Αστρονομικά Νέα

Mars touchdown: NASA spacecraft survives supersonic plunge

A NASA spacecraft designed to drill down into Mars' interior landed on the planet Monday after a perilous, supersonic plunge through its red skies, setting off jubilation among scientists who had waited in white-knuckle suspense for confirmation to arrive across 100 million miles of space. Flight controllers at NASA's Jet Propulsion Laboratory in Pasadena, California, leaped out of their chairs, screaming, dancing and hugging, upon learning that InSight had arrived on Mars, the graveyard for a multitude of previous missions. "Touchdown confirmed!" a flight controller called out just before 3 p.m. EST, instantly dispelling the anxiety that had gripped the control room as the spacecraft made its six-minute descent.

This illustration made available by NASA in October 2016 shows an illustration of NASA's InSight lander about to land on the surface of Mars. NASA's InSight spacecraft will enter the Martian atmosphere at supersonic speed, then hit the brakes to get to a soft, safe landing on the alien red plains. After micromanaging every step of the way, flight controllers will be powerless over what happens at the end of the road, nearly 100 million miles away. (NASA/JPL-Caltech via AP)

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Ultra-close stars discovered inside a planetary nebula

An international team of astronomers have discovered two stars in a binary pair that complete an orbit around each other in a little over three hours, residing in the planetary nebula M3-1. Remarkably, the stars could drive a nova explosion, an entirely unexpected event based on our current understanding of binary star evolution.

An image obtained with the Hubble Space Telescope of the planetary nebula M3-1, the central star of which is actually a binary system with one of the shortest orbital periods known. (Credit: David Jones / Daniel López – IAC)

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How Does a Black Hole Form?

There's something inherently fascinating about black holes. Maybe it's that they're invisible beasts lurking in space that sometimes rip passing stars in half and scatter their remains. Whatever it is, these strange cosmic objects continue to captivate scientists and laypeople alike. But where do black holes come from? How do they form, and what gives them such awesome destructive power?

Supermassive black holes blast winds outward in a spherical shape, as depicted here in this artist's conception of a black hole. (Credit: NASA/JPL-Caltech)

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NASA's Opportunity Rover on Mars Still Silent 2 Months into Epic Dust Storm

It's now been more than two months since NASA's long-lived Opportunity Mars rover last phoned home. Opportunity hasn't made a peep since June 10, when dust in the Red Planet's air got so thick that the solar-powered rover couldn't recharge its batteries. Opportunity's handlers think the six-wheeled robot has put itself into a sort of hibernation, and they still hope to get a ping once the dust storm has petered out.

These side-by-side images, captured several months apart by NASA's Mars Reconnaissance Orbiter, show the dramatic effects of the dust storm currently blanketing the Red Planet. (Credit: NASA/JPL-Caltech/MSSS)

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First confirmed image of newborn planet

Astronomers led by a group at the Max Planck Institute for Astronomy in Heidelberg, Germany have captured a spectacular snapshot of planetary formation around the young dwarf star PDS 70. By using the SPHERE instrument on ESO's Very Large Telescope (VLT)—one of the most powerful planet-hunting instruments in existence—the international team has made the first robust detection of a young planet, named PDS 70b, cleaving a path through the planet-forming material surrounding the young star.

This spectacular image from the SPHERE instrument on ESO's Very Large Telescope is the first clear image of a planet caught in the very act of formation around the dwarf star PDS 70. The planet stands clearly out, visible as a bright point to the right of the center of the image, which is blacked out by the coronagraph mask used to block the blinding light of the central star. (Credit: ESO/A. Müller et al.)

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How solar prominences vibrate

An international team led by researchers from the Instituto de Astrofísica de Canarias (IAC) and the Universidad de La Laguna (ULL) has cataloged around 200 oscillations of the solar prominences during the first half of 2014. Its development has been possible thanks to the GONG network of telescopes, of which one of them is located in the Teide Observatory. When we look at the surface of the Sun the solar prominences are seen as dark filaments that populate the disk or as a blaze of plasma above it. Solar prominences are very dense plasma structures that levitate in the solar atmosphere. It is generally believed that the star's magnetic field supports them so that they do not fall on the surface due to their own weight. These magnetic structures can accumulate a large amount of energy that, when released, produces eruptions ejecting the prominence material into the interplanetary space.

(Credit: Instituto de Astrofísica de Canarias)

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Ushering in the next phase of exoplanet discovery

Ever since scientists discovered the first planet outside of our solar system, 51 Pegasi b, the astronomical field of exoplanets has exploded, thanks in large part to the Kepler Space Telescope. Now, with the successful launch of the Transiting Exoplanet Survey Satellite (TESS), scientists see a revolution not only in the amount of new planetary data to analyze, but also in the potential for new avenues of scientific discovery. So far, scientists have confirmed 3,717 exoplanets in 2,773 systems. As an all-sky survey, TESS will build on this, observing 85 percent of the cosmos containing more than 200,000 nearby stars, and researchers expect to identify some 20,000 exoplanets.

An artist concept depicts TESS in front of a lava planet orbiting its host star. (Credit: Credit: NASA Goddard Space Flight Center)

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ExoMars returns first images from new orbit

The ExoMars Trace Gas Orbiter has returned the first images of the Red Planet from its new orbit. The spacecraft arrived in a near-circular 400 km altitude orbit a few weeks ago ahead of its primary goal to seek out gases that may be linked to active geological or biological activity on Mars. The orbiter's Colour and Stereo Surface Imaging System, CaSSIS, took this stunning image, which features part of an impact crater, during the instrument's test period. The camera was activated on 20 March and was tested for the start of its main mission on 28 April.

The image captures a 40 km-long segment of Korolev Crater located high in the northern hemisphere. The bright material on the rim of the crater is ice. It is assembled from three images in different colours that were taken almost simultaneously on 15 April. (Credit: ESA)

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70-year-old mystery of how magnetic waves heat the Sun cracked

Scientists at Queen's University Belfast have led an international team to the ground-breaking discovery that magnetic waves crashing through the Sun may be key to heating its atmosphere and propelling the solar wind. The Sun is the source of energy that sustains all life on Earth but much remains unknown about it. However, a group of researchers at Queen's have now unlocked some mysteries in a research paper, which has been published in Nature Physics. In 1942, Swedish physicist and engineer Hannes Alfvén predicted the existence of a new type of wave due to magnetism acting on a plasma, which led him to obtain the Nobel Prize for Physics in 1970. Since his prediction, Alfvén waves have been associated with a variety of sources, including nuclear reactors, the gas cloud that envelops comets, laboratory experiments, medical MRI imaging and in the atmosphere of our nearest star -- the Sun. Scientists have suggested for many years that these waves may play an important role in maintaining the Sun's extremely high temperatures but until now had not been able to prove it.

A view of a sunspot on the solar surface, visible here as a dark collection of plasma with magnetic field strengths similar to those found in modern hospital MRI machines. However, it is the size of the sunspot, which is comparable to that of our own Earth (see the scale Earth depicted in the lower-right corner), that gives these structures immense power and energy. The recent work published in Nature Physics reveals first-time evidence for how a rare breed of magnetic waves, which originate within the centre of sunspots, can form shockwaves that heat the surrounding plasma by thousands of degrees. (Credit: Image courtesy of Queen's University, Belfast)

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Eclipse season starts for NASA's SDO

On Sunday, Feb. 11, 2018, NASA's Solar Dynamics Observatory, or SDO, saw a total solar eclipse in space when Earth crossed its view of the Sun. Also known as a transit, Earth's passage was brief, lasting from 2:10 a.m. to 2:41 a.m. EST and covering the entire face of the Sun. So marks the beginning of SDO's eclipse season—as well as the mission's eighth launch anniversary. SDO's eclipse season is a three-week period that comes twice a year near the equinoxes during which Earth blocks SDO's view of the Sun for a short while each day. The eclipses are fairly short near the beginning and end of the season but ramp up to 72 minutes in the middle. Most spacecraft observing the Sun from an orbit around Earth have to contend with such eclipses. SDO's orbit is designed to maximize the amount of data the spacecraft can send back to Earth, but twice a year Earth gets in the way of the spacecraft's view. The spring eclipse season began on Feb. 10 with a partial eclipse and concludes March 5, 2018.

On Sunday, Feb. 11, 2018, NASA's SDO saw a total solar eclipse in space. These images were taken in a wavelength of extreme ultraviolet light, a type of light that is typically invisible to our eyes, but is colorized here in purple. Credit: NASA's Goddard Space Flight Center/SDO/Joy Ng

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A better way to weigh millions of solitary stars

Astronomers have come up with a new and improved method for measuring the masses of millions of solitary stars, especially those with planetary systems. Getting accurate measurements of how much stars weigh not only plays a crucial role in understanding how stars are born, evolve and die, but it is also essential in assessing the true nature of the thousands of exoplanets now known to orbit most other stars. The method is tailor-made for the European Space Agency's Gaia Mission, which is in the process of mapping the Milky Way galaxy in three dimensions, and NASA's upcoming Transiting Exoplanet Survey Satellite (TESS), which is scheduled for launch next year and will survey the 200,000 brightest stars in the firmament looking for alien earths. "We have developed a novel method for 'weighing' solitary stars," said Stevenson Professor of Physics and Astronomy Keivan Stassun, who directed the development. "First, we use the total light from the star and its parallax to infer its diameter. Next, we analyze the way in which the light from the star flickers, which provides us with a measure of its surface gravity. Then we combine the two to get the star's total mass."

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Discovery of new planet reveals distant solar system to rival our own

The discovery of an eighth planet circling the distant star Kepler-90 by University of Texas at Austin astronomer Andrew Vanderburg and Google's Christopher Shallue overturns our solar system's status as having the highest number of known planets. We're now in a tie. The newly discovered Kepler-90i—a sizzling hot, rocky planet orbiting its star once every 14.4 days—was found using computers that "learned" to find planets in data from NASA's Kepler space telescope. Kepler finds distant planets beyond the solar system, or exoplanets, by detecting the minuscule change in brightness when a planet transits (crosses in front of) a star. Vanderburg, a NASA Sagan fellow at UT Austin, and Shallue, a Google machine learning researcher, teamed up to train a computer to learn how to identify signs of an exoplanet in the light readings from distant stars recorded by Kepler. Similar to the way neurons connect in the human brain, this "neural network" sifted through the Kepler data to identify the weak transit signals from a previously missed eighth planet orbiting Kepler-90, a sun-like star 2,545 light-years from Earth in the constellation Draco. "For the first time since our solar system planets were discovered thousands of years ago, we know for sure that our solar system is not the sole record holder for the most planets," Vanderburg said.

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Fifty years ago, Jocelyn Bell discovered pulsars!

A pulsar is a small, spinning star – a giant ball of neutrons, left behind after a normal star has died in a fiery explosion. With a diameter of only 30 km, the star spins up to hundreds of times a second, while sending out a beam of radio waves (and sometimes other radiation, such as X-rays). When the beam is pointed in our direction and into our telescopes, we see a pulse. 2017 marks 50 years since pulsars were discovered. In that time, we have found more than 2600 pulsars (mostly in the Milky Way), and used them to hunt for low-frequency gravitational waves, to determine the structure of our galaxy and to test the general theory of relativity. The discovery In mid-1967, when thousands of people were enjoying the summer of love, a young PhD student at the University of Cambridge in the UK was helping to build a telescope. It was a poles-and-wires affair – what astronomers call a "dipole array". It covered a bit less than two hectares, the area of 57 tennis courts. By July it was built. The student, Jocelyn Bell (now Dame Jocelyn Bell Burnell), became responsible for running it and analysing the data it churned out. The data came in the form of pen-on-paper chart records, more than 30 metres of them each day. Bell analysed them by eye.

CSIRO Parkes radio telescope has discovered around half of all known pulsars. (Credit: Wayne England, Author provided)

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Ο νάνος πλανήτης Haumea έχει δακτύλιο!

Κατά τη διάρκεια μια σπάνιας επιπρόσθησης ενός μακρινού αστέρα από έναν μικροσκοπικό πλανήτη, έγινε μια απρόσμενη ανακάλυψη: Ο νάνος πλανήτης Haumea βρέθηκε να έχει έναν δακτύλιο από σκόνη και θραύσματα πάχους 43 μιλίων (70 km). Η Haumea είναι πλέον επίσημα ο πρώτος νάνος πλανήτης που έχει ένα σύστημα δακτυλίων, ενώ μέχρι σήμερα γνωρίζαμε ότι αυτό ήταν προνόμιο μόνο των τεσσάρων αέριων γιγάντων πλανητών του Ηλιακού Συστήματος (Δίας, Κρόνος, Ουρανός, Ποσειδώνας) και του μικρού αστεροειδή με όνομα Χαρικλώ. Η ανακάλυψη αυτή σηματοδοτεί και την πρώτη φορά που έχουν βρεθεί δακτύλιοι σε ένα αντικείμενο της ζώνης Kuiper, η οποία είναι μια περιοχή με παγωμένα αντικείμενα πέρα από την τροχιά του Ποσειδώνα.

Το Γεροσταθοπούλειο Πανεπιστημιακό Αστεροσκοπείο Αθηνών (UOAO) και συγκεκριμένα ο Δρ. Κοσμάς Γαζέας και ο φοιτητής Λ. Τζουγανάτος, συμμετείχαν στο διεθνές αυτό πρόγραμμα παρατηρήσεων, ενώ τα ερευνητικά αποτελέσματα της σπάνιας αυτής επιπρόσθησης δημοσιεύθηκαν στο περιοδικό Nature.

Η πρωτότυπη δημοσίευση βρίσκεται εδώ.

Μια λεπτή ζώνη από θραύσματα περικυκλώνει τον νάνο πλανήτη Haumea, σε μια σχηματική αναπαράσταση με βάση την πρόσφατη ανακάλυψη. (ILLUSTRATION BY IAA-CSIC/UHU)

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Fly me to the Moon

By 2040, a hundred people will live on the Moon, melting ice for water, 3D-printing homes and tools, eating plants grown in lunar soil, and competing in low-gravity, "flying" sports. To those who mock such talk as science fiction, experts such as Bernard Foing, ambassador of the European Space Agency-driven "Moon Village" scheme, reply the goal is not only reasonable but feasible too. At a European Planetary Science Congress in Riga this week, Foing spelt out how humanity could gain a permanent foothold on Earth's satellite, and then expand.

The 1969-72 Apollo landings left us with an image of a lunar environment that was hostile and sterile. But scientists today says there is bounty in the Moon that can be unlocked with advanced technology, opening the way to a permanent human colony.

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Μερική Έκλειψη Σελήνης - 7 Αυγούστου 2017

Στις 7 Αυγούστου 2017 θα γίνει ορατή από την Ελλάδα μια Μερική Έκλειψη Σελήνης. Το ποσοστό της απόκρυψης στην έκλειψη αυτή αγγίζει το 25% και έτσι η γήινη σκιά θα καλύψει μόλις το 1/4 της σεληνιακής επιφάνειας. Το φαινόμενο θα είναι ορατό κατά τις πρώτες βραδινές ώρες και ιδιαίτερα κατά την ανατολή της Πανσελήνου από τον ανατολικό ορίζοντα. Η ανατολή της Σελήνης αναμένεται να πραγματοποιηθεί κατά τις 20:20 (τοπική ώρα), ταυτόχρονα με την έναρξη του φαινομένου. Η κορύφωση της έκλειψης θα σημειωθεί στις 21:22, όταν η Σελήνη θα βρίσκεται λίγες μοίρες επάνω από τον ορίζοντα, ενώ το φαινόμενο θα λήξει στις 22:20, όταν η Σελήνη θα εξέλθει από τη σκιά της Γης. Η μερική αυτή έκλειψη θα είναι ορατή από όλες τις περιοχές της Ελλάδας, ενώ μετά τη λήξη του φαινομένου η Πανσέληνος θα λάμπει κανονικά στον ουρανό για την υπόλοιπη νύχτα. Μην ξεχάσετε λοιπόν να απολαύσετε την Αυγουστιάτικη Πανσέληνο όπου κι αν βρίσκεστε, σε συνδυασμό με το φαινόμενο της μερικής έκλειψης!

Η Μερική Έκλειψη Σελήνης, όπως φωτογραφήθηκε από το Πανεπιστημιακό Αστεροσκοπείο Αθηνών στις 25 Απριλίου 2013 από τον Δρ. Κ. Γαζέα.

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Ολική Έκλειψη Ηλίου - 21 Αυγούστου 2017

Στις 21 Αυγούστου 2017 οι κάτοικοι της βορείου Αμερικής θα παρατηρήσουν τον Ήλιο να αποκρύπτεται σταδιακά από τη Σελήνη, μετατρέποντας την ημέρα σε νύχτα. Ταυτόχρονα, η θερμοκρασία θα πέσει αισθητά, ενώ στον ουρανό θα φανούν αστέρια και πλανήτες, ενώ ο Ήλιος θα εμφανίσει τους πίδακες πλάσματος που περιβάλλουν το ηλιακό στέμμα. Την ημέρα αυτή, οι ΗΠΑ θα βρίσκονται στο μονοπάτι της σκιάς της Σελήνης, σε μια Ολική Έκλειψη Ηλίου. Η συγκεκριμένη έκλειψη αποκαλείται "Great American Total Solar Eclipse" και η σκιά της Σελήνης διασχίζει τους ουρανούς από το Oregon μέχρι τη South Carolina, σε μια ζώνη μόλις 113 χιλιομέτρων στο έδαφος. Όσοι βρεθούν μέσα σε αυτήν τη "ζώνη της ολικότητας" θα γίνουν μάρτυρες ενός εξαιρετικά εντυπωσιακού φαινομένου.

Η Ολική Έκλειψη Ηλίου, όπως φωτογραφήθηκε από το Svalbard της Νορβηγίας στις 20 Μαρτίου 2015 από τον Δρ. Κ. Γαζέα.

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Four new short-period giant planets discovered

Astronomers have detected four new giant exoplanets as part of the Hungarian-made Automated Telescope Network-South (HATSouth) exoplanet survey. The newly found alien worlds are about the size of Jupiter, but less massive. They transit moderately bright stars and have short orbital periods. The findings were presented July 22 in a paper published on arXiv.org. HATSouth is a network of six astrograph telescope systems located in South America, Africa, and Australia. These telescopes are designed to detect transiting extrasolar planets in orbit around relatively bright stars visible from the Southern hemisphere. Since its launch in 2009, the network has already detected dozens of transiting exoplanets.

Unbinned transit light curves for HATS-43. Credit: Brahm et al., 2017.

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Japan reveals plans to put a man on moon by 2030

Japan has revealed ambitious plans to put an astronaut on the Moon around 2030 in new proposals from the country's space agency. This is the first time the Japan Aerospace Exploration Agency (JAXA) has said it aims to send an astronaut beyond the International Space Station, an agency spokeswoman told AFP on Friday. The idea is to first join a NASA-led mission in 2025 to build a space station in the moon's orbit, as part of a longer-term effort by NASA to reach Mars. Tokyo hopes that contributing to the multinational mission and sharing Japanese technology will land it a coveted spot at the station, from which it could eventually send an astronaut to the Moon, the spokeswoman said.

Japan has unveiled ambitious plans to put an astronaut on the moon around 2030 under new proposals from the country's space agency.

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Construction begins on the world's first super telescope

Scientists are a step closer to understanding the inner-workings of the universe following the laying of the first stone, and construction starting on the world's largest optical and infrared telescope. With a main mirror 39 metres in diameter, the Extremely Large Telescope (ELT), is going to be, as its name suggests, enormous. Unlike any other before it, ELT is also designed to be an adaptive telescope and has the ability to correct atmospheric turbulence, taking telescope engineering to another level. To mark the construction's milestone, a ceremony was held at ESO's Paranal residencia in northern Chile, close to the site of the future giant telescope which will be on top of Cerro Armazones, a 3046-metre peak mountain.

Artist's impression of the European Extremely Large Telescope (E-ELT) in its enclosure on Cerro Armazones. A 3046-metre mountaintop in Chile's Atacama Desert. The 39-metre E-ELT will be the largest optical/infrared telescope in the world.

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Brown dwarf binary discovered by microlensing

Using gravitational microlensing, astronomers have recently found a binary star composed of two brown dwarfs. The newly discovered system is the third brown-dwarf binary detected with this technique. The finding was presented in a paper published May 16 on the arXiv pre-print server. Gravitational microlensing is an invaluable method of detecting new extrasolar planets and brown dwarfs, regardless of the light they emit. This technique is therefore sensitive to the mass of the objects, rather than their luminosity, which allows astronomers to study objects that emit little or no light at all. Hence, due to their extremely low luminosities, brown-dwarf systems seem to be ideal targets for microlensing observations.

Light curve of the microlensing event OGLE-2016-BLG-1469. The upper panel shows the enlarged view of the anomaly around the peak.

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Επιτυχία του ΕΚΠΑ στον διαγωνισμό του Europlanet

Φοιτητές του Τμ. Φυσικής του ΕΚΠΑ σημείωσαν μεγάλη επιτυχία στον διαγωνισμό που διοργανώθηκε φέτος από το ευρωπαϊκό δίκτυο πλανητολογίας Europlanet. Στο πλαίσιο του φετινού διαγωνισμού Europlanet Funding Scheme 2017 βραβεύτηκαν δύο ομάδες, με την ομάδα του ΕΚΠΑ να λαμβάνει μια από τις δύο πρώτες θέσεις σε πανευρωπαϊκό επίπεδο.

Το Europlanet θα χρηματοδοτήσει τους φοιτητές του Τμήματός μας με το ποσό των 7000 ευρώ για την υλοποίηση της πρότασης με τίτλο "Planets in Your Hands" και τη προσομοίωση των διαφορετικών συνθηκών που επικρατούν σε κάθε πλανήτη του Ηλιακού μας Συστήματος.

Η ομάδα αποτελείται από προπτυχιακούς και μεταπτυχιακούς φοιτητές του Τμήματος Φυσικής του ΕΚΠΑ. Συγκεκριμένα, στην πρόταση αυτή συμμετέχουν οι φοιτητές: Αθανασόπουλος Δημήτριος, Καραμπότσιου Σέβη, Κεφαλά Κυριακή, Κωνσταντίνου Άννα, Παλαφούτα Σόφη, Παπαδάμη Αργυρώ, Σκλήρης Βασίλης, Τζουγανάτος Λευτέρης, Τριβυζά Μαρίλια, Χλιάρας Βαγγέλης, Χριστοπούλου Έλενα. Επιστημονικός υπεύθυνος για την υλοποίηση της πρότασης είναι ο Κοσμάς Γαζέας, Λέκτορας Παρατηρησιακής Αστροφυσικής του ΕΚΠΑ.

Στον φετινό διαγωνισμό, οι φοιτητές πρότειναν να κατασκευάσουν μακέτες πλανητικών επιφανειών, με τη μορφή κάδρων, παρουσιάζοντας τις ιδιαιτερότητες που έχει ο κάθε πλανήτης του Ηλιακού μας Συστήματος. Το σύνολο των κατασκευών θα παρουσιαστεί σε διάφορους χώρους (σχολεία, πανεπιστήμια, ιδρύματα κτλ) και θα λειτουργεί ως διαδραστικό έκθεμα. Έτσι θα δοθεί η δυνατότητα σε όλους τους επισκέπτες, ακόμη και σε άτομα με ειδικές ανάγκες, να δουν, να μάθουν και να αντιληφθούν δια της αφής και της όρασης τις ιδιαιτερότητες του κάθε πλανήτη.

Η χρηματοδότηση της πρότασης και η έναρξη των κατασκευών θα γίνει άμεσα, με σκοπό την έναρξη της έκθεσης το Σεπτέμβριο του 2017 και τη λειτουργία της για ένα χρόνο.

Στο πλαίσιο της υλοποίησης της πρότασης, θα δημιουργηθεί ιστοσελίδα ενημέρωσης, καθώς και επικοινωνίας μέσω των διαφόρων social media. Για την πρόοδο και την εξέλιξη της πρότασης θα γίνονται σχετικές ανακοινώσεις μέσω των παραπάνω μέσων ενημέρωσης.

Διαβάστε περισσότερα εδώ: Planets in your hands

Πληροφορίες για το διαγωνισμό: Europlanet

Η διάβαση του Ερμή στις 9 Μαΐου 2016

Οι πλανητικές διαβάσεις μπροστά από τον ηλιακό δίσκο είναι ένα σπάνιο φαινόμενο. Στο Ηλιακό μας Σύστημα μόνο ο Ερμής και η Αφροδίτη μπορούν να προβληθούν επάνω στην Ήλιο, εφόσον η τροχιά τους είναι πιο μικρής ακτίνας από αυτήν της Γης. Ο Ερμής περιφέρεται γύρω από τον Ήλιο σε ελλειπτική τροχιά κάθε 88 ημέρες. Ο συνδυασμός της τροχιακής περιόδου, της κλίσης της τροχιάς του και της απόστασής του από τον Ήλιο και τη Γη, δημιουργεί τις κατάλληλες προϋποθέσεις για διάβαση περίπου 13-14 φορές μέσα σε έναν αιώνα. Οι πιο πρόσφατες διαβάσεις του πλανήτη Ερμή ήταν το 2003 (ορατή από την Ελλάδα) και το 2006 (αόρατη από την Ελλάδα) και η επόμενη είναι στις 9 Μαΐου 2016. Δεδομένου ότι οι μελλοντικές διαβάσεις του Ερμή θα είναι το 2019 (μερικώς ορατή από Ελλάδα) και η επόμενη το 2032, γίνεται σαφές ότι το φαινόμενο της διάβασης είναι σχετικά σπάνιο. Το Γεροσταθοπούλειο Πανεπιστημιακό Αστεροσκοπείο Αθηνών, του Τμ. Φυσικής ΕΚΠΑ διοργανώνει μια ημερίδα με αφορμή το σπάνιο αυτό αστρονομικό γεγονός. Το φαινόμενο θα συμβεί κατά τις ώρες 11:12-18:42 UT (14:12-21:42 τοπική ώρα). Η εκδήλωση θα λάβει χώρα στις 9 Μαΐου 2016 στο Τμήμα Φυσικής του ΕΚΠΑ από τις 16:00 μέχρι τις 22:00.

Εικόνα από τη διάβαση του Ερμή το 2003.

Διαβάστε περισσότερα εδώ: (Δελτίο Τύπου) (Αφίσα)

Evidence for a habitable region within Saturn's moon Enceladus

Scientists from Southwest Research Institute (SwRI) have discovered hydrogen gas in the plume of material erupting from Saturn's moon Enceladus. Analysis of data from NASA's Cassini spacecraft indicates that the hydrogen is best explained by chemical reactions between the moon's rocky core and warm water from its subsurface ocean. The SwRI-led team's discovery suggests that Enceladus' ocean floor could include features analogous to hydrothermal vents on Earth, which are known to support life on the seafloor.

Read more here... (details)

NASA tests robotic ice tools

Since 2015, NASA's Jet Propulsion Laboratory in Pasadena, California, has been developing new technologies for use on future missions to ocean worlds. That includes a subsurface probe that could burrow through miles of ice, taking samples along the way; robotic arms that unfold to reach faraway objects; and a projectile launcher for even more distant samples.

Read more here... (details)

Comet 45P/Honda-Mrkos-Pajdušáková is coming!

Comet hunters still have a chance to see comet 45P/Honda-Mrkos-Pajdušáková in the next few days using binoculars or a telescope. It's the first of a trio of comets that will-between now and the end of 2018-pass close enough to Earth for backyard observers to try to spot and for scientists to study using ground-based instruments. Comet 45P will come closest to Earth on the morning of Saturday, Feb. 11, when it passes by at a distance of about 7.7 million miles (12.4 million kilometers), or more than roughly 30 times the distance between Earth and the moon. It is currently in the early morning eastern sky, though the full moon may make the comet more difficult to spot. Ground-based observations also are planned for comet 41P/Tuttle-Giacobini-Kresak, which will pass closest to Earth on April 1, 2017, and for comet 46P/Wirtanen, passing closest to Earth on Dec. 16, 2018.

Read more here... (details)

A contact binary will explode in 2022!

Calvin College professor Larry Molnar and his students along with colleagues from Apache Point Observatory (Karen Kinemuchi) and the University of Wyoming (Henry Kobulnicky) are predicting a change to the night sky that will be visible to the naked eye. Molnar's prediction is that a binary star he is monitoring will merge and explode in 2022, give or take a year; at which time the star will increase its brightness ten thousand fold, becoming one of the brighter stars in the heavens for a time. The star will be visible as part of the constellation Cygnus, and will add a star to the recognizable Northern Cross star pattern.

Read more here... (details)

NASA seeks planets like those in 'Star Wars: Rogue One'

In the "Star Wars" universe, ice, ocean and desert planets burst from the darkness as your ship drops out of light speed. But these worlds might be more than just science fiction. Some of the planets discovered around stars in our own galaxy could be very similar to arid Tatooine, watery Scarif and even frozen Hoth, according to NASA scientists. Sifting through data on the more than 3,400 confirmed alien worlds, scientists apply sophisticated computer modeling techniques to tease out the colors, light, sunrise and sunsets we might encounter if we could pay them a visit. Some of these distant worlds are even stranger than those that populate the latest Star Wars film, "Rogue One: A Star Wars Story." And others are eerily like the fictional planets from a galaxy far, far away.

Read more here... (details)

NASA completes Webb Telescope Center of Curvature pre-test

Engineers and technicians working on the James Webb Space Telescope successfully completed the first important optical measurement of Webb's fully assembled primary mirror, called a Center of Curvature test. Taking a "before" optical measurement of the telescope's deployed mirror is crucial before the telescope goes into several stages of rigorous mechanical testing. These tests will simulate the violent sound and vibration environments the telescope will experience inside its rocket on its way out into space. This environment is one of the most stressful structurally and could alter the shape and alignment of Webb's primary mirror, which could degrade or, in the worst case, ruin its performance.

Read more here... (details)

New crater on the Moon!

The moon's surface is being "gardened" by small impacts—more than 100 times faster than scientists previously thought. This means that surface features believed to be young are perhaps even younger than assumed. It also means that any structures placed on the moon as part of human expeditions will need better protection. This new discovery comes from more than seven years of high-resolution lunar images studied by a team of scientists from Arizona State University and Cornell University. The team is led by ASU's Emerson Speyerer, who is also the lead author of the scientific paper published Oct. 13 in Nature. When the team examined the new craters found by the LROC survey, they noticed that the craters were surrounded by starburst patterns that obviously formed during the impact. While the pattern details are complex, the researchers found that an impact throws out several kinds of debris. Some of it lands nearby. But impacts also throw small amounts of debris in hyper-velocity jets at speeds of 16 kilometers (10 miles) per second. This material—vaporized and molten rock—shoots over the surface, disturbing the upper layer of lunar soil and changing its brightness.

Read more here... (details)

Σεληνιακή Έκλειψη Παρασκιάς ορατή από την Αθήνα

Μια Σεληνιακή Έκλειψη Παρασκιάς θα είναι ορατή από την Αθήνα την Παρασκευή 16 Σεπτεμβρίου 2016! Η Σελήνη θα αρχίσει να εισέρχεται στην γήινη παρασκιά στις 19:55 (τοπική ώρα) και το μέγιστο της έκλειψης θα σημειωθεί στις 21:55 (τοπική ώρα). Το φαινόμενο θα διαρκέσει μέχρι τις 23:54 (τοπική ώρα), όταν η πανσέληνος θα ξαναλάμψει στον νυχτερινό ουρανό της Αθήνας. Κατά τη διάρκεια της μέχιστης φάσης της έκλειψης, η παρασκιά θα κρύψει ένα μικρό μέρος του σεληνιακού φωτός και δε θα είναι εύκολα αντιληπτό με το μάτι. Μην ξεχάσετε να παρατηρήσετε και να απολαύσετε το φαινόμενο αλλά και να βγάλετε φωτογραφίες! Η επόμενη Σεληνιακή Έκλειψη Παρασκιάς θα συμβεί στις 11 Φεβρουαρίου 2017.

Read more here... (details) and here... (map)

Supercomputer model of an impossibly bright 'monster pulsar'

Ultra Luminous X-ray sources (ULX), which are remarkably bright X-ray sources, were thought to be powered by black holes. But in 2014, the X-ray space telescope "NuSTAR" detected unexpected periodic pulsed emissions in a ULX named M82 X-2. The discovery of this object named "ULX-pulsar" has puzzled astrophysicists. Black holes can be massive enough to provide the energy needed to create ULXs, but black holes shouldn't be able to produce pulsed emissions. In contrast, "pulsars," a kind of neutron star, are named for the pulsed emissions they produce, but they are much fainter than ULXs. A new theory is needed to explain "ULX-pulsar."

Read more here... (article)

China's lunar-based telescope observes a binary star system

China's Chang'e-3 mission landed on the moon in December 2013 and deployed a lunar rover known as Yutu or Jade Rabbit; it also carried a robotic telescope designed to observe various celestial objects such as galaxies, active galactic nuclei, variable stars, binaries, novae, quasars and blazars in the near-ultraviolet band. The Lunar-based Ultraviolet Telescope (LUT) was recently used by a team of Chinese astronomers to observe a peculiar binary star designated V921 Her.

One can compare the light curve of the very same binary system with the one observed from the University of Athens Observatory here: (paper)

Read more here... (article)

First atmospheric study of Earth-sized exoplanets reveals rocky worlds

On May 2, scientists from MIT, the University of Liege, and elsewhere announced they had discovered a planetary system, a mere 40 light years from Earth, that hosts three potentially habitable, Earth-sized worlds. Judging from the size and temperature of the planets, the researchers determined that regions of each planet may be suitable for life.

Read more here... (article)

Theft Behind Planet 9 in Our Solar System

Through a computer-simulated study, astronomers at Lund University in Sweden show that it is highly likely that the so-called Planet 9 is an exoplanet. This would make it the first exoplanet to be discovered inside our own solar system. The theory is that our sun, in its youth some 4.5 billion years ago, stole Planet 9 from its original star.

Read more here... (article)

Astronomers find giant planet around very young star

In contradiction to the long-standing idea that larger planets take longer to form, U.S. astronomers today announced the discovery of a giant planet in close orbit around a star so young that it still retains a disk of circumstellar gas and dust. The planet, CI Tau b, is at least eight times larger than Jupiter and orbits a 2 million-year-old star about 450 light years from Earth in the constellation Taurus. Johns-Krull and a dozen co-authors from Rice, Lowell Observatory, the University of Texas at Austin, NASA and Northern Arizona University made the peer-reviewed study available online this week.

Read more here... (article)

Earth-like planet may exist in a nearby star system

An Earth-like planet may be lurking in a star system located just 16 light years away, according to a new research. The star, named Gliese 832, was recently investigated by a team of astronomers searching for additional exoplanets that may be residing between the two currently known alien worlds in this system. Gliese 832 is a red dwarf and has just under half the mass and radius of our sun. The star is orbited by a giant Jupiter-like exoplanet designated Gliese 832b and by a super-Earth mass planet Gliese 832c. The gas giant, with a mass of 0.64 Jupiter masses, is orbiting the star at a distance of 3.53 AU, while the other planet is potentially a rocky world, around five times more massive than the Earth, residing very close its host star—about 0.16 AU.

Read more here... (article)

Dance of Two Monster Black Holes

OJ 287 is one of the largest supermassive black holes known, weighing in at 18 billion solar masses. Located about 3.5 billion light-years away, this monster quasar is bright enough that it was first observed as early as the 1890s. This past December, researchers all over the world watched an outburst from the enormous black hole in OJ 287, an outburst that had been predicted years ago using the general theory of relativity. The University of Athens participates actively on photometric observations of this highly interesting target since 2006. The daily variations of OJ287 and the corresponding light curve is uptaded very frequently.

image credit: S. Zola & NASA/JPL

Read more here... (article) ...here... (article) ...here... (article) ...and here... (light curve)

Hubble breaks cosmic distance record

Using the NASA/ESA Hubble Space Telescope an international team of astronomers has measured the distance to this new galaxy, named GN-z11. This galaxy existed just 400 million years after the Big Bang and provides new insights into the first generation of galaxies. This is the first time that the distance of an object so far away has been measured from its spectrum, which makes the measurement extremely reliable.

Read more here... (full article)

Gravitational waves have been detected!

After 100 years of searching, an international team of physicists has confirmed the existence of Einstein's gravitational waves, marking one of the biggest astrophysical discoveries of the past century. It's a huge deal, because it not only improves our understanding of how the Universe works, it also opens up a whole new way of studying it.

Read more here... (full article)

James Webb Space Telescope mirror halfway complete

The 9th flight mirror was installed onto JWST structure with a robotic arm at NASA's Goddard Space Flight Center. This marks the halfway completion point for the James Webb Space Telescope's segmented primary mirror. The JWST team has been working tirelessly to install all 18 of Webb's mirror segments onto the telescope structure. The full installation is expected to be complete early in 2016.

Read more here... (full article)

Hubble checks out a home for old stars

This image, taken with the Wide Field Planetary Camera 2 on board the NASA/ESA Hubble Space Telescope, shows the globular cluster Terzan 1. Lying around 20,000 light-years from us in the constellation of Scorpius (The Scorpion), it is one of about 150 globular clusters belonging to our galaxy, the Milky Way. Terzan 1, like many globular clusters, is a source of X-rays. It is likely that these X-rays come from binary star systems that contain a dense neutron star and a normal star. The neutron star drags material from the companion star, causing a burst of X-ray emission. The system then enters a quiescent phase in which the neutron star cools, giving off X-ray emission with different characteristics, before enough material from the companion builds up to trigger another outburst.

Read more here... (full article)

LRO finds Apollo 16 booster rocket impact site

After decades of uncertainty, the Apollo 16 S-IVB impact site on the lunar surface has been identified. S-IVBs were portions of the Saturn V rockets that brought astronauts to the moon. The site was identified in imagery from the high-resolution LROC Narrow Angle Camera aboard NASA's Lunar Reconnaissance Orbiter. Beginning with Apollo 13, the S-IVB rocket stages were deliberately impacted on the lunar surface after they were used. Seismometers placed on the moon by earlier Apollo astronauts measured the energy of these impacts to shed light on the internal lunar structure. Locations of the craters that the boosters left behind were estimated from tracking data collected just prior to the impacts. Earlier in the LRO mission, the Apollo 13, 14, 15 and 17 impact sites were successfully identified, but Apollo 16's remained elusive. In the case of Apollo 16, radio contact with the booster was lost before the impact, so the location was only poorly known. Positive identification of the Apollo 16 S-IVB site took more time than the other four impact craters because the location ended up differing by about 30 km (about 19 miles) from the Apollo-era tracking estimate. (For comparison, the other four S-IVB craters were all within 7 km—about four miles—of their estimated locations.)

Read more here... (full article)

New Horizons returns new images of Pluto

NASA's New Horizons spacecraft has sent back the first in a series of the sharpest views of Pluto it obtained during its July flyby – and the best close-ups of Pluto that humans may see for decades. Each week the piano-sized New Horizons spacecraft transmits data stored on its digital recorders from its flight through the Pluto system on July 14. These latest pictures are part of a sequence taken near New Horizons' closest approach to Pluto, with resolutions of about 250-280 feet (77-85 meters) per pixel – revealing features less than half the size of a city block on Pluto's diverse surface. In these new images, New Horizons captured a wide variety of cratered, mountainous and glacial terrains.

Read more here... (full article)

First photo of planet in making captured

There are 450 light-years between Earth and LkCa15, a young star with a transition disk around it, a cosmic whirling dervish, a birthplace for planets. Despite the disk's considerable distance from Earth and its gaseous, dusty atmosphere, University of Arizona researchers captured the first photo of a planet in the making, a planet residing in a gap in LkCa15's disk. Of the roughly 2,000 known exoplanets—planets that orbit a star other than our sun—only about 10 have been imaged, and that was long after they had formed, not when they were in the making. This is the first time that we've imaged a planet that we can say is still forming.

Read more here... (full article)

The extreme binary system VFTS 352

Using ESO's Very Large Telescope, an international team of astronomers have found the hottest and most massive double star with components so close that they touch each other. The two stars in the extreme system VFTS 352 could be heading for a dramatic end, during which the two stars either coalesce to create a single giant star, or form a binary black hole.

Read more here... (full article)

The Curious Case of KIC 8462852

For the past few days, the media has been abuzz with one of the most peculiar astronomical observations for many years. As described in a recent paper, a faint star in the northern constellation Cygnus has been seen acting incredibly strangely.

Read more here... (full article) ...and here... (full article)

Ανανεώστε την ταπετσαρία σας!

Βαρεθήκατε τις ίδιες αφίσες και τις φωτογραφίες που κυκλοφορούν στο διαδίκτυο; Εδώ μπορείτε να βρείτε δύο φωτογραφίες-συνθέσεις από τις πρόσφατες εξορμήσεις μου για τη φωτογράφηση ολικών ηλιακών εκλείψεων. Η πρώτη (αριστερά) είναι από την Gabon στις 3 Νοεμβρίου 2013 και η δεύτερη (δεξιά) είναι από το νησί Svalbard στον Βόρειο Πόλο στις 20 Μαρτίου 2015. Αν τις χρησιμοποιήσετε για κάποια ανακοίνωση/δημοσίευση/ανάρτηση, παρακαλω να με ενημερώσετε και να αναφέρετε απαραιτήτως τον δικαιούχο.

Ώρες γραφείου - Πώς θα με βρείτε

Βρίσκομαι καθημερινά στη σχολή για αρκετές ώρες, συνήθως από τις 12 το μεσημέρι μέχρι αργά το βράδυ. Πολλές φορές βρίσκομαι στο Πανεπιστημιακό Αστεροσκοπείο (4ος όροφος του Κτηρίου IV του Τμήματος Φυσικής), είτε στο Εργαστήριο Αστρονομίας και Εφαρμοσμένης Οπτικής, είτε στο Εργαστήριο Αστροφυσικής (2ος όροφος του Κτηρίου IV του Τμήματος Φυσικής).

Εάν χρειαστεί να αφήσετε κάτι για μένα μπορείτε να το βάλετε στο γραμματοκιβώτιό μου (έναντι της Γραμματείας του Τομέα Αστροφυσικής) ή να το αφήσετε μέσα στη Γραμματεία με σημείωμα.

Η ιστοσελίδα είναι έτοιμη

Με την έναρξη του χειμερινού 6μήνου 2015-2016 δημιουργήθηκε η παρούσα ιστοσελίδα, με σκοπό την ενημέρωση των φοιτητών σε θέματα διδασκαλίας και λοιπά θέματα που αφορούν το Τμήμα Φυσικής, το Πανεπιστημιακό Αστεροσκοπείο και τον ευρύτερο ερευνητικό χώρο, στον οποίο εργάζομαι τα τελευταία χρόνια. Τα κείμενα, οι φωτογραφίες και οι ανακοινώσεις θα ανανεώνονται συχνά και ελπίζω να βρείτε τις πληροφορίες χρήσιμες.

Παρακαλώ τους επισκέπτες της ιστοσελίδας να είναι προσεκτικοί στη χρήση του διδακτικού, συγγραφικού και φωτογραφικού υλικού που παρέχεται. Οποιαδήποτε αναδημοσίευση αυτούσιων κειμένων ή τμημάτων αυτών, φωτογραφιών και άλλων προσωπικών αρχείων χωρίς την έγγραφη άδεια του δικαιούχου εμπίπτει στον νόμο περί κλοπής πνευματικής ιδιοκτησίας.


Η σελίδα αυτή δημιουργήθηκε από τον Κ.Γαζέα, και είναι βασισμένη σε πρότυπο της σελίδας: Free CSS Templates