In the Sky This Week – July 7, 2020

The Moon appears with Saturn and Jupiter in the southeastern sky at midnight on July 8th.

The Moon appears near Saturn and Jupiter in the southeastern sky near midnight on July 8th. Credit: Stellarium / Bob Trembley.

The Moon appears near mars in east-southeastern sky during the early morning hours on July 11th & 12th.

Venus appears in conjunction with the star Aldebaran in the eastern predawn all week.

The Moon is a waning gibbous – rising after sunset, visible high in the sky after midnight, and visible to the southwest after sunrise.

The third quarter Moon occurs on  July 12th – rising around midnight, and visible to the south after sunrise.

After July 12th, the Moon will be a waning crescent – visible low to the east before sunrise.

The Moon from 2020-07-07 – 2020-07-13. Visualizations by Ernie Wright / NASA’s Scientific Visualization Studio.

Moon News

The Sun is currently spotless, but SpaceWeather.com reports that a sunspot appears to be emerging on the northern hemisphere, near the center of the Sun’s face. Coronal holes appear at both poles, with no significant coronal holes on the Earthside of the Sun.

The Sun seen in 193 angstroms (extreme ultraviolet)  July 6, 2020:

A couple long-lived prominences on the Sun’s limb over the last couple days made for great astrophoto targets.

The Sun seen in 304 angstroms (extreme ultraviolet) July 6, 2020:

Facebook: SolarActivity – Run by Solar System Ambassador Pamela Skivak

https://www.facebook.com/photo.php?fbid=10222794561833528&set=gm.3338424676168853&type=3&theater&ifg=1

Solar Corona

Solar wind speed is 426.2 km/sec (↑), with a density of 4.8 protons/cm³ (↓) at 1310 UT.

Near real-time animation of the corona and solar wind from the Solar & Heliospheric Observatory (SOHO):

Animated LASCO C2 Coronograph showing the solar corona above the Sun’s limb (the white circle). Credit: NASA/JPL-Caltech-SOHO

Upcoming Earth-asteroid encounters:

Notes: LD means “Lunar Distance.” 1 LD = 384,401 km, the distance between Earth and the Moon. Red highlighted entries are asteroids that either pass very close, or very large with high relative velocities to the Earth. Table from SpaceWeather.com

Asteroid Day Recap

On July 6, 2020, the NASA All Sky Fireball Network reported 3 fireballs. 
(3 sporadics)

In this diagram of the inner solar system, all of the fireball orbits intersect at a single point–Earth. The orbits are color-coded by velocity, from slow (red) to fast (blue). Credit: SpaceWeather.com

Fireball News

Position of the planets and a couple spacecraft in the inner solar system – the Parker Solar Probe is heading towards an encounter with Venus on July 10th.

Position of the planets and a couple spacecraft in the inner solar system, 2020-07-07. Credit: NASA Eyes on the Solar System / Bob Trembley.

Close up of Parker Solar Probe approaching Venus:

Parker Solar Probe approaching Venus, 2020-07-07. Credit: NASA Eyes on the Solar System / Bob Trembley.

Artist impression of the Parker Solar Probe flying by Venus on July 10th:

Parker Solar Probe flying by Venus, 2020-07-07. Credit: NASA Eyes on the Solar System / Bob Trembley.

Position of the planets in the middle solar system:

Position of the planets in the middle solar system, 2020-07-07 – the orbit of comet 67P/Churyumov-Gerasimenko is highlighted. Credit: NASA Eyes on the Solar System / Bob Trembley.

Position of the planets some transneptunian objects in the outer solar system:

Position of the planets in the outer solar system, 2020-07-07. Credit: NASA Eyes on the Solar System / Bob Trembley.

Highlight: Dwarf Planet Ceres

Approximate true-color image of Ceres, using the F7 (‘red’), F2 (‘green’) and F8 (‘blue’) filters, projected onto a clear filter image. Images were acquired by Dawn at 04:13 UT May 4, 2015, at a distance of 13641 km. At the time, Dawn was over Ceres’ northern hemisphere. The prominent, bright crater at right is Haulani. The smaller bright spot to its left is exposed on the floor of Oxo. Ejecta from these impacts appears to have exposed high albedo material similar to deposits found on the floor of Occator Crater. Image Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / Justin Cowart

Ceres /ˈsɪəriːz/ (minor-planet designation: 1 Ceres) is the largest object in the main asteroid belt that lies between the orbits of Mars and Jupiter. With a diameter of 940 km (580 mi), Ceres is both the largest of the asteroids and the only unambiguous dwarf planet currently inside Neptune’s orbit. It is the 25th-largest body in the Solar System within the orbit of Neptune.

Ceres was the first asteroid to be discovered (by Giuseppe Piazzi at Palermo Astronomical Observatory on 1 January 1801). It was originally considered a planet, but was reclassified as an asteroid in the 1850s after many other objects in similar orbits were discovered.

Ceres is the only object in the asteroid belt currently known to be rounded by its own gravity, although detailed analysis was required to exclude Vesta. From Earth, the apparent magnitude of Ceres ranges from 6.7 to 9.3, peaking once at opposition every 15 to 16 months, which is its synodic period. Thus even at its brightest, it is too dim to be seen by the naked eye, except under extremely dark skies.

Ceres appears to be partially differentiated into a muddy (ice-rock) mantle, with a crust that is 60 percent rock and 40 percent ice or less than 30 percent ice. It probably no longer has an internal ocean of liquid water, but there is brine that can flow through the outer mantle and reach the surface. The surface is a mixture of water ice and various hydrated minerals such as carbonates and clay. Cryovolcanoes such as Ahuna Mons form at the rate of about one every fifty million years. In January 2014, emissions of water vapor were detected from several regions of Ceres. This was unexpected because large bodies in the asteroid belt typically do not emit vapor, a hallmark of comets. Any atmosphere, however, would be the minimal kind known as an exosphere.

The robotic NASA spacecraft Dawn entered orbit around Ceres on 6 March 2015. – Wikipedia

Dawn Spacecraft at Ceres. Credit: NASA Eyes on the Solar System / Bob Trembley.

Read more about Ceres on NASA’s Solar System Exploration site: https://solarsystem.nasa.gov/planets/dwarf-planets/ceres/overview/

OSIRIS-REx Asteroid Sample Return Mission

International Space Station

NASA Perseverance Mars Rover

Hubble Space Telescope

Climate

ex·o·plan·et /ˈeksōˌplanət/, noun: a planet orbiting a star other than the Sun.

Data from the NASA Exoplanet Archive
* Confirmed Planets Discovered by TESS refers to the number planets that have been published in the refereed astronomical literature.
* TESS Project Candidates refers to the total number of transit-like events that appear to be astrophysical in origin, including false positives as identified by the TESS Project.
* TESS Project Candidates Yet To Be Confirmed refers to the number of TESS Project Candidates that have not yet been dispositioned as a Confirmed Planet or False Positive.

The Local Stellar Neighborhood

Continuing with my visual tour of nearby stars and their systems, we travel to Luyten’s Star, 12.36 light years distant.

Distance to Luyten’s Star (Gliese 273) from Sol; the plane (green) is aligned with the orientation of the plane of the Milky Way galaxy. Credit: SpaceEngine / Bob Trembley.

Luyten’s Star

Luyten’s Star /ˈlaɪtənz/ (GJ 273) is a red dwarf in the constellation Canis Minor located at a distance of approximately 12.36 light-years (3.79 parsecs) from the Sun. It has a visual magnitude of 9.9, making it too faint to be viewed with the unaided eye. It is named after Willem Jacob Luyten, who, in collaboration with Edwin G. Ebbighausen, first determined its high proper motion in 1935. 

This star is approximately a quarter the mass of the Sun and has 35% of the Sun’s radius. Luyten’s Star is at the maximum mass at which a red dwarf can be fully convective, which means that most if not all of the star forms an extended convection zone. It has a stellar classification of M3.5V, with the V luminosity class indicating this is a main-sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. The projected rotation rate of this star is too low to be measured, but is no greater than 1 km/s. Measurements of periodic variation in surface activity suggest a leisurely rotation period of roughly 116 days (which would give a velocity of ~0.15 km/s). The effective temperature of the star’s outer envelope is a relatively cool 3,150 K, giving the star the characteristic red-orange hue of an M-type star.

At present, Luyten’s Star is moving away from the Solar System. The closest approach occurred about 13,000 years ago when it came within 3.67 parsecs. The star is currently located 1.2 light years distant from Procyon, and the latter would appear as a visual magnitude −4.5 star in the night sky of one of the planets orbiting Luyten’s Star. The closest encounter between the two stars occurred about 600 years ago when Luyten’s Star was at its minimal distance of about 1.12 ly from Procyon. The space velocity components of Luyten’s Star are U = +16, V = −66 and W = −17 km/s.

In March 2017, two candidate planets were discovered orbiting Luyten’s Star. The outer planet, GJ 273b, is a Super Earth in its star’s habitable zone. It has a mass of 2.89 ± 0.26 Earth masses and orbits at a distance of 0.09110 ± 0.00002 AU, completing one orbital period in 18.650 ± 0.006 days. While the planet is on the innermost edge of the star’s conservative habitable zone, the incident flux is only 1.06S⊕, so it may be potentially habitable if water and an atmosphere are present; depending on albedo, its equilibrium temperature could be anywhere between 206 and 293 Kelvin. The inner planet, GJ 273c, is one of the lightest exoplanets detected by radial velocities, with a mass of only 1.18 ± 0.16 Earth masses. However, it orbits much further in, with an orbital period of only 4.7234 ± 0.00004 days.

GJ 273b is one of the closest known planets in its star’s habitable zone.

In 2019, two more candidate planets were detected by radial velocity, making a total of four known planets in the system. – Wikipedia

Luyten’s Star System Architecture

Luyten’s Star (Gliese 273) System Diagram. Note: exoplanet surface features are procedurally generated. Credit: SpaceEngine / Bob Trembley.

Luyten’s Star Exoplanet Orbital Diagram

Top-down view of the inner exoplanet orbits around Luyten’s Star (Gliese 273). Credit: SpaceEngine / Bob Trembley.

Top-down view of the outer exoplanet orbits around Luyten’s Star (Gliese 273). Credit: SpaceEngine / Bob Trembley.

Artist’s Rendering of Exoplanet Gliese 273 b

Artistic rendering of Luyten’s Star seen from above the surface of exoplanet Gliese 273 b. Credit: SpaceEngine / Bob Trembley.

Stay safe, be well, and look up!

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.
Universe Sandbox: a space simulator that merges real-time gravity, climate, collision, and material interactions to reveal the beauty of our universe and the fragility of our planet. Includes VR support.
SpaceEngine: a free 3D Universe Simulator for Windows. Steam version with VR support available.
Stellarium: a free open source planetarium app for PC/MAC/Linux. It’s a great tool for planning observing sessions. A web-based version of Stellarium is also available.

Section header image credits:
The Sky – Stellarium / Bob Trembley
Observing Target – Turn Left at Orion / M. Skirvin
The Moon – NASA/JPL-Caltech
The Sun – NASA/JPL-Caltech
Asteroids – NASA/JPL-Caltech
Fireballs – Credited to YouTube
Comets – Comet P/Halley, March 8, 1986, W. Liller
The Solar System – NASA Eyes on the Solar System / Bob Trembley
Spacecraft News – NASA Eyes on the Solar System / Bob Trembley
Exoplanets – Space Engine / Bob Trembley
Light Pollution – NASA’s Black Marble
The Universe – Universe Today