In the Sky This Week – October 9, 2018

The constellations Orion and Canis Major have migrated from the east to the south, and now appear high in the southern predawn sky.

The constellations Orion, Taurus, and Canis Major in the southern predawn sky on Oct. 9, 2018. Credit: Stellarium / Bob Trembley.

The constellation Leo with the bright star Regulus rise in the eastern predawn sky.

The bright star Regulus in the constellation Leo in the eastern predawn sky.

Ursa Major (with the Big Dipper asterism) and Ursa Minor (the Little Dipper) appear in the northern predawn sky.

Ursa Major, Ursa Minor, and Draco in the northern predawn sky. Credit: Stellarium / Bob Trembley.

Mars and Saturn continue to be excellent viewing targets in the southern sky after sunset – this week the Moon will not be present to wash them out.

Mars and Saturn in the southern sky after sunset on Oct. 9, 2018. Credit: Stellarium / Bob Trembley.

Jupiter appears in the southwestern sky at dusk, and sets at 8:36 PM.

Jupiter low in the southwestern sky after sunset on Oct. 9, 2018. Credit: Stellarium / Bob Trembley.

Observing Target: Mizar and Alcor

Mizar and Alcor are a naked-eye double star in the handle of the “Big Dipper” (in Ursa Major).

Location of Mizar and Alcor. Credit: Stellarium / Bob Trembley.

In a small telescope, Mizar and Alcor can easily be “split” or resolved into individual stars:

Mizar and Alcor, drawn by Galileo.

Mizar is actually quadruple star system, with two sets of double stars orbiting around their common center of gravity – also known as their barycenter.

Mizar Barycenter, Credit: Space Engine/Bob Trembley

The two stars of Mizar Aa are similar – each over twice the mass of the Sun, and each hotter than our Sun.

Mizar Aa Star. Credit: Space Engine/Bob Trembley

The two stars of Mizar Ba are also similar – each massing about 1.5 times our Sun, and both are hotter than our Sun.

Mizar Ba Star. Credit: Space Engine/Bob Trembley

Alcor is itself a double star, with a much smaller and dimmer star orbiting a more massive companion.

Alcor Barycenter. Credit: Space Engine/Bob Trembley

Mizar and Alcor’s proper motions show that they move together, but it unknown if the two star-systems are gravitationally bound.

The Moon

The Moon is new, and in a couple days will appear as a waxing crescent on southwestern horizon at dusk.

The Moon from Oct. 9-15, 2018. Visualizations by Ernie Wright.

The Sun

The Sun is once again spot-free; it’s been 4 days since a sunspot has been seen; there’s a small region of coronal loop activity along the equator, but it’s not strong enough to form a spot. The large coronal hole at the Sun’s north pole has remained for several weeks now; two other coronal near the horizon have solar wind streaming out them..

SpaceWeather.com says: “For the 3rd day in a row, Earth remains inside a stream of high-speed solar wind flowing from a canyon-shaped hole in the sun’s atmosphere. NOAA forecasters say there is a 40% chance of minor G1-class geomagnetic storms on Oct. 9th as our planet’s magnetic field is buffeted by the gaseous material. Arctic sky watchers should remain alert for auroras.”

There have been some impressive prominences on the Sun’s limb in the last couple days!

The solar wind speed is 629.1 km/sec, with a density of 6.5 protons/cm3 – much faster and a bit more dense than last week.

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: 81, this year: 1517, all time: 18914.
Potentially hazardous asteroids: 1923 (as of October 9, 2018)
Minor Planets discovered: 785,045 (as of October 9, 2018)

Fireballs

On Oct. 8, 2018, the NASA All Sky Fireball Network reported 24 fireballs.

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

The Solar System

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

Position of the planets and several spacecraft in the inner solar system, Oct. 9, 2018. Credit: NASA Eyes on the Solar System / Bob Trembley.

Position of the planets in the middle solar system, Oct. 9, 2018. Credit: NASA Eyes on the Solar System / Bob Trembley.

Outer solar system showing dwarf planets, some trans-Neptunian objects, and a few spacecraft, Oct. 9, 2018. Credit: NASA Eyes on the Solar System / Bob Trembley.

Spacecraft

Hubble in Trouble!

Voyager 2 – Outta here! … Well almost!

The Voyager Tour in NASA Eyes on the Solar System allows you to turn on the Sun’s heliosphere – it’s pretty cool to be able to visualize the Sun’s magnetic environment this way.

Voyager 2 at the Heliopause. Credit: NASA Eyes on the Solar System / Bob Trembley.

Voyagers 1 & 2 and the Heliotail. Credit: NASA Eyes on the Solar System / Bob Trembley.

Exoplanets

Confirmed Exoplanets: 3,791 (9/27/2018)
Multi-Planet Systems: 629 (9/27/2018)
Kepler Candidate Exoplanets: 4,717 (8/16/2018)
TESS Candidate Exoplanets: 2
-Data from the NASA Exoplanet Archive
Latest Exoplanet Discoveries: https://exoplanets.nasa.gov

World Space Seek: Oct. 4-10

Since its United Nations declaration in 1999, World Space Week has grown into the largest public space event on Earth. More than 3,700 events in 80 countries celebrated the benefits of space and excitement about space exploration in 2017.  The 2018 theme is “Space Unites The World” and 2019 theme “The Moon:  Gateway to the Stars.”

“The General Assembly declares 4 to 10 October World Space Week to celebrate each year at the international level the contributions of space science and technology to the betterment of the human condition”

– UN General Assembly resolution, 6 December 1999

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.
Space Engine: a free 3D universe simulator.

2018 is NASA’s 60th Anniversary!