Exoplanet Study Suggests our Solar System is the Norm

Astrobiology Magazine

Exoplanet Study Suggests our Solar System is the Norm
Source: Centro de Astrofisica da Universidade do Porto press release

Cosmic Evolution  Posted:   04/14/12

Summary: A new study reveals that planetary orbits around Sun-like stars have a tendency to be strongly aligned, similar to the disk-like alignment of the planets in our own solar system.

 

Exoplanets with non-coplanar orbits.
Credit: Ricardo Reis, Centro de Astrofísica da Universidade do Porto

Recently, the HARPS spectrograph and the Kepler satellite made a census of the planetary population around stars like our own, revealing a bounty of planetary systems. A follow-up study lead by members of the EXOEarths team (Centro de Astrofísica da Universidade do Porto -- CAUP), in collaboration with Geneva University, did a joint analysis of the data which showed that the planetary orbits in a system are strongly aligned, like in a disk, just as we have in our own solar system.

The two most effective methods for detecting extrasolar planets are the radial-velocity method and the transit method. The radial-velocity method detects planets through the reflex motion induced by the planet on the star’s velocity on the radial direction (hence the name). This velocity variation is detected through the Doppler effect, the same that leads to a pitch change in the sound of an traveling ambulance. On the other hand, a planetary transit is akin to a mini-eclipse. As a planet travels around the star, its orbit can locate it in front of the star, and the light we collect from the star is reduced because the planet blocks part of it (even though we cannot image the planet).

Astrobiology Magazine

Youngest Planet Seen As It’s Forming

Kamuela, HI – The first direct image of a planet in the process of forming around its star has been captured by astronomers who combined the power of the 10-meter Keck telescopes with a bit of optical sleight of hand.

What astronomers are calling LkCa 15 b, looks like a hot “protoplanet” surrounded by a swath of cooler dust and gas, which is falling into the still-forming planet. Images have revealed that the forming planet sits inside a wide gap between the young parent star and an outer disk of dust.

“LkCa 15 b is the youngest planet ever found, about 5 times younger than the previous record holder,” said astronomer Adam Kraus of the University of Hawaii’s Institute for Astronomy. “This young gas giant is being built out of the dust and gas. In the past, you couldn’t measure this kind of phenomenon because it’s happening so close to the star. But, for the first time, we’ve been able to directly measure the planet itself as well as the dusty matter around it.”

Kraus will be presenting the discovery at an Oct. 19 meeting at NASA’s Goddard Space Flight Center. The meeting follows the acceptance of a research paper on the discovery by Kraus and Michael Ireland (of Macquarie University and the Australian Astronomical Observatory), in The Astrophysical Journal (available at http://arxiv.org/abs/1110.3808)

Figure 1 Left: The transitional disk around the star LkCa15. All of the light at this wavelength is emitted by cold dust in the disk. the hole in the center indicates an inner gap with radius of about 55 times the distance from the Earth to the Sun. Right: An expanded view of the central part of the cleared region, showing a composite of two reconstructed images (blue: 2.1 microns, from November 2010; red: 3.7 microns) for LkCa 15. The location of the central star is also marked.

The optical sleight of hand used by the astronomers is to combine the power of Keck’s Adaptive Optics with a technique called aperture mask interferometry. The former is the use of a deformable mirror to rapidly correct for atmospheric distortions to starlight. The latter involves placing a small mask with several holes in the path of the light collected and concentrated by a giant telescope. With that, the scientists can manipulate the light waves.

“It’s like we have an array of small mirrors,” said Kraus. “We can manipulate the light and cancel out distortions.” The technique allows the astronomers to cancel out the bright light of stars. They can then resolve disks of dust around stars and see gaps in the dusty layers where protoplanets may be hiding.

“Interferometry has actually been around since the 1800’s, but through the use of adaptive optics has only been able to reach nearby young suns for about the last 7 years.” said Dr. Ireland. “Since then we’ve been trying to push the technique to its limits using the biggest telescopes in the world, especially Keck.”

The discovery of LkCa 15 b began as a survey of 150 young dusty stars in star forming regions. That led to the more concentrated study of a dozen stars.

“LkCa 15 was only our second target, and we immediately knew we were seeing something new,” said Kraus. “We could see a faint point source near the star, so thinking it might be a Jupiter-like planet we went back a year later to get more data.”

Figure 2 The location of LkCa 15 can be found using this chart.

In further investigations at varying wavelengths, the astronomers were intrigued to discover that the phenomenon was more complex than a single companion object.

“We realized we had uncovered a super Jupiter-sized gas planet, but that we could also measure the dust and gas surrounding it. We’d found a planet, perhaps even a future solar system at its very beginning” said Kraus.

Drs. Kraus and Ireland plan to continue their observations of LkCa 15 and other nearby young stars in their efforts to construct a clearer picture of how planets and solar systems form.

# # #

The W. M. Keck Observatory operates two 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Big Island of Hawaii. The twin telescopes feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectroscopy and a world-leading laser guide star adaptive optics system which cancels out much of the interference caused by Earth’s turbulent atmosphere. The Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

Source: "Youngest Planet Seen As It's Forming." W. M. Keck Observatory. 2011. Web. 19 Oct. 2011. <http://www.keckobservatory.org/news/first_close-up_view_of_a_planet_being_formed/>

Methuselah - Addendum

© John Whatmough

The Methuselah - 13 Billion Yr Old Planet (Garden of Eden?) post has been updated, thanks to a reader's feedback who correctly pointed out that I mislabeled M4 as an open cluster. I also addressed the issue of the low metallic nature of early globular clusters more clearly - early stellar nurseries should not be capable of producing planets, yet here we have at least one that was formed 13 billion years ago. The probability of life forming on that planet is rather low (at least life as we know it) as it is most likely a gaseous planet, but not zero. And it does raise the possibility (this blog is about speculation, after all) that other ancient planets exist - including a smaller terrestrial planet orbiting in the same system as Methuselah which current methods do not allow us to detect. And that raises the possibility, even if a slim one, that life did arise far earlier in the universe than first thought.

Methuselah - 13 Billion Yr Old Planet (Garden of Eden?)

© John Whatmough

In 2003, astronomers using the Hubble Space Telescope discovered something amazing deep in the M4 globular cluster 7,200 light years away - something that shouldn't be: a planet, 2.5 times the size of Jupiter, orbiting 23 AUs from a pulsar (a rotating, pulsating neutron star), PSR B1620-26. The primary star, the pulsar, has a companion white dwarf orbiting approx 1 AU out.

According to current theories, planets could not form in the early universe (1) - for one thing, early stellar nurseries shouldn't have enough heavy elements to create stars with planets. But somehow at least one planet was formed in the young universe - while the universe is 14 to 15 billion years old, this planet, dubbed Methuselah, is nearly 13 billion years old.

Imagine that - a planet almost as old as the universe itself. Could a civilization have arisen there? Or died out and rose again (that old of a planet, life would have time to restart several times)? And in the final years, moved out into the stars?

I can't help but think of old races often called "The Ancients" or similar such nomenclature in science fiction tales - very old races that seed the rest of the galaxy before ascending or mysteriously moving on to other galaxies, leaving this one behind.

And if life first began in this universe on such an old planet (or, more likely, a smaller sister planet), could that then be the real Garden of Eden, from which Adam and Eve where exiled from?

Of course, orbiting a pulsar is dangerous for life for two reasons: 1) a pulsar is a result of a supernova which tends to destroy worlds (strip away the atmospheres at the very least) and 2) pulsars give off extremely intense beams of radiation along the lines of its magnetic axis - if any planet is in the path of the beam of the rapidly spinning star, the radiation would be too intense for life to survive or form (2).

As we have seen in a previous post, Planets, planets everywhere, planets can reform around a pulsar - from the rocky debris of the original planets, blasted from the supernova explosion.

Scientists, however, do not feel that Methuselah is a "reconstituted" planet. One theory is that the planet (and maybe others too small to be detected by present means) was captured from a sideswipe with another younger system later on - a system that existed for 10 billion years before wandering too deep into the core of the globular cluster, where distances between star systems can sometimes be less than 1 light year.

Recall from an earlier post, An Aside - Are There Alien Worlds in Our Own Solar System?, there is some evidence that our own solar system has "adopted" objects from an alien solar system passing by in the distant past - possibly when it was still in an open globular cluster (scientists theorize that our sun was first formed in an open cluster).

In fact, the scientists feel that the white dwarf companion was also "adopted" by the primary neutron star. They theorize that the pulsar did have a dwarf companion at first, but when a yellow star system came too close, the gravitational tug-of-war kicked out the dwarf and the yellow star took its place, along with at least one of its planets. The new system then moved out from the core of the globular cluster - reducing any chances for further collisions.

In this new binary system, some of the mass from the yellow star got sucked into the pulsar, speeding up its rotation, giving it the incredible spin rate of 100 revolutions every second. After some millions of years, the yellow star became a red giant and then a white dwarf.

So it is quite possible that the Methuselah, and any other world(s) circling PSR B1620-26, were "adopted," right along with their sun. If so, could one of them developed life before being captured by the pulsar/dwarf system? Early planetary systems would most likely be made up of gaseous planets - there shouldn't be enough heavy elements for terrestrial planets to form. But then we didn't think any planets as old as Methuselah should exist either. Maybe, just maybe, a small terrestrial planet does exist along with Methuselah. And even if not, life is not necessarily restricted to terrestrial planets - life could begin and thrive on non-terrestrial planets (albeit, such life would not be life as we know it).

One problem such life would face is that being captured by the pulsar would prove to be quite the dramatic change. If they are lucky, the radiation beam from the pulsar would point far above the ecliptic, thus avoiding being bathed in intense radiation every 1/100th of a second; but even then, the difference in light (and heat) would be devastating as it is rather certain the planets' new orbits around the binary pair would be different than when they were just circling around their single parent star. But as we see on Earth, life, once formed, is tenacious and will find a way to survive, even during the occasional mass extinctions.

For intelligent life, depending upon their level of technological advancement, they could migrate to a sister world circling the new binary system, one that was now more hospitable than their home world. Otherwise, they would be forced to adapt to their new, darker, colder world. Or, if they were highly advanced at the time the collision was imminent, and finding themselves in a crowded neighborhood, could explore nearby systems and move to one that was safer -though it is doubtful any planetary system in the core of cluster would be safer, especially any system that was lingering in the core, and thus increased chances of itself colliding with another star system. No, more likely they would have to figure out how best to ride out the collision.

At first scientists thought planetary systems couldn't survive long in a cluster, especially a globular cluster - but increasing evidence is showing that sometimes this is not the case. Although, lingering too long in a cluster is still thought not the best environment for life; for one thing, a globular cluster has many stars in relatively close proximity - a supernova from a nearby star can have devastating effects for life on the planets of neighboring star systems and being in a globular cluster, chances for being near a supernova are rather high. For the Earth, a supernova 30 light years or closer would be quite devastating for life - for other planets, the distance could be greater, depending upon how thick their protective atmospheres are (to show you how protective our atmosphere is, for astronauts outside the Earth's atmosphere, a supernova 3,000 light years away could be deadly).

But, it is not impossible. That extrasolar system could have been one of the earliest gardens of life in the universe. 12.7 billion years ago the planetary system was formed. Our own system is "merely" 4.5 billion years. It is thought that the first 10 billion years Methuselah led a "normal" life around a normal sun like star. And if it was, was that life able to evolve to a space faring species? Are there descendants scattered about the Milky Way (or at least in that region of the Milky Way)?

Notes:

1. Early stars were poor in heavy elements, and thus could not form planets, but when they died, they produced heavy elements which then became part of new nebulae within which new stars were born - and with heavy elements now in the mix, allowing planets to finally be formed as well.

2. While pulsars are formed from massive stars, white dwarfs are formed from the average main sequence star - most stars in the galaxy will end their lives as white dwarves.

References:

Britt, Robert Roy. "Primeval Planet: Oldest Known World Conjures Prospect of Ancient Life." Science. SPACE.com. 10 July 2003. 6 January 2008. <http://www.space.com/scienceastronomy/oldest_planet_030710-1.html>

"Extrasolar Visions - 'Methuselah' PSR B1620-26 c." Extrasolar Planet Guide. 5 January 2008. <http://www.extrasolar.net/planettour.asp?PlanetID=30>

"Messier Object 4." The Messier Catalog. SEDS. 21 August 2007. 6 January 2008. <http://www.seds.org/Messier/M/m004.html>

Mukai, Koji and Eric Christian. "Destruction of the Earth by a Nearby Supernova." Ask an Astrophysicist. Imagine the Universe! 1 December 2005. 5 January 2008. <http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980521a.html>

"Oldest Planet Challenges Existing Theories." This Week in Science. 11 July 2003. 5 January 2008. <http://www.twis.org/2003_07_11_science_news.html>

Richmond, Michael. "Will a Nearby Supernova Endanger Life on Earth?" 8 April 2005. 5 January 2008. <http://stupendous.rit.edu/richmond/answers/snrisks.txt>

Terrestrial Planets Forming in the Subaru!

© Lynette R. Cook, for Gemini Observatory.

In the Pleiades (known as Subaru in Japanese - yes, the car company is named for it), astronomers have discovered evidence of terrestrial planets forming, or having recently formed, around two young (100 - 400 million years old) stars in the Pleiades cluster.

"This is the first clear evidence for planet formation in the Pleiades, and the results we are presenting may well be the first observational evidence that terrestrial planets like those in our solar system are quite common," said Joseph Rhee, a UCLA postdoctoral scholar in astronomy and lead author of the research (UCLA, par. 3).

The Pleiades is a young open cluster 400 light years away. Some scientists feel that our Sun was formed in an open cluster as well; stars in an open cluster tend to wander from the "nest" as they age. So, we may see the beginnings of home worlds for future Subaruians (Pleiadians?).

Reference:

UCLA News Results. "Planets found forming in Pleiades star cluster." SpaceFlight Now. 15 November 2007. 22 December 2007. <http://spaceflightnow.com/news/n0711/15pleiades/>

Once In A Blue Moon: Earth's Moon Even More Rare?

Yet more evidence suggests that a moon like ours is rare. Oh, moons are found aplenty around planets, but they tend to be rather small in comparison to the planet they orbit, and most of them are captured. Our Moon, however, was not captured, and is very large in comparison to the Earth. The ratio of the difference in size is so small that some astronomers propose calling the Earth-Moon system a double planet system.

Around 4.5 billion years ago, a large Mars-sized planet collided with the Earth in such away that part of the Earth's mantle was thrown into space. The Mars-sized impactor was absorbed by the Earth, it's iron core joining the Earth's. It also increased the Earth's spin. Most of the section of mantle that was thrown into space coalesced quickly into the Moon (may have taken as little as a year). The rest of the debris that was "kicked up" by the collision, and which did not coalesced, continued to circle the sun for millions of years before gravity and solar radiation cleaned it up.

Again, why is this important information, and included in this blog?

Well, as reported before in this blog (Astronomers Say Moons Like Ours Are Uncommon - How Important is That?), some scientists feel that the Moon was essential to the origin of life on the Earth due to the tidal mixing which helped to mix, mainly from erosion caused by the tides, chemicals from the soil with the oceans, creating the chemical soup from which life arose. This is especially true for the young Earth when the Moon was closer and had a much more dramatic effect on the tides. Only 1/3 of the today's tidal effects is attributed to the Sun, the rest to our Moon.

In the original report, it was stated that maybe only 5 to 10% of planets would a moon like Earth's. However, a new report by Nadya Gorlova of the University of Florida in the November 2007 issue of The Astrophysical Journal, states that the percentage may even be smaller: 1 in 400. As reported by Physics News:

Using the cryogenically-cooled infrared orbiting Spitzer Space Telescope, Gorlova and her colleagues surveyed the 30-million-year old star cluster NGC 2547. They selected this cluster because of its age. The planetary building process usually ends by approximately 50 million years, making the odds of a giant impact unlikely to occur outside this window. The other advantage of NGC 2547 is that it is old enough for the material left out from the original cloud of

which solar systems formed to dissipate (this takes about 3-10 million years). By focusing on radiation at a wavelength of about 8 microns, they could detect the heat they would expect from dust at a distance of about one astronomical unit (1 AU) from a solar-type star. The NGC 2547 cluster was previously surveyed spectroscopically, so they could cross-check to make sure that the emission they detected was not due to gas (which would be evident by spectral emission lines). Out of about 400 stars in the NGC 2547 cluster, they found only one that showed evidence of dust from a massive impact.

What needs to be kept in mind are 1) this is just one sampling. There may be other factors at play here that, for instance, may have sped up the cleaning of debris after the collision, or otherwise minimized the debris; 2) statistically, an average is not found everywhere - that is, if 1 out of 10 planets, on average, form a Moon like Earth's, you would find some regions where the percentage was higher, and some regions where it was lower; 3) even without the Moon, enough mixing may still occur for life to begin (albeit maybe would've taken longer); and 4) there may be other situations such as a habitable moon orbiting a gas giant - where the tidal effects from the gas giant would be strong enough to mix chemicals on the young terrestrial moon.

Reference:

PHYSICS NEWS UPDATE. The American Institute of Physics Bulletin of Physics News. Number 849 December 5, 2007 by Phillip F. Schewe and Jason S. Bardi <www.aip.org/pnu>

Wait a Minute - What About the Asteroid Belt?

"Dark Matter" © DigitalBlasphemy.com

In three previous posts, "Planets, Planets Everywhere," "Young Sun-like Star Already Parent," as well as The Introduction to this blog, we learn that planets seem rather common-place: they form readily. All you need is debris or dust circling a star, gravity, and time (a million to several million years). Planets even are reborn around pulsars - regenerated from the blasted debris of the star's original planets (planets destroyed by the enormous supernova explosion that preceded the star becoming a pulsar).

And this got me to thinking - how come the rocky and dusty debris of the asteroid belt has never coalesced into a planet or dwarf planet? Possibly the tidal influence of Jupiter? If anyone has any input on this matter, it would be gratefully received.

Planets, planets everywhere

Watching the "Alien Planets" episode of the History Channel's Universe program, we learn an interesting discovery: planets around a pulsar (for example PSR B1257+12). That should be impossible - a pulsar is what is formed after a massive supernova explosion, an explosion so powerful that any planets should be destroyed. However, three small rocky planets were found. What they now hypothesize is that these are planets that formed from the debris of the destroyed orignial planets. If this is so, then this is more proof that planets can form even under extreme conditions; gravity wants to clump debris together, it is a natural consequence of matter and gravity. Thus, planets are probably very, very common.

By the way, life on a planet around a pulsar is very unlikely - there is far too much radiation flooding the system, especially if the planet happens to be in the way of the emission beams from the pulsar's magnetic poles.

Reference:

Pennsylvania State University. "Scientists announce smallest extra-solar planet yet discovered." 10 February 2005. 29 November 2007. <http://live.psu.edu/story/10180>

Wolszczan, A. (1994). "Confirmation of Earth Mass Planets Orbiting the Millisecond Pulsar PSR B1257+12". Science 264 (5158): 538 – 542.