Hello Space Fans and welcome to another edition of Space Fan News.
Last week, on November 28th, 2013, the world watched as Comet ISON made it's closest approach
to the Sun.
Expectations were high as this comet was touted as the comet of a century (at least for a
while) and for a bit there, it seemed like maybe the predictions were going to be close.
As the comet came into the field of view of solar telescopes looking at the Sun, ISON
already had a tail that was 20 times wider than the full Moon and a head bright enough
to see in the pre-dawn eye with the unaided eye.
Everyone wondered if Comet ISON would survive it's trip around the Sun.
Would it break up?
Would it stay intact?
Here are images from the solar observatories STEREO - which watches the sun from two spots
in orbit - and SOHO which has two coronagraphs of differing fields of view that block out
the solar disk and show the corona.
ISON approached as Coronal Mass Ejections went off all around it, and as it went behind
the occulter of SOHO's C3 coronagraph, everyone wondered if it would emerge again.
The Solar Dynamics Observatory, or SDO, never saw anything which lead many astronomers to
guess that maybe the comet had disintegrated completely.
But after a bit, something did reappear in SOHO and STEREO coronagraphs and whatever
it was, was significantly less bright.
It's not clear exactly what came out the other side, a cloud of dust that once was a comet,
or is there still an intact comet nucleus in there?
just don't know yet.
What they're saying is that as of December 1st, it seems likely there was no nucleus
left.
So they're going to keep looking at it and monitor its changes in brightness over time,
and maybe later they can estimate whether there's a nucleus or not.
But our best chance at knowing for sure will be when the Hubble Space Telescope makes observations
later this month.
What they're gonna do is point Hubble at the spot of sky where ISON should have been if
it had survived and take a really close look at what's there.
Hopefully those images will show us something we can't see yet.
I'll let you know.
Next astronomers using the Hubble Space Telescope have found faint evidence of water in the
atmospheres of five exoplanets.
Now we've found atmospheric water before on a few exoplanets orbiting stars beyond our
solar system, but this is the first study to conclusively measure and compare the profiles
and intensities of these signatures on multiple worlds.
The five planets, called WASP-17b, HD209458b, WASP-12b, WASP-19b and
XO-1b, all orbit nearby stars and the strengths of their water signatures varied.
WASP-17b, a planet with an especially puffed-up atmosphere, and HD209458b had the strongest
signals.
The signatures for the other three planets, WASP-12b, WASP-19b and XO-1b, were fainter,
but showed signals consistent with water.
Two different teams used Hubble's Wide Field Camera 3 to explore the details of absorption
of light through the planets' atmospheres.
The observations were made in a range of infrared wavelengths where the water signature, if
present, would appear.
The teams compared the shapes and intensities of the absorption profiles, and the consistency
of the signatures gave them confidence they saw water.
Hubble's Wide Field Camera 3 is one of few instruments capable of peering into the atmospheres
of exoplanets many trillions of miles away, and the way they did this was very clever.
We can only see these atmospheres if the planets are spotted while they are passing in front
of their stars.
As they pass in front, researchers can identify the gases in a planet's atmosphere by determining
which wavelengths of the star's light are transmitted and which are partially absorbed.
So basically they appear just a little brighter at the wavelengths we know water vapor exists
if they have water, and dimmer if they don't.
Finally, astronomers at the University of Arizona have found a peculiar exoplanet.
This planet is orbiting its star from a distance farther than anyone has ever seen before.
The planet, known as HD 106906 b, is 11 times the mass of Jupiter's and orbiting its star
at a whopping 650 times the distance of the Earth from the Sun, which is called an astronomical
unit.
Finding this planet so far away from it's stars has astronomers second-guessing some
of their planet formation theories.
It is thought that planets close to their stars, like Earth, coalesce from small asteroid-like
bodies born in the primordial disk of dust and gas that surrounds a forming star.
However, this doesn't work for giant planets far from their star, the process acts too
slowly for the planets to grow this big.
Another proposed mechanism is that giant planets can form from a fast, direct collapse of disk
material.
The problem with that though, is that primordial disks rarely contain enough mass in their
outer reaches to allow a planet like HD 106906 b to form.
Others are suggesting that maybe this is a mini-binary star system and we should use
those theories to explain the distance.
A binary star system can be formed when two adjacent clumps of gas collapse more or less
independently to form stars, and these stars are close enough together to exert a gravitation
attraction which binds them together in an orbit.
It is possible that in the case of the HD 106906 system the star and planet collapsed
independently from clumps of gas, but for some reason the planet's progenitor clump
was starved for material and never grew large enough to ignite and become a star.
I like that theory the best.
It seems like with every exoplanet we discover, our ideas of how and where planets can form
in a system are pushed just a little bit.
And that - along with an infinite number of other reasons - is why we look up.
That's it for this week Space Fans, thank you for watching and as always, Keep Looking
Up!