Remember the other day, when we told you that scientists had found some potentially habitable planets hiding in Kepler data? Well, scientists have found 18 more – and they're just as important. Scientists led by Guillermo Torres from the Harvard-Smithsonian Center for Astrophysics re-analyzed some data from the Kepler space telescope to confirm some of its candidate planets really existed.
These are known as Kepler
objects of interest (KOIs). The research is available on arXiv. Importantly, most of the
planets are not only similar in size to Earth, but also orbit in their star's habitable
zone where liquid water could exist.
“These are not the first
small planets in the habitable zone, but they are important because they
increase the sample of such objects, which is important for statistical studies
that aim to tell us how common these planets are in the Universe,” Torres
told IFLScience.
Of the 18 planets, 15 have a
confidence level of 99.73 percent that they exist. The others are slightly
lower. Almost all of them orbit M dwarf stars, or red dwarfs, so they're not
quite the same as us. The planets range in size from 0.8 times Earth’s
radius to 2.76, and have orbits ranging from 18 Earth days to almost two years.
Five of the planets
definitely orbit in their star’s habitable zone, and of those, two have a
greater than 97 percent chance of being similar in size to Earth. They are
KOI-2626.01 and KOI-4036.01. Another, KOI-2418.01, is definitely similar in
size to Earth, and most likely orbits in its star’s habitable zone.
Kepler finds planets by
noticing the dip in light as they pass in front of their star, known as a
transit. Three dips, or orbits, and you can confirm the planet exists.
For planets with longer
orbits, however, this can be a bit tricky. This is because Kepler only looked
at one portion of the sky for four years before moving
on to its K2 mission. Finding planets on Earth-like orbits is
therefore quite tough.
“The currently operating K2
mission is finding small planets orbiting close-by bright stars similar to our
Sun, but only stares at them for 85 days – a far cry from the many years needed
for true analogs of Earth to be found,” NASA's Steve Howell, a co-author on the
study, told IFLScience.
That’s where this latest
research comes in. The scientists used a method that’s called BLENDER. This
involves looking at information contained in the initial transit light curve of
the planet. Doing this means that false positives, like a passing star, can be
ruled out.
Many of the candidates had
already been validated by other methods. However, those methods failed to take
into account the possibility that these planets orbited a different star on the
same line of sight. If that were the case, these seemingly rocky planets would
actually be much larger.
It also serves as a bit of a
useful test of the BLENDER technique, which could be used to confirm other
candidate planets in future too. And when it comes to finding worlds like our
own, every tool is going to be key.
Via IFLScience