has made Kepler such an effective tool for identifying exo-planets. Pointing it towards a tiny target like 2007 OR10, and monitoring the reflected light as the object rotates, is a logical use for Kepler.

Even so, Kepler alone wasn’t able to give the team a thorough understanding of the dwarf planet with the clumsy name.

Enter the Herschel Space Observatory, a powerful infrared space telescope. Herschel and its 3.5 metre (11.5 ft.) mirror were in operation at LaGrange 2 from 2009 to 2013. Herschel discovered many things in its mission-span, including solid evidence for comets being the source of water for planets, including Earth.

But the Herschel Observatory also bequeathed an enormous archive of data to astronomers and other space scientists. And that data was crucial to the new measurement of 2007 OR10.

Combining data and observations from multiple sources is not uncommon, and is often the only way to learn much about distant, tiny objects. In this case, the two telescopes were together able to determine the amount of sunlight reflected by the dwarf planet, using Kepler’s light sensitivity, and then measure the amount of that light later radiated back as heat, using Herschel’s infrared capabilities.

Combining those datasets gave a much clearer idea of the size, and reflectivity, of 2007 OR10. In this case, the team behind the new paper was able to determine that 2007 OR10 was significantly larger than previously thought. It’s measured size is now 1535 km (955 mi) in diameter. This is 255 km (160 mi) larger than previously measured.

It also tells us that the dwarf planet’s gravity is stronger, and the surface darker, than previously measured. This further cements the oddball status of 2007 OR10, since other dwarf planets are much brighter. Other observations of the planet have shown that is has a reddish color, which could be the result of methane ice on the surface.

Lead researcher Andras Pal said, “Our revised larger size for 2007 OR10 makes it increasingly likely the planet is covered in volatile ices of methane, carbon monoxide and nitrogen, which would be easily lost to space by a smaller object. It’s thrilling to tease out details like this about a distant, new world — especially since it has such an exceptionally dark and reddish surface for its size.”

Now that more is known about 2007 OR10, perhaps its time it was given a better name, something that’s easier to remember and that helps it fit in with its peer planets Pluto, Ceres, Eris, Haumea, and Makemake. According to convention, the honor of naming it goes to the planet’s discoverers, Meg Schwamb, Mike Brown and David Rabinowitz. They discovered it in 2007 during a search for distant bodies in the Solar System.

According to Schwamb, “The names of Pluto-sized bodies each tell a story about the characteristics of their respective objects. In the past, we haven’t known enough about 2007 OR10 to give it a name that would do it justice. I think we’re coming to a point where we can give 2007 OR10 its rightful name.”

The Universe is vast, and we need some numbered, structured way to name everything. And these names have to mean something scientifically. That’s why objects end up with names like 2007 OR10, or SDSS J0100+2802, the name given to a distant, ancient quasar. But objects closer to home, and certainly everything in our Solar System, deserves a more memory-friendly name.

So what’s it going to be? If you think you have a great name for the oddball dwarf named 2007 OR10, let us hear it in a tweet, or in the comments section.

December 1, 2015December 23, 2015 by Nancy Atkinson

Spinning Worlds: Orrery of Kepler’s Exoplanets, Part IV

A mechanical orrery from the 1800's. Image credit: Armagh Observatory.

The past few years, Daniel Fabrycky from the Kepler spacecraft science team has put together some terrific orrery-type visualization of all the multiple-planet systems discovered by the Kepler spacecraft. An orrery, as you probably know, is a a mechanical model of a solar system, and the metal or plastic ones available these days usually show the relative positions and motions of our own Sun, Earth, Moon and other planets.

However, the Kepler version of the orreries that have been created are video visualizations of the planetary systems discovered by the Kepler mission that have more than one transiting object. This latest version was created by astronomy graduate student Ethan Kruse and it shows all of the Kepler multi-planet systems (1705 planets in 685 systems as of November 24, 2015) on the same scale as our own Solar System (the dashed lines on the right side of the video).

In the description of the video Kruse said the size of the orbits are all to scale, but the size of the planets are not. “For example, Jupiter is actually 11 times larger than Earth, but that scale makes Earth-size planets almost invisible (or Jupiters annoyingly large),” he explained. “The orbits are all synchronized such that Kepler observed a planet transit every time it hits an angle of 0 degrees (the 3 o’clock position on a clock).”

Additionally, planet colors are based on their approximate equilibrium temperatures, as shown in the legend.

If you think these orreries are pretty great, you can now try your hand at making your own. Kruse said he likes open source and that any software he writes will be available on GitHub. You can get the source code here.

Enjoy!

October 16, 2015December 23, 2015 by Bob King

What’s Orbiting KIC 8462852 – Shattered Comet or Alien Megastructure?

Something other than a transiting planet makes the Kepler star KIC fluctuate wildly and unpredictably in brightness. Astronomers suspect a shattered comet, but who knows? Credit: NASA

“Bizarre.” “Interesting.” “Giant transit”. That were the reactions of Planet Hunters project volunteers when they got their first look at the light curve of the otherwise normal sun-like star KIC 8462852 nearly.

Of the more than 150,000 stars under constant observation during the four years of NASA’s primary Kepler Mission (2009-2013), this one stands alone for the inexplicable dips in its light. While almost certainly naturally-caused, some have suggested we consider other possibilities.

Kepler-11 is a sun-like star around which six planets orbit. At times, two or more planets pass in front of the star at once, as shown in this artist's conception of a simultaneous transit of three planets observed by NASA's Kepler spacecraft on Aug. 26, 2010. Image credit: NASA/Tim Pyle — Kepler-11, a sun-like star orbited by six planets. At times, two or more planets pass in front of the star at once, as shown in this artist’s conception of a simultaneous transit of three planets observed by the Kepler spacecraft on Aug. 26, 2010. During each pass or transit, the star’s light fades in a periodic way.
Credit: NASA/Tim Pyle

You’ll recall that the orbiting Kepler observatory continuously monitored stars in a fixed field of view focused on the constellations Lyra and Cygnus hoping to catch periodic dips in their light caused by transiting planets. If a drop was seen, more transits were observed to confirm the detection of a new exoplanet.

And catch it did. Kepler found 1,013 confirmed exoplanets in 440 star systems as of January 2015 with 3,199 unconfirmed candidates. Measuring the amount of light the planet temporarily “robbed” from its host star allowed astronomers to determine its diameter, while the length of time between transits yielded its orbital period.

Graph showing the big dip in brightness of KIC 8462852 around 800 days (center) followed after 1500 days whole series of dips of varying magnitude. Credit: Boyajian et. all — Graph showing the big dip in brightness of KIC 8462852 around 800 days (center) followed after 1500 days whole series of dips of varying magnitude up to 22%. The usual drop in light when an exoplanet transits its host star is a *fraction of a percent*. The star’s normal brightness has been set to “1.00” as a baseline. Credit: Boyajian et. all

Volunteers with the Planet Hunters project, one of many citizen science programs under the umbrella of Zooniverse, harness the power of the human eye to examine Kepler light curves (a graph of a star’s changing light intensity over time), looking for repeating patterns that might indicate orbiting planets. They were the first to meet up with the perplexing KIC 8462852.

dsafad — A detailed look at a small part of the star’s light curve reveals an unknown, regular variation of its light every 20 days. Superimposed on that is the star’s 0.88 day rotation period. Credit: Boyajian et. all

This magnitude +11.7 star in Cygnus, hotter and half again as big as the Sun, showed dips all over the place. Around Day 800 during Kepler’s run, it faded by 15% then resumed a steady brightness until Days 1510-1570, when it underwent a whole series of dips including one that dimmed the star by 22%. That’s huge! Consider that an exo-Earth blocks only a fraction of a percent of a star’s light; even a Jupiter-sized world, the norm among extrasolar planets, soaks up about a percent.

Exoplanets also show regular, repeatable light curves as they enter, cross and then exit the faces of their host stars. KIC 8462852’s dips are wildly a-periodic.

Could a giant comet breakup followed by those pieces crumbling into even smaller comets be the reason for KIC's erratic changes in brightness? Credit: NASA — Could a giant comet breakup and subsequent cascading breakups of those pieces be behind KIC 8462852’s erratic changes in brightness? Credit: NASA

Whatever’s causing the flickering can’t be a planet. With great care, the researchers ruled out many possibilities: instrumental errors, starspots (like sunspots but on other stars), dust rings seen around young, evolving stars (this is an older star) and pulsations that cover a star with light-sucking dust clouds.

What about a collision between two planets? That would generate lots of material along with huge clouds of dust that could easily choke off a star’s light in rapid and irregular fashion.

A great idea except that dust absorbs light from its host star, warms up and glows in infrared light. We should be able to see this “infrared excess” if it were there, but instead KIC 8462852 beams the expected amount of infrared for a star of its class and not a jot more. There’s also no evidence in data taken by NASA’s Wide-field Infrared Survey Explorer (WISE) several years previously that a dust-releasing collision happened around the star.

Our featured star shines around 12th magnitude in the constellation Cygnus the Swan (Northern Cross) high in the southern sky at nightfall this month. A 6-inch or larger telescope will easily show it. Use this map to get oriented and the map below to get there. Source: Stellarium — Our featured star shines at magnitude +11.7 in the constellation Cygnus the Swan (Northern Cross) high in the southern sky at nightfall this month. A 6-inch or larger telescope will easily show it. Use this map to get oriented and the map below to get there. Source: Stellarium

After examining the options, the researchers concluded the best fit might be a shattered comet that continued to fragment into a cascade of smaller comets. Pretty amazing scenario. There’s still dust to account for, but not as much as other scenarios would require.

Detailed map showing stars to around magnitude 12 with the Kepler star identified. It's located only a short distance northeast of the open cluster NGC 6886 in Cygnus. North is up. Source: Chris Marriott's SkyMap — Detailed map showing stars to around magnitude 12 with the Kepler star identified. It’s located only a short distance northeast of the open cluster NGC 6886 in Cygnus. North is up. Click to enlarge. Source: Chris Marriott’s SkyMap

Being fragile types, comets can crumble all by themselves especially when passing exceptionally near the Sun as sungrazing comets are wont to do in our own Solar System. Or a passing star could disturb the host star’s Oort comet cloud and unleash a barrage of comets into the inner stellar system. It so happens that a red dwarf star lies within about 1000 a.u. (1000 times Earth’s distance from the Sun) of KIC 8462852. No one knows yet whether the star orbits the Kepler star or happens to be passing by. Either way, it’s close enough to get involved in comet flinging.

So much for “natural” explanations. Tabetha Boyajian, a postdoc at Yale, who oversees the Planet Hunters and the lead author of the paper on KIC 8462852, asked Jason Wright, an assistant professor of astronomy at Penn State, what he thought of the light curves. “Crazy” came to mind as soon he set eyes on them, but the squiggles stirred a thought. Turns out Wright had been working on a paper about detecting transiting megastructures with Kepler.

There are Dyson rings and spheres and this, an illustration of a Dyson swarm. Could this or a variation of it be what we're detecting around KIC? Not likely, but a fun thought experiment. Credit: Wikipedia — There are Dyson rings and spheres and a Dyson swarm depicted here. Could this or a variation of it be what we’re seeing around KIC 8462852? Not likely, but a fun thought experiment. Credit: Wikipedia

In a recent blog, he writes: “The idea is that if advanced alien civilizations build planet-sized megastructures — solar panels, ring worlds, telescopes, beacons, whatever — Kepler might be able to distinguish them from planets.” Let’s assume our friendly aliens want to harness the energy of their home star. They might construct enormous solar panels by the millions and send them into orbit to beam starlight down to their planet’s surface. Physicist Freeman Dyson popularized the idea back in the 1960s. Remember the Dyson Sphere, a giant hypothetical structure built to encompass a star?

From our perspective, we might see the star flicker in irregular ways as the giant panels circled about it. To illustrate this point, Wright came up with a wonderful analogy:

“The analogy I have is watching the shadows on the blinds of people outside a window passing by. If one person is going around the block on a bicycle, their shadow will appear regularly in time and shape (like a regular transiting planet). But crowds of people ambling by — both directions, fast and slow, big and large — would not have any regularity about it at all. The total light coming through the blinds might vary like — Tabby’s star.”

The Green Bank Telescope is the world's largest, fully-steerable telescope. The GBT's dish is 100-meters by 110-meters in size, covering 2.3 acres of space. — The Green Bank Telescope is the world’s largest, fully-steerable telescope. The GBT’s dish is 100-meters by 110-meters in size, covering 2.3 acres of space. Credit: NRAO/AUI/NSF

Even Wright admits that the “alien hypothesis” should be seen as a last resort. But to make sure no stone goes unturned, Wright, Boyajian and several of the Planet Hunters put together a proposal to do a radio-SETI search with the Green Bank 100-meter telescope. In my opinion, this is science at its best. We have a difficult question to answer, so let’s use all the tools at our disposal to seek an answer.

Star with a mystery, KIC 8462852, photographed on Oct. 15, 2015. Credit: Gianluca Masi — KIC 8462852, photographed on Oct. 15, 2015. It’s an F3 V star (yellow-white dwarf) located about 1,480 light years from Earth. Credit: Gianluca Masi

In the end, it’s probably not an alien megastructure, just like the first pulsar signals weren’t sent by LGM-1 (Little Green Men). But whatever’s causing the dips, Boyajian wants astronomers to keep a close watch on KIC 8462852 to find out if and when its erratic light variations repeat. I love a mystery, but answers are even better.

November 10, 2014December 23, 2015 by Matt Williams

NASA’s Next Exoplanet Hunter Moves Into Development

A conceptual image of the Transiting Exoplanet Survey Satellite. Image Credit: MIT

NASA’s ongoing hunt for exoplanets has entered a new phase as NASA officially confirmed that the Transiting Exoplanet Survey Satellite (TESS) is moving into the development phase. This marks a significant step for the TESS mission, which will search the entire sky for planets outside our solar system (a.k.a. exoplanets). Designed as the first all-sky survey, TESS will spend two years of an overall three-year mission searching both hemispheres of the sky for nearby exoplanets.

Previous sky surveys with ground-based telescopes have mainly picked out giant exoplanets. In contrast, TESS will examine a large number of small planets around the very brightest stars in the sky. TESS will then record the nearest and brightest main sequence stars hosting transiting exoplanets, which will forever be the most favorable targets for detailed investigations. During the third year of the TESS mission, ground-based astronomical observatories will continue monitoring exoplanets identified by the TESS spacecraft.

“This is an incredibly exciting time for the search of planets outside our solar system,” said Mark Sistilli, the TESS program executive from NASA Headquarters, Washington. “We got the green light to start building what is going to be a spacecraft that could change what we think we know about exoplanets.”

“During its first two years in orbit, the TESS spacecraft will concentrate its gaze on several hundred thousand specially chosen stars, looking for small dips in their light caused by orbiting planets passing between their host star and us,” said TESS Principal Investigator George Ricker of the Massachusetts Institute of Technology..

Artistic representations of the only known planets around other stars (exoplanets) with any possibility to support life as we know it. Credit: Planetary Habitability Laboratory, University of Puerto Rico, Arecibo. — *Artistic representations of known exoplanets with any possibility to support life. Image Credit: Planetary Habitability Laboratory, University of Puerto Rico, Arecibo.*

All in all, TESS is expected to find more than 5,000 exoplanet candidates, including 50 Earth-sized planets. It will also find a wide array of exoplanet types, ranging from small, rocky planets to gas giants. Some of these planets could be the right sizes, and orbit at the correct distances from their stars, to potentially support life.

“The most exciting part of the search for planets outside our solar system is the identification of ‘earthlike’ planets with rocky surfaces and liquid water as well as temperatures and atmospheric constituents that appear hospitable to life,” said TESS Project Manager Jeff Volosin at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Although these planets are small and harder to detect from so far away, this is exactly the type of world that the TESS mission will focus on identifying.”

Now that NASA has confirmed the development of TESS, the next step is the Critical Design Review, which is scheduled to take place in 2015. This would clear the mission to build the necessary flight hardware for its proposed launch in 2017.

“After spending the past year building the team and honing the design, it is incredibly exciting to be approved to move forward toward implementing NASA’s newest exoplanet hunting mission,” Volosin said.

TESS is designed to complement several other critical missions in the search for life on other planets. Once TESS finds nearby exoplanets to study and determines their sizes, ground-based observatories and other NASA missions, like the James Webb Space Telescope, would make follow-up observations on the most promising candidates to determine their density and other key properties.

*The James Webb Space Telescope. Image Credit: NASA/JPL*

By figuring out a planet’s characteristics, like its atmospheric conditions, scientists could determine whether the targeted planet has a habitable environment.

“TESS should discover thousands of new exoplanets within two hundred light years of Earth,” Ricker said. “Most of these will be orbiting bright stars, making them ideal targets for characterization observations with NASA’s James Webb Space Telescope.”

“The Webb telescope and other teams will focus on understanding the atmospheres and surfaces of these distant worlds, and someday, hopefully identify the first signs of life outside of our solar system,” Volosin said.

TESS will use four cameras to study sections of the sky’s north and south hemispheres, looking for exoplanets. The cameras would cover about 90 percent of the sky by the end of the mission.

This makes TESS an ideal follow-up to the Kepler mission, which searches for exoplanets in a fixed area of the sky. Because the TESS mission surveys the entire sky, TESS is expected to find exoplanets much closer to Earth, making them easier for further study.

In addition, Ricker said TESS would provide precision, full-frame images for more than 20 million bright stars and galaxies.

“This unique new data will comprise a treasure trove for astronomers throughout the world for many decades to come,” Ricker said.

Now that TESS is cleared to move into the next development stage, it can continue towards its goal of being a key part of NASA’s search for life beyond Earth.

“I’m still hopeful that in my lifetime, we will discover the existence of life outside of our solar system and I’m excited to be part of a NASA mission that serves as a key stepping stone in that search,” Volosin said.

Further Reading: NASA

February 19, 2014January 13, 2016 by Nancy Atkinson

Kepler’s Universe: More Planets in Our Galaxy Than Stars

Kepler space telescope's field of view. Credit: NASA

Astronomers estimate that the Milky Way contains up to 400 billion stars and thanks to the Kepler mission, we can now estimate that every star in our galaxy has on average 1.6 planets in orbit around it.

This new video from our friends Tony Darnell and Scott Lewis focuses on the discoveries that the Kepler Space Telescope has made, which has opened up a whole new universe and a new way of looking at stars as potential homes for other planets. Only about 20 years ago, we didn’t know if there were any other planets around any other stars besides our own. But now we know we live in a galaxy that contains more planets than stars.

If you extrapolate that number to the rest of the Universe, it’s mind-blowing. According to astronomers, there are probably more than 170 billion galaxies in the observable Universe, stretching out into a region of space 13.8 billion light-years away from us in all directions.

And so, if you multiply the number of stars in our galaxy by the number of galaxies in the Universe, you get approximately 10²⁴ stars. That’s a 1 followed by twenty-four zeros, or a septillion stars.

However, it’s been calculated that the observable Universe is a bubble of space 47 billion years in all directions… or it could be much bigger, possibly infinite. It’s just that we can’t detect those stars because they’re outside the observable Universe.

So, there’s a lot of stars out there.

As the video says, space telescopes give us “a glimpse of our humble place in the cosmic ocean.”

November 27, 2013December 23, 2015 by Shannon Hall

Second Planetary System Like Ours Discovered

A comparison between our solar system and a second solar system: KOI-351. Image Credit:

A team of European astronomers has discovered a second planetary system, the closest parallel to our own solar system yet found. It includes seven exoplanets orbiting a star with the small rocky planets close to their host star and the gas giant planets further away. The system was hidden within the wealth of data from the Kepler Space Telescope.

KOI-351 is “the first system with a significant number of planets (not just two or three, where random fluctuations can play a role) that shows a clear hierarchy like the solar system — with small, probably rocky, planets in the interior and gas giants in the (exterior),” Dr. Juan Cabrera, of the Institute of Planetary Research at the German Aerospace Center, told Universe Today.

Three of the seven planets orbiting KOI-351 were detected earlier this year, and have periods of 59, 210 and 331 days — similar to the periods of Mercury, Venus and Earth.

But the orbital periods of these planets vary by as much as 25.7 hours. This is the highest variation detected in an exoplanet’s orbital period so far, hinting that there are more planets than meets the eye.

In closely packed systems, the gravitational pull of nearby planets can cause the acceleration or deceleration of a planet along its orbit. These “tugs” cause the variations in orbital periods.

They also provide indirect evidence of further planets. Using advanced computer algorithms, Cabrera and his team detected four new planets orbiting KOI-351.

But these planets are much closer to their host star than Mercury is to our Sun, with orbital periods of 7, 9, 92 and 125 days. The system is extremely compact — with the outermost planet having an orbital period less than the Earth’s. Yes, the entire system orbits within 1 AU.

While astronomers have discovered over 1000 exoplanets, this is the first solar system analogue detected to date. Not only are there seven planets, but they display the same architecture — rocky small planets orbiting close to the sun and gas giants orbiting further away — as our own solar system.

Most exoplanets are strikingly different from the planets in our own solar system. “We find planets in any order, at any distance, of any size; even planetary classes that don’t exist in the solar system,” Cabrera said.

Several theories including planet migration and planet-planet scattering have been proposed to explain these differences. But the fact of the matter is planet formation is still poorly understood.

“We don’t know yet why this system formed this way, but we have the feeling that this is a key system in understanding planetary formation in general and the formation of the solar system in particular,” Cabrera told Universe Today.

The team is extremely hopeful that the upcoming mission PLATO will receive funding. If so, it will allow them to take a second look at this system — determining the radius and mass of each planet and even analyzing their compositions.

Follow-up observations will not only allow astronomers to determine how this planetary system formed, it will provide hints as to how our own solar system formed.

The paper has been accepted for publication in the Astrophysical Journal and is available for download here.