The monthly session of AASTRO Thiruvananthapuram was conducted on 5th January at its usual venue and time. This time it was a talk lead by Dr. Ajith Prasad from M G College on 'Extraplanetary objects in the solar system'. Usually the word 'solar system' brings to our mind the sun and the eight planets around it. We often forget the other members of sun's family such as dwarf planets, asteroids, comets, jupiter trojans, oort clouds etc.
AASTRO 2012 Feb Public Lecture
Dr. Ajith Prasad gave a brief outline of such objects. There followed a discusion on the topic where teachers, students and other interested people in the subject participated. After the session, there was a short observation session on the mercy of the available sky.
Astronomers have announced the discovery of orbiting stars like our sun, and one of these — named HD85512b — is generating excitement among scientists as a possible candidate for harboring life. This extraordinary haul of new planets, made by a team of astronomers using data gathered at the European Southern Observatory in Chile, increases the number of known "exoplanets" orbiting distant suns to 573. Here, a brief guide:
How did astronomers discover these planets?
They used an instrument known as the High Accuracy Radial velocity Planet Searcher, or HARPS. The HARPS instrument can tell when a distant star "wobbles" slightly. This consistent pattern of back-and-forth movement suggests that a distant star is being orbited by a planet, and the star's wobbling is the result of that planet's gravitational pull. That's how the astronomers located 16 "" among the 50 new planets.
This artist’s impression shows the planet HD 85512b orbiting the Sun-like star HD 85512 about 35 light-years from Earth. This planet is about 3.6 times as massive as the Earth is at the edge of the habitable zone around the star, where liquid water, and perhaps even life, could potentially exist. CREDIT: ESO/M. Kornmesser View full size image
What exactly is a "super-Earth"?
Any planet that's up to 10 times the size of Earth. Dozens are known to exist. These planets may be rocky or gaseous, and there's no guarantee that they are in the "Goldilocks" zone of not too hot and not too cold to contain liquid water or other criteria needed to sustain life. However, many astronomers believe that a planet the size of a super-Earth is the ideal place for finding the right conditions for biological activity.
Could planet HD85512b really harbor life?
Maybe. The conditions seem ideal, since the planet is close enough to its sun to have liquid water on its surface, and its size suggests that it could have a solid, rocky surface. "If we are really, really lucky, this planet could be a habitat" says astronomer Lisa Kaltenegger of the Max Planck Institute in Germany, .
How will we know for sure
First, astronomers need a photograph of the planet to look for signs of water, carbon dioxide, and other compounds. No telescope is sensitive enough for that high-resolution image, since the planet is about 36 light-years away. But construction on a powerful new telescope, the European Extremely Large Telescope, will begin next year, and that instrument could answer many questions about distant planets like HD85512b.
NASA's Kepler space telescope, in an Earth trailing Solar Orbit, designated Kepler-11 about two thousand light years from Earth.
Five of the planets, ranging from 2.3 to 13.5 times the mass of the Earth, are orbiting Kepler-11 in a tight orbit that has a period of only about fifty days, closer to the their star than Mercury is to the Sun. The sixth planet is larger and farther out with an orbital period of 118 days and has a mass yet to be determined.
The Kepler space telescope's mission is to find Earth-like planets orbiting other stars, which would be about the same size and mass as the Earth with an orbit around a star similar to the Sun in the "zone of habitability", far enough out to not be too warm, but not so far as to be too cold. While Kepler has been, it has yet to discover another Earth. The discovery at Kepler-11 comes close and is, in itself, scientifically significant.
The Kepler detects planets by measuring the slight decrease in a star's brightness when a planet transits in front. The size is determined by the amount of decrease. The orbital period is determined by the time between transits.
Usually when a new planet is discovered, its mass is measured with Doppler spectroscopy which determines the amount of star's wobble that the gravitational pull of the planet causes. But Kepler-11 is too far away and the planets too small to use this method. Instead scientists measured the variations of the orbital periods caused by gravitational interactions among the planets.
Most new planets that have been discovered orbiting other stars have been gas giants, some of them much larger than Jupiter, the largest planet in our solar system, and mostly just one planet per star. The Kepler-11 discovery is remarkable in the number, size, and orbits of the newly discovered planets. Though none of Kepler-11's world could sustain life (at least as we know it) the discovery will allow scientists to study the interactions of a multi planet solar system, other than our own, for the first time in history.
The Kepler-11 discovery, while remarkable, is still short of the hoped filled detection of an Earth-like world orbiting another star. When that happens, whether it is on the Kepler mission or by some other means, the perception of humankind's role in the universe will change. Other Earth-like planets have been a staple of science fiction for many decades and scientists, simply by the law of averages, believe that other Earths exist. But the confirmation of one would be the most significant scientific discovery of this century so far.
CREDIT : Mark Whittington,Yahoo Contributors Network
Mark R. Whittington is the author of Children of Apollo and The Last Moonwalker. He has written on space subjects for a variety of periodicals
Jupiter has lost one of its prominent stripes, leaving its southern half looking unusually blank. Scientists are not sure what triggered the disappearance of the band.Jupiter's appearance is usually dominated by two dark bands in its atmosphere – one in the northern hemisphere and one in the southern hemisphere.But recent images taken by amateur astronomers show that the southern band – called the south equatorial belt – has disappeared.The band was present at the end of 2009, right before Jupiter moved too close to the sun in the sky to be observed from Earth. When the planet emerged from the sun's glare again in early April, its south equatorial belt was nowhere to be seen.
This is not the first time the south equatorial belt has disappeared. It was absent in 1973 when NASA's spacecraft took the first closeup images of the planet and also temporarily vanished in the early 1990s.The bands may normally appear dark simply because pale, high-altitude clouds prevalent in other regions of the planet are missing there, revealing darker clouds below.
The belts are composed of ammonia ice, with a little sulfur and phosphorus thrown in. Scientists aren't quite sure how to account for them - one theory is that they are simply gaps in higher, paler clouds that allow the darker, deeper levels to show through.
It's not the first time the belt has disappeared - indeed, it happens every three to fifteen years. it last went missing in the early 1990s, and before that in 1973.This time, though, the disappearance happened as the planet spent a three-month period behind the sun, so that on its emergence the transformation appears rather more sudden.Over the next few months, we can expect to see a white spot appear which will gradually get stretched out by the planet's 350mph winds to form a new SEB.
AASTRO Kerala Thrissur chapter inaugurated yesterday here by by Prof K Pappootty CMS Higher Secondary School, Thrissur on a function presided by eminent amateur astronomer and AASTRO Thrissur Chapter Chairman Shri.P R Chandramohan.District coordinator Shri.K S Sudheer gave the welcome address and Shri.Venugopalan delivered vote of thanks.Astronomy and science popularisation activists ,teachers,students and public from various parts of the district were participated in the programme.
Soon after the function there was an interactive session on Evolution of Solar System lead by Prof.Pappootty which nourished the audience.Vivid activities and programmes for AASTRO Thrissur chapter were planned in the meeting and responsibilities assigned for members to implement it. More details regarding are available with District point of contact;Ph :+91-9495576123
The planet Saturn reached opposition this past weekend, rising as the sun sets and making its closest approach to Earth this year. The planet saunters across Virgo over the next few weeks: it’s the brightest object between the stars Porrima in Virgo and Denebola in Leo. Saturn is truly one of the prettiest sights you can see with a telescope.
planet saturn_closest encounter
As a gas giant and the second largest planet in the solar system, Saturn is much like Jupiter. It has no solid surface. It’s made of cold hydrogen and helium gas in its outer layers, with no solid surface. Like Jupiter, it likely has a solid rocky core that’s 10x Earth’s mass. And it has a strong magnetic field and a huge collection of 60 moons, almost as many as Jupiter.But Saturn differs from Jupiter and the other gas giants is ways that make it especially fascinating.
Its rings, for example. While Jupiter and Uranus have faint rings, Saturn has the brightest and most complex ring system in the solar system. No one knows for sure how or when the rings were formed. They might have assembled with the planet 4.5 billion years ago. Or they may have formed just 100 million years ago when a small moon or comet came too close to the planet and was ripped to pieces by tidal forces. In any case, Saturn’s rings are made mostly from tiny ice particles that extend from 6,600 km to 120,000 km directly above the equator of the planet. The whole set of rings, despite their extent, are just 10-20 meters thick.
Saturn Rings
The gravity of the planet and several embedded “shepherd moons” segment the rings into amazingly complex filamentary structures.The rings are organized into four main sections labelled from A, the outermost ring, to D which is closest to the planet. On a clear night with a small scope, you can see the A and B rings. And you can see the narrow gap between these rings. This gap is the Cassini division.
While it’s a mighty big planet, Saturn is just 30% as massive as Jupiter. But it spans 84% of Jupiter’s diameter. That means it’s far less dense than Jupiter, or any other planet in the solar system. It has just 68% the density of water, which means it would float in the bathtub (if you had a big enough bathtub).
Saturn also rotates quickly… just once every 10 hours… so it’s flattened at the poles more than any other planet. Although since the surface isn’t solid, it’s a little tricky to get a good estimate of the rotational period; astronomers figured out the true rotation period of the planet by measuring the magnetic field.
The face of Saturn shows a few faint bands, but few other features. Though there is the matter of the strange white storm that appears on the surface every 30 years or so…
The “Great White Spot”, as it’s called was observed from Earth in 1876, 1903, 1933, and 1960, and 1990. The spot is presumably a storm that assembles in the atmosphere or bubbles up to the outer layers. It starts small, then spreads out for several weeks before disappearing. It seems to correspond to summer solstice in Saturn’s northern hemisphere, and occurs one per revolution of the planet around the sun. The next appearance of this mysterious spot is due around 2020.
As for moons, well, Saturn has a gaggle of them, each as distinct as snowflakes. Titan is the largest. It’s bigger than our moon, and is large enough to have .
But Enceladus, Saturn’s sixth largest moon, is perhaps the most intriguing. Though its surface is cold, Enceladus has liquid water under its surface. The water is warmed by tidal forces, and sometimes which were recently imaged by the Cassini space probe. Warm liquid water suggests the interior of Enceladus is a good place to search for life in the solar system.
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