Strange New Worlds
Imagine if a star could tell you it had planets. That would be really helpful because finding planets orbiting distant stars – exoplanets – is hard. We found Neptune, the most distant planet in our own solar system, in 1846. But we didn’t have direct evidence of a planet around ANOTHER star until….1995.…149 years later. Think about that. Any science fiction you watched or read that was written before 1995 which depicted travel to exoplanets assumed that other planets even existed. Star Trek: The Next Generation aired its last season in 1994. We didn’t even know if Vulcan was out there. (Now we do!…sortof)
Since 1995, with the advent of planet hunting telescopes like Kepler and TESS, we’ve found THOUSANDS of planets orbiting other stars. These missions find exoplanets literally by looking for their shadows. Sometimes an exoplanet’s orbit crosses our view of a distant star blocking out some of the star’s light. This “transit” of the planet creates a shadow in the observed light from the star which we can then use to determine the size of the planet, whether it’s a rocky planet like Earth or a gas giant like Jupiter, and the length of the planet’s year around its parent star.
But planets are very small compared to their host stars. The amount of light they block is a fraction of the star’s overall light, so our equipment needs to be very sensitive. And if the planets are not orbiting in such a way that they cross our view of the star, say if we are looking at the distant solar system from the top down, we may have a harder time detecting their presence. So, scientists are looking for alternative means of discovering planets and one might be to study the parent stars themselves. Stars are big and bright and easy to spot. If stars that give birth to a solar system are somehow unique to stars that don’t, we might have a powerful new way of planet hunting. Specifically, astronomers are paying close attention to a star’s chemical composition – the right star stuff.
Building a Solar System
Planets and stars share the same stuff. Our solar system formed from one enormous rotating cloud of dust and gas called a protoplanetary disk. 99.8% of the stuff was concentrated in the centre drawn together by gravity to form the Sun.
The remaining 0.2% of whatever didn’t end up within the Sun itself flattens out to form the disk – imagine like how a ball of dough flattens into a pizza as it is spun. This flattening is why all the planets orbit the Sun along a similar plane called the Plane of the Ecliptic. Within the spinning disk, material begins to accrete forming planetesimals which become the seeds of future planets. But what is this stuff? It’s important! It’s what the planets and you and I are made of. Astronomers refer to it as “metals.” In astronomy, “metals” are considered anything on the periodic table above atomic number 2 – so anything heavier than hydrogen and helium like the calcium in your bones or the iron in your blood. In fact, at the birth of the Universe, there was ONLY hydrogen, helium, and small amounts of lithium. None of the other elements existed. Those elements are themselves created by the stars, deep in their interior, as they convert hydrogen fuel through nuclear fusion into heavier and heaver elements – the metals. Once these stars explode at the end of their lives as supernova, they spill their guts into the interstellar void seeding it with the stuff that makes other stars as well as PLANETS. Likely the first generation of stars in the early universe had no planets at all. There wasn’t yet the raw material to build them. We call those Population III stars.
The next generation of stars, Population II, were the first to form in a universe that was enriched with heavier elements. We’re not entirely sure if this group of stars formed with enough metals to make planets. We want to pinpoint when exactly the first planets formed in the Universe to estimate how early life could have existed. But if planets did form around Population II stars, likely they were quite small and orbited very closely to their parent stars – far closer than Mercury does in our own solar system. Probably not ideal for life at a sweltering 1600K surface temperature. Even if life did form around these stars, it is likely extinct by now as these stars lived shorter lives than our Sun and have already burned out. (Unless of course that life left its solar system to explore the Universe and still exists somewhere as an ancient space-faring civilization from a long-dead star…one can imagine.)
Which brings us to Population I, the group of stars our Sun belongs to. Our Sun formed in a Universe where billions of years of star births and deaths had already occurred. The Universe had been fertilized with more metals. Not only do the metals in a protoplanetary disk create the raw material for planet formation, but also protect the disk itself from being blown away by the parent star’s radiation. More metals mean more time available for the planets to form before the star’s energy eventually evaporates the remaining material that hasn’t yet formed planets
“Where to Look”
Understanding how planets form give us our first clue as to where to look for them – stars with metals. Remember, the host star and their planets form from the same cloud of stuff, so some of those metals are mixed into the star. By looking at the light from a star using spectroscopy, we can tell how highly enriched it is with metals – the star’s “metallicity.” Studying these metal-rich stars, we know terrestrial rocky planets like Earth are 1.72 times more likely to form around them. Even gas giants are more likely to form around metal-rich stars. Although made from gases rather than metals, gas giants like Jupiter are theorized to form around an initial rocky seed or from the disruptions in the flows of hydrogen gas orbiting in the disk caused by the introduction of metals.
But while a star’s chemistry can tell us the likelihood that planets are there – can the chemistry tell us exoplanets ARE there!? Is there a key chemical fingerprint for a star to tell us in a booming stellar voice “Yes indeed, I host planets! Behold my children!”
The research so far SAAAYYYYYSS……no. I know. Kind of anticlimactic.
BUT there is still hope. Last week, the Monthly Notices of the Royal Astronomical Society posted a study by the National Centre of Competence in Research PlanetS. NCCR PlanetS researched 84 stars observed by the 10M Keck Telescope in Hawaii. The team of researchers were trying to determine if planet formation leaves a unique chemical tell on a star – a beacon for us to know that indeed the star had given rise to planets – but a unique indicator couldn’t be found. Comparing 16 stars with planets and 68 without, the team found that planets orbit chemically diverse stars. But the findings are still useful. The team issued a warning that given the preponderance of planet discoveries, most of the stars in the study “probably have planets” (pg 8/3698 of the study) that just haven’t been found yet. So, the study might not be entirely accurate. However, this research could yield future discoveries of what KIND of planets, in terms of size or composition, form around a star with a certain chemical signature especially if/when planets are discovered around more stars used in the study. So, while we may not be able to know IF planets exist because of a star’s chemistry, in the future we may be able to infer with more accuracy what types of exoplanets orbit a star given a certain metallicity. For example, we know that metal-rich stars on average give rise to more planets – perhaps the types and quantities of each metal result in a certain arrangement of the solar system, or the quantities of terrestrial vs gas giants, or whether the planets are habitable. More research is needed.
In the meantime, we continue searching for planets using transits. TESS completed its primary mission, imaging 75% of the sky in a two-year survey, just this past August 20th. We don’t yet know what discoveries will be found in the data including perhaps new ways to understand the relationships between a host star and its planets. Whatever we find will certainly inform both future planet hunting missions as well as provide inspiration to the fictional stories boldly going to the strange new worlds our research has discovered. Engage!
“Revealing a Universal Planet-Metallicity Correlation for Planets of Different Sizes Around Solar-Type Star (Astronomical Journal) https://iopscience.iop.org/article/10.1088/0004-6256/149/1/14
“The First Planets: The Critical Metallicity for Planet Formation” – Johnson and Li (2012) https://arxiv.org/abs/1203.4817
“When Stellar Metallicity Sparks Planet Formation” – Astrobiology Magazine
“Do Metal-Rich Stars Make Metal-Rich Planets?” New Insights on Giant Planet Formation from Host Star Abundances – Johanna K. Teske, Daniel Thorngren, Jonathan J. Fortney, Natalie Hinkel, John M. Brewer 2019 https://arxiv.org/abs/1912.00255
Full Moon rises tonight for this year's Harvest Moon – iNFOnews
The next few nights promise to be clear and warmer than normal – good weather for some celestial viewing.
The next Full Moon is the Harvest Moon, which reaches its official status tomorrow.
The Harvest Moon is the first of two full moons in October, the next one being a Blue Moon on Halloween.
A Harvest Moon is the full moon that occurs closest to the autumn equinox.
According to NASA Science, the Harvest Moon normally falls in September. The moon should appear full to the naked eye tonight but isn’t technically a full moon until tomorrow and will remain full until Saturday, Oct. 3.
This year’s Harvest Moon should be easily viewable in Kamloops and the Okanagan as Environment Canada is forecasting clear night skies today, Sept. 30 through Saturday, Oct. 3.
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‘Extreme planet’ orbits star in three Earth days, has temperatures of 3120 degrees Celsius
Research on data from a new satellite is revealing strange new details about one of the “most extreme planets” in our known universe, and the blue, oddly-shaped star it orbits.
WASP-189b is 322 light years away from Earth in the constellation of Libra, has a permanent dayside and night side, and takes less than three Earth days to fully orbit its star — far faster than our 365 days.
“It is 20 times closer to [its star] than Earth is to the Sun,” Monika Lendl, lead author of the study from the University of Geneva, said in a press release.
WASP-189b is a gas giant, but it’s not any old gas giant. It is around one and a half times as large as Jupiter, and is part of a group called “ultra-hot Jupiters,” which are gas giants that are much larger and hotter than any planet we see in our solar system.
And this planet is even hotter than most other ultra-hot exoplanets scientists have identified. A paper published in the Astronomy & Astrophysics journal last week which detailed the new research described WASP-189b as “one of the most highly irradiated planets known thus far.”
It not only orbits incredibly close to its star, but the star itself, known as HD 133112, is one of the hottest stars we know of that has its own planetary system, at around 2,200 degrees Celsuis hotter than our Sun.
“Because it is so hot, the star appears blue and not yellow-white like the sun,” Willy Benz, professor of astrophysics at the University of Bern and head of the CHEOPS consortium, said in the release.
The dayside of the WASP-189b — the side that faces the star — is roughly 3,400 Kelvin, which is more than 3,120 degrees Celsius. It’s so hot that if there were iron present in the planet’s makeup, it would be gaseous.
In our solar system, the way that our planets spin while they rocket around the sun in their orbit gives them a night and day and allows multiples sides of the planet to get some face time with the sun. This isn’t the case for planetary objects like WASP-189b.
“They have a permanent day side, which is always exposed to the light of the star, and, accordingly, a permanent night side,” Lendl explained.
These details were discovered using data from the CHaracterising ExOPlanets Satellite (CHEOPS), the first European Space Agency (ESA) mission dedicated solely to extra-solar planets. The mission was launched in partnership with Switzerland, and benefitted from contributions from numerous European countries.
The satellite, with its mounted telescope, was launched in December of 2019, and has been orbiting 700 km above Earth ever since. Unlike many previous exoplanet-focused missions, CHEOPS is not interested in identifying new exoplanets, but was designed to peer closely at systems where we already knew an exoplanet is present.
Exoplanets — or extrasolar planets — are planets orbiting stars outside of our solar system, and because they’re so far away, we identify them not by finding a coloured speck in the sky, but by measuring dips in the light from stars.
When a star dims, it means something has passed in front of it, blocking some of the light from reaching the Earth. Using this “transit method,” researchers can figure out how large exoplanets are, how big or long their orbit is, and even what materials they are likely composed of.
There is also a change in light when a particularly bright planet goes behind its star, something called an “occultation.”
“Only a handful of planets are known to exist around stars this hot, and this system is by far the brightest,” Lendl said in an ESA release. “WASP-189b is also the brightest hot Jupiter that we can observe as it passes in front of or behind its star, making the whole system really intriguing.
“As the planet is so bright, there is actually a noticeable dip in the light we see coming from the system as it briefly slips out of view.”
While CHEOPS was pointed at WASP-189b, cataloguing all of its strange properties, researchers discovered that the star was unusual for more than just its bright blue colour.
It is spinning so rapidly that it is actually thicker at the equator, distorting the shape itself.
“The star itself is interesting — it’s not perfectly round, but larger and cooler at its equator than at the poles, making the poles of the star appear brighter,” said Lendl. “It’s spinning around so fast that it’s being pulled outwards at its equator! Adding to this asymmetry is the fact that WASP-189 b’s orbit is inclined; it doesn’t travel around the equator, but passes close to the star’s poles.”
This misaligned orbit implies that the planet had been formed further away from the star, and then been somehow pushed closer to it. Lendl suggested that this could mean the planet had interacted with other planets, or even other stars that had changed its orbital path.
According to the research, the planetary and star system is fairly young, which means researchers will be able to use this system to track the “atmospheric evolution of close-in gas giants.”
The new research is exciting to scientists not only for what it reveals about this planet and star, but for what it reveals about the telescope that provided such clear information.
“This first result from Cheops is hugely exciting: it is early definitive evidence that the mission is living up to its promise in terms of precision and performance,” Kate Isaak, CHEOPS project scientist at ESA, said in the ESA release.
Researchers point out in the paper that CHEOPS allowed them to refine and correct the size of the planet, which had been estimated incorrectly years earlier when the exoplanet’s existence was discovered by telescopes on the ground on Earth.
The paper concludes that the levels of the precision in the data shows that CHEOPS will be an invaluable tool in studying more exoplanets.
“We are expecting further spectacular findings on exoplanets thanks to observations with CHEOPS,” Benz said. “The next papers are already in preparation.”
Source: orbits star
Buried lakes of salty water on Mars may provide conditions for life – MENAFN.COM
(MENAFN – The Conversation) In 2018 a team of Italian scientists announced to the world that there was a lake on Mars . Using satellite radar data, the team detected a very bright area approximately 20 kilometres across located about 1.5 kilometres deep under the ice and dust of the south polar cap.
After analysis, they concluded that the bright area was a subglacial lake filled with liquid water. The discovery raised some fundamental questions.
Was this the only lake hidden beneath the ice on Mars? How could liquid water exist in the extreme cold of the Martian south polar region, where the average surface temperatures are lower than -100 °C?
After acquiring additional satellite data, my colleagues and I have discovered three more distinct ‘lakes’ near the one found in 2018 and confirmed that all four bodies contain liquid water.
Read more: Mars: mounting evidence for subglacial lakes, but could they really host life?
How can we see lakes under the ice on Mars?
The radar sounder MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) is one of eight instruments on board the European Space Agency orbiter Mars Express. This scientific spacecraft has been circling the red planet since December 2003.
The orbiting radar directs radio ‘chirps’ toward the planetary surface. These signals are partly reflected back by the surface, and partly penetrate deeper, where they may be absorbed, scattered, or reflected back to the radar. Liquid water reflects radar signals better than many other materials, so the surface of a body of liquid water shines brightly in a radar image.
Radar sounders are used on Earth to detect subglacial lakes in Antarctica, Greenland and Canada. Here, a technique called radio-echo sounding (RES) is commonly used to analyse the signals.
There are some obvious differences between how radar sounding is used on Earth and on Mars. For a start, MARSIS operates from altitudes between 250 km and 900 km above the surface, it has a 40-metre long antenna, and it operates at much lower frequencies (1.8-5 MHz) than Earth-based radar sounders.
These differences meant we had to do some work to adapt standard radio-echo sounding techniques for use with signals from MARSIS. However, we were able to analyse data from 134 MARSIS tracks acquired between 2010 and 2019 over an area 250 km wide and 300 km long near the south pole of Mars.
In this area, we identified three distinct bright patches around the lake already ‘seen’ in 2018. We then used an unconventional probabilistic method to confirm that the bright patches really do represent bodies of liquid water.
We also obtained a much clearer picture of the shape and extent of the lake discovered in 2018. It is still the largest of the bodies of water, measuring 20 km across on its shortest axis and 30 km on its longest.
How could liquid water exist beneath the Martian ice?
The surface temperatures in our study area are around -110 °C on average. The temperatures at the base of the ice cap may be slightly warmer, but still way below the freezing point of pure water.
So how can bodies of liquid water exist here, let alone persist for periods of time long enough for us to detect them?
After the first lake was found in 2018, other groups had suggested the area might be warmed from below by magma within the planet crust. However, there is to date no evidence this is the case, so we think extremely high salt levels in the water are a more likely explanation.
Read more: What on Earth could live in a salt water lake on Mars? An expert explains
Perchlorate salts, which contain chlorine, oxygen, and another element, such as magnesium or calcium, are everywhere in the Martian soil. These salts absorb moisture from the atmosphere and turn to liquid (this process is termed ‘deliquescence’), producing hypersaline aqueous solutions (brines), which crystallise at temperatures far below the freezing point of pure water. Furthermore, laboratory experiments have shown that solutions formed by deliquescence can stay liquid for long periods even after temperatures drop below their own freezing points.
We therefore suggested in our paper that the waters in the south polar subglacial lakes are ‘salty’. This is particularly fascinating, because it has been shown that brines like these can hold enough dissolved oxygen to support microbial life.
Could conditions be right for life beneath the ice?
Our discoveries raise new questions. Is the chemistry of the water in the south polar subglacial lakes suitable for life? How does this modify our definitions of habitable environments? Was there ever life on Mars?
To address these questions new experiments and new missions must be planned. In the meantime, we are gearing up to continue acquiring MARSIS data to collect as much evidence as possible from the Martian subsurface.
Each new piece of evidence brings us one step closer to answering some of the most fundamental scientific questions about Mars, the solar system and the universe.
Read more: Mars: mounting evidence for subglacial lakes, but could they really host life?
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