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.


Keplers over 1200 Planet candidates sorted by size

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 FOV of view of Kepler with the location of the exoplanet candidates and their family classification per size (credit: NASA-Kepler team)

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!

The figure summarizes the candidate size versus orbital period and candidate equilibrium temperature. The horizontal lines mark the limit between these families of 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.

Artistic illustration of the multiple planetary system Kepler-11 (credit: Nature / NASA / Ames / JPL-Caltech / T. Pyle)

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.


Hayabusa's sample return canister was opened to reveal a small particle inside. Credit:

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.

Magnified view of a dust particle in the Hayabusa canister. Credit: JAXA

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!

An aurora seen over the South Pole, from the ISS. Credit: Doug Wheelock, NASA.

From Doug Wheelock’s Twitpic page, an astronaut on the International Space Station (ISS), comes this brilliant image of the Southern Lights (Aurora Australis) as seen from the ISS.

The northern (Aurora Borealis) and The southern (Aurora Australis) are caused when the charged particles (ions) from the Sun hit the Earth. The ions from the Sun excite the electrons of the atoms in the atmosphere which in turn emit a photon (light). Different atoms release light in different colours, the greenish colour seen here is emitted by oxygen atoms.

Doug Wheelock has some out of this world pictures on Twitpic page, check it out!

Welcome back, Hayabusa!

June 14, 2010

After long and treacherous journey the Japanese probe Hayabusa has returned to Earth safely. It put a spectacular show over the Australian outback, making a fiery re-entry. In the video of the falling debris shot from a DC-8 plane you can see a speck: that speck is the sample return canister which, hopefully, contains some material from the asteroid Itokawa. It was separated three hours before reaching Earth via parachute. The canister has been recovered successfully, it is in good condition and it has been taken back to the Japanese scientist, who will find out if there is anything in the canister. JAXA has said that it is going to share the material with scientists around the world. They say that even if it contains one grain of material it can be cut up into 100 or more samples and distributed to scientists around the world.

The probe was scheduled to return in 2007 but due to several problems the arrival date was pushed back to 2010. JAXA is not sure if it managed to collect a sample but even a grain of material would be a great achievement and it will give us some insight about asteroids and it might tell us something about our past. It is speculated that early asteroid impacts may have seeded Earth with materials to form life, but it is unlikely that something like that will show up in the materials collected, it’s too early to say anyhing. For now, we can keep our fingers crossed and hope that it managed to collect some material from Itokawa, a potato shaped ball of debris and rocks held together by gravity.

If something like that was headed towards Earth we would want to know as much about it as possible.