At last night’s meeting of the Warren Astronomical Society, the topic of the Starlink satellite constellation came up during the “In the News” segment, and a groan of dismay could be heard from the entire audience. If you are unfamiliar with Starlink, it is a constellation of potentially tens of thousands of communication satellites created by SpaceX with the goal of providing global high-speed internet – that concept sounds great!
The first time I became aware of Starlink was after the 2nd satellite deployment mission of May of 2019, when 60 satellites were put into a 53° Earth orbit. Almost immediately satellite sightings started pouring in from around the world. Videos show a long trail of lights traversing the sky, virtually painting the orbits of the satellites in your mind’s eye, and literally painting them in the cameras of astronomers and astrophotographers – who have started complaining loudly!
The NGC 5353/4 galaxy group is obscured by more than 25 Starlink satellite trails in this May 2019 image, taken from Lowell Observatory in Flagstaff, Arizona. Credit: Victoria Girgis/Lowell ObservatoryThe International Astronomical Union posted this statement on June 3, 2019:
Over the past decades, considerable effort has gone into designing, building, and deploying satellites for many important purposes. Recently networks, known as satellite constellations, have been deployed and are planned in ever greater numbers in mainly low-Earth orbits for a variety of purposes, including providing communication services to underserved or remote areas. Until this year, the number of such satellites was below 200, but that number is now increasing rapidly, with plans to deploy potentially tens of thousands of them. In that event, satellite constellations will soon outnumber all previously launched satellites.
The International Astronomical Union (IAU) is concerned about these satellite constellations. The organisation, in general, embraces the principle of a dark and radio-quiet sky as not only essential to advancing our understanding of the Universe of which we are a part, but also as a resource for all humanity and for the protection of nocturnal wildlife. We do not yet understand the impact of thousands of these visible satellites scattered across the night sky and despite their good intentions, these satellite constellations may threaten both.
The scientific concerns are twofold. Firstly, the surfaces of these satellites are often made of highly reflective metal, and reflections from the Sun in the hours after sunset and before sunrise make them appear as slow-moving dots in the night sky. Although most of these reflections may be so faint that they are hard to pick out with the naked eye, they can be detrimental to the sensitive capabilities of large ground-based astronomical telescopes, including the extreme wide-angle survey telescopes currently under construction. Secondly, despite notable efforts to avoid interfering with radio astronomy frequencies, aggregate radio signals emitted from the satellite constellations can still threaten astronomical observations at radio wavelengths. Recent advances in radio astronomy, such as producing the first image of a black hole or understanding more about the formation of planetary systems, were only possible through concerted efforts in safeguarding the radio sky from interference.
The IAU is a science and technology organisation, stimulating and safeguarding advances in those areas. Although significant effort has been put into mitigating the problems with the different satellite constellations, we strongly recommend that all stakeholders in this new and largely unregulated frontier of space utilisation work collaboratively to their mutual advantage. Satellite constellations can pose a significant or debilitating threat to important existing and future astronomical infrastructures, and we urge their designers and deployers as well as policy-makers to work with the astronomical community in a concerted effort to analyse and understand the impact of satellite constellations. We also urge appropriate agencies to devise a regulatory framework to mitigate or eliminate the detrimental impacts on scientific exploration as soon as practical.
The IAU’s Commission B7 Protection of Existing and Potential Observatory Sites welcomes the opportunity to work proactively with everyone involved in these efforts. – IAU
Elon Musk initially dismissed astronomer’s complaints, but has since agreed to take steps to reduce the albedo of the satellites; I’ve seen comments by supporters (or quite possibly internet trolls) accusing detractors of being Luddites – these Luddites would include astronomers who use high-tech multi-million dollar equipment… While I was researching the Starlink launch date for this post, I was surprised at the rather lengthy history section of the Wikipedia entry, and embarrassed at my near total lack of knowledge of that history. This story certainly has my attention now; I’m certain this story will be on-going and developing over the next several years.
The Moon appears in the sky at 3:00 PM for several days this week – about the time schools get out. If it’s clear, I want to bring my ‘scope to my after-school club and have the students see it.
The Moon appears above the east-southeastern horizon at 3:00 PM from Dec. 3-6th. Credit: Stellarium / Bob TrembleyMercury, Mars and the star Spica align above the southeastern horizon before sunrise this week.
Mercury, Mars and the star Spica align above the southeastern horizon before dawn this week. Credit: Stellarium / Bob TrembleySeveral planets appear above the southwestern horizon shortly after sunset this week. Jupiter sets soon after sunset, leaving Saturn and Venus above the southwestern horizon – great observing targets!
The Moon appears high above the south-southeastern horizon after sunset for several days this week – this is an ideal time to observe the Moon with binoculars or a telescope.
The Moon high above the south-southeastern horizon after sunset for several days this week. Credit: Stellarium / Bob TrembleyThe Andromeda galaxy appears almost directly overhead around 8:30 PM this week – as do the constellations Andromeda and Pegasus.
The constellations Pegasus and Andromeda appear directly overhead around 8:30 PM this week. Credit: Stellarium / Bob Trembley
Starlink Satellites
Let me know if you have an observing session this week where you do NOT see a Starlink satellite.
The Moon is a waxing crescent, visible toward the southwest in early evening – the Moon is a great observing target this week!
The Moon will be at first quarter on Dec. 4th, it will be visible high in the southern sky in early evening.
After Dec. 4th, the Moon will be a waxing gibbous, visible to the southeast in early evening, up for most of the night.
Moon News
The Sun has been spotless for 20 days; large coronal holes appear at both poles – the southern hole has gotten very large .
The Sun seen in 193 angstroms (extreme ultraviolet) Dec. 2, 2019:
Several prominences on the Sun’s l today! I’m going to have to crack out my solar telescope when I finish this post!
The Sun seen in 304 angstroms (extreme ultraviolet) Dec. 2, 2019:
Videos courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.
The solar wind speed is 297.0 km/sec (↓), with a density of 4.5 protons/cm3 (↑) at 1550 UT.
Facebook: SolarActivity
https://www.facebook.com/photo.php?fbid=10220517404466017&set=gm.2821213917889934&type=3&theater&ifg=1
Animated LASCO C2 Coronograph showing the solar corona above the Sun’s limb (the white circle). Credit: NASA/JPL-CaltechYou 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.
Sun News
Upcoming Earth-asteroid encounters:
| Asteroid |
Date(UT)
|
Miss Distance
|
Velocity (km/s)
|
Diameter (m)
|
| 2017 AP4 |
2019-Dec-03
|
8.5 LD
|
7.5
|
15
|
| 2019 WW |
2019-Dec-05
|
8.6 LD
|
9.8
|
43
|
| 2019 WB5 |
2019-Dec-06
|
18.7 LD
|
22
|
48
|
| 2019 WR3 |
2019-Dec-06
|
14.2 LD
|
7.5
|
98
|
| 2019 WJ6 |
2019-Dec-07
|
7.5 LD
|
21.1
|
47
|
| 2018 XW2 |
2019-Dec-07
|
17.4 LD
|
13
|
28
|
| 2019 VH5 |
2019-Dec-08
|
18 LD
|
9.8
|
73
|
| 2019 XB |
2019-Dec-09
|
17.4 LD
|
7.9
|
67
|
| 2019 WT3 |
2019-Dec-09
|
9.8 LD
|
11
|
41
|
| 2019 WO2 |
2019-Dec-09
|
4.8 LD
|
7.6
|
34
|
| 2019 XF |
2019-Dec-18
|
9.5 LD
|
24.4
|
78
|
| 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
|
4.3
|
21
|
| 2019 AE3 |
2020-Jan-02
|
4.9 LD
|
8.2
|
13
|
| 2019 UO |
2020-Jan-10
|
11.8 LD
|
9.4
|
361
|
| 2019 WC5 |
2020-Jan-11
|
6.4 LD
|
13
|
112
|
| 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
|
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)
Minor Planets discovered: 840,470 (+178)
Asteroid News: Hera Mission to Deflect an Asteroid Funded!
https://twitter.com/SupportHera/status/1200042769919750147
More on the Hera Mission:
On Dec. 3, 2019, the NASA All Sky Fireball Network reported 50 fireballs.
(47 sporadics, 2 Nov. omega Orionids, 1 Quadrantids)
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
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. 3, 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. 3, 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 420356 Praamzius is highlighted in red:
Position of the planets in the outer solar system, D
