Champaign-Urbana Astronomical Society
Looking Up,April 2021
Happy April! Hopefully, as the weather warms, we’ll see more members at the observatory, whether they are using the instruments inside the buildings or using their own at the site. Given all the things we hear on the news, I bet we could all use a “star break.” So what will we be see-ing?
Starting in the evening sky, April brings us the emergence of Venus and Mercury, though they won’t be easy to see. Mercury went behind the Sun on April 18 and rises from the glare fairly quickly. Venus did the same on March 26th but its rise is much slower. The two pass each other by a degree on the evening of April 25th, though you have to look very low in the west-northwest. The pair set at 8:30pm CDT, a bit over 40 minutes after sunset and a full hour before twilight ends. Mercury is headed for a great evening view next month.
Next up, planet-wise, is Mars. In mid-April, Mars is about 45 de-grees high in the west as the twilight begins to fade. At a distance of 1.9 A.U.s, Mars is nearly twice as far from us as the Earth is from the Sun. Point being, it’s not much to look at. A simple red dot with-out much detail visible. A crescent Moon ap-pears below Mars on the evening of the 16th. There’s an occultation the next day visible in southeast Asia.
The excitement regarding Mars has to do with the Perse-verance rover and the helicopter Ingenuity. As this issue goes to press, the helicopter isn’t due to have its first flight until after April 8. It was also announced that the helicopter contains a small piece of the original Wright Brothers’ flyer! My how far we’ve come in 118 years!!! Several factors will determine the precise time for the flight, including modeling of local wind patterns plus measurements taken by the Mars Environmental Dynam-ics Analyzer (MEDA) aboard Perseverance. Ingenuity will run its rotors to 2,537 rpm and, if all final self-checks look good, lift off. After climbing at a rate of about 3 feet per second, the helicopter will hover at 10 feet above the sur-face for up to 30 seconds. Then, the Mars Helicopter will descend and touch back down on the Martian surface. Stay tuned.
You have to wait a while to see another easily-visible plan-et as Saturn, then Jupiter rise in the morning sky. At the beginning of April, Sat-urn rises in the south-east at 4:30am CDT with Jupiter following a half hour later. By the end of April, Sat-urn appears at 2:30am with Jupiter 40 minutes behind. The Moon is below Saturn on the morning of the 6th. Before that, though (on the morn-ing of April 2nd), early risers may want to point a telescope at Jupiter to see a “5th moon!” The moon Io appears only 0.5 arc seconds from the star 44 Capricorni.
That wraps up the month. Be sure to make an effort to get outside for “Dark Sky Week” April 5th through 12th. Spread the word through social media and your networks.
-DCL
Looking Up, March 2021
Is it spring yet? You know, despite the single digit temps we had for a bit in February, it has been pretty mild. But spring does begin on March 20 this year with the vernal equinox occur-ring at 4:37am. The Sun will appear straight up at noon if you live on the Earth’s equator. For us in Central Illinois, we’ll see the Sun 50 degrees (five fists held at arms length) at mid-day.The only planet easily visible in the evening sky is Mars. Of course Mars drew a lot of attention with the successful landing of Perseverance rover. Hopefully this month we’ll get to see the Ingenuity helicopter fly. Estimates put the inaugural mission about four weeks after landing. In our sky, Mars sets around midnight (CST). At magnitude +1.3, it’s still bright but now you have to find it among the many bright winter stars. The first week of March, Mars is very near the Pleiades, coming between the star cluster and the eye of Taurus, the Bull, the star Aldeba-ran on March 8th. A crescent Moon appears near Mars in the west on the evening of the 19th. Mars will go about halfway between the horns of the Bull on April 12th. Mars isn’t much to look at through a telescope due to its distance but you can watch it “wander” amongst the stars of Taurus this month.The rest of the action occurs on the morning sky. If you get up around 5:30am at the beginning of the month and look low in the east-southeast, you’ll find three planets in the morning twi-light. Saturn rises first, then Mercury, then Jupiter. At magni-tude -0.3, Jupiter will be the brightest of the trio. On the morn-ing of the 5th, Mercury comes to within 0.4 degrees of Jupiter. If you keep watching, Jupiter will gain altitude day by day while Mercury gets lower. On the morning of the 9th, a thin crescent Moon joins up, situated just to the right of Saturn (see the im-age). The next morn-ing, the Moon is below and to the right of Jupiter.Venus passes behind the Sun on March 26th and technically enters the evening sky this month, but it sets basically minutes after the Sun at the end of March. We’ll check back on Venus next month.If you want a challenge, look for the asteroid Vesta early this month. Opposition for this 326 mile diameter rock is March 4th. It just so happens that, this night, the asteroid is only 1.2 de-grees northeast of the star Chertan. This is the star that helps form the triangle that follows the backwards-question-mark shape of Leo, the Lion. The image below shows the path of Vesta over 10 days starting March 2nd. Vesta will appear like a 6th magnitude “star” (asteroid means “starlike”). The key is the movement. Use binoculars and look over several nights, even making a rough map of the field of view. When you detect movement, you can say you found the asteroid. Vesta isn’t the largest asteroid but it’s the brightest as it is relatively close to our Earth. Leo is already above the horizon, nearly due east, as the evening twilight ends. Why not give it a shot?DCL
Looking Up, February 2021
If we start in the western sky at the beginning of February, Mercury is finishing the first of three evening views for the year. Though this one is good, it won’t rival the one com-ing in May. Greatest separation from the Sun occurred on January 23rd so Mercury is on its way back towards the Sun to pass between the Sun and Earth. After the first week of February it’ll be very difficult to see. It’s setting in the twilight as it is but, at magnitude +1.5, you still can give it a shot. Look low in the west-southwest. If you can find the Great Square of Pegasus, a line drawn from the upper left to the lower right square star roughly points to Mercury. Mercury will appear in the morning sky begin-ning February 20th, but it’s not the best view.
Mars becomes a focus this month because of the Perse-verance lander’s arrival on the 18th. It’s too bad that we have the virus as I clearly recall the Curiosity landing in Au-gust of 2012. The planetari-um was one of only two facili-ties in the state to livestream the landing, but it was at roughly 2am (No Zoom back then!). I unlocked the place at midnight thinking I may get 2-3 people to join me. Well it was standing-room only and people cheered when the news came back of a successful landing. And then no one would leave! That was one of the highlights of my 30 years in that dome. I wish we could do a repeat. Here’s hoping the 30-mile diameter Jezero crater gets company on the 18th. See the last page of this newsletter for info on how to watch the events that day.
You can see Mars in the evening sky. Though it has faded some, it’s still magnitude +0.5 and in a star-poor section of Aries. I saw it last week, though you have to strain your neck it’s up so high (over 60 degrees at sunset). Mars appears to be heading towards the Pleiades star cluster (it’ll pass by there early next month). A thick crescent Moon is below Mars on the evening of the rover landing. Mars won’t set until after midnight this month.
Unless you’re looking for Uranus & Neptune, that’s about it for planets until the morning twilight begins. Early in February you might catch Venus in the east-southeast but its really low. After February 7th, it’s all but impossible to see. It’ll pass behind the Sun next month. Jupiter and Saturn will emerge from the Sun’s glare after December’s con-junction, but, again, they are low on the eastern horizon. On the morning of the 15th, Jupiter, Saturn and Mercury make a trian-gle, but you’re looking into brighter twilight. The image is from Feb-ruary 28 at 6am. By the end of the month, the sky is a bit darker and Mercury is closing in on Jupiter. They’ll come to 0.4 degrees of separation early in March. -DCL
Looking Up This Month January 2021
Happy New Year, everyone! I think it’s an understatement to say that 2020 was certainly a “unique” year. Hopefully we can get back under the stars together as a group in 2021. Did you see the Jupiter/Saturn “great conjunction last December 21st? The forecast for that night wasn’t good so several went out the night before. Jim Wehmer reported about 30 cars at the obser-vatory that Sunday (of course there was no official viewing ses-sion). But then it cleared off for the 21st and about 20 cars joined me at the observatory that night. Dr. Paul Ricker and several others (including News-Gazette photographer Robin Schultz) were there doing some imaging. Though the closest approach has occurred (you have to wait 20 years for the next one), the two planets are still fairly close in the southwest after sunset. Jupiter is, of course, moving eastward, away from Saturn. They’ll be within a couple of degrees for the first week in January.
And, as a bonus, the duo becomes a trio for the January 8th weekend. Mercury rises from the glare of the Sun to meet Jupiter and Saturn. On the evening of the 9th they’ll make a nice triangle with Mercury directly below Jupiter and Saturn halfway between and to the right. Again, look soon after sun-set in the southwest. You might even use binoculars. The trio are technically closest on the 11th with Jupiter and Mercury separated by 1.4 degrees. The Moon is new late in the day on the 12th, then reappears in the evening sky, being to the upper left of Mercury on the 14th. Look for the Earthshine if you can glimpse the Moon. Saturn and Jupiter pass behind the Sun on the 23rd and the 28th respectively and will appear in the morn-ing sky next month. Do try to catch Mercury as this is one of the two best evening views for all of 2021. Mercury is in the sky more or less on its own later in January and the greatest separation from the Sun occurs on the 23rd. It will be at magni-tude -0.07. Then it quickly slides back into the Sun’s glare.
Mars begins the month in Pisces but swiftly moves into Aries. The angular diameter of Mars is near 10 arc seconds now which many consider to be the limit as far as seeing surface features. At magnitude 0.1, it’s still pretty bright and in a star-poor region, so it should be easy to find. The challenge with Mars in January is that it passes by the planet Uranus. The two are closest on January 21st with Uranus being 1.6 degrees south. Uranus will be at magnitude 5.8, which you should be able to see in binocu-lars as there are no other stars just south of Mars that are that bright. The bad timing comes from the first quarter Moon being six degrees from Mars the night before (the 20th).
Venus pretty much rules the morning sky, now rising at about 6:30am. A beautiful (and thin) crescent Moon will be to the right of Mars on the morning of January 18th.
The Quandrantid Meteor Shower peaks the first weekend of the year. The shower is predicted to peak after the Sun rises on the morning of the 3rd, but you still might see a few meteors before. The radiant is situated between the pole star and the head of Draco in the north. The waning gibbous Moon will outshine the fainter meteors but the Quandrantids are also known to pro-duce a few fireballs. Maybe we’ll get lucky! -DCL
Looking Up, December 2020
Looking Up This Month We have three major events in December, two of which will be visible . . . .well, provided it’s clear; and the third you might watch online. We begin with the Geminid Meteor Shower. If it’s clear, we have the perfect conditions this year. The shower occurs on a weekend and the Moon is new on the following Monday, producing dark skies. The Geminids are just as potent as the August Perseids but usually don’t get the press due to the clouds and cold of a typical December. Start looking Saturday maybe 9pm and see how long you can stay out. Numbers typically increase after midnight and, though meteors sometimes appear in groups, they average two a minute. Recall meteors occur when pea-sized dust hits our atmosphere at 80,000 miles per hour and, in slowing down, their kinetic energy is transferred to the air, causing it to glow. Geminid meteors will appear to come from the northeast, but just look upwards and obviously dress as warm as you can. On Monday morning, the 24th, we have the new Moon. And it just so happens that, this time around the Earth, the Moon will pass in front of the Sun and we have a total solar eclipse. We won’t see this from our backyards as the Moon’s shadow goes from west to east in the south Pacific ocean, crossing South America at Chile and Argentina. Totality is just over two minutes long. You can watch the event on livestream (can’t you see about anything on livestream anymore?) by going to the San Francisco Exploratorium site (www.exploratorium.edu/ eclipse). I believe coverage starts at about 8:30am. Hopefully you have been keeping track of Jupiter and Saturn as they close in on each other. They will be the two brightest star-like objects in the southwest right after sunset. They start the month about two degrees apart. On the 16th, a thin crescent Moon should be visible below the pair of planets. The long-awaited grand conjunction occurs on the evening of Monday, the 21st. The planets will be a tenth of a degree apart and you should be able to see them (and their moons) in the same low power telescope field of view. Saturn is 1.8 times farther away than Jupiter. This conjunction occurs every 20 years and was one of the sky events that greatly interested Johannes Kepler which lead to his laws of planetary motion. The magazines report the last time these two planets were this close was 400 years ago, but that approach wasn’t visible. The last visible gathering occurred in March of 1226 CE!! Though there isn’t an official observing session due to the virus, the observatory (with its low horizon) would be a nice place to check out the event. Again, look quickly as the pair will be 14 degrees high and will set soon after 6:30pm. Mars is rapidly fading and shrinking though still showing some surface features this month. It’s still bright at magnitude -0.7 and, being in the star-poor region of Pisces, it’s easy to pick out. A waxing gibbous Moon is just below Mars on the evening of the 23rd . Shifting to the morning sky, Venus rises at roughly 5:15am as it glides through Libra. On the morning of the 12th a thin crescent Moon is just above this brilliant planet. On the morning of the 26th, Venus rises to the left of the red star Antares. Mercury is briefly visible early in the month (though quite low) and it passes behind the Sun on the 19th . Late-breaking news . . . .Comet Erasmus (C/2020 S3) was discovered this past September 17th by an amateur skywatcher in South Africa. As this issue goes to press, the comet has brightened from 7th magnitude to possibly 5th magnitude. Perihelion is December 12. The comet is in the morning sky, in the southeast, to the right of Venus. Let us know if you see something! -DCL
Looking Up, November 2020
Did you get a good look at Mars last month? Hope so! This month the Earth speeds away from all the visible outer planets. Mars, Jupiter and Saturn will all dim and shrink in apparent diameter. Jupiter and Saturn are in the south at sunset and they are creeping closer to each other. This month they’ll go from 5 degrees down to 2.3 degrees. The big conjunction (a once every 20 year event) is next month.
Jupiter sets at 10:30pm CDT at the beginning of the month and then 8pm CST by the end of November. A beautiful crescent Moon makes a nice triangle with these two planets on the evening of the 19th (pictured here). Of course the four Galilean moons of Jupiter and the rings of
Saturn still impress. The rings are tilted at a nice 22 degree angle. Mars will still draw the attention of telescopes this month, even though closest approach occurred last month. The planet dims from magnitude –2.1 to -1.2 and shrinks from 20.1 to 14.8 arc seconds. Still large enough to see a few surface features.
Better yet, wait until 9-10pm when Mars is highest in the sky so you’re looking through less terrestrial air. Sky & Telescope magazine has a nice site that will show you which side of Mars you’re seeing. Check it out at: https://is.gd/marsprofiler. A waxing gibbous Moon is just below Mars on the evening of the 25th.
The rest of the action is in the morning sky where Mercury joins Venus. Venus rises not quite three hours before the Sun in early November to 2 ¼ hours at the end of the month. Venus is inside the constellation boundary of Virgo. Mercury joins Venus early in the month in what could be argued as its best morning view of the year. Mercury rises rapidly and reaches greatest separation from the Sun on November 10th (20 degrees). But look early in the month and catch Mercury just to the left of the star Spica. Mercury rises about an hour after Venus and shines at magnitude +1.6, but it will brighten to -0.6. It almost seems like these two planets are destined to meet each other as Mercury gets higher and Venus gradually gets lower, but Mercury makes the big turn-around November 7th and heads back towards the Sun. It’ll be tough to see by the end of the month. Venus will also pass Spica on the morning of the 17th. Look east-southeast.
A very thin waning crescent Moon will rise between the planets on the morning of the 13th (pictured here at 6am) We’ll have a penumbral lunar eclipse on November 30th beginning 1:32am CST. Remember this is a “penumbral” eclipse, meaning the Moon goes through the lighter part of the Earth’s shadow. There is a lighter part of the shadow and a darker part, all due to the fact the light source (Sun) is not a point source. So the Moon won’t go dark but you may see a faint shading of the lunar surface. Mid-eclipse occurs at 3:43am when 83% of the Sun is within the penumbral shadow. The event is over by 5:53am. This is the fourth penumbral lunar eclipse in a row.
The Leonid Meteor Shower peaks on the morning of November 17th. No outburst is expected (in face the predicted hourly rate is 10-15 meteors per hour) but you never know. Though not the most potent shower of the year, the Moon is in a good spot leaving some dark skies for observation. Meteors are the dust shed by Comet Tempel-Tuttle.
-DCL