#39: - Demographics of Exoplanets - Half a Year of Mars Weather - & 3 more
TGT 1/17/23: Finding and Explaining Exoplanets; Venus and Saturn, Moon Over Mars, Comet Near Polaris; The General Weather at Jezero; A Starry Drink.
Cover Photo - Venus (with Various Worlds) Conjunctions
In This Issue:
Cover Photo — Venus (with Various Worlds) Conjunctions
Welcome to Issue 39!
This Just In -
- The First 250 Sols of Weather on MarsAAS: The Demographics of Exoplanets
Sky Planning Calendar —
* Moon-Gazing - The Moon Flies By and Over Planets
* Observing—Plan-et - Conjunction of Venus and Saturn, Mars Occultation, Comet ZTF Peaks
* Border Crossings - A Day in CapricornusAstronomy in Everyday Life - Starry Starry Drink…..
Welcome to The Galactic Times Newsletter-Inbox Magazine #39 !
Can I return 2023 to the factory? It is defective. A deep freeze → burst pipe. Under the house wire fritzed → dead oven. Two rounds of tornadoes → damage to me, and to neighborhood and a tree here. Separate storms. And it is only mid-January!
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“Back” from the virtual AAS meeting and collating the collection of stories. One here already, more to come. Meanwhile, twisters and storms and weather permitting, the end of the month skies look like fun, with a comet and another Mars occultation!
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Publisher — Dr. Larry Krumenaker Email: newsletter@thegalactictimes.com
This Just In
* The First 250 Sols of Weather on Mars
Perseverance at Jezero Crater on Mars has been monitoring the local conditions as the first permanently operating weather station on Mars. It has been recording temperature, air pressure, winds, atmospheric opacity, and other factors since shortly after the craft’s landing in February 2021, nearly a year ago. The station records data for about half a Martian day (sol), an hour at a time, alternating between even and odd hours. Having analyzed nearly half a Martian year, the team issued a report on that first ‘six months’.
Night time has a thermal inversion where it is warmer above than lower, and then the daytime gets highly turbulent and convective, with large vertical thermal gradients. Aerosol concentrations are higher in the morning than in the afternoon. Winds are mainly controlled by local topography, but there is a small contribution from the larger regional winds. Winds usually peak at 7 meters per second, but can gust as high as 25. There is a water cycle, though it is complex and varies with the day and seasons. Relative humidities can range up to even 30% locally. These observations suggest that changes in some local surface properties, such as surface albedo and thermal inertia, play an influential role. There are also changes in air pressure and weather due to various fluid waves and motions caused by mass motions of the air from gravity and other forces.
Dust devils are numerous and are detected in pressure and temperature sensors as well as audio and video. Clouds, both day and night, are also detectable.
Jose Rodriguez-Manfredi et al, The Diverse Meteorology of Jezero Crater Over the First 250 Sols of Perseverance on Mars, Nature Geoscience, January, 2023. 10.1038/s41561-022-01084-0 (Open Access)
AAS: The Demographics of Exoplanets
In this first article, based on a plenary at last week’s American Astronomical Society’s meeting, Jessie Christiansen of Caltech went through all the various ways that exoplanets are detected, what they are all missing, and what this means for what kinds of exoplanets are out there, and why we want to know.
Using the NASA Exoplanet Archive and its over 5000 confirmed exoplanets, she first showed that there are four principle methods of detection, regardless of whether ground- or satellite-based: transits, radial velocity motions, microlensing (seeing them through gravity lenses) or direct imaging. Each finds planets in various mass ranges and orbital distances from the host stars. Transits, for example, find planets that are all close to the star, usually less than an astronomical unit (1 AU is the Earth-Sun distance). Masses can be tiny to almost 10,000 Earth masses, but there are two main groups with a gap between 10 and 100 Earth masses, and virtually no planets found beyond 1 AU. Radial Velocity hunting —detecting them through lines in the stellar spectrum periodically shifting—finds many high mass planets in the range of 1 to 50 AU, extending the high mass population, and some of the low mass and close-in ones, too, found by transits, but not as many. Not many of the high mass-close-in ones show up. Microlensing finds all masses, but only in a narrow range of distances while direct imaging finds mostly distant worlds and only massive ones.
So what?
What astronomers want to know is what is the true underlying general population and their distribution of planets in the galaxy. Why? Because knowing what that is will help us learn what physical mechanisms drive planet formation, planetary migration in star systems, and evolution of planetary systems, says Christensen. Additionally, what we want to know is the quantity called Eta-Earth, the frequency of (1) Earth-like planets (2) in habitable zones (3) around Sun-like stars.
Eta-Earth is a poorly known value. Currently is estimated to be from 5% to 50%, with some estimates going 10% to 100%. Accuracy is obviously nowhere near on target yet, despite new data from Kepler, Gaia and other missions past or present.
There is one hypothesis that says there are Earth-like planets in all systems that have small inner planets clustering in a “peas-in-a-pod” arrangement. Another hypothesis generated from observations is that systems with a Jupiter analog should, 50-100% of the time, have a super-Earth in them. Could this be extended to having normal Earths? Some recent things noted—metal poor stars have no planets, and among M dwarf stars, at about 1.5 Earth radius, there is a split between rocky planets and water planets being found. Why? Can these facts predict Earths?
Further, that diagram above—“is a lie!” Those different observational methods, unfortunately, don’t measure the same stars. They measure stars of different masses, and luminosities. The overlaps aren’t that great. But the soon-to-be active Nancy Roman Telescope will have a wide overlap over the different groupings and could solve the mystery, and narrow in on the true Eta-Earth value.
Sky Planning Calendar
Moon-Gazing
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.
View or Download this information on our Sky Event Online Calendar on The Galactic Times homepage!
January 21 New Moon and Perigee, too. A Super-New Moon…too bad you can’t see it!
January 23 The two-day-old Moon plays tag with two planets: 4 degrees south of Saturn and three degrees south of Venus. You’ll find them lower right of the Moon in evening twilight. And look closely at them — they are CLOSE (see below).
January 25 Next tagged, Jupiter; find it 1.8-degrees north (below) of Luna during evening hours.
January 28 First Quarter Moon. The Moon passes over Uranus but only if you are in the Pacific Rim from eastern China-Japan through Alaska and north Canada.
January 30 The Red Planet Mars is tagged last, in fact, it is occulted, and largely for all those missed out on the November occultation (see below). All others can find it to the lower left of the Moon at sunset.
Observing---Plan-et
Mercury bursts into the morning dawn like a rocket and reaches a maximum elongation away from the Sun on the 30th, only 23 days after having been in solar conjunction. Not the best apparition, but with most of the other planets not only in the evening but having set before morning twilight has begun, it has the dawn almost to itself.
Venus is already climbing well into twilight view in the evening and has its first interesting and fairly-easy-to-view event of the apparition, a close conjunction with the ringed planet Saturn. Passing it on the 22nd by a mere 0.4-degrees, the two make a close, but very very different in brightness, pair. Venus is at almost magnitude -4 but Saturn is barely brighter than first magnitude, hard to see in the twilight without optics. On the 23rd, the Moon is about 3 - 4 degrees below them, depending on from which planet you measure to the Moon. Look while you can; Saturn vanishes from view in just a few more days.
Jupiter is high up and obvious once the Sun sets, the brightest star-like thing in the sky once Venus sets early. And it reaches its perihelion, the closest it gets to the Sun, for the next 11.9 years…..so it really is as bright as it ever gets….
Finally, there’s Mars, bright and red in Taurus. Remember that cool occultation of Mars about a month ago? Observers in the Southern USA [the line of Moon graze and not possible further north of here runs from Southern California through the Texas Panhandle to central Alabama to the south Georgia coastline] and much of the rest of the hemisphere down to equatorial South America and much of Oceania get their chance on the 30th-31st.
Here are some sample local times for disappearance and reappearance:
Los Angeles 8:36 PM, 9:29 PM, on the 30th.
Austin, TX 11:10 PM, 12:12 AM, starts on the 30th, ends the 31st.
Miami, FL 12:38 AM, 1:27 AM, all on the morning of the 31st.
Other Sky Events
The winter comet C/2022 E3 (ZTF) broaches naked eye limit (6.0 or better) on January 26, if predictions hold. It stays in the 5th magnitude range, with a maximum 5.6, January 30th until February 2nd—it will pass its closest to us on February 1 and thus be at its brightest then—then fading.
The chart below shows you where to hunt for it.
And Further Afield….
This is a good time of year to watch the eclipses of Algol, the Demon Star, high in the sky in Perseus. Its eclipses cycle through the hours of the day and night. Most of the time is moderately bright, magnitude 2.1, but every 2 days 20 hours and some change, it dims to 3.3. The entire eclipse takes about 10 hours from start to finish. For the winter and early spring, we’ll list the evening eclipse apparition dates for easier scheduling. The thing to do is, of course, to compare the brightness of Algol to stars of known brightness on a periodic basis and make a graph of progress of the dimming and the light recovery and, in this case, try to find the time of max eclipse!
January 21 (near midnight), 24 and 27
Border Crossings
This is the time of the year where reality and ‘signs’ have the least coordination, but there is a ONE-DAY OVERLAP!! Woo-hoo!! On January 19th, the Sun enters Capricornus for real. According to the horoscopes, that’s its LAST day in that constellation before entering Aquarius. Oh, well…
Astronomy in Everyday Life
Somebody explain this to me…how did lemon-lime soda get a celestial connotation? I can see how lemon might get a Sunny one, but what’s the cosmic connection here?
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