To our knowledge, Earth is the only known planet to contain life. Considering we have discovered thousands of planets since the discovery of the first exoplanet in the mid-1990s, this is a bit shocking. Since then, we have found multiple methods of detecting planets around stars other than our Sun, the most prominent of which are planetary transits, and Doppler shifts, also known as radial velocity measurements. Recently, the technology to directly image the planets has been invented, but these images are still very low resolution and does not provide much information about the planets. In order to possibly contain life, a planet must be within a star’s habitable zone. A habitable zone is the are of a star’s orbit where liquid water could potentially exist on its surface. NASA’s Kepler mission has been very successful discovering planets that are potentially habitable, notably Kepler-22b. Conversely, it has discovered many more planets that have very extreme environments.
Kepler-70: A Dying Star
Far away in the constellation Cygnus, 3,849 light-years to be precise, lies a subdwarf-B star known as Kepler-70. It is a much smaller star than the Sun, with a radius of 0.203 solar radii, only 1/5 of the Sun. It is also much less massive at 0.496 solar masses. The luminosity is, however, 18.9 times greater than that of the Sun. For the luminosity of the star, the following equation was used:
In this equation, r is the radius of the star, σ is the Stefan-Boltzmann constant, and T is the average temperature of the star. Kepler-70 is an ancient star, having evolved completely through the main sequence and red giant stages of its life. Estimates determine that Kepler-70 exited the red giant stage 18.4 million years ago. Since then, the star’s core has been fusing Helium. Once the supply is exhausted, the star will complete its lifetime by contracting into a white dwarf.
An example of the brightness dip from a transiting planet.
Discovering Planets around Kepler-70
When a planet’s orbit lies on the same orbital plane viewable from Earth, the planet will cross in front, or transit, the star once every orbital period. This causes the observed brightness of the star to drop relative to the size of the both the star and the planet. Unlike other planetary detection methods, this allows the transit method to discern the radius of a transiting planet. Three or four transits are required for conformation of an extrasolar planet. NASA’s Kepler mission uses the transit method to discover new planets around stars, including two that have been discovered around Kepler-70 by Stephane Charpinet. The discovery of these planets was announced on December 12, 2011.
The innermost planet, Kepler-70b, has one of the most extreme environments ever found on a planet, yet some of its characteristics are very similar to Earth. It has a very similar density at 5500 kg/m3, compared to Earth’s 5515 kg/m3. However, it is only 44% of Earth’s mass. Despite some similarities, the environment on Kepler-70b is just too hostile for any forms of life as we know it to exist there. The main obstacles, and large ones at that, standing in the way of life on Kepler-70b are its lack of an atmosphere, proximity to its host star, extreme temperatures, and it was actually inside its host star during the recent past.
What is Kepler-70b Like?
Today, Kepler-70b is not really a planet in the tradition sense. Rather, it is all that remains of a gas giant that formed with the original star system. Millions of years ago, Kepler-70b was likely a hot Jupiter, a Jovian-sized planet that orbits unusually close to its host star. In the case of Kepler-70b, the planet orbits just 0.006 AU from the star. Comparatively, Mercury orbits 65 times further from the Sun. This is far inside the inner boundary for the habitable zone of Kepler-70, both conservative and optimistic measurement, which range from 4.13-6.08 AU and 1.95-7.39 AU respectively. Usually, these orbital distances compare to those of Mercury or Venus. The inner and outer boundaries of a star’s habitable zone can be calculated using the following equations where the conservative measurement is the upper pair of equations and the optimistic is the lower two.
As Kepler-70 aged, the star expanded to become a red giant about 18.4 million years ago. Because of 70b’s extreme proximity to the host star, the planet was actually enveloped in the expanding star’s atmosphere, consequently destroying its atmosphere. Normally, planets in this situation are disintegrated by the extreme temperature and pressure. However, some Jovian-sized planets are large enough that they can actually survive. As the star exits its red giant stage and begins to shrink, the remaining iron core of the planet is all that remains. Naturally, the temperatures of such an object are extremely high. Kepler-70b currently holds the record for the hottest known planet with an surface equilibrium temperature of 7288˚K. The equilibrium temperature of a planet can be calculated using the equation:
where Ab is the albedo of the planet, D is the distance in astronomical units from the host star to the body, and L☉ is the brightness of the host star in solar luminosities. The estimated surface temperature of Kepler-70b was calculated using an assumed bond albedo of 0.1 because the true albedo of the planet cannot be determined by the transit method and remains unknown. Kepler-70b also orbits its star with one of the shortest orbital periods of any exoplanet: just over 5 hours. In order to complete its orbit this quickly, it orbits at just under 5% of light speed.
Can Life Exist on This Planet?
Life as we know it cannot exist on Kepler-70b in its current state. It orbits Kepler-70 far inside both the conservative and optimistic habitable zones, roughly 65 times closer to its sun than Mercury to ours. Not only does this create surface temperatures that exceed any temperature on Earth where life is found, but it results in the complete lack of water in any form on the planet. In our Solar System, planets without surface water might perhaps have water vapor high in their atmosphere where conditions allow it, but Kepler-70b has no atmosphere to house water vapor. Without an atmosphere, there is also no potential energy source that organic compounds could draw from to make energy. Further evidence against life on Kepler-70b comes from the planet’s “solid”iron composition. In fact, the surface is very likely completely molten, which is hostile to life.
It is possible that life could have existed on it in the past. Scientists theorize that microbial life could exists on Jovian planets like Kepler-70b. This life would need to live in extremely high elevations in the atmosphere in order to be at habitable pressures and temperatures, as well be near the water vapor that exists there. In order to do so, it would need to be be buoyant enough to stay at that elevation. Even so, any life on the planet would have been irradiated when the Kepler-70 became a red giant. The atmosphere was completely demolished by the expanding star, and temperatures quick rose. The final nail in the coffin would have come when the planet was finally engulfed by the Kepler-70. It would be impossible for any organic compounds to survive the inside of a star. Even after Kepler-70b left the star, it has only been 18.4 million years, far too short for any life to evolve on the planet even if it its conditions were perfect.
Additionally, Kepler-70b is orbiting a star very late in its lifetime. Soon, cosmically speaking, this star will become a white dwarf, entering the final stages of its life. Observations of planets orbiting similarly sized stars, especially this close, show that the planets become tidally locked far sooner than it would take for life to evolve on the planet. This holds true even for planets in the habitable zone, let alone planets only 0.006 AU from the star. Once the planet becomes tidally locked, it will be impossible for life to evolve.
What About Sci-Fi Life?
Take a step back for a second and imagine a universe where life could evolve and adapt to changing environment conditions very quickly. For example, if the microbial life hidden in the clouds of Kepler-70b became extremely heat resistant. This shell of theirs would be able to shield them from the 28,000˚K interior of Kepler-70 while also protecting them from the immense pressure. They would be able to swim, if you will, freely in the now molten surface of what used to be a gigantic Jovian planet. As the planet emerged, the drop in both pressure and temperature allowed these organisms to drop their protective shells and float along the surface of the iron core freely. If only such life could exist, one could argue that it would be more evolutionarily successful than any species on Earth.
Unfortunately, for Kepler-70b, there are too many factors standing in the way of life. At least, life as we know it could not exist there. If its complete lack of liquid water and location far outside of the star’s habitable zone was not enough, then the scorching temperatures and five hour day surely prevent life from evolving there. Not to mention that the planet was literally inside a star. Any life that could have possibly arisen there was immediately stopping in its evolutionary track, and any change of life appearing again are very slim. Kepler-70b can hold the record for hottest temperature, shortest orbital period, and smallest mass, but it will not hold the record for being the first exoplanet to be home to life. That is a guarantee.
“Kepler Discoveries.” <i>NASA</i>. N.p., n.d. Web. 23 Oct. 2013. <http://kepler.nasa.gov/Mission/discoveries/>.
Anderson, Paul Scott. “Two More Earth-Sized Planets Discovered by Kepler, Orbiting Former Red Giant Star.” <i>Universe Today</i>. N.p., n.d. Web. 23 Oct. 2013. <http://www.universetoday.com/92127/two-more-earth-sized-planets-discovered-by-kepler-orbiting-former-red-giant-star/>.
“Planet KOI-55 b.” The Extrasolar Planet Encyclopedia. N.p., n.d. Web. 23 Oct. 2013. <http://exoplanet.eu/catalog/koi-55_b/>.
Talcott, Richard. “Top 10 Exoplanets.” Astronomy 1 Oct. 2013: 22-27. Print.
It’s no secret that a greater education level will result in a more financially profitable career later in life. However, one variable that if often overlooked is the age of the worker. I was curious about how these two variables affected the income of American citizens specifically, and found an NPR article about age/income and an Infoplease article about education/income.
Due to limitations of Numbers, I was unable to successfully combine both data sets onto one chart. Even though the y-axis is identical, the x-axis is dramatically different, which forced me to make two separate graphs.
Let’s start with the Age graph:
Note that all numbers are in pre-tax dollars.
Age plays a surprising role in the amount of income that a person makes. For example, an American adult, ages 25-34, regardless of gender or educational background, makes about $25,000-$55,000 USD annually. To put this into perspective, this time period of their working life corresponds to the proto-star stage of stellar evolution. During the “main-sequence”, if you will, the average American adult (ages 35-64) income will remain very constant. An American spends the vast majority of their working life making around $75,000 USD annually. As a person nears retirement, likely working part time, they make only about $41,000 USD annually. This could be considered the red giant stage of someone’s working career, before retiring to a white dwarf and making only residual income from Social Security.
According to NPR, these numbers are not surprising. Studies over decades have shown that the peak of one’s career comes between ages 40 and 60. While the numbers are not surprising, these are averages for the nation as a whole. There are still plenty of people making the same money in their forties as a 25-year-old on this graph.
Here is the graph involving Educational Level, this time separated by gender.
Note that all numbers are in pre-tax dollars. Numbers also prevented every x-axis label from appearing due to clutter.
These numbers should not be surprising to anyone. The more educated you are, the more likely you are to land yourself a high-skill, high-paying job. Unlike the first graph that was an average based solely on age, this data takes into consideration educational background like I mentioned, but gender as well. What surprises me is that women make significantly less than men do with the same degrees. With a PhD, a women will make only about $85,000 USD annually while a man will make over $100k USD. This means that women are not being hired for the same jobs even if they have similar qualifications since the same job will pay the same.
I hope this data has enlightened you to the importance of getting an education to secure your future. Most importantly, ages 40-60 are when you want to maximize your potential for making money.
A planet’s lifetime is finite. Even our own cosmic utopia Earth will die out when the Sun reaches later stages of its life. As a star ages, it expands, heating up and shifting its habitable zone further than the orbit of Earth-like planets. As a result, liquid water ceases to exist on these planets, killing any chance of surface life on the planet. In our case, we have about 1.7 billion years left before Earth turns into a terrestrial hot-house like Venus is today. The Sun will be about 118% brighter and hotter than it is today, evaporating out oceans. Considering Earth has been around for about 4.5 billion years, about 70% of its lifetime in the Sun’s habitable zone has already passed.
Scientists believe that the best place to look for intelligent aliens is around small stars called red dwarf stars. These stars are only about 1/5 the size of the Sun, but this results in a habitable lifetime for planets that well exceeds Earth’s. These stars, scientists believe, should be the main targets of SETI (Search for Extraterrestrial Intelligence) missions, since any civilization there doesn’t have the same time constraints as those around large stars. Additionally, NASA’s Kepler mission has turned up evidence of many Earth-like planets possibly located around red dwarfs.
A visual guide to a star’s habitable zone based on its size. Source: Discovery
Kepler gives us information about distance from Earth, orbital period, and size. It does not, however, give us any information about the atmospheric composition, tectonic activity, or tilt of the planet. It also doesn’t help us determine the age of the host star, meaning we do not the evolutionary status of any hypothetical life that exists on these worlds. Using this information, researchers have determined that the exoplanet Gilese 518g is “the most habitable exoplanet found to date”. It orbits a red dwarf star, which means that its habitable conditions are believed to exist for another 5 billion years longer than Earth’s.
There is, of course, the threat of tidal locking occurring quickly on planets that are close to the red dwarf, because its smaller size actually accelerates the process. If tidal locking occurs, life on planet will become impossible.
In a talk delivered on Monday, the speaker elaborated on the evolving state of the Earth’s ecosystem. The majority of his talk was focused on the constant degradation of the natural environment and the consequential effects on the native animal species.
As a resident of California, I was disturbed to hear that the famous California Grizzly Bear actually doesn’t reside in California anymore. In fact, a species that was native to California, Oregon, Idaho, Montana, and Washington has been restricted more and more until now it only can be found wild in parts of Montana like Yosemite Park and western Canada. Sadly, only 500-600 California Grizzly Bears actually live in Yosemite Park, an infinitesimal number compared to the population size a century ago. The simple fact is that these animals are constricted because of our need to expand. Now I’m not going to go on a rant blaming human ignorance and arrogance for this, but just consider how we affect them.
California Grizzly Bears are not the only species affected by human expansion. Down on the border between Arizona and Mexico, relatives of deer are being blocked from their migration path by a 15-foot-high wall that is ironically more effective at stopping animals than humans. Other migration paths, in Montana for example, are cut off by expansive inter-state highways and railways. With the frequency of trains exceeding 4 dozen a day, incidents of groups of animals dying while waiting for an opportunity to cross the tracks are becoming more and more frequent.
An concept of an animal highway crossing. Source: Web Ecoist
For human infrastructure that has overrun migratory paths in use for thousands of year s, plans to build an artificial crossing for native species. The above picture is a concept art for a new crossing, but it bears many similarities to already constructed ones. These bridges are a simple, cost-effective (relative to the total budget), and effectively solve one of the greatest problems facing the animal kingdom at the moment.
I never really understood the gravity that animal species were being effected by human expansion. Hopefully we will see some changes soon that can help reduce the problems we’ve created for them.
SpaceX’s primary rocket engine craft, the Falcon 9, debuted in 2010 along with their Dragon spacecraft. The engine is a very advanced, twin-engine rocket. Unfortunately, the engine suffers from all the same problems as other engines, it’s single use. Like all other rockets, the engine is used to propel the spacecraft into orbit, then it falls back to Earth in two stages. On September 29, 2013 SpaceX tested a prototype replacement engine, the Falcon 9 v1.1. What makes this so exciting is that it is able to restart itself after detaching from the rocket and slow its decent to Earth, allowing the rocket to be used multiple times. According to SpaceX CEO Elon Musk, the engines are 75% of the cost of the rocket.
The new Falcon 9 v1.1 launching from Vandenberg AFB in California. Source: Discovery
After dropping off its payload, Falcon 9 v1.1 reignited its first-stage engines, slowing its decent as it passed through Earth’s atmosphere. For an engine to survive re-entry, this is the most important step. Eventually, the rocket can make a soft ocean landing or even return to the launch pad and land itself. This stage required two engine re-ignitions, the first of which was successful. The second re-ignition was stopped after it was discovered that the engine was spinning in mid-air, causing the gas-lines to choke due to centrifugal forces. According to Musk, “It caused the boost stage to run out of propellant… before hitting the water. It hit relatively hard. We recovered portions of the stage, but the most important thing is we now believe we have all the pieces of the puzzle”.
SpaceX has been developing a different engine which is codenamed Grasshopper. This engine has the capacity to take-off and land itself, which aims to solve one of the greatest problems facing interplanetary travel at the moment. Currently, all trips to other planets are strictly one-way. In conjunction with tests run with Grasshopper and Falcon 9 v1.1, scientists believe they have sufficient data covering all aspects of a round-trip back to Earth. Musk claims that “[we] have all the pieces necessary to achieve a full recovery of the boost stage … That’s actually what has got me most excited about this flight”.
SpaceX expects to demonstrate a full recovery of Falcon 9 v1.1 in 2014.
Yesterday, October 1st, the highly publicized Comet ISON passed its closet point to Mars. ISON flew by mars at 10.5 million kilometers, or about 6.5 million miles for you non-science people. An image taken from the 2 meter Liverpool telescope in the United Kingdom captured the comet just before its closest pass by Mars. Here is the image:
Source: Universe Today
The image taken from the Liverpool telescope in the United Kingdom is a composite of 20 different exposures, each an 11 second duration. According to scientists Ernesto Guido, Nick Howes and a new team member named Martino Nicolin, “[the image shows a] well developed coma and tail measuring at least 3 arc minutes”.
Comet ISON imaged from Liverpool. Mars is in the bottom right. Source: Universe Today
Above is another image taken from Wesminster, Maryland. This image is a composite of 44 30-second exposures, and shows the comet in the top left with Mars appearing in the bottom right. This image shows the distance between the closest pass of ISON. According to the photographers, ISON was not visible with the telescope’s eyepiece, and stacking the images was required to view the comet.
Nick Howes explains that there was an internal debate regarding whether or not the comet had additional jet streams coming off it. Tests run by the team showed that these were maybe spontaneous events, but one test showed that the additional jet stream might be a constant feature of the comet. Later comparisons of data between Liverpool and The Planetary Science Institute confirmed that this feature is a in fact constant. Additionally, it can be seen in previous ISON observations, including those from Hubble.
ISON will reach its perihelion, the closest point to the sun, on November 28. If it survives, it will be at its closest point to Earth on December 26. It will be some 64 million miles above the Earth’s surface. Some might even call it a Christmas miracle.
Despite the government shutdown, observations from the Mars rover Curiosity are still ongoing because the rover is operated from the Jet Propulsion Laboratory, and will continue to operate unless previous NASA funding runs out.
NASA’s Kepler mission to discover exoplanets has recently reported over 1,000 planets beyond our solar system. Of these, only 10 are Earth-sized planets orbiting in its parent star’s habitable zone. Within this selection, Kepler-22b is the smallest of these 10 planets. On December 5, 2011, NASA’s Kepler mission confirmed Kepler-22b to be the mission’s first potentially habitable planet discovered. This is because it orbits in its sun’s habitable zone, the area around a star where liquid water can exist.
A diagram of Kepler-22b’s orbit compared to the inner solar system. Source: Wikipedia
The planet is from the constellation Cygnus, a whopping 600 light-years from Earth. So any goals of reaching this planet are, unfortunately, extremely unrealistic. Compared to Earth, it’s radius is roughly 2.4 times the size of our planet. Despite its relatively similar size to Earth, the composition of the planet (solid, liquid, gas) is still unknown. The orbit of the planet is estimated to be around 290 days, not that different from Earth. Kepler-22, the host star, is a bit smaller and cooler than our sun, but it is of the same classification as the Sun, a G-Type star. According to NASA scientist Doug Hudgins, “This is a major milestone in discovering Earth’s twin”.
Artists rendering of Kepler-22b. Source: Wikipedia
Planets are discovered with the Kepler spacecraft by studying stars and looking for transits of planets. That is, when a planet crosses in front of its parent star, in this case Kepler-22. Kepler requires three separate transits of a planet before it can be verified as a possible planet. 22b’s first transit came only three days after the mission began, and the final transit came in the holiday season of 2010. Further research is then done by ground based telescopes and the Spitzer Space Telescope.
Overall, the amount of exoplanets discovered as of December 2011 had increased by 200 (140%) since February of the same year and more planets are being discovered all the time. Who knows how many planets have been found since.