The Astronomy Thread

BrutulTM said:

Did anyone see Halley's comet in 1986? I was 9 years old and I remember my dad going out early in the morning to try to see it through his rifle scope but I don't think he ever did. You couldn't get as much good advice about when and where to look as you can now. I'll be 84 next time it comes around if I make it that long. I am lucky enough to live in a great place to look at stars.

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Ground-Based and Orbital Telescopes (Early Observations)​

• Gemini South and NASA's Infrared Telescope Facility
  • Found evidence for water ice in the cloud surrounding the nucleus 02:15 Opens in a new window . This was considered a not-surprising and expected finding.
• Hubble Space Telescope (HST)
  • Definitively observed a dust cloud (coma) around the object 02:43 Opens in a new window .
  • Set an upper limit on the size of the object at 2.8 km 02:50 Opens in a new window .
  • Measured that the coma was being fed by tens to hundreds of kilograms of material every second 02:56 Opens in a new window .
• James Webb Space Telescope (JWST)
  • Performed infrared spectroscopy and identified signatures of water and carbon dioxide 03:31 Opens in a new window .
  • Discovered that the comet was emitting significantly more carbon dioxide than water, with an estimated ratio of 8:1 03:36 Opens in a new window . This high ratio is extremely rare for comets.
  • The comet appeared to be carbon chain depleted, meaning it has much simpler carbon molecules (not larger carbon molecules) 05:02 Opens in a new window .
• Sphere X
  • Confirmed the measurement of the high carbon dioxide-to-water ratio previously observed by JWST 03:51 Opens in a new window .
• Very Large Telescope (VLT) - Near Ultraviolet Observation
  • Found a surprisingly large amount of nickel using spectroscopy, which is unusual as nickel processes typically also form iron 05:21 Opens in a new window .
  • Later observations, as the comet came closer, started to show more iron, making the numbers consistent with the likely process of volatile nickel carbonyls evaporating and then producing the nickel seen 05:43 Opens in a new window .

Spacecraft Around Mars (Close Approach)​

• European Space Agency's ExoMars Trace Gas Orbiter (TGO)
  • Performed improved astrometry by combining its positional information with ground-based observations 06:54 Opens in a new window .
  • Obtained a much better position and orbit for the comet because it was observing the object from a different angle than Earth-based telescopes 07:01 Opens in a new window .
• NASA's Mars Reconnaissance Orbiter (MRO)
  • Was able to detect and get a smeared image of the comet's coma 08:00 Opens in a new window .
  • Provided some idea about the shape of the coma as viewed from Mars 08:23 Opens in a new window .
• MAVEN (Mars Atmosphere and Volatile EvolutioN)
  • Used its imaging ultraviolet spectrograph to look at hydrogen emission 08:34 Opens in a new window .
  • The resulting image showed three distinct blue blobs of hydrogen emission corresponding to:
    1. Hydrogen from the comet 3I/ATLAS (shifted in frequency due to its high velocity) 09:01 Opens in a new window .
    2. Hydrogen in deep space moving by the planet 09:14 Opens in a new window .
    3. Hydrogen from near Mars (very low velocity relative to Mars) 09:35 Opens in a new window .
• NASA's Perseverance Rover (Mastcam)
  • Took an image from the surface of Mars that captured a tiny smear of the comet 10:14 Opens in a new window .

Solar and Deep Space Missions​

• SOHO (Solar and Heliospheric Observatory)
  • Detected the comet on the opposite side of the sun by stacking multiple images to bring out the comet's image against the background 10:36 Opens in a new window .
• Punch Spacecraft (Polarimeter for Unifying the Corona and Heliosphere)
  • Observed the comet by stacking multiple images 11:23 Opens in a new window .
• STEREO Spacecraft
  • Picked out the comet because it brightened just enough and was in the frame 11:51 Opens in a new window .
• Psyche Mission
  • Used its onboard imager to track the object and its data could be used to more tightly constrain the orbit 12:32 Opens in a new window .
• Lucy Mission (Long Range Reconnaissance Imager)
  • Picked out the comet and showed the tail was coming out from it 13:07 Opens in a new window .
  • Provided a completely different view of the comet by viewing it from an almost 90-degree angle compared to other instruments 13:17 Opens in a new window .