MESSENGER's new solar system portrait, from the inside out
[/caption]
Say cheese! The MESSENGER spacecraft has captured the first portrait of our Solar System from the inside looking out. The images, captured Nov. 3 and 16, 2010, were snapped with the Wide Angle Camera (WAC) and Narrow Angle Camera (NAC) of MESSENGER’s Mercury Dual Imaging System (MDIS).
All of the planets are visible except for Uranus and Neptune, which at distances of 3.0 and 4.4 billion kilometers were too faint to detect with even the longest camera exposure time of 10 seconds. Their positions are indicated. The dwarf-planet Pluto, smaller and farther away, would have been even more difficult to observe.
Earth’s Moon and Jupiter’s Galilean satellites (Callisto, Ganymede, Europa, and Io) can be seen in the NAC image insets. Our Solar System’s perch on a spiral arm provided a beautiful view of part of the Milky Way galaxy, bottom center.
The following is a graphic showing the positions of the planets when the graphic was acquired:
The new mosaic provides a complement to the Solar System portrait – that one from the outside looking in – taken by Voyager 1 in 1990.
These six narrow-angle color images were made from the first ever 'portrait' of the solar system taken by Voyager 1, which was more than 4 billion miles from Earth and about 32 degrees above the ecliptic. The spacecraft acquired a total of 60 frames for a mosaic of the solar system which shows six of the planets. Mercury is too close to the sun to be seen. Mars was not detectable by the Voyager cameras due to scattered sunlight in the optics, and Pluto was not included in the mosaic because of its small size and distance from the sun. These blown-up images, left to right and top to bottom are Venus, Earth, Jupiter, and Saturn, Uranus, Neptune. The background features in the images are artifacts resulting from the magnification. The images were taken through three color filters -- violet, blue and green -- and recombined to produce the color images. Jupiter and Saturn were resolved by the camera but Uranus and Neptune appear larger than they really are because of image smear due to spacecraft motion during the long (15 second) exposure times. Earth appears to be in a band of light because it coincidentally lies right in the center of the scattered light rays resulting from taking the image so close to the sun. Earth was a crescent only 0.12 pixels in size. Venus was 0.11 pixel in diameter. The planetary images were taken with the narrow-angle camera (1500 mm focal length). Credit: NASA/JPL
“Obtaining this portrait was a terrific feat by the MESSENGER team,” says Sean Solomon, MESSENGER principal investigator and a researcher at the Carnegie Institution. “This snapshot of our neighborhood also reminds us that Earth is a member of a planetary family that was formed by common processes four and a half billion years ago. Our spacecraft is soon to orbit the innermost member of the family, one that holds many new answers to how Earth-like planets are assembled and evolve.”
Keplers 1200 Planet candidates by size. Finding exoplanets is getting easier, LUVOIR will helps us find signs of life, if any, on them. Credit: NASA/Wendy Stenzel
[/caption]
With the startling new finding of dozens of Earth-sized extrasolar planets, NASA’s Kepler planet hunting space telescope has just revolutionized our understanding of Earths place in the Universe and the search for Extraterrestrial Life. And the historic science discovery is based on data collected in just the first few months of operation of the powerful telescope as it scans only a tiny portion of the sky.
The discovery of 1235 new extrasolar planet candidates was announced today (Feb.2) by NASA and Kepler scientists at a media briefing. 68 of these planet candidates are Earth-sized. Another 288 are Super-Earth-size, 662 are Neptune-size and 165 are Jupiter-size. Most of these candidates orbit stars like our sun.
Even more significant is that 54 of the planet candidates are located within the ‘habitable zone’ of their host stars and 5 of those are Earth-sized. Before today we knew of exactly ZERO Earth-sized planets within the habitable zone. Now there are 5.
Finding a ‘Pale Blue Dot’ or ‘Second Earth’ inside a habitable zone that harbors water and environmental conditions that can support life is the ‘Holy Grail’ of science.
Are We Alone ?
“We went from zero to 68 Earth-sized planet candidates and zero to 54 candidates in the habitable zone – a region where liquid water could exist on a planet’s surface. Some candidates could even have moons with liquid water,” said William Borucki of NASA’s Ames Research Center, Moffett Field, Calif.. Borucki is the science principal investigator for NASA’s Kepler mission.
“Five of the planetary candidates are both near Earth-size and orbit in the habitable zone of their parent stars.”
Earth-sized water worlds are the most conducive to the formation and evolution of alien life forms. Water is an essential prerequisite for life as we know it.
“Kepler’s blown the lid off everything we know about extrasolar planets,” said Debra Fischer, professor of Astronomy at Yale University, New Haven, Conn
Kepler's over 1200 planet candidates as of Feb. 1, 2011. Credit: NASA/Wendy Stenzel
Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zones around their parent stars. The mission uses the transit method to detect the tell tale signatures of planets. The goal is to determine how common are planets the size of Earth orbiting inside the habitable zone of stars like our sun.
Kepler measures the miniscule decreases in the brightness of stars caused by planets crossing in front of them and blocking the starlight. Imagine calculating the difference in light transmission caused by a flea sitting on a cars headlight.
Follow up observations over a period of several years will be required to confirm these results, the scientists explained. Astronomers expect that over 80% of the candidate planets will be positively confirmed as real planets by utilizing ground based observatories and the Spitzer Space Telescope.
For an Earth-sized planet orbiting a sun-like star inside the habitable zone, transits occur about once per year. Since three transits are required to verify a planets status, it will therefore take about three years to reach a definitive conclusion.
These remarkable new planet discoveries are based on observations from only the first four months of Kepler’s telescopic operations – May 12, 2009 to Sept. 17, 2009. The space based observatory continuously monitors more than 156,000 stars using 42 CCD detectors with a field of view that covers only 1/400 of the sky.
“Kepler is making good progress towards its goals,” said Borucki
“We have found over twelve hundred candidate planets – that’s more than all the people have found so far in history.”
“Imagine if we could look wider. Kepler looks at one 400th of the sky. If we had 400 of these fields of view, we’d see 400 times that number of candidates. We would see 400,000 candidate planets.”
Keplers over 1200 Planet candidates sorted by size
“The fact that we’ve found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting stars like our sun in our galaxy,” Borucki amplified. “Our results indicate there must be millions of planets orbiting the stars that surround our sun.”
“If we find that Earth’s are common in the habitable zones of stars, very likely that means life is common around these stars.”
“Kepler has shown that planetary systems like our own are common,” said Debra Fischer.
Planets in Keplers Field of View.
Before and after the discovery of over 1200 planet candidates by NASA’s Kepler Space Telescope.
“The search for planets is motivated by the search for life,” Fischer added.
“We have allowed the public to participate though the website Planethunters.org,” she added. “And now we have over 16,000 dedicated users. The public is excited to be a part of research and history.”
“Thanks to Kepler for this treasure chest of data!” Fisher concluded.
Kepler is just the first step in finding Earth sized and Earth like planets. “We are building the foundation for future generations of explorers,” said Borucki.
“Future missions will be developed to study the composition of planetary atmospheres to determine if they are compatible with the presence of life. The design for these missions depends on Kepler finding whether Earth-size planets in the habitable zone are common or rare.”
The first planets beyond our solar system were discovered in 1995. Up to today there were just over 500 known extrasolar planets.
Kepler now has 15 confirmed extrasolar planet discoveries and over 1200 possible candidates.
NASA’s Kepler spacecraft was launched on March 6, 2009 from Launch Complex 17-B atop a Delta II rocket at Cape Canaveral Air Force Station in Florida. See spacecraft and launch photos below
Kepler’s science operations are currently funded for three and one half years of operations until November 2012. The mission’s lifetime – and its goal of discovering multitudes of new planets as small as Earth – can be extended if NASA funding is approved by Congress and the President.
William Borucki – Explains Keplers Discovery of Earth Sized Planets
Science principal investigator for NASA’s Kepler mission, NASA’s Ames Research Center
Video Caption: NASA’s Kepler mission has discovered its first Earth-size planet candidates and its first candidates in the habitable zone, a region where liquid water could exist on a planet’s surface. Five of the potential planets are near Earth-size and orbit in the habitable zone of smaller, cooler stars than our sun.
Kepler also found six confirmed planets orbiting a sun-like star, Kepler-11. This is the largest group of transiting planets orbiting a single star yet discovered outside our solar system. Located approximately 2,000 light years from Earth, Kepler-11 is the most tightly packed planetary system yet discovered. All six of its confirmed planets have orbits smaller than Venus, and five of the six have orbits smaller than Mercury’s.
What is an Earth like planet ? Explantion here
David Charbonneau, an exoplanet researcher at Harvard University, explains what scientists mean when they say “earthlike planet” and “super Earth.” This interview was recorded at NASA’s Goddard Space Flight Center on December 10, 2010, by NASA science writer Daniel Pendick.
Kepler Mission Star Field
An image by Carter Roberts of the Eastbay Astronomical Society in Oakland, CA, showing the Milky Way region of the sky where the Kepler spacecraft/photometer will be pointing. Each rectangle indicates the specific region of the sky covered by each CCD element of the Kepler photometer. There are a total of 42 CCD elements in pairs, each pair comprising a square.
Credit: Carter Roberts / Eastbay Astronomical Society.Kepler's target region in the Milky Way. Credit: Jon LombergKepler being prepared in the clean room at Astrotech
prior to launch on March 6, 2009. Credit: nasatech.net
More Kepler photos courtesy of nasatech.net here
Delta 2 rocket streaks to the heavens.
Launch of NASA’s Kepler planet hunting space telescope from Cape Canaveral Air Force Station, FL, Complex 17, on March 6, 2009 at 10:49 p.m. Credit: Ben CooperBen Cooper Featured on Astronomy Picture of the Day (APOD); March 9, 2009
Launch Pad 17 B and a Delta II rocket
from my perch on the 8th floor of Launch Pad 17 A as rocket is encased in launch tower. Credit: Ken KremerView of Launch Complex 17 B and cryogenic storage tanks by Ken Kremer
Artist illustration of Eris and its moons. Image credit: NASA
[/caption]
Here’s part 2 of our conversation with astronomer Mike Brown. Yesterday, he talked about the latest findings on Eris, the Haumea controversy and more; today he talks about being known as the “killer” of Pluto, his reflections on Brian Marsden and his hopes for the New Horizons mission to Pluto.
Universe Today: You seem to actually relish the role of Pluto Killer…
Mike Brown: You know, I didn’t initially. I really wanted to be the thoughtful person who explained to people what was going on and I tried very hard. And the reason I have become a sort of more militantly Pluto-killer-ish over the past couple of years is because — against what I think is reason — there are other astronomers who have been militantly pro-Pluto and saying things that are generally misleading in public. And it pains me to have scientists say things that I know they don’t actually think are true.
To hear an astronomer say that there is no logical reason why you would come up with eight planets, it makes no scientific sense. No one can say that and actually believe it. There are good arguments for one side or the other and I would enjoy it more if they would make the arguments instead of just trying to sort of manipulate public opinion, but I don’t think they do. Mostly the small number of the pro-Pluto crowd tends to be more manipulative. I thought somebody needs to defend the very reasonable idea of eight planets, so I have taken on that role.
UT: The Pluto-is-a-planet people are definitely vociferous.
Mike Brown: And honestly, I think manipulative is the word. They don’t believe what they say, they know what they say is not true and they say it in ways that are deceitful. That is maybe a strong statement to make, but they know what they are saying is not true. That bothers me. You shouldn’t say things that you know is not true just to make a point.
UT: Could you talk a little about Brian Marsden? He played a rather big role in the book, and in how things turned out with your discoveries – and the planet debate. He’ll obviously be missed.
Mike Brown: I have a book sitting at home that I had actually signed that I was going to send to him, and I didn’t get a chance to do it. I’m really sad that he didn’t get to see it. Everybody has their ‘Brian Marsden story’, and some are versions of the same story where he was incredibly supportive of interesting things in the solar system. When we started finding these large objects, there were a lot of people who were less supportive and not really happy about the discoveries. Brian was just happy about everything – if you were discovering new objects or comets, or different observations of asteroids – he just loved it all and he was always the first, you could just hear it in his voice when you talked to him, he was just genuinely excited about these new things that were being discovered.
He can’t be replaced. I like the people at the minor planet center and I like what they are doing, but he was unique. We won’t ever replace that energy and enthusiasm and the absolute love of the solar system that he had.
UT: How much are you looking forward to the New Horizons mission flyby of Pluto – and do you have any inklings of what it might come across in the Kuiper Belt?
Mike Brown. Credit: CalTech
Mike Brown: It going to be really interesting. The funny thing is, the answer to that question three weeks ago was “I can’t wait because all of these objects are sort of the same out there in the Kuiper Belt, and going to the closest one, even if it is not the biggest one will really teach you about everything that is out there.” That statement is no longer true. With Eris and Pluto being so different, we won’t learn as much about Eris as I had initially hoped, but like everyone else, I’ll be waiting anxiously for those first pictures to come back. I can’t wait to see them. Every time we go somewhere we’ve never gone before we learn things – the things we learn are never the things you think you are going to learn. I’m prepared to be astounded.
I am looking forward to, as much if not more perhaps, the later flyby of New Horizons of a small KBO. I think that scientifically understanding the smaller more typical objects is perhaps even more important than understanding the rare, big crazy objects.
Artist concept of the New Horizons spacecraft. Credit: NASA
UT: And are you still actively looking for objects out there?
Brown: Yes, we are looking very hard in the southern hemisphere now. We’ve finished the northern hemisphere, at least the bright objects, so I don’t think there will be too many more big ones discovered.
For the northern hemisphere, we knew that — at least — Clyde Tombaugh had been there first. We weren’t going to find something as bright as Pluto in the northern hemisphere because Clyde would have found it. In the southern hemisphere, it is basically wide open, because there was no Clyde Tombaugh, and we’re not even quite sure what the limit is. There’s not something 6th magnitude out there because someone would have seen it, but I don’t know how bright the brightest thing could be – that doesn’t mean that there’s something that bright there, but every day when we’re looking the possibilities are exciting.
UT: What telescopes are you using?
Brown: We have two that are working right now. One is actually an old data set from a near Earth asteroid survey and we are reprocessing the data in a way to make is sensitive to the types of objects we are looking for. This is the Uppsala ½ meter telescope at Siding Spring in Australia. It is the same telescope and the same data that the Catalina Sky Survey uses for the southern hemisphere.
And then as soon as telescope is finally online, we’ll use the Australian National University Skymapper telescope, which is kind of a Pan-STARRS south type of telescope that can do big surveys of the southern skies for many different purposes, including finding large Kuiper Belt objects.
It is fun to know again that some morning we might wake up and find something big and cool. That is always a fun way to go through life.
"How I Killed Pluto" -- a new book by planet hunter (and killer) Mike Brown.
[/caption]
It’s hard to imagine, but in 1992 astronomer Mike Brown didn’t know what the Kuiper Belt was. He had never heard of it. But just a few years later in 1999, he bet another scientist that within five more years he would find another planet out there at the edge of the solar system, past Pluto. It took a five-day extension of the bet, but Brown did it. And so began the death of Pluto as a planet, but the rise of a whole new class of objects called dwarf planets. Brown has written a book about his adventures as a planet hunter and eventual planet killer, called “How I Killed Pluto and Why it Had it Coming.”
His book is a highly readable, first person account of an astronomer who, by chance, realized he had remarkable penchant for discovering small, far away objects. The book is filled with humor, candor, geeky tendencies (he thought the first sonogram of his daughter looked like images from Venera 2 spacecraft from Venus), engaging personal anecdotes – and even romance, intrigue, mystery, fatherly love, and science.
“Discovery is exciting,” Brown writes in his book, “no matter how big or small or close or distant. But in the end, even better is discovering something that is capable of transforming our entire view of the sun and the solar system.”
And Brown’s discoveries have transformed our view of the solar system (some people have changed the world — how many can claim they have changed the solar system?!)
The discoveries of more objects in the Kuiper Belt turned on the heat of the debate of whether everyone’s favorite misfit planet, Pluto, was actually a planet or just a member of a new, quickly growing class of what are now called dwarf planets.
From this, some will claim, our planetary mnemonic went from “My Very Educated Mother Just Served Us Nine Pizzas” to “Mean Very Evil Men Just Shortened Up Nature.”
Mean and evil or educated? You decide.
Want a chance to win a copy of the book? Universe Today has 5 copies to giveaway!
UPDATE: We have winners! They are:
Gadi Eidelheit
Jason McInerney
Sten Thaning
Pam Jacobson
John Wenskovitch
Congrats!
Just send an email to [email protected] with the subject line of “Killing Pluto” by Monday, December 6 at 12 Noon Pacific Daylight Time. We’ll randomly choose 5 emails and notify the winners.
An artist's impression of a transiting exoplanet. Credit: ESA C Carreau
[/caption]
It was only a little over a year ago that the 400th extrasolar planet was confirmed, but time flies when you’re discovering exoplanets. The 19th of November 2010 marked the date that over 500 exoplanets had been confirmed on The Extrasolar Planets Encyclopedia.
Though it’s an arbitrary number to celebrate, the fact that we’ve confirmed the existence over 500 exoplanets since their initial discovery 20 years ago is deserving of merriment. Discovery of exoplanets has really ramped up over the last few years, thanks in part to the ESA’s COROT satellite, the Hubble and Spitzer space telescopes, the Keck Interferometer, and the improvement of observational techniques to discover and confirm exoplanets. NASA’s Kepler spacecraft has over 700 candidates for exoplanets. Only 7 planets have been confirmed after being discovered by the Kepler spacecraft so far, though.
Jean Schneider, an astrobiologist at the Paris-Meudon Observatory, keeps up a database of the confirmed exoplanetary discoveries at The Extrasolar Planets Encyclopedia. He posted a warning about how muddle the declaration of “the discovery of the 500th exoplanet” could be. He wrote in the warning:
“The number of exoplanets, recored for instance at http://exoplanet.eu is necessarily subject to some uncertainty for several reasons:
– the mass limit below which a substellar object is called a planet
is somewhat arbitrary
– the mass measurement is always affected by some instrumental inaccuracy
– whatever this mass limit is, the true mass for most planets is subject
to some uncertainty, intrinsic to the detection method (unkown
inclination of the orbit, modelisation of planet atmosphere)
– some planet detections, even published in refereed papers, are sometimes
retracted afterwards
For all these reasons
1/ The boundary between “confirmed”/”unconfirmed” planets is somewhat fuzzy
2/ The number of planet candidates at http://exoplanet.eu ;(collected
in the survey of professional litterature, conferences or websites)
is affected by an uncertainty of a few units.”
In essence, to say that there is a “500th exoplanet” is really not possible, given that there needs to be confirmation of the planet. Even after that confirmation, there could be the possible retraction of the planet from the database. 5 confirmations were posted on the 19th, all of them published in refereed papers and discovered in 2010. This kicked the total over 500. But then another was announced the next day, and it was discovered in 2007 but only recently confirmed. So, putting a number on the 500th extrasolar planet to be confirmed is pretty much impossible, arbitrary at best.
Schneider was interviewed by Scientific American on just why he is the keeper of the encyclopedia, and some of his thoughts on the discoveries made so far and the future of the field. The text of the interview is available here.
Complicating matters even further, there is another running tally of extrasolar planets maintained by the NASA’s Jet Propulsion Laboratory at PlanetQuest. Their count on the 22nd of November was only 497, and today rests at 500. The Extrasolar Planets Encyclopedia now stands at 504.
PlanetQuest has this video that succinctly describes the history of extrasolar planet discovery, for those interested:
Even if it’s arbitrary, you can still have that “500th exoplanet” party if you’d like, complete with Kepler satellite-shaped hats. Nobody will likely stop you; if they do, there will likely be another few dozen planets discovered – or a few retracted – by then anyways, making their point rather moot.
On November 6, 2010, the dwarf planet Eris occulted a faint 16 magnitude star and this was the first time astronomers were able to witness an occultation by Eris. Additionally, at 96.6 Astronomical Units away, it was the most distant object for which this kind of occultation — where one astronomical object passes in front of another — had been seen. Why was this dim, distant event important? It has helped refine the size of what is (was?) thought to be the biggest dwarf planet (yes, I know, an oxymoron) we know of.
“Most of the ways we have of measuring the sizes of objects in the outer solar system are fraught with difficulties,” wrote astronomer and discoverer of Eris, Mike Brown, on his website ‘Mike Brown’s Planets.’ “But, precisely timed occultations like these have the potential to provide incredibly precise answers.” Continue reading “Stellar Occultation by Eris”
Eris — that pesky big dwarf planet that caused all the brouhaha about planets, dwarf planets, plutoids and the like — has gotten a closer look by a team of astronomers from several different universities, and guess what? Eris and Pluto have a lot in common. Eris appears to have a frozen surface, predominantly covered in nitrogen ice and methane, just like Pluto.
The scientists integrated two years of work conducted in Northern Arizona University’s new ice research laboratory, in addition to astronomical observations of Eris from the Multiple Mirror Telescope Observatory from Mount Hopkins, Ariz., and of Pluto from Steward Observatory from Kitt Peak, Ariz.
“There are only a handful of such labs doing this kind of work in the world,” said Stephen Tegler, from NAU and lead author of “Methane and Nitrogen Abundances on Eris and Pluto,” which was presented this week at the American Astronomical Society’s Divison of Planetary Science meeting. “By studying surfaces of icy dwarf planets, we hope to get a better understanding of the processes that affect their surfaces.”
NAU’s ice lab grew optically clear ice samples of methane, nitrogen, argon, methane-nitrogen mixtures, and methane-argon mixtures in a vacuum chamber at temperatures as low as minus 390 degrees Fahrenheit to simulate the planets’ cold surfaces. Light passed through the samples revealed the “chemical fingerprints” of molecules and atoms, which were compared to telescopic observations of sunlight reflected from the surfaces of Eris and Pluto.
“By combining the astronomical data and laboratory data, we found about 90 percent of Eris’s icy surface is made up of nitrogen ice and about 10 percent is made up of methane ice, which is not all that different from Pluto,” said David Cornelison, coauthor and physicist at Missouri State University.
The scientists say the recent findings will directly enhance NASA’s New Horizons spacecraft mission, currently scheduled to fly by Pluto in 2015, by lending greater value to the continued research of Eris and Pluto.
The Sun, Earth and Jupiter orbit a common barycentre. credit – D. Champion, MPIfR
[/caption]
Finding the mass of other planets is tricky, and usually is done by measuring the orbits of their moons or of spacecraft flying past them. But an international group of astronomers have found a new way to weigh planets, and they have now weighed entire planetary systems using radio signals from pulsars. “This is first time anyone has weighed entire planetary systems — planets with their moons and rings,” said team leader Dr. David Champion of the Max-Planck-Institut fuer Radioastronomie in Bonn, Germany. “And we’ve provided an independent check on previous results, which is great for planetary science.”
Champion says measuring the masses of planets in this new way could feed into data needed for future space missions. Because mass creates gravity, and a planet’s gravitational pull determines the orbit of anything that goes around it — both the size of the orbit and how long it takes to complete – it will help more accurate navigation for future missions.
The new method is based on corrections astronomers make to signals from pulsars, small spinning stars that deliver regular ‘blips’ of radio waves.
The Earth is traveling around the Sun, and this movement affects exactly when pulsar signals arrive here. To remove this effect, astronomers calculate when the pulses would have arrived at the Solar System’s center of mass, or barycenter, around which all the planets orbit. Because the arrangement of the planets around the Sun changes all the time, the barycenter moves around too. To work out its position, astronomers use both a table (called an ephemeris) of where all the planets are at a given time, and the values for their masses that have already been measured. If these figures are slightly wrong, and the position of the barycenter is slightly wrong, then a regular, repeating pattern of timing errors appears in the pulsar data.
“For instance, if the mass of Jupiter and its moons is wrong, we see a pattern of timing errors that repeats over 12 years, the time Jupiter takes to orbit the Sun,” said Dr. Dick Manchester of CSIRO Astronomy and Space Science. But if the mass of Jupiter and its moons is corrected, the timing errors disappear. This is the feedback process that the astronomers have used to determine the planets’ masses.
Data from a set of four pulsars have been used to weigh Mercury, Venus, Mars, Jupiter and Saturn with their moons and rings. Most of these data were recorded with CSIRO’s Parkes radio telescope in eastern Australia, with some contributed by the Arecibo telescope in Puerto Rico and the Effelsberg telescope in Germany. The masses were consistent with those measured by spacecraft. The mass of the Jovian system, .0009547921(2) times the mass of the Sun, is significantly more accurate than the mass determined from the Pioneer and Voyager spacecraft, and consistent with, but less accurate than, the value from the Galileo spacecraft.
The new measurement technique is sensitive to a mass difference of two hundred thousand million million tons — just 0.003% of the mass of the Earth, and one ten-millionth of Jupiter’s mass.
“In the short term, spacecraft will continue to make the most accurate measurements for individual planets, but the pulsar technique will be the best for planets not being visited by spacecraft, and for measuring the combined masses of planets and their moons,” said CSIRO’s Dr. George Hobbs, another member of the research team.
Repeating the measurements would improve the values even more. If astronomers observed a set of 20 pulsars over seven years they’d weigh Jupiter more accurately than spacecraft have. Doing the same for
Saturn would take 13 years.
“Astronomers need this accurate timing because they’re using pulsars to hunt for gravitational waves predicted by Einstein’s general theory of relativity”, said Professor Michael Kramer, head of the ‘Fundamental Physics in Radio Astronomy’ research group at the Max-Planck-Institut fuer Radioastronomie. “Finding these waves depends on spotting minute changes in the timing of pulsar signals, and so all other sources of timing error must be accounted for, including the traces of Solar System planets.”
Astronomers from Australia, Germany, the UK, Canada and the USA are involved in this project.
Next time you hear someone complaining that it’s too hot outside, you can make them feel better by pointing out that at least their planet isn’t so hot it is vaporizing into space. Unless of course you happen to be speaking to someone from the gaseous extrasolar planet HD 209458b.
New observations from the Hubble Cosmic Origins Spectrograph (COS) confirm suspicions from 2003 that the planet HD 209458b is behaving like a Jupiter-sized comet, losing its atmosphere in a huge plume due to the powerful solar wind of its too-close star.
HD 209458b is a “hot Jupiter”: a gas giant that orbits extremely close to its star. It whips around its star in 3.5 days, making even speedy little Mercury with its 88 day orbit around the sun look like a slacker.
Astronomers have managed to learn a lot about HD 209458b because it is a transiting planet. That means that its orbit is aligned just right, so from our point of view it blocks some of the light from its star. When that happens, it gives hints at the planet’s size, and gives a much better constraint on the mass. HD 209458b is a little more than two thirds the mass of Jupiter, but heat from its star has puffed it up to two and a half times Jupiter’s diameter.
In the case of HD 209458b, during transits some of the star’s light passes through the planet’s escaping, 2,000-degree-Fahrenheit atmosphere, allowing scientists to tell what it is made of and how fast it is being lost to space.
“We found gas escaping at high velocities, with a large amount of this gas flowing toward us at 22,000 miles per hour,” said astronomer Jeffrey Linsky of the University of Colorado in Boulder, leader of the COS study. “This large gas flow is likely gas swept up by the stellar wind to form the comet-like tail trailing the planet.”
The escaping planetary gases absorbed starlight at wavelengths characteristic of heavier elements like carbon and silicon, suggesting that the star’s intense heat is driving circulation deep in HD 209458b’s atmosphere, dredging up material that would otherwise remain far beneath lighter elements like hydrogen.
Even though its atmosphere is constantly streaming away into space, HD 209458b won’t be disappearing anytime soon. At the measured rate of loss, the planet would last about a trillion years, far longer than the lifetime of its host star.
So, be thankful that even on hot summer days, your planet is in no danger of being vaporized by its star. And if you do happen to be speaking to someone from HD 209458b, you can reassure them that their planet will still be there when they return home. Well, most of it, anyway.
Where will you be when the lights go out? Earth Hour 2010 will take place on Saturday, March 27 at 8:30 pm local time. Even though it will spark a tirade of controversy just asking folks to turn off their lights for one hour, let’s see who would rather fight than turn off a switch. In 2009 hundreds of millions of people around the world showed their support and Earth Hour 2010 will continue to be a global call to action to every individual, every business and every community. A call to stand up, to show leadership and be responsible for our future. Do you have what it takes to make such a simple gesture?
Then let’s rock the house…
Earth Hour started in 2007 in Sydney, Australia when 2.2 million homes and businesses turned their lights off for one hour to make their stand against climate change. A year later Earth Hour had become such a global force that more than 50 million people in 35 countries showed their support by switch off for a simple 60 minutes. Icons stood in dark silence as Sydney Harbour Bridge, The CN Tower in Toronto, The Golden Gate Bridge in San Francisco, and Rome’s Colosseum, all did their part as symbols of hope for the future.
Can you still use your imagination? Can you? Then imagine Earth Hour from space…
This year China’s Forbidden City heads up a list of some of the world’s most iconic landmarks that have confirmed their participation in Earth Hour – including The Great Pyramids of Giza and the Sphinx. They will be joined by Italy’s Trevi Fountain in Rome and Leaning Tower of Pisa, Big Ben and Houses of Parliament in London, Edinburgh Castle in Scotland, India Gate and Red Fort in Delhi, Victoria Falls in Zimbabwe, Bosphorous Bridge in Istanbul, Hohensalzburg Castle in Salzburg, and Independence Angel in Mexico City. They join a comprehensive list of the world’s great man-made marvels and natural wonders, including the Eiffel Tower, Brandenburg Gate, Hiroshima Peace Memorial, Empire State Building, London Eye, Table Mountain, Christ the Redeemer statue, Sydney Opera House and the world’s tallest building, Burj Khalifa, which will plunge into darkness for Earth Hour
Before you say “Why bother?” or “My contribution won’t make a difference.”, then think on this… Earth Hour has truly managed to raise our awareness of climate change issues. But there’s more to it than switching off your lights for one hour once a year. It’s all about giving people a voice on the future of our planet and working together. Even if you’d rather fight than flick the switch… you are participating. Whether you are an individual, a business, a school or a city, you can show your support for Earth Hour by turning off your lights at 8.30 pm on March 27 wherever you are on the planet. No one is saying you can’t use your computer or watch television. Bake a pizza and eat it by candlelight with your family! All it takes is the guts to show you understand and care enough to take action.
