2 Rocky Earth-Like Worlds; Most Distant Quasar Found in Reionization Era; ESPRESSO Better Than HARPS
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2 Rocky Earth-Like Worlds; Most Distant Quasar Found in Reionization Era; ESPRESSO Better Than HARPS

September 4, 2019


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. I want to thank these Patreon Patrons for
their above and beyond support of Deep Astronomy and SFN, they along with all other patrons,
ensure that Deep Astronomy can keep the doors open and the lights on so thank you! Thanks to all of you for watching and as always,
Keep Looking Up!

Only registered users can comment.

  1. Your enthusiasm, in not only astronomy, but in creating videos sure shines bright like a brown dwarf in infrared.

    Keep up the great work, Tony. I love SFN to keep up with the latest news. Thanks!

  2. Goddammit, I love your enthusiasm. Not that the universe is difficult to get excited about but you just put out that sincere vibe of a man that's happy in his work. Thanks Tony.

  3. I don`t get this so.. how can light emitted from a distant early galaxy/quasar "13 billion" years ago reach us first now. have this galaxy travelled away from us almost at the speed of light or is it something else

  4. (abstract)
    The Frist Foundation of the Universe
    (B) First Baby Galaxy's Epoc — First Light
    (A><B) Hydrogen Reionization — Phase Transition
    (A) Dark Ages — from the Bottom-Up

  5. Don't the planets usually start with the letter B because A is reserved for the star? (Unless there is more than one star)

  6. I am probably at least partly wrong here, but I always assumed that candidate planets who turn out to not be planets are phenomena of the star itself, such as star-spots (the equivalent on the star of sunspots on the sun). Thing is, this is just my presumption — I haven't seen any lay-person oriented discussion.

    It also seems to me, although this may only reflect the bias of my sources, that interest in the object dries up once it is found to not be a planet. I would think there is regardless a lot to be leaned from data regarding star-spots, or whatever they are. Statistics regarding the occurrence and frequency and sizes of star-spots and the kinds of stars that have them sounds to me to be interesting.

    Starting with the "-b" designation is probably because the star itself gets the "-a".

    Thanks for the informative and readily understood posts.

  7. Let's say that you are observing an L6 brown dwarf with an effective temperature of 1600K and a radius of 68900 kilometers.

    The Planck integral for radiant flux is

    F = π ∫(v₁,v₂) 2hv³/{c² exp[hv/(kT)]−1} dv

    Integrating over the entire spectrum, we find that this brown dwarf has a flux,

    F = 371614 W m⁻²

    The brown dwarf has an effective surface area of 5.96552e+16 square meters, so its bolometric luminosity is

    L = 2.21687e+22 W = 5.794e-5 Lsun

    And its bolometric absolute magnitude,

    ℳbol = +15.34

    Solving the Planck integral again for the visible spectrum only (i.e. from 3900 angstroms to 7000 angstroms wavelength),

    Fv = 406.927 W m⁻²
    Lv = 2.4275e+19 W

    And again for the near infrared spectrum (i.e. from 7000 angstroms to 25000 angstroms wavelength),

    Fnir = 178289 W m⁻²
    Lnir = 1.06359e+22 W

    The part of this brown dwarf's luminosity that falls in the near-IR is 48% of the total luminosity, while the visible part is only 0.11% of the total luminosity.

    The part of the brown dwarf's luminosity that falls in the far infrared (wavelengths longer than 25 micrometers) is

    Lfir = 1.15086e+22 W

    So this brown dwarf's radiation is about evenly divided between the near IR and far IR, with only a little smidgen of output in the visible part of the spectrum. The Wien law peak is at 18111 angstroms.

  8. Sure as heck I was expecting to hear "just like downtown" today… Guess I'll wait for JWST to confirm all sorts of theories and models of the early universe. Keep us posted, Tony 🙂

  9. Hi Tony thanks for another great video, but please turn of that horrible noise in the background. I cannot understand you due to it. The irritation just takes over. Sorry about my complaint for your otherwise extremely pleasant and interesting sfn

  10. Why does it start with "b"? Because the star itself is "a". Companions are then labeled sequentially by discovery date b,c,d, etc. Not labeled or later re-labeled if more planets are found at varying distance from host, for example.

  11. Thanks for all you do for people like me: meaning, interested parties with no formal education in Astronomy. Adults renewing a childhood interest, but lacking the scientific base to start from. You make it so a layperson can understand and that's just like downtown.

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