In the Sky This Week – December 4, 2018

A very thin waning crescent Moon joins the weeks-long conjunction of Venus and Spica in the southeastern predawn sky on Dec. 4th.

Conjunction of Venus, Spica and a very thin crescent Moon low in the southeastern sky before sunrise on Dec. 4, 2018. Credit: Stellarium / Bob Trembley.

Mars remains high in southern sky after sunset all week; Mars is slowly fading in brightness as the Earth pulls away from it in its orbit (see solar system image below).

Mars high in the southern sky after sunset on Dec. 4, 2018. Credit: Stellarium / Bob Trembley.

The very thin waxing crescent Moon will appear near Saturn in the southwestern sky at dusk on Dec. 8^th.

Conjunction of Saturn and a very thin crescent Moon low in the southwestern sky at dusk on Dec. 8, 2018. Credit: Stellarium / Bob Trembley.

The constellation Orion is high in the southeastern sky at midnight.

Orion high in the southeastern sky at midnight, Dec. 4, 2018. Credit: Stellarium / Bob Trembley.

Observing Target: M33 – The Triangulum Galaxy

Messier 33 (or NGC 598) is a spiral galaxy located approximately 3 million light-years from Earth in the constellation Triangulum.

Location of M33 – Triangulum Galaxy Credit: Stellarium / Bob Trembley.

The Triangulum Galaxy is the third-largest member of the Local Group of galaxies, which includes the Andromeda Galaxy and our Milky Way. M33 is one of the most distant objects that can be viewed with the naked eye.

M33 – The Triangulum Galaxy. Credit: Alexander Meleg / CC BY-SA 3.0.

NGC 604 is a large star-birth region within The Triangulum Galaxy. NGC 604 is similar to the Orion Nebula in our Milky Way galaxy, but nearly 100 times larger!

Starbirth region in NGC 604. Credits: NASA and The Hubble Heritage Team (AURA/STScI);
Acknowledgment: D. Garnett (U. Arizona), J. Hester (ASU), and J. Westphal (Caltech).

More than 200 bright blue stars ionize the gases within the cloud, which shines with more than 6000 times the luminosity of the Orion Nebula!

Close-up of starbirth region in NGC 604. Credits: NASA and The Hubble Heritage Team (AURA/STScI);
Acknowledgment: D. Garnett (U. Arizona), J. Hester (ASU), and J. Westphal (Caltech).

The Moon

The Moon is a waning crescent, visible low to the east before sunrise. The new Moon will be on Dec. 7^th, after which the Moon will be a waxing crescent, visible toward the southwest in early evening.

The Moon from Dec. 4-10, 2018. Visualizations by Ernie Wright.

The Sun

The Sun has been spot-free for 8 days. Coronal holes remain open at both poles – the northern hole appearing much larger than the southern hole; a large blotchy coronal hole is rotating along the Sun’s equator.

“NOAA forecasters say there is a 45% chance of G1-class geomagnetc storms on Dec. 5th when a coronal mass ejection (CME) is expected to hit Earth’s magnetic field. CMEs are rare during solar minimum because their usual launching pads–that is, sunspots–are absent. This one was produced not by a sunspot, but rather by a filament of magnetism erupting from the sun’s southern hemisphere (movie). CMEs are very good at producing auroras, so even a glancing blow could light up the Arctic Circle this Wednesday night.” – SpaceWeather.com

Over the last couple days, a couple long-lived prominences appeared on the Sun, as well as several short-lived prominences, which popped up all over the Sun’s limb.

The solar wind speed is 467.2 km/sec (↑), with a density of 9.1 protons/cm³ (↑).

Animated LASCO C2 Coronograph showing the solar corona above the Sun’s limb (the white circle).

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: 1, this year: 1837, all time: 19236.
Potentially hazardous asteroids: 1936 (as of Nov. 20, 2018)
Minor Planets discovered: 789,069 (as of Oct. 30, 2018)

Fireballs

On Dec. 3, 2018, the NASA All Sky Fireball Network reported 26 fireballs.
(24 sporadics, 1 Geminid, 1 November omega Orionid)

In this diagram of the inner solar system, all of the fireball orbits from Dec.3, 2018 intersect at a single point–Earth. Source: Spaceweather.com

Comets

Comet 41P/Wirtanen (and a supernova) – imaged by astrophotographer buddy Doug Bock, Nov. 30, 2018

The Solar System

This is the position of the planets and a couple spacecraft in the solar system; the Parker Solar Probe will soon cross the orbit of Venus.

Position of the planets in the inner solar system, Dec. 4, 2018. Credit: NASA Eyes on the Solar System / Bob Trembley.

Position of the planets in the middle solar system, Dec. 4, 2018. Credit: NASA Eyes on the Solar System / Bob Trembley.

Spacecraft

OSIRIS-REx- Arrives at Asteroid Bennu!

See my Bennu arrival post here: [Link]

Mars InSight – HAS THE POWER!

MarCO CubeSats – After InSight Landing

RHESSI Spacecraft Retired

-Data from the NASA Exoplanet Archive

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!