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annarita ruberto
Worked at Ministry of National Education
Attended University of Salento
Lives in Ravenna (Italy)
25,469 followers|22,894,879 views


Astrometry As A Method For Detecting Extrasolar Planets 

The planets, in comparison to the stars, emit much less light in the cosmos. For this reason, the direct detection of exoplanets is extremely difficult: in normal conditions of visibility, the planets have usually a brightness equal to about a million times less than that one of a star. In addition to this intrinsic difficulty of detection, the greater brightness of the stars, around which planets revolve, causes a glow that tends to cover the light, weakly  reflected by the celestial bodies of the respective system.

For these reasons, current telescopes can provide only indirect information about the physical and orbital parameters of exoplanets, whose presence can be detected only in extraordinary circumstances, using indirect techniques of investigation.
There are various indirect methods for detecting exoplanets, one of which is the Astrometry.

This method consists in measuring the precise position of a star in the sky and in observing how this position changes over time. If the star has a planet, then the gravitational influence of the planet will cause the star a light circular motion or an elliptical orbit around a common center of mass. This movement is determined through the Doppler effect.

Animated diagram below shows how a smaller object (such as an extrasolar planet) orbiting a larger object (such as a star) could produce changes in position and velocity of the latter as they orbit their common center of mass (red cross in the image at this link: 

Because the motion is so small, however, this method has not yet been very productive. It has produced only a few disputed detections, though it has been successfully used to investigate the properties of planets found in other ways. 

Astrometry is also the branch of Astronomy that deals with the measurements, positions, distances and motions of the stars and other celestial bodies. Among the its  various objectives, there is  that one to build a cosmic distance scale.

It's one of the oldest application fields of astronomy, dating back to Hipparchus, who was the first to compile a star catalog of the stars visible to him. To do this he invented the system of the apparent magnitude scale of brightness, still in use today.
The modern Astrometry was founded by Friedrich Bessel, who with his Fundamenta astronomiae gave the average positions of 3222 stars observed between 1750 and 1762 by James Bradley.

In addition to the basic function of providing astronomers with a precise reference system on which to base observations, the Astrometry is also the basis of celestial mechanics, stellar dynamics and galactic astronomy. The Astrometry is essential to keep track of time, because the time zone UTC represents the International Atomic Time, synchronized with the rotation of the Earth, achieved thanks to extremely precise astrometric observations.

NASA's planned Space Interferometry Mission (SIM PlanetQuest) (now cancelled) was to utilize astrometric techniques to detect terrestrial planets orbiting 200 or so of the nearest solar-type stars, and the European Space Agency's Gaia Mission, launched in 2013, which will be applying astrometric techniques in its stellar census. 

References and further reading:
- Gaia Mission (
- Space Interferometry Mission (
- Apparent magnitude (

Gif source:

#astrometry #exoplanets #astronomy #space #scienceongoogleplus #sciencesunday #scienceeveryday
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A friend once told me "Math is a statement of physical reality." True. True.
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Ten Rotating Cubes

The cube is the only regular hexahedron and one among the five Platonic solids.

I wrote about them in another my post, titled " Cubes in motion ":

Now I propose to you an original and very suggestive gif, where you can see ten rotating cubes.

Watch them attentively and at least for a minute.

Do you observe something in particular?

Gif source:

Credits: Benjamin Zimmermann

#matemathics #cube #platonic_solids #animated_gif #science #sciencesunday #scienceeveryday
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Turning in different directions.
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Minimal Math Concepts

Today is Easter Monday. In Italy it's an official holiday named " Pasquetta ", that means small Easter (Easter is said Pasqua in Italian).

I made this parenthesis for saying that I don't work today!;)...and you? In any case, I wish you Happy Easter Monday!

I propose to you this nice infographic " Minimal Math Concepts ".

What are your favorites?


#mathematics #infographic
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I wish you Happy Easter with this thought from Gabriel García Márquez

It is not true that people stop pursuing dreams because they grow old, they grow old because they stop pursuing dreams.

Pursue your dreams because they keep you alive and make livable the future.

The  image below shows my Ionian Sea.

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+Ali Fadakar :)
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SECC: a concrete mix that is  superhydrophobic and durable for up to 120 years 

Superhydrophobic Engineered Cementitious Composite (SECC) is a durable and superhydrophobic concrete mix, developed by University of Wisconsin-Milwaukee civil engineers.

This new water-repellant concrete is impregnated with tiny superstrong fibers that prevent liquid from getting inside, freezing and causing it to crack. It promises to leave roads and bridges free of major cracks for up to 120 years.

The new developed concrete is significantly more ductile than traditional concrete, what means that cracks that do form do not propagate and cause failure.

My  summary is sinthetic, therefore read the article "At Long Last: A Concrete That’s Nearly Maintenance-Free" at NEWSWISE:

Gif source:

#science #tech #civil_engineering #roads #bridge #concrete #superhydrophobic #water_repellent #infrastructure #Materials_Science #highway_construction 
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What +annarita ruberto? Are you telling me something?
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Have her in circles
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Ancient Bristlecone Pines...and Sky
(California, USA, 2013 July 11)

In this breath-taking shot from astrophotographer Alexis Burkevics, you can see some ancient bristlecone pines under the Milky Way, with Corona Australis and Sagittarius constellation.

The photographer was able to capture a magical and enchanting atmosphere that touches the spirit.

Corona Australis, in the Southern Hemisphere, is one of the 88 modern constellations. It is also one of the original 48 constellations listed by  the 2nd-century astronomer Ptolemy. According to legend, it symbolizes the crown worn by the centaur Sagittarius

For more information, you can read at the links below.

What do you think of this photograph? I consider it really spectacular.

Alexis Burkevics website:

Photo source:

Sagittarius constellation:

Corona Australis:

#astrophotography #space  #milkyway #constellations #science #sciencesunday #scienceeveryday
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The tree seams to be the same as the one in TimeScapes documentary.
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Earth Day 2014: Green Cities

Every year on April 22, over a billion people in 190 countries take action for Earth Day. From San Francisco to San Juan, Beijing to Brussels, Moscow to Marrakesh, people plant trees, clean up their communities, contact their elected officials, and more—all on behalf of the environment.

Visit the official web site:

The banner below was designed by NASA:

Visit the web site Earth Right Now:

#earthday #NASA #environment #science
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+Isaiah Shomoye I perfectly agree.☺
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This picture was created by me when I still attended high school. 
The theme expresses a particular frame of mind, therefore you can freely interpret it according to the feelings aroused in each of you.

#frame_of_mind #informal
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I can see a blackhole in it!
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Golden angle and Fibonacci a gif 

Looking at this animated gif, they came up in my mind the golden angle and the Fibonacci numbers
So I thought to use that one at school to introduce these two concepts. 

In fact, if you look closely the uniform distribution of the dots in the gif, it seems that they pop up according to golden angle, while the spirals in these configurations count up to Fibonacci numbers!

Many people know surely the Fibonacci series (1,2,3,5,8,13 ...), where each term is the sum of the two preceding it. This numbers sequence is not only a "mathematical little game", but it is closely linked to the concept of Golden Ratio. In a few words, it is a law of proportionality between two elements. When their ratio approaches a given value, the golden number that is equal to φ = 1,618033...(the divine number is not born by chance, but by mathematical calculations) they appear harmonious, golden ... divine!

The golden ratio is approximately the ratio among adjacent terms in the Fibonacci series: 3/2 = 1.5; 8/5 = 1.6; 13/8 = 1.625.
What fascinates is the recurrence of this number in Nature. If you build a spiral, whose radius tends to increase with a factor of accretion equal to the golden number, you get a golden spiral. This geometric pattern is taken up by many mollusks in their shells and even by spiral galaxies.

If you look at some flowers or plants, you can see how the leaves  or petals are disposed to each other at a constant angle equal to about 137°. It is the golden angle, namely the angle that is in a "golden ratio" with the angle equal to 360°.

This kind of pattern plays an important role in the theory of Phyllotaxis, a word that has a Greek origin, composed of the term " " phyllon " (leaf) and " taxis " (order). Phyllotaxis is a branch of Botany that studies the way in which the leaves and the flowers of the plants are distributed along the stem. Often, this provision follows numeric and geometric patterns, as if there were a manifestation of intelligence.
The leaves are arranged in an intelligent way: they have the necessary space to receive the rain and light, but also the arrangement follows a pattern, ie an organization.
The Greeks had already noticed this property, but Leonardo da Vinci was the first to study it. He noted that the leaves are distributed following spirals around the stem in groups of 5. This situation implies that the angle of rotation has to do with multiples of 1/5.

Johannes Kepler (1571-1630) observed that the pentagon is much important regard the shape of flowers, which often have 5 petals, or regard the fruits, such as apples where the seeds are distributed in a pattern of a pentagram (or star pentagon). 

And there would be much more to say. In short, you have figured out how they can be taken interesting teaching suggestions from this beautiful animated gif.

Gif source:

#mathematics #fibonacci_numbers #golden_angle #golden_ratio #golden_number #sciencesunday #scienceeveryday
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seems like inflated balloon!
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Cheetah: Nature’s Speed Machine

The cheetah is a large feline inhabiting most of Africa and parts of the Middle East.
The cheetah can run faster than any other land animal, as fast as 112 to 120 km/h in short bursts covering distances up to 500 m, and has the ability to accelerate from 0 to 100 km/h in three seconds.

Jacob O'Neal created a nice animated infographic into which you can find many information about this splendid feline.

Watch the source

#nature #feline #animals #science 
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+Martine Adriana there is another kind of problem. ;)
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Have her in circles
25,469 people
I teach mathematics and science and work at educational research.
Science communication and e-learning. Scientific blogging
  • Ministry of National Education
    Tenured teacher at secondary school
  • "Scuola & Didattica" - Educational fortnightly magazine in Italian
    Freelance journalist of scientific and educational articles
  • Collaboration with various educational websites
Map of the places this user has livedMap of the places this user has livedMap of the places this user has lived
Ravenna (Italy)
Lecce - Firenze
We can achieve what strongly we want!
I teach mathematics and science and I write for "Scuola e Didattica"- Educational fortnightly magazine in Italian (Editrice La Scuola).

I'm also interested in web 2.0, social network and much more. I love reading, writing, painting, photography, good music, and more.

My posts are prevalently about Science and Mathematics for a general audience, but also about Art, beautiful images/photo and interesting  gifs. I share often scientific news that can be useful to many people.

I would like to look at the profiles of everyone who circles me, but there are too many. ;)
Anyway, I will definitely look at your profile if you engage with my posts.

Furthermore, I am interested in following people who post quality original content, regardless of the number of their followers. 

Instead I am not interested in following people if they never engage with my own content.

If you consider interesting my posts, you can circle me:). I'd like to read your posts and to interact with you here on Googleplus
Bragging rights
I experimented at school a research scholarship in Science, producing approximately over 200 pages of Materials for Science, published by IRRE- ER (Institute of Educational Research Emilia-Romagna, Italy). I was also part, along with 50 teachers selected nationwide, of The SENIS Project, a pilot project from Ministry of National Education for improving the scientific formation of teachers at secondary school. This Project has collected a lot of educational resources, published in a book by Ministry of National Education.
  • University of Salento
    Master's Degree in Physics
  • Classical Lyceum
  • University of Florence
    Advanced course in methods of communication and networked learning
  • University of Tuscia
    1. Advanced course on assessment/evaluation and managing portfolio. 2. Master in elearning and Learning Object
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