Space Fan News #81: Six Super Earths around HD 40307; Planets Can Form at Galactic Centers


Uploaded by tdarnell on 09.11.2012

Transcript:
Hello Space Fans and welcome to another edition of Space Fan News.
I hope you're not getting sick of hearing about exoplanets because you better get used
to lots more announcements of new planets.
I mean, we are looking for them pretty hard after all using a lot of different telescopes
around the world and in space, so the deluge has begun.
This week, our old friends from the University of Hertfordshire in the U.K. have been at
it again. You've heard me mention these guys many times, they are using UKIRT, the UK Infrared
Telescope and this week they've announced the discovery of a really interesting planet.
This planet is a Super Earth in orbit around HD 40307, a very old dwarf star that was previously
thought to have only three stars in orbit around it. Those planets were also Super Earths,
these are rocky planets that can be up to about 10 times the size of the Earth.
Initially, they found three of these Super Earths around HD 40307, but they tweaked their
processing code to filter the activity of the star in certain wavelengths which reduced
the influence of activity from this star on the signal.
This had the effect of significantly increasing the sensitivity they found three more planets,
making it into a system with six-planets overall.
Now what's cool is, one of these new planets - the one farthest out - is in an orbit that's
about as far as the Earth is from the Sun, so it receives a similar amount of energy
from the star as the Earth receives from the Sun.
This makes it more likely that it may have liquid water and the longer orbit may make
any climate or atmosphere it has more habitable.
However, the planet (HD 40307g) is about seven times the size of Earth, so if it was habitable,
we'd all have to either get real strong or lose a lot of weight, you'd weigh seven times
more here.
One thing I wanted to highlight with this story is that a lot of exoplanet scientists
are starting to say that the cooler dwarf stars are where we are more likely to be finding
planets like the Earth, and they want to concentrate more of our efforts looking around stars like
these.
They are cooler and harder to see, but there are so many of them that the likelihood of
finding a planet around one of them that can support life in dramatically increased.
They are also less active, meaning there is less of a chance of wiping out any life with
a solar storm or other activity from the star, they are quite benign and may offer a quiet
lagoon for life to emerge.
Next, I've had this on my list for a while, but have only now gotten around to telling
you about it. Kepler has added to it's list of confirmed planets by 50 percent. As of
last August (I know, I know), there are now 116 confirmed planets hosted in 67 systems,
and over half of those contain more than one planet.
Oh well, better late than never.
Next, staying on the exoplanet theme, astronomers using the Very Large Telescope in Chile have
found that it is possible for planets to form in the centers of galaxies.
As you can imagine, the center of a galaxy can be a pretty inhospitable place. I mean,
it's very crowded in there and you've got stars whipping past each other very fast;
supernovae are going off sending out shock waves out into nearby space and bathing everything
in intense radiation;
Not to mention the supermassive black hole that's probably nearby feeding on whatever
it can and sending out enormous gamma ray jets.
You see, newborn stars retain a surrounding disk of gas and dust for millions of years.
If one of these stars dived toward our galaxy's central black hole, radiation and gravitational
tides would rip apart its disk in a matter of years, leaving no time for planets to form.
So yeah, not a quiet place for a planet to have time to form, much less harbor life.
Well, turns out it's possible. Planets can form in the centers of active galaxies.
For proof, these astronomers point to the recent discovery of a cloud of hydrogen and
helium plunging toward our galactic center which everybody thought at the time was the
resulting cloud from a collision of two stars.
This team however, argue that this cloud represents the shredded remains of a planet-forming disk
orbiting an unseen star.
Now I've told you about this cloud before, it was the subject of the video I made called
"The Darkness in the Heart of Our Galaxy", I put a link to it in the description box
if you haven't seen it yet.
So as I said, these astronomers are saying that the cloud is the remains of a protoplanetary
disk, not a collision from two stars.
They claim this unfortunate star got tossed toward the central black hole and now it's
on the ride of its life, and while the star will survive the encounter, its protoplanetary
disk won't be so lucky.
They also identify where the stray star came from - a ring of stars known to orbit the
galactic center at a distance of about one-tenth of a light-year.
Astronomers have detected dozens of young, bright O-type stars in this ring, which suggests
that hundreds of fainter Sun-like stars also exist there. Interactions between the stars
could fling one inward along with its accompanying disk.
Although this protoplanetary disk is being destroyed, the stars that remain in the ring
can hold onto their disks. Therefore, they may form planets despite their hostile surroundings.
As the star continues its plunge over the next year, more and more of the disk's outer
material will be torn away, leaving only a dense core. The stripped gas will swirl down
into the maw of the black hole. Friction will heat it to high enough temperatures that it
will glow in X-rays.
Not sure I'd want to be on one of those.
Finally, I wanted to let you know that there is a total eclipse next Tuesday, on November
13th, in Austrailia. The cool thing is though that you don't need to be in Australia to
see it.
Thanks to the wonders of Hangouts On Air, the SLOOH telescope will be offering a live
feed throughout the event. The event is scheduled to start at 2:30 PM Eastern time, so I would
encourage you to check it out. I'll be there and hope to see you there as well.
That's it for this week Space Fans, thank you for watching and as always, Keep Looking
Up!