Canis Major, with the bright star Sirius, is now fully above the horizon in the southeastern predawn sky.

The Moon joins Mars and Saturn in the southwestern sky after dusk for several days this week.
Venus is very low on the Southwestern sky, and is only visible for about 1/2 hour at dusk before being obscured by trees or buildings on the horizon. Jupiter sets shortly before 10:00 PM

The Moon
The Moon is a waxing gibbous just after first quarter; visible in the southern sky after dusk, the Moon is an excellent observing target for the next several days. The Moon will be full on September 24th.
Observing Target: The Lunar Terminator
The lunar terminator – NOT a rampaging cyborg from a dystopian future… but rather the division between the illuminated and dark hemispheres of the Moon.
Observing the terminator on the Moon around the time of first or third quarters can be fascinating! Over the course of several hours, you can watch the shadows slowly change shape, and the tips of mountains and crater walls come into view, or vanish. Each night, a whole new set of craters and mountains become visible. The full Moon shows none of these shadows, and is considered much less interesting to look at by most sidewalk astronomers.
The Sun
The Sun has been spot-free for 5 days. The huge coronal hole at the Sun’s north pole has gotten bigger – with a limb extending down towards the equator; several regions of coronal loop activity appear all along the equator. The coronal hole that started forming at the south pole last week has also grown in size. The solar wind speed is 530.4 km/sec, with a density of 12.0 protons/cm3 – the highest density I’ve seen in a while!
SpaceWeather.com says: “Earth is entering a stream of solar wind flowing from a hole in the sun’s atmosphere. It’s not a very fast stream, but at this time of year it could be enough to ignite Arctic auroras. Equinox cracks in Earth’s magnetic field are lowering our planet’s defenses against the solar wind, setting the stage for Northern Lights.”
Solar observing enthusiasts have been getting a treat for the last several days; numerous prominences appear all over the Sun’s limb! I saw a beautiful straight pillar prominence through Diane Hall and Jonathan Kade’s 40mm PST at last weekend’s Astronomy at the Beach event near Milford, Michigan.
You can create your own time-lapse movies of the Sun here: AIA/HMI Browse Data.
You can browse all the SDO images of the Sun from 2010 to the present here: Browse SDO archive.
Asteroids
Upcoming Earth-asteroid encounters:
Asteroid |
Date(UT)
|
Miss Distance
|
Velocity (km/s)
|
Diameter (m)
|
2018 RD5 |
2018-Sep-12
|
4.4 LD
|
6.5
|
24
|
2018 RT5 |
2018-Sep-12
|
1.6 LD
|
9.3
|
22
|
2018 RR4 |
2018-Sep-12
|
3.2 LD
|
8.9
|
14
|
2018 RY5 |
2018-Sep-12
|
0.5 LD
|
23.7
|
18
|
2018 RZ5 |
2018-Sep-12
|
0.1 LD
|
20.2
|
4
|
2018 RA6 |
2018-Sep-12
|
4.7 LD
|
13
|
29
|
2018 RO8 |
2018-Sep-13
|
11 LD
|
11.8
|
27
|
2018 RE3 |
2018-Sep-13
|
1.8 LD
|
10.3
|
13
|
2018 RE8 |
2018-Sep-13
|
1.2 LD
|
10.1
|
14
|
2018 RF6 |
2018-Sep-14
|
13.1 LD
|
12.4
|
36
|
2018 RC4 |
2018-Sep-14
|
10.5 LD
|
8.1
|
24
|
2018 RE5 |
2018-Sep-15
|
1.5 LD
|
15.3
|
12
|
2018 RQ2 |
2018-Sep-15
|
9.8 LD
|
14.4
|
93
|
2018 RC1 |
2018-Sep-15
|
16.7 LD
|
2.2
|
20
|
2018 RB6 |
2018-Sep-16
|
1.5 LD
|
13.6
|
25
|
2018 RN7 |
2018-Sep-16
|
2 LD
|
18.5
|
11
|
2018 RG5 |
2018-Sep-16
|
4.5 LD
|
8.3
|
15
|
2018 RA2 |
2018-Sep-16
|
8 LD
|
9.3
|
28
|
2018 RG8 |
2018-Sep-16
|
3.6 LD
|
7
|
15
|
2018 RM7 |
2018-Sep-17
|
2.8 LD
|
17.4
|
8
|
2018 RK6 |
2018-Sep-17
|
2.4 LD
|
6.4
|
9
|
2018 RQ4 |
2018-Sep-17
|
11.9 LD
|
7.8
|
15
|
2018 RM4 |
2018-Sep-18
|
11 LD
|
11.2
|
29
|
2018 RF8 |
2018-Sep-19
|
1.4 LD
|
15.8
|
26
|
2018 RB4 |
2018-Sep-19
|
17.9 LD
|
3.6
|
15
|
2017 SL16 |
2018-Sep-20
|
8.5 LD
|
6.4
|
25
|
2018 RH6 |
2018-Sep-22
|
8.6 LD
|
6
|
11
|
2018 RQ1 |
2018-Sep-24
|
4.1 LD
|
3.1
|
54
|
2018 EB |
2018-Oct-07
|
15.5 LD
|
15.1
|
155
|
2014 US7 |
2018-Oct-17
|
3.2 LD
|
8.7
|
19
|
2013 UG1 |
2018-Oct-18
|
10.4 LD
|
13.4
|
123
|
2016 GC221 |
2018-Oct-18
|
8.7 LD
|
14.4
|
39
|
475534 |
2018-Oct-29
|
7.5 LD
|
18.1
|
204
|
2002 VE68 |
2018-Nov-04
|
14.7 LD
|
8.6
|
282
|
2010 VQ |
2018-Nov-07
|
15.6 LD
|
3.8
|
10
|
Notes: LD means “Lunar Distance.” 1 LD = 384,401 km, the distance between Earth and the Moon. Table from SpaceWeather.com
Near-Earth objects (NEOs) discovered this month: 142, this year: 1255, all time: 18805.
Potentially hazardous asteroids: 1923 (as of September 18, 2018)
Minor Planets discovered: 779,736 (as of July 31, 2018 – I emailed them about this value not changing for months…)
Fireballs
On Sept. 10, 2018, the NASA All Sky Fireball Network reported 94 fireballs. (This value has not updated either… bad luck for me this week, I guess…)

Comets
Comet 21P/Giacobini-Zinner is a binocular-viewable comet, visible in the eastern sky after midnight, and before dawn. The comet is fading – catch a glimpse soon!
The Solar System
This is the position of the planets and a couple spacecraft in the solar system:



I was playing around with NASA’s Eyes for this post, and noticed that Pluto really isn’t a member of the “Ecliptic-Plane Club.”

Spacecraft
The instrument-cover on a student-built x-ray spectrometer on NASA’s OSIRIS-REx asteroid sample return spacecraft has opened!
The Parker Solar Probe, the first mission to the outer corona of the Sun, is on its way to a Venus fly-by on Oct. 3rd.
The Mars InSight spacecraft will land on Mars on Nov. 26th. InSight has a seismometer and other instruments that will study the interior of Mars.

Exoplanets
Confirmed Exoplanets: 3,779 (9/6/2018 – not updated since last week either! Arrrgh!)
Multi-Planet Systems: 626 (9/6/2018)
Kepler Candidate Exoplanets: 4,496 (8/31/2017)
TESS Candidate Exoplanets: 0
-Data from the NASA Exoplanet Archive
Latest Exoplanet Discoveries: https://exoplanets.nasa.gov
Apps used for this post:
NASA Eyes on the Solar System: an immersive 3D solar system and space mission simulator – free for the PC /MAC.
I maintain the unofficial NASA Eyes Facebook page.
Stellarium: a free open source planetarium app for PC/MAC/Linux. It’s a great tool for planning observing sessions.