In the Sky This Week – August 4, 2020

Today is my 36th anniversary! Connie and I met at Michigan Tech, and spent many hours under aurora-filled skies while we were in the Keweenaw Peninsula. We have two adult daughters, a six month old granddaughter, and are currently living with Connie’s elderly parents after having sold our house. Connie is a middle-school science teacher, and typically catches something from her students at least three times a year; the thought of her being required to return to an in-classroom environment during on ongoing global pandemic has me both infuriated and nearly frantic.

The image below is from the Keweenaw Rocket Range; Connie and I, along with several members of the MTU Science Fiction Club (The PFRC), and a group of SF-fans and teckies (GT) helped fund the monument a couple decades ago – we visited the site in 2016.

Bob & Connie Trembley at the Keweenaw Rocket Range in 2016. Credit: Bob Trembley

Jupiter and Saturn appear in the southern sky during the early morning and predawn hours this week.

Jupiter and Saturn appear in the southern sky during the early morning hours this week. Credit: Stellarium / Bob Trembley.

The Moon appears in conjunction with Mars in the eastern sky after midnight from August 7-10th.

The Moon appears in conjunction with Mars in the eastern sky at 1:00 AM from August 7-10. Credit: Stellarium / Bob Trembley.

The Moon appears less than 2 degrees from Mars in the early morning hours on August 9th.

The Moon very close to Mars in the eastern sky at 1:00 AM on August 9th. Credit: Stellarium / Bob Trembley.

Venus appears between the constellations Gemini and Orion in the eastern predawn sky all week.

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

The third-quarter Moon occurs on Tuesday August 11th – rising around midnight, and visible to the south after sunrise.

The Moon from 2020-08-04 – 2020-08-10. Visualizations by Ernie Wright / NASA’s Scientific Visualization Studio.

Moon News

The Sun has a couple more spots! Sunspot AR2770, rotating into view along the Sun’s limb, is a member of Solar Cycle 25; AR2769 appears more towards the center of the Sun’s face.

False-color image of the sun, intense magnetic fields are denoted by yellow (-) and green (+). Credit: NASA/SDO and the AIA, EVE, and HMI science teams.

The coronal hole at the Sun’s north pole as a large friend; the coronal hole at the south pole appears to have diminished a bit from last week. A lot of coronal loop activity appears in the regions over the two sunspots.

The Sun seen in 193 angstroms (extreme ultraviolet) August 3, 2020:

Lots of prominences everywhere on the Sun’s limb over the last few days.

The Sun seen in 304 angstroms (extreme ultraviolet) August 3, 2020:

Solar Activity on Facebook – Run by Solar System Ambassador Pamela Shivak

https://www.facebook.com/photo.php?fbid=10223050456190727&set=gm.3416953211649332&type=3&theater&ifg=1

Solar Corona

Solar wind speed is 652.3 km/sec (↑↑), with a density of 6.3 protons/cm³ (↑↑) at 1335 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

Sun News

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

On August 3, 2020, the NASA All Sky Fireball Network reported 6 fireballs. 
(3 sporadics, 2 southern Delta Aquariids, 1 Perseid)

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.

Position of the planets and a couple spacecraft in the inner solar system, 2020-08-04. 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, 2020-08-04. Credit: NASA Eyes on the Solar System / Bob Trembley.

Position of the planets, dwarf planets and asteroids (highlighted) in the outer solar system:

Oblique view of the planets and asteroids in the outer solar system, 2020-08-04. Credit: SpaceEngine / Bob Trembley.

Highlight: Neptune

This picture of Neptune was produced from the last whole planet images taken through the green and orange filters on the Voyager 2 narrow angle camera. The images were taken at a range of 4.4 million miles from the planet, 4 days and 20 hours before closest approach. The picture shows the Great Dark Spot and its companion bright smudge; on the west limb the fast moving bright feature called Scooter and the little dark spot are visible. These clouds were seen to persist for as long as Voyager’s cameras could resolve them. North of these, a bright cloud band similar to the south polar streak may be seen. Credit: NASA/JPL-Caltech.

Neptune is the eighth and farthest-known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth, slightly more massive than its near-twin Uranus. Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 AU (4.5 billion km; 2.8 billion mi). It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune’s trident.

Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. After Bouvard’s death, the position of Neptune was predicted from his observations, independently, by John Couch Adams and Urbain Le Verrier. Neptune was subsequently observed with a telescope on 23 September 1846 by Johann Galle within a degree of the position predicted by Le Verrier. Its largest moon, Triton, was discovered shortly thereafter, though none of the planet’s remaining 13 known moons were located telescopically until the 20th century. The planet’s distance from Earth gives it a very small apparent size, making it challenging to study with Earth-based telescopes. Neptune was visited by Voyager 2, when it flew by the planet on 25 August 1989; Voyager 2 remains the only spacecraft to visit Neptune. The advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics has recently allowed for additional detailed observations from afar.

Like Jupiter and Saturn, Neptune’s atmosphere is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, though it contains a higher proportion of “ices” such as water, ammonia and methane. However, similar to Uranus, its interior is primarily composed of ices and rock; Uranus and Neptune are normally considered “ice giants” to emphasize this distinction. Traces of methane in the outermost regions in part account for the planet’s blue appearance.

In contrast to the hazy, relatively featureless atmosphere of Uranus, Neptune’s atmosphere has active and visible weather patterns. For example, at the time of the Voyager 2 flyby in 1989, the planet’s southern hemisphere had a Great Dark Spot comparable to the Great Red Spot on Jupiter. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 km/h (580 m/s; 1,300 mph). Because of its great distance from the Sun, Neptune’s outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching 55 K (−218 °C; −361 °F). Temperatures at the planet’s centre are approximately 5,400 K (5,100 °C; 9,300 °F). Neptune has a faint and fragmented ring system (labelled “arcs”), which was discovered in 1984, then later confirmed by Voyager 2. – Wikipedia

There is an lot more about Neptune in this Wikipedia article.

Neptune’s Moons

Neptune has 14 known moons. Triton is the largest Neptunian moon, comprising more than 99.5% of the mass in orbit around Neptune, and it is the only one massive enough to be spheroidal. Triton was discovered by William Lassell just 17 days after the discovery of Neptune itself. Unlike all other large planetary moons in the Solar System, Triton has a retrograde orbit, indicating that it was captured rather than forming in place; it was probably once a dwarf planet in the Kuiper belt. It is close enough to Neptune to be locked into a synchronous rotation, and it is slowly spiralling inward because of tidal acceleration. It will eventually be torn apart, in about 3.6 billion years, when it reaches the Roche limit. In 1989, Triton was the coldest object that had yet been measured in the Solar System, with estimated temperatures of 38 K (−235 °C).

Neptune’s second-known satellite (by order of discovery), the irregular moon Nereid, has one of the most eccentric orbits of any satellite in the Solar System. The eccentricity of 0.7512 gives it an apoapsis that is seven times its periapsis distance from Neptune. – Wikipedia

Size comparison of Neptune’s seven inner moons. Credit: SETI Institute.

Global color mosaic of Triton, taken in 1989 by Voyager 2 during its flyby of the Neptune system. Color was synthesized by combining high-resolution images taken through orange, violet, and ultraviolet filters; these images were displayed as red, green, and blue images and combined to create this color version. With a radius of 1,350 (839 mi), about 22% smaller than Earth’s moon, Triton is by far the largest satellite of Neptune. It is one of only three objects in the Solar System known to have a nitrogen-dominated atmosphere (the others are Earth and Saturn’s giant moon, Titan). Triton has the coldest surface known anywhere in the Solar System (38 K, about -391 degrees Fahrenheit); it is so cold that most of Triton’s nitrogen is condensed as frost, making it the only satellite in the Solar System known to have a surface made mainly of nitrogen ice. The pinkish deposits constitute a vast south polar cap believed to contain methane ice, which would have reacted under sunlight to form pink or red compounds. The dark streaks overlying these pink ices are believed to be an icy and perhaps carbonaceous dust deposited from huge geyser-like plumes, some of which were found to be active during the Voyager 2 flyby. The bluish-green band visible in this image extends all the way around Triton near the equator; it may consist of relatively fresh nitrogen frost deposits. The greenish areas includes what is called the cantaloupe terrain, whose origin is unknown, and a set of “cryovolcanic” landscapes apparently produced by icy-cold liquids (now frozen) erupted from Triton’s interior. Credit: NASA/JPL/USGS

Read more about Neptune on NASA’s Solar System Exploration site: https://solarsystem.nasa.gov/planets/neptune/overview/

Artist’s conception of Neptune seen from the surface of Triton. Credit: SpaceEngine / Bob Trembley.

NASA’s OSIRIS-REx Asteroid Sample Return Mission

International Space Station

NASA Perseverance Mars Rover

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 Kruger 60 , 13.15 light years distant.

Distance to Kruger 60 from Sol; the plane (green) is aligned with the orientation of the plane of the Milky Way galaxy. Credit: SpaceEngine / Bob Trembley.

Kruger 60

Kruger 60 (DO Cephei) is a binary star system located 13.15 light-years from the Sun. These red dwarf stars orbit each other every 44.6 years.

The larger, primary star is designated component A, while the secondary, smaller star is labeled component B. Component A has about 27% of the Sun’s mass and 35% of the Sun’s radius. Component B has about 18% of the Sun’s mass and 24% of the Sun’s radius. Component B is a flare star and has been given the variable star designation “DO Cephei”. It is an irregular flare that typically doubles in brightness and then returns to normal over an 8-minute period.

On average, the two stars are separated by 9.5 AUs, which is roughly the average distance of Saturn from the Sun. However, their eccentric mutual orbit causes their distance to vary between 5.5 AUs at periastron, to 13.5 at apastron.

This system is orbiting through the Milky Way at a distance from the core that varies from 7–9 kpc with an orbital eccentricity of 0.126–0.130. The closest approach to the Sun will occur in about 88,600 years when this system will come within 1.95 parsecs.

Considering the orbit of the members of Kruger 60, detecting an exoplanet through radial velocity could prove difficult, as its orbit would be inclined only 13 degrees from our point of view, and create 1/5th as strong a radial velocity signal as an exoplanet orbiting edge-on from the point of view of the Solar System.

Kruger 60 has been proposed as the origin of interstellar comet 2I/Borisov (formerly named C/2019 Q4 (Borisov)) by Dybczyński, Królikowska, and Wysoczańska. These authors have from other work a list of stars and stellar systems that can potentially act as perturbers of the Oort cloud comets, and searched it for a past close proximity of 2I/Borisov at a very small relative velocity. While hampered by continuing uncertainty about the orbit of 2I/Borisov and particularly its non-gravitational acceleration (due to cometary outgassing), they reach a conclusion that 1 Myr ago 2I/Borisov passed Kruger 60 at a small distance of 1.74 pc while having an extremely small relative velocity of 3.43 km/s. Perturbations of the 2I/Borisov’s incoming orbit altered the intersection distance with relatively small changes in the relative velocity. At the time of publication, the results were considered preliminary as the orbit of 2I/Borisov was still being improved by new observations. – Wikipedia

Kruger 60 System Diagram

Kruger 60 System Diagram. Credit: SpaceEngine / Bob Trembley

Kruger 60 System Orbital Diagram

Kruger 60 System Orbital Diagram. 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