Hello Space Fans and welcome to another edition of Space Fan News.
This week, astronomers at ESO find yet another system with rocky, earth-sized planets; the
most distant quasar from the most distant supermassive black hole has been observed
in the early universe and finding such a big black hole so early after the universe has
astronomers confused; and a new planet finding spectrograph sees first light ushering in
a new phase of precision for ground-based exoplanet research.
So last week I told you about Ross 128b, a new earth-sized exoplanet discovery that is
only 11 light years away and is travelling towards us, well this week, I’m telling
you about the addition of two more earth-sized exoplanets from another system that were just
observed by the HARPS Planet finding spectrograph.
Discovered by the rebooted Kepler Space Telescope Mission, or K2, in 2015 astronomers using
the HARPS instrument (HARPS stands for High Accuracy Radial Velocity Planet Searcher),
have just confirmed a pair of exoplanets around the star K2-18.
Remember how this works: space telescopes like Kepler observe wide areas of the sky
looking for dips in brightness caused by a planet moving in front of its host star and
when they think they have something, they label it as a candidate and send the location
out to ground-based observatories for follow-up observations to confirm whether what they
saw was in fact, a planet moving in front a star and not some artifact.
Or spaceship, or dyson sphere getting in the way.
Well that’s what happened here.
K2 saw something it thought might be a planet, tagged it as an object of interest and waited
for other observatories to follow up.
Astronomers using the HARPS spectrograph confirmed the existence of the planets by using a second
method of finding exoplanets: the radial velocity method.
This looks at wobbles in the star’s spectrum that are caused by the gravitational tugging
of the planet as it orbits the star.
So, it appears there are two, not one planets in orbit around the star K2-18, a red-dwarf
star located about 111 light years away in the constellation Leo.
The first one: K2-18b (don’t ask me why they start with b, I have no idea), was found
to be orbiting within the star’s habitable zone, which as we all know by now gets astronomers
all hot and bothered because there may be liquid water present - if it has any water
at all - and that means a good chance for life.
It appears to be revolving around the star once over 33 days and the star itself rotates
once every 39 days.
The planet is thought to be either a little larger than earth, if it’s rocky, or a little
less massive than Neptune, if it’s mostly gas.
So to figure that out, they did more work.
The radial velocity method is great for getting the masses of a planet but not radius so they
used some machine learning algorithms to to figure out the radius measurement, the team
members were able to determine the planet is either a mostly rocky planet with a small
gaseous atmosphere – like Earth, but bigger – or a mostly water planet with a thick
layer of ice on top of it.
But, located within those signals, HARPS saw something else, another signal rotating once
every nine days.
So after doing a careful analysis of the data to make sure it wasn’t noise, the astronomers
collaborated with other international teammates and confirmed that signal was the existence
of the second planet K2-18c.
It is closer to the star, and probably too hot to be in the habitable zone, but like
K2-18b it also appears to be a Super-Earth.
What we need now are observations of this system from JWST because it has instruments
on board that are designed to measure the spectra coming from starlight that shines
through planetary atmospheres.
From those results, we can get more information about the habitability of K2-18b.
Next, astronomers engaged in a years-long effort using data from many telescopes and
instruments, have found the most distant quasar ever seen.
This quasar was found in the center of a galaxy located some 13.1 billion light years away,
meaning the light that left this quasar did so when the universe was only about 690 million
years old.
You may remember that quasars are among the brightest objects in the universe, they are
the radiation given off by huge jets of high energy released as material falls into a supermassive
black hole.
The black holes are enormous, millions of times the mass of our Sun, and they are thought
to be at the centers of almost all galaxies.
Even though quasars are bright, because this one was so far away, it was not easy to find.
There are lots of bright things in the universe, especially in the infrared, the region of
the spectrum you have to look at for really far away things.
But after years of poring over data, astronomers found this quasar spewing out radiation at
an interesting time in the universe when no quasars had yet been seen.
The early universe is a hot topic among astronomers now because for the first time, we have the
tools to actually start seeing things here.
No one knows for sure, but the first stars are believed to have formed only a few million
years after the Big Bang and the first galaxies a little while after that.
This quasar and its attendant galaxy was found when the universe was very young, only 690
million years old, and that is smack in the middle of a time in our history called the
Reionization Era.
Watch my video “First Light” to learn more about this, but this was a period in
the universe after stars began to shine and the radiation from them started to ionize
the hydrogen and helium that was everywhere early on.
Ionize in this case just means stripping electrons away from neutral atoms, the stellar winds
from the first stars in the universe, blew away some of the electrons away from hydrogen
atoms.
So what’s interesting here is that this quasar appears to be right in the middle of
the reionization era.
How do they know?
By carefully looking at the spectra around the quasar, they see lots and lots of neutral
hydrogen, atoms that have one proton, one neutron and one electron, just as theories
of the early universe expect you would see if they are right about their history.
Another thing I found really interesting about this story that I did not know prior to looking
into it, is that apparently brown dwarf stars in our own galaxy look a lot like quasars
in the distant universe to our infrared detectors on Earth.
Which I guess makes sense, brown dwarf stars are dark and warm, but don’t actually shine
like regular stars so they are hard to see in optical wavelengths but are bright in the
infrared.
And they are close - inside our own galaxy - so they can throw off people trying to find
these really dim (to us anyway) distant quasars which are also bright in the infrared.
Really bright close things, versus really dim far away things.
Anyway, I thought that was interesting, I didn’t know something as innocuous as a
brown dwarf could be mistaken for a quasar.
Again, not to beat a dead horse, but JWST will be uniquely qualified to help us learn
about this time in the universe’s history.
We just gotta hurry up and get it up there!
Finally, ESO has been very busy lately because this week they’ve announced that a new instrument,
called ESPRESSO, which stands for The Echelle SPectrograph for Rocky Exoplanet and Stable
Spectroscopic Observations, has successfully made its first observations.
Like HARPS (which confirmed K2-18b and c), ESPRESSO is designed to look for and characterize
exoplanets using the Radial Velocity method, which like I said earlier, uses shifts in
the spectra to look at the gravitational pull of any planets in orbit around stars.
But while HARPS is accurate to within one metre per second in velocity measurements,
ESPRESSO aims to achieve a precision of just a few centimetres per second, so way more
sensitive.
This new sensitivity means that ESPRESSO can find smaller, rocky planets than HARPS can
and hopefully increase our census of rocky habitable worlds by quite a bit.
The less massive the planet, the smaller the wobble, and so for rocky and possibly life-bearing
exoplanets to be detected, an instrument with very high precision is required.
With this method, ESPRESSO will be able to detect some of the lightest planets ever found.
In addition to finding planets and characterizing their atmospheres, astronomers say they can
also use ESPRESSO to test whether the physical constants of nature have changed since the
Universe was young.
Such tiny changes are predicted by some theories of fundamental physics, but have never been
convincingly observed.
What they don’t say in that press release though is exactly what they heck they mean
by that.
Oh well, don’t worry though I will keep you posted.
Well that’s it for this week Space Fans.
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and SFN, they along with all other patrons, ensure that Deep Astronomy can keep the doors
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Thanks to all of you for watching and as always, Keep Looking Up!