Posted on by Matt Williams

James Webb is Enduring its Final Stage of Testing Before it Ships off for Kourou, French Guiana

The combined optics and science instruments of NASA’s James Webb Space Telescope being removed from the Space Telescope Transporter for Air, Road and Sea (STTARS) at the Northrop Grumman company headquarters on March 8th, 2018. Credits: NASA/Chris Gunn

Once deployed, the James Webb Space Telescope (JWST) will be the most powerful telescope ever built. As the spiritual and scientific successor to the Hubble, Spitzer, and Kepler space telescopes, this space observatory will use its advanced suite of infrared instruments to the look back at the earliest stars and galaxies, study the Solar System in depth, and help characterize extra-solar planets (among other things).

Unfortunately, the launch of the JWST has been subject to multiple delays, with the launch date now set for some time in 2019. Luckily, on Thursday, March 8th, engineers at the Northrop Grumman company headquarters began the final step in the observatory’s integration and testing. Once complete, the JWST will be ready to ship to French Guiana, where it will be launched into space.

This final phase consisted of removing the combined optics and science instruments from their shipping containers – known as the Space Telescope Transporter for Air, Road and Sea (STTARS) – which recently arrived after being testing at NASA’s Johnson Space Center in Houston. This constitutes half the observatory, and includes the telescope’s 6.5 meter (21.3 foot) golden primary mirror.

The Space Telescope Transporter for Air, Road and Sea (STTARS) being opened at Northrop Grumman on March 8th, 2018, to reveal the combined optics and science instruments of NASA’s James Webb Space Telescope. Credits: NASA/Chris Gunn

The science payload was also tested at NASA’s Goddard Space Flight Center last year to ensure it could handle the vibrations associated with space launches and the temperatures and vacuum conditions of space. The other half of the observatory consists of the integrated spacecraft and sunshield, which is in the final phase of assembly at the Northrop Grumman company headquarters.

These will soon undergo a launch environment test to prove that they are ready to be combined with the science payload. Once both halves are finished being integrated, addition testing will be performed to guarantee the  fully assembled observatory can operate at the L2 Earth-Sun Lagrange Point. As Eric Smith, the program director for the JWST at NASA Headquarters, said in a recent NASA press statement:

“Extensive and rigorous testing prior to launch has proven effective in ensuring that NASA’s missions achieve their goals in space. Webb is far along into its testing phase and has seen great success with the telescope and science instruments, which will deliver the spectacular results we anticipate.”

These final tests are crucial to ensuring that that the observatory deploys properly and can operate once it is in space. This is largely because of the telescope’s complicated design, which needs to be folded in order to fit inside the Ariane 5 rocket that it will carry it into space. Once it reaches its destination, the telescope will have to unfold again, deploying its sunshield, mirrors and primary mirror.

The James Webb Space Telescope’s sunshield being deployed inside a cleanroom at Northrop Grumman’s company headquarter’s, in October 2017. Credits: Northrop Grumman

Not only does all of this represented a very technically-challenging feet, it is the first time that any space telescope has had to perform it. Beyond that, there are also the technical challenges of building a complex observatory that is designed to operate in space. While the JWST’s optics and science instruments were all built at room temperature here on Earth, they had to be designed to operate at cryogenic temperatures.

As such, its mirrors had to be precisely polished and formed that they would achieve the correct shape once they cool in space. Similarly, its sunshield will be operating in a zero gravity environment, but was built and tested here on Earth where the gravity is a hefty 9.8 m/s² (1 g). In short, the James Webb Space Telescope is the largest and most complex space telescope ever built, and is one of NASA’s highest priority science projects.

It is little wonder then why NASA has had to put the JWST through such a highly-rigorous testing process. As Smith put it:

“At NASA, we do the seemingly impossible every day, and it’s our job to do the hardest things humankind can think of for space exploration. The way we achieve success is to test, test and retest, so we understand the complex systems and verify they will work.”

The James Webb Space Telescope (which is scheduled to launch in 2019) will be the most powerful telescope ever deployed. Credit: NASA/JPL

Knowing that the JWST is now embarking on the final phase of its development – and that its engineers are confident it will perform up to task – is certainly good news. Especially in light of a recent report from the US Government Accountability Office (GAO), which stated that more delays were likely and that the project would probably exceed its original budget cap of $8 billion.

As the report indicated, it is the final phase of integration and testing where problems are most likely to be found and schedules revised. However, the report also stated that “Considering the investment NASA has made, and the good performance to date, we want to proceed very systematically through these tests to be ready for a Spring 2019 launch.”

In other words, there is no indication whatsoever that Congress is considering cancelling the project, regardless of further delays or cost overruns. And when the JWST is deployed, it will use its 6.5 meter (21-foot) infrared-optimized telescopes will search to a distance of over 13 billion light years, allow astronomers to study the atmospheres of Solar Planets, exoplanets, and other objects within our Solar System.

So while the JWST may not make its launch window in 2019, we can still expect that it will be taking to space in the near future. And when it does, we can also expect that what it reveals about our Universe will be mind-blowing!

Further Reading: NASA

Posted on by Matt Williams

James Webb Telescope is Probably Going to be Delayed Again, and Could Exceed a Congress Spending Cap

The James Webb Space Telescope will be the first of the Super Telescopes to see first light. It is scheduled to be launched in October, 2018. Image credit: NASA/Desiree Stover
The James Webb Telescope will be the most powerful telecope once it is deployed. However, delays and cost overruns could be a problem. Credit: NASA/Desiree Stover

When the James Webb Space Telescope takes to space, some tremendous scientific discoveries are expected to result. As the spiritual and scientific successor to the Hubble, Spitzer, and Kepler Space Telescopes, this space observatory will use its advanced suite of infrared instruments to the look back at the early Universe, study the Solar System, and help characterize extra-solar planets.

Unfortunately, the launch of this mission has been delayed several times now, with the launch date now set for some time in 2019. And based on the amount of work NASA needs to do complete the JWST before launch, the Government Accountability Office (GAO) believes that more delays are coming and believes that the project is likely to exceed the cost cap set by Congress in 2011 at $8 billion. 

Part of the problem is that all the remaining schedule reserve – the extra time set aside in the event of delays or unforeseen risks – was recently used to address technical issues. These include the “anomalous readings” detected from the telescope during vibration testing back in December 2016. NASA responded to this by giving the project up to 4 months of schedule reserve by extending the launch window.

The JWST sunshield being unfolded in the clean room at Northrop Grumman Aerospace Systems in Redondo Beach, California. Credits: Northrop Grumman Corp.

However, in 2017, NASA delayed the launch window again by 5 months, from October 2018 to a between March and June 2019. This delay was requested by the project team, who indicated that they needed to address lessons learned from the initial folding and deployment of the observatory’s sunshield. As Eric Smith, the program director for the James Webb Space Telescope at NASA Headquarters, explained to Congress at the time:

“Webb’s spacecraft and sunshield are larger and more complex than most spacecraft. The combination of some integration activities taking longer than initially planned, such as the installation of more than 100 sunshield membrane release devices, factoring in lessons learned from earlier testing, like longer time spans for vibration testing, has meant the integration and testing process is just taking longer. Considering the investment NASA has made, and the good performance to date, we want to proceed very systemmatically through these tests to be ready for a Spring 2019 launch.”

Given the remaining integration and test work that lies ahead, more delays are expected. According to the GAO, it is this phase where problems are most likely to be found and schedules revised. Coupled with the fact that only 1.5 months of schedule reserves remain until the end of the launch window, they anticipate that additional launch delays are likely, which will also require budget increases.

Initially, the budget estimates that were set by Congress indicated that the observatory would cost $1.6 billion and would launch by 2011, with an overall cost cap set at $8 billion. However, NASA has revised the budget multiple times since then (in conjunction with the multiple delays) and estimates that the budget for a 2019 launch window would now be $8.8 billion.

The James Webb Space Telescope being placed in the Johnson Space Center’s historic Chamber A on June 20th, 2017. Credit: NASA/JSC

Once deployed, the JWST will be the most powerful space telescope ever built and will serve thousands of astronomers worldwide. As a collaborative project between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA), it also representative of the new era of international cooperation. But by far, the most impressive thing about this mission is the scientific discoveries it is expected to make.

It’s 6.5 meter (21-foot) infrared-optimized telescopes will search to a distance of over 13 billion light years, allowing it to study the first stars and galaxies that formed. It will also allow astronomers to study the atmospheres of Solar Planets and exoplanets and other objects within our Solar System. As such, and delays and cost overruns in the project are cause for concern.

In the meantime, the project’s Standing Review Board will conduct an independent review in early 2018 to determine if the June 2019 launch window can still be met. With so many experiments and surveys planned for the telescope, it would be no exaggeration to say that a lot is riding on its successful completion and deployment. Best of luck passing review James Webb Space Telescope!

Further Reading: Government Accountability Office

Posted on by Matt Williams

Astronomers Find Another Solar System with 8 Planets. Uh, Pluto, About that Deplaneting…

In a series of papers, Professor Loeb and Michael Hippke indicate that conventional rockets would have a hard time escaping from certain kinds of extra-solar planets. Credit: NASA/Tim Pyle
In a series of papers, Professor Loeb and Michael Hippke indicate that conventional rockets would have a hard time escaping from certain kinds of extra-solar planets. Credit: NASA/Tim Pyle

With every passing year, more and more extra-solar planets are discovered. To make matters more interesting, improvements in methodology and technology are allowing for the discovery of more planets within individual systems. Consider the recent announcement of a seven-planet system around the red dwarf star known as TRAPPIST-1. At the time, this discovery established the record for most exoplanets orbiting a single star.

Well move over TRAPPIST-1! Thanks to the Kepler Space Telescope and machine learning, a team from Google AI and the Harvard-Smithsonian Center of Astrophysics (CfA) recently discovered an eighth planet in the distant star system of Kepler-90. Known as Kepler -90i, the discovery of this planet was made possible thanks to Google algorithms that detected evidence of a weak transit signal in the Kepler mission data.

Continue reading “Astronomers Find Another Solar System with 8 Planets. Uh, Pluto, About that Deplaneting…”

Posted on by Matt Williams

What is the Transit Method?

In a series of papers, Professor Loeb and Michael Hippke indicate that conventional rockets would have a hard time escaping from certain kinds of extra-solar planets. Credit: NASA/Tim Pyle
In a series of papers, Professor Loeb and Michael Hippke indicate that conventional rockets would have a hard time escaping from certain kinds of extra-solar planets. Credit: NASA/Tim Pyle

Welcome all to the first in our series on Exoplanet-hunting methods. Today we begin with the most popular and widely-used, known as the Transit Method (aka. Transit Photometry).

For centuries, astronomers have speculated about the existence of planets beyond our Solar System. After all, with between 100 and 400 billion stars in the Milky Way Galaxy alone, it seemed unlikely that ours was the only one to have a system of planets. But it has only been within the past few decades that astronomers have confirmed the existence of extra-solar planets (aka. exoplanets).

Astronomers use various methods to confirm the existence of exoplanets, most of which are indirect in nature. Of these, the most widely-used and effective to date has been Transit Photometry, a method that measures the light curve of distant stars for periodic dips in brightness. These are the result of exoplanets passing in front of the star (i.e. transiting) relative to the observer.

Description:

These changes in brightness are characterized by very small dips and for fixed periods of time, usually in the vicinity of 1/10,000th of the star’s overall brightness and only for a matter of hours. These changes are also periodic, causing the same dips in brightness each time and for the same amount of time. Based on the extent to which stars dim, astronomers are also able to obtain vital information about exoplanets.

For all of these reasons, Transit Photometry is considered a very robust and reliable method of exoplanet detection. Of the 3,526 extra-solar planets that have been confirmed to date, the transit method has accounted for 2,771 discoveries – which is more than all the other methods combined.

Advantages:

One of the greatest advantages of Transit Photometry is the way it can provide accurate constraints on the size of detected planets. Obviously, this is based on the extent to which a star’s light curve changes as a result of a transit.  Whereas a small planet will cause a subtle change in brightness, a larger planet will cause a more noticeable change.

When combined with the Radial Velocity method (which can determine the planet’s mass) one can determine the density of the planet. From this, astronomers are able to assess a planet’s physical structure and composition – i.e. determining if it is a gas giant or rocky planet. The planets that have been studied using both of these methods are by far the best-characterized of all known exoplanets.

In addition to revealing the diameter of planets, Transit Photometry can allow for a planet’s atmosphere to be investigated through spectroscopy. As light from the star passes through the planet’s atmosphere, the resulting spectra can be analyzed to determine what elements are present, thus providing clues as to the chemical composition of the atmosphere.

Artist’s impression of an extra-solar planet transiting its star. Credit: QUB Astrophysics Research Center

Last, but not least, the transit method can also reveal things about a planet’s temperature and radiation based on secondary eclipses (when the planet passes behind it’s sun). On this occasion, astronomers measure the star’s photometric intensity and then subtract it from measurements of the star’s intensity before the secondary eclipse. This allows for measurements of the planet’s temperature and can even determine the presence of clouds formations in the planet’s atmosphere.

Disadvantages:

Transit Photometry also suffers from a few major drawbacks. For one, planetary transits are observable only when the planet’s orbit happens to be perfectly aligned with the astronomers’ line of sight. The probability of a planet’s orbit coinciding with an observer’s vantage point is equivalent to the ratio of the diameter of the star to the diameter of the orbit.

Only about 10% of planets with short orbital periods experience such an alignment, and this decreases for planets with longer orbital periods. As a result, this method cannot guarantee that a particular star being observed does indeed host any planets. For this reason, the transit method is most effective when surveying thousands or hundreds of thousands of stars at a time.

It also suffers from a substantial rate of false positives; in some cases, as high as 40% in single-planet systems (based on a 2012 study of the Kepler mission). This necessitates that follow-up observations be conducted, often relying on another method. However, the rate of false positives drops off for stars where multiple candidates have been detected.

Number of extrasolar planet discoveries per year through September 2014, with colors indicating method of detection – radial velocity (blue), transit (green), timing (yellow), direct imaging (red), microlensing (orange). Credit: Public domain

While transits can reveal much about a planet’s diameter, they cannot place accurate constraints on a planet’s mass. For this, the Radial Velocity method (as noted earlier) is the most reliable, where astronomers look for signs of “wobble” in a star’s orbit to the measure the gravitational forces acting on them (which are caused by planets).

In short, the transit method has some limitations and is most effective when paired with other methods. Nevertheless, it remains the most widely-used means of “primary detection” – detecting candidates which are later confirmed using a different method – and is responsible for more exoplanet discoveries than all other methods combined.

Examples of Transit Photometry Surveys:

Transit Photometry is performed by multiple Earth-based and space-based observatories around the world. The majority, however, are Earth-based, and rely on existing telescopes combined with state-of-the-art photometers. Examples include the Super Wide Angle Search for Planets (SuperWASP) survey, an international exoplanet-hunting survey that relies on the Roque de los Muchachos Observatory and the South African Astronomical Observatory.

There’s also the Hungarian Automated Telescope Network (HATNet), which consists of six small, fully-automated  telescopes and is maintained by the Harvard-Smithsonian Center for Astrophysics. The MEarth Project is another, a National Science Foundation-funded robotic observatory that combines the Fred Lawrence Whipple Observatory (FLWO) in Arizona with the Cerro Tololo Inter-American Observatory (CTIO) in Chile.

The SuperWasp Cameras at the South African Astronomical Observatory. Credit: SuperWASP project & David Anderson

Then there’s the Kilodegree Extremely Little Telescope (KELT), an astronomical survey jointly administered by Ohio State University, Vanderbilt University, Lehigh University, and the South African Astronomical Society (SAAO). This survey consists of two telescopes, the Winer Observatory in southeastern Arizona and the Sutherland Astronomical Observation Station in South Africa.

In terms of space-based observatories, the most notable example is NASA’s Kepler Space Telescope. During its initial mission, which ran from 2009 to 2013, Kepler detected 4,496 planetary candidates and confirmed the existence of 2,337 exoplanets. In November of 2013, after the failure of two of its reaction wheels, the telescope began its K2 mission, during which time an additional 515 planets have been detected and 178 have been confirmed.

The Hubble Space Telescope also conducted transit surveys during its many years in orbit. For instance, the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS) – which took place in 2006 – consisted of Hubble observing 180,000 stars in the central bulge of the Milky Way Galaxy. This survey revealed the existence of 16 additional exoplanets.

Other examples include the ESA’s COnvection ROtation et Transits planétaires (COROT) – in English “Convection rotation and planetary transits” – which operated from 2006 to 2012. Then there’s the ESA’s Gaia mission, which launched in 2013 with the purpose of creating the largest 3D catalog ever made, consisting of over 1 billion astronomical objects.

NASA’s Kepler space telescope was the first agency mission capable of detecting Earth-size planets. Credit: NASA/Wendy Stenzel

In March of 2018, the NASA Transiting Exoplanet Survey Satellite (TESS) is scheduled to be launched into orbit. Using the transit method, TESS will detect exoplanets and also select targets for further study by the James Webb Space Telescope (JSWT), which will be deployed in 2019. Between these two missions, the confirmation and characterization or many thousands of exoplanets is anticipated.

Thanks to improvements in terms of technology and methodology, exoplanet discovery has grown by leaps and bounds in recent years. With thousands of exoplanets confirmed, the focus has gradually shifted towards the characterizing of these planets to learn more about their atmospheres and conditions on their surface.

In the coming decades, thanks in part to the deployment of new missions, some very profound discoveries are expected to be made!

We have many interesting articles about exoplanet-hunting here at Universe Today. Here’s What are Extra Solar Planets?, What are Planetary Transits?, What is the Radial Velocity Method?, What is the Direct Imaging Method?, What is the Gravitational Microlensing Method?, and Kepler’s Universe: More Planets in our Galaxy than Stars.

Astronomy Cast also has some interesting episodes on the subject. Here’s Episode 364: The COROT Mission.

For more information, be sure to check out NASA’s page on Exoplanet Exploration, the Planetary Society’s page on Extrasolar Planets, and the NASA/Caltech Exoplanet Archive.

Sources:

Posted on by Matt Williams

Astronomers Find Comets Orbiting a Star 800 Light-Years Away

An artist’s conception of a view from within the Exocomet system KIC 3542116.. Credit: Danielle Futselaar

In the past thirty years, thousands of extra-solar planets have been discovered beyond our Solar System. For the most part, they have been detected by the Kepler Space Telescope using a technique called Transit Photometry. For this method, astronomers measure periodic dips in a star’s brightness – which are the result of planets passing in front of them relative to an observer – to confirm the presence of planets.

Thanks to a new research effort conducted by a team of professional and amateur astronomers, something much smaller than planets were recently detected orbiting a distant star. According to a new study published by the research team, six exocomets were observed orbiting around KIC 3542116, a spectral type F2V star located 800 light years from Earth. These comets are the smallest objects to date detecting the Transit Photometry method.

The study which details their findings, titled “Likely Transiting Exocomets Detected by Kepler“, recently appeared in the Monthly Notices of the Royal Astronomical Society. Led by Saul Rappaport of MIT’s Kavli Institute for Astrophysics and Space Research, the team also consisted of amateur astronomers, members of the Harvard-Smithsonian Center for Astrophysics (CfA), the University of Texas, Northeastern University, and NASA’s Ames Research Center.

Artist’s impression of an orbiting swarm of dusty comet fragments around Tabby’s Star. Credit: NASA/JPL-Caltech

This is the first time that Transit Photometry has been used to detect object as small as comets. These comets were balls of ice and dust – comparable in size to Halley’s Comet – that were found to be traveling at speeds of about 160,934 km/h (100,000 mph) before they vaporized. The researchers were able to detect them by picking out their tails, the clouds of dust and gas that form when comets get closer to their star and begin to sublimate.

This was no easy task, since the tails managed to obscure only about a tenth of 1% of the star’s light. As Saul Rappaport, who is also the professor emeritus of physics at the Kavli Institute for Astrophysics and Space Research, explained in an MIT press release:

“It’s amazing that something several orders of magnitude smaller than the Earth can be detected just by the fact that it’s emitting a lot of debris. It’s pretty impressive to be able to see something so small, so far away.”

Credit for the original detection goes to Thomas Jacobs, an amateur astronomer who lives in Bellevue, Washington, and is a member of Planet Hunters. This citizen scientist project was first established by Yale University and consists of amateur astronomers who dedicated their time to the search for exoplanets. Members are given access to data from the Kepler Space Telescope in the hopes that they would notice things that computer algorithms might miss.

NASA’s Kepler space telescope was the first agency mission capable of detecting Earth-size planets. Credit: NASA/Wendy Stenzel

Back in January, Jacobs began scanning four years of data obtained during Kepler‘s main mission. During this phase, which lasted from 2009 to 2013, Kepler scanned over 200,000 stars and conducted measurements of their light curves. After five months of sifting through the data (on March 18th), he noticed several curious light patterns amid background noise coming from KIC 3542116. As Jacobs said:

“Looking for objects of interest in the Kepler data requires patience, persistence, and perseverance. For me it is a form of treasure hunting, knowing that there is an interesting event waiting to be discovered. It is all about exploration and being on the hunt where few have traveled before.”

Specifically, Jacobs was searching for signs of single transits, which are not like those that are caused by planets orbiting a star (i.e. periodic). While looking at KIC 3542116, he noticed three single transits, and then alerted Rappaport and Andrew Vanderburg, as astrophysicist at University of Texas and member of the CfA. Jacobs had worked with both men in the past, and wanted their opinion on these findings.

As Rapport recalled, the process of interpreting the data was challenging, but rewarding. Initially, they noted that the lightcurves did not resemble those caused by planetary transits, which are characterized by a sudden and sharp drop in light, followed by a sharp rise. In time, Rapport noted the asymmetry in the three lightcurves resembled those of disintegrated planets, which they had observed before.

Artist’s impression of the Epsilon Eridani system, showing Epsilon Eridani b (a Jupiter-mass planet) and a series of asteroid belts and comets. Credit: NASA/SOFIA/Lynette Cook.

“We sat on this for a month, because we didn’t know what it was — planet transits don’t look like this,” said Rappaport. “Then it occurred to me that, ‘Hey, these look like something we’ve seen before’… We thought, the only kind of body that could do the same thing and not repeat is one that probably gets destroyed in the end. The only thing that fits the bill, and has a small enough mass to get destroyed, is a comet.”

Based on their calculations, which indicated that each comet blocked out about one-tenth of 1% of the star’s light, the research team concluded that the comet likely disintegrated entirely, creating a dust trail that was sufficient to block out light for several months before it disappeared. After conducting additional observations, they also noted three more transits in the same time period that were similar to the ones noticed by Jacobs.

The fact that these six exocomets appear to have transited very close to their star in the past four years raises some interesting questions, and answering them could have drastic implications for extra-solar research. It could also advance our understanding of our own Solar System. As Vanderburg explained:

“Why are there so many comets in the inner parts of these solar systems? Is this an extreme bombardment era in these systems? That was a really important part of our own solar system formation and may have brought water to Earth. Maybe studying exocomets and figuring out why they are found around this type of star… could give us some insight into how bombardment happens in other solar systems.”

This artist’s conception illustrates a storm of comets around a star near our own. Credit: NASA/JPL-Caltech

Between 4.1 and 3.8 billion years ago, the Solar System also experienced a period of intense comet activity known as the Late Heavy Bombardment. During this time, asteroids and comets are believed to have impacted bodies in the inner Solar System on a regular basis. Interestingly, this period of heavy bombardment is believed to be what was responsible for the distribution of water to Earth and the other terrestrial planets.

As noted, KIC 3542116 belongs to the spectral type F2V, a yellow-white class of star that is typically 1 to 1.4 times as massive as our Sun and quite bright. Since it is comparable in size and mass to our Sun, it is possible that the bombardment period it is experiencing is similar to what the Solar System went through. Watching it unfold could therefore tell us much about how similar activity influenced the evolution of our Solar System billions of years ago.

In addition to the study’s significance to the study of astrophysics and astronomy, it also demonstrates the important role citizen scientists play today. Were it not for the tireless work performed by Jacobs, who sifts through Kepler data between working his day job and on the weekends, this discovery would not have been possible.

“I could name 10 types of things these people have found in the Kepler data that algorithms could not find, because of the pattern-recognition capability in the human eye,” said Rappaport. “You could now write a computer algorithm to find this kind of comet shape. But they were missed in earlier searches. They were deep enough but didn’t have the right shape that was programmed into algorithms. I think it’s fair to say this would never have been found by any algorithm.”

In the future, the research team expects that the deployment Transiting Exoplanet Survey Satellite (TESS) – which will be led by MIT – will continue to conduct the type of research performed by Kepler.

Further Reading: MIT, MNRAS

Posted on by Matt Williams

This is Kind of Sad. Astronomers Find a Failed Star Orbiting a Dead Star

Artist's impression of a brown dwarf orbiting a white dwarf star. Credit: ESO

Death is simply a part of life, and this is no less the case where stars and other astronomical objects are concerned. Sure, the timelines are much, much greater where these are concerned, but the basic rule is the same. Much like all living organism, stars eventually reach old age and become white dwarfs. And some are not even fortunate enough to be born, instead becoming a class of failed stars known as brown dwarfs.

Despite being familiar with these objects, astronomers were certainly not expecting to find examples of both in a single star system! And yet, according to a new study, that is precisely what an international team of astronomers discovered when looked at WD 1202-024. Using data from the Kepler space telescope, they spotted a binary system consisting of a failed star (a brown dwarf) and the remnant of a star (a white dwarf).

Continue reading “This is Kind of Sad. Astronomers Find a Failed Star Orbiting a Dead Star”
Posted on by Matt Williams

Focusing On ‘Second-Earth’ Candidates In The Kepler Catalog

Artist’s impression of how an an Earth-like exoplanet might look. Credit: ESO.

The ongoing hunt for exoplanets has yielded some very interesting returns in recent years. All told, the Kepler mission has discovered more than 4000 candidates since it began its mission in March of 2009. Amidst the many “Super-Jupiters” and assorted gas giants (which account for the majority of Kepler’s discoveries) astronomers have been particularly interested in those exoplanets which resemble Earth.

And now, an international team of scientists has finished perusing the Kepler catalog in an effort to determine just how many of these planets are in fact “Earth-like”. Their study, titled “A Catalog of Kepler Habitable Zone Exoplanet Candidates” (which will be published soon in the Astrophysical Journal), explains how the team discovered 216 planets that are both terrestrial and located within their parent star’s “habitable zone” (HZ).

The international team was made up of researchers from NASA, San Francisco State University, Arizona State University, Caltech, University of Hawaii-Manoa, the University of Bordeaux, Cornell University and the Harvard-Smithsonian Center for Astrophysics. Having spent the past three years looking over the more than 4000 entries, they have determined that 20 of the candidates are most like Earth (i.e. likely habitable).

This figure shows the habitable zone for stars of different temperatures, as well as the location of terrestrial size planetary candidates and confirmed Kepler planets described in new research from SF State astronomer Stephen Kane. Some of the Solar System terrestrial planets are also shown for comparison. Credit: Chester Harman Read more at: http://phys.org/news/2016-08-team-second-earth-candidates.html#jCp
Figure showing the habitable zone for different types of stars, as well as the location of terrestrial size Kepler candidates. Credit: Chester Harman

As Stephen Kane, an associate professor of physics and astronomy at San Fransisco University and lead author of the study, explained in a recent statement:

“This is the complete catalog of all of the Kepler discoveries that are in the habitable zone of their host stars. That means we can focus in on the planets in this paper and perform follow-up studies to learn more about them, including if they are indeed habitable.”

In addition to isolating 216 terrestrial planets from the Kepler catalog, they also devised a system of four categories to determine which of these were most like Earth. These included “Recent Venus”, where conditions are like that of Venus (i.e. extremely hot); “Runaway Greenhouse”, where planets are undergoing serious heating; “Maximum Greenhouse”, where planets are within their star’s HZ; and “Recent Mars”, where conditions approximate those of Mars.

From this, they determined that of the Kepler candidates, 20 had radii less than twice that of Earth (i.e. on the smaller end of the Super-Earth category) and existed within their star’s HZ. In other words, of all the planets discovered in our local Universe, they were able to isolate those where liquid water can exist on the surface, and the gravity would likely be comparable to Earth’s and not crushing!

Earlier today, NASA announced that Kepler had confirmed the existence of 1,284 new exoplanets, the most announced at any given time. Credit: NASA
Earlier today, NASA announced that Kepler had confirmed the existence of 1,284 new exoplanets, the most announced at any given time. Credit: NASA

This is certainly exciting news, since one of the most important aspects of exoplanet hunting has been finding worlds that could support life. Naturally, it might sound a bit anthropocentric or naive to assume that planets which have similar conditions to our own would be the most likely places for it to emerge. But this is what is known as the “low-hanging fruit” approach, where scientists seek out conditions which they know can lead to life.

“There are a lot of planetary candidates out there, and there is a limited amount of telescope time in which we can study them,” said Kane. “This study is a really big milestone toward answering the key questions of how common is life in the universe and how common are planets like the Earth.”

Professor Kane is renowned for being one of the world’s leading “planet-hunters”. In addition to discovering several hundred exoplanets (using data obtained by the Kepler mission) he is also a contributor to two upcoming satellite missions – the NASA Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency’s Characterizing ExOPLanet Satellite (CHEOPS).

These next-generation exoplanet hunters will pick up where Kepler left off, and are likely to benefit greatly from this recent study.

Further Reading: arXiv

Posted on by Evan Gough

Life On Kepler-62f?

Exoplanet Kepler 62f would need an atmosphere rich in carbon dioxide for water to be in liquid form. Artist's Illustration: NASA Ames/JPL-Caltech/T. Pyle
Exoplanet Kepler 62f would need an atmosphere rich in carbon dioxide for water to be in liquid form. Artist's Illustration: NASA Ames/JPL-Caltech/T. Pyle

A team of astronomers suggests that an exoplanet named 62f could be habitable. Kepler data suggests that 62f is likely a rocky planet, and could have oceans. The exoplanet is 40% larger than Earth and is 1200 light years away.

62f is part of a planetary system discovered by the Kepler mission in 2013. There are 5 planets in the system, and they orbit a star that is both cooler and smaller than our Sun. The target of this study, 62f, is the outermost of the planets in the system.

Kepler can’t tell us if a planet is habitable or not. It can only tell us something about its potential habitability. The team, led by Aomawa Shields from the UCLA department of physics and astronomy, used different modeling methods to determine if 62f could be habitable, and the answer is, maybe.

According to the study, much of 62f’s potential habitability revolves around the CO2 component of its atmosphere, if it indeed has an atmosphere. As a greenhouse gas, CO2 can have a significant effect on the temperature of a planet, and hence, a significant effect on its habitability.

Earth’s atmosphere is only 0.04% carbon dioxide (and rising.) 62f would likely need to have much more CO2 than that if it were to support life. It would also require other atmospheric characteristics, .

The study modelled parameters for CO2 concentration, atmospheric density, and orbital characteristics. They simulated:

  • An atmospheric thickness from the same as Earth’s up to 12 times thicker.
  • Carbon dioxide concentrations ranging from the same as Earth’s up to 2500 times Earth’s level.
  • Multiple different orbital configurations.

It may look like the study casts its net pretty wide in order to declare a planet potentially habitable. But the simulations were pretty robust, and relied on more than a single, established modelling method to produce these results. With that in mind, the team found that there are multiple scenarios that could make 62f habitable.

“We found there are multiple atmospheric compositions that allow it to be warm enough to have surface liquid water,” said Shields, a University of California President’s Postdoctoral Program Fellow. “This makes it a strong candidate for a habitable planet.”

Earth as seen on July 6, 2015 from a distance of one million miles by a NASA scientific camera aboard the Deep Space Climate Observatory spacecraft. Credits: NASA
Our dear, sweet Earth is the only planet where life is confirmed. Here it is, as seen on July 6, 2015 from a distance of one million miles by a NASA scientific camera aboard the Deep Space Climate Observatory spacecraft. Credits: NASA

As mentioned earlier, CO2 concentration is a big part of it. According to Shields, the planet would need an atmospheric entirely composed of CO2, and an atmosphere five times as dense as Earth’s to be habitable through its entire year. That means that there would be 2500 times more carbon dioxide than Earth has. This would work because the planet’s orbit may take it far enough away from the star for water to freeze, but an atmosphere this dense and this high in CO2 would keep the planet warm.

But there are other conditions that would make 62f habitable, and these include the planet’s orbital characteristics.

“But if it doesn’t have a mechanism to generate lots of carbon dioxide in its atmosphere to keep temperatures warm, and all it had was an Earth-like amount of carbon dioxide, certain orbital configurations could allow Kepler-62f’s surface temperatures to temporarily get above freezing during a portion of its year,” said Shields. “And this might help melt ice sheets formed at other times in the planet’s orbit.”

Shields and her team used multiple modelling methods to produce these results. The climate was modelled using the Community Climate System Model and the Laboratoire de Me´te´orologie Dynamique Generic model. The planet’s orbital characteristics were modelled using HNBody. This study represents the first time that these modelling methods were combined, and this combined method can be used on other planets.

Shields said, “This will help us understand how likely certain planets are to be habitable over a wide range of factors, for which we don’t yet have data from telescopes. And it will allow us to generate a prioritized list of targets to follow up on more closely with the next generation of telescopes that can look for the atmospheric fingerprints of life on another world.”

There are over 2300 confirmed exoplanets, and many more candidates yet to be confirmed. Only a handful of them have been confirmed as being in the habitable zone around their host star. Of course, we don’t know if life can exist on other planets, even if they do reproduce the same kind of habitability that Earth has. We just have no way of knowing, yet.

That will change when instruments like the James Webb Space Telescope are able to peer into the atmospheres of exoplanets and tell us something about any bio-markers that might be present.

But until then, and until we actually visit another world with a probe of some design, we need to use modelling like the type employed in this study, to get us closer to answering the question of life on other worlds.

Posted on by Matt Williams

Starshade Prepares To Image New Earths

Artist's concept of the prototype starshade, a giant structure designed to block the glare of stars so that future space telescopes can take pictures of planets. Credit: NASA/JPL
Artist's concept of the prototype starshade, a giant structure designed to block the glare of stars so that future space telescopes can take pictures of planets. Credit: NASA/JPL

For countless generations, people have looked up at the stars and wondered if life exists somewhere out there, perhaps on planets much like ours. But it has only been in recent decades that we have been able to confirm the existence of extrasolar planets (aka. exoplanets) in other star systems. In fact, between 1988 and April 20th of 2016, astronomers have been able to account for the existence of 2108 planets in 1350 different star systems, including 511 multiple planetary systems.

Most of these discoveries have taken place within just the past three years, thanks to improvements in our detection methods, and the deployment of the Kepler space observatory in 2009. Looking ahead, astronomers hope to improve on these methods even further with the introduction of the Starshade, a giant space structure designed to block the glare of stars, thus making it easier to find planets – and perhaps another Earth!

Continue reading “Starshade Prepares To Image New Earths”

Posted on by Shannon Hall

First Exoplanet Discovered Beyond the “Snow Line”

This artist's conception shows the Uranus-sized exoplanet Kepler-421b, which orbits an orange, type K star about 1,000 light-years from Earth. Kepler-421b is the transiting exoplanet with the longest known year, circling its star once every 704 days. It is located beyond the "snow line" – the dividing line between rocky and gaseous planets – and might have formed in place rather than migrating from a different orbit. David A. Aguilar (CfA)

Data from NASA’s crippled Kepler space telescope has unleashed a windfall of hot Jupiters — sizzling gas giants that circle their host star within days — and only a handful of Earth-like planets. A quick analysis might make it seem as though hot Jupiters are far more common than their smaller and more distant counterparts.

But in large surveys, astronomers have to be careful of the observational biases introduced into their data. Kepler, for example, mainly finds broiling furnace worlds close to their host stars. These are easier to spot than small exoplanets that take hundreds of days to transit.

New data, however, shows a transiting exoplanet, Kepler-421b, with the longest known year, clocking in at 704 days.

“Finding Kepler-421b was a stroke of luck,” said lead author David Kipping from the Harvard-Smithsonian Center for Astrophysics in a press release. “The farther a planet is from its star, the less likely it is to transit the star from Earth’s point of view. It has to line up just right.”

Kepler-416b's folded light curve. Image Credit:
Kepler-421b’s folded light curve. Blue points are data from the first transit observed, and red points are the second transit.  Image Credit: Kipping et al.

Kepler-421b is roughly 4 times Earth’s girth and at least 60 times Earth’s mass. It circles its host star at about 1.2 times the distance from the Earth to the Sun. But because its host star is much smaller than our Sun, this places its orbit beyond the snow line — the dividing line between rocky and gas planets.

On Earth, snow lines typically form at high elevations where falling temperatures turn atmospheric moisture to snow. Similarly, in planetary systems, snow lines are thought to form in the distant, colder reaches of the stars’ disk.

Depending on the distance from the star, however, other more exotic molecules — such as carbon dioxide, methane, and carbon monoxide — can freeze and turn to snow. This forms a frost on dust grains: the building blocks of planets and comets.

“The snow line is a crucial distance in planet formation theory. We think all gas giants must have formed beyond this distance,” said Kipping.

The fact that this gas giant is still beyond this distance, roughly 4 billion years after formation, suggests that it’s the first non-migrating gas giant in a transiting system found.

Astronomers currently think gas giants form by small rocky cores that glom together until the body is massive enough to accrete a gaseous envelope. As they grow, they migrate inward, sometimes moving as close to their host star as Mercury is to the Sun.

Kepler-421b may be the first exoplanet discovered to have formed in situ. But further observations, especially those of its atmosphere, will help shed light on its formation history. Unfortunately given its long year, it won’t transit again until February, 2016.

The research has been accepted for publication in The Astrophysical Journal and is available online.