05/18/2020 – Ephemeris – Comets are fragile, especially this month’s crop

This is Ephemeris for Monday, May 18th. Today the Sun will be up for 14 hours and 57 minutes, setting at 9:08, and it will rise tomorrow at 6:09. The Moon, half way from last quarter to new, will rise at 5:04 tomorrow morning.

Last month most of us astronomers were looking forward to seeing at least two naked-eye comets this month, with another just below naked-eye visibility. Our hopes have been dashed with the first two, Comet ATLAS is disintegrating and Comet SWAN has stopped brightening, and at its brightest, which would be barely visible in a dark sky, would be invisible in bright twilight, where it will be located. Comets are unpredictable. Each is their own beast. They are small bodies of ices dust and bits of rock. When they come inside the orbit of Jupiter the Sun’s heat sublimates their frozen gasses which shoot out along with dust and build a huge tenuous head called a coma that can be larger than Jupiter and a tail that extends millions of miles (kilometers).

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Comet ATLAS disintegrates as witnessed by the Hubble Space Telescope. Currently there are 5 nuclear fragments being separately tracked. The color here is most not likely the true visual color. Click on the image to enlarge. Credit: NASA/ESA Hubble Space Telescope.

04/17/2020 – Ephemeris – More on Comet ATLAS

One of the problems that can happen when you record programs several days before they are aired is that events can get ahead of you. Comet ATLAS is disintegrating and won’t get any brighter than it already is. This program was written after I read reports that the comet had faded but the full ramifications of the fading were not known.

This is Bob Moler with Ephemeris for Friday, April 17th. Today the Sun will be up for 13 hours and 36 minutes, setting at 8:31, and it will rise tomorrow at 6:52. The Moon, 3 days past last quarter, will rise at 5:32 tomorrow morning.

Lets talk more about Comet C/2019 Y4 (ATLAS). For this program I talk about celestial sights visible to the naked-eye or are easily found in binoculars. Each program script is posted on this blog usually with images and charts. The blog postings are generally illustrated. Anyway, it seems that Comet ATLAS is breaking up. With the Neil Sedaka’s 1960 song “Breakin up is hard to do” to the contrary, for comets breaking up is quite easy. They are porous assemblages of bits of dust, pebbles and frozen gasses. It is already most likely a chip off the old block.. er comet. It follows the same orbit as the Great Comet of 1844. Both of these could be parts of an even larger comet passing the Sun 6 or maybe even 12 thousand years ago.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Comet ATLAS C/2019 Y4 showing two nuclei on April 15, 2020. Credit: Jose De Queiroz and Michael Deyerler from Switzerland’s public Mirasteilas Observatory. Copied from Spaceweather.com.  The streaks are stars as the telescope was tracking the comet during the exposure.

An even newer discovered comet may make it to naked-eye visibility late next month, if it holds together.  I’ll talk about Comet C/2020 F8 (SWAN) next Tuesday.

04/16/2020 – Ephemeris – Comet C/2019 Y4 (ATLAS)

One of the problems that can happen when you record programs several days before they are aired is that events can get ahead of you. Comet ATLAS is disintegrating and won’t get any brighter than it already is. This program was written and recorded before I realized that it was falling apart.

This is Bob Moler with Ephemeris for Thursday, April 16th. Today the Sun will be up for 13 hours and 33 minutes, setting at 8:29, and it will rise tomorrow at 6:54. The Moon, 2 days past last quarter, will rise at 5:05 tomorrow morning.

There’s a new comet about, which may reach naked-eye visibility next month. It is comet C/2019 Y4 (ATLAS). It was discovered three days after Christmas last year by the apocalyptic sounding Asteroid Terrestrial-Impact Last Alert System (ATLAS), run out of the University of Hawai’i. Despite the name of the search system the comet they snagged will not come close to the Earth, contrary to some misleading posts on social media. Comet ATLAS, yes it’s an acronym, could reach first magnitude when it’s close to the Sun at the end of May, but will be in the bright evening twilight by then. I don’t think that it can be picked up in binoculars yet. I’ll have more about it tomorrow.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

This image starts at 10 p.p. looking north-northwest. Also plotted was Comet PANSTARRS. I removed some of its labels that plotted over the ATLAS labels. The labels have the comet name, month-day and magnitude. Any magnitude value greater than 6.0 is invisible to the naked-eye. We were hoping that ATLAS would get a lot brighter. Click on the image to enlarge.  Created using Cartes du Ciel (Sky Charts).