February 3, 2011
First, a little about the mission, The Kepler spacecraft is a mission launched in March 2009 which was designed to search for small exoplanets by measuring almost constantly the brightness of more than 156,000 stars in a small patch of the sky. The 0.95m-telescope is able to detect a dip in the light coming from the host stars which could be due to the transit of an exoplanet passing between its star and us, like the Moon passes between the Earth and the Sun during a solar eclipse. When this happens it can give us a direct estimate of the size and orbit of the eoxplanet.
The Kepler mission has released 1,200 exoplanet candidates from data collected with the Kepler spacecraft around 150 days of observation time. This marks a new age in astronomy, there will be before and after Kepler era.
The Kepler team released the data from the first 150 or so days of operation. A careful statistical analysis done by the team concludes that 80-90% of these candidates are probably real. The total count of explanets currently contains 519 exoplanets which were discovered over 15 years of observations. In almost 4 months of operation, the Kepler mission has found 1,200 exoplanets!
Many of these exoplanets orbit around smaller and cooler stars than our Sun. The surface temperature of the exoplanets could allow liquid water to exist on the surface of these planets. In their paper, the Kepler team lists ~60 candidates with sizes ranging from Earth-size to larger than that of Jupiter which are in the Habitability Zone of their host star. This is one of the most extraordinary result of this survey! If we wish to find Earth-like planets with water on them, we need to look for exoplanets in the Habitability Zone, an area which isn’t too hot or too cold for water to exist. This zone is also called the Goldilocks Zone.
With these results, we can now say that stars in the Milky Way galaxy are more likely to have small exoplanets since 70% of the exoplanets discovered are smaller than Neptune, with a peak of exoplanets only 2-3 times larger than Earth. Using model predictions the team calculated that 6% of the stars in our Milky way have Earth and super-Earth size exoplanets. Since the Milky Way has around ~200 billion stas, that makes it ~12,000,000,000 stars with Earth-like planets!
The Kepler mission is still in operation and collecting new data. In a few years time, we can expect to have a more accurate and complete catalogue, which might contain smaller exoplanets, exoplanets orbiting further from their host star and even the exomoons of these exoplanets. Different groups of astronomers are now going to go through the catalogue and study the vast variety of worlds found. We can expect a lot of exciting news in the coming weeks. To start it off, here’s a very cool mini solar system with a lot more still to come.
If you go out tonight, take some time out to look at the sky and think that among the 2,500 stars that you can see with the naked eye, a third of them may have an exoplanet. Worlds which might be very different or very similar to ours, how many different worlds can you think of?
There are a lot of interesting worlds out there, now we just need to explore them. Welcome to the golden age of astronomy.
August 1, 2010
Right now, the Earth is passing through fragments and dust trails created by the Comet Swift-Tuttle and this means the Perseids Meteor Shower has begun and will be getting stronger each day and it will peak from August 11-14. Lewis Swift and Horace Parnell-Tuttle discovered the Swift-Tuttle Comet in July of 1862. The comet passed by Earth in 1992 and will not return again until 2126, however the dust left behind by this comet creates a dependable annual meteor shower, the Perseids. The Perseids is named after constellation Perseus because meteors seem to spread out from an area surrounding the constellation, this is called the radiant.
The Perseids Meteor Shower will peak in the morning of August 12, meteors can be seen anywhere in the sky. The main thing to viewing any meteor shower is to find a safe, dark place away from man-made lights and lean back in a relaxing position looking toward the darkest part of the sky. Sometimes the Moon can be a hindrance, but this year the Moon will not be shedding much light, as during the peak it will be a waxing crescent Moon phase, so this means more visible meteors.
It is predicted that The Perseids Meteor Shower is going to have some great activity this year, up to 100 meteors per hour! It promises to be the best meteor shower this year. The meteors (shooting stars) are produced when debris left behind by a comet ranging from, as big as grains of sand to the size of a pebble, enter the Earth’s atmosphere with speeds reaching, 70 kilometres per second, and burn high up in the atmosphere due to friction and vaporise which causes them to glow brightly. A lot of junk hits our atmosphere so a good way to find out if you’re looking at a sporadic meteor or one from Perseids is to find where it originates from, if its moving away from the radiant it probably belongs to Perseids, if it’s going towards the radiant it’s a sporadic one, it’s always a good idea NOT to look directly at the radiant, as most meteors are going away from it. If you’re unlucky and have cloudy skies, don’t’ worry, you can hear the meteors! Just take an old radio out and tune it to the lowest frequency and you can hear the meteor echoes which sound like this. You can find more about meteor echoes here.
Meteor showers are one of the most spectacular astronomical events and it’s really easy to catch them, all you have to do is go out and look up, you don’t need anything but a dark clear patch of sky! And like most outdoor activities it’s best when you share the experience with your friends and family, the more eyes you have on the sky the more chances you have of catching the meteors streak across. I have a deep connection with meteor showers, when I saw my first one, it mesmerised me and inspired me to learn more about the sky above!
The Perseids Meteor Shower promises to be one of the best meteor showers of the year with lots of meteors streaking across the sky, you should definitely go out and see it!
July 12, 2010
Click to Embiggen
From Cassini, 1,460,000,000 km away, comes this great image of the majestic rings of Saturn lit up brightly by the Sun. This is a raw image, it hasn’t been processed, that spot in the middle of the image is probably a cosmic ray hit.
Saturn’s rings are not a simple disk, but it is actually made up of thousands of separate rings. The big dark gap in the rings is called the Cassini Division, discovered by the astronomer Giovanni Domenico Cassini in the 17th century. Saturn’s moon Mimas is responsible for that gap; any particle in the Cassini Division orbits Saturn in half the time Mimas does, and so it feels a periodic tug from the moon (called a resonance). That pulls the particles clear from that region, carving a gap. Other broad gaps in the rings are from other moon resonances, while some of the narrow ones are from small moons in the gaps gravitationally clearing out nearby ring particles.The rings are made up of icy particles,they range in size from, about a grain of sand to the size of a small house, but on average they are the size of your clenched fist. The rings extend from about 74,000 kilometres to about 180,000 kilometres from Saturn’s centre, but they are very thin, less than a hundred metres thick! A scale model of the rings as thick as a single piece of tissue paper would cover an entire football field! It’s still unclear how Saturn, or the other three gas giants, got their rings, but there is more than one mechanism to get them, a moon could get hit by an asteroid or comet shattering it.
There’s a lot we don’t know about Saturn and its rings, but Cassini has been orbiting Saturn for a while, it’s taken some amazing images of Saturn and everything around it. Cassini is helping us solve the mysteries of the Saturn and its surroundings in far better detail than ever before. It has produced some of the highest resolution images of the ringed planet and its moons.
You can scour the Cassini image gallery yourself, click here.
July 9, 2010
The sample canister of Hayabusa, the troubled probe which had a dramatic re-entry back in June, has now been opened and it has some material in it! This is great news! Due to malfunctions it wasn’t clear if the probe managed to collect material from the rubble pile asteroid Itokawa, but JAXA has found a very small amount of dust particles in the container. It isn’t clear if the dust grains which are very small, about 0.01-millimeter in size, are from the asteroid itself, or if it could be from Earth — left in the container from before launch, or it possibly could have made its way in there during the landing/post landing handling. “Material on the planet or asteroid or particulate matter is at this stage is unknown, we will consider in detail,” is the Google translate version of the JAXA press release. The image above was taken on June 28, 2010, and below is a magnified view of one of the particles.
This magnified view was taken on June 29, and shows a magnified view of one very small particle being picked up by a quartz manipulator, which appears as a stripe on the image. It will take several weeks to confirm whether the particles are from the asteroid, but if so, would be the first-ever asteroid sample return.
What do you think about this? Do you think Hayabusa brought some asteroid dust back? Or maybe we can just ask Paul the Octopus! Leave a comment!
Astronomers have now confirmed that an object imaged back in 2008 is a direct image of an exoplanet orbiting a star.
This image, taken in 2008 by the Gemini North telescope in Hawaii, shows the star 1RXS J160929.1-210524 (I’ll call it 1RXS 1609) in the center, and the planet (1RXS 1609b) indicated by the red circle. The star is a bit smaller and slightly cooler than our sun.
The problem was, that the object might have been a background object like a star or a background galaxy. It has happened before. However, follow-up observations have shown that it is neither a star nor a galaxy, it is indeed a planet orbiting the star.
On this graph, the separation of the object and the star are shown in the y-axis, and time is shown on the x. The star is moving slowly as it orbits the centre of our galaxy. If the object was moving separately it would be near the or on the purple line, changing as they moved separately. If the object were a planet the separation wouldn’t change much as they moved together across the sky. The observation of the planet is shown as black dots in this picture, they fall right on the line making it an object orbiting a star, which pretty much makes this a planet.
The star is about 500 light years away and the planet has a mass 8 times that of Jupiter, it orbits the star 47 billion kilometres away, that’s about 300 times the distance of Earth form the sun and has a temperature of about 1500 C. The star is a bit less massive than the sun and not nearly hot enough to heat the planet up to that temperature. The reason the planet is so hot is that it’s very young. The contraction of the planet under its own gravity during its formation quickly raised its temperature to thousands of degrees. Once this contraction phase is over, the planet will slowly cool down by radiating infrared light. In billions of years, the planet will eventually reach a temperature similar to that of Jupiter.
This discovery is a great technological achievement because the planet and the star are very close together, it’s very difficult to separate them. From the ground the Earth’s atmosphere blurs out the image and scatters the light of the star, making it very difficult to see objects like this. Even more remarkable thing is that they even got the spectra of the planet and used that to determine the temperature of the planet.
However, it’s not he the first the first planet which has been directly imaged. That title belongs to planet 2M1207b, which orbits a brown dwarf about 230 light years away. While brown dwarfs are cooler and smaller than the Sun, and they don’t fuse hydrogen into helium in their core, some people don’t consider them real stars. So it’s not really a sun-like star. But a planet orbiting a sun-like star has already been observed by telescopes in space. Since this observation was made from a ground based telescope, it is the first planet directly observed orbiting another star from a ground based telescope, which is very cool. It’s easier to make observations from space than it is from the ground, on the ground there is a lot of atmospheric scattering which makes the task a lot more difficult and that makes it much more remarkable.
We’re directly seeing worlds orbiting other stars from our world…THAT’S AWESOME!