Shannon Hall is a freelance science journalist. She holds two B.A.'s from Whitman College in physics-astronomy and philosophy, and an M.S. in astronomy from the University of Wyoming. Currently, she is working toward a second M.S. from NYU's Science, Health and Environmental Reporting program. You can follow her on Twitter @ShannonWHall.
A new map of wind patterns is so visually stunning it’s easily mistaken for art.
This interactive visualization of wind patterns — modeled from the U.S. National Weather Service’s Global Forecast System database — provides nearly current weather conditions on the global scale. And it’s beautiful.
In an interactive form, this data set allows the user to move the globe around (simply drag with your mouse) and zoom in and out (use your scroll wheel). After a few seconds the colors appear in snaking lines, depicting wind patterns at varying speeds. Gentle breezes are thin lines of green, strong winds are light streaks of yellow, and the strongest current are thick lines of red and purple.
A screen capture of the Earth’s north pole at 5,500 meters. The thick purple line is the polar jet stream.
Adjustable parameters also allow the user to view the wind patterns at various heights in the atmosphere, from 100 meters (noted as 1000 hPa in the program) to 26,500 meters (10 hPa) above the Earth’s surface. Simply click on the word “earth” in the lower left-hand corner of the web browser.
At the surface the map is a mirage of blue and green — with fairly gentle wind patterns in green. Circling patterns over the oceans are cyclones. They rotate clockwise over the southern Indian ocean and counter-clockwise over the northern Pacific ocean. If you turn your eyes toward land, you can compare the light summer winds across Australia with the swirling gusts off the northeast coast of Japan.
But you can also graze the jet streams, where thick bands of purple and red dance among the less violent green and yellow streaks. The wavy polar jet stream is entering the U.S. near Seattle, dropping southward near the Rocky Mountains, and then turning northward again just beyond the Great Lakes. It creates a temperature boundary, where south of the jet stream is warm and north of the jet stream is cold.
Users can view seven different altitudes using eight different map projections. This surprising new look at our own world is stunning in its artistic and educative beauty.
The theory of Lithopanspermia states that life can be shared between planets within a planetary system. Credit: NASA
With the recent discovery that Europa has geysers, and therefore definitive proof of a liquid ocean, there’s a lot of talk about the possibility of life in the outer solar system.
According to a new study, there is a high probably that life spread from Earth to other planets and moons during the period of the late heavy bombardment — an era about 4.1 billion to 3.8 billion years ago — when untold numbers of asteroids and comets pummeled the Earth. Rock fragments from the Earth would have been ejected after a large meteoroid impact, and may have carried the basic ingredients for life to other solar system bodies.
These findings, from Pennsylvania State University, strongly support lithopanspermia: the idea that basic life forms can be distributed throughout the solar system via rock fragments cast forth by meteoroid impacts.
Strong evidence for lithopanspermia is found within the rocks themselves. Of the over 53,000 meteorites found on Earth, 105 have been identified as Martian in origin. In other words an impact on Mars ejected rock fragments that then hit the Earth.
The researchers simulated a large number of rock fragments ejected from the Earth and Mars with random velocities. They then tracked each rock fragment in n-body simulations — models of how objects gravitationally interact with one another over time — in order to determine how the rock fragments move among the planets.
“We ran the simulations for 10 million years after the ejection, and then counted up how many rocks hit each planet,” said doctoral student Rachel Worth, lead author on the study.
Their simulations mainly showed a large number of rock fragments falling into the Sun or exiting the solar system entirely, but a small fraction hit planets. These estimations allowed them to calculate the likelihood that a rock fragment might hit a planet or a moon. They then projected this probability to 3.5 billion years, instead of 10 million years.
In general the number of impacts decreased with the distance away from the planet of origin. Over the course of 3.5 billion years, tens of thousands of rock fragments from the Earth and Mars could have been transferred to Jupiter and several thousand rock fragments could have reached Saturn.
“Fragments from the Earth can reach the moons of Jupiter and Saturn, and thus could potentially carry life there,” Worth told Universe Today.
The researchers looked at Jupiter’s Galilean satellites: Io, Europa, Ganymede and Callisto and Saturn’s largest moons: Titan and Enceladus. Over the course of 3.5 billion years, each of these moons received between one and 10 meteoroid impacts from the Earth and Mars.
It’s statistically possible that life was carried from the Earth or Mars to one of the moons of Jupiter or Saturn. During the period of late bombardment the solar system was much warmer and the now icy moons of Saturn and Jupiter didn’t have those protective shells to prevent meteorites from reaching their liquid interiors. Even if they did have a thin layer of ice, there’s a large chance that a meteorite would fall though, depositing life in the ocean beneath.
In the case of Europa, six rock fragments from the Earth would have hit it over the last 3.5 billion years.
It has previously been thought that finding life in Europa’s oceans would be proof of an independent origin of life. “But our results suggest we can’t assume that,” Worth said. “We would need to test any life found and try to figure out whether it descended from Earth life, or is something really new.”
The paper has been accepted for publication in the journal Astrobiology and is available for download here.
Fast radio bursts — eruptions of extreme energy that occur only once and last a thousandth of a second — are continuing to defy astronomers. At first observations suggested they came from billions of light years away. A new study, however, points to sources much closer to home: nearby flaring stars.
“We have argued that fast radio burst sources need not be exotic events at cosmological distances, but rather could be due to extreme magnetic activity in nearby Galactic stars,” said Harvard professor Abraham Loeb in the study.
All radio bursts show a dispersion measure — a frequency dependent time delay — as the long-wavelength component arrives a fraction of a second after the short-wavelength component. When the burst travels through a medium, the long-wavelength component moves slightly slower than short-wavelength component.
This dispersion may easily be created when light travels through intergalactic space. The farther the light travels, the more electrons it will have to travel through, and the greater time delay between the arriving wavelength components.
With this assumption, fast radio bursts are likely to have originated anywhere from five to 10 billion light years away. Universe Today covered an extra-galactic origin a few months ago (read it here).
However, Loeb and his colleagues turned their eyes instead to electrons in stellar corona. These electrons are tightly packed, more so than diffuse intergalactic electrons, and would create the same observable effect.
Flaring stars — variable stars that can undergo unpredictable increases in brightness — are a likely source of fast radio bursts. Two circumstances may create flaring stars: young, low mass stars and solar-mass contact binaries, which orbit so close to one another that they share a common envelope.
In order to test this theory, Loeb and his colleagues searched the vicinities of three of the six known fast radio bursts for flaring stars.
“We were surprised that, apparently, no one had done this before,” said graduate student Yossi Shvartzvald in a press release. Shvartzvald led the observations at Tel-Aviv University’s Wise Observatory in Mitspe Ramon, Israel.
The team discovered a contact binary system in one location. Two sun-like stars orbit one another every 7.8 hours. They calculate a five percent chance that the contact binary is there by coincidence.
No flaring stars, however, were detected in the two other fields.
“Whenever we find a new class of sources, we debate whether they are close or far away,” Loeb said in a press release. Initially we thought gamma-ray bursts were faint stars within the Milky Way. Today we know they are bright explosions in distant galaxies.
It seems the distance debate for fast radio bursts has only begun.
The paper has been accepted for publication in the Monthly Notices of the Royal Astronomical Society and is available for download here. The original press release may be found here.
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.
A simulated dwarf galaxy when the universe was 0.5 billion years old. Magenta represents cool gas, green is warm ionized gas, and red is hot gas. Check out the movie. Image credit: Hopkins et al. 2013.
For the first time, astronomers are able to accurately simulate galaxies from shortly after the big bang to today by including a realistic treatment of the effects stars have on their host galaxies.
For the past few decades astronomers have simulated galaxies by mixing the basic physical ingredients — gravity, gas chemistry and the evolution of the universe — into their models.
For years their simulations have shown that gas cools off quickly and falls to the center of the galaxy. Eventually all of the gas forms stars. But observations show only “10 percent of the gas in the universe actually does so,” CalTech astronomer Dr. Philip Hopkins explained. “And in very small or very large galaxies, the number can go down to well below a percent.”
Models of galaxies create far too many stars and as a result end up weighing more than real galaxies in the observable universe. But in theory the solution is simple: the missing physics is a process known as stellar feedback.
For that, astronomers have to look at how stars help shape the evolution of the galaxies in which they reside. And what they have found is that stars affect their environments drastically.
When stars are very young they are extremely hot and blast off a high amount of radiation into space. This radiation heats up and pushes on the nearby interstellar gas. Later on stellar winds – particles streaming from the surface of stars — also push on the gas, further disrupting nearby star formation. Finally, explosions as supernovae can push the gas to nearly sonic speeds.
While astronomers have understood the missing physics for quite a while, they have not been able to successfully incorporate it a priori into their models. Despite their efforts their simulated galaxies have always weighed more than observed galaxies actually weigh.
Understanding the missing physics is a completely different question than being able to incorporate the missing physics directly into their models.
Instead, astronomers made big assumptions based on what galaxies should look like. At some point in their simulations, they had to go in by hand and tune certain parameters. They would get rid of so much gas until the results roughly matched the galaxies we observe.
“Basically, they (astronomers) said ‘we need there to be winds to explain the observations, so we’re going to insert those winds by hand into our models, and adjust the parameters until it looks like what’s observed,’ ” Hopkins told Universe Today.
At the time tuning their models in this way was the best astronomers could do and their models did help improve our understanding of galaxy evolution. But Hopkins and a team of astronomers from across North America have found a way to incorporate the missing physics — stellar feedback — directly into their models.
The research team is creating simulations that draw from stellar feedback explicitly. The FIRE (Feedback in Realistic Environments) project is a multi-year, multi-institution effort.
While it was no easy task, they incorporated the necessary and dare I say messy physics into their models, allowing for unprecedented accuracy. They tracked the affects radiation and stellar winds have on their environments and included a realistic supernovae rate.
“The result is that we see these stars pushing on the gas, and supernovae explosions sweeping up and ‘blowing out’ large amounts of material from galaxies,” Hopkins explained. “When you follow all of this, the story holds together, and indeed we can explain the observed masses of galaxies just from the input of stars.”
A simulated galaxy when the universe was 11.7 billion years old. Blue regions are young star clusters that have blown away their gas. Red regions are obscured by dust. Make sure the check out the movie by clicking on the image above. Image credit: Hopkins et al. 2013.
The results have been rewarding — providing some pretty cool videos of galaxies forming across the observable universe — and surprising.
It has become clear that the different types of stellar feedback don’t work alone. While the energy given off by stellar winds can push away interstellar gas, it cannot launch the gas out of the galaxy entirely. The necessary propulsion occurs, instead, when a supernova explosion happens nearby.
But this isn’t to say that supernova explosions play a larger role than stellar winds. If the authors left out any stellar feedback mechanism (the radiation from hot young stars, stellar winds, or supernova explosions) the results were equally poor — with too many stars and masses much too large.
“We’ve just begun to explore these new surprises, but we hope that these new tools will enable us to study a whole host of open questions in the field.”
The paper has been submitted for publication in the Monthly Notices of the Royal Astronomical Society and is available for download here.
Hopkins discusses the “Cosmological zoom-in simulation using new stellar feedback” at at workshop at the University of California, Santa Cruz earlier this year:
The early universe was sizzling with active galactic nuclei (AGN) — intensely luminous cores powered by supermassive black holes — most of which could outshine their entire host galaxies and be seen across the observable universe.
While our central supermassive black hole Sgr A* lies rather dormant at the moment, new evidence suggests that it too was once a powerful AGN.
The first hint occurred two years ago when astronomers discovered Fermi bubbles — massive lobes of high-energy radiation that expand 30,000 light years north and south of the galactic center.
Of course the source of these bubbles is “a hot topic today,” Dr. Joss Hawthorn from the Sydney Institute for Astronomy and lead author on the paper, told Universe Today. “Some think the bubbles were inflated by powerful star formation in the disk, others, like me, (think) that they were inflated by a powerful jet from Sgr A*.”
It’s becoming more and more plausible that the Fermi bubbles were created by a recently powerful jet protruding from the center of our galaxy — demonstrating they are remnants of a much more violent past.
But astronomers from the Sydney Institute for Astronomy in Australia, the University of Colorado, Boulder, and the University of Cambridge have found further evidence linking Sgr A* to a recent AGN.
The Magellanic Stream — a long ribbon of gas stretching nearly half way around the Milky Way and trailing our galaxy’s two small companion galaxies, the Magellanic Clouds — is likely to be another ancient remnant of our recent activity.
The problem is that the Magellanic Stream is extremely red. It is emitting a large number of photons that clock in at a particular wavelength: 656 nanometers. This wavelength not only falls in the visible spectrum, but corresponds to a red color.
The Magellanic Stream is emitting so much red light because it contains extremely energetic hydrogen atoms. When atoms have high-energy electrons, these electrons lose energy by emitting photons.
But astronomers cannot explain why the Magellanic Stream has so many energetic hydrogen atoms, why it is such a bright red color — unless they invoke recent AGN activity from the Milky Way galaxy.
If we assume Sgr A* was once very bright, it would have lit up the Magellanic Stream, causing hydrogen atoms to absorb energy from the incoming light — an effect still visible millions of years later.
A huge outburst of energy in our recent past is likely the cause of a Seyfert flare — an eruption of light and radiation when small clouds of gas fall onto the hot disk of matter that swirls around the black hole.
“If you hurl a bucket of water into a sink, you would be shocked if it all disappeared down the plug hole. Of course, the water spins around the plughole first. (The) same thing (occurs) with gas falling onto a black hole. the spinning disk heats up and generates powerful outbursts: Seyfert flares,” Dr. Hawthorn explained.
This provides further evidence that Sgr A* was once a very powerful AGN, causing Fermi bubbles and a brighter Magellanic Stream. It’s likely it was active as recent as one to three million years ago.
The paper has been published in the Astrophysical Journal and is available for download here.
With an annual cost of $30.8 million, the Keck Observatory costs $53.7 thousand for a single night’s worth of operation. It will cost the James Webb Space Telescope approximately $8.8 billion to reach orbit. And the Space Launch System that will carry the Orion capsule is expected to cost $38 billion.
Why should we be spending such a vast amount of money on astronomy? How is it useful and beneficial to society?
Astronomers face this question on a daily basis. Recently a ream of European astronomers have provided tangible answers relating advancements in astronomy to advancements in industry, aerospace, energy, medicine, international collaboration, everyday life and humankind.
“I get this question quite often,” Dr. Marissa Rosenberg, lead author on the paper, told Universe Today. “One very personal reason for writing this article is that I wanted to share with my parents (both business people) why what I am doing is important and a necessary facet of society.”
Today, millions of people across the world are affected by advances in astronomy.
Industry
— Your iPhone’s camera is a charge-coupled device (CCD) — an instrument, which converts the movement of electrical charge into a digital value. Originally developed for astronomy, CCD’s are now used in most cameras, webcams and cell phones.
Every iPhone with has a built-in CCD
— The computer language Forth, originally developed for the 36-foot telescope on Kitt Peak is now used by FedEx to track packages.
— AT&T uses IRAF — software written by the National Optical Astronomy Observatory — to analyze computer systems.
— Kodak film, originally created by astronomers studying the sun, is used extensively by the medical and industrial industries, photographers and artists.
Aerospace
— Space-based telescopes have advanced defense satellites, which require identical technology and hardware.
— Global Positioning System satellites rely on astronomical objects — quasars and distant galaxies — to determine accurate positions.
Energy
— Technology gained from imaging X-rays is now used to monitor fusion — where two atomic nuclei combine to form a heavier nucleus — that may prove to be our answer for clean energy.
Medicine
Magnetic resonance imaging utilizes aperture synthesis – first an astronomical technique and now a medical technique.
Astronomy struggles to see increasingly faint objects; Medicine struggles to see things obscured within the human body.
— Aperture synthesis — the process of combining data from multiple telescopes to produce a single image seemingly created from a telescope the size of the entire collection — first developed by a radio astronomer has been used for multiple medical imaging tools, including CAT scanners and MRIs.
— Building space-based telescopes requires an extremely clean environment in order to avoid dust particles from obscuring the mirrors or instruments. Similar methods and instruments are now used in hospitals and pharmaceutical labs.
International Collaboration
— Collaboration also inspires competition. The Space Race — a competition between the Soviet Union and the United States for supremacy in space exploration — landed Neil Armstrong, Michael Collins and Buzz Aldrin on the moon.
— Astronomy is a collaborative effort. In 1887 astronomers from around the world pooled their telescope images in order to create the first map of the entire sky. Today, astronomers travel around the globe to attend conferences, learn from one another, and utilize telescopes elsewhere.
Everyday Life
— Airports utilize advances in technology designed for astronomy. X-ray observatory technology is used in X-ray luggage belts. A gas chromatograph — an instrument designed for a Mars mission — is used to analyze luggage for explosives.
— Stephen Hawking’s “A Brief History of Time” has sold over 10 million copies. Carl Sagan’s television series “Cosmos: A Personal Voyage” has been watched in over 60 countries.
Humankind
“Perhaps the most important reason to study astronomy is that astronomy seeks to satisfy our fundamental curiosity about the world we live in, and answer the ‘big’ questions,” Dr. Rosenberg told Universe Today. “How was the universe created? Where did we come from? Are there other intelligent life forms?”
Every advance in astronomy moves society closer to being able to answer these questions. With advanced technology — increasingly complex CCDs and larger ground- and space-based telescopes — we have peered into the distant, early universe, we have searched for habitable worlds, and we have come to the conclusion that we, ourselves, are stardust.
“Astronomy constantly reminds people of two seemingly contradictory things. First that the universe is infinite and we are of but the tiniest fraction of importance. And Second that life is rare and precious. A home as beautiful and unique as earth does not come often. We must protect it.”
An upcoming version of this paper will not only cover the tangible aspects of astronomy discussed here, but also the intangible aspects of astronomy.
The paper has been accepted has been published on the International Astronomical Union website and is available for download here.
Artist's depiction of TESS. Image Credit: TESS team.
Last week I held an interview with Dr. Sara Seager – a lead astronomer who has contributed vastly to the field of exoplanet characterization. The condensed interview may be found here. Toward the end of our interview we had a lengthy conversation regarding the future of exoplanet research. I quickly realized that this subject should be an article in itself.
The following is a list of approved missions that will continue the search for habitable worlds, with input from Dr. Seager about their potential for finding planets that might harbor life.
Transiting Exoplanet Survey Satellite (TESS)
Slated to launch in 2017, TESS will search for exoplanets by looking for faint dips in brightness as the unseen planet passes in front of its host star. With a price tag of $200 million, TESS will be the first space-based mission to scan the entire sky for exoplanets.
While the Kepler space telescope confirmed hundreds of exoplanets (with thousands of candidates yet to be confirmed) it stared 3000-light-years deep into a single patch of sky. TESS will scan hundreds of thousands of the brightest and closest stars in our galactic neighborhood.
“TESS will find many planets,” explained Seager in our interview. “The ones we’re highlighting it will find are rocky planets transiting small stars.” One of the missions goals is to find earth-like exoplanets in the habitable zone – the band around a star where water can exist in its liquid state.
The team hopes that TESS will find up to 1000 exoplanets in the first two years of searching. This will give astronomers a wealth of new worlds to study in more detail.
While the stars Kepler examined were faint and difficult to study in follow-up observations, the stars TESS will focus on are bright and close to home. These stars will be prime targets for further scrutiny with other space based telescopes.
“We plan to have a pool of planets, maybe a handful of them, that we can follow up with the James Webb Space Telescope … which will look at the atmospheres of those transiting planets, looking for signs of life,” Seager said.
ExoplanetSat
While slightly under the radar, ExoplanetSat will monitor bright stars using nano-satellites. Each nano-satellite will be capable of monitoring a single, bright, sun-like star for two years.
The current design of ExoplanetSat. The telescope is approximately the size of a loaf of bread. Image Credit: Pong et al. 2010 (SPIE 7731).
“The way that we describe this mission is not that we will find earth,” Seager said. “But if there is a transiting earth-like planet around a bright sun-like star, we will find it.”
Currently no planned mission has the capability to survey the brightest stars in the sky. TESS will observe stars of magnitude 5 through 12 – the dimmest our eyes can see and fainter.
The brightest stars are too widely spaced for a single telescope to continuously monitor. The best method is to monitor the brightest sun-like stars in a targeted star search instead.
The mission is pretty far along in terms of funding. It has already received a few million dollars and is about one million short of launching the first prototype.
After a successful demonstration the goal is to launch a fleet of nano-satellites to observe enough bright stars to find a number of interesting exoplanets. One day we may be able to look at a bright star in our night sky and know it has a planet.
Direct Imaging Missions
Disentangling a faint, barely reflective, exoplanet from its overwhelmingly bright host star in a direct image seems nearly impossible. A common analogy is looking for a firefly next to a searchlight across North America. Needless to say, very few exoplanets have been seen directly.
Because of the difficulties NASA is fostering a study and soliciting applications with a single goal in mind: create a mission that will directly image exoplanets under a price cap of one billion dollars.
Seager is working with a team that plans to utilize a star shade – “a specially shaped screen that will fly far from the telescope and block out the light from the star so precisely that we will see any planets like earth.”
The shade isn’t circular but shaped like a flower. Light waves would bend around a circle and create spots brighter than the planets themselves. The flower-like shape avoids this while blocking out the starlight – making a planet that is one ten billionth as bright as its host star visible.
The star shade and the telescope have to be aligned perfectly at 125,000 miles away. Once aligned, the system will observe a distant star, and then move to another distant star and re-align. This is technologically speaking, unchartered territory.
While this mission may not occur in full tomorrow, or even years from tomorrow, astronomers’ synapses are firing. We’re coming up with new techniques that will advance technology and find earth-like worlds.
Etc.
Above is a list of only a handful of future exoplanet missions – all at various stages in their production – with some still on the drawing board and others having received full funding and preparing for launch. With creativity and advancing technology we’ll detect a true-earth analogue in the near future.
Planetary Scientist Sara Seager. Image courtesy MIT.
Astronomers have now discovered one thousand extrasolar planets, reaching a milestone in modern astronomy. (See a recent Universe Today article on the subject.) While many have contributed to this achievement, Dr. Sara Seager of MIT has played a large role over the past two decades by contributing vastly to the field of exoplanet characterization. Her theoretical work led to the first detection of an exoplanet atmosphere.
The following is a condensed interview I held with Seager earlier this week.
What first pulled you in to the field of astronomy?
When I was 10 I got to see a really dark sky (well outside her hometown of Toronto, Canada). I stepped out in the middle of the night and I just saw so many stars. I wish you and everyone could see that. So many stars, I just couldn’t believe it.
You were working at Harvard for your PhD in the mid ‘90s when we first detected exoplanets. What was that like?
The mood was quite different. Today everybody wants to talk about it (exoplanets) and write about it. There’s a lot of hype. But back then it was very quiet.
There was a huge amount of skepticism too. People don’t like change. I want you to imagine a world where the gas giants like Jupiter and Saturn are very far from the star and the terrestrial planets like Earth, Mercury, Venus, and Mars are very close to the star. People had constructed theories on how planetary bodies form based on that one example.
So when the first planets around sun-like stars were found, they were Jupiter-mass planets, but they were several times closer to their star than Mercury is to our Sun. It offended all thoughts, theories, and paradigms … As scientists we’re supposed to be skeptical and push back on new discoveries and theories that are upsetting the system. There was huge skepticism.
An exoplanet seen from its moon (artist’s impression). Via the IAU.
How difficult was it during this time to work on exoplanets?
Many people, including my graduate student peers and faculty said, “Why are you doing this (working on exoplanet research)? This is not going to happen. And even if exoplanets are real we’re never going to be able to study their atmospheres,” which is what my PhD was on.
What pushed you through despite all the skepticism?
Ironically, I was not committed to a career in science. I didn’t feel like I needed to be involved with something that was at the 100 percent certainty level. I was free because I didn’t have a plan. I had nothing to lose by doing something I thought was really cool and exciting.
When you’re doing a PhD you’re really learning how to answer a tough question. Usually if you do a homework set in high school, or college, there’s already a known answer. But when you’re doing a PhD, if you’re asking a really hard question that has never been asked before you’re answering that question with your own tools that you’ve developed yourself.
At that time, I knew… the real thing is not just what you’re working on but it’s the tools that you’re using and the things that you’re learning. At the end of the day if you don’t stay in science you have gained a skill that most people don’t have.
Artist concept of an exoplanet. Credit: David A. Hardy. What changed then? What kept you in science after graduate school?
I had freedom and really enjoyed what I was doing.
What is your motivation for studying exoplanets? Why should we study exoplanets?
We want to know: Are we alone? We want to know if there is life beyond earth. Eventually we will have dozens to hundreds of potential earth-like planets to study in detail. We want to look at their atmospheres for signs of life by way of biosignature gases.
What do you think is the likelihood that we will discover an earth-like planet orbiting a sun-like star?
Well, it really just depends if we can rally resources and interest in doing this problem. We think we know how to find an earth-like planet around a sun-like star. But it’s a very very very hard endeavor. We think that the earths are out there. It’s just a matter of building the sophisticated space telescopes that we need.
So what are the chances? It’s really more of a political and economical question more than anything else. I think it’s inevitable that eventually we will find one.
Do you have a favorite planet?
I always like to say my favorite planet is the next planet. We have a sort of ADD (attention deficit disorder) in this field where we’re propelled and motivated forward by finding the next exciting planet. Artist’s impression of exoplanets around other stars. Credits: ESA/AOES Medialab We’ve reached a huge milestone in astronomy of detecting one thousand exoplanets. What does this milestone mean to you?
There’s a caveat here, an uncertainty. We don’t know which one is going to be number one thousand because we don’t agree on the definition of a planet. And even if we did, there’s an uncertainty in the mass and size measurements such that some objects that are called planets probably aren’t planets depending on what definition you want. Occasionally a planet is retracted.
But in general, we’re about to pass the one thousandth mark. What do I think? I think it’s phenomenal. I mean I’m so excited.
The study of exoplanets really started as a field where no one wanted to work on it. People thought it was never going to happen, they thought even if there were real planets we’d never get any measurements beyond stamp collecting – a derogatory phrase we sometimes use in astronomy for science that is not that useful. You just find discoveries and they pile up because you don’t know what to do with them.
We’ve changed the paradigm of planet formation, found exotic types of planets, and we’re right on our way to finding another Earth. So I think it couldn’t be better.
Full sky map of the cosmic microwave background. The color red indicates a cool spot while the color blue indicates a hot spot. Image credit: NASA.
Warped visions of the cosmic microwave background – the earliest detectable light – allow astronomers to map the total amount of visible and invisible matter throughout the universe.
Roughly 85 percent of all matter in the universe is dark matter, invisible to even the most powerful telescopes, but detectable by its gravitational pull.
In order to find dark matter, astronomers look for an effect called gravitational lensing: when the gravitational pull of dark matter bends and amplifies light from a more distant object. In its most eccentric form it results in multiple arc-shaped images of distant cosmic objects.
The Hubble Space Telescope shows the effect of gravitational lensing as background galaxies are warped by the galaxy cluster MACS J1206. Image Credit: NASA
But there’s one caveat here: in order to detect dark matter there must be an object directly behind it. The ‘stars’ have to be aligned.
In a recent study led by Dr. James Geach of the University of Hertfordshire in the United Kingdom, astronomers have set their eyes on the cosmic microwave background (CMB) instead.
“The CMB is the most distant/oldest light we can see,” Dr. Geach told Universe Today. “It can be thought of as a surface, backlighting the entire universe.”
The photons from the CMB have been hurling toward the Earth since the universe was only 380,000 years old. A single photon has had the chance to run into plenty of matter, having effectively probed all the matter in the universe along its line of sight.
“So our view of the CMB is a bit distorted from what it intrinsically looks like – a bit like looking at the pattern on the bottom of a swimming pool,” Dr. Geach said.
By noting the small distortions in the CMB, we can probe all of the dark matter throughout the entire universe. But doing just this is extremely challenging.
The team observed the southern sky with the South Pole Telescope, a 10 meter telescope designed for observations in the microwave. This large, groundbreaking survey produced a CMB map of the southern sky, which was consistent with previous CMB data from the Planck satellite.
The characteristic signatures of gravitational lensing by intervening matter can not be extracted by eye. Astronomers relied on the use of a well-developed mathematical procedure. We wont go into the nasty details.
This produced a “map of the total projected mass density between us and the CMB. That’s quite incredible if you think about it – it’s an observational technique to map all of the mass in the universe, right back to the CMB,” Dr. Geach explained.
But the team didn’t finish their analysis there. Instead, they continued to measure the CMB lensing at the positions of quasars – powerful supermassive black holes in the centers of the earliest galaxies.
“We found that regions of the sky with a large density of quasars have a clearly stronger CMB lensing signal, implying that quasars are indeed located in large-scale matter structures,” Dr. Ryan Hickox of Dartmouth College – second author on the study – told Universe Today.
Finally, the CMB map was used to determine the mass of these dark matter halos. These results matched those determined in older studies, which looked at how the quasars clustered together in space, with no reference to the CMB at all.
Consistent results between two independent measurements is a powerful scientific tool. According to Dr. Hickox, it shows that “we have a strong understanding of how supermassive black holes reside in large-scale structures, and that (once again) Einstein was right.”
The paper has been accepted for publication in the Astrophysical Journal Letters and is available for download here.
