In the Sky This Week – September 11, 2018

Orion is high in the southeastern predawn sky as fall stars rise earlier each morning.

The constellation Orion high in the predawn sky to the southeast on Sept. 11, 2018. Credit: Stellarium / Bob Trembley.

The Moon joins Venus and Jupiter in the southwestern sky after dusk for several days early this week.

The Moon will join Mars and Saturn in the Southern sky after dusk, appearing very near Saturn on September 17^th.

The Moon, Mars and Saturn in the southern sky shortly at 10:30 PM, Sept. 17, 2018. Credit: Stellarium / Bob Trembley.

The Moon

The Moon from Aug. 21-27, 2018. Visualizations by Ernie Wright

The Moon is a waxing crescent, visible in the southwestern sky after dusk. The Moon will be at first-quarter on September 17^th, and should be a good observing target all week.

Observing Target: The Zodiacal Light

Zodiacal light (also called the “false dawn” when seen before sunrise) is a faint, diffuse, and roughly triangular white glow that is visible in the night sky and appears to extend from the Sun’s direction and along the zodiac, straddling the ecliptic. Sunlight scattered by interplanetary dust causes this phenomenon.

Zodiacal light is best seen during twilight after sunset in spring and before sunrise in autumn, when the zodiac is at a steep angle to the horizon. However, the glow is so faint that moonlight and/or light pollution outshine it, rendering it invisible. ~from Wikipedia

You can see the Zodiacal light now if you escape the city lights – look to the east before dawn.

Zodiacal light seen behind the Submillimeter Array from the summit of Mauna Kea. Credit: Steven Keys / Creative Commons

https://youtu.be/UoWYWJmTdB4

The Sun

The Sun has been spot-free for 1 day. A huge coronal hole continues to dominate the Sun’s north polar region, while a smaller equatorial hole is about to rotate out of view. There’s something active with a lot of coronal loop activity within the equatorial hole The south pole appears to have have a small coronal hole forming. You can see the Moon in a couple frames of the animations below. The solar wind speed is 569.7 km/sec, with a density of 5.4 protons/cm³.

SpaceWeather.com says: “Right now, G1-class geomagnetic storms are sparking bright auroras around the Arctic Circle as a stream of high-speed solar wind buffets Earth’s magnetic field.” They have some very nice submissions to their aurora gallery.

Get your solar telescope out and look for some prominences – because they have been all over the Sun’s limb for the last couple days!

Asteroids

Upcoming Earth-asteroid encounters:

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: 51, this year: 1164, all time: 18715.
Potentially hazardous asteroids: 1923 (as of September 11, 2018)
Minor Planets discovered: 779,736 (as of July 31, 2018)

Fireballs

On Sept. 10, 2018, the NASA All Sky Fireball Network reported 94 fireballs.

In this diagram of the inner solar system, all of the fireball orbits intersect at a single point–Earth. Source: Spaceweather.com

Comets

Comet 21P/Giacobini-Zinner is a binocular-viewable comet, visible in the eastern sky after midnight, and before dawn.

Comet 21P/Giacobini-Zinner. Credit: Alexander Vasenin, 18 Aug 2018

Location of Comet 21P/Giacobini-Zinner Sept. 12, 2018 4:00 AM. Credit: Stellarium / Bob Trembley.

The Solar System

This is the position of the planets and a couple spacecraft in the solar system:

Position of the planets in the inner solar system, Sept. 11, 2018. Credit: NASA Eyes on the Solar System / Bob Trembley.

Position of the planets in the middle solar system, Sept. 11, 2018. Credit: NASA Eyes on the Solar System / Bob Trembley.

Position of the planets in the outer solar system, Sept. 11, 2018. Credit: NASA Eyes on the Solar System / Bob Trembley.

Spacecraft

The OSIRIS-REx asteroid sample return spacecraft continues to close-in on asteroid Bennu.

In other news, I am now a volunteer OSIRIS-REx Ambassador! So, you can expect to see me post a LOT more about this mission!

The Dawn mission to the asteroid belt is coming to a close.

NASA’s Juno spacecraft is looking for hints of water in Jupiter’s atmosphere.

Exoplanets

Confirmed Exoplanets: 3,779 (9/6/2018)
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.

2018 is NASA’s 60th Anniversary!