Starship Asterisk*

Mass and density of smallest exoplanet finally measured
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In February 2009, the discovery by the CoRoT satellite [1] of a small exoplanet around a rather unremarkable star named TYC 4799-1733-1 was announced one year after its detection and after several months of painstaking measurements with many telescopes on the ground, including several from ESO. The star, now known as CoRoT-7,
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The initial set of measurements, however, could not provide the mass of the exoplanet. Such a result requires extremely precise measurements of the velocity of the star, which is pulled a tiny amount by the gravitational tug of the orbiting exoplanet.
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To get an answer, astronomers had to call upon the best exoplanet-hunting device in the world, the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph attached to the ESO 3.6-metre telescope at the La Silla Observatory in Chile.
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HARPS delivered, allowing the astronomers to tease out the 20.4-hour signal in the data. This figure led them to infer that CoRoT-7b has a mass of about five Earth masses, placing it in rare company as one of the lightest exoplanets yet found.
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As a further testament to HARPS' sublime precision, the astronomers found from their dataset that CoRoT-7 hosts another exoplanet slightly further away than CoRoT-7b. Designated CoRoT-7c, it circles its host star in 3 days and 17 hours and has a mass about eight times that of Earth, so it too is classified as a super-Earth. Unlike CoRoT-7b, this sister world does not pass in front of its star as seen from Earth, so astronomers cannot measure its radius and thus its density.

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About 330 exoplanets have been discovered so far, most of which are gas giants with characteristics similar to Jupiter and Neptune.

The new find, COROT-Exo-7b, is different: its diameter is less than twice that of Earth
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The density of the planet is still under investigation
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This discovery is significant because recent measurements have indicated the existence of planets of small masses but their size remained undetermined until now.

The internal structure of COROT-exo-7b particularly puzzles scientists

TimeTravel123456789 wrote:I have discussed elsewhere that some identifications may be wrong. This may just be a decrease in brightness of a related star. Think logically, could a star's brightness decrease in a regular way? Yes.

I do not have the measurements in front of me, but I still maintain that there is a possibility that this is just stellar variability. When we find that an exoplanet is stellar variation, that will help us understand this.Think of looking at the Sun; we see stellar variation all the time.

TimeTravel123456789 wrote:I have discussed elsewhere that some identifications may be wrong. This may just be a decrease in brightness of a related star. Think logically, could a star's brightness decrease in a regular way? Yes.

I do not have the measurements in front of me, but I still maintain that there is a possibility that this is just stellar variability. When we find that an exoplanet is stellar variation, that will help us understand this.Think of looking at the Sun; we see stellar variation all the time.

We are driven to discoveries by the system of rewards-grants, articles, prizes, but sometimes a discovery can be made by admitting to a less popular alternative thesis that a star's brightness decreased. I think that alternative thesis is the topic of just as important an article is Astro Phys Letters or AstroPh Journal. Stars do vary in brightness. Be careful when coming to the US, guardians are taking everything and rights to decide from people with diagnoses or differences. Just something to plan for when coming here

http://www.daviddarling.info/encycloped ... _star.html

<<A short-period, yellow or white giant pulsating variable; RR Lyrae stars belong to Population II and are often found in globular clusters (hence one of their older names – cluster variables) or elsewhere in the galactic halo. They have periods of 0.2 to 2 days, amplitudes of 0.3 to 2 magnitudes, and spectral types of A2 to F6. Some of them have similar light curves to those of Cepheid variables and, like Cepheids, obey a period-luminosity relation that enables them to serve as reliable distance indicators. RR Lyrae variables, however, are older, less massive, and fainter (with luminosities typical around 45 L{sun}) than Cepheids.>>

http://en.wikipedia.org/wiki/RR_Lyrae_variable wrote:
<<RR Lyrae variables are periodic variable stars, commonly found in globular clusters, and often used as standard candles to measure galactic distances. RR Lyraes are pulsating horizontal branch stars of spectral class A (and rarely F), with a mass of around half the Sun's. They are thought to have previously shed mass and consequently, they were once stars with similar or slightly less mass than the Sun, around 0.8 solar masses.

RR Lyrae stars pulse in a manner similar to Cepheid variables, so the mechanism for the pulsation is thought to be similar, but the nature and histories of these stars is thought to be rather different. In contrast to Cepheids, RR Lyraes are old, relatively low mass, metal-poor "Population II" stars. They are much more common than Cepheids, but also much less luminous. (The average absolute magnitude of an RR Lyrae is 0.75, only 40 or 50 times brighter than our Sun.) Their period is shorter, typically less than one day, sometimes ranging down to seven hours.

The relationship between pulsation period and absolute magnitude of RR Lyraes makes them good standard candles for relatively near objects, especially within the Milky Way. They are extensively used in globular cluster studies, and also used to study chemical properties of older stars.>>



RR Lyrae stars were formerly called "cluster variables" because of their strong (but not exclusive) association with globular clusters; conversely, about 90% of all variables known in globular clusters are RR Lyraes. RR Lyrae stars are found at all galactic latitudes, as opposed to classical Cepheid variables, which are strongly associated with the galactic plane.

Several times as many RR Lyraes are known as all Cepheids combined; in the 1980s, about 1900 were known in globular clusters. Some estimates have about 85000 in the Milky Way.

From 1915 to the 1930s, the RR Lyraes became more accepted as a distinct class of star from classical Cepheids, on account of their shorter periods, different location within the galaxy, and finally, they are chemically different from classical Cepheids, being mostly metal-poor, Population II stars.

RR Lyraes have proven difficult to observe in external galaxies, because of their intrinsic faintness. (In fact, Walter Baade's failure to find them in the Andromeda galaxy led him to suspect that the galaxy was much farther away than predicted, and to re-consider the calibration of Cepheid variables and to propose stellar populations.) They were finally found in the 1980s by Pritchet & van den Bergh in the halo of the Andromeda galaxy, and more recently in its globular clusters by the Hubble Space Telescope.

The RR Lyrae stars are conventionally divided into three main types[1], following a classification of S.I. Bailey based on the shape of the stars' brighness curve:

* RRab — the majority, with steep rise in brightness (about 91%)
* RRc — having shorter periods, more sinusoidal variation (about 9%).
* RRd — rare double-mode pulsators.

TimeTravel123456789 wrote:I have discussed elsewhere that some identifications may be wrong. ...
I think that alternative thesis is the topic of just as important an article

TimeTravel123456789 wrote:I do not have the measurements in front of me, ...

TimeTravel123456789 wrote:Be careful when coming to the US, guardians are taking everything and rights to decide from people with diagnoses or differences. Just something to plan for when coming here

Mass and density of smallest exoplanet finally measured

The longest set of HARPS measurements ever made has firmly established the nature of the smallest and fastest-orbiting exoplanet known, CoRoT-7b, revealing its mass as five times that of Earth's. Combined with CoRoT-7b's known radius, which is less than twice that of our terrestrial home, this tells us that the exoplanet's density is quite similar to the Earth's, suggesting a solid, rocky world. The extensive dataset also reveals the presence of another so-called super-Earth in this alien solar system.

• Exeter: Yes, they're concentrating all their attention on Metaluna. Those flashes of light... they're meteors... hundreds of them! Intense heat is turning Metaluna into a radioactive sun. Temperature must be... thousands of degrees by now. A lifeless planet. And yet... yet still serving a useful purpose, I hope. Yes, a sun. Warming the surface of some other world. Giving light to those who may need it.

http://en.wikipedia.org/wiki/This_Island_Earth

<<Dr. Cal Meacham, a noted scientist, receives an unusual substitute for electronic condensers that he ordered. He receives instruction and parts to build a complex communication device called an interocitor. When finished, a mysterious man named Exeter appears on the interocitor's screen and tells Meacham he has passed the test. His ability to build the interocitor demonstrates that he is gifted enough to be part of Exeter's special research project.

Intrigued, Meacham is picked up the next day at the airport by an unmanned, computer-controlled Douglas DC-3 aircraft with no windows. Landing in a remote area of Georgia, he finds an international group of top-flight scientists already present – including an old flame, Dr. Ruth Adams. Cal is almost immediately suspicious of the odd-looking group of men leading the project.

Cal and Ruth try to flee with a third scientist, Steve Carlson, but their car is attacked and Carlson is killed. When they take off in a small plane, Cal and Ruth watch as the facility and all its inhabitants are incinerated, and their plane is drawn by a mysterious beam into a flying saucer.

They learn that Exeter and his band are from the planet Metaluna, having come to Earth seeking uranium deposits as well as scientists to help defend their planet in a war against the evil Zagons. Exeter informs the Earthlings that he is taking them back to his world.

After a mind-bending journey, they arrive to find the planet under full bombardment and falling quickly to the enemy. Metalunan society is breaking down and there is little hope. Their leader, The Monitor, reveals that the Metalunans intend to relocate to Earth and insists that Meacham and Adams be subjected to a Thought Transference Chamber in order to subjugate their free will so they cannot object. Exeter believes this to be immoral and misguided since it constrains their ability to help the Metalunans. Exeter decides to help Cal and Ruth escape, thus revolting against his own kind, before they enter the brain-reprogramming facility.

The three escape from Metaluna and begin the journey back to Earth, observing the final destruction of the planet shortly before they leave its star system. However, a mutant creature has somehow boarded the craft. Cal manages to overpower it, but not before it badly wounds Exeter.

As they enter Earth's atmosphere, Exeter sends Cal and Ruth on their way in their small plane, but he himself is dying and the ship is nearly depleted of energy. With no other options, Exeter uses the craft's remaining power to fly it out to sea and crash.>>