TGT #27 - AAS: Venus’ Atmosphere, Signs of Life?; + 7 more [July 1, 2022]
This Just In--Life on Venus?, Kepler's Epiphany, Kitt Peak Fire, How Planets Form?; Sunrises and Sunsets; End of the Grand Line-up, Planets Shifting From Dawn to Night.
Cover Photo - Where Life Could Be on Venus?
In This Issue:
Cover Photo — Where Life Could Be on Venus?
Welcome to Issue 27!
This Just In —
* AAS: How Do Planets and Systems Form?
* Observatory Fire
* AAS: Venus’ Atmosphere, Signs of Life?
* AAS: When Did Kepler Realize Ptolemy Was Wrong?
Sky Planning Calendar —
* Moon-Gazing - A Lazy Evening Moon Glides Through Stars—Only
* Observing—Plan-et —
- Planets Entering the Evening, Mercury Leaving the Dawn
* Border Crossings
Astronomy in Everyday Life - AAS: Sunrise, Sunset
The Classroom Astronomer Newsletter-Inbox Magazine #30 July 1, 2022 Issue Highlights.
Welcome to The Galactic Times Newsletter-Inbox Magazine #27 !
At the tail end of three straight astronomy conferences, we bring you news and views from the American Astronomical Society and sky events for the first half of July!
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This Just In
* AAS: How Do Planets and Systems Form?
Rebekah Dawson’s plenary talk was one of a host of talks on the topic of the formation of planetary systems. It all used to be so simple….
A cloud of gas and dust collapses, spinning. Planets form in the cloud, rocky smaller ones close in. The gas disk dampens all non-circular motion and collisions, forcing a system of co-planar and co-orbiting, circular (or barely elliptical ones) bodies. Voila! You have a planetary system! Only the thousands of discovered exoplanets have indicated that all three points ain’t necessarily so.
The bulk of the exoplanets found are large, massive Jupiters, 1 to 10 times the size of ours. Terrestrials like Earth are too often too hard to find yet. In between are Super-Earth’s 2-3 times our size, and mini-Neptunes (sometimes called Neptini’s and Neptunos), bigger than Super-Earth’s but smaller than Neptune itself). Often these giant worlds are hotter than ours, frequently because of closeness to the star.
The Pennsylvania State University astronomer points out that unlike our solar system, these gas giants orbit anywhere from just above the star’s surface to way out towards the edge of a star’s system. And their orbits can be eccentric, not circular, and tilted relative not only any other planets there but also to the star’s rotational axis (all our planets’ orbits are more or less along the Sun’s equator. And this is where the classical picture of planetary formation falls apart.
Dawson sees three origin scenarios for where the gas giants call home.
First, they could be formed right where they are found. Or they could be formed elsewhere and migrate in or outwards. Or a companion could force them to move. As in all cases of scientific query, you have to test these with data from other factors. One of those turns out to be the metallicity of the stars, that is, the amount of elements heavier than helium in the star. If there are high amounts of metals, the gas giants are found in eccentric orbits, and at greater distances with no nearby companions. You rarely get tidal migration if you don’t have nearby companions; you might get in situ or disk migration if there are. And the latter seem to include the creating of small nearby-to-the-star planets. We don’t know much about them.
But there is a continuum of Super-Earths to mini-Neptunes. With these, the clues are contained in the amount of gas and dust, and whether the planets and system are dynamically hot or cold. In both cases, there is clearly history involved; a Gas Era, and or a Post-gas Era. In the Gas Era, the gas damps motions, and the scattering of the worlds, their ejections, and mergers. This is more evident with systems with Super Earths, which form during a Residual Gas Era, before total dissipation. Once the gas is dissipated, terrestrials form in the remains of the gas disk close to the star while gas giants, formed outside of it, scatter. If there are sufficient solid materials in the system, and it is dynamically cold, you get mini-Neptunes, with systems being flat with circular orbits and tightly packed. If the nebula is hot, you get rocky Super Earths, with various inclined and eccentric orbiting worlds, and with more gas giants.
Laura Kriedberg of the Max Planck Institute for Astronomy points to findings that many planets found seem to be with little water. To her this indicates that many planets are formed in regions where there are not planetesimals but pebbles, all dry. They don’t bring water with them into planet formation. All stars form in nebulae where there is a water-ice line, where the temperature drops below the freezing point. Apparently the distance that line is helps determine where types of planets will form, and whether the planetary system is hot or cold.
Laura Dressing of UC Berkeley points out that many multi-planet systems show their planets orbit in regularly spaced orbits, a ‘peas in a pod’ regularity. Indeed, as various case study papers showed, quite a few systems have planets orbiting in various resonances with each other, e.g. 2:1 or 3:1 orbital periods, for example. Which probably enforces the scenario that do not permit tidal migration. If you want regularity of spacing, you want things cold, and you do not want to have companion objects disturbing the peace.
So much for the simple picture.
* Observatory Fire
The American Southwest have had wildfires raging for weeks (climate change, anyone?), and one, the Contreras fire, has reached the Kitt Peak National Observatory near Tucson, AZ. As of June 19th, it had not reached any telescope building but all have been shut down. Four buildings were destroyed, used primarily as daytime dormitories for visiting nighttime observers, plus infrastructure such as that for electricity and roads. Instrumentation may be damaged elsewhere due to dust and smoke and heat. Most staff have been evacuated and those that are there are apparently not staying but come mostly for inspection and aiding firefighters who create firebreaks. Public outreach and tours have been long shut down. [Based on KPNO reports and New York Times reporting on June 19th, 2022].
* AAS: Venus’ Atmosphere, Signs of Life?
Is there life on Venus? You are kidding me, right?
From at least the 1960s, it has been known that the atmosphere of Venus has been hellishly hot, not a white-cloud enshrouded tropical world as early observers had dreamt of. But a theory came up that as the greenhouse effect took over, life took up in the residence in the cooler realms of the atmosphere. It wasn’t until recently that some evidence for that far-fetched idea came into existence and, as astronomer Jane Greaves of Cardiff University explained, it isn’t yet a settled question.
The evidence is a spectral line in the atmosphere for the molecule Phosphene, PH3, one that is found (noted humorously) in waste emissions in penguins. While nobody expects penguins in Venus’ atmosphere, one wonders nevertheless as to how and why the gas would be there.
The hypothesis is that spores would float 45 or more miles up in the atmosphere, where it would be cooler in temperature, they would not burn up, and they’d find refuge in moisture droplets of some kind (see Cover Photo). Phosphene on its own is not stable in oxygen environments, like Earth. It can be produced industrially (not on Venus, of course), in volcanic plumes (yes, they are there but rare), and anaerobically biologically. It has been proposed as a biosignature to search for on exoplanets.
The Phosphene line in the radio spectrum was found in 2019 on Venus. But a single line does not proof make. Other lines of other molecules can be located there. Ideally finding other phosphene lines would be helpful, but lines in the infrared are blocked by Earth’s atmosphere . So the radio spectrum of other molecules, notably HDO, SO2, and H2SO4 (a big component of Venus’ clouds) are being monitored to see if 1) do any of the molecules vary together—gives clues to sources, 2) do the spectral lines have ‘wings’?—they give a clue to the pressures on the molecules, and thus locations and heights of the sources in the atmosphere, and 3) do the lines Doppler shift with Venus’ motions, proving they are real and not artefacts?
So far the case is more against life being the source of phosphene. Volcanoes, meteors and lightning are a more likely source of phosphene than tiny Venusians. The clouds are very low on liquid content, especially water, and they are very acidic. But they are also non-uniform and changeable and thus there could be niche favorable environments. For life, what would be needed would be something to make the favorable environments, such as a base compound to reduce the acidic nature of the clouds and atmospheric liquids. A base would reduce the SO2, neutralize the acids, and explain why the clouds have less SO2 than expected and more O2.
So current Venusian research is looking for such bases in Venus’ clouds, as will be five upcoming Venus missions: Rocket Labs (2023), ISRO Shukrayaan-1 (2024/6?), a UAE yet to be named mission in 2028, NASA/Veritas and DaVINCI (2028-9), and ESA/Envision (2031).
* AAS: When Did Kepler Realize Ptolemy Was Wrong?
It is hard to break old habits. In the 1600s the Universe was Earth-centered and everything moved in circles at a constant speed. Okay, you need extra circles, those pesky epicycles, to make the retrograde and direct motions of the planets work out, but overall, that’s all you needed, right. And a lot of math, with no computers or slide rules or calculators. And an accuracy of a degree was cool….unless you had Tycho Brahe’s amazingly accurate-to-seconds of arc observations.
William Donahue of St. Johns College can point to perhaps the two most important pages in planetary history where the world (universe?) went from geocentric to heliocentric, in Johannes Kepler’s notebook. There he was working the calculations between his heliocentric hypothesis and the geocentric theory of Ptolemy. Using arduous handwritten calculations he tried to take observations of theory and derive Tycho’s positions in the sky.
Kepler called Ptolemy’s theory the Vicarious hypothesis and his the Physical hypothesis. Distance to the planet Mars in its orbit from Earth was called its altitude. As usual, the non-circularity of the orbit was its eccentric.
For the Vicarious hypothesis, the distances didn’t match up anywhere. The physical hypothesis gets ALMOST the right eccentricity but the distances are right only at aphelion and perihelion, i.e. when the planet is closest or farthest from the Sun. He found a 9 minutes of arc discrepancy, an area of the triangle Mars-Earth-center of the orbit between the two hypotheses’ values.
Kepler was holding to the speed-is-constant hypothesis. What do you do when the hypothesis doesn’t work? You reject, modify or adopt a new hypothesis. And that’s what he did. Rejected Ptolemy, rejected the constant speed, and changed our view of the universe. Right there.
Sky Planning Calendar
Moon passages by a star, planet or deep sky object are a good way to find a planet or other object if you’ve never located it before.
Our evenings are finally no longer planet-free, but not very yet interesting, and there aren’t any Moon passages by evening planets this fortnight until its end.
July 6 First Quarter.
July 13 It is Perigee and Full Moon (only ten hours apart) so we have a legitimate Super Moon! The (almost) largest possible Full Moon one can have on planet Earth. By dawn it will be on top of Scorpius’ stinger stars. Take a selfie…..
July 15 The waning gibbous Moon is 4-degrees south of the ringed planet Saturn.
There are far more planetary happenings in July than Moon events, and they are somewhat evenly split between late evening and dawn.
Mercury is on the way out. We start the month on the tail end of June’s Grand Line-Up (and see the June 29th photo on Astronomy Picture of the Day for the BEST photo of it!), with Mercury actually increasing its brilliance until July 6th, but it does so at the time that it is diving deeper into the morning twilight closer to the Sun, making it harder to find despite the brighter light. In just about 4 more days, it rises only 45 minutes before the Sun, the usual last possible condition for ‘easy’ chances to see it. After this, you might find it with binoculars for 1-2 more days if you’ve been following it and thus know where to look but by the 16th it is in conjunction with the Sun and totally gone (and don’t go looking for it with binoculars then or even close to the 16th unless you like getting your retina burned….).
Venus is hanging brightly in the early morning twilight. Want to see planetary motion? On July 1 it is on one side of Taurus’ face. Two days later it is on the other side.
Earth is at its farthest distance from the Sun, aphelion, about 94.5 million miles, on July 4. For those of you in the Northern Hemisphere, this should be conclusive proof that summer is NOT caused by the Earth being at its closest distance to the Sun, right?
Jupiter joins Saturn in the evening sky, rising before midnight Daylight Saving Time after July 12th. Mars does this, kinda sorta, on the 15th, only its rising then in the eastern half of the sky at midnight Standard Time (for those who don’t do DST). Saturn, meanwhile, rises when evening twilight ends on the 7th; get out your telescopes for ring-watching and Titan-spying!
The Sun’s cruising across the feet and bodies of the Gemini Twins. The astrologers say it is boiling Cancer the Crab. (Given the current heat dome over Alabama, I might be inclined to agree with the latter this time around…..)
Astronomy in Everyday Life
AAS: Sunrise, Sunset
These are not simple geometrical functions, when the upper edge of the Sun touches the horizon. The atmosphere distorts the Sun’s shape, and its passage downward towards that horizon. Refraction causes the all-important times of rise and set to be off by minutes to days, that last in the Arctic. Who gets predictions most correct?
An AAS poster by Jennifer Lynn Bartlett et al. discussed research on sunrises on the Maryland coastline. They compared common calculators and formulae to predict sunrises with observed times.
Belgian astronomer Jean Meeus’ formulae (from 1998) had slightly better results, about a minute less in discrepancies, than those used in USNO Almanacs and computer programs. A value for refraction of 34 minutes of arc seems to be a good approximation.
The Classroom Astronomer Newsletter-Inbox Magazine #30 July 1, 2022 Issue Highlights
Cover Photo - A Robotic Telescope in Texas
Welcome to Issue 30!
- AAS: An Outline for Doing an Astronomy Mastery Course
Astronomy Remotely —
- RTSRE: What Kinds of Research Can You Do? (Cover Story)
Connections to the Sky -
- AAS: Astronomer Biography Calendar
- AAS: USNO Sky Information
The RAP Sheet
- What Hides Within a Photograph: Analysis of a Light Curve in the Classroom
- Grade Level Influence in Middle School Students' Spatial-Scientific Understandings of Lunar Phases
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