Archive
Ephemeris: 12/12/2023 – The source of the Geminid meteor shower
This is Bob Moler with Ephemeris for Tuesday, December 12th. Today the Sun will be up for 8 hours and 51 minutes, setting at 5:02, and it will rise tomorrow at 8:11. The Moon is new today, and won’t be visible.
The Geminid meteor shower, which will peak this Thursday, is caused by a small body called 3200 Phaethon which looks like an asteroid but has the orbit of a comet, coming close to the Sun and back out to the asteroid belt. It’s probably a dead comet, with all the volatiles sublimated away leaving only the rocky bits. It is named Phaethon, because at the time it was the asteroid that came closest to the Sun. In Greek mythology Phaethon, the son of Helios the Sun god borrowed his father’s chariot that carried the Sun to take it out for a spin one day with disastrous results. The Geminid meteor shower was first recognized in 1862. The hourly rates of the Geminids have increased every year since then. The meteor stream has completely filled in the orbit of Phaethon, and they’re being pushed around by the gravitational effect of the planets and the pressure of sunlight.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT –5 hours). They may be different for your location.
Addendum
Ephemeris: 11/15/2023 – Other possible contact binary solar system bodies
This is Ephemeris for Thursday, November 16th. Today the Sun will be up for 9 hours and 32 minutes, setting at 5:13, and it will rise tomorrow at 7:42. The Moon, 3 days past new, will set at 7:34 this evening.
Thinking about it after seeing the contact the binary satellite of the asteroid that the Lucy spacecraft just flew by I have memories of several other bodies that could be contact binaries. The first one is that the New Horizons spacecraft passed four years ago which looked like two bodies stuck together, actually two pancakes because they weren’t spherical, but they were rather flattened. That Kuiper Belt Object now has the name Arrokoth. Comet 67 P, I won’t try to pronounce its name (Churyumov-Gerasimenko), that the Rosetta spacecraft orbited a few years ago, kinda looked like a rubber ducky with a small part attached to a larger part. It could be a contact binary. Again and there are a couple of comet nuclei that look like bowling pins. They may be contact binaries too.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT –5 hours). They may be different for your location.
Addendum
Ephemeris: 11/14/2023 – Lucy sees an asteroid with a double moon
This is Bob Moler with Ephemeris for Tuesday, November 14th. Today the Sun will be up for 9 hours and 37 minutes, setting at 5:15, and it will rise tomorrow at 7:39. The Moon, 1 day past new, will set at 5:48 this evening.
Two years ago a spacecraft called Lucy was sent out towards the Trojan Asteroids of Jupiter. On the way there it was going to pass another small asteroid, but they found another one that Lucy would come close to, the mission planners tweaked its orbit earlier this year. So Lucy can get close to the small asteroid called Dinkinesh. When Lucy got close to Dinkinesh earlier this month, it took photos, and they found that it had a satellite, and they took other photos from a different angle, and they found out that the satellite actually was two satellites in contact, a contact binary, two bodies stuck together. So that was quite a surprise. Neither body looked smooshed, so their collision appears to have been very gentle.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT –5 hours). They may be different for your location.
Addendum
Dinkinesh is the Ethiopian name for the fossil, since it was found in Ethiopia. The name for the fossil given by the discoverers was Lucy, mainly because The Beatles song Lucy in the sky with diamonds was a big hit back then, and it was constantly played in the camp.
The next main belt asteroid that Lucy is going to pass on its way out to Jupiter’s Trojan asteroids is named Donaldjohansson in honor of the discoverer of the Lucy fossil. Jupiter’s Trojan asteroids are two groups of asteroids in the same orbit as Jupiter. One set is 60 degrees ahead of Jupiter in its orbit and the second set is 60 degrees behind Jupiter in its orbit. They’re there because they are at special gravitational points called Lagrangian points. The point ahead of Jupiter is the L4 point and the one trailing is L5. You may have heard me talk about L1 and L2 points having to do with the Earth and Sun system. These are two other Lagrangian points in line with the Sun-Earth axis, that are useful to orbit spacecraft around. There’s another one, but we don’t think there’s anything out there because that’s on the other side of the Sun from us, and none of the other planets have a body opposite to the Sun from them either, so the L3 point is not a viable point.
Ephemeris: 10/02/2023 – This week: Launch to Psyche
This is Bob Moler with Ephemeris for Monday, October 2nd. Today the Sun will be up for 11 hours and 40 minutes, setting at 7:21, and it will rise tomorrow at 7:42. The Moon, 3 days past full, will rise at 9:00 this evening.
This Thursday, October 5th at 10:38 AM will be the first opportunity to launch a SpaceX Falcon Heavy rocket with the Psyche spacecraft to the asteroid 16 Psyche. It’ll be a nearly 5 1/2 year trip to this asteroid, which is metal rich, and quite unlike any asteroid that we’ve ever studied before with a spacecraft. There is a 20 day launch window starting October 5th with lunch possibilities during the 10 o’clock hour each day. Due to the design of SpaceX Falcon rockets there is only one time a day they can launch, due to the fact that they super chill their fuel and oxidizer to make them more dense to squeeze the most fuel and oxidizer into the rocket. They need to load them immediately prior to launch. Any hold in the countdown will allow them to expand and in the case of the liquid oxygen, to boil off.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT –4 hours). They may be different for your location.
Addendum
Ephemeris: 09/26/2023 – I’ve got some asteroid news today
This is Ephemeris for Tuesday, September 26th. Today the Sun will be up for 11 hours and 58 minutes, setting at 7:33, and it will rise tomorrow at 7:35. The Moon, 3 days before full, will set at 4:59 tomorrow morning.
I’ve got some asteroid news today. It’s good news. Two days ago, Sunday the 24th the OSIRIS REx return capsule landed in Utah with its precious cargo of rock and dust from the asteroid Bennu. And as of the time I’m recording this, I don’t know what was in the capsule. Although when they captured the material from Bennu they actually captured much more than they thought they would get, and had trouble closing the cover on the collection device.
Today is the one-year anniversary of the DART spacecraft’s collision with the small asteroid satellite Dimorphos. The latest news is that the original increase in the period of the orbit around Didymos by 33 minutes increased by another minute since. Nobody seems to know exactly why.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT –4 hours). They may be different for your location.
Addendum
11/14/2022 – Ephemeris – Psyche spacecraft to launch to its namesake asteroid next October after a 14-month delay
/
This is Ephemeris for Monday, November 14th. Today the Sun will be up for 9 hours and 37 minutes, setting at 5:15, and it will rise tomorrow at 7:39. The Moon, 2 days before last quarter, will rise at 10:07 this evening.
The launch of the Psyche spacecraft to the asteroid of the same name this past August was canceled due to problems with the spacecraft itself, not the SpaceX Falcon Heavy rocket. NASA thinks they have a handle on the problem and are now wanting to launch in October of next year. If they launched this year, they could have gotten a gravity assist by passing close to Mars on their way to the asteroid belt, where the asteroid Psyche resides. Next year’s launch will not have a Mars flyby and take 2 more years to reach Psyche, a total of 6 years, arriving in 2029. The long flight time is because of the attempt to orbit Psyche rather than just flying by the asteroid. To handle such a maneuver, the spacecraft will also use ion thrusters like the Dawn spacecraft did last decade, which orbited both the asteroids Vesta and Ceres. Psyche is a special metal rich asteroid that may have been the core of a protoplanet.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). They may be different for your location.
Addendum
An artist’s rendition of the Psyche spacecraft at the asteroid Psyche. Credit: NASA.
10/02/2022 – Ephemeris Extra – NASA goes on the offensive
DART images of both Didymos, the big one, and Dimorphos, on approach. Credit NASA / JHAPL
This is a slightly revised version of my article in the Stellar Sentinel, the newsletter of the Grand Traverse Astronomical Society. Educators may receive a free PDF copy of this monthly publication via email, which covers astronomical topics and events visible from Northwest Lower Michigan. Send your request, stating your affiliation, to info@gtastro.org.
The score is: Asteroids-billions, NASA-1. It’s a bit unfair, since asteroids have been hitting the Earth for 4.567 billion years or so, and NASA has been around for 64 years before DART spacecraft collided with the asteroid Dimorphos. Hey, this was their first attempt at a small asteroid. As far as the 21st century destructive asteroid score is 1 to NASA’s 1, as far as I know.
That strike was in Chelyabinsk, Russia. That was February 15, 2013. We were all waiting on another asteroid making a close pass of the Earth, when the Chelyabinsk meteoroid exploded 14 miles above the city. Over a thousand people were injured by the blast wave. They saw the bright flash and rushed to the windows to see what it was. Then the blast wave hit, shattering the windows, causing glass cuts for over a thousand people. One building’s wall collapsed, and a fragment fell into a lake outside of town.
NASA’s record in attempting to hit a planetary object dates back to the early 1960s and the nine Pioneer missions to crash a probe on the Moon, sending back pictures all the way down. Back in the early 60s, just hitting a 2,100-mile (3380 kilometer) wide object a quarter of a million miles away was a dicey prospect. It’s one thing to miss the Moon on one side or the other, but to not have enough oomph to even make it all the way is downright embarrassing. NASA did much better by the end of the decade with the Apollo manned landings and bombarding the Moon with used space vehicles for seismic studies of its interior.
NASA actually collided a spacecraft into a comet. That was July 4, 2005, when the impactor part of the Deep Impact spacecraft hit Comet Tempel 1’s nucleus, attempting to study part of its subsurface. The non-impactor part was later renamed EPOXI and went on to fly by the dog-bone shaped Hartley 2 comet nucleus. Another reused comet explorer spacecraft Stardust after collecting cometary dust from Comet Wild 2 (pronounced Vilt 2), and possible interstellar dust penetrating the solar system, and after dropping the sample re-entry capsule back on Earth it ended in solar orbit. Later it was repurposed as the Stardust-NexT mission and flew by Tempel 1 six years later to study the crater the Deep Impact Impactor made in the comet.
To study the effect of a collision of a spacecraft from the Earth despite the fact that Dimorphos cannot be seen is a trick. However, the pair is an eclipsing binary from our point of view, so the brightness of the unresolved pair changes as they eclipse each other.
Before the collision, Dimorphos had an 11.9 hour orbit of Didymos. Dimorphos is a fifth the size of Didymos orbiting it at three times the primary’s radius. If the orbit is near circular, Dimorphos’ orbital velocity is only 0.39 mph (0.63 kph). It should be relatively easy to see a tiny change in Dimorphos’ orbital period.
Last frame Dimorphos fit in from DART. Credit NASA / JHAPL.
Two images from the LiciaCube satellite launched from the DART spacecraft 15 days before the impact, and trailing it to record the collision with its wide and narrow angle imagers. Dimorphos does appear to be a rubble pile asteroid from its appearance and the amount of ejecta caused by the impact. The ejecta adds to the effect of the spacecraft’s kinetic energy by pushing away from the asteroid by Newton’s third law of motion. Credit: Italian Space Agency.
A frame from a time-lapse video taken from the ATLAS Project’s South African observatory of the unresolved Didymos – Dimorphos pair and the expanding ejecta cloud. The asteroid pair developed a dust tail like a comet for a while.
ATLAS is an acronym for a rather apocalyptic title “Asteroid Terrestrial-impact Last Alert System”. Developed by the University of Hawai’i and funded by NASA. It has two telescopes in Hawai’i, one in Chile, and one in South Africa. Credit: NASA/UH.
Days later, Dimorphos was exhibiting a thin dust tail, like a comet.
Now we wait on Earth’s observatories to observe of the period of Dimorphos’ orbit. It should decrease the orbital time.
02/17/2022 – Ephemeris – Mission to a metallic asteroid
This is Ephemeris for Thursday, February 17th. Today the Sun will be up for 10 hours and 34 minutes, setting at 6:14, and it will rise tomorrow at 7:38. The Moon, 1 day past full, will rise at 7:21 this evening.
In August this year, one of the three scheduled Falcon-Heavy rocket launches this year will send the Psyche spacecraft on a four-year journey to its namesake asteroid, 16 Psyche. It is an unusual asteroid, thought to be 30 to 60 percent iron-nickel in composition. The spacecraft will swing by Mars for a gravitational boost. After the chemical powered boost into solar orbit, the spacecraft will open its huge solar panels in the shape of two crosses to feed its power hungry electric thrusters to complete the journey and to orbit 16 Psyche. The thrusters are Hall Effect thrusters, the first used in space, that use magnetic fields instead of electric fields to eject xenon gas ions to provide thrust. It is expected to arrive at 16 Psyche in 2026.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). They may be different for your location.
Addendum
Artist’s visualization of the spacecraft Psyche orbiting asteroid 16 Psyche. This imagining seems to assume the asteroid is nearly 100% metallic. Credit: NASA.
02/14/2022 – Ephemeris – A celestial Valentine’s Day encounter
This is Bob Moler with Ephemeris for St Valentine’s Day, Monday, February 14th. Today the Sun will be up for 10 hours and 25 minutes, setting at 6:10, and it will rise tomorrow at 7:43. The Moon, 2 days before full, will set at 7:40 tomorrow morning.
Twenty-two years ago to the day, the NEAR-Shoemaker* spacecraft entered into orbit of the near Earth asteroid 433 Eros. It wasn’t originally planned to enter orbit of the asteroid named after the Greek god of love on Valentine’s Day, 2000. It arose after an aborted course correction a year earlier. After solving the problem, a new course was plotted and NEAR-Shoemaker was gently inserted into orbit of this 21 mile long asteroid shaped like a bent bread stick with a bite taken out of the center of it. The spacecraft spent almost a year orbiting Eros at various altitudes. The spacecraft ended its mission gently crashing into the middle of the asteroid, where it stayed alive for two weeks before succumbing to the cold.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). They may be different for your location.
*The name Shoemaker was added to the NEAR spacecraft name after it was launched. NEAR stands for Near Earth Asteroid Rendezvous. It was named for Eugene Shoemaker, a geologist who proved that the Barringer Crater in Arizona was an impact crater rather than a volcanic crater, thus proving, before the Apollo 11 landing on the Moon, that the Moon’s craters were mostly impact craters produced by small asteroids like Eros. Shoemaker and his wife Carolyn, the astronomer in the family, along with David Levy discovered the Comet Shoemaker-Levy 9. The comet had broken into more than 22 pieces and crashed into Jupiter over a week in July 1994, making blemishes in the Jovian clouds that lasted many months.
Addendum
“These color images of Eros were taken by the NEAR probe on February 12, 2000, at a distance of 1,800 kilometers, during the final approach imaging sequence before insertion into orbit. The images show the approximate color of Eros as it would be seen with the naked eye.” Click on the image to enlarge it. Credit
NASA/JPL/JHUAPL. Caption from: https://eros2019.imcce.fr/eros.html via Google Translate.
By the way, the Roman equivalent to Eros was the god Cupid, whose love dart is the constellation Sagitta, which resides within the Summer Triangle of bright stars, to be seen in the evening sky four months from now.
I’ll end with a Valentine heart. The red color is real, it’s due to hydrogen.
IC 1805 (Heart Nebula) Credit: s58y [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons.
11/23/2021 – Ephemeris – NASA to launch a mission to crash into an asteroid overnight tonight
This is Ephemeris for Tuesday, November 23rd. Today the Sun will be up for 9 hours and 17 minutes, setting at 5:07, and it will rise tomorrow at 7:51. The Moon, half-way from full to last quarter, will rise at 8:17 this evening.
As of last Sunday night, it was GO for launch of NASA’s DART Mission at 1:21 am Eastern Standard Time tomorrow morning on a Falcon 9 rocket from Vandenberg Space Force Base. DART stands for Double Asteroid Redirection Test. The DART spacecraft is to smash into a small asteroid named Dimorphos, that slowly orbits another somewhat larger asteroid, Didymos. Dimorphos orbits at only 7 inches per second, so even the smallest impact should alter the orbit noticeably. About a week before the planned collision, DART will release a small CubeSat to arrive 3 minutes after the collision to survey the crash site. In 2024 the European Space Agency will launch a satellite to survey the asteroid pair and note any long-term effects, to see if this technique for diverting asteroids is feasible.
Addendum
DART spacecraft with Dimorphos and Didymos. The DART spacecraft is not to scale with the asteroids. See below. CREDIT: NASA/JHUAPL
Dart and asteroids to scale with terrestrial landmarks. Credit: NASA/JHUAPL
Bob Moler's Ephemeris Blog 