#24M - Directly Viewing Exoplanets - Moon and Mars Both Visiting Other Worlds
TGT 7/16/24: Imaging Beta Pictoris and Other Exoplanet Systems--Figuring Out How Planets Form; Products With Temperatures; Moon and Mars Visit Other Worlds;
Cover Photo - 100,000 Exoplanets, Only 15 Actually Seen
In This Issue:
Cover Photo — 100,000 Exoplanets, Only 15 Actually Seen
Welcome to Issue 24M!
Sky Planning Calendar —
* Moon-Gazing - Moon Passes Three Planets; Meteors in the Moonlight
* Observing—Plan-et -
- Mars Challenge (Still)—Compare Brightness and Color With Two Nearby Red Stars
- Jupiter—THREE Moons Cast Shadows on the Giant Planet on the Same Night
- Saturn Becomes an All-Night World
* Border Crossings - One Day to be a TwinThis Just In
- Exoplanet Viewings and FindingsAstronomy in Everyday Life - How HOT is it??
Welcome to The Galactic Times Newsletter-Inbox Magazine #24M!
A pair of exoplanet reports from the American Astronomical and Royal Astronomical Societies’ meetings, all on the same star visible in our winter (and more Southern) skies with an unexpected actively changing surrounding disk and two planets, which we can actually see, one of the few such systems.
Use the Moon to find three planets, if you’ve never seen them: 1) the Moon passes close to Saturn, Mars and then Jupiter, and also the Pleiades star cluster (nominally a winter star grouping) these two weeks. Then, 2) once you’ve seen Mars, follow *it* in the pre-dawn as it enters Taurus and passes (slowwwwly) a few degrees by the red star Aldebaran, the eye of the Bull (and not too far from Orion’s red giant Betelgeuse)—a chance to learn to compare brightness and colors of the three objects, and figuring out when they match in brightness. But before Mars reaches nearest to Aldebaran, it *also* passes the Pleiades. Finally, 3) once the Moon has pointed out Jupiter to you, a telescope of all but the smallest sizes will show it one night to have two dark eyes— two shadows of moons cast on its face, at the same time. In fact, three moons, as one moves off, another will come on. Two 'doubles’ in one night.
We end the issue with a look at astronomical temperature systems, appropriate for the heat waves currently abounding on Earth.
- - - - -
Back ‘from’ Toulouse, France, and Padua, Italy, now heading to Hull, UK, for the Royal Astronomical Society’s National Astronomy Meeting (NAM). Lots to report on overall… and yours truly will be preparing reports like what went out in Issue 24K Xtra for Paid Subscribers, as promised. Annual subscribers pay roughly $1.25 per Galactic Times Issue and get the Xtras. Your support is very welcome; you get extra issues that lower that cost! Subscribe with the button at the end of this newsletter.
Note that we are taking off for a summer break in August so there will be no August 15th or September 1st issues. At least, not ‘live’ ones. Planning to send out pre-written/pre-scheduled versions of the Sky Planning Calendar and some Astronomy in Everyday Life columns I’ve been holding on to, just to keep you abreast of sky happenings.
Enjoy!
Publisher — Dr. Larry Krumenaker Email: newsletter@thegalactictimes.com
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.
July 17 The star Antares is only 0.2-degrees (less than half the Moon’s diameter) south of the Moon. It is actually covered up by the Moon…if you observe from Africa. North Americans will see the Moon to Antares’ left (east) in the evening.
July 21 Full Moon.
July 24 Double duty for the Moon tonight. It reaches Perigee, this month’s closest distance to Earth, making the largest phase of the month, a Super Waning Gibbous! (Woo Hoo!). Add to that, Saturn lies 0.4-degrees (80% of the Moon’s apparent diameter, roughly) South of the Moon. Luna occults this planet, too, but that’s visible just about everywhere except in North America.
July 27 Last Quarter.
July 29 The Moon skirts the edges of the Pleiades star cluster.
July 30 The Moon has a party day. First it flirts with Mars, for the second time this month, passing 5-degrees north of the red world around 5AM CDT. Then it does the same with Jupiter at 6PM (again, for the second time), still too bright a sky to see but if you look at the Moon at that time with binoculars, the Giant Planet is bright enough to be seen even in daylight, sometimes by eye but easier by binoculars, that same 5-degrees South of the Moon. Given that the Moon moves about 1/2-degree per hour, can you figure out how many degrees apart in the sky the two planets are??
Observing---Plan-et
==Watch Mars Nearing Jupiter, Matching a Red Star This Month?==
==A So-so Meteor Shower.==
==See Mercury Best NOW.==
Earth-view—Southern Delta Aquarid Meteor Shower
This middling meteor shower peaks on the 28th. It can produce 23 meteors per hour, sometimes more, sometimes fewer, and is active at lesser rates for about 2.5 days on either side. Because the Moon is a day past Last Quarter, your best chances are in the hours just before and after local midnight/Moonrise. You won’t see that many before local midnight because the radiant where meteors come from amongst the constellations (hint: Aquarius) is below the horizon—Earth blocks your view—and then Moonlight will drown out all but the brightest shower members afterwards. It might be better to watch the night after peak—less Moonlight—but considering the heat situation in the USA, it will be at least climatologically comfortable to sit in that lawn chair or recliner and watch them come out of the Southeast, early on. And the fireflies….
Mercury is having a nice apparition in the evening, especially for Southern Hemisphereans, but it isn’t too bad for Northerners either. It doesn’t set until more than 45 minutes after Sunset all the rest of July even though it has faded from max brightness. It reaches its maximum distance this time around from the Sun, 27-degrees, on the 22nd. On the 24th it hangs below (as seen in North America and Europe) the star Regulus by only two degrees. Use binoculars to make that easier to find.
Venus. Knowing how bright she can be, this planet is letting all the other gods, er, planets have the show, so to speak. It sets earlier than Mercury, in bright twilight, still hard to find. But by month’s end it sets more than an hour after the Sun. After that, Venus will claim her limelight.
Mars is one of two planets to really keep an eye on. It is still a morning world but it will next month rise before local midnight. On the 21st it passes 5-degrees south of the star cluster Pleiades (the Seven Sisters), days before the Moon does the same thing but MUCH closer, even IN the star cluster, if you are in the correct part of the world to view that. And it is closing in bright Jupiter to its east (left).
Are you still watching, as per the last issue of TGT, Mars’ brightness and color compared to nearby Aldebaran and further away Betelgeuse? Can you tell when its brightness matches one or the other star? How about its color and theirs?
Mars gets passed by the Moon on the 30th.
The other planet to watch is Jupiter, rising in the East about an hour after Mars. On the 30th, the two planets share Moon passages, see above. Earlier, on the evening of the 23rd, two moons cast their shadows on Jupiter’s clouds, in the evening. Twice! Three different moons….
The Moon passes close by Saturn, even over it in some places, on the 24th. Afterwards, the king of the evening sky rises at the end of evening twilight, becoming a party-, er, visible-all-night planet, on the last day of the month.
Border Crossings
You can be an astronomical and astrological Gemini Twin for one whole day, July 21st! Astronomically, it leaves behind Taurus on that day. Astrologically it enters Cancer on the 22nd. No bull….
This Just In
Exoplanet Viewings and Findings
The star Beta Pictoris (in the very southern constellation of Pictor the Easel) isn’t visible in the sky right now, but it is highly visible in the universe of exoplanets. It became one of the first known exoplanetary systems, primarily because it had a tremendous dust disk around its white star, only 63 light years from us. The disk was first detected because of a high excess of infrared (IR) radiation, shortly thereafter visually detected, way back in the 1980s. The disk is made up of several circular rings of material, all edge-on to our view of the system.
Or so it did…..
New 2023 observations by the James Webb Space Telescope (JWST) seem to indicate that at least two of the rings have vanished, and there were several new features. On one side was a curved arc of material nicknamed the Cat’s Tail. On the other side were material ejected as a secondary disk at an angle to the main disk.
A comparison of the disk’s IR spectra of 2003 and 2023, shows the erasure of the spectral features of some of the disk’s hot dust and cold Mg2SiO4, a compound found even on Earth, called fosterite—known as Hawaii’s Green Sand.
It appears that in the 20 intervening years, there was a collision of asteroidal-sized objects that (1) caused the two new features to appear, and (2) swept a lot of material out of the system, and taking out some of the rings. It appears that this system, which has two exoplanets as well, isn’t in a quiet steady-state but is dynamically active…and filled with materials common to Earth and possibly Earth-like planets, per Christine Chen et al at the recent American Astronomical Society meeting.
Indeed, Beta Pic is one of only 15-20 exoplanetary systems that have their planets actually directly imaged (See Cover Photo).
The vast majority of exoplanets are found by two methods, according to astronomer Sasha Hinkley of UK’s University of Exeter, at the Royal Astronomical Society National Annual Meeting (NAM) on Monday. One is by the planet transiting in front of the star, causing a slight dimming of the light. The second method is the Doppler Shifting (or Radial Velocity Shifting) where the gravitational pull of the planet causes the speed of the main star to vary in a periodic way—tiny bit faster, then tiny bit slower, and repeat.
The challenge for visually or directly detecting the exoplanets anywhere is that the brightness contrast between star and planet is pretty extreme, and they are usually very very close on the sky, closer than what can usually be separated by any telescope. Dr. Hinkley provided an elegant and amusing analog….like trying to see a firefly on the rim of a searchlight….from 135 miles away.
To directly see this ‘firefly’ in the sky Hinkley discusses a three-part method he and others are now trying to use.
View them with Adaptive Optics. These are telescopes with ‘mirrors’ made of many rapidly moving reflective parts. Before the starlight reaches the Earth’s surface, it is widened and deformed by our atmosphere’s motions and pockets of density changes, which act as lenses, all distorting the wavefront of light coming from space, from a pinpoint to a variegated spread out irregularly-shaped disk, both in size and in the third dimension as well. The mirrors rapidly move in and out the same way (most often using a parallel laser beam to the sky to make an artificial star the system observes doing the same distortions) which restores the wave front.
2. Then a coronagraph blocks the resultant bright disk, similarly to the way the Sun’s disk is blocked to make artificial solar eclipses every day in some solar observatories to look at the Sun’s Corona.
3. But starlight tends to spread out from around that blocked star and the residuals have to be corrected. This is done by following the object through changes in altitude and azimuth and those things that aren’t constantly in all the images cancel out, leaving exoplanets visible.
These above four photographs, courtesy S. Hinkley. [Note that we aren’t actually seeing the planet’s surface but the reflecting of light from the atmosphere.] But directly imaging is only part of what astronomers want to do. They want to know HOW planets form and their early histories. There are two main theories on formation, and three questions they ask.
Planets may form from accretion of smaller pieces, building up a rocky core. Or they form from condensing out of a gravitational disk of materials. The two forms have different histories—planets building up start cool and heat up, planets condensing from dust and gas start hot and then cool. The graphs of those changes over time are far from identical, at any planetary mass, so getting a data point of temperature and mass is a good indicater of an exoplanet’s history. Those atmospheres often have different compositions—an accretion world will have heavier metal atoms in it—a condensing world will have a more solar (or stellar) lighter-atoms composition. Turns out, the JWST is very good at getting IR spectra that can tell planetary atmosphere compositions. Previously we could only get IR spectrum at wavelengths of 1-2 microns. Now we can view “redder” as far as 15 microns.
A new method of detecting exoplanets is about to provide a data “earthquake.” The satellite Gaia is measuring stellar positions so accurately that it can now measure the wobbling of a star as it slowly annually moves across the sky, the deviation from a straight path being due to the gravitational pull of the exoplanets ON the star. This is just like Radial Velocity Shifting, only this time it is the side-to-side motions, not towards-and-away.
So directly imaging an exoplanet is more than just potentially seeing its surface. It also measures the atmosphere composition, temperature, may gauge how it formed, its orbital distance, and mass.
One day we may know a lot more about the two planets and apparently dynamic active system of Beta Pictoris, directly as a WORLD.
Astronomy in Everyday Life
How HOT Is It??
It’s hot. No. It is HOT. H. O. T. hot. Hot enough to make a Venusian comfy visiting Earth.
How HOT is it? What temperature system do you want to use? How about this one?
Its manufacturer is also apparently even more astronomically inclined— they call themselves Galaxy Vibe!
Oh. You don’t get Celsius? So let’s do temperature in Fahrenheit!
Interesting that the non-metric unit seems to be more commercially popular. You have your choice (clockwise from upper left) an expensive fragrance (at least you’ll smell nice as your sweat), a chocolate treat (provided it hasn’t melted), a gel (comes in two kinds, a heating gel and a cooling gel! How thermodynamic!) and finally, a glue to put your melted things (sorta) back together.
Now astronomers don’t use EITHER unit for stellar properties. They use Kelvin. Regrettably, the only two such commercial-found names even close to Kelvin was Kelvan, a brand name (a whole line of products, not heat related) and the Andromeda-based empire from the original Star Trek series. Wholly not appropriate.
Cool off however you can…..
More reports from the AAS were sent out in TGT 24 Xtra to Paid and Education Professional subscribers. More of them, and from the CAP and NAM conferences will be coming out in future Free and Paid issues. In July yours truly also unexpectedly attended the European Astronomical Society annual meeting. Want to read all these meeting reports and news, and educational tips? Upgrade!