Space and astronomy news
Adam Steiner took this picture of Venus transit on the 8/6/04 from Melbourne, Victoria, Australia.
Do you have photos you’d like to share? Post them to the Universe Today astrophotography forum or email them to me directly, and I might feature one in Universe Today.
X-ray full-field view of the globular star cluster 47 Tucanae. Image credit: NASA/CXC/Northwestern U./C.Heinke et al. Click to enlarge
New Chandra observations give the best information yet on why such neutron stars, called millisecond pulsars, are rotating so fast. The key, as in real estate, is location, location, location – in this case the crowded confines of the globular star cluster 47 Tucanae, where stars are less than a tenth of a light year apart. Almost two dozen millisecond pulsars are located there. This large sample is a bonanza for astronomers seeking to test theories for the origin of millisecond pulsars, and increases the chances that they will find a critical transitional object such 47 Tuc W.
47 Tuc W stands out from the crowd because it produces more high-energy X-rays than the others. This anomaly points to a different origin of the X-rays, namely a shock wave due to a collision between matter flowing from a companion star and particles racing away from the pulsar at near the speed of light. Regular variations in the optical and X-ray light corresponding to the orbital period of the stars support this interpretation.
A team of astronomers from the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA pointed out that the X-ray signature and variability of the light from 47 Tuc W are nearly identical to those observed from an X-ray binary source known as J1808. They suggest that these similarities between a known millisecond pulsar and a known X-ray binary provide the long-sought link between these types of objects.
In theory, the first step toward producing a millisecond pulsar is the formation of a neutron star when a massive star goes supernova. If the neutron star is in a globular cluster, it will perform an erratic dance around the center of the cluster, picking up a companion star which it may later swap for another.
As on a crowded dance floor, the congestion in a globular cluster can cause the neutron star to move closer to its companion, or to swap partners to form an even tighter pair. When the pairing becomes close enough, the neutron star begins to pull matter away from its partner. As matter falls onto the neutron star, it gives off X-rays. An X-ray binary system has been formed, and the neutron star has made the crucial second step toward becoming a millisecond pulsar.
The matter falling onto the neutron star slowly spins it up, in the same way that a child’s carousel can be spun up by pushing it every time it comes around. After 10 to 100 million years of pushing, the neutron star is rotating once every few milliseconds. Finally, due to the rapid rotation of the neutron star, or the evolution of the companion, the infall of matter stops, the X-ray emission declines, and the neutron star emerges as a radio-emitting millisecond pulsar.
It is likely that the companion star in 47 Tuc W – a normal star with a mass greater than about an eighth that of the Sun – is a new partner, rather than the companion that spun up the pulsar. The new partner, acquired fairly recently in an exchange that ejected the previous companion, is trying to dump on the already spun-up pulsar, creating the observed shock wave. In contrast, the X-ray binary J1808 is not in a globular cluster, and is very likely making do with its original companion, which has been depleted to a brown dwarf size with a mass less than 5% that of the Sun.
Most astronomers accept the binary spin-up scenario for creating millisecond pulsars because they have observed neutron stars speeding up in X-ray binary systems, and almost all radio millisecond pulsars are observed to be in binary systems. Until now, definitive proof has been lacking, because very little is known about transitional objects between the second and final steps.
That is why 47 Tuc W is hot. It links a millisecond pulsar with many of the properties of an X-ray binary, to J1808, an X-ray binary that behaves in many ways like a millisecond pulsar, thus providing a strong chain of evidence to support the theory.
Original Source: Chandra X-ray Observatory</a
Artist?s conception of the gamma ray flare expanding from SGR 1806-20. Image credit: NASA.Click to enlarge
A gigantic explosion on a neutron star halfway across the Milky Way galaxy, the largest such explosion ever recorded in the universe, should allow astronomers for the first time to probe the interiors of these mysterious stellar objects.
An international team of astrophysicists, combing through data from a NASA X-ray satellite, the Rossi X-ray Timing Explorer, reports in the July 20th issue of Astrophysical Journal Letters that the explosion produced vibrations within the star, like a ringing bell, that generated rapid fluctuations in the X-ray radiation it emitted into space. These X-ray pulses, emitted during each seven second rotation by the fast-spinning star, contained the frequency vibrations of the neutron star?s massive quakes.
Much as geologists probe the Earth?s interior from seismic waves produced by earthquakes and solar astronomers study the sun using shock waves traveling through the sun, the X-ray fluctuations discovered from this explosion should provide critical information about the internal structure of neutron stars.
?This explosion was akin to hitting the neutron star with a gigantic hammer, causing it to ring like a bell,? said Richard Rothschild, an astrophysicist at the University of California?s Center for Astrophysics and Space Sciences and one of the authors of the journal report. ?Now the question is, What does the frequency of the neutron star?s oscillations?the tone produced by the ringing bell?mean?
?Does it mean neutron stars are just a bunch of neutrons packed together? Or do neutron stars have exotic particles, like quarks, at their centers as many scientists believe? And how does the crust of a neutron star float on top of its superfluid core? This is a rare opportunity for astrophysicists to study the interior of a neutron star, because we finally have some data theoreticians can chew on. Hopefully, they?ll be able to tell us what this all means.?
The biggest star quakes ripped through the neutron star at an incredible speed, vibrating the star at 94.5 cycles per second. ?This is near the frequency of the 22nd key of a piano, F sharp,? said Tomaso Belloni, an Italian member of the team who measured the signals.
The international team?led by GianLuca Israel, Luigi Stella and Belloni of Italy?s National Institute of Astrophysics?discovered the oscillations from data it retrieved two days after Christmas by the Rossi X-Ray Timing Explorer, a satellite designed to study the fluctuating X-ray emissions from stellar sources. The peculiar oscillations the researchers found began three minutes after a titanic explosion on a neutron star that, for only a tenth of a second, released more energy than the sun emits in 150,000 years. The oscillations then gradually receded after about 10 minutes.
Neutron stars are the dense, rapidly spinning cores of matter that result from the crushing collapse of a star that has depleted all of its nuclear fuel and exploded in a cataclysmic event known as a supernova. The collapse is so crushing that electrons are forced into the atomic nucleus and combine with protons to become neutrons. The resulting sphere of neutrons is so dense?packing the mass of the sun in a sphere only 10 miles in diameter?that a spoonful of its matter would weigh billions of tons on Earth.
Most of the millions of neutron stars in our Milky Way galaxy produce magnetic fields that are a trillion times stronger than those of the Earth. But astrophysicists have discovered less than a dozen ultra-high magnetic neutron stars, called ?magnetars,? with magnetic fields a thousand times greater?strong enough to strip information from a credit card at a distance halfway to the moon.
These intense magnetic fields are strong enough they sometimes buckle the crust of neutron stars, causing ?star quakes? that result in the release of gamma rays, a more energetic form of radiation than X-rays. Four of these magnetars are known to do just that and are termed ?soft gamma repeaters,? or SGRS, by astrophysicists because they flare up randomly and release a series of brief bursts of gamma rays.
SGR 1806-20, the formal designation of the neutron star that exploded and sent X-rays flooding through the galaxy on December 27, 2004?producing a flash brighter than anything ever detected beyond the solar system?is one of them. The flash was so bright that it blinded all X-ray satellites in space for an instant and lit up the Earth?s upper atmosphere.
Astrophysicists suspect the burst of gamma-ray and X-ray radiation from this unusually large explosion could have come from a highly twisted magnetic field surrounding the neutron star that suddenly snapped, creating a titanic quake on the neutron star.
?The scenario was probably analogous to a twisted rubber band that finally broke and in the process released a tremendous amount of energy,? said Rothschild. ?With this energy release, the magnetic field surrounding the magnetar was presumably able to relax to a more stable configuration.?
The December 27 flash of energy was detected by several other NASA and European satellites and recorded by radio telescopes around the world. It already has been the subject of numerous scientific papers published in recent months.
?The sudden and surprising occurrence of this giant flare, which will help us learn more about the nature of magnetars and the internal make-up of neutron stars,? said Rothschild, ?underlines the importance of having satellites and telescopes with the capacity to record unusual and unpredictable phenomena in the universe.?
Other members of the international team were Pier Giorgio Casella, Simone Dall?Osso and Massimo Persic of Italy?s National Institute of Astrophysics; Yoel Rephaeli of UCSD and the University of Tel Aviv; Duane Gruber, formerly of UCSD and now at the Eureka Scientific Corporation in Oakland, Calif; and Nanda Rea of the National Institute for Space Research in the Netherlands.
Original Source: UCSD News Release
Here’s a link to the biggest stars in the Universe.
Artist’s conception of the 25-million-year-old protoplanetary disk. Credit: David A, Aguilar (CfA) Click to enlarge
Every rule has an exception. One rule in astronomy, supported by considerable evidence, states that dust disks around newborn stars disappear in a few million years. Most likely, they vanish because the material has collected into full-sized planets. Astronomers have discovered the first exception to this rule – a 25-million-year-old dust disk that shows no evidence of planet formation.
“Finding this disk is as unexpected as locating a 200-year-old person,” said astronomer Lee Hartmann of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author on the paper announcing the find.
The discovery raises the puzzling question of why this disk has not formed planets despite its advanced age. Most protoplanetary disks last only a few million years, while the oldest previously known disks have ages of about 10 million years.
“We don’t know why this disk has lasted so long, because we don’t know what makes the planetary formation process start,” said co-author Nuria Calvet of CfA.
The disk in question orbits a pair of red dwarf stars in the Stephenson 34 system, located approximately 350 light-years away in the constellation Taurus. Data from NASA’s Spitzer Space Telescope shows that its inner edge is located about 65 million miles from the binary stars. The disk extends to a distance of at least 650 million miles. Additional material may orbit farther out where temperatures are too low for Spitzer to detect it.
Astronomers estimate the newfound disk to be about 25 million years old. They calculated the age by modeling the central stars within the system, since stars and disk share the same age. The appearance of the disk itself also supports an advanced age.
“The disk looks a lot different than most other disks we’ve seen. This disk looks a lot more evolved than those around younger stars,” said Hartmann.
Hartmann and Calvet hold opposite opinions about the eventual fate of the disk around Stephenson 34.
“Most stars, by the age of 10 million years, have done whatever they’re going to do,” said Hartmann. “If it hasn’t made planets by now, it probably never will.”
Calvet disagreed. “This disk still has a lot of gas in it, so it may still form giant planets.”
Both astronomers emphasize that such debates are a natural part of the scientific process.
“Some people expect scientists to have all the answers. But research is all about exploring the edge of what is known,” said Hartmann. “That’s what makes it so exciting!”
In the future, Hartmann and Calvet plan to search for more old disks in order to learn why some disks survive so much longer than most others.
“It’s important to find more objects like this because they give us clues about the conditions that influence the formation of planets,” said Calvet.
This research will be published in The Astrophysical Journal Letters.
Original Source: CfA News Release
Could layers of ice on Europa hide a history of past life? Image credit: NASA/JPL. Click to enlarge.
Was there once life on Mars? Is there life in the Europan ocean? These are two questions which are deeply fascinating to people throughout the world, yet no one has a realistic proposal for answering them within the next twenty years ? until now.
George Maise heads a team which was recently received a NIAC Phase 1 award*, to develop an idea into just such a plan.
“In-depth exploration of the Martian polar caps,” says Maise et al.**, echoing a view common among planetary scientists, would give a wonderful opportunity to find “evidence of past Martian biological activity, including microfossils, bacteria, and biochemical residues.”
“Using a practical, compact, lightweight, powerful thermal source, small robotic devices could melt their way through the ice cap, gathering data like that described above, and transmitting it in real time back to Earth. Scientists monitoring the results on Earth could then control the path of the robotic units directing them to explore particularly promising regions inside the ice sheet.”
And what would work for the Martian polar ice caps would also work for Europa, Ganymede, and Callisto, all of which may have primeval oceans under thick crusts of ice; oceans in which may swim alien fish whose ultimate source of energy is prokaryote-like cellular lifeforms with a curious resemblance to some Archaea found here on Earth.
A mission to search for signs of ancient life in the Martian ice cap would involve landing a spacecraft on that ice cap, and deploying several MICE (Martian Ice Cap Explorers), which are nuclear powered ice-melters plus an instrument package designed to look for signs of ancient life. The MICE would then melt their way through the ice cap, with water freezing behind them, in a search pattern that could extend for many kilometers, both horizontally and vertically. Each probe would communicate with its nearest neighbours (and the mothership) via high-powered radios, which could easily penetrate up to a km of ice. The network protocol would allow for good datarates and resilience, and permit near real time command and control from scientists back on Earth.
The secret ingredient? Water! Melted ice would be used to make hot water and hydrogen; the hot water would be used as directional jets to melt the ice and then be circulated back through the water-filled cavity in the ice, moving the probe in the direction of the jet. The water would also be the shield for the instruments, attenuating the radiation from the reactor by a factor of a million, a billion, or more, whatever is needed. The hydrogen, produced by electrolysis, would give the probe the required buoyancy. Finally, water would be the primary coolant for the nuclear reactor and steam the working fluid for the generator.
All wrapped up in a reactor, power plant, water jet package of 100 kg or less!
The beauty of Maise et al.’s concept is that it uses robust, proven technology; the reactors would use highly reliable zirconium-uranium oxide ceramic fuel rods, and an autonomous control system based on stable industrial designs. In size the entire reactor/power/hot water section of a MICE unit would be no more than 50 cm in diameter and 1.2m in length. “The start and stop of the reactor would be performed with control rods as directed by the autonomous control system. This is no different than any other nuclear reactor.” Each unit would also have redundant, autonomous fail-safes; in the event of something catastrophic, the reactor would shut itself down fast enough to prevent damage.
But what about looking for signs of ancient life? Modular design is the key to Maise et al.’s approach; the instrument package – attached to the reactor/power/hot water unit by a rigid, 2m-long tube – would comprise several different instruments, hot water jets, and the radio communications unit. Modularity allows a wide range of possible instruments to be considered, with the final selection being made close to launch. As melt-water is circulated through the instrument package, sample collection is very straight-forward. Just as on Earth, eyes will likely give the best indications of ancient Martian life, so the premier instrument is a microscope. Complementing that is the ‘lab-on-a-chip’ analyzer, capable of detecting a wide range of ‘biosignatures’, including the presence of nucleic acids. Perhaps most exciting, because it may reveal contemporary life on Mars, similar to the proteobacteria and actinomycetes found in 1999 under 3.6 km of Antarctic ice, is a ‘growth chamber-based life detection instrument’, an “extremely sensitive life detection [instrument] with minimal assumptions.”
In addition, instruments designed to study glaciology, paleoclimates, geology, and geophysics could be built, and added to each MICE probe, or to only selected probes.
How many MICE? A Martian polar ice cap mission could have from one to dozens of MICE; the primary limitation is the total mass and size of the spacecraft. With today’s rockets, a mission with twelve MICE should be possible; with planned rockets, such as those based on MITEE (MIniature reacTor EnginE) technology, the upper limit would likely be about 60.
What about Europa? The biggest difference between a Europan and Mars polar ice cap mission would be adapting the MICE to swim, once they penetrated the 10 km or so of ice that caps the Europan ocean. Oh, and perhaps a much greater chance of finding life today than merely traces of yesterday’s life.
The bottom line: MICE find life on Mars (dateline 31 June, 2015)!
*Multi-MICE: A Network of Interactive Nuclear Cryoprobes to Explore Ice Sheets on Mars and Europa: http://www.niac.usra.edu/files/studies/abstracts/1059Maise.pdf
**J. Powell, J. Powell, G. Maise and J. Paniagua, Plus Ultra Technologies, Shoreham, NY, AIAA-2004-6049. Space 2004 Conference and Exhibit, San Diego, California, Sep. 28-30, 2004
Spirit’s view of Mars. Image credit: NASA/JPL. Click to enlarge.
Unless something goes terribly wrong with human civilization, our descendants in the near and distant future will explore and colonize our solar system. As we venture further into our celestial neighborhood, the number of worlds that are decidedly alien and hostile to human astronauts only increases.
As the distances increase, communications between controllers on Earth and any place much past the Moon can take minutes to hours for a two-way relay. For a robot probe, this time-lag, plus an unfamiliar and dangerous place, means that the exploring machine must rely on sophisticated, independent programming to keep itself safe and conduct complex and serious science.
A group of scientists in Spain has been working for that day with the development of a computer system designed to assist future astronauts on Mars looking for signs of life in the rocks of the Red Planet.
Patrick McGuire and Jens Ormo of the Center for Astrobiology in Madrid and Enrique Diaz-Martinez of the Geological and Mineral Institute have developed a wearable computer and video camcorder system that they are using to test and train a computer-vision system which will enhance astronauts as they explore alien worlds.
In 2004 and 2005, the team conducted field tests with the system in Rivas Vaciamadrid and northern Guadalajara. They examined certain rocks that resembled locations explored by NASA’s Mars Exploration Rover Opportunity in Meridiani Planum.
Approaching a rock face, the investigator uses the device to examine the surface for anything unusual, which appears to the computer system as a larger amount of pixels than normal. The computer takes in the data and makes a judgment about whether these spots are organic or not.
In the second survey, the conclusions of the Cyborg Astrobiologist matched those of human geologists 68 percent of the time in northern Guadalajara, a definite technological improvement over the first survey. The computer’s ability was quite useful in helping the geologist sort out what was termed “false positives” in the rocks.
If the artificial intelligence part of what is called the Cyborg Astrobiologist can be enhanced ? as it must ? to eventually determine on its own what is and is not living matter on some extraterrestrial globe, will the human element of the astronaut be required? Transporting humans across deep space is expensive and requires far more support than any machine. Plus the potential for loss of life in distant and dangerous realms of our solar system make a smart robot look all the more appealing.
At present, humans brains can still out-perform the most sophisticated computers on Earth. However, by the time humans are scheduled to be sent to Mars, perhaps in the 2030s, will the AI and other space robot technology have reached a point where they could do just as well as any human, and with far less need for excess supplies and a higher ability to survive any dangers?
Having actual people aboard spacecraft journeying to other worlds has an appeal and a romance that no current or near-future machine can muster, especially when it comes to catching the attention and the support of the general public. I grew up with the manned Apollo missions to the Moon, so I certainly understand this. But I also recall how quickly the interest faded once astronauts did walk on the Moon and returned safely to Earth. Just view the 1995 film Apollo 13 to see what I mean.
Apollo lunar missions happened in a matter of days. How long will the public majority care about a crewed mission to Mars lasting several years at the least? And imagine how long it will last when other manned missions follow to the Red Planet. I for one would be excited, as would others, but the public wants Star Wars and Star Trek, which is just not the reality of space exploration.
While I certainly applaud what is being done by the Spanish team and think it goes a long way to helping us search for life on Mars and other worlds, I also think that how this technology can best be used and where the state of space exploration will be in the coming decades needs to be seriously considered. Perhaps the public and the governments footing the bill will be more enthralled by having humans at the forefront of the exploring and “seeking new life”, but will they be the best way to conduct real astrobiological science? Already the current Cyborg Astrobiologist is showing real progress in detecting life from non-life. Just imagine what can be done and by what in thirty years or so, when the first manned Mars missions are supposed to take place.
If going back to the Moon and on to Mars is more about politics than science as much of Apollo really was, then it should be stated as such, rather than let it drain away from real science missions that may be better served and cheaper with automation.
I have no doubt that humans will colonize the solar system and beyond one day. But for now to make that happen, we need to seriously explore and understand our celestial neighborhood. If robots with advanced AI are the more sensible and less costly choice, then this is how we must proceed. Otherwise our overfocus on getting humans “out there” may end up either delaying the process or stopping it altogether.
Written by Larry Klaes
Saturn’s moon Tethys glides past in its orbit. Image credit: NASA/JPL/SSI Click to enlarge
The majesty of Saturn overwhelms in this image from Cassini. Saturn’s moon Tethys glides past in its orbit, and the icy rings mask the frigid northern latitudes with their shadows. Tethys is 1,071 kilometers (665 miles) across.
The image was taken in visible green light with the Cassini spacecraft wide-angle camera on June 10, 2005, at a distance of approximately 1.4 million kilometers (900,000 miles) from Saturn. The image scale is 80 kilometers (50 miles) per pixel.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.
For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .
Original Source: NASA/JPL/SSI News Release
The Space Shuttle sits on the Mobile Launcher Platform. Image credit: NASA/KSC. Click to enlarge
Space Shuttle managers now say the launch of NASA’s Space Shuttle Return to Flight mission, STS-114, will take place no earlier than late next week. At 1 p.m. EDT today, managers officially stopped the current launch countdown for Space Shuttle Discovery at Kennedy Space Center, Fla. Space Shuttle managers are optimistic that Discovery can lift off by July 31, the end of this launch window.
This weekend, managers and engineers will continue troubleshooting the problem with a liquid hydrogen low-level fuel sensor inside the External Tank. The sensor failed a routine prelaunch check during the launch countdown Wednesday, causing mission managers to postpone Discovery’s first launch attempt. A dozen teams, with hundreds of engineers across the country, are working on the issue.
Once the problem is resolved and the countdown can be restarted, it will take about four days to launch. A countdown from this point will be a complete start over at T-43 (time minus 43) hours. Currently, there are no plans to roll Discovery back from the launch pad.
For now, Commander Eileen Collins and her six Discovery crew mates will stay at Kennedy Space Center while engineers work on the solution.
For the latest information about the STS-114 mission, visit:
http://www.nasa.gov/returntoflight
Original Source: NASA News Release
Artist illustration of Canada’s Most Telescope. Image credit: MOST. Click to enlarge.
Canada’s first space telescope, MOST, looks for minute variations in the brightness of nearby stars. As Jaymie Matthews, of the University of British Columbia, explains in this talk given at a recent symposium on extrasolar planets, MOST can provide scientists with a unique perspective on how distant worlds interact with their host stars.
I’d like to describe a powerful new small instrument in space called MOST, which stands for Microvariability and Oscillations of Stars (and because it’s Canadian, it stands for Microvariabilit? et Oscillations Stellaire as well). MOST is Canada’s first space telescope. It is literally a suitcase in space: 60 by 60 by 30 centimeters (24 by 24 by 12 inches), 54 kilos, about 124 pounds. I weigh more than the MOST satellite; I think I’m the only mission scientists that out-masses his space satellite. And you can check it on the plane; they can lose it for you.
MOST was actually designed to do seismology of stars, to probe the interiors and histories of stars. That’s relevant to the exoplanets search, because the more we know about parent stars, the more we know about their planetary systems. But we realized, once MOST was underway, that we could actually do some additional exciting things in the exoplanet field. One of the things that MOST can do that nobody else can do at the moment is to stare at stars for up to 2 months at a time, putting stars on a stakeout, to detect variations in the brightnesses of stars or the brightnesses of the planets orbiting those stars, down to a level of 1 part per million, 1 ten-thousandth of a percent.
Just to emphasize to you how small that is, if you were to go to New York City and look at the Empire State Building at night, all the lights were on, all the office window blinds were open and you wanted to make the Empire State Building darker by 1 part per million, you would lower one shade by 3 centimeters, by a little more than an inch. That’s the level of signal that we are looking for in stars. And there is no other instrument on Earth or in space right now that’s capable of doing this. And I should point out that this whole mission has an end-to-end budget of $10 million Canadian, or $7 million US. So we’re the Wal-Mart of space telescopes.
MOST has a unique vantage point in space. It has a very different orbit from the Hubble Space Telescope, or from Spitzer, a pole-to-pole orbit. We communicate with it with our own little custom ground-station network in Toronto, Vancouver and Vienna, and we got into that orbit on the top of a former Soviet Intercontinental Ballistic Missile. A honest-to-goodness weapon of mass destruction. So not only did we put up a scientific instrument, but we destroyed a weapon of mass destruction in the bargain. MOST launched from northern Russia on June 30, 2003, so we’re approaching our second anniversary in space.
Being able to give a star that kind of intense long-term coverage is really important for astronomers to understand what’s going on in systems that have exoplanets. To give an analogy, we’re trying to read the messages that stars and exoplanets are telling us, but from the ground, we only get part of that message. If you have a network of telescopes on the ground, spread in a longitude, you can start to fill in some of the gaps, you can start to recognize some things that look like words. If you have some theories and expectations ahead of time, you might be able to infer a bit of the story, but you could very well get the completely wrong story if you’ve made the wrong assumptions. Having this kind of continuous coverage of a star allows us to really see what stars are doing, and in the case of exoplanets systems, what the exoplanets around them are doing.
MOST is primarily intended to study very tiny variations in stars’ output light. We’re trying to put our own Sun in context by looking at other sunlike stars, looking at some of the senior citizens our galactic city, trying to put some limits on the age of the universe. But the point that’s most important for us today is the fact that MOST also does exoplanet science. What we are looking for is reflected light, the same kind of wavelengths that you see with your eye, from close-in giant planets that have become known as hot Jupiters.
We’re not an exoplanets hunter. We’re too small a telescope to have a statistical chance of finding new planets. We would have to be very lucky. But we are an exoplanet explorer. We take advantage of the work of Drs. Mayor and Brown, and Geoff Marcy, and other groups, who find the planets with their Doppler surveys, and then we can go in and take a closer look. We’ve examined 3 known exoplanet systems already, Tau Bootis, HD 209458 – the telephone-book numbers that astronomers love for stars – and 51 Pegasi, the very first exoplanet around a normal star, which Dr. Mayor and his colleague, Didier Queloz, discovered 10 years ago.
When we looked at Tau Bootis, in a trial run last year, for 11 days, continuously, we saw a signal that very closely matched the planet’s orbital period. But it was far too large to be associated with the planet. It’s about .25 percent, and this is almost certainly originating in the star itself. Tau Bootis, the star, is far more active and variable than we imagined. And we’ve now been able to combine the Doppler data with the data from MOST and the light cures line up, beautifully. The star’s brightness is varying with exactly the same period as the planet orbiting around it.
We’re accustomed to bodies tidally locking each other through their gravitational influence if they’re close enough. The Earth has locked the Moon into a rotation period related to its orbit, so the Moon always keeps the same face to us. We’re convinced that these exoplanets close to their parent stars are tidally locked, so that they always keep one face to the star. But it’s almost counter-intuitive, like the tail wagging the dog, that a planet should be able to tidally lock the star. Now, in this case, it’s probably not locking the entire star, but rather its outer envelope, but there may be a kind of a spot complex, like a super-sunspot, on the surface of Tau Bootis, which has been somehow triggered by the influence of the planet, Tau Bootis b, and tracks it in its orbit. This was suspected by some of the ground-based data, but MOST has been able to confirm that these things are in perfect lockstep.
The good news is that we’re learning a lot about the star that we didn’t know before, and maybe about the interactions between the planet and the star. Possibly their magnetic fields are interacting. Usually rapidly rotating stars are young, but we don’t really know anything about the age of Tau Bootis other than information based on its rotation rate and its activity. It’s hard for us to tell: Is it genuinely young, or maybe it’s an older star, and when the planet migrated in the star was spun up and rejuvenated, kind of going through a second childhood. The bad news is that this stellar activity is going to make it hard to see reflected light from the planet, although we’re not going to give up on that, and we’re going to continue to observe Tau Bootis.
Original Source: NASA Astrobiology
Omicron Cygni. Image credit: Simone Bolzoni. Click to enlarge.
Monday, July 18 – Twenty five years ago today, India launched its first satellite. Tonight about 45 minutes after sunset, watch as Venus and Regulus begin their dance over the week. Tonight the pair will appear about half a fist apart, with Regulus to the south (left) and slightly east (above) sparkling Venus. While magnitude 1 Regulus is the brightest star in Leo, you may initially need binoculars to pick it out of the bright twilight. Be sure to monitor the pair each night as they make their closest appearance on Friday.
While the Moon will dominate tonight’s sky, we can still take a very unusual and beautiful journey to a bright and very colorful pair of stars known as Omicron 1 Cygni. Easily located about halfway between Alpha (Deneb) and Delta on the western side, this is a pure delight in binoculars or any size telescope. The striking gold color of 3.7 magnitude 31 Cygni (Omicron 1) is easily highlighted against the blue of same field companion, 5th magnitude 30 Cygni. Although this wide pairing is only an optical one, the K-type giant is a double star – an eclipsing variable around 150 times larger than or own Sun – and is surrounded by a gaseous corona more than double the size as the star itself. If you are using a scope, you can easy spot the blue tinted, 7th magnitude B star about one third the distance as between the two giants. Although our true pair are some 1.2 billion miles apart, they are oriented nearly edge-on from our point of view – allowing the smaller star to be totally eclipsed during each revolution. This total eclipse lasts for 63 days and happens about every 10.4 years, but don’t stay up too late… We’ve still got 7 years to wait!
Tuesday, July 19 – Today in 1846, Edward Pickering was born. Although his name is not well known, he became a pioneer in the field of spectroscopy. Pickering was the Harvard College Observatory Director from 1876 to 1919, and it was during his time there that photography and astronomy began to merge. Known as the Harvard Plate Collection, these archived beginnings still remain a valuable source of data.
Tonight bright, fat Selene will hold court directing in the middle of the constellation of Saggitarius. Can you still make out the “teapot” pattern? The tip of the “spout” – Al Nasl – will be a little less than a fist width to the Moon’s northwest and the top of the “lid” – Kaus Borealis will be half a fist above it. Can you see than “handle” a half a fist away to the east? For viewers in most of Australia, you will have the chance to see the Moon occult 3.3 magnitude Tau and you will find locations and times on this IOTA webpage.
Wednesday, July 20 – Today is a busy day in astronomy history! In 1969, the world held its breath as the Apollo 11 lander touched down and Neil Armstong and Edwin Aldrin became the first humans to touch the lunar surface. We celebrate our very humanity because even Armstrong was so moved that he messed up his lines! The famous words were meant to be “A small step for a man. A giant leap for mankind.” That’s nothing more than one small error for a man, and mankind’s success continued on July 20, 1976 when Viking 1 landed on Mars – sending back the first images ever taken from that planet’s surface.
For most of us, tonight the Moon will be about as full as it’s going to get, but it is great fun just to trace its bright ray systems. In the northeast quarter, look for a faded ray which cuts its way diagonally from Menelaus, across Mare Crisium and all the way to Atlas and Hercules. Notice how bright the ejecta blankets around Copernicus, Keplar and Aristarchus are. Who cannot be amazed at Tycho and its broad system that covers the entire southern region?
Thursday, July 21 – The Moon will become officially full at 11:00 UT. Sometimes known as the Summer Moon or Thunder Moon, at 20:00 UT, it will reach perigee and the second closest Earth-Moon separation of the year.
With only a short time until Luna rises tonight, let’s take a look at a pair of stars who also have a close separation – Epsilon Lyrae. Known to most of us as the “Double Double”, look about a finger width northeast of Vega. Even the slightest optical aid will reveal this tiny star as a pair, but the real treat is with a telescope – for both components are double stars! Both sets of stars appear as primarily white and both are very close to each other in magnitude. What is the lowest power that you can use to split them?
Friday, July 22 – Be sure to watch the western horizon about 45 minutes after sunset to catch Venus dancing by Regulus tonight. Just barely more than a degree (a finger width) separates the two pair, with the stately star having moved west (below) and slightly south (left) of the bright planet. If you continue your observations, you will note the pair continues to move apart about a degree a day until Regulus is lost.
Tonight we will note the work of Friedrich Bessel, who was born on this day in 1784. Bessel was a German astronomer and mathematician whose functions still carry his name in many areas of mathematical physics. But, you may put away your calculator, because Bessel was also the very first person to measure a star’s parallax. In 1837, he chose 61 Cygni and the measurement was no more than a third of an arc second. His work ended a debate that had stretched back two millenia to Aristotle’s time and the Greek’s theories about the distances to the stars.
With the slightly later rise of the Moon, this would be a great evening to check out 61 Cygni for yourself. Like finding Omicron earlier in the week, you’ll easily locate 61 between Deneb and Zeta on the eastern side. Look for a small trio of just visible stars and choose the westernmost. Not only is it famous because of Bessel’s work, but it is one of the most noteworthy of double stars for a small telescope. Of the unaided visible stars in the constellation of Cygnus, 61 is the fourth closest star to Earth, with only Alpha Centauri, Sirius, and Epsilon Eridani closer. Just how close is it? Try right around 11 light years.
Visually, the two components have a slightly orange tint, are less than a magnitude apart in brightness and a nice separation of around 30″ to the south/southeast. Back in 1792, Piazzi first noticed its abnormally large proper motion and dubbed it “The Flying Star”. At that time, it was only separated by around 10″ and the B star was to the northeast. It takes nearly 7 centuries for the pair to orbit each other, but there is another curiosity here. Orbiting the A star around every 4.8 years is an unseen body that is believed to be about 8 times larger than Jupiter. A star – or a planet? With a mass considerably smaller than any known star, chances are good that when you view 61 Cygni, you’re looking toward a distant world!
If you are up late enough tonight, you can also see the lunar crater named for Bessel as a small, bright ring located just slightly southwest of the center of Mare Crisium.
Saturday, July 23 – Tonight we have awhile to enjoy early dark skies, so let’s head toward an outstanding globular cluster that can be seen in anything from small binoculars to a huge telescope. It’s as easy as finding Antares, so slide 1.3 degrees west and behold the M4.
To binoculars, this huge, very loose globular cluster will look much like a “gone to seed” dandelion with its soft, white round form – yet even the smallest of telescopes can begin to resolve out individual stars in this 5700 light year distant system. As you step up in aperture, you step up in resolution and individual chains and bars of stars begin to swim forward from its more than 10,000 members. Enjoy it tonight!
Sunday, July 24 – If you have the chance to arise before dawn, be sure to look for Mars about halfway up the southeast skies. Now cruising through Pices at around a half a degree a day, most observers will see 4th magnitude Omicron about a finger width above the Red Planet this morning. Just as we’ve watched the motions of Saturn, Venus and Mercury over the last few weeks, use this star to judge Mars’ motion over the next few mornings. Which way is it heading?
Tonight let’s just enjoy a little stargazing and revel in the beauty of our own galaxy’s spiral arm – the Milky Way. For those living in the city, you owe it to yourself to get away to a dark location to enjoy this veritable “river of stars” which spans out of the galactic center south and runs overhead. Almost directly behind you from the galactic anti-center stretches the Perseus arm, and the sight is a beautiful one. If skies are fine, you can easily see the dark dust rift where the arm separates and the billows of light of unresolved stars. It’s the most glorious sight of summer! While we have many days yet before the Aquarid meteor shower officially reaches its peak, you will be pleasantly surprised at this year’s high activity. They’ve been flying out of the night sky for almost two weeks now, and it would not surprise me if you saw ten or more per hour of these quick, bright visitors.
In the mean time? Ask for the Moon, but keep reaching for the stars! May all your journeys be at Light Speed… ~Tammy Plotner
