Hello Space Fans and welcome to another edition of Space Fan News.
This week, astronomers using ESO’s MPG telescope in Chile have discovered the first atmosphere
around a super-Earth Exoplanet; the Event Horizon Telescope began its observations this
week, what do astronomers expect to see?; and today marks the closest point between
the orbits of the Earth and Jupiter.
The big news this week comes from a story many of you sent me via email, texts and tweets
about astronomers using the 2.2 meter Max Planck Gesellschaft telescope in La Silla
Chile have detected an atmosphere around a super-Earth exoplanet some 39 light years
away around a red dwarf star called GJ 1132 located in the constellation Vela.
On the one hand, this is a bit of a big deal because this marks the first detection of
an atmosphere around a low-mass super-Earth so far and having an atmosphere is almost
certainly an important component for finding life elsewhere and this observation, which
all things considered used relatively modest equipment on the ground, means they can get
lots of practice studying exoplanet atmospheres before the James Webb Space Telescope is launched in October 2018.
On the other hand, this planet is not a very promising candidate for life.
GJ 1132b orbits its star once every 1.6 days, and that alone gives it some strange properties.
It isn’t known for sure if it’s tidally locked, but chances are high that it is given
how close it is to the star.
The planet has 1.6 times the mass of the Earth and has a radius that is 1.4 times larger
than Earth.
The effective temperature of the planet is 644 Kelvin or 370 Celsius and 700 degrees Fahrenheit.
Astronomers love this exoplanet though because it is relatively close to the Earth, large,
bright and easy to study for ground-based telescopes to study.
The 2.2 meter MPG telescope was used to make this detection, specifically the GROND instrument
or Gamma-Ray Burst Optical/Near-Infrared Detector.
This instrument acquires images simultaneously in four optical and three near-infrared passbands
and they used it to measure a total of nine transits, these are passes of the planet between
us and the star.
As the light travelled through the atmosphere of GJ 1132b, the detector was able to measure
those brightness in all of those wavelengths at once.
As i was reading the paper, which came out in The Astrophysical Journal this week, I
was reading the table of the properties of GJ 1132b and was struck by all the different
things you can find out using the transit method.
In addition to the size and mass of the the planet, they also determined that the surface
gravity was 7.8 meters per second squared, which I thought was strange given that the
planet was 1.6 times the mass of the Earth.
On Earth that value is 9.8 meters per second squared.
So how could gravity be weaker than Earth’s if it’s bigger and more massive? the next
line in the table told that story: the density of the planet is almost half of that of Earth’s.
The density of the Earth is almost 6 grams per cubic centimeter and on GJ1132b, it was
only 3.1 grams per cubic centimeter, so that must be why gravity is weaker there.
Since it’s 1.4 times the radius of the Earth and the density is lower, then the surface
gravity is lower.
I would love to get these guys on a hangout and ask them how they teased all of these
characteristics of the planet from nine transit measurements in these wavelengths.
So, at 1.6 Earth masses GJ 1132b is by a huge factor the lowest mass planet with an atmosphere
which has been observationally detected.
The two other low-mass planets with claimed atmosphere detections are 55 Cancri e, with
a mass of 8.0 earth masses and GJ 3470 b, with a mass of 13.7 Earth Masses.
There is no doubt in my mind that the guys who observed this exoplanet are dying to get
their hands on JWST, this is exactly the kind of science it was designed to do at a level
never before possible.
I’m also sure that by the time JWST gets done, these kinds of discoveries will become
passe.
What?
Another planet with an atmosphere?
What else is on?
Next, remember a couple of weeks ago I told you that radio astronomers from around the
world are getting together to try and directly image the black hole at the center of our
galaxy, known as Sgr A*?
Well those observations began this week and they will be spending months processing and
analyzing the data so we probably won’t see anything from this effort for about six
months to a year.
Still, it occurred to me that I didn’t go into very much detail into what they hope
to see.
What astronomers are doing this week both amazing and unprecedented and I can’t stop
talking about it.
A couple of weeks ago, I told you how they were going to make the observations and for
how long, but today I want to give you a better idea of what they expect to see when it’s
all over.
As I said before, they are trying to see a tiny thing very far away and do image it directly,
we need resolution, which means a big telescope.
They were saying something like trying to image a coke can on the moon, yada yada something
something tiny small far away.
Translation: this is a hard, hard observation to make.
As you can imagine astronomers have run hundreds of simulations predicting what they might
see and after all the observations are collected, petabytes of some of the highest resolution
radio images ever taken, then synchonized, processed, calibrated, combined and analyzed,
astronomers expect, when all is said and done, to have an image of a crescent of light created
by the glowing gas spinning around the black hole, and a dramatic Doppler effect that should
make the stuff moving towards the Earth appear much brighter, appearing as a crescent in
the image.
The rest of the ring will also emit, but what they want to pick up is a crescent, they don’t
want to see a ring.
Why?
As with all things black holes, you knew sooner or later it would come down to Einstein.
Didn’t you?
Einstein's theory states that a mass - especially one as big as a black hole - bends space-time.
And that curvature can be calculated mathematically.
So the size of the shadow cast by Sgr A* will either match what is predicted by general
relativity, or it won't.
And they are predicting that as the matter falls into this black hole
and due to this dramatic Doppler shift and the other distortions of spacetime
they should see a crescent and not a ring.
So much has to happen to make this observation, it is really astonishing.
The wavelength they’ve chosen need to be bright in the event they are trying to see,
but also get through the gas and dust of the galaxy, get through our atmosphere and be
detectable by our detectors.
And this wavelength, 1.3 mm, is pretty tweaky when it comes to clouds too, so the weather
has to be good in all of these locations around the world.
So Godspeed Event Horizon Telescope.
I’m so impressed by this endeavor and I’ll be sure to keep you posted.
Finally, since it is our job as Space Fans to Keep Looking Up, today is an important
day for those of us who dutifully go about our job.
Today, the Earth passes by Jupiter in its orbit around the Sun.
When the Sun, Earth and Jupiter line up, or any planet for that matter, doesn’t have
to be Jupiter, (sun, earth, mars, sun earth, saturn, whatever) we call it opposition.
And today, Jupiter is at opposition.
It is the brightest it will be for a while and if the skies are clear where you live,
the grab some binoculars and go outside and enjoy the view.
The conditions will be good for this alignment for about a week or so so you if you can’t
see anything today, you still have some time.
Well to commemorate the occasion and to rub it in about how much better the view is from
space, the Hubble Space Telescope took this picture of Jupiter on April 3rd, 2017.
Hubble has spent a lot of time over the years looking at Jupiter and this new image of Jupiter
is part of Hubble's Outer Planets Atmospheres Legacy program, which is one of many ways
Hubble provides science on the Jupiter system.
Now a correction.
Last week I reported that the solid rocket boosters used during the space shuttle program
were not reused.
This is not true, NASA collected the SRB’s from the Atlantic Ocean after they splashed
down and refurbished and reused them.
I was trying to make the point that reusing SRB’s doesn’t really save all that money,
but the expensive first stage of the Falcon 9 rocket used by SpaceX did because customers
could save 30% or so from each launch by choosing a rocket that had been reused.
So thanks to Chris Marshall who pointed out the error along with the fact that I kept
calling the Falcon 9 rocket the Dragon 9, which it isn’t.
The Dragon 9 is the SpaceX vehicle designed to carry people.
Honestly I don’t know why I did that.
Well, that’s it for this week Space Fans, please check out the new submission guidelines
if you’d like to submit a story of your own for SFN.
This show is made possible by the generous support of SFN Patreon Patrons so thank you
all so much.
Thanks to all of you for watching and as always, Keep Looking Up!