Category Astronomy

In 2009, NASA launched a mission specifically to look for and detect exoplanets. What was it called?

In 2009, NASA launched a spacecraft called Kepler to look for exoplanets. Kepler looked for planets in a wide range of sizes and orbits. And these planets orbited around stars that varied in size and temperature.

Kepler detected exoplanets using something called the transit method. When a planet passes in front of its star, it’s called a transit. As the planet transits in front of the star, it blocks out a little bit of the star’s light. That means a star will look a little less bright when the planet passes in front of it.

When a planet passes in front of a star as viewed from Earth, the event is called a “transit”. On Earth, we can observe an occasional Venus or Mercury transit. These events are seen as a small black dot creeping across the Sun—Venus or Mercury blocks sunlight as the planet moves between the Sun and us. Kepler finds planets by looking for tiny dips in the brightness of a star when a planet crosses in front of it—we say the planet transits the star.

Once detected, the planet’s orbital size can be calculated from the period (how long it takes the planet to orbit once around the star) and the mass of the star using Kepler’s Third Law of planetary motion. The size of the planet is found from the depth of the transit (how much the brightness of the star drops) and the size of the star. From the orbital size and the temperature of the star, the planet’s characteristic temperature can be calculated. 

 

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Which was the first-ever exoplanet discovered?

Gamma Cephei Ab is an exoplanet approximately 45 light-years away in the constellation of Cepheus (the King). The planet was confirmed to be in orbit around Gamma Cephei A in 2002, but was first suspected to exist around 1988 (making this planet arguably the first true exoplanet discovered).

The first indications of Gamma Cephei Ab were reported in July 1988. The planet was tentatively identified by a Canadian team of astronomers, which was led by Bruce Campbell, Gordon Walker, and Stephenson Yang, while its existence was also announced by Anthony Lawton and P. Wright in 1989. Though not confirmed, this would have been the first true discovery of an extrasolar planet, and it was hypothesized based on the same radial velocity technique later used successfully by others. However, the claim was retracted in 1992 due to the quality of the data not being good enough to make a solid discovery.

On September 24, 2002, Gamma Cephei Ab was finally confirmed. The team of astronomers (including William D. Cochran, Artie P. Hatzes, et al.) at the Planetary Systems and their Formation Workshop announced the preliminary confirmation of a long-suspected planet Gamma Cephei Ab with a minimum mass of 1.59 MJ (1.59 times that of Jupiter). The parameters were later recalculated when direct detection of the secondary star Gamma Cephei B allowed astronomers to better constrain the properties of the system.

 

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What is a Telescope and it’s various types?

TELESCOPES

A telescope is an instrument that makes distant objects appears closer, allowing the viewer to see details that are not visible with the naked eye. Terrestrial telescopes are used for spotting wildlife (binoculars are made up of two telescopes, one for each eye), on gun sights and in periscopes. Astronomical telescopes are used to study objects in space. Terrestrial telescopes and most astronomical telescopes are optical telescopes, which collect light coming from distant objects and use it to produce images of the objects.

Italian scientist Galileo used the first astronomical telescope in 1609, with which he discovered moons around Jupiter.

There are two main types of optical telescope – refracting telescopes and reflecting telescopes. In a refracting telescope, a convex (bulging) lens collects light from the distant object and focuses it to form an image of the object. This image is very small, but is much larger than the image formed in the human eye. In a reflecting telescope, a concave (dish-shaped) mirror collects the light from the object and focuses it to form the image. Larger telescopes are nearly always reflecting telescopes because large mirrors are easier to manufacture than large lenses.

The Keck telescope in Hawaii has a main mirror 10 metres across. It is housed in a special building called an observatory.

The larger the lens of a refracting telescope or the mirror of a reflecting telescope, the brighter the image of the object observed, and the fainter the objects that can be seen with the telescope. The image is viewed with an eyepiece lens, which works like a magnifying glass to make it appear much larger.

RADIO TELESCOPES

Objects in space, such as stars and galaxies, do not just give off light. They also give off radiation from other parts of the electromagnetic spectrum, such as infrared radiation, radio waves, X-rays and ultraviolet radiation. These can show up objects that are otherwise invisible. They cannot be seen with ordinary optical telescopes, so special telescopes are needed.

Radio telescopes have a huge dish that acts as a reflector, collecting radio waves and focusing them on to a detector. Radio astronomy has allowed the discovery of new celestial objects, such as pulsars.

SPACE TELESCOPES

The Earth’s atmosphere stops many types of radiation from reaching the surface. To study these sorts of radiation, space telescopes must be launched into Earth orbit. They need special mirrors to reflect and focus the radiation, and electronic detectors to record the images formed, which are radioed back to Earth. Optical telescopes also benefit from being in orbit because the atmosphere distorts light rays as they pass through it. The Hubble Space Telescope, launched by space shuttle in 1990, is the most complex space telescope so far. It can detect visible light, infrared and ultraviolet rays.

The Hubble Space Telescope can see 10 times more detail than Earth-based telescopes and objects 50 times as faint. Solar panels provide its power. Images are transmitted via antennae.

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What are the phases of the Moon?

Every night many of us eagerly wait for the Moon to rise. But each night, the Moon looks slightly different from what it did the previous night. Sometimes the Moon looks like a narrow crescent, while at other times it looks like a big circle. On some nights, you might not see the Moon at all. These different shapes of the Moon that we see at different times of the month are called the Moon’s phases.

Does the Moon really change shapes?

No, the Moon does not change its shape. But it appears different to us because our view of the Moon changes based on how much of the Moon is illuminated by the Sun. The Moon does not produce its own light. It depends entirely on the Sun for light, like all the planets in our solar system. The Sun’s light comes from one direction, thereby illuminating one half of the Moon that is facing the sun, while the other half remains in darkness.

On Earth, our view of the illuminated part of the Moon changes each night depending on where the Moon in its orbit around the Earth. When we see the completely illuminated part of the Moon, that phase of the Moon is known as a Full Moon.

Each night following the Full Moon, as the Moon orbits around the Earth, we start to see less of the Moon illuminated by the Sun until we see no Moon at all. This phase is called the New Moon, when the far side of the Moon is facing the Sun and the side facing the Earth is dark.

The eight phases

According to NASA, the Moon has eight phases which we see one after the other as the Moon completes its cycle around the Earth. It takes the Moon 27 days to orbit Earth. The eight phases are:

New – When we cannot see the Moon at all

Waxing Crescent – When we see the Moon as a think crescent opening to the left. Waxing is when the Moon is growing with light.

First Quarter – When we see the first quarter phase of the Moon which appears to us as a Half Moon.

Waxing Gibbous – The phase between Half and Full Moon, when most part of the Moon can be seen.

Full – When we see the Moon completely illuminated.

Waning Gibbous – The phase between Half and Full Moon. Now, the view of the Moon is getting smaller.

Third Quarter – The third quarter of the Moon, seen as Half Moon on Earth. In this, the opposite half of the First Quarter is illuminated and visible.

Waning Crescent – When we see the Moon as a thin crescent opening to the right.

 

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What are Asteroids?

ASTEROIDS

Asteroids are small, mostly rocky, irregular-shaped bodies. They are found orbiting the Sun in a band filling the 550-million-kilometre gap between Mars and Jupiter. The largest, Ceres, measures just under 1000 kilometres across, but only a handful have diameters greater than 100 kilometres. About 4000 have been recorded, but there are many thousands more too small to be identified.

Astronomers believe that, during the formation of the Solar System, Jupiter’s strong gravitational pull caused nearby planetesimals to smash into one another rather than build up into another planet. This left the belt of fragments we call the asteroids.

The asteroids have continued to collide with one another since their formation, producing smaller fragments called meteoroids. These have occasionally crashed on to Earth’s surface (when they are known as meteorites). It is feared that one day a large meteorite may devastate Earth, causing climatic change sufficient to wipe out many life-forms.

            Most asteroids are rocky, indicating they come from the outer layers of a former minor planet. But some are metallic – they come from the core of such a planet.

            A close-up view of the irregular shaped objects that make up the asteroid belt between Mars and Jupiter. From study of asteroid fragments that have fallen to Earth, scientists have dated the age of the Solar System to 4.6 million years ago.

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What are comets?

COMETS

Comets are potato-shaped lumps of dust measuring only a few kilometres across, but accompanied by (when near the Sun) tails of has or dust that stretch for hundreds of millions of kilometres across space. The lump of dust is fused together by frozen gases and water ice. Like all other objects in the Solar System, comets orbit the Sun, although their orbits are often very elliptical (elongated ovals), looping in towards the Sun from distant reaches of the Solar System. When a comet approaches the Sun, part of its ices melt and the gas and dust escape, forming a surrounding cloud, or coma. As it rounds the Sun, the coma is swept back into two tails, a straight gas tail and a broader, curved dust tail, always pointing away from the Sun.

Sometimes, small pieces of debris break off from comets. Great showers of these fragments, called meteors, sometimes come quite close to Earth. Millions of tiny particles burn up in Earth’s atmosphere. Commonly known as shooting stars, they appear to us as split-second streaks of light in the night sky.

FAMOUS COMETS

The English astronomer Edmund Halley (1656-1742) was the first to realise that comets were orbiting objects. He once made a famous prediction: a comet that he observed in 1682 would return to the skies in 1758. Halley believed that comets recorded in 1531 and 1607 were simply earlier sightings of the one he saw in 1682. Halley did not live to see his prediction come true. Halley’s Comet, as it has been known ever since, was duly sighted on Christmas Day 1758 and has reappeared every 75 to 76 years. When Halley’s Comet appeared in March 1986, the space probe Giotto flew within 600 kilometres of it, sending back pictures and sampling the gases and dust particles given off by it.

A sighting of a comet is always a great event. The 1997 appearance of Comet Hale-Bopp was the most spectacular of recent years. Comets can also be destructive if they pass too close to a planet. In July 1994, drawn in by gravity, fragments of Comet Shoemaker-Levy smashed into Jupiter, creating massive fireballs on impact.

            On 30th June 1908 there was a huge explosion in the Tunguska region of Siberia, Russia. Trees in an area about 100 km across were felled by the blast, but no crater was found. The Tunguska fireball may have been a comet exploding at an altitude of about 6 km.

Picture Credit : Google