In the Sky This Week – December 10, 2019
I mentioned the Starlink satellite constellation to students in my after-school astronomy and space science club, and afterwards got into a discussion about space junk. I told the students that when I was their age, there were only a handful of man-made objects in Earth orbit. Today, there are thousands of objects in orbit - some useful, many not so much.
Animation showing different types of space debris objects and different debris sizes in orbit around Earth. Credit: ESA
Many satellites and space probes require multi-stage rockets to get them into orbit and/or to their destination. When a rocket stage is spent, it decouples - and continues in whatever orbit the vessel was currently in at that moment. If the vessel was in a sub-orbital trajectory, the spent stage either burns up, or is guided back to a safe landing - as has been known to happen. If the vessel was in orbit at the moment of decoupling, the spent stage remains in that orbit, becoming space debris. When a satellite or space probe has reached the end of its life, it can simply stay where it is, or if it is in low-Earth orbit, it can be de-orbited. It the satellite is in high-Earth orbit, it can be moved outward into a graveyard orbit. Note the use of the word "can;" there really aren't any "rules or regulations" or international governing agencies to cover this.
The European Space Agency (ESA) has a "Space debris by the numbers" website: https://www.esa.int/Safety_Security/Space_Debris/Space_debris_by_the_numbers. At the time of this writing, the final statistics on that page show the number of debris objects estimated by statistical models to be in orbit:
- 34,000 objects >10 cm
- 900,000 objects from 1 cm - 10 cm
- 128 million objects from 1 mm - 1 cm
One might wonder, with so much junk in orbit, have there been any satellite collisions? The simple answer is yes, several.
Kessler Syndrome
The Kessler syndrome (also called the Kessler effect, collisional cascading, or ablation cascade), proposed by the NASA scientist Donald J. Kessler in 1978, is a scenario in which the density of objects in low Earth orbit (LEO) is high enough that collisions between objects could cause a cascade in which each collision generates space debris that increases the likelihood of further collisions. One implication is that the distribution of debris in orbit could render space activities and the use of satellites in specific orbital ranges difficult for many generations. - Wikipedia
The Kessler syndrome is illustrated effectively, if a bit theatrically, in this clip from the movie Gravity:
One of the things I learned from a NASA lecturer at a science fiction convention was:
Everything is space is moving REALLY FAST relative to everything else in space.
All that debris whizzing by the shuttle... yea, it's actually going several kilometers per second relative to them... Ain't no one gonna "get a visual" on that stuff... That speed is also the big problem: a grain of sand travelling at orbital velocities is a projectile with enough kinetic energy to damage satellites or, heaven forbid, an astronaut.
In an encouraging note, I saw this tweet last week from the European Space Agency discussing a mission to de-orbit space junk:
ESA commissions world’s first space debris removal!
ClearSpace-1 will be the first space mission to remove an item of debris from orbit, planned for launch in 2025
Find out more: ➡️https://t.co/aP9zZdfPdA#SpaceDebris#CleanSpace pic.twitter.com/xtY5qfzo8N
— ESA Operations (@esaoperations) December 9, 2019
This video shows several different concepts for removal of space debris:
As a player of Kerbal Space Program, I try to design my rockets to clean up their own garbage, but I still end up with spent stages and rocket bodies in high orbit when sending missions to far-off destinations.
A great resource to visualize all the stuff in space is with the interactive website: Stuffin.Space - the image below shows stuff orbiting near-ish the Earth, with the orbit of a Falcon rocket body highlighted in blue. You can just make out the nighttime lights of the U.S. beneath all the gray and red dots.
Stuff in Space (red=satellite, blue=rocket body, gray=debris), a Falcon rocket body orbit is highlighted in blue. Source: http://stuffin.space
There will be a conjunction of Saturn and Venus in the southwestern sky after sunset (~5:30 PM) for the next week.
Conjunction of Saturn and Venus in the southwestern sky at 5:30 PM from Dec. 10-16, 2019. Credit: Stellarium / Bob Trembley.
Mercury, Mars and the star Spica align above the southeastern horizon before sunrise this week - Mercury moves down toward the horizon a bit with each morning.
Mercury, Mars and the star Spica align above the southeastern horizon before dawn this week. Credit: Stellarium / Bob Trembley
The Moon appears near the star Aldebaran above the eastern horizon after sunset on Dec. 11th; a bit higher above the horizon is star Capella and the Pleiades star cluster.
The Moon near the star Aldebaran above the eastern horizon after sunset on Dec. 11th; the Pleiades and the star Capella are also prominent. Credit: Stellarium / Bob Trembley
NGC 6910
NGC 6910: stacked images from modded Canon 500D using OIII and Ha filters. Image credit: Erik Larsen derivative work: Roberto Mura / Creative Commons CC BY 2.0
NGC 6910 is an open cluster in the constellation Cygnus. It was discovered by William Herschel on October 17, 1786. The cluster was also observed by John Herschel on September 18, 1828. It is a poor cluster and with prominent central concentration, with Trumpler class I2p. NGC 6910 is the core cluster of the stellar association Cygnus OB9.
NGC 6910 is located half a degree east-north east of Gamma Cygni, also known as Sadr. It may be physically related with the nebula IC 1318, which is also known as the Gamma Cygni nebula complex and lies at a similar distance, behind the galactic Great Rift. Cygnus OB9 is located within the Orion arm of the Milky Way. Cygnus OB9's dimensions in the sky are 2.5 degrees by 1.5 degrees, which corresponds at its distance to 175×105 light years across. It includes many OB stars, along with supergiant stars, like the red supergiant RW Cygni. Gamma Cygni is a foreground star, lying at a distance of approximately 1,500 light years. Because it lies behind a number of molecular clouds, the light from NGC 6910 is dimmed by more than one magnitude. - Wikipedia
I discovered NGC 6910 quite by accident, scanning my 8" Dobsonian reflector telescope around the star Sadr:
Location of NGC 6910, the Inchworm cluster, in the constellation Cygnus. Credit: Stellarium / Bob Trembley.
This is pretty much what the cluster looks like in my 8" Dob:
NGC 6910 through a small telescope. Image credit: Peter Wienerroither, http://homepage.univie.ac.at/~pw/
The Moon will be a waxing gibbous, visible to the southeast in early evening, up for most of the night.
The full Moon occurs on Dec. 12th, rising at sunset, visible high in the sky around midnight, and visible all night.
After Dec. 12th, the Moon will be a waning gibbous, rising after sunset, visible high in the sky after midnight, and visible to the southwest after sunrise.
The Moon from Dec. 10-16, 2019. Visualizations by Ernie Wright / NASA's Scientific Visualization Studio.
Moon News
My wife has used this countless times in her classroom at at conventions:
This is our favorite way to celebrate #NationalCookieDay.
Here's how to make your own cookie Moon phases: https://t.co/bBzlwP1UB5 pic.twitter.com/mgxBsJr8Ik
— NASA Moon (@NASAMoon) December 4, 2019
The Sun has been spotless for 26 days; coronal holes appear at both poles - the southern hole remains very large .
The Sun seen in 193 angstroms (extreme ultraviolet) Dec. 9, 2019:
I seemed to have timed this post well - I got a disconnected prominence and some loops on the Sun's today!
The Sun seen in 304 angstroms (extreme ultraviolet) Dec. 9, 2019:
You can view the Sun in near real-time, in multiple frequencies here: SDO-The Sun Now.
You can create your own time-lapse movies of the Sun here: AIA/HMI Browse Data.
You can browse all the SDO images of the Sun from 2010 to the present here: Browse SDO archive.
The solar wind speed is 426.6 km/sec (↑↑), with a density of 5.6 protons/cm3 (↑) at 2359 UT.
Facebook: SolarActivity
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
Scientists have just announced the first discoveries from #ParkerSolarProbe’s daring mission to the Sun. What they’ve learned has changed our understanding of the way the Sun releases material and particles, influencing Earth and the entire solar system: https://t.co/3WFfZStojM pic.twitter.com/Q3BZAV7lrT
— NASA Sun & Space (@NASASun) December 4, 2019
Upcoming Earth-asteroid encounters:
| Asteroid |
Date(UT)
|
Miss Distance
|
Velocity (km/s)
|
Diameter (m)
|
| 2019 WO2 |
2019-Dec-09
|
4.8 LD
|
7.6
|
32
|
| 2019 XW |
2019-Dec-10
|
10.8 LD
|
15.6
|
59
|
| 2019 XO1 |
2019-Dec-13
|
7.9 LD
|
7.9
|
44
|
| 2019 WP6 |
2019-Dec-14
|
6.4 LD
|
4.4
|
22
|
| 2019 XF |
2019-Dec-18
|
9.4 LD
|
24.1
|
77
|
| 216258 |
2019-Dec-20
|
15.3 LD
|
11.8
|
324
|
| 2013 XY20 |
2019-Dec-21
|
18.3 LD
|
1.9
|
28
|
| 2017 XQ60 |
2019-Dec-22
|
11 LD
|
15.6
|
47
|
| 310442 |
2019-Dec-26
|
19 LD
|
12.3
|
372
|
| 2019 WR4 |
2019-Dec-31
|
11.7 LD
|
4.2
|
21
|
| 2019 AE3 |
2020-Jan-02
|
4.9 LD
|
8.2
|
13
|
| 2019 UO |
2020-Jan-10
|
11.8 LD
|
9.4
|
356
|
| 2019 WC5 |
2020-Jan-11
|
6.3 LD
|
13
|
108
|
| 2011 EP51 |
2020-Jan-15
|
19.6 LD
|
7.1
|
32
|
| 2017 RZ15 |
2020-Jan-15
|
12.1 LD
|
7.4
|
14
|
| 2009 BH2 |
2020-Jan-18
|
14.6 LD
|
17.9
|
118
|
| 2013 DU |
2020-Jan-20
|
15.3 LD
|
6.4
|
59
|
| 2019 TF2 |
2020-Jan-23
|
16.2 LD
|
1.6
|
18
|
| 2018 BM5 |
2020-Jan-23
|
13.1 LD
|
8.6
|
12
|
| 2018 AL12 |
2020-Jan-30
|
18.2 LD
|
17.7
|
39
|
| 2018 BU1 |
2020-Feb-02
|
19.4 LD
|
10
|
41
|
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
Potentially hazardous asteroids: 2018 (last updated Oct. 1, 2019)
Total Minor Planets discovered: 856,474 (+16,004!!)
On Dec. 9, 2019, the NASA All Sky Fireball Network reported 6 fireballs.
(6 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). From: Spaceweather.com
It's mind-boggling to imagine the interstellar journey that brought Comet Borisov from a distant star system to ours. This simulation shows just its last 300,000 years of travel. https://t.co/mSawdLacG9 pic.twitter.com/FP4uiRtKfR
— Corey S. Powell (@coreyspowell) December 9, 2019
Position of the planets and a couple spacecraft in the inner solar system:
Position of the planets and some spacecraft in the inner solar system, Dec. 10, 2019. Credit: NASA Eyes on the Solar System / Bob Trembley.
Position of the planets and a couple bodies in the middle solar system:
Position of the planets in the middle solar system, Dec. 10, 2019. Credit: NASA Eyes on the Solar System / Bob Trembley.
Position of the planets in the outer solar system, transneptunian object (TNO) and possible dwarf planet 120347 Salacia is highlighted in red:
Position of the planets in the outer solar system, Dec. 10, 2019 - the orbit of transneptunian object 120347 Salacia is highlighted in red. Credit: SpaceEngine / Bob Trembley.
120347 Salacia, provisional designation 2004 SB60, is a trans-Neptunian object in the Kuiper belt, approximately 850 kilometers in diameter. As of 2018, it is located about 44.8 astronomical units from the Sun, and reaches apparent magnitude 20.7 at opposition.
Salacia was discovered on 22 September 2004, by American astronomers Henry Roe, Michael Brown and Kristina Barkume at the Palomar Observatory in California, United States. It has been observed 124 times, with precovery images back to 25 July 1982. Salacia orbits the Sun at an average distance that is slightly greater than that of Pluto. It was named after the Roman goddess Salacia and has a single known moon, Actaea.
Brown estimated that Salacia is very likely a dwarf planet. However, William Grundy et al. argue that objects such as Salacia, in the size range of 400–1000 km, with albedos less than ≈0.2 and densities of ≈1.2 g/cm3 or less, have likely never compressed into fully solid bodies, let alone differentiated or collapsed into hydrostatic equilibrium, and so are highly unlikely to be dwarf planets. - Wikipedia
Orbital plane of Actaea around 120347 Salacia compared to the plane of the ecliptic. Credit: SpaceEngine / Bob Trembley.
Artist conception of 120347 Salacia seen from above Actaea - with planetshine on Actaea from Salacia. Credit: SpaceEngine / Bob Trembley.
Artist conception of Actaea seen from the surface of transneptunian object, 120347 Salacia. Credit: SpaceEngine / Bob Trembley.
NASA's Interactive Real-Time Web-based Orrery:
Solar System News
📷 This image shows what appears to be a large patch of fresh, untrodden snow – but it's probably a bit too far away for a spontaneous snowball fight 😉. This is #Korolev crater on #Mars, seen by ESA's Mars Express on 4 April 2018 👉 https://t.co/1XkuyXCGAU pic.twitter.com/8aXELRWHkd
— ESA (@esa) December 9, 2019
Saturn’s moon Enceladus blasts a plume of material from its underground ocean into space, and our Cassini spacecraft flew right through the material to sample it. Now, an ongoing deep-dive into Cassini data has found new kinds of organic molecules there: https://t.co/VPM4VGLRQS pic.twitter.com/ThKMdWF6cx
— NASA Solar System (@NASASolarSystem) October 2, 2019
Announcing our speakers for #IceGiants2020 Day 2 (January 21st) @RoyalSociety:
Heidi Hammel (@hbhammel of AURA) helps us to celebrate the 30th anniversary of Voyager 2's flyby of Neptune, and looking ahead to future missions.https://t.co/hXML141SuLhttps://t.co/awWhFRnigW pic.twitter.com/XEjeZKf48o
— IceGiants (@IcyGiants) December 5, 2019
OSIRIS-REx Asteroid Sample Return Mission
After discovering Bennu’s mysterious particle ejections, our science team investigated possible causes of this activity.
Learn more about what they found: https://t.co/kbLlu03pEe pic.twitter.com/LmDWeN2aNj— NASA's OSIRIS-REx (@OSIRISREx) December 5, 2019
International Space Station
The Exp 61 crew has begun unpacking several tons of new supplies from the @SpaceX and @Roscosmos space freighters. Read more... https://t.co/q54wsgToYX pic.twitter.com/fWlp10NBqu
— Intl. Space Station (@Space_Station) December 9, 2019
Juno Mission at Jupiter
This is the kind of view you can get when you skim just 3,200 miles (5,200 kilometers) above Jupiter's cloud tops. Image processed by Björn Jónsson. See details: https://t.co/k5K3Z8ESXS pic.twitter.com/51ly0ziCOh
— NASA's Juno Mission (@NASAJuno) December 6, 2019
NASA Climate
Australia is burning.
Downtown Sydney was partially evacuated due to the smoke. Ferry service was cancelled due to low visibility. Fire alarms are randomly going off inside buildings. Schools are keeping children inside.
This is a climate emergency.https://t.co/DjL7YueIQw
— Eric Holthaus (@EricHolthaus) December 10, 2019
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.
Beaver Island Seeking Dark-Sky Designation
This get's a LARGE thumbs up from me! You guys need any help?
Michigan’s Beaver Island seeks international dark sky designation https://t.co/JtGojOheG7
— MLive (@MLive) November 25, 2019
We are all made of stardust. Now, chemical sleuthing can even tell us what *kind* of stardust: Earth in particular is full of dust from dying, red giant stars. https://t.co/Utuw41kCCk pic.twitter.com/rFGqf4ZYKC
— Corey S. Powell (@coreyspowell) December 10, 2019
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. A web-based version of Stellarium is also available.
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.
Kerbal Space Program: Create and manage your own space program; build and launch rockets, aircraft, space planes, space probes, landers, rovers and more!
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